Purpose: To evaluate the influence of age and trabecular microstructure on peri-implant strain in aging and young mice models under compressive load.
Materials and methods: Eighteen 4-week-old female C57BL/6 mice (n = 6) were subjected to a 1.2% calcium content diet (young normal calcium group), and 7-month-old mice (n = 12) were randomly subjected to 0.01% and 1.2% calcium content diets (aging low and normal calcium groups, respectively) for 3 weeks. Histomorphometric and microcomputed tomography (micro-CT) analyses were used to investigate local alveolar bone microstructure. One maxilla segment from each group was reconstructed using micro-CT images to highlight the trabecular microstructure. A finite element analysis based on a computational model of the maxilla segment was performed to investigate peri-implant strain. Implants with three different diameters (0.3, 0.4, and 0.5 mm) were analyzed in these models.
Results: The aging low calcium group showed worse cancellous microstructure in hematoxylin and eosin (HE) staining, significantly increased osteoclast numbers (P < .05), and reduced bone volume fraction and trabecular thickness compared with the aging normal calcium group (P < .05). However, the young normal calcium group presented no difference in trabecular microstructure and osteoclast numbers compared with the aging normal calcium group. The aging low calcium group demonstrated increased strain intensity compared with the aging normal calcium group, whereas the young normal calcium and aging normal calcium groups showed comparable strain magnitude. The strain intensity of peri-implant bone increased with worse cancellous microstructure. When the diameter increased from 0.3 mm to 0.4 mm, the percentages of pathologic overload decreased regardless of bone microstructure.
Conclusion: Deteriorated bone microstructure induced by a low calcium diet determined higher strain intensity, whereas, whenever age had no significant effect on trabecular microstructure, consequently, there was no substantial influence on strain. An increase of implant diameters can improve the strain distribution. Clinical decision-making should take into consideration the patient-specific and site-specific trabecular microstructure in preoperative assessment.
