Distribution of 35S-sulfate within the transseptal ligament of the mouse

Comparative35S-sulfate and3H-proline metabolism within the interdental septal bone and adjacent periodontal ligament

Tooth movements require rapid remodeling of the periodontal ligament (PDL) and adjacent alveolar bone. Our objective was to compare the regional metabolism of sulfated-glycosaminoglycans (sGAG) within the PDL and adjacent alveolar bone and compare it to the metabolism of collagenous proteins using radioautographic techniques. Rats were injected with either (3)H-proline or (35)S-sulfate and maxillae were removed at 1, 6, and 12 hr 1-7 days later. Silver grains were counted over the PDL and adjacent alveolar bone and the incorporation and removal rates for each radioisotope were determined. In general, net collagenous protein incorporation and removal were greatest within the distal and net sGAG incorporation and removal were greatest within the mesial compartments of the periodontium. The rate of removal of (3)H-proline was significantly greater within the distal alveolar bone surface than the adjacent PDL at all levels (P < 0.001). In contrast, the rate of removal of (35)S-sulfate was significantly greater in the PDL than within the adjacent mesial surface of the interdental septum at all levels (P < 0.001). The mesial surfaces of the interdental septum had a slower rate of removal of both isotopes than distal surfaces at all levels (P < 0.001). Our data suggest significant regional differences in the metabolism of (35)S-sulfate and (3)H-proline within the PDL and alveolar bone, which likely result from the characteristics of the forces produced by the adjacent teeth and may be a factor in the remodeling of the alveolar wall coincident to tooth movement.

Distribution of 3H-proline within transseptal fibers of the rat following release of orthodontic forces

Maxillary right first molar teeth of rats were tipped mesially with an orthodontic appliance for 2 weeks (experimental group), 3H-proline was injected, and orthodontic forces were removed 6 hr later (time 0). The contralateral molar teeth of treated (internal control group) and age- and weight-matched untreated animals (external control group) were also studied. Diastemata were created between the molar teeth by the orthodontic appliance, and transseptal fibers between first and second (P less than 0.001) and second and third molars (P less than 0.005) were significantly lengthened as compared to external and internal controls at time 0. Diastemata between molar teeth were closed 5 days after removal of orthodontic force. Transseptal fibers adjacent to the source of the orthodontic force (mesial region) had the highest mean number of 3H-proline-labeled proteins at time 0 and at all times following removal of the force (P less than 0.001), and had the highest rate of labeled protein removal (P less than 0.001). Half-lives for removal of 3H-proline-labeled transseptal fiber proteins were significantly greater in mesial and distal regions and significantly less in middle regions of experimentals than in corresponding regions of external controls (P less than 0.001). These data suggest the following: 1) transseptal fibers adjust their length by rapid remodeling in regions experiencing a tensile force; 2) collagenous protein turnover within the middle third of the transseptal fibers is more rapid subsequent to release of orthodontic force than during normal physiologic drift, suggesting that this region adapts rapidly to changes in adjacent tooth position and that these fibers do not play a significant role in relapse of orthodontically relocated teeth; and 3) significant differences in turnover rates of 3H-proline-labeled transseptal ligament proteins of external and internal control quadrants suggest that tooth movement produces both local and systemic effects on collagenous protein metabolism.