Implants in regenerated bone in a primate model.

BACKGROUND: Earlier publications from our laboratory described the use of guided bone regeneration to fill large bone voids in the mandible created through en bloc resection in primates. The present report describes placement of implants into the regenerated bone with subsequent prostheses construction and loading. METHODS: Lesions were created in the mandibles of 9 monkeys in a standardized mandibular defect of 8 x 19 mm. Reinforced expanded polytetrafluoroethylene membranes were placed in the animals and held in place with mini screws and sutures for anywhere from 1 to 12 months. No material was added to the defect. In each animal a root-form implant was placed 12 mm distal to the abutment teeth into the regenerated bone and was loaded with a prosthesis for 12 months. These implants were compared to original implants placed in the same monkeys years earlier in the same location in non-regenerated bone. Digital radiology and histomorphometry are described. RESULTS: The results show that root-form implants placed in regenerated bone show the same radiological and histomorphometric characteristics as in normal bone when loaded. In addition, the percentage of bone contact with implants seen in regenerated bone versus non-regenerated bone is the same when both are loaded (65 +/- 13% SD in regenerated bone versus 59 +/- 15% SD in non-regenerated bone). CONCLUSIONS: In a primate model root-form implants placed in regenerated bone and prosthetically loaded show no difference when compared to root-form implants placed in non-regenerated bone and prosthetically loaded.

Guided bone regeneration of large mandibular defects in a primate model.

BACKGROUND: An earlier publication from our laboratory described the use of guided bone regeneration to fill large bone voids in the mandible created through en bloc resection in primates. The present report is an embellishment of this paper and describes bone regeneration experiments in 18 adult male Macaca mulatta monkeys to determine how long membranes must be in position to promote guided bone regeneration. METHODS: Thirty-six lesions were created in the mandibles of 18 monkeys in a standardized mandibular defect of 8 x 19 mm. Reinforced ePTFE membranes were placed in the animals and held in place with mini screws and sutures for anywhere from 1 to 12 months. No material was added to the defect. In addition to clinical studies, digital subtraction radiology and fluorescent labeling with tetracycline and histomorphometry are described. RESULTS: The results indicate that no bone gain was observed in membranes exposed for 1 month or less, but bone gain (approximately well over 90% of defects) was observed at 12 months when membranes were left in situ for 2 to 12 months (P <0.0001). No significant difference in the amount of bone gained at 12 months was observed for membranes left in place for intervals ranging from 2 to 12 months. A significant correlation between the amount of bone gain observed at 3 and 12 months was observed (P <0.0001). CONCLUSIONS: Data therefore suggest that membranes left in situ for 1 month or less result in minimal bone gain compared with membranes left in place from 2 to 12 months. In addition, labeling and stained sections clearly showed that the bone produced after 2 months of membrane placement is mature.

Evaluation of wear: enamel opposing three ceramic materials and a gold alloy.

STATEMENT OF PROBLEM: The wear of human enamel and of the restorative material is often a critical concern when selecting a restorative material for any given clinical restorative treatment. PURPOSE: This in vitro wear investigation evaluated three ceramic restorative materials and one type III gold (the control) opposing enamel. MATERIAL AND METHODS: The area of enamel lost at specified time intervals, the stylus area lost, and the combined stylus and enamel vertical height lost were evaluated. RESULTS: Enamel wear opposing one type III gold was statistically similar to that of Dicor MGC, which was lower than that of Vita Mark II and IPS Empress, which were also statistically similar in value. CONCLUSIONS: The total vertical height lost from the type III gold specimens and opposing enamel was statistically lower than that of Dicor MGC and IPS Empress (alpha < 0.05).

Experimental peri-implantitis in consecutively placed, loaded root-form and plate-form implants in adult Macaca mulatta monkeys.

This study is part of an on-going project describing the character of round- and plate-form implants placed in a primate model. In this paper 20 loaded plate-form and 23 root-form implants were connected to prostheses and experimental peri-implantitis was induced by ceasing scaling procedures and placing braided silk ligature around the implants. Twenty-four prostheses utilizing natural teeth were studied for comparison. Clinical measurements were carried out monthly for 6 months and radiographic measurements at 3 and 6 months post-ligature placement and cessation of scaling. Both root-form implants and plate-form implants showed a significant loss of crestal bone height at 3 and 6 months after ligature placement (P < .001 after 6 months). The difference in bone loss between plate- and root-form implants, however, was not significant.

Analysis of consecutively placed loaded root-form and plate-form implants in adult Macaca mulatta monkeys.

The present paper describes 36 consecutively treated non-human primates (Macaca mulatta) as part of a balanced block design study to examine osseointegration in root- and plate-form implants prepared by atraumatic preparation of bone. Clinical measurements around selected teeth and digital radiology were utilized to monitor periodontal disease and bone loss around root- and plate-form implants which were loaded with a fixed prosthesis. Results indicate that once monthly regimen of scaling and root planing can prevent attachment loss in natural teeth, serving as abutments of loaded bridges. Root-form implants exhibited a significant loss of crestal bone height during the first year (P < 0.03) while plate-form implants showed less loss in bone height. There was an increase in bone mass over time for root-form or plate-form implants. Both root-form and plate-form implants provided radiographic evidence of osseointegration in loaded bridges.

The effect of systemic flurbiprofen on bone supporting dental implants.

This article describes a study of the efficacy of the non-steroidal anti-inflammatory drug flurbiprofen in maintaining alveolar bone around mandibular root-form dental implants. The preliminary results indicate that, in appropriate doses, flurbiprofen may spare bone around such implants.

Prospective investigation of the single-crystal sapphire endosteal dental implant in humans: ten-year results.

This study conducted a longitudinal prospective clinical study of the single-crystal sapphire (Al2O3) cylindrical screw-shaped endosteal dental implant, and attempted to establish clinical parameters to evaluate implant success or failure. Twenty-eight mandibular implants (17 patients) were placed. After six weeks' healing, 23 implants in 15 patients served as distal abutments for fixed prostheses (baseline). Implants were evaluated for bleeding index, crevicular fluid volume index, plaque accumulation index, radiographic index, mobility index, and patient comfort. Any implant failing in three of these criteria or implants removed were judged as failures. After 10 years, of the 21 baseline implants recalled (two implants were lost to recall), 17 were fully functional, for an 81% success rate. The use of qualitative and quantitative clinical evaluation parameters as utilized in this study appears to be important and useful in assessments of the clinical serviceability of dental implants. These parameters can be used in human clinical trials as well as in experimental animal studies.

Scanning electron microscopic studies of the oral tissue responses to dental implants.

Scanning electron microscopy (SEM) and its associated technologies have proven invaluable in elucidating the interfacial oral tissue responses to dental implants. Since the dental implant must extend from the mandibular or maxillary jaw, through the oral mucosa, and into the oral cavity, these tissue responses include epithelium, connective tissue and bone. The continual occlusal forces acting upon these tissues reinforce the dynamic character of these tissue responses. Immediately upon implantation, a healing phase begins as a response to the implanted biomaterial. Following this immediate response a longer healing phase occurs, beginning approximately 1 week after implantation, resulting in the modeling of bone to the implant as well as the formation of epithelial attachment to the implant. This later, delayed healing continues throughout the lifetime of the implant since these tissues must die and be replaced by similar tissues. Current dental research employing scanning electron microscopy is now documenting these tissue responses. This paper reviews, in detail, SEM observations of these tissue responses.

Ultrastructural investigations of the bone and fibrous connective tissue interface with endosteal dental implants.

The interface between the tissues of the oral cavity and ceramic and titanium cylindrical endosteal dental implants was investigated with correlated light microscopy, transmission electron microscopy and scanning electron microscopy. This study suggested that mandibular bone can directly interface and form an intimate association with one-stage endosteal dental implants. This potential attachment matrix is composed of a composite of calcified bone, and an osteoid unmineralized matrix in association with an apparent osteogenic connective tissue. Further, results from this study suggested that at a level inferior to the junctional epithelium, and superior to the level of crestal bone, fibrous connective tissue can attach to the dental implant. This non-loadbearing attachment of gingival connective tissue could, by contact inhibition, prevent apical epithelial migration. In association with previously documented epithelial attachment, such apical support and connective tissue attachment appears to suggest that endosteal dental implants can be adequately maintained in the oral cavity.

Ultrastructural comparisons of ceramic and titanium dental implants in vivo: a scanning electron microscopic study.

Identically prepared, screw-type ceramic and titanium endosteal dental implants were inserted in the jaws of adult mongrel dogs for periods of up to 6 months. Sixteen of the 32 total implants supported fixed bridgework. The interface of bone and soft connective tissues with the dental implants was examined by routine and innovative scanning electron microscopic (SEM) techniques using both secondary and backscattered electron imaging. Results demonstrated excellent bone adaptation to both titanium and ceramic implants. Direct adaptation of bone to the upper third of both type implants was observed with only minimal amounts of any intervening fibrous connective tissue. A composite of trabecular bone and fibrous connective tissue was observed in the lower two-thirds of the implants examined. Areas of bone alteration suggestive of osteoid were observed at the thread apicis of some loaded implants. From this investigation we concluded that similar longitudinal tissue responses were generated to one-piece, cylindrical screw-type titanium and alpha alumina oxide ceramic dental implants. Possible bone remodeling was observed at the thread apicis of the loaded implants, an area where occlusal forces may be distributed. We further suggest that one-stage endosteal implants are capable of maintaining a proportional bone-to-implant interface at the apical support region, similar to that suggested to two-stage implant systems.

The scientific basis for dental implant therapy.

Dental and oral implantology have rapidly moved into the mainstream of dentistry in the last ten years with a phenomenal growth based on rapidly expanding technology, increasing public interest, and the reporting of sound scientific data. This paper reviews current knowledge about implant tissue reactions and identifies areas where additional scientific inquiry is needed. Bone- and soft-tissue healing around dental implants varies greatly depending upon the form of the implant, biomaterial used, and surgical approach. Controversy exists as to whether a direct bony-biomaterial interface is preferable over a bone-connective tissue-biomaterial interface. Scientific data are required to document whether intervening molecular layers of glycoproteins exist between implant and bone, and what role is played by these structures relative to the implant-bone interface. The adaptation of regenerated gingival epithelium to an implant is critical for the development of a perimucosal seal. Many scientific questions remain unanswered about this seal and its role in maintenance of implant longevity. Controlled clinical trials must be carried out to determine clinical serviceability standards for patients. Resolving these areas of concern and understanding the biological reactions involved will require in-depth scientific inquiry by clinician and scientist alike to make dental implantology a highly acceptable and predictable treatment modality. Even with these controversies and lack of comprehensive comparison studies, dental implantology is an exciting treatment concept that makes considerable demands upon the surgical, prosthetic, periodontal, and restorative skills of today's practitioners, and on their scientific understanding as well.

Evaluation of kallikrein in human parotid and submandibular saliva.

Saliva was collected from 10 subjects using a universal-design parotid collector and individually-adapted submandibular collectors. The enzymic activity of kallikrein was measured using D-leucylvalylarginine-p-nitroanilide as the substrate. Mean kallikrein activity was much higher in parotid saliva than in submandibular saliva; the difference was statistically significant. Protein concentrations were not significantly different, whereas alpha-amylase was, as expected, much higher in parotid saliva.