The effect of long-term water storage on the tensile strength of orthodontic brackets bonded with resin-reinforced glass-ionomer cements

Effect of different concentrations of papain gel on orthodontic bracket bonding

Background

The objective of this study was to verify the hypothesis that enamel deproteinization with papain gel at concentrations of 2%, 4%, 6%, 8%, and 10% increases shear bond strength as concentration increases.

Methods

A total of 180 bovine mandibular permanent incisors were used, divided into six groups (n = 30), and denominated as follows: group 1 is the control group (CG) in which brackets are bonded with resin-modified glass ionomer cement (RMGIC) according to the manufacturer's recommendations and groups 2, 3, 4, 5, and 6 have brackets bonded with RMGIC after enamel deproteinization with papain gel at concentrations of 2%, 4%, 6%, 8%, and 10%, respectively. After bonding, teeth were immersed in artificial saliva and kept at a temperature of 37°C for 24 h. Mechanical tests were then performed in a universal mechanical test machine EMIC DL 5000 (Sao Jose dos Pinhais, Brazil). Values obtained were submitted to analysis of variance and then to Tukey's test (p < 0.05).

Results

The results demonstrated that groups 5 and 6 showed the highest shear bond strength, differing statistically from the other groups (p < 0.05). CG with no papain gel used showed the lowest value and in turn showed no differences for groups 2, 3, and 4. As regards adhesive remnant index, CG showed statistical differences from the others. Groups 2, 3, 4, 5, and 6, in which papain gel was used, presented no statistical differences among them (p > 0.05).

Conclusions

It was concluded that enamel deproteinization with 8% and 10% papain gel increases shear bond strength of orthodontic brackets bonded with RMGIC.

Torque stability of plastic brackets following multiple loading and artificial material aging--an in-vitro comparison

OBJECTIVE

The objective of this study was to compare the loaddeflection behavior of plastic brackets made of various materials in response to repeated torque loads with each other and with steel brackets. Material fatigue during wire's play in the bracket slot, the brackets' elasticity and the torsional forces applied were analyzed.

MATERIAL AND METHODS

Groups of ten brackets, each made of pure polycarbonate or variously reinforced polycarbonate or polyurethane, with and without a metal slot, were artificially aged and then torqued with a testing machine five times consecutively in a torque- measuring apparatus. The control group consisted of ten steel brackets. The resulting forces were recorded with the testing machine, and the wire's deflection recorded with a digital goniometer on a PC and submitted to one-way variance analysis at p < 0.05.

RESULTS

There were strong fluctuations among the bracket types in both the play of the wire in the bracket slot as well as the brackets' elasticity. The slot of all the polycarbonate-based brackets was bent open after a single load, except for those with a metal slot. After a single load of up to 20 degrees torque, all the brackets exhibited a significant loss of torque stability ranging between 5% for pure polyurethane and 28.5% for ceramic-reinforced polycarbonate. The loss of torque stability was roughly 17% on average. This loss did not increase significantly when additional loads were applied.

CONCLUSIONS

Each bracket material requires its own torque value to transfer identical torque values onto the tooth in clinical practice. Comparison with steel brackets revealed that only plastic brackets with a metal slot are suitable for clinical use. Adding ceramic and glass fibers to polycarbonate, or using polyurethane has no benefit in terms of torque stability. In addition, after a single application of torque, all brackets lose torque stability in response to a renewed load.

An in vitro comparison of the shear bond strength of a resin-reinforced glass ionomer cement and a composite adhesive for bonding orthodontic brackets

The shear bond strength (SBS) of a light-cured, resin-reinforced glass ionomer and a composite adhesive in combination with a self-etching primer was compared after different setting times to evaluate when orthodontic wires could be placed. Additionally, the fracture site after debonding was assessed using the Adhesive Remnant Index (ARI). Eighty freshly extracted human premolars were used. Twenty teeth were randomly assigned to each of four groups: (1) brackets bonded with Transbond XT with a Transbond Plus etching primer and debonded within 5 minutes; (2) brackets bonded with Fuji Ortho LC and debonded within 5 minutes; (3) brackets bonded as for group 1 and debonded within 15 minutes; (4) brackets bonded as for group 2 and debonded within 15 minutes. The SBS of each sample was determined with an Instron machine. The mean SBS were, respectively: (1) 8.8 +/- 2 MPa; (2) 6.6 +/- 2.5 MPa; (3) 11 +/- 1.6 MPa and (4) 9.6 +/- 1.6 MPa. Interpolating the cumulative fracture probability by means of a Weibull analysis, the 10 per cent probabilities of fracture for the groups were found to be attained for shear stresses of 6.1, 3.1, 8.3 and 7.1 MPa, respectively. Chi-square testing of the ARI scores revealed that the nature of the remnant did not vary significantly with time, but the type of bonding material could generally be distinguished in leaving more or less than 10 per cent of bonding material on the tooth. After debonding, the Transbond system was likely to leave adhesive on at least 10 per cent of the bonded area of the tooth. The present findings indicate that brackets bonded with either Transbond XT in combination with Transbond Plus etching primer and Fuji Ortho LC had adequate bond strength at 5 minutes and were even stronger 15 minutes after initial bonding.

Effects of buccal versus lingual surfaces, enamel conditioning procedures and storage duration on brackets debonding characteristics

OBJECTIVES

To determine the influence of two enamel conditioning techniques on buccal and lingual tooth surfaces at two different times on debonding strength and tooth damage.

METHODS

The study included 50 premolars. Buccal and lingual surfaces of 10 teeth were scanned using SEM before (N=4) and after enamel conditioning by either acid etching or sandblasting prior to acid etching (N=6) for their morphology. The remaining 40 teeth were divided into 2 equal groups, differing in enamel conditioning prior to metallic bracket bonding on the buccal and lingual surfaces. Each group was equally subdivided into short-term (48h) or long-term (12m) water storage. Debonding strength was measured followed by SEM and EDAX for adhesive remnant index (ARI) and calcium remnant index (CRI) left on bracket bases. ANOVA with repeated measures was applied to the results.

RESULTS

The buccal enamel was rougher than the lingual one. The surface morphology after the two types of conditioning showed a different pattern. A significantly higher debonding strength was needed to debond the buccal brackets compared to the lingual ones (p<0.05). A significantly higher ARI (p<0.002) and higher CRI (p<0.005) were found in the lingual surface compared with the buccal. No differences were found in debonding strength ARI or CRI regarding the different conditioning or storage duration.

CONCLUSIONS

Lingual bonding leads to higher ARI and CRI than buccal bonding. Sandblasting prior to etching does not improve bonding strength for lingual or buccal bonding.

A comparison of 3 alloy surface treatments for resin-bonded prostheses

PURPOSE

The most frequent cause of clinical failure of resin-bonded fixed partial dentures is a debonding at the metal-cement interface. The purpose of this in vitro study was to compare the tensile bond strengths of 3 different alloy-surface treatments when cemented to human enamel with a resin cement.

MATERIALS AND METHODS

Cylinders of a nickel-chromium-beryllium (Ni-Cr-Be) and a gold-palladium (Au-Pd) alloy were fabricated and assigned to different surface treatment groups as follows: Group 1: Ni-Cr-Be, chemically etched; Group 2: Au-Pd, airborne particle-abraded and tin-plated; and Group 3: Au-Pd, airborne particle-abraded and treated with the Alloy Primer (Kuraray Co, LTD, Osaka, Japan). The cylinders were bonded to the enamel surfaces of extracted, human third molars and stored in normal saline at 37 degrees C for 48 hours. The tensile bond strength of 21 specimens from each group was measured on a Universal Testing Machine (Instron, Canton, MA). Three failed specimens of each group were evaluated using scanning electron microscopy and energy dispersive spectroscopy.

RESULTS

Statistically significant differences (p <.05) were found between all 3 treatment groups. The mean tensile bond strengths (+/- the standard error of mean) recorded as follows: Group 1: 10.6 MPa (+/-1.3), Group 2: 0.9 MPa (+/-0.2), and Group 3: 13.4 MPa (+/-1.0). Specimens from groups 1 and 3 revealed a trend towards mixture of cohesive, within the resin cement, and adhesive failures at the metal-cement interface. Group 2 specimens exhibited primarily adhesive failures at the metal-cement interface.

CONCLUSIONS

The tensile bond strength of Au-Pd alloy specimens was significantly increased with the Alloy Primer.