Effects of groove placement on retention/resistance of maxillary anterior resin-bonded retainers.

Debonding of resin-bonded fixed partial dentures has been partly resolved with modification of tooth preparations. Tooth preparations for resin-bonded retainers were completed on a maxillary central incisor, a lateral incisor, and a canine. Fifteen metal replicas were constructed (five of each tooth morphotype). The three tooth morphotypes were then modified with proximal grooves prepared parallel to the long axes, and another 15 metal replicas were prepared. Cast metal retainers were constructed and cemented to the replicas with a resin cement. Tensile shearing dislodging loads were applied at 20 degrees to the long axes of the teeth with a testing machine. The addition of proximal grooves made statistically significant differences in resistance to debonding forces for all three tooth morphotypes (p < 0.01). An increase of 76.7% was seen in dislodging forces for lateral incisors with proximal grooves compared with incisors without grooves.