The three dimensional analysis of microstructure of Mandibular trabecular bone

Aim This study has used Micro-Computerized Tomograph(micro-CT) to compare morphology of alveolar and basal bone of specific measuring sites of premolar regions of mandible Materials and Methods Three specimens were prepared and Micro-CT was taken. The structural analysis of the trabecular bone of alveolar and basal bone between the first and second premolar were carried out. The cross sectional image was consisted of 1024×1024 pixels and the size of each pixel was 21.3×21.3µm2. The cross-section scanning distance was also 21.3µm2. The three dimensional image was constructed with two dimensional images. After scanning the specimen, the volume of interest(VOL) was established and two and three dimensional structures were measured. From these image layers Tb Th(trabecular thickness), Tb. SP(trabecular separation), Tb. N(trabecular number), BS/BV(bone surface density), BV/TV(bone volume fraction), SMI(structural model index) were analyzed. Result The trabecular bone structure of specimens varied greatly depend on the sites and especially more so at the basal trabecular bone, inferior to the inferior dental nerve. Both alveolar and basal bone, a mixture of plate and rod-like structures were observed. On average alveolar bone had higher measurement of Th.T, Tb.N, Bs/Tv, but lower Tb.Sp value than basal bone. Conclusion Alveolar bone is consisted of condensed large quantity of trabecular bone and this structural property allows effectively resist occlusal load. However, nearer to the basal bone, the has lower bone density and reduced trabecular bone.ope

Adjunctive hyperbaric oxygen therapy for irradiated rat calvarial defects

Purpose: The aim of this study was to conduct a histologic evaluation of irradiated calvarial defects in rats 4 weeks after applying fibroblast growth factor-2 (FGF-2) with hyaluronan or biphasic calcium phosphate (BCP) block in the presence or absence of adjunctive hyperbaric oxygen (HBO) therapy. Methods: Twenty rats were divided into HBO and non-HBO (NHBO) groups, each of which was divided into FGF-2 and BCP-block subgroups according to the grafted material. Localized radiation with a single 12-Gy dose was applied to the calvaria of rats to simulate radiotherapy. Four weeks after applying this radiation, 2 symmetrical circular defects with a diameter of 6 mm were created in the parietal bones of each animal. The right-side defect was filled with the materials mentioned above and the left-side defect was not filled (as a control). All defects were covered with a resorbable barrier membrane. During 4 weeks of healing, 1 hour of HBO therapy was applied to the rats in the HBO groups 5 times a week. The rats were then killed, and the calvarial specimens were harvested for radiographic and histologic analyses. Results: New bone formation was greatest in the FGF-2 subgroup, and improvement was not found in the BCP subgroup. HBO seemed to have a minimal effect on new bone formation. There was tendency for more angiogenesis in the HBO groups than the NHBO groups, but the group with HBO and FGF-2 did not show significantly better outcomes than the HBO-only group or the NHBO group with FGF-2. Conclusions: HBO exerted beneficial effects on angiogenesis in calvarial defects of irradiated rats over a 4-week healing period, but it appeared to have minimal effects on bone regeneration. FGF-2 seemed to enhance new bone formation and angiogenesis, but its efficacy appeared to be reduced when HBO was applied.ope

Rehabilitation of a patient with a post radiotherapy trismus with an obturator and a maxillary denture using magnet attachments

Construction of an obturator for rehabilitation of a patient who underwent a maxillectomy is vital. Routinely a constructed obturator includes denture portion. A patient who may present anatomical limitations due to surgical or radiotherapy complications often challenges the clinician. Purpose: This clinical report describes a patient with severe trismus after surgical resection and radiotherapy treatment of a tumor in the upper left maxilla. Conclusion: This report describes the concepts of using a rotational path insertion for an obturator and a separately constructed maxillary denture. The stability and retention of the obturator were obtained from anatomical features. Where as these were achieved through magnetic attachments and the remaining edentulous ridge to ensure esthetic and function of the prosthesis.ope

외과적 정출술을 통한 치은 하방 치경부 파절선이 있는 상악 전치부의 심미 보철 치료

Surgical extrusion, immediate extrusion following tooth luxation, is a method to preserve one's natural tooth and achieve esthetic restoration without additional periodontal surgery when subgingival dental caries or crown fracture occurs. A 16-year-old male was referred to the clinic from the department of operative dentistry for the esthetic restoration of maxillary left lateral incisor. Due to the crown to root fracture, the tooth was endodontically treated with a buccal crown length of 4 mm. When the palatal flap was elevated, the mesiopalatal cervical fracture area was situated 3 - 4 mm subgingivally. Crown lengthening was achieved through surgical extrusion. After 3 months of clinical observation and provisional restoration, the maxillary left central incisor was restored with all ceramic crown and obtained a satisfactory clinical result.ope

Marginal tissue response to different Implant neck design

STATEMENT OF PROBLEM: Loss of the marginal bone to the first thread have been accepted but continuous effort have been made to reduce this bone loss by varying implant design and surface texture. PURPOSE: This animal study has examined the histomorphometric variations between implants with micro-thread, micro-grooved and turned surfaced neck designs. MATERIAL AND METHODS: Four mongrel dogs have been used the premolars removed and left to heal for three months. One of each implant systems with turned neck, micro-thread and micro-grooved were placed according to the manufacturers' protocol and left submerged for 8 and 12 weeks. These were then harvested for histological examination. RESULTS: The histologically all samples were successfully ossointegrated and active bone remodelling adjacent to implants. With the micro-grooved implants 0.40 mm and 0.26 mm of the marginal bone level changes were observed at 8 and 12 weeks respectively. The micro-threaded implants had changes of 0.79 mm and 0.56 mm at 8 and 12 weeks respectably. The turned neck designed implants had marginal bone level changes of 1.61 mm and 1.63 mm in 8 and 12 weeks specimens. A complex soft tissue arrangement could be observed against micro-threaded and micro-grooved implant surfaces. CONCLUSION: Within the limitations of this study, it could be concluded that implants with micro-grooved had the least and the turned neck designed implants had the most changes in the marginal bone level. The textured implant surfaces affect soft tissue responses.ope

Bone Regeneration Effect of Hyperbaric Oxygen Therapy Duration on Calvarial Defects in Irradiated Rats

Objective: In this study, we evaluated changes in bone remodeling in an irradiated rat calvarial defect model according to duration of hyperbaric oxygen therapy. Materials and Methods: The 28 rats were divided into four groups. Radiation of 12 Gy was applied to the skull, and 5-mm critical size defects were formed on both sides of the skull. Bone grafts were applied to one side of formed defects. From the day after surgery, HBO was applied for 0, 1, and 3 weeks. At 6 weeks after bone graft, experimental sites were removed and analyzed for radiography, histology, and histomorphometry. Results: Micro-CT analysis showed a significant increase in new bone volume in the HBO-3 group, with or without bone graft. When bone grafting was performed, BV, BS, and BS/TV all significantly increased. Histomorphometric analysis showed significant increases in %NBA and %BVN in the HBO-1 and HBO-3 groups, regardless of bone graft. Conclusion: Hyperbaric oxygen therapy was effective for bone regeneration with only 1 week of treatment.ope

Reinforcing the retention of provisional restoration using provisional implant on maxillary anterior region: clinical case report

Proper management of provisional prosthesis is key to success in prosthodontics. Provisional restoration on maxillary anterior missing area frequently come across a incident of falling off especially in patients with long span pontics and oval arch shape. This is because maxillary anterior teeth are more exposed to horizontal force than the posterior teeth and additional anterior cantilever effect will negatively affect to the retention of provisional prosthesis. Beside that maxillary anterior provisional prosthesis should provide proper incisal guidance during the mandibular functional movements. However occlusal contacts on the prosthesis in maximum intercuspal position are located on opposite side of fulcrum line of prosthesis which will cause removing force against the provisional prosthesis. This case report present that provisional implant prevent pre-described harmful effect on maxillary anterior fixed provisional prosthesis and provide comfort and satisfactory result during post-extraction healing period.ope

Tensile bond strength between elastomeric impression materials and tray resins depending on the thickness of the tray adhesive

Statement of problem: Elastomeric impression materials have been widely used to obtain an accurate impression. However there have not been enough studies on the influence of the thickness of the tray adhesives on the bonding strength between the trays and the elastomeric impression materials. Purpose: In order to understand the relationship between the thickness of the tray adhesive and the tensile bond strength and to suggest the thickness at which the bonding strength is strongest, tensile bond strength related to the thickness of adhesives of 3 different elastomeric impression materials were tested. Materials and methods: 3 impression materials, Permlastic^{®}. Regular Set(Kerr Corp., Romulus, Michigan, U.S.A.), Impregum^{TM} Penta^{TM}(3M ESPE, Seefeld, Germany), and Aquasil Ultra Monophase Regular Set Smart Wetting.(Dentsply Caulk, Milford, Delaware, U.S.A.), were used in this study, and tray adhesives from the same manufacturers of the impression materials were used, which were Rubber Base Adhesive, Polyether Adhesive, and Silfix, respectively. The tray specimens were prepared by autopolymerizing the tray material(Instant Tray Mix, Lang, Wheeling, Illinois, U.S.A.), and a PVC pipe was used to house the impression material. In group A, tray adhesives were applied in multiple thin layers of 1 to 5 and in group B, adhesives were applied only once, in the thickness equivalent to several applications. Lightness(L^*) of the adhesion surface was measured with a spectrophotometer(CM-3500d, Konica Minolta, Sakai, Osaka, Japan). The tensile bond strength of the elastomeric impression material and the tray resin was measured with universal materials testing machines(Instron, Model 3366, Instron Corp, Nowood, Massachusetts, U.S.A.). A formula between the number of adhesive application layers and the lightness of the adhesion surface was deduced in group A, and the number of adhesive layers in group B was estimated by applying the lightness(L^*) to the deduced formula. Results. 1. In group A, a statistically significant increase in tensile bond strength appeared when the number of application layers increased from 1 to 2 and from 4 to 5, and no significant difference was present between 2, 3, and 4 layers in Permlastic. In Impregum, the tensile bond strength was significantly increased when the number of adhesive layers increased from 1 to 3, but no significant difference after 3 layers. In Aquasil, the tensile bond strength significantly increased as the number of application layers increased up to 4 but showed no significant difference between 4 and 5. 2. In group B, the tensile bond strength was decreased when the thickness of the adhesive increased in Permlastic. Impregum showed an increased tensile bond strength when the thickness of the adhesive was increased. In Aquasil, the tensile bond strength increased as the number of adhesive application layers increased up to approximately 2.5 layers but it sharply decreased after approximately 4.5. Conclusion: From the study, the common idea that it is better to apply a thin and single coat of tray adhesive needs correction in more detailed ways, and instructions on some of the tray adhesives should be reconsidered since there were several cases in which the tensile bond strength increased according to the increase in the thickness of the adhesives.ope

Fabrication of immediate complete denture using Campagna tray technique

An immediate complete denture is considered as restoration for lost natural teeth, which is fabricated following the extraction of the remaining teeth. Current esthetics and function can be retained by using immediate denture without edentulous period. However, the major disadvantages of immediate denture relate to the difficulties associated with taking accurate definitive impression and predicting the results of immediate denture. In this case report, the Campagna tray technique was used to take the final impression in a 49-year-old male patient presented with all remaining teeth diagnosed as hopeless teeth. Surgical templates were used for alveoloplasty after extraction. The immediate complete dentures were then delivered. The clinical assessments of immediate dentures showed good esthetic and functional outcomes. The patient showed high level of satisfaction.ope

Postoperative irradiation after implant placement: A pilot study for prosthetic reconstruction

PURPOSE: On maxillofacial tumor patients, oral implant placement prior to postoperative radiotherapy can shorten the period of prosthetic reconstruction. There is still lack of research on effects of post-implant radiotherapy such as healing process or loading time, which is important for prosthodontic treatment planning. Therefore, this study evaluated the effects of post-implant local irradiation on the osseointegration of implants during different healing stages. MATERIALS AND METHODS: Custom-made implants were placed bilaterally on maxillary posterior edentulous area 4 weeks after extraction of the maxillary first molars in Forty-eight Sprague-Dawley rats. Experimental group (exp.) received radiation after implant surgery and the other group (control) didn't. Each group was divided into three sub-groups according to the healing time (2, 4, and 8 week) from implant placement. The exp. group 1, 2 received 15-Gy radiation 1 day after implant placement (immediate irradiation). The exp. group 3 received 15-Gy radiation 4 weeks after implant placement (delayed irradiation). RESULTS: The bone mineral density (BMD) was significantly lower in the immediate irradiation groups. BMD was similar in the delayed irradiation group and the control group. The irradiated groups exhibited a lower bone-to-implant contact ratio, although the difference was not statistically significant. The irradiated groups also exhibited a significantly lower bone volume and higher empty lacuna count than the control groups. No implant failure due to local irradiation was found in this study. CONCLUSION: Within the limits of this study, the timing of local irradiation critically influences the bone healing mechanism, which is related to loading time of prosthesesope