INTRODUCTION

A contributor to the success of fixed appliance therapy is reliable attachment of the bonded or banded components to the teeth so that they survive masticatory and mechanical forces during the treatment episode. Bonded attachments are used routinely as part of fixed appliance therapy; however, bands rather than bonded tubes remain popular for molars.12 Orthodontic bands are subjected to a large number of forces in the mouth, resulting in complex stress distribution within the adhesive and its junctions with the enamel and the band interior.34 Optimally, adhesive strength should be sufficient to keep the band on the tooth for the length of the treatment but not of such a magnitude that the tooth surface is damaged when the band is removed. In addition, the adhesive should ideally be easy to use, protective against dental caries, and of reasonable cost.

Band retention is affected mechanically by its close adaptation to the tooth assisted by the cement lute.5 Zinc phosphate, zinc silicophosphate, and zinc polycarboxylate cements were used as principal band cements until the early 1990s.6 Zinc phosphate cements have solubility intraorally and rely entirely on mechanical adhesion for their retentive effect.78 In contrast, polycarboxylate cements react chemically with enamel and stainless steel,7 but high viscosity, short setting time, and high intraoral solubility led to their waning popularity as a band luting agent.8

Some zinc phosphate–based cements are still used by a small proportion of orthodontists, although most now use a glass ionomer or glass ionomer–based cement.9 Glass ionomer cements have become the most commonly used cement for band cementation because of their favorable properties of fluoride release and uptake,10 microbial inhibition,11 and adhesion to both enamel and metal.612 These cements, however, require up to 24 hours to reach maximum strength and are susceptible to moisture contamination during the setting reaction.13 Adding resin to the cement formulation has allowed light curing, a snap set, and rapid strength development.14

These newer cements may be classified as follows15: (1) polyacid-modified composite resin (compomer) and (2) resin-modified glass ionomer cements. In vitro studies of modified composites16–18 and resin-modified glass ionomers1617 have shown significantly greater bond strengths compared with zinc phosphate16 or glass ionomer cement.1718 Glass polyphosphonate has also been used as an orthodontic band cement, but it does not belong to the zinc phosphate or glass ionomer groups.19 Because of the number of adhesives available to apply bands to teeth, it is important to understand which group bonds most reliably and which reduces or prevents dental decay during the treatment period.

This article is based on a Cochrane review published in The Cochrane Library.20 Cochrane reviews are regularly updated as new evidence emerges and in response to comments and criticisms, and the Cochrane Library should be consulted for the most recent version of the review. The aim of this review was to evaluate the effectiveness of the adhesives used to attach bands to teeth during fixed appliance treatment, in terms of how often the bands come off during treatment and whether they protect the banded teeth against decay during fixed appliance treatment.

MATERIALS AND METHODS

To be included in the review trials had to meet the following criteria:

• Study design: Randomized and controlled clinical trials, including split-mouth design.

• Participants: Patients with full arch fixed orthodontic appliance(s) that had bands attached to molars. Patients with cleft lip or palate or other craniofacial syndromes were excluded.

• Interventions: Any adhesives used to attach orthodontic bands to molar teeth. This excludes adhesives used to cement brackets to teeth, which was the subject of a separate review.21

• Exclusions: Studies were excluded that used headgear to molar bands, intermaxillary elastic traction to molar bands, soldered lingual or palatal arches to molar teeth, bands cemented to primary molars or premolars, or different molar types on opposite sides of the mouth. Studies in which patients were followed up for less than 12 months were also excluded.

• Outcome measures: The primary outcome measures were adhesive band failure and decalcification.

Dichotomous data on the success of each adhesive (whether the metal band stays cemented to the tooth or not) were recorded. Where these data were not available, annualized failure rates of adhesives were noted. The presence or absence of decay (decalcification) associated with or around the bands was recorded, along with the size/area of decalcifications if available. Data on adverse events, length of treatment, treatment cost, and time to replace bands with an adhesive were also recorded.

RESULTS

Twenty-four trials were deemed potentially relevant to the review. After subsequent assessment of the full articles only eight were found to meet the inclusion criteria: five randomized controlled trials1923–26 and three controlled clinical trials.27–29 Sixteen studies were excluded, details of which are presented in the full Cochrane review.20 A description of each included trial is presented in Table 1.

Table 1.  Characteristics of Included Trials.^a

View Fullscreen

All included trials were of split-mouth design. Interventions assessed were zinc phosphate cement, glass ionomer cement, polyacid-modified composite resin (compomer), resin-modified glass ionomer cement, and glass polyphosphonate cement. No trial examined the effectiveness of zinc silicophosphate cement or zinc polycarboxylate.

All trials reported failure, typically defined as band loosening. Only two trials stated the date used for assessing failure: one trial recorded the date the patient returned for band recementation23 and another recorded the date the patient became aware of band loosening.25 Only two trials clearly reported follow-up of patients until the end of the treatment period.2329 In one study the observation period was unclear.25

The methodologic quality of the included trials is presented in Table 2. The generation of the random number sequence was considered adequate in only three trials.192526 All three trials used a random numbers table. The generation of the sequence was unclear in three trials,232429 and in the other trials adhesives were allocated using a quasi-random method.2728 Only one of the trials reported adequate allocation concealment,26 and in none of the trials was it clear whether outcome assessment was truly blind. Only one of the trials reported an a priori sample-size calculation.26 In four trials there were no dropouts.19242627 In two trials, the number of dropouts was clearly described, although reasons were not reported.2329 In two trials, the number of dropouts was unclear.2528 Only one trial was considered to be at low risk of bias.26 Data analysis was not always appropriate within the included trials.

Table 2.  Methodologic Quality of Included Trials

View Fullscreen

DISCUSSION

Following application of the exclusion criteria adopted for this review, only eight trials were identified as relevant. In general, trials were considered to be at medium to high risk of bias. The method of randomization and allocation concealment was often inadequate or poorly reported, and blinding of the outcome assessor was unclear in all trials. A sample-size calculation was only reported in one trial.26 Five studies had no dropouts; one dropout occurred in one trial, but the number of dropouts was not adequately clarified in two trials. The overall high rates of patient follow-up suggest that it is possible to minimize attrition bias in trials of orthodontic band adhesives; however, all dropouts and withdrawals should still be recorded and included in the analysis.

Reporting of band failure rate was insufficient in all studies. Greater care is required to ensure that the statistical analyses are most appropriate for the trial design adopted. Split-mouth trials can be used when the adhesives being assessed do not release an agent that could influence failure or decalcification. However, where a split-mouth design is used, the mean failure rate or mean survival time per band adhesive type per patient should be reported along with standard deviation or 95% confidence intervals. Where individual patients are allocated to one or other band adhesive type, then the outcome data with respect to adhesive failure /survival should be reported in the same manner. Future trials should involve a statistician in the study design, sample-size calculation, and projected data analyses.

Only two trials report outcome assessment at the completion of the treatment period.2329 A previously published systematic review examining the effectiveness of adhesives for fixed orthodontic brackets excluded all trials that did not follow patients until the end of the appliance treatment period.21 While the current review has been less restrictive in its inclusion criteria, future trials should report outcomes after the completion of treatment to enable a more objective assessment of the effectiveness of one band adhesive over another.

Because of the inherent bias in most of the trials included, their results should be interpreted with great caution. There is insufficient evidence to support or refute the use of one adhesive over the other with regard to band failure. There is weak evidence from two trials2429 that there is less decalcification on teeth where bands had been cemented with glass ionomer rather than zinc phosphate.

CONCLUSIONS

• There is insufficient evidence to make firm recommendations for the use of one band adhesive over another. Further high quality randomized controlled trials are required.