Jae Kook Cha

Acceleration of Bone Regeneration by BMP-2-Loaded Collagenated Biphasic Calcium Phosphate in Rabbit Sinus

PURPOSEnThe objective of this study was to determine the effectiveness of collagenated biphasic calcium phosphate (CBCP) as a carrier for bone morphogenetic protein-2 (BMP-2) at the early stage of healing in rabbit sinus.nnnMATERIAL AND METHODSnIn 16 rabbits, BMP-2-loaded CBCP was grafted into one sinus (the BMP group) and saline-soaked CBCP was grafted into another sinus (the CTL group). The groups were assigned randomly. After 2 weeks (n = 8) or 4 weeks (n = 8), radiographic and histological analysis was performed.nnnRESULTSnTotal augmented volume was significantly larger in the BMP group at both healing periods. Furthermore, new bone volume was significantly greater in the BMP group at 4 weeks. Marked bone formation near the schneiderian membrane was found in the BMP groups at the early healing period. At 4 weeks, evenly distributed new bone was observed in the BMP group, whereas the new bone was sparsely distributed in the central portion in the CTL group.nnnCONCLUSIONnIt can be concluded that the addition of BMP-2 to CBCP resulted in a greater initial augmented volume as a result of postoperative swelling, which is replaced by early bone formation, and it was prominent near the Schneiderian membrane.

Comparative evaluation of roughness of titanium surfaces treated by different hygiene instruments

Purpose The use of appropriate instruments to clean surfaces with minimal change, is critical for the successful maintenance of a dental implant. However, there is no consensus about the type and methodology for such instruments. The aim of this study was to characterize changes in the roughness of titanium surfaces treated by various scaling instruments. Methods Thirty-seven identical disks (5 mm in diameter) were investigated in this study. The specimens were divided into eight groups according to the types of instrumentation and the angle of application. Ultrasonic scaling systems were applied on a titanium disk to simulate standard clinical conditions. The equipment included a piezoelectric ultrasonic scaler with a newly developed metallic tip (NS group), a piezoelectric ultrasonic scaler with a conventional tip (CS group), a piezoelectric root planer ultrasonic scaler with a conventional tip (PR group), and a plastic hand curette (PH group). In addition, the sites treated using piezoelectric ultrasonic scaler systems were divided two sub-groups: 15 and 45 degrees. The treated titanium surfaces were observed by scanning electron microscopy (SEM), and the average surface roughness (Ra) and mean roughness profile depth (Rz) were measured with a profilometer. Results SEM no significant changes in the titanium surfaces in the NS group, regardless of the angle of application. The PH group also showed no marked changes to the titanium surface, although some smoothening was observed. All CS and PR sites lost their original texture and showed irregular surfaces in SEM analysis. The profilometer analysis demonstrated that the roughness values (Ra and Rz) of the titanium surfaces increased in all, except the PH and NS groups, which showed roughness decreases relative to the untreated control group. The Ra value differed significantly between the NS and PR groups (P<0.05). Conclusions The results of this study indicated that changes in or damage to titanium surfaces might be more affected by the hardness of the scaler tip than by the application method. Within the limitations of this study, the newly developed metallic scaler tip might be especially suitable for peri-implant surface decontamination, due to its limited effects on the titanium surface.

Treatment concepts for the posterior maxilla and mandible: short implants versus long implants in augmented bone

The aim of this narrative review is to describe treatment options for the posterior regions of the mandible and the maxilla, comparing short implants vs. longer implants in an augmented bone. The dental literature was screened for treatment options enabling the placement of dental implants in posterior sites with a reduced vertical bone height in the maxilla and the mandible. Short dental implants have been increasingly used recently, providing a number of advantages including reduced patient morbidity, shorter treatment time, and lower costs. In the posterior maxilla, sinus elevation procedures were for long considered to be the gold standard using various bone substitute materials and rendering high implant survival rates. More recently, implants were even placed without any further use of bone substitute materials, but the long-term outcomes have yet to be documented. Vertical bone augmentation procedures in the mandible require a relatively high level of surgical skill and allow the placement of standard-length dental implants by the use of autogenous bone blocks. Both treatment options, short dental implants, and standard-length implants in combination with vertical bone augmentation procedures, appear to result in predictable outcomes in terms of implant survival rates. According to recent clinical studies comparing the therapeutic options of short implants vs. long implants in augmented bone, the use of short dental implants leads to a number of advantages for the patients and the clinician.

Assessment of dehydrothermally cross‐linked collagen membrane for guided bone regeneration around peri-implant dehiscence defects: a randomized single-blinded clinical trial

Purpose The aim of this study was to determine the clinical feasibility of using dehydrothermally cross‐linked collagen membrane (DCM) for bone regeneration around peri-implant dehiscence defects, and compare it with non-cross-linked native collagen membrane (NCM). Methods Dehiscence defects were investigated in twenty-eight patients. Defect width and height were measured by periodontal probe immediately following implant placement (baseline) and 16 weeks afterward. Membrane manipulation and maintenance were clinically assessed by means of the visual analogue scale score at baseline. Changes in horizontal thickness at 1 mm, 2 mm, and 3 mm below the top of the implant platform and the average bone density were assessed by cone-beam computed tomography at 16 weeks. Degradation of membrane was histologically observed in the soft tissue around the implant prior to re-entry surgery. Results Five defect sites (two sites in the NCM group and three sites in the DCM group) showed soft-tissue dehiscence defects and membrane exposure during the early healing period, but there were no symptoms or signs of severe complications during the experimental postoperative period. Significant clinical and radiological improvements were found in all parameters with both types of collagen membrane. Partially resorbed membrane leaflets were only observed histologically in the DCM group. Conclusions These findings suggest that, compared with NCM, DCM has a similar clinical expediency and possesses more stable maintenance properties. Therefore, it could be used effectively in guided bone regeneration around dehiscence-type defects.

Changes in periodontium after extraction of a periodontally-involved tooth in rats

Purpose Recent interest has focused on intentional replantation to restore an original tooth. Some studies have shown successful results with intentional replantation for periodontally involved teeth. For long-term success of replantation, a healthy periodontal status of the recipient site is required so that delayed replantation is more suitable for periodontally involved teeth. To reveal the ideal timing for delayed replantation of periodontally involved teeth, the healing process of extraction sockets after extraction of periodontitis-induced teeth in rats was evaluated. Methods Twenty-eight rats were randomly divided into two groups: a control group (n=8) and test group (n=20). In the test group, periodontitis was induced by a ligature around the cervix of the mandibular first molar of all of the rats. Two weeks later, the mandibular first molars were extracted in all of the animals. The animals were sacrificed on days 0, 3, 7, and 10 after extraction and histological and immunohistochemical analysis was performed. Results In histological analysis of the test group, inflammatory cell infiltrate was found abundantly in the remaining periodontium 3 days after tooth extraction and decreased gradually at later time points. In immunohistochemical analysis of the test group, both interleukin-6 (IL-6) and, tumor necrosis factor-α (TNF-α) were numerous in the furcation area at each postextraction day. IL-6 was stained more heavily between 3 and 7 days after extraction; at day 10 after extraction, little staining was observed. TNF-α staining was more intense at 3 days after extraction and gradually weakened at later points in time. Conclusions Within the limits of this study, it takes at least 10 days to resolve periodontal inflammation in rat extraction sockets.

Localized bone regeneration around dental implants using recombinant bone morphogenetic protein‐2 and platelet‐derived growth factor‐BB in the canine

OBJECTIVESnTo test whether or not one of two biological mediators (recombinant human bone morphogenetic protein-2 (rhBMP-2) and recombinant human platelet-derived growth factor (rhPDGF-BB)) is superior to the other and compared with control groups for bone regeneration around implants based on histomorphometrical outcome measures.nnnMATERIALS AND METHODSnBox-type defects (10xa0×xa05xa0×xa05xa0mm) were prepared on the buccal sides of the left and right edentulous ridge in ten mongrel dogs. Implants were placed at each site, the defects either received (i) bovine-derived particulated bone mineral (DBBM) mixed with rhBMP-2 and a collagen membrane (CM) (DBBM/BMP-2), (ii) DBBM mixed with rhPDGF-BB and CM (DBBM/PDGF), (iii) DBBM and CM (DBBM) and (iv) empty control (control). Animals were euthanized post-surgery at 8xa0weeks and 16 weeks. Histomorphometrical analyses were performed.nnnRESULTSnThe mean percentages of regenerated area within total defect area amounted to 56.95% for DBBM/BMP-2, 48.86% for DBBM/PDFG, 33.44% for DBBM and 1.59% for control at 8 weeks, and 26.79% for DBBM/BMP-2, 23.78% for DBBM/PDFG, 30.21% for DBBM and 5.07% for control at 16 weeks with no statistically significant differences between the groups (Pxa0>xa00.05). The mean amount of regenerated bone was 26.97% for DBBM/BMP-2, 22.02% for DBBM/PDFG, 5.03% for DBBM and 1.25% for control at 8 weeks, and at 16 weeks, these values were lower in the two groups with biological mediators (DBBM/BMP-2xa0=xa013.35%; DBBM/PDGFxa0=xa06.96%) and only slightly increased in group DBBM (10.68%) and the control group (4.95%) compared with 8 weeks. The first bone-to-implant contact values on the buccal side were minimal for DBBM/BMP-2 (0.57xa0mm) and maximal for control (3.72xa0mm) at 8 weeks.nnnCONCLUSIONSnThe use of biological mediators (rhBMP-2 and rhPDGF-BB) can increase the amount of bone regeneration at dehiscence-type defects compared with controls at 8 weeks, but not at 16 weeks due to enhanced hard tissue remodeling processes.

Sequential healing of onlay bone grafts using combining biomaterials with cross‐linked collagen in dogs

OBJECTIVESnThe aim of this study was to observe the sequential healing of onlay grafts in terms of the volumetric and histologic changes using different bone substances and absorbable membranes according to the presence of collagen cross-linking.nnnMATERIAL AND METHODSnFour groups involving onlay grafting with different materials were randomly assigned to both sides of the maxillae of 15 beagle dogs: (i) control group without any treatment; (ii) group NN, bovine hydroxyapatite incorporated into a non-cross-linked collagen matrix (BHC)xa0+xa0non-cross-linked collagen membrane (NCCM); (iii) group NC, BHCxa0+xa0cross-linked collagen membrane (CCM); and (iv) group CC, porcine hydroxyapatite incorporated into a cross-linked collagen matrixxa0+xa0CCM. Radiographic and histological analyses were performed after three different healing periods: 4, 8 and 12xa0weeks.nnnRESULTSnAt week 4, the bone substances were well localized under the barrier membrane in groups NC and CC, while the bone substances became spread out and flattened in group NN. Similarly, the augmented height was significantly greater in groups NC and CC (2.55 and 2.51xa0mm, respectively; median) than in group NN (1.96xa0mm, Pxa0<xa00.001, both). The percentages of newly formed bone were significantly higher at week 12 than at weeks 4 and 8 in all of the groups. The NCCM showed an earlier angiogenesis pattern than the CCM; however, earlier degradation was observed at week 12.nnnCONCLUSIONnCombining biomaterials with cross-linked collagen might contribute to maintaining its initial morphology with excellent biocompatibility in early healing period of lateral onlay grafts.

In situ dental implant installation after decontamination in a previously peri-implant diseased site: a pilot study

Purpose The aim of this study was to examine whether a previous peri-implantitis site can affect osseointegration, by comparing implant placement at a site where peri-implantitis was present and at a normal bone site. A second aim of this study was to identify the tissue and bone reaction after treating the contaminated implant surface to determine the optimal treatment for peri-implant diseases. Methods A peri-implant mucositis model for dogs was prepared to determine the optimal treatment option for peri-implant mucositis or peri-implantitis. The implants were inserted partially to a length of 6 mm. The upper 4 mm part of the dental implants was exposed to the oral environment. Simple exposure for 2 weeks contaminated the implant surface. After 2 weeks, the implants were divided into three groups: untreated, swabbed with saline, and swabbed with H2O2. Three implants from each group were placed to the full length in the same spot. The other three implants were placed fully into newly prepared bone. After eight weeks of healing, the animals were sacrificed. Ground sections, representing the mid-buccal-lingual plane, were prepared for histological analysis. The analysis was evaluated clinically and histometrically. Results The untreated implants and H2O2-swabbed implants showed gingival inflammation. Only the saline-swabbed implant group showed re-osseointegration and no gingival inflammation. There was no difference in regeneration height or bone-to-implant contact between in situ implant placement and implant placement in the new bone site. Conclusions It can be concluded that cleaning with saline may be effective in implant decontamination. After implant surface decontamination, implant installation in a previous peri-implant diseased site may not interfere with osseointegration.

Prevalence of Cervical Enamel Projection and Its Impact on Furcation Involvement in Mandibular Molars: A Cone-Beam Computed Tomography Study in Koreans

This study evaluated the prevalence of cervical enamel projections (CEPs) in mandibular molars, and analyzed the correlation between CEPs and furcation involvement (FI) based on cone‐beam computed tomography (CBCT) data in a Korean population. CBCT images obtained from March 2012 to August 2012 were analyzed. CEPs and FI on the buccal and lingual surface were classified in three‐dimensionally reconstructed images and cross‐sectional views, and the correlation between these two parameters was analyzed. In total, 982 teeth in 425 patients were analyzed. The overall prevalence rate of CEPs was 76% (71% and 27% on the buccal and lingual surfaces, respectively). Grade I CEPs were the most common, followed by CEPs of grades II and III. There was a statistically significant, but negligible correlation between the CEP grade and the degree of FI on the buccal and lingual surfaces. Within the limitations of this cross‐sectional study, a high prevalence of CEPs were found in a Korean population, but the role of CEPs in provoking FI appeared not to be decisive. Anat Rec, 299:379–384, 2016.

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

AIMnThe 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.nnnMATERIALS AND METHODSnBoth inflamed and healthy periodontal tissues were obtained from periodontitis patients (nxa0=xa011), and the chemokine expression levels were analyzed. The periodontal-tissue-specific chemokines were applied to healthy hPDLSCs from extracted teeth (nxa0=xa03), 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.nnnRESULTSnChemokines 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.nnnCONCLUSIONnThe 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.