Jarkko T. Korpi

Healing of extraction sockets in collagenase‐2 (matrix metalloproteinase‐8)‐deficient mice

Matrix metalloproteinase-8 (MMP-8) participates in skin wound healing and inflammation. We hypothesized that MMP-8 plays a role in wound healing after tooth extraction and in periapical inflammation. Bone formation, collagen metabolism, and inflammation in tooth extraction socket and in periapical lesions were analyzed in wild-type mice and in MMP-8-deficient (MMP-8(-/-)) mice. New trabecular bone area in the extraction sockets and in periapical lesions were similar in both groups. In extraction sockets significantly more type III procollagen was synthesized, and the neutrophil and MMP-9 levels were lower in MMP-8(-/-) mice. The amount of Fas ligand, identified as a substrate for MMP-8, was lower in alveolar mucosa but higher in alveolar bone of MMP-8(-/-) mice. These results indicate that MMP-8 can modulate inflammation and collagen metabolism of alveolar bone and mucosa.

Long-term follow-up of severely resorbed mandibles reconstructed using tent pole technique without platelet-rich plasma.

PURPOSE To investigate the results of edentulous patients with severely resorbed mandibles who were treated with a modified tent pole procedure. PATIENTS AND METHODS Twenty-two edentulous patients (3 men, 19 women; mean age, 62 yr; range, 51 to 72 yr) with a history of conservative prosthodontic treatment failures were included this study. Using a transcutaneous submental approach, 4 endosseous dental implants were placed in the anterior mandible of each patient and covered with autogenous bone grafts harvested from the posterior iliac crest without the addition of platelet-rich plasma. Follow-up ranged from 3 to 9 years. RESULTS The postoperative course of the patients was uneventful, without any surgical infections. At 3 months postoperatively, the density of the grafted bone appeared to closely resemble that of the surrounding alveolar bone on panoramic radiographs. The average alveolar augmentation was 6.3 mm (standard deviation, 1.59 mm; range, 4 to 10 mm) and long-term follow-up showed no bone resorption around the endosseous implants. CONCLUSIONS The modified tent pole technique without the addition of platelet-rich plasma is a safe and effective method to reconstruct the severely resorbed mandible.

Matrix metalloproteinase-8 regulates transforming growth factor-β1 levels in mouse tongue wounds and fibroblasts in vitro.

Matrix metalloproteinase-8 (MMP-8)-deficient mice (Mmp8-/-) exhibit delayed dermal wound healing, but also partly contradicting results have been reported. Using the Mmp8-/- mice we investigated the role of MMP-8 in acute wound healing of the mobile tongue, and analyzed the function of tongue fibroblasts in vitro. Interestingly, in the early phase the tongue wounds of Mmp8-/- mice healed faster than those of wild type (wt) mice resulting in significant difference in wound widths (P=0.001, 6-24h). The Mmp8-/- wounds showed no change in myeloperoxidase positive myeloid cell count, but the level of transforming growth factor (TGF)-β1 was significantly increased (P=0.007) compared to the wt tongues. Fibroblasts cultured from wt tongues expressed MMP-8 and TGF-β1. However, higher TGF-β1 levels were detected in Mmp8-/- fibroblasts, and MMP-8 treatment decreased phosphorylated Smad-2 levels and α-smooth muscle actin expression in these fibroblasts suggesting reduced TGF-β1 signaling. Consistently, a degradation of recombinant TGF-β1 by MMP-8 decreased its ability to activate the signaling cascade in fibroblasts. Moreover, collagen gels with Mmp8-/- fibroblasts reduced more in size. We conclude that MMP-8 regulates tongue wound contraction rate and TGF-β1 levels. In vitro analyses suggest that MMP-8 may also play a role in regulating TGF-β1 signaling of stromal fibroblasts.

Tent-Pole Approach to Treat Severely Atrophic Fractured Mandibles Using Immediate or Delayed Protocols: Preliminary Case Series

PURPOSE To investigate the outcomes of patients with severely resorbed fractured mandibles who were managed with a modified tent-pole procedure. PATIENTS AND METHODS Four edentulous patients (2 male and 2 female; mean age, 59.5 years; range, 52 to 64 years) with a severely atrophic fractured mandible and less than 10 mm of vertical height of the body of the mandible were treated with an immediate or a delayed protocol (n=2 in each group). In the immediate group, a transcutaneous submental approach was used to provide open reduction with rigid fixation, immediate dental implant placement in the anterior mandible, and an autogenous particulate iliac bone grafting harvested from the posterior iliac crest. In the delayed protocol group, the fractures were treated with an open reduction and rigid fixation. Six months after fracture treatment, the fixation hardware was removed and a tent-pole approach was used to place the dental implants to the anterior mandible with an autogenous bone graft harvested from the posterior iliac crest. Implant fixtures were loaded at 3 months as the patients were fitted with healing caps, and the dental implants were loaded using provisional screw-retained acrylic resin prostheses and bar-retained overdentures afterward. The mean follow-up was 19.8 months (range, 13 to 28 months). RESULTS The postoperative course and healing of the 4 patients was uneventful, without any fracture nonunion. The average alveolar augmentation±standard deviation was 7.5±1.17 mm (range, 6.6 to 9.0 mm). There was no bone resorption around any of the endosseous implants on follow-up. All 4 patients wore their dental implant-supported prosthesis comfortably. CONCLUSIONS This preliminary evidence indicates that the modified tent-pole technique may be a safe and effective method to manage the fractured severely resorbed mandible using an immediate or a delayed protocol. Much larger-scale prospective evidence is required to further validate this observation.

Navigation-assisted Le Fort I osteotomy with midpalatal split to treat compressive pathologies of the craniovertebral junction.

This report describes the management of the case of an 11-year-old girl with serious compressive pathology of the craniocervical junction using a navigation-guided Le Fort I level maxillotomy and midline split. In this pediatric case, image guidance significantly enhanced intraoperative orientation and helped to determine the correct location of the horizontal osteotomy lines at the Le Fort I level.

Iron-labeled adipose stem cells and neovascularization in rabbit calvarial critical-sized defects

OBJECTIVE The aim of this study was to evaluate the presence of iron-labeled adipose stem cells at the 2-week time point and vascular changes at the 2-week and 6-week time points using two different types of scaffolds. STUDY DESIGN This study included 22 White New Zealand adult male rabbits. In six rabbits, full-thickness calvarial critical-sized defects were filled with autogenous adipose stem cells labeled with iron oxide seeded onto two scaffolds, namely, solid bioactive glass (BAG) or porous tricalcium phosphate granules (TCP) used on reciprocal sides of the skull. Eleven rabbits were implanted with adipose stem cell-seeded scaffolds without iron labeling for analysis of vascular changes. Five defects were left empty as negative control defects. The specimens were analyzed histologically at the 2-week and 6-week time points. RESULTS The TCP group showed significantly more vascularity compared with the BAG group. A greater number of labeled stem cells were identified in the TCP group compared with the BAG group, but the difference was not statistically significant. CONCLUSIONS This study revealed the differences in stem cell distribution and revascularization of the calvarial defect, which may be biomaterial dependent.