Evaluation of instrumentation and pedicle screw design for posterior lumbar fixation: A pre-clinical in vivo/ex vivo ovine model
Background: Stabilization procedures of the lumbar spine are routinely performed for various conditions, such as spondylolisthesis and scoliosis. Spine surgery has become even more common, with the incidence rates increasing ~30% between 2004 and 2015. Various solutions to increase the success of lumbar stabilization procedures have been proposed, ranging from the device's geometrical configuration to bone quality enhancement via grafting and, recently, through modified drilling instrumentation. Conventional (manual) instrumentation renders the excavated bony fragments ineffective, whereas the "additive" osseodensification rotary drilling compacts the bone fragments into the osteotomy walls, creating nucleating sites for regeneration. Methods: This study aimed to compare both manual versus rotary Osseodensification (OD) instrumentation as well as two different pedicle screw thread designs in a controlled split animal model in posterior lumbar stabilization to determine the feasibility and potential advantages of each variable with respect to mechanical stability and histomorphology. A total of 164 single thread (82 per thread configuration), pedicle screws (4.5 Ã— 35 mm) were used for the study. Each animal received eight pedicles (four per thread design) screws, which were placed in the lumbar spine of 21 adult sheep. One side of the lumbar spine underwent rotary osseodensification instrumentation, while the contralateral underwent conventional, hand, instrumentation. The animals were euthanized after 6- and 24-weeks of healing, and the vertebrae were removed for biomechanical and histomorphometric analyses. Pullout strength and histologic analysis were performed on all harvested samples. Results: The rotary instrumentation yielded statistically (p = 0.026) greater pullout strength (1060.6 N ± 181) relative to hand instrumentation (769.3 N ± 181) at the 24-week healing time point. Histomorphometric analysis exhibited significantly higher degrees of bone to implant contact for the rotary instrumentation only at the early healing time point (6 weeks), whereas bone area fraction occupancy was statistically higher for rotary instrumentation at both healing times. The levels of soft tissue infiltration were lower for pedicle screws placed in osteotomies prepared using OD instrumentation relative to hand instrumentation, independent of healing time. Conclusion: The rotary instrumentation yielded enhanced mechanical and histologic results relative to the conventional hand instrumentation in this lumbar spine stabilization model.
Effect of leukocyte-platelet-rich fibrin in bone healing around dental implants placed in conventional and wide osteotomy sites: A pre-clinical study
Leukocyte-platelet-rich fibrin (L-PRF) has been suggested for gap management for immediate implant placement when the distance is greater than 2â€‰mm. However, there remains a paucity in hierarchically designed research to support this application. The present study aimed to evaluate the effect of L-PRF on the osseointegration parameters of dental implants placed after conventional osteotomy of surgically created bone defects that simulate post extraction sockets in a canine model after 3, 6, and 12â€‰weeks in vivo. Eighty dental implants (Intra-Lock, Boca Raton, FL) were placed in the radius of 13 beagle dogs. The experiment consisted of 4 groups (nÂ =Â 20 implants/group): 1) Regular osteotomy (Reg n/L-PRF); 2) Regular osteotomy and implant placement with L-PRF membrane (Reg L-PRF); 3) Wide osteotomy with no gap management performed, where an osteotomy/bony defect (6â€‰mm of diameter and ~5â€‰mm deep) was created to simulate immediate implant placement in post-extraction sockets, and the gap was left for spontaneous healing (Wide nL-PRF); and 4) Wide osteotomy with L-PRF gap management (Wide L-PRF). L-PRF membranes were obtained by blood drawn from each subject and centrifuged at 2700â€‰rpm (408 RCF-clot) for 12â€‰min. In the experimental groups where L-PRF was utilized, the membrane was inserted into the osteotomy site prior to implant placement. Six dogs had implants placed in the radius for 3â€‰weeks; and 7 dogs had implants placed in the left radius for 6â€‰weeks and in the right radius for 12â€‰weeks. At the corresponding experimental time points, samples were harvested, and subjected to histological processing for qualitative and quantitative analyses, via bone-to-implant contact (BIC) and bone-area-fraction occupancy (BAFO). Qualitative analysis demonstrated increased amounts of bone formation around the implant and within the healing chambers over time for all groups. While comparable histological features were observed for both Reg groups (L-PRF and nL-PRF), the gap management performed in Wide L-PRF group resulted in effective gap filling with improved bone growth in close proximity to the implant surface. Quantitative analyses of BIC and BAFO yielded higher values for both variables at 3â€‰weeks for Wide L-PRF (~38% and ~56% respectively) compared to Wide nL-PRF (~20% for BIC and BAFO) (pâ€‰<â€‰.03). No statistical differences were detected between Wide groups at 6 and 12â€‰weeks, neither between Reg groups, independent of the association with or without the L-PRF membrane at all healing times. L-PRF placed within wide osteotomies, prior to implant placement, resulted in increased early bone formation compared to unfilled wide osteotomies at the early healing time (3â€‰weeks inÂ vivo).
An inÂ vivo preclinical study assessing biocompatibility of Pd-based bulk metallicÂ glass
BACKGROUND:The bulk metallic glass (BMG), Pd79Ag3.5P6Si9.5Ge2, has a high fracture toughness and has been found to accommodate post-yield stress, unlike most other BMG. Moreover, due to its greater noble gas composition it has a intrinsic corrosion resistance, ideal for dental and orthopedic implants. OBJECTIVE:This present study aimed to evaluate the inÂ vivo application of Pd79Ag3.5P6Si9.5Ge2 in a large translational sheep model to assess its efficacy to be utilized as an endosteal device. METHODS:Twelve implants in the form of cylindrical rods (3Â mm in diameter) were produced through rapid quenching. Each sheep (n =Â 12) received one osteotomy in the mandibular region using rotary instrumentation, which was subsequently filled with Pd79Ag3.5P6Si9.5Ge2. After 6- and 24-weeks the animals were euthanized, and samples collected en bloc to conduct histomorphometric analysis. The level/degrees of osseointegration were assessed through bone-to-implant contact (BIC). RESULTS:Favorable BIC was observed with fibrous connective tissue layers at both 6- and 24-weeks. Bone along with interfacial remodeling was observed in proximity with the metallic glass surface at 6 weeks with higher degrees of bone organization being observed at the later healing time, 24 weeks. CONCLUSIONS:The introduced BMG revealed potential to serve as an alternative biomaterial to commonly used Ti alloys given its unique combination of toughness and strength.
Bone regeneration at extraction sockets filled with leukocyte-platelet-rich fibrin: An experimental pre-clinical study
BACKGROUND:We aimed to histomorphometrically evaluate the effects of Leucocyte-Platelet-Rich Fibrin (L-PRF), with and without the combination of a bone grafting material, for alveolar ridge preservation using an in vivo canine model. MATERIAL AND METHODS/METHODS:Seven dogs (Female Beagles, ~18-month-old) were acquired for the study. L-PRF was prepared from each individual animal by drawing venous blood and spinning them through a centrifuge at 408 RCF-clot (IntrasSpin, Intra-Lock, Boca Raton, FL). L-PRF membranes were obtained from XPression fabrication kit (Biohorizons Implant Systems, Inc., AL, USA). A split mouth approach was adopted with the first molar mesial and distal socket defects treated in an interpolated fashion of the following study groups: 1) Empty socket (negative control); 2) OSS filled defect 3) L-PRF membrane; and 4) Mix of Bio-OssÂ® with L-PRF. After six weeks, samples were harvested, histologically processed, and evaluated for bone area fraction occupancy (BAFO), vertical/horizontal ridge dimensions (VRD and HRD, respectively), and area of coronal soft tissue infiltration. RESULTS:BAFO was statistically lower for the control group in comparison to all treatment groups. Defects treated with Bio-OssÂ® were not statistically different then defects treated solely with L-PRF. Collapsed across all groups, L-PRF exhibited higher degrees of BAFO than groups without L-PRF. Defects filled with Bio-OssÂ® and Bio-OssÂ® with L-PRF demonstrated greater maintenance of VRD relative to the control group. Collapsed across all groups, Bio-OssÂ® maintained the VRD and resulted in less area of coronal soft tissue infiltration compared to the empty defect. Soft tissue infiltration observed at the coronal area was not statistically different among defects filled with L-PRF, Bio-OssÂ®, and Bio-OssÂ® with L-PRF. CONCLUSIONS:Inclusion of L-PRF to particulate xenograft did not promote additional bone heading at 6 weeks in vivo. However, we noted that L-PRF alone promoted alveolar socket regeneration to levels comparable to particulate xenografts, suggesting its potential utilization for socket preservation.
A feasibility and acceptability study of using an intra-oral camera and an asynchronous tele-mentoring protocol to detect and identify oral lesions
Background/UNASSIGNED:To examine the feasibility and acceptability of integrating a tele-mentoring component into the identification of oral lesions at the dental clinics of a Federally Qualified Health Center network. Design and Methods/UNASSIGNED:General Practice Residency faculty and residents completed research ethics courses and trained dentists to use intra-oral cameras at chairside to photograph oral lesions of patients at routine dental visits. These images were then uploaded into the patient electronic health records (EHRs) with attendant descriptions and an oral surgeon was notified, who reviewed the charts, placed his observations in the EHR, and communicated his findings via secure e-mail to the involved residents, who in turn contacted their patients regarding follow-up actions. Feasibility was assessed via checklists completed by provider participants and semi-structured interviews. Acceptability was assessed via brief exit interviews completed by patient participants. Results/UNASSIGNED:All 12 of the dentist participants reported that they had successfully provided the tele-mentoring intervention, and that the process (from EHR data entry to interaction with the oral surgeon over findings to patient referral) was clear and straightforward. Of 39 patient participants, most strongly agreed or agreed that the use of an intra-oral camera by their dentists helped them to better understand oral cancer screening (94.9%) and that dentists answered their questions about oral cancer and were able to provide them with resources (94.8%). Conclusions/UNASSIGNED:Findings support further implementation research into adapting tele-mentoring using intra-oral cameras for training dental residents to detect and identify oral lesions and educating patients about oral cancer across settings.
Transforming the Degradation Rate of Î²-tricalcium Phosphate Bone Replacement Using 3-Dimensional Printing
BACKGROUND:Î²-Tricalcium phosphate (Î²-TCP) is one of the most common synthetic bone grafting materials utilized in craniofacial reconstruction; however, it is limited by a slow degradation rate. The aim of this study was to leverage 3-dimensional (3D) printing in an effort to accelerate the degradation kinetics of Î²-TCP. METHODS:Twenty-two 1-month-old New Zealand white rabbits underwent creation of calvarial and alveolar defects, repaired with 3D-printed Î²-TCP scaffolds coated with 1000 Î¼M of osteogenic agent dipyridamole. Rabbits were euthanized after 2, 6, and 18 months after surgical intervention. Bone regeneration, scaffold degradation, and bone mechanical properties were quantified. RESULTS:Histological analysis confirmed the generation of vascularized and organized bone. Microcomputed tomography analysis from 2 to 18 months demonstrated decreased scaffold volume within calvarial (23.6% Â± 2.5%, 5.1% Â± 2.2%; P < 0.001) and alveolar (21.5% Â± 2.2%, 0.2% Â± 1.9%; P < 0.001) defects, with degradation rates of 54.6%/year and 90.5%/year, respectively. Scaffold-inducted bone generation within the defect was volumetrically similar to native bone in the calvarium (55.7% Â± 6.9% vs 46.7% Â± 6.8%; P = 0.064) and alveolus (31.4% Â± 7.1% vs 33.8% Â± 3.7%; P = 0.337). Mechanical properties between regenerated and native bone were similar. CONCLUSIONS:Our study demonstrates an improved degradation profile and replacement of absorbed Î²-TCP with vascularized, organized bone through 3D printing and addition of an osteogenic agent. This novel additive manufacturing and tissue engineering protocol has implications to the future of craniofacial skeletal reconstruction as a safe and efficacious bone tissue engineering method.
Effects of relative centrifugation force on L-PRF: An in vivo submandibular boney defect regeneration study
Properties and composition of leukocyte- and platelet-rich fibrin (L-PRF) clots may be largely affected by centrifugation protocols (function of relative centrifugal force [RCF]), which may impact biological potential repair in bone regeneration. The present in vivo study sought to assess the effect of the RCF on the composition of L-PRF clots, as well as to compare the repair potential of L-PRF clots obtained with different RCF protocols in submandibular boney defects using PLGA scaffolds for bone regeneration. Complete blood count and volumetric evaluations were performed on L-PRF clots obtained through centrifugation for 12â€‰min at 200, 400, and 600 RCF-clot centrifugation speeds. These evaluations were completed from blood collected immediately prior to any surgical procedures. The in vivo portion comprised of three submandibular unilateral, full thickness, osteotomies (~0.40cm3 ) which were created in the submandibular region of six sheep, using rotary instrumentation under continuous irrigation. Subsequently, poly(lactic-co-glycolic acid) (PLGA) scaffolds were enveloped in a L-PRF membrane from one of the three spinning speeds (nÂ =Â 6/RCF) and inserted into the defect (sites were interpolated to avoid site bias). Six-weeks after surgery, the mandibles were harvested en bloc and prepared for volumetric and histomorphometric evaluations. Membranes harvested from 600 RCF produced significantly larger L-PRF clots (6.97gâ€‰Â±â€‰0.95) in comparison to the lower 200 RCF (5.7gâ€‰Â±â€‰0.95), with no significant differences between 600 and 400, and from 400 and 200 RCF. The three tested RCFs did not alter the platelet count of the L-PRF clot. For the in vivo component, quantitative bone regeneration analyses demonstrated significantly higher values obtained with L-PRF membranes extracted post 600 RCF (27.01â€‰Â±â€‰8%) versus 200 RCF (17.54â€‰Â±â€‰8%), with no significant differences regarding 400 RCF (~23â€‰Â±â€‰8%). At the qualitative histological analyses, L-PRF membranes obtained at 600 and 400 RCFs yielded improved healing throughout the defect, where the L-PRF sourced from the lowest speed, 200 RCF, presented healing primarily at the margins along with the presence of connective tissue at the central aspect of the surgical defect. Higher 600 RCF yielded larger L-PRF clots/membranes, resulting in enhanced bone repair potential in association with PLGA scaffolds for the treatment of critical size bone defects.
Effect of supplemental acid-etching on the early stages of osseointegration: A preclinical model
PURPOSE:To evaluate the effect of two surface modifications on early osseointegration parameters of conical implants in a translational pre-clinical model. MATERIALS AND METHODS:), surface energy and contact angle. Subsequently, implants were installed in the ilium crest of nine female sheep (weighing ~65Â kg). Torque out, histological and histomorphometric analyses were conducted after 3 and 6 weeks in-vivo. The percentage of bone to implant contact (%BIC) and bone area fraction occupancy within implant threads (%BAFO) were quantified, and the results were analyzed using a general linear mixed model analysis as function of surface treatment and time in-vivo. RESULTS:. Torque-out testing yielded significantly higher values for IMP SurÂ +Â AE in comparison to the IMP Sur at 3- (62.78Â Â±Â 15 and 33.49Â Â±Â 15Â N.cm, respectively) and 6-weeks (60.74Â Â±Â 15 and 39.80Â Â±Â 15Â N.cm, respectively). Histological analyses depicted similar osseointegration features for both surfaces, where an intramembranous-type healing pattern was observed. At histomorphometric analyses, IMP SurÂ +Â AE implants yielded higher values of BIC in comparison to IMP Sur at 3- (40.48Â Â±Â 38 and 27.98Â Â±Â 38%, respectively) and 6-weeks (45.86Â Â±Â 38 and 34.46Â Â±Â 38%, respectively). Both groups exhibited a significant increase in %BAFO from 3 (~35%) to 6 weeks (~44%), with no significant differences between surface treatments. CONCLUSION:Supplemental acid-etching and its interplay with implant thread design, positively influenced the BIC and torque-out resistance at early stages of osseointegration.
Osseodensification Versus Subtractive Drilling Techniques in Bone Healing and Implant Osseointegration: Ex Vivo Histomorphologic/Histomorphometric Analysis in a Low-Density Bone Ovine Model
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.
Osseodensification drilling vs conventional manual instrumentation technique for posterior lumbar fixation: Ex-vivo mechanical and histomorphological analysis in an ovine model
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 4.5â€‰mmâ€‰Ã—â€‰45â€‰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- (387â€‰N vs 292â€‰N) and 12-week (312â€‰N vs 212â€‰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.