Characteristics of the aging rat mandible

Effects of Mandibular Advancement plus Prohibition of Lower Incisor Movement on Mandibular Growth in Rats

Introduction: To test the hypothesis that mandibular advancement with the use of a fixed functional appliance combined with prohibition of labial movement of the lower incisors will have no effect on mandibular growth in growing rats.

Materials and Methods: Fifteen 4-week-old male rats were divided into fixed, unfixed, and control groups (n = 5, each). Bite-jumping appliances were used in the fixed and unfixed groups. Sites of bone perforation and the lower incisors were connected with ligature wires in the fixed group. The ramus height, mandibular length, and inclination of lower incisors were examined for 4 weeks, and those values were compared among five intervals and three groups by through one-way analysis of variance models and the Bonferroni multiple comparison test for post hoc comparison.

Results: Increases in ramus height and mandibular length during the experimental period were 1.5 mm and 2.5 mm in the fixed group, 1 mm and 1.5 mm in the unfixed group, and 1.2 mm and 1.9 mm in the control group, respectively. Growth of ramus height and growth of mandibular length in the fixed group were greater than in the unfixed and control groups during the experimental period. The inclination of lower incisors in the unfixed group was increased 8.0 degrees throughout the experimental period, which differed from results obtained in the other groups.

Conclusions: Mandibular growth was accelerated effectively before and during the pubertal period in rats by mandibular advancement with a fixed functional appliance combined with prohibition of labial movement of the lower incisor.

Effect of donor age on cultivation of human oral mucosal keratinocytes

Cultured mucosal grafts (CMG) are among recently developed biological grafting materials to cover large oral mucosal defects following resection of mucosal pathology. This study evaluates the effect of donor's age on the cultivation process of oral mucosal keratinocytes for grafting. Human mucosal epithelial cells were utilized and classified into three donor age groups: 3-30 years (14 patients); 31-60 years (9 patients); and >60 years (6 patients) (11 males and 18 females). Isolation and cultivation of oral mucosal keratinocytes were according to Rheinwald and Green [Cell 6 (1975) 331], originally developed for epidermal keratinocytes. Isolated primary cell lines were seeded and cultivated. Propagation of cell lines ("passages"), time period required to reach confluence, yield of cells and plating efficiency were recorded. All cells propagated well up to the fourth passage. Thereafter, a decline was observed and was more distinct with age. Period to confluence was longer among the old age group. Yield of cells in fourth passage was high among the young age group and decreased with age. Plating efficiency in passages 4-6 decreased with age. These results suggest that age-related changes in cultivation of oral keratinocytes are not general phenomena, but rather limited to the donor age of 60 years and above. In this age group all the parameters studied were adversely affected. Oral mucosal keratinocytes may be a useful model for oral aging.