Impact of oral-health-related quality of life and self-esteem on patients with missing maxillary lateral incisor after orthodontic space closure: a single-blinded, randomized, controlled trial

Summary

Background

The maxillary lateral incisor is one of the teeth most likely to suffer agenesis, resulting in spacing between the central incisor and the canine.

Objective

To compare maxillary lateral incisor agenesis with space closure treatment versus non-treatment based on measurements of the self-perceived oral-health-related quality of life (OHRQoL) and self-esteem of the participants.

Subjects and methods

A total of 44 people, aged 17–49 years, with missing lateral incisors were randomly assigned to two groups (n = 22 in each)—a treated group in which the space was orthodontically closed (TG) and a control group that remained untreated (CG). Randomization was performed by a researcher who was not involved in the clinical part of the study. The outcomes were assessed using the Oral Health Impact Profile and Rosenberg’s Self-Esteem Scale, which were applied before (phase 1) and after (phase 2) the orthodontic treatment in the TG, and at baseline (phase 1) and 12 months after (phase 2) in the CG. All the data were blindly evaluated, supporting the single-blinded design of the study.

Results

All participants finished the randomized controlled trial, and the demographic characteristics were similar between the groups. In phase 1, the levels of self-esteem and OHRQoL at baseline were similar (P = 0.079, P = 0.693, respectively). In phase 2, the self-esteem scores of the CG decreased and the OHRQoL increased (P = 0.005, P < 0.001, respectively), while self-esteem increased in the TG and the OHRQoL decreased (P < 0.001). The CG had lower scores than the TG for self-esteem, but the opposite was observed for OHRQoL (P < 0.001).

Limitations

Information bias may have occurred. Since the questionnaires could not have been applied at the same time in both groups, the time difference between the two assessments may have led to random and systematic error.

Conclusions

The spacing resulting from missing maxillary lateral incisors had a negative impact on the OHRQoL and self-esteem of the participants, while orthodontically closing those spaces had a positive impact on those aspects.

Clinical trial registration

This study was not registered.

Protocol

The protocol was not published before trial commencement.

Introduction

Malocclusion is a highly prevalent public health problem and, in Brazil, it is considered to be one of the main issues relating to oral health, ranking third after dental caries and periodontal problems (1). Oral-health-related quality of life (OHRQoL) is an important part of people’s general health, connecting dental health with psychological and social conditions (2, 3). Despite not being considered a disease, malocclusion requires orthodontic treatment, since it may impair oral function, increase susceptibility to other diseases and even alter a person’s psychological and social aspects (4).

Recently, numerous studies have been published relating psychological well-being to oral health, in order to understand the impact of oral conditions on people’s daily lives and routines (5, 6). An assessment of quality of life is not easy to perform, however, since it reflects the subjective experiences of individuals whose feelings and judgments are modified according to their own physical and emotional development (7). Considering that orthodontic treatment alters people’s functional and aesthetic aspects, which can influence social integration and self-esteem, it can be involved in this process (8).

Tooth agenesis is a common anomaly in humans, its prevalence varying among ethnic groups (9). The maxillary lateral incisor is one of the most commonly missing teeth, and its absence can not only cause functional problems, such as diastemas and speech difficulty, but can also interfere with people’s relationships and self-esteem (10). There is ongoing discussion concerning the ideal treatment for this agenesis; however, a systematic review of the literature has shown that space closure followed by canine recontouring can present an optimal outcome, with aesthetic and periodontal advantages when compared with a prosthetic solution (11). The impact of this treatment on the self-esteem and OHRQoL of a person is, however, as yet unknown.

Observational studies have already shown a connection between malocclusion and OHRQoL, and an association between orthodontic treatment (the treatment of malocclusion) and the improvement in OHRQoL and self-esteem (5, 12–14). Since orthodontic treatment is an intervention, however, such findings are limited. Nevertheless, an interventional study has recently demonstrated that orthodontic treatment can even increase the OHRQoL in children (2). Thus, acquiring data concerning older people, who can express their own issues and are more likely to stay committed to the treatment, can provide valuable information for orthodontists.

Although there are different approaches to treating maxillary lateral incisors’ absence, closure of the space followed by canine recontouring has already been acknowledged as being an excellent and aesthetic alternative, especially considering recent improvements in cosmetic dentistry, which can provide optimal results that appear similar to the intact dentition (15). Despite the aesthetic and functional aspects of the treatment, important questions yet to be answered include how patients react to the space closure and, alternatively, how the presence of this spacing interferes with their lives.

Specific objectives/hypotheses

This study was designed to investigate the impact on OHRQoL and self-esteem of participants following the orthodontic closure of missing maxillary lateral incisor spacing versus non-treatment. The trial was single-blinded, randomized, and controlled.

The null hypothesis was that the orthodontic closure of missing maxillary lateral incisor spacing would not impact the participant’s OHRQoL and self-esteem compared with non-treatment.

Methods

Trial design and changes after trial commencement

The study was conducted as a prospective, parallel-grouped, randomized, single-blinded, non-treatment-controlled clinical trial with a 1:1 allocation ratio. No changes were made to the study design after its commencement. This study followed the Consolidated Standards of Reporting Trials guidelines, and was revised and approved by the Research Ethics Committee of Southwest Bahia State University (16). At the beginning of the study, all patients (and parents, where required) were asked to sign a consent form and patient information sheet, in full compliance with the Declaration of Helsinki.

Participants, eligibility criteria, and settings

A total of 44 participants were recruited from the orthodontic clinic at Southwest Bahia State University, between January 2013 and November 2018. The participants were aged from 17 to 49 years, and all had a space between their maxillary central incisor and canine due to a missing maxillary lateral incisor. All individuals had skeletal class I and Angle Class I or II malocclusions without need for orthognathic surgery. Patients with either unilateral or bilateral agenesis were suited to participate in the study. The exclusion criteria were: absence of maxillary lateral incisor due to trauma; cleft lip or palate; presence of syndromes; the presence of structural dental changes; and patients who were uncooperative.

The diagnosis of agenesis was carried out through an evaluation of all available diagnostic elements (e.g. photographs, orthodontic models, and radiographs) associated with the clinic inquiry made to the patient.

Interventions

The patients’ orthodontic records were analysed and the sample was randomly split into two groups. The treated group (TG, n = 22) received orthodontic treatment for space closure. This procedure involved all the teeth being bonded with brackets, the canines being mesialized and placed in the positions of the missing lateral incisors, and the canines being aesthetically recontoured. In addition, the premolars were mesialized and placed in the position of the canines. The control group (CG, n = 22) did not receive orthodontic treatment during the first year of the study. The participants in both groups were informed about the importance of regularly attending the orthodontic appointments in order for the progress of the treatment and/or malocclusion to be monitored, to emphasize the importance of oral hygiene, and to answer the questionnaires. For ethical reasons, the CG was treated after 12 months of follow-up. Out of the 22 participants in each group, TG had 6 participants with 2 lateral incisors missing, while CG had 7 participants.

Outcomes (primary and secondary) and changes after trial commencement

The primary outcomes were OHRQoL and self-esteem. To evaluate the former, the Oral Health Impact Profile (OHIP-14) questionnaire was administered. This evaluates OHRQoL in four domains—oral symptoms, functional limitations, emotional well-being, and social well-being. In addition, the questionnaire contained questions on the participants’ overall perceptions of their general well-being and oral health.

The OHIP-14 had already been validated in Brazilian Portuguese and the participants’ answers were scored and tabulated to obtain a frequency scale: 0–never; 1–once or twice; 2–sometimes; 3–many times; and 4–every day or almost every day (17). The scores for each domain were calculated as the sum of individual answers in each questionnaire. This index could range from 0 to 56. The complete OHIP-14 has 14 questions and, in all domains and in the overall score, 0 indicated absence of impact of the oral condition on OHRQoL, while an increasing score suggested an increasingly negative impact of the oral condition on OHRQoL. A score of 56 would indicate the maximum impact on a person’s OHRQoL.

Aside from the OHIP-14, to evaluate self-esteem, Rosenberg’s Self-Esteem Scale (RSES) was applied. RSES had previously been validated and adapted for use in Brazilian participants (18). This scale includes 10 questions, 5 relating to positive opinions and 5 to negative ones. The questions are interposed in order to increase the reliability of the questionnaire. For each question, a four-point Likert scale (strongly disagree, disagree, agree, strongly agree) was applied. The scores ranged from 1 to 4; the lower the score, the lower the participant’s self-esteem, the higher the score, the higher the self-esteem. This scale has already been proven to be a reliable method for assessing self-esteem in orthodontic patients (13).

Both questionnaires (OHIP-14 and RSES) were applied in both groups. In the TG, they were applied before orthodontic treatment (baseline, phase 1) and after space closure (phase 2), which was, approximately, 3 years after the baseline. In the CG, on the other hand, the questionnaires were applied at baseline (phase 1) and after 12 months (phase 2), in order to detect possible changes in the scores over time, allowing the participants to assess how the treatment influenced their OHRQoL (17).

Demographic data (i.e. participant age at the beginning of the study, participant age 12 months after the beginning of the study, and number of missing teeth) were also collected by the questionnaire.

No changes to the study design were made after its commencement.

Sample size calculation

The sample size was calculated using G*Power (version 3.1.9.2) and the following parameters for a bilateral test: effect size f = 0.8; α = 0.05; and 80% power. A minimum sample of 15 patients in each group was estimated. The effect size was defined by means of a preliminary analysis using data from a pilot study conducted with 10 subjects (5 controls and 5 treated). Analysis of these data indicated a great effect for changes in the treated group and differences between the control and treated groups (Cohen’s f > 0.8). Considering the possibility of using nonparametric statistics, 15% was added, which increased the minimum number of individuals to 18 (19). With an expected attrition of approximately 20% (patient dropouts), 4 patients were added in each group, totalling 44 individuals (22 per group).

Interim analyses and discontinuation guidelines

Not applicable.

Randomization

Randomization was performed by a researcher who was not involved in the clinical part of the study, thus guaranteeing allocation concealment. BioEstat 5.0 software (Civil Society Mamiraurá, Amazônia, Brazil) was used to build a table of random numbers, taking into consideration the sample size for each group, the population size, and the treatment used (i.e. treatment or non-treatment). Confidentiality was ensured by using 44 sequentially numbered brown envelopes containing the groups, following the order of the randomly drawn numbers. In total, 22 envelopes for the CG and 22 envelopes for the TG were created. This procedure was also carried out by the researcher in charge of the randomization. The envelopes were sealed and assigned to each participant the moment they were included in the study. In addition, they were opened sequentially and only after they had been assigned to a participant.

Blinding

Blinding during treatment and questionnaire application was not possible, either for the participants or the operators. Nevertheless, patients were given random numbers as identification and the outcome assessor was not able to identify in which group subjects belonged to, being blinded to the treatment allocation. Therefore, all the data were blindly evaluated, supporting the single-blinded design of the study.

Statistical analysis

The statistical analyses were performed using SPSS software for Windows (IBM SPSS 21.0, 2012, IBM Corp., Armonk, NY). The descriptive analysis consisted of the mean and standard deviation, median and interquartile range (IQR) and relative and absolute frequencies. Frequencies were compared using the chi-square test. Normality was verified by means of the Shapiro–Wilk test. The student’s t-test or Mann–Whitney test were applied to make intergroup comparisons. Intragroup comparisons were analysed by means of the student’s t-test for paired data or the Wilcoxon test. Multiple linear regression analyses were performed to assess the influence of sociodemographic and clinical variables and self-esteem and OHRQoL scores at baseline on outcomes. Significance level was set at α = 0.05.

Results

Participant flow

A total of 44 participants, out of 153 people evaluated for eligibility, were selected, and all of them completed the study. In the control group, there were 16 (72.7%) women and 6 (27.3%) men and in the experimental group, 15 (68.2%) women and 7 (31.8%) men (P-value = 1.000). The attrition rate was 0%. A flow chart with the reasons for dropping out is presented in Figure 1.

Figure 1.

CONSORT 2010 flow diagram

Baseline data

The sociodemographic and clinical data for each group at baseline and at the end of the study for both the TG and CG are presented in Table 1. Both groups presented similar characteristics regarding baseline age, final age, race/colour, schooling, space between the central incisor and the canine, absent lateral incisors, and type of dental malocclusion.

Table 1.

Sociodemographic and clinical characteristics of the control and treated groups.

Variable	Group		P-value*
	Control	Treated
Baseline age, years, median (IQR)	24.00 (15.00)	27.00 (13.00)	0.397
Final age, years, median (IQR)	25.00 (15.00)	30.00 (13.00)	0.088
Race/colour, n (%)
White	15 (68.2)	13 (59.1)	0.754
Black	7 (31.8%)	9 (40.9)
Schooling, years of study, median (IQR)	9.00 (7.00)	9.00 (5.00)	0.431
Absent lateral incisors, n (%)
Unilateral	15 (68.2)	16 (72.7)	1.000
Bilateral	7 (31.8%)	6 (27.3)
Space MCI-canine, mm, median (IQR)	6.90 (3.30)	6.35 (4.90)	0.681
Dental malocclusion, n (%)
Class I	14 (63.6)	15 (68.2)	1.000
Class II	8 (36.4%)	7 (31.8)

IQR, interquartile range; MCI, maxillary central incisor.

*Mann–Whitney test (baseline age, final age, schooling, and space MCI-canine) or chi-square test (race/colour, absent lateral incisors, and malocclusion).

Numbers analysed for each outcome, estimation, and precision

Table 2 presents the comparison of OHRQoL and self-esteem at baseline (phase 1) between the CG and TG. There were no significant differences between the groups, suggesting that the levels of self-esteem and OHRQoL at baseline were similar (P > 0.05).

Table 2.

Intergroup comparison of self-esteem and OHRQoL at baseline, intragroup comparison (baseline and final phase) of self-esteem and OHRQoL scores for the control group, intragroup comparison (baseline and final phase) of self-esteem and OHRQoL scores for the treated group and Intergroup comparison of changes (baseline and final phase) in the sample’s self-esteem and OHRQoL scores.

	Intergroup comparison of self-esteem and OHRQoL at baseline			Comparison of self-esteem and OHRQoL for CG			Comparison of self-esteem and OHRQoL for TG			Intergroup comparison of changes (baseline and final phase) in the self-esteem and OHRQoL
Variable	Group		P value*	Study phase		P value**	Study phase		P value***	Group		P value****
	Control	Treated		Baseline	Final		Baseline	Final		Control	Treated
RSES	6.00 ± 4.00	5.00 ± 4.00	0.079	6.41 ± 3.31	5.95 ± 2.92	0.005	5.00 ± 4.00	22.00 ± 3.00	< 0.001	0.00 ± 1.00	17.50 ± 4.00	< 0.001
OHIP-14	31.50 ± 2.48	31.82 ± 2.82	0.693	31.50 ± 2.48	35.82 ± 1.89	< 0.001	31.82 ± 2.82	6.91 ± 2.05	< 0.001	4.32 ± 2.66	−24.91 ± 2.18	< 0.001

RSES, Rosenberg’s Self-Esteem Scale; OHIP-14, Oral Health Impact Profile.

*Mann–Whitney test (RSES) and Student’s t-test for independent samples (OHIP-14). Results are expressed as median ± interquartile range (RSES) and mean ± standard deviation (OHIP-14).

**Student’s t-test for paired data. Results are expressed as mean ± standard deviation.

***Wilcoxon test (RSES) Student’s t-test for paired data (OHIP-14). Results are expressed as median ± interquartile range (RSES) and mean ± standard deviation (OHIP-14).

****Mann–Whitney test (RSES) and Student’s t-test for independent data (OHIP-14). Results are expressed as median ± interquartile range (RSES) and mean ± standard deviation (OHIP-14).

A comparison of the scores of the CG, at baseline and at the end of the study, showed that, after 12 months (phase 2), the non-treated participants presented a decrease in the self-esteem score and an increase in the OHRQoL score, representing a significant worsening in both parameters (P < 0.05; Table 2).

A comparison of the TG between phase 1 and phase 2 of the study showed that, after space-closure treatment, the participants presented an increase in the self-esteem score and a decrease in the OHRQoL score, indicating a significant improvement in both parameters (P < 0.05; Table 2).

A comparative analysis of the differences in the self-esteem and OHRQoL scores showed statistical dissimilarities between the TG and CG, indicating a beneficial effect of orthodontic treatment on self-esteem and OHRQoL in participants with missing lateral incisors (P < 0.05; Table 2).

The multiple regression analysis demonstrated that, regardless of sociodemographic and clinical factors and the participants’ initial condition in relation to self-esteem and OHRQoL, the treated group had better outcomes compared with the control group. In addition, the self-esteem outcome was associated with the initial score of self-esteem and the OHRQoL outcome was related to the initial OHIP-14 score and education. These results demonstrate that participants with higher self-esteem and OHRQoL and less education level were the ones who benefitted most from the treatment (Table 3).

Table 3.

Multiple linear regression analysis to predict self-esteem and OHRQoL scores after treatment.

Dependent variable	Independent variable	βadjusted (Pvariable)*	R2 (Pmodel)
RSES	Group (treated)	16.991 (< 0.001)	0.98 (< 0.001)
	Age (continuous)	0.036 (0.311)
	Race/colour (black)	−0.040 (0.937)
	Schooling (continuous)	0.074 (0.275)
	Absent lateral incisors (bilateral)	−0.065 (0.913)
	Space MCI-canine (continuous)	−0.135 (0.516)
	Dental malocclusion (class II)	0.335 (0.767)
	RSESbaseline (continuous)	0.711 (0.001)
OHIP-14	Group (treated)	−29.141 (< 0.001)	0.99 (< 0.001)
	Age (continuous)	−0.066 (0.099)
	Race/colour (black)	−0.620 (0.272)
	Schooling (continuous)	0.233 (0.011)
	Absent lateral incisors (bilateral)	0.666 (0.319)
	Space MCI-canine (continuous)	0.064 (0.784)
	Dental malocclusion (class II)	−0.644 (0.599)
	OHIP-14baseline (continuous)	0.473 (< 0.001)

RSES, Rosenberg’s Self-Esteem Scale; OHIP-14, Oral Health Impact Profile; MCI, maxillary central incisor.

*Adjusted for all table variables.

Harms

The decrease in the self-esteem score and the increase in the OHRQoL score in the non-treated control group was considered to indicate a serious harm.

Discussion

Main findings in the context of the existing evidence

The OHIP-14 questionnaire has already been validated in Brazilian Portuguese, and is an important tool for assessing the impact of oral health on the general well-being of patients (3). The questionnaire covers four domains—oral symptoms, functional limitations, emotional well-being, and social well-being. Responses about the first two domains are of paramount importance to orthodontists because they involve clinically relevant issues, which can lead patients to change their diets and habits, and even abandon treatment (20, 21). The last domain, on the other hand, covers emotional and sensitive issues, which are directly related to facial and smile aesthetics and patient self-perception, which are important reasons for people seeking and adhering to orthodontic treatment (22).

Since there were no significant differences between the CG and TG (Table 1), the OHRQoL scores for both groups at baseline were similar (Table 2); however, in phase 2, the OHRQoL scores increased in the CG, indicating a decrease in OHRQoL (Table 2). This finding corroborates those of previous authors (23), who showed that patients who had not previously been treated were twice as likely to have a poor OHRQoL. Understanding this is important to the orthodontist and general dentist because it highlights both the importance of treating malocclusion and the negative impact that this condition can have on people.

It is important to emphasize that the increase in OHIP-14 scores happened in all four domains, indicating a negative impact on OHRQoL. Since there was no intervention in the CG, one possible explanation for this could be that the participants, after answering the questionnaire at baseline, became more conscious of their malocclusion, thus increasing the frequency of answers that indicated higher frequencies. The authors stress that the CG was monitored regularly and treated 12 months after the baseline, in order to avoid them suffering a decline in OHRQoL, as has been previously observed (24).

When evaluating Table 2, a decrease in the OHRQoL score is apparent, indicating a significant improvement in the OHRQoL in the TG. Previous studies have already made this connection (2, 25); closing the space orthodontically improved the participants’ OHRQoL versus not treating them, indicating the psychological and social importance of orthodontics (23).

RSES has already been validated and adapted for patients, including in orthodontic studies, and has already proven to be an effective tool for evaluating self-esteem (18, 25). The scale contains 5 questions related to positive opinions and 5 to negative ones, totalling 10 questions. Table 2 shows that, at baseline, both the CG and TG presented similar levels of self-esteem, as expected, since both groups were demographically similar. In phase 2, however, the self-esteem scores decreased and were statistically significant different from baseline, indicating a decrease in self-esteem of the CG. Since the presence of malocclusion may reduce social acceptance and thereby induce low self-esteem, it is natural to assume that its continuance would decrease patient morale (26). Bullying can also be related to dissatisfaction with one’s body image, which is known to reduce self-esteem (4, 27).

On the other hand, Table 2 shows that patients who had their lateral space orthodontically closed presented an increase in self-esteem, which corroborates the findings of previous authors, and also indicates the positive impact that closing the lateral incisor space can have on the patient (25). This is of paramount importance because the orthodontist has to decide whether to leave the space open or close it. In cases where patients have to wait for their growth to cease to have implants installed, the overall treatment time will be augmented, which can lead to more time with teeth missing and lower self-esteem (28). Moreover, Table 2 shows that there is a statistical difference between the CG and TG in phase 2, supporting previous findings (25, 29).

An important finding was that the individuals’ initial clinical factors did not influence the outcomes of self-esteem and OHRQoL (Table 3). As previously reported by different authors (10, 30), diastemas can affect patients’ self-esteem and social relationships, and our findings not only corroborate them, but also suggest that the absence of both lateral incisors has a similar impact as a unilateral agenesis. Hence, orthodontic treatment can be an important tool to improve patients’ lives and perception about their self, independently of their age, size of the space between the central incisor and canine, and the bilateral absence of lateral incisors. Moreover, the sociodemographic and initial condition in relation to self-esteem and OHRQoL did not interfere with the final outcomes, since the treated group had better outcomes compared with the control one. Therefore, the results demonstrate that participants with higher self-esteem and OHRQoL and less education level were the ones who benefitted most from the treatment.

Since this was a questionnaire-based study, information bias may have occurred, as the results depended on the participants’ memory, accuracy, and honesty (31). In order to avoid bias, the scoring system was thoroughly explained to the participants. In addition, the questionnaire and scale were self-administered, thus reducing the risk of observer bias.

Generalizability

Considering that the participants in the study all came from a single state-run university located in southwestern Bahia, a state in northeastern Brazil, the results should not be generalized to other regions. Clinical trials with other populations should be executed, in order to be able to make valid generalizations.

Limitations

Since this was a questionnaire-based study, information bias may have occurred, as the results depended on the participants’ memory, accuracy, and honesty (31). In order to avoid bias, the scoring system was thoroughly explained to the participants. In addition, the questionnaire and scale were self-administered, thus reducing the risk of observer bias. Also, since the OHIP-14 and RSES could not have been applied at the same time in both groups, the time difference between the two assessments may have led to random and systematic error. It seems likely that random error could be greater over a longer a period of time, and trends in quality of life which take place over time could have maximized differences between the groups. The sample is older than commonly seen in orthodontic studies (27 years median age), however, since average life expectancy has increased, there has been an increase in the number of adults and older patients seeking orthodontic treatment, which justifies our sample age average (32, 33). The study was not registered and, moreover, the fact that this was a randomized controlled trial makes this study prone to sample bias, since the selection of subjects who are seeking orthodontic treatment may maximize the impact of treatment. However, this kind of bias is already expected in this type of study (34).

Conclusions

Spaces caused by missing maxillary lateral incisors have a negative impact on patients’ OHRQoL and self-esteem, while orthodontically closing such spaces has a positive impact on those aspects. Orthodontists can play a key role in increasing patients’ OHRQoL and self-esteem, using space closure followed by canine recontouring as an effective solution for both the orthodontist and patient.

Funding

This study was financed by Conselho Nacional de Desenvolvimento Científico e Tecnológico – CNPq process numbers 2075138608339821.

Data availability

The data underlying this article cannot be shared publicly due to the privacy of individuals that participated in the study. The data will be shared on reasonable request to the corresponding author.