The International Journal of Oral & Maxillofacial Implants, 04/1999

The aim of this article was to review the literature on differential diagnosis and treatment of biologic complications and failing implants. All types of publications, with the exception of abstracts, published in English up to December 1998, were included. A multi-layered search strategy was used. Controlled clinical trials (CCTs) were searched in the Cochrane Oral Health Group's Specialized Register of Trials. This database contains all CCTs identified in MEDLINE and EMBASE. PubMed was searched using various key words and the "related articles" feature. All identified publications were obtained and none were excluded. Infection, impaired healing, and overload are considered the major etiologic factors for the loss of oral implants. Only a few clinical and animal investigations were found that tested the validity of the proposed therapeutic approaches. The treatment of failing implants is still based mainly on empirical considerations, often derived from periodontal research, from data extrapolated from in vitro findings, or from anecdotal case reports performed on a trial-and-error basis. Keywords: complication, dental implant, evidence-based treatment, failing implants, guided bone regeneration, infection, peri-implantitis, therapy

With the introduction of new techniques for the fabrication of frameworks for implant-supported prostheses comes the need to understand how the components used compare to those used for conventional cast frameworks. The relationship of measured machining tolerances between conventional implant components and those components used for stereo laser-welded implant frameworks was determined using a standardized protocol. Statistically significant differences in the horizontal interface relationship were found between paired implant components, which had a mean range from 23.1 to 51.7 µm. From a laboratory and clinical perspective, machining tolerances of implant components represent a variable associated with their manufacturing, which can ultimately affect the fit of a completed prosthesis. Keywords: implant components, machining tolerances, titanium feet

Replacing small, single incisors with implants can be esthetically challenging and difficult because of the limited amount of bone. In this investigation, 3.0-mm-diameter implants were used to support 30 single maxillary and mandibular incisors in 21 patients. The implants have been in function for 3 to 7 years, and 29 are still stable. Only 2 complications in the mandibular incisor region have occurred; 1 implant fractured (after 5 years of function) and 1 prosthesis was replaced. The overall success rate is 96.7%. The favorable results and esthetic appearance achieved suggest that replacing small incisors where light occlusal forces are present with narrower implants is a feasible treatment option. Keywords: Brånemark System, congenital aplasia, single-tooth restorations, 3-mm-diameter implants

The purpose of this study was to evaluate differences between the occlusal contacts of edentulous patients with mandibular implant-supported hybrid dentures opposing maxillary complete dentures and those of patients with conventional maxillary and mandibular complete dentures. Six parameters related to occlusion were measured in the 2 groups (n = 40 for each group) using pressure-sensitive film. The mean values generated by each test group for each parameter were compared using a t test. Pearson's correlation coefficients between occlusal force, age, and time in function were examined. Occlusal force and area in the implant denture wearers were larger than those in the conventional denture wearers. No significant difference was seen in occlusal force balance between the left and right sides. The center of occlusal load in the implant denture wearers was more anterior. The maxillary denture may become more unstable in implant denture wearers. It is suggested that the stability and retention of a maxillary denture be checked and the occlusion be adjusted more frequently in the hybrid denture wearer than in the conventional denture wearer. Keywords: center of occlusal loads, hybrid denture, occlusal force, pressure-sensitive film, stability

The purpose of this pilot study was to make a histologic and histomorphometric comparison of hydroxyapatite- (HA) coated and titanium plasma-sprayed (TPS) root-form implants that were placed in 2 mongrel dogs immediately after extraction of mandibular premolars. After 8 weeks of healing, the implant-containing segments of the mandible were removed en bloc and bone blocks including implants were sectioned. Histologic and histomorphometric analyses were performed by evaluating bone sections. The mean bone contact percentage of HA-coated implants was 61.84 ± 7.84%, with a range of 52.09% to 75.7%, and the mean bone contact percentage of TPS implants was 51.35 ± 12.1%, with a range of 30.1% to 70.6%. This pilot study suggests that HA-coated implants placed into fresh extraction sockets can achieve better bone contact than TPS implants, but there was evidence that the surface of the HA layer can be resorbed, so long-term stability of HA coatings in immediate implantation must be investigated. Keywords: experimental study, hydroxyapatite-coated implants, immediate implantation, titanium plasma-sprayed implants

This report involves the retrospective evaluation of ITI implants placed by a group of 12 clinicians located throughout the United States. Of the original 174 single implants placed in 129 patients reported previously, 157 were examined in 110 patients after 2 or more years (average 40.1 months). Twenty-two implants remained in the anterior and 135 implants (86%) remained in the posterior areas of the mouth, with 81 being restored with an octabutment screw-retained crown and 76 restored with a conical-abutment cemented crown (in function 2 years or longer). Occlusal screw loosening was observed in 22.2% of implants over both periods, with only 1 tooth loosening in both study periods (6 months to 2 years and > 2 years). Loosening of a solid conical abutment occurred in 1 additional patient, for cumulative conical abutment loosening of 5.3%. Significant radiographic bone loss was observed around 4 implants, with implant fracture noted with 3 additional implants (all mandibular first molars with hollow-screw or hollow-cylinder implant design). The survival rate at > 2 years was 95.5%. The data suggest that ITI implants can be a satisfactory choice for posterior single-tooth restorations. Keywords: implant fracture, implant survival, ITI implant, multicenter study, single-tooth implant

Between 1988 and 1997, 18 irradiated patients (group 1, 83 implants) and 22 nonirradiated patients (group 2, 92 implants) received resection of the cancer-involved mandible and floor of the mouth and subsequently underwent mandibular rehabilitation with endosseous implants. Implant-supported prostheses were placed in 26 patients, while 13 patients received implant-tissue-supported prostheses. Between 1988 and 1991, patients were restored with implant-tissue-supported prostheses (based on 2 to 4 implants). This strategy was later changed because of the development of denture-related lesions. Since 1992, group 1 patients have been restored exclusively with implant-supported prostheses on 5 to 6 implants; group 2 patients have been rehabilitated alternatively with implant-tissue-supported prostheses on 4 implants. Special criteria for determining the success of implant-supported maxillofacial prostheses were developed. With a mean follow-up period of 37 months, 160 implants (91%) were clinically osseointegrated. Both types of restorations provided sufficient oral rehabilitation. However, only completely implant-supported prostheses avoided soft tissue ulcers. The cumulative success rate was approximately 75% after 7 years for group 1 patients and about 86% after 10 years for group 2 patients. The success rates for implants placed after the change in strategy were approximately 86% (group 1) and 94% (group 2) after 5 years. Based on these experiences, it is suggested that irradiated patients should be restored with exclusively implant-supported prostheses, without any mucosal contact. Keywords: dental implants, irradiation, maxillofacial prosthetics, oral cancer patients, success criteria

This article presents preliminary clinical evidence of the beneficial effect of the use of plasma rich in growth factors of autologous origin. The plasma is obtained from the individual patient by plasmapheresis. The macroscopic and microscopic results obtained with bone regeneration using this technique, which uses no membrane or barrier, can be observed. The incorporation of these concepts can introduce several advantages, including the enhancement and acceleration of bone regeneration and more rapid and predictable soft tissue healing. Keywords: growth factors, plasma growth factors

A technique is described for accomplishing both localized sinus augmentation and guided bone regeneration at the time of maxillary molar extraction. One hundred nine sites were treated in 92 patients. Of these, 102 procedures (94.0%) were successful and 7 (6.0%) were partially successful. Success was defined as the ability to ideally position an implant at least 10 mm in length and 4.8 mm in width without perforating the floor of the sinus or generating an implant fenestration or dehiscence. Partially successful procedures required an additional osteotome sinus lift at the time of implant placement. Keywords: guided bone regeneration, implants, osteotome, sinus augmentation

The purpose of this prospective clinical study was to investigate the outcome of 3 different types of endosseous, nonsubmerged implants in the anterior part of the mandible. Fourteen older edentulous patients, 10 females and 4 males, were included. All participants received 3 different types of endosseous implants in the anterior mandible: 1 titanium plasma-sprayed cylindric implant (4 mm in diameter), 1 titanium cylindric implant with hydroxyapatite (HA) coating (4 mm in diameter), and 1 standard threaded titanium implant (3.75 mm in diameter). The 3 types of implants were originally designed to be placed in a 2-step surgical procedure. However, at this stage all implants were simultaneously provided with a temporary abutment that penetrated the mucosa. Three months later the temporary abutments were replaced by ball abutments, which were connected to an overdenture. At 12, 24, and 36 months after surgery, marginal bone resorption and Periotest values were recorded. Two patients died within the 2 first postoperative years. Five of 42 implants (11.9%) failed to osseointegrate. After 3 years, marginal bone resorption around titanium plasma-sprayed implants was significantly greater than that seen around both HA-coated and threaded titanium implants. Threaded titanium implants also had significantly better scores for marginal bone resorption than the HA-coated implants. Periotest values for HA-coated cylinders were significantly lower than test values for the other implants after 3 years (P .05). The conclusion from this investigation is that nonsubmerged implants showed impaired prognoses compared to implants placed according to the 2-stage concept. Marginal bone resorption around titanium plasma-sprayed cylindric implants was clearly increased compared to the 2 other implant systems. Periotest values for HA-coated cylindric implants were superior to titanium plasma-sprayed and pure titanium implant surfaces. Keywords: hydroxyapatite-coated implants, marginal bone resorption, nonsubmerged implants, overdentures, titanium plasma spray-coated implants, titanium threaded implants

This study assessed the efficacy of augmentation grafting of the maxillary sinus with simultaneous placement of dental implants in patients with less than 5 mm of alveolar crestal bone height in the posterior maxilla prior to grafting, although the procedure has traditionally been contraindicated based on empirical data. A total of 160 hydroxyapatite-coated implants was placed into 63 grafted maxillary sinuses in 63 patients whose crestal bone height in this region ranged from 3 to 5 mm. Patients were followed for 2 to 4 years after the placement of definitive prostheses. There were no postoperative sinus complications. Following uncovering of the implants at 9 months after surgery, there was no clinical or radiographic evidence of crestal bone loss around the implants. Histologic examination of bone cores from the grafted sites revealed successful integration and a high degree of cellularity. All patients maintained stable implant prostheses during follow-up. These findings indicate that the single-step procedure is a feasible option for patients with as little as 3 mm of alveolar bone height prior to augmentation grafting, utilizing hydroxyapatite-coated implants and autogenous bone. Keywords: atrophic maxilla, bone graft, dental implants, sinus augmentation, sinus mucosa

Between 1991 and 1995, 216 sinus-lift procedures were accomplished as part of a clinical study. The study involved placing 467 implants in the atrophic posterior maxillae of 142 female and 74 male patients. The initial bone height at the implant site was between 1 and 5 mm. The implants were supported subantrally with bone block grafts harvested from the retromolar or symphysis areas of the mandible. Perforations of the maxillary sinus membrane were observed in 51 patients; these were repaired with fibrin adhesive. The spaces remaining above the bone graft were filled with various materials. A total of 28 implants failed. All the remaining implants were deemed successfully osseointegrated, based on radiographic and clinical (including periodontal health) criteria. No patients experienced maxillary sinus complications. Clinically and radiographically, the best bone regeneration was observed in those patients in whom the surgically created space was completely grafted with autogenous bone that included a high percentage of resorption-resistant cortical bone. In those patients having bone grafts harvested from the mandibular symphysis, none of their facial profiles were adversely affected; however, some patients experienced neurosensory deficits involving the mandibular anterior incisors and adjacent alveolar mucosa. Occasionally, these symptoms persisted for up to 1 year following the procedure. Keywords: atrophic maxilla, autogenous bone augmentation, bony lid, mandibular bone block, sinus floor elevation

Study of the implant-tissue interface is one of the fundamental issues in implantology, both odontologic and orthopedic. The characteristics of this interface will influence the success or failure of an implant. The aim of the present study was to evaluate histomorphometrically the capacity of different metals to osseointegrate employing laminar implants of zirconium, titanium, aluminum, and zirconium coated with diamond-like carbon. The experimental model herein allowed for the quantitative evaluation of the tissue-implant interface for different metals. The implants were placed in the tibiae of Wistar rats under anesthesia and allowed to remain in situ for a 30-day period. The interfaces of the zirconium and diamond-like coated zirconium implants exhibited better responses than the interface of titanium implants. Aluminum produced a local toxic effect, evidenced by osteoid formation. Keywords: biocompatibility, experimental implants, histomorphometry, interface, osseointegration

A surgical procedure for the rehabilitation of severely resorbed maxillae is described. Twenty-five patients, made up of a development group of 5 and a routine group of 20, were treated with Le Fort I osteotomy using interpositional bone grafts from the iliac crest and, in a second stage, titanium implants. Altogether, 181 Brånemark implants were placed, and the patients were followed for up to 5 years. The implant survival rate for the development group was 60.0% after 5 years. Life table analysis for the routine group showed a 5-year survival rate of 85.6%. Twenty-two patients received fixed prostheses and 2 received overdentures. One patient lost all implants and was rehabilitated with a prong denture. Keywords: bone graft, implants, maxillary osteotomy, two-stage procedure

Postmortem examination of human specimens is an extremely important aspect of evaluating the relative compatibility and long-term success of endosseous implant surfaces. The bone-implant interface of 5 commercially pure titanium screw-type mandibular implants after 85 months of service and 2 hydroxyapatite- (HA) coated maxillary implants after 38 months of service were examined. All implants were stable at the time of the patient's death. The mandibular implants had an average of 65% contact with bone and the maxillary implants had an average of 47% contact. The HA coating had separated from the maxillary implants in some areas and was free within surrounding connective tissue or surrounded by invaginating sulcular epithelium. The arrangement and pattern of bone contact appeared different between HA-coated and titanium implant surfaces. Keywords: dental implant, Dental Implant Clinical Research Group, endosseous, histology, hydroxyapatite, osseointegration, postmortem, titanium

This article reports the treatment and 5-year follow-up of an 80-year-old female with a history of severe osteoporosis and chronic polyarthritis. Treatment included methotrixate disodium and acemetacin. After the last tooth was removed from the mandible, the patient was successfully treated with a fixed mandibular prosthesis supported by 6 implants placed between the mental foramina. The implants have remained osseointegrated, and peri-implant smears have been negative for bacterial colonization. Radiographic follow-up examination has revealed bone loss that is slightly greater than expected. This article focuses on the placement of implants in a patient receiving medication for chronic polyarthritis and osteoporosis. Keywords: dental implants, osseointegration, osteoporosis, rheumatoid arthritis