The International Journal of Oral & Maxillofacial Implants, 05/1999

Computer-assisted planimetry, computer-assisted lineal analysis, and point-counting stereology have been compared with respect to their reproducibility and the time required to analyze bone-implant integration. Sections of 6 threaded dental implants selected from a bone augmentation experiment for their wide range of new bone formation were analyzed by each method 3 times. The bone density and percentage of osseous integration were evaluated at 4 sites around each implant section. It was found that computer-assisted planimetry demonstrated a modest but significantly greater variance (P .05) in bone density estimates when compared to the computer-assisted lineal analysis and point-counting methods. Computer-assisted planimetry requires a different method of measuring each parameter and separate fields of view to evaluate fields distant from the implant. However, this can all be accomplished with line probes, as in computer-assisted lineal analysis, which extend from the implant surface into the surrounding alveolar bone. Whereas computer-assisted planimetry requires a separate identification of the perimeter of each field to be analyzed (next to and distant from the implant), computer-assisted lineal analysis allows expansion of the field to be evaluated without creating a new field of view. Also, following a limited learning curve, both point-counting and computer-assisted lineal analysis required less time to complete than did computer-assisted planimetry. Keywords: bone density, histomorphometry, osseointegration

A total of 127 partially edentulous patients, treated according to the Brånemark protocol, was followed for 10 years after completion of prosthetic treatment. The patients ranged in age from 18 to 70 years, and 57% were female. Four hundred sixty-one implants were placed in 56 maxillae and 71 mandibles. In 125 patients, 163 fixed partial prostheses were attached to the implants; a majority of the prostheses (83%) were located in posterior regions. At the end of the 10-year period, 73% of the implants could be traced either as failed or in function, providing cumulative implant survival rates of 90.2% and 93.7% for the maxilla and mandible, respectively. Of the original fixed prostheses, 63% (cumulatively 86.5%) were still in use, whereas the level of continuous cumulative prosthesis function, including primary and remade restorations, was 94.3% at the end of the evaluation period. Marginal bone resorption at the implants was low (mean = 0.7 mm), and mucosal health was good. No severe complications apart from the above-mentioned implant and prosthetic failures were reported. The Brånemark Implant System is a safe and predictable method for restoring partially edentulous patients, as demonstrated by this 10-year follow-up investigation. Keywords: Brånemark System, osseointegration, partial edentulism, titanium implants

The goal of this study was to provide evidence to support simplified treatment of mandibular edentulism using denture fabrication and implant placement to circumvent the need for second-stage surgeries or prosthodontic superstructures. A 5-year prospective clinical trial is reported, which involved treatment of mandibular edentulism using the single-stage surgical placement of a TiOblast microthreaded titanium screw implant with immediate replacement of a relieved mandibular overdenture and eventual retention of the overdenture with reduced ball abutments. Fifty-eight patients were treated; 116 implants were placed using a single-stage surgical approach, with a duplicate mandibular denture as the tomographic/surgical template. Mandibular dentures were relieved and relined with a tissue conditioning material and placed immediately after implant surgery. After 3 months, Conical Seal Design ball abutments were placed and attachments were secured in the overdentures by heat-polymerizing laboratory reline methods. Five of the 116 consecutively placed implants failed at 2 to 4 months, providing an immediate implant survival rate of 95.69% at the time of attachment connection. Pain and inflammation were not common to all failures, and infection was not reported in any of the 5 failures. The immediate placement of implants by a single-stage surgical procedure in the parasymphyseal region of the mandible, followed by placement of a relined mandibular denture, results in predictable and asymptomatic healing of implants that display the clinical and radiographic features of osseointegration. Encouraging results at the immediate observation period (attachment connection) must be tempered by the need for prudent and detailed clinical and radiologic evaluation over the 5-year trial period. Keywords: endosseous implants, overdentures, single-stage surgery

Previous in vitro studies have shown that a mean gap of less than 4 µm between prefabricated crowns and implants of the Ha-Ti implant system is not a barrier to infiltration by Staphylococcus aureus. These studies confirmed earlier in vivo work showing that a multitude of oral microorganisms could colonize and infiltrate these gaps. In the present investigation, 30 Ha-Ti implant-crown assemblies were tested for bacterial leakage after the gaps were sealed with the chlorhexidine-containing varnish Cervitec. S. aureus leakage into the totally submerged test specimens was detected in 1 of 5 samples incubated for 4 weeks, while no leakage was detected in specimens incubated for 3, 5, 6, 7, and 8 weeks. When the sealed test specimens were partially submerged (that is, excluding the screw hole of the crown) and incubated for 3 to 11 weeks, none of the internal surfaces of the 30 test specimens manifested contamination. The clinical relevance of gap sealing in maintaining inflammation-free marginal mucosa and in achieving clinically successful treatment of peri-implantitis has yet to be determined. Keywords: bacterial leakage, dental implants, prefabricated crowns

The purpose of this study was to investigate the crystallographic characteristics of 3 sets of plasma-sprayed hydroxyapatite (HA) coatings prepared with different degrees of crystallinity on Ti-6Al-4V substrates. X-ray diffraction analyses were performed on the coatings to determine mean percent crystallinity, calcium phosphate phases present, average crystallite size, and residual strain. The mean percent crystallinity for the 3 sets of coatings ranged from 49 to 60%. The coatings that achieved the highest crystallinity consisted almost entirely of HA. As the coating crystallinity decreased, increasing amounts of a- and ß-tricalcium phosphate and tetracalcium phosphate were detected. The mean HA crystallite size for the 3 sets of coatings ranged from 0.02 to 0.05 µm. Differences in mean interplanar spacing for selected crystallographic planes of HA, compared with the pure ICDD (International Center for Diffraction Data) powder standards, implied that the coatings were in an uneven state of tensile strain. Keywords: crystallinity, hydroxyapatite, plasma-spraying, titanium, x-ray diffraction

Seventeen mostly elderly patients, 13 men and 4 women, were consecutively admitted for implant-prosthodontic treatment after they had undergone resection of malignant tumors in the oral cavity. A total of 53 dental implants (ITI-Straumann) was placed, 12 in the maxilla, 41 in the mandible. The prosthetic rehabilitation consisted of overdenture therapy in 15 patients, and 2 patients were treated with fixed partial prostheses. Thirty-three implants were prescribed for patients who received radiotherapy either before or after implant placement. The average dose varied between 50 and 74 Gy. Eighteen implants were located in grafted bone from the fibula, scapula, or hip. For 2 patients, hyperbaric oxygen therapy was also prescribed after osteoradionecrosis had developed. One implant was lost before prosthetic loading. During an observation period of up to 7 years after loading, 3 more implants were removed. All implant losses occurred in the mandibles of patients who had received radiotherapy. A life table analysis was performed, and the cumulative survival rates, calculated for 2, 3, and 5 years, were 93%, 90%, and 90%, respectively. No failures or complications were observed with technical components of the implants or prostheses. All prostheses could be maintained during the entire observation time. Although in the present investigation the survival rate of implants was slightly lower than under standard conditions, the treatment with implant-supported prostheses seemed to be advantageous for patients who had undergone intraoral resections. Keywords: implant prosthesis, irradiated bone, life table analysis, malignant tumors, oral implants

Maintenance of the integrity of the abutment/implant interface is essential and is dependent on the abutment screw retaining a preload. Evaluation of this joint is usually done by manual assessment. The purpose of the current study was to determine whether the Periotest instrument could be used to evaluate abutment screw loosening. A custom-designed apparatus was constructed to measure abutment screw loosening. Abutment screws were torqued to 10, 20, 32, and 45 Ncm and then loosened. Objective assessment of screw loosening was carried out with the Periotest device. Subjective evaluation was done by 3 experienced clinicians. The Periotest was found to be more sensitive than manual detection of abutment screw loosening. With a change of 2 in the Periotest value, it was found that the tensile preload in the joint was lost. While the Periotest was more sensitive than manual evaluation, the instrument was not sensitive enough to indicate deterioration of abutment screw loosening prior to loss of tensile preload. Keywords: abutment/implant interface, abutment screw, abutment screw loosening, Periotest, Periotest value, tensile preload

The aim of this investigation was to conduct a comparative histometric analysis of bone-implant interface between a rough titanium surface and smooth implants in low-density human jawbone after 3, 6, and 12 months of submerged, undisturbed healing. Six adult volunteer patients undergoing standard implant placement were enrolled in this project. Each patient received 1 smooth and 1 rough implant. After 3, 6, and 12 months, the implants were harvested for histometric analysis. The values of bone-implant contact were the following: 3 months smooth 6.2%, 3 months rough 58.9%, 6 months smooth 3.55%, 6 months rough 72.9%, 12 months smooth 6.7%, and 12 months rough 76.75%. The results showed that in low-density bone the rough surface dramatically enhanced the amount of bone-to-implant contact. Because of the small number of implants examined, definite conclusions cannot be drawn, even though the statistical analysis showed significant differences between the smooth and rough groups (P = .0129; F = 76.065). Nevertheless, a trend was evident in these observations: while a rough implant surface may enhance the rate of osseointegration, it is not able to significantly change the bone density, and an implant placed in low-density bone is at a higher risk of failure when occlusal loading begins. Keywords: histometry, human histology, implant surface, rough implants

The present study was undertaken to histomorphometrically analyze early peri-implant bone tissue reactions that occur after radiotherapy and to determine whether hyperbaric oxygen therapy (HBO) affects bone tissue at the microscopic level by altering bone morphology. Twelve rabbits received a single dose (15 Gy) of cobalt60 radiation to one hind leg and the other hind leg served as a control. Titanium screws were placed into the femur and tibia directly after irradiation. Six animals received HBO during the first 4 postoperative weeks. After 8 weeks of follow-up, bone specimens containing the screws were prepared for histomorphometry. Bone-metal contact and the amount of bone in the thread areas and in the mirror areas were measured in a blinded manner. Periosteal bone formation and bone remodeling decreased after irradiation; also after HBO treatment. Hyperbaric oxygen therapy improved bone formation in nonirradiated bone and to some extent also in the irradiated bone. Bone maturation was improved in the HBO animals after irradiation. It was concluded that irradiation reduces the capacity for osseointegration of titanium implants. Hyperbaric oxygen treatment may improve bone formation and especially has positive effects on bone maturation after irradiation. Keywords: acute tissue reactions, histomorphometry, hyperbaric oxygen treatment, irradiation, osseointegrated implants

During a 12-year period (1984-1996), 118 maxillary inlay autogenous bone grafts and 248 commercially pure titanium threaded root-form endosseous implants were placed in 54 consecutively treated patients with compromised maxillary bone. In this retrospective clinical study, 3 groups of patients were reviewed, group selection being based on anatomic location and surgical access to the recipient site. Group 1 included patients with bone grafts placed in the antrum floor via an intraoral antrostomy exposure, group 2 included patients with bone grafts placed in the nasal floor via an anterior intraoral nasotomy exposure, and group 3 included patients with bone grafts placed in the antral and nasal floor via an intraoral Le Fort I osteotomy downfracture exposure. Each patient received an implant-supported dental prosthesis. For the combined 3 groups, survival rates were 87% for endosseous implants and 100% for autogenous bone grafts. The success rate for the dental prostheses in the 3 groups was 95%. Sixty-nine dental prostheses functioned a mean of 57.1 months, whereas 3 prostheses required remaking because of implant loss. Of the medical and mechanical risk factors tabulated in this study, current use of nicotine, history of sinusitis, molar site implant placement, and shorter implant lengths had the most influence on implant failure. Keywords: atrophic maxilla, autogenous bone graft, endosseous implants

The purpose of this study was to investigate the rate of pull-out strength gain of an etched titanium implant surface. Rabbit tibiae were used to compare machined titanium and proprietary dual-etched titanium implants. Two custom cylindric implants (3 mm in diameter and 4 mm in length) were placed in each right anteromedial tibia in 31 rabbits. At weeks 1, 2, 3, 4, 5, and 8, the implants in 5 rabbits were subjected to failure shear loading in a pull-out test. For shear failure testing, each tibial segment was mounted in a precision alignment jig, and an Instron pull-out test was performed on each implant. Beginning at week 3, there was a statistically significant difference (P .01) between the dual-etched and the machined implants. There was a significant increase in strength for dual-etched implants between week 5 and week 8, while the machined implants did not show an increase during this time interval. The etched implants maintained a significantly greater pull-out strength for the remainder of the study, with a 3.2-fold greater mean strength at 8 weeks, equivalent to 6 months in humans. At 3 weeks, the etched implant's strength exceeded the strength that the machined implant had achieved at 8 weeks. In short-term healing in the rabbit tibia, the dual-etched surface demonstrated a more rapid rate of pull-out strength gain than the machined surface and remained significantly stronger throughout the 8 weeks of the study. Keywords: dual-etched titanium implants, healing speed, machined titanium implants, pull-out strength

The aim of this study was to compare the characteristics of the bone-to-implant interface of hydroxyapatite-coated and non-coated commercially pure titanium threaded implants after different periods of healing in humans. To eliminate possible variations of the results from differences in bone quality and in surgical techniques used in the different test and control sites, only one half of each implant was coated with hydroxyapatite. The coated portions of the implants showed a tendency toward a higher percentage of direct bone-to-implant contact at each period of healing that was observed, although the small number of specimens does not allow definitive conclusions to be made. Keywords: hydroxyapatite, osseointegration

The purpose of this investigation was to evaluate the outcome of treatment with implant-retained prostheses in patients suffering from Sjögren syndrome. Eight women were included in the study; all had suffered oral symptoms of Sjögren syndrome for many years. Seven patients were edentulous in both arches, and 1 patient was edentulous in the maxilla only. All patients reported poor or very poor comfort levels with their conventional dentures. It was the intention to treat each arch that showed subjective and objective denture problems with a complete fixed prosthesis after placement of 6 implants. In all, 54 Brånemark dental implants were placed in these patients. No implants were lost, but 7 implants in 4 patients were clinically not osseointegrated at the time of the abutment connection procedure. Because of nonosseointegrated implants and lack of jawbone, 3 arches were treated with an implant-retained overdenture. Fixed prostheses were made with a titanium framework of premachined components welded together (Procera) and acrylic resin teeth and flanges. Patients answered a questionnaire regarding their oral function before the onset of treatment and 1 month and 2 years after treatment. An average radiographic bone loss of 0.7 mm from the time of implant placement to 1 year after treatment was observed; additional bone loss of less than 0.6 mm was recorded 4 years after treatment. During the first year of function 2 implants lost osseointegration. No prostheses were lost or remade. Treatment with implant-retained prostheses considerably increased the prosthetic comfort and function of the patients. Two years after prosthetic treatment, only 1 patient indicated poor comfort of the prostheses, while the remaining patients reported good or very good comfort levels. Keywords: complete denture, dental implants, fixed prosthesis, implant-supported prosthesis, osseointegration, overlay denture, patient satisfaction, prosthesis retention, Sjögren syndrome

Bone resorptive patterns may prevent the ideal placement of endosseous implants. Numerous techniques have been described to create a more favorable surgical site for implant placement. This retrospective review was conducted to determine the frequency of need for implant site preparation in an outpatient clinical setting. In addition, different techniques of surgical site preparation were evaluated to determine their frequency of use and surgical outcome. A history review was conducted of all consecutively treated partially edentulous patients between January 1993 and December 1997. This review evaluated the number of implants placed, the age and gender of the patient, the type of graft used, and the status of the implant. In all, 542 patients were seen in this time interval, with a total of 1,313 implants placed. Implant site preparation was needed in 4.4% of the patients, with the requirement for grafts occurring more frequently in the maxilla. Implant site preparation is a relatively infrequent requirement in the general population. Grafts are required more frequently in the maxilla than in the mandible. Complications following grafting were relatively infrequent and were not severe. Keywords: grafting, implants, outcome assessment, site preparation

In a retrospective study, Kaplan-Meier implant survival analyses were conducted on 883 patients with 1,964 implants of various systems placed, followed up, documented, and statistically evaluated at an oral surgery and dentistry practice between January 1981 and January 1997. The goal of this study was to evaluate the success of osseointegrated implants of the Brånemark, Frialit-1 (Tübinger Implant), Frialit-2, and IMZ systems and Linkow blade implants. For all systems, mandibular implants were generally more successful than maxillary implants. The preprosthetic loss rate was 1.9%, and 4.3% of implants were lost after prosthetic treatment. The lowest loss rates were seen with implants in intermediate and distal extension spaces and with single-tooth replacements using IMZ, Frialit-2, and Brånemark implants. In edentulous arches, implants of the IMZ and Brånemark systems had the lowest failure rates. Keywords: dental implants, longitudinal study, long-term results