Bone reactions around dental implants subjected to progressive static load: an experimental study in dogs.

OBJECTIVE: To evaluate histologically and histomorphometrically, the peri-implant bone reaction around implants subjected to controlled progressive orthodontic loading. MATERIALS AND METHODS: In three beagle dogs, bilateral edentulous flat alveolar ridges were created in the maxillary area posterior to the canines. After 8 weeks of healing, 24 implants (Biomet 3i) were inserted in the edentulous sites. Two experimental groups were created. Progressive loading group: Twelve implants were left to heal for 8 weeks uncovered, and abutments were adapted and connected by pairs with Ni-Ti orthodontic springs. A gradual static force of 100, 200 and 300 g was applied for a 3-week period each. Thus, a total progressive loading period of 9 weeks was exercised. Unloaded control group: Twelve implants were left to heal undisturbed. At the end of the experimental period, all implants of both groups were removed with the surrounding bone. Histologic and histomorphometric analyses were performed, and the following parameters were measured: bone-to-implant contact, bone density 1 and 2 mm distant to the implant threads and crestal bone resorption. Median regression models are used for statistical analysis. RESULTS: Implants of the progressive loading group exhibited significantly higher percentage of bone-to-implant contact compared to the unloaded control implants (P = 0.018). Bone density 1 and 2 mm distant to the threads was found to be the same between the two groups (P = 0.734 and P = 0.961, respectively). Crestal bone resorption did not differ between loaded and unloaded implants (P = 0.813). CONCLUSION: The application of progressive loading by controlled orthodontic force on osseointegrated implants provoked significant increase in the percentage of bone-to-implant contact of the low-density bone of the dog maxilla.

Comparison of histomorphometry and microradiography of different implant designs to assess primary implant stability.

OBJECTIVES: To contribute toward optimizing the long-term stability of dental implants. Our working hypothesis was that the degrees of immediate implant-bone contact, and hence of primary stability, would demonstrably differ between implant systems due to their different external geometries and thread designs (macro-design). This demonstration was provided in a bovine model (ex vivo) by employing and comparing histomorphometry and microradiography as evaluation methods. MATERIALS AND METHODS: A total of 120 implants, representing six different implant thread designs, were inserted following the recommended surgical protocol in ribs of freshly slaughtered cattle. Twenty specimens of implants with surrounding bone were prepared per system and were divided into two equally sized groups of 60 specimens for analysis by either histomorphometry or micro-computed tomography. Data were analyzed by Mann-Whitney U test (P ≤ .05). RESULTS: One of the implant systems, featuring a slight tapered external geometry and a progressive thread design, consistently revealed the most favorable bone-implant contacts in both histomorphometric and microradiographic evaluations. Overall, consistently higher values of bone-implant contact were obtained with the microradiographic than the histomorphometric approach, and this difference reached statistical significance in three of the six implant systems tested. CONCLUSIONS: Progressive threads offering a bone-condensing effect can significantly help to maximize implant-bone contact percentages. Compared to histomorphometry, microradiography is likewise a suitable method to evaluate bone-implant contact, offering the additional benefits of being noninvasive and less time consuming.

Bone regeneration using beta-tricalcium phosphate in a calcium sulfate matrix.

The aim of the study was the histomorphometric comparison of the osteogenic potential of beta-tricalcium phosphate (beta-TCP) alone or in a calcium sulfate matrix. Three round defects, 10 mm (diameter) x 5 mm (depth), were created on each iliac crest of 4 dogs. The defects were divided into 3 groups. Ten defects were filled with beta-TCP in a calcium sulfate (CS) matrix (Fortoss Vital; group A), 10 defects were filled with beta-TCP alone (Fortoss Resorb; group B), and 4 defects were left ungrafted to heal spontaneously (group C). All defects were left to heal for 4 months without the use of a barrier membrane. Histologic evaluation and morphometric analysis of undecalcified slides was performed using the areas of regenerated bone and graft remnants. All sites exhibited uneventful healing. In group A sites (beta-TCP/CS), complete bone formation was observed in all specimens, graft granules dominated the area, and a thin bridge of cortical bone was covering the defect. Group B (beta-TCP) defects were partially filled with new bone, the graft particles still dominated the area, while the outer cortex was not restored. In the ungrafted sites (group C), incomplete new bone formation was observed. The outer dense cortical layer was restored in a lower level, near the base of the defect. The statistical analysis revealed that the mean percentage of new bone regeneration in group A was higher than in group B (49.38% and 40.31%, respectively). A statistically significant difference existed between the 2 groups. The beta-TCP/CS group exhibited significantly higher new bone regeneration according to a marginal probability value (P = .004 < .05). The use of beta-TCP in a CS matrix produced significantly more vital new bone fill and preserved bone dimensions compared with the use of beta-TCP alone.

Effect of autogenous harvest site location on the outcome of ridge augmentation for implant dehiscences.

Treatment planning for the placement of an implant in a site with a thin crestal ridge should address the probability that a buccal dehiscence will result. The aim of the present investigation was to perform guided bone regeneration (GBR) around implants with buccal dehiscences and evaluate the outcomes of using autogenous bone grafts harvested from three different intraoral sites. Forty-six Osseotite implants, 4 mm in diameter, were placed in thin crestal ridges, resulting in an uncovered implant surface from the buccal aspect. The lengths of the buccal dehiscences ranged from 3 to 7 mm as measured from the implant cervix to the most apical extent of the uncovered threads. A standard GBR technique was carried out to augment the bone defect around the buccal implant surface immediately after implant placement. The cases were divided into three groups according to receipt of an autogenous bone graft from the ramus, tuberosity, or mandibular symphysis. In all cases, e-PTFE membranes were used to cover the grafted areas. Grafted sites were exposed after 6 months, membranes were removed, and residual distance between the implant cervix and most uncovered thread was recorded. All grafting materials were able to produce a certain degree of bone regeneration. In terms of bone change level, the three groups were not equal. The mandibular symphysis group exhibited the highest mean bone growth level, followed by the ramus group. The tuberosity produced the poorest result. Mandibular and ramus autogenous bone grafts represent the best choice in materials for GBR procedures around implants, while tuberosity bone grafts can be used as an alternative.

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.

Bone regeneration around implants using spherical and granular forms of bioactive glass particles.

PURPOSE: It has been reported that previous Biogran (3i Implant Innovations, Inc., Palm Beach Gardens, FL) can be converted in vitro into hydroxyapatite (Biogran II) to accelerate new bone formation. The purpose of this study was to evaluate the bone regeneration around implants placed in critical-sized defects in rabbit tibia using granular and spherical forms of Biogran II in regards to implant contact, bone-to-graft contact, bone graft area, and total bone volume. MATERIALS AND METHODS: Twelve adult New Zealand rabbits were used, offering 24 surgical sites (1 in each tibia), where 6-mm round defects were created allowing the homocentric insertion of a screw type experimental implant with Osseotite (3i Implant Innovations, Inc.) surface. Half of the defects (group A) were filled up with spherical and half (group B) with granular forms of Biogran II. Ossix (3i Implant Innovations, Inc.) membranes covered the surgical sites. RESULTS: The histological evaluation after 8 weeks showed new bone formation in both groups, without any statistically significant differences in regards to bone-to-implant contact, bone-to-graft contact, bone graft area, and bone volume. Both dissolution of the outer shell and inner silica gel of the particles were observed mostly in spherical particles. In addition, new bone formation within the protected pouch interconnected with the surrounding new bone was observed exclusively in spherical particles of Biogran II. CONCLUSION: Faster dissolution of both outer and inner portions of spherical particles of Biogran II led to better integration with the surrounding new bone during an 8-week period of healing.

Osseointegration of Osseotite and machined titanium implants in autogenous bone graft. A histologic and histomorphometric study in dogs.

It has been shown that a roughened implant surface results in a higher percentage of bone to implant contact (%BIC) than a machined one. A modified implant surface using a dual thermo-acid etching process (Osseotite) has been introduced and evaluated clinically, mechanically and histologically. The aim of the present study was the histological evaluation of the %BIC between the Osseotite or machined surfaces and the autogenous bone graft. Twenty-two custom-made split-type 10-mm-long implants having two opposing surfaces (Osseotite and machined) were placed between the cranial and caudal dorsal iliac spine at the iliac wing of two adult mongrel dogs. An artificial bone defect was created leaving a 2 mm empty space around the coronal 5 mm of the implants, while the apical 5 mm was stabilized in the existing basal bone. The defects around the implants were filled with particulate autogenous bone graft, covered by an Osseoquest membrane, and left to heal for 5 months. All inserted implants showed a complete integration in the bone tissue. It was found that the resulting %BIC at the Osseotite surface was significantly higher than at the machined one in both regenerated (46.44+/-15.81% vs. 28.59+/-12.04%) and basal bone areas (32.32+/-15.09% vs. 17.25+/-7.40%). The findings of this study imply that the use of autogenous bone graft resulted in significantly higher %BIC values in the regenerated area than in the basal bone area itself, for both implant surfaces.