A finite element analysis of cracked mandibular first molar with crown

Background: Tooth fracture has gradually become a leading cause of tooth loss, following caries and periodontal disease, but the protection of cracked teeth is still a challenge. This study aimed to assess the stress distribution in cracked mandibular first molars restored with zirconia crown using finite element analysis. Materials and Methods: Three-dimensional models of a mandibular first molar and a zirconia crown were constructed using reverse engineering software. The study comprised six experimental models and one control group, with the latter featuring an intact tooth. The experimental models included three types of cracks, each oriented from mesial to distal across the tooth surface. Two spatial relationships were evaluated: crack tips either encompassed by the crown edges or extending beyond them. Forces of 200 N and 600 N were applied vertically to simulate central occlusion, and a 200 N force was applied at a 45-degree angle in the Bucco-lingual direction to simulate lateral movement. Maximum principal stress was analyzed in all models. Results: The areas of significantly higher maximum principal stress were observed in models with crack tips protruding beyond the crown edges compared to the control, with the most pronounced differences under oblique loads. Stress concentration was consistently observed at the crack termini on the proximal surface under both loading conditions. However, the maximum principal stress in dentin showed no significant differences under any load when compared to the control group. Conclusion: A crown fully encompassing the crack can offer superior protection for cracked teeth. Clinical Relevance: Thus, this study provides clinical support on preservation of cracked teeth of AOB to inform preventative and management strategies.