Publications by authors named "Lukasz Witek"

96 Publications

Hydrothermal aging affects the three-dimensional fit and fatigue lifetime of zirconia abutments.

J Mech Behav Biomed Mater 2021 Sep 8;124:104832. Epub 2021 Sep 8.

Department of Prosthodontics and Periodontology, Bauru School of Dentistry - University of Sao Paulo, 9-75 Octavio Pinheiro Brizolla, 17012-901, Bauru, SP, Brazil.

Objective: Evaluate the effect of aging using two different methods on the three-dimensional fit of zirconia abutments at the implant-abutment connection and estimate the probability of survival of anterior crowns supported by straight and 17-degree angled abutments.

Materials And Methods: Two different zirconia abutment designs, straight and 17-degree angled abutments (n = 63/group), were evaluated in the current study. The abutments were randomly allocated into three experimental groups according to laboratory aging condition (134°C, 2.2 bar, 20 h): (i) control, (ii) autoclave aging, and (iii) hydrothermal reactor aging. Crystalline content was determined by X-Ray diffraction (XRD) and Raman spectroscopy, and microstructure was analyzed using field-emission gun scanning electron microscope (FEG-SEM). Implant-abutment volume misfit was determined in the straight abutments by micro-computed tomography using the silicone replica technique. For fatigue testing, abutments were torqued to the implants and connected to standardized maxillary incisor zirconia crowns. The assemblies were subjected to step-stress accelerated life testing (SSALT) in water until fracture or suspension. The use level probability Weibull curves and probability of survival for a mission of 50,000 cycles at 50, 100, 150 and 200 N were calculated and plotted. Fractured samples were analyzed using a stereomicroscope and scanning electron microscope.

Results: The crystalline spectra depicted a zirconia system primarily composed of the tetragonal phase. Laboratory aging yielded a 20%- and 37%-increase in the monoclinic content for abutments aged in autoclave and hydrothermal reactor relative to control, respectively. A fully crystalline matrix with a regular grain size was observed in the FEG-SEM for control abutments, with a considerable presence of intergranular defects. While autoclave aging triggered no significant alteration to the microstructure, defect population was reduced after hydrothermal reactor aging. Control abutments presented a significantly higher volume misfit (2.128 ± 0.54 mm) relative to aged abutments using autoclave (1.244 ± 0.48 mm) or hydrothermal reactor (1.441 ± 0.41 mm). The beta (β) values indicated that failures were predominantly controlled by material strength rather than fatigue damage accumulation for all groups, except for straight control abutments. Irrespective of aging, the probability of survival of straight and angled zirconia abutments was up to 95% (95-100%) at 50 and 100 N. A 50N-increase in the load resulted in wider range of survival estimate, with straight autoclave abutments percentage significantly lower probability of survival (77%) than angled hydrothermal reactor abutments (99%). At 200N, angled hydrothermal reactor (97%) or autoclave (82%) aged abutments demonstrated the highest probability of survival, angled control (71%) and straight hydrothermal reactor (69%) abutments intermediate values, and straight autoclave (23%) and control (7%) abutments the lowest estimate. The failure mode predominantly involved abutment and/or abutment screw fracture for both straight and angled abutments.

Conclusions: Hydrothermal aging significantly influenced volume misfit, as well as the probability of survival of zirconia abutments at higher loads for both angled and straight abutments.
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http://dx.doi.org/10.1016/j.jmbbm.2021.104832DOI Listing
September 2021

Effect of supplemental acid-etching on the early stages of osseointegration: A preclinical model.

J Mech Behav Biomed Mater 2021 10 13;122:104682. Epub 2021 Jul 13.

Department of Biomaterials, New York University College of Dentistry, New York, NY, USA; Department of Biomedical Engineering, New York University Tandon School of Engineering, Brooklyn, NY, USA. Electronic address:

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: Conical implants with progressive trapezoidal threads and healing chambers were evaluated consisting of two different surface conditions: 1) Implacil surface (IMP Sur), and 2) Implacil surface + Supplemental Acid-etching (IMP Sur + AE). Surface characterization comprised of the evaluation of roughness parameters (S, S and S), surface energy and contact angle. Subsequently, implants were installed in the ilium crest of nine female sheep (weighing ~65 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: Supplemental acid etching significantly increased S and S roughness parameters without compromising the surface energy or contact angle, and no significant differences with respect to S. Torque-out testing yielded significantly higher values for IMP Sur + AE in comparison to the IMP Sur at 3- (62.78 ± 15 and 33.49 ± 15 N.cm, respectively) and 6-weeks (60.74 ± 15 and 39.80 ± 15 N.cm, respectively). Histological analyses depicted similar osseointegration features for both surfaces, where an intramembranous-type healing pattern was observed. At histomorphometric analyses, IMP Sur + AE implants yielded higher values of BIC in comparison to IMP Sur at 3- (40.48 ± 38 and 27.98 ± 38%, respectively) and 6-weeks (45.86 ± 38 and 34.46 ± 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.
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http://dx.doi.org/10.1016/j.jmbbm.2021.104682DOI Listing
October 2021

Physiochemical and bactericidal activity evaluation: Silver-augmented 3D-printed scaffolds-An in vitro study.

J Biomed Mater Res B Appl Biomater 2021 Jul 1. Epub 2021 Jul 1.

Department of Biomaterials, New York University College of Dentistry, New York, New York, USA.

Hypothesis: Injuries requiring resection of tissue followed by autogenous bone transfer may be prone to infection by Staphylococcus aureus, impeding recovery and increasing medical costs. For critical sized defects, the common approach to reconstruction is a tissue transfer procedure but is subject to limitations (e.g., donor site morbidity, cost, operating time). Utilizing beta tricalcium phosphate (β-TCP) as bone grafting material augmented with silver (Ag), a custom graft may be 3D printed to overcome limitations and minimize potential infections.

Experiments: Scaffolds were 3D printed and augmented with Ag by external attack on the surface by silver nitrate (AgNO ) at varying concentrations (0.1, 1.0, 10% wt/wt of scaffold). The augmented scaffolds were evaluated utilizing X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and inductively coupled plasma mass spectroscopy (ICP-MS) to verify the presence of Ag and phosphate (PO ) groups followed by electron microscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) to gather information of chemical and physical properties. Preliminary biocompatibility and bactericidal capacity of the scaffolds were tested using human osteoprogenitor (hOP) cells and methicillin-sensitive S. aureus strain, respectively.

Results: XRD, FTIR, ICP-MS, TGA, and DSC confirmed presence of Ag and PO groups, whereas electron microscopy showed a decrease in Ca and an increase in Ag ions, decreasing Ca/P ratio with increasing surfactant concentrations. PrestoBlue assays yielded an increase in fluorescence cell counts among experimental groups with lower concentrations of Ag characterized by their characteristic trapezoidal shape whereas cytotoxicity was observed at higher concentrations. Similar observations were made with alkaline phosphatase assays. Antimicrobial evaluation showed reduced colony-forming units (CFU) among all experimental groups when compared to 100% β-TCP. β-TCP scaffolds augmented with Ag ions facilitate antibacterial effects while promoting osteoblast adhesion and proliferation.
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http://dx.doi.org/10.1002/jbm.b.34902DOI Listing
July 2021

Heat shock protein 27 (hsp27) in patients with ovarian cancer.

Ginekol Pol 2021 Jun 9. Epub 2021 Jun 9.

Department of Gynaecology, Obstetrics and Oncological Gynaecology, Faculty of Medical Sciences in Zabrze Medical University of Silesia, Bytom, Poland.

Objectives: Ovarian cancer remains a very common cause of death among women worldwide. The cause is to be found in too late of a diagnostic process and therapeutic difficulties The presence of heat shock proteins in the serum of ovarian cancer patients is still a new area of study. It is necessary to continue studies on the possibilities for using these markers to predict a patient's response to a specific therapy and to monitor treatment progress.

Material And Methods: The study included 52 women with ovarian cancer, hospitalised at the Department of Obstetrics, Gynaecology and Oncological Gynaecology, Medical University of Silesia. The control group consisted of 25 healthy women. The levels of HSP27 in the studied sera were determined by an immunoenzymatic method (ELISA).

Results: The mean concentration of HSP27 in the group of patients with ovarian cancer was significantly higher than in the control group of healthy women. We have shown that mean HSP27 levels in ovarian cancer patients increase with tumour progression and further depend on the clinical stage of the disease (FIGO). Positivity values analysis revealed in all clinical stages of ovarian cancer, excluding stage 1, it was significantly higher than in the control group, and at the 4th stage, it is significantly higher than at the 1st, 2nd, and 3rd stages. However, both for the untreated patients and those patients after chemotherapy, the mean HSP27 levels were significantly higher than in the control group.

Conclusions: Our studies indicate a significant contribution of HSP27 to the pathogenesis of ovarian cancer. It seems that serum HSP27 can be a marker for this cancer's development, and a marker for the clinical stage.
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http://dx.doi.org/10.5603/GP.a2021.0061DOI Listing
June 2021

Effects of relative centrifugation force on L-PRF: An in vivo submandibular boney defect regeneration study.

J Biomed Mater Res B Appl Biomater 2021 Jun 3. Epub 2021 Jun 3.

Department of Biomaterials and Biomimetics, NYU College of Dentistry, New York, New York, USA.

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 12 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 (~0.40cm ) 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 (n = 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 (6.97g ± 0.95) in comparison to the lower 200 RCF (5.7g ± 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 (27.01 ± 8%) versus 200 RCF (17.54 ± 8%), with no significant differences regarding 400 RCF (~23 ± 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.
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http://dx.doi.org/10.1002/jbm.b.34885DOI Listing
June 2021

Comparative barrier membrane degradation over time: Pericardium versus dermal membranes.

Clin Exp Dent Res 2021 May 5. Epub 2021 May 5.

Institute of Dentistry, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK.

Objective: The effectiveness of GBR procedures for the reconstruction of periodontal defects has been well documented. The objective of this investigation was to evaluate the degradation kinetics and biocompatibility of two resorbable collagen membranes in conjunction with a bovine xenograft material.

Materials And Methods: Lower premolars and first molars were extracted from 18 male Yucatan minipigs. After 4 months of healing, standardized semi-saddle defects were created (12 mm × 8 mm × 8 mm [l˙̇ × W˙ × d]), with 10 mm between adjacent defects. The defects were filled with a bovine xenograft and covered with a either the bilayer collagen membrane (control) or the porcine pericardium-derived collagen membrane (test). Histological analysis was performed after 4, 8, and 12 weeks of healing and the amount of residual membrane evaluated. Non-inferiority was calculated using the Brunner-Langer mixed regression model.

Results: Histological analysis indicated the presence of residual membrane in both groups at all time points, with significant degradation noted in both groups at 12 weeks compared to 4 weeks (p = .017). No significant difference in ranked residual membrane scores between the control and test membranes was detected at any time point.

Conclusions: The pericardium-derived membrane was shown to be statistically non-inferior to the control membrane with respect to resorption kinetics and barrier function when utilized for guided bone regeneration in semi-saddle defects in minipigs. Further evaluation is necessary in the clinical setting.
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http://dx.doi.org/10.1002/cre2.414DOI Listing
May 2021

Are IgG antibodies to heat shock proteins HSP27 and HSP60 useful markers in endometrial cancer and cervical cancer?

Ginekol Pol 2021 Apr 29. Epub 2021 Apr 29.

Department of Gynaecology, Obstetrics and Oncological Gynaecology, Faculty of Medical Sciences in Zabrze, Medical University of Silesia, Bytom, Poland.

Objectives: Heat shock proteins are overexpressed in many human malignancies. The role of heat shock proteins as a therapeutic target in cancer as well as their association with drug resistance were widely documented. The aim of this study was to evaluate the concentration of IgG class HSP27 and HSP60 antibodies in serum of patients with endometrial and cervical cancer, as well as to analyse the variability of concentrations of the examined antibodies depending on the cancer stage.

Results: In both endometrial and cervical cancer, the serum concentration of IgG anti-HSP27 antibody was significantly higher than in the healthy control group. The concentration of IgG anti-HSP60 antibody in endometrial cancer, cervical cancer and healthy control was similar. The median IgG anti-HSP27 antibody serum concentration of endometrial cancer patients was not correlated with FIGO-stage. In cervical cancer inverse correlation between concentration of this antibody and FIGO stage was observed. The median IgG anti-HSP60 antibody concentration in serum of endometrial cancer patients was lower in FIGO stage I and II compared to FIGO stage IV and in FIGO stage IA compared to FIGO stage IB. Concentrations of examined antibodies correlated positively with each other, both in the group of women with cancer and in the group of healthy women. The strongest correlations were found in the group of patients with endometrial cancer.

Conclusions: Concentration of anti-HSP27 antibody could help in detection of cervical and endometrial cancer. We need to look for the cut-off point in large cohort studies. Anti-HSP27 and anti-HSP60 antibodies should be further evaluated for their potential usage as biomarkers in cervical and endometrial cancer as they shown some correlation with stage of disease.
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http://dx.doi.org/10.5603/GP.a2021.0060DOI Listing
April 2021

Histomorphometric analysis of implant osseointegration using hydrophilic implants in diabetic rats.

Clin Oral Investig 2021 Oct 25;25(10):5867-5878. Epub 2021 Mar 25.

Department of Restorative Dentistry, School of Dentistry, Federal University of Pelotas, Gonçalves Chaves Street 457, Pelotas, RS, 96015-560, Brazil.

Objectives: To evaluate peri-implant bone formation of titanium implants using an in vivo rat model with and without uncontrolled diabetes mellitus (DM) to evaluate osseointegration of hydrophobic (Neoporos®) and hydrophilic (Acqua®) surfaces.

Materials And Methods: 54 rats were divided into two groups: DM group (DMG) (streptozotocin-induced diabetes) and a control group (CG). Implants with hydrophobic (Neoporos®) and hydrophilic surfaces (Acqua®) were placed in the left or right tibia of animals. Animals were further divided into three groups (n = 9) euthanized after 7, 14, or 28 days. Bone-to-implant contact (BIC) and bone area fraction occupancy (BAFO) were assessed in total, cortical, and medullary areas.

Results: The DMG group, after a 7-day healing period, yielded with the Acqua implants presented significantly higher total BIC (+37.9%; p=0.03) and trabecular BIC (%) (+46.3%; p=0.02) values in comparison to the Neoporos implants. After 28 days of healing, the CG yielded that the cortical BAFO of Acqua implants to be significantly, 14%, higher (p=0.04) than Neoporos implants.

Conclusion: The positive effects of the Acqua surface were able to counteract the adverse impact of uncontrolled DM at early osseointegration periods. After 28 days in vivo, the metabolic systemic impairment caused by DM overcame the surface treatment effect, leading to impaired osseointegration in both hydrophilic and hydrophobic implants.

Clinical Relevance: The adverse effects of diabetes mellitus with respect to bone healing may be minimized by deploying implants with strategically modified surfaces. This study evaluated the effects of implants with Acqua® and Neoporos® surfaces in both diabetic and healthy animals. During the initial healing period in diabetic animals, the hydrophilic surface was demonstrated to have beneficial effect on osseointegration in comparison to the hydrophobic surface. The results provide an insight into early healing, but the authors suggest that a future short-term and long-term clinical study is needed to assess the possible benefit of the Acqua® implant as well as in increasing the predictability of implant osseointegration.
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http://dx.doi.org/10.1007/s00784-021-03892-xDOI Listing
October 2021

Comparison of Surface Treatments of Endosteal Implants in Ovariectomized Rabbits.

Int J Oral Maxillofac Implants 2021 Jan-Feb;36(1):38-46

Purpose: The aim of this work was to evaluate osseointegration of endosteal implants with two different surface treatments at early stages (~3 weeks) in the tibia of healthy and ovariectomized rabbits.

Materials And Methods: The study comprised 10 adult New Zealand female rabbits (Oryctolagus cuniculus; 6 months and 3.0 ± 0.5 kg). Five animals were subjected to bilateral ovariectomy to mimic osteoporotic-like conditions, and the remaining rabbits (n = 5) served as the healthy control group. After 3 months, specimens from the ovariectomized and control groups were subject to implant placement in both tibiae, using two different types of surface treatment. A total of 36 implants were placed, n = 18 acid-etched and n = 18 anodized. After 3 weeks, euthanasia of the animals was performed, and samples were obtained for processing. Bone-to-implant contact and bone area fraction occupancy were quantified to evaluate the osseointegration parameters around the implant surface and within the thread area, respectively, and nanoindentation tests were performed to determine elastic modulus and hardness of the new bone. Both analyses were performed on the entire implant (total), as well as individually within the cortical and bone marrow cavity area.

Results: All animals were evaluated with no signs of infection or postoperative complications. The total bone-to-implant contact and bone area fraction occupancy results, independent of surface treatment, yielded significant differences between the ovariectomized and control groups (P = .002 and P < .001, respectively). In the marrow cavity, analyzing the surface treatments independently as a function of bone condition, the only differences detected were in the anodized treatment (P = .04). Regarding the elastic modulus, differences were detected only with the anodized implants between the ovariectomized and control groups (P = .015).

Conclusion: At 3 weeks after implant placement, there were better osseointegration values of the implants in the healthy control group compared with the ovariectomized group independent of surface treatment. Also, specifically in the medullary region of the rabbit tibia, the acid-etched implants had more uniform osseointegration values in conditions of low-quality bone in comparison to the anodized implants, histomorphometrically and biomechanically.
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http://dx.doi.org/10.11607/jomi.8459DOI Listing
February 2021

Clinical application of a FOXO1 inhibitor improves connective tissue healing in a diabetic minipig model.

Am J Transl Res 2021 15;13(2):781-791. Epub 2021 Feb 15.

Department of Periodontics, School of Dental Medicine, University of Pennsylvania Philadelphia, PA, USA.

The forkhead box O1 (FOXO1) transcription factor plays a key role in wound healing process. Recently it has been reported that lineage-specific genetic ablation of FOXO1 significantly improves diabetic wound healing in a mouse model. To investigate the clinical usefulness of these findings, translational preclinical studies with a large animal model are needed. We report for the first time that the local application of a FOXO1 inhibitor (AS1842856) significantly improves connective tissue healing in a preclinical T2DM minipig model, reflected by increased collagen matrix formation, increased myofibroblast numbers, improved angiogenesis, and a shift in cell populations from pro-inflammatory (IL-1β, TNF-α and iNOS) to pro-healing (CD163). Our results set up the basis for the clinical application of a FOXO1 antagonist in early diabetic wounds where there is impaired connective tissue healing.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7868841PMC
February 2021

Histological and Nanomechanical Properties of a New Nanometric Hydroxiapatite Implant Surface. An In Vivo Study in Diabetic Rats.

Materials (Basel) 2020 Dec 13;13(24). Epub 2020 Dec 13.

Department of Oral and Maxillofacial Surgery and Periodontology, School of Dentistry of Ribeirao Preto, University of Sao Paulo, Av do Café, s/n., Ribeirao Preto, SP 14040-904, Brazil.

Implant therapy is a predictable treatment to replace missing teeth. However, the osseointegration process may be negatively influenced by systemic conditions, such as diabetes mellitus (DM). Microtopography and implant surface developments are strategies associated to better bone repair. This study aimed to evaluate, in healthy and diabetic rats, histomorphometric (bone to implant contact = %BIC; and bone area fraction occupancy = %BAFO) and nanomechanical (elastic modulus = EM; and hardness = H) bone parameters, in response to a nanometric hydroxyapatite implant surface. Mini implants (machined = MAC; double acid etched = DAE, and with addition of nano-hydroxyapatite = NANO) were installed in tibias of healthy and diabetic rats. The animals were euthanized at 7 and 30 days. NANO surface presented higher %BIC and %BAFO when compared to MAC and DAE (data evaluated as a function of implant surface). NANO surface presented higher %BIC and %BAFO, with statistically significant differences (data as a function of time and implant surface). NANO surface depicted higher EM and H values, when compared to machined and DAE surfaces (data as a function of time and implant surface). Nano-hydroxyapatite coated implants presented promising biomechanical results and could be an important tool to compensate impaired bone healing reported in diabetics.
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http://dx.doi.org/10.3390/ma13245693DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7764315PMC
December 2020

Influence of Abutment Fabrication Method on 3D Fit at the Implant-Abutment Connection.

Int J Prosthodont 2020 Nov/Dec;33(6):641-647

Purpose: To three-dimensionally evaluate the internal fit at the implant-abutment interface of abutments fabricated with different workflows using a combination of the silicone replica technique and microcomputed tomography (μCT).

Materials And Methods: Thirty abutments were fabricated to restore internal-connection implants and were divided into three groups according to fabrication method: (1) full digital (abutment machined using CAD/CAM system); (2) Ti-Base (prefabricated standard Ti-Base abutments); and (3) UCLA (UCLA-type abutments) (n = 10/group). Linear and volume measurements were performed to assess the internal misfit using a silicone replica of the implant-abutment interface misfit area, which was three-dimensionally reconstructed after μCT. The internal discrepancies in three different regions of interest (Gap, Gap, and Gap) were assessed. Data were statistically evaluated using ANOVA and Tukey test (P < .05).

Results: Ti-Base and UCLA abutments presented significantly lower misfit volume (0.49 mm, 95% CI: ± 0.045 mm and 0.48 mm, 95% CI: ± 0.045 mm, respectively) and mean internal gap (25.20 μm, 95% CI: ± 3.14 μm and 27.97 μm, 95% CI: ± 3.14 μm, respectively) than the full digital group (0.70 mm, 95% CI: ± 0.045 mm; 34.90 μm, 95% CI: ± 3.14 μm) (P < .001), but did not differ from each other (P = .825). While Gap was significantly higher in the full digital group (P < .001), Gap and Gap did not demonstrate significant differences among groups. All regions were statistically similar within groups, except for Gap in the full digital group, which exhibited higher mean values compared to the other regions (P = .000). The 3D measurements for quantification of internal discrepancy were strongly associated with the 2D measurements.

Conclusion: Ti-Base and UCLA abutments exhibited better internal fit at the implant-abutment interfaces compared to a fully digitalized workflow (CAD/CAM custom abutments).
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http://dx.doi.org/10.11607/ijp.6574DOI Listing
December 2020

Effect of Surgical Instrumentation Variables on the Osseointegration of Narrow- and Wide-Diameter Short Implants.

J Oral Maxillofac Surg 2021 02 8;79(2):346-355. Epub 2020 Oct 8.

Professor, Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY, USA; Professor, Hansjörg Wyss Department of Plastic Surgery, New York University School of Medicine, New York, NY, USA; and Professor, Department of Mechanical Engineering, Tandon School of Engineering, New York University, Brooklyn, NY.

Purpose: 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: 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.
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http://dx.doi.org/10.1016/j.joms.2020.09.041DOI Listing
February 2021

Analysis of microRNA regulating cell cycle-related tumor suppressor genes in endometrial cancer patients.

Hum Cell 2021 Mar 29;34(2):564-569. Epub 2020 Oct 29.

Department of Gynecology, Obstetrics and Oncological Gynecology, Medical University of Silesia, Bytom, Poland.

Endometrial cancer remains the most common malignancy of the female genital system in developed countries. Tumor suppressor genes are responsible for controlling the cells fate in the cell cycle and preventing cancerogenesis. Gene expression affects cancer progression and is modulated by microRNAs defined as both tumor suppressors and oncogenes. These molecules indirectly regulate multiple processes like cell proliferation, differentiation and apoptosis. The aim of this study was to analyze miRNAs expression that can regulate the activity of tumor suppressor genes related to the cell cycle in patients with endometrioid endometrial cancer. The study group consisted of 12 samples that met the inclusion criteria from a total of 48 obtained. The 12 samples were used to analyze microRNA expression. Complementary miRNAs were identified using TargetScan Database and statistical analysis. MicroRNAs were determined for the tumor suppressor genes: CYR61, WT1, TSPYL5, HNRNPA0, BCL2L1 and BAK1. All the miRNAs were complementary to the described target genes based on TargetScan Database. There were five miRNAs differentially expressed that can regulate tumor suppressor genes related to the cell cycle. The distinguished miRNAs: mir-340-3p, mir-1236-5p, mir-874-3p, mir-873-5p.2 and mir-548-5p were differentially expressed in endometrial cancer in comparison to the control. Among the distinguished miRNAs, the most promising is mir-874-3p, which may have an important role in endometrial adenocarcinoma proliferation.
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http://dx.doi.org/10.1007/s13577-020-00451-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7900021PMC
March 2021

Three-Dimensionally-Printed Bioactive Ceramic Scaffolds-Construct Effects on Bone Regeneration: A Pilot Study.

J Craniofac Surg 2020 Sep 28. Epub 2020 Sep 28.

Department of Biomaterials, New York University College of Dentistry.

Background/purpose: 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: 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: 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.
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http://dx.doi.org/10.1097/SCS.0000000000007146DOI Listing
September 2020

WE43 and WE43-T5 Mg alloys screws tested in-vitro cellular adhesion and differentiation assay and in-vivo histomorphologic analysis in an ovine model.

J Biomater Appl 2021 03 9;35(8):901-911. Epub 2020 Sep 9.

New York University, New York, NY, USA.

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. assay of cell growth, adhesion and differentiation was also conducted to investigate possible mechanisms underlying the behavior expressed from the alloys . In conclusion WE43-T5 indicated bone/implant interaction properties that makes it more suitable for fabrication of endosteal bone screws.
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http://dx.doi.org/10.1177/0885328220956788DOI Listing
March 2021

Three-Dimensional Printing for Craniofacial Bone Tissue Engineering.

Tissue Eng Part A 2020 12 1;26(23-24):1303-1311. Epub 2020 Oct 1.

Department of Oral and Maxillofacial Surgery, School of Dentistry, The University of Texas Health Science Center at Houston, Houston, Texas, USA.

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.
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http://dx.doi.org/10.1089/ten.TEA.2020.0186DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7759279PMC
December 2020

Comparative analysis of elastomeric die materials for semidirect composite restorations.

Int J Esthet Dent 2020 ;15(3):344-354

Aim: Die silicone materials are used to build chairside composite restorations. The purpose of this study was to compare the flowability, dimension accuracy, and tear strength of four elastomeric die materials.

Material And Methods: Materials were divided into four groups: Mach-2 (M2), Scan Die (SD), GrandioSO Inlay System (GIS), and Impregum-F (IM). Flowability analysis was carried out using the shark fin test (SFT). For dimension accuracy, impressions were taken from a premolar Class I preparation and an elastomeric model was cast. Composite resin restorations were built and positioned into the premolar for gap measurement. The mean gap length was divided into three levels: acceptable (A), not acceptable (NA), and misfit (M). For tear strength, strip specimens were made with a V-shaped notch (n = 6). The specimens were tested in a universal machine until tear. All data were analyzed statistically with a confidence interval of 95%.

Results: GIS showed the lowest flowability values, with no differences between IM, M2, and SD. For dimension accuracy, IM showed 100% 'A' gap values, followed by M2 (80%), SD (60%), and GIS (60%). For tear strength, IM showed the highest values, followed by M2, GIS, and SD.

Conclusions: M2, SD, and IM had similar flowability, while GIS had the lowest. IM presented higher tear strength than M2, followed by GIS and SD. IM showed the highest degrees of acceptable gap filling, followed by M2.
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August 2020

Clinical, histological, and nanomechanical parameters of implants placed in healthy and metabolically compromised patients.

J Dent 2020 09 30;100:103436. Epub 2020 Jul 30.

Department of Mechanical and Aerospace Engineering - NYU Tandon School of Engineering, Brooklyn, NY, USA; Hansjörg Wyss Department of Plastic Surgery, NYU Langone Health School of Medicine, New York, NY, USA.

Objectives: To evaluate the clinical outcomes, histological parameters, and bone nanomechanical properties around implants retrieved from healthy and metabolic syndrome (MS) patients.

Methods: Twenty-four patients with edentulous mandibles (12/condition), received four implants between the mental foramina. An additional implant prototype was placed for retrieval histology. The following clinical outcomes were evaluated: insertion torque (IT), implant stability quotient (ISQ) values at baseline and after 60 days of healing, and implant survival. The prototype was retrieved after the healing and histologically processed for bone morphometric evaluation of bone-to-implant contact (%BIC) and bone area fraction occupancy (%BAFO), and bone nanoindentation to determine the elastic modulus (Em) and hardness (H). Descriptive statistical procedures and survival tests were used to analyze the data.

Results: The final study population was comprised of 10 women and 11 men (∼64 years). A total of 105 implants were placed, 21 retrieved for histology. Implant survival rates were similar between groups (>99 %). Similarly, IT and ISQ analyses showed no significant association with systemic condition (p > 0.216). Histological micrographs depicted similar bone morphology, woven bone, for both conditions. While MS (33 ± 5.3 %) and healthy (39 ± 6.5 %) individuals showed no significant difference for %BIC (p = 0.116), significantly higher %BAFO was observed for healthy (45 ± 4.6 %) relative to MS (30 ± 3.8 %) (p < 0.001). No significant differences on bone nanomechanical properties was observed (p > 0.804).

Conclusions: Although no significant influence on clinical parameters and bone nanomechanical properties was observed, MS significantly reduced bone formation in the peri-implant area in the short-term.

Clinical Significance: A lower amount of bone formation in the peri-implant area was observed in comparison to healthy patients, although the other short-term clinical outcomes were not significantly different. Considering the escalating prevalence of MS patients in need for implant treatment, it becomes crucial to understand bone-to-implant response to determine the ideal loading time in this population.
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http://dx.doi.org/10.1016/j.jdent.2020.103436DOI Listing
September 2020

3D Printing of Microgel-Loaded Modular Microcages as Instructive Scaffolds for Tissue Engineering.

Adv Mater 2020 Sep 23;32(36):e2001736. Epub 2020 Jul 23.

Division of Biomaterials and Biomechanics, Department of Restorative Dentistry, School of Dentistry, Oregon Health and Science University, Portland, OR, 97201, USA.

Biomaterial scaffolds have served as the foundation of tissue engineering and regenerative medicine. However, scaffold systems are often difficult to scale in size or shape in order to fit defect-specific dimensions, and thus provide only limited spatiotemporal control of therapeutic delivery and host tissue responses. Here, a lithography-based 3D printing strategy is used to fabricate a novel miniaturized modular microcage scaffold system, which can be assembled and scaled manually with ease. Scalability is based on an intuitive concept of stacking modules, like conventional toy interlocking plastic blocks, allowing for literally thousands of potential geometric configurations, and without the need for specialized equipment. Moreover, the modular hollow-microcage design allows each unit to be loaded with biologic cargo of different compositions, thus enabling controllable and easy patterning of therapeutics within the material in 3D. In summary, the concept of miniaturized microcage designs with such straight-forward assembly and scalability, as well as controllable loading properties, is a flexible platform that can be extended to a wide range of materials for improved biological performance.
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http://dx.doi.org/10.1002/adma.202001736DOI Listing
September 2020

Obesity/Metabolic Syndrome and Diabetes Mellitus on Peri-implantitis.

Trends Endocrinol Metab 2020 08 23;31(8):596-610. Epub 2020 Jun 23.

Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY, USA; Hansjörg Wyss Department of Plastic Surgery, NYU Langone Health School of Medicine, New York, NY, USA; Department of Mechanical and Aerospace Engineering, NYU Tandon School of Engineering, Brooklyn, NY, USA. Electronic address:

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.
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http://dx.doi.org/10.1016/j.tem.2020.05.005DOI Listing
August 2020

Aging resistant ZTA composite for dental applications: Microstructural, optical and mechanical characterization.

Dent Mater 2020 09 17;36(9):1190-1200. Epub 2020 Jun 17.

Department of Prosthodontics and Periodontology, University of São Paulo, Bauru School of Dentistry, Bauru, SP, Brazil.

Objective: To synthesize a zirconia toughened alumina (ZTA) composite with 70% alumina reinforced by 30% zirconia for dental applications and to characterize its microstructure and optical properties for comparison with the isolated counterpart materials and a first-generation 3Y-TZP.

Methods: Disc-shaped specimens were divided in four groups (n = 70/material): (1) 3YSB-E (first generation 3Y-TZP), (2) Zpex (second generation 3Y-TZP), (3) alumina, and (4) ZTA-Zpex 70/30. After synthesis, ceramic powders were pressed, and green-body samples sintered following a predetermined protocol. Specimens were polished to obtain a mirror surface finish. Apparent density was measured by Archimedes principle. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to characterize the crystalline content and microstructure. Reflectance tests were performed to determine the contrast-ratio (CR) and translucency-parameter (TP). Mechanical properties were assessed by biaxial flexural strength (BFS) test. All analyses were conducted before and after artificial aging (20 h, 134 °C, 2.2 bar). Optical parameters were evaluated through repeated-measures analysis of variance and Tukey tests (p < 0.05). BFS data were analyzed using Weibull statistics (95% CI).

Results: High density values (95-99%) were found for all ceramic materials and SEM images exhibited a dense microstructure. While XRD patterns revealed the preservation of crystalline content in the ZTA composite, an increase in the monoclinic peak was observed for pure zirconias after aging. Significantly higher CR and lower TP values were observed for the ZTA composite, followed by alumina, 3YSB-E, and Zpex. The highest characteristic stress was recorded for 3YSB-E, followed by intermediate values between ZTA and Zpex, and the lowest for alumina. Aging affected the optical and mechanical properties of both zirconias, while remained stable for ZTA composite and alumina.

Significance: The synthesis of experimental 70-30% ZTA composite was successful and its relevance for dental applications relies on its higher masking ability, aging resistance, and strength similar to zirconia.
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http://dx.doi.org/10.1016/j.dental.2020.05.011DOI Listing
September 2020

Osseodensification drilling vs conventional manual instrumentation technique for posterior lumbar fixation: Ex-vivo mechanical and histomorphological analysis in an ovine model.

J Orthop Res 2021 07 14;39(7):1463-1469. Epub 2020 May 14.

Hansjörg Wyss Department of Plastic Surgery, New York University School of Medicine, New York, New York.

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.
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http://dx.doi.org/10.1002/jor.24707DOI Listing
July 2021

Presence of human papilloma virus in Caucasian women living in the central Europe diagnosed with vulvar intraepithelial neoplasia.

Ginekol Pol 2020 1;91(4):181-184. Epub 2020 Apr 1.

Medical University of Silesia, Katowice, Poland.

Objectives: The role of human papilloma virus (HPV) in the development of cancerous states of female reproductive tract has been widely debated. However, the information about presence of HPV in the Caucasian women living in the central Europe diagnosed with vulvar intraepithelial neoplasia (VIN) is missing. So far, no recommendation was made to complete HPV detection in time of vulvar biopsy or after the results of positive VIN are obtained. We aimed to assess the presence of HPV in women with vulvar intraepithelial neoplasia diagnosed at the Department of Gynecology, Obstetrics and Oncological Gynecology in Bytom, Poland.

Material And Methods: The retrospective examination of 120 consecutive vulvar biopsies obtained from women with persistent vulvar itching was done. Only patients with diagnosis of VIN were included in the further analysis. HPV DNA was detected using HPV Linear Array Genotyping Test including 14 HPV genotypes (16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66, 68).

Results: Out of 120 vulvar samples retrieved, 18 women were positive for VIN, including15 usual VIN (uVIN) and three differentiated type (dVIN ). 10 samples were eligible for DNA detection. HPV DNA was found in two women with uVIN (HPV 16 and 51).

Conclusions: It is advisable to recommend HPV genotyping in women with VIN, regardless of their age and histologic type. The incidence of HPV infection in Caucasian women from the central Europe with VIN should be further studied.
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http://dx.doi.org/10.5603/GP.a2020.0035DOI Listing
June 2021

Bone Tissue Engineering in the Growing Calvaria Using Dipyridamole-Coated, Three-Dimensionally-Printed Bioceramic Scaffolds: Construct Optimization and Effects on Cranial Suture Patency.

Plast Reconstr Surg 2020 Feb;145(2):337e-347e

From the Hansjörg Wyss Department of Plastic Surgery, New York University Langone Health; New York University School of Medicine; the Icahn School of Medicine at Mount Sinai; the Department of Biomaterials, New York University College of Dentistry; and the Division of Translational Medicine, New York University School of Medicine.

Background: Three-dimensionally-printed bioceramic scaffolds composed of β-tricalcium phosphate delivering the osteogenic agent dipyridamole can heal critically sized calvarial defects in skeletally mature translational models. However, this construct has yet to be applied to growing craniofacial models. In this study, the authors implanted three-dimensionally-printed bioceramic/dipyridamole scaffolds in a growing calvaria animal model and evaluated bone growth as a function of geometric scaffold design and dipyridamole concentration. Potential adverse effects on the growing suture were also evaluated.

Methods: Bilateral calvarial defects (10 mm) were created in 5-week-old (approximately 1.1 kg) New Zealand White rabbits (n = 16 analyzed). Three-dimensionally-printed bioceramic scaffolds were constructed in quadrant form composed of varying pore dimensions (220, 330, and 500 μm). Each scaffold was coated with collagen and soaked in varying concentrations of dipyridamole (100, 1000, and 10,000 μM). Controls consisted of empty defects. Animals were killed 8 weeks postoperatively. Calvariae were analyzed using micro-computed tomography, three-dimensional reconstruction, and nondecalcified histologic sectioning.

Results: Scaffold-induced bone growth was statistically greater than bone growth in empty defects (p = 0.02). Large scaffold pores, 500 μm, coated in 1000 μM dipyridamole yielded the most bone growth and lowest degree of scaffold presence within the defect. Histology showed vascularized woven and lamellar bone along with initial formation of vascular canals within the scaffold lattice. Micro-computed tomographic and histologic analysis revealed patent calvarial sutures without evidence of ectopic bone formation across all dipyridamole concentrations.

Conclusion: The authors present an effective pediatric bone tissue-engineering scaffold design and dipyridamole concentration that is effective in augmentation of calvarial bone generation while preserving cranial suture patency.
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http://dx.doi.org/10.1097/PRS.0000000000006483DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7212767PMC
February 2020

Implant-abutment fit influences the mechanical performance of single-crown prostheses.

J Mech Behav Biomed Mater 2020 02 31;102:103506. Epub 2019 Oct 31.

University of Sao Paulo - Bauru School of Dentistry, Department of Prosthodontics and Periodontology, Bauru, SP, Brazil.

Objectives: To evaluate the three-dimensional fit of abutments fabricated by the industry to those either milled or cast by a commercial laboratory and to correlate the implant-abutment connection fit with stress at fatigue failure of prostheses. Probability of survival (reliability) and fractography to characterize failure modes were also performed for cemented and screw-retained prostheses.

Methods: One-hundred and twenty-six maxillary central incisor crowns were milled to restore implants and divided in 3 cemented and 3 screwed-retained groups (n = 21/each), as follows: [Digital-Sc]: milled one-piece monolithic abutment/crown; [TiB-Sc]: milled crowns cemented onto Ti-base abutments; [UCLA]: screw-retained crown using UCLA abutments; [Digital-Ce]: milled two-piece assembly comprised by screwed monolithic abutment and a cemented crown; [TiB-Ce]: milled coping cemented onto Ti-base abutments to receive a cemented crown; [UCLA-Ce]: UCLA abutments that received an overcast coping and a cemented crown. Implant-abutment volume misfit was assessed by micro-computed tomography using the silicone replica technique. Implant/crown systems were subjected to step-stress accelerated life testing (SSALT) in water. The use-level probability Weibull curves and reliability for a mission of 50,000 cycles at calculated stress at failure of 2,300, 3300 and 4300 MPa were plotted. Fractographic analysis was performed with scanning electron microscopy. Internal misfit was analyzed through one-way ANOVA following post-hoc comparisons by Tukey test (p < 0.05). Correlation between misfit volume and the stress at fatigue failure was assessed by Pearson test.

Results: Similar misfit volumes were observed for TiB-Sc (0.458 mm), TiB-Ce (0.461 mm), UCLA (0.471 mm) and UCLA-Ce (0.480 mm), which were significantly lower than Digital-Sc (0.676 mm) and Digital-Ce (0.633 mm). The mean β values were: 1.68, 1.39, 1.48, 2.41, 2.27 and 0.71 for Digital-Sc, TiB-Sc, UCLA, Digital-Ce, TiB-Ce and UCLA-Ce, respectively, indicating that fatigue was an accelerating factor for failure of all groups. Higher stress at failure decreased the reliability of all groups, more significantly for screw compared to cement-retained groups, especially for Digital-Sc that demonstrated the lowest reliability. The failure mode was restricted to abutment screw fracture. A negative correlation was observed between misfit values and stress at failure (r = -0.302, p = 0.01).

Conclusions: Abutments milled by a commercial lab presented higher misfit compared to those provided by the industry and a moderate correlation was observed between higher misfit and lower stress at failure during fatigue. Probability of survival decreased at higher stress, especially for screw compared to cement-retained groups, and failures were confined to abutment screws.
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http://dx.doi.org/10.1016/j.jmbbm.2019.103506DOI Listing
February 2020

Dipyridamole-loaded 3D-printed bioceramic scaffolds stimulate pediatric bone regeneration in vivo without disruption of craniofacial growth through facial maturity.

Sci Rep 2019 12 5;9(1):18439. Epub 2019 Dec 5.

Department of Biomaterials & Biomimetics, NYU College of Dentistry, 433 1st Avenue, New York, NY, 10010, USA.

This study investigates a comprehensive model of bone regeneration capacity of dypiridamole-loaded 3D-printed bioceramic (DIPY-3DPBC) scaffolds composed of 100% beta-tricalcium phosphate (β -TCP) in an immature rabbit model through the time of facial maturity. The efficacy of this construct was compared to autologous bone graft, the clinical standard of care in pediatric craniofacial reconstruction, with attention paid to volume of regenerated bone by 3D reconstruction, histologic and mechanical properties of regenerated bone, and long-term safety regarding potential craniofacial growth restriction. Additionally, long-term degradation of scaffold constructs was evaluated. At 24 weeks in vivo, DIPY-3DPBC scaffolds demonstrated volumetrically significant osteogenic regeneration of calvarial and alveolar defects comparable to autogenous bone graft with favorable biodegradation of the bioactive ceramic component in vivo. Characterization of regenerated bone reveals osteogenesis of organized, vascularized bone with histologic and mechanical characteristics comparable to native bone. Radiographic and histologic analyses were consistent with patent craniofacial sutures. Lastly, through application of 3D morphometric facial surface analysis, our results support that DIPY-3DPBC scaffolds do not cause premature closure of sutures and preserve normal craniofacial growth. Based on this novel evaluation model, this DIPY-3DPBC scaffold strategy is a promising candidate as a safe, efficacious pediatric bone tissue engineering strategy.
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http://dx.doi.org/10.1038/s41598-019-54726-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6895073PMC
December 2019

The effect of platelet-rich fibrin exudate addition to porous poly(lactic-co-glycolic acid) scaffold in bone healing: An in vivo study.

J Biomed Mater Res B Appl Biomater 2020 05 19;108(4):1304-1310. Epub 2019 Aug 19.

Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, New York.

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 cm , 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.
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http://dx.doi.org/10.1002/jbm.b.34478DOI Listing
May 2020

Biomaterial and biomechanical considerations to prevent risks in implant therapy.

Periodontol 2000 2019 10;81(1):139-151

Department of Biomaterials, Hansjörg Wyss Department of Plastic Surgery, Mechanical and Aerospace Engineering, New York University, New York City, New York, USA.

This paper is aimed to present a biomaterials perspective in implant therapy that fosters improved bone response and long-term biomechanical competence from surgical instrumentation to final prosthetic rehabilitation. Strategies to develop implant surface texturing will be presented and their role as an ad hoc treatment discussed in light of the interplay between surgical instrumentation and implant macrogeometric configuration. Evidence from human retrieved implants in service for several years and from in vivo studies will be used to show how the interplay between surgical instrumentation and implant macrogeometry design affect osseointegration healing pathways, and bone morphologic and long-term mechanical properties. Also, the planning of implant-supported prosthetic rehabilitations targeted at long-term performance will be appraised from a standpoint where personal preferences (eg, cementing or screwing a prosthesis) can very often fail to deliver the best patient care. Lastly, the acknowledgement that every rehabilitation will have its strength degraded over time once in function will be highlighted, since the potential occurrence of even minor failures is rarely presented to patients prior to treatment.
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http://dx.doi.org/10.1111/prd.12288DOI Listing
October 2019

Regeneration of a Pediatric Alveolar Cleft Model Using Three-Dimensionally Printed Bioceramic Scaffolds and Osteogenic Agents: Comparison of Dipyridamole and rhBMP-2.

Plast Reconstr Surg 2019 08;144(2):358-370

From the Hansjörg Wyss Department of Plastic Surgery and the Division of Translational Medicine, Department of Medicine, New York University Langone Health; the Department of Biomaterials and Biomimetics, New York University College of Dentistry; and the Icahn School of Medicine at Mount Sinai.

Background: Alveolar clefts are traditionally treated with secondary bone grafting, but this is associated with morbidity and graft resorption. Although recombinant human bone morphogenetic protein-2 (rhBMP-2) is under investigation for alveolar cleft repair, safety concerns remain. Dipyridamole is an adenosine receptor indirect agonist with known osteogenic potential. This study compared dipyridamole to rhBMP-2 at alveolar cleft defects delivered using bioceramic scaffolds.

Methods: Skeletally immature New Zealand White rabbits underwent unilateral, 3.5 × 3.5-mm alveolar resection adjacent to the growing suture. Five served as negative controls. The remaining defects were reconstructed with three-dimensionally printed bioceramic scaffolds coated with 1000 μm of dipyridamole (n = 6), 10,000 μm of dipyridamole (n = 7), or 0.2 mg/ml of rhBMP-2 (n = 5). At 8 weeks, new bone was quantified. Nondecalcified histologic evaluation was performed, and new bone was evaluated mechanically. Statistical analysis was performed using a generalized linear mixed model and the Wilcoxon rank sum test.

Results: Negative controls did not heal, whereas new bone formation bridged all three-dimensionally printed bioceramic treatment groups. The 1000-μm dipyridamole scaffolds regenerated 28.03 ± 7.38 percent, 10,000-μm dipyridamole scaffolds regenerated 36.18 ± 6.83 percent (1000 μm versus 10,000 μm dipyridamole; p = 0.104), and rhBMP-2-coated scaffolds regenerated 37.17 ± 16.69 percent bone (p = 0.124 versus 1000 μm dipyridamole, and p = 0.938 versus 10,000 μm dipyridamole). On histology/electron microscopy, no changes in suture biology were evident for dipyridamole, whereas rhBMP-2 demonstrated early signs of suture fusion. Healing was highly cellular and vascularized across all groups. No statistical differences in mechanical properties were observed between either dipyridamole or rhBMP-2 compared with native bone.

Conclusion: Dipyridamole generates new bone without osteolysis and early suture fusion associated with rhBMP-2 in skeletally immature bone defects.
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http://dx.doi.org/10.1097/PRS.0000000000005840DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6668366PMC
August 2019
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