A prospective, randomized, controlled, multicenter evaluation of extraction socket preservation comparing two bovine xenografts: clinical and histologic outcomes.

The aim of this prospective, randomized, controlled, multicenter study was to evaluate and compare the histologic and histomorphometric aspects of extraction sockets grafted with two commercially available bovine bone xenografts: Endobon (test group) and Bio-Oss (control group). The study was designed to ensure that baseline variables between groups were as similar as possible to allow for a direct comparison of graft healing characteristics. Thirty-eight patients contributed 62 augmented extraction sites to the study. All sites were grafted with one type of bovine bone mineral and covered with a resorbable collagen membrane for 6 months of healing prior to implant placement surgery. The histologic outcomes between the two treatment groups are similar, with de novo bone (mean ± SD) for the test group at 28.5% ± 20% and for the control group, 31.4% ± 18%. Histologic specimens also include membrane remnants. All but two implants integrated successfully after 1 year of follow-up. This investigation provides support for the efficacy of bovine bone xenograft for socket preservation when subsequent implant placement is planned.

A prospective, multicenter, randomized-controlled 5-year study of hybrid and fully etched implants for the incidence of peri-implantitis.

BACKGROUND: The dual acid-etched (DAE) implant was commercially introduced in 1996 with a hybrid design incorporating a machined surface in the coronal region from approximately the third thread to the seating surface. This design was intended to reduce the risks of peri-implantitis and other related soft tissue complications that were reported for implants with surface roughness in the coronal region. The objective of this prospective, randomized-controlled clinical trial was to determine the incidence of peri-implantitis for a fully etched implant with the DAE surface extending to the implant platform. METHODS: Patients had implant sites randomly assigned to receive one hybrid control implant and at least one fully etched test implant in support of a short-span fixed restoration to ensure that variables (e.g., demographics, jaw locations, and bone density) were consistent between groups. Prostheses were inserted 2 months after implant placement with follow-up evaluations scheduled annually for 5 years to assess mucosal health based on bleeding on probing, suppuration, and probing depths. Evaluations also included radiographic and mobility assessments. RESULTS: One hundred twelve patients who were enrolled at seven centers received 139 control and 165 test implants (total: 304 implants). With >5 years of postloading evaluations, there was one declaration of peri-implantitis associated with a control implant that was successfully treated later. Clinical probing and radiographic assessments did not reveal differences between groups in mucosal health outcomes or other signs of peri-implantitis. CONCLUSION: Five-year results of this randomized-controlled study showed no increased risk of peri-implantitis for fully etched implants compared to hybrid-designed implants.

A prospective, randomized, controlled comparison of platform-switched and matched-abutment implants in short-span partial denture situations.

Recent observations suggest that less bone loss may result from placing a more medialized abutment on an implant (platform switching). The objective of this study was to measure the radiographic crestal bone loss and biologic width around conventional and platform-switched implants. Implants were randomly assigned into conventional or switched categories within the same prosthesis. Twenty-five implants were placed and observed in the mandibles of 10 patients for 2 years. A regression analysis demonstrated a significant difference between groups (P < or = .0001). These findings suggest that less crestal bone loss occurs around a platform-switched dental implant versus a conventional implant.

Osseointegration of Osseotite and machined-surfaced titanium implants in membrane-covered critical-sized defects: a histologic and histometric study in dogs.

The texture of an implant's surface can influence the rate and extent of bone fixation as expressed by the amount of linear bone-to-implant contact (BIC). The purpose of this study was to compare the bone density and linear BIC between Osseotite and machined-surface implants placed in bony defects without graft material and covered by a membrane. Thirty 2 mm diameter, 10 mm length custom implants were prepared for this study having a 'split surface,' with one side having the acid-etched surface and the opposite side having a machined surface. Defects were created in the iliac wing of three adult mongrel dogs where a 6-mm-diameter drill was used to generate a 5-mm-deep defect. The implants were inserted into the center of the defect with 5 mm secured into the bone leaving 5 mm free in the defect with a 2 mm gap between the implant and surrounding bone. Expanded polytetrafluroethelyene membranes were placed over the defect sites stabilized with Biotack pins. The healing times were 2, 3, and 5 months. Histologic and histometric analysis showed significantly lower BIC in the defect region as compared with the portion of implant placed into native bone for both implant surfaces in all groups. There was no difference in BIC values at 2- and 5-month periods between the two surfaces in the regenerated area, while BIC values for Osseotite surfaces were significantly higher than the machined surfaces at 3 months' healing time. Changes in bone density, observed between the three groups, affected correspondingly the BIC values in both implant surfaces, the effect being more pronounced in the Osseotite surface.

Reintegration success of osseotite implants after intentional countertorque liberation in the endentulous human mandible.

PURPOSE: Implants that rotate during abutment screw tightening may not necessarily constitute implant failure. This prospective study was designed to determine to what degree integrated implants could gain a state of reintegration after intentional countertorque to liberation from the bone. MATERIALS AND METHODS: There were 11 patients with fully edentulous mandibles restored with 2 "clinical" implants (3.75 x 10 mm) placed in the canine sites and an additional nonused "test" implant (3.75 x 10 mm) placed at the symphysis of the anterior mandible. At second-stage surgery, the test implant was countertorqued (T1) using a torque-metering wrench until it detached from the bone. The implant was returned to its original position and allowed to heal for a period until a second countertorque test (T2) was performed. In group A, patients (n = 5) received the countertorque T1 at 3 months and T2 at 5 months. In group B (n = 6) T1 was at 1.5 months, and T2 was at 3.5 months. After completion of T2, the group A test implants were removed with a 5-mm trephine for histologic examination. RESULTS: For both groups, peak forces, all higher than 37.4 Ncm at T1, indicate that all implants were integrated. At T2, torque values were higher than T1 values for most of the test implants. The clinical implants were restored with "patrix" abutments and an overdenture. Histology staining showed distinction between old and new bone, which formed during the remodeling process. DISCUSSION: The increase in peak forces needed to detach implants at T2 may be explained by bone-to-bone healing or the additional bone contact promoted by bleeding that occurred during the T1 procedure. CONCLUSION: The results suggest that all implants were reintegrated after being intentionally countertorqued to liberation and resumed healing in the original osteotomy position.

Direct assessment of profilometric roughness variability from typical implant surface types.

PURPOSE: Protocols for quantifying the surface roughness of implants are varied and dependent upon the roughness parameter produced by the particular measurement device. The objective of this study was to examine the accuracy and precision of typical roughness characterization instruments used in the dental implant industry. MATERIALS AND METHODS: The average roughness (Ra) was measured using 2 common surface characterization instruments: an interferometer and a stylus profilometer. Titanium disks were prepared to represent 4 typical dental implant surfaces: machined, acid-etched, hydroxyapatite-coated, and titanium plasma-sprayed. Repeated measurements from multiple sites on each surface were undertaken to establish statistical inferences. Qualitative images of the surfaces were also acquired using a laser scanning confocal microscope. After surface measurements were conducted, the disks were diametrically cut and cross-sectional profiles were examined using a scanning electron microscope (SEM) as a comparative measure of surface topography. An analysis of variance was applied to isolate the effects of the measurement site, measurement sequence, surface treatment, and instrument type on Ra values. RESULTS: The results indicated that surface treatment (P = .0001) and instrument (P = .0001) strongly influenced Ra data. By design, measurement site (diametrical: P = .9859; area: P = .9824) and measurement sequence (P = .9990) did not influence roughness. In the assessment of individual instrument accuracy, the interferometer was the most accurate in predicting SEM-based roughness (P = .6688) compared with the stylus (P = .0839). As a measure of aggregate precision over all measurements, the most repeatable instrument was the stylus (coefficient of variation [CV] = 0.108), followed by the interferometer (CV = 0.125) and SEM (CV = 0.273). DISCUSSION: These results indicate dependencies in accuracy and precision related to the surface characterization technique. CONCLUSION: Instrument variability may obscure functional correlations between implant surface topography and osseointegration.

Dual-etched implants loaded after 1- and 2-month healing periods: a histologic comparison in baboons.

The purpose of this study was to evaluate the effect of early loading of Osseotite dual acid-etched commercially pure titanium dental implants in an established baboon model. Implant sites were prepared by removal of premolars and first molars at maxillary and mandibular sites in 10 adult female baboons (Papio anubis). The resultant edentulous ridges were allowed to heal for 6 weeks. Following the placement of 80 implants, 2-mm healing abutments were placed on each implant and protruded through the mucosa after flap closure. Each implant was functionally loaded with a single crown after either 1 month (n = 40) or 2 months (n = 40) of implant healing. All implants were removed in block section after 3 months of functional loading and prepared for histologic evaluation. Photographs of histologic slides were digitized for data collection. The amount of osseous tissue contact along the implant surface in the buccolingual plane was determined using image analysis. The fraction of direct bone-tissue contact along a standardized region of each implant perimeter was calculated and compared using analysis of variance. Implants loaded after 1 month of healing had a mean of 76.6% + 14.4% bone contact, and implants loaded after 2 months of healing had a mean of 77.2% +/- 12.2% bone contact. Statistically, the 1- and 2-month groups were similar (P = .81). No implant failures were observed in either treatment group. Reducing the surgical healing time from 2 months to 1 month did not statistically affect the amount of bone observed at the tissue-implant interface in baboons under functionally loaded conditions.