title: Effect of loading on the migration of periodontal fibroblasts in the rat incisor.
abstract: The influence of occlusal loading on periodontal fibroblasts was investigated in hypoloaded (shortened out of occlusion), functionally loaded and hyperloaded (constant linguointrusive mechanical loads of 9.4 +/- 0.06 g) lower left rat incisors. One hour following injection of 3H-thymidine, half of the animals in each group were killed, while the remaining rats were killed 2 weeks later. The decalcified incisors were embedded in glycolmethacrylate and sectioned (2 microns) serially, perpendicularly to the long tooth axis. Labeled and unlabeled fibroblasts in the tooth-related periodontal ligament were counted in 8 x 80 microns consecutive layers. Cell density (CD) and labeling index (LI) were plotted according to their location on the apico-incisal and cementum-bone axes. Loading caused a decrease in CD and a shift of cells from the cementum towards the middle of the ligament, proportionally to load intensity and duration. The average tooth-to-bone movement of the cells was 2 microns/day in the hypoloaded and 4 microns/day in the two loaded groups. The mean daily tooth eruption rate was 975 +/- 60 microns, 499 +/- 18 microns and 103 +/- 27 microns in the hypo-, functionally- and hyperloaded teeth, respectively. The respective concomitant average daily cell migration rates in the incisal direction were 786 microns, 500 microns, and 500 microns, i.e. 80%, 100% and 485% of the tooth eruption rates. The gross disparity between cell velocity and tooth movement under conditions of restrained eruption indicates active motility of the fibroblasts, rather than their passive tooth-eruption dependent translation.
authors.affiliation: Department of Occlusion, School of Dental Medicine, Tel Aviv University, Jerusalem, Israel.
authors.forename: Y
authors.initials: Y
authors.lastname: Michaeli
authors.forename: D
authors.initials: D
authors.lastname: Shamir
authors.forename: M
authors.initials: M
authors.lastname: Weinreb
authors.forename: S
authors.initials: S
authors.lastname: Steigman
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002465:Cell Movement; D003739:Dental Cementum / Q000166:cytology; D003799:Dental Stress Analysis; D005260:Female; D005347:Fibroblasts / Q000502:physiology; D010513:Periodontal Ligament / Q000166:cytology*; D051381:Rats; D011919:Rats, Inbred Strains; D013314:Stress, Mechanical; D014078:Tooth Eruption / Q000502:physiology*