Impact of malocclusion and common oral diseases on oral health–related quality of life in young adults


The aim of this study was to assess the association between malocclusion and oral health–related quality of life in young adults without orthodontic treatment, controlling for sociodemographic factors and common oral diseases.


The sample consisted of 429 Korean patients (328 men, 101 women) 18 to 32 years of age. They completed the Korean version of the oral health impact profile-14 questionnaire and had a clinical examination, including an assessment with the index of orthodontic treatment need−dental health component. We collected sociodemographic information (age, sex, and education level) and evaluated other common oral diseases (decayed, missing, and filled teeth; periodontal health status; temporomandibular disorder; and oral soft tissue diseases).


Multiple logistic regression analysis showed that patients requiring extensive orthodontic treatment were more than 2.7 times as likely to have poor oral health–related quality of life as the corresponding “no treatment needed” reference group (odds ratio, 2.74; 95% confidence interval, 1.60-4.59; P <0.001). Severe malocclusion is significantly associated with functional limitations, physical pain, and social disability in young adults.


Malocclusion is a key factor associated with poor quality of life caused by limited oral function, pain, and social disability in young adults.


  • A weak positive correlation was found between the orthodontic treatment need–dental health component (IOTN-DHC) and previous caries.

  • A weak positive correlation was found between IOTN-DHC and community periodontal index.

  • Oral soft tissue diseases and malocclusion were associated with poor oral health–related quality of life (OHRQOL).

  • Patients needing extensive treatment were more likely to have poor OHRQOL.

  • Severe malocclusion is associated with functional limitation, pain, social disability.

Traditionally, oral health epidemiology studies have predominantly measured clinical oral conditions, such as dental caries and periodontal disease, to determine a patient’s decayed, missing, and filled teeth (DMFT) index and community periodontal index (CPI). However, there is a growing consensus that conventional clinical-epidemiologic measurements by professionals differ from the self-assessment of oral health by individuals. Thus, the concept of oral health–related quality of life (OHRQOL), as typically applied in health outcomes research, has been developed to quantify the extent to which oral health problems interfere in a patient’s daily life and well-being. OHRQOL is a multidimensional concept that includes socioeconomic status, physical oral health status, and self-perceived oral health–related psychological factors.

Patients with severe malocclusion may report various oral health impacts of the malocclusion that can affect their quality of life in many ways. Orthodontic treatment or orthognathic surgery not only improves oral function and facial esthetics, but also reduces emotional suffering, enhancing the patient’s self-esteem, socialization, and quality of life. However, the impact of malocclusion on a patient’s quality of life has received much less attention than the impact of other common oral diseases because malocclusion is considered to be “a set of dental deviations” rather than a disease and because orthodontic treatment does not cure a condition but, rather, corrects variations from a somewhat arbitrary norm. A better understanding of the effects of malocclusion from a patient’s point of view is needed in the planning and evaluation of public health interventions and for appropriate allocation of resources. Data currently available on the impact of malocclusion on quality of life are mostly derived from a few clinical studies in which a limited number of covariates were controlled for; this restricts the ability to generalize these findings to wider populations. Most previous studies used the generic oral health impact profile-14 scale (OHIP-14). It captures not only the impacts caused by malocclusion, but also those related to other oral diseases, and it does not distinguish the specific causes of the impacts that are recorded. Since many young people with a malocclusion also have dental caries, missing teeth, periodontitis, temporomandibular disorder (TMD), or stomatitis, neglecting to consider or separate the impact of these disease conditions can seriously affect the assessment of the association between malocclusion and the patient’s quality of life. Therefore, problems arise in the data analyses of these types of studies not because of the use of a generic OHIP-14 measure per se, but because of the failure to recognize and control for other conditions that are occurring simultaneously in the mouth that also impact the OHRQOL measurement.

Using data from Korean young adults who had not received orthodontic treatment, in this study we aimed to assess the association between malocclusion and OHRQOL. Patients were assessed with the OHIP-14, and the effects of malocclusion were evaluated independently from the impacts attributable to sociodemographic factors and to common oral diseases also present in these patients. In this study, 2 null hypotheses were tested. The first null hypothesis was that malocclusion is not associated with OHRQOL in patients without orthodontic treatment. The second null hypothesis was that malocclusion is not associated with OHRQOL when controlling for other oral diseases and sociodemographics.

Material and methods

This study was a cross-sectional evaluation of 440 young adults who arrived at the dental department of the Health Services of the Capital Defense Command, Seoul, Republic of Korea, seeking oral health screening and education between December 2013 and August 2014. The center is funded by the Republic of Korea Army to provide primary medical care to soldiers and local residents. Patients were considered as candidates for the study if they met the following criteria: (1) over 18 years old, (2) no current or past history of orthodontic treatment or orthognathic surgery, and (3) no severe dentofacial anomalies, such as a cleft lip or palate. Patients with serious medical conditions for which they had been hospitalized in the past 3 months or patients taking medications were excluded to prevent any possible confounding effects of these conditions or medications on the patient’s quality of life. Eleven patients refused to complete the questionnaire and were consequently excluded from the study. Thus, in total, 429 male and female patients, 18 to 32 years of age, were eligible for the study. This study was performed with the understanding of each participant, and written informed consent was obtained from each participant. This study followed the guidelines of the Declaration of Helsinki and was approved by the ethics committee of the Republic of Korea Army Headquarters.

Data were collected through both face-to-face interviews and clinical examinations. During the interviews, the patients provided information on their sociodemographics, including age, sex, and educational level. OHRQOL was assessed using the Korean version of the OHIP-14 questionnaire, which was previously translated and validated. All 14 OHIP questions ask how frequently the patient has experienced an adverse impact from oral conditions during the preceding 3 months. For example, 1 item asks “how often during the past 3 months have you had painful aching in your mouth because of problems with your teeth, mouth, or dentures?” The 14 questions cover the following 7 domains of oral health impact: functional limitation, physical pain, psychological discomfort, physical disability, psychological disability, social disability, and handicap. The responses followed a Likert-type scale coded as follows: 0, never; 1, hardly ever; 2, occasionally; 3, fairly often; and 4, very often. The OHIP-14 total score is calculated as the sum of the 14 scores, generating scores from 0 to 56, with a higher score indicating more negative impacts and a lower OHRQOL.

In the clinical assessments, dentition status was evaluated using the World Health Organization criteria for DMFT; the sum of the numbers of decayed teeth (DT), missing teeth (MT), or filled teeth (FT) was recorded. The teeth not counted included congenitally missing teeth, supernumerary teeth, unerupted teeth, teeth removed for reasons other than dental caries, and deciduous teeth retained in the permanent dentition. When a carious lesion or both a carious lesion and a restoration were present, the tooth was listed as a DT. When a tooth had been extracted because of caries (verified by interview), it was listed as a MT. When a permanent restoration was present and when a restoration was defective but not decayed, it was listed as a FT.

Periodontal health status was evaluated using the CPI. The teeth selected for evaluation included 8 first and second molars, the maxillary right central incisors, and the mandibular left central incisors. Clinical conditions were rated with the CPI as follows: 0, no sign of disease; 1, gingival bleeding after gentle probing; 2, supragingival and subgingival calculus; 3, pathological pocket of 4 to 5 mm in depth; and 4, pathological pocket of 6 mm or more in depth.

The presence and severity of signs and symptoms of TMD were detected using a questionnaire composed of questions regarding common TMD symptoms based on the modified Helkimo’s anamnestic index. TMD was diagnosed in patients with pain in their masticatory muscles, the temporomandibular joint area, or both, since such pain is the defining feature of TMD and the primary reason for seeking care.

Oral soft tissue diseases observed in the patient population included burning mouth syndrome, dry mouth, recurrent aphthous stomatitis, angular stomatitis, and herpetic gingivostomatitis of the oral mucosa. Pericoronitis of the wisdom teeth was included in the list of soft tissue diseases when the soft tissues surrounding a partially erupted third molar exhibited inflammation, and the participant had mild to moderate pain.

The dental health component of the index of orthodontic treatment need (IOTN-DHC) is a simple, easy, and reasonably reproducible method of determining the need for orthodontic treatment. It involves assessment of the following 10 malocclusion traits: overjet, reverse overjet, overbite, open bite, crossbite, crowding, impeded eruption, cleft lip and palate defects or other craniofacial anomalies, Class II and Class III buccal occlusions, and hypodontia. If multiple traits were present, the highest scoring trait was used to assess treatment need. The patient’s treatment needs are categorized as grade 1 (no treatment needed), grade 2 (little treatment needed), grade 3 (borderline treatment needed), and grades 4 and 5 (treatment needed).

Clinical assessments for malocclusion and common oral diseases were performed by a trained and calibrated dentist (S.C.). To assess intraexaminer reliability, 30 people who were not part of this study were randomly selected and reexamined at a 2-week interval after their first examinations. The kappa value was 0.85.

Statistical analysis

The Kolmogorov-Smirnov test was applied to verify the data distribution and normality. The data were not normally distributed; thus, nonparametric tests were used. Descriptive statistics, such as means and accompanying standard deviations, were used to describe the distribution of the OHIP-14 scores. To facilitate the comparison of oral conditions, we categorized the IOTN-DHC as “no treatment needed” (grades 1 and 2), “moderate treatment needed” (grade 3), and “extensive treatment needed” (grades 4 and 5).

The bivariate relationships between IOTN-DHC, common oral diseases, OHIP-14 total, and component domain scores were evaluated using the Kruskal-Wallis test with the Bonferroni correction and the Mann-Whitney U test.

Spearman rank correlation coefficients were used to explore the relationships between the IOTN-DHC and common oral diseases. To assess the strength of the correlation, r greater than 0.40 was considered to indicate a moderate to strong correlation, and r less than 0.40 was considered to indicate a weak correlation.

Unadjusted and adjusted multivariate regression analyses were conducted to determine whether IOTN-DHC was associated with OHRQOL when accounting for sociodemographic factors, including sex, age, educational level, and other common oral diseases. The selected independent variables for the sociodemographic factors and common oral diseases were categorized based on the data distributions to facilitate analytic analyses as follows: sex (male, 0; female, 1), age (18-22 years, 0; 23-27 years, 1; 28-32 years, 2), educational level (secondary education, 0; postsecondary education, 1), DT (DT <2, 0; DT ≥2, 1), DMFT (DMFT <6, 0; DMFT ≥6, 1), MT (no, 0; yes, 1), FT (FT <4, 0; FT ≥4, 1), CPI (CPI <3, 0; CPI ≥3, 1), TMD (no, 0; yes, 1), and oral soft tissue disease (no, 0; yes, 1). Because quality of life is relative rather than absolute, patients were categorized as having “poor OHRQOL” if their respective OHIP-14 total and its domain scores were in the upper quartile of the study group (highest 25% scores), and this was used as the dependent variable in the bivariate and multivariate regression analyses (0, not in the highest 25% quartile; 1, in the highest 25% quartile). The model-building strategy involved the inclusion of any variable for which the bivariate test has a P value lower than 0.05. Then, we performed backward elimination of any variable that did not contribute to the model on the grounds of the likelihood ratio test (logistic regression), using a significance cutoff of a P value of 0.05. Based on the dichotomized dependent variable, adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. All statistical analyses were performed using SPSS software for Windows (version 17.0; SPSS, Chicago, Ill).


Complete data were obtained for 429 young adults with a mean age of 22.4 years (SD, 1.4). Sex was not evenly distributed among the participants (76.5% men), nor was education, with 79.2% reporting a postsecondary education background. The sociodemographic profile and the common oral diseases observed in the study group are presented in Table I . The mean DT value was 1.8 (SD, 2.3; range, 0-12), the mean MT value was 0.1 (SD, 0.4; range, 0-5), the mean FT value was 4.3 (SD, 3.9; range, 0-17), and the mean DMFT index was 6.1 (SD, 4.0; range, 0-18). The prevalence of periodontal pocketing was assessed: 35.4% of the patients (n = 152) had pockets of 4 mm or greater depth (CPI ≥3). Forty-seven patients (11.0%) reported pain and symptoms in their masticatory muscles or temporomandibular joint area. Seventy patients (16.3%) reported current symptoms of moderate pain or swelling of their oral soft tissues.

Table I
Sociodemographic characteristics and common oral diseases (N = 429)
Variable Value
Sociodemographic characteristics
Sex (%)
Male 328 (76.5)
Female 101 (23.5)
Age (y), mean (SD) 22.4 (1.4)
Education level, n (%)
Up to secondary education 89 (20.8)
Postsecondary education 340 (79.2)
Common oral diseases
Dentition status, mean (SD)
DT 1.8 (2.3)
MT 0.1 (0.4)
FT 4.3 (3.9)
DMFT 6.1 (4.0)
Periodontal health status (CPI), n (%)
CPI score <3 277 (64.6)
CPI score ≥3 152 (35.4)
TMD, n (%)
No 382 (89.0)
Yes 47 (11.0)
Soft tissue diseases, n (%)
No 359 (83.7)
Yes 70 (16.3)

The means, standard deviations, highest 25% quartiles, and ranges of the OHIP-14 total score and its domain scores are presented in Table II . The mean OHIP-14 total score was 7.5 (SD, 6.6; range, 0-38). The physical pain domain of OHIP-14 had the highest reported impact with a mean of 1.8 (SD, 1.8).

Table II
OHIP-14 (N = 429)
OHIP-14 domain Mean (SD) Highest 25% score Range
Functional limitation 0.9 (1.3) 2 0-7
Physical pain 1.8 (1.8) 3 0-8
Psychological discomfort 1.7 (1.5) 3 0-8
Physical disability 1.1 (1.7) 2 0-8
Psychological disability 0.9 (1.4) 2 0-6
Social disability 0.6 (1.0) 1 0-6
Handicap 0.4 (1.0) 1 0-8
OHIP-14 total 7.5 (6.6) 10 0-38

The results from the Kruskal-Wallis test with the Bonferroni correction comparing groups defined by the IOTN-DHC are presented in Table III . One hundred eighty-five patients (43.1%) were scored as “no treatment needed” (grades 1 and 2), 108 (25.2%) were scored as “moderate treatment needed” (grade 3), and 136 (31.7%) were scored as “extensive treatment needed” (grades 4 and 5). When the mean OHIP-14 total scores were analyzed, the IOTN-DHC, DT, MT, CPI, and soft tissue diseases were shown to have negative impacts on OHRQOL. Patients needing extensive orthodontic treatment had significantly greater mean OHIP-14 total scores than the patients needing no treatment ( P <0.001).

Table III
Mean differences between the IOTN-DHC and common oral diseases for OHIP-14 total score and its domain scores (N = 429)
Variable n (%) Functional limitation Physical pain Psychological discomfort Physical disability Psychological disability Social disability Handicap OHIP-14 total
No treatment needed (reference group) 185 (43.1) 0.7 (1.1) 1.4 (1.5) 1.6 (1.5) 0.8 (1.5) 0.7 (1.3) 0.5 (0.9) 0.3 (0.8) 6.1 (5.3)
Moderate treatment needed 108 (25.2) 1.1 (1.5) 1.9 (2.0) 1.7 (1.6) 1.1 (1.6) 0.8 (1.3) 0.4 (1.0) 0.5 (1.2) 7.5 (7.0)
Extensive treatment needed 136 (31.7) 1.1 (1.4) 2.2 (1.8) 2.0 (1.5) 1.6 (2.1) § 1.1 (1.5) § 0.8 (1.2) 0.5 (1.0) 9.2 (7.3)
Common oral diseases
DT <2 261 (60.8) 0.9 (1.2) 1.7 (1.8) 1.6 (1.5) 0.9 (1.6) 0.8 (1.3) 0.6 (1.0) 0.3 (0.9) 6.8 (6.1)
DT ≥2 168 (39.2) 1.1 (1.4) 1.9 (1.7) 2.0 (1.6) 1.5 (1.9) 1.0 (1.5) 0.6 (1.0) 0.5 (1.1) 8.5 (7.1)
MT = 0 397 (92.5) 0.9 (1.3) 1.7 (1.8) 1.7 (1.5) 1.0 (1.6) 0.8 (1.3) 0.5 (1.0) 0.4 (1.0) 7.2 (6.3)
MT ≥1 32 (7.5) 1.1 (1.4) 2.6 (1.6) § 2.3 (1.7) 2.3 (2.4) 1.2 (1.8) 0.9 (1.2) 0.6 (1.0) 10.9 (8.7) §
FT <4 209 (48.7) 0.9 (1.3) 1.8 (1.8) 1.6 (1.7) 1.0 (1.6) 0.8 (1.4) 0.5 (1.0) 0.5 (1.1) 7.2 (6.9)
FT ≥4 220 (51.3) 1.0 (1.3) 1.8 (1.8) 1.8 (1.4) 1.3 (1.8) 0.9 (1.3) 0.6 (1.1) 0.4 (0.8) 7.8 (6.3)
DMFT <6 195 (45.5) 0.9 (1.3) 1.9 (1.9) 1.6 (1.6) 1.0 (1.7) 0.9 (1.5) 0.5 (1.1) 0.5 (1.1) 7.2 (6.9)
DMFT ≥6 234 (54.5) 1.0 (1.3) 1.7 (1.7) 1.9 (1.5) 1.2 (1.8) 0.9 (1.3) 0.6 (1.0) 0.4 (0.9) 7.6 (6.3)
CPI score <3 277 (64.6) 0.9 (1.3) 1.6 (1.7) 1.6 (1.5) 1.0 (1.7) 0.8 (1.2) 0.6 (1.0) 0.4 (0.8) 6.8 (6.0)
CPI score ≥3 152 (35.4) 1.0 (1.3) 2.1 (1.9) 1.9 (1.6) 1.3 (1.8) 1.0 (1.6) 0.6 (1.1) 0.5 (1.2) 8.6 (7.4)
No 382 (89.0) 0.9 (1.3) 1.8 (1.8) 1.8 (1.5) 1.1 (1.7) 0.8 (1.4) 0.6 (1.0) 0.4 (0.8) 7.3 (6.2)
Yes 47 (11.0) 1.5 (1.6) 1.8 (1.8) 1.6 (1.6) 1.3 (2.0) 1.1 (1.5) 0.7 (1.4) 0.8 (1.7) 8.8 (8.9)
Soft tissue diseases
No 359 (83.7) 0.9 (1.3) 1.6 (1.7) 1.6 (1.6) 1.0 (1.6) 0.8 (1.4) 0.6 (1.1) 0.4 (1.0) 7.1 (6.5)
Yes 70 (16.3) 0.9 (1.2) 2.6 (1.9) 2.2 (1.3) 1.7 (2.1) § 1.1 (1.4) 0.5 (0.8) 0.4 (1.1) 9.5 (6.6) §
Values are expressed as mean (standard deviation).

Kruskal-Wallis test with the Bonferroni correction.

Mann-Whitney U test.

P <0.05.

§ P <0.01.

P <0.001.

As shown in Table IV , Spearman correlation coefficients showed weak positive correlations between IOTN-DHC and previous caries (DT, MT, and DMFT), and between IOTN-DHC and CPI, demonstrating a weak association of malocclusion with the patients’ physical conditions ( P <0.01, with correlation coefficients ranging from 0.151 to 0.339).

Table IV
Correlation coefficients between IOTN-DHC and common oral diseases (N = 429)
Common oral diseases
DT MT FT DMFT CPI TMD Soft tissue disease
IOTN-DHC 0.151 0.339 0.08 0.164 0.194 0.00 −0.09

P <0.01.

Two key factors were found to be significantly associated with poor OHRQOL (upper quartile OHIP-14 scores) after adjusting for sex, age, educational level, and common oral diseases ( Table V ). Patients with oral soft tissue diseases were more than 2.8 times as likely to have poor OHRQOL as the “no treatment needed” reference group (OR, 2.85; 95% CI, 1.60-5.08; P <0.001). Patients requiring extensive orthodontic treatment were more than 2.7 times as likely to have poor OHRQOL as the corresponding “no treatment needed” reference group (OR, 2.74; 95% CI, 1.60-4.59; P <0.001). Dental caries was associated with poor OHRQOL, but this was not statistically significant (OR, 1.53; 95% CI, 0.96-2.46; P >0.05). A significant interrelationship was observed between malocclusion and some of its dependent variables, such as the functional limitation, physical pain, and social disability domains ( Table VI ). These domains of OHIP-14 occurred about 2 times more often among patients with a severe malocclusion than in those without a severe malocclusion.

Table V
Unadjusted and adjusted multivariate regression analysis predicting OHIP-14 total scores (N = 429)
Independent variable Unadjusted OR 95% CI P value Adjusted OR 95% CI P value
Male 1.00 (reference)
Female 1.14 0.91-1.45 0.244
Age (y)
18-22 1.00 (reference)
23-27 1.06 0.66-1.70 0.819
28-32 2.11 0.35-12.91 0.417
Education level
Up to secondary education 1.00 (reference)
Postsecondary education 1.09 0.60-1.98 0.786
No treatment needed 1.00 (reference) 1.00 (reference)
Moderate treatment needed 1.44 0.80-2.59 0.224 1.55 0.85-2.83 0.155
Extensive treatment needed 2.61 1.55-4.38 <0.001 2.74 1.60-4.59 <0.001
Common oral diseases
DT <2 1.00 (reference) 1.00 (reference)
DT ≥2 1.51 0.97-2.35 0.071 1.53 0.96-2.46 0.075
MT = 0 1.00 (reference)
MT ≥1 1.45 0.66-3.16 0.356
FT <4 1.00 (reference)
FT ≥4 1.23 0.79-1.92 0.351
DMFT <6 1.00 (reference)
DMFT ≥6 1.04 0.67-1.62 0.870
CPI score <3 1.00 (reference)
CPI score ≥3 1.52 0.97-2.39 0.068
No 1.00 (reference)
Yes 1.36 0.70-2.65 0.371
Soft tissue disease
No 1.00 (reference) 1.00 (reference)
Yes 2.26 1.32-3.89 0.003 2.85 1.60-5.08 <0.001
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Apr 6, 2017 | Posted by in Orthodontics | Comments Off on Impact of malocclusion and common oral diseases on oral health–related quality of life in young adults
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