Alix Young Vik

• Nesvold, Marianne Bakke; Jensen, Janicke Liaaen; Hove, Lene Hystad; Singh, Preet Bano; Young, Alix; Palm, Øyvind; Andersen, Lene Frost; Carlsen, Monica Hauger & Iversen, Per Ole (2018). Dietary intake, body composition and oral health parameters among female patients with primary Sjögren’s syndrome. Nutrients.  ISSN 2072-6643.  10(866) . doi: 10.3390/nu10070866
• Singh, Preet Bano; Young, Alix; Lind, Synnøve; Leegaard, Marie Cathinka; Capuozzo, Alessandra & Parma, Valentina (2018). Smelling anxiety chemosignals impairs clinical performance of dental students.. Chemical Senses.  ISSN 0379-864X.
• Aqrawi, Lara Adnan; Galtung, Hilde; Vestad, Beate; Øvstebø, Reidun; Thiede, Bernd; Rusthen, Shermin; Young, Alix; Guerreiro, Eduarda; Utheim, Tor Paaske; Chen, Xiangjun; Utheim, Øygunn Aass; Palm, Øyvind & Jensen, Janicke Liaaen (2017). Identification of potential saliva and tear biomarkers in primary Sjögren’s syndrome, utilising the extraction of extracellular vesicles and proteomics analysis. Arthritis Research & Therapy.  ISSN 1478-6362.  19(1) . doi: 10.1186/s13075-017-1228-x Fulltekst i vitenarkiv.
• Pistone, Sara; Goycoolea, Francisco M.; Young, Alix; Smistad, Gro & Hiorth, Marianne (2017). Formulation of polysaccharide-based nanoparticles for local administration into the oral cavity. European Journal of Pharmaceutical Sciences.  ISSN 0928-0987.  96, s 381- 389 . doi: 10.1016/j.ejps.2016.10.012 Fulltekst i vitenarkiv.
• Rusthen, Shermin; Young, Alix; Herlofson, Bente Brokstad; Aqrawi, Lara Adnan; Rykke, Morten; Hove, Lene Hystad; Palm, Øyvind; Jensen, Janicke Liaaen & Singh, Preet Bano (2017). Oral disorders and oral health-related quality of life in patients with primary Sjögren’s Syndrome. European Journal of Oral Sciences.  ISSN 0909-8836.  125(4), s 265- 271 . doi: 10.1111/eos.12358 Fulltekst i vitenarkiv.
• Tashbayev, Behzod; Rusthen, Shermin; Young, Alix; Herlofson, Bente Brokstad; Hove, Lene Hystad; Singh, Preet Bano; Rykke, Morten; Aqrawi, Lara Adnan; Chen, Xiangjun; Utheim, Øygunn Aass; Utheim, Tor Paaske; Palm, Øyvind & Jensen, Janicke Liaaen (2017). Interdisciplinary, comprehensive oral and ocular evaluation of patients with primary Sjögren's syndrome. Scientific Reports.  ISSN 2045-2322.  7:10761, s 1- 9 . doi: 10.1038/s41598-017-10809-w Fulltekst i vitenarkiv.
• Tonetti, Maurizio S.; Bottenberg, Peter; Conrads, Georg; Eickholz, Peter; Heasman, Peter; Huysmans, Marie-Charlotte; López, Rodrigo; Madianos, Phoebus; Müller, Frauke; Needleman, Ian; Nyvad, Bente; Preshaw, Philip M.; Pretty, Iain; Renvert, Stefan; Schwendicke, Falk; Trombelli, Leonardo; van der Putten, Gert-Jan; Vanobbergen, Jacques; West, Nicola; Young, Alix & Paris, Sebastian (2017). Dental caries and periodontal diseases in the ageing population: call to action to protect and enhance oral health and well-being as an essential component of healthy ageing - Consensus report of group 4 of the joint EFP/ORCA workshop on the boundaries between caries and periodontal diseases. Journal of Clinical Periodontology.  ISSN 0303-6979.  44, s S135- S144 . doi: 10.1111/jcpe.12681 Fulltekst i vitenarkiv.
• Vanberg, Karin Elisabeth; Husby, Iselin Elise; Stykket, Liv; Young, Alix & Willumsen, Tiril (2016). Tannhelse blant et utvalg injiserende heroinmisbrukere i Oslo :. Den norske tannlegeforenings tidende.  ISSN 0029-2303.  126(7), s 528- 534
• Hjortsjø, Carl; Young, Alix; Kiesow, Andreas; Cismak, Andreas; Berthold, Lutz & Petzold, Matthias (2015). A Descriptive in vitro Electron Microscopic Study of Acidic Fluoride-Treated Enamel: Potential Anti-Erosion Effects. Caries Research.  ISSN 0008-6568.  49(6), s 618- 625 . doi: 10.1159/000441195
• Soares, Lèo; Jonski, Grazyna; Tinoco, Eduardo Muniz Barretto & Young, Alix (2015). Short-term effect of strontium- and zinc-containing toothpastes and mouthrinses on volatile sulphur compounds in morning breath: A randomized, double-blind, cross-over clinical study. European Journal of Oral Sciences.  ISSN 0909-8836.  123(2), s 72- 79 . doi: 10.1111/eos.12169
• Hjortsjø, Carl; Jonski, Grazyna; Young, Alix & Saxegaard, Erik (2014). Etching effect of acidic fluorides on human tooth enamel in vitro. Archives of Oral Biology.  ISSN 0003-9969.  59(12), s 1328- 1333 . doi: 10.1016/j.archoralbio.2014.08.007
• Huysmans, Marie-Charlotte; Young, Alix & Ganss, Carolina (2014). The role of fluoride in erosion therapy. Monographs in Oral Science.  ISSN 0077-0892.  25, s 230- 243 . doi: 10.1159/000360555
• Hjortsjø, Carl; Mjølnerød, Jol Anders; Skaare, Anders; Jonski, Grazyna; Young, Alix & Ekfeldt, Anders (2012). A replica technique for studying the effect of fluoride solutions on enamel erosion. Swedish Dental Journal.  ISSN 0347-9994.  36, s 169- 178
• Mulic, Aida; Vidnes-Kopperud, Simen; Skaare, Anne B; Tveit, Anne Bjørg & Young, Alix (2012). Opinions on Dental Erosive Lesions, Knowledge of Diagnosis, and Treatment Strategies among Norwegian Dentists: A Questionnaire Survey. International Journal of Dentistry.  ISSN 1687-8728.
• Ganss, Carolina; Young, Alix & Lussi, Adrian (2011). Tooth wear and erosion: Methodological issues in epidemiological and public health research and the future research agenda. Community Dental Health.  ISSN 0265-539X.  28(3), s 191- 195 . doi: 10.1922/CDH_2796Ganss05 Vis sammendrag

  Background: This paper addresses methodological issues in the field of tooth wear and erosion research including the epidemiological indices, and identifies future work that is needed to improve knowledge about tooth wear and erosion. Methods: The paper is result of the work done at the meetings of the Special Interest Group “Tooth Surface Loss and Erosion” at the 2008, 2009 and 2010 conferences of the European Association for Dental Public Health, and the Workshop “Current Erosion indices- flawed or valid” which took place in Basel in 2007. Results: Although there is consensus about the definition and the diagnostic criteria of various forms of tooth wear, gaps in research strategies have been identified. A basic problem is that fundamental concepts of wear and erosion as an oral health problem, have not yet been sufficiently defined. To a certain extent, tooth wear is a physiological condition, and there is no consensus as to whether it can be regarded as a disease. Furthermore, the multitude of indices and flaws in existing indices, make published data difficult to interpret. Conclusion: Topics for the research agenda are: the initiation of a consensus process towards an internationally accepted index, and the initiation of data collection on the prevalence of various forms of wear on a population-based level. There should be an emphasis on promoting communication between basic and clinical sciences, and the area of Public Health Dentistry. Furthermore, the question of whether tooth wear is a public health problem remains open for debate.

• Rölla, Gunnar; Young, Alix & Øgaard, Bjørn (2011). Om fluoriders virkningsmekanismer :. Den norske tannlegeforenings tidende.  ISSN 0029-2303.  121(6), s 366- 370
• Young, Alix & Jonski, Grazyna (2011). Effect of a single brushing with two Zn-containing toothpastes on VSC in morning breath: a 12 h, randomized, double-blind, cross-over clinical study. Journal of Breath Research.  ISSN 1752-7155.  5(4) . doi: 10.1088/1752-7155/5/4/046012
• Young, Alix & Tenuta, Livia M.A. (2011). Initial erosion models. Caries Research.  ISSN 0008-6568.  45, s 33- 42 . doi: 10.1159/000325943 Vis sammendrag

  Initial dental erosion - the very first tooth surface changes caused by short-term acidic exposures before any tissue loss is observed - has been studied using in vitro and in situ/in vivo protocols. This paper describes the events that should be considered when modeling initial erosion, the available protocols and their strengths and limitations. In vitro initial erosion models can provide relevant information about the erosive outcome. However, the published studies vary considerably regarding the erosive parameters used, and few of these studies have been validated. On the other hand, relevant in situ/in vivo studies are available that have studied the effect of salivary pellicle and preventive treatments on initial erosion, as well as the changes in salivary pH following exposure to acid solutions. Guidelines for good methodology in modeling initial erosion are proposed.

• Hjortsjø, Carl; Jonski, Grazyna; Young, Alix & Saxegaard, Erik (2010). Effect of acidic fluoride treatments on early enamel erosion lesions-A comparison of calcium and profilometric analyses. Archives of Oral Biology.  ISSN 0003-9969.  55(3), s 229- 234 . doi: 10.1016/j.archoralbio.2010.01.003 Vis sammendrag

  Objective: The protective effect of fluoride solutions against acidic challenge on enamel was tested in vitro using calcium- and profilometer analyses. Methods: HF-, SnF2-, TiF4- and NaF solutions (0.1M F-) and H2O as negative control were tested on a total of 60 enamel specimens divided into ten groups. Prior to and after F-treatment five groups were exposed for 1min to 0.01M citric acid, and the other five groups for 10min to 0.1M citric acid. Enamel specimens were measured by profilometry at baseline and before and after each acidic challenge. [Ca] in the collected citric acid samples was measured by atom absorption spectroscopy (AAS). ΔCa and Δ surface height were calculated for each specimen and the data were analysed using one way ANOVA, Tukeys test and Pearson r correlation. Results: AAS showed that F-treatments reduced enamel dissolution for both the 1min and 10min acidic challenge. Profilometry showed no significant differences between the F-solutions for the 1min groups. Significant differences could be seen between the fluorides for the 10min groups and there was a large correlation between the profilometric and AAS results. In conclusion, all fluoride solutions reduced enamel dissolution when specimens were exposed to a typical dietary acid. Conclusions: The profilometer was not sensitive enough to measure the effects of the different fluorides against a low acidic challenge as represented by this in vitro experiment. AAS was able to show these differences and for the 10 min acidic challenge there was a good correlation between the results from the two methods.

• Thrane, Per Stanley; Jonski, Grazyna & Young, Alix (2010). Comparative effects of various commercially available mouth-rinse formulations on halitosis. Dental Health.  ISSN 0011-8605.  49(1), s 6- 10
• Hjortsjø, Carl; Jonski, Grazyna; Thrane, Per Stanley; Saxegaard, Erik & Young, Alix (2009). Effect of Stannous Fluoride and Dilute Hydrofluoric Acid on Early Enamel Erosion over Time in vivo. Caries Research.  ISSN 0008-6568.  43(6), s 449- 454 . doi: 10.1159/000261415
• Hjortsjø, Carl; Jonski, Grazyna; Thrane, Per Stanley; Saxegaard, Erik & Young, Alix (2009). The Effects of Acidic Fluoride Solutions on Early Enamel Erosion in vivo. Caries Research.  ISSN 0008-6568.  43(2), s 126- 131 . doi: 10.1159/000209345
• Hjortsjø, Carl; Saxegaard, Erik; Young, Alix & Dahl, Jon Einar (2009). In vivo and in vitro irritation testing of low concentrations of hydrofluoric acid. Acta Odontologica Scandinavica.  ISSN 0001-6357.  67(6), s 360- 365 . doi: 10.1080/00016350903117118 Vis sammendrag

  Objective. Acidic fluorides are proposed for the treatment of dental erosion. The aim of this study was to examine the irritation properties of dilute hydrofluoric acid (HF) solutions for potential use in the oral cavity. Material and Methods. Hen’s Egg Test - chorioallantoic membrane (HET-CAM): The CAM was accessed by careful dissection through the egg shell (n=36, 6 eggs/test solution) and exposed to 300 µL of the HF solutions (0.05, 0.10, 0.20 and 1.0%) under macroscope examination over 5 min. Mean time-to-coagulation and average irritation score were recorded based on appearance of hemorrhage, coagulation and lysis of the blood vessels in the membrane. Mouse skin test: Sixty male mice were randomly divided into 10 groups of 6 animals (control, 0.05, 0.10, 0.20 and 1.0% HF), shaved on the back, exposed to test solution and sacrificed after 2h or 24h. Skin samples were evaluated by light microscopy, scoring epithelial leukocyte infiltration, vascular congestion, and edema. Results. HET-CAM: 0.05% HF was slightly irritant, 0.1% HF moderately irritant, 0.2% and 1% HF were strongly irritant. 0.1-1% HF solutions were severely eye irritating. Mouse skin test: HF concentration was significantly correlated with tissue response and 24-h exposure to 1% HF-solution showed focal erosion of the epithelium and marked localized subepithelial leukocyte infiltration. Conclusion. The results of these studies suggest that accidental exposure of soft tissues to solutions containing more than 0.2% HF may be harmful.

• Thrane, Per Stanley; Jonski, Grazyna; Young, Alix & Rølla, Gunnar (2009). Zn and CHX mouthwash effective against VSCs responsible for halitosis for up to 12 hours. Dental Health.  ISSN 0011-8605.  48(3), s 8- 12
• Hove, Lene Hystad; Holme, Børge; Young, Alix & Tveit, Anne Bjørg (2008). The protective effect of TiF4, SnF2 and NaF against erosion-like lesions in situ. Caries Research.  ISSN 0008-6568.  42 . doi: 10.1159/000112816
• Young, Alix; Amaechi, Bennett T; Dugmore, Christopher; Holbrook, Peter; Nunn, June; Schiffner, Ulrich; Lussi, Adrian & Ganss, Carolina (2008). Current erosion indices - flawed or valid? Summary. Clinical Oral Investigations.  ISSN 1432-6981.  12 . doi: 10.1007/s00784-007-0180-6 Vis sammendrag

  The problem of erosive tooth wear appears increasingly to be encountered by clinicians. An adequate way of defining and recording erosive tooth wear is essential in order to assess the extent of this clinical phenomenon, both on an individual level and in the population, and for the adequate provision of preventive and therapeutic measures. Many studies have been carried out in order to examine levels of dental erosion in the population and in one case, to look also at erosion progression. Well-established erosion indices have been used in most of these studies, although in many cases modifications have been made to suit the different research aims. This use of different indices is one reason why it still cannot be claimed that there is enough current knowledge on this clinical phenomenon. This article summarizes the proceedings of a workshop to discuss the topic of dental erosion indices. The result of the workshop is a proposal for a new scoring system (Basic Erosive Wear Examination, BEWE) designed for use both within the research field and for dental clinicians, with the aims of standardising assessment of erosion for international comparisons, raising awareness and providing guidelines for treatment of erosive tooth wear in dental practice.

• Hove, Lene Hystad; Holme, Børge; Young, Alix & Tveit, Anne Bjørg (2007). The erosion-inhibiting effect of TiF4, SnF2, and NaF solutions on pellicle-covered enamel in vitro. Acta Odontologica Scandinavica.  ISSN 0001-6357.  65(5), s 259- 264 . doi: 10.1080/00016350701477581
• Hove, Lene Hystad; Young, Alix & Tveit, Anne Bjørg (2007). An in vitro study on the effect of TiF4 treatment against erosion by hydrochloric acid on pellicle-covered enamel. Caries Research.  ISSN 0008-6568.  41(1), s 80- 84 . doi: 10.1159/000096111
• Thrane, Per Stanley; Young, Alix; Jonski, Grazyna & Rølla, Gunnar (2007). A new mouthrinse combining zinc and chlorhexidine in low concentrations provides superior efficacy against halitosis compared to existing formulations: a double-blind clinical study. The Journal of clinical dentistry.  ISSN 0895-8831.  18(3), s 82- 86
• Young, Alix; Thrane, Per Stanley; Saxegaard, Erik; Jonski, Grazyna & Rølla, Gunnar (2006). Effect of stannous fluoride toothpaste on erosion-like lesions: an in vivo study. European Journal of Oral Sciences.  ISSN 0909-8836.  114, s 180- 183
• Jonski, Grazyna; Young, Alix; Wåler, Sonni Mette & Rølla, Gunnar (2004). Insoluble zinc, cupric and tin pyrophosphates inhibit the formation of volatile sulphur compounds. European Journal of Oral Sciences.  ISSN 0909-8836.  112, s 429- 432
• Young, Alix; Jonski, Grazyna & Rølla, Gunnar (2003). Combined effect of zinc ions and chlorhexidine on intraoral volatile sulfur compounds (VSC). International Dental Journal.  ISSN 0020-6539.  53, s 237- 242
• Young, Alix; Jonski, Grazyna & Rølla, Gunnar (2003). Inhibition of orally produced volatile sulfur compounds by zinc, chlorhexidine or cetylpyridinium chloride - effect of concentration. European Journal of Oral Sciences.  ISSN 0909-8836.  111, s 400- 404
• Young, Alix; Jonski, Grazyna & Rølla, Gunnar (2002). The oral anti-volatile sulphur compound effects of zinc salts and their stability constants. European Journal of Oral Sciences.  ISSN 0909-8836.  110, s 31- 34
• Young, Alix; Jonski, Grazyna & Rølla, Gunnar (2002). Variation in oral sulphur compound (VSC) formation. Acta Odontologica Scandinavica.  ISSN 0001-6357.  60(6), s 321- 324 Vis sammendrag

  Several authors have suggested that the level of orally produced volatile sulphur compounds (VSC) can be of use for monitoring oral malodour or determining patients at risk of periodontal disease in longitudinal studies. It is not known, however, to what extent the level of VSC in mouth air is a stable, individual characteristic over time. This would be essential for its use for such purposes. Aim: The hypothesis to be tested was that the level of VSC in mouth air is an individual trait that is stable over time. Methods: Two groups of dental students participated for the study (n=30 and n=11). The amount of available substrate for VSC formation was standardised by rinses with 6 mM aqueous solutions of cysteine (pH 7.2). Part 1 used a Halimeter® to measure 'morning breath' and response to cysteine rinses. Part 2 measured response to cysteine rinsing using a gas chromatograph. Repeated measurements gathered information concerning the longitudinal intra-individual variations in level of oral VSC formation. Results: Both groups showed large intra-individual variations in oral VSC. The differences were enhanced by cysteine rinses. Conclusion: The hypothesis was not supported. Oral VSC levels do not lend themselves as diagnostic criteria in a normal population due to marked intra-individual variations over time.

• Rølla, Gunnar; Jonski, Grazyna & Young, Alix (2002). The significance of the source of zinc and its anti-VSC effect. International Dental Journal.  ISSN 0020-6539.  52, s 233- 235 Vis sammendrag

  The anti-VSC (volatile sulphur compounds) effect of zinc is known to be associated with free zinc ions. Objective: To examine whether zinc salts with low stabilty constants were more suitable sources of zinc in zinc lozenges than zinc salts with high stability constants. The former provide free zinc ions upon dissolution in water, whereas the latter provide few such ions. Design and participants: Identical lozenges were produced which contained either zinc acetate, zinc gluconate (low stability constants), zinc citrate or amino-acid chelated zinc (extremely high stability constants). All the lozenges contained 0.1% of zinc. A test panel of 10 volunteers used the different lozenges randomly. VSC were measured by GC. Results and conclusions: The lozenge with the highest stability constant was as effective as those with very low stability constants. The anti-VSC effect was thus not limited to this constant. These findings may be explained by the possibility that alternative ligands with stronger affinity for zinc than the original ligands in the lozenges may be present in the oral cavity. An in vitro experiment indicated that the sulphide ion (S2-) may be such a ligand.

• Young, Alix; Jonski, Grazyna & Rølla, Gunnar (2002). A study of triclosan and its solubilizers as inhibitors of oral malodour. Journal of Clinical Periodontology.  ISSN 0303-6979.  29, s 1078- 1081 Vis sammendrag

  Background: It is known that the detergents or organic solvents used to solubilize the lipid soluble triclosan can affect the biological activities exhibited by this molecule, such as its antibacterial, anti-plaque, and anti-inflammatory effect. Objective: To examine whether solubilizing agents influence the effect of triclosan against formation of volatile sulphur compounds (VSC), as these are known to be a major component of oral malodour. Material & methods: Part A: One ml of human whole saliva (n=10) was incubated for 24 h at 37°C in a closed test tube with addition of 10 ml triclosan solubilized in alcohol. Part B: In a clinical experiment, VSC formation enhanced by mouth rinses with cysteine was followed by subjects (n=9) rinsing with triclosan solubilized in different detergents and organic solvents. The amount and nature of VSC in the saliva headspace and in the mouth air of the test subjects was measured by gas chromatography. Results: Triclosan had a marked dose-dependent effect against VSC in vitro when solubilized in alcohol, independent of the alcohol per se. In vivo, triclosan lost its anti-VSC effect when solubilized in oil, in an uncharged detergent or in a chromophor, whereas it maintained its effect when solubilized in a combination of sodium lauryl sulphate, propylene glycol and water. Conclusion: The solubilizing agent does influence the anti-VSC effect of triclosan.

• Wåler, Sonni Mette; Jonski, Grazyna; Young, Alix & Rølla, Gunnar (2001). Halitosis - Nytt om diagnostikk og behandling, I: Palle Holmstrup (red.),  Odontologi 2001.  Munksgaard, København.  ISBN 87-16-12369-7.  s 27 - 40
• Young, Alix; Jonski, Grazyna; Rølla, Gunnar & Wåler, Sonni Mette (2001). Effects of metal salts on the oral production of volatile sulfur-containing compounds (VSC). Journal of Clinical Periodontology.  ISSN 0303-6979.  28, s 776- 781 Vis sammendrag

  Background, aim: Halitosis, mainly caused by bacteria located on the posterior dorsum of the tongue and in periodontal pockets, is due to formation of volatile sulfur compounds (VSC). The hypothesis to be tested was that the affinity of a metal for sulfur determines its anti-VSC activity. Method: Clinical tests were carried out on 12 subjects who rinsed with cysteine to induce halitosis (baseline) before rinsing with 7.34mM ZnCl2, SnF2 and CuCl2. Mouth air VSC analyses were repeated following cysteine rinses at 1h, 2h and 3h using a gas chromatograph. In-vitro experiments tested toxic metals Hg2+, Pb2+ and Cd2+. 10-µl aliquots of metal salts were added to 1-ml aliquots of human whole saliva from 30 subjects. Samples were incubated overnight at 37oC and saliva headspace was analyzed for VSC in a gas chromatograph. Clinical results: Cu2+ > Sn2+ > Zn2+ (supports hypothesis). Zn2+ had significantly less anti-VSC effect compared with Cu2+ and Sn2+ at 1, 2 and 3h. In-vitro results indicated that Hg2+, Cu2+ and Cd2+ had close to 100% anti-VSC effect, and that Pb2+ was less effective and Cd2+ more effective than expected in inhibiting VSC. Conclusion: Apart from Hg2+ and Cu2+, the metals had a significantly greater effect on H2S than on CH3SH. Cu2+ and Hg2+ have well known antibacterial activity and may presumably also operate by this mechanism.

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• Rusthen, Shermin; Kristoffersen, Anne Karin; Young, Alix; Galtung, Hilde; Enersen, Morten & Jensen, Janicke Liaaen (2018). The Salivary Microbiota Profile in Reduced and Normal Salivation.
• Hove, Lene Hystad; Young, Alix; Hjortsjø, Carl; Stevning, Karen & Løvik, Sara Emilie (2017). Effect of Whitening Toothpastes on Dental Enamel In Vitro.
• Jensen, Janicke Liaaen; Herlofson, Bente Brokstad; Young, Alix; Hove, Lene Hystad & Galtung, Hilde (2017). Verdien av spytt.
• Rusthen, Shermin; Young, Alix; Preet, Bano; Tashbayev, Behzod; Garen, Torhild Oddveig; Aqrawi, Lara A.; Rykke, Morten; Hove, Lene Hystad; Herlofson, Bente Brokstad; Palm, Øyvind & Jensen, Janicke Liaaen (2017). Is Health-related Quality of Life Correlated to Oral Status in Primary Sjögren’s Syndrome Patients?.
• Tashbayev, Behzod; Rusthen, Shermin; Chen, X; Utheim, Tor Paaske; Utheim, Øygunn Aass; Young, Alix; Herlofson, Bente Brokstad; Aqrawi, Lara Adnan; Rykke, Morten; Hove, Lene Hystad; Palm, Øyvind & Jensen, Janicke Liaaen (2017). Dry Mouth and Dry Eye Examinations of a Norwegian Cohort of Primary Sjögren´s Syndrome Patients.
• Hove, Lene Hystad; Aqrawi, Lara Adnan; Rusthen, Shermin; Young, Alix; Rykke, Morten; Herlofson, Bente Brokstad; Singh, Preet Bano; Palm, Øyvind; Utheim, Tor Paaske & Jensen, Janicke Liaaen (2016). Establishment of a Dry Mouth Clinic at the Faculty of Dentistry, University of Oslo, Norway.
• Jensen, Janicke Liaaen; Utheim, Øygunn Aass; Chen, Xiangjun; Thiede, Bernd; Aqrawi, Lara Adnan; Rusthen, Shermin; Young, Alix; Utheim, Tor Paaske & Galtung, Hilde (2016). Searching for Disease Biomarkers for Primary Sjögren’s Syndrome Based on Oral and Ocular Patient Examinations.
• Rusthen, Shermin; Singh, Preet Bano; Young, Alix; Aqrawi, Lara Adnan; Rykke, Morten; Hove, Lene Hystad; Herlofson, Bente Brokstad; Palm, Øyvind & Jensen, Janicke Liaaen (2016). Oral quality of life, salivary, gustatory and olfactory status in patients with primary Sjögren’s syndrome.
• Singh, Preet Bano; Rusthen, Shermin; Aqrawi, Lara A.; Young, Alix; Rykke, Morten; Hove, Lene Hystad; Herlofson, Bente Brokstad; Palm, Øyvind & Jensen, Janicke Liaaen (2016). Chemosensory disorders, burning mouth sensation, and halitosis in patients with Sjögren’s syndrome.
• Young, Alix; Rusthen, Shermin; Aqrawi, Lara Adnan; Rykke, Morten; Hove, Lene Hystad; Herlofson, Bente Brokstad; Singh, Preet Bano; Palm, Øyvind & Jensen, Janicke Liaaen (2016). Dental health status of patients diagnosed with primary Sjögren's Syndrome. Vis sammendrag

  This clinical study aims to assess some oral health parameters in patients diagnosed with primary Sjögren’s Syndrome (pSS), and is part of a larger project studying groups of patients suffering from dry mouth. Material and methods: Twenty female pSS patients (mean age 54±12.7y) and 32 healthy controls (mean age 50±12.4y), were recruited to the study and examined at a newly established Dry Mouth Clinic at the Faculty of Dentistry, University of Oslo, after giving written consent. A questionnaire was filled out and clinical and radiological examinations were performed. Differences between the patient and control groups were calculated using t-test or Chi-squared tests. Results: Approximately 1/3 of patients considered their general and oral health as ‘poor’ or ‘very poor’. No controls considered their general health as ‘poor’ or ‘very poor’, and only 1 control considered their oral health as ‘poor’ or ‘very poor’. Ninety percent of patients and 75% of controls had visited the dentist within the last year. There was no between-group difference in the mean number of teeth present (patients 25.5±2.7; controls 26.1±3.8). The patients had higher mean caries experience: DMFT (patients: 18.0±6.45; controls 12.9±7.26, p=0.014), FT (patients: 15.35±5.77; controls 11.28±6.10, p=0.02), and D3-5T (patients: 0.60±0.94; controls: 0.28±0.58, p=0.136). Visible plaque was observed in 30% of patients and 9.4% of controls (p=0.056). Signs of gingivitis were observed in 25% of patients and 6% of controls (p=0.054). Conclusion: Compared to controls, pSS patients reported poorer general and oral health. They had significantly higher dental caries experience, and a tendency to more plaque and gingivitis. However, the pSS patients reported visiting their dentist more regularly than the controls, suggesting an awareness of the oral consequences of reduced salivary function.

• Hjortsjø, Carl; Jonski, Grazyna & Young, Alix (2015). Effect of Mouth-rinsing with Two Fluoride Solutions on Enamel Solubility Using an in vivo Experimental Model.
• Young, Alix; Stenhagen, Kjersti Refsholt; Mulic, Aida & Amaechi, Bennett T (2015). Dental erosive wear risk assessment, In Bennett T Amaechi (ed.),  Dental erosion and its clinical management.  Springer Science+Business Media B.V..  ISBN 978-3-319-13993-7.  Chapter 7.  s 121 - 132 Vis sammendrag

  This chapter presents a newly developed dental erosive wear risk assessment tool designed for use by general dental practitioners, dental educators and dental students. The tool guides the user through the most common risk factors associated with dental erosive wear, and when combined with the Basic Erosive Wear Evaluation (BEWE) or other similar scoring system, leads to a final decision on patient risk status. An initial screening section helps the dentist to decide whether it is necessary to perform a more comprehensive dental erosive wear risk assessment. When there is clearly a need for further assessment, all dental erosive wear lesions are then recorded using the index of choice, and the dentist decides how the recorded conditions will be documented. The dentist then uses the Dental erosive wear risk assessment (DEWRA) form, where dietary and oral hygiene habits, general health status and clinical conditions are evaluated using a thorough patient interview. An overall patient risk category is chosen and the section for treatment planning and advice to the patient can then be used. The last part of the chapter provides a brief explanation of the various risk factors that are included in the DEWRA form.

• Young, Alix (2014). Halitose - årsaker og behandling, I: Palle Holmstrup (red.),  Aktuel Nordisk Odontologi 2014.  Munksgaard Forlag.  ISBN 9788762812512.  Chapter: Halitose - årsaker og behandling.  s 57 - 68 Vis sammendrag

  Halitosis, also known as bad breath or oral malodour, is a term used to describe noticeably unpleasant odour coming from the mouth or the nearby respiratory system. This condition is reported to affect about 25 % of the population on a daily basis. Morning bad breath, experienced by many upon waking in the morning, most likely due to local oral conditions, is usually only a temporary problem that can be easily prevented or treated. However, some cases of halitosis, especially those associated with extra-oral causes can be more chronic and can adversely affect a person’s social and work situation. Dental health workers regularly meet patients who either complain of bad breath, or have halitosis without being aware of the situation. Knowledge of the usual causes of halitosis and treatment methods for oral malodour should therefore be mandatory. In this short overview the most common physiological and pathological oral causes of halitosis will be described, as well as possible extra-oral causes. Simple preventive and treatment strategies with a focus on the oral cavity will be presented.

• Hjortsjø, Carl; Jonski, Grazyna & Young, Alix (2013). A modified in vivo experimental model for evaluating fluoride treatment against initial erosion lesions.
• Hjortsjø, Carl; Young, Alix; Kiesow, Andreas; Cismak, Andreas; Berthold, Lutz & Petzold, Matthias (2013). An electron microscopic study comparing effects of human enamel exposure to SnF2-, TiF4- and NaF-solutions.
• Young, Alix (2012, 04. februar). Hvorfor får vi sovesmak i munnen?. [Internett].  Forskning.no.
• Hjortsjø, Carl; Jonski, Grazyna; Young, Alix & Saxegaard, Erik (2011). Erosive effect of acidic fluoride solutions on enamel in vitro. Vis sammendrag

  Acidic fluoride solutions have been shown to exhibit erosion-inhibiting properties on dental enamel. The aim of this in vitro study was to investigate the possible erosive effect of dilute hydrofluoric acid (HF) on enamel. A 0.2% HF solution (0.1 mol/l F-, pH 3.02) was compared with two acidic fluorides containing 0.5 mol/l F- (3.9% SnF2-pH 2.65 and 1.6% TiF4-pH 1.42) and 1.8% citric acid (acidic control, pH 2.27). 24 human third molar enamel specimens were randomly divided into 4 groups (6 specimen/solution). Enamel surfaces were ground flat by wet grinding with a grit 2500 abrasive paper and half of each flat surface was isolated using a A-silicon impression material. The enamel surfaces were exposed to 20ml of the test solutions for ten minutes in plastic containers. The isolation material was removed. and changes in the enamel surfaces were analysed by LED blue light profilometry (λ=470 nm, 50x magnification). The specimen area analysed included both treated and untreated ground enamel, a total area of 254.64 x 190.90 µm2 for each sample. The difference in surface height between treated and untreated enamel was calculated for each specimen and etching depth data were analysed using oneway ANOVA and Tukeys test. The mean etching depths (µm±SD) were 0.14(0.86), -2.00(0.52), -3.25(2.91) and 5.42(1.00) for, HF, SnF2, TiF4 and control respectively. HF had significantly less etching effect than the control, but was significantly more erosive than TiF4 (p<0.05). In conclusion, while both SnF2 and TiF4 treatments resulted in an average deposition on the enamel surface, HF showed an average etching effect close to zero. Further studies are needed to examine the mechanism of the previously described anti-erosive effect of HF.

• Young, Alix; Hjortsjø, Carl; Berthold, Lutz; Cismak, Andreas & Petzold, Matthias (2011). An electron microscopic study of enamel treated with hydrofluoric acid. Vis sammendrag

  Previous studies have demonstrated the effectiveness of treating enamel with acidic fluorides as a means of reducing the effects of erosive challenges. The aim of the present in vitro study was to investigate the surface characteristics of dental enamel treated with hydrofluoric acid (HF). Natural surfaces of enamel specimens from extracted human third molars were treated for 10 min with either native solutions of HF (pH 3) or sodium fluoride (NaF, pH 7) containing both 0.1 and 0.2 mol/l F-. Untreated samples functioned as controls. All specimens were examined by SEM/EDX with respect to surface microstructure variation and fluoridation. For selected specimens, samples were prepared by FIB allowing cross-sectional investigations using TEM and nanospot-EDX. Following treatment with HF, SEM/EDX analyses did not show obvious erosive damage but clearly indicated surface fluoridation. Using TEM, an enamel surface microstructure modification to a depth of approximately 200 nm with a clear boundary to non-affected apatite was revealed. The fluoride content in this layer was above 40at% F with a F/Ca ratio of roughly 2 indicating the transformation of surface hydroxyapatite into CaF2-like material. In previous studies, isolated fluoride-rich globular precipitates were found if medium-acidulated solutions of NaF were applied. The atomic composition of the HF-induced CaF2-like material resembled that of these precipitates. In contrast, no fluoridation effects were found for the NaF at pH 7 and the controls in this study. These results suggest that the general reaction between fluoride solutions and enamel leading to a formation of CaF2-like material does not significantly depend on the dissociated fluoride cation. On the other hand, the reaction rate for the acidic HF treatments is higher since the amount of dissolved calcium increases with decreasing pH.

• Young, Alix (2010). Halitose.
• Young, Alix (2010). Halitose – et åndelig problem?.
• Young, Alix; Jonski, Grazyna & Rølla, Gunnar (2010). Dental erosion inhibition by SnF2 and TiF4 compared with the effect of HF. Vis sammendrag

  Background: The aim of this in vitro pilot study was to compare the effect of three acidic equimolar fluoride solutions (and subsequent water treatment to remove all un-reacted fluoride) on the acid resistance of teeth. Cleaned whole teeth (n=24, 6 teeth/group) were each pre-etched by immersion in 10 ml-aliquots of 0.1 mol/L citric acid for 5 min. The teeth were then incubated in 10 ml of the test fluoride solutions containing 0.1 M F: SnF2 (pH 2.9), TiF4 (pH 1.5) or hydrofluoric acid (HF, pH 2.0) for 20 min. Six teeth were not treated with any fluoride (control). Teeth were then incubated in distilled water for 24 h before re-etching as for the pre-etch. The citric acid solutions before and after F-treatment were retained for Ca-analysis using atom absorption spectroscopy. Mean pre- and post etch [Ca] for each F-solution and % ΔCa were calculated for each F-solution and for the control. Mean pre-etch [Ca] and mean post F-treatment [Ca] with (SD) results in mg/L were for HF: 8.894 (2.52) and 1.418 (1.188); SnF2: 8.201 (1.92) and 2.525 (1.19); TiF4: 7.683 (1.75) and 2.822 (0.93) and control: 7.318 (2.31) and 7.470 (1.69). The % reduction in Ca dissolution was 86, 70, 64 and -6, for HF, SnF2, TiF4 and the control respectively. At this low fluoride concentration, HF was more effective than the two metal fluorides, suggesting that the metal ions may not contribute directly to the inhibition of mineral dissolution. The role of the metal ions may be to provide an acidic environment in these solutions (and formation of HF), as they react with the hydroxyl ions of water during the solubilization of their salts.

• Hjortsjø, Carl; Jonski, Grazyna; Saxegaard, Erik & Young, Alix (2009). Profilometric study of the effects of acidic fluoride solutions on early dental erosion. Vis sammendrag

  An in-vivo experimental model for dental erosion has been utilised to assess the effects of treating dental enamel with fluorides. This in-vitro study aimed to examine the effects of the same acidic fluoride solutions using profilometry. Crowns of intact, surgically extracted human third molar teeth were cut into 2-4 pieces, washed (deionised water, 50% ethanol then 96% ethanol), embedded in acrylic resin and polished (grit 4000). Nail varnish was applied in a line across the block separating the enamel surface from the acrylic resin surface. Specimens were exposed to 5 ml of 100 mmol/L citric acid for 10 min before (etch I) and after (etch II) fluoride treatments. Aqueous solutions of TiF4, SnF2, HF or NaF, (all 0.1 M F-) and deionised water (negative control) were tested (n=6 specimens/test solution). All solutions were applied in a cell culture well (Nunclon, Nunc, Roskilde, Denmark) and enamel specimens were exposed to all the fluids in these wells. Specimens were analysed at all stages in a high power LED blue light profilometer (PLµ2300 Optical Imaging Profiler, Sensofar Tech, Spain) at 150x magnification and λ=470 nm. Areas including one half of exposed enamel and the other half varnish-covered enamel (220.98 x 165.68µm) were analysed to a depth of 40µm. Data analysis compared the step-height differences between the exposed and the varnished reference areas. Paired t-test and Kruskal-Wallis ANOVA on Ranks were used in the statistical analysis. There was a significant reduction in step height difference following HF-, SnF2-, and TiF4-treatments (p ≤0.005), but not for the NaF and water. The acidic fluoride solutions were capable of reducing the erosive effect of the citric acid challenge as previously shown in the in vivo experimental model.

• Hjortsjø, Carl; Jonski, Grazyna; Saxegaard, Erik & Young, Alix (2009). Validation of a dental erosion model I–chemical analysis in-vitro. Vis sammendrag

  An in vivo experimental model for dental erosion has been utilised to assess the effects of treating dental enamel with fluorides as a preventive and/or treatment measure. Objective: To validate the in-vivo experimental model results in-vitro using chemical analysis. Methods: Crowns of intact, surgically extracted human third molar teeth were cut into 2-4 pieces, washed (deionised water, 50% ethanol, 96% ethanol), embedded in acrylic resin and polished (grit 4000). Specimens were exposed to 5 ml of 10 mmol/L citric acid for 1 min before (etch I) and after (etch II) fluoride treatment. Aqueous solutions of TiF4, SnF2, HF and NaF (all 0.1 M F-) and deionised water (negative control) were tested (n = 6 tooth specimens/test solution). The citric acid and test solutions were applied using a peristaltic pump (flow: 6 ml/min, Gilson model Minipuls 3). Etch and fluoride solutions were collected in coded tubes and analysed blind for calcium content using atomic absorption spectrometry (Model 3300, Perkin Elmer Analytical Instruments, USA) using air-acetylene flame and λ = 422.7 nm. ∆ ppm calcium (etch I minus etch II) was calculated for each tooth and mean percentage reduction in calcium loss was determined for each test solution. Results were analysed using one way ANOVA and the Bonferroni t-test for multiple comparisons. Results: The HF- and SnF2-treatments were significantly more effective in reducing calcium dissolution than the TiF4 and NaF-treatments (p≤0.004). There was no statistical difference between TiF4 and NaF- treatments (p=0.138). The water control resulted in an increase in calcium dissolution. Conclusion: These results correlate well with results from the in vivo model and help validate the use of calcium analysis in the in-vivo dental erosion model.

• Young, Alix (2009). Halitose.
• Young, Alix (2009). Halitose.
• Young, Alix; Hjortsjø, Carl; Saxegaard, Erik & Jonski, Grazyna (2009). A study on the effect of age on enamel dissolution using a dental erosion model. Vis sammendrag

  The prevailing expert opinion suggests that there is little evidence to support the concept that pathological levels of dental erosion are age-dependant. However, some evidence seems to indicate that normal levels of erosion may be age-dependant. Many factors may contribute to this type of wear and presumably the enamel solubility is one of these factors. An in-vivo experimental model for dental erosion using volunteers of various ages has been utilised to assess the effects of treating dental enamel with fluorides to reduce damage due to erosion. The aim of the present study was to examine the possible relationship between the age of the test individuals and the degree of enamel dissolution upon acidic challenge. The in-vivo model has been described previously. In 176 test subjects (age range 18 - 69 years), labial surfaces of 342 healthy anterior teeth were exposed to 5 ml 0.18% citric acid, at 6 ml/min using a peristaltic pump. The acid was collected in coded test tubes for blind analysis of calcium content using atom absorption spectrometry. Mean calcium concentration was calculated separately for central incisors (0.924 mg/L, range 0.033-4.434) and lateral incisors (0.654 mg/L, range 0.051-3.048). The age of the subjects was not normally distributed with a mean age of 27.8 years. Statistical analysis using Spearman’s rho showed no correlation between the age of the test subjects and the calcium concentration in the acid etch (central incisors rs = 0.048, lateral incisors rs = 0.161, p<0.05). Despite the skewed age distribution these results do not support a correlation between age and degree of enamel dissolution following a brief acidic challenge.

• Hjortsjø, Carl; Dahl, Jon Einar; Saxegaard, Erik & Young, Alix (2008). HET-CAM testing of diluted hydrofluoric acid solutions. Vis sammendrag

  It has been suggested that diluted hydrofluoric acid (HF) solutions (≤ 0.2%) can reduce enamel dissolution in a clinical dental erosion model. The toxic effect of concentrated solutions of HF is well known. The possible effects of low concentrations of HF are less well known. This study aimed to examine the irritative effects of four HF solutions (1%, 0.2%, 0.1% and 0.05%) using the Hen’s Egg Test - chorioallantoic membrane (HET-CAM) (Kalweit et al., Toxicol in Vitro 1990;4:702-706). The hypothesis to be tested was that low concentrations of HF do not provoke any response on the blood vessels of the CAM of fertilized hens’ eggs. The CAM was accessed by careful dissection through the egg shell. 300 μl of the test solutions was dripped on the CAM under constant examination using a macroscope. The time for appearance of haemorrhage, vessel lysis and coagulation in the membrane was recorded. An average irritation score (IS) for each test solution (n=24 eggs in total) was calculated and a score was assigned: 0-0.9 = non irritant, 1-4.9 = slight irritant, 5-8.9 = moderate irritant and 9-21 = strong irritant. Mean time to coagulation (mtc100) was also calculated, values below 100 were classified as R41 - severely eye irritating. Results showed that 0.05% HF scored as slightly irritant (IS=3.26), 0.1% HF as moderately irritant (IS=7.49) while both 0.2% and 1% HF were recorded as strongly irritant (IS=9.92 and 12.22 respectively). 0.1%, 0.2% and 1% HF were classified as severe eye irritants (mtc100= 75, 80 and 50). In conclusion all four HF solutions provoked reactions on the chorioallantoic membrane of fertilized hen’s eggs. Care must therefore be taken when using diluted HF solutions under experimental clinical conditions.

• Hjortsjø, Carl; Jonski, Grazyna; Rølla, Gunnar; Thrane, Per Stanley; Saxegaard, Erik & Young, Alix (2008). Short term effect of NaF-, SnF2- and dilute HF-treatments on enamel erosion-like lesions in vivo. Vis sammendrag

  Dental erosion is a clinical problem in many countries today partly due to increased exposure to dietary acids. Citric acid for example is commonly found in fruit juices, mineral water, flavoured teas and bottled still water. Recent studies have shown that several acidic fluoride preparations hold promise in the prevention and treatment of dental erosion. This study aimed at comparing the effect of sodium fluoride (NaF, pH 7.3), stannous fluoride (SnF2, pH 2.9) and dilute hydrofluoric acid (HF, pH 2.0) solutions, on enamel dissolution in an experimental in vivo model as described previously (Young et al., Eur J Oral Sci 2006;114;180-183). Four healthy anterior teeth in each subject (n=29) were isolated using plastic strips and a light bodied impression material for complete palatal coverage. The labial surfaces of the test teeth were exposed to 5 ml citric acid (0.18%) using a peristaltic pump (6 ml/min), before (etch I) and 5 min after (etch II) application of test fluoride preparations. The acid was collected in a test tube for later analysis. NaF, SnF2 or HF solutions (all 0.1 M F-) were applied to the labial surfaces of the teeth for 1 min using a peristaltic pump (6 ml/min). Enamel dissolution was examined by measuring calcium content in the citric acid using atom absorption spectrometry. Mean values for etch I minus etch II were calculated and statistical analysis with the Bonferroni t-test for between group comparisons. HF and SnF2 gave mean calcium reductions of 0.37 ppm (76%) and 0.67 ppm (68%) respectively (NS). NaF gave no calcium reduction (-0.34 ppm (-52%). In conclusion, while neutral NaF had no protective effect 5 min after treatment, SnF2 and dilute HF markedly reduced calcium loss.

• Young, Alix (2008). Halitose.
• Young, Alix (2008). Halitose. Vis sammendrag

  Halitose. Hvorfor har vi dårlig ånde og hvordan behandler vi det? Emnet er fortsatt tabubelagt, men alle i tannpleien bør kunne gi pasienter best mulig råd. De fleste årsaker til dårlig ånde skyldes lokale faktorer i munnhulen og kan lett behandles. Foredraget vil inneholde en gjennomgang av årsaker og sammenhenger og forskningsbaserte tips for behandling.

• Young, Alix (2008). Halitose. Vis sammendrag

  Halitose. Hvorfor har vi dårlig ånde og hvordan behandler vi det? Emnet er fortsatt tabubelagt, men alle i tannpleien bør kunne gi pasienter best mulig råd. De fleste årsaker til dårlig ånde skyldes lokale faktorer i munnhulen og kan lett behandles. Foredraget vil inneholde en gjennomgang av årsaker og sammenhenger og forskningsbaserte tips for behandling.

• Young, Alix (2008). Halitose. Vis sammendrag

  Halitose. Hvorfor har vi dårlig ånde og hvordan behandler vi det? Emnet er fortsatt tabubelagt, men alle i tannpleien bør kunne gi pasienter best mulig råd. De fleste årsaker til dårlig ånde skyldes lokale faktorer i munnhulen og kan lett behandles. Foredraget vil inneholde en gjennomgang av årsaker og sammenhenger og forskningsbaserte tips for behandling.

• Hjortsjø, Carl; Jonski, Grazyna; Saxegaard, Erik; Thrane, Per Stanley & Young, Alix (2007). Effect of time on dilute hydrofluoric acid-treatments of enamel in vivo. Vis sammendrag

  Dental erosion is currently considered to be one of the main reasons for tooth wear. It has been suggested in an in vivo study that hydrofluoric acid (HF) successfully reduces enamel dissolution and protects enamel against acidic challenges. The aim of this study was to evaluate the protective effect of 0.2% HF solution over time, using a newly established indirect experimental in vivo model. Test subjects (n=28) took part in this study. Healthy anterior teeth (n=107) with intact pellicle were kept dry during the experiment using cotton rolls and saliva suction, and isolated using plastic strips and a light-bodied impression material for complete coverage of palatinal surfaces. The labial surfaces were exposed to diluted citric acid (10mmol/l) using a peristaltic pump (5ml, 6ml/min). The acid was collected in a test tube before (etch I) and after 24 h (n=54 teeth) or 7 days (n=53 teeth) (etch II), following application of aqueous 0.2% HF solution (6ml, 6ml/min). The teeth were rinsed for 5s with water after both etch I and II. Enamel dissolution was examined by assessment of calcium content in the citric acid of etch I and II using atom absorption spectroscopy. The reductions in calcium content in the citric acid between etch I and etch II were calculated for each tooth (p< 0.05). A significant reduction in post HF-treatment calcium loss was observed for both time periods, though the protective effect decreased with time. Mean percent calcium loss reduction was 49 (S.E. 3.6) for the 24-h group and 29 (S.E. 5.4) for the 7-d group. The results suggest that 0.2% HF has a protective effect on sound enamel that lasts for at least one week.

• Rølla, Gunnar; Young, Alix; Saxegaard, Erik & Jonski, Grazyna (2006). On calcium fluoride formation on enamel. Vis sammendrag

  A controversy exists concerning the role of calcium fluoride deposited on enamel during fluoride treatments. Some authors maintain that such calcium fluoride can protect enamel surfaces from erosive acids, whereas others claim that calcium fluoride is soluble in such acids. We have shown that calcium fluoride formed on enamel at neutral pH after exposure to 0.5 mol/l of an aqueous solution of NaF for 24 h, was unable to protect the enamel against 0.1 mol/l of citric acid for 30 min, whereas a similarly treated enamel (0.5 mol/l of an aqueous solution of hydrofluoric acid for 10 min with a pH of 3), did protect the enamel almost completely. The aim of this abstract was to discuss these results. It is suggested that the difference in dissolution rates may depend on the nature of the phosphate contaminations found in calcium fluorides formed on enamel. These phosphate contaminations originate from the enamel and are probably in the form of calcium phosphates. More acid-soluble phosphates are available on the enamel surface at pH 7, than at pH 3. These are dibasic/monobasic phosphates, and monobasic phosphate/phosphoric acid, respectively. It is also suggested that undissociated HF which is the major component of hydrofluoric acid at pH 3, may have an important role in calcium fluoride formation as previously shown [Larsen and Jensen: Caries Res 1986; 20:56-64]. It is thought that HF can probably get closer to the intercrystalline regions on the enamel due to its uncharged state, than the charged species of fluoride. The use of NaF in acidic fluoride solutions may be unfortunate in this respect, as Na inhibits the formation of HF due to its extremely high affinity for fluorine.

• Young, Alix; Thrane, Per Stanley; Saxegaard, Erik; Jonski, Grazyna & Rølla, Gunnar (2006). A clinical model for evaluating fluoride treatment of erosion-like lesions. Vis sammendrag

  Dental erosion is an increasingly important clinical problem and treatment of serious cases often both difficult and expensive. Prevention and treatment involving fluoride application in various forms has been studied both in vitro and in situ. The present in vivo model was developed to examine the effect of fluoride on erosion-like lesions. Results are presented for two fluoride toothpastes. Material and methods: Four healthy anterior teeth in each subject (n=20) with intact pellicle were exposed to diluted citric acid (100mmol/l or 10mmol/l) applied using a peristaltic pump (5 ml, 7 ml/min) and the acid collected in a test tube before and after application of the respective toothpastes (etch I and etch II). Toothpastes (neutral 0.15 % NaF and acidic 0.4 % SnF2) were applied to the labial surfaces with a soft brush (4 x 1min) with gentle water rinsing between applications. Each subject had one pair of teeth treated with each of the test toothpastes. Enamel solubility was examined by assessment of calcium content in the citric acid applied before and after the treatment with toothpaste. Results: SnF2-toothpaste reduced the solubility of teeth in vivo by 20 % (etch II < etch I). NaF-toothpaste provided no protection (etch II > etch I). Conclusion: This model promises the possibility for studying the effect of preventive treatment measures for dental erosion. SnF2 toothpaste is more effective than NaF in preventing loss of enamel due to acid attack.

• Hjortsjø, Carl; Jonski, Grazyna; Thrane, Per Stanley; Rølla, Gunnar & Young, Alix (2006). Effect of dilute hydrofluoric acid-treatments on enamel in vivo. Vis sammendrag

  Dilute hydrofluoric acid (HF) solutions have in earlier tests been proven to reduce enamel solubility. Objectives: To examine the effect of different concentrations of dilute HF in reducing enamel solubility using an in vivo model. Methods: Four healthy anterior teeth in each subject (n=72) with intact pellicle were exposed to diluted citric acid (10mmol/l) applied using a peristaltic pump (5 ml, 6 ml/min) and the acid collected in a test tube before and after application of the respective HF preparations (etch I and etch II). Four different concentrations of HF solutions (0.20%, 0.15%, 0.10%, 0.05%) where dripped on the labial surfaces of each of 18 teeth using the peristaltic pump (1 min, 6 ml/min). The teeth where rinsed for 5s with water between applications and left for five minutes after the treatment with HF before etch II. Enamel solubility was examined by assessment of calcium content in the citric acid applied before and after the treatment with the HF solutions using atom absorption spectroscopy. The reductions in calcium content in the citric acid between etch I and etch II were calculated for each tooth. Results: A greater reduction in calcium loss was observed for the three most concentrated solutions (0.20% HF – 69.7%, 0.15% HF – 61.6%, 0.15% HF – 70.1%) compared to the least concentrated solution (0.05% HF – 41.2%). Conclusions: Even extremely diluted HF seems to provide a very promising level of protection against the effects of acid on enamel solubility. Further studies are planned to determine the clinical relevance of these findings.

• Rølla, Gunnar; Jonski, Grazyna; Saxegaard, Erik & Young, Alix (2006). Effect of acidified fluoride solutions on dissolution rate of enamel in erosive acid. Vis sammendrag

  It is well known that aqueous solutions of SnF2 and TiF4 reduce the dissolution rate of enamel in erosive acid, and it has recently been shown that highly diluted solutions of hydrofluoric (HF) acid shares this property. All these solutions have “natural” acidity, and induce formation of calcium fluoride on enamel. Objective: To compare the dissolution-reducing capacity of HF with NaF acidified with HCl or H3PO4. The latter are also known to cause calcium fluoride formation. Material and methods: The diluted HF and acidified NaF-solutions all had a pH of 3 and contained 0.09% fluorine. Enamel samples (n=18) were individually pre-treated with 10ml of 0.01M citric acid for 10 min (Etch 1) and the amount of calcium released measured by atomic absorption. These enamel samples were subsequently treated with one of the fluoride containing solutions for 10 min, and again etched and analyzed as before (Etch 2). The difference between Etch 1 and Etch 2 was assumed to be due to the respective fluoride treatments. Data were analysed using one way ANOVA. Results: It was found that the HF-treatment was more effective than treatment with acidified NaF-solutions. Mean reductions were HF - 50%, NaF with H3PO4 - 30% (p=0.26) and NaF with HCl - 20% (p=0.03). Conclusion: As HF contains mainly un-dissociated molecules at pH 3, it is suggested that these very small, uncharged molecules of covalently bound H and F, can diffuse rapidly together into enamel, opposed to ionic F-Na+ in acidified solutions. The HF molecules can form calcium fluoride as follows: CaHPO4 + 2HF > CaF2 + H2PO4 + H+. The acids used with NaF are fully dissociated and these protons are free to individually penetrate into enamel and cause mineral loss. The movement of fluoride is however restricted due to its high affinity for Na.

• Saxegaard, Erik; Young, Alix; Hjortsjø, Carl; Jonski, Grazyna & Rølla, Gunnar (2006). Dentin pre-treatment with diluted hydrofluoric acid reduces solubility. Vis sammendrag

  We have previously reported that enamel and cementum are protected against dissolution in citric acid by brief pre-treatments with highly diluted hydrofluoric acid (HF, pH=3). (Saxegaard et al IADR 2005). Deposition of calcium fluoride-like material (hereafter CaF2) was shown to account for the effect which was also concentration dependent. However, advanced cases of dental erosion may penetrate the enamel and reach the dentin. Objective: To examine the effect of similar pre-treatments on the solubility of dental dentin. Methods: In 42 intact human third molars the dentin was exposed by cutting off the tooth-enamel using a diamond bur. The roots were cut off and the exposed cervical surface covered with acid-resistant nail varnish. In 6 groups each specimen was treated with 0.1M citric acid (10ml, 30min) before (etch-I) and after (etch-II) treatment with the different HF-solutions ((0.1%-1.0%, 10ml, 10min). Samples were briefly rinsed in deionised water between treatments. Dissolution of dentin was assessed by comparing the calcium content in etch I and II using atomic absorption spectroscopy. Remaining dentin samples similarly underwent etch I and various HF-treatments before examination in EDXA and SEM (Phillips type XL30 ESEM). Results: Treatment with 0.1%HF reduced the solubility of dentin by ~80%, whereas 0.2-1.0%HF gave reductions of 93-98%. This reduction was somewhat lower than for cementum but higher than for enamel. SEM images showed that dentin was covered with a CaF2, whereas results of EDXA analyses were inconsistent. Conclusion: As with enamel and cementum the CaF2 produced on dentin in the presence of HF appears to exert a protective effect against clinical erosion. It can be speculated that the effect may be due to the low pH at which the CaF2 was formed. It seems likely that the nature of the phosphate contamination of the CaF2 determines its rate of dissolution in erosive acids.

• Skaar, Mari; Mulic, Aida; Hove, Lene Hystad; Young, Alix & Tveit, Anne Bjørg (2006). Erosive effect of acidic drinks and acids on bovine enamel in vitro.
• Young, Alix; Thrane, Per Stanley; Saxegaard, Erik; Hjortsjø, Carl; Jonski, Grazyna & Rølla, Gunnar (2006). Preventive effect of acidic fluoride treatments on erosion-like lesions. Vis sammendrag

  Dental erosion is an increasingly important clinical problem and treatment of serious cases often both difficult and expensive. Prevention and treatment involving fluoride application in various forms has been studied both in vitro and in situ. Objectives: To compare the effect of acidic fluoride against neutral fluoride on erosion-like lesions using an in vivo model. Methods: Four healthy anterior teeth in each subject (n=40) with intact pellicle were individually exposed to citric acid (100mmol/l or 10mmol/l) applied using a peristaltic pump (5ml, 7ml/min) and the acid collected in test tubes before (etch I) and after (etch II) applications of the respective fluoride preparations. Fluoride toothpastes (0.15% NaF and 0.4% SnF2) were applied to the labial surfaces with a soft brush (4 x 1min) with gentle water rinsing between applications. Fluoride solutions (0.15% HF, pH 2.5 and 0.35% NaF, pH 8.8) were dripped continuously on the labial surfaces of each tooth (1 min, 4 ml/min), followed by 5 s water rinse/tooth. Subjects rested 1 min prior to etch II. Enamel solubility was examined by assessment of calcium content (Ca) in etch I and II using atom absorption spectroscopy. Results: Toothpastes – SnF2 provided far better protection of the enamel than NaF reducing Ca-loss by 20% when the weakest acid was used. NaF resulted in large Ca-loss with both acid concentrations. Solutions – HF reduced Ca-loss by 60 % whereas the NaF resulted in large Ca-loss with both acid concentrations. Conclusions: The experiments showed that SnF2 and highly dilute HF are promising preventive treatment measures for dental erosion.

• Young, Alix; Thrane, Per Stanley; Saxegaard, Erik; Hjortsjø, Carl; Jonski, Grazyna & Rølla, Gunnar (2006). Preventive effects of acidic fluoride treatments on erosion-like lesions.
• Hove, Lene Hystad; Tveit, Anne Bjørg; Øgaard, Bjørn; Young, Alix & Holme, Børge (2005). The protective effect of TiF4, SnF2 and NaF against erosion-like lesions in pellicle-covered enamel.
• Jonski, Grazyna; Saxegaard, Erik; Young, Alix & Rølla, Gunnar (2005). A comparison of biological activities of three SnF2-containing toothpastes. Vis sammendrag

  Freshly made aqueous solutions of SnF2 exhibit a solubility-reducing effect on enamel in erosive acids, and can inhibit oral malodour by interaction with volatile sulphur compounds (VSC) which may form in the mouth. It is unclear to what extent these biological activities are present in SnF2-containing toothpastes, it is known that both the [F-] and [Sn2+] may be reduced. OBJECTIVE: The aim of the present study was to assess the biological activities outlined above in three commercial toothpastes containing SnF2 in slightly different concentrations. METHOD: Three toothpastes containing 0.14%, 0.15% and 0.10% F respectively were tested. Aqueous extracts of the toothpastes (toothpaste/water 1:3) were incubated 1 h and centrifuged at 10000 x g for 30 min. Solubility reduction: hydroxyapatite granules (HA) were treated with the respective toothpaste extracts for 10 min, washed, dried and exposed to 10 ml 0.1M citric acid for 30 min. Solubility was compared with that of untreated HA by calcium analyses of the acid using atomic absorption spectroscopy. Inhibition of VSC formation: Human saliva (n=6) was incubated overnight at 37oC, resulting in production of copious amounts of VSC. 10-ul aliquots of the toothpaste extracts were added to 1-ml saliva samples, and the VSC in the tubes compared with the untreated control using gas chromatography. RESULTS: Solubility reduction was about 40 % for the toothpastes. Toothpaste B was numerically best, followed by A and C, but there were no statistically significant differences. This reflects probably the different fluoride concentrations. Anti-VSC effects were of the same order of magnitude with A, B and C inhibiting VSC 97-99%, indicating available Sn2+. CONCLUSION: The experiments showed SnF2 toothpaste can be a vehicle for solubility-reducing activity, and that Sn2+ is also available.

• Rølla, Gunnar; Lamolle, Sebastien Francis; Young, Alix; Jonski, Grazyna & Saxegaard, Erik (2005). Comparison of the properties of CaF2-like particles formed under different conditions. Vis sammendrag

  Treatment with dilute hydrofluoric acid (HF) induces the immediate formation of a continuous layer of CaF2-like particles on dental enamel. This is associated with a marked cariostatic effect. More recently it was observed that this treatment reduced the solubility of enamel in erosive acid and that this effect was concentration dependent. It has been suggested that deposition of CaF2-like material may provide protection of the underlying enamel and that the amount of such material formed could be essential. OBJECTIVE: To examine the CaF2-like particles formed by treatment of enamel with either neutral or acidic fluoride. METHOD: Tooth enamel specimens (n=6) were treated with either1% NaF (0.5M F-) at neutral pH for 24h, or 1% HF (0.5M F-) for 10 min. The solubility of the CaF2-like particles formed on the specimens was examined by exposing them to 0.1M citric acid for 30 min. Acid was analysed for Ca2+ by atomic absorption spectroscopy. The enamel samples were also examined by atomic force microscopy (AFM) and by SEM. RESULTS: It was found that enamel solubility was reduced 96% by HF and 6.2% by NaF. Effect of NaF was not significantly different from the control (p<0.000). AFM showed that the amount of particles formed during the two different treatments was of the same order of magnitude, that they covered the whole surface of the enamel and that they had a similar particle size of ~20 nm diameter. SEM showed that a complete layer of CaF2-like material covered the enamel. HF-treatment gave particles which were resistant to 0.1M citric acid for 30 min and to KOH for 24h (here some of the material was lost). CONCLUSION: HF treatment thus seems to give a very resistant enamel surface, presumably due to low solubility of the CaF2-like material formed under these conditions.

• Rølla, Gunnar; Saxegaard, Erik; Jonski, Grazyna & Young, Alix (2005). The solubility-reducing effect on teeth by SnF2. Vis sammendrag

  It is well established that stannous fluoride (SnF2) reduces the solubility of teeth, whereas stannous chloride or sodium fluoride salts have no such effect. Objective: To examine whether fluoride at the concentration and pH at which it is present in 0.4% SnF2, can reduce solubility of teeth without the presence of Sn2+. As the pH of an aqueous solution of 0.4 % SnF2 is 3, due to an immediate hydrolysis reaction (Sn2+ +2H2O > Sn(OH)2 +2H+), it appears that the fluoride part of the SnF2-molecule is always exposed to acidic conditions. This fluoride is thus present as partly non-dissociated hydrofluoric acid (HF). Methods: Whole intact human premolars were pre-treated with 0.4% SnF2 or 0.1% HF (10 min) and then exposed to 0.1M citric acid or 0.01M HCl (30 min). Tooth solubility after acid exposure was estimated by measuring the [Ca2+] in the acids, by atomic absorption spectroscopy. Teeth were also examined by EDXA and SEM (Phillips type XL30 ESEM). Results: Solubility reduction by both 0.4% SnF2 and 0.1% HF were similar in both acids, and not statistically different. This indicated that the fluoride part of SnF2 alone accounts for its solubility reduction and that Sn2+ appears only to provide a suitable pH for the fluoride. The teeth treated with HF were covered with dense layers of CaF2, which probably caused the solubility reduction in acids. Conclusion: It is thus possible to separate the solubility reduction by stannous fluoride from stannous ions. As stannous ions may cause discoloration of teeth, and tend to be both oxidized and hydrolyzed during storage, the aqueous solution of HF may have advantages and be of potential interest in the prevention of dental erosions.

• Saxegaard, Erik; Jonski, Grazyna; Young, Alix & Rølla, Gunnar (2005). Dilute hydrofluoric acid reduces solubility of cementum in citric acid. Vis sammendrag

  It has been reported that pre-treatment with diluted aqueous solutions of hydrofluoric acid (HF) reduced the solubility of human dental enamel in 0.1M citric acid between 50-100% (Saxegaard et al #3272 IADR 2005). The effect was concentration dependent. OBJECTIVE: To examine the corresponding solubility reducing effect on dental cementum by a similar series of aqueous solutions of HF. METHODS: [HF] ranging from 0.1% to 1.0% was examined. Intact human third molars (n=36) were cut at the collum and the exposed cervical dentin and pulp was covered with acid-resistant nail varnish while the root cementum was carefully cleaned and lightly polished with pumice, using a rubber cup in a slow speed handpiece. In six groups (n=6) each specimen was initially treated in 0.1M citric acid (10ml, 30 min), rinsed briefly with water and dried. Samples were then pre-treated with different concentrations of HF (10ml, 10min), rinsed and dried as before, and then re-exposed to 0.1M citric acid (10ml, 30min). Solubility of the cementum was determined by measuring [Ca2+] using atomic absorption spectroscopy. Reduction in dissolution between the first and second exposure was assumed to be due to the HF-treatment. Additional cementum samples treated with HF dilutions were examined by EDXA and SEM (Phillips type XL30 ESEM). RESULTS: HF in the range 0.1-1.0% reduced the solubility of cementum by 97-100%. The pre-treated cementum was covered with a dense layer of a calcium fluoride-like material. Since cementum contains more protein than enamel, and the mineral crystals are smaller than in enamel, the mechanism of dissolution of cementum is most likely different from that of enamel. CONCLUSION: It appears that the calcium fluoride produced in the presence of HF is acid resistant and may exert a protective effect against clinical erosion of the cementum.

• Saxegaard, Erik; Jonski, Grazyna; Young, Alix & Rølla, Gunnar (2005). Effect of pre-treatment with dilute hydrofluoric acid on enamel solubility. Vis sammendrag

  It is reported in another paper at this meeting (Rölla et al.) that an aqueous solution of 0.1% hydrofluoric acid (HF) reduced the solubility of human teeth in 0.1M citric acid and in 0.01M HCl to the same extent as 0.4% SnF2. It was suggested that 0.1% HF was the part of the SnF2-molecule which reduces the solubility of teeth in aqueous SnF2, and that Sn2+ only provided a suitable pH for the reaction (pH 3). Objective: To examine the solubility reducing effect of a series of aqueous solutions of HF, on human dental enamel. Methods: [HF] ranged from 0.1% to 1.0%. Intact human third molars (n=36) were cut at the collum and the exposed dentin was covered with acid-resistant nail varnish. All teeth were initially treated with 10ml of 0.1M citric acid for 30 min, rinsed in deionised water and dried. The acid solutions were kept until Ca analysis (control). Six teeth were pre-treated with 10 ml of the 6 different concentrations of HF for 10 min. The teeth were then rinsed briefly in de-ionized water and dried. The pre-treated specimens were subsequently exposed to 10ml of 0.1M citric acid for 30 min. The solubility of the teeth was determined by measuring [Ca2+] in the acids before and after HF pre-treatment, using atomic absorption spectroscopy. The enamel was examined by EDXA and SEM (Phillips type XL30 ESEM). Results: Pre-treatment with 0.1% HF reduced the solubility of dental enamel by 50-60%, whereas 0.2-1.0% HF gave reductions of 90-100%. Conclusion: The pre-treated teeth were covered by a dense layer of a calcium fluoride-like material. Treatment with non-dissociated dilute aqueous solutions of HF may result in the formation of a protective layer on the enamel which potentially reduces the effects of erosive attack.

• Young, Alix; Hove, Lene Hystad; Kohli, Priya & Tveit, Anne Bjørg (2005). An in vitro study on the effect of titanium fluoride pre-treatment of enamel against acid attack. Vis sammendrag

  Today�s lifestyle in many ways promotes the acidic destruction of tooth substance: dental erosions. Simple measures are needed to prevent serious treatment problems after long exposure to acids. The aim of the present study was to examine the effect of fluoride treatment (simulating professional F-application) on enamel exposed to an acidic challenge aimed at simulating gastric reflux. 16 bovine anterior teeth were sectioned to obtain 4 pieces large enough to locate a circular enamel window (4mm diameter). Nail varnish was used to block out the surrounding tooth substance. Specimens were dealt into 4 groups: group 1- control (no treatment), group 2- pellicle (2-h); group 3- titanium fluoride (TiF4) pre-treatment (2min, 0.5M F-) and group 4- pellicle + TiF4 pre-treatment. Pellicle was created by 2-h incubation of tooth specimens in freshly collected, clarified paraffin wax-stimulated human whole saliva pooled from 5 healthy subjects. Specimens in groups 3 and 4 were then subjected to 3-ml TiF4-solution for 2min under gentle agitation. All specimens were subsequently subjected to 3ml 0.01M HCl stepwise for 4+4+4 min, and the acid aliquots retained for calcium analysis in a Model 3300 Atomic Absorption Spectrophotometer, Perkin Elmer Analytical Instruments (Norwalk, CT, USA). Statistical analysis (one-way ANOVA/Bonferroni) showed that TiF4 reduced Ca-release from enamel by 75, 62 and 57% respectively compared with the control after the three acid exposures (p<0.05). The effect of TiF4 on pellicle-covered enamel was slightly better than for TiF4 alone, but this was not significant. These results may suggest that pre-treatment of enamel with a TiF4 solution with or without pellicle-removal provides protection for the enamel against acid attack.

• Young, Alix (2004, 18. januar). Darlig ande. [Internett].  Helsenytt- for alle.
• Young, Alix (2004, 02. desember). Dårlig ånde og laser behandling av mandlene. [Radio].  Kanal 24.
• Young, Alix (2003, 27. mai). Dårlig ande. [Radio].  Klinisk forskningslaboratorium, Nitimen.
• Young, Alix (2003, 04. april). Slik dreper du darlig ande. [Internett].  Apollon.
• Rølla, Gunnar; Jonski, Grazyna & Young, Alix (2002). Anti-volatile sulfur compounds (VSC) effect of zinc chelates with high stability constants.
• Young, Alix (2002). Brus og tannhelse.
• Young, Alix; Jonski, Grazyna & Rølla, Gunnar (2002). A comparison of the inhibiting potential against oral malodour of zinc ions and two antibacterial agents.
• Olsen, Ingar & Young, Alix (2002, 21. september). Brustenner og dårlig ånde. Forskningsdagene 2002. [Radio].  Forskningstorget, Universitetsplassen, Oslo : Nitimen.
• Young, Alix; Jonski, Grazyna & Rølla, Gunnar (2002). Comparison of the effects of antibacterial agents on oral malodour.
• Young, Alix; Jonski, Grazyna & Rølla, Gunnar (2001). Synergistic effects of zinc and some cationic antibacterial agents in inhibiting oral malodor. Vis sammendrag

  Zinc salts that are known to inhibit oral malodor have a more marked effect on the formation of hydrogen sulfide (HS) than on methyl mercaptan (MM). MM has a more unpleasant odor and a greater pathogenic potential than HS. As zinc is thought to inhibit oral malodor mainly by forming sulfides of low solubility with HS- and S2-, and not through its moderate antibacterial effect, it is possible that addition of antibacterial agents to the zinc solution may improve its effect against MM. The present study aimed at examining the anti-VSC effects of zinc acetate (Zn), chlorhexidine (CHX) and cetylpyridinium chloride (CPC) alone and in combination. 1-ml aliquots of saliva, controls without additions and test samples with 10µl additions of 0.3% Zn, 0.025% CHX, 0.025% CPC or a combination of Zn and either CHX or CPC, were incubated 24h. VSC levels in the saliva headspace were measured directly in a gas chromatograph (GC). In-vivo testing used a cysteine challenge (Kleinberg and Codipilly, 1999). Baseline VSC was established by direct GC measurements of mouth air. On separate days, subjects rinsed for 1 min with 10-ml of each of the test solutions and combinations. Cysteine challenges were then repeated at 1h, 2h and 3h. For both experiments % reduction in VSC were calculated in relation to the control/baseline levels. In-vitro results demonstrated synergism between Zn and CHX and between Zn and CPC. The synergism was stronger for MM than for HS. In-vivo results also showed synergism between Zn and the antibacterial agents although the combination with CHX was stronger than with CPC.

• Young, Alix; Jonski, Grazyna & Rølla, Gunnar (2001). The importance of the source of zinc ions for the anti-VSC effect.
• Rølla, Gunnar; Jonski, Grazyna & Young, Alix (2000). Cysteine-induced oral production of volatile sulfur compounds (VSC).
• Young, Alix; Jonski, Grazyna & Rølla, Gunnar (2000). The effect of aqueous solutions of metal salts on volatile sulfur compounds (VSC) production from human saliva in vitro.

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