Faculty Bibliography

PURPOSE/OBJECTIVE:The aim of this study was to qualitatively and quantitatively assess the effect of osteotomy preparation by conventional, subtractive, or osseodensification instrumentation on osteotomies, treated with or without endosteal implants, and healing capacity. MATERIALS AND METHODS/METHODS:Seven sheep were used, and 56 osteotomies were made in the left and right ilium of the sheep (n = 8/sheep [4 per side/time point (3 and 6 weeks)]). Two different instrumentation techniques were used: (1) conventional/regular drilling in a three-step series of a 2-mm pilot and 3.2-mm and 3.8-mm twist drills and (2) osseodensification drilling with a Densah Bur 2.0-mm pilot and 2.8-mm and 3.8-mm multi-fluted tapered burs. Drilling was performed at 1,100 rpm with saline irrigation. RESULTS:Qualitative histomorphometric evaluation of the osteotomies after 3 and 6 weeks did not indicate any healing impairment due to the instrumentation. In all samples, histologic examination suggested bone remodeling and growth (empty and treated with an implant), irrespective of preparation technique. Osteotomies prepared using the osseodensification instrumentation showed the existence of bone chips autografted into the trabecular spaces along the length of the osteotomy wall. CONCLUSION/CONCLUSIONS:The osseodensification group yielded higher osseointegration rates, as distinguished through qualitative assessment, bone-to-implant contact, and bone-area-fraction occupancy, indicating an increased osteogenic potential in osteotomies prepared using the osseodensification technique.

Lumbar fusion is a procedure associated with several indications, but screw failure remains a major complication, with an incidence ranging 10% to 50%. Several solutions have been proposed, ranging from more efficient screw geometry to enhance bone quality, conversely, drilling instrumentation have not been thoroughly explored. The conventional instrumentation (regular [R]) techniques render the bony spicules excavated impractical, while additive techniques (osseodensification [OD]) compact them against the osteotomy walls and predispose them as nucleating surfaces/sites for new bone. This work presents a case-controlled split model for in vivo/ex vivo comparison of R vs OD osteotomy instrumentation in posterior lumbar fixation in an ovine model to determine feasibility and potential advantages of the OD drilling technique in terms of mechanical and histomorphology outcomes. Eight pedicle screws measuring 4.5 mm × 45 mm were installed in each lumbar spine of eight adult sheep (four per side). The left side underwent R instrumentation, while the right underwent OD drilling. The animals were killed at 6- and 12-week and the vertebrae removed. Pullout strength and non-decalcified histologic analysis were performed. Significant mechanical stability differences were observed between OD and R groups at 6- (387 N vs 292 N) and 12-week (312 N vs 212 N) time points. Morphometric analysis did not detect significant differences in bone area fraction occupancy between R and OD groups, while it is to note that OD showed increased presence of bone spiculae. Mechanical pullout testing demonstrated that OD drilling provided higher degrees of implant anchoring as a function of time, whereas a significant reduction was observed for the R group.

BACKGROUND/PURPOSE/OBJECTIVE:The utilization of three-dimensionally (3D)-printed bioceramic scaffolds composed of beta-tricalcium phosphate in conjunction with dipyridamole have shown to be effective in the osteogenesis of critical bone defects in both skeletally immature and mature animals. Furthermore, previous studies have proven the dura and pericranium's osteogenic capacity in the presence of 3D-printed scaffolds; however, the effect galea aponeurotica on osteogenesis in the presence of 3D scaffolds remains unclear. METHOD/DESCRIPTION/UNASSIGNED:Critical-sized (11 mm) bilateral calvarial defects were created in 35-day old rabbits (n = 7). Two different 3D scaffolds were created, with one side of the calvaria being treated with a solid nonporous cap and the other with a fully porous cap. The solid cap feature was designed with the intention of preventing communication of the galea and the ossification site, while the porous cap permitted such communication. The rabbits were euthanized 8 weeks postoperatively. Calvaria were analyzed using microcomputed tomography, 3D reconstruction, and nondecalcified histologic sectioning in order assess differences in bone growth between the two types of scaffolding. RESULTS:Scaffolds with the solid (nonporous) cap yielded greater percent bone volume (P = 0.012) as well as a greater percent potential bone (P = 0.001) compared with the scaffolds with a porous cap. The scaffolds with porous caps also exhibited a greater percent volume of soft tissue (P < 0.001) presence. There were no statistically significant differences detected in scaffold volume. CONCLUSION/CONCLUSIONS:A physical barrier preventing the interaction of the galea aponeurotica with the scaffold leads to significantly increased calvarial bone regeneration in comparison with the scaffolds allowing for this interaction. The galea's interaction also leads to more soft tissue growth hindering the in growth of bone in the porous-cap scaffolds.

PURPOSE/OBJECTIVE:The aim of the present study was to systematically analyze how a multifactorial surgical instrumentation approach affects osseointegration on both narrow-diameter and wide-diameter short implants. MATERIALS AND METHODS/METHODS:Twelve skeletally mature female sheep were used in the study along with 144 plateau-root-form healing chamber titanium (Ti-6Al-4V) implants (Bicon LLC, Boston, MA), evenly distributed between narrow (3.5 mm) and wide (6.0 mm) diameters. The presence or the absence of irrigation, different drilling speeds, and 2 time points quantifying bone-implant contact (BIC) and bone area fraction occupancy (BAFO) to evaluate the osteogenic parameters around the implants. RESULTS:There were no signs of inflammation, infection, or failure of the implants observed at either healing period. The narrow 3.5-mm implant, at 6 weeks, yielded significant differences in terms of BIC at a drilling speed of 50 rotations per minute (RPM), with higher values of the samples using irrigation (30.6 ± 6.1%) compared with those without (19.7 ± 6.1%). No statistical differences were detected for 500 and 1,000 RPM with or without irrigation. The wide 6-mm diameter implant showed differences with respect to drilling speed, 500 and 1,000 RPM, with higher values associated with samples subjected to irrigation. BAFO results, for both diameters, only detected statistical differences between the 2 times (3 vs 6 weeks); no statistical differences were detected when evaluating as a function of time, drilling speed, and irrigation. CONCLUSIONS:Surgical instrumentation variables (ie, drilling speed [RPM] and irrigation) yielded to be more of an effect for BIC at longer healing time (6 weeks) for the wider implants. Furthermore, deploying narrow or wide plateau-root-form implants, where conditions allow, has shown to be a safe alternative, considering the high BIC and BAFO values observed, independent of irrigation.

The basic concepts from the fields of biology and engineering are integrated into tissue engineering to develop constructs for the repair of damaged and/or absent tissues, respectively. The field has grown substantially over the past two decades, with particular interest in bone tissue engineering (BTE). Clinically, there are circumstances in which the quantity of bone that is necessary to restore form and function either exceeds the patient's healing capacity or bone's intrinsic regenerative capabilities. Vascularized osseous or osteocutaneous free flaps are the standard of care with autologous bone remaining the gold standard, but is commonly associated with donor site morbidity, graft resorption, increased operating time, and cost. Regardless of the size of a craniofacial defect, from trauma, pathology, and osteonecrosis, surgeons and engineers involved with reconstruction need to consider the complex three-dimensional (3D) geometry of the defect and its relationship to local structures. Three-dimensional printing has garnered significant attention and presents opportunities to use craniofacial BTE as a technology that offers a personalized approach to bony reconstruction. Clinicians and engineers are able to work together to produce patient-specific space-maintaining scaffolds tailored to site-specific defects, which are osteogenic, osseoconductive, osseoinductive, encourage angiogenesis/vasculogenesis, and mechanically stable upon implantation to prevent immediate failure. In this work, we review biological and engineering principles important in applying 3D printing technology to BTE for craniofacial reconstruction as well as present recent translational advancements in 3D printed bioactive ceramic scaffold technology.

PURPOSE/OBJECTIVE:This study sought to estimate patient-reported outcomes and compare quality-of-life (QOL) measures between patients electing for either open reduction internal fixation (ORIF) or closed reduction with intermaxillary fixation (CRIMF). PATIENTS AND METHODS/METHODS:This was a retrospective cohort study of patients with unilateral condyle fractures who had undergone either ORIF or CRIMF at the New York University Tisch Hospital and Bellevue Hospital Center. The primary study predictor was treatment choice (ORIF or CRIMF). Other study predictors were patient age, gender, and the presence of any other coexisting facial fractures. The 9 study outcomes were derived from an 11-item postoperative QOL questionnaire evaluating self-reported perceptions of pain and function. Univariate comparisons and multivariate regression models were calculated. RESULTS:A total of 38 patients (21 CRIMF and 17 ORIF) comprised the study sample. All patients were eligible for either ORIF or CRIMF, and the choice of treatment was decided through shared decision making after a comprehensive discussion of risks and benefits. With respect to pain outcomes, patients who underwent ORIF reported lower overall pain scores at 2 weeks (P < .01) and 2 months (P = .01), less mastication pain at 3 months (P = .01), and a lower rate of persistent headaches after 6 weeks (P = .04). With respect to functional outcomes, patients who underwent ORIF reported better range of motion at 3 months (P = .01), less treatment-related weight loss (P = .01), and more ease when performing physical (P < .01) and work-related (P < .01) activities. In the multivariate regression models, ORIF was independently associated with decreased pain at 2 weeks (P < .01) and decreased difficulty in obtaining nutrition (P < .01), performing physical activities (P = .02), and performing work-related activities (P < .01). CONCLUSIONS:Patients who underwent ORIF appeared to experience subjective favorable pain and functional QOL outcomes. Given the clinical controversy, the choice of treatment should synthesize patient-reported outcomes and be approached through shared decision making.

WE43 Mg alloy proved to be an ideal candidate for production of resorbable implants in both clinical and trial settings. In previous studies we tested biocompatibility and degradation properties of WE43 (as-cast) and artificially aged (WE43-T5) Mg alloys in a sheep model. Both alloys showed excellent biocompatibility with the as-cast, WE43, form showing increased degradability compared to the artificially aged, WE43-T5. In the present study, our group assessed the biological behavior and degradation pattern of the same alloys when implanted as endosteal implants in a sheep model. Twelve screws (3x15 mm) were evaluated, one screw per each composition was placed bi-cortically in the mandible of each animal with a titanium (2x12 mm) screw serving as an internal positive control. At 6 and 24 weeks histomorphological analysis was performed, at 6 weeks as cast, WE43, yielded a higher degradation rate, increased bone remodeling and osteolysis compared to the WE43-T5 alloy; however, at 24 weeks WE43-T5 showed higher degradation rate and increased bone remodeling than as-cast. In vitro assay of cell growth, adhesion and differentiation was also conducted to investigate possible mechanisms underlying the behavior expressed from the alloys in vivo. In conclusion WE43-T5 indicated bone/implant interaction properties that makes it more suitable for fabrication of endosteal bone screws.

Literature has reported that up to 50% of dental implants may be affected by peri-implantitis, a bacteria-induced chronic inflammatory process, which promotes osteoclast-mediated bone resorption and inhibits bone formation, leading to progressive bone loss around implants. Current evidence points toward an increased risk for the development of peri-implantitis in both obesity/metabolic syndrome (MetS) and diabetes mellitus (DM) conditions relative to the healthy population. Currently, there is no effective treatment for peri-implantitis and the 50% prevalence in MetS and DM, along with its predicted increase in the worldwide population, presents a major concern in implant dentistry as hyperglycemic conditions are associated with bone-healing impairment; this may be through dysfunction of osteocalcin-induced glucose metabolism. The MetS/DM proinflammatory systemic condition and altered immune/microbiome response affect both catabolic and anabolic events of bone-healing that include increased osteoclastogenesis and compromised osteoblast activity, which could be explained by the dysfunction of insulin receptor that led to activation of signals related with osteoblast differentiation. Furthermore, chronic hyperglycemia along with associated micro- and macro-vascular ailments leads to delayed/impaired wound healing due to activation of pathways that are particularly important in initiating events linked to inflammation, oxidative stress, and cell apoptosis; this may be through deactivation of AKT/PKB protein, which possesses a pivotal role in drive survival and eNOS signaling. This review presents an overview of the local and systemic mechanisms synergistically affecting bone-healing impairment in MetS/DM individuals, as well as a rationale for hierarchical animal model selection, in an effort to characterize peri-implantitis disease and treatment.

Bone grafting procedures have been widely utilized as the current state-of-the-art for bone regeneration, with autogenous bone graft being the gold-standard bone reconstructive option. However, the use of autografts may be limited by secondary donor-site comorbidities, a finite amount of donor supply, increased operating time, and healthcare cost impact. Synthetic materials, or alloplasts, such as the polymeric material, poly(lactic-co-glycolic acid) (PLGA) has previously been utilized as a transient scaffold to support healing of bone defects with the potential to locally delivery osteogenic additives. In this study a novel procedure was adopted to incorporate both the dissolved contents and mechanical components of leukocyte- and platelet-rich fibrin (L-PRF) into an PLGA scaffold through a two-step method: (a) extraction of the L-PRF membrane transudate with subsequent immersion of the PLGA scaffold in transudate followed by (b) delivering a fibrin gel as a low-viscosity component that subsequently polymerizes into a highly viscous, gel-like biological material within the pores of the PLGA scaffold. Two, ~0.40 cm³ , submandibular defects (n = 24) were created per side using rotary instrumentation under continuous irrigation in six sheep. Each site received a PLGA scaffold (Intra-Lock R&D, Boca Raton, FL), with one positive control (without L-PRF exudate addition [nL-PRF]), and one experimental (augmented with PLGA/L-PRF Blocks [L-PRF]). Animals were euthanized 6 weeks postoperatively and mandibles retrieved, en bloc, for histological analysis. Histomorphometric evaluation for bone regeneration was evaluated as bone area fraction occupancy (BAFO) within the region of interest of the cortical bone (with specific image analysis software) and data presented as mean values with the corresponding 95% confidence interval values. Qualitative evaluation of nondecalcified histologic sections revealed extensive bone formation for both groups, with substantially more bone regeneration for the L-PRF induced group relative nL-PRF group. Quantitative BAFO within the defect as function of the effect of L-PRF exudate on bone regeneration, demonstrated significantly (p = .018) higher values for the L-PRF group (38.26% ± 8.5%) relative to the nL-PRF group (~28% ± 4.0%). This in vivo study indicated that L-PRF exudate has an impact on the regeneration of bone when incorporated with the PLGA scaffold in a large translational model. Further studies are warranted in order to evaluate the L-PRF exudate added, as well as exploring the preparation methods, in order to facilitate bone regeneration.

Background/Purpose: b-Tricalcium phosphate (b-TCP), the most common synthetic bone replacement product, is frequently used in craniofacial reconstruction. Although solid b-TCP can be absorbed over time, the slow degradation rate (1%-3%/year) predisposes this product to exposure, infection, and fracture, limiting its use in the growing face where implants are required to grow and remodel with the patient. Our tissue engineering laboratory has successfully leveraged 3D printers to manufacture 3D-printed bioactive ceramic (3DPBC) scaffolds composed of b-TCP in an architecture which optimizes the needs of rigidity with efficient vascular ingrowth, osteogenesis, and degradation kinetics. The latter qualities are further optimized when the osteogenic agent dipyridamole (DIPY) is used. This long-term animal study reports on the new degradation kinetics profile achievable through this novel manufacturing and tissue engineering protocol. Methods/Description: Twenty-two 1-month-old (immature) New Zealand white rabbits underwent creation of unilateral 10 mm calvarial defects with ipsilateral 3.5 +/- 3.5 mm alveolar defects. Each defect was repaired with b-TCP 3DPBC scaffolds coated with 1000 mM DIPY. Rabbits were killed at 8 weeks (n = 6), 6 months (n = 8), and 18 months (n = 8). Bone regeneration and scaffold degradation were calculated using micro-CT images and analyzed in Amira software. Cranial and maxillary suture patency and bone growth were qualitatively analyzed using histologic analysis.
Result(s): Results are reported as a percentage of volumetric space occupied by either scaffold or bone. When comparing time points 8 weeks, 6 months, and 18 months, scaffolds showed significant decreased defect occupancy in calvaria (23.6% +/- 3.6%, 15.2% +/- 1.7%, 5.1% +/- 3.4%; P < .001) and in alveoli (21.5% +/- 3.9%, 6.7% +/- 2.7%, 0.1% +/- 0.2%; P < .001), with annual degradation rates 55.9% and 94.2%, respectively. Between 8 weeks and 18 months, significantly more bone regenerated in calvarial defects (25.8% +/- 6.3% vs 55.7% +/- 10.3%, P < .001) and no difference was found in alveolar defects (28.4% +/- 6.8% vs 32.4% +/- 8.0%, P = .33). Histology showed vascularized, organized bone without suture fusion.
Conclusion(s): The degradation kinetics of b-TCP can be altered through 3D printing and addition of an osteogenic agent. Our study demonstrates an acceleration of b-TCP degradation from 1% to 3% a year to 55% to 95% a year. Absorbed b-TCP is replaced by vascularized bone and there is no damage noted to the growing suture. This additive manufacturing and tissue engineering protocol has implication to future reconstruction of the craniofacial skeleton