The International Journal of Oral & Maxillofacial Implants, 01/1995

A modified self-tapping implant (MkII) with improved cutting characteristics has been designed for use in both maxillae and mandibles. Four sequential studies were conducted to evaluate the outcome of the MkII implant compared to the standard implant. The results presented here are from the extended pilot study that has been conducted as an intra-individual study of 103 patients; ie, each patient received both test (MkII) and control (standard Brånemark System) implants. Seventy patients were treated in the mandible and 33 in the maxilla. The cumulative survival rates and marginal bone resorption showed equivalent results for both test and control implants. Three-year cumulative survival rates were 87.9% and 86.8% for test and control implants in maxillae, respectively, and 99.5% and 100% in mandibles, respectively. The mean marginal bone resorption was approximately 0.5 (control) to (MK II) 0.6 mm after 3 years of function. A total of 288 test implants and 275 control implants were placed. All implants, both test and control, could be placed in an appropriate implant position, but 21.2% of the implants were not fully seated by machine power only; the use of a manual cylinder wrench for the final turns was necessary. During the last phase of the study, however, with an increase in twist-drill diameter from 3.0 to 3.15 mm and an increased motor torque, the prerequisites of successful implant placement into final position were met. Keywords: Brånemark System, self-tapping implant, tapping ability

To test the osteopromotive activity in large non-spacemaking alveolar bone sites, a total of 20 titanium dental implants were placed superior to a previously modified mandibular alveolar process in five adult beagle dogs. The supracrestal implant position resulted in a mean buccal dehiscence of 5.1 ± 1.03 mm and a mean supra-crestal bone deficit of 2.69 ± 0.45 mm. Three treatment groups were randomly assigned: group I, ten implants treated with a titanium-reinforced expanded polytetrafluoroethylene (ePTFE) membrane (TR); group II, six implants treated with a standard ePTFE membrane (ST); and group III, four implants that received no membrane (control). Before mucoperiosteal flap closure, the bone surface was perforated and peripheral blood was injected around the implants and underneath the membranes. Clinical evaluation of submerged implant sites showed evidence of complete regeneration of the peri-implant bone defects in groups I and II, minimal bone formation in control group III, and a widening of the ridge in group I. Corresponding histologic examination of undecalcified sections demonstrated large amounts of newly formed bone beneath both types of membranes with a superficial layer of loose connective tissue. Mean gain of supracrestal regenerated bone amounted to 1.82 ± 1.04 mm (TR group), 1.90 ± 0.30 mm (ST group), and 0.53 ± 1.34 mm (control group). Mean bone regeneration at the buccal dehiscences was 3.33 ± 1.44 mm (TR group), 2.46 ± 0.51 mm (ST group), and 2.76 ± 0.84 mm (control group). The TR membranes showed evidence of increased alveolar bone width compared to ST membranes and control sites. These results suggest that supracrestal bone regeneration can successfully be enhanced by a submerged membrane technique in the dog model and that the titanium-reinforced membranes were able to maintain a large, protected space for blood clot stabilization without the addition of bone grafts and produced a larger bone quantity when compared to standard membranes. Keywords: bone regeneration, blood clot, dental implants, supracrestal implant placement, titanium-reinforced membranes

An international prospective study of Brånemark implants retaining overdentures was conducted at nine clinical centers. One hundred thirty-three subjects were recruited in a 12-month period and provided with 510 implants, 117 of which were in maxillae and 393 were in mandibles. This study reports the 3-year follow-up status of 120 overdentures and 444 implants. There were 11 overdenture failures (9.2%). Maxillary overdenture failure rates (27.6%) were nearly nine times greater than mandibular overdenture failure rates (3.3%). Maxillary overdenture treatment was less successful than previously reported fixed implant-supported restorations. However, their mandibular counterparts had success rates slightly higher than those reported for fixed implant-supported restorations. At 3 years, 150 implants remained submerged and 66 implants had been withdrawn because the subjects discontinued study participation. Eleven mandibular and 29 maxillary implants had failed and had been removed from 21 subjects. Logistic regression with forward model selection indicated that one two-way interaction was significantly related to implant failure. At highest risk were the subjects who possessed dental arches with bone quantity E and bone quality 4. Subjects with one implant failure were likely to have more than one failure. The Generalized Estimating Equation was used to adjust for the cluster effect in this population because multiple implants (2 to 6) were placed and evaluated in each of the 133 subjects. Keywords: Brånemark implants, multicenter study, overdentures

Determination of glycosaminoglycans (GAGs) in peri-implant sulcus fluid (PISF) may monitor tissue changes around implants. This study investigated osseointegrated IMZ titanium implants at five stages from initial exposure to occlusal loading from prostheses. Two peri-implant sulcus fluid glycosaminoglycans (PISF GAGs), hyaluronic acid (HA) and chondroitin-4 sulfate (CS), were determined by cellulose acetate electrophoresis and densitometric scanning. Compared to longer-serving implants, CS contents at early stages was higher and with full occlusal loading was three times greater, without significant changes in HA contents. These observations appeared to reflect predominantly responses in the supporting bone, particularly when compared to our previous studies on ceramic implants and teeth affected by periodontal disease. This study supports the potential of PISF GAG analysis to detect adverse tissue responses, notably bone resorption. Keywords: dental implants, glycosaminoglycans, implant monitoring, peri-implant sulcus fluid

This study determined the microbiota of the mucosa- and implant facing parts of expanded polytetrafluoroethylene augmentation material, and the influence of major periodontopathogens on the healing process associated with guided bone regeneration around dental implants. Seventeen patients with nine dehiscence and eight extraction defects were studied. Prior to surgery and at membrane removal, microbial morphotypes, total viable counts, and the occurrence of selected microbial species were examined by phase-contrast microscopy, nonselective and selective cultures, and DNA probes. Nine sites with submerged barrier membranes throughout the 9-month study were free of cultivable microorganisms and experienced significantly more osseous healing than eight sites with prematurely exposed membrane. Patients with few or no deep periodontal pockets demonstrated significantly fewer residual osseous defects than patients showing several pockets of increased depths. In addition, patients with prematurely exposed membranes revealed several deep periodontal pockets. Three patients with less than 1 mm of osseous gain yielded either Porphyromonas gingivalis or Actinobacillus actinomycetemcomitans. Peptostreptococcus micros occurred in high proportions in seven of the eight patients with premature membrane exposure and inadequate osseous healing. These findings associate putative periodontal pathogens with unsuccessful guided bone regeneration. The control of periodontal pathogens in the oral cavity prior to placement of barrier membranes around implants might increase the prognosis of osseous regeneration. Keywords: guided tissue regeneration, implants, pathogenic bacteria, Peptostreptococcus micros, Porphyromonas gingivalis

Late loss of initially integrated endosseous implants has generally been attributed to implant overload often the result of inappropriate prosthesis design. Implant placement is rarely contraindicated by preexisting systemic diseases, and no instances of medication-induced implant failure have been reported in the literature. This paper reports a case in which a patient lost five endosseous implants that had successfully osseointegrated and had been restored with a lower hybrid prosthesis approximately 6 months after diphosphonate therapy for osteoporosis was started. Keywords: diphosphonate, etidronate disodium, osseointegration, osteoporosis

Two groups of patients were provided with implant-stabilized mandibular overdentures supported by straight ovoid prefabricated bars with a resilient joint or parallel-sided bars with a rigid joint. Measurements of plaque index, mucosal cuff health and height, marginal bone height, pathology of the denture-bearing mucosa, and patient satisfaction were correlated with the different bar designs. Ovoid bars with a resilient joint between the denture and the bar have been shown to give a slightly increased incidence of problems associated with the denture-bearing mucosa. Furthermore, the only significant mean increase in recession of the mucosal cuff was found on the distal surfaces of the distal abutments in this group of patients. Keywords: Brånemark implants, overdentures

One hundred eighty-seven implants were placed in the maxillary posterior areas of 44 partially edentulous patients (29 female; 15 male). The mean age was 62 years (range 36 to 82 years). Fifty-one of the 187 implants were placed in the pterygomaxillary area and further restored with fixed prostheses. The mean number of implants per prosthesis was 3.7 (range 1 to 6) for the maxillary posterior area. These 51 implants are the subject of this report. During stage II surgery and before loading, six implants were not osseointegrated and were removed. After a mean loading period of 12.6 months (range 1 to 63 months), one additional implant was lost. Seven of 51 implants were removed (13.7%). Failure rates according to implant size and bone quality were also analyzed. The average loss of marginal bone height was 1.3 mm on the mesial and 1.1 mm on the distal surfaces between 1 and 3 years of loading. This study demonstrates the possible and successful use of the pterygomaxillary site for implant placement. Keywords: Brånemark implants, fixed partial prostheses, marginal bone height, osseointegration, pterygomaxillary

Vertical forces applied to dental implants during oral functions have not been quantified precisely. The key problem has been the lack of suitable measuring devices. This article introduces a new technique for placing a transducer directly in the implant without any increase in vertical dimension. Results were compared to loads applied to teeth. Implants in the molar position that were fixed to a premolar with a prosthesis withstood maximum vertical forces of 60 to 120 N during chewing. Single molars and premolars carried maximum vertical forces of 120 to 150 N. Clenching in centric occlusion caused a load level of approximately 50 N for both natural and artificial abutments. Occlusal prematurities on the implant restoration that were less than 200 µm in height showed no significant increase of the implant load level. Keywords: bending moments, chewing forces, clenching, implant loading, interface, measuring device, occlusion, prematurities

Guided tissue regeneration (GTR) is a useful modality in the management of periodontal disease and for bone augmentation around osseointegrated implants. This study evaluated the in vivo use of atelocollagen membrane (AC) on which osteoblastic cells (OBCs) were cultured in vitro, for application as a GTR membranous material. Osteoblastic cells isolated in our laboratory from mouse calvaria formed a thin film on the AC in vitro which was easily manipulated after 21 days in culture. The AC and OBCs complex material (ACOB) was subjected to freezing and thawing and implanted in mouse subcutaneous tissue for the study of histologic events surrounding the implanted ACOB. Histologic findings in the subcutaneous tissue showed calcification on the ACOB at 28 days postimplantation, while no such finding was evident at the control site, where only AC without OBCs were grafted. The present study suggests the possibility of membrane calcification for GTR through ACOB produced by OBCs on an AC in vitro. Keywords: atelocollagen, calcified material, culture, guided tissue regeneration, osteoblastic cell