The International Journal of Oral & Maxillofacial Implants, 01/1997

Six hundred twenty-six titanium plasma-sprayed cylindrical implants that had been functioning in regenerated bone for a p eriod of up to 51 months were evaluated according to Albrektsson's criteria. These implants had been placed either with concomitant guided bone regeneration procedures or in bony ridges that had previously been augmented. According to Albrektsson's criteria, absolute success rates of 97.6% overall, 98.8% in the maxilla, and 98.2% in the mandible were recorded, as were cumulative success rates of 94.9% in the maxilla and 91.9% in the mandible. The overall cumulative success rate was 93.8%. One patient, who underwent protracted chemotherapy 14 months after implant function began, accounted for 33% (3 of 9) of the total implant loss in the study. If this patient is excluded from the study, the cumulative success rates are 94.9% (maxilla), 96.7% (mandible), and 95.8% (overal l). These findings support the theory that regenerated bone will achieve osseointegration with titanium plasma-sprayed cylindrical implants, and that this osseointegration can be maintained under function over time.

The purpose of this study was to investigate the microstructure of plasma-sprayed hydroxyapatite coatings and the elemental composition near the coating-substrate interface for two commercial implants, using the scanning electron microscope. Both coating surfaces and cross-secttioned specimens were examined. The results indicated that while the surface microstructures of both implants were consistent with the plasma-spraying process, the scale of the constituents was much finer for one product. In cross-section, both coatings exhibited minimal porosity and intimate contact with the titanium alloy substrate. It was found that limited interdiffusion of titanium and calcium occurred near the interface.

The goal of this study was to provide new data regarding levels of inflammatory and growth factor mediators and bacterial pathogens associated with failing implants, as compared to healthy implants. Twenty-one patients with failing implant sites (group 1) and 8 patients with only healthy implants (group 2) were included. Fifteen of the 21 failing implant patients (group 1) also presented with at least one stable nondiseased implant. Plaque samples were examined, using DNA oligonucleotide probes for 40 different microbes. Gingival crevicular fluid samples were collected for the analyses of catabolic bone resorbing agonists prostaglandin E2 (PGEx), interleukin-1B (IL-1B) and IL-6 and anabolic bone-forming growth factors transforming growth factor B (TGF-B) and platelet-derived growth factor (PDGF). Although positive trends were noted, there were no significant differences in any of the microbial, inflammatory, or growth factors mediators comparing failing to stable implants in group 1. This study found greater detection frequencies of P. nigrescens, P. micros, F. nucleatum ss vincentii, and F. nucleatum ss nucleatum, as well as significant elevations in GCF levels of PGEx, IL-1B, and PDGF in mouths with failing implant sites as well as significant elevations in GCF levels of PGEx, IL-1B, and PDGF in mouths with failing implant sites as compared to mouths with healthy control implants. Risk appears to be primarily at a patient level and secondarily at a site or implant level from a clinical, microbial (P. micros and P. nigrescens), and biochemical (PGE2 and IL-1B) perspective. Furthermore, the counts of P. nigrescens and P. micros were found to coorelate with concentrations of PGEx at a site level.

Various techniques of soft tissue management following the immediate placement of implants into extraction sockets are evaluated; the merits of the Rehrman-plasty, the free mucosal graft, the pedicled isalnd flap, and membranes to seal the socket are discussed as are the esthetic effects of various surgical techniques used at abutment connection. Two treatment strategies are suggested. Presently, the treatment of choice seems to be to close the extraction socket after implant placement by means of either a pedicled island flap or a thin cortical bone membrane. In addition, a new excisional technique is described for use at abutment connection. If a flap has to be raised to extract the tooth, the implant should be covered by means of either a Rehrman-plasty or a cortical bone membrane. If a Rehrman-plasty is chosen, the apically repositioned flap should be used at abutment connection.

A 3-year multicenter study on 63 maxillary and 10 mandibular fixed prostheses in 71 patients is reported. Angulated abutments or a combination of angulated and standard abutments were used to support prostheses; all components were from the Branemark System. Of 425 implants initially placed, 4 were lost before abutment connection. Of the remaining 421 implants, 209 angulated (test) abutments and 212 standard (control) abutments were placed to support fixed prostheses. The prosthesis success rates were 96.8% for maxillae and 100% for mandibles. A total of 5.3% of the loaded test implants and 7.5% of the loaded control implants failed. The survival rates after 3 years were 91.3% for maxillary control implants, 94.8% for maxillary test implants, 97.4% for mandibular control implants, and 94.1% for mandibular test implants. The findings in this study pointed out that angulated abutments will not necessarily promote peri-implant mucosal problems. The study indicated that angulated abutments on Branmark System implants have exhibited good preliminary results and should be comparable to the standard abutment as a predictable modality in prosthetic rehabilitation.

The positive predictive value of radiographic identification of unstable Branemark implants was evaluated. Based on approximately 2,000 patients with implants followed during a 3-year period, a total of 84 patients were radiographically detected to have suspected failing implants. A total of 481 implants had been placed in these patients, but because of the study design and some patient dropouts, the evaluation was carried out in only 79 of the identified patients, who had 413 implants. Calculations were performed based on the number of occasions the implants were examined (n = 482) because some patients were assessed on more than one occasion. Results indicated a high positive predictive value (83%) to ra diographically identify failing implants, and only 5% were clinically found to be failing without having been detected radiographically. In nine jaws (11%), the fixed prost hetic restorations were unnecessarily detached because of inaccurate radiographic diagnosis. The study indicated that when examining patients on a long-term routine basis. The timing for these assessments should be annual during the first 3 years of follow up for the unexperienced clinician and may thereafter be individualized with more clinical experience.

Between January 1992 and October 1992, 100 Minimatic screw implants made of titanium alloy with rough acid-etched surfaces were placed in 63 consecutive partially edentulous patients. At second-stage (uncovering) surgery performed after a 4- to 6-month healing period, none of the implants showed any signs of mobility, peri-implant infection, or bone loss. After an additional healing phase averaging 2 weeks, the patients were restored with fixed prostheses. Patients were reexamined every 3 months for 1 year, with all 63 patients available for evaluation during this period. Periapical radiographs were taken preoperatively, immediately after surgery, and at 6 and 12 months after implantation. There were no signs of peri-implant radiolucencies in any of the implants, and alveolar bone loss was less than 1 mm on average 1 year after implantation. Based on Plaque Index, sulcular bleeding index, pocket probing depth, attachment level, width or keratinized mucosa, and hand-tested mobility, 99 implants were considered successful and 1 (which developed per i-implant infection) was considered a failure. Study results substantiate other reports that implants with a rough surface can yield predictable good results.

In this study, a possible correlation between peri-implant mucosal inflammation and marginal bone loss in a group of patients who received two-stage hydroxyapatite-coated dental implants was evaluated 3 years after implantation. Thirty-two implants were evaluated as to their Plaque Index, Gingival Index, and crevicular fluid volume. Patients were divided into three groups: a control group with no inflammatory signs; a borderline group with moderate inflammation; and a gingivitis group with an established inflammatory process. Three dental radiographs per implant were analyzed at 2 months, 9 months, and 3 years after implantation by measuring bone height at the mesial and distal sides. Preliminary results indicated increas ed bone resorption in the gingivitis group compared with the control and borderline groups at both the mesial and distal surfaces (P .05), suggesting correlation between mucosal inflammation and marginal resorption observed around these implants. Statistical analysis of correlation between the assessed mucosal parameters and bone loss indicated significance for Gingival Index and crevicular fluid volume (P .05).

A simple laboratory-made acrylic resin guide offers rapid location of angulated abutments after the healing abutments are removed. An impression recording the relation of the implants to the dental arch enables the choice of abutments to be made in the laboratory. The precise position and angulation of each abutment can be transferred to the mouth.

A surgical technique with the objective of obtaining and maintaining soft tissue closure over membranes used for guided bone regeneration is described. This procedure achieves primary closure in extraction sockets or in association with immediate implants without creating mucogingival problems around adjacent teeth.

In this study, clinical and histologic responses to a bioresorbable membrane used to obturate an osteotomy site in the lateral wall of the maxillary sinus and to facilitate graft containment were examined. Expanded polytetrafluoroethylene (e-PTFE) membranes were used as a cont rol to compare biocompatibility and resorption characteristics. Twelve sinus augmentation procedures were performed to facilitate placement of implants in nine patients with insufficient bone in the edentulous posterior maxillae. In five procedures, the lateral wall was obturated to ensure graft containment with an e-PTFE membr ane; the other seven were covered with a bioresorbable barrier (poly[lactic acid]). The presence or absence of inflammation, dehiscence, suppuration, and encleftation were recorded. All patients healed without complication or adverse biologic reaction to either barrier material. Biopsy specimens of the graft site were taken from the lateral wall with overlying soft tissue prior to reflection of the full-thickness flap at stage 2 surgery. Findings suggest that a poly(lactic acid) membrane can provide results similar to those with e-PTFE memb ranes for use in lateral obturation during sinus augmentation.

Bioglass cones acting as space fillers after removal of tooth roots delay the resorption of alveolar ridges. In 1987, 242 implants in 29 patients with a mean postimplantation interval of 19.9 months were reported by the authors. Bioglass cones had been fitted snugly at least 2 mm below the alveolar crest, and dentures were placed no sooner than 6 weeks following tooth removal; 2.9% had been lost and 3.7% developed dehiscences. The present report on 168 implants in 20 recalled patients (mean postimplantation interval of 63.2 months) revealed a loss of 14.3% implants in the anterior mandible; however, the present data demonstrate a statistically significant reten tion rate in the anterior maxilla. With this high rate of Bioglass cone retention (85.7%) after 5 years, their placement into fresh sockets to maintain the alveolar ridge is recommended.

The objective of this study was to examine inflammatory tissue in deep peri-implant bone pockets (> 5 mm) for anaerobic bacteria colonization. The peri-implant inflammatory tissue of bone defects from 12 edentulous patients with 18 unsuccessful implants (IMZ type) was removed after surgical opening of the defects. After grinding the tissue with glass beads in nutrient solution, an aliquot of the suspension was plated and incubated on appropriate culture media. The quantitative and qualitative distribution of bacteria as a function of the tissue dry weight was determined (cell count/mg dry weight). The mean total cell count was 67 x 10 to the third power cells/mg dry weight. The following bacteria dominated: species of the family Bacteroidaceae (Prevotella in termedia, Prevotella buccae, Prevotella oralis, Prevotella melaninogenica, Prevotella denticola); Actinobacillus actinomycetemcomitans; Fusobacterium nucleatum; Capnocytophaga spp; and Eikenella corrodens. Bacteroidaceae and Actinobacillus actinomycetemcomitans were found particularly frequently. The increased colonization of these bacteria in deep peri-implant bone pockets is consistent with the currently held view of advanced periodontal lesions, whereby certain pathogens grow at a disproportionate rate in comparison with the total b acteria count under specific circumstances.

The entire course of the mandibular canal is normally not visible on a panoramic radiograph. Locating the course of the mandibular canal at the site of implant placement is important. This study was carried out to determine whether the course of the mandibular canal can be more clearly visualized by tilting the patient's head approximately 5 degrees downward with reference to the Frankfort horizontal reference bar of the Orthopantomogram machine. In 91% of the radiographs taken in this position, the mandibular foramen, mandibular canal, and mental foramen were visible. The angulation of the patient's head reduced the chances of superimposition on the contralateral sides, making these structures clearly visible.

When a natural tooth connected to an implant abutment by a framework is displaced within physiologic limits under functional loads, the superstructure acts as a cantilever moment arm and the implant is loaded additionally during that moment effect. The effects of a deflecting support connected to an IMZ implant, with either the IMC resilient or the titanium rigid element, were evaluated through an experimental model. The strain values measured when the moment arm was not allowed to deflect were only 30% lower than the strains measured when it was deflected within the limits of physiologic tooth mobility. The IMC was effective and achieved a reduction in the cervical strains up to 60% when compared with the rigid connector.