Clinical Comparison of Direct Versus Indirect Bonding with Different Bracket Types and Adhesives

A longitudinal clinical trial was made in forty-two children to compare some commonly used techniques for orthodontic bracket bonding. A particular study design (Figs. 1 and 5) allowed blind quadrantwise comparisons in the same patient of six different variables, including direct versus indirect bonding, adhesives of the filled diacrylate resin type with small versus large filler particles, and metal brackets with mesh-backed versus perforated bases. The same person bonded all brackets within one week and performed the orthodontic treatment by a friction-free edgewise light-wire technique. Efforts were made to minimize gingival irritation by using eccentrically placed brackets on small bases, by careful trimming of excess adhesives flash around the bases, and by directing much emphasis on oral hygiene measures. The plaque situation around the brackets and along the gingival margins and the gingival condition were assessed according to the criteria of the plaque and gingival index systems by a dental hygienist at each monthly visit during a test period of 6 months. The study demonstrated that both direct and indirect bonding with the different adhesives and bracket types could give clinically satisfactory results. Still, there were statistically significant differences in plaque retention, gingival inflammation, and bond strength. The bonding adhesive with small filler particles was more hygienic than and about as strong as two adhesives with larger, coarser filler particles. The mesh-backed brackets retained less plaque and gave stronger bonds than the brackets with perforated pads. Advantages of direct bonding over the indirect procedure were that (1) the bracket bases were fitted closer to the tooth surface (which improved bond strength), (2) it was easier to work clean and to remove excess adhesive flash around the bracket bases (to help prevent gingival inflammation and decalcification and facilitate debonding), and (3) the bonding adhesive constantly filled out the entire contact surface of the brackets (thus avoiding artificial undercuts and deficiency areas which are prone to promote decalcification). A number of other clinical observations were also discussed.