Which orthodontic appliance is best for oral hygiene? A randomized clinical trial

Introduction

Clear aligners and to a lesser extent self-ligated brackets are considered to facilitate better oral hygiene than traditional fixed orthodontic appliances. This 3-arm parallel-group prospective randomized clinical trial compared the long-term and short-term effects of clear aligners, self-ligated brackets, and conventional (elastomeric-ligated) brackets on patients’ oral hygiene during active orthodontic treatment.

Methods

Seventy-one participants (41 boys, 30 girls; mean age, 15.6 years) undergoing orthodontic treatment were randomly allocated through a computer-generated randomization schedule to one of the groups based on the choice of intervention: Clear Aligners (CLA) (Align Technology, San Jose, Calif) (n = 27), preadjusted edgewise fixed appliance with self-ligated brackets (SLB) (Carriere, Carlsbad, Calif (n = 22), or preadjusted edgewise fixed appliance with elastomeric ligated brackets (ELB) (Ortho Organizers Inc., Carlsbad, CA) (n = 22). For each participant, the primary outcome, plaque index (PI), and secondary outcomes, gingival Index (GI) and periodontal bleeding index (PBI), were measured at baseline (T0), after 9 months of treatment (T1), and after 18 months of treatment (T2). Blinding of the clinicians and the patients to the intervention was impossible. It was only done for outcome assessment and for the statistician. Ten participants did not receive the allocated intervention for various reasons.

Results

The means and standard deviations of PI at T0 (CLA, 0.50 ± 0.51; SLB, 0.65 ± 0.49; ELB, 0.70 ± 0.73), T1 (CLA, 0.83 ± 0.48; SLB, 1.38 ± 0.72; ELB, 1.32 ± 0.67), and T2 (CLA, 0.92 ± 0.58; SLB, 1.07 ± 0.59; ELB, 1.32 ± 0.67) were similar. The odds ratio (OR) for plaque index (0 or ≥1) comparing SLB or CLA to ELB was not significant. OR for SLB vs ELB = 1.54 at T0 (95% CI, 0.39-6.27), 0.88 at T1 (95% CI, 0.03-24.69), and 0.83 at T2 (95% CI, 0.02-27.70); OR for CLA vs ELB = 1.07 at T0 (95% CI, 0.30-3.88), 0.24 at T1 (95% CI, 0.01-1.98), and 0.17 at T2 (95% CI, 0.01-1.71). However, the odds ratios comparing CLA with ELB for GI (OR = 0.14; P = 0.015) and PBI (OR = 0.10; P = 0.012) were statistically significant at T1.

Conclusions

In this prospective randomized clinical trial, we found no evidence of differences in oral hygiene levels among clear aligners, self-ligated brackets, and conventional elastomeric ligated brackets after 18 months of active orthodontic treatment.

Registration

The trial is registered at ClinicalTrials.gov ( NCT02745626 ).

Protocol

The protocol was not published before trial commencement.

Highlights

  • Effects of clear aligners, self-ligated brackets, and conventional (elastomeric-ligated) brackets on oral hygiene were evaluated.

  • Seventy-one patients were randomly assigned to the 3 groups based on appliance type for orthodontic treatment.

  • Short-term (9 month) and long-term (18 month) evaluations of plaque index, gingival index, and periodontal bleeding index were carried out through treatment.

  • Periodontal parameters worsened for all groups as treatment progressed.

  • Long-term outcomes showed no significant difference in oral hygiene between groups.

Dental plaque is considered to be the primary etiologic factor for gingival inflammation and periodontitis. Its development has been associated with several environmental and individual factors including diet, oral hygiene, fluoride exposure, quality of saliva, composition of oral microflora, and immune factors. Plaque accumulation is also a concern with orthodontic devices such as bonded brackets, archwires, and elastics because they hinder access to good oral hygiene measures causing gingival inflammation and subsequent decalcification. Numerous studies have evaluated the effect of fixed orthodontic appliances on microbial flora and periodontal status ; however, only a few have compared different appliances or modalities of treatment as an additional factor. The choice of orthodontic appliance might be an important factor to consider, assuming that orthodontic therapy results in small detrimental effects to the periodontium.

Although self-ligated brackets and clear aligners are considered to facilitate better oral hygiene when compared with conventional (elastomeric-ligated) brackets, there are conflicting reports in the literature. Tuncer and Baylas found significant differences in probing pocket depth between removable and fixed appliances. Karkhanechi et al also reported decreased periodontal status with fixed appliances compared with removable aligners. In contrast, Årtun et al reported similar periodontal indexes between removable and fixed appliances. This agrees with other studies that reported fixed appliances as opposed to removable appliances do not increase the risk of periodontal disease. Similarly, conflicting reports also exist between self-ligated and elastomeric-ligated fixed appliances.

In a systematic review, Rossini et al concluded that most of the previous studies have several methodologic problems. In addition, sufficient clinical data are lacking regarding their overall biologic compatibility to support higher levels of evidence-based dentistry (eg, randomized clinical trials). Little data seem to be available on the accumulation of plaque on teeth during treatment and its effect on the gingival architecture, especially in the long term. Such quantification will provide invaluable information for improvements in these treatment modalities.

Specific objectives and hypotheses

The aim of this prospective randomized clinical trial was to compare the effects of clear aligners, self-ligated brackets, and elastomeric-ligated brackets on patients’ oral hygiene during active orthodontic treatment. The null hypothesis was that oral hygiene in orthodontic patients is not affected by the type of orthodontic appliance.

Material and methods

Trial design

We report a 3-arm parallel-group, randomized, single blinded, clinical trial with an allocation ratio of 1:1:1 conducted in the United States. The Institutional Review Board at the University of Connecticut Health approved the study on December 12, 2011 (number 12-025-2), and written informed consent was received from all parents, guardians, and children. No changes to the methodology occurred after trial commencement. The study follows the Declaration of Helsinki guidelines The trial is registered at ClinicalTrials.gov ( NCT02745626 ). The presentation of this report is according to the CONSORT guidelines for reporting trials. All methods were performed in accordance with the approved guidelines and regulations.

Participants, eligibility criteria, and settings

The participants were recruited from the outpatient orthodontic clinic, University of Connecticut Health, Farmington, Conn, between December 2011 and March 2014. Eligibility criteria for the participants included the following: (1) physically healthy with no relevant allergies or medical problems, (2) older than 12 years of age at commencement of treatment, (3) permanent dentition, (4) less than 5 mm of anterior crowding or spacing with adequate overjet and overbite, (5) ability to maintain adequate oral hygiene, and (6) optimum dental health without immediate need for any allied dental procedure. The exclusion criteria were (1) skeletal anteroposterior discrepancies between the maxilla and the mandible (ANB, ≥5°), (2) centric relation-centric occlusion discrepancies greater than 3 mm; and (3) active periodontal disease.

Interventions

Participants were randomly assigned to 1 of the 3 treatment groups based on the choice of intervention: (1) Clear Aligners (CLA) (Invisalign, Align technology, San Jose, Calif); (2) preadjusted edgewise fixed appliance with self-ligated brackets (SLB) (Carriere, Carlsbad, Calif); and (3) preadjusted edgewise fixed appliance with elastomeric ligated brackets (ELB) (Ortho Organizers Inc., Carlsbad, CA). In addition to the consent form for routine orthodontic care currently used in the University of Connecticut Health orthodontic clinic, the parent or guardian of each subject was given a written explanation of the background of the study, its objectives, and their involvement. The study called for no additional treatments or procedures not normally performed during routine oral care for initial bonding or orthodontic adjustment visits.

Participants were requested to refrain from eating, drinking, or brushing 1 hour before the sampling appointments. They were given oral hygiene instructions and oral hygiene supplements at regular intervals throughout the treatment. The supplements consisted of a toothbrush, toothpaste, interdental brush, dental floss, and an information brochure on oral hygiene maintenance. The orthodontic treatment was performed in all patients by treating both arches simultaneously. All teeth were bonded with a direct technique using Transbond XT (3M, St. Paul, Minn). The first molars were banded. Participants with aligners were instructed to wear them at least 20 hours per day. The aligners were replaced every 2 to 3 weeks with a new set, which had been previously developed according to the treatment plan of each patient.

Outcomes (primary and secondary)

Periodontal measurements were recorded specifically for the maxillary second premolar before treatment (T0), after 9 months of treatment (T1), after 18 months or completion of treatment (T2), whichever came sooner. Clinical assessment of the periodontal health status was achieved by measuring plaque index (PI), gingival index (GI), and papillary bleeding index (PBI) ( Fig 1 ). All clinical measurements were performed by examiners (A.C., S.A., M.U.), calibrated to a single examiner. At least 90% intraexaminer agreement was achieved for each index before the study to ensure reliability of clinical evaluations.

Fig 1
CONSORT diagram showing the flow of subjects through the trial.

The PI was assessed by visual inspection of the accumulated plaque in the gingival area and was classified into 1 of 4 grades of the modified index of Loe ( Fig 1 ). The GI was assessed referring to color and tissue consistency according to the severity of existing inflammation of the marginal gingiva. The PBI was assessed by carefully inserting a periodontal probe (Hu-Friedy, Chicago, Ill) into the gingival sulcus. The data were registered 20 seconds after probing. The original indexes were modified because all evaluations took place during regular control visits.

The primary outcome measure was dental plaque surrounding the bracket of the maxillary second premolar at the 3 time points, whereas the secondary outcomes were gingival health and papillary bleeding. There were no outcome changes reported after the commencement of the trial. Adverse events during the study were also recorded.

Sample size

The power analysis was performed using the computer application G-Power to detect the mean differences among the treatment groups in the PI at T2. The effect size for analysis of variance was given by the following equation.

f = ∑ p i ( μ i − μ ) 2 σ 2

where n i = number of observations in group i where (i = 1, 2, 3; N = total number of observations; p i = n i N 😉 μ i = mean of group I; μ = grand mean; and σ 2 = error variance within groups.

It was assumed that all 3 groups would have the same sample size, ie, p 1 = p 2 = p 3 = 1/3. The mean PI at T2 in the ELB group was assumed to be 1.0 with the 3 groups sharing a common standard deviation of 0.5. The mean PI at T2 in the CLA or SLB group if ≤0.5 or ≥1.5 was considered clinically significant: ie, μ 1 = 1, μ 2 = 1, μ 3 = 0.5, or μ 1 = 1; μ 2 = 0.5, μ 3 = 0.5 or μ 1 = 1, μ 2 = 1; μ 3 = 1.5 or μ 1 = 1, μ 2 = 1.5, μ 3 = 1.5, all leading to f = 0.471. To detect this effect size by an analysis of variance F test, 16 patients per group were needed to achieve 80% power at the 5% significance level. It may be optimistic to assume that the PI would follow a normal distribution across the treatment groups. To maintain the same power, when the parametric assumptions are violated and a nonparametric test is used, a rule of thumb is to add 15% to the sample. This finalized the sample size to 19 per group.

Interim analyses and stopping guidelines

Not applicable.

Randomization (random number generation, allocation concealment, implementation)

The randomization sequence was generated by the statistician (C.L.K.) with a computer-generated list of random numbers by using an online software program ( mahmoodsaghaei.tripod.com/Softwares/randalloc.html#Random%20Allocation%20Software ), independent of the clinical investigators (A.C., S.A) involved in recruitment. To ensure a 1:1:1 allocation ratio, block randomization was done with random block sizes of 15, 6, 9, and 3. For all participants once the clinical investigators had obtained consent, they telephoned or texted a contact (M.U.) who was independent of the recruitment process for allocation consignment. Therefore, different persons performed sequence generation, allocation concealment, and implementation.

Blinding

Blinding of the clinical investigators and participants to the intervention in each group was impossible. Therefore, blinding was done for outcome assessment only. Unique identifiers that were created for each patient coded the extracted data appropriately. This was maintained in a secure, locked location separate from the collected data. The coding of the data was broken after the end of the analysis, and no breach of blinding was identified.

Interrater reliability

The examiners underwent training and calibration exercises for the collection of the clinical data (determination of PI, GI, and PBI). The calibration exercise consisted of 2 steps. The first was a theoretical step procedure that involved discussion of the indexes by analysis of photographs of the conditions. A periodontist with considerable experience coordinated this step, training 2 examiners in how to perform the examination. The second step was the clinical part, in which the examiners examined 20 randomly selected participants. Interexaminer agreement was tested. To examine measurement reliability, concordance correlation coefficients were calculated for the various parameters. Data analysis used the Cohen kappa coefficient on a tooth-by-tooth basis. Very good interexaminer agreements were obtained where all values of kappa were greater than 0.81.

Statistical analysis (primary and secondary outcomes)

Demographic and clinical characteristics were summarized with conventional descriptive statistics. Since most patients had periodontal scores of 0 or 1 across the 3 time points, the scores for the outcome variables (PI, GI, and PBI) were dichotomized as 0 and 1+ (1, 2, 3, or 4). A between-group comparison within the framework of a logistic regression model was conducted. The sample size was not sufficiently large for us to fit a logistic mixed effects model or its alternative of generalized estimating equations (GEE) model with the mixed effects of treatment group, time, and their interaction. Based on our graphic exploration of the relevant data, the effect of time was not found to be linear—ie, treatment groups and the differences among the groups varied with time. Therefore, time was modeled as a categorical variable to include the interaction between time and treatment groups. Logistic regression models were used to model the 3 outcomes at T0, T1, and T2 separately. We were able to include age and sex for adjustment to improve precision. In each model, the ELB group was considered as the reference group and compared with another treatment group via odds ratio. A P value smaller than 5% was considered statistically significant. All statistical analyses were performed in R 3.3.1 (R Core Team 2016; www.R-project.org ).

Material and methods

Trial design

We report a 3-arm parallel-group, randomized, single blinded, clinical trial with an allocation ratio of 1:1:1 conducted in the United States. The Institutional Review Board at the University of Connecticut Health approved the study on December 12, 2011 (number 12-025-2), and written informed consent was received from all parents, guardians, and children. No changes to the methodology occurred after trial commencement. The study follows the Declaration of Helsinki guidelines The trial is registered at ClinicalTrials.gov ( NCT02745626 ). The presentation of this report is according to the CONSORT guidelines for reporting trials. All methods were performed in accordance with the approved guidelines and regulations.

Participants, eligibility criteria, and settings

The participants were recruited from the outpatient orthodontic clinic, University of Connecticut Health, Farmington, Conn, between December 2011 and March 2014. Eligibility criteria for the participants included the following: (1) physically healthy with no relevant allergies or medical problems, (2) older than 12 years of age at commencement of treatment, (3) permanent dentition, (4) less than 5 mm of anterior crowding or spacing with adequate overjet and overbite, (5) ability to maintain adequate oral hygiene, and (6) optimum dental health without immediate need for any allied dental procedure. The exclusion criteria were (1) skeletal anteroposterior discrepancies between the maxilla and the mandible (ANB, ≥5°), (2) centric relation-centric occlusion discrepancies greater than 3 mm; and (3) active periodontal disease.

Interventions

Participants were randomly assigned to 1 of the 3 treatment groups based on the choice of intervention: (1) Clear Aligners (CLA) (Invisalign, Align technology, San Jose, Calif); (2) preadjusted edgewise fixed appliance with self-ligated brackets (SLB) (Carriere, Carlsbad, Calif); and (3) preadjusted edgewise fixed appliance with elastomeric ligated brackets (ELB) (Ortho Organizers Inc., Carlsbad, CA). In addition to the consent form for routine orthodontic care currently used in the University of Connecticut Health orthodontic clinic, the parent or guardian of each subject was given a written explanation of the background of the study, its objectives, and their involvement. The study called for no additional treatments or procedures not normally performed during routine oral care for initial bonding or orthodontic adjustment visits.

Participants were requested to refrain from eating, drinking, or brushing 1 hour before the sampling appointments. They were given oral hygiene instructions and oral hygiene supplements at regular intervals throughout the treatment. The supplements consisted of a toothbrush, toothpaste, interdental brush, dental floss, and an information brochure on oral hygiene maintenance. The orthodontic treatment was performed in all patients by treating both arches simultaneously. All teeth were bonded with a direct technique using Transbond XT (3M, St. Paul, Minn). The first molars were banded. Participants with aligners were instructed to wear them at least 20 hours per day. The aligners were replaced every 2 to 3 weeks with a new set, which had been previously developed according to the treatment plan of each patient.

Outcomes (primary and secondary)

Periodontal measurements were recorded specifically for the maxillary second premolar before treatment (T0), after 9 months of treatment (T1), after 18 months or completion of treatment (T2), whichever came sooner. Clinical assessment of the periodontal health status was achieved by measuring plaque index (PI), gingival index (GI), and papillary bleeding index (PBI) ( Fig 1 ). All clinical measurements were performed by examiners (A.C., S.A., M.U.), calibrated to a single examiner. At least 90% intraexaminer agreement was achieved for each index before the study to ensure reliability of clinical evaluations.

Fig 1
CONSORT diagram showing the flow of subjects through the trial.

The PI was assessed by visual inspection of the accumulated plaque in the gingival area and was classified into 1 of 4 grades of the modified index of Loe ( Fig 1 ). The GI was assessed referring to color and tissue consistency according to the severity of existing inflammation of the marginal gingiva. The PBI was assessed by carefully inserting a periodontal probe (Hu-Friedy, Chicago, Ill) into the gingival sulcus. The data were registered 20 seconds after probing. The original indexes were modified because all evaluations took place during regular control visits.

The primary outcome measure was dental plaque surrounding the bracket of the maxillary second premolar at the 3 time points, whereas the secondary outcomes were gingival health and papillary bleeding. There were no outcome changes reported after the commencement of the trial. Adverse events during the study were also recorded.

Sample size

The power analysis was performed using the computer application G-Power to detect the mean differences among the treatment groups in the PI at T2. The effect size for analysis of variance was given by the following equation.

f = ∑ p i ( μ i − μ ) 2 σ 2

where n i = number of observations in group i where (i = 1, 2, 3; N = total number of observations; p i = n i N 😉 μ i = mean of group I; μ = grand mean; and σ 2 = error variance within groups.

It was assumed that all 3 groups would have the same sample size, ie, p 1 = p 2 = p 3 = 1/3. The mean PI at T2 in the ELB group was assumed to be 1.0 with the 3 groups sharing a common standard deviation of 0.5. The mean PI at T2 in the CLA or SLB group if ≤0.5 or ≥1.5 was considered clinically significant: ie, μ 1 = 1, μ 2 = 1, μ 3 = 0.5, or μ 1 = 1; μ 2 = 0.5, μ 3 = 0.5 or μ 1 = 1, μ 2 = 1; μ 3 = 1.5 or μ 1 = 1, μ 2 = 1.5, μ 3 = 1.5, all leading to f = 0.471. To detect this effect size by an analysis of variance F test, 16 patients per group were needed to achieve 80% power at the 5% significance level. It may be optimistic to assume that the PI would follow a normal distribution across the treatment groups. To maintain the same power, when the parametric assumptions are violated and a nonparametric test is used, a rule of thumb is to add 15% to the sample. This finalized the sample size to 19 per group.

Interim analyses and stopping guidelines

Not applicable.

Randomization (random number generation, allocation concealment, implementation)

The randomization sequence was generated by the statistician (C.L.K.) with a computer-generated list of random numbers by using an online software program ( mahmoodsaghaei.tripod.com/Softwares/randalloc.html#Random%20Allocation%20Software ), independent of the clinical investigators (A.C., S.A) involved in recruitment. To ensure a 1:1:1 allocation ratio, block randomization was done with random block sizes of 15, 6, 9, and 3. For all participants once the clinical investigators had obtained consent, they telephoned or texted a contact (M.U.) who was independent of the recruitment process for allocation consignment. Therefore, different persons performed sequence generation, allocation concealment, and implementation.

Blinding

Blinding of the clinical investigators and participants to the intervention in each group was impossible. Therefore, blinding was done for outcome assessment only. Unique identifiers that were created for each patient coded the extracted data appropriately. This was maintained in a secure, locked location separate from the collected data. The coding of the data was broken after the end of the analysis, and no breach of blinding was identified.

Interrater reliability

The examiners underwent training and calibration exercises for the collection of the clinical data (determination of PI, GI, and PBI). The calibration exercise consisted of 2 steps. The first was a theoretical step procedure that involved discussion of the indexes by analysis of photographs of the conditions. A periodontist with considerable experience coordinated this step, training 2 examiners in how to perform the examination. The second step was the clinical part, in which the examiners examined 20 randomly selected participants. Interexaminer agreement was tested. To examine measurement reliability, concordance correlation coefficients were calculated for the various parameters. Data analysis used the Cohen kappa coefficient on a tooth-by-tooth basis. Very good interexaminer agreements were obtained where all values of kappa were greater than 0.81.

Statistical analysis (primary and secondary outcomes)

Demographic and clinical characteristics were summarized with conventional descriptive statistics. Since most patients had periodontal scores of 0 or 1 across the 3 time points, the scores for the outcome variables (PI, GI, and PBI) were dichotomized as 0 and 1+ (1, 2, 3, or 4). A between-group comparison within the framework of a logistic regression model was conducted. The sample size was not sufficiently large for us to fit a logistic mixed effects model or its alternative of generalized estimating equations (GEE) model with the mixed effects of treatment group, time, and their interaction. Based on our graphic exploration of the relevant data, the effect of time was not found to be linear—ie, treatment groups and the differences among the groups varied with time. Therefore, time was modeled as a categorical variable to include the interaction between time and treatment groups. Logistic regression models were used to model the 3 outcomes at T0, T1, and T2 separately. We were able to include age and sex for adjustment to improve precision. In each model, the ELB group was considered as the reference group and compared with another treatment group via odds ratio. A P value smaller than 5% was considered statistically significant. All statistical analyses were performed in R 3.3.1 (R Core Team 2016; www.R-project.org ).

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Dec 12, 2018 | Posted by in Orthodontics | Comments Off on Which orthodontic appliance is best for oral hygiene? A randomized clinical trial
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