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TMD burden, not malocclusion severity, is associated with impaired OHRQoL in orthodontic patients
Adrian Ujin Yap1,2,3, Abd Aziz Alias4, Aziz Khakimov5
1Department of Restorative Dentistry, Faculty of Dentistry, Universiti Malaya, Jalan Universiti, Lembah Pantai, 50603 Kuala Lumpur, Malaysia.
Objectives:
This study compared the impact of malocclusion severity and temporomandibular disorder (TMD) burden on oral health-related quality of life (OHRQoL) in orthodontic patients. Age-stratified analyses examined the moderating and mediating roles of oral behaviors, somatic symptoms, and psychological distress.
Materials And Methods:
A cross-sectional study was conducted with 274 orthodontic patients, comprising 113 adolescents (10-19 years) and 161 adults (20-30 years). Validated instruments assessed oral behaviors (OBC), TMD severity/burden (SFAI/5Ts-B), somatic symptoms (SSS-8), psychological distress (PHQ-4), and OHRQoL (OHIP-14). Malocclusion severity was determined using the Index of Orthodontic Treatment Need (IOTN). Group differences were analyzed with Chi-square and Mann-Whitney U tests. Associations were examined using Spearman's correlations, and moderation/mediation analyses were performed with Hayes' PROCESS macro (α = 0.05).
Results:
Nearly all participants (94.9%) demonstrated definite orthodontic treatment need. TMDs were present in 49.6% of the cohort, with adults showing greater symptom severity and somatic burden. Malocclusion severity exhibited negligible correlations with OHRQoL, whereas TMD burden was moderately associated with impaired OHRQoL across age groups. Mediation analyses showed that oral behaviors, somatic symptoms, and psychological distress mediated the impact of TMD burden on OHRQoL, with age-specific moderation effects. In adolescents, mediation effects were consistently weakened by moderation. In adults, oral behaviors and somatic symptoms mediated without moderation, while psychological distress showed weakened mediation.
Limitations:
Cross-sectional design precluded causal inference, restricting interpretation to associations.
Conclusions:
Malocclusion severity did not directly impair OHRQoL in orthodontic patients. Instead, TMD burden affected OHRQoL primarily through psychosocial pathways, underscoring the need for integrated biopsychosocial screening in orthodontic care.
