Vulnerability of third molars to internal resorption: two case reports of in situ and transplanted third molars

Internal tooth resorption is a rare, inflammation-mediated pathological process that is most often detected incidentally. Third molars appear to be disproportionately affected, possibly due to their anatomical and developmental characteristics. Reports comparing internal resorption of third molars in situ and after autologous transplantation remain scarce.

This case series presents two uncommon clinical scenarios involving internal resorption of third molars. The first case describes simultaneous internal resorption affecting three third molars in situ without any identifiable triggering factors. The second case reports very late-onset internal resorption of a transplanted third molar, occurring nineteen years after successful autologous transplantation with long-term functional survival.

The presented cases support the hypothesis of an intrinsic vulnerability in third molars to pulpal resorptive processes. Large pulp chambers, thin dentinal walls, delayed eruption, chronic low-grade inflammation, and cumulative biological stressors may contribute to odontoclastic activation. While autologous third molar transplantation can provide excellent long-term outcomes, late complications such as internal resorption may still arise after prolonged asymptomatic periods.

Third molars may be particularly susceptible to internal resorption, both in situ and following transplantation. Although autologous transplantation is a reliable long-term treatment option, lifelong clinical and radiographic follow-up is essential to detect late-onset internal resorptive processes.