The distribution of 3H-proline in alveolar bone of the mouse as seen by radioautography

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.

The effects of dietary naringenin supplementation on physiological changes in molar crestal alveolar bone-cemento-enamel junction distance in young rats

The objective of this study was to evaluate the influence of dietary naringenin (NAR) supplementation on physiological molar crestal alveolar bone (CAB)-cemento-enamel junction (CEJ) distances in young male albino rats. The effects of diets supplemented with 0.09%, 0.18%, 0.36%, and 0.72% NAR, at the expense of dextrose, were tested on 40 young rats, divided equally into five groups, for a period of 42 days. Rat skulls were defleshed, and CAB-CEJ distance was scored according to the modified method of Keyes and Gold. Data were analyzed using one-way analysis of variance, post hoc Tukey's test, and Spearman's (R(2)) correlation. P < .05 was used to reject the null hypothesis. NAR showed a statistically significant inverse dose-dependent relationship on CAB-lingual alveolar bone distance (P < .05). In all cases lingual CAB-CEJ distance was larger than buccal CAB-CEJ distance. Thus dietary NAR supplementation was shown to significantly reduce molar CAB-CEJ distance (P < .001-.05) during alveolar development in young male rats.

The Effects of Dietary Bioflavonoid (Rutin, Quercetin, and Naringin) Supplementation on Physiological Changes in Molar Crestal Alveolar Bone–Cemento-Enamel Junction Distance in Young Rats

The objective of this study was to evaluate the influence of dietary bioflavonoid (rutin [R], quercetin [Q], and naringin [N]) supplementation on physiological molar crestal alveolar bone(CAB)-cemento-enamel junction (CEJ) distances in young male albino rats. The effects of diets supplemented with 0.57% R, Q, or N, at the expense of dextrose, were tested on 40 young rats, divided into four groups, for a period of 42 days. Rat skulls were defleshed, and CAB-CEJ distance was scored according to the modified method of Keyes and Gold (Oral Surg Oral Med Oral Pathol 1955;8:492). Data were analyzed using one-way analysis of variance, post hoc Tukey's test, and Spearman's (R(2)) correlation. P <.05 was used to reject the null hypothesis. The N group demonstrated the lowest CAB-CEJ distance, followed by the R and Q groups (P <.001-.05), except in the mandibular lingual region, where the Q group had a lower CAB-CEJ distance than the N and R groups (P <.05). The control group showed the largest CAB-CEJ distances. Dietary bioflavonoid supplementation was shown to significantly reduce molar CAB-CEJ distance (P <.001-.05) during alveolar development in male young rats.

Age-dependent changes of the periodontal ligament in rats

Even after the end of the natural tooth eruption, there is a continuous renewal of the periodontal collagenous fiber system, depending on functional demands. The aim of this study was to analyse the age-dependent changes and regional differences of the collagen renewal rate of the periodontal ligament in healthy rats. The study was performed by autoradiography of the molars of rats aged 1, 8, and 18 months, where collagen was labelled by intravenously applied 3H-proline. After an 8-hour incorporation period, the animals were killed. For comparative examinations, molar roots were subdivided into cervical, middle, and apical thirds. Structural and quantitative analyses were performed by light microscopy and autoradiography, using an image-analysing computer-assisted operating unit that determined the 3H-proline-labelled collagen by photometry based on extinction measurement. With increasing age of the animals, the number of silver grains (3H-proline-blackened collagen) was reduced and the quantitative evaluation indicated a reduction of 3H-proline in the periodontal ligament. The lowest level of 3H-proline activities was observed in the middle, and the highest level in the apical root third, independent of age. All preparations revealed condensations of silver grains, which were located in the region of the periodontal ligament adjacent to the alveolar bone, but did not reveal any preferred position with regard to the dental topography. With progressive age, the uptake of 3H-proline in the periodontal ligament was reduced by about 20 to 30%, a result that corresponds to a decrease in collagenous fiber production. Collagen was mainly formed in the apical and cervical root third, starting from the alveolar bone side, presumably in response to functional strain.

Morphological characteristics of the depository surface of alveolar bone of diabetic mice

Sharpey's fibers support teeth by attachment of periodontal ligament fibers to alveolar bone. The effects of diabetes mellitus on this support mechanism have not been described and were the subject of this study. Male Swiss mice were rendered diabetic by streptozotocin. Mandibles were removed 9 weeks after injections, the mineralizing front of the depository surface of the interdental septum was exposed by fracture through the periodontal ligament, rendered anorganic, and examined by scanning electron microscopy. No significant reduction in alveolar crest height was evident in diabetic as compared to control animals; however, significant changes in the a) mineralization patterns of bone depository surfaces and Sharpey's fibers, and b) number of Sharpey's fibers inserting into alveolar bone were evident in diabetics. Unmineralized fissures, characteristic of Sharpey's fibers of control, were nearly obliterated by mineralized tissue in diabetic animals. The mineralizing front of the middle and apical thirds of the diabetic alveolar wall was covered by numerous large calcified globules resembling enlarged calcospherites, which were not evident over the cervical third or control tissues. The mean Sharpey fiber density was greater in controls than in diabetics (p less than 0.001); however, there was no significant difference between their mean diameters. These observations suggest that, in early diabetes, Sharpey's fibers and depository surfaces of the middle and apical thirds of the interdental septum have morphologic evidence of aging, which precedes significant reduction in alveolar crest height. These changes may weaken the attachment of periodontal ligament fibers to bone and reduce resistance of the periodontium to intrusive forces.

Effects of tooth function on adjacent alveolar bone and Sharpey's fibers of the rat periodontium

There is little information about the effects of short-term non-hypo-, and hyperfunction of teeth on the 1) mineralization patterns of intrinsic and extrinsic (Sharpey's) fibers and 2) mean number and diameter of Sharpey's fibers of adjacent alveolar bone. The mineral density of intrinsic and Sharpey's fibers and the size and number of Sharpey's fibers could indicate the relative strength of the attachment of a tooth to bone in various functional situations. In the present study, non- and hypofunctional situations were created by selective extraction of right molar teeth of the rat; the contralateral teeth were placed in hyperfunction by the surgery. In non- and hypofunctionals, intrinsic and Sharpey's fibers of the crestal third of the alveolus were less densely mineralized than in hyperfunctionals or untreated controls. Mean Sharpey's fiber diameters were significantly greater and their mean number/unit area significantly less in non- than in hypo- or hyperfunctionals or untreated controls (P less than 0.001). Mean Sharpey's fiber diameters in hyperfunctionals were significantly less than in untreated controls (P less than 0.05). Hypofunction ameliorated the effects of nonfunction on mean diameter and number of Sharpey's fibers, but had little effect on the density of mineralization of either the intrinsic or Sharpey's fibers of the alveolus, suggesting that their mineralization may be controlled by factors other than occlusal forces from the adjacent teeth. Thus changes in the stress/strain environment within the periodontium, coincident to altered occlusal function of the adjacent teeth, rapidly affects the morphology of intrinsic and Sharpey's fibers of alveolar bone and ensures that adequate tooth support is maintained in the new functional situation.

Effect of altered occlusal function on transseptal ligament and new bone thicknesses in the periodontium of the rat

Alteration of tooth function is assumed to change stress/strain on the adjacent alveolar bone and its mucoperiosteum, producing changes in morphology similar to those described for other load-bearing bones. The present study suggested that crestal alveolar bone and its mucoperiosteum respond differently to stress/strain than load-bearing bones in other locations, possibly due to differences in the mechanism of bone loading by muscles and teeth. Occlusal hypofunction was initiated by extraction of agonist teeth; the contralateral teeth were placed in hyperfunction by the surgery. Untreated animals were also studied. 3H-proline was injected, animals were killed 1-5 weeks later, and the thicknesses of new bone and transseptal ligament were measured. After 5 weeks of altered function, total thickness (new bone + transseptal ligament) was similar in untreated and in hypofunctional and hyperfunctional situations; however, a new ratio between transseptal ligament and new bone thicknesses was established. Occlusal force was negatively correlated with new bone and positively correlated with transseptal ligament thickness; both thicknesses were statistically correlated in each functional situation (P less than 0.001). Hyperfunction resulted in increased transseptal ligament thickness, but decreased new bone thickness as compared to untreated controls (P less than 0.001). In contrast, hypofunction resulted in an increased new bone thickness, but a decreased transseptal ligament thickness (P less than 0.001). Tissue responses assure appropriate support for the teeth in each functional situation.

Effects of hypofunction on the distribution of 3H-proline in the transseptal fibers of the periodontium of the rat

There is little information concerning the effect of altered occlusal forces on the turnover of collagenous proteins of transseptal fibers of the periodontium. In the present study, hypofunction was induced in rats by extraction of the maxillary teeth, allowing the mandibular teeth to supererupt (hypofunctional side, herein). The contralateral side served as an internal control, although it was likely experiencing occlusal hyperfunction (hyperfunctional side, herein). Untreated animals were also studied (external controls, herein). Animals were injected with 3H-proline and silver grains were counted on radioautographic preparations. The study demonstrated significant differences in the synthesis and degradation of collagenous proteins coincident to altered occlusal function; 3H-proline was most heavily incorporated into the transseptal fibers of hyperfunctional and least rapidly into the external control tissues (P less than .001). Significant differences in grain counts were evident during the first 3 weeks after injections. Collagenous proteins were degraded most rapidly in transseptal fibers of the hyperfunctional and least rapidly in hypofunctional tissues (P less than .001). The study also demonstrated regional variability in the turnover of labeled collagenous proteins, that is, proteins were synthesized and degraded most rapidly in the middle third and least rapidly in the mesial third of the ligament (P less than .001). "Whole" counts (mean of counts over middle, mesial, and distal thirds) were not similar to those of any specific region and could provide erroneous information concerning remodeling of collagenous proteins of transseptal fibers. Transseptal fibers, labeled by the 3H-proline pulse, migrated occlusally with the teeth; new transseptal fibers and bone were formed at the crest of the interdental septum.

Effect of low-protein diet on alveolar bone loss in streptozotocin-induced diabetic rats

The present study demonstrated that hyperglycemic diabetic rats fed a low-protein (8%) diet maintained an alveolar bone height similar to controls; in contrast, those fed a standard protein diet (24%) had reduced alveolar bone height (P less than 0.05). Euglycemic diabetic and untreated control rats fed low-protein diets did not have significant differences in alveolar bone height compared to those fed standard protein diets. There was no evidence of gingival or periodontal inflammation or osteoclastic bone resorption at the alveolar crest in any animal studied. Thus, (1) hyperglycemic diabetic rats have significant alveolar bone loss in the absence of periodontal inflammation (P less than 0.001) and (2) this bone loss can be alleviated by diet (P less than 0.05). This data, taken together with previous studies on the effects of low-protein diet on the kidney, suggest that relieving the protein load on the diabetic kidney in poorly controlled diabetics is beneficial to the longevity of that organ, as well as the preservation of alveolar bone surrounding the teeth.

Coordinated regulation of endothelial and fibroblast cell proliferation and matrix synthesis in periodontal ligament adjacent to appositional and resorptive bone surfaces

Little is known about the remodeling of blood vessels and soft connective tissue or the proliferation of endothelial cells in the periodontal ligament (PL) of teeth undergoing physiological drift. To determine whether there is evidence for coordinated regulation of endothelial cell and fibroblast proliferation and matrix synthesis in sites within the PL adjacent to bone-appositional (A) and bone-resorptive (R) surfaces, the PL in mouse mandibular molar was subdivided into A and R sectors on the basis of 3H-proline incorporation into alveolar bone. Computer-assisted morphometry of radioautographs showed that the number and area of blood vessels were similar in A and R sectors. Proliferation of endothelial cells and fibroblasts was assessed from radioautographs prepared from mice continuously labeled with 3H-thymidine at times between 2 and 60 days. Significantly more labeled endothelial cells (P less than .001) and fibroblasts (P less than .05) were seen in the A sector. The percent of labeled endothelial cells and the percent of labeled fibroblasts increased linearly to 25 days and then formed a plateau. The rate of increase of labeled fibroblasts was higher in the A sector than in the R sector (P less than .025). In addition, 3H-proline grain counts over extracellular matrix were significantly higher in the appositional sector than in the resorptive sector (P less than .025).(ABSTRACT TRUNCATED AT 250 WORDS)

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

The distribution of 35S-sulfate-labeled macromolecules was examined within three regions of the transseptal ligament: the 1) mesial, 2) middle and 3) distal thirds. Swiss mice, 6 weeks of age, were injected with 35S-sulfate and killed after 1, 6, and 12 hours and 1, 2, 3, 4, 5, and 7 days. Silver grains and cell nuclei were counted on autoradiographs which had been counterstained by the Van Gieson method, and mean counts were analyzed statistically. Analysis of variance revealed no significant differences in mean number of cell nuclei between regions throughout the course of the experiment. 35S-sulfate was rapidly incorporated into the transseptal ligament macromolecules. Grain counts were highest 6 hours after injections: counts were highest over the middle and lowest over the mesial thirds of the ligament. The rate of grain removal was significantly higher in the middle third compared to the mesial or distal thirds (P less than 0.001) and was significantly lower in the mesial third compared to the middle or distal thirds (P less than 0.001). The half-life of labeled macromolecules was significantly greater in the mesial and distal thirds than in the middle third (P less than 0.005). The data demonstrate significantly higher rates of turnover of 35S-sulfate-labeled macromolecules in the middle region of the transseptal ligament. Since cellular density was similar throughout the transseptal ligament, higher turnover rates of 35S-sulfate-labeled macromolecules probably indicate higher rates of cellular activity in this region, possibly a result of tissue remodeling coincident to stresses generated by occlusal forces and physiologic drift of the adjacent teeth.

Paravascular cells in endosteal spaces of alveolar bone contribute to periodontal ligament cell populations

Endosteal spaces of alveolar bone communicate with the periodontal ligament and may contribute to its cell populations. We examined cell proliferation and migration in endosteal spaces and in the periodontal ligament contiguous with these spaces. Radioautographs of mouse mandibular molar were prepared from animals pulse-injected with 3H-Tdr and sacrificed in groups of 22 mice each at 1 h, 1, 3, and 7 d after labeling. Cell counts, labeling indices, grain counts, and progenitor cell ratios were determined. The data indicate that endosteal spaces are enriched with 3H-Tdr-labeled progenitor cells whose progeny rapidly migrate out of the compartment. The periodontal ligament contiguous with the endosteal spaces exhibited 5 times as many labeled cells as other sites in this tissue. Thickened areas of cementum were coincident with the openings of endosteal spaces in over 64% of observations. The data are consistent with the hypothesis that cells migrate from endosteal spaces into the periodontal ligament and there express the phenotype for osteoblasts or cementoblasts.