Minh Khai Le Thieu

• Thieu, Minh Khai Le; Haugen, Håvard Jostein; Esporrin, Javier Sanz; Sanz, Mariano; Lyngstadaas, Ståle Petter & Verket, Anders (2021). Guided bone regeneration of chronic non-contained bone defects using a volume stable porous block TiO2 scaffold: An experimental in vivo study. Clinical Oral Implants Research.  ISSN 0905-7161. . doi: 10.1111/clr.13708 Vis sammendrag

  Objectives To evaluate new lateral bone formation and lateral volume augmentation by guided bone regeneration (GBR) in chronic non‐contained bone defects with the use of a non‐resorbable TiO2‐block. Materials and methods Three buccal bone defects were created in each hemimandible of eight beagle dogs and allowed to heal for eight weeks before treatment by GBR. Each hemimandible was randomly allocated to 4 or 12‐week healing time after GBR and three intervention groups were assigned by block randomization: TiO2 block: TiO2‐scaffold and a collagen membrane, DBBM particles: Deproteinized bovine bone mineral (DBBM) and a collagen membrane, Empty control: Collagen membrane only. Microcomputed tomography (microCT) was used to measure the lateral bone formation and width augmentation. Histological outcomes included descriptive analysis and histomorphometric measurements. Results MicroCT analysis demonstrated increasing new bone formation from four to twelve weeks of healing. The greatest width of mineralized bone was seen in the empty controls, and the largest lateral volume augmentation was observed in the TiO2 block sites. The DBBM particles demonstrated more mineralized bone in the grafted area than the TiO2 blocks, but small amounts and less than the empty control sites. Conclusion The TiO2 blocks rendered the largest lateral volume augmentation but also less new bone formation compared to the DBBM particles. The most new lateral bone formation outward from the bone defect margins was observed in the empty controls, indicating that the presence of either graft material leads to slow appositional bone growth.

• Haugen, Håvard Jostein; Marovic, Danijela; Par, Matej; Thieu, Minh Khai Le; Reseland, Janne Elin & Johnsen, Gaute Floer (2020). Bulk Fill Composites Have Similar Performance to Conventional Dental Composites. International Journal of Molecular Sciences.  ISSN 1422-0067.  21(15), s 5136 . doi: 10.3390/ijms21145136 Fulltekst i vitenarkiv. Vis sammendrag

  The aim of the study was to perform comprehensive characterization of two commonly used bulk fill composite materials (SDR Flow (SDR) and Filtek™ Bulk Fill Flowable Restorative (FBF) and one conventional composite material (Tetric EvoCeram; TEC). Eleven parameters were examined: flexural strength (FS), flexural modulus (FM), degree of conversion, depth of cure, polymerisation shrinkage (PS), filler particle morphology, filler mass fraction, Vickers hardness, surface roughness following simulated toothbrush abrasion, monomer elution, and cytotoxic reaction of human gingival fibroblasts, osteoblasts, and cancer cells. The degree of conversion and depth of cure were the highest for SDR, followed by FBF and TEC, but there was no difference in PS between them. FS was higher for bulk fill materials, while their FM and hardness were lower than those of TEC. Surface roughness decreased in the order TEC→SDR→FBF. Bisphenol A-glycidyl methacrylate (BisGMA) and urethane dimethacrylate were found in TEC and FBF eluates, while SDR released BisGMA and triethylene glycol dimethacrylate. Conditioned media accumulated for 24h from FBF and TEC were cytotoxic to primary human osteoblasts. Compared to the conventional composite, the tested bulk fill materials performed equally or better in most of the tests, except for their hardness, elastic modulus, and biocompatibility with osteoblasts.

• Hussain, Badra; Thieu, Minh Khai Le; Johnsen, Gaute Floer; Reseland, Janne Elin & Haugen, Håvard Jostein (2017). Can CAD/CAM resin blocks be considered as substitute for conventional resins?. Dental Materials.  ISSN 0109-5641.  33(12), s 1362- 1370 . doi: 10.1016/j.dental.2017.09.003 Vis sammendrag

  Objective Dentists are facing a myriad of new CAD/CAM product for dental filling therapies. Are the new materials any worthwhile using? Are they succeeding the standard filling materials? Here we compare for the first time the new resin-composite blocks (RCBs) with conventional materials (Filtek Z250 and Tetric EvoCeram). Methods The material were tested for residual monomer elution by HPLC, thermogravimetric analysis (TG) was used to determine the percentage of fillers by weight, hardness was evaluated by Vickers method, morphology of fillers and distribution in the matrix were examined by scanning electron microscopy (SEM), elemental analysis for elemental determination of the filler particles was performed by energy-dispersive X-ray spectroscopy (EDX) cytotoxicity using human gingival fibroblasts and an epithelial cell line. Results The RBC outperformed conventional composite regarding mechanical characteristics (hardness) and monomer eluation, but showed some worrisome results regarding cytotoxicity. Significance The cost benefit is not in favour of RBCs in comparison to conventional composites, as the cytotoxicity was found higher for RBCs.

• Johnsen, Gaute Floer; Thieu, Minh Khai Le; Hussain, Badra; Pamula, Elzbieta; Reseland, Janne Elin; Lyngstadaas, Ståle Petter & Haugen, Håvard Jostein (2017). Own brand label restorative materials - A false bargain?. Journal of Dentistry.  ISSN 0300-5712.  56, s 84- 98 . doi: 10.1016/j.jdent.2016.11.004 Vis sammendrag

  Objectives This study aims at evaluating and comparing mechanical, chemical, and cytotoxicological parameters of a commercial brand name composite material against two ‘own brand label' (OBL) composites. Methods Parameters included depth of cure, flexural strength, degree of conversion, polymerization shrinkage, filler particle morphology and elemental analyses, Vickers hardness, surface roughness parameters after abrasion, monomer elution, and cytotoxicity. Results The conventional composite outperformed the OBLS in terms of depth of cure (p < 0.001), degree of cure at the first and last time intervals (p < 0.001), hardness (p < 0.001), and post-abrasion roughness (p < 0.05). The polymerization volumetric shrinkage ranged from 2.86% to 4.13%, with the highest shrinkage seen among the OBLs. Both Monomer elution from the OBLs was statistically significantly higher (p<0.001). Statistically significantly higher cytotoxicity combined with altered morphology and loss of confluence was detected in the cells exposed to extracts from the OBLs. Conclusions The OBLs were in general outdone by the conventional composite. Clinical Significance: OBLs restorative materials have become pervasive in the dental market. Manufacturers often promise equal or better characteristics than existing brand-name composites, but at a lower price. Dentists are highly recommended to reconsider utilization of OBLs lacking sound scientific scrutiny, and our findings underscore this recommendation

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• Haugen, Håvard Jostein; Johnsen, Gaute Floer; Reseland, Janne Elin; Hussain, Badra & Thieu, Minh Khai Le (2017). Can CAD/CAM Resin Blocks be Considered as a Substitute to Conventional Resins?.

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