Faculty Bibliography

OBJECTIVES: To evaluate the influence of implant-abutment interface (IAI) placement depth on bone remodeling around implants with two different types of tapered internal IAI: screwed-in (SI) and tapped-in (TI) connections in dogs. MATERIALS AND METHODS: Eight weeks post mandibular tooth extraction in six beagle dogs, two SI implants (OsseoSpeed , Astra Tech, DENTSPLY) and two TI implants (Integra-CP , Bicon LLC) were placed in one side of the mandible. The four experimental groups were as follows: (i) SI-placed equicrestally (SIC); (ii) TI-placed equicrestally (TIC); (iii) SI-placed 1.5 mm subcrestally (SIS); and (iv) TI-placed 1.5 mm subcrestally (TIS). Healing abutments were connected 12 weeks after implant placement. Sixteen weeks later, the dogs were sacrificed and histomorphometric analysis was performed. Histometrical outcomes were evaluated using a nonparametric Brunner-Langer model. RESULTS: Mean distance from the IAI to first bone-implant contact (IAI-fBIC) was 0.88 mm (median: 0.77; SD: 0.54) for SIC group, 1.23 mm (median: 1.22; SD: 0.66) for TIC group, 0.41 mm (median: 0.31; SD: 0.36) for SIS group, and 0.41 mm (median: 0.26; SD: 0.45) for TIS group. Subcrestal groups showed lower IAI-fBIC compared with equicrestal groups (P < 0.001). Connective tissue presented similar measurements regardless of the IAI placement depth and IAI type (P > 0.05), but the epithelium length and peri-implant soft tissue length in subcrestal groups were significant larger than that in the equicrestal groups (P < 0.001 and P = 0.004, respectively). CONCLUSION: Subcrestal implant placement with tapered internal IAI is beneficial for bone contact with the implant neck, and concurrently, it may not increase the soft tissue inflammation around IAI.

PURPOSE:: To investigate the bone regenerative effect of polymer and collagen incorporation to synthetic bone graft materials. MATERIALS AND METHODS:: The bone ingrowth of biphasic graft materials was tested in a rabbit calvaria defect model after chemical characterization: HA/TCP (25%/75%) with collagen, HA/TCP (25%/75%) without collagen, (HA/TCP)/PLGA (85%/15%) with collagen, (HA/TCP)/PLGA (65%/35%) with collagen and a commercially available (HA/TCP)/PLGA (50%/50%) was used as control. After 4 and 8 weeks, the retrieved samples were subjected to histomorphometrical analysis. RESULTS:: Histomorphometry presented no significant differences concerning the bone formation between the different groups at both 4 and 8 weeks. Evidently, the (HA/TCP)/PLGA (65%/35%) with collagen presented the least amount of soft tissue incorporation within the defect. The same group possessed higher amounts of bone graft material within the defect throughout the 8-week observation period, whereas the other groups seemed to decrease in volume from 4 to 8 weeks. CONCLUSION:: Increase of the PLGA percentage within the biphasic graft material seemed to maintain its volume and prevented soft tissue migration, which could be clinically beneficial.

This study assessed the osseointegrative effects of atmospheric pressure plasma (APP) surface treatment for implants in a canine model. Control surfaces were untreated textured titanium (Ti) and calcium phosphate (CaP). Experimental surfaces were their 80-second air-based APP-treated counterparts. Physicochemical characterization was performed to assess topography, surface energy, and chemical composition. One implant from each control and experimental group (four in total) was placed in one radius of each of the seven male beagles for three weeks, and one implant from each group was placed in the contralateral radius for six weeks. After sacrifice, bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) were assessed. X-ray photoelectron spectroscopy showed decreased surface levels of carbon and increased Ti and oxygen, and calcium and oxygen, posttreatment for Ti and CaP surfaces, respectively. There was a significant (P < 0.001) increase in BIC for APP-treated textured Ti surfaces at six weeks but not at three weeks or for CaP surfaces. There were no significant (P = 0.57) differences for BAFO between treated and untreated surfaces for either material at either time point. This suggests that air-based APP surface treatment may improve osseointegration of textured Ti surfaces but not CaP surfaces. Studies optimizing APP parameters and applications are warranted.

Numerous studies have demonstrated that Schwann cells (SCs) play a role in nerve regeneration; however, their role in innervating a bioceramic scaffold for potential application in bone regeneration is still unknown. Here we report the cell growth and functional behavior of SCs on beta-tricalcium phosphate (beta-TCP) scaffolds arranged in 3D printed-lattice (P-beta-TCP) and randomly-porous, template-casted (N-beta-TCP) structures. Our results indicate that SCs proliferated well and expressed the phenotypic markers p75LNGFR and the S100-beta subunit of SCs as well as displayed growth morphology on both scaffolds, but SCs showed spindle-shaped morphology with a significant degree of SCs alignment on the P-beta-TCP scaffolds, seen to a lesser degree in the N-beta-TCP scaffold. The gene expressions of nerve growth factor (beta-ngf), neutrophin-3 (nt-3), platelet-derived growth factor (pdgf-bb), and vascular endothelial growth factor (vegf-a) were higher at day 7 than at day 14. While no significant differences in protein secretion were measured between these last two time points, the scaffolds promoted the protein secretion at day 3 compared to that on the cell culture plates. These results together imply that the beta-TCP scaffolds can support SC cell growth and that the 3D-printed scaffold appeared to significantly promote the alignment of SCs along the struts. Further studies are needed to investigate the early and late stage relationship between gene expression and protein secretion of SCs on the scaffolds with refined characteristics, thus better exploring the potential of SCs to support vascularization and innervation in synthetic bone grafts.

This study investigated whether the use of a dual-layer polytetrafluoroethylene (PTFE)/porcine-derived bioresorbable pericardium membrane enhances the osseointegration around implants compared to a single-layer porcine-derived bioresorbable pericardium membrane and a no-membrane control group. Endosseous implants were placed in the fresh extraction sockets of beagles. At 6 weeks, bone loss and apical soft tissue migration occurred in the control group, whereas bone successfully formed to the neck of the implant for the single-layer porcine-derived bioresorbable pericardium membrane group. The dual-layer PTFE/ porcine-derived bioresorbable pericardium membrane showed bone growth coronal to the neck of the implant. Bone-to-implant contact and buccal bone loss were respectively higher and lower relative to the single-layer but not statistically different.

In this study, the physicochemical characteristics of calcium phosphate based bioactive ceramics of different compositions and blends presenting similar micro/nanoporosity and micrometer scale surface texture were characterized and evaluated in an in vivo model. Prior to the animal experiment, the porosity, surface area, particle size distribution, phase quantification, and dissolution of the materials tested were evaluated. The bone regenerative properties of the materials were evaluated using a rabbit calvaria model. After 2, 4, and 8weeks, the animals were sacrificed and all samples were subjected to histologic observation and histomorphometric analysis. The material characterization showed that all materials tested presented variation in particle size, porosity and composition with different degrees of HA/TCP/lower stoichiometry phase ratios. Histologically, the calvarial defects presented temporal bone filling suggesting that all material groups were biocompatible and osteoconductive. Among the different materials tested, there were significant differences found in the amount of bone formation as a function of time. At 8weeks, the micro/nanoporous material presenting ~55%TCP:45%HA composition ratio presented higher amounts of new bone regeneration relative to other blends and a decrease in the amount of soft tissue infiltration.

The aim of this study was to evaluate mechanically and morphologically the effect of a specific peptide sequence P-15, when incorporated into implant surfaces. Three types of implants were used for the study: Group A: commercially pure titanium implant (blasted and acid etched) + electrochemical thin calcium phosphate deposition, Group B: commercially pure titanium implant (blasted and acid etched) + electrochemical thin calcium phosphate deposition + P-15 incorporation, and as control, Group C: commercially pure titanium implant (blasted and acid etched). After a topographical characterization, transcortical osteotomies were made, and all implant groups (102 implants per group) were randomly placed bilaterally in the tibiae of adult beagle dogs (n = 24). At, 1, 2, and 4 weeks post-surgery, the animals were sacrificed and the samples were retrieved for removal torque tests, for nano indentation, and for histomorphometrical analysis. The results (mean +/- 95% CI) showed that Group B (34.4 +/- 8.7%) presented statistically higher bone-to-implant contact than the other groups (A = 23.9 +/- 7.8%; C = 21.7 +/- 8.3%) at 1 week, indicating an enhanced osteogenesis due to the peptide incorporation. The results suggested that the incorporation of P-15 to implant surfaces increased its bioactivity and the effects were notable especially in the early stages of the healing process. (c) 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2013.

Successful repair of craniofacial and periodontal tissue defects ideally involves a combined therapy that includes inflammation modulation, control of soft tissue infiltration, and bone regeneration. In this study, an anti-inflammatory polymer, salicylic acid-based poly(anhydride-ester) (SAPAE) and a three-dimensional osteoconductive ceramic scaffold were evaluated as a combined guided bone regeneration (GBR) system for concurrent control of inflammation, soft tissue ingrowth, and bone repair in a rabbit cranial defect model. At time periods of 1, 3, and 8 weeks, five groups were compared: (1) scaffolds with a solid ceramic cap (as a GBR structure); (2) scaffolds with no cap; (3) scaffolds with a poly(lactide-glycolide) cap; (4) scaffolds with a slow release SAPAE polymer cap; and (5) scaffolds with a fast release SAPAE polymer cap. Cellular infiltration and bone formation in these scaffolds were evaluated to assess inflammation and bone repair capacity of the test groups. The SAPAE polymers suppressed inflammation and displayed no deleterious effect on bone formation. Additional work is warranted to optimize the anti-inflammatory action of the SAPAE, GBR suppression of soft tissue infiltration, and stimulation of bone formation in the scaffolds and create a composite device for successful repair of craniofacial and periodontal tissue defects. (c) 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 655-664, 2014.

This in vivo study investigated the in vivo performance of two newly developed synthetic bone substitutes and compared them to commercially available xenografts (Bio-Oss, Geistlich Pharma AG, Switzerland; OsteoGraf, Dentsply, USA). The materials were tested in a rabbit calvaria model, and the bone forming properties were observed at 4 and 8 weeks after implantation by means of histomorphometry and micro computed tomography (micro-CT). Defects without any graft material were used as negative controls. Micro-CT showed that all materials tested presented new bone formation that filled the defects at both time points, whereas the negative control presented less bone formation, with soft tissue infiltration into the defects. Comparable bone fill percentages were observed for histomorphometric and micro-CT results. Even though no statistically significant difference was found quantitatively between all of the bone graft substitute groups, a higher mean decrease in graft material filling the defects, along with higher remodelling activity, was evident for the experimental materials compared to the commercially available xenografts at 8 weeks. The results indicate that the experimental materials possess high degradability, along with osteoconduction comparable to commercially available xenografts.