Local tissue effects of various barrier membranes in a rat subcutaneous model

Purpose@#The purpose of this study was to examine the local tissue reactions associated with 3 different poly(lactic-co-glycolic acid) (PLGA) prototype membranes and to compare them to the reactions associated with commercially available resorbable membranes in rats. @*Methods@#Seven different membranes—3 synthetic PLGA prototypes (T1, T2, and T3) and 4 commercially available membranes (a PLGA membrane, a poly[lactic acid] membrane, a native collagen membrane, and a cross-linked collagen membrane)—were randomly inserted into 6 unconnected subcutaneous pouches in the backs of 42 rats. The animals were sacrificed at 4, 13, and 26 weeks. Descriptive histologic and histomorphometric assessments were performed to evaluate membrane degradation, visibility, tissue integration, tissue ingrowth, neovascularization, encapsulation, and inflammation. Means and standard deviations were calculated. @*Results@#The histological analysis revealed complete integration and tissue ingrowth of PLGA prototype T1 at 26 weeks. In contrast, the T2 and T3 prototypes displayed slight to moderate integration and tissue ingrowth regardless of time point. The degradation patterns of the 3 synthetic prototypes were similar at 4 and 13 weeks, but differed at 26 weeks. T1 showed marked degradation at 26 weeks, whereas T2 and T3 displayed moderate degradation.Inflammatory cells were present in all 3 prototype membranes at all time points, and these membranes did not meaningfully differ from commercially available membranes with regard to the extent of inflammatory cell infiltration. @*Conclusions@#The 3 PLGA prototypes, particularly T1, induced favorable tissue integration, exhibited a similar degradation rate to native collagen membranes, and elicited a similar inflammatory response to commercially available non–cross-linked resorbable membranes.The intensity of inflammation associated with degradable dental membranes appears to relate to their degradation kinetics, irrespective of their material composition.

Implant survival and risk factor analysis in regenerated bone: results from a 5-year retrospective study

Purpose@#The aims of this study were to evaluate the 5-year cumulative survival rate (CSR) of implants placed with guided bone regeneration (GBR) compared to implants placed in native bone, and to identify factors contributing to implant failure in regenerated bone. @*Methods@#This retrospective cohort study included 240 patients who had implant placement either with a GBR procedure (regenerated bone group) or with pristine bone (native bone group). Data on demographic features (age, sex, smoking, and medical history), location of the implant, implant-specific features, and grafting procedures and materials were collected.The 5-year CSRs in both groups were estimated using Kaplan-Meier analysis. Risk factors for implant failure were analyzed with a Cox proportional hazards model. @*Results@#In total, 264 implants in the native bone group and 133 implants in the regenerated bone group were analyzed. The 5-year CSRs were 96.4% in the regenerated bone group and 97.5% in the native bone group, which was not a significant difference. The multivariable analysis confirmed that bone status was not an independent risk factor for implant failure. However, smoking significantly increased the failure rate (hazard ratio, 10.7; P=0.002). @*Conclusions@#The 5-year CSR of implants placed in regenerated bone using GBR was comparable to that of implants placed in native bone. Smoking significantly increased the risk of implant failure in both groups.

Local tissue effects of various barrier membranes in a rat subcutaneous model

Purpose@#The purpose of this study was to examine the local tissue reactions associated with 3 different poly(lactic-co-glycolic acid) (PLGA) prototype membranes and to compare them to the reactions associated with commercially available resorbable membranes in rats. @*Methods@#Seven different membranes—3 synthetic PLGA prototypes (T1, T2, and T3) and 4 commercially available membranes (a PLGA membrane, a poly[lactic acid] membrane, a native collagen membrane, and a cross-linked collagen membrane)—were randomly inserted into 6 unconnected subcutaneous pouches in the backs of 42 rats. The animals were sacrificed at 4, 13, and 26 weeks. Descriptive histologic and histomorphometric assessments were performed to evaluate membrane degradation, visibility, tissue integration, tissue ingrowth, neovascularization, encapsulation, and inflammation. Means and standard deviations were calculated. @*Results@#The histological analysis revealed complete integration and tissue ingrowth of PLGA prototype T1 at 26 weeks. In contrast, the T2 and T3 prototypes displayed slight to moderate integration and tissue ingrowth regardless of time point. The degradation patterns of the 3 synthetic prototypes were similar at 4 and 13 weeks, but differed at 26 weeks. T1 showed marked degradation at 26 weeks, whereas T2 and T3 displayed moderate degradation.Inflammatory cells were present in all 3 prototype membranes at all time points, and these membranes did not meaningfully differ from commercially available membranes with regard to the extent of inflammatory cell infiltration. @*Conclusions@#The 3 PLGA prototypes, particularly T1, induced favorable tissue integration, exhibited a similar degradation rate to native collagen membranes, and elicited a similar inflammatory response to commercially available non–cross-linked resorbable membranes.The intensity of inflammation associated with degradable dental membranes appears to relate to their degradation kinetics, irrespective of their material composition.

Implant survival and risk factor analysis in regenerated bone: results from a 5-year retrospective study

Purpose@#The aims of this study were to evaluate the 5-year cumulative survival rate (CSR) of implants placed with guided bone regeneration (GBR) compared to implants placed in native bone, and to identify factors contributing to implant failure in regenerated bone. @*Methods@#This retrospective cohort study included 240 patients who had implant placement either with a GBR procedure (regenerated bone group) or with pristine bone (native bone group). Data on demographic features (age, sex, smoking, and medical history), location of the implant, implant-specific features, and grafting procedures and materials were collected.The 5-year CSRs in both groups were estimated using Kaplan-Meier analysis. Risk factors for implant failure were analyzed with a Cox proportional hazards model. @*Results@#In total, 264 implants in the native bone group and 133 implants in the regenerated bone group were analyzed. The 5-year CSRs were 96.4% in the regenerated bone group and 97.5% in the native bone group, which was not a significant difference. The multivariable analysis confirmed that bone status was not an independent risk factor for implant failure. However, smoking significantly increased the failure rate (hazard ratio, 10.7; P=0.002). @*Conclusions@#The 5-year CSR of implants placed in regenerated bone using GBR was comparable to that of implants placed in native bone. Smoking significantly increased the risk of implant failure in both groups.

Cone-beam computed tomographic analysis of the alveolar ridge profile and virtual implant placement for the anterior maxilla

PURPOSE: To analyze the ridge profile of the anterior maxilla using cone-beam computed tomography and to assess the clinical significance of the ridge profile by performing virtual implant placement. METHODS: Thirty-two cone-beam computed tomography scans of anterior maxillae were included. For each tooth, a vertical line was made along the longitudinal axis, and 3 horizontal lines at 1-, 3-, and 5-mm levels below the labial bone crest were drawn perpendicularly to the vertical reference. At these levels, the thickness of the alveolar ridge (RT), and the labial (LT) and palatal bone plate (PT) were measured. Then, virtual implant placement using standard and tapered implants was performed. A generalized linear mixed model was used for statistical analysis. RESULTS: The teeth were located labially based on the proportion of LT and PT with respect to RT. At the 1-mm level, the value of LT was between 1.0±0.4 mm for central incisors and 1.3±0.6 mm for canines. A large number of teeth had area(s) with less than 1-mm-thick labial bone between the 1- and 5-mm levels below the crest. The mean PT was generally thicker than the LT in all tooth types. The greatest mean value of labial concavity was observed for canines, compared to other tooth types. Men had a greater RT than did women, but had a comparable LT. Less apical fenestration was observed when tapered implants were used. CONCLUSIONS: Most teeth in the anterior maxilla had a thin labial bone plate, with no significant difference between sexes. Tapered implants may be advantageous for the anterior maxilla.

Primary stability of implants with peri-implant bone defects of various widths: an in vitro investigation

PURPOSE: This study aimed to evaluate the effects of i) the extent of peri-implant bone defects and ii) the application of bone cement on implant stability with respect to the measurement direction. METHODS: In 10 bovine rib bones, 4 implant osteotomies with peri-implant bone defects of various widths were prepared: i) no defect (D0), ii) a 2-mm-wide defect (D2), iii) a 4-mm-wide defect (D4), and iv) a 8-mm-wide defect (D8). The height of all defects was 10 mm. Implant stability quotient (ISQ) values and Periotest values (PTVs) were measured after implant placement and bone cement application. RESULTS: With increasing defect width, decreased ISQs and increased PTVs were observed. Statistically significant differences were found between groups D0 and D8, D0 and D4, and D2 and D8. Prior to bone cement application, inconsistent PTVs were found in group D8 depending on the measurement direction. Bone cement increased the implant stability. CONCLUSION: Peri-implant bone deficits measuring around 50% of the implant surface compromised implant stability. Clinically, PTVs should be cautiously interpreted in implants with large peri-implant defects due to inconsistent recordings with respect to the measurement direction.

Tissue integration of zirconia and titanium implants with and without buccal dehiscence defects

PURPOSE: The purpose of the present study was to validate an experimental model for assessing tissue integration of titanium and zirconia implants with and without buccal dehiscence defects. METHODS: In 3 dogs, 5 implants were randomly placed on both sides of the mandibles: 1) Z1: a zirconia implant (modified surface) within the bony housing, 2) Z2: a zirconia implant (standard surface) within the bony housing, 3) T: a titanium implant within the bony housing, 4) Z1_D: a Z1 implant placed with a buccal bone dehiscence defect (3 mm), and 5) T_D: a titanium implant placed with a buccal bone dehiscence defect (3 mm). The healing times were 2 weeks (one side of the mandible) and 6 weeks (the opposite side). RESULTS: The dimensions of the peri-implant soft tissue varied depending on the implant and the healing time. The level of the mucosal margin was located more apically at 6 weeks than at 2 weeks in all groups, except group T. The presence of a buccal dehiscence defect did not result in a decrease in the overall soft tissue dimensions between 2 and 6 weeks (4.80±1.31 and 4.3 mm in group Z1_D, and 4.47±1.06 and 4.5±1.37 mm in group T_D, respectively). The bone-to-implant contact (BIC) values were highest in group Z1 at both time points (34.15%±21.23% at 2 weeks, 84.08%±1.33% at 6 weeks). The buccal dehiscence defects in groups Z1_D and T_D showed no further bone loss at 6 weeks compared to 2 weeks. CONCLUSIONS: The modified surface of Z1 demonstrated higher BIC values than the surface of Z2. There were minimal differences in the mucosal margin between 2 and 6 weeks in the presence of a dehiscence defect. The present model can serve as a useful tool for studying peri-implant dehiscence defects at the hard and soft tissue levels.

Alveolar ridge preservation with an open-healing approach using single-layer or double-layer coverage with collagen membranes

PURPOSE: The aim of this prospective pilot study was to compare alveolar ridge preservation (ARP) procedures with open-healing approach using a single-layer and a double-layer coverage with collagen membranes using radiographic and clinical analyses. METHODS: Eleven molars from 9 healthy patients requiring extraction of the maxillary or mandibular posterior teeth were included and allocated into 2 groups. After tooth extraction, deproteinized bovine bone mineral mixed with 10% collagen was grafted into the socket and covered either with a double-layer of resorbable non-cross-linked collagen membranes (DL group, n=6) or with a single-layer (SL group, n=5). Primary closure was not obtained. Cone-beam computed tomography images were taken immediately after the ARP procedure and after a healing period of 4 months before implant placement. Radiographic measurements were made of the width and height changes of the alveolar ridge. RESULTS: All sites healed without any complications, and dental implants were placed at all operated sites with acceptable initial stability. The measurements showed that the reductions in width at the level 1 mm apical from the alveolar crest (including the bone graft) were −1.7±0.5 mm in the SL group and −1.8±0.4 mm in the DL group, and the horizontal changes in the other areas were also similar in the DL and SL groups. The reductions in height were also comparable between groups. CONCLUSIONS: Within the limitations of this study, single-layer and double-layer coverage with collagen membranes after ARP failed to show substantial differences in the preservation of horizontal or vertical dimensions or in clinical healing. Thus, both approaches seem to be suitable for open-healing ridge preservation procedures.

Sinus augmentation using rhBMP-2-loaded synthetic bone substitute with simultaneous implant placement in rabbits

PURPOSE: The aim of this study was to determine the effect of recombinant human bone morphogenetic protein-2 (rhBMP-2)-loaded synthetic bone substitute on implants that were simultaneously placed with sinus augmentation in rabbits. METHODS: In this study, a circular access window was prepared in the maxillary sinus of rabbits (n=5) for a bone graft around an implant (Ø 3×6 mm) that was simultaneously placed anterior to the window. Synthetic bone substitute loaded with rhBMP-2 was placed on one side of the sinus to form the experimental group, and saline-soaked synthetic bone substitute was placed on the other side of the sinus to form the control group. After 4 weeks, sections were obtained for analysis by micro-computed tomography and histology. RESULTS: Volumetric analysis showed that the median amount of newly formed bone was significantly greater in the BMP group than in the control group (51.6 mm3 and 46.6 mm3, respectively; P=0.019). In the histometric analysis, the osseointegration height was also significantly greater in the BMP group at the medial surface of the implant (5.2 mm and 4.3 mm, respectively; P=0.037). CONCLUSIONS: In conclusion, an implant simultaneously placed with sinus augmentation using rhBMP-2-loaded synthetic bone substitute can be successfully osseointegrated, even when only a limited bone height is available during the early stage of healing.

Erratum: Body text. Bone formation around rhBMP-2-coated implants in rabbit sinuses with or without absorbable collagen sponge grafting

The authors recently found a mistake in their previously published article and sincerely regret these errors.

Effects of a mouthwash containing potassium nitrate, sodium fluoride, and cetylpyridinium chloride on dentin hypersensitivity: a randomized, double-blind, placebo-controlled study

PURPOSE: We evaluated the efficacy of a mouthwash containing potassium nitrate (KNO3) as its main component, along with sodium fluoride (NaF) and cetylpyridinium chloride (CPC). The primary endpoint was the relief of dentin hypersensitivity (DH) against the cold stimuli. The effects on other DH tests and periodontal inflammation were also evaluated. METHODS: We used a single-center, double-blind, placebo-controlled, randomized design. A total of 82 patients with DH (40 in the test group, 42 placebo controls) were analyzed using visual analog scales (VASs) for a cold test, a tactile test, a compressive air test, and self-reported pain during daily activities, as well as clinical parameters including plaque index, gingival index, modified sulcular bleeding index (mSBI), gingival recession, and probing depth, which were collected at baseline and after four and six weeks of mouthwash use. RESULTS: VAS scores for cold sensations, tactile sensations, the compressive air test, and self-reported pain significantly decreased from baseline during the six weeks in both groups (P<0.01), and no significant differences between the groups were found. In male patients (10 in the test group and 7 in the control group), both groups showed significant reductions in VAS scores for the cold test over the six weeks, and greater reductions were found in the test group than in the control group between four and six weeks (P=0.01) and between baseline and six weeks (P<0.01). In addition, the mSBI in the test group significantly decreased from baseline during the six weeks (P<0.01), and the changes at four and six weeks from baseline were significantly greater in the test group compared to the control group (P=0.03 and P=0.02, respectively). CONCLUSIONS: A mouthwash containing a mixture of KNO3, NaF, and CPC reduced DH and gingival inflammation, however, the efficacy was comparable to the control group.

Late-term healing in an augmented sinus with different ratios of biphasic calcium phosphate: a pilot study using a rabbit sinus model

PURPOSE: The aim of this pilot study was to determine the osteoconductivity and dimensional stability of augmented sinuses using different ratios of biphasic calcium phosphate (BCP) in a rabbit sinus model. METHODS: Each sinus of New Zealand white rabbits (2.5-3.5 kg) was assigned to one of two groups: BCP with a hydroxyapatite to beta-tricalcium phosphate (HA:beta-TCP) ratio of 70:30 (group TCP30) and BCP with an HA:beta-TCP ratio of 30:70 (group TCP70). After preparing a window in the antral wall of a sinus, the Schneiderian membrane was elevated, and the applicable material was grafted. A fluorochrome calcein green was injected five days before euthanizing the animals at four months post-surgery. The specimens were analyzed histologically, histomorphometrically, and by using micro-computed tomography (micro-CT). RESULTS: Micro-CT analysis revealed that the total augmented volume and the new bone volume did not differ significantly between the two groups whereas the resorption of materials was greater in the TCP70 group. The trabecular thickness, number, and separation also did not differ significantly between the two groups. Histomorphometrically, the areas of total augmentation, new bone, and residual material, as well as the ratio of new-bone-material contact did not differ significantly between the groups. Histologically, the residual particles were more scattered in the TCP70 group than in the TCP30 group. The fluorescence of the calcein green did not differ notably between the two groups. CONCLUSIONS: The osteoconductivity and dimensional stability of the two BCPs with different ratios tested in this study were comparable after four months of healing. Therefore, we conclude that both BCPs show promise as a bone substitute for sinus augmentation.

The hidden X suture: a technical note on a novel suture technique for alveolar ridge preservation

PURPOSE: The present study investigated the impact of 2 different suture techniques, the conventional crossed mattress suture (X suture) and the novel hidden X suture, for alveolar ridge preservation (ARP) with an open healing approach. METHODS: This study was a prospective randomized controlled clinical trial. Fourteen patients requiring extraction of the maxillary or mandibular posterior teeth were enrolled and allocated into 2 groups. After extraction, demineralized bovine bone matrix mixed with 10% collagen (DBBM-C) was grafted and the socket was covered by porcine collagen membrane in a double-layer fashion. No attempt to obtain primary closure was made. The hidden X suture and conventional X suture techniques were performed in the test and control groups, respectively. Cone-beam computed tomographic (CBCT) images were taken immediately after the graft procedure and before implant surgery 4 months later. Additionally, the change in the mucogingival junction (MGJ) position was measured and was compared after extraction, after suturing, and 4 months after the operation. RESULTS: All sites healed without any complications. Clinical evaluations showed that the MGJ line shifted to the lingual side immediately after the application of the X suture by 1.56±0.90 mm in the control group, while the application of the hidden X suture rather pushed the MGJ line slightly to the buccal side by 0.25±0.66 mm. It was demonstrated that the amount of keratinized tissue (KT) preserved on the buccal side was significantly greater in the hidden X suture group 4 months after the procedure (P<0.05). Radiographic analysis showed that the hidden X suture had a significant effect in preserving horizontal width and minimizing vertical reduction in comparison to X suture (P<0.05). CONCLUSIONS: Our study provided clinical and radiographic verification of the efficacy of the hidden X suture in preserving the width of KT and the dimensions of the alveolar ridge after ARP.

Preferences and flexibility in decision-making among dental clinicians regarding the treatment of multirooted teeth: an interactive communication device-based survey at two academic conferences

PURPOSE: Decision-making by dental and medical experts can be influenced by their biases, interests, and experiences, and academic arguments about controversial issues may additionally be considered indirect experiences capable of affecting decision-making. This study reports on the use of interactive communication devices to evaluate preferences and flexibility in decision-making among dental care providers who attended two distinct academic conferences. METHODS: Two debates were presented by a team of two lecturers at two academic conferences (focusing on periodontology and implant dentistry, respectively) and the audience members of each session were surveyed. Before each lecture, two case modules about the diagnosis and treatment of multirooted molar lesions were provided, and interactive communication devices were used to collect responses about decision-making preferences in treatment planning immediately before and after a debate about treatment strategies. RESULTS: In total, 81 and 84 completed answers from both conferences were obtained for the first and second case modules, respectively. The preferred treatment plan differed significantly according to the focus of the conference, and a tendency emerged for the clinicians participating in each conference to express uniform preferences. However, attending the debates resulted in significant changes in decision-making preferences regardless of the conference focus or the characteristics of the participants. CONCLUSIONS: Our findings suggest that providing continuing education via debates on controversial issues may be effective in widening conceptual knowledge and reducing biases among experts in the dental and medical fields.

Primary implant stability in a bone model simulating clinical situations for the posterior maxilla: an in vitro study

PURPOSE: The aim of this study was to determine the influence of anatomical conditions on primary stability in the models simulating posterior maxilla. METHODS: Polyurethane blocks were designed to simulate monocortical (M) and bicortical (B) conditions. Each condition had four subgroups measuring 3 mm (M3, B3), 5 mm (M5, B5), 8 mm (M8, B8), and 12 mm (M12, B12) in residual bone height (RBH). After implant placement, the implant stability quotient (ISQ), Periotest value (PTV), insertion torque (IT), and reverse torque (RT) were measured. Two-factor ANOVA (two cortical conditions×four RBHs) and additional analyses for simple main effects were performed. RESULTS: A significant interaction between cortical condition and RBH was demonstrated for all methods measuring stability with two-factor ANOVA. In the analyses for simple main effects, ISQ and PTV were statistically higher in the bicortical groups than the corresponding monocortical groups, respectively. In the monocortical group, ISQ and PTV showed a statistically significant rise with increasing RBH. Measurements of IT and RT showed a similar tendency, measuring highest in the M3 group, followed by the M8, the M5, and the M12 groups. In the bicortical group, all variables showed a similar tendency, with different degrees of rise and decline. The B8 group showed the highest values, followed by the B12, the B5, and the B3 groups. The highest coefficient was demonstrated between ISQ and PTV. CONCLUSIONS: Primary stability was enhanced by the presence of bicortex and increased RBH, which may be better demonstrated by ISQ and PTV than by IT and RT.

Effectiveness of biphasic calcium phosphate block bone substitutes processed using a modified extrusion method in rabbit calvarial defects

PURPOSE: This study evaluated the mechanical and structural properties of biphasic calcium phosphate (BCP) blocks processed using a modified extrusion method, and assessed their in vivo effectiveness using a rabbit calvarial defect model. METHODS: BCP blocks with three distinct ratios of hydroxyapatite (HA):tricalcium phosphate (TCP) were produced using a modified extrusion method:HA8 (8%:92%), HA48 (48%:52%), and HA80 (80%:20%). The blocks were examined using scanning electron microscopy, X-ray diffractometry, and a universal test machine. Four circular defects 8 mm in diameter were made in 12 rabbits. One defect in each animal served as a control, and the other three defects received the BCP blocks. The rabbits were sacrificed at either two weeks (n=6) or eight weeks (n=6) postoperatively. RESULTS: The pore size, porosity, and compressive strength of the three types of bone block were 140-170 microm, >70%, and 4-9 MPa, respectively. Histologic and histomorphometric observations revealed that the augmented space was well maintained, but limited bone formation was observed around the defect base and defect margins. No significant differences were found in the amount of new bone formation, graft material resorption, or bone infiltration among the three types of BCP block at either of the postoperative healing points. CONCLUSIONS: Block bone substitutes with three distinct compositions (i.e., HA:TCP ratios) processed by a modified extrusion method exhibited limited osteoconductive potency, but excellent space-maintaining capability. Further investigations are required to improve the processing method.

Assessment of dehydrothermally cross-linked collagen membrane for guided bone regeneration around peri-implant dehiscence defects: a randomized single-blinded clinical trial

PURPOSE: The aim of this study was to determine the clinical feasibility of using dehydrothermally cross-linked collagen membrane (DCM) for bone regeneration around peri-implant dehiscence defects, and compare it with non-cross-linked native collagen membrane (NCM). METHODS: Dehiscence defects were investigated in twenty-eight patients. Defect width and height were measured by periodontal probe immediately following implant placement (baseline) and 16 weeks afterward. Membrane manipulation and maintenance were clinically assessed by means of the visual analogue scale score at baseline. Changes in horizontal thickness at 1 mm, 2 mm, and 3 mm below the top of the implant platform and the average bone density were assessed by cone-beam computed tomography at 16 weeks. Degradation of membrane was histologically observed in the soft tissue around the implant prior to re-entry surgery. RESULTS: Five defect sites (two sites in the NCM group and three sites in the DCM group) showed soft-tissue dehiscence defects and membrane exposure during the early healing period, but there were no symptoms or signs of severe complications during the experimental postoperative period. Significant clinical and radiological improvements were found in all parameters with both types of collagen membrane. Partially resorbed membrane leaflets were only observed histologically in the DCM group. CONCLUSIONS: These findings suggest that, compared with NCM, DCM has a similar clinical expediency and possesses more stable maintenance properties. Therefore, it could be used effectively in guided bone regeneration around dehiscence-type defects.

Bone formation around rhBMP-2-coated implants in rabbit sinuses with or without absorbable collagen sponge grafting

PURPOSE: The purpose of this study was to evaluate bone formation around recombinant human bone morphogenetic protein (rhBMP-2)-coated implants placed with or without absorbable collagen sponge (ACS) in rabbit maxillary sinuses. METHODS: The Schneiderian membrane was elevated and an implant was placed in 24 sinuses in 12 rabbits. The space created beneath the elevated membrane was filled with either blood (n=6) or ACS (n=6). In the rabbits in which this space was filled with blood, rhBMP-2-coated and non-coated implants were alternately placed on different sides. The resulting groups were referred to as the BC and BN groups, respectively. The AC and AN groups were produced in ACS-grafted rabbits in the same manner. Radiographic and histomorphometric analyses were performed after eight weeks of healing. RESULTS: In micro-computed tomography analysis, the total augmented volume and new bone volume were significantly greater in the ACS-grafted sinuses than in the blood-filled sinuses (P<0.05). The histometric analysis showed that the areas of new bone and bone-to-implant contact were significantly larger in the AC group than in the AN group (P<0.05). In contrast, none of the parameters differed significantly between the BC and BN groups. CONCLUSIONS: The results of this pilot study indicate that the insertion of ACS after elevating the Schneiderian membrane, simultaneously with implant placement, can significantly increase the volume of the augmentation. However, in the present study, the rhBMP-2 coating exhibited limited effectiveness in enhancing the quantity and quality of regenerated bone.

The effect of overlaying titanium mesh with collagen membrane for ridge preservation

PURPOSE: The aim of this study was to determine the effect of overlaying titanium mesh (TM) with an adjunctive collagen membrane (CM) for preserving the buccal bone when used in association with immediate implant placement in dogs. METHODS: Immediate implant placements were performed in the mesial sockets of the third premolars of five dogs. At one site the TM was attached to the fixture with the aid of its own stabilizers and then covered by a CM (CM group), while the contralateral site received only TM (TM group). Biopsy specimens were retrieved for histologic and histomorphometric analyses after 16 weeks. RESULTS: All samples exhibited pronounced buccal bone resorption, and a high rate of TM exposure was noted (in three and four cases of the five samples in each of the TM and CM groups, respectively). A dense fibrous tissue with little vascularity or cellularity had infiltrated through the pores of the TM irrespective of the presence of a CM. The distances between the fixture platform and the first bone-implant contact and the bone crest did not differ significantly between the TM and CM groups. CONCLUSIONS: Our study suggests that the additional use of a CM over TM does not offer added benefit for mucosal healing and buccal bone preservation.

Comparative analysis of carrier systems for delivering bone morphogenetic proteins

PURPOSE: The objective of this study was to comparatively assess the bone regenerative capacity of absorbable collagen sponge (ACS), biphasic calcium phosphate block (BCP) and collagenated biphasic calcium phosphate (CBCP) loaded with a low dose of recombinant human bone morphogenetic protein-2 (rhBMP-2). METHODS: The CBCP was characterized by X-ray diffraction and scanning electron microscopy. In rabbit calvaria, four circular 8-mm-diameter defects were created and assigned to one of four groups: (1) blood-filled group (control), (2) rhBMP-2-soaked absorbable collagen sponge (0.05 mg/mL, 0.1 mL; CS group), (3) rhBMP-2-loaded BCP (BCP group), or (4) rhBMP-2-loaded CBCP (CBCP group). The animals were sacrificed either 2 weeks or 8 weeks postoperatively. Histological and histomorphometric analyses were performed. RESULTS: The CBCP showed web-like collagen fibrils on and between particles. Greater dimensional stability was observed in the BCP and CBCP groups than in the control and the CS groups at 2 and 8 weeks. The new bone formation was significantly greater in the BCP and CBCP groups than in the control and CS groups at 2 weeks, but did not significantly differ among the four groups at 8 week. The CBCP group exhibited more new bone formation in the intergranular space and in the center of the defect compared to the BCP group at 2 weeks, but a similar histologic appearance was observed in both groups at 8 weeks. CONCLUSIONS: The dose of rhBMP-2 in the present study enhanced bone regeneration in the early healing period when loaded on BCP and CBCP in rabbit calvarial defects.