Youi Chen ,Tinqi Li ,Yujin Xu ,Jihu Xing ,Weiqin Jing ,Xingye Yin ,Hizhong Zhng,Mereith August,Ktherine P.Kleinc,,**,Tong Zhng,*
a Department of Plastic and Reconstructive Surgery,The First Medical Center,Chinese PLA General Hospital,Beijing 100853,China
b Department of Stomatology,The First Medical Center,Chinese PLA General Hospital,Beijing 100853,China
c Department of Oral and Maxillofacial Surgery,Massachusetts General Hospital,Boston,MA 02114,USA
d Harvard School of Dental Medicine,Boston,MA 02115,USA
Keywords:Oral Health Impact Profile Orthodontic treatment Quality of life Chinese PLA General Hospital Massachusetts General Hospital
ABSTRACT Background:Although oral health-related quality of life(OHRQoL)in orthodontic patients has been assessed in the past,to date,no study has compared the OHRQoL between two nations.We aimed to compare the OHRQoL between Chinese and American orthodontic patients.Methods: We conducted a two-center questionnaire-based cross-sectional study among patients who underwent orthodontic treatments at the Chinese PLA General Hospital(PLAGH)in Beijing,China and Massachusetts General Hospital (MGH) in Boston,Massachusetts,United States.Candidate variables included the participating center,patients’" age,sex,Angle’s classification of malocclusion,evaluation stage,and appliances used.The primary outcome was patients’OHRQoL assessed with the Oral Health Impact Profile-14(OHIP-14).Descriptive statistics,stratification,and univariate and multivariate analyses were performed.Results:The average age was lower for PLAGH patients than for MGH patients(21.1±7.9 vs.33.1±14.6 years,P＜0.001).The most common type of malocclusion was Angle’s Class III malocclusion at PLAGH(39%)and Class I malocclusion at MGH (59.5%).Clear aligners were used in 34.1% and 2.7% of the patients at MGH and PLAGH,respectively.OHIP-14 scores were lower for PLAGH patients than for MGH patients (18.4 ± 4.7 vs.22.3 ± 7.4,P＜0.001),particularly in functional limitation,psychological discomfort/disability,and handicap.Univariate regression analysis demonstrated that participating center,age,Class I malocclusion,and the use of clear aligners were significantly associated with overall OHIP-14 scores.Multivariate regression analysis demonstrated that patients at PLAGH were associated with lower OHIP-14 scores(coefficient:-3;95%CI:-5,-1.3;P=0.001),and age was positively associated with OHIP-14 scores (coefficient: 0.1;95% CI: 0.004,0.13; P=0.038).Conclusion: Chinese orthodontic patients had lower OHIP-14 scores,indicating a higher OHRQoL than American patients.In addition to the younger age,this difference may be attributed to the different ethical,cultural,educational,and socioeconomic background of Chinese and American orthodontic patients.
Oral health-related quality of life(OHRQoL)has become increasingly important in modern orthodontics,as it is recognized that objective measures alone do not completely capture the impact of malocclusion and orthodontic treatment on patient well-being.1OHRQoL is a multidimensional construct that includes dentofacial aesthetics,function,pain,and psychosocial aspects.2
The Oral Health Impact Profile (OHIP-14) questionnaire is the most commonly used measure for OHRQoL evaluation because of its reliability,validity,and responsiveness.The OHIP-14 includes 14 items covering seven domains: functional limitation,physical pain,psychological discomfort,physical disability,psychological disability,social disability,and handicap.3Many single-center studies have reported OHIP-14 scores in orthodontic patients;however,the results have been inconsistent between different patient cohorts from various countries.Chen et al.4found that OHIP-14 was 8.7 before orthodontic treatment,11.7 one week after fixed appliance placement,8.5 at one month,5.4 at three months,5.1 at six months,and 2.7 after orthodontic treatment in 222 Chinese patients.Javed et al.5showed that OHIP-14 was 12.8 before orthodontic treatment in 222 Pakistani adults.Jamilian et al.6demonstrated a significantly decreased OHIP-14 score in the retention phase of orthodontic treatment compared to that in untreated patients with moderate or severe malocclusion in 100 Iranian patients.Feu et al.7reported an OHIP-14 of 10.4 at baseline,9.2 one year after orthodontic treatment,and 1.6 two years after orthodontic treatment in 87 Brazilian orthodontic pediatric patients.Choi et al.8noted that OHIP-14 scores were 10.8 at baseline,14.1 one year after orthodontic treatment,and 9.6 at debonding in 66 Korean adults.Nichols et al.9showed that OHIP-14 was 12.4 at baseline,4.7 after orthodontic treatment,and 9.4 at the 5-year follow-up in 16 patients in New Zealand.Johal et al.10found that the OHIP-14 score was 10 at baseline,16 at 1 month after the start of the treatment,12.5 at 3 and 6 months after the start of the treatment,and 10 after the end of orthodontic treatment in 60 patients in the UK.Mehrstedt et al.11reported an average OHIP-14 score of 4.1 in the German general population.Silvola et al.12noted that OHIP-14 decreased from 17.6 to 4.1 after orthodontic treatment in 51 Finnish adults.Gera et al.13demonstrated that OHIP-14 was 5.5 in 22 Danish patients with a mean age of 24.7 years before orthodontic treatment.
However,all existing studies that have assessed orthodontic OHRQoL were conducted in a single country.Whether the OHRQoL in orthodontic patients differs between two countries is unclear due to the lack of direct comparison across nations,particularly between China and the US.Immigrants from China are the third largest immigrant group in the US,behind only to those from Mexico and India.In the greater Boston area,there were 74 317 Chinese immigrants in 2020,making it the largest immigrant group.Similarly,an increasing number of American expatriates and immigrants live in China due to rapid economic development and globalization.Therefore,it is important for general dentists and orthodontists to understand the differences in OHRQoL between Chinese and American patients to provide better dental care and meet their orthodontic needs.Our study aimed to compare the OHRQoL between Chinese and American orthodontic patients.
2.1.Study design
This study was conducted and reported in accordance with the STROBE statement and checklist for cross-sectional studies.14After approval from the Institution Research Boards,we designed a two-center questionnaire-based cross-sectional study at the Division of Dentistry at Massachusetts General Hospital(MGH)in Boston,Massachusetts,United States and the Department of Stomatology at Chinese PLA General Hospital(PLAGH)in Beijing,China,from June 1,2016 to June 1,2017.
2.2.Eligibility
The following inclusion criteria were applied:patients who presented with malocclusion at the two hospitals and agreed to participate.Exclusion criteria are as follows: patients who underwent combined orthognathic surgery;patients with craniofacial syndromes,cleft lip or palate,facial trauma,or tumor;sole usage of a removable appliance for orthodontic treatment;and patients who refused to participate.
2.3.Variables
The primary predictor variable was the participating center(PLAGH or MGH).Other predictor variables included patients’ sex,age,Angle’s classification of malocclusion(Class I,II,or III),evaluation stages(at the initial consultation before orthodontic treatment,during orthodontic treatment,or after the removal of appliances),and appliance type(fixed brackets or clear aligners).Angle’s classification was assessed by a single researcher at each center based on both clinical examination and radiographic images.
The primary outcome was OHIP-14 score.OHIP-14 includes 14 items:(1) I have problems pronouncing words;(2) I feel a sense of worsened taste;(3)I have painful aching in my mouth;(4)I find it uncomfortable to eat food;(5)I have been self-conscious;(6)I feel tense;(7)I have an unsatisfactory diet;(8)I have to interrupt meals;(9)I find it difficult to relax;(10)I have been a bit embarrassed;(11)I have been irritable with people;(12) I have difficulty doing useful jobs;(13) I feel life in general less satisfactory;(14)I have been unable to function.Responses were recorded on a 4-point Likert scale (0=never,1=hardly ever,2=sometimes,3=often,and 4=very frequently),with overall scores ranging from 0 to 56.Higher OHIP-14 score indicates worse OHRQoL.The original English version15and the validated Chinese version16of OHIP-14 were used for patients at MGH and PLAGH,respectively.
2.4.Statistical analysis
Continuous variables (age and OHIP-14 scores) were expressed as mean ± standard deviation or median (range),depending on their distributions.Categorical variables (malocclusion classification and evaluation stages) and dichotomous variables (center,sex,and type of appliance) were expressed as percentages or proportions.Comparison between patients at PLAGH and at MGH was performed using thet-test,Mann-WhitneyUtest,or Fisher’s exact test,depending on the type and distribution of variables.Stratification analysis was performed by comparing the OHIP-14 scores between PLAGH and MGH patients of different sexes,classifications of malocclusion,evaluation stages,and types of appliances.Univariate and multivariate linear regression analyses were conducted to evaluate the association between predictor variables and overall OHIP-14 scores.Statistical significance was set atP＜0.05.Data analysis was performed using Stata v16.0 (StataCorp,College Station,Texas,USA).
3.1.Descriptive analysis
The results of our descriptive analysis are shown in Table 1.A total of 308 patients(182 at the PLAGH and 126 at the MGH)responded to the questionnaire.PLAGH patients were significantly younger than MGH patients(21.1±7.9 years vs.33.1±14.6 years,P＜0.001)(Fig.1).Out of 182 PLAGH patients,81(44.5%)were less than 18 years old,compared to only 19/126 (15.1%) MGH patients.Most patients were female(72.1%),and sex distribution was similar in both groups.The most common type of malocclusion was Class III in patients at PLAGH (39%)and Class I in patients at MGH(59.5%).Most patients(73.7%)completed the questionnaire during orthodontic treatment.Fixed braces were commonly used in 84.4%of patients,whereas clear aligners were used in 34.1%of patients at MGH and only 2.7%of patients at PLAGH.Patients at PLAGH had lower overall scores of OHIP-14 than patients at MGH(18.4±4.7 vs.22.3±7.4,P＜0.001).Among the seven domains of OHIP-14,scores for functional limitation(P＜0.001),physical pain(P=0.022),psychological discomfort(P＜0.001),psychological disability(P＜0.001),and handicap (P＜0.001) were significantly lower in the PLAGH cohort(Fig.2).
3.2.Stratification analysis
The results of our stratification analysis are shown in Table 2.PLAGH patients had lower OHIP-14 scores than MGH patients when stratified according to sex,Class I or Class III malocclusion,their response to the questionnaires during or after orthodontic treatment,and treatment with fixed brackets.
Table 1 Descriptive analysis and comparison between PLAGH and MGH patients.
3.3.Regression analysis
The results of univariate and multivariate regression analyses are shown in Table 3.Univariate regression analysis demonstrated that participating center,age,Class I malocclusion,and the use of clear aligners were significantly associated with OHIP-14 scores.However,multivariate regression analysis demonstrated that only the participating center and age were significantly associated with OHIP-14 scores.The coefficient for age in the multivariate analysis was 0.1(95%CI:0.004,0.13),indicating that the overall OHIP-14 scores increased by 0.1 as the patient’s age increased by one year when other covariates were constant(Fig.3).
Table 2 Stratification analysis comparing the overall OHIP-14 scores within different subgroups.
Table 3 Univariate and multivariate linear regression analyses using OHIP-14 as the dependent variable.
Fig. 1.Histograms showing the age distribution in MGH and PLAGH patients.MGH,Massachusetts General Hospital;PLAGH,Chinese PLA General Hospital.
Fig. 2.Box plots showing the total and domain OHIP-14 scores in MGH and PLAGH patients.*P＜0.05.MGH,Massachusetts General Hospital;PLAGH,Chinese PLA General Hospital.
Fig. 3.Scatter plot and linear regression line between overall OHIP-14 scores and age at MGH and PLAGH.Blue dots indicate OHIP-14 scores corresponding to patients’age;Red lines indicate linear regression fit line.MGH,Massachusetts General Hospital;PLAGH,Chinese PLA General Hospital;OHIP-14,Oral Health Impact Profile-14.
4.1.Major findings
The results of this study showed that PLAGH patients had higher OHRQoL than MGH patients,and older patients had lower OHRQoL than younger patients.The inter-center difference may be attributed to the different ethical,cultural,educational,and socioeconomic background between Chinese and American patients.
4.2.Sex
The association between sex and OHRQoL in orthodontic patients was controversial in previous studies.Females may be more aware of their dentofacial appearance and reported greater social detriment compared to males.Silvola et al.17investigated the sex-specific associations of different malocclusions using OHIP-14in 1885 Finnish adults and concluded that the quality of life of women was affected more than that of men.Sfreddo et al.18showed that female sex was associated with lower OHRQoL in 1 134 12-year-old Brazilian schoolchildren.In contrast,Grewal et al.19found a similar influence of sex on the improvement of Psychosocial Impact of Dental Aesthetics Questionnaire scores in 400 young Indian adults between 18.1 and 25.3 years old,although males showed the least psychological impact on matrimonial concerns both before and after orthodontic treatment.Similarly,Sun et al.20also demonstrated that sex was not a significant factor of OHRQoL in 300 18-year-old adults in Hong Kong.In accordance with the latter,we found that sex did not affect OHIP-14 scores after adjusting for covariates.
4.3.Malocclusion
It is well recognized that malocclusion affects OHRQoL,but different types of malocclusions may have distinct patterns of impact on OHRQoL both before and after orthodontic treatment.Previous studies showed that patients with Class III malocclusion were more aware of their physical appearance and felt less attractive and insecure regarding their dentofacial appearance compared with Class II patients before orthodontic treatment;however,Class III patients also reported more aesthetic and psychosocial improvements than Class II patients after orthodontic treatment.21Zheng et al.22compared OHIP-14 scores in 35 Class I,32 Class II,and 14 Class III patients aged 15-24 years who underwent comprehensive orthodontic treatment.They found that Class II patients benefited the most from the stage of space closure,whereas Class I patients benefited during the first stage (alignment and leveling) of treatment in psychological domains.Furthermore,Class III patients had the lowest OHRQoL,for example,in functional issues,pain,social disability,and handicap,compared to Class I and II patients.In contrast,Liu et al.23found that orthodontic patients with Class II malocclusion showed higher psychological stress and aesthetic sensitivity than those with Class I and III malocclusion.Although we observed a lower OHIP-14 score in Class II patients treated at MGH,we did not identify a significant association between the type of malocclusion and overall OHIP-14 scores after adjustment for covariates.
4.4.Appliances
Clear aligners are advanced orthodontic appliances with the advantages of comfort,better aesthetics,convenience,and hygiene.24However,the effect of clear aligners on the OHRQoL in orthodontic patients isinconclusive due to the lack of sufficient studies.Gao et al.25found that application of clear aligners was associated with lower pain,less anxiety,and lower OHIP-14 scores(higher OHRQoL)than fixed appliances in 110 adult patients.AlSeraidi et al.26showed,in a cohort of 117 adult patients,that patients who underwent clear aligner therapy reported a higher OHRQoL score than those with braces during the initial stages of treatment.In contrast,Antonio-Zancajo et al.27noted,in a cohort of 120 patients,that patients treated with lingual appliances had lower levels of pain and OHIP-14 scores,indicating higher OHRQoL than those treated with clear aligners.Alajmi et al.28demonstrated that treatment with clear aligners was associated with better food consumption and absence of mucosal ulcerations,albeit with impaired pronunciation and speech delivery in the short term.A systematic review by Zhang et al.29showed no significant difference in OHRQoL between patients treated with clear aligners and fixed appliances,although clear aligners were associated with fewer eating disturbances.Similarly,we did not find a significant association between the type of orthodontic appliances used and overall OHIP-14 scores in multivariate analysis.
4.5.Age
The effect of age on OHRQoL in orthodontic patients remains controversial in previous studies.Feu et al.7found that age did not affect OHRQoL in orthodontic patients.Hanisch et al.30demonstrated that age did not influence OHIP-14 scores in people without any oral conditions.In contrast,Sun et al.31showed that age had an influence on OHRQoL in adolescents 12-18 years old.Choi et al.8also reported a significant increase in total OHIP-14 scores (decreased OHRQoL) at treatment initiation and debonding in older patients.Silva et al.32assessed the OHRQoL in 898 orthodontic patients in different age groups (children,adolescents,and adults),with a mean age of 17 years.They found that the mean OHIP-14 score was 8.3 for the 6-to 11-year-old cohort,8.9 for the 12-to 17-year-old cohort,and 12.6 for the adult cohort.They concluded that children and adolescents had better OHRQoL than adults.Furthermore,adolescents were more prone to complaining of aesthetic/pain problems compared to adults who were more prone to complaining of functional/pain events.In a systematic review and meta-analysis by Kragt et al.,33children between 11 and 14 years old were most likely to report an impact of malocclusions on OHRQoL,whereas the biggest difference in OHRQoL scores was noted in children over 14 years old.In accordance with these studies,we found that age was positively associated with OHIP-14 scores,indicating that older patients had a lower OHRQoL.The lower OHRQoL in MGH patients may be attributed to their older age,as shown in Fig.1.Notably,44.5%PLAGH patients were less than 18 years old,compared to only 15.1% of patients at MGH.This finding is also supported by a systematic review and meta-analysis by Javidi et al.,34who found that patients who underwent orthodontic treatment below 18 years old had higher OHRQoL in emotional and social well-being dimensions than older patients.
4.6.Ethical,cultural,educational,and socioeconomic differences
Patients in different countries may have distinct ethical,educational,socioeconomic,and cultural background,which affect OHRQoL.35Lunteren et al.36compared OHIP-14 scores between different ethnic groups(native Dutch,Indonesian,Moroccan,Surinamese,Turkish) in 3 121 9-year-old children in the Netherlands.They reported that Surinamese children had a significantly lower OHRQoL than Dutch children,after adjusting for covariates.Sfreddo et al.18showed that adolescents from low socioeconomic background reported worse OHRQoL at the 2-year follow-up compared to those from high socioeconomic background in 747 14-year-old adolescents in Brazil.Sun et al.20further identified that household income had the greatest influence on OHRQoL,including aspects such as physical pain,psychological discomfort/disability,and total OHIP-14,while parents’ education had some effect on functional limitation,physical pain,and psychological discomfort.
With the rapid development of China,the educational and economic background of citizens in Chinese metropolitan cities,such as Beijing,has substantially improved.However,some time is still required to change the cultural perception of the OHRQoL.In developed countries,such as the US,it is a cultural tradition to pursue orthodontic treatment for well aligned teeth.People in developed countries are more aware of dentofacial appearance than people in developing countries,such as China.It is not uncommon to encounter a well-educated or wealthy person with poorly aligned teeth in China.37Chinese people seem to adapt and pay less attention to malocclusion and its psychological and social impacts,unless it results in pain or functional limitations.Ethical,educational,socioeconomic,and cultural differences may partially explain the significant differences in OHRQoL between PLAGH and MGH patients.
4.7.Limitations
This study has several limitations.First,several potential confounders such as periodontal and endodontic disease,temporomandibular joint dysfunction,and severity of dentofacial deformity are unavailable,which could substantially affect OHRQoL.Most patients underwent routine periodontal and endodontic treatment for existing diseases before orthodontic treatment.Therefore,their periodontal and endodontic conditions were appropriate for orthodontic treatment and should not significantly affect OHRQoL.Jamilian et al.6found that patients with moderate malocclusion had better improvement in OHRQoL than patients with severe malocclusion in 100 participants aged 17-21 years.In a systematic review and meta-analysis by Sun et al.,38more severe malocclusion was associated with higher OHIP-14 scores,including physical disability/pain,psychological discomfort/disability,and social disability.Patients at MGH may have had more severe malocclusion than patients at PLAGH,but more data are required to define and classify the severity of malocclusion.Second,follow-up data were not obtained in this cross-sectional study.Thus,more research is required to determine the OHRQoL of orthodontic patients in different countries and areas,preferably through a multicenter prospective longitudinal study.Despite these limitations,this is the first study to directly compare the OHRQoL between Chinese and American patients.Our study may help general dentists and orthodontists to understand the differences in OHRQoL between Chinese and American patients and to provide better dental care to meet their orthodontic needs.
Orthodontic patients at PLAGH had lower OHIP-14 scores,indicating higher OHRQoL,than patients at MGH.In addition to the younger age,this difference may be attributed to ethical,cultural,educational,and socioeconomic differences in the perception and evaluation of OHRQoL in PLAGH patients.
Ethics approval and consent to participate
This study was approved by the Institution Research Boards of the Chinese PLA General Hospital and Massachusetts General Hospital.All participates provided written informed consent prior to study enrolment.
Consent for publication
All the patients included in this research gave written informed consent to publish the data contained within this study.
Authors’ contributions
Chen Y:Conceptualization,Methodology,Software,Writing-Original draft.Li T: Data curation,Writing-Original draft.Xu Y: Visualization,Investigation.Xing J: Formal analysis,Validation.Jiang W: Software,Validation.Yin X: Writing-Review and editing.Zhang H: Supervision.August M: Writing-Review and editing.Klein K: Conceptualization,Supervision.Zhang T:Conceptualization,Supervision,Writing-Review and editing.
Competing interests
The authors declare that they have no competing interests.