The International Journal of Oral & Maxillofacial Implants, 04/1993

Maxillary skeletal and dental growth results in dramatic changes in all three dimensions during active growth. Experimental evidence and the behavior of ankylosed teeth suggest that an osseointegrated object remains stationary in the bone surrounding it and does not move or adapt to bone remodeling. Growth changes may result in the burying or loss of implants depending on the placement site. Hence, implants placed in the early mixed dentition have a poor prognosis of continued usefulness through puberty. When placed early implants may disturb growth or have to be replaced. Implants placed during late puberty or early adulthood have the best chance for long-term usefulness. Keywords: dental implants, maxillary growth, osseointegration

Since August 1989, 35 consecutive patients were treated with immediate implants to replace 50 teeth requiring extractions as a result of root fractures, endodontic instability, nonrestorable carious lesions, or periodontal disease. Defects relative to the implant were morphologically grouped and were treated for bone regeneration with demineralized freeze-dried crushed cancellous bone (DFDBA), e-PTFE membrane, or both. Thread exposure initially ranged from 4 to 20 threads, while implant lengths varied from 8.5 to 18 mm. The mean implant length was 15 mm, with mean thread exposure of 11.34 threads, or 54% of the threaded length of the implant. Reentry confirmed 100% thread coverage in all but one implant in the no-wall group treated with DFDBA alone. Histologic evaluation of three cases confirmed viability of the regenerated bone. The patients were followed through April 1993, with 49 implants (98%) remaining osseointegrated and functional, supporting the predictability of immediate implant placement. The age of the patients ranged from 16 to 80 years, hence implant placement considerations relative to adolescents are also discussed. Keywords: bone regeneration, immediate implant, retrospective study

This paper describes a new 5.0-mm-diameter self-tapping implant, a modification of the standard Brånemark fixture designed to increase the amount of bone-to-titanium surface contact and to capture dense bone at the lateral and crestal borders of the alveolus. Indications for its use include (1) areas of inadequate bone height, (2) areas of poor bone quality (type IV), and (3) immediate replacement of non-integrated or fractured implants. This preliminary report discusses the design alterations and surgical techniques available to treat these difficult bone situations. Keywords: 5.0-mm fixture, osseointegration, rescue fixture, type IV bone, wide fixture

The cause of mechanical failure of the fixture component of an osseointegrated dental implant was investigated. The surfaces of five clinical specimens that had fractured were compared to those of new specimens fractured in the laboratory under monotonic and cyclic loads. Scanning electron microscopy revealed striations on the fractured surfaces of the clinical specimens, similar to striations on the laboratory-fatigued specimens and in contrast to the dimpled surfaces on the overloaded specimens. The investigation demonstrated that fractures of the fixture component of this dental implant occurred by fatigue under physiologic loads, with marginal alveolar bone loss around the fixture. Keywords: endosseous dental implant, fatigue, fixture fracture, threaded implant

This study investigated the influence of a single 15-Gy dose of irradiation on the capacity of titanium screws to integrate in irradiated bone tissue. The biomechanical force necessary to unscrew the titanium implants 8 weeks after placement was 54% lower for implants in irradiated bone tissue compared to implants in nonirradiated bone tissue. Postirradiation use of hyperbaric oxygen treatment at 2.8 ATA (2-hour daily treatments for 21 days) increased the biomechanical force necessary to unscrew the titanium implants by 44% in irradiated bone and by 22% in nonirradiated bone. Keywords: hyperbaric oxygen, implant interface, irradiation, osseointegration, titanium implants

This study developed methodology to evaluate the healing of 15 IMZ implants placed in the sockets of freshly extracted mandibular premolars in three adult mongrel dogs. Six surgical sites were prepared in each animal and one site was left as a control. Porous hydroxyapatite was placed around the top half of two implants in each animal; one implant was also covered with polytetrafluoroethylene membrane. All implants were covered with a mucoperiosteal flap and sutured closed. Upon animal sacrifice, the mandibles were retrieved for block dissection and the blocks were embedded in plastic. Serial longitudinal wafers were ground to 50 to 100 ,µm and stained. Standard photomicrographs were taken so that tracings of the implant-bone interface could be measured on a sonic digitizer. The mean percent amount of bone to plasma-sprayed portion of the implant on the longitudinal sections was 47.9% ± 5.2% with a range of 17.4% to 84.7%. The horizontal sections were measured at 53.5% ± 3.7% with a range of 0.0% to 100%. This pilot study suggests that IMZ implants placed in fresh extraction sockets can achieve a degree of intimate contact with bone; however, wide variation in the implant-to-bone interface was found even in the same specimen. Keywords: endosseous implant, extraction site, interface

This long-term study has demonstrated the successful use of osseointegrated implants to replace posterior teeth in the partially dentate patient. A total of 1,203 Nobelpharma implants placed by two periodontists practicing in traditional office settings were included in the survey. Of the 551 implants placed in the mandible, 25 failed, for a success rate of 95.5%. Of the 247 mandibular prostheses fabricated for 200 mandibles, 8 failed, for a prosthesis stability rate exceeding 97%. Of the 652 implants placed in the maxilla, 31 failed, for a success rate of 95.2%. Of the 250 maxillary prostheses fabricated for 193 maxillae, 2 failed, for a success rate exceeding 99%. The results compare favorably to previous reports in terms of implant survival and stability. Keywords: implant prosthesis stability, mandibular posterior implants, maxillary posterior implants, osseointegration, retrospective clinical study

Information gained by preoperative imaging techniques must be accurately related to the surgical site. The inability to do this severely diminishes the benefit of the diagnostic imaging. The CT scan is capable of providing considerable information regarding the jaws. The use of radiopaque markers to identify preselected points on the image is readily done by placing markers in the wax registration rims that are worn during the scan. The position of these markers is transferred to the mouth with a surgical template, facilitating surgery and reducing the incidence of anatomic accidents caused by lack of orientation. Keywords: CT scan, esthetics, osseointegrated implants, surgical templates

This study compared the accuracy of three techniques used to fabricate master casts for implant prostheses. A metal model with six implants and standard abutments and a matching template were fabricated. Impressions of the model were made in Impregum and cast in Die Keen. The casts were divided into three groups of 15 casts: group A-solid casts; group B-Pindex; and group C-Zeiser system. Each cast was visually evaluated for fit of the template. Positional accuracy of the abutments was numerically assessed using an optical comparator. Visual analysis showed that only casts sectioned with the Zeiser system allowed a passive fit of the template. Statistical analysis of numerical findings indicated that casts made with the Zeiser system were significantly more accurate than solid casts, which in turn were more accurate than those made with the Pindex system. Keywords: abutment positioning, die stone, die systems, setting expansion

Guided tissue regeneration has been shown to establish new attachment in periodontal defects and to facilitate hard tissue repair around dental implants. This case report describes a patient treated with guided tissue regeneration adjacent to an endosseous dental implant. Histologic analysis showed the regenerated tissue to be mature, cortical bone possessing a high level of mineralization. Keywords: bone regeneration, dental implants, guided tissue regeneration, histology, implantology

A flap technique designed for use in dental implantology is described. This technique creates a more homogeneous mucosa around the implants and reduces its thickness to prevent the introduction of deep mucosal pockets around the implants. The technique results in the preservation of a maximum of fixed mucosa and a shallow pocket next to the implant, which aids in optimizing oral hygiene and prognosis. The technique can be performed at the time of implant placement. The flap covers the implants completely and closes the wound primarily. This technique was compared to a conventional flap technique and was clinically found to give significantly better results. Keywords: dental implants, surgical flaps, vestibuloplasty

This case report demonstrates that the position of malaligned osseointegrated implants can be corrected by a segmental osteotomy procedure with no loss of implants or bone support. The patient was a healthy teenage girl who sustained facial trauma with loss of teeth and alveolar bone. The defect was initially bone grafted. Brånemark implants were simultaneously placed in the graft. Their initial unfavorable positions and inclinations were later corrected by a segmental osteotomy. Keywords: dental implants, segmental osteotomy