Alveolar ridge regeneration in two-wall-damaged extraction sockets of an in vivo experimental model.

AIM: To determine the healing outcome following grafting with deproteinized porcine bone mineral (DPBM) with or without collagen membrane coverage in two-wall (both buccal and lingual)-damaged extraction sockets. MATERIALS AND METHODS: Distal roots of three mandibular premolars in six beagle dogs were extracted, and the whole buccal and lingual bony walls were surgically removed. Three treatment protocols were then applied according to the following group allocation: no graft (None), grafting DPBM (BG), and grafting DPBM with coverage by a collagen membrane (BG + M). Two observational periods (2 and 8 weeks) were used with the split-mouth design, and quantitative and qualitative analyses were performed by microcomputed tomography and histology. RESULTS: The dimensions of the alveolar ridge at both grafted sites (BG and BG + M) remained similar to those of the pristine ridge in the histologic and radiographic analyses, whereas the ungrafted sites (None) collapsed both vertically and horizontally. Both grafting protocols produced substantial bony regeneration, but the addition of a covering membrane enhanced the proportion of mineralized tissue within the augmented area, and the BG + M group also showed a significantly larger area of regenerated ridge than the None group (p < .05). CONCLUSIONS: Bone grafting with collagen membrane can maintain the alveolar ridge dimensions with substantial bone regeneration in a two-wall-damaged extraction socket.

Histologic analysis following grafting of damaged extraction sockets using deproteinized bovine or porcine bone mineral: A randomized clinical trial.

OBJECTIVES: This study histologically analyzed biopsy samples obtained from sites of damaged extraction socket grafting using deproteinized bovine bone mineral (DBBM) or deproteinized porcine bone mineral (DPBM) with coverage by a collagen membrane. MATERIAL AND METHODS: One hundred patients participated in this randomized controlled clinical trial of extraction socket grafts performed in cases of periodontally compromised teeth. All participants were blinded to their group allocations, and each material was grafted with coverage by collagen membranes after extraction of the tooth and removal of granulation tissue. At implant placement at 4 months, a biopsy was harvested at the implant site using a trephine was analyzed histologically. RESULTS: Eighty-five biopsy samples were acquired, of which 81 were finally included in the histologic analysis (42 in DBBM and 39 in DPBM group). Both DBBM and DPBM groups showed comparable proportions of residual biomaterial (12.37 ± 5.67% and 12.21 ± 5.75%, respectively), newly formed bone (15.07 ± 10.52% and 18.47 ± 11.47%, respectively), and nonmineralized tissue (72.56 ± 10.07% and 71.55 ± 15.47%, respectively). There were no significant differences in these histologic parameters between the two groups with different biomaterials. CONCLUSION: Comparable histologic bone formation was found in both socket grafted groups with DBBM or DPBM covered by collagen membranes in periodontally damaged extraction sockets. However, a wide variation in new bone formation was found after 4 months of postsurgical healing and a tendency of higher new bone formation was shown at damaged sockets that had an intact unilateral residual wall regardless of buccal or lingual side.

Clinical Factors and Cellular Responses of In Situ Human Alveolar Bone-Derived Mesenchymal Stromal Cells Associated With Early Periimplant Marginal Bone Loss: A Prospective Cohort Pilot Study.

PURPOSE: To investigate clinical factors and cellular responses of in situ human alveolar bone-derived mesenchymal stromal cells involved in early periimplant marginal bone loss. MATERIALS AND METHODS: Thirty-seven completely or partially edentulous patients were enrolled in this study. Periapical radiographs were taken at the time of implant surgery, at 3-month follow-up, and at 1-year follow-up. Univariate analysis and multiple logistic regression were performed to investigate the associations between marginal bone loss and study variables. The mRNA expression levels of 21 bone-remodeling- and tissue-healing-associated genes were analyzed by subgroup. RESULTS: Thirty-one patients with 98 implants were followed. The incidence and mean amount of bone loss were higher for overdentures than for other prosthesis and higher for the maxilla than for the mandible. The bone loss group showed lower mRNA expression levels of runt-related transcription factor-2, bone morphogenetic protein-2, and peroxisome proliferator-activated receptor gamma-2 and higher receptor activator of NKκB ligand/osteoprotegerin (RANKL/OPG) ratio. CONCLUSION: Within the limitations of the study, certain genes involved in bone remodeling (runt-related transcription factor-2 [Runx-2], bone morphogenetic protein-2 [BMP-2], and peroxisome proliferator-activated receptor gamma-2 [PPARγ-2]) and RANKL/OPG are correlated with early periimplant bone loss, with the type of suprastructure and the involved jaw being significant clinical factors.

Resonance Frequency Analysis of Tapered Implants Placed at Maxillary Posterior Sites After Lateral Sinus Augmentation: A 1.5-year Follow-Up Prospective Study.

OBJECTIVES: To use resonance frequency analysis to evaluate tapered implants placed at maxillary posterior sites after lateral sinus augmentation. MATERIALS AND METHODS: Patients who had missing teeth in the maxillary posterior area and required lateral sinus augmentation before implant placement were enrolled in this study. After a 6-month healing period, a tapered implant (Osstem TSIV) was placed. Implant success rate, survival rate, and marginal bone loss of the implants were measured. For resonance frequency analysis, implant stability quotient (ISQ) values were measured at each visit during a 1.5-year follow-up period. RESULTS: Twenty-four patients completed the study procedure. The residual bone height was 2.57 ± 1.10 mm (mean ± SD). Healing of the grafted area was uneventful in all cases, and 55 tapered implants were installed. The implant success rate was 95.56%, and the survival rate was 100% throughout the observation period. The marginal bone loss was limited to 0.22 ± 0.44 mm. ISQ increased gradually from 68.40 ± 11.14 to 82.24 ± 4.75 during the 1.5-year follow-up period. CONCLUSION: The tapered implants showed good initial and final stability after placement in the soft bone of the maxillary posterior area after lateral sinus augmentation.

Characteristics of Local Delivery Agents for Treating Peri-Implantitis on Dental Implant Surfaces: A Preclinical Study.

Local delivery agents (LDAs) are widely used in peri-implantitis treatments. The aim of this study was to identify LDAs remaining on the dental implant surfaces and to analyze the components of these residues after applying various cleaning methods. Implants were prepared with a sand-blasted, large-grit, acid-etched surface. Four kinds of LDAs were applied on the implant surfaces: chlorhexidine gel (group 2), tetracycline solution (group 3), and 2 kinds of minocycline hydrochloride agents (groups 4 and 5). Group 1 received normal saline as a control. Two cleaning methods were applied for different durations as follows: (1) running distilled water for 10 seconds (subgroup A), 5 minutes (subgroup B), and 15 minutes (subgroup C); and (2) water spray of a dental-unit chair for 10 seconds (subgroup D) and 5 minutes (subgroup E). Scanning electron microscopy and energy-dispersive x-ray spectroscopy were used to analyze the surface morphology and residue components for all implants. The amount of LDA removed from the implant surfaces in groups 1, 2, 3, and 5 increased with the cleaning duration and pressure. However, Minocline remained coated on the implant surfaces in group 4 under all cleaning conditions. Minocline could not be cleaned off well by water due to its hydrophobicity. Therefore, directly using this agent on implant surfaces with peri-implantitis should be carefully considered. The presence of LDA residues without drug efficacies on implant surfaces might interfere with reosseointegration and act as a reservoir of microorganisms.

Radiographic and histologic observations of sequential healing processes following ridge augmentation after tooth extraction in buccal-bone-deficient extraction sockets in beagle dogs.

OBJECTIVES: To evaluate dimensional ridge alterations and sequential healing processes following ridge augmentation after tooth extraction in damaged extraction sockets with buccal-bone-deficiency. MATERIAL AND METHODS: Bilateral dental roots of three mandibular premolars were extracted with entire removal of the buccal-bone plate in eight beagle dogs. Unilateral sites were grafted with biomaterials (test group) and contralateral sites were healed without grafting (control group). Observations were made after 1, 2, 4, and 8 weeks, and all sites were distributed evenly (n = 6 for each group and period). Radiographic/histomorphometric analyses were performed. RESULTS: In spontaneous healing of damaged extraction sockets, the dimension of regenerated alveolar ridge gradually increased until 4 weeks and then remained stable, but radiographic/histomorphometric analyses revealed evident dimensional shrinkage compared to the pristine tissue at 8 weeks in the coronal and middle areas. Bone grafting retained the pristine dimension of alveolar ridge, and newly formed bone area within the augmented space continuously expanded during the observational period to the outermost border of the space. CONCLUSIONS: Spontaneous healing of damaged extraction sockets caused substantial dimensional shrinkage. However, ridge augmentation can provide space into which new bone may grow continuously, resulting in the final dimensions comparable to those of the pristine alveolar ridge.

Chemokine in inflamed periodontal tissues activates healthy periodontal-ligament stem cell migration.

AIM: The present study aimed to characterize the expression pattern of chemokines obtained from inflamed periodontal defects and to determine the characteristics of human periodontal-ligament stem cells (hPDLSCs) migrated by each specific chemokine. MATERIALS AND METHODS: Both inflamed and healthy periodontal tissues were obtained from periodontitis patients (n = 11), and the chemokine expression levels were analyzed. The periodontal-tissue-specific chemokines were applied to healthy hPDLSCs from extracted teeth (n = 3), with FGF-2 acting as a positive control. Cells were separated by selected chemokines using transwell method into migrated/unmigrated hPDLSCs. The characteristics of the hPDLSC subpopulation recruited by each chemokine were assessed, and gene expression pattern was analyzed by microarray. RESULTS: Chemokines were categorized into three groups by specific patterns of "appearing," "increasing," and "decreasing/disappearing" from healthy to inflamed tissues. A representative chemokine from each group enhanced the capacities for colony formation and osteogenic/adipogenic differentiation while maintaining the surface markers of hPDLSCs. RANTES/CCL5 significantly increased the cellular migration of hPDLSCs, via enhancement of signaling pathways, regulation of the actin skeleton, and focal adhesion. CONCLUSION: The present study found a specific chemokine profile induced by inflammation in periodontal tissues, with RANTES/CCL5 appearing to play a role in the migration of hPDLSCs into inflammatory periodontal lesions.

In Vivo Evaluation of Commercially Available Gel-Type Polyethylene Glycol Membrane for Carrier of Recombinant Human Bone Morphogenetic Protein-2.

PURPOSE: This study evaluated a commercially available, 3-dimensional gel-type polyethylene glycol (PEG) membrane as a carrier for recombinant human bone morphogenetic protein-2 (rhBMP-2) using a rat calvarial defect model. Another gel-type carrier, fibrin-fibronectin system (FFS), was used as a positive control. MATERIALS AND METHODS: Critical-size defects were made in the rat calvarium, which were allocated to 1 of 10 groups comprising 2 healing periods and biomaterial conditions: 1) sham control, 2) FFS only, 3) FFS plus BMP-2, 4) PEG only, and 5) PEG plus BMP-2. Radiographic and histologic analyses were performed at 2 and 8 weeks after surgery. RESULTS: After 2 weeks, some parts of the FFS were biodegraded and extensive cellular infiltration was observed at sites that received FFS or FFS plus BMP-2. The PEG membrane retained its augmented volume without cellular infiltration at sites that received PEG or PEG plus BMP-2. After 8 weeks, the FFS was completely degraded and replaced by new bone and connective tissues. In contrast, the volume of residual PEG was similar to that at 2 weeks, with slight cellular infiltration. In particular, there was progressive bone regeneration around micro-cracks and resorbed outer surface in the PEG + BMP-2 group. Although the PEG + BMP-2 group showed increased area and percentage of new bone, there was no statistical relevance after 2 and 8 weeks in histomorphometric analyses. However, the appearance of the healing differed (with new bone formation along micro-cracks in the PEG + BMP-2 group), and further studies with longer healing periods are needed to draw conclusions about clinical applications. CONCLUSION: Evidence of mechanical stability and new bone formation along micro-cracks when using PEG plus BMP-2 might support the PEG membrane as a candidate carrier material for rhBMP-2.

Ridge regeneration of damaged extraction sockets using rhBMP-2: an experimental study in canine.

OBJECTIVES: This study evaluated the dimensional ridge alteration in a buccal-bone-deficient extraction socket, and ridge regeneration following socket grafting accompanied by recombinant human bone morphogenetic protein 2 (rhBMP-2) or a collagen membrane covering. MATERIAL AND METHODS: In five beagle dogs, entire buccal bone of the extracted sockets of premolars was surgically removed and immediately grafted using one of the following graft protocols: (1) sham surgery without any grafting, and grafting with (2) deproteinized bovine bone mineral (DBBM), (3) DBBM/rhBMP-2 and (4) DBBM covered with a collagen membrane (DBBM/Membrane). Quantitative/qualitative analyses were performed radiographically/histologically after 8 weeks. RESULTS: Buccal-deficient extraction sockets healed with significant reduction in buccolingual dimension along the entire length of the socket, but all grafting techniques reduced the dimensional changes compared to the non-grafted control sites. Histologically, sites received DBBM only exhibited minimal regeneration, whereas sites grafted with DBBM/rhBMP-2 or DBBM/Membrane exhibited greater new bone formation extending the entire augmented area. CONCLUSIONS: Buccal-bone-deficiency may lead to significant volume reduction after tooth extraction along the entire length of the socket, and socket grafting accompanied by rhBMP-2 or covered with a membrane can be candidate therapies for preservation of the buccolingual dimension and successful ridge regeneration.

Apatite-coated collagen sponge for the delivery of bone morphogenetic protein-2 in rabbit posterolateral lumbar fusion.

Bone morphogenetic proteins (BMPs) need an effective delivery system for efficient bone regeneration. In this study, we evaluated the efficiency of an apatite-coated collagen sponge for the long-term delivery of BMP-2 in a rabbit model of lumbar posterolateral fusion. A total of 15 rabbits, divided into three groups, underwent posterolateral lumbar fusion. The first group (control group) received uncoated collagen sponges without BMP-2. The second group (uncoated group) received uncoated collagen sponges with BMP-2 (40 µg each side). The third group (apatite-coated group) received apatite-coated collagen sponges with the same level of BMPs (40 µg each side). All rabbits were euthanized 6 weeks after operation, and the fusion status was assessed by radiographic study, micro-CT, manual palpation, biomechanical study, and histological examination. Fusion rates as determined by radiographic study, micro-CT, and manual palpation showed that the apatite-coated group had a significantly higher rate of fusion than the control group (P = 0.024), while the uncoated group did not (P = 0.083). Biomechanical study showed significantly higher tensile strength in the apatite-coated group than the uncoated group (P = 0.032). Denser trabeculations were found in the apatite-coated group compared with the uncoated group. It is concluded that the use of apatite-coated collagen sponges for BMP-2 delivery enhanced bone regeneration.