Investigation of the Relationship between Increased Vertical Overlap with Minimum Horizontal Overlap and the Signs of Temporomandibular Disorders.

Purpose: The purpose of this study was to test the null hypothesis that there was no relationship between increased vertical overlap (vertical overlap ≥4 mm) with minimal horizontal overlap (horizontal overlap ≤2 mm) and the signs of temporomandibular disorders.

Materials And Methods: Thirty participants (20 women, aged 20 to 45 years) with increased vertical overlap and minimal horizontal overlap, and 30 participants (20 women, aged 20 to 45 years) with no contact between the anterior teeth (control group) were examined. Diagnoses, psychological status (depression and nonspesific physical symptoms), and chronic pain severity were judged according to the Research Diagnostic Criteria for Temporomandibular Disorders and then compared. For statistical analysis of quantitative data, along with the descriptive statistical methods (mean, standard deviation, frequency), Student's t-test was used to compare parameters that reflected a normal distribution. Comparison of qualitative data between groups was performed using Chi-square and Fisher's exact tests. The level of significance was set at p < 0.05.

Results: In this study, deviation upon maximum opening was found significantly more frequently in the increased vertical overlap group than in the control group (p < 0.05). Tenderness upon palpation of lateral pterygoid muscles was observed more often in the increased vertical overlap group compared with the control group (p < 0.05). Opening-closing joint sounds occurred significantly more often in the increased vertical overlap group than in the control group (p = 0.050).

Conclusion: Within the limitations of this study, deviation upon maximum opening, tenderness of lateral pterygoid muscles (upon palpation), and opening-closing joint sounds occurred more often in the increased vertical overlap occlusions with minimum horizontal overlap compared to the control groups. These results indicated that clinicians should pay special attention to the tempormandibuar joint status of patients with significant vertical overlap anteriorly and position of the incisors when performing dental treatments that require reestablishment of incisor relationships.