The International Journal of Oral & Maxillofacial Implants, 04/1997

.

Correlated transmission electron and high-voltage electron microscopic analyses examined the undecalcified bone and associated support tissues of 60 endosseous titanium blade and titanium and ceramic root-form implants in dogs. The implants supported fixed partial dentures for up to 2 years. Data obtained from this investigration suggest that a range of tissues, both mineralized and unmineralized, support osseointegrated dental implants. This study examined the tissues apposing not just isolated aspects of the implant surface, but the entire length of the implant, and found that mineralized and unmineralized tissues existed concurrently. Much fo the implant surface was apposed by mandibular bone, and both root-form and blade implants osseointegrated. The densely mineralized collagen fibril matrix was often separated from the implant by only a 20-nm to 50-nm electron-dense, ruthenium-positive deposit. H igh-voltage electron microscope stereology demonstrated that cellular porcesses extended directly to the implant from underlying osteocytes. In the same implants, areas containing an unmineralized collagen matrix interposed between the bone and implant surface were observed. In this region osteoblasts interacted with this matrix, and Howship's lacunae, containing vascular elements and osteoclasts, were also observed. The remodeling activities appear to be a homeostasis of catabolic activyt (osteoclasts) and metabolic activity (osteoblasts). The apex of the implant was often apposed by a fibrofatty stroma. The support tissue response appears to be the result of the interrelations of osteoblasts, osteocytes, and osteoclasts in association with vascular elements. Therefore, the support tissue response to osseointegrated implants is a dynamic activity that involves the ehalthy interaction of these cells and tissues along the entire length of the implant.

This prospective longitudinal multicenter study evaluated the clinical outsomes after placement and restoration of one-step Branemark implants into the maxillae and mandibles of completely and partially edentulous patients. Six surgical treatment centers participated in this study, in which 135 implants were placed into 63 adult patients. All implants were stable after placement. The majority of impl ants were placed into type B bone with minimal jaw resorption and type 2 bone quality. After implant placement, standard transmucosal healing abutments were firmly placed. The average amount of time between implant placement and prosthetic abutment connection was 170 days in the maxillae and 147 days in the mandibles. To evaluate crestal bone changes caused by implant placement, a periodontal probe was used to measure midbuccally from the top of the implant cylinder to the alveolar crest; in 29 patients, 54 midbuccal bone crest sites were remeasured following prosthetic abutment connection. Crestal bone changes in mandibles and maxillae were statistically and clinically insignificant. Six implants were lost prior to loading and one implant has not been restored. No implants or restorations were lost after loading. At 1 year, the implant success rate was 95.6%. Mesiodistal radiographic measurements from 34 patients were averaged, and changes from prosthetic abutment connection to, on average, 12 months follow-up were compared. The radiographs, which were d igitalized, measured from the bottom of the implant cylinder to the most coronal bone in contact with implant thread. For mandibular implants, the mean radiographic bone level at prosthetic abutment connection was 1.07 mm; after loading, it was 1.35 mm. For maxillary implants, the mean radiographic bone height at prosthetic abutment connection was 1.16 mm; after loading, it was 1.36 mm. These changes were not statistically significant. The 1-year outcomes from this patient series indicate that one-step Branemark implants provide excellent clinical results when placed in patients with good bone quality and quantity.

This retrospective study evaluated neurosensory dysfunction and the implant success rate associated with 64 implants placed in 15 patients following transposition of the inferior alveolar nerve. A total of 21 inferior alveola r nerve mobilization surgeries were performed. The mean postoperative follow-up time was 41.3 months, with a range of 10 to 67 months. The effects of surgical technique and implant surface geometry on neurosensory dysfunction were evaluated by using light touch, brush stroke direction, and two-point discrimination. The implant su ccess rate was 93.8% (60/64). The surgical technique that involved detaching the mental foramen resulted in a significantly greater incidence of neurosensory disturbance (77.8%, 7/9) than did the technique that left the bony foramen intact (33.3%, 4/12). The overall incidence of neurosensory disturbance was 52.4% (11/21).

The tissue response of rat tibiae to the surgical placement of commercially pure titanium implants was examined at 2, 6, 10, and 28 days. The transcortical placement of 1.5-mm x 2-mm implants resulted in the apposition of threaded implant surfaces within cortical and cancellous regions of the tibia. In all regions, evidence of bone formation was obtained through pre-embedding fracture of the implant from the bone tissue interface. Scanning electron microscopy examination of early responses revealed a fibrin clot and rapid formation of a loosely organized collagenous matrix. Many extravasated blood cells contacted the implant surface. At day 6, a more organized matrix containing many blood vessels opposed the implant surfaces, and few extravasated blood cells remained in contact with the implant surface. By day 10, the surgical wound was filled with woven bone that approximated the contours of the threaded implant. Later, few cells were attached to the retrieved implants. The consolidation of the forming matrix was clearly evident at 28 days. The tissue interface was an amorphous metrix that revealed the surface characteristics of the machined implant. Ligh microscopic analysis of ground sections indicated that, from day 6 onward, cells morphologically consistent with the osteoblastic phenotype were predominant within the gap between the surgical margin and implant surface. Osteoblastic cells had achieved the formation of on osteoid seam upon which bone form ation progressed. The amtrix that had formed represented woven bone containing many osteocytes. At day 6, evidence of remodeling was observed at sites distant from t he surgical site, and by day 28 osteoclastic activity was observed at trabecular sites adjacent to the impl ant surface. The rat tibia model provides evidence of rapid formation of bone at implant surfaces.

Screw-shaped implants were prepared with three different surface topographies: One was left as machined, ie, a truned surface, and two were blasted surfaces with differing degrees of surface roughness. The surface topography was measured with a confocal laser scanning profilometer and the surface roughness was characterized using height and spatial descriptive parameters. The turned surface had an average surface roughness of 0.96 um and an average peak spacing of 8.6 um. The two blasted surfaces had surface roughness values of 1.16 um and 1.94 um, respectively; the corresponding values for the peak spacin g parameter were 10.00 um and 13.22 um, respectively. After 1 year in rabbit bone, the bone response to the turned implants was compared with the response to the two blasted implant surfaces. Firmer bone fixation was found for the two blasted surfaces, with statistically significant increases in removal torque and percentage of bone-to-metal contact. Furthermore, about 2 mm from the implant surface, the titanium release was similar for the turned and the 25-um aluminumoxide-blasted implants.

This investigation was initiated to develop a method to provide patients with a fixed provisional prosthesis placed at the time of implant placement. Sixty-three standard 3.75-mm Nobel Biocare implants of varying lengths were placed into mandibular sites in 10 patients and followed for up to 10 years. Twenty-eight implants were immediately loaded at implant placement, providing support for fixed provisional prostheses, while 35 adjacent implant were allowed to heal submerged and stress-free. Following a 3-month healing period, the submerged implants were exposed and definitive reconstruction was accomplished. All 10 prostheses supported by 28 implants placed into immediate function at the time of implant placement were successful during the 3-month healing period. Of these 28 implants placed into immediate function, 4 ultimately failed. Of teh 35 submerged implants, all are osseointegrated and in function to date. Lif te-table analysis demonstrates an overall 10-year survival rate of 93.4% for all implants. The 10-year life-table analysis of survival is 84.7% for immediately loaded implants and 100% for submerged implants. Statistical analysis of the submerged versus immediately loaded implants demonstrates failure rates for immediately loaded implants to be significantly higher (P = .22 by the log rank test). These data demonstrate that although mandibular implants can be successfully placed into immediate function in the short term to support fixed provisional prostheses, long-term prognosis is guarded for those implants placed into immediate function distal to the incisor region.

A proposed protocol and differentiated success criteria for long-term evaluation of oral implants are presented. The protocol and criteria were applied to a retrospective patient material treated during a 1-year period and followed for 5 years. The protocol comprised a two-stage analysis of the collected clinical data. First, a quantitiatve analysis of the otucome was made using a life table. Based on the information obtained during the follow-up, each implant was categorized into one of three groups: unaccounted for, failure, or survival. A qualitative analysis of the survival group was then performed by active testing against defined criteria. Depending on the modes of clinical and radiographi examinations and their results, surviving implants were either further assigned to one of three success grades or remained in the survival group. The data are presented in a four-field table at one level of success. Strict success criteria together with individual stability testing and radiographic examination of each consecutive implant should be used when a new implant system is evaluated or when a new application is explored. Radiography alone and more moderate success criteria may be used to document routine treatments, provided that an already well-documented implant system is studied.

The aim of this study was to compare implant-retained mandibular overdentures and two conventional treatments for their effects on functional ability (chewing, speaking, etc) patient satisfaction, and quality of life (psychosocial functioning). Assignment of 90 patients was executed by means of a balancing allocation computer program to ensure the pretreatment comparability of the three groups. Twelve months after treatment, the average scores for almost all specific quality-of-life measures had improved significantly in all three groups. On average, all patients experienced fewer restrictions in their social activities and had fewer psychological problems because of their full dentures. No impact on the general quality of life was established. One year after treatment, all three dental treatment modalities had a comparably positive effect on dental health0related quality of life.

Ten patients (3 maxilla, 7 mandible), who had been treated for a head and neck malignancy by undergoing radiotherapy, had 42 implants (10 maxillary, 32 mandibular) placed into the irradiated sites and either an overdenture or a fixed prosthesis fabricated. Of the 10 implants placed in the maxilla, 6 were lost; however, there was a 100% survival rate of the implants placed in the m andible (mean duration = 33 months). The use of longer implants and pre- or postimplant hyperbaric oxygen may be necessary in maxillary situations.

Two-stage implant systems result in gaps and cavities between implant and abutment that can act as a trap for bacteria and thus possibly cause inflammatory reactions in the peri-implant soft tissues. These gaps between the components are inevitable, and their clinical significance has so far been mostly neglected by both manufacturers and clinicians. The aim of the study was to determine whether there is microbial leakage at the implant-abutment interface. Thirteen different implant-abutment combinations were subjected to an in vitro experiment, in which the penetration of bacteria (Escherichia coli) was observed for 10 assemblies of each type. All implant systems presented microbial leakage. When the Frialit-2 implant was supplied with a silicon washer, there were fewer c ases of leakage. The width of the marginal gap between the prefabricated components, measured with a scanning electron microscope, was less than 10 um in all systems.

The changes in crestal bone height observed in standardized radiographs of porous-coated dental implants after 3 to 4 years of function in the support of mandibular overdentures is reported for a group of 48 completely edentulous patients. Possible correlations between bone height and each of probing attachment level, Plaque Index, and Sulcular Bleeding Index were investigated. Mean bone loss values were determined to be 0.43 mm in year 1, decreasing to 0.17 mm and 0.13 mm in years 2 and 3, respectively. During year 4, there was an apparent mean gain of 0.05 mm. While the mean mucosal tissue thickness (1.3 mm) was similar to that reported by other investigators, it was not possible to show a correlation between bone height and probing attachment level. Likewise, correlations between bone height and Plaque Index or between bone height and Sulcular Bleeding Index could not be demonstrated. Keywords: crestal bone height, Plaque Index, probing attachment level, Sulcular Bleeding Index

Three patients irradiated as a part of cancer treatment, both before and after placement of endosseous implants, were studied. Total irradiation doses varied from 80 to 195 Gy in the tumor/implant area. Implants failed at a rate of 64.2% during a 3-year follow-up period. All patients developed osteoradionecrosis in the tumor cavities adjacent to the implants. The combined effects of the pre- and postoperative irradiation, in conjunction with the placement of implants, appear to challenge the limits of osseointegration. Until further knowledge is obtained regarding how such highly radiated tissue should be handled, it is recommended that if anchorage of craniofacial prostheses is attempted according to osseointegration principles, it should be performed with the utmost care.

Following radical oral cancer surgery and postoperative adjuvant radiotherapy with a total dose of 60 Gy, 71 IMZ and 1 50 Branemark implants were placed in the mandibles and 28 Branemark implants were placed in the maxillas of 60 patients between 1985 and 1995. Adjunctive hyperbaric oxygen therapy was not used. Osteoradionecrosis of the mandible occurred in two patients (3.4%), and necrosis of soft tissue in the floor of the mouth region occurred in three patients (5.2%). Twenty-one implants (18 in the mandible and 2 in the maxilla) were not osseointegrated when surgically exposed. In subsequent follow-up, 17 mandibular implants and 5 maxilary implants lost their osseointegration. The life table method indicated that 5-year actuarial implant success rates in the irradiated mandible were 77.5% for the IMZ system and 83.5% for the Branemark system. These differences were not statistically significant. Retrospective analysis indicated that the success of implants in the irradiated mandible is determined after an interval of 18 to 24 months. For a small number of Branemark implants in the irradiated maxilla, an actuarial success rate of 85.5% was found.

This report describes a life-threatening hemorrhage in the floor of a patient's mouth during routine implant placement in the anterior mandible. Airway obstruction caused by hematoma development resulted in acute nasotracheal intubation and subsequent surgical intervention. Surgical, radiographic, and anatomic considerations to prevent severe bleeding are discussed. An extraoral submental appraoch in cases with large sublingual hematomas is recommended. An outpatient should be treated in or close to a hospital where these complications can be dealt with promptly and effectively.