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A gravity sintering fabrication technique has been developed for producing Co-Cr-Mo alloy dental implants having a porous coating on the root portion. This process allows for control of pore structure enabling ingrowth of either bone or fibrous tissue. The microstructure and mechanical properties of these materials have been determined.
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There is a growing interest in bruxism, as evidenced by the rapidly increasing number of papers about this subject during the past 5 years. The aim of the present review was to provide an update of two previous reviews from our department (one about the aetiology of bruxism and the other about the possible role of this movement disorder in the failure of dental implants) and to describe the details of the literature search strategies used, thus enabling the readers to judge the completeness of the review. Most studies that were published about the etiology during the past 5 years corroborate the previously drawn conclusions. Similarly, the update of the review about the possible causal relationship between bruxism and implant failure reveals no new points of view. Thus, there is no reason to assume otherwise than that bruxism is mainly regulated centrally, not peripherally, and that there is still insufficient evidence to support or refute a causal relationship between bruxism and implant failure. This illustrates that there is a vast need for well-designed studies to study both the aetiology of bruxism and its purported relationship with implant failure.
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In order to determine the effect of electrical stimulation on canine alveolar bone, porous PMMA dental implants with a solid core (on which a Pt-13% Rh electrode was wound) were implanted in the mesial socket of the canine mandibular fourth premolars bilaterally. The positive electrode was implanted into the distal socket. The power pack was placed over the masseteric fossa. The implants, wires and power packs were all implanted subcutaneously. Each animal had an experimental and control implant. Mechanical push-out samples were prepared by sectioning a 2mm thick section of the mandible with the implant in the middle. The samples were tested immediately and the load-deflection curves were obtained.
Traumatic tooth loss leads to alveolar resorption especially in sagittal direction. This can be due to avulsion of bone substance during the accident itself or due to resorption of the alveolar crest that takes place afterwards. Shortage of bone can prevent proper positioning of dental implants unless the volume of bone is increased before implantation. In the maxillary anterior area, this is also an esthetic problem. Several treatment modalities have been presented to augment the bone. This report reviews the latest literature on bone grafting, bone substitutes, guided bone regeneration, osteocompression and distraction which are potentially useful in the anterior maxilla. A special emphasis is paid to the versatility of using a crestal split osteotomy, by means of chisels and osteotomes to widen the narrow ridge. Three examples are illustrated showing onlay grafting, preservation of alveolar width with alloplastic coral material and lateral widening of a narrow maxillary alveolar ridge, using the crestal splitting technique.
A clinical, histological, and radiographic examination was performed on 77 permucosal dental implants, made of dense sintered hydroxylapatite: 34 solid cylinders and 43 hollow cylinders. The hollow cylinders were pre-compressed between two titanium caps. The implants were placed in partly edentulous mandibles of dogs, and were physiologically loaded. Healing was clinically and radiographically evaluated during a six-month to five-year period. At various times, implants with their surrounding tissues were removed and prepared for light and electron microscopy. All implants showed a good initial fit and were maintained in place without undercut or mechanical stabilization. After 18 months, 76% of the solid cylinders had fractured at the implant/bone junction due to fatigue. However, the submerged portions of the solid cylinders were preserved without clinical problems, and became entirely embedded in bone. The pre-stressed implants did not fracture, and 91% were functioning 24 months after placement. The average scores of pocket depths and gingival bleeding showed no significant differences between implants and surrounding natural teeth. Bone deposition occurred on the entire surface of the implant below the crest of the alveolar bone, and intimate bone contact was confirmed by electron microscopy. It was also observed that a layer of bone tissue was deposited on the implant surface in the permucosal area just above the alveolar bone level. Embedding of gingival fibers in this layer resulted in gingival attachment to the implant, comparable with that of natural teeth.
A STUDY HAS BEEN CARRIED OUT ON THE STRUCTURE AND SURFACE TEXTure of a new dental implant material composed of vitreous carbon balloons (3 wt % or 6 wt %) and poly(methyl methacrylate). Tooth replica implants using this material had been successfully placed in baboons, and histologic study revealed normal alveolar bone and a peri-implant membrane with the connective tissue fibers oriented in a horizontal direction. Square wafers (10 mm X 10 mm X 1 mm) were studied, with the surface sandblasted in one-half of the specimens. Light microscopy revealed that in the 3% carbon specimens, the vitreous carbon micro-balloons were evenly spaced and often appeared to be fragmented within their spaces. S.E.M. studies revealed a finely porous surface with numerous large craters. Microballoons were often seen within the craters in the nonsandblasted specimens.
There are literally thousands of published accounts of the performance of medical and dental implants that employ metals and ceramics for which little or no materials characterization has been accomplished. Before the current decade, the level of sophistication of research was such that many materials did not even receive postprocessing analysis of the "bulk" composition, a minimal characterization we now realize is inadequate. Instead, research focused upon mechanical properties and corrosion studies at the macroscopic level, along with the search for a mythical property called biocompatibility. There were sound scientific reasons for this focus. The state of knowledge of the biology associated with implants did not allow the creation of experiments at the cellular or molecular level. Experiments progressed slowly from clinical observations to histologic observations, from which inferences of past events were made. The complete characterization of implant surfaces was virtually impossible because the analytical instrumentation and the associated understanding of physical and chemical processes occurring at surfaces were lacking. Materials were selected because of their apparently inert state, as defined by corrosion studies and histological examination of implant specimens. The focus in the 1970s was on micron-sized surface features. Porosity, grooves, textures, etc., were emphasized along with the macroscopic design features. A proliferation of designs, many of which were based on inspiration, rather than experimentation and optimization, were brought to the marketplace. Perhaps the exception to this lack of surface analysis was the development of the surface-active biomaterials based on calcium phosphates, the tricalcium phosphates, hydroxylapatites, and surface active glasses. Unfortunately, investigators did not pursue the same analyses for the "inert" materials.(ABSTRACT TRUNCATED AT 250 WORDS)
BACKGROUND: Although most patients with implants have lost their natural teeth because of poor oral hygiene, limited data exist to guide practitioners in their recommendations of home-care regimens for their patients' endosseous dental implants and maintenance of peri-implant soft-tissue health. The authors conducted a study to compare the home-care effectiveness of a counter-rotational powered tooth-brush with that of conventional home-care regimens. METHODS: Before starting the six-year study, the authors trained 85 clinical investigators at 32 dental research centers across the United States in gathering periodontal data. Data for 2,966 implants were entered into a centralized database. Outcomes were derived from 24-month observations of a subset of the implants studied. RESULTS: Repeated-measures analysis of the toothbrushing methods used on 2,966 implants showed that the counter-rotational powered toothbrush removed plaque significantly better than manual methods (P < .0001 Wald statistic) from all implant surfaces and at all recall intervals up to 24 months. Similar results were demonstrated for the gingival index. CONCLUSIONS: The counter-rotational powered brush appears to be well-suited for home-care regimens aimed at maintaining optimal peri-implant soft-tissue health in patients with dental implants. CLINICAL IMPLICATIONS: The importance of maintaining the health of the peri-implant tissues is well-recognized by the dental profession. The counter-rotational powered toothbrush is an effective tool in meeting the oral hygiene challenges associated with implant prosthesis maintenance.
A study has been carried out on the structure and surface texture of a new dental implant material composed of silica microspheres (3 or 5 wt%) and poly(methyl methacrylate). A recently developed composite material composed of vitreous carbon microballoons and poly(methyl methacrylate) has proven highly successful in clinical use, but the black color presents aesthetic problems at the gingival margin. The new material was developed in order to reproduce the many desirable qualities of the vitreous carbon-polymethacrylate composite, while omitting the black color. Square wafers (10 mm X 10 mm X1 mm) were studied, with the surface sandblasted in half of the specimens. Light microscopy revealed an even spacing of spherical configurations throughout the material. Scanning electron microscope studies revealed a finely porous surface with many large craters in the sandblasted specimens.
A 69-year-old male, under active treatment for multiple myeloma, fractured his left maxillary second premolar palatal abutment tooth and requested treatment because his upper partial denture no longer fit. Several other teeth were deemed hopeless, and construction of a maxillary complete denture presented problems. There are general contraindications regarding dental implant surgery in the terminally ill patient; however, in this case, the patient wished to maximize his quality of life and opted to undergo implant surgery. With close management, the treatment was successful.
The combination of a relatively new alveolar ridge augmentation material composed of purified fibrillar bovine collagen (PFC) and particulate hydroxylapatite (HA) (Alveoform Biograft Collagen Corp., Palo Alto, Calif.), along with endosseous root form dental implants, was simultaneously placed by a combined flap and tunneling technique to reconstruct and augment endentulous and atrophic mandibles. Prosthodontic and patient surveys reported great satisfaction with overdenture stability, retention, comfort, esthetics, speech, and function. Six reported cases showed that clinically significant alveolar ridge augmentation and form were achieved and maintained with the added prosthetic support and improved stability and retention produced by the combination of procedures. Histologic study of core specimens obtained through the ridge augmentation graft material provided evidence of supracortical bone ingrowth into the graft matrix.
Older adults present special problems for the dentist trying to establish or reestablish esthetics. Periodontal diseases are of concern for this population since tooth loss from these widespread problems increases with age. In general, this loss occurs because of increased exposure time to pathogenic bacteria, not some change inherent in the body brought on by the aging process. The profession has begun to place more emphasis on systemic risk factors and their role in modifying periodontal inflammation. The current thinking is that bacteria are necessary to initiate and sustain periodontal diseases, but the clinical manifestation is dictated to a significant extent by systemic factors. Smoking, diabetes, and being positive for the interleukin-1 genotype predispose the patient to developing more severe disease. For those older adults who lose teeth, dental implants have emerged as reliable replacements, and concerns about placing these devices in patients who have lost teeth as a result of periodontitis appear to be largely unfounded.
The objective of this study was to evaluate the orientation of collagen in the canine gingival connective tissue to a titanium surface (TI), and to hydroxyapatite coatings applied by plasma-spraying (HAPS) and ion beam assisted deposition (IBAD), on the supracrestal region of dental implants after 3 and 4 months. The effects of induced peri-implantitis on the soft connective tissue apposed to the implant were also evaluated. The use of these three surface types allowed for the evaluation of the effects of chemical composition (TI vs. IBAD; same topography) and topography (HAPS vs. IBAD; similar chemical composition) on the collagen fiber orientation. The majority of collagen fibers were found to be parallel to the implant surface, and there was no significant effect of surface type on orientation. There was a significant effect of inflammation on the connective tissue attachment length. The loss of bone height and concomitant gingival recession reduced the length of soft connective tissue apposed to the implant zone designed for collagen fiber attachment.
The treatment design of most dental restorations is largely empirical and based on the experience of the individual practitioner. Because the biomechanical aspects of implant-supported restorations are difficult to assess on an individual basis, there is a possibility for compromised biomechanical performance of the implant-retained restoration to achieve satisfactory esthetics and phonetics. Through repeated loading cycles, the restoration or its components may fatigue and fail. This study evaluated the biomechanical behavior of the crown component relative to the gold retaining screw and abutment under load to provide insight into the mechanism of loosening and fracture of the retaining screw. A two-dimensional finite element model of the dental implant components was developed for nonlinear contact analysis. A simulation of tightening of the retaining screw was followed by axial loading of a cusp tip on the implant-supported crown. Loading of the cusp tip resulted in separation of the contact between (1) the gold retaining screw and abutment, and (2) the crown and the abutment. Repeated loading and unloading cycles resulted in alternating contact and separation between the retaining screw head base and the crown. Clinical findings of screw loosening and failure probably result from these separation events and from elevated strains in the screw as demonstrated by the model.