The aim of this study was to evaluate the effect of malocclusion severity on oral health–related quality of life and food intake ability in adult patients, controlling for sex, age, and the type of dental clinic visited.
The sample consisted of 472 Korean patients (156 male, 316 female) with a mean age of 21.1 (SD, 8.6) years in a dental hospital and a private clinic. The correlations between the Korean version of the Oral Health Impact Profile-14 (OHIP-14K), subjective food intake ability (FIA) for 5 key foods, and Index of Orthodontic Treatment Need-Dental Health Component (IOTN-DHC) were investigated.
The mean IOTN-DHC and OHIP-14K scores were significantly higher for the dental hospital patients than for the private clinic patients (IOTN-DHC, P <0.001; OHIP-14K, P <0.05). Malocclusion severity was significantly higher in male than in female subjects ( P <0.001). Older patients perceived their oral health–related quality of life more negatively than did the teens ( P <0.001). As the severity of the malocclusion increased, oral health–related quality of life and masticatory function worsened (OHIP-14K, P <0.001; FIA, P <0.05).
As the severity of the malocclusion and the age of the patients increased, oral health–related quality of life and masticatory function relatively deteriorated. This finding provides evidence that severe malocclusions are associated with lower quality of life and less masticatory efficiency in older patients.
Malocclusion severity was compared in private practice and dental hospital patients.
Malocclusions were more severe in dental hospital patients ( P <0.001).
Masticatory efficiency was decreased in older patients, particularly those in their 30s.
Negative perceptions of oral health–related quality of life (OHRQoL) were increased in older patients.
As malocclusion severity increased, OHRQoL worsened and masticatory efficiency fell.
People with a severe malocclusion can be less self-confident in social relationships because of their dentition and facial morphology, since a severe malocclusion can affect how a person is perceived in a negative manner throughout his or her entire life. von Wezel et al reported that facial satisfaction is a significant predictor for all expectations of orthodontic treatment in subjects 17 years and older. Thus, patients with a severe malocclusion expect psychological comfort by esthetic improvement after orthodontic treatment as well as improvement in oral function.
Previous epidemiologic investigations on oral health have depended on clinical indexes, such as the Community Periodontal Index of Treatment Needs or the Decayed, Missing, and Filled teeth index. Consequently, these studies have limitations because of the emphasis only on the presence or absence of oral disease. To overcome these limitations, the oral health–related quality of life (OHRQoL) index was introduced and has recently gained more attention. OHRQoL is defined as the “absence of physical and psychological negative effects by oral health status in daily life and self-confidence about the maxillofacial region.” Patients desire orthodontic treatment to gain psychological stability by functional and esthetic improvements instead of merely treating oral disease. Thus, OHRQoL may be the most appropriate method to measure the necessity for and the results of orthodontic treatment.
A person’s self-perceived masticatory function has a great effect on his or her daily life. An improvement in masticatory function by orthodontic treatment can maintain the healthy status of patients via the intake of various foods and improvement in their quality of life. Masticatory function can be evaluated by subjective and objective methods. Subjective methods measure masticatory function using a questionnaire or an interview to determine food intake ability (FIA) of various types of foods. Clinically, the FIA questionnaire was developed as a simple and easy method to assess subjective masticatory function.
The aim of this study was to investigate the effects of malocclusion severity on OHRQoL and chewing ability. The Korean version of the Oral Health Impact Profile-14 (OHIP-14K) survey was used to evaluate OHRQoL, and the FIA questionnaire was used to evaluate chewing ability in patients who came for orthodontic treatment. The null hypothesis was that malocclusion severity was not correlated with OHRQoL and FIA in patients, controlling for sex, age, and type of dental clinic visited.
Material and methods
This study was a cross-sectional evaluation of 472 patients aged 21.1 ± 8.6 years who visited the Department of Orthodontics at Yonsei University Dental Hospital in Seoul, Korea, and private clinics in Gyeonggi province from April 2012 to January 2014. In this study, 228 patients were from the dental hospital, and 244 patients were from the private practices (316 female, 156 male) ( Table I ).
|Total||244 (51.7)||228 (48.3)||472 (100)|
|Female||188 (59.5)||128 (40.5)||316 (66.9)|
|Male||56 (35.9)||100 (64.1)||156 (33.1)|
|Teens||97 (45.3)||117 (54.7)||214 (45.3)|
|20-29||111 (57.2)||83 (42.8)||194 (41.1)|
|30-39||28 (60.9)||18 (39.1)||46 (9.7)|
|Over 40||8 (44.4)||10 (55.6)||18 (3.8)|
Patients with the following conditions were excluded from this study: (1) severe dentofacial anomalies, including cleft lip and palate; (2) current or past history of orthodontic treatment and orthognathic surgery; and (3) serious medical conditions for which they had been hospitalized in the past 3 months, or patients taking medications. These criteria were used to form a homogeneous group by excluding factors affecting the participants’ quality of life. This study was performed with the understanding of each participant, and written informed consent was obtained from each subject. This study followed the guidelines of the Declaration of Helsinki and was approved (2-2013-0052) by the institutional review board of Yonsei University Dental Hospital.
Data were collected in face-to-face interviews. During the interviews, the patients provided information on their sex and age. OHRQoL was assessed using the OHIP-14K questionnaire, which was previously translated and validated. All 14 OHIP-14K questions asked how frequently the patient had experienced an adverse effect from oral conditions during the preceding 3 months. The 14 questions covered these 7 domains of oral health: functional limitation, physical pain, psychological discomfort, physical disability, psychological disability, social disability, and handicap. The responses were recorded with a Likert-type scale coded as follows: 0, never; 1, hardly ever; 2, occasionally; 3, fairly often; and 4, very often. The OHIP-14K total score was calculated as the sum of the 14 scores, generating scores from 0 to 56, with higher scores indicating poor OHRQoL.
To evaluate subjective masticatory ability, the FIA self-assessed questionnaire requested the patients’ masticatory abilities for 5 key foods (dried cuttlefish, raw carrots, peanuts, cubed white radish kimchi, and caramel) according to previous studies. The subjects answered the FIA questionnaires using a 5-point Likert scale: cannot chew at all (1 point), difficult to chew (2 points), cannot say either way (3 points), can chew some (4 points), and can chew well (5 points). The total FIA score was calculated as the average of the 5 key foods, which generated scores from 5 to 25, with higher scores indicating good chewing ability. A lower score indicated poor chewing ability.
The Dental Health Component of the Index of Orthodontic Treatment Need (IOTN-DHC) involves an 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. The IOTN-DHC consists of 5 grades. Grades 1 and 2 describe conditions that do not require treatment or require minimal treatment. Grade 3 describes a moderate or borderline need for treatment. Grades 4 and 5 describe conditions that require treatment.
For the OHIP-14K and the FIA questionnaire, the reliability of internal consistency was verified by measuring the Cronbach α coefficient. Forty people who did not participate in this study were randomly selected and reexamined 2 weeks after their initial examination. The Cronbach α values were 0.860 for the OHIP-14K and 0.886 for the FIA questionnaire. The IOTN-DHC was measured by 2 trained and calibrated orthodontists (J-S.K., J-Y.C.). To assess interexaminer and intraexaminer reliability, the kappa values were 0.99 for interrater reliability and 0.988 and 0.99 for intrarater reliability.
All statistical analyses were performed with SPSS software for Windows (version 21.0; SPSS, Chicago, Ill). The Kolmogorov-Smirnov test was applied to confirm the data distribution and normality.
Descriptive analyses, including the means and standard deviations, were performed with respect to general characteristics, including sex and age, type of orthodontic clinic visited (dental hospital or private clinic), IOTN-DHC, OHIP-14K, and FIA questionnaire. The chi-square test, Mann-Whitney U test, independent t test, or 1-way analysis of variance was used to evaluate the differences in the IOTN-DHC, OHIP-14K, and FIA questionnaire according to sex, age, and type of orthodontic clinic. Spearman rank correlation coefficients were used to examine relationships between the variables. To assess the strength of the correlation, r >0.50 was considered to indicate a moderate to strong correlation, and r <0.50 indicated a weak correlation. Multiple linear regression analysis was used to investigate the effects of malocclusion severity on quality of life and masticatory function, controlling for sex, age, and type of dental clinic. The selected independent variables for sex and type of clinic were categorized on the basis of data distributions to facilitate analytic analyses as follows: sex (female, 0; male, 1) and type of clinic (private, 0; dental hospital, 1).
There were sex differences in patients between the dental hospital and the private clinics. The proportion of female patients in private clinics was greater than in the dental hospital ( P <0.001). However, there was no statistically significant difference in age between the 2 clinics ( Table I ).
Malocclusion severity was significantly greater in the dental hospital patients (mean rank, 301.60) than in the private clinic patients (mean rank, 175.67) ( P <0.001) ( Table II ). The proportion of patients with severe malocclusion was significantly higher in the dental hospital than in the private clinic ( P <0.001). One hundred thirty-seven patients (60.1%) in the dental hospital were scored at grades 4 and 5. Patients in the dental hospital had significantly greater mean OHIP-14K total scores than did the patients in the private clinics ( P <0.05).
|IOTN-DHC n (%)||<0.001 ∗|
|Grade 1||39 (8.3)||38 (15.6)||1 (0.4)|
|Grade 2||94 (19.9)||72 (29.5)||22 (9.6)|
|Grade 3||137 (29.0)||69 (28.3)||68 (29.8)|
|Grade 4||134 (28.4)||65 (26.6)||69 (30.3)|
|Grade 5||68 (14.4)||0 (0.0)||68 (29.8)|
|Mean rank||175.67||301.60||<0.001 †|
|Total||8.32 (7.35)||7.55 (5.89)||9.15 (8.59)||0.019|
|Functional limitation||0.61 (0.68)||0.56 (0.60)||0.68 (0.75)||0.057|
|Physical pain||0.78 (0.82)||1.46 (1.48)||0.83 (0.89)||0.189|
|Psychological discomfort||0.94 (0.96)||1.08 (1.08)||1.60 (1.63)||0.002|
|Physical disability||0.61 (0.78)||1.10 (1.41)||0.67 (0.85)||0.104|
|Psychological disability||0.45 (0.63)||0.88 (1.18)||0.46 (0.67)||0.733|
|Social disability||0.45 (0.67)||0.83 (1.18)||0.49 (0.75)||0.241|
|Handicap||0.33 (0.60)||0.57 (0.99)||0.38 (0.67)||0.093|
|FIA||22.15 (3.82)||22.24 (3.95)||22.07 (3.69)||0.625|
Malocclusion severity was significantly higher in male subjects (mean rank, 279.75) than in female subjects (mean rank, 215.15) ( P <0.001) ( Table III ). The proportion of male patients with a severe malocclusion was significantly higher than female patients ( P <0.001). Ninety males (57.7%) were scored at grades 4 and 5. There was no difference in total OHIP-14K scores and the subdomains between the sexes.
|IOTN-DHC n (%)||<0.001 ∗|
|Grade 1||39 (8.3)||35 (11.1)||4 (2.6)|
|Grade 2||94 (19.9)||70 (22.2)||24 (15.4)|
|Grade 3||137 (29.0)||99 (31.3)||38 (24.4)|
|Grade 4||134 (28.4)||78 (24.7)||56 (35.9)|
|Grade 5||68 (14.4)||34 (10.8)||34 (21.8)|
|Mean rank||215.15||279.75||<0.001 †|
|Total||8.32 (7.35)||8.25 (7.26)||8.47 (7.55)||0.759|
|Functional limitation||0.61 (0.68)||0.60 (0.66)||0.63 (0.72)||0.643|
|Physical pain||0.78 (0.82)||0.78 (0.85)||0.78 (0.75)||0.930|
|Psychological discomfort||0.94 (0.96)||0.94 (0.94)||0.92 (1.01)||0.849|
|Physical disability||0.61 (0.78)||0.59 (0.79)||0.65 (0.75)||0.407|
|Psychological disability||0.45 (0.63)||0.46 (0.63)||0.42 (0.62)||0.489|
|Social disability||0.45 (0.67)||0.45 (0.67)||0.46 (0.68)||0.873|
|Handicap||0.33 (0.60)||0.31 (0.59)||0.37 (0.63)||0.309|
|FIA||22.15 (3.82)||22.12 (3.88)||22.22 (3.72)||0.798|
Among the questions regarding quality of life, patients in their teens positively assessed their OHRQoL in 6 subdomains except for the physical pain domain. In contrast, other age groups had a relatively negative view of their quality of life. In particular, with regard to psychological discomfort, the OHRQoL was assessed negatively in patients in their 20s or older compared with patients in their teens ( P <0.001). Regarding the FIA questionnaire, masticatory function was significantly higher in patients in their teens than in those in their 30s (teens: mean, 22.43 ± 3.41; 30s: mean, 20.85 ± 4.70) ( P <0.05) ( Table IV ).
|Total||Teens a||20–29 b||30–39 c||Over 40 d||P value||Post hoc|
|Mean rank||194.86||211.52||221.5||258.97||0.006||d>b,c>a ∗|
|Total||8.32 (7.35)||6.90 (6.46)||9.04 (7.58)||11.76 (8.85)||8.83 (7.21)||<0.001||c>b,d>a|
|Functional limitation||0.61 (0.68)||0.55 (0.64)||0.64 (0.71)||0.87 (0.70)||0.47 (0.63)||0.021||c>a,b>d|
|Physical pain||0.78 (0.82)||0.75 (0.77)||0.75 (0.85)||1.09 (0.86)||0.67 (0.87)||0.057|
|Psychological discomfort||0.94 (0.96)||0.73 (0.87)||1.12 (1.01)||1.10 (1.07)||1.00 (0.79)||<0.001||b,c>d>a|
|Physical disability||0.61 (0.78)||0.48 (0.73)||0.66 (0.77)||0.91 (0.96)||0.67 (0.79)||0.003||c>b,d>a|
|Psychological disability||0.45 (0.63)||0.33 (0.54)||0.52 (0.66)||0.71 (0.74)||0.44 (0.62)||<0.001||c>b,d>a|
|Social disability||0.45 (0.67)||0.37 (0.60)||0.48 (0.72)||0.67 (0.70)||0.56 (0.73)||0.031||c>b,d>a|
|Handicap||0.33 (0.60)||0.24 (0.53)||0.36 (0.60)||0.53 (0.81)||0.61 (0.72)||0.003||d>c>a,b|
|FIA||22.15 (3.82)||22.43 (3.41)||22.31 (3.69)||20.85 (4.70)||20.61 (6.08)||0.021||a>c|