Association between unilateral third molar elongation, temporomandibular joint space asymmetry, and posterior tooth wear: a CBCT study

Elongated third molars have been associated with occlusal interference, mandibular deviation, and temporomandibular joint (TMJ) disorders. However, their impact on TMJ space morphology and posterior tooth wear remains insufficiently explored.

This study aimed to assess the relationship between unilateral third molar elongation, TMJ space asymmetry, and asymmetrical posterior tooth wear.

Thirty patients presenting with unilateral third molar elongation (experimental group) and 30 controls with fully aligned dentition and absent third molars were included (Ethical approval ID:2023015). Cone-beam computed tomography (CBCT) was utilized to measure anterior, superior, and posterior TMJ spaces. Some of these CBCT scans were obtained specifically for this study. Some of CBCT scans were taken for therapeutic purposes. Bilateral differences in mean wear index (DBMWI) and the mean standard deviation (MSD) of posterior tooth wear were calculated using Lagan’s modified scoring system. Statistical analysis was conducted using SPSS 22.0.

Significant intergroup differences in TMJ space asymmetry (ΔAS, ΔSS, and ΔPS) were observed (p < 0.05). The experimental group demonstrated higher DBMWI (0.50 ± 0.30 vs. 0.19 ± 0.14, p = 0.015) and MSD values (0.81 ± 0.30 vs. 0.36 ± 0.16, p = 0.001), indicating more pronounced irregular posterior tooth wear.

Unilateral elongation of the third molar is associated with TMJ space asymmetry and increased posterior tooth wear. Early intervention, including extraction of the elongated third molar, may help prevent occlusal imbalance and related complications such as tooth fractures.