Bisphosphonate Effects on Alveolar Bone During Rat Molar Drifting

Abstract

The remodeling of bone during molar drifting and cortical growth in the rat maxilla and the effects of dichloromethylene bisphosphonate (Cl2MBP) on these processes were investigated in 30 age-matched rats. A control group of six rats was killed at 10 weeks of age. Beginning at 10 weeks of age, 12 rats were treated with daily subcutaneous injections of Cl2MBP (10 mg/kg), and 12 control rats were injected daily with normal saline. Six rats of each group were killed at 12 and at 20 weeks of age. All rats were injected with fluorescent bone labels eight and one days before termination. Calcified and decalcified vertical sections through the lingual roots of maxillary molars were prepared for histomorphometry. Bone apposition rates, remodeling activity, and bone cell populations were quantified by image analysis on depository and resorptive surfaces of alveolar bone and on cortical bone surfaces. The drift rates of the first and second molars were calculated. Results showed that in control animals the drift rate of the first molar exceeded that of the second molar (p less than 0.05), supporting a previously proposed mechanism for age-dependent narrowing of interdental bone. Cl2MBP treatment decreased remodeling activity on resorptive surfaces of alveolar bone, despite a transient increase in osteoclasts. Cl2MBP also decreased the osteoblast number and bone apposition rate on depository surfaces of alveolar bone, and reduced the rate of molar drifting (p less than 0.05). However, Cl2MBP treatment had no detectable effect on osteoblast number or bone apposition on cortical bone surfaces. These results support the concept that bisphosphonates influence bone formation indirectly through a coupling mechanism which links formation with resorption.

Alveolar bone turnover in male rats: Site‐ and age‐specific changes

“…In contrast, the distal surfaces contain 20% double-label, but 12% osteoclast surface, suggesting more coupled bone remodeling. These findings are consistent with previous reports of formative modeling on the mesial and remodeling on the distal acting to create alveolar shape changes that facilitate distal drift of the molars (Vignery and Baron, 1980;Hardt, 1988;King et al, 1991a,b). Despite persistent site-specific osteoclast differences in the adult rats, the dynamic measures of bone formation on the mesial of the adults decline to the level found on the distal.…”

Imaging an Adapted Dentoalveolar Complex

“…In general, adequate interdental bone and PDL-space are maintained through combined resorption (distal) and apposition (mesial) related events, accomodating movement of the molars [8]. Based on our observations and previous reports by others, we suggest different migration rates of the individual molars [40]. …”

Comparison of expression patterns of cathepsin K and MMP-9 in odontoclasts and osteoclasts in physiological root resorption in the rat molar

“…For the purposes of the current study, physiological root resorption in the rat molar is a useful model because the histological features are similar to the odontoclasts and osteoclasts of human permanent teeth (Sicher and Weinmann, 1944;Hardt, 1988;Nagaoka et al, 2002;Kashiwazaki et al, 2003;Kimura et al, 2003). Since moderate mechanical stress causes a physiological drift of molars in a distal direction with aging (Sicher and Weinmann, 1944;Roberts and Morey, 1985), root resorption possesses spatial and temporal characteristics (Kimura et al, 2003).…”

“…Since moderate mechanical stress causes a physiological drift of molars in a distal direction with aging (Sicher and Weinmann, 1944;Roberts and Morey, 1985), root resorption possesses spatial and temporal characteristics (Kimura et al, 2003). First, the tartrate-resistant acid phosphate (TRAP)-positive precursor cells for odontoclasts or osteoclasts start appearing in periodontal tissues at 3 weeks of age, and then odontoclasts actively resorb the distal surface on the distal roots of rat maxillary second molars from 4 to 6 weeks of age (Sicher and Weinmann, 1944;Hardt, 1988). After the decrease followed by the peak of root resorption at 5 weeks, newly formed resorption lacunae on the distal roots of second molars are mostly undetectable by 8 weeks even though the osteoclasts keep resorbing the alveolar bone facing the distal roots of the second molar (Nagaoka et al, 2002).…”