The International Journal of Oral & Maxillofacial Implants, 03/1997

In an observational study of 696 Frialit-2 implants in 376 patients that was carried out between 1990 and 1995, implants of varying diameters and lengths were delivered for a range of indications in the maxilla and mandible. Single-tooth replacement was performed in 42% of cases; of these, 22.4% were placed immediately following extraction. Stu dy parameters (Plaque Index, Gingival Index, probing depth, Periotest value, and peri-implant bone loss) are reported in detail. Statistical analysis is based on a 97.6% rate of recall. The overall success rate was found to be 96% using the Kaplan-Meier statistical analysis. No difference was apparent between single-tooth applications and prosthesis restorations.

This report describes a surgical technique for reconstruction of the buccolingually reduced alveolar process. The technique involves the preparation of an artificial socket with immediate implant placement, which reduces total treatment time compared with two-stage procedures. Alveolar preparation comprises lamellar cortical splitting of the alveolus, interlamellar implant placement, and primary stabilization based on a microfixation technique. It was used for a wide range of indications involving single and multiple alveoli related to the partially dentate and the edentulous alveolar process. The results of 24 Branemark standard implants and 97 ITI implants with 44 consecutively treated patients have been reviewed with a mean observation time of 34.3 months (range 6 to 68 months). The main indicator for alveolar reconstruction was the narrow anterior maxillary arch. The 5-year cumulated success rate was 86.2%. Twelve imp lants failed during the observation period. The mean marginal bone loss was 1.7 mm (range 0 to 7.5 mm). There was a low infection rate compared with membrane-based GTR techniques. Treatment costs were low as a result of shorter treatment time.

Immediate loading of threaded implants with a fixed provisional restoration at stage 1 surgery was evaluated in 10 consecutive patients. The patients selected had to be completely edentulous and have adequate bone for a minimum of 10-mm-long implants. A minimum of 10 implants were placed in each patient's arch. A minimum of five implants were submerged initially for medicolegal reasons and allowed to heal without loading. The remaining implants were loaded the day of stage 1 surgery. Once the provisional restoration was relined, it was cemented or screw retained. A total of 107 implants were placed in these 10 patients; 6 had them placed in the mandible, and 4 in the maxilla. Six patients were treated with Nobel Biocare implants, one with ITI Bonefit implants, two with Astra Tech TiOblast implants, and one with a 3i implant. Sixty-seven of 69 implants that were loaded integrated, and 37 of 38 submerged implants integrated. All 10 patients have been restored with a definitive prosthesis, and all had a fixed provisional prosthesis from stage 1 surgery. The results of this study indicate that immediate loading of multiple implants rigidly splinted around a completely edentulous arch can be a viable treatment modality.

Polylactic membranes were evaluated for vertical ridge augmentation around immediate implants in periodontally compromised extraction sites. Ligature-induced periodontitis was produced in 10 adult beagle dogs. The periodontium was allowed to heal for 6 weeks. All premolar teeth were extracted and three implants were placed immediately into the extraction sockets on either side of the mandible so that the polished cone extended above the alveolar bone level. On one side of the mandible, the implants were covered with a 0.2-mm-thick polylactic membrane (DL-lactide-co-trimethylene carbonate in a ratio of 7:3). Histologic and morphometric analyses performed after 3 and 5 months revealed that the membrane group did not exhibit significantly greater bone-implant contact that the controls. The occurrence of dehiscences correlated significantly with use of the membrane. Use of the membrane was associated with significantly less peri-implant bone height after 5 months. No remnants of the membrane material could be identified after 3 or 5 months, indicating rapid resorption during the first weeks of implantation. The tested membrane material did not fulfill the requirements of resorption kinetics and space maintenance for guided bone regeneration in vertical ridge augmentation.

in vivo measurements of vertical forces and bending moments during biting and chewing were carried out on 10 three-unit prostheses in the posterior mandibles of five patients. Each patient had two prostheses, one supported by two implants and the other supported by one implant and one tooth. The results demonstrated no major difference in functional load magnitudes related to the support type. The distribution of load between the abutments was influenced more by the prosthesis geometry and implant placement than by the difference in load characteristics of tooth and implant. This conclusion, however, is limited to one implant connected to a tooth, because multiple implants form a considerably stiffer unit than do teeth. An increase in vertical load resulting from cantilever extensions on the prostheses was documented, both at bite fork measurements and during chewing. No substantial lateral bending was registered, probably because the flat occlusal surfaces and the presence of the opposing complete denture reduced lateral forces.

Temperature was measured during drilling in bovine cortical bone specimens. A surgical drill fitted with a custom-designed speedometer and mounted on a drill press was used to drill holes at one speed, 49,000 rpm, and at forces in the range of 1.5 to 9.0 N. The resulting temperatures were recorded by thermocouples placed at various locations. The distribution of maximum local temperature rise (AT) was best fitted by the function AT = aR-b, where R is the distance from the center of the drilled hole and a and b are constants that were found by regr ession analysis. It was also found that the temperature increased with force, up to about 4.0 N, and then decreased at forces greater than that because of decreased drilling time. A separate series of tests revealed that temperatures were higher in the longitudinal direction than in the circumferential direction; this difference was attibuted to the anisotropic thermal properties of bone.

Magnetic resonance imaging is used more and more frequently as a diagnostic tool. Because high magnetic fields are used, knowledge on how these will affect implanted material and the patient is of great importance. Ferromagnetic properties of implant materials are seldom described by the manufacturer, but a doctor requesting magnetic resonance imaging of a patient must know about these properties. Not only is the composition of an alloy important, but also the size and shape of the metallic material as well as its position in the body. Implants from the Branemark System were tested; findings indicated that the implants were not influenced when exposed to magnetic resonance imaging. The artifacts caused by the implants were minor and did not jeopardize the evaluation of the scans. However, magnet keepers attached to the implants were found to cause major artifacts and must be removed before an implant patient is referred for a magnetic resonance imaging examination.

There are inherent biomechanical differences in the implant treatment of completely edentulous arches and posterior partially edentulous segments. The partial prosthesis does not benefit from cross-arch stabilization and is, therefore, more susceptible to bending loads. Because of the difference in mobility between teeth and implants, implants may carry a major share of load when mixed with teeth in the same quadrant. However, the frequency of implant overload in posterior partial resotrations is low, and, with appropriate treatment planning, overload in these situations is almost always preventable. A checklist procedure is proposed to help the clinician enumerate and evaluate deleterious load factors. By screening patients for such factors in advance, the clinician may identify and avoid potential overload situations when conceiving and fabricating implant-supported posterior partial prostheses. A second checklist, for use at follow-up appointments, lists alarm factors that serve as an early warning of overload once the prosthesis is in place.

Machining tolerance, an intrinsic characteristic that exists between machined implant components, identifies the amount of horizontal shift possible between paired components. Machining tolerances between implant components (abutment, gold, cylinder, impression coping, and brass abutment replicas) were measured with a coordinate measuring machine. The measured tolerances ranged from 22 to 100 um. Machining tolerances between implant components should be included in future studies of accuracy, because it is an inherent characteristic of the component itself.

The use of osseointegrated implants to retain facial prostheses in craniofacial rehabilitation is a reliable procedure. Proper location of the implants is critical for fab rication of a prosthesis with ideal shape and contour. The use of a positioner at time of surgery can guide placement of the implants to achieve an optimum result. The positioner is also useful as a guide to the shape of the retentive element and as a quick method for obtaining a wax pattern for the prosthesis. This article describes the fabrication and application of a positioner.

The objective of this study was to analyze the efficacy and correlation between clinical and histologic parameters used to evaluate oral implants. After extraction of the premolars and a healing time of 4 months in 16 Dutch goats, four Branemark implants were placed in the maxillary left and right premolar regions. After a healing time of 6 months, followed by another 4 months with the permucosal abutments, the goats were sacrificed and the jaws were block-resected. Before histologic preparation, long-cone radiographs were made and Periotest scores of the implants were recorded. Bone level measured histomorphometrically were found to be 0.85 mm more apically, compared to that measured radiologically (P = .001). Furthermore, statistically significant correlations (P > .02) were not found between the Periotest values of the calcium-phosphate-coated and uncoated implants for (1) the first thread in contact with bone, or (2) with the total number of threads in contact with bone. It was concluded that the radiologic data overscored the real marginal bone level around screw-shaped oral implants, and that the Periotest device is neither able to discriminate between the first thread nor between the total number of threads in contact with bone.

Dissolution of stainless steel type 304 in artificial saliva was studied by electrochemical methods, electron spectroscopy for chemical analysis, and atom absorption spectroscopy. The samples were polarized in the -400 mV (saturated calomel electrode) to -50 mV (saturated calomel electrode) range. The total thickness of the passive film was found to be 25 ± 3 A, independent of the potential. The passive film consists of a duplex structure: an inner laye r of (Cr0.5Fe0.5)xO3 and an outer layer of a mixture of Cr(OH)3 and (CrxFey)PO4.2H2O. The analysis indicated that 1 1 ug/cm2 of the alloying elements were disollved during exposure for 1 year.

Reaction times were employed to assess whether implants have longer detection times than natural teeth. A soft push was applied to an endosseous implant or to the corresponding natural tooth. Patients were asked for a speeded manual response upon the detection of the push. The temporal interval from the onset of the push to the onset of the manual response denoted the reaction time. This measure was only slightly longer for endosseous implants than for natural teeth, indicating that an implant's ability to detect rapid load changes is almost unimpaired.

This study describes a novel animal model of the maxillary sinus floor augmentation procedure used to assess bone formation during 12 weeks in response to a recombinant human bone morphogenetic protein-2 (rhBMP-2)/absorbable collagen sponse (ACS) sinus implant. A buffer-ACS implant was used as a control. Animal response was monitored using computerized tomography and physical, hematologic, gross pathologic, and histologic evaluations. The rhBMP-2/ACS implants maintained a relatively constant size postsurgery and showed a time-dependent increase in mineralization. The buffer/ACS control implants failed to mineralize and were resorbed by 4 weeks. The model served effectively and without complication. Results indicate rhBMP-2/ACS implants deserve consideration as alternatives to traditional grafting procedures.