The International Journal of Oral & Maxillofacial Implants, 05/1996

A total of 1,920 IMZ implants, placed between March 1984 and December 1993, were evaluated retrospectively. The Kaplan-Meier cumulative survival rate of the implants was 89.9% after 60 months and 83.2% after 100 months. Life table analysis revealed a statistically significantly lower cumulative survival rate for maxillary implants (71.6% at 60 months and 37.9% at 100 months) than for mandibular implants (90.4% at 100 months). Implants placed in the anterior region of the maxilla failed significantly more often than those placed in the posterior region. This was not observed in the mandible. The age and sex of the patients, the status of the jaw (edentulous, partially edentulous), the time of implant placement in relation to tooth extraction, and the length and diameter of the implants had no statistically significant influence on the cumulative survival rate. Keywords: IMZ implant, life table analysis, success rate

This study reviews fundamental concepts related to the use of screws and presents data describing the effect of fabrication, finishing, and polishing procedures on as-received preload for implant cylinders. Specifically, this study measured and compared preload produced when using as-received gold cylinders (the reference or gold standard), and cast cylinders produced from premade gold and plastic cylinders in the as-cast condition and following postcast finishing and polishing manipulations. The results reveal that preload in the gold screw-gold cylinder-abutment joint can be affected by the casting process, and that the choice of cylinder type, casting alloy, investment, and finishing/polishing technique may affect the resultant preload as compared to as-received joint conditions. The data from this study indicate that when plastic patterns are used as part of the framework, finishing and polishing of implant cylinder components should provide an increased preload compared to no such manipulations. Also, if maximum preload is desired, the use of premade metal cylinders offers an advantage over plastic patterns in both preload magnitude and precision. Keywords: friction, preload, screw joints, torque

The purpose of this retrospective clinical investigation was to study possible soft tissue complications and marginal bone resorption related to exposed threads of osseointegrated Brånemark oral implants during a 5-year period. Group 1 comprised 27 patients with 38 test implants that had not become completely covered with bone at implant placement. Thirty control implants in 25 of the patients were each next to a test implant and had no exposed threads initially. Group 2 comprised 51 patients with 107 test implants that had developed marginal bone loss beyond the second thread, as judged radiographically at the first annual checkup. Forty-eight control implants showed no or minor marginal bone resorption up to the first thread. Initial marginal defects and fenestrations at Brånemark implants (group 1) did not lead to mucosal problems or progressive marginal bone resorption during the first 5 years of function. Moreover, bone resorption, seen after the first year of loading at initially completely bone-covered implants, did not lead to any specific soft tissue problems, nor did it result in any further progressive bone resorption during a subsequent 4-year period. Based on the observed low incidence of soft tissue pathology at implants with exposed threads, it is suggested that bone augmentation techniques in the situations studied be used with restriction. Keywords: clinical follow-up, complications, exposed thread, marginal bone height, osseointegration, soft tissue conditions, dental implant

Inflamed human periodontal and peri-implant (ITI Bonefit) gingival tissues were studied immunohistochemically to evaluate the possible presence of structural differences in the extracellular matrix protein localization. Collagen types I, III, IV, V, VI, and VII and fibronectin showed a similar distribution in these tissues. Data show that morphologic structural differences between these inflamed tissues are not present. According to these findings, the connective tissue response of inflamed peri-implant as well as periodontal gingival tissues should be similar during treatment when the inflammation is localized only in the soft tissue level. Keywords: collagen, extracellular matrix, fibronectin, gingiva, inflammation, peri-implant soft tissues

A prospective study involving 24 treatment centers and 145 patients was conducted to evaluate the long-term osseointegration success rate for titanium implants anchoring a craniofacial prosthesis (auricular, orbital, and nasal), and to evaluate the long-term retention and stability of the prosthesis. Twenty patients (14%) in this study had received prior irradiation therapy, and 60 implants were placed in these 20 irradiated patients. Nine of the 60 implants were lost (85% survival rate). Although the few patients and few implants may not allow for conclusions to be drawn, analysis and review of the data on these irradiated patients may assist in reliable and valid comparisons to be made with other published studies. Keywords: bone-anchored, craniofacial, irradiated, prosthesis

The objective of this study was to statistically correlate in vivo measurements of prosthesis misfit and change of marginal bone level in implants placed in the edentulous maxilla. Two groups, each comprising seven patients, were followed up either prospectively for 1 year or retrospectively for the last 4 years of the 5-year period after second-stage surgery. Measurements of prosthesis misfit were performed by means of a three-dimensional photogrammetric technique, and marginal bone levels were measured from standard intraoral radiographs. Results showed that none of the prostheses presented a completely passive fit to the implants in vivo. Furthermore, similar distortions of the prostheses were found in the two groups, indicating that the implants seem to be stable and do not move, even after several years in function. The maximal range of three-dimensional distortion of cylinder center points was about 275 µm for both groups. Mean center point misfit was 111 (SD 59) and 91 (SD 51) µm for the 1-year and 5-year groups, respectively. The corresponding mean marginal bone loss was 0.5 and 0.2 mm for the two follow-up groups. No statistical correlations (P > .05) between change of marginal bone levels and different parameters of prosthesis misfit were observed in the two groups. The study indicated that a certain biologic tolerance for misfit may be present. The degree of misfit reported in the study was clinically acceptable with regard to observed marginal bone loss. Keywords: bone loss, complication, follow-up, framework, implant, misfit, precision

A total of 443 hydroxyapatite-coated cylindrical implants were placed into the posterior mandibles of consenting patients from July 1985 through December 1991. Implants were placed into ridges that had sufficient bone volume. Implants were also placed in ridges with thin bone, grafted bone, or immediate extraction sites, which occasionally resulted in increased morbidity. All were followed yearly with clinical and radiographic examinations. Life table analyses were performed using SAS software. Ten-year cumulative survival and nonmorbid (based on bone loss criteria) rates were determined for the four posterior tooth locations and for all posterior locations combined. Cumulative survival for implants was 0.858 ± 0.056 in the first premolar region, 0.833 ± 0.041 for the second premolar region, 0.785 ± 0.041 for the first molar region, and 0.718 ± 0.064 for the second molar region. When all posterior mandibular locations were taken together, the cumulative survival was 0.793 ± 0.025. Cumulative nonmorbid rates were 0.816 ± 0.056 for the first premolar, 0.729 ± 0.049 for the second premolar, 0.600 ± 0.046 for the first molar, and 0.507 ± 0.066 for the second molar. The cumulative nonmorbid rate was 0.646 ± 0.028 for all sites combined. Comparisons between sites indicated that the second molar site had statistically more morbidity than did the other three sites. Most of the problems were identified with 8-mm-long implants, especially in the second molar location. Clinical parameters, including the presence of keratinized gingiva and a hygienic restoration, were associated with survival. Both mechanical and inflammatory compromise were found to be reasons for implant failure. Keywords: hydroxyapatite, implant, posterior mandible, survival

A device to measure bur temperature using thermocouple technology was developed. A block of bovine bone was subjected to computerized tomography scanning to confirm bone density and configuration similar to that of a human mandible. Bone temperature was measured via a thermocouple probe. During osteotomy preparation, bur temperature was shown to exceed the surrounding bone temperature. Irrigation greatly reduced bur temperature. Osteotomies were made to depths of 8.5, 10.5, 13.5, 15.5, 18.5, and 20.5 mm. Bone density played a far greater role in bur temperature elevation than did osteotomy depth. Adding a pilot drill to the drill sequencing tended to lower bur temperature; widening of osteotomies from 2 to 3 mm wide generated as much heat as did the making of the 2-mm-wide osteotomy. Keywords: bone temperature, bur bone interface, bur temperature, irrigation, osteotomy depth, thermocouple

This article compares the survival rates of two root-form implants- hydroxyapatite-coated (HA-coated) Micro-Vent and pure titanium Swede-Vent implants-during a 6-year period. A total of 390 implants were placed in 166 patients aged 18 to 81 years. Fifteen implants were lost before prosthesis placement, and one was lost after prosthesis loading. The overall success rates were 96.8% for the HA-coated Micro-Vent implants and 95.2% for the titanium Swede-Vent implants. The survival rates were similar for both the maxilla and the mandible and for the anterior and the posterior areas. Although most of the HA-coated implants were generally placed in types 3 and 4 bone, results indicated that the survival rate was similar to that of pure titanium implants, which were placed more often in types 1 and 2 bone. Keywords: hydroxyapatite coated, implant, survival, titanium

This study presents a follow-up of 92 implant-supported fixed partial dentures that have been cement retained for 6 months up to 3 years. Included in the study were 41 women and 29 men. A total of 225 implants were placed (86 in the maxilla and 139 in the mandible). Fixed partial dentures, including single-tooth restorations, were temporarily cemented using Temp-Bond or IRM. Complications encountered were cement washout, porcelain fracture, loose central screws, and implant failure. This study suggests an alternative to screw-retained prostheses; the method presented may lower the reported complications. Keywords: cement retained, fixed partial prosthesis, implant

Image quality in preimplant computerized tomography (CT) examinations made with different radiation doses (40 to 280 mAs) and scanning modes (standard and helical axial, 15-degree angled, and frontal) and in conventional spiral tomography (Scanora) was compared. Mandibular canal and alveolar bone crest visibility was evaluated in images from mandibular jaw segments. Visibility was unaffected by radiation dose in CT examinations except in frontal scanning, where a small actual difference was statistically significant. Differences among CT scanning modes and between CT and conventional spiral tomography were highly significant. Low-dose mandibular preimplant tomography can be performed with CT using lower-than-normal radiation doses or with conventional spiral tomography. Keywords: computerized tomography, dental implantation, mandible, radiation dose, x-ray tomography

An analysis of 4,045 implants placed in function during a 5-year period yielded eight fractured implants (0.2%). All fractures had associated marginal bone loss. The majority (six of eight) were supporting posterior prostheses. All patients with fractured implants were diagnosed to have parafunctional habits. Most patients presented with loosening or fracture of prosthetic gold screws or abutment screws prior to fracture. Treating fractured implants can be accomplished by refacing the fractured titanium and adapting new abutments or replacing the entire implant with subsequent prosthesis refabrication. Keywords: bone resorption, fractured implant, implant repair, implant replacement, occlusal load, osseointegrated implant, parafunctional forces

Use of bioresorbable and biodegradable materials for guided tissue and guided bone regeneration is under intense investigation and is being tested in clinical trials. This study presents a basic overview of material properties of bioresorbable and biodegradable polymers and devices for guided tissue and guided bone regeneration treatment. Collagens and aliphatic polyesters, such as poly(glycolic acid), poly(glactic acid), and polycaprolactone, are discussed, as well as biocompatibility, mechanical properties, and sterilization. Keywords: biocompatibility, bioresorbable device, bioresorbable polymer, guided bone regeneration

Hazards of oral implant treatment include the inadvertent ingestion or inhalation of components or instruments dropped accidentally into the oropharynx. A case is reported of a swallowed screwdriver, and attention is drawn to the potentially serious consequences. Guidance is given on management. Inhalation of foreign bodies is an even more serious event. The importance of prevention is emphasized both from a medicolegal point of view and as a matter of proper patient care. Keywords: colonoscopy, endoscopy, hemorrhage, infection, ingestion, inhalation, obstruction, perforation, prevention

When attempting to restore an edentulous posterior segment of the mandible into which space the opposing maxillary segment has supererupted, it is necessary to idealize the maxillary occlusal plane to accommodate the final restoration. This report discusses superior repositioning of the posterior segment of the maxilla using rigid fixation with simultaneous implant placement into the corresponding posterior edentulous mandibular space. Keywords: Le Fort I, miniplates, osteotomy, rigid fixation