Indiana University-Purdue University Indianapolis (IUPUI) / This is the first in a series of experiments designed to investigate the effect of local and systemic factors on osteoblast histogenesis in rats. A soft diet is an experimental means thought to decrease the overall mechanical loading (a local factor) on the masticatory apparatus.
Eighteen Sprague-Dawley rats were divided into three equally sized groups: 1) an experimental group, which was maintained on a soft paste diet; 2) a control group, pair fed with the experimental group; and 3) a control group fed ad libitum. Both control groups continued to eat standard Purina rat chow pellets. Twenty-three days later all animals were injected subcutaneously with 1.0 μCi/ g tritiated thymidine and sacrificed one hour later. The maxillae of the animals were dissected and sectioned. The periodontal ligament (PDL) of the mesial surface of the mesial root of the first molar was analyzed microscopically 110 μm above and below the mid root area.
Nuclear size was used to determine the stage of osteoblast differentiation. The labeling index was used to determine the proliferative activity of the cells. The distance of cells from the nearest major blood vessel (NMBV) was measured and the cells were grouped into one to four extravascular zones. For each zone, cell density was determined. PDL widths were measured to evaluate tooth function.
If osteogenesis is due primarily to stress and strain on bones, then rats maintained on the soft diet should show a decreased labeling index, increased number of A and A' cells, decreased number of C and D cells, and an unaltered vascularly-oriented cell density gradient. The number of osteoblastic precursor cells (A and A' cells) close to blood vessels should increase relative to the number of preosteoblastic cells (C and D) further from the vessels. Also, the width of the PDL space in the soft diet rats should be narrower since their function was decreased.
The results of this study did not support the hypothesis that a decrease in masticatory stress and strain within the rat periodontal ligament due to softened dietary consistency reduces osteoblast histogenesis. No differences were seen in the PDL widths or the vascularly-oriented cell density gradient between groups. High levels of A+A' cells were seen paravascularly for all groups, and their relative numbers decreased as one moved away from the blood vessel into a lower cell density area, supporting previous studies. No differences were seen in the fractional distribution of A+A' cells or C+D cells between groups, as was hypothesized, except for a higher level of A+A' cells in the pair fed group across all zones. This latter finding was probably due to physiologic variation and the small sample sizes used in this study.
Decreased masticatory stress and strain due to a softened diet did not reduce osteoblast histogenesis. Further research needs to investigate systemic factors which may influence bone formation.
| Identifer | oai:union.ndltd.org:IUPUI/oai:scholarworks.iupui.edu:1805/34133 |
| Date | January 1991 |
| Creators | Colter, Robert D. |
| Contributors | Roberts, W. Eugene, Garetto, Lawrence P., Hohlt, William F., Newell, Donald, Shanks, James C. |
| Source Sets | Indiana University-Purdue University Indianapolis |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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