Braz Dent J (1997) 8(1): 9-12 ISSN 0103-6440
| Introduction | Material and Methods | Results and Discussion | Acknowledgments | References |
The chronology of alveolar wound healing was analyzed by a standard stereological method (point-counting volumetry) in normal rats. The upper right incisors were extracted and the animals were killed 1, 2, 3 and 6 weeks postoperatively. A light camera was used to determine the volume fraction of histologic components in the apical, middle and cervical thirds of the alveolus. Progressive bone neoformation was quantified, in parallel to a decrease in percent volume of connective tissue. A significantly smaller volume fraction of bone trabeculae in the cervical third of the socket was observed at all periods except the 6th week. The present histometric data show that bone neoformation continued to proceed beyond the 3rd postoperative week.
Key Words: alveolar wound healing, histometry.
Few studies deal with quantitative histometric evaluation of the healing of dental extraction wounds. Histometric analysis of alveolar healing in normal, uranyl nitrate-intoxicated and X-irradiated rats was carried out by Guglielmotti and Cabrini (1985) and Guglielmotti et al. (1985, 1986) with the use of an image analyzing system. Histometric studies of dental healing around implants have recently been performed in dogs (Parr et al., 1993) and rabbits (Matsui et al., 1994) using a computer system for image analysis also.
The purpose of the present study was to quantify the time course of dental wound healing in the apical, middle and cervical thirds of the alveolus of normal rats, using a simple standard stereological method.
A light camera (Zeiss, Jena) was used to measure the volume fraction of alveolar components by a differential point-counting method (Weibel et al., 1966). Microscopic images of the alveolus, at a final magnification of 420X, were superimposed on sheets of paper with a grid containing 100 equidistant points. Six thousand points lying on clot and blood vessels, connective tissue and bone trabeculae were counted in the apical, middle and cervical thirds of each alveolus.
Data were analyzed for statistical significance by a non-parametric test (Kruskall-Wallis, ANOVA).
Histometric analysis permitted us to quantify progressive bone neoformation in parallel to a decrease in the volume fraction of connective tissue up to the 6th week after dental extraction and showed a significantly smaller volume fraction of bone trabeculae in the cervical third of the socket at all time points except the 6th week (Table 1, Figure 1). It has been assumed that, in rats, healing following dental extraction is fully complete by the 21st postoperative day (Okamoto and Russo, 1973; Santos Jr. and Melhado, 1990). However, results from the present study showed that bone neoformation continued to proceed beyond this time.
Figure 1- Volume fraction of connective tissue and bone trabeculae in the apical (Api), middle (Mid) and cervical (Cer) thirds of the alveolus 1 to 6 weeks after tooth extraction (mean ± SEM for 5-7 rats per group).
Using an image analyzing system, Guglielmotti and Cabrini (1985) quantified alveolar wound healing in Wistar rats on the basis of histometric parameters including bone volume density. Measurements, however, were confined to a rectangle outlined on the apical third of the alveolus. Although no statistical analysis was applied, maximal bone volume density was apparently reached by the 30th postoperative day. The authors reported that maximal bone formation and maximal alveolar volume occurred on the 14th day after tooth extraction. The marked differences in methodology rendered unviable comparisons between our results and those reported by Guglielmotti and Cabrini (1985).
Even though the method presented here is simple and does not require sophisticated equipment, it appears to be precise and might be useful in comparative studies of alveolar wound healing under different types of experimental conditions.
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Correspondence: Teresa Lúcia Lamano Carvalho, Departamento de Estomatologia, Laboratório de Patologia, Faculdade de Odontologia de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil.
Accepted January 3, 1997
Electronic publication: September, 1997