Faculty Bibliography

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.

Osseointegration, the direct functional and structural connection between device and bone is influenced by multiple factors such as implant macrogeometry and surgical technique. This study investigated the effects of osseodensification drilling techniques on implant stability and osseointegration using trabecular metal (TM) and tapered-screw vent (TSV) implants in a low-density bone. Six skeletally mature sheep were used where six osteotomy sites were prepared in each of the ilia, (n = 2/technique: regular [R] (subtractive), clockwise [CW], and counterclockwise [CCW]). One TM and one TSV implant was subsequently placed with R osteotomy sites prepared using a conventional (subtractive) drilling protocol as recommended by the implant manufacturer for low density bone. CW and CCW drilling sites were subjected to osseodensification (OD) (additive) drilling. Evaluation of insertion torque as a function of drilling technique showed implants subjected to R drilling yielded a significant lower insertion torque relative to samples implanted in OD (CW/CCW) sites (p < 0.05). Histomorphometric analysis shows that the osseodensification demonstrates significantly greater values for bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO). Histological analysis shows the presence of bone remnants, which acted as nucleating surfaces for osteoblastic bone deposition, facilitating the bridging of bone between the surrounding native bone and implant surface, as well as within the open spaces of the trabecular network in the TM implants. Devices that were implanted via OD demonstrated atemporal biomechanical stability and osseointegration.

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.

Craniomaxillofacial congenital anomalies comprise approximately one third of all congenital birth defects and include deformities such as alveolar clefts, craniosynostosis, and microtia. Current surgical treatments commonly require the use of autogenous graft material which are difficult to shape, limited in supply, associated with donor site morbidity and cannot grow with a maturing skeleton. Our group has demonstrated that 3D printed bio-ceramic scaffolds can generate vascularized bone within large, critical-sized defects (defects too large to heal spontaneously) of the craniomaxillofacial skeleton. Furthermore, these scaffolds are also able to function as a delivery vehicle for a new osteogenic agent with a well-established safety profile. The same 3D printers and imaging software platforms have been leveraged by our team to create sterilizable patient-specific intraoperative models for craniofacial reconstruction. For microtia repair, the current standard of care surgical guide is a two-dimensional drawing taken from the contralateral ear. Our laboratory has used 3D printers and open source software platforms to design personalized microtia surgical models. In this review, we report on the advancements in tissue engineering principles, digital imaging software platforms and 3D printing that have culminated in the application of this technology to repair large bone defects in skeletally immature transitional models and provide in-house manufactured, sterilizable patient-specific models for craniofacial reconstruction.

PURPOSE: To evaluate the reliability of narrow diameter dental implants (NDIs) with similar macrogeometry and 3 implant-abutment connection designs. MATERIALS AND METHODS: Eighty-four NDIs (3.5 x 10 mm) were selected and divided into 4 groups (n = 21/group) according to implant-abutment connection design, as follows:

Adenosine receptor activation has been explored as a modulator of the inflammatory process that propagates osteoarthritis. It has been reported that cartilage has enhanced regenerative potential when influenced by adenosine receptor activation. As adenosine's role in maintaining chondrocyte homeostasis at the cellular and molecular levels is explored, successful in vivo applications of adenosine delivery for cartilage repair continue to be reported. This review summarizes the role adenosine receptor ligation plays in chondrocyte homeostasis and regeneration of articular cartilage damaged in osteoarthritis. It also reports on all the modalities reported for delivery of adenosine through in vivo applications.

OBJECTIVE:To characterize the mechanical properties of different coating methods of DLC (diamond-like carbon) onto dental implant abutment screws, and their effect on the probability of survival (reliability). METHODS:Seventy-five abutment screws were allocated into three groups according to the coating method: control (no coating); UMS - DLC applied through unbalanced magnetron sputtering; RFPA-DLC applied through radio frequency plasma-activated (n=25/group). Twelve screws (n=4) were used to determine the hardness and Young's modulus (YM). A 3D finite element model composed of titanium substrate, DLC-layer and a counterpart were constructed. The deformation (μm) and shear stress (MPa) were calculated. The remaining screws of each group were torqued into external hexagon abutments and subjected to step-stress accelerated life-testing (SSALT) (n=21/group). The probability Weibull curves and reliability (probability survival) were calculated considering the mission of 100, 150 and 200N at 50,000 and 100,000 cycles. RESULTS:DLC-coated experimental groups evidenced higher hardness than control (p<0.05). In silico analysis depicted that the higher the surface Young's modulus, the higher the shear stress. Control and RFPA showed β<1, indicating that failures were attributed to materials strength; UMS showed β>1 indicating that fatigue contributed to failure. High reliability was depicted at a mission of 100N. At 200N a significant decrease in reliability was detected for all groups (ranging from 39% to 66%). No significant difference was observed among groups regardless of mission. Screw fracture was the chief failure mode. SIGNIFICANCE/CONCLUSIONS:DLC-coating have been used to improve titanium's mechanical properties and increase the reliability of dental implant-supported restorations.

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