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.

Application of the break-even point to express the bone dynamics around implants.

PURPOSE: The aim of this study was to apply the break-even point concept to express the dynamics of bone formation and resorption around implants. METHODS: Published data on new bone and parent bone densities around implants from one human and three dog studies were selected and used for analysis. The break-even point (BEP) of the bone density (BD) was assessed. The BEP is the point at which, in a graph, the lines representing the formation of new bone and resorption of old bone intersect. BEP is expressed in time (x; days) of occurrence and percentage of bone (y; %) at which the break-even point occurs and illustrates the grade of bone modeling. The sooner the occurrence, the faster the bone formation in relation to the resorption of the old bone. RESULTS: In the marrow and cortical compartments, BEP of bone density occurred after 7.9 days (BD% 24.5%) and >30 days, respectively. Different surfaces presented similar BEP, ranging between 9.7 and 11.2 days (BD% 19.1-22.5%). BEP at implants installed in the human maxilla occurred after 29-30.4 days (BD% 28.3-29.6%). CONCLUSION: The present study showed that the parameters used to express the break-even point can provide information on the influence of the model used, surface characteristics, and bone quality on bone modeling/remodeling around implants.

Mucosal adhesion phenomenon after maxillary sinus floor elevation: A preclinical study.

AIM: To describe the histological events that occur after maxillary sinus floor elevation when the elevated and undetached sinus mucosa are in close proximity or in contact with each other. MATERIALS AND METHODS: From 76 rabbits, 152 elevated maxillary sinuses were analyzed histologically. Sites without adhesions were classified as "No proximity," whereas the adhesion stages were divided into "Proximity," "Fusion," and "Synechia stages." The width of the pseudostratified columnar epithelium and the distance between the two layers of the elevated and undetached sinus mucosae were measured at various standardized positions. RESULTS: Thirty-one sites presenting with adhesions were found. Twelve sites were in the proximity stage," presenting cilia of the two epithelial layers that were shortened and interlinked within the mucous context. Hyperactivity of the goblet cells was also observed. In the other cases, the hyperplastic epithelium showed attempts to reach the contralateral mucosa. The 15 "fusion stage" sites presented regions with epithelial cells of the two mucosal layers that penetrated each other. Four sites presented "synechiae stages," represented by bridges of connective tissue connecting the two lamina propria. CONCLUSIONS: Close proximity or tight contact between the elevated and undetached mucosa adhering to the bone walls might occur after maxillary sinus floor elevation. This induced hyperplasia of the epithelial cells and adhesion of the two layers until synechiae formation.

The Effect of Anticoagulants on Early Implant Failure: A Retrospective Cohort Study.

BACKGROUND: Anticoagulants (AC) are among the most often prescribed drugs in the world. Data regarding ACs' effect on the osseointegration of dental implants is lacking. PURPOSE: The aim of the present retrospective cohort study was to evaluate the effect of anticoagulants (AC) on early implant failure (EIF). The null hypothesis was that the use of AC increases the incidence of EIF. MATERIALS AND METHODS: The research included 687 patients who underwent 2971 dental implant placements in the department of oral and maxillofacial surgery in Rabin medical center, Beilinson hospital, by specialists in oral and maxillofacial surgery. The study group comprised 173 (25.2%) patients and 708 (23.8%) implants using AC. The rest of the cohort served as a control. A structured form was used to collect data at patient and implant level. EIF was defined as implant failure within a period of up to 12 months from loading. EIF was the primary outcome parameter. A logistic regression model was used to predict EIF. RESULTS: Implants placed in individuals ≥ 80 (odds ratio (OR) = 0.34, p = 0.05), and ASA 2/3 vs. ASA 1 individuals (OR = 0.30, p = 0.02/OR = 0.33, p = 0.03, respectively) had decreased odds of EIF, and implants in those using anticoagulants (OR = 2.64, p = 0.01) had increased odds of EIF. At the patient level, the odds of EIF in ASA 3 (OR = 0.53, p = 0.02) and IHD (OR = 0.40, p = 0.02) individuals decreased. In AF/VF (OR = 2.95, p = 0.01) individuals, EIF odds increased. CONCLUSIONS: Within the limitations of the present study, the use of AC is significantly associated with an increased likelihood of EIF: the OR was 2.64. Future research is required to validate and examine the prospective impact of AC on the osseointegration phenomena.

Schneiderian Membrane Collateral Damage Caused by Collagenated and Non-Collagenated Xenografts: A Histological Study in Rabbits.

BACKGROUND: The Schneiderian membrane (SM) that is in contact with biomaterial granules may become thinner and eventually perforate. It has been shown that these events are related to the biomaterial used. Hence, the main aim of the present study was to compare the damaging effects of two xenografts with different resorbability rates on SM. The secondary aim was to evaluate the possible protection from damage offered by a collagen membrane placed adjacent to the SM and by inward displacement of the bone window with the SM during elevation. METHODS: Thirty-six albino New Zealand rabbits underwent bilateral sinus elevation. One group of 18 animals received deproteinized bovine bone mineral (DBBM group) and the other received swine-collagenated corticocancellous bone (collagenated group). Moreover, in the DBBM group, the bone window was displaced inward during elevation in one sinus together with the SM. In the collagenated group, a collagen membrane was placed adjacent to the SM in one sinus. Six animals were assessed per period after 2, 4, and 8 weeks. RESULTS: The mean pristine mucosa width ranged between 67 µm and 113 µm, and none had a width of <40 µm. In the 2-week group, the elevated mucosa of the DBBM group presented 59 thinned sites and five perforations, while in the collagenated group, 14 thinned sites and one perforation were observed. Damage to SM decreased in number in the 4-week treatment group. In the 8-week group, the number of thinned sites in the DBBM group increased to 124, and the perforations to 8. In the collagenated group, 7 thinned sites and 1 small perforation were observed. CONCLUSIONS: More damage to the Schneiderian membrane was observed in the DBBM group than in the collagenated group. The presence of the inward bone window offered protection from damage to the Schneiderian membrane.

Healing Patterns of Non-Collagenated Bovine and Collagenated Porcine Xenografts Used for Sinus Floor Elevation: A Histological Study in Rabbits.

Objective: To compare healing of collagenated and non-collagenated xenografts used for maxillary sinus floor elevation. Materials and Methods: Two different xenografts were used: deproteinized bovine bone (DBBM group) and collagenated corticocancellous porcine bone (collagenated group). Healing was studied after 2, 4, and 8 weeks. The loss of dimensions of the elevated area and the percentages of new bone, xenograft remnants, osteoclastic zones, vessels, inflammatory infiltrates, and soft tissues were analyzed. Three regions were evaluated: close to the bone walls (bone wall region), subjacent the sinus mucosa (submucosa region), and the center of the elevated area (middle region). The primary variables were the percentage of new bone and xenograft remnants. Results: Between 2 and 8 weeks, the elevated areas showed a reduction of 16.3% and 52.2% in the DBBM and collagenated groups, respectively (p < 0.01 between the two areas after 8 weeks). After 8 weeks, the highest content of new bone was observed in the bone wall region, which was higher in the collagenated group than in the DBBM group (41.6% and 28.6%, respectively; p < 0.01). A similar quantity of new bone was found between the two groups in other regions. A higher percentage of vessels in all regions evaluated (p < 0.01) and soft tissue in the sub-mucosa region (p < 0.05) was found in the collagenated group than in the DBBM group. Conclusions: The present study showed that both xenografts allowed new bone formation. In comparison with the non-collagenated xenograft, the collagenated xenograft underwent higher resorption, resulting in greater shrinkage of the elevated space after sinus lifting and a higher content of new bone in the regions close to the bone walls. Clinical relevance: In this study, the region adjacent to the bone wall showed the highest new bone content. This region resembles the base of the sinus, closest to the sinus floor and walls, and is the most important region from a clinical point of view because it is where the implant will be installed. Residues of the biomaterial remained after 8 weeks of healing. Other reports have shown that these biomaterial residues may interfere with the integration of implants.

Contribution to Bone Formation of the Schneiderian Membrane after Sinus Augmentation: A Histological Study in Rabbits.

AIM: to evaluate bone formation in close contact with the sinus mucosa after different periods from sinus augmentation and the influence on healing of the presence of an inward dis-placed bone window. MATERIAL AND METHODS: Eighteen rabbits were included in the experiment. A trap-door technique was applied at the test sites, and the bony window was elevated inward (inward window; IW) together with the sinus mucosa. At the control sites, the bony window was removed before the elevation of the sinus mucosa. The elevated space was filled with deproteinized bovine bone mineral (DBBM) and both access windows were covered with a collagen membrane. Histometric measurements were performed subjacent the sinus mucosa after 2, 4, and 8 weeks of healing. RESULTS: Very few sinuses presented small percentages of new bone in close contact with the sinus mucosa in the various period examined. The presence of bone in the neighbor areas might have influenced bone formation close to the sinus mucosa. The inward displaced bone window supported bone formation close to the sinus mucosa only in the earliest period of healing, while the bone walls increased their influence over time. The lack of increased new bone percentage over time in the most central regions of the elevated sinus mucosa do not support the hypothesis that the sinus mucosa may express its potential in bone formation. It can be speculated that the new bone found in the intermediate and middle regions of the control sites in the earliest period of healing might be due to residual of bone from the osteotomy. CONCLUSIONS: Very small amounts of new bone were found subjacent to the sinus mucosa, mostly formed from the bone walls, the inward displaced bone window or from possible bone residues from the osteotomy procedures. The lack of increased new bone percentage over time in the most central regions of the elevated sinus mucosa indicates that the contribution to bone formation provided by the sinus mucosa is limited.

Sinus Mucosal Damage Triggered by Synthetic or Xenogeneic Bone Substitutes: A Histological Analysis in Rabbits.

Background: It has been shown in rabbit models that the sinus mucosa in contact with graft particles might experience a progressive thinning and perforations. The phenomenon depends on the graft used. Hence, the aim of the present study was to compare the damaging effects of a synthetic of a xenogeneic graft. Methods: Forty New Zealand rabbits received a bilateral sinus elevation. Both sinuses of twenty rabbits were grafted with a biphasic 60% hydroxyapatite and 40% ß-tricalcium phosphate while the other twenty received a deproteinized bovine bone mineral graft. Thinned sites (<40 µm) and perforations on the mucosa in contact with graft particles were evaluated after 2 and 10 weeks (ten animals each period). The width of the pseudostratified epithelium was also measured as control. Results: After 2 weeks of healing, 61 thinned sites were detected in the Synthetic group and 49 in the Xenogeneic group. After 10 weeks, the number of thinned mucosae increased to 79 sites in the Synthetic group (p = 0.222 between periods), and to 114 sites in the Xenogeneic group (p = 0.030 between groups; p = 0.001 between periods). Perforations were few in the 2-week period, two in two sinuses out of 20 in the Synthetic group, and four in two sinuses out of 20 in the Xenogeneic group (p = 0.721). In the 10-week period, the perforations increased to eight in the Synthetic group, distributed in six sinuses out of 20, and to sixteen in the Xenogeneic group, distributed in 11 sinuses out of 20 (p = 0.082). The pseudostratified epithelium presented a reduced width at the thinned sites. Conclusions: The contact with synthetic or xenogeneic grafts will induce thinning and possible perforations of the sinus mucosa. This effect will increase over time, and it is stronger at the xenogeneic than the synthetic graft.

Maxillary Sinus Floor Augmentation with Two Different Inorganic Bovine Bone Grafts: an Experimental Study in Rabbits.

OBJECTIVE: To compare the sequential healing of maxillary sinuses grafted with two different xenogeneic bone substitutes processed at either a low (300°C) or high (1200°C) temperature. METHODS: A sinus augmentation procedure was performed bilaterally in 20 rabbits and two different xenogeneic bone grafts were randomly used to fill the elevated spaces. Healing was studied after 2 and 10 weeks, in 10 rabbits during each period. RESULTS: After 2 weeks of healing, very small amounts of new bone were observed in both groups, and were mainly confined to close to the sinus bone walls and osteotomy edges. After 10 weeks of healing, new bone was found in all regions, with higher percentages in those close to the bone walls and to the osteotomy. In this period of healing, the proportion of new bone in the 300°C group was 20.0% ± 4.3%, and in the 1200°C group it was 17.2% ± 4.3% (P = 0.162). In the 1200°C group, translucent, dark fog-like shadows in regions of the grafts were hiding portions of new bone (interpenetrating bone network). CONCLUSION: Both biomaterials provided conditions that allowed bone growth within the elevated space, confirming that both biomaterials are suitable to be used as a graft for sinus floor augmentation.

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.

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.

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.

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 Mucosa Thinning and Perforations after Sinus Lifting Performed with Different Xenografts: A Histological Analysis in Rabbits.

BACKGROUND: Experimental studies have shown a progressive thinning and perforations of the sinus mucosa associated with sharpened edges and the cutting projections of graft particles used simultaneously for maxillary sinus augmentation. Hence, the aim of the present study was to evaluate the damaging effects of two different bovine grafts on the sinus mucosa after sinus augmentation. METHODS: Twenty New Zealand rabbits received a bilateral sinus lifting using, as fillers, two different types of deproteinized bovine bone in granules, one processed at low temperature (low-T group), and the other at high temperature (high-T group). Thinned mucosa sites (<40 µm) and perforations were evaluated in the sinus mucosa that were in contact with graft granules after 2 and 10 weeks, in ten animals per period. RESULTS: After 2 weeks of healing, the number of thinned mucosa sites was 118 in the low-T group, and 149 in the high-T group (p = 0.191). At the 10-week assessment, the thinned sites increased to 237 and 195 sites, respectively. The numbers of sinus mucosa perforations after 2 weeks were eight and three in the low-T and high-T group, respectively. At the 10-week evaluation, the perforations increased to 19 in the low-T group, and to 14 in the high-T group. CONCLUSIONS: The contact with bovine xenografts yielded thinning and perforations of the sinus mucosa. Despite the differences in characteristics and dimensions, no differences were found between the two xenografts in the numbers of thinning mucosa sites and perforations. However, a trend of more events was found in the low-T compared to the high-T group.

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.