Impact of malocclusion on oral health related quality of life in young people
© Masood et al.; licensee BioMed Central Ltd. 2013
Received: 25 September 2012
Accepted: 28 December 2012
Published: 26 February 2013
The objectives for this study were to assess Oral Health Related Quality of Life (OHRQoL) in young people aged 15–25 who sought orthodontic treatment, and to measure the association between orthodontic treatment need (using the IOTN), sex, age and education level, and oral health related quality of life (OHRQoL).
Survey of a consecutive series of 323 young adults aged 15 to 25 years, attending orthodontic clinics at the Faculty of Dentistry, Universiti Teknologi MARA. Participants completed the Oral Health Impact Profile-14 (OHIP-14) and had a clinical examination including the Index of Orthodontic Treatment Need- Dental Health Component (IOTN-DHC). Data analyses included descriptive statistics, One-way ANOVA and bivariate and multivariate regression models.
The mean overall score (± SD) for OHIP-14 in young people aged 15–25 was 22.6 ± 12.5. The psychological discomfort domain was the domain where highest impact was recorded with a mean (± SD) of 4.0 ± 1.9. The regression analyses showed a significant association of IOTN-DHC with overall OHIP-14 score (p < 0.05). Although females reported a slightly higher impact than males, this was not significant in both bivariate and multivariate analyses. Age group had a significant negative association with overall OHIP-14 score (p < 0.05). The 15–18 year old group showed the highest impact on their quality of life due to malocclusion. Participants with a university education report a significantly higher impact on OHRQoL as compared to participants with only secondary education.
Malocclusion has a significant negative impact on OHRQoL and its domains. This is greatest for the psychological discomfort domain. Younger people and those with a university education report higher levels of impact. There was no reported difference in impact between male and females.
The concept of Oral Health-Related Quality of Life (OHRQoL) corresponds to the impact of oral health or disease on an individual’s daily functioning, well-being or overall quality of life . Conditions affecting oral health, including malocclusion, are highly prevalent, and have consequences not only for physical and economical well being, but can also impair quality of life by affecting function, appearance, interpersonal relationships, socializing, self-esteem and psychological well-being . Research on the physical, social, and psychological impact of malocclusion on OHRQoL sheds light on the effects of malocclusion on people’s lives and provides a greater understanding of the demand for orthodontic treatment beyond the measurement of clinical parameters. In addition, since social and psychological effects are often the key motives for seeking orthodontic treatment, OHRQoL can be considered the best measurement for orthodontic treatment need and outcome . Such research may be of great value to researchers, health planners, and oral health care providers .
Malocclusion differs from the majority of medical and dental conditions in that it is ‘a set of dental deviations’ rather than a disease, and orthodontic treatment does not cure a condition but rather corrects variations from an arbitrary norm . This has led to debate about defining the point at which the extent of variation means that orthodontic treatment is desirable . Further it has been suggested that the majority of oral health measures developed in dentistry are not applicable to orthodontic patients because most malocclusions are asymptomatic and related to esthetic challenges, as opposed to loss of function [4, 6]. Additionally, a malocclusion can be perceived differently by the affected person, and a person’s degree of awareness of their malocclusion might not be related to its severity . Therefore, when evaluating the impact of a malocclusion, it is important to consider the different domains that can be affected and their relationships to the severity of malocclusion. Some people with a severe malocclusion are satisfied with or indifferent to their dental esthetics, whereas others are concerned about minor irregularities .
Need assessment for orthodontic treatment in dental clinics is traditionally normatively assessed using measures such as the Index of Orthodontic Treatment Need (IOTN [3, 7]. However there is evidence that many adolescents with normative orthodontic treatment need measured by IOTN experience no impacts on their OHRQoL [8, 9]. Therefore, the use of IOTN alone to establish orthodontic treatment need may be potentially problematic since some patients who have no psychosocial need for treatment would be perceived as requiring treatment [10, 11]. The use of OHRQoL measures in addition to professional indices offers a potentially useful combination [7, 12]. OHIP-14 can be used as a potential proxy measure to replace subjective clinical opinions for determining treatment need in youth .
Previous research exploring the relationship between malocclusions and OHRQoL, as well as the impact of orthodontic treatment on OHRQOL has been equivocal. Some authors found a strong relationship between malocclusion or orthodontic treatment need and OHRQoL [12, 14, 15], but others reported no clear relationship [4, 16, 17]. Therefore, this study was conducted to assess OHRQoL in young people aged 15 to 25 years who sought orthodontic treatment in the Department of Orthodontics at Universiti Teknologi MARA Malaysia and to measure the association between orthodontic treatment need (using the IOTN), sex, age and education level, and OHRQoL.
Participants in the study were children and young adults aged 15 to 25 years, attending orthodontic clinics at the Faculty of Dentistry, Universiti Teknologi MARA, in Malaysia. The orthodontic clinic at Faculty of Dentistry UiTM is the biggest orthodontic clinic in Shah Alam city and nearby areas. It is a government clinic and all the patients who are judged to have a clinical need or who request for orthodontic treatment are referred to the Orthodontic clinic at Faculty of Dentistry UiTM.
All children and young adults aged 15 to 25 years, who either self-referred or were referred by their general dental practitioners to the orthodontic clinics at the Faculty of Dentistry, Universiti Teknologi MARA, in Malaysia. Most participants were motivated by their parents to seek orthodontic consultation. A convenience consecutive sampling approach was used. The participants were recruited at their first visit for orthodontic screening before starting any orthodontic treatment. The participants or where appropriate their parents were fully informed of the nature of the study and signed a consent form agreeing to participate in the study. To be eligible, the participant had to be in good general health. Participants who required a surgical intervention or who had chronic medical conditions, had received previous orthodontic treatment, had severe dentofacial anomalies such as cleft lip and palate, untreated dental caries, or poor periodontal health status as indicated by a community periodontal index score of 3 or more were excluded. This was to prevent possible confounding effects of these conditions on the participants’ quality of life and to achieve a homogeneous group population. The Universiti Teknologi MARA (UiTM) Research Ethics Board approved all study procedures.
Outcome variable (OHIP-14)
OHRQoL was measured using a Malay language translated version of the 14-item Oral Health Impact Profile (OHIP-14). It has been shown that the OHIP-14 has good reliability, validity, and precision [18, 19]. The Malay version of OHIP-14 has also been found to be valid and reliable and had been used in a nationally representative survey to determine population estimates for prevalence, extent, and severity of impact on OHRQoL . OHIP-14 assesses the burden of oral health status on life quality across seven conceptual domains (two items per domain) by asking respondents to rate the frequency of occurrence of a particular problem as captured by the individual item. The dimensions are: functional limitation, physical pain, psychological discomfort, physical disability, psychological disability, social disability, and handicap . These dimensions are based on Locker’s conceptual model of oral health . Responses are rated on a 5-point Likert scale: 0 = never; 1 = hardly ever; 2 = occasionally; 3 = fairly often; 4 = very often/every day. Summary OHIP-14 scores can range from 0 to 56 and are calculated by summing the ordinal values for the 14 items. Domain scores can range from 0 to 8. Higher OHIP-14 scores indicate worse, and lower scores indicate better, oral health-related quality of life. All participants completed the OHIP-14 before any orthodontic treatment.
After participants were interviewed using OHIP-14, clinical examinations were conducted to assess normative orthodontic treatment need using the Dental Health Component (DHC) of the Index of Orthodontic Treatment Need (IOTN). This index has gained international acceptance because it is valid, reliable and easy to use . For the Dental Health Component (DHC) of IOTN, 10 traits of malocclusion are assessed: overjet, reverse overjet, overbite, open bite, cross bite, crowding, impeded eruption, defects of cleft lip and palate as well as any craniofacial anomaly, Class II and Class III buccal occlusions, and hypodontia. Only the highest scoring trait is used to assess treatment need . The treatment needs of the patients were categorized as Grade 1 (no treatment need), Grade 2 (little treatment need), Grade 3 (borderline need), and Grade 4 and 5 (high treatment need). Age, sex, and educational background were recorded because of their potential associations with both the outcome and explanatory variables.
IOTN-DHC ratings were recorded independently by two trained and calibrated examiners. To assess intra- and inter-examiner reliability, 20 young people who were not part of the present study were randomly selected and re-examined at a 2 to 4 week interval after their first examinations. Intra-examiner reliability for the IOTN-DHC examiners was almost perfect with kappa = 0.91 and 0.96. Excellent agreement was found for the inter-examiner reliability with Kappa = 0.85.
The data were analyzed by using R-Project software (version 2.13.2) . Additive scale and subscale scores for the OHIP-14 were calculated by summing the item response codes. Data analyses included descriptive statistics and One-way ANOVA with Tukey Post Hoc test to assess differences in OHRQoL across groups defined by IOTN-DHC. Bivariate and multivariate regression models were used to measure the association between OHRQoL and IOTN-DHC, sex, age and education level. In linear regression analysis, OHIP-14 scores were used as continuous outcome variable, IOTN-DHC was recoded as a series of dummy variables. Age was recoded into three categories, and dummy variables calculated for use in the regression analyses. Bivariate linear regressions were performed individually in separate models with each explanatory variable; model 1 included IOTN-DHC (No treatment required = 0, little treatment required = 1, borderline treatment required = 2 and high treatment required = 3), model 2 included gender (Male = 0 and Female = 1), model 3 included age groups (15–18 years = 0, 19–21 years = 1, 22–25 years = 2) and model 4 included educational level (secondary education = 0 and university education = 1). Finally, all the explanatory variables were combined into a multivariate linear regression model.
A total of three hundred and twenty five young adults participated in this study, two records were excluded from analysis due to missing values in their OHIP-14 questionnaires. The mean (± SD) age was 22.05 (± 3.20) years which included 63 participants (19.5%) aged 15–18 years, 89 (27.5%) aged 19–21 years and 171 (53.0%) in the 22–25 age group. Most of the participants (273, 85.4%) had education to university level and 49 (15.1%) were educated only to secondary level. Of the 323 participants, 132 (40.8%) were boys and 191 (59.1%) were girls. Normative treatment need according to IOTN-DHC was present in 252 (78.0%) participants, the remaining 71 participants (22%) did not have any normative treatment need for orthodontic treatment as assessed by the IOTN-DHC.
Mean, standard deviation (SD), median and range observed in Oral Health Impact Profile- 14 (OHIP- 14)
Mean ± SD
3.6 ± 2.1
3.3 ± 1.7
4.0 ± 1.9
3.2 ± 2.0
2.6 ± 1.8
2.7 ± 2.1
3.2 ± 2.0
22.6 ± 12.5
Mean scores in overall and seven domains of Oral Health Impact Profile- 14 (OHIP- 14) OHIP -14 among different types of Index of Orthodontic Treatment Need- Dental Health Component (IOTN- DHC) groups
No treatment need (Reference Group)
2.2 ± 1.8
2.1 ± 1.6
2.6 ± 1.8
2.0 ± 1.6
2.0 ± 1.6
1.8 ± 1.6
2.4 ± 1.7
15.2 ± 10.9
Little treatment need
3.2 ± 1.9
3.0 ± 1.6
3.8 ± 1.8***
3.0 ± 1.9
2.0 ± 1.6
2.2 ± 2.0
2.9 ± 1.8
20.2 ± 11.1*
Borderline treatment need
3.9 ± 2.0**
3.4 ± 1.3**
4.5 ± 1.6***
3.4 ± 1.9*
2.9 ± 1.7*
2.9 ± 1.9*
3.2 ± 1.9
24.1 ± 11.2**
High Treatment need
4.8 ± 2.0***
4.2 ± 1.7***
4.9 ± 1.7***
4.0 ± 2.0***
3.6 ± 1.9***
3.8 ± 2.2***
4.1 ± 2.0**
29.5 ± 12.5***
Bivariate and multivariate linear regression models showing association of Oral Health Impact Profile- 14 (OHIP- 14) with Index of Orthodontic Treatment Need- Dental Health Component (IOTN- DHC) and other covariates
No treatment need
Little treatment need
Borderline treatment need
High Treatment need
15 - 18 years
19 - 21 years
22 - 25 years
R2 = 0.22
This study evaluated the impact of orthodontic treatment need on overall OHRQoL and its various domains in 15–25 year olds seeking orthodontic treatment at UiTM Dental clinics. Nearly 1.5 times as many girls as boys sought orthodontic treatment at the university clinic during the recruitment period for this study, this agrees with previous studies which show higher utilization of orthodontic treatment services by females [3, 15, 26, 27]. This may suggest that women are responding to social expectations of the importance of esthetics rather than an objectively greater orthodontic treatment need in comparison to their male counterparts . Alternatively parents may be more prone to seek orthodontic treatment for their female children than their male. It was expected that the impact of malocclusion on quality of life would be significantly greater in girls as compared to boys, since boys may be less self-conscious about their appearance . Young women were more likely to have had a higher dental impact than male youths but the difference was not significant. Similar findings were reported by Oliveira and Sheiham (29) in adolescents  and other age groups by Birkeland et al., Hunt et al., 57 and Bernabe ´et al. [8, 30, 31]. However, Peres (2008) et al. found females adolescents had greater dissatisfaction with their dental appearance . It is possible that the lack of a difference in impact between males and females in this and other studies is due to selection: the reluctance of males to attend clinics resulting in those who feel little or no impact not attending.
Bivariate and multivariate regression analysis showed that those participants with more severe malocclusions reported a greater impact on quality of life after controlling for the effects of covariates (sex, age, and education level). Young people with little, borderline and high orthodontic treatment need had 5, 9 and 15 points higher scores on the OHIP-14 scale, respectively, when compared to the "no treatment need" group. This relationship between malocclusions and OHRQOL mirrors that found by Heravi et.al., Bernabe et. al. and Foster-Page et. al. [8, 14, 28], but not by Taylor et al. or Oliveria et al. (2008)[16, 33]. There are several possible reasons for such differences. First, the use of different measures to measure quality of life. Secondly it is possible that different age groups have a different perception towards esthetics and quality of life, and studies have varied widely in the age groups studied. In addition, different cultures, traditions, and social norms across countries may influence the perception of esthetics different in each society. Finally, a high frequency or severity of malocclusions in some races and ethnic groups can make malocclusion perceived as normal for the given group and vice versa .
A negative association was observed between age and impact on quality of life due to malocclusion, the impact of malocclusion decreases as age increases. This may be the result of ‘response shift’ with age – the longer an individual lives with a malocclusion, the greater the likelihood that they will adjust to the limitations it places upon their activities thereby reducing impact. In order to explore this, future studies should look at treatment need changes with age. Education level had a positive association in the multivariate regression analysis which may be due to increased self awareness and self esteem with increasing education.
Exploring each OHIP-14 domain, IOTN scores were most closely correlated with impact on the psychological discomfort and functional limitation domains of OHRQoL. Similar results have been reported in children aged 11–14 years [4, 14] and in young adults [3, 29]. This is logical when we consider that the most common reason for seeking orthodontic treatment is to correct dental esthetics and improve self-esteem . Thus, orthodontists should be aware that young patients might expect orthodontic treatment to provide not only improved oral functioning and health but enhancement of esthetics, self-esteem and social life . When these expectations are not met this may lead to dissatisfaction with treatment outcome. The use of the OHRQoL measure as a part of the diagnostic procedure can provide information on priorities for treatment in order to maximize patient satisfaction [3, 12, 35]. In this study, significant impact on the handicap domain was only present when patients had high treatment need. Some authors have suggested that malocclusion might become handicapping not because of the functional disability, but because it can adversely affect social relationships and self-perceptions .
The findings of this study must be tempered by a consideration of its limitations. The participants in this study were 15–25 year-old patients seeking orthodontic treatment at a university clinic in a large urban city in Malaysia. Therefore the results from this study cannot be extrapolated to the entire youth population who may have differing levels of malocclusion and orthodontic treatment needs and, therefore, different impacts on their daily activities . Although many studies have assessed the impact of oral conditions on children’s quality of life using convenience samples in hospitals or universities [1, 4, 14], future studies should be based on a representative sample with or without normative need. Furthermore participants may have exaggerated the impact in order to increase their chances to obtain treatment for their malocclusion.
OHIP-14 and IOTN-DHC were used in this study, both of these instruments are valid and reliable but have some limitations . IOTN may be a relatively insensitive instrument to measure minor occlusal traits and irregularities which mostly affect patient appearance and about which a patient is deeply concerned [8, 10]. The OHIP-14 was developed for adults, but has been successfully applied to adolescents by many authors [3, 27, 29, 37] because adolescents of 12 years of age and above are capable of abstract thinking, reasoning about the timing of past events, and relating them with good or bad experiences . Another limitation with OHIP-14 is, it does not elicit the specific cause(s) of the impacts recorded, which can be related to a variety of oral health conditions and not necessarily the subject’s malocclusion. However the participants in this study were selected to be free of untreated caries, periodontal disease and any other oral health problem suggesting the results form OHIP-14 were not confounded with other oral health condition.
Malocclusion has a negative impact on oral health related quality of life and its domains, this is highest for the psychological discomfort domain. Reported impact is greatest in younger people and those with a university education, whereas this study did not find any significant difference in the impact on oral health related quality of life in male and females.
- Aldrigui JM, Abanto J, Carvalho TS, Mendes FM, Wanderley MT, Bonecker M, Raggio DP: Impact of traumatic dental injuries and malocclusions on quality of life of young children. Health Qual Life Outcomes 2011, 9: 78. 10.1186/1477-7525-9-78PubMed CentralPubMedView ArticleGoogle Scholar
- Masood M, Masood Y, Saub R, Newton JT: Need of minimal important difference for oral health-related quality of life measures. J Public Health Dent 2012.Google Scholar
- Feu D, de Oliveira BH, de Oliveira Almeida MA, Kiyak HA, Miguel JA: Oral health-related quality of life and orthodontic treatment seeking. Am J Orthod Dentofacial Orthop 2010, 138: 152–159. 10.1016/j.ajodo.2008.09.033PubMedView ArticleGoogle Scholar
- O'Brien C, Benson PE, Marshman Z: Evaluation of a quality of life measure for children with malocclusion. J Orthod 2007, 34: 185–193. discussion 176 10.1179/146531207225022185PubMedView ArticleGoogle Scholar
- Petersen PE, Bourgeois D, Ogawa H, Estupinan-Day S, Ndiaye C: The global burden of oral diseases and risks to oral health. Bull World Health Organ 2005, 83: 661–669.PubMed CentralPubMedGoogle Scholar
- Rusanen J, Lahti S, Tolvanen M, Pirttiniemi P: Quality of life in patients with severe malocclusion before treatment. Eur J Orthod 2010, 32: 43–48. 10.1093/ejo/cjp065PubMedView ArticleGoogle Scholar
- Onyeaso CO: Orthodontic treatment complexity and need with associated oral health-related quality of life in Nigerian adolescents. Oral Health Prev Dent 2009, 7: 235–241.PubMedGoogle Scholar
- Bernabe E, Sheiham A, Tsakos G, Messias de Oliveira C: The impact of orthodontic treatment on the quality of life in adolescents: a case–control study. Eur J Orthod 2008, 30: 515–520. 10.1093/ejo/cjn026PubMedView ArticleGoogle Scholar
- de Oliveira CM, Sheiham A: The relationship between normative orthodontic treatment need and oral health-related quality of life. Community Dent Oral Epidemiol 2003, 31: 426–436. 10.1046/j.1600-0528.2003.00002.xPubMedView ArticleGoogle Scholar
- De Baets E, Lambrechts H, Lemiere J, Diya L, Willems G: Impact of self-esteem on the relationship between orthodontic treatment need and oral health-related quality of life in 11- to 16-year-old children. Eur J Orthod 2012, 34: 731–737. 10.1093/ejo/cjr088PubMedView ArticleGoogle Scholar
- Kok YV, Mageson P, Harradine NW, Sprod AJ: Comparing a quality of life measure and the Aesthetic Component of the Index of Orthodontic Treatment Need (IOTN) in assessing orthodontic treatment need and concern. J Orthod 2004, 31: 312–318. discussion 300–311 10.1179/146531204225020625PubMedView ArticleGoogle Scholar
- Johal A, Cheung MY, Marcene W: The impact of two different malocclusion traits on quality of life. Br Dent J 2007, 202: E2. 10.1038/bdj.2006.122PubMedView ArticleGoogle Scholar
- Agou S, Malhotra M, Tompson B, Prakash P, Locker D: Is the child oral health quality of life questionnaire sensitive to change in the context of orthodontic treatment? A brief communication. J Public Health Dent 2008, 68: 246–248. 10.1111/j.1752-7325.2008.00093.xPubMedView ArticleGoogle Scholar
- Foster Page LA, Thomson WM, Jokovic A, Locker D: Validation of the Child Perceptions Questionnaire (CPQ 11–14). J Dent Res 2005, 84: 649–652. 10.1177/154405910508400713PubMedView ArticleGoogle Scholar
- Locker D, Jokovic A, Clarke M: Assessing the responsiveness of measures of oral health-related quality of life. Community Dent Oral Epidemiol 2004, 32: 10–18. 10.1111/j.1600-0528.2004.00114.xPubMedView ArticleGoogle Scholar
- de Oliveira CM, Sheiham A, Tsakos G, O'Brien KD: Oral health-related quality of life and the IOTN index as predictors of children's perceived needs and acceptance for orthodontic treatment. Br Dent J 2008, 204: 1–5. discussion 384–385 10.1038/bdj.2007.1207PubMedView ArticleGoogle Scholar
- Zhang M, McGrath C, Hagg U: The impact of malocclusion and its treatment on quality of life: a literature review. Int J Paediatr Dent 2006, 16: 381–387. 10.1111/j.1365-263X.2006.00768.xPubMedView ArticleGoogle Scholar
- Allen PF, McMillan AS, Walshaw D, Locker D: A comparison of the validity of generic- and disease-specific measures in the assessment of oral health-related quality of life. Community Dent Oral Epidemiol 1999, 27: 344–352. 10.1111/j.1600-0528.1999.tb02031.xPubMedView ArticleGoogle Scholar
- Slade GD: Derivation and validation of a short-form oral health impact profile. Community Dent Oral Epidemiol 1997, 25: 284–290. 10.1111/j.1600-0528.1997.tb00941.xPubMedView ArticleGoogle Scholar
- Saub R, Locker D, Allison P: Derivation and validation of the short version of the Malaysian Oral Health Impact Profile. Community Dent Oral Epidemiol 2005, 33: 378–383. 10.1111/j.1600-0528.2005.00242.xPubMedView ArticleGoogle Scholar
- Slade GD, Spencer AJ: Development and evaluation of the Oral Health Impact Profile. Community Dent Health 1994, 11: 3–11.PubMedGoogle Scholar
- Locker D: Measuring oral health: a conceptual framework. Community Dent Health 1988, 5: 3–18.PubMedGoogle Scholar
- Jarvinen S: Indexes for orthodontic treatment need. Am J Orthod Dentofacial Orthop 2001, 120: 237–239. 10.1067/mod.2001.114830PubMedView ArticleGoogle Scholar
- Brook PH, Shaw WC: The development of an index of orthodontic treatment priority. Eur J Orthod 1989, 11: 309–320.PubMedGoogle Scholar
- Team R: R: A Language and Environment for Statistical Computing. Vienna: Austria; 2012.Google Scholar
- Al Yami EA, Kuijpers-Jagtman AM, van't Hof MA: Orthodontic treatment need prior to treatment and 5 years postretention. Community Dent Oral Epidemiol 1998, 26: 421–427. 10.1111/j.1600-0528.1998.tb01982.xPubMedView ArticleGoogle Scholar
- Broder HL, Slade G, Caine R, Reisine S: Perceived impact of oral health conditions among minority adolescents. J Public Health Dent 2000, 60: 189–192. 10.1111/j.1752-7325.2000.tb03326.xPubMedView ArticleGoogle Scholar
- Heravi F, Farzanegan F, Tabatabaee M, Sadeghi M: Do malocclusions affect the oral health-related quality of life? Oral Health Prev Dent 2011, 9: 229–233.PubMedGoogle Scholar
- de Oliveira CM, Sheiham A: Orthodontic treatment and its impact on oral health-related quality of life in Brazilian adolescents. J Orthod 2004, 31: 20–27. discussion 15 10.1179/146531204225011364PubMedView ArticleGoogle Scholar
- Birkeland K, Boe OE, Wisth PJ: Subjective assessment of dental and psychosocial effects of orthodontic treatment. J Orofac Orthop 1997, 58: 44–61.PubMedGoogle Scholar
- Hunt O, Hepper P, Johnston C, Stevenson M, Burden D: The aesthetic component of the index of orthodontic treatment need validated against lay opinion. Eur J Orthod 2002, 24: 53–59. 10.1093/ejo/24.1.53PubMedView ArticleGoogle Scholar
- Peres KG, Barros AJ, Anselmi L, Peres MA, Barros FC: Does malocclusion influence the adolescent's satisfaction with appearance? A cross-sectional study nested in a Brazilian birth cohort. Community Dent Oral Epidemiol 2008, 36: 137–143. 10.1111/j.1600-0528.2007.00382.xPubMedView ArticleGoogle Scholar
- Tonelli R, McIntyre A, Camerin C, Walters ZS, Di Leo K, Selfe J, Purgato S, Missiaglia E, Tortori A, Renshaw J, et al.: Antitumor activity of sustained N-myc reduction in rhabdomyosarcomas and transcriptional block by antigene therapy. Clin Cancer Res 2012, 18: 796–807. 10.1158/1078-0432.CCR-11-1981PubMedView ArticleGoogle Scholar
- Tung AW, Kiyak HA: Psychological influences on the timing of orthodontic treatment. Am J Orthod Dentofacial Orthop 1998, 113: 29–39. 10.1016/S0889-5406(98)70274-4PubMedView ArticleGoogle Scholar
- Agou S, Locker D, Muirhead V, Tompson B, Streiner DL: Does psychological well-being influence oral-health-related quality of life reports in children receiving orthodontic treatment? Am J Orthod Dentofacial Orthop 2011, 139: 369–377. 10.1016/j.ajodo.2009.05.034PubMedView ArticleGoogle Scholar
- Prahl-Andersen B: The need for orthodontic treatment. Angle Orthod 1978, 48: 1–9.PubMedGoogle Scholar
- Thomas CW, Primosch RE: Changes in incremental weight and well-being of children with rampant caries following complete dental rehabilitation. Pediatr Dent 2002, 24: 109–113.PubMedGoogle Scholar
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