Evaluation of fluoride release from an orthodontic bonding system

Comparative Evaluation of Fluoride Release From Chemically Cured and Light-Cured Orthodontic Bonding Agents and Surface Alteration of Enamel: An in vitro Study

Introduction: Fluoride is known to reduce demineralization and enhance remineralization which is desirable around orthodontic brackets.

Material and methods: This study was carried out to determine the rate of fluoride release, fluoride content of enamel, and surface alteration of enamel from orthodontic bonding agents. Thirty extracted maxillary first premolars were divided into 2 groups of 15 teeth each. Group A—teeth were bonded with a chemically cured orthodontic bonding agent containing fluoride (Rely-a-Bond, Reliance, Itasca) and group B—teeth were bonded with a light-cured orthodontic bonding agent containing fluoride (Light Bond Reliance, Itasca). All individual sample teeth were used to estimate fluoride release and fluoride content of enamel. The same samples were also used to evaluate enamel surface alterations. The rate of fluoride release from the above 2 orthodontic bonding agents were measured in artificial saliva on day 1, 2, 3, 4, 5, 6, 7, 14, 30, 60, and 90. The fluoride content of the enamel was evaluated on day “0” and day “90” of bonding. The samples were also evaluated for the surface changes in enamel using scanning electron microscope (SEM).

Results: The results showed that (a) chemically cured and light-cured bonding agent showed a dramatic decrease in the concentration of fluoride release from day “1” to day “2,” (b) the concentration of fluoride release kept decreasing from day “1” to day “90” of measurement in both the groups, and (c) SEM of the bracket margins bonded with chemically cured bonding agent and light-cured bonding agent revealed particle depositions of irregular shape and size on day “90.”

Conclusion: Light-cured bonding agent (Light Bond) released higher concentration of fluoride as compared to chemically cured bonding agent (Rely-a-Bond). Light-cured bonding agent (Light Bond) showed higher increase in fluoride content of enamel than chemically cured bonding agent (Rely-a-Bond).

Antimicrobial properties of an orthodontic adhesive combined with cetylpyridinium chloride

INTRODUCTION

Patients undergoing fixed appliance treatment are at greater risk for increases in salivary and plaque levels of Streptococcus mutans and an elevated risk of dental caries. Cetylpyridinium chloride (CPC) is known to be an effective antiplaque agent. The purpose of this study was to investigate whether incorporating CPC into a commercially available orthodontic adhesive would impart antimicrobial properties without altering the diametral tensile strength of the material.

METHODS

CPC was added to a commercially available, filled, photo-activated bracket adhesive (Transbond XT, Unitek 3M, Monrovia, Calif) in varying amounts, to obtain specimens with CPC concentrations of 0% (control), 2.5%, 5.0%, and 10.0% by weight. Adhesive discs 2 mm thick and 4 mm in diameter were incubated with Streptococcus mutans for 48 hours. The diameters of the zones of bacterial inhibition were measured in an agar disc diffusion assay; specimens of each concentration were tested every other week for 196 days. Other discs were soaked in distilled water for 180 days. The amount of CPC released into the water from the modified discs was measured and recorded on days 7, 15, 30, 60, and 180 by using a spectrophotometer at 254 nm. Diametral tensile strength of the modified adhesive discs was measured with a universal testing machine, and the effect of water aging was also evaluated.

RESULTS

The measured zone of bacterial inhibition increased as CPC content increased. All CPC-adhesive specimens maintained antimicrobial activity up to 196 days. No zone of bacterial inhibition was measured around the control specimens. CPC release was observed through the end of 180-day period, but the greatest release was recorded in the first week. There was no significant difference (P < .05) in diametral tensile strength between the 2.5% CPC-adhesive group and the control; there were significant differences among the 5.0% and 10.0% CPC-adhesive groups and the control. Water aging had no significant effect on diametral tensile strength other than decreasing it for the test group containing 10.0% CPC.

CONCLUSIONS

The incorporation of 2.5% CPC in adhesive material imparted antimicrobial activity without altering diametral tensile strength.

Fluorides for the prevention of white spots on teeth during fixed brace treatment

BACKGROUND

White spots can appear on teeth during fixed brace treatment because of early decay around the brace attachments. Fluoride is effective at reducing decay in susceptible individuals and is routinely prescribed in various different forms to patients during orthodontic treatment.

OBJECTIVES

To evaluate the effectiveness of fluoride in preventing white spots during orthodontic treatment and to compare the different modes of delivery of fluoride.

SEARCH STRATEGY

We searched the Cochrane Oral Health Group's Trials Register (to 22 August 2002); CENTRAL (The Cochrane Library Issue 3, 2002); MEDLINE (January 1966 to July 2003); EMBASE (January 1980 to week July 2003). Authors of trials were contacted for further data.

SELECTION CRITERIA

Trials were selected if they met the following criteria: a randomised or quasi-randomised clinical trial, involving the use of a fluoride-containing product compared with no use or use of a non-fluoride control and enamel demineralisation was assessed during or after orthodontic treatment.

DATA COLLECTION AND ANALYSIS

Six reviewers independently, in duplicate, extracted data. The primary outcome was the difference in the presence or absence of white spots between experimental and control patients for parallel design studies, and between experimental and control quadrants, for split-mouth design studies. Potential sources of heterogeneity were examined. Sensitivity analyses were undertaken for the items assessed for quality and publication bias.

MAIN RESULTS

The primary outcome of the review was the presence or absence of white spots by patient at the end of treatment. Secondary outcomes included any quantitative assessment of enamel mineral loss or lesion depth. Other outcomes such as differences in size and severity of white spots, any patient based outcomes, such as perception of white spots could not be included because there were insufficient data. Fifteen trials, with 723 participants, provided data for this review. None of the studies fulfilled all of the methodological quality assessment criteria. There is some evidence that a daily sodium fluoride mouthrinse reduces the severity of enamel decay surrounding a fixed brace (weighted mean difference for lesion depth -70.0; 95% CI -118.2 to -21.8) and that use of a glass ionomer cement for bracket bonding reduces the prevalence (Peto OR 0.35; 95% CI 0.15 to 0.84) and severity of white spots (weighted mean difference for mineral loss -645 vol%.microm; 95% CI -915 to -375) compared with composite resins.

REVIEWERS' CONCLUSIONS

There is some evidence that the use of topical fluoride or fluoride-containing bonding materials during orthodontic treatment reduces the occurrence and severity of white spot lesions, however there is little evidence as to which method or combination of methods to deliver the fluoride is the most effective. Based on current best practice in other areas of dentistry, for which there is evidence, we recommend that patients with fixed braces rinse daily with a 0.05% sodium fluoride mouthrinse. More high quality, clinical research is required into the different modes of delivering fluoride to the orthodontic patient.

Fluoride release from orthodontic cements-effect of specimen surface area and depth

OBJECTIVE

The aims of this in vitro study were firstly to compare fluoride release from a disc model of two orthodontic cements with various surfaces varnished, reducing the surface area by 25, 50 and 75%; secondly, to measure the fluoride release from previously exhausted discs of the same cements following removal of various depths of surface material.

METHODS

Forty discs of each cement, Fuji Ortho LC and Ultra Band-Lok, (6mm diameter by 3mm) were divided into two groups of 20 discs each. For each material, the first group was divided further into four groups of five discs, one group acting as control, while the other three groups were varnished reducing the surface area by 25, 50 and 75%, respectively. The second group was exhausted initially over a 60 day pre-experimental period and was subsequently divided into four groups of five discs, one group acting as control. The other three groups had material ground from one of the flat surfaces, to depths of 10, 100 or 1000 microm, to reveal a fresh surface. In both studies, the discs were immersed either daily (up to day 20) or twice weekly (up to day 60) in fresh 2ml aliquots of deionised water. The fluoride concentration in the deionised water was measured at the end of the experimental period.

RESULTS

For each cement, the relationship between the cumulative fluoride release and the percentage of the surface covered was clearly non linear at both 5 and 60 days. Fuji Ortho LC proved to release significantly greater amounts of fluoride at both 5 days and 60 days compared with Ultra Band-Lok. The results for Ultra Band-Lok were also significant when compared to the control group, but significantly less fluoride was released when compared with Fuji Ortho LC. When comparing the 25 and 50% covered discs, the amount of fluoride released was not significantly different for both cements. Furthermore, the relationship between fluoride release and depth was clearly non linear for both cements.

CONCLUSIONS

For the materials tested in this study, reducing the surface area of the discs did not reduce the cumulative fluoride release in a linear fashion. In addition, the previously exhausted discs began to release fluoride again, but this fell to concentrations similar to the control discs after the initial 5-day period for both cements. This suggests that further traces of previously unreleased fluoride had become available from the subsurface of these cements. The pattern of fluoride release was similar for all models tested.

Metallic bracket to enamel bonding with a photopolymerizable resin-reinforced glass ionomer

Enamel acid etching plays an important role in treatment on direct bracket bonding. Several studies have been carried out concerning the damage this procedure causes to the enamel. A valuable alternative seems to be the use of photopolymerizable resin-reinforced glass ionomer without acid etching of enamel. This study compares the strength of bracket debonding, the amount of remnant adhesive on the tooth, and the enamel condition in 3 adhesive systems. Three groups were set; in the first group, a glass ionomer with a photopolymerizable resin reinforce and enamel etching with orthophosphoric acid at 37% was used; in the second group, the same ionomer was used but without acid etching; and in the third group, a photopolymerizable resin was used after etching enamel with orthophosphoric acid at 37%. Debonding strength was determined in MPa; a stereoscopic microscope was used to determine the amount of remnant adhesive on the tooth in accordance to ARI and a scanning electron microscope study was made to observe the enamel conditions, existing in debonding among groups (P <.0001), with etching and without etching. The remnant adhesive on the tooth did not show a significant difference (P = 1.000); greater irregularities were found in the enamel in the etching groups. It was demonstrated that the etching was a critical factor in obtaining adequate adhesion strength and that it alters the enamel conditions. Teeth with ionomer and etching had a greater material remnant.

Effect of a fluoride varnish on demineralization adjacent to orthodontic brackets

Home fluoride regimens have long been used to reduce the amount of demineralization adjacent to orthodontic appliances. In the absence of patient compliance, another method of applying the fluoride must be used. The purpose of this study was to evaluate, in vitro, the ability of a fluoride varnish, Duraflor, to directly inhibit demineralization of enamel surrounding orthodontic brackets. Brackets were bonded to 36 extracted human canines and premolars with a traditional composite resin and randomly assigned to three equal groups of twelve. Group 1 served as the control with no topical application after bonding. Group 2 was treated with a single application of a nonfluoridated placebo varnish. Group 3 was treated with a single application of Duraflor. All groups were cycled in an artificial caries challenge for 1 hour two times daily for 37 days and were brushed with a medium bristled toothbrush to simulate mechanical wear of the varnish. Demineralization of enamel was evaluated in longitudinal buccolingual tooth sections using polarized light microscopy. Both average depth and area of demineralization were measured with a sonic digitizer. ANOVA (P </=. 0001) and Duncan's test (P </=.05) indicated significant differences in depth and area of demineralized enamel. Those teeth treated with Duraflor exhibited 50% less demineralization than the control teeth and an even greater difference when compared to the placebo group. Fluoride varnishes should be considered for use as a preventive adjunct to reduce enamel demineralization adjacent to orthodontic brackets, particularly in patients who exhibit poor compliance with oral hygiene and home fluoride use.

In vitro measurement of enamel demineralization in the assessment of fluoride-leaching orthodontic bonding agents

The aim of this study was to measure in vitro demineralization around orthodontic brackets, bonded with five different bonding agents. Two conventional bonding agents, two fluoride-leaching agents, and a glass ionomer were tested. A sixth group utilized a fluoride varnish after bonding. The amount of dissolved enamel mineral was determined from increases in the phosphorus concentration in the demineralizing solution and measurements were made over a 4 week period. The results confirmed that when fluoride is present in the form of a fluoride-leaching bonding agent or a fluoride varnish, resistance to demineralization is enhanced. Analysis of variance showed that Ketac-cem, Concise with Duraphat, and Pulpdent O.B.A. performed statistically significantly better than Concise, Bond-fast, and Rely-a-bond, in resisting enamel demineralization.

Fluoride released from orthodontic bonding agents alters the enamel surface and inhibits enamel demineralization in vitro

In this study, we examined two fluoride-releasing orthodontic agents in respect to fluoride release, enamel demineralization inhibition, as well as alterations observed on the enamel surface after their use. Fluoride release was found to occur in the highest concentrations within the first 24 hours for both materials examined. After this period, a dramatic decline in fluoride release was observed in both adhesives, and after 90 days no fluoride was detectable. Both fluoride-releasing materials showed significant differences on enamel demineralization around the brackets when compared with a conventional adhesive, and the agent with the initial higher amounts of fluoride release showed the best results. Scanning electron microscopy of the enamel surface revealed particle depositions of microglobular form, after the examined adhesives were used. These particles most likely represent deposition of calcium fluoride, a salt with clearly cariostatic properties. The results of this in vitro study show that certain fluoride-releasing orthodontic bonding systems may provide an additional degree of safety against caries susceptibility in patients with fixed appliances for a limited period.

Retention capacity of the bracket bases of new esthetic orthodontic brackets

Tensile bond strength and bond failure locations were evaluated in vitro for three types of direct bonding cements (self-cured diacrylate, dual-cured diacrylate, and dual-cured glass ionomer) with four types of brackets (stainless steel, polycarbonate, ceramic, and ceramic-polycarbonate) by using a plastic cylinder as the substrate. A highly filled, self-cured diacrylate cement gave the highest bond strength values with the polycarbonate, stainless steel, and ceramic-polycarbonate brackets. A dual-cured diacrylate cement gave the highest bond strength with a mechanically retained ceramic bracket. The dual-cured glass ionomer cement gave the highest bond strength values with a silanated ceramic bracket. All bond failures occurred at the bracket/cement interface with the stainless steel bracket, whereas failure locations were at the bracket/cement interface and within the cement with the polycarbonate bracket. Bond failures occurred between bracket and cement, within the cement, and within the bracket with the ceramic brackets.

[An in-vitro study of the bonding and fracture pattern of light-hardening, fluoride-releasing bonding materials in metal brackets]

Three hundred bovine incisors, which were divided into 6 groups of 50 teeth each, were used in this study. Two types of metal brackets, 1 with a conventional foil mesh base and the other with a photo-etched Micro-Loc base, were adhered to the teeth with 3 different bonding agents, namely, Sequence, a fluoride-releasing, light-activated composite, Photac-Fil, a light-hardened glass ionomer cement, and, in the control group, Concise, a 2-component composite which hardens chemically. A universal testing machine was employed to test tensile bonding strength and the site of failure was visually determined and analyzed. The study showed that Sequence can be considered as a qualitatively equal alternative to Concise. Both composites demonstrate equal tensile bonding strength. The use of Photac-Fil, the light-hardened glass ionomer bonding agent, cannot be recommended. It possesses significantly less tensile bonding strength than the other 2 bonding agents. Sequence and Concise, which showed better results with the brackets with conventional foil mesh base than with the brackets with photo-etched Micro-Loc base, had no significant differences in their failure sites. The interface of the composite with the bracket was the main failure site. Both composites demonstrated a significantly reduced rate of failure at the interface of the composite with the enamel, when they were used with the brackets with the Micro-Loc base. This differed from the failure site of Photac-Fil, when the photo-etched base was used. With Photac-Fil the main site of failure came at the interface of the enamel with this glass ionomer cement.(ABSTRACT TRUNCATED AT 250 WORDS)

The clinical evaluation of a fluoride-containing orthodontic bonding material

A clinical trial comparing a conventional adhesive, Concise, with a new fluoride-containing composite cement is described. The bond failure rate, plaque score, gingival health, and enamel decalcification were assessed for each material after a minimum period of 1 year. The preliminary results show no significant difference between the two materials for each of the variables examined, although there was a reduction in the number of white spot lesions using the fluoride-containing composite. The level of fluoride ion concentration required to inhibit the growth of oral micro-organisms is discussed.

Decalcification during orthodontic treatment with fixed appliances--an overview

The prevalence and aetiology of decalcification during orthodontic treatment with fixed appliances is discussed and consideration given to the methods of reducing this problem.