Efficacy of customized crown-level position jig in measuring peri-implant crestal bone level on periapical radiographs: An in vitro study.

Background/purpose: Accuracy of using implant length on periapical radiographs as calibration reference for measurements has not been verified. This study aimed to verify the measurements of peri-implant crestal bone level (piCBL) on periapical radiographs taken by the paralleling technique and using the implant length for calibration; and to propose a customized crownlevel position (CLP) jig to improve the measurement accuracy of piCBL. Materials and methods: A typodont installed an implant and a screw-retained crown at maxillary central incisor was used. To simulate piCBL, a metal post was placed near the implant at the same height of implant platform. The CLP jig was designed and 3-dimensionally printed out to allow implant projected orthogonally on periapical film. Thirty periapical radiographs were taken using paralleling technique with and without the jig by three examiners. The implant axis and implant length on radiographs were acquired by image segmentation. The discrepancy of piCBL determination (ΔD) from these measurements were compared and further analyzed when using the implant length for calibration. Results: The piCBL measurement errors were smaller when the jig was used for all examiners (P < 0.001). The inter-rater differences were insignificant. After calibration, ΔD with and without jig were 0.09 (0.07-0.11) and 0.43 (0.38-0.49) mm, respectively. Conclusion: Conventional long-cone paralleling technique using true implant length for calibration demonstrated imprecise piCBL measurement on periapical radiographs. Transferring the implant axis to the CLP jig allowed orthogonal projection of radiography which provided reliable measurements of piCBL with an accuracy of less than 0.1 mm.

Effects of postpolymerization time and temperature on the flexural properties and hardness profile of three-dimensional printed provisional resin.

Background/purpose: Three-dimensional (3D) printing technique was widely used for provisional restorations in clinical use. However, the effects of post-polymerization temperature and time on the flexural properties and hardness profile were not fully elucidated yet. The purpose of this study is to investigate the effects of post-polymerization temperature and time on the flexural properties and hardness profile of the provisional restoration. Materials and methods: 3D-printing provisional resin was printed and post-polymerized at various temperatures (room temperature, 40 °C, 60 °C and 80 °C) and periods (0, 15, 30, 60, 90 and 120 min of photopolymerization). Afterwards, the flexural strength, flexural modulus, surface hardness, and internal hardness at different depth were evaluated. Results: The group post-polymerized without concurrent heating had significantly shallow depth of cure comparing to the heating counterparts. The surface hardness of the groups post-polymerized at different temperatures did not show any difference. All groups with post-polymerization temperature at 40 °C, 60 °C and 80 °C and post-polymerization time ranged between 15 and 90 min, had curing depth between 3 and 4 mm. Group post-polymerized without concurrent heating has significantly shallow depth of cure comparing to the heating counterparts. Conclusion: Post-polymerization at an elevated temperature, preferably 60 °C, is suggested. The wall thickness of the 3D-printing provisional prosthesis thinner than 3-4 mm is recommended.

Systemic antibiotics adjuvants to scaling and root planing in type 2 diabetic and periodontitis individuals: Systematic review with network meta-analysis.

Targeting inflammatory pathways is considered a common strategy to control type 2 diabetes (T2D) and periodontitis. This overview was to validate systemic antibiotics as an adjuvant to scaling and root planing (SRP) for the treatments of periodontal patients with T2D. Literature searches were conducted using Web of Science, PubMed, Cochrane, and EMBASE. Randomized trials comparing SRP and systemic antibiotics on glycated hemoglobin (HbA1c) and probing pocket depth (PPD) in adults with T2D and periodontitis were analyzed using network meta-analysis and meta-regression. At 3-month postintervention, meta-analyses of 16 studies revealed that SRP and SRP plus systemic antibiotics (SRPa) had similar significant effects in reducing HbA1c levels of - 0.72% and - 0.96% respectively. While SRP and SRPa also, respectively, reduced PPD of - 0.67 and - 0.89 mm, SRPa showed a better reduction than SRP. At 6-month postintervention, meta-analyses of 7 trials revealed that only SRP was effective in reducing HbA1c levels (-0.29%) but not SRPa. Although both SRP and SRPa still significantly reduced PPD by - 0.56 and - 0.81 mm, respectively, there was no difference between them. The current overview suggested that routine SRP alone is highly recommended for patients with T2D and periodontitis, since systemic antibiotics as an adjuvant provide a rather short-term effect.

Long-term evaluation of peri-implant keratinized mucosa stability after free epithelialized graft and keratinized mucosa shifting procedures: A retrospective study up to 13 years.

OBJECTIVES: This study aimed to assess the risk of less than 2 mm keratinized mucosa (KM) width occurrence after free epithelialized graft (FEG) and keratinized mucosa shifting (KMS) procedures using survival analysis. In addition, KM dimensional changes were evaluated. MATERIALS AND METHODS: This study included 76 implants in 36 patients with insufficient KM (<2 mm). The implants underwent either FEG or KMS procedures. The mid-buccal KM width was measured from surgery to the end of a one 13-year follow-up period. RESULTS: Mean follow-up durations were 9.2 ± 3.9 years for FEG and 6.3 ± 4.2 years for KMS. Two implants in FEG and nine implants in KMS exhibited a KM width of less than 2 mm during follow-up. The hazard ratios for KMS compared to FEG were 6.48 (crude) and 6.54 (adjusted), both statistically significant (p < .05). The incidence rate of KMS (4.06%) was higher than that of FEG (0.63%), with an average incidence time of 3.38 years for KMS and 8.82 years for FEG post-surgery. FEG showed a significant shrinkage within 6 months (33% ± 22%), whereas KMS demonstrated a gradual decrease over 13 years (34% ± 25%). FEG exhibited significantly greater width change than KMS during a 5-year follow-up (p < .05). CONCLUSIONS: FEG and KMS enhanced PIKM but exhibited different long-term reduction patterns. FEG demonstrated rapid shrinkage, while KMS displayed gradual and continuous reduction. Moreover, KMS presented a higher risk and incidence of KM width less than 2 mm compared to FEG.

Alterations in kinematics of temporomandibular joint associated with chronic neck pain.

BACKGROUND: Temporomandibular disorder (TMD) is an umbrella term for pain and dysfunction of the temporomandibular joint (TMJ) and its associated structures. Patients with TMD show changes in TMJ kinematics and masticatory muscle activation. TMD is commonly comorbid with non-specific chronic neck pain (NCNP), which may be one of the risk factors for TMD. OBJECTIVES: This study aimed to investigate whether patients with NCNP have altered TMJ kinematics and masticatory muscle activity. METHODS: This was a cross-sectional exploratory study including 19 healthy participants and 20 patients with NCNP but without TMD symptoms. TMJ kinematics was measured during mouth opening and closing, jaw protrusion and jaw lateral deviation. Surface electromyography was used to record the muscle activity of the anterior temporalis, masseter, sternocleidomastoid and upper trapezius while clenching. Furthermore, cervical posture, cervical range of motion (ROM) and pressure-pain threshold of the neck and masticatory muscles were measured. RESULTS: Compared with the healthy group, the NCNP group showed significantly reduced upper cervical rotation ROM (p = .041) and increased condylar path length (p = .02), condylar translation (opening p = .034, closing p = .011) and mechanical pain sensitivity of the upper trapezius (p = .018). Increased condylar translation was significantly correlated with reduced upper cervical mobility and poor cervical posture (r = -0.322 to -0.397; p = .012-.046). CONCLUSION: Increased condylar translation and path length in patients with NCNP may indicate poor control of TMJ articular movement, which may result from neck pain or may be a compensation for limited neck mobility. Evaluation of excessive TMJ translation may be considered in patients with NCNP.

Evaluation of students' self-assessment performance in preclinical endodontic training by means of rubrics and a 3D printed model.

BACKGROUND/PURPOSE: Effective evaluation of students' self-assessment ability is crucial. This study was to develop a standardized 3D printed teaching model accompanied by structured scoring rubrics for preclinical endodontic training, to appraise students' self-assessment ability, and to evaluate their perceptions of the training system. METHODS: The 3D printing model was designed to house a standardized central incisor. Forty-four undergraduate dental students were enrolled and their endodontic performance was self-assessed and also rated by a teaching assistant and a tutor using 3 structured rubrics including access cavity, mechanical preparation, and obturation assessments. In total, 21 rubric evaluation items of preclinical tasks were assessed, and the assessment results from the student, teaching assistant, and tutor were compared. Furthermore, questionnaires were used to evaluate students' experiences with the new system. RESULTS: The tutor, teaching assistant, and students all had similar scorings and high intraclass correlation coefficients (ICC) for mechanical preparation and obturation rubrics, while the students had underestimated scores on the access cavity rubric with a rather low ICC of 0.387, which also lead to the underestimated overall scoring (P < 0.05). Among the 21 evaluation criteria, 9 items were rated statistically different (P < 0.05), which denoted the major deficiencies of students' self-assessments. More than 80% of students rated satisfied for most of the questions regarding the new training system, except the tactile sensation, hardness, and radiopacity. CONCLUSION: The proposed standardized 3D printed model and structured scoring rubrics is feasible for preclinical endodontic training, and standardized evaluation of students' self-assessment ability.

Degree of polarization uniformity for dental calculus visualization.

During the treatment for periodontitis, the removal of dental calculus is essential. Previously, we have proposed the DAM algorithm for intuitive identification of the site of lesion, enabling the non-contact assessment during the operation. Nonetheless, the delineation of dental calculus was still imperfect. To this end, here we utilized the power of polarization-sensitive optical coherence tomography and evaluated the contrast called degree of polarization uniformity for dental calculus visualization. The result showed that the selected index demonstrated excellent contrast of dental calculus from other normal dental hard tissues. The proposed contrast is promising for accurate dental calculus delineation.

Low masseter muscle mass is associated with frailty in community-dwelling older adults: I-Lan Longitudinal Aging Study.

BACKGROUND: Sarcopenia, defined as age-related diminution of muscle mass and strength, is a key determinant of frailty status and progression. We investigated the hypothesis that changing masseter muscle structure with advancing age may contribute to the development of frailty. METHODS: Study data were excerpted from the I-Lan Longitudinal Aging Study, a research cohort of community-dwelling residents aged ≥53 years from Yilan (I-Lan) County, Taiwan. The study sample comprised 56 subjects classified as frail, 41 pre-frail, and 41 robust, according to Cardiovascular Health Study criteria; all groups were matched by age and sex. Masseter muscle volume was quantified based on T1-weighted magnetic resonance imaging, and adjusted for height to derive the masseter volume index (MVI). Appendicular skeletal muscle mass index (SMI) was determined by dual-energy X-ray absorptiometry, and used to derive the height-adjusted skeletal mass index (SMI). Nutrition status was assessed with the Mini-Nutritional Assessment (MNA) form. RESULTS: The MVI was significantly smaller in frail versus pre-frail subjects. Among frail individuals, only the MVI was significantly correlated with MNA scores. MVI, but not SMI, was associated with increased risk of being frail versus pre-frail. An MVI cut-off score of 9.5 cm3/m2 in males discriminated frail from pre-frail status with acceptable sensitivity and specificity. Low MVI was associated with the frailty criteria of slowness. CONCLUSIONS: MVI is a potential clinical index for evaluating phenotypic frailty. Diminished masseter muscle volume may predispose pre-frail/frail elders to depletion of physical reserves, consequent to its detrimental effect on oral functioning and nutrient intake.

Risk assessment of interproximal contact loss between implant-supported fixed prostheses and adjacent teeth: A retrospective radiographic study.

STATEMENT OF PROBLEM: Studies of interproximal contact loss (ICL) associated with implant-supported fixed prostheses (ISFPs) have typically used dental floss or metal strips to determine ICL and have shown a high prevalence of 34% to 66%, which does not match the authors' experience. Moreover, the implant prosthetic factors contributing to ICL have seldom been reported. PURPOSE: The purpose of this clinical study was to examine follow-up radiographs of ISFPs to determine the prevalence of open contacts between the ISFP and adjacent teeth and to assess the risk factors associated with ICL at patient, implant prosthesis, and adjacent tooth levels. MATERIAL AND METHODS: Patients treated with ISFPs at a single clinical center were included. Digital radiographs obtained at the time of ISFP delivery and subsequent follow-up were assessed, and a total of 180 ISFPs with 296 interproximal contacts in 147 patients were screened for analyses. The prevalence and risk factors of ICL at the levels of patient (age, sex, diabetes, smoking, and bruxism), implant prosthesis (follow-up period, arch location, splinting, ceramic or metal materials, screw or cement-retained, and abutment-fixture connection), and adjacent tooth (mesial or distal side, contact with unrestored tooth, composite resin restoration, or fixed prosthesis, vitality, bone height, and contralateral spacing) were analyzed with logistic regressions and generalized estimating equation (GEE) analyses (α=.05). RESULTS: The onset of ICL was from 6 to 96 months after ISFP delivery. The prevalence of ICL at the patient level was 15.0%, at the implant prosthesis level 13.3%, and at the adjacent tooth levels 8.8%. Twenty-six of the participants had 2 or more ISFPs. The multivariable GEE analysis reported that sex at patient level; longer follow-up period and implant prostheses with external hexagonal and internal octagonal connections at implant prosthesis level; and contralateral spacing, contact with composite resin filling and mesial side of ISFP at adjacent tooth level were significant risk factors of ICL, where contralateral spacing had the highest adjusted odds ratio of 20.88 (P=.002). CONCLUSIONS: Most of the ICL were found at the mesial side of ISFPs, and the odds of ICL was significant in participants with longer follow-up periods. Internal hexagonal connections reported relatively lower risk than others. Factors relevant to the anterior component of occlusal force, such as male sex, contralateral spacing at adjacent tooth, and proximal contact of ISFP with resin filling, seem to be high risk factors for ICL.

Multiresin Additive Manufacturing Process for Printing a Complete Denture and an Analysis of Accuracy.

A complete denture, consisting of teeth and a gum base, is a standard device used to restore masticatory and esthetic functions in patients with complete edentulism. The different colors and mechanical properties for teeth and the gum base mean a complete denture is manufactured using two materials with different mechanical properties. This study proposes a method to make a complete denture using a laboratory-developed, multiresin additive manufacturing (MRAM) system with two resins and different mechanical properties. A tenon joint is used to create the bottom of the teeth that fit into the gum base, ensuring automatic alignment and higher bending strength. The mechanical properties, material waste, fabrication time, and effect of the tenon joint on the bending strength of a complete denture printed using the MRAM system are compared with the values for a computer-aided design and computer-aided manufacturing (CAD/CAM) system. Experimental results show that the printed denture is manufactured 3 times faster and produces 14 times less material waste, but is 35.08% less inaccurate than one produced using a CAD/CAM system. The proposed tenon joint increases the bending strength by 31.94%. The MRAM system is applicable for printing a complete denture.

Biofabrication of Cell-Laden Gelatin Methacryloyl Hydrogels with Incorporation of Silanized Hydroxyapatite by Visible Light Projection.

Gelatin methacryloyl (GelMA) hydrogel is a photopolymerizable biomaterial widely used for three-dimensional (3D) cell culture due to its high biocompatibility. However, the drawback of GelMA hydrogel is its poor mechanical properties, which may compromise the feasibility of biofabrication techniques. In this study, a cell-laden GelMA composite hydrogel with a combination incorporating silanized hydroxyapatite (Si-HAp) and a simple and harmless visible light crosslinking system for this hydrogel were developed. The incorporation of Si-HAp into the GelMA hydrogel enhanced the mechanical properties of the composite hydrogel. Moreover, the composite hydrogel exhibited low cytotoxicity and promoted the osteogenic gene expression of embedded MG63 cells and Human bone marrow mesenchymal stem cells (hBMSCs). We also established a maskless lithographic method to fabricate a defined 3D structure under visible light by using a digital light processing projector, and the incorporation of Si-HAp increased the resolution of photolithographic hydrogels. The GelMA-Si-HAp composite hydrogel system can serve as an effective biomaterial in bone regeneration.

Synthesis and Formulation of PCL-Based Urethane Acrylates for DLP 3D Printers.

In this study, three PCL-based polyurethane acrylates were synthesized and further formulated into twelve resins for digital light processing (DLP) 3D printing. Three PCL diols with different molecular weights were synthesized via ring-opening reaction of ε-caprolactone on diethylene glycol, with the catalyst stannous octoate. Isophorone diisocyanate (IPDI) was reacted with 2-hydroxyethyl acrylate (2-HEA) and the PCL diols form PCL-based polyurethane acrylates. Twelve resins composed of different percentages of PCL-based polyurethane acrylates, poly (ethylene glycol) diacrylate (PEGDA), propylene glycol (PPG) and photo-initiator were further printed from a DLP 3D printer. The viscosities of twelve resins decreased by 10 times and became printable after adding 30% of PEGDA. The degree of conversion for the twelve resins can reach more than 80% after the post-curing process. By changing the amount of PEGDA and PPG, the mechanical properties of the twelve resins could be adjusted. PUA530-PEG-PPG (70:30:0), PUA800-PEG-PPG (70:30:0), and PUA1000-PEG-PPG (70:30:0) were successfully printed into customized tissue scaffolds. Twelve PCL-based polyurethane photo-curable resins with tunable mechanical properties, cytotoxicity, and degradability were successfully prepared. With the DLP 3D printing technique, a complex structure could be achieved. These resins have great potential for customized tissue engineering and other biomedical application.

Mechanical properties, accuracy, and cytotoxicity of UV-polymerized 3D printing resins composed of Bis-EMA, UDMA, and TEGDMA.

STATEMENT OF PROBLEM: Three-dimensional printing has the potential for clinical applications, and additive manufacturing materials for dental use merit further investigation. PURPOSE: The purpose of this in vitro study was to evaluate the properties of materials formulated with ethoxylated bisphenol A-dimethacrylate (Bis-EMA), urethane dimethacrylate (UDMA), and triethylene glycol dimethacrylate (TEGDMA) as 3D printing resins for ultraviolet digital light processing (UV-DLP) 3D printers and to characterize the mechanical and biological properties and accuracy of the printed objects. MATERIAL AND METHODS: Ten different light-polymerized resins were formulated using Bis-EMA, UDMA, and TEGDMA. Their viscosities were measured, and only 7 resins with viscosities lower than 1500 centipoise (cP) were selected for 3D printing and further material characterization. The light-polymerized resins were printed into representative shapes using a custom-made 3D printer equipped with a 405-nm UV-DLP projector as the light source. The printed specimens were subjected to biologic, mechanical, and accuracy tests, and the data were submitted to 1-way ANOVA and Tukey post hoc comparisons (α=.05). RESULTS: Photopolymerizable resins made of Bis-EMA, UDMA, and TEGDMA were successfully formulated for 3D printing to fabricate objects of various shapes and sizes. TEGDMA served as the diluent to reduce the viscosity and increase the degree of conversion, while UDMA and Bis-EMA provided strength as demonstrated by the mechanical testing. All the printed objects passed cytotoxicity testing. The flexural strengths of the printed specimens ranged between 60 MPa and 90 MPa; flexural modulus ranged between 1.7 GPa and 2.1 GPa; and surface hardness ranged between 14.5 HV and 24.6 HV. These represent similar mechanical properties to those of currently used clinical resin materials. In the accuracy test, the resin mixture composed of 80% Bis-EMA, 10% UDMA, and 10% TEGDMA had the highest accuracy, with a 0.051-mm deviation from the original design. CONCLUSIONS: Bis-EMA, UDMA, and TEGDMA are good candidates for the formulation of 3D printing resins for dental use. The printed objects demonstrated favorable biological and mechanical properties. Further, the accuracy of the printed specimens showed potential for clinical application.

OCT-Based Periodontal Inspection Framework.

Periodontal diagnosis requires discovery of the relations among teeth, gingiva (i.e., gums), and alveolar bones, but alveolar bones are inside gingiva and not visible for inspection. Traditional probe examination causes pain, and X-ray based examination is not suited for frequent inspection. This work develops an automatic non-invasive periodontal inspection framework based on gum penetrative Optical Coherence Tomography (OCT), which can be frequently applied without high radiation. We sum up interference responses of all penetration depths for all shooting directions respectively to form the shooting amplitude projection. Because the reaching interference strength decays exponentially with tissues' penetration depth, this projection mainly reveals the responses of the top most gingiva or teeth. Since gingiva and teeth have different air-tissue responses, the gumline, revealing itself as an obvious boundary between teeth and gingiva, is the basis line for periodontal inspection. Our system can also automatically identify regions of gingiva, teeth, and alveolar bones from slices of the cross-sectional volume. Although deep networks can successfully and possibly segment noisy maps, reducing the number of manually labeled maps for training is critical for our framework. In order to enhance the effectiveness and efficiency of training and classification, we adjust Snake segmentation to consider neighboring slices in order to locate those regions possibly containing gingiva-teeth and gingiva-alveolar boundaries. Additionally, we also adapt a truncated direct logarithm based on the Snake-segmented region for intensity quantization to emphasize these boundaries for easier identification. Later, the alveolar-gingiva boundary point directly under the gumline is the desired alveolar sample, and we can measure the distance between the gumline and alveolar line for visualization and direct periodontal inspection. At the end, we experimentally verify our choice in intensity quantization and boundary identification against several other algorithms while applying the framework to locate gumline and alveolar line in vivo data successfully.

Optical Polarimetric Detection for Dental Hard Tissue Diseases Characterization.

Dental enamel constitutes the outer layer of a crown of teeth and grows nearly parallel. This unique nanostructure makes enamel possess birefringence properties. Currently, there is still no appropriate clinical solution to examine dental hard tissue diseases. Therefore, we developed an optical polarization imaging system for diagnosing dental calculus, caries, and cracked tooth syndrome. By obtaining Stokes signals reflected from samples, Mueller images were constructed and analyzed using Lu-Chipman decomposition. The results showed that diattenuation and linear retardance images can distinguish abnormal tissues. Our result also aligns with previous studies assessed by other methods. Polarimetric imaging is promising for real-time diagnosing.

Interactive OCT-Based Tooth Scan and Reconstruction.

Digital dental reconstruction can be a more efficient and effective mechanism for artificial crown construction and period inspection. However, optical methods cannot reconstruct those portions under gums, and X-ray-based methods have high radiation to limit their applied frequency. Optical coherence tomography (OCT) can harmlessly penetrate gums using low-coherence infrared rays, and thus, this work designs an OCT-based framework for dental reconstruction using optical rectification, fast Fourier transform, volumetric boundary detection, and Poisson surface reconstruction to overcome noisy imaging. Additionally, in order to operate in a patient's mouth, the caliber of the injector is small along with its short penetration depth and effective operation range, and thus, reconstruction requires multiple scans from various directions along with proper alignment. However, flat regions, such as the mesial side of front teeth, may not have enough features for alignment. As a result, we design a scanning order for different types of teeth starting from an area of abundant features for easier alignment while using gyros to track scanned postures for better initial orientations. It is important to provide immediate feedback for each scan, and thus, we accelerate the entire signal processing, boundary detection, and point-cloud alignment using Graphics Processing Units (GPUs) while streamlining the data transfer and GPU computations. Finally, our framework can successfully reconstruct three isolated teeth and a side of one living tooth with comparable precisions against the state-of-art method. Moreover, a user study also verifies the effectiveness of our interactive feedback for efficient and fast clinic scanning.

Stiffness modification of photopolymerizable gelatin-methacrylate hydrogels influences endothelial differentiation of human mesenchymal stem cells.

For stem cell differentiation, the microenvironment can play an important role, and hydrogels can provide a three-dimensional microenvironment to allow native cell growth in vitro. A challenge is that the stem cell's differentiation can be influenced by the matrix stiffness. We demonstrate a low-toxicity method to create different stiffness matrices, by using a photopolymerizable gelatin methacrylate (GelMA) hydrogel cross-linked by blue light (440 nm). The stiffness and porosity of GelMA hydrogel is easily modified by altering its concentration. We used human bone marrow mesenchymal stem cells (MSCs) as a cell source and cultured the GelMA-encapsulated cells with EGM-2 medium to induce endothelial differentiation. In our GelMA blue light hydrogel system, we found that MSCs can be differentiated into both endothelial-like and osteogenic-like cells. The mRNA expressions of endothelial cell markers CD31, von Willebrand factor, vascular endothelial growth factor receptor-2, and CD34 were significantly increased in softer GelMA hydrogels (7.5% and 10%) compared with stiffer matrices (15% GelMA). On the other hand, the enhancements of osteogenic markers mRNA expressions (Alkaline phosphatase (ALP), Runx2, osteocalcin, and osteopontin) were highest in 10% GelMA. We also found that 10% GelMA hydrogel offered optimal conditions for MSCs to form capillary-like structures. These results suggest that the mechanical properties of the GelMA hydrogel can influence both endothelial and osteogenic differentiation of MSCs and sequent capillary-like formation.

Synthesis, Characterization, and Visible Light Curing Capacity of Polycaprolactone Acrylate.

Polycaprolactone (PCL) is drawing increasing attention in the field of medical 3D printing and tissue engineering because of its biodegradability. This study developed polycaprolactone prepolymers that can be cured using visible light. Three PCL acrylates were synthesized: polycaprolactone-530 diacrylate (PCL530DA), glycerol-3 caprolactone triacrylate (Glycerol-3CL-TA), and glycerol-6 caprolactone triacrylate (Glycerol-6CL-TA). PCL530DA has two acrylates, whereas Glycerol-3CL-TA and Glycerol-6CL-TA have three acrylates. The Fourier transform infrared and nuclear magnetic resonance spectra suggested successful synthesis of all PCL acrylates. All are liquid at room temperature and can be photopolymerized into a transparent solid after exposure to 470 nm blue LED light using 1% camphorquinone as photoinitiator and 2% dimethylaminoethyl methacrylate as coinitiator. The degree of conversion for all PCL acrylates can reach more than 80% after 1 min of curing. The compressive modulus of PCL530DA, Glycerol-3CL-TA, and Glycerol-6CL-TA is 65.7 ± 12.7, 80.9 ± 6.1, and 32.1 ± 4.1 MPa, respectively, and their compressive strength is 5.3 ± 0.29, 8.3 ± 0.18, and 3.0 ± 0.53 MPa, respectively. Thus, all PCL acrylates synthesized in this study can be photopolymerized and because of their solid structure and low viscosity, they are applicable to soft tissue engineering and medical 3D printing.

Synthesis and Characterization of Polycaprolactone-Based Polyurethanes for the Fabrication of Elastic Guided Bone Regeneration Membrane.

The aim of this research is to synthesize polycaprolactone-based polyurethanes (PCL-based PUs) that can be further used for the fabrication of guided bone regeneration (GBR) membranes with higher tensile strength and elongation at break than collagen and PTFE membranes. The PCL-based PUs were prepared by the polymerization of polycaprolactone (PCL) diol with 1,6-hexamethylene diisocyanate (HDI) at different ratios using either polyethylene glycol (PEG) or ethylenediamine (EDA) as chain extenders. The chemical, mechanical, and thermal properties of the synthesized polymers were determined using NMR, FTIR, GPC, DSC, and tensile tester. The PCL and polyurethanes were fabricated as nanofiber membranes by electrospinning, and their mechanical properties and SEM morphology were also investigated. In vitro tests, including WST-1 assay, SEM of cells, and phalloidin cytoskeleton staining, were also performed. It was shown that electrospun membranes made of PCL and PCL-HDI-PEG (2 : 3 : 1) possessed tensile strength of 19.84 MPa and 11.72 MPa and elongation at break of 627% and 362%, respectively. These numbers are equivalent or higher than most of the commercially available collagen and PTFE membrane. As a result, these membranes may have potential for future GBR applications.

Parathyroid hormone gene-activated matrix with DFDBA/collagen composite matrix enhances bone regeneration in rat calvarial bone defects.

BACKGROUND: Gene-activated matrix (GAM) induces sustained local production of growth factors to promote tissue regeneration. GAM contains a plasmid DNA (pDNA) encoding target proteins that is physically entrapped within a biodegradable matrix carrier. GAM with a pDNA encoding the first 34 amino acids of parathyroid hormone (PTH 1-34) and a collagen matrix enhances bone regeneration in long bone defects. Demineralized freeze-dried bone allograft (DFDBA) is a widely used osteoinductive bone graft. The present study determined the osteogenic effects of PTH-GAM with a collagen or DFDBA/collagen composite (D/C) matrix for treating craniofacial bone defects. METHODS: We constructed a pDNA encoding human PTH 1-34 and performed cyclic AMP ELISA to verify the bioactivity of PTH 1-34. Next, we generated a D/C matrix and PTH-GAMs containing a collagen matrix (PTH-C-GAM) or D/C matrix (PTH-D/C-GAM). Rats with critical-sized calvarial bone defects were divided into four groups, namely, untreated rats (sham group) and rats grafted with D/C matrix, PTH-C-GAM, or PTH-D/C-GAM (D/C, PTH-C-GAM, or PTH-D/C-GAM groups, respectively). PTH expression was determined by performing immunohistochemical staining after 4 and 8 weeks. New bone formation was evaluated by performing radiography, dual-energy X-ray absorptiometry, microcomputed tomography, and histological examination. RESULTS: PTH pDNA-transfected cells secreted bioactive PTH 1-34. Moreover, PTH was expressed at 4 and 8 weeks after the surgery in rats in the PTH-C-GAM group but not in rats in the D/C group. New bone formation in the calvarial bone defects, from more to less, was in the order of PTH-D/C-GAM, PTH-C-GAM, D/C, and sham groups. CONCLUSION: Our results indicate that PTH-GAM with a collagen matrix promotes local PTH production for at least 8 weeks and bone regeneration in craniofacial bone defect. Moreover, our results indicate that replacement of the collagen matrix with the D/C matrix improves the osteogenic effects of PTH-GAM.