Accuracy and Consistency of Three Large Language Models on Fixed Prosthodontics Questions

Abstract

Large language models (LLMs) are increasingly used in dental education and clinical settings, but their accuracy and consistency in fixed prosthodontics remain uncertain. Objectives: To compare the accuracy (using a strict three-attempt criterion) and repeated response consistency of ChatGPT-5.4, Gemini 3.1 Pro, and Claude Opus 4.8 in answering binary fixed prosthodontics questions across six clinical domains. Methods: Forty binary questions covering six core fixed prosthodontic domains were developed by the principal investigator. Two experienced faculty members independently answered the questions, and disagreements were resolved through discussion to establish the gold standard. Each question was submitted thrice to each LLM in a new chat session on the same day. Accuracy was the percentage of correct responses compared with the gold standard across all three attempts, while consistency was the percentage of identical responses across three attempts, regardless of correctness. Accuracy and consistency were expressed as percentages with 95% confidence intervals. Cochran’s Q test, Cohen’s kappa, and Fleiss’ kappa were used for statistical analysis. Results: Pre-consensus examiner agreement was moderate, 77.5% (Cohen’s κ=0.55). Claude Opus 4.8 achieved the highest accuracy (95% and consistency (97.5%, followed by ChatGPT-5.4 87.5% accuracy and 92.5% consistency and Gemini 3.1 Pro (85% accuracy and 87.5% consistency. No significant difference was observed in accuracy among models (Q=5.20, p=0.074). Intra-model consistency for three models was almost perfect (κ=0.83–0.97). Conclusions: The evaluated LLMs demonstrated high accuracy and consistency for structured fixed prosthodontics questions, with Claude Opus 4.8 highest, though not significant.