Douglas Deporter

The effect of sol–gel-formed calcium phosphate coatings on bone ingrowth and osteoconductivity of porous-surfaced Ti alloy implants

Ti-6Al-4V implants formed with a sintered porous surface for implant fixation by bone ingrowth were prepared with or without the addition of a thin surface layer of calcium phosphate (Ca-P) formed using a sol-gel coating technique over the porous surface. The implants were placed transversely across the tibiae of 17 rabbits. Implanted sites were allowed to heal for 2 weeks, after which specimens were retrieved for morphometric assessment using backscattered scanning electron microscopy and quantitative image analysis. Bone formation along the porous-structured implant surface, was measured in relation to the medial and lateral cortices as an indication of implant surface osteoconductivity. The Absolute Contact Length measurements of endosteal bone growth along the porous-surfaced zone were greater with the Ca-P-coated implants compared to the non-Ca-P-coated implants. The Ca-P-coated implants also displayed a trend towards a significant increase in the area of bone ingrowth (Bone Ingrowth Fraction). Finally, there was significantly greater bone-to-implant contact within the sinter neck regions of the Ca-P-coated implants.

A Histological Assessment of the Initial Healing Response Adjacent to Porous-surfaced, Titanium Alloy Dental Implants in Dogs

We report here the results of a histological assessment of the initial healing response following implantation into the dog mandible of a porous-surfaced, titanium alloy endosseous dental implant. Two implants were placed in edentulous areas on each side of the mandible of each dog and covered with a full-thickness mucoperiosteal flap. The implant sites on one side of the mandible were allowed to heal for four weeks, while those on the other side were allowed to heal for eight weeks before the animals were killed. Histological specimens were obtained and assessed both qualitatively and by computer-assisted morphometry. All but one of the 24 implants were well-tolerated and healed with a variable ingrowth of bone into the porous-surface geometry. The histomorphometric measurements revealed that bone ingrowth had reached a plateau by four weeks of initial healing.

Basic Biological Sciences Induction of Chondrogenesis in Muscle, Skin, Bone Marrow, and Periodontal Ligament by Demineralized Dentin and Bone Matrix in vivo and in vitro

Induction of chondrogenesis in vivo by rolls of demineralized dentin implanted in muscle, subcutaneous connective tissue of skin, medullary cavity of femur, and periodontal ligament of rat was investigated. Specimens were examined at various times up to 21 days after implantation, using light microscopy and morphometric analysis. Induction of cartilage occurred most quickly in muscle, followed by subcutaneous connective tissue of skin and medullary cavity of femur, and most slowly in periodontal ligament. Significantly more cartilage was found in muscle than in subcutaneous connective tissue of skin and medullary cavity of femur at the times examined, and least of all in periodontal ligament. Outgrowth of cells from rat muscle, dermis and subcutaneous tissue, bone marrow and periodontal ligament cultured in vitro on demineralized bone matrix for up to 35 days produced similar results.

The Effect of Partial Coating with Hydroxyapatite on Bone Remodeling in Relation to Porous-coated Titanium-alloy Dental Implants in the Dog

For inhibition of crestal bone resorption due to stress shielding and disuse atrophy, an hydroxyapatite (HA) plasma coating was added to the coronal portion of partially porous-coated endosseous dental implants. These implants, as well as control non-HA-coated implants were placed in healed mandibular premolar extraction sites in dogs for a 72-week period of function. Histological examination showed that both implant designs became securely fixed by bone ingrowth into the porous-coated apical region of the implants. The plasma-sprayed HA coating resulted in significantly greater bone height formation and maintenance next to the coronal portion of the implant compared with non-HA-coated implants of similar design. In addition, significant resorption of the 20-to-50-μm-thick plasma-sprayed HA coating occurred over the 18-month period of function.

Reconstituted bovine skin collagen enhances healing of bone wounds in the rat calvaria

SummaryThe value of reconstituted fibrillar collagen (Zyderm Collagen Implant I, a concentrated solution of pepsin-solubilized, bovin skin collagen) as a bone graft material was tested in 4 mm diameter surgically created defects of rat calvaria. All wounds were allowed to heal for 4 weeks, and were assessed both qualitatively and by computer-assisted morphometry. The fibrillar collagen was found to produce significantly more new bone than no graft or than heat-denatured fibrillar collagen. The fibrillar collagen was generally well tolerated, appeared to act as a hospitable osteoconductor, and became incorporated into the newly formed bone. The effect of collagen concentration was also tested by comparing the fibrillar collagen at 3.5% (Zyderm Collagen Implant I) with 6.5% suspension of collagen (Zyderm Collagen Implant II). There were no significant differences observed, but a definite trend was evident for Zyderm II to encourage more bone formation than Zyderm I. It is concluded that reconstituted fibrillar collagen is a hospitable, osteoconductive substance that enhances bone healing of calvarial defects in the rat.

A Clinical and Radiographic Assessment of a Porous-surfaced, Titanium Alloy Dental Implant System in Dogs

A new endosseous dental implant system incorporating a porous-surface geometry with a tapered, truncated-cone shape was placed bilaterally in edentulous areas of dog mandibles in a two-stage procedure. All implants had been stabilized by bone ingrowth by the time of the second procedure (insertion of a transgingival collar and implant-supported bridge). The transgingival collar had a porous-surface geometry on its apical one-third, and was meant to encourage gingival connective tissue ingrowth and attachment, but in fact provided an excellent milieu for bacterial contamination. As a consequence, many of the implants showed clinical and radiographic signs of impending failure by eight months. Only those implants for which the porous coat, including that of the transgingival collar, was completely submerged in bone were observed to be successful. This study reports on the radiographic and clinical assessment of this implant system in dogs during the period of function.

Use of a tapered, porous-surfaced dental implant in combination with osteotomes to restore edentulism in the difficult maxilla.

The maxilla is the more difficult arch to restore with endosseous dental implants because of hurdles such as low bone density, narrow buccopalatal width, minimal bone height, and proximity to the maxillary sinus. In this article, a technique to resolve all of these problems using a short, tapered, porous-surfaced implant and a placement protocol using hand osteotomes rather than surgical burs is presented.

A quantitative comparison of collagen phagocytosis in periodontal ligament and transseptal ligament of the rat periodontium

The phagocytosis of collagen within soft connective tissues can be used as an index of collagen turnover and remodeling. The objective of this study was to compare the levels of collagen phagocytosis in periodontal and transseptal ligaments in the rat in order to provide an indication of the relative collagen-turnover activities within these two tissues. Periodontal and transseptal ligaments from two rats were examined by the techniques of electron microscope stereology. Parameters quantitated included cytoplasm (CC), extracellular collagen (ECC), and intracellular or phagocytosed collagen (ICC). The results indicated that the cells of the transseptal ligament have significantly more ICC than those of periodontal ligament. This suggests that the transseptal ligament in the rat may have a high rate of collagen turnover. There seems to be an increasing body of evidence, including the present results, that the transseptal ligament region of gingiva has a high level of collagen turnover. It seems likely, therefore, that, unless there are marked species differences in collagen turnover, slow remodeling of the transseptal ligament is not responsible for orthodontic relapse. Why relapse of rotated teeth can be reduced by surgical severing or removal of the transseptal tissue remains to be determined.

Performance of titanium alloy sintered porous-surfaced (SPS) implants supporting mandibular overdentures during a 20-year prospective study.

OBJECTIVE This study was undertaken to assess short, sintered porous-surfaced (SPS), press-fit implants with mandibular overdentures to restore edentulous patients with severe mandibular resorption. MATERIALS AND METHODS Implant lengths of 7, 8, 9, and 10 mm were used, all with 2-mm polished collars, making the designed intrabony lengths 5, 6, 7, and 8 mm. Each patient received three non-splinted implants placed using a two-stage protocol. RESULTS Only 22 (with 53 implants) of the original 52 patients were available after 20 years. All but one of these patients was functioning with their implant-retained overdentures. Life table analysis accounted for all patients and implants, and showed a 20-year survival of 73.4%. Analysis of carefully standardized radiographs revealed mean cumulative bone loss after 20 years of 0.67 mm relative to the polished collar-SPS junction. CONCLUSIONS Short SPS implants with mandibular overdentures can provide an acceptable treatment over a 20-year period for fully edentulous patients with severe alveolar resorption.

The effects of laser microgrooves on hard and soft tissue attachment to implant collar surfaces: a literature review and interpretation.

This paper summarizes current knowledge on the benefits of laserablated microgrooves in neck regions of endosseous dental implants. Like machine-tooled coronal microthreads with particle-blasted surfaces, laser-ablated microgrooves help to preserve crestal bone. However, they also appear to uniquely favor a true gingival connective tissue attachment comparable to that of natural teeth.