Osteocyte Density Change in Buccal Alveolar Bone After Tooth Extraction

Objectives: We previously found that tooth extraction during adolescence resulted in reduction of buccal alveolar bone surface growth, increase of intracortical bone density and reduction of sclerostin (SOST) expression. To further understand these changes, this study evaluated changes in osteocyte density and empty lacunae density in buccal intracortical bone.

Methods: Ten juvenile domestic pigs underwent extractions of a unilateral mandibular deciduous second molar, then were terminated hours (acute group, n=5) or 6 weeks (chronic group, n=5) later. Buccal alveolar plates from the extraction and contralateral non-extraction sites of each pig were processed into Hematoxylin & Eosin stained sections. Blinded of animal group identity and treatment site information, a trained rater independently quantified the number of osteocytes and empty lacunae density as well as bone area. This data was used to calculate osteocyte and open lacunae density. A randomly selected subset of sections was reanalyzed with a two-week interval for assessment of reliability by intraclass correlation (ICC) tests. Differences between the extraction and non-extraction sites in each group were compared using paired t-tests.

Results: The coefficients of ICC tests for all measurement parameters were above 0.9. Comparison between the extraction and non-extraction sites in the acute group showed that neither osteocyte density nor open lacunae density was significantly different. In the chronic group, however, osteocyte density was significantly higher at the extraction site than the contralateral non-extraction site (p=0.009), with the density of empty lacunae also showing a tendency to decrease at the extraction site compared to the non-extraction site (p=0.089).

Conclusions: The increase of buccal alveolar bone osteocyte density 6 weeks after tooth extraction is likely the result of decreased local SOST expression. Combined, these two factors may help increase local intracortical bone density, a compensatory change in response to reduced buccal surface growth after tooth extraction.