Faculty Bibliography

BACKGROUND:Autologous bone grafts remain a standard of care for the reconstruction of large bony defects, but limitations persist. The authors explored the bone regenerative capacity of customized, three-dimensionally printed bioactive ceramic scaffolds with dipyridamole, an adenosine A2A receptor indirect agonist known to enhance bone formation. METHODS:Critical-size bony defects (10-mm height, 10-mm length, full-thickness) were created at the mandibular rami of rabbits (n = 15). Defects were replaced by a custom-to-defect, three-dimensionally printed bioactive ceramic scaffold composed of β-tricalcium phosphate. Scaffolds were uncoated (control), collagen-coated, or immersed in 100 μM dipyridamole. At 8 weeks, animals were euthanized and the rami retrieved. Bone growth was assessed exclusively within scaffold pores, and evaluated by micro-computed tomography/advanced reconstruction software. Micro-computed tomographic quantification was calculated. Nondecalcified histology was performed. A general linear mixed model was performed to compare group means and 95 percent confidence intervals. RESULTS:Qualitative analysis did not show an inflammatory response. The control and collagen groups (12.3 ± 8.3 percent and 6.9 ± 8.3 percent bone occupancy of free space, respectively) had less bone growth, whereas the most bone growth was in the dipyridamole group (26.9 ± 10.7 percent); the difference was statistically significant (dipyridamole versus control, p < 0.03; dipyridamole versus collagen, p < 0.01 ). There was significantly more residual scaffold material for the collagen group relative to the dipyridamole group (p < 0.015), whereas the control group presented intermediate values (nonsignificant relative to both collagen and dipyridamole). Highly cellular and vascularized intramembranous-like bone healing was observed in all groups. CONCLUSION:Dipyridamole significantly increased the three-dimensionally printed bioactive ceramic scaffold's ability to regenerate bone in a thin bone defect environment.

This study investigated the effects of osseodensification drilling on the stability and osseointegration of machine-cut and acid-etched endosteal implants in low-density bone. Twelve sheep received six implants inserted into the ilium, bilaterally (n = 36 acid-etched, and n = 36 as-machined). Individual animals received three implants of each surface, placed via different surgical techniques: (1) subtractive regular-drilling (R): 2.0 mm pilot, 3.2 and 3.8 mm twist drills); (2) osseodensification clockwise-drilling (CW): Densah Bur (Versah, Jackson, MI) 2.0 mm pilot, 2.8, and 3.8 mm multifluted tapered burs; and (3) osseodensification counterclockwise-drilling (CCW) Densah Bur 2.0 mm pilot, 2.8 mm, and 3.8 mm multifluted tapered burs. Insertion torque was higher in the CCW and CW-drilling compared to the R-drilling (p < 0.001). Bone-to-implant contact (BIC) was significantly higher for CW (p = 0.024) and CCW-drilling (p = 0.006) compared to the R-drilling technique. For CCW-osseodensification-drilling, no statistical difference between the acid-etched and machine-cut implants at both time points was observed for BIC and BAFO (bone-area-fraction-occupancy). Resorbed bone and bone forming precursors, preosteoblasts, were observed at 3-weeks. At 12-weeks, new bone formation was observed in all groups extending to the trabecular region. In low-density bone, endosteal implants inserted via osseodensification-drilling presented higher stability and no osseointegration impairments compared to subtractive regular-drilling technique, regardless of evaluation time or implant surface. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 00B: 000-000, 2018.

Background/Purpose: Alveolar cleft surgery is the most common bone reconstruction performed in patients with a cleft. Osteogenic agents such as BMP-2 have been used to restore the bony cleft without the morbidity of bone graft, but concerns remain regarding premature fusion of sutures, exuberant bone formation, and malignant degeneration. We have recently demonstrated that dipyridamole-coated, 3D printed bio-ceramic (3DPBC) scaffolds generate comparable bone amounts to BMP2 and significantly greater bone compared to negative controls in short-term growing animal model studies. No detrimental effects to growth sutures were noted in any animals. This study investigates the long-term osteogenic properties, degradation kinetics, and effects on facial growth of these tissue engineering constructs in growing animal models. Methods/Description: Twenty-two 1-month-old (immature) New Zealand white rabbits underwent creation of unilateral 3.5 x 3.5 mm alveolar defects. Each alveolar defect was repaired with either 3DPBC scaffolds coated with 1000 muM dipyridamole (n = 14) or with autogenous bone graft from the radius (n = 8). Six rabbits from the 3DPBC scaffold group were sacrificed at 8 weeks. The remaining rabbits (n = 8 each group) were euthanized following completion of craniofacial growth (6 months). Bone regeneration, scaffold degradation, and maxillary suture patency were calculated using CT images reconstructed and analyzed in Amira software. Facial symmetry was evaluated using dense-surface 3D modeling and validated with bilateral cephalometric measurements of maxillary projection. Bone growth and suture patency were qualitatively evaluated through histologic analysis.
Result(s): After 6 months, animals with defects repaired with 3DPBC scaffolds regenerated an average of 52.9% +/- 3.3% bone (mean +/- SEM), compared to 40.7%+/-4.0% in defects repaired with bone graft (P = .02). This is compared to unoperated alveolus occupied by 39.3% +/- 1.6% bone. Scaffolds showed significant degradation at 6 months (6.7% +/- 1.6%) compared to at 8 weeks (27.1% +/- 1.9%; P >= .001). Morphometric analysis using dense surface modeling showed similar symmetry indices of 55.0 +/- 3.3 for scaffold animals and 61.7% +/- 1.6% for bone graft animals (P = .10). Comparative measurements of operated and unoperated sides showed no significant differences in asymmetry between scaffold and bone graft animals (P = .86). Histologic analysis of scaffold samples revealed vascularized, organized bone within scaffold interstices without evidence of ectopic bone, excess inflammatory cells, or suture fusion.
Conclusion(s): In a growing animal model, dipyridamole-coated 3DPBC scaffolds can regenerate bone comparable to autogenous bone graft by radiographic and histologic analysis. Over 6 months, scaffolds show significant, favorable degradation and do not result in premature suture fusion or disruption of facial growth compared to bone graft. These results support long-term safety and efficacy of this tissue engineering strategy in the repair of alveolar cleft defects

Background/Purpose: Our tissue engineering laboratory has previously demonstrated that dipyridamole-coated, 3D printed bioceramic (3DPBC) scaffolds comprised of B-tricalcium phosphate generate significantly more bone compared to negative controls in short-term growing animal model studies. No detrimental effects to the cranial suture were observed in any experimental animals. The longterm osteogenic efficacy and safety of our 3DPBC scaffold for tissue engineering in growing calvaria was assessed by describing bone regeneration compared to autogenous bone graft, scaffold degradation kinetics, and the effects of the construct on cranial growth over time. Methods/Description: Twenty-two 1-month-old (immature) New Zealand white rabbits underwent unilateral 11-mm craniotomy within 2 mm of the coronal and sagittal sutures. Rabbits' calvarial defects were repaired by 1 of 2 interventions: 3DPBC scaffolds coated with 1000 mM dipyridamole (n = 14) or autogenous calvarial bone graft (n = 8). Six rabbits from the 3DPBC scaffold group were sacrificed at 8 weeks. The remaining rabbits (n = 8 each group) were observed until craniofacial growth was completed (6 months) and then euthanized. Bone regeneration, scaffold degradation, and cranial suture patency were analyzed in Amira software using reconstructed microcomputed tomography (muCT) images. Cranial growth was assessed by comparing bilateral cephalometric measurements based on muCT images. Bone growth and suture patency were qualitatively evaluated through histologic analysis.
Result(s): After 6 months of healing, animals with defects repaired with 3DPBC scaffolds regenerated an average of 53.9% +/- 3.6% (mean +/- SEM) bone, compared to 53.5% +/- 3.6% in defects repaired with bone graft (P = .95). Unoperated calvarial bone porosity was 49.4%+/-2.0%. Scaffolds showed significant degradation at 6 months (15.1% +/-0.7%) compared to 8 weeks (23.2% +/- 0.9%; P<=.001). Comparative measurements of operated and unoperated sides showed no significant differences in asymmetry between scaffold and bone graft animals (P > .24). Analysis of histologic sections revealed well-vascularized, organized bone formation within scaffold interstices with no evidence of ectopic bone formation, excess inflammatory cells, or suture fusion.
Conclusion(s): Dipyridamole-coated 3D-printed bioceramic scaffolds bone regeneration is comparable to autogenous bone graft without showing signs of adverse events such as premature cranial suture fusion, or detrimental effects to facial growth. The scaffold demonstrates favorable absorption kinetics, highlighting the potential for this technology in pediatric bone tissue engineering

Background/Purpose: Previous in vivo and in vitro animal studies demonstrate that the adenosine A2A receptor (A2AR) agonist dipyridamole (DIPY) stimulates robust osteogenic differentiation and proliferation without adverse effects on craniofacial suture development. However, no studies to date have been performed on human tissue. This study compares the effects of DIPY, BMP-2, and standard osteogenic media on osteogenic differentiation by human mesenchymal stem cells to lay the foundation for translating this bone tissue engineering approach to pediatric craniofacial reconstruction. Methods/Description: Pediatric mesenchymal stem cells were isolated from surplus bone taken from consented patients undergoing craniofacial surgery. Cells were cultured at early passage for 3 weeks in 1 of 7 experimental conditions: control media; osteogenic media (control + 100 muM beta-glycerophosphate, 0.1 muM dexamethasone and 100 mg/ mL L-ascorbic acid); osteogenic media + 200 ng/mL BMP-2; osteogenic media + 10, 100, 1000, or 10 000 muM DIPY. All experiments were performed in biological triplicates. Samples were analyzed using Alkaline phosphatase (ALP) assay at 6 hours, 24 hours, 48 hours, and 7 days as a marker of early osteogenic differentiation. At the end of the 3-week differentiation period, cells underwent immunocytochemistry to verify phalloidin, osteocalcin, and collagen I expression. Alizarin red staining was used to detect mineralization. Statistical analysis used 1-way ANOVA with Tukeys post hoc correction and multiple t test comparison of means.
Result(s): In all osteogenic conditions, relative peak ALP activity occurred at 48 hours. One thousand micrometer DIPY showed significantly increased peak ALP activity compared to BMP-2 (3.6 +/- 0.1 fold increase vs 3.1 +/- 0.1; P = .006). There was no significant difference between 1000 muM DIPY and osteogenic media (4.1 +/- 0.1; P = .36). At 3 weeks, immunocytochemistry revealed differentiation in all osteogenic conditions compared to control. One thousand micrometer DIPY cells showed greater evidence of mature osteogenic differentiation including cuboidal cell morphology and deposition of collagen I in an extracellular fibrillar network pattern compared to both control osteogenic media and BMP-2. Alizarin red quantification demonstrated significantly increased extracellular matrix mineralization at 100 muM(2.4+/-0.4; P = .002), 1000 muM (4.3+/-0.6; P = .001), and 10 000 muM (5.1 +/- 0.2; P < .0001) DIPY compared to nonosteogenic control medium (1.0 +/- 0.1). Matrix mineralization was not significantly different between BMP-2 (2.4 +/- 0.2) and 1000 muM DIPY (P = .08). ImageJ analysis revealed increased proportion of osteocalcin expressing cells (40.0% +/- 2.8%) in stem cells treated with 1000 muM of dipyridamole compared to control (1.0% +/- 0.6%), osteogenic (5.8% +/- 1.0%), and BMP-2 (16.9% +/- 2.2%; P < .0001).
Conclusion(s): Dipyridamole promotes early osteogenic differentiation and maturation of human bone-derived mesenchymal stem cells. These data suggest that dipyridamole may be an effective tissue engineering strategy for pediatric craniofacial reconstruction

OBJECTIVE:To evaluate the probability of survival of monolithic and porcelain veneered lithium disilicate crowns comprised by a conventional or modified core when loaded on marginal ridges. METHODS:Lithium disilicate molar crowns (n=30) were fabricated to be tested at mesial and distal marginal ridges and were divided as follows: (1) bilayered crowns with even-thickness 0.5mm framework (Bi-EV); (2) bilayered crowns with modified core design (Bi-M-lingual collar connected to proximal struts), and: (3) monolithic crowns (MON). After adhesively cemented onto composite-resin prepared replicas, mesial and distal marginal ridges of each crown (n=20) were individually cyclic loaded in water (30-300N) with a ceramic indenter at 2Hz until fracture. The 2-parameter Weibull was used to calculate the probability of survival (reliability) (90% 2-sided confidence bounds) at 1, 2, and 3 million cycles and mean life. RESULTS:The reliability at 1 and 2 million cycles was significantly higher for MON (47% and 19%) compared to Bi-EV (20% and 4%) and Bi-M (17% and 2%). No statistical difference was found between bilayered groups. Only the MON group presented crown survival (7%) at 3 million cycles. The mean life was highest for MON (1.73E+06), lowest for Bi-M (573,384) and intermediate for Bi-E (619,774). Fractographic analysis showed that the fracture originated at the occlusal surface. The highest reliability was found for MON crowns. The modified framework design did not improve the fatigue life of crowns. SIGNIFICANCE/CONCLUSIONS:Monolithic lithium disilicate crowns presented higher probability of survival and mean life than bilayered crowns with modified framework design when loaded at marginal ridges.

OBJECTIVE:The aim of this in vivo study is to compare the osseointegration of endosteal implants placed in atrophic mandibular alveolar ridges with alveolar ridge expansion surgical protocol via an experimental osseodensification drilling versus conventional osteotome technique. METHODS:Twelve endosteal implants, 4 mm × 13 mm, were placed in porcine models in horizontally atrophic mandibular ridges subsequent to prior extraction of premolars. Implants were placed with osseodensification drilling technique as the experimental group (n = 6) and osteotome site preparation as the control group (n = 6). After 4 weeks of healing, samples were retrieved and stained with Stevenel's Blue and Van Gieson's Picro Fuschin for histologic evaluation. Quantitative analysis via bone-to-implant contact (BIC%) and bone area fraction occupancy (BAFO%) were obtained as mean values with corresponding 95% confidence interval. A significant omnibus test, post-hoc comparison of the 2 drilling techniques' mean values was accomplished using a pooled estimate of the standard error with P-value set at 0.05. RESULTS:The mean BIC% value was approximately 62.5% in the osseodensification group, and 31.4% in the regular instrumentation group. Statistical analysis showed a significant effect of the drilling technique (P = 0.018). There was no statistical difference in BAFO as a function of drilling technique (P = 0.198). CONCLUSION/CONCLUSIONS:The combined osseodensification drilling-alveolar ridge expansion technique showed increased evidence of osseointegration and implant primary stability from a histologic and biomechanical standpoint, respectively. Future studies will focus on expanding the sample size as well as the timeline of the study to allow investigation of long-term prognosis of this novel technique.

Background/UNASSIGNED:Rhinoplasty relies on clear patient communication and precise execution of a three-dimensional (3D) plan to achieve optimal results. As 3D imaging and printing continue to grow in popularity within the medical field, rhinoplasty surgeons have begun to leverage these resources as an aid to preoperative planning, patient communication, and the technical performance of this challenging operation. Objective/UNASSIGNED:Utilizing departmentally-available resources and open access 3D imaging platforms, we have developed an affordable, reproducible protocol for rapid in-house virtual surgical planning (VSP) and subsequent manufacture of 3D-printed rhinoplasty models. Methods/UNASSIGNED:Preoperative 3D photographic images underwent virtual rhinoplasty using a freely-available 3D imaging and sculpting program (BlenderTM [Version 2.78, Amsterdam, The Netherlands]). Once the ideal postoperative result was digitally achieved, scaled, sterilizable and patient-specific 3D models of the preoperative and ideal postoperative result were manufactured in-house using a departmentally-owned 3D printer. Results/UNASSIGNED:3D-printed models have successfully been manufactured and employed for 12 patients undergoing rhinoplasty. The average time to prepare a set of pre- and postoperative models was 3 hours, while the printing process required 18-24 hours per model. Each set of surgical models can be manufactured at a total materials cost of approximately $5.00. Conclusions/UNASSIGNED:We describe an affordable means to construct sterilizable, scaled, patient-specific 3D-printed models for rhinoplasty. This technique may become of increasing interest to academic and cosmetic centers as hardware costs of 3D printers continues to fall.

PURPOSE/OBJECTIVE:To evaluate the pullout resistance of CAD/CAM implant-supported crowns cemented with provisional and definitive cements on Ti-base implant abutments. MATERIALS AND METHODS/METHODS:Sixty crowns were milled for use in Ti-base implant abutments and divided (n = 15/group) according to material, as follows: (a) [Pr] Temporary acrylic resin; (b) [Co-Cr] Cobalt-Chromium alloy; (c) [Zr] polycrystalline zirconia; and (d) [Ti] titanium. The cementation was performed with RelyX Temp NE (RxT) cement or RelyX U200 self-etching resin cement, under a 50 N (5 kg) load for 10 minutes. Twenty-four hours after cementation, the crowns were subjected to the pullout test in a universal test machine, at a 1.0 mm/min crosshead speed. The tests were performed first without cement to evaluate frictional resistance (Baseline), then with provisional cement (RelyX Temp NE without cement again (Baseline After RxT), and finally with resin cement (U200). The results were analyzed by ANOVA and Tukey test (p < 0.05). RESULTS:Data evaluation as a function of cement type demonstrated the superiority of resin-based cements relative to provisional and baseline groups (p < 0.01). While Co-Cr crowns presented the highest pullout strength values, Pr showed the lowest values (data collapsed over cement) (p < 0.001). Retentiveness data as a function of both factors demonstrated similar pullout resistance between groups without cement (p < 0.001), except Zr baseline. Also, Co-Cr presented higher pullout strength compared to other materials. CONCLUSIONS:Self-adhesive resin cement exhibited superior retention compared to temporary cement, regardless of crown material. Co-Cr and titanium presented higher levels of retention to Ti-base abutment after being cemented.