Effect of 2 Different Drilling Speeds on the Osseointegration of Implants Placed With Flapless Guided Surgery: A Study in Rabbits.

OBJECTIVE: The aim of this study was to evaluate the influence of the drilling speed on bone healing and the osseointegration of implants placed with a guided flapless surgical technique in rabbit tibias. METHODS: For the evaluation of bone healing, a total of 30 perforations (defects) were made in both tibias of 15 rabbits using 2 different drilling speeds (1500 rpm-control group; 50 rpm-test group). The regeneration of bone tissue in the surgical sites was evaluated at 0, 7, and 14 days. For the evaluation of implant osseointegration, another 15 rabbits underwent drilling in both tibias for implant placement. Thirty implants (3.75 × 10 mm) were placed to evaluate osseointegration at 4, 8, and 12 weeks after surgery. RESULTS: Both groups showed a progressive healing of the defect, which involved the complete closure of the perforation. The osseointegration occurred in all groups with no statistically significant differences in the assessment of the osseointegration between the groups. CONCLUSION: In the experimental models used, the drilling speed does not prejudice the pattern of bone healing and osseointegration of implants placed with guided flapless surgery.

NOD1 in the modulation of host-microbe interactions and inflammatory bone resorption in the periodontal disease model.

Periodontitis is a chronic inflammatory condition characterized by destruction of non-mineralized and mineralized connective tissues. It is initiated and maintained by a dysbiosis of the bacterial biofilm adjacent to teeth with increased prevalence of Gram-negative microorganisms. Nucleotide-binding oligomerization domain containing 1 (NOD1) is a member of the Nod-like receptors (NLRs) family of proteins that participate in the activation of the innate immune system, in response to invading bacteria or to bacterial antigens present in the cytoplasm. The specific activating ligand for NOD1 is a bacterial peptidoglycan derived primarily from Gram-negative bacteria. This study assessed the role of NOD1 in inflammation-mediated tissue destruction in the context of host-microbe interactions. We used mice with whole-genome deletion of the NOD1 gene in a microbe-induced periodontitis model using direct injections of heat-killed Gram-negative or Gram-negative/Gram-positive bacteria on the gingival tissues. In vitro experiments using primary bone-marrow-derived macrophages from wild-type and NOD1 knockout mice provide insight into the role of NOD1 on the macrophage response to Gram-negative and Gram-negative/Gram-positive bacteria. Microcomputed tomography analysis indicated that deletion of NOD1 significantly aggravated bone resorption induced by Gram-negative bacteria, accompanied by an increase in the numbers of osteoclasts. This effect was significantly attenuated by the association with Gram-positive bacteria. In vitro, quantitative PCR arrays indicated that stimulation of macrophages with heat-killed Gram-negative bacteria induced the same biological processes in wild-type and NOD1-deficient cells; however, expression of pro-inflammatory mediators was increased in NOD1-deficient cells. These results suggest a bone-sparing role for NOD1 in this model.

Histological analysis and gene expression profile following augmentation of the anterior maxilla using rhBMP-2/ACS versus autogenous bone graft.

AIM: The objective of this report was to present histological characteristics and gene expression profile of newly formed bone following horizontal augmentation of the atrophic anterior maxilla using recombinant human bone morphogenetic protein-2 in an absorbable collagen sponge carrier (rhBMP-2/ACS) versus an autogenous bone graft (ABG). METHODS: Bone core biopsies from 24 subjects participating in a randomized clinical trial were obtained at dental implant placement, 6 months following alveolar ridge augmentation using rhBMP-2/ACS (rhBMP-2 at 1.5 mg/ml; total dose 4.2 mg) or a particulate ABG harvested from the mandibular retro-molar region. A titanium mesh was used to provide wound stability and space for bone formation. Analysis included histological/histometric observations and gene expression profile of the newly formed bone. RESULTS: rhBMP-2/ACS yielded bone marrow rich in capillaries, undifferentiated cells and bone lining cells compared with the ABG (p = 0.002). Whereas no significant differences were observed in total bone fraction (p = 0.53), non-vital bone particles trapped in lamellar vital bone were observed in the ABG group (p < 0.001). Real-time PCR showed greater BMP-2 and RUNX2 expression for rhBMP-2/ACS over the ABG (p = 0.001 and 0.0021, respectively), while the ABG exhibited greater expression of RANKL:OPG, BSP and OPN over rhBMP-2/ACS (p = 0.01, 0.005 and 0.0009, respectively). CONCLUSIONS: Our observations suggest that formative biological processes explain bone formation following implantation of rhBMP-2/ACS, whereas remodelling, resorptive/formative processes, characterizes sites receiving ABGs.

Evaluation of the host response in various models of induced periodontal disease in mice.

BACKGROUND: The aim of this study is to characterize and evaluate the host response caused by three different models of experimental periodontitis in mice. METHODS: C57BL/6 wild-type female mice were distributed into six experimental groups and sacrificed at 7, 15, and 30 days after the induction of periodontal disease: 1) group C: no treatment control group; 2) group L: periodontal disease induced by ligature; 3) group G-Pg: oral gavage with Porphyromonas gingivalis (Pg); 4) group G-PgFn: oral gavage with Fusobacterium nucleatum + Pg; 5) group I-Pg: heat-killed Pg injected into the palatal mucosa between the molars; and 6) group I-V: phosphate-buffered saline injected into the palatal mucosa. The samples were used to analyze the immune-inflammatory process in the gingival tissue via descriptive histologic and real-time polymerase chain reaction analyses. The alveolar bone loss was evaluated using microcomputed tomography. The data were analyzed using the Kruskal-Wallis test, followed by a post hoc Dunn test and analysis of variance, followed by a Tukey test using a 5% significance level. RESULTS: Only the ligature model displayed significant alveolar bone loss in the initial period (7 days), which was maintained with time. The group injected with heat-killed Pg displayed significant alveolar bone loss starting from day 15, which continued to progress with time (P <0.05). A significant increase (P <0.05) in the gene expression of proinflammatory cytokines (interleukin-6 and -1ß) and proteins involved in osteoclastogenesis (receptor activator of nuclear factor-κB ligand and osteoprotegerin) was observed in the ligature group on day 7. CONCLUSION: The ligature and injection of heat-killed Pg models were the most representative of periodontal disease in humans, whereas the oral gavage models were not effective at inducing the disease under the experimental conditions.

SOCS3 expression correlates with severity of inflammation, expression of proinflammatory cytokines, and activation of STAT3 and p38 MAPK in LPS-induced inflammation in vivo.

SOCS3 is an inducible endogenous negative regulator of JAK/STAT pathway, which is relevant in inflammatory conditions. We used a model of LPS-induced periodontal disease in rats to correlate SOCS3 expression with the inflammatory status. In vitro we used a murine macrophage cell line to assess the physical interaction between SOCS3 and STAT3 by coimmunoprecipitation. 30 ug of LPS from Escherichia coli were injected in the gingival tissues on the palatal aspect of first molars of the animals 3x/week for up to 4 weeks. Control animals were injected with the vehicle (PBS). The rats were sacrificed at 7, 15, and 30 days. Inflammation and gene expression were assessed by stereometric analysis, immunohistochemistry, RT-qPCR, and western blot. LPS injections increased inflammation, paralleled by an upregulation of SOCS3, of the proinflammatory cytokines IL-1 ß , IL-6, and TNF- α and increased phosphorylation of STAT3 and p38 MAPK. SOCS3 expression accompanied the severity of inflammation and the expression of proinflammatory cytokines, as well as the activation status of STAT3 and p38 MAPK. LPS stimulation in a macrophage cell line in vitro induced transient STAT3 activation, which was inversely correlated with a dynamic physical interaction with SOCS3, suggesting that this may be a mechanism for SOCS3 regulatory function.

Orthodontic force increases interleukin-1ß and tumor necrosis factor-α expression and alveolar bone loss in periodontitis.

BACKGROUND: The present study aims to evaluate the effects of orthodontic movement (OM) on the periodontal tissues of rats with ligature-induced periodontal disease. METHODS: Eighty-eight rats were divided into four groups: 1) negative control (sham operated); 2) periodontal disease; 3) OM; and 4) periodontal disease followed by OM (OMP). Rats were sacrificed 3 hours or 1, 3, or 7 days after OM commencement. Bone volume fraction (BVF) and bone mineral density (BMD) were assessed in hemimaxillae by microcomputed tomography analysis. Expression of the proinflammatory cytokines interleukin (IL)-1ß and tumor necrosis factor (TNF)-α were evaluated in gingival samples by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, and in the furcation region by immunohistochemistry analysis (IHC). RESULTS: The OMP group had lower BVF and BMD levels compared to the other groups at day 7 (P <0.05). Maximum messenger ribonucleic acid expression of both cytokines was observed in the OMP group at day 1 (P <0.05). In the same period, all proteins were expressed in high levels for all test groups compared to the control group. The number of cells positive for IL-1ß and TNF-α by IHC was highest in the OMP group at day 1, with progressive reduction thereafter. CONCLUSION: The results suggest that OM acts synergistically with periodontal disease in periodontal breakdown through upregulation of proinflammatory cytokines.