Cellular and Molecular Dynamics during Early Oral Osseointegration: A Comprehensive Characterization in the Lewis Rat

OBJECTIVE

There is a need to improve the predictability of osseointegration in implant dentistry. Current literature uses a variety of in vivo titanium (Ti) implantation models to investigate failure modes and test new materials and surfaces. However, these models produce a variety of results, making comparison across studies difficult. The purpose of this study is to validate an oral osseointegration in the Lewis rat to provide a reproducible baseline to track the inflammatory response and healing of Ti implants.

METHODS

Ti screws (0.76 mm Ø × 2 mm length) were implanted into the maxillary diastema of 52 adult male Lewis rats. Peri-implant tissues were evaluated 2, 7, 14, and 30 days after implantation (n = 13). Seven of the 13 samples underwent microtomographic analysis, histology, histomorphometry, and immunohistochemistry to track healing parameters. The remaining six samples underwent quantitative polymerase chain reaction (qPCR) to evaluate gene expression of inflammation and bone remodeling markers over time.

RESULTS

This model achieved a 78.5% success rate. Successful implants had a bone to implant contact (BIC)% of 68.86 ± 3.15 at 30 days on average. Histologically, healing was similar to other rodent models: hematoma and acute inflammation at 2 days, initial bone formation at 7, advanced bone formation and remodeling at 14, and bone maturation at 30. qPCR indicated the highest expression of bone remodeling and inflammatory markers 2-7 days, before slowly declining to nonsurgery control levels at 14-30 days.

CONCLUSION

This model combines cost-effectiveness and simplicity of a rodent model, while maximizing BIC, making it an excellent candidate for evaluation of new surfaces.

TNF-alpha modulates alveolar bone repair under homeostatic conditions in mice (44.1)

Cytokines have been implicated in the pathogenesis of bone diseases, but its role in bone repair process remains unknown. Our objective was to characterize the role of TNF-alpha in alveolar bone healing after tooth extraction in mice. Following the extraction of the right upper incisor of C57Bl/6(WT) and TNFp55KO strains, the maxilla containing the remaining alveolus was collected for histomorphometric and molecular (RealTimePCR) analysis. In WT mice the initial formation of clot was followed by the transient inflammatory infiltrate and a granulation tissue, gradually substituted by bone. In WT mice TNF-a mRNA was detected with an initial peak at 7 days, followed by a decreasing expression over time and a second peak at 28 days. Bone markers expression presented an initial high expression of COL-I, followed by CBFA-1 and ALP and subsequently by OCN and PHEX. TNFp55KO strain presented a delayed angiogenesis and osteogenesis processes, increased inflammatory reaction, despite of a decrease in CXCL1, CCL-2 and CCL3 levels; and increased COL-I mRNA levels and decreased CBFA-1, ALP, OCN and PHEX expression. The results presented here demonstrate that the absence of TNF-alpha interferes in alveolar bone repair through mechanisms that involve the modulation of inflammatory cell migration and osteogenic markers expression during the course of alveolar bone repair.

T helper cytokines expression in leprosy forms and reactional states: serum and in situ analysis (59.9)

Leprosy is a chronic infectious disease of the skin and peripheral nerves characterized by a broad spectrum of clinical forms, namely tuberculoid (TT) and lepromatous (LL), the borderline forms (BB, BT and BL) and the reverse reaction (RR) and erythema nodosum leprosum (ENL) reactional states. Since the immunological basis of leprosy is still unclear, we analyzed the profile of T helper (Th1, Th2, Th17, Treg) cytokines, in serum (ELISA) and in situ (qPCR), of 72 leprosy patients and 10 healthy controls. ELISA data shows that the frequency of IL-10, IL-6 and IL-22 detection was significantly higher in patients than in controls, while TGF-b was detected in all the samples from both groups. IFN-g, IL-4 and IL-17 levels were not detectable in the serum of both controls and patients. Comparing the leprosy subgroups, IL-6 was higher in ENL patients when compared to paucibacillary (BT/TT) and multibacillary (BB/BL/LL); while IL-10 was higher in multi versus paucibacillary forms. qPCR analysis demonstrated that IL-17, IFN-g, IL-6 and TGF-b prevail in diseased sites versus controls, but no significant differences were found between the clinical forms. Our results suggest that a broader analysis of cytokine profile can contribute to a better characterization of leprosy forms than the traditional Th1/Th2 archetype, and a larger sample must be evaluated in order to confirm these findings.