Effects of crown morphology and interproximal contact on vertical food impaction in mandibular molars: a three-dimensional finite element analysis

Background Vertical food impaction (VFI) in posterior teeth is a common clinical problem linked to crown morphology and interproximal contacts. However, the synergistic biomechanical effects of key morphological parameters remain quantitatively unclear. This study aimed to investigate, via three-dimensional finite element analysis (FEA), the combined effects of the interproximal horizontal distance (IHD), marginal ridge height (MRH), and occlusal embrasure angle (OEA) on the biomechanics of VFI in the mandibular molar region. Methods Based on CBCT data, a parametric finite element model of the mandibular second premolar, first molar, and second molar with periodontal tissues was developed. A full-factorial design was employed, incorporating IHD (0, 0.1, 0.2, 0.3 mm), MRH (125°, 145°, 165°), and OEA (60°, 80°, 100°), resulting in 36 simulation models. A 15 N vertical load was applied to a simulated food bolus. Stress distributions and tooth deformations were analyzed, and data were evaluated using multivariate analysis of variance (ANOVA). Results The results indicated that OEA and MRH significantly influenced molar stress, with stress concentration exacerbated at an OEA of 100°. PDL stress was positively correlated with MRH. Tooth deformation was significantly affected by all three parameters, increasing markedly when IHD reached 0.3 mm. The optimal combination for minimizing occlusal stress was MRH = 145° with OEA = 60°, while the best overall stability (minimal deformation) was achieved with IHD = 0 mm, MRH = 125°, and OEA = 60°. Conclusions To mitigate the risk of vertical food impaction, a morphologically stable design is recommended. This involves maintaining a tight interproximal contact (IHD ≤ 0.1 mm), contouring a moderate marginal ridge (MRH approximating 145°), and controlling the occlusal embrasure geometry (OEA between 60° and 80°). This parameter combination minimizes adverse stress values and tooth displacement.