Critical-sized marginal defects around implants treated with xenografts in rabbits.

BACKGROUND: Healing of critical-size defects is a well-known problem that has been challenged in several studies. The aim of the experiment was to evaluate bone formation and osseointegration of implants installed in critical defects of the mandibular body simultaneously grafted with Bio-Oss® or Cerabone®. MATERIAL AND METHODS: Defects, 10 mm wide and 3 mm deep, were prepared at both lateral aspects of the mandible in 12 rabbits. One implant was installed in the center of the defect, and bovine xenografts produced either at low (Bio-Oss®; Low-T) or high (Cerabone®; High-T) temperatures were used to fill the defects. A collagen membrane was placed to cover the sites. Healing was evaluated 10 weeks after surgery. RESULTS: In both groups, most sites showed optimal healing with closure of the coronal entrance of the defects. However, residual defects occupied by soft tissues and biomaterial particles were observed, even though generally limited to some regions of the defect. Osseointegration of the implant surface in the region of the defect was poor in both groups. CONCLUSIONS: Circumferential marginal critical-size defects around implants filled with bovine xenografts presented regions with a complete healing in both groups. However, the healing was not complete at all regions in most defects; therefore, a complete optimal healing of critical-size marginal defects cannot be predicted.

Implants Placed with a Ring Technique Using Inlay and Onlay Block Xenografts in the Mandible of Rabbits.

BACKGROUND: Xenogenous bone has been proposed as an alternative to overcome the disadvantages of autogenous grafting. The aim of the present study was to study bone dynamics at inlay and onlay xenografts used for bone augmentation applying a ring technique. METHODS: The bone at the lateral surface of the mandibular angle of 12 adult male New Zealand White rabbits was exposed bilaterally. The cortical layer received multiple perforations on one side of the mandible, and a xenograft block of collagenated cancellous equine bone, 7 mm in diameter and 3 mm in width, was fixed on the prepared surface using an implant (onlay group). On the opposite side, a defect 7 mm in diameter and 3 mm in depth was prepared, and the xenograft block was adapted to the defect and fixed with an implant (inlay group). RESULTS: After ten weeks of healing, in the onlay grafts, new bone was mainly formed on the trabeculae surface, reaching in some specimens the most coronal regions of the block. In the inlay grafts, new bone was found arranged on the trabecular surfaces but also occupying the spaces among the trabeculae. The entrance of the defect was often found close to the top of the block by newly formed bone. A higher percentage of new bone was found in the inlay (19.0 ± 9.3%) compared to the onlay (10.4 ± 7.4%) groups (p = 0.031). The mean gain in osseointegration at the implant in relation to the base of the original 3 mm deep defect was 0.95 ± 1.05% in the onlay group and 0.78 ± 0.71% in the inlay group (p = 0.603). CONCLUSION: The inlay grafts exhibited a higher new bone percentage than the onlay block grafts possibly due to the defect conformation that presented more sources for bone growth. The trabecular conformation and the composition of the grafts made possible the expression of the osteoconductive properties of the material used. This resulted, in several specimens, in the growth of bone on the graft trabeculae toward the most superior regions in both groups and in the closure of the coronal entrance of the defects in the inlay group. The clinical relevance of this experiment is that the ring technique applied as an inlay method could be suitable for bone augmentation.

Histological Comparison of Collagenated Cancellous Equine Bone Blocks Used as Inlay or Onlay for Lateral Bone Augmentation in Rabbits.

BACKGROUND: The conformation of the recipient site for an inlay graft presents an increased contact with the parent bone compared to an onlay graft. This might favor bone growth within the inlay compared to onlay grafts. Hence, the objective of this study was to compare the bone incorporation and remodeling processes of xenogeneic en bloc grafts placed using two bone grafting techniques, i.e., onlay vs. inlay. METHODS: In this prospective, randomized, split-mouth study (test and control sides in the same animal), two bone grafting techniques were comparatively evaluated. The lateral aspect of the rabbit mandible was used as the recipient site, bilaterally. On one side of the mandible, the cortical bone was perforated with drills to allow a better bone formation from the bone wound and the marrow spaces. A xenogeneic bone block was fixed in the center of the prepared region, representing the onlay site. On the other side of the mandible, a 7 mm wide and 3 mm deep circumferential defect was prepared using trephines and drills. A xenogeneic bone block was fixed in the center of the defect, representing the inlay site. Two healing periods were applied in the study: 2 and 10 weeks, each represented by 10 rabbits (n = 10 for each period). RESULTS: After 2 weeks of healing, the mean percentage of new bone was 10.4% and 23.3% at the onlay and inlay grafts, respectively (p = 0.022). After 10 weeks of healing, new bone increased to 13.2% at the onlay sites and 25.4% at the inlay sites (p = 0.080). In the 10-week period, the inlay grafts presented a homogeneous growth of new bone in all regions, while in the onlay grafts, low percentages of new bone were observed in the external regions. CONCLUSION: The percentage of new bone increased faster and was higher in the inlay grafts than in the onlay grafts. This outcome might be related to the self-contained conformation of the recipient site in the inlay group, which offered more sources for new bone formation compared to the one-wall conformation of the recipient sites in the onlay group. The osteoconductive properties of the biomaterial allowed the newly formed bone to reach the most peripheral regions in both groups. The osteoconductive properties of the biomaterial, together with the protection offered by the collagen membrane, allowed marginal closure of the defects by newly formed bone in the inlay group.

Fixation screw minimizes bone graft loss following autogenous lateral block graft augmentation: An experimental in vivo study.

PURPOSE: Assess the role of tenting screws in the remodeling processes of autogenous bone blocks used for mandibular lateral augmentation in rabbits. METHODS: Eighteen rabbits, approximately 3.5-4.0 kg of weight and 4-5 months of age, were included in this study. One lateral side of the angle of the mandible was augmented with block autografts. Animals were euthanized after 7, 20 and 60 days of healing, respectively. Biopsies were taken for each period and specimens underwent microtomographic scanning. The total volume (TV, mm3), bone volume (BV: residual graft plus new bone, mm3), periimplant bone volume (PIBV), bone implant contact (BIC) along the screw and linear bone gain at five vertical points symmetrically dispersed from the fixation screw in the midline were measured. ANOVA and the t-test were performed. RESULTS: The total volume (TV) of autografts decreased between 7 and 60 days from 258.13±15.3 mm3 to 107.2 ± 17.5 mm3 (p < 0.05). Contraction rates of 58.5% were observed. BV was 52.8 ± 7.7 mm3, 27.2 ± 11.1 mm3, and 33.1 ± 2.8 mm3 after 7, 20, and 60 days of healing, respectively. PIBV and BIC remained unchanged along time demonstrating no contraction around the screw. Total linear bone gain demonstrated a total of 18% linear contraction after 60 days. Point 1, demonstrated no changes along time representing no resorption along time. Points 2 and 4 demonstrate a minimum linear contraction (10-15%) with borderline significance. Resembling the total results, contraction starts after 20 days. Points 3 and 5 demonstrate a statistically significant contraction (p<0.05) of 35-40% starting at 20 days. CONCLUSION: Tenting screws may reduce bone resorption symmetrically in a model of lateral block augmentation.

Histomorphometric, Immunohistochemical and Microtomographic Comparison between Autogenous and Xenogenous Bone Blocks for Mandibular Lateral Augmentation in Rabbits.

BACKGROUND: The volumetric and biological behaviors of equine block grafts compared with autogenous block grafts have not yet been assessed. Hence, the aim of the present study was to compare-by means of histomorphometry, immunohistochemistry and microtomography-the graft incorporation and remodeling processes of autogenous and equine xenogenous bone blocks used for mandibular lateral augmentation in rabbits. METHODS: Autogenous bone grafts harvested from the iliac bony crest and equine block grafts were secured to the lateral aspect of the mandible angle of eighteen rabbits. The healing after 7, 20 and 60 days was assessed in six animals each period. RESULTS: After 60 days, new bone was present 24.2 ± 11.2% and 31.6 ± 13.3% in the autograft and xenograft groups, respectively. A better integration to the recipient sites was observed in the autogenous compared with the xenogenous blocks. CONCLUSIONS: Both xenogenous and autogenous bone blocks presented similar percentages of newly formed bone over time. However, bone volume, the quality of the grafted area and graft incorporation to the recipient sites were superior in the autogenous compared with the equine xenogenous graft sites.

Effects of Induced Malocclusion on Vertebral Alignment in Rats: A Controlled Study by CBCTs.

This study aimed to evaluate with CBCTs the alteration of vertebral alignment over time of induced malocclusion in rats. Crown pads increasing the vertical dimension of 0.5 mm were applied on the upper molars at one randomly selected side of the maxilla in rats (premature contact side) while the opposite side was left untreated (control side). Four groups were organized, ten animals each. In groups A, B, and C, the crowns were applied at time 0 (t-0). In group A, the crowns were removed after 2 weeks (t-2w) and euthanized after two more weeks, while in groups B and C, the animals were euthanized after 2 and 4 weeks (t-4w), respectively. No premature contacts were applied in group D. CBCTs were taken at t-0 in all animals before applying the crowns, at t-2w in group A before removing the crowns, and in all groups before the euthanasia. The changes in the iliac crest angle (ICA) that formed between the superior external margin of the iliac crest and the vertebral spine were evaluated. In groups A and B, after 2 weeks, the changes in ICA were statistically significant at p = 0.028 and p = 0.042, respectively. In group C, and in the control group D, the changes of ICA were not statistically significant (p = 0.058 and p = 0.414, respectively). In conclusion, the incease in monolateral occlusion in the molar region yielded a rotation of the lumbo-sacral segment towards the same side of the occlusal bite-raising.

Incidence of Sinus Mucosa Perforations During Healing After Sinus Elevation Using Deproteinized Bovine Bone Mineral as Grafting Material: A Histologic Evaluation in a Rabbit Model.

PURPOSE: To examine the reaction of mucosa over time to a close contact with biomaterial after sinus elevation performed with deproteinized bovine bone mineral (DBBM) granules of two different sizes. MATERIALS AND METHODS: Bilateral sinus mucosa elevation was performed in 18 New Zealand rabbits through access on the nasal dorsum. DBBM with granule dimensions of either 1 to 2 mm (large group) or 0.250 to 1.0 mm (small group) were used to randomly fill the subantral hollow spaces. Biopsy specimens of the experimental sites from six animals in each group were obtained 2, 4, and 8 weeks after the surgery. RESULTS: The integrity of the sinus mucosa was clinically evaluated during surgery using a ×2.5 magnifying visual device. The sinus mucosa in contact with the biomaterial granules was found to be thinned compared with the pristine mucosa in all periods examined. Three hundred fifty-two thinned zones were found considering all 36 sinuses treated. Perforations of the sinus mucosa with extrusion of granules toward the sinus were observed, increasing in number over time. In the 8-week healing period, five perforations in three sinuses and eight perforations in four sinuses were found in the large and small groups, respectively. No differences were seen between the large and small groups. The differences between 2 and 8 weeks were statistically significant for the thinned mucosa width in both the large and the small groups and for the number of sinuses and perforations for the small group. CONCLUSION: Thinning zones and perforations of the sinus mucosa were seen increasing in number over time in regions in contact with graft granules in both the large and small groups.

The Impact on the Healing of Bioactivation with Argon Plasma of a Xenogeneic Graft with Adequate Fixation but Poor Adaptation to the Recipient Site: An Experimental Study in Rabbits.

PURPOSE: To evaluate the impact on healing of bioactivation with argon plasma of a xenogeneic graft with adequate fixation but poor adaptation to the native host bone. MATERIALS AND METHODS: Xenogeneic grafts were either treated with argon plasma or left untreated and randomly secured with a titanium screw to both lateral aspects of the mandible angle of rabbits. A discrepancy was obtained between the xenograft and the mandible due to the convexity of the recipient site. Collagen membranes were placed on the grafts. Thirty animals were included and euthanized in groups of 10 after 2, 6, and 10 weeks, respectively. Histomorphometric evaluations were performed on ground sections. Newly formed bone was the primary outcome, while the distance between the peak of new bone inside the graft and the upper surface of the graft, the xenograft percentages, and the area of the xenograft were considered as secondary variables. The Wilcoxon test was applied for statistical analyses. RESULTS: After 2 weeks of healing, gaps of ~0.5 mm were observed at the interface between the graft and the recipient sites, and new bone was mainly located in the interface and within the inferior regions of the grafts. New bone increased over time in all regions, including those in the upper zones of the graft, reaching proportions of 20.3% ± 6.5% and 19.3% ± 7.4% (P = .484) after 10 weeks in the plasma and control groups, respectively. The mean distance between the peak of new bone inside the graft and the upper surface of the graft decreased between 2 and 10 weeks of healing from 1.4 mm to 0.4 mm and from 1.7 mm to 0.3 mm at the plasma and control sites, respectively. CONCLUSION: The xenogeneic grafts of both groups were incorporated into the recipient sites by newly formed bone that presented a growth close to the upper surface of the graft. The bioactivation with argon plasma did not improve healing.

Maxillary Sinus Augmentation Using Ceramic Alloplastic Granules or Paste: An Experimental Study in Rabbits.

BACKGROUND: Due to the lack of data comparing the biological behavior of two formulations, granules and paste, of alloplastic graft from microtomographic and histomorphometric points of view, the aim of the present experiment was to compare the histomorphometric and microtomographic healing of two formulations, i.e., granules (MR sites) or paste (MR-inject sites) of an alloplastic graft composed of a combination of beta-tricalcium phosphate and hydroxyapatite used for maxillary sinus lifting. METHODS: A sinus lifting procedure was carried out bilaterally in 20 rabbits, and the elevated space was filled with either paste or granules of an alloplastic material. A collagen membrane was placed on the antrostomy and the animals were euthanized after 2 or 10 weeks, 10 animals each group. Microtomographic and histological analyses were performed. RESULTS: Higher proportions of new bone formation were found at the MR, compared to the MR-inject sites both after 2 weeks (2.65 ± 2.89% vs. 0.08 ± 0.12%; p < 0.01) and 10 weeks of healing (34.20 ± 13.86 vs. 23.28 ± 10.35%; p = 0.022). CONCLUSIONS: It was concluded that new bone formation was faster in the MR sites, compared to the MR-inject. However, a longer time of healing should be allowed to make final conclusions about the efficiency in bone formation of the paste formulation of the biomaterial used in the present study.

Osteoconductivity of Bovine Xenograft Granules of Different Sizes in Sinus Lift: A Histomorphometric Study in Rabbits.

BACKGROUND: Due to the lack of data on bone-to-graft contact (BGC) over time in the various regions within the subantral space of the augmented sinus floor, the present study aimed to evaluate the osteoconductivity of deproteinized bovine bone mineral (DBBM) with granules of different sizes applied in maxillary sinus floor elevation. METHODS: A maxillary sinus augmentation was performed bilaterally in 18 rabbits using DBBM with particle dimensions of either 0.125-1.0 mm or 1-2 mm. The antrostomy was covered using a collagen barrier. The animals were euthanized in groups of six after 2, 4, and 8 weeks of healing. MicroCT and histological analyses were performed. RESULTS: After 2 weeks of healing, BGC was 10.9% and 11.9% for the small and large granule sites, respectively. After 8 weeks of healing, the BGC increased to 65% and 62% at the small and large granule sites, respectively. The highest values were located close to the bony walls and the bony window. New bone content developed between 2 and 8 weeks from 7.0% to 27.6% and from 6.1% to 27.6% at the small and large granule sites, respectively. CONCLUSIONS: Similar outcomes in osteoconductivity and bone formation were found at both small and large DBBM granule sites.

Sinus augmentation - autograft vs. fresh frozen allograft: Bone density dynamics and implant stability.

OBJECTIVES: Compare bone density changes and initial implant stability following sinus augmentation with autogenous bone (AB) vs. fresh frozen bone (FFB). MATERIALS AND METHODS: Randomized, prospective, split mouth study. Sinus augmentation executed using either AB or FFB. Dental implants were inserted after 6 months of healing. Implant dimensions and insertion torques were recorded. Prostheses were delivered 6 months thereafter. All patients had computerized tomography (CT) scans 1 week (T1) and 6 months (T2) after initial bone grafting. Third CT (T3) was taken 12 months after prosthesis delivery. Data from CT scans was used to analyze bone density at each period. RESULTS: A total of 15 patients (8 males, 7 females) following bilateral sinus augmentation procedures, were included. Mean age was 54 ± 5 years (range 48-60 years). All patients had 3 CT examinations. The initial augmented AB density was higher than the initial FFB density. Nevertheless, density differences between the two groups were not statistically significant at any time frame. At T2 density of both grafts showed a statistically significant increase. A significant increase from T2 to T3 was noted only for the FFB group. Implant insertion torque was significantly higher in the FFB group. Insertion torque ≥32 N/cm was achieved in significantly more patients in the FFB group. CONCLUSION: The use of FFB for sinus augmentation is a reliable option of graft material. The newly formed bone quality performance, evaluated by CBCT density, is as good as AB, allowing predictable initial implant stability and osseointegration. Unnecessary morbidity associated with AB harvesting is thus avoided.

The Influence on Healing of Bony Window Elevated Inward in the Sinus Cavity as Cortical Bone Graft: A Histomorphometric Study in Rabbit Model.

PURPOSE: To evaluate the influence on healing of the bony window elevated inward in the sinus cavity as a cortical bone graft. MATERIALS AND METHODS: Eighteen rabbits were included in the experiment. At the test sites (bony window), the antrostomy was prepared and the remaining bony window was elevated together with the sinus mucosa. At the control sites, the bony window was gently detached before the sinus mucosa elevation and discarded. The space obtained was grafted with deproteinized bovine bone mineral (DBBM). A collagen membrane was positioned on the antrostomy at both sides. The rabbits were euthanized after 2, 4, and 8 weeks in groups of six each. Histologic analyses in different regions of the elevated space were carried out, and a Wilcoxon test was used to estimate differences. Microcomputed tomography (microCT) analyses were also performed. RESULTS: After 2 weeks of healing, higher proportions of new bone were found in the test group compared with the control group due to the higher amount of bone formed in the region subjacent to the sinus mucosa. In this region, higher amounts of new bone were also found in the test group after 4 (P = .028) and 8 weeks of healing (P = .345). After 8 weeks of healing, the percentage of new bone was higher at the control sites compared with the test sites, with the proportions being 25.4% ± 3.2% and 21.3% ± 6.1%, respectively. In this period of evaluation, the bony window contributed with 20.1% ± 5.3% of vital bone in the test group. A fraction of 60.4% ± 10.8% of its surface was surrounded by new bone. In the microCT analysis, after 8 weeks of healing, fractions of 22.3% ± 1.6% and 22.2% ± 0.7% of bone were found in the test and control groups, respectively. CONCLUSION: The presence of the bony window positively influenced the healing in the elevated space, especially in the submucosa region. The bony window was vital and incorporated into newly formed bone.

Histologic and Micro-CT Analyses at Implants Placed Immediately After Maxillary Sinus Elevation Using Large or Small Xenograft Granules: An Experimental Study in Rabbits.

PURPOSE: To compare the osseointegration at the portion of the implant within the elevated space after sinus elevation using different sizes of xenograft. MATERIALS AND METHODS: Eighteen New Zealand rabbits were selected, antrostomies were prepared bilaterally through the nasal dorsum, and the sinus mucosa was elevated. Deproteinized bovine bone mineral with granules of either 1 to 2 mm (large sites) or 0.250 to 1.0 mm (small sites) were randomly used to fill the elevated space of the two sinuses. Subsequently, mini-implants were placed through the antrostomy, one in each sinus. The animals were euthanized 2, 4, and 8 weeks after surgery, six animals for each group. Microcomputed tomography (micro-CT) and histologic analyses were performed. RESULTS: In the elevated space, at the histologic analysis after 2 weeks of healing, new bone formed on the implant surface was found in fractions of 18.8% ± 6.8% and 15.8% ± 9.6% in the large and small sites, respectively (P = .249). After 4 weeks, the respective fractions of new bone were 20.3% ± 3.5% and 23.3% ± 5.6% (P = .249). After 8 weeks, the proportions reached 33.9% ± 9.5% and 28.5% ± 10.3% (P = .173), respectively. At the micro-CT analysis, bone-to-implant contact percentage (BIC%) was 21.0% ± 2.3% and 21.2% ± 2.4% in the large and small sites, respectively (P = 1.000). The respective proportions of BIC% at the large and small sites were 20.5% ± 3.3% and 23.4% ± 5.4% after 4 weeks (P = .463), and 23.0% ± 2.7% and 25.8% ± 4.1% after 8 weeks (P = .249). CONCLUSION: The use of xenograft granules of different dimensions resulted in similar amounts of bone-to-implant contact at implants placed simultaneously with sinus floor augmentation.

Effect of lack of plaque control after the surgical treatment of peri-implantitis at surfaces with different characteristics: an experimental study in dogs.

OBJECTIVE: The aim of the present study was to evaluate the effect of the induction of peri-implantitis and of plaque accumulation on implants with different surface characteristics after the surgical treatment. MATERIAL AND METHODS: All mandibular premolars and first molars were extracted bilaterally in six dogs. After 3 months, two non-submerged implants were installed, each with either a hydrophilic sandblasted and acid-etched surface stored in saline solution (SLActive) or an acid-etched and modified with calcium ions surface (UnicCa). After 3 months, ligatures were placed in the sulcus around the implants to induce an experimental peri-implantitis and plaque accumulation was allowed. After 3 months, ligatures were removed and, after one more month of plaque accumulation, a surgical treatment was performed using gauzes soaked in saline and irrigations. X-rays were taken at this stage. Plaque control maintenance was established at the control sites, while plaque accumulation was allowed at the test sites (plaque sites). After 5 months, biopsies were obtained. Marginal bone levels were compared between x-rays and histological assessments. RESULTS: At the time of peri-implantitis treatment, two SLActive implants were lost. At the euthanasia, seven more implants were lost only in the plaque group, one control and six test implants. The calculated mean values of the marginal bone level of the two surfaces at the treatment were 3.65 ± 1.71 mm in the control group, and 3.65 ± 1.76 mm in the plaque group (p = 0.463). The additional marginal bone loss after 5 months from surgical treatment was 0.67 ± 0.67 mm (UnicCa, 0.48 ± 1.06 mm and SLActive, 0.79 ± 2.10 mm) and 3.11 ± 1.38 mm (UnicCa, 2.67 ± 1.87 mm and SLActive, 3.94 ± 2.11 mm) for the control and plaque groups, respectively (p = 0.028). CONCLUSIONS: The lack of plaque control after the surgical treatment of the peri-implantitis strongly influenced the marginal bone loss.

Antrostomy Preparation for Maxillary Sinus Floor Augmentation Using Drills or a Sonic Instrument: A Microcomputed Tomography and Histomorphometric Study in Rabbits.

PURPOSE: To evaluate the healing after sinus floor augmentation at antrostomies prepared with either drills or a sonic instrument. MATERIALS AND METHODS: Sinus mucosa elevation was performed bilaterally in 18 rabbits. The antrostomy was prepared with either drills or a sonic instrument. The elevated space was filled with a collagenated porcine bone, and the access antrostomy was covered by a collagen membrane. The animals were euthanized in groups of six after 2, 4, and 8 weeks of healing. Microcomputed tomorgraphy (microCT) and a histologic analysis was performed. RESULTS: After 8 weeks of healing, remaining defects occupying about 28.9% and 26.0% of the antrostomy were found at the microCT analysis. At the histologic analysis, new bone was formed from the margins of the antrostomy, reaching the central region over time. After 8 weeks of healing, 29.1% ± 18.6% and 28.4% ± 15.6% of new mineralized bone was occupying the analyzed zone in the antrostomy at the drill and sonic sites, respectively. CONCLUSION: The use of a sonic device to prepare the antrostomy resulted in similar healing outcomes in both the antrostomy and the elevated regions.

Histological and micro-computed tomography evaluations of newly formed bone after maxillary sinus augmentation using a xenograft with similar density and mineral content of bone: An experimental study in rabbits.

The objective of this study was to evaluate possible differences in the assessment of bone formation between histological and micro-computed tomography (CT) analyses in maxillary sinuses augmented with a xenograft with similar density and mineral content of bone. A collagen membrane was placed subjacent the elevated sinus mucosa at the test sites of 18 rabbits, and the elevated spaces were filled with xenograft. The antrostomy was covered with collagen membranes, bilaterally. Six rabbits per group were sacrificed after 2, 4, and 8 weeks of healing. Biopsies were retrieved and scanned in a high-resolution micro-CT at two different gray thresholds. Histological assessments were subsequently performed. At the histological analyses, bone increased over time, from 7.5 ± 2.4% to 27.0 ± 5.3%, between 2 and 8 weeks of healing. The highest content of bone was found close to the sinus bone walls, whereas the middle regions contained lower amounts. At the micro-CT analyses, discrepancies were found in bone content percentages compared with the histological analyses, especially after 2 weeks of healing and within the middle regions of the sinus, in which new bone was ~15-22% at the micro-CT analyses and only 1.6% at the histological evaluation. The outcomes of a micro-CT analysis performed in an early phase of healing may be altered when a resorbable bone substitute with similar density and mineral content of bone is applied.

Healing at the Interface Between Autologous Block Bone Grafts and Recipient Sites Using n-Butyl-2-Cyanoacrylate Adhesive as Fixation: Histomorphometric Study in Rabbits.

The aim of the present split-mouth (split-plot) study was to describe the sequential healing in the interface between autologous bone grafts and recipient parent bone, fixed using an n-butyl-2-cyanoacrylate adhesive with or without an additional titanium fixation screw. Bone grafts were collected from the calvaria and fixed to the lateral aspect of the mandible in 24 rabbits. The cortical layers of the recipient sites were perforated, and the grafts were randomly fixed using an n-butyl-2-cyanocrylate adhesive, either alone or in conjunction with a 1.5 mm × 6.0 mm titanium fixation screw. The animals were sacrificed after 3, 7, 20, and 40 days, and histomorphometric evaluations of the interface between graft and parent bone were performed. Only 2 of 6 grafts in each group were partially incorporated to the parent bone after 40 days of healing. The remaining grafts were separated from the parent bone by adhesive and connective tissue. It was concluded that the use of n-butyl-2-cyanoacrylate as fixation of an autologous bone graft to the lateral aspect of the mandible was able to maintain the fixation over time but did not incorporate the graft to the recipient sites. Use of fixation screws did not improve the healing.

Volumetric Stability of Fresh Frozen Bone Blocks in Atrophic Posterior Mandible Augmentation.

Fresh frozen bone allografts (FFB) have become an alternative for bone augmentation in the past decades, especially because of the absence of recent reports of disease transmission or immunologic reactions when it is used. The aim of this prospective controlled study is to evaluate volumetric changes of newly created bone following reconstruction of the atrophic posterior mandible. Twenty consecutive patients presenting for reconstruction of posterior mandibular alveolar bone ridge width ≤6.0 mm and/or height ≤6.0 who met all inclusion and exclusion criteria were included. FFB blocks were used. The main outcome variable investigated was bone volume dynamics. Vertical, horizontal, and 3-dimensional bone gain data were measured from computerized tomography scans. The main predictor variable was time evaluated at 3 points: immediately after surgery (T1), at implant placement (T2), and 1 year after functional loading (T3). Secondary outcome parameters evaluated were implant survival, histologic findings, and microtomographic morphometry. The study included 28 hemi-mandibles, 50 FFB bone blocks, and 15 female and 5 male patients (mean age, 51.8 years). Block and implant survival rates were 100% and 96%, respectively, after 31.75 months of follow-up. Vertical and horizontal bone gain at T2 was 5.15 and 6.42 mm, respectively. Volumetric resorption was 31% at T2, followed by an additional 10% reduction at T3. Histologic evaluation showed newly formed vital bone in intimate contact with the remaining FFB. Microtomography revealed 31.8% newly formed bone, 14.5% remaining grafted bone, and 53.7% connective tissue and bone marrow. Thus, FFB blocks may lead to new bone formation and consolidation, with satisfactory volumetric bone maintenance, allowing implant-supported rehabilitation with high success rates.

Maxillary sinus grafting with fresh frozen allograft versus bovine bone mineral: A tomographic and histological study.

We evaluated histologically and tomographically the effects of fresh frozen bone allograft (FFB) or bovine bone mineral (BBM) in maxillary sinus floor augmentations. In total, 30 maxillary sinuses from 30 patients (mean age = 51.17 ± 10.86 years) underwent sinus augmentation. Patients were divided in two test groups (15 sinuses each). The first group was grafted with allograft bone, and the second group received bovine bone mineral. After 6 months, bone samples from each group were collected for histological examination. Implant survival rates were 97.78% (FFB group) and 100% (BBM group) 6 months after functional loading. Median volumetric reductions of 31.2% (11.33-40.56) and 12.22% (9.91-20.59) were observed in the FFB and BBM groups, respectively. Comparisons between the groups for differences in initial and final volumes of bone (p = 0.015) and the rate of resorption (p = 0.009) showed statistically significant differences. The FFB group showed osteoblastic cells in close contact with osteoid matrix, connected through bridges between allograft bone particles and new bone formation. The BBM group showed BBM particles in close contact with new bone, with visible osteoid matrix bridges and osteoblastic cells surrounding it. None showed signs of acute or chronic inflammatory infiltrate. Despite better results with BBM, both FFB and BBM in maxillary sinus augmentation resulted in high percentages of new bone formation, and allowed implant placement with a low rate of failure of osseointegration at a 6-month follow-up.