Objectives <p>The aim of this study is to evaluate the effectiveness of ChatGPT 4o in planning tooth-supported fixed prostheses by examining the accuracy, repeatability, and consistency of its responses across various prosthodontic cases.</p> Materials and methods <p>1,140 responses were generated for 38 questions regarding simple and complex prosthetic cases, using case schemas from <i>Fundamentals of Fixed Prosthodontics</i>. Each question was asked 30 times at different times of day (morning, afternoon, and evening) to assess response consistency.</p> Results <p>ChatGPT demonstrated high accuracy (97.08%) for simple fixed prostheses but struggled with complex cases, showing a low accuracy rate of 19.69%. Statistically significant differences were observed in the response accuracy between question categories, indicating that ChatGPT performs better with straightforward cases than with complex ones. Repeatability was high across all question types, though accuracy varied, especially in complex scenarios.</p> Conclusions <p>The findings highlight ChatGPT’s potential as an assistive tool in simple prosthodontic cases yet emphasize the need for clinician expertise in more complex treatment planning.</p> Clinical relevance <p>While ChatGPT shows promise as a supplementary tool for dental education and practice, reliance on AI alone for intricate cases remains premature.</p>