The Root Surface Areas and Ratios of the Maxillary Canine, Fourth Premolar, and First Molar Teeth in Mesaticephalic Dogs

In active force orthodontics in dogs, the ratio of root surface area (RSA) between the anchorage and target dentition is the primary factor when determining the expected relative movement patterns. Reinforced anchorage involves bonding of adjacent structures together (ie, 2 or more teeth) in the anchorage unit to increase the total attachment or RSAs. This methodology is commonly implemented in the movement of the maxillary canine tooth using active force orthodontics by bonding the maxillary fourth premolar and first molar teeth together. Cone beam computed tomography scans of mesaticephalic dogs were evaluated using third-party viewing software to determine the RSAs of the maxillary canine, fourth premolar, and first molar teeth. The RSA ratios were then calculated for the following comparisons: canine to fourth premolar (C:PM4), canine to first molar (C:M1), and canine to combined fourth premolar and first molar (C:PM4 + M1). Forty-eight dogs and 86 dental arcades met the inclusion parameters. 20.93% of dental arcades had a C:PM4 RSA ratio <1, none of the dental arcades had a C:M1 RSA ratio <1, and all but one arcade (98.81%) had a C:PM4 + M1 RSA ratio <1. Increased weight was significantly correlated with an increase in all RSA ratios. Based on these findings, the authors recommend continuing the practice of bonding the maxillary fourth premolar and first molar teeth together when applying active force orthodontics for the maxillary canine tooth in mesaticephalic patients.