Faculty Bibliography

The study evaluated the effects of a Supercritical CO₂ (scCO₂ ) on a commercially available decellularized/delipidized naturally derived porcine pericardium collagen membrane, Vitala®. The Vitala® and scCO₂ treated experimental membranes were evaluated for guided tissue regeneration (GTR) of periodontal tissue in class III furcation defects utilizing a dog model. Physical material characterization was performed by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The in vivo portion of the study was allocated to three-time points (6, 12, and 24-weeks) using standardized class III furcation defects created in the upper second and third premolars. The experimental defects (n = 5) were covered with either a collagen membrane (positive control), scCO₂ -treated collagen membrane (experimental) or no membrane (negative control). Following sacrifice, histologic serial sections were performed from cervical to apical for morphologic/morphometric evaluation. Morphometric evaluation was carried out by ranking the presence of collagen membrane, amount of bone formation within the defect site and inflammatory cell infiltrate content. SEM showed the experimental scCO₂ -treated membrane to have a similar gross fibrous appearance and chemical structure in comparison to the Vitala® Collagen membrane. A significant increase in membrane thickness was noted in the scCO₂ -treated membranes (366 ± 54 μm) vs non-treated membranes (265 ± 75 μm). TGA and DSC spectra indicated no significant qualitative differences between the two membranes. For the in vivo results, both membranes indicated significantly greater amounts of newly formed bone (scCO₂ : 2.85 ± 1.1; Vitala®: 2.80 ± 1.0) within the covered defects relative to uncovered controls (0.8 ± 0.27) at 24 weeks. Both membrane types gradually degraded as time elapsed in vivo from 6 to 12 weeks, and presented nearly complete resorption at 24 weeks. The inflammatory infiltrate at regions in proximity with the membranes was commensurate with healthy tissue levels from 6 weeks in vivo on, and periodontal ligament regeneration onset was detected at 12 weeks in vivo. The effect of the supplementary scCO₂ treatment step on the collagen membrane was demonstrated to be biocompatible, allowing for the infiltration of cells and degradation over time. The treated membranes presented similar performance in GTR to non-treated samples in Class III furcation lesions. Defects treated without membranes failed to achieve regeneration of the native periodontium. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res B Part B: Appl Biomater 00B: 000-000, 2018.

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/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.

Adenosine receptor activation has been investigated as a potential therapeutic approach to heal bone. Bone has enhanced regenerative potential when influenced by either direct or indirect adenosine receptor agonism. As investigators continue to elucidate how adenosine influences bone cell homeostasis at the cellular and molecular levels, a small but growing body of literature has reported successful in vivo applications of adenosine delivery. This review summarizes the role adenosine receptor ligation plays in osteoblast and osteoclast biology and remodeling/regeneration. It also reports on all the modalities described in the literature at this point for delivery of adenosine through in vivo models for bone healing and regeneration.

Background/Purpose: 3D-printed bioactive ceramic (3DPBC) scaffolds composed of beta-tricalcium phosphate (b-TCP) and coated in the osteogenic agent dipyridamole have been previously shown to heal critically sized calvarial defects in an adult animal model. This bone tissue engineering construct has yet to be applied in a pediatric craniofacial model and there has been evidence that other osteogenic agents such as BMP-2 can prematurely fuse growing sutures. The purpose of this study is to apply the described bone tissue engineering construct in a pediatric growing animal model and 1) quantify osteogenic potential in a growing calvarium; 2) maximize the scaffold design and dipyridamole (DIPY) concentration for the growing calvarium; and 3) characterize the effects of this bone tissue engineering construct on the growing suture. Methods/Description: Bilateral calvarial defects (10 mm) were created in 5-week-old New Zealand White rabbits (n = 14) 2 mm posterior and lateral to the coronal suture and sagittal sutures, respectively. 3DPBC scaffolds were constructed in quadrant form composed by varying pore dimensions (220, 330, and 500 mum). Each scaffold was collagen coated and soaked in varying concentrations of DIPY (100, 1000, and 10 000 muM). Controls comprised empty defects and collagen-coated scaffolds. Scaffolds were then placed into the calvarial defects to fill the bone space. Animals were euthanized 8 weeks postoperatively. Calvaria were analyzed using micro-computed tomography and 3D reconstruction.Mixed model analyses were conducted considering pore size and dosage effects on bone growth (a = 0.05).
Result(s): Scaffold group healing presented bone formation throughout the scaffold structure (defect marginal and central regions) while bone healing in empty sites was restricted to the defect margins, confirming its critical size dimension at 8 weeks in vivo. No significant difference in bone formation was detected when experimental groups were collapsed over pore size (P > .40). When pore size was collapsed over DIPY concentration, higher mean values were observed for the DIPYimmersed groups, and significance was shown between the 1000-muM and collagen groups (P < .05). Pore size and DIPY interaction was more pronounced for the 330-mum pore size where both the 100-and 1000-mum dosages presented significantly higher bone formation compared to collagen (P < .05). Across all concentrations of DIPY, including 10 000 mM (10 times greater than the experimental concentration, yielding the highest bone formation), sutures remained patent.
Conclusion(s):We present an effective bone tissue engineering scaffold design and dipyridamole concentration that significantly improve bone growth in a pediatric growing calvarial model and preserves cranial suture patency

This work describes the kinetics of conversion of brushite coatings, produced by chemical deposition, to hydroxyapatite. The conversion was performed in alkaline solution at three temperatures: 50 °C, 55 °C, and 60 °C. The evolution of the transformation was assessed by X-ray diffraction, and the phase fractions were determined by Rietveld refinement. The Johnson-Mehl-Avrami equation was applied to the data in order to describe the conversion mechanisms. The value of 42 kJ/mol obtained for the conversion activation energy is of the same order as found in similar surface-controlled dissolution processes. The Avrami exponent was n = 3.5, which is consistent with an interface-controlled growth of three-dimensional HA crystals with decreasing nucleation rate.

OBJECTIVES/OBJECTIVE:To evaluate and compare the outcomes of shear (S) and microtensile (μT) bond strength tests of CAD/CAM fiber-reinforced composite (FRC) to dentin. Aging with either fatigue or thermocycling were conducted for comparison with baseline microtensile group. METHODS:CAD/CAM FRC (Trinia, Bicon LLC, Boston, USA) blocks were milled to 3-mm diameter cylinders for shear and to blocks (5×5×5mm) for μT. Sixty extracted human molars were flattened to obtain dentin surfaces and randomly divided in four groups (n=15): (1) SC: samples tested in shear 24h after bonding; (2) μTC: samples tested in μT 24h after bonding); (3) μTF: samples submitted to mechanical fatigue prior to μT test, and; (4) μTT: thermocycling prior to μT test. Bonding system was applied onto the FRC material (Cera-Resin Bond, CRB, Shofu Dental, Kyoto, Japan). A conventional three-step adhesive system (All-bond 3, Bisco, Schaumburg, USA) was use with a self-cure resin cement (C&B resin cement, Bisco, Schaumburg, USA). Bond strength tests were conducted at 0.75mm/min and data analyzed using Weibull distribution (p<0.05). RESULTS:Weibull contour plots showed a significantly lower characteristic strength (η) and Weibull modulus (m) for SC (η=6.9MPa and m=1.4) compared to μTC (η=20.9MPa and m=4.5). Fatigued and thermocycled μT groups presented significantly reduced characteristic strength (η=3.1MPa and η=4.1MPa, respectively) compared to μTC. Weibull modulus was significantly reduced only for SC and μTF groups compared μTC. Failure predominantly occurred at the cement/FRC interface. SIGNIFICANCE/CONCLUSIONS:FRC bonded to dentin samples presented lower Weibull modulus and characteristic bond strength when immediately tested in shear compared to microtensile. Aging through thermocycling or mechanical fatigue significantly reduced the characteristic strength in microtensile testing, with the majority of failures emerging between restoration material and cement interface.

PURPOSE/OBJECTIVE:To evaluate Ti-Base abutment height and cement type on the retentiveness of zirconia-based restorations. MATERIAL AND METHODS/METHODS:Four millimeter (tall) and 2.5-mm-height (short) abutments along with temporary (provisional), glass ionomer (Meron), self-adhesive (U200), and conventional resin cement (Ultimate) were evaluated using pull-out testing (n = 10 crowns/group). RESULTS:Tall and short abutments demonstrated similar retention for all within cement comparisons, except U200 (P = 0.032). Resin cements exhibited superior retentiveness than others (P < 0.01). Although no significant difference was evidenced between resin cements for short abutments, Ultimate evidenced higher retention than U200 for tall abutments (P = 0.043). CONCLUSIONS:Although Ti-Base abutment height has not influenced zirconia superstructures' retentiveness, resin-based cements significantly evidenced higher retention than glass ionomer and temporary cements.

STATEMENT OF PURPOSE/OBJECTIVE:Injuries to the extremities often require resection of necrotic hard tissue. For large bone defects, autogenous bone grafting is ideal, but similar to all grafting procedures, is subject to limitations. Synthetic biomaterial driven engineered healing offers an alternative approach. This work focuses on three-dimensional (3D) printing technology of solid-free form fabrication (SFF), more specifically robocasting/direct write. The research hypothesizes that a bioactive calcium-phosphate scaffold may successfully regenerate extensive bony defects in vivo and that newly regenerated bone will demonstrate mechanical properties similar to native bone as healing time elapses. METHODS:) and hardness (H) using nanoindentation. RESULTS:) data for the newly regenerated bone presented statistically homogenous values analogous to native bone at the three-time points, while hardness (H) values were equivalent to the native radial bone at 24 weeks. The negative control samples showed limited healing at 8 weeks. CONCLUSIONS:Custom engineered β-TCP scaffolds are biocompatible, resorbable, and can directionally regenerate and remodel bone in a segmental long bone defect in a rabbit model. Custom designs and fabrication of β-TCP scaffolds for use in other bone defect models warrant further investigation.