Bond Strength Comparison of Orthodontic Brackets Bonded Using Four Indirect Bonding Transfer Techniques

After the introduction of the straight wire appliance by Andrews in 1972 to the orthodontic profession, it became important to position the brackets accurately on the teeth to achieve the desired results from the prescription built in the appliance. Silverman et al. in 1972 introduced the indirect bonding technique to help position the appliances accurately on the teeth. Indirect bonding technique is achieved by positioning the orthodontic brackets on the dental model of the patient and fabricating a transfer tray that holds the brackets and allows for bonding of a section or the entire dental arch simultaneously. There has been many modifications to the original indirect bonding technique described by Silverman. Most of the current techniques are based on a technique introduced by Thomas (1979) in which the brackets are attached to the dental cast with composite resin to form a custom-fit bonding pad.;With the introduction of different IDB techniques, the orthodontist is faced with the task of choosing a technique that is consistent and efficient. One that requires the least amount of laboratory preparation and cost. The purpose of this in vitro study was to compare the tensile bond strength of four indirect bonding (IDB) transfer techniques that allows for using light-cure adhesive to bond the orthodontic brackets with the custom composite base to the teeth, and to compare them to direct bonding (DB). Three hundred and thirty permanent bovine incisors were collected and mounted in acrylic blocks in groups of 6 representing an upper moderately crowded anterior arch with 2 teeth in the central position, 2 teeth at the palatally crowded lateral incisor position, and 2 teeth at the canine position. The blocks were randomly assigned to 5 groups; (1) Double Tray IDB, (2) RMbond(TM) IDB, (3) RMbond(TM) with an overlay hard tray, (4) Glue Gun IDB techniques, and (5) a control group of DB.;Tensile bond testing was performed for the test groups within 1 hour of the bonding procedure. Mean Tensile Bond Strength (TBS) (+/- SD) was 4.87 (+/-1.5), 3.98 (+/-1.41), 4.52 (+/-1.61), 4.5 (+/-1.42) and 3.83 (+/-1.24) for groups 1--5 respectfully. A one way ANOVA test showed that group (1) had a significantly higher TBS compared to groups (2) and (5); F = 5.621, p < 0.001. When the tooth position was considered, a one way ANOVA revealed a significant difference at the central position with group (3) having higher TBS compared to the control group (5), F = 4.436, p = 0.002. For each tooth, a modified Adhesive Remnant Index (ARI) was determined. All test groups had 81% of failure at the bracket adhesive interface where the entire adhesive was left on the tooth surface, 100% of the Direct bonding group (5) sample included. All IDB groups had some adhesive left on the tooth surface in 16% of the sample and no adhesive left on the tooth in 1.9%.