Critical-sized marginal defects around implants in the rabbit mandible

BACKGROUND

The mandible of the rabbit is considered a reliable model to be used to study bone regeneration in defects. The aim of the present study was to evaluate the formation of new bone around implants installed in defects of either 5 or 10 mm in the mandible of rabbits.

MATERIALS AND METHODS

In 12 rabbits, 3 mm deep circumferential defect, either 5 or 10 mm in diameter, were prepared bilaterally and an implant was placed in the center. A collagen membrane was placed to close the entrance. After 10 weeks, biopsies were taken, histological slides were prepared, and different regions of the defects were analyzed.

RESULTS

Similar amounts of new bone were found in both defects. However, most of the 5 mm defects were filled with new bone. New bone was observed closing the entrance of the defect and laid onto the implant surface. Only in a few cases the healing was incomplete. Despite a similar percentage of new bone found within the 10 mm defects, the healing was incomplete in most of the cases, presenting a low rate of bone formation onto the implant surface within the defect. Only one case presented the closure of the entrance.

CONCLUSIONS

The dimensions of the defect strongly influenced the healing so that a circumferential marginal defect of 10 mm around an implant in the mandible body should be considered a critical-sized defect. The presence of the implant and of residues of teeth might have strongly influenced the healing.

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.

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.

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.

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.

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.

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% β-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.

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.

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.

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.

Argon Bioactivation of Implants Installed Simultaneously to Maxillary Sinus Lifting without Graft. An Experimental Study in Rabbits

Background: The treatment of the surface of titanium implants with argon plasma improved its hydrophilicity and cell adhesion, resulting in higher bone apposition on implant and graft surfaces. The spontaneous perforation over time of the sinus mucosa after sinus augmentation has been documented in experimental studies at both implants and graft particles. The aim of the present study was to evaluate the influence of plasma argon treatment of the implant surface on bone apposition and on the rate of sinus mucosa perforations. Methods: A sinus lifting procedure was performed bilaterally in sixteen rabbits, and implants, either treated with argon plasma or left without treatment (control), were placed simultaneously without grafts. After 8 weeks, histological analyses were carried out. Results: A collapse of the sinus mucosa was observed at all implants. Twenty-four out of thirty-two implants presented sinus mucosa perforations at the apex. Several perforations were also found at the threads. Thinned mucosa sites (width < 40 µm) were found around almost all implants. About 2.6–2.9 mm of the apical regions of the implant did not present signs of osseointegration and about 1.3 mm were exposed to the sinus cavity. No statistically significant differences were found between plasma and control sites. Conclusions: In conclusion, the sinus mucosa was damaged and perforated by direct contact with treated and non-treated implant surfaces. The treatment of the implant surface with argon plasma did not affect the outcomes.

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.

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.

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.

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.

Anterior lingual mandibular bone cavity: a case report

Stafne’s bone cavity (SBC) is an asymptomatic lingual bone cavity situated near the angle of the mandible. The anterior variant of SBC, which shows a radiolucent unilateral ovoid lingual bone concavity in the canine-premolar mandibular region, is uncommon. A 73-year-old man was referred for assessment of loss of mandibular bone. Panoramic radiographs and computerized tomography scans showed a well-defined lingual bony defect in the anterior mandible. Analysis of imaginological documentation, made 14 years ago, revealed a progressive increase in mesiodistal diameter and intraosseous bony defect. The soft tissue obtained within the bony defect, microscopically revealed fibrous stroma containing blood vessels of varied caliber. The current anterior lingual mandibular bone defect case is probably caused by the salivary gland entrapped or pressure resorption, which can explain the SBC pathogenesis.KEYWORDSBone defect; Mandible; Cone beam computed tomography; Diagnosis; Case report.

Hard and soft tissue changes around implants activated using plasma of argon: A histomorphometric study in dog

OBJECTIVE

To histologically assess the hard and soft tissue changes after insertion of cleaned and activated titanium implants using plasma of argon.

MATERIALS AND METHODS

Eight dogs were included in this study. The mandibular premolars and first molars were extracted. For each hemi-mandible, four implants, 7 mm long and 3.3 mm of diameter, with a ZirTi surface were used. The surface of two implants was randomly treated with argon plasma (test), while the other two implants were left untreated (control). After 1 month, the same procedure was performed in the contralateral hemi-mandible. The amount of old bone, new bone, overall value of old bone plus new bone, and soft tissue was histologically evaluated.

RESULTS

After 1 month of healing, high percentages of new bone in close contact with the implant surface were found at both the treated (60.1% ± 15.6%; 95% CI 56.5%-78.0%) and untreated (57.2% ± 13.1%; 95% CI 49.3%-67.5%) implants. Low percentages of old bone were found at this stage of healing, at both the treated (4.4% ± 3.0%; 95% CI 1.2%-5.4%) and untreated (3.4% ± 3.1%; 95% CI 0.6%-4.9%) implants. Not statistically significant differences were found between groups (p > .05). After 2 months of healing, treated implants presented a significantly higher (p = .012) new bone formation (72.5% ± 12.4%; 95% CI 69.6%-86.8%) compared to untreated sites (64.7% ± 17.3%; 95% CI 59.4%-83.3%). Controversially, no difference (p = .270) in terms of old bone was present between treated (3.1% ± 1.7%, 95% CI 1.8%-4.2%) and untreated implants (3.8% ± 1.9%, 95% CI 3.2%-5.8%). Significant differences (p = .018) in terms of total mineralized bone were found between treated (75.6% ± 13.0%, 95% CI 73.3%-91.3%) and untreated implants (68.4% ± 16.8%; 95% CI 64.2%-87.6%).

CONCLUSIONS

Implants treated using plasma of argon was demonstrated to reach a higher bone-to-implant contact when compared to untreated implants.

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.

Maxillary Sinus Grafting with Autograft Versus Fresh-Frozen Allograft: A Split-Mouth Evaluation of Bone Volume Dynamics

PURPOSE

To compare volumetric changes after sinus augmentation of completely edentulous maxillae with either autogenous or allogeneic fresh-frozen bone particles.

MATERIALS AND METHODS

This split-mouth study in patients who required bilateral sinus grafting used autograft particles for one sinus and allograft particles for the contralateral sinus. The grafted sinuses were left to heal for 6 months prior to implant insertion. All patients underwent four computed tomography scans: prior to augmentation and 1 week, 6 months, and 12 months after grafting. Computer software was used to analyze bone graft volume in each scan.

RESULTS

Fifteen patients (8 men, 7 women) with a mean age of 54 ± 5 years (range, 48 to 60 years) took part and underwent 30 sinus augmentation procedures. Mean autograft and allograft volumes were not statistically significantly different at each time point (1 week: 2.01 ± 0.43 cm³ vs 2.46 ± 0.79 cm³; 6 months: 1.53 ± 0.49 cm³ vs 1.75 ± 0.64 cm³; and 12 months: 1.38 ± 0.43 cm³ vs 1.59 ± 0.56 cm³, respectively). Mean volumetric reductions of 31.35% and 35.36% (23.9% and 29.9% in the 6 months prior to implant insertion, followed by an additional 9% and 9% in the following 6 months), relative to 1 week postgrafting, were noted for the autograft and allograft groups, respectively, after 12 months.

CONCLUSION

On the basis of this split-mouth study of 15 patients, there was no statistically significant volumetric difference after 12 months between the use of autograft or allografts for sinus augmentation. Fresh-frozen bone allograft may serve as an alternative that avoids the morbidity associated with autograft harvesting.

Enlargement of the Pharynx Resulting From Surgically Assisted Rapid Maxillary Expansion

PURPOSE

Given that transverse maxillary deficiency is an etiologic factor of obstructive sleep apnea and is intimately connected to pharyngeal size, the objective of this study was to determine whether surgically assisted rapid maxillary expansion (SARME) would promote pharyngeal enlargement in adults.

MATERIALS AND METHODS

This prospective study was conducted in patients with uni- or bilateral posterior crossbite who underwent SARME. Participants were recruited from the Integrated Center for the Study of Face Defects, School of Medicine of Ribeirão Preto, University of São Paulo (São Paulo, Brazil). All patients underwent computed tomography of the pharynx before and after surgery (171.5 days on average), and the sagittal and transverse planes and the total area across 3 levels of the pharynx, including the upper (posterior nasal spine), middle (first cervical vertebra), and lower (second cervical vertebra) levels, were measured on the images. A paired-samples t test was used to evaluate changes in the pharynx before and after surgery.

RESULTS

The studied sample consisted of 18 adult patients (10 women and 8 men) with an average age of 37.11 years (standard deviation, 11.73 yr); all patients resided in the region of Ribeirão Preto, São Paulo, Brazil. No statistical changes were observed in the upper level. An enlargement of 17.82% (P = .0107) was observed in the sagittal plane of the middle level. The cross-sectional and area values of this same portion were enlarged (16.96 and 37.38%, respectively), with a trend toward statistical significance (P = .067 and .051, respectively). The airway enlargements in the lower level were 26.41, 24.87, and 53.87% in the sagittal and transverse planes and total area, respectively; these differences were statistically significant (P = .0003, .0033, and .0016, respectively) for all 3 measurements.

CONCLUSIONS

SARME promotes pharyngeal enlargement, especially in the lower levels of the pharynx.

Effects of surgically assisted rapid maxillary expansion on obstructive sleep apnea and daytime sleepiness

PURPOSE

The aim of the study was to evaluate the effects of surgically assisted rapid maxillary expansion (SARME) on obstructive sleep events and daytime sleepiness in adults with obstructive sleep apnea syndrome (OSAS).

METHODS

Sixteen individuals (7 women/9 men) aged 40.2 ± 10.2 (range, 24.4 to 62.2 years) with maxillary transverse deficiency and OSAS (respiratory disturbance index [RDI] greater than 5) confirmed with full-night polysomnography (PSG) underwent SARME to evaluate its efficiency for OSAS treatment.

RESULTS

Several PSG parameters and the Epworth Sleepiness Scale (ESS) results were compared in selected individuals before and after they underwent SARME. An RDI reduction from 35.4 ± 38.5 to 16.0 ± 19.7 was found, corresponding to a mean decrease of 54.6 % (p = 0.0013). A 56.2 % (33.23 ± 39.5 to 14.5 ± 19.4, p = 0.001) decrease was found in the apnea-hypopnea index (AHI), in addition to decreases in the desaturation and microarousal rates, among other parameters. The ESS scores improved from 12.5 ± 5.3 to 7.2 ± 3.5 (p < 0.001).

CONCLUSIONS

SARME promotes an improvement in OSAS symptoms; decreases the rates of respiratory disturbances; microarousal, and desaturation; and reduces daytime sleepiness.

Effect of autogenous and fresh-frozen bone grafts on osteoblast differentiation

OBJECTIVE

Fresh-frozen bone allograft (FFBA) is an alternative to autogenous bone (AB) for reconstructing maxillary bone. Despite the promising clinical results, cell responses to FFBA and AB were not evaluated. Thus, our aim was to compare cells harvested from maxillary reconstructed sites with either AB or FFBA in terms of osteoblast differentiation and to evaluate the effect of culturing cells in contact with FFBA.

METHODS

Cells harvested from three patients submitted to bilateral maxillary reconstruction with AB and FFBA were cultured to evaluate: proliferation, alkaline phosphatase activity, extracellular matrix mineralization and gene expression of osteoblastic markers. The effect of FFBA on osteoblast differentiation was studied by culturing cells harvested from AB in contact with FFBA and evaluating the same parameters. Data were compared using either two-way ANOVA followed by Tukey-b test or Student's t test (p≤0.05).

RESULTS

Cell proliferation was higher in cultures from AB grafted sites and extracellular matrix mineralization was higher in cultures derived from FFBA grafted sites. The gene expression of alkaline phosphatase, RUNX2, bone sialoprotein and osteocalcin was higher in cells derived from FFBA compared with cells from AB grafted sites. However, the exposure of cells derived from AB to FFBA particles did not have any remarkable effect on osteoblast differentiation.

CONCLUSIONS

These results indicate the higher osteogenic activity of cells derived from FFBA compared with AB reconstructed sites, offering an explanation at cellular level of why FFBA could be a suitable alternative to AB for reconstructing maxillary bone defects.

Mesenchymal stem cells and bovine bone mineral in sinus lift procedures--an experimental study in sheep

INTRODUCTION

New reconstructive and less invasive methods have been searched to optimize bone formation and osseointegration of dental implants in maxillary sinus augmentation.

PURPOSE

The aim of the presented ovine split-mouth study was to compare bovine bone mineral (BBM) alone and in combination with mesenchymal stem cells (MSCs) regarding their potential in sinus augmentation.

MATERIAL AND METHODS

Bilateral sinus floor augmentations were performed in six adult sheep. BBM and MSCs were placed into the test side and only BBM in the contra-lateral control side of each sheep. Animals were sacrificed after 8 and 16 weeks. Augmentation sites were analyzed by computed tomography, histology, and histomorphometry.

RESULTS

The initial volumes of both sides were similar and did not change significantly with time. A tight connection between the particles of BBM and the new bone was observed histologically. Bone formation was significantly (p = 0.027) faster by 49% in the test sides.

CONCLUSION

The combination of BBM and MSCs accelerated new bone formation in this model of maxillary sinus augmentation. This could allow early placement of implants.

Mesenchymal stem cells and inorganic bovine bone mineral in sinus augmentation: comparison with augmentation by autologous bone in adult sheep

Our aim was to compare the osteogenic potential of mononuclear cells harvested from the iliac crest combined with bovine bone mineral (BBM) (experimental group) with that of autogenous cancellous bone alone (control group). We studied bilateral augmentations of the sinus floor in 6 adult sheep. BBM and mononuclear cells (MNC) were mixed and placed into one side and autogenous bone in the other side. Animals were killed after 8 and 16 weeks. Sites of augmentation were analysed radiographically and histologically. The mean (SD) augmentation volume was 3.0 (1.0) cm(3) and 2.7 (0.3) cm(3) after 8 and 16 weeks in the test group, and 2.8 (0.3) cm(3) (8 weeks) and 2.8 (1.2) cm(3) (16 weeks) in the control group, respectively. After 8 weeks, histomorphometric analysis showed 24 (3)% BBM, and 19 (11)% of newly formed bone in the test group. The control group had 20 (13%) of newly formed bone. Specimens after 16 weeks showed 29 (12%) of newly formed bone and 19 (3%) BBM in the test group. The amount of newly formed bone in the control group was 16 (6%). The results show that mononuclear cells, including mesenchymal stem cells, in combination with BBM as the biomaterial, have the potential to form bone.

Central mucoepidermoid carcinoma: Report of 2 cases

Central mucoepidermoid carcinoma is a rare mandibular neoplasm. The objective of this paper was to report two cases.

In vitro osteogenesis induced by cells derived from sites submitted to sinus grafting with anorganic bovine bone

OBJECTIVES

This study evaluated key parameters of the in vitro osteogenesis induced by osteoblastic cells obtained from sites submitted to sinus grafting with anorganic bovine bone (ABB) in comparison with cells derived from bone sites of the same patients.

MATERIALS AND METHODS

In three patients, the augmentation of maxillary sinus was carried out using ABB (Bio-Oss). After at least 6 months, during the surgical intervention for titanium implants placement, biopsies were taken from these areas using trephine burs (grafted group). Bone fragments, of the same patients, from sites that had not received graft were also obtained with trephine burs and used as a control group. Osteoblastic cells were obtained from grafted and control groups by enzymatic digestion and cultured under standard osteogenic condition until subconfluence. First passaged cells were cultured in 24-well culture plates. Cell adhesion was evaluated at 24 h. For proliferation and viability assay, cells were cultured for 1, 3, 7, and 10 days. Total protein content and alkaline phosphatase (ALP) activity were measured at 3, 7, 10, 14, 17, and 21 days. Cultures were stained with Alizarin red S at 21 days, for detection of mineralized matrix. Data were compared by Student's t-test.

RESULTS

Cell adhesion and viability were not affected by cell source (P>0.05). Total protein content was greater (P<0.05) for grafted group. Cell proliferation, ALP activity, and bone-like nodule formation were all greater (P<0.05) for the control group.

CONCLUSION

Taken together, these results indicate that the in vivo long-term contact of cells with ABB downregulates the expression of osteoblast phenotype and consequently the in vitro osteogenesis.

Lactational performance of Quackenbush Swiss line 5 mice

We evaluated 2 strains of mice for their utility in the investigation of nutritional and molecular regulatory mechanisms of lactation. The lactational performance and milk composition were characterized for an inbred mouse strain, inbred Quackenbush Swiss line 5 (QSi5) selected persistently for fecundity, and a nonselected strain, CBA. The milk yield assessed by changes in BW in response to suckling of sustainable litter sizes for each strain was 3-fold greater (P < 0.001) in QSi5 mice than the CBA strain. The QSi5 mice also produced milk more efficiently (P < 0.001) than CBA mice, despite having the same quantity of mammary tissue per unit of BW. Milk composition did not vary between strains or by stage of lactation, with the exception of lactose concentration, which was greater (P = 0.003) in QSi5 mice. Expression of epsilon-casein was > or = 10-fold greater, and alpha(S1)-casein was > or = 3-fold greater, during mid and late lactation compared with early lactation in both strains, whereas kappa-casein underwent an apparent alteration in posttranslational modifications in both strains from early to mid lactation. Changes in casein composition coincided with an increased susceptibility to proteolytic degradation; hence milk from early lactation may be more readily degraded to facilitate digestion in the neonate. The greater milk synthetic capacity of QSi5 mice over the lactation cycle provides a useful model for studies of nutritional and molecular regulation of lactation.

In vivo bone tissue response to a canasite glass-ceramic

The aim of this study was to determine the biocompatibility and osteoconductive potential of a high-strength canasite glass ceramic. Glass-ceramic rods were produced using the lost-wax casting technique and implanted in the mid-shafts rabbit femurs. Implants were harvested at 4, 13 and 22 weeks and prepared for light and electron microscopy. Hydroxyapatite was used as a control material. Hydroxyapatite implants were surrounded by new mineralised bone tissue after 4 weeks of implantation. The amount of bone surrounding the implant increased slightly at 13 weeks. In contrast, canasite glass and glass ceramic implants were almost entirely surrounded by soft tissue during all the time periods. Close contact between bone and canasite glass-ceramic implant without the intervening fibrous tissue was observed in only a few regions. The canasite formulation evaluated was not osteoconductive and appeared to degrade in the biological environment. It was therefore concluded that the canasite formulation used was unsuitable for use as implant. Further work is required to improve the biocompatibility of these materials with bone tissue. It is possible that this could be achieved by reducing the solubility of the glass and glass ceramic.

Clinical effectiveness of lidocaine and benzocaine for topical anesthesia

The effectiveness of lidocaine and benzocaine in reducing pain produced by needle insertion into the palate was evaluated in a double-blind and placebo-controlled study using a more suitable method. Twenty subjects, 10 men and 10 women, submitted to 4 sessions in which they were randomly treated with 5% lidocaine, a placebo that tasted like lidocaine, 20% benzocaine, and a placebo that tasted like benzocaine. At each session, a 27-gauge needle was inserted into the palate twice, once before (baseline) and once after drug application for 1 minute. Immediately after each insertion, subjects indicated on a visual analog scale the pain intensity perceived. Lidocaine and benzocaine were equally efficient, and both were better than placebo in reducing pain caused by insertion of needles into the palate.