Biomedical subjects
Publications and source records attributed to D E Fehr.
This article reviews some of the characteristics of ceramic brackets that are of particular interest to the clinician. Various factors that may significantly influence bond strength and bracket removal are discussed. The information provided should enable the clinician to debond ceramic brackets safely applying available scientific information.
Debonding ceramic brackets is an area of concern to clinicians. Reports of enamel fractures and cracks have raised questions about the safety of the procedures used to remove these attachments. The purpose of this study was to compare the differences between the actual forces generated during bracket removal in the clinical setting and the shear forces applied during laboratory testing. Adhesive Remnant Index (ARI) scores are presented as a percentage of the total number of teeth tested and are compared between the two types of debonding methods. The ARI scores quantitatively express where the bond failure occurs during bracket removal. The results indicate that there is a significant difference between the mean bond strengths of the shear (107.8 kg/cm2) and the modified diametral compression (67.8 kg/cm2) forces. Debonding ceramic brackets with pliers requires the application of 30% less force to the enamel surface than debonding with the shear forces as tested in the laboratory. There were no significant differences in the ARI scores of the two groups--i.e. where the bond failures occurred.
The removal of most ceramic brackets is accomplished by specially designed pliers that apply some form of tensile or shear force to the tooth surface. While the shear and tensile bond strengths for ceramic brackets in vitro have been reported, a simulation of the actual force application when using sharp-edged debonding pliers to debond a bracket has not. The purpose of this study is to determine the effectiveness and the force levels generated by the use of both the wide and the narrow blades in the debonding of ceramic brackets. The present findings indicate that the narrow blades effectively debonded ceramic brackets with a significantly lower mean debonding force (120 kg/cm2) than the wider blades (150 kg/cm2). The surface area of the blade in contact with the bracket-adhesive interface is less for the narrow blade (2.0 mm) than for the wide blade (3.2 mm). This relatively smaller contact area is sufficient to debond a bracket at a significantly lower debonding force.
The purpose of this study is to evaluate the use of a sharp-edged debonding instrument on four different ceramic brackets with three different bonding materials and two different enamel conditioning techniques. The effectiveness of the debonding instrument was determined by evaluating the following variables: the amount of force required to debond the bracket, the amount of residual adhesive remaining on the enamel surface, the frequency of bracket failure, and the prevalence of any visible enamel damage. The results indicated that the bracket type, the adhesive, as well as the enamel conditioner, all have an effect on bond strengths when using a sharp-bladed debonding instrument. The following conclusions were derived from the present findings: (1) The mean debonding strength values for the different bracket, adhesive, and enamel conditioner combinations ranged between a low of 40 kg/cm2 and a high of 194 kg/cm2. Most debonding values were between 60 and 115 kg/cm2. (2) A number of bracket, adhesive, and conditioner combinations are considered to have clinically adequate bonding strength and are relatively safe (Table IX). (3) The use of polyacrylic crystal growth enamel conditioner resulted in significantly less adhesive being left on the tooth as compared with the phosphoric acid enamel conditioner.