Remodeling dynamics in the alveolar process in skeletally mature dogs

Abstract

Bone turnover rates can be altered by metabolic and mechanical demands. Due to the difference in the pattern of loading, we hypothesized that there are differences in bone remodeling rates between the maxillary and mandibular alveolar processes. Furthermore, in a canine model, the alveolar process of teeth that lack contact (e.g., second premolars) would have a different turnover rate than bone supporting teeth with functional contact (e.g., first molars). Six skeletally mature male dogs were given a pair of calcein labels. After sacrifice, specimens representing the anterior and posterior locations of both jaws were prepared for examination by histomorphometric methods to evaluate the bone volume/total volume (BV/TV; %), bone volume (mm2), mineral apposition rate (MAR; microm/day), and bone formation rate (BFR; %/year) in the alveolar process. There were no significant differences (P>0.05) in the BV/TV within the jaws. The bone volume within the alveolar process of the mandible was 2.8-fold greater than in the maxilla. The MAR was not significantly different between the jaws and anteroposterior locations. However, the BFR was significantly (P<0.0001) greater in the mandible than in the maxilla. The anterior location had higher (P=0.002) remodeling than the posterior location in the maxilla but not in the mandible. While there was a greater bone mass and increased remodeling in the mandible, no remodeling gradient in the coronal-apical direction was apparent in the alveolar process. Bone adaptation probably involves a complex interplay of bone turnover, mass, and architecture.

Fig. 1

Schematic of alveolar process and method for collection of histomorphometric data. Merz grid is represented by square on alveolar process. The entire alveolar bone from buccal/lingual/palatal crest to the root apex was sampled. After the data was collected, the alveolar process was divided into thirds (1-coronal, 2-middle, 3-apical). Only bone within the alveolar process is included in the measurements, certain parts of the Merz grid will extend beyond the alveolar bone.

Fig. 2

Composite epifluorescent photomicrographs of a representative (a) Maxillary left 4^th premolar and (b) Mandibular right 2^nd premolar. Multiple images were stitched to make the entire composite. Each individual image was taken at 100X as epifluorescense is not clearly seen at low magnification that would be needed to obtain a photomicrograph of an entire tooth and supporting alveolar bone. The maxillary tooth ( B is buccal, and P is palatal) has a very thin alveolar process. Bone remodeling is seen by the presence of single and double calcein bone labels in the mandibular alveolar process (B is buccal and L is lingual) and body of mandible.

Fig. 2

Composite epifluorescent photomicrographs of a representative (a) Maxillary left 4^th premolar and (b) Mandibular right 2^nd premolar. Multiple images were stitched to make the entire composite. Each individual image was taken at 100X as epifluorescense is not clearly seen at low magnification that would be needed to obtain a photomicrograph of an entire tooth and supporting alveolar bone. The maxillary tooth ( B is buccal, and P is palatal) has a very thin alveolar process. Bone remodeling is seen by the presence of single and double calcein bone labels in the mandibular alveolar process (B is buccal and L is lingual) and body of mandible.