Aim was to determine the association between malocclusion and oral health-related quality of life (OHRQoL) and to test and modify the conceptual model of perceived oral health for malocclusion patients. 

Two different datasets were used. Malaysian data consisted of a sample of 323 young adult patients seeking orthodontic treatment. Finnish data was obtained from 4085 adult participants of the national Health 2000 Survey. In Malaysian patients, malocclusion was measured using Index of Orthodontic Treatment Need. In the Finnish data, malocclusion was registered using malocclusion traits (increased overjet and overbite, and cross-bite, scissor-bite and open bite). OHRQoL was measured using OHIP-14. The association of malocclusion and OHRQoL was evaluated using multivariable linear and zero inflated Poisson regressions. Modified model of oral health for malocclusion patients was tested using structural equation. 

Malocclusion was significantly associated with OHRQoL and of its seven domains, the impact was highest in the psychological discomfort domain. Among adult Finns OHRQoL was significantly poorer in people with overjet. Overjet was associated only with the physical disability domain. Cross-bite and scissor-bite were associated with the social disability domain. Psychological disability was associated with increased overbite and open bite. Fit indexes for previous conceptual model indicated that it did not fit the data well. Therefore, a modified model was developed to incorporate additional paths between levels to better fit the data. 

Malocclusion has a negative impact on OHRQoL and its domains. Previous conceptual model of perceived oral health was not found appropriate for people with malocclusion. Thus, an alternative model is proposed.