Assessment of tooth devitalization as a risk factor for enamel and dentin functional overload using mathematical modeling

Background: Cracks and fractures of devitalized teeth caused by functional overload are common in dental practice, necessitating an assessment of the stress-strain state of intact and devitalized tooth tissues under similar loading conditions.

Aim: An experimental comparison of the stress-strain state of intact and devitalized hard tooth tissues and the surrounding bone tissue using mathematical modeling.

Methods: A 3D mathematical modeling of the stress-strain state of a mandibular segment with an intact and devitalized tooth was performed. A vertical and oblique (45°) load of 150 N was applied; the maximum stress and its location in the enamel, dentin, cortical bone, and cancellous bone were analyzed by comparing them to the respective strength limits.

Results: Devitalized hard tissues are subjected to a higher stress than intact teeth, especially when an oblique load is applied, by 49.3, 11.0, and 13.1% (86.186, 31.371, and 5.037 MPa) for the enamel, cortical bone, and cancellous bone, respectively. When a vertical load is applied, tooth devitalization increases the stress in the enamel and cancellous bone of the socket by 33.1 and 29.2% (51.147 and 1.953 MPa), respectively. Devitalized dentin shows almost no changes in stress under a vertical load due to the deterioration of physical properties (and, thus, a decrease in the strength limit), whereas an oblique load results in a decrease of 28.1%. Functional load in a devitalized tooth results in stress values close to the strength limit in the enamel (under a vertical and oblique load) and dentin (under an oblique load). Periapical resorption and root apex resection further increase the stress.

Conclusion: Tooth devitalization increases the stress in the enamel and bone tissues, especially under an oblique load. Despite the reduced stress in devitalized dentin caused by a decrease in its mechanical strength, stress values under an oblique load are close to the dentin strength limit in the tooth neck area. Due to tooth devitalization, the stress in the enamel exceeds its strength limit under both oblique and vertical loads (in the tooth neck area and along the occlusal surface, respectively). Periapical resorption and root apex resection cause a similar increase in the stress in the enamel compared to a devitalized tooth under both loads, as well as in the cortical bone under an oblique load.