Trude Handal

• Torgersen, Gerald; Winsnes, Karianne Ervik; Handal, Trude; Diep, My Tien; Ørstavik, Dag Solmund & Sunde, Pia Titterud (2026). Open‐Weight Deep Learning for Periapical Index Scoring: Training and Comparison of Convolutional Neural Network Models Based on Three Distinct Architectures and an Ensemble Approach. International Endodontic Journal. ISSN 0143-2885. doi: 10.1111/iej.70268. Full text in Research Archive Show summary

  Aim This study aimed to (i) train and compare three convolutional neural network (CNN) architectures for Periapical Index (PAI) scoring on intraoral radiographs, and (ii) assess whether an ensemble of these models improves performance compared with any single architecture. Methods A dataset of 17,549 apex‐centred image clips extracted from intraoral radiographs was annotated by a calibrated observer (KW) with PAI scores (1–5) and used to train three CNN architectures (ResNet50, EfficientNet‐B3 and ConvNeXt‐Tiny) for PAI scoring. The image clips were split 80/20 into training and validation sets, and model selection was based on validation performance of quadratic weighted kappa (QWK). The three CNN models were combined into an equal‐weight soft‐voting ensemble model, and all four models were evaluated on an independent balanced test set of 200 images (40 per PAI score). QWK was used as the primary outcome metric, and bootstrapping was used to estimate the confidence intervals (CIs). The PAI scale was dichotomized into healthy (PAI 1–2) and diseased (PAI 3–5), and accuracy, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and F1 score were calculated. Results The ensemble model achieved the highest performance with a QWK of 0.79 on the test set, followed by EfficientNet‐B3 (QWK = 0.77), ResNet50 (QWK = 0.76) and ConvNeXt‐Tiny (QWK = 0.70), with overlapping confidence intervals (CIs). For the binary PAI classification, the performance of the three CNN models and the ensemble model was comparable. The ensemble model achieved the following results: accuracy 86%, sensitivity 83%, specificity 90%, PPV 93%, NPV 78% and F1 score 0.88. Conclusion Optimization and evaluation of three CNN models and an ensemble model for PAI scoring showed comparable performance on both the five‐class PAI scale and the binary PAI scale on an independent test set. The ensemble model did not show statistically significant improvement over the three individual CNN architectures. The AI models trained and tested in this study are made open‐source under the open‐source MIT licence.

• Sunde, Pia Titterud; Giving, Erika Madeléne; Dilshad, Tabish; Handal, Trude & Ørstavik, Dag Solmund (2025). Radiographic Outcome of Endodontic Treatment of Teeth with Primary Apical Periodontitis: Results from a Postgraduate Clinic. Dentistry Journal. 13(12). doi: 10.3390/dj13120593. Full text in Research Archive
• Stueland, Håvard; Ørstavik, Dag Solmund & Handal, Trude (2023). Treatment outcome of surgical and non-surgical endodontic retreatment of teeth with apical periodontitis. International Endodontic Journal. ISSN 0143-2885. 56(6), p. 686–696. doi: 10.1111/iej.13914. Full text in Research Archive
• Døving, Mats; Handal, Trude & Galteland, Pål (2020). Bakterielle odontogene infeksjoner. Tidsskrift for Den norske legeforening (Tidsskriftet). ISSN 0029-2001. doi: 10.4045/tidsskr.19.0778. Full text in Research Archive
• Ehrmann, Elodie; Handal, Trude; Tamanai-Shacoori, Zohreh; Bonnaure-Mallet, MB & Fosse, Thierry (2014). High prevalence of β-lactam and macrolide resistance genes in human oral Capnocytophaga species. Journal of Antimicrobial Chemotherapy. ISSN 0305-7453. 69(2), p. 381–384. doi: 10.1093/jac/dkt350. Full text in Research Archive
• Søraas, Arne Vasli Lund; Olsen, Ingar; Sundsfjord, Arnfinn; Handal, Trude; Bjørang, Ola & Jenum, Pål (2014). Extended-spectrum beta-lactamase-producing bacteria are not detected in supragingival plaque samples from human fecal carriers of ESBL-producing Enterobacteriaceae. Journal of Oral Microbiology. 6. doi: 10.3402/jom.v6.24026. Full text in Research Archive Show summary

  Background: The prevalence of infections caused by Cefotaximase-Munich (CTX-M)-type extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) has rapidly increased during the past 15 years. Enterobacteriaceae are commonly found in the gastrointestinal tract and long-term intestinal carriage is considered important for the spread of ESBL and as a source of clinical infections. Oral biofilm such as supragingival plaque is known to contain numerous antibiotic resistance determinants and may also represent a poorly investigated site for ESBL carriage and further spread. Objective: To investigate possible carriage of ESBL-producing bacteria in supragingival plaque of known fecal carriers of these bacteria. Design: We screened for the presence of aerobic and anaerobic ESBL-producing bacteria and blaCTX-M in supragingival plaque samples from healthy human adults with culture-verified fecal carriage of CTX-M-producing Escherichia coli. The presence or absence of Enterobacteriaceae and ESBL-producing bacteria in plaque samples was evaluated using culture-based methods and consensus CTX-M PCR. Results: Oral samples were obtained from 17 participants with known previous carriage of ESBL-producing E. coli. No ESBL-producing bacteria or ESBL genes were detected using culture-based and molecular methods. One colony of Rahnella aquatilis harboring the class A ESBL gene blaRAHN-1/2 was identified in an oral sample from one of the participants. Conclusion: This pilot study supports the notion that the presence of CTX-M-producing bacteria is uncommon in oral plaque of healthy human adult fecal carriers. Due to the limited number of persons tested, a low prevalence of oral ESBL-carriage in healthy adults or carriage in selected groups of patients cannot be excluded. To our knowledge, this is the first description of an R. aquatilis with the RAHN-1/2 gene in the oral cavity.

• Handal, Trude; Caugant, Dominique A; Olsen, Ingar & Sunde, Pia Titterud (2009). Bacterial diversity in persistent periapical lesions on root-filled teeth. Journal of Oral Microbiology. 1, p. 1–7. doi: 10.3402/jom.v1iO.1946. Full text in Research Archive
• Handal, Trude; Giraud-Morin, Chantal; Caugant, Dominique A; Madinier, Isabelle; Olsen, Ingar & Fosse, Thierry (2005). Chromosome- and plasmid-encoded beta-lactamases in Capnocytophaga spp. Antimicrobial Agents and Chemotherapy. ISSN 0066-4804. 49(9), p. 3940–3943. doi: 10.1128/AAC.49.9.000-000.2005. Full text in Research Archive
• Handal, Trude; Olsen, Ingar; Walker, Clay B & Caugant, Dominique A (2005). Detection and characterization of beta-lactamase genes in subgingival bacteria from patients with refractory periodontitis. FEMS Microbiology Letters. ISSN 0378-1097. 242(2), p. 319–324. Full text in Research Archive Show summary

  Fifty-three beta-lactamase-producing strains of oral bacteria isolated from patients with refractory periodontitis in Norway and USA were screened for the presence of the bla(TEM), bla(SHV), bla(OXA), bla(ampC), bla(cfxA), and bla(cepA/cblA) genes by the polymerase chain reaction (PCR). The PCR products were characterized by direct sequencing of the amplified DNA. Thirty-four of the 53 enzyme-producing strains (64%) were positive in one of the PCR assays. All beta-lactamase-producing Prevotella and Capnocytophaga spp. were CfxA positive. TEM-type beta-lactamases were identified in one strain each of Escherichia coli and Neisseria sp., and one strain of Citrobacter freundii possessed an AmpC-type beta-lactamase. Screening for gene cassettes and genes known to be associated with integrons did not reveal the presence of integrons in these oral bacteria. Sequence analyses showed that most CfxA positive Prevotella and Capnocytophaga isolates from patients with refractory periodontitis harboured variants of the CfxA2 and CfxA3 enzyme. The present study also showed that many different genetic determinants of beta-lactamase production are found in bacteria isolated from refractory periodontitis, many of which remain to be characterized.

• Handal, Trude; Olsen, Ingar; Walker, Clay B & Caugant, Dominique A (2004). beta-lactamase production and antimicrobial susceptibility of subgingival bacteria from refractory periodontitis. Oral Microbiology and Immunology. ISSN 0902-0055. 19, p. 303–308. Full text in Research Archive
• Handal, Trude; Caugant, Dominique A & Olsen, Ingar (2003). Antibiotic resistance in bacteria isolated from subgingival plaque in a Norwegian population with refractory marginal periodontitis. Antimicrobial Agents and Chemotherapy. ISSN 0066-4804. 47(4), p. 1443–1446. Full text in Research Archive Show summary

  The prevalence of beta-lactamase-producing bacteria in subgingival plaque from patients with refractory periodontitis in Norway was assessed by the chromogenic nitrocefin method. beta-Lactamase activity was detected in 68% of the patients. Enzyme-producing strains belonged predominantly to the genus Prevotella; others were staphylococci, enteric gram-negative rods, and Bacillus spp.

• Handal, Trude & Olsen, Ingar (2002). Antibakteriell resistens med vekt på betalaktamaser. Tandläkartidningen. ISSN 0039-6982. 94(1), p. 30–35. Full text in Research Archive
• Handal, Trude & Olsen, Ingar (2002). Bakteerien resistenssi ja beetalaktamaasit. Suomen hammaslaakarilehti. ISSN 0355-4090. IX(6), p. 282–286. Full text in Research Archive
• Handal, Trude & Olsen, Ingar (2002). Antibakteriell resistens med vekt på betalaktamaser. Den norske tannlegeforenings Tidende. ISSN 0029-2303. 112(1), p. 20–24. Full text in Research Archive
• Olsen, Ingar; Handal, Trude & Løkken, Per (2001). Bakteriedrepende virus som alternativ til antibiotika. Den norske tannlegeforenings Tidende. ISSN 0029-2303. 111(1), p. 14–17. Full text in Research Archive
• Olsen, Ingar; Handal, Trude & Løkken, Per (2001). Bakteriedrepende virus, stalinister og "superbugs". Tidsskrift for Den norske legeforening (Tidsskriftet). ISSN 0029-2001. 121(27), p. 3197–3200. Full text in Research Archive
• Handal, Trude & Olsen, Ingar (2000). Antimicrobial resistance with focus on beta-lactamases. European Journal of Oral Sciences. ISSN 0909-8836. 108, p. 163–174. Full text in Research Archive

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• Torgersen, Gerald R.; Winsnes, Karianne Ervik; Handal, Trude & Sunde, Pia Titterud (2025). Visualizing AI Decisions in Automated Periapical Index Assessment. Full text in Research Archive Show summary

  Objective: Explainable artificial intelligence (XAI) is critical for clinical acceptance of AI models in dental radiology. This study explores the use of XAI—primarily Grad-CAM and LayerCAM—to interpret deep learning-based Periapical Index (PAI) scoring from intraoral radiographs, with a focus on exploring attentions patterns, meaning the areas contributing to the models decision of PAI score. Methods: We trained an open-source deep learning model for PAI classification on 300×300 pixel radiographic clips, using expert-labeled data. Grad-CAM and LayerCAM were applied to visualize model attention, generating class-specific average heatmaps and analyzing individual cases for anatomical plausibility and potential artifacts. Additional XAI methods were explored for comparison. Code and weights will be published together with the main publication. Results: XAI visualizations revealed that model attention patterns systematically varied with PAI class: lower scores showed focused periapical activation, while higher scores exhibited more diffuse and multi-focal attention. Individual heatmaps highlighted both expected anatomical focus and occasional peripheral activations, suggesting areas for further model refinement. LayerCAM and Grad-CAM provided complementary insights into model interpretability. Conclusions: Grad-CAM and related XAI methods offer valuable insights into the decision-making of AI models for PAI scoring. Ongoing work aims to refine XAI techniques and analyze individual attention maps to improve both model performance and interpretability.

• Handal, Trude (2022). Er du kalibrert? Full text in Research Archive
• Handal, Trude & Sunde, Pia Titterud (2020). Rotresorpsjoner. Full text in Research Archive
• Handal, Trude & Enersen, Morten (2017). Antibiotikabruk i primærhelsetjenesten Tannhelse, 1) Akutte odontogene infeksjoner; 2) Marginal periodontitt. Antibiotikabruk i Primærhelsetjenesten. Full text in Research Archive
• Danielsen, Sigurd Haugan; Handal, Trude & Enersen, Morten (2015). Marginal periodontitt. Antibiotikabruk i Primærhelsetjenesten. Full text in Research Archive
• Danielsen, Sigurd Haugan; Handal, Trude & Enersen, Morten (2015). Akutte odontogene infeksjoner. Antibiotikabruk i Primærhelsetjenesten. Full text in Research Archive
• Handal, Trude; Ehrmann, E; Fosse, Thierry; Giraud-Morin, Chantal; Madinier, Isabelle & Bonnaure-Mallet, MB (2008). Prevalénce des genes de résistance aux Beta lactamines et aux macrolides chez Capnocytophaga selon les espèces et l´origine des souches. Full text in Research Archive
• Handal, Trude (2008). Periodontitt og antibiotikaresistens. Full text in Research Archive
• Sunde, Pia Titterud; Handal, Trude; Olsen, Ingar & Caugant, Dominique A (2007). Microbial diversity in therapy resistant periapical lesions. Full text in Research Archive
• Handal, Trude (2006). Antibiotikaresistens - en økende utfordring i Norge. Full text in Research Archive
• Handal, Trude; Giraud-Morin, C; Caugant, Dominique A; Madinier, I; Olsen, Ingar & Fosse, T (2005). Characterization of chromosome- and plasmid-encoded beta-lactamases in Capnocytophaga spp. Full text in Research Archive
• Handal, Trude; Caugant, Dominique A & Olsen, Ingar (2001). B-lactamases and antimicrobial susceptibilities in periodontal bacteria isolated in Norway. Full text in Research Archive
• Handal, Trude; Caugant, Dominique A & Olsen, Ingar (2000). B-Lactamases from subgingival bacteria isolated from refractory periodontitis in Norway. Full text in Research Archive
• Handal, Trude; Caugant, Dominique A & Olsen, Ingar (2000). Beta-lactamases in refractory marginal periodontitis detected by nitrocefin test and isoelectric focusing. Full text in Research Archive
• Handal, Trude; Olsen, Ingar & Caugant, Dominique A (2005). Antimicrobial resistance with focus on β-lactamases in subgingival bacteria from patients with refractory periodontitis. Universitetet i Oslo. ISSN 9788291757322. Full text in Research Archive

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