Rate of bond failure of adhesive precoated brackets - A clinical survey

by Bruce M. Oliver, DDS, MS. , Mike Dama, MA., and Gina Normandin, HD

ABSTRACT

A subset of 33 respondents was selected from a survey sent to 106 orthodontists. Criteria for selection required orthodontist have clinical experience with both conventional non-precoated brackets and APC bracket/bonding systems. Respondents were asked to estimate bond failure frequencies at initial arch wire insertion and during subsequent treatment. A statistically significant difference was found for the estimated bond failure rates on initial arch wire insertion for the two techniques, but not for failure rates during treatment. Respondents using adhesive precoated brackets (APC) estimated the bond failures experienced on initial arch wire insertion to be significantly greater than that claimed by the manufacturer.

INTRODUCTION

APC brackets are promoted as a product that saves time and may decrease bond failures.¹ Research indicates 40 seconds rather then 20 seconds curing time may be more appropriate for metal APC brackets.² In vitro studies indicate that bond strength increase in the order of 20% when APC brackets are stressed after a 5 minute setting time, placing in question the advisability of engaging arch wires immediately after curing.²

The manufacturer of APC has referred to clinical studies suggesting less than 1% bond failure rate on initial arch wire insertion.¹ Retrospective clinical trials of APC over 6 months has demonstrated a failure rate of 3.28% on initial arch wire insertion.³ Such a large difference in reported efficacy of the product is disturbing. The purpose of this study was to evaluate if differences existed between estimated bond failure frequencies when clinicians use a precoated bracket system compared to a non-precoated bracket, bonded with light-cure adhesive; and to test if clinicians using the APC bracket/bonding system estimate bond failures frequencies to be less than 1% on initial arch wire insertion.

MATERIALS AND METHODS

In 1994 a survey requesting information on bonding procedures circulated to all orthodontists in Quebec (106). The survey consisted of 77 questions divided into 5 sections and provided anecdotal information regarding expected frequencies of bond failures which may prove useful to operators when choosing between various bracket/bonding systems.

Of 106 surveys circulated, 65 were completed by orthodontists, none of whom were involved in the design or editing of the survey. Table 1 describes the questions selected for analysis. A subset of 33 experienced operators were selected from the respondents. Criteria for selection required that the orthodontist have experience with both conventional non-precoated brackets and APC bracket/bonding systems and not delegate bonding procedures to auxillary staff. Four questions (#38,41,57,59) dealing specifically with frequencies of bond failures were selected for analysis.

Two operators entered the raw data and information transferals were verified three times for accuracy. The data was compiled by one statistician and standard statistical measurements were generated.

RESULTS

A total of 33 clinicians reported having had clinical experience with both conventional non-precoated bracket and adhesive precoated metal brackets. Twenty clinicians responded to both questions #38 and #57, and 28 responded to both questions #41 and #59, making a comparison possible between estimated frequencies of initial bond failures and subsequent bond failures during treatment for the two bracket/bonding systems. Table 2 gives the mean and standard deviations for the estimated failure rates for the non precoated brackets bonded with light-cure adhesive and the APC bracket/bonding system; both for initial arch wire insertion failures and for failures during treatment. Comparisons between the two bracket/bonding systems were done using matched t-tests. Responses were scored using the mid-point for a given response. For example, reporting a failure rate of 0-2% was scored as a 1% failure rate.

DISCUSSION

There was a significant difference between estimated frequencies of bond failure at initial arch wire insertion for the two bracket/bonding systems ( t(19) = -2.35, p < .05 ) suggesting that the estimated initial failure rate is higher for APC brackets. There was no significant difference between the estimated failure rates subsequent to initial arch wire insertion for the two bracket/bonding systems (t(26)= -1.07, p > .05 ). However, it should be noted that a closer analysis of questions #41 and 59 show that 40% of respondents who reported using the APC system evaluated failure rates during treatment to be 9% or greater, while only 23% of respondents using non precoated brackets bonded with light-cure indicated the same.

The manufacturer of the APC brackets has claimed that the failure rate of the APC brackets on initial arch wire insertion is less than 1 percent.¹ To test this hypothesis, a one sample t-test was performed on responses to item #57. Responses to item # 57 questioning failure rate of APC on initial arch wire insertion indicated the mean APC failure rate was 5.174% with a standard deviation of 5.149, and a standard error of 1.073, (N = 23). The estimated APC failure rate at initial arch wire insertion was significantly greater than 1 percent, (t(22)=3.89, p < .01) ). The mean estimated failure rate for APC at initial arch wire insertion being 5.14% suggest initial bond failures are occuring at a much higher rate than that claimed by the manufacturer.

CONCLUSION

Anecdotal information and testimonials as to the advocacy of certain products provide only a point from which various information can be gathered in order to test an assumption. Orthodontic manufacturers have introduced products to the market claiming the product to be the new standard in orthodontic treatment. A review of the literature suggests only limited scientific scrutiny has been performed on the APC product to validate the manufacturer's claims.

Information reported in this study can only serve as an initial step to decide if more controlled in vitro and clinical trials are warranted regarding the efficacy of the precoated bracket/bonding system. The results of this study would suggest more clinical and in vitro testing of bond failures both at initial arch wire insertion and during subsequent treatment are required of the APC product before the manufacturer can assure the orthodontists of the accuracy of previous advertisement claims.

Acknowledgment:

The authors gladly and gratefully recognize Dr. Edward Shields, Associate Professor, Faculty of Dentistry and Mrs. Rhonda Amsel, Faculty Lecturer, Department of Psychology, McGill University, for their suggestions while developing the questionaire, as well as Mrs. Johanne Labreque for compilation of the survey data.

TABLE 1 Format of Survey on Bonding Procedures sent to Quebec Orthodontists in 1994.

TABLE 2

Means and standard deviations (S.D.) of estimated bond failure rates measured as a percentage for bracket/bonding systems investigated.

References:

1. 3M Unitek Corporation. Advertisement adhesive precoated brackets. Am. J. Orthod., and Dentofac. Orthop. 1993;103:6,Second Cover-1A
2. Oesterle, L.J., Messersmith, M.L., Devine, S.M., Ness, , C.F. Light and setting times of visible lightcured orthodontic adhesives. J. Clin. Orthod, 1995;29:31-35.
3. Oliver, B.M., A retrospective 6 months clinical trial of adhesive precoated bracket bonding system (A.P.C.) - [In Press] 1996. J.C.D.A.

   ---

[Next]	The Cantilever Bite Jumper
[Up]	Clinic and Research
[Home]	Home Page
[Mail]	Send EMail to The Orthodontic CYBERjournal
[Search]	Search The Orthodontic CYBERjournal
[Contents]	The Orthodontic CYBERjournal Contents