In Vitro Study of Zirconia Surface Modification for Dental Implants by Atomic Layer Deposition.

Zirconia is a promising material for dental implants; however, an appropriate surface modification procedure has not yet been identified. Atomic layer deposition (ALD) is a nanotechnology that deposits thin films of metal oxides or metals on materials. The aim of this study was to deposit thin films of titanium dioxide (TiO2), aluminum oxide (Al2O3), silicon dioxide (SiO2), and zinc oxide (ZnO) on zirconia disks (ZR-Ti, ZR-Al, ZR-Si, and ZR-Zn, respectively) using ALD and evaluate the cell proliferation abilities of mouse fibroblasts (L929) and mouse osteoblastic cells (MC3T3-E1) on each sample. Zirconia disks (ZR; diameter 10 mm) were fabricated using a computer-aided design/computer-aided manufacturing system. Following the ALD of TiO2, Al2O3, SiO2, or ZnO thin film, the thin-film thickness, elemental distribution, contact angle, adhesion strength, and elemental elution were determined. The L929 and MC3T3-E1 cell proliferation and morphologies on each sample were observed on days 1, 3, and 5 (L929) and days 1, 4, and 7 (MC3T3-E1). The ZR-Ti, ZR-Al, ZR-Si, and ZR-Zn thin-film thicknesses were 41.97, 42.36, 62.50, and 61.11 nm, respectively, and their average adhesion strengths were 163.5, 140.9, 157.3, and 161.6 mN, respectively. The contact angle on ZR-Si was significantly lower than that on all the other specimens. The eluted Zr, Ti, and Al amounts were below the detection limits, whereas the total Si and Zn elution amounts over two weeks were 0.019 and 0.695 ppm, respectively. For both L929 and MC3T3-E1, the cell numbers increased over time on ZR, ZR-Ti, ZR-Al, and ZR-Si. Particularly, cell proliferation in ZR-Ti exceeded that in the other samples. These results suggest that ALD application to zirconia, particularly for TiO2 deposition, could be a new surface modification procedure for zirconia dental implants.

Bone Tissue Engineering in Rat Calvarial Defects Using Induced Bone-like Tissue by rhBMPs from Immature Muscular Tissues In Vitro.

This study aimed to induce bone-like tissue from immature muscular tissue (IMT) in vitro using commercially available recombinant human bone morphogenetic protein (rhBMP)-2, rhBMP-4, and rhBMP-7, and then implanting this tissue into a calvarial defect in rats to assess healing. IMTs were extracted from 20-day-old Sprague-Dawley (SD) fetal rats, placed on expanded polytetrafluoroethylene (ePTFE) with 10 ng/µL each of rhBMP-2, BMP-4, and BMP-7, and cultured for two weeks. The specimens were implanted into calvarial defects in 3-week-old SD rats for up to three weeks. Relatively strong radiopacity was observed on micro-CT two weeks after culture, and bone-like tissue, comprising osteoblastic cells and osteoids, was partially observed by H&E staining. Calcium, phosphorus, and oxygen were detected in the extracellular matrix using an electron probe micro analyzer, and X-ray diffraction patterns and Fourier transform infrared spectroscopy spectra of the specimen were found to have typical apatite crystal peaks and spectra, respectively. Furthermore, partial strong radiopacity and ossification were confirmed one week after implantation, and a dominant novel bone was observed after two weeks in the defect site. Thus, rhBMP-2, BMP-4, and BMP-7 differentiated IMT into bone-like tissue in vitro, and this induced bone-like tissue has ossification potential and promotes the healing of calvarial defects. Our results suggest that IMT is an effective tissue source for bone tissue engineering.

Accuracy of a titanium maxillary complete denture baseplate fabricated by using the electron beam melting technique: An in vitro study.

STATEMENT OF PROBLEM: Electron beam melting (EBM) is a promising additive manufacturing technique for fabricating denture baseplates; however, studies evaluating its accuracy are sparse. PURPOSE: The purpose of this in vitro study was to compare the fit accuracy of titanium maxillary complete denture baseplates fabricated by using the EBM technique with those fabricated by using the conventional casting technique and to evaluate the dimensional accuracy of the EBM baseplate by using a 3-dimensional inspection software program. MATERIAL AND METHODS: Definitive casts of an edentulous maxilla were prepared. After the casts were optically scanned, computer-aided designs for the EBM baseplate were created by using a software program for standard tessellation language file editing. The EBM baseplates were fabricated with an EBM machine by using a Grade II titanium powder as the raw material. The cast baseplates were fabricated with a lost-wax casting technique by using refractory casts duplicated from the definitive casts. After fitting the EBM and cast baseplates to their corresponding definitive cast, they were embedded in a Type IV stone. The embedded baseplates on the casts were sectioned at 3 regions: posterior palatal seal, molar, and premolar. The maximum gaps between the baseplate and definitive cast were measured in these 3 regions. The virtual casts obtained by scanning the EBM baseplate were superimposed on the computer-aided design to evaluate the dimensional accuracy. Distribution color maps were then generated, and the mean absolute deviations and root mean square deviations were calculated. One-way analysis of variance and t tests were used for statistical analysis (α=.05). RESULTS: No significant differences in the maximum gaps among the 3 regions were found in the cast or EBM baseplate groups (P>.05). The EBM baseplate group showed significantly lower values than the cast baseplate group in all regions (premolar: P=.008; molar: P=.003; posterior palatal seal: P=.004). The mean maximum gap for the 3 regions in the cast baseplates was 168.0 µm and that in the EBM baseplates was 60.7 µm. The distribution color map of the EBM baseplate showed a favorable dimensional accuracy. The mean absolute deviation value was 19.7 µm, and the root mean square deviation value was 25.1 µm. CONCLUSIONS: The EBM baseplates had a significantly higher fit accuracy than the cast baseplates. Thus, the fit accuracy of the EBM technique is suitable for fabricating metal baseplates.

Proliferation of mouse fibroblast-like and osteoblast-like cells on pure titanium films manufactured by electron beam melting.

The physical characteristics and biological compatibility of surfaces produced by electron beam melting (EBM) are not well known. In particular, there are not many reports on biocompatibility qualities. In this study, pure Ti films were manufactured using EBM. While it is reported that moderately hydrophilic biomaterial surfaces display improved cell growth and biocompatibility, contact angle measurements on the EBM-produced pure Ti films showed slight hydrophobicity. Nonetheless, we found the cell count of both fibroblast-like cells (L929) and osteoblast-like cells (MC3T3-E1) increased on pure Ti films, especially the MC3T3-E1, which increased more than that of the control. In addition, the morphology of L929 and MC3T3-E1 was polygonal and spindle-shaped and the cytoskeleton was well developed in the pure Ti surface groups. Upon staining with Alizarin red S, a slight calcium deposition was observed and this level gradually rose to a remarkable level. These results indicate that pure Ti films manufactured by EBM have good biocompatibility and could be widely applied as biomedical materials in the near future.

Enhanced bioactivity of polyvinylidene chloride films using argon ion bombardment for guided bone regeneration.

Polyvinylidene chloride (PVDC) is a long chain carbon synthetic polymer. The objective of this study was to improve the bioactivity of PVDC films through surface modification using argon (Ar) ion bombardment to create Ar-modified PVDC films (Ar-PVDC) to address the clinical problems of guided bone regeneration (GBR), which is technique-sensitive, and low bone regenerative ability. First, the effects of Ar ion bombardment, a low temperature plasma etching technique widely used in industry, on PVDC film wettability, surface chemistry, and morphology were confirmed. Next, fibroblast-like and osteoblast-like cell attachment and proliferation on Ar-PVDC were assessed. As a preclinical in vivo study, Ar-PVDC was used to cover a critical-sized bone defect on rat calvaria and osteoconductivity was evaluated by micro-computed tomography analysis and histological examinations. We found that the contact angle of PVDC film decreased by 50° because of the production of -OH groups on the PVDC film surface, though surface morphological was unchanged at 30 min after Ar ion bombardment. We demonstrated that cell attachment increased by about 40% and proliferation by more than 140% because of increased wettability, and 2.4 times greater bone regeneration was observed at week 3 with Ar-PVDC compared with untreated PVDC films. These results suggest that Ar ion bombardment modification of PVDC surfaces improves osteoconductivity, indicating its potential to increase bone deposition during GBR.

Loss-of-function OGFRL1 variants identified in autosomal recessive cherubism families.

Cherubism (OMIM 118400) is a rare craniofacial disorder in children characterized by destructive jawbone expansion due to the growth of inflammatory fibrous lesions. Our previous studies have shown that gain-of-function mutations in SH3 domain-binding protein 2 (SH3BP2) are responsible for cherubism and that a knock-in mouse model for cherubism recapitulates the features of cherubism, such as increased osteoclast formation and jawbone destruction. To date, SH3BP2 is the only gene identified to be responsible for cherubism. Since not all patients clinically diagnosed with cherubism had mutations in SH3BP2, we hypothesized that there may be novel cherubism genes and that these genes may play a role in jawbone homeostasis. Here, using whole exome sequencing, we identified homozygous loss-of-function variants in the opioid growth factor receptor like 1 (OGFRL1) gene in 2 independent autosomal recessive cherubism families from Syria and India. The newly identified pathogenic homozygous variants were not reported in any variant databases, suggesting that OGFRL1 is a novel gene responsible for cherubism. Single cell analysis of mouse jawbone tissue revealed that Ogfrl1 is highly expressed in myeloid lineage cells. We generated OGFRL1 knockout mice and mice carrying the Syrian frameshift mutation to understand the in vivo role of OGFRL1. However, neither mouse model recapitulated human cherubism or the phenotypes exhibited by SH3BP2 cherubism mice under physiological and periodontitis conditions. Unlike bone marrow-derived M-CSF-dependent macrophages (BMMs) carrying the SH3BP2 cherubism mutation, BMMs lacking OGFRL1 or carrying the Syrian mutation showed no difference in TNF-ɑ mRNA induction by LPS or TNF-ɑ compared to WT BMMs. Osteoclast formation induced by RANKL was also comparable. These results suggest that the loss-of-function effects of OGFRL1 in humans differ from those in mice and highlight the fact that mice are not always an ideal model for studying rare craniofacial bone disorders.

Effect of crystal orientation on flexural strength of pressable lithium disilicate glass-ceramics.

This study examined the crystal orientation of four kinds of pressable lithium disilicate glass-ceramics and evaluated the effect of crystal orientation on flexural strength. Bar-shaped (24 mm in length, 1.2 mm in thickness, 4.0 mm in width), disk-shaped (12 mm in diameter, 0.5 mm in thickness), and crown-shaped (maxillary first molar) specimens were prepared according to the manufacturer's instructions. Three-point and biaxial flexural strengths were measured for bar- and disk-shaped specimens. Microstructure analysis was performed using X-ray diffractometry and scanning electron microscopy. Three-point flexural strength was improved by parallel crystal orientation along the longitudinal direction of the bar-shaped specimen. There was no relationship between two-dimensional crystal orientation and biaxial flexural strength. The results of this study assumed that biaxial flexural strength was improved by the crystal orientation in the cross-sectional direction. Pressed restorations are expected to possess higher strength than milled restorations due to their crystal orientation.

Bonding Characteristics of Silane Coupling Agent and MMA-Containing Primer to Various Composite CAD/CAM Blocks.

This study evaluated the bonding characteristics of a silane coupling agent (SCA) and a methyl methacrylate (MMA)-containing primer (MCP) for 11 types of commercial composite blocks (CBs) for sandblasted and non-sandblasted surfaces. The shear bond strength (SBS) was measured according to ISO 29022: Notched-edge shear bond strength test. The SBS results demonstrated statistically significant differences between the CBs under all identical conditions. For the non-sandblasted groups, the SBSs of MCP-treated specimens were significantly higher than those of SCA-treated specimens for all but two CBs. Comparing the two treatments in sandblasted groups, the SBS was significantly higher for seven out of 11 MCP-treated RCB specimens, in contrast with three cases for the SCA-treated group. Two-way ANOVA for SBS showed the interaction effect between sandblasting and primer type for specific CBs, indicating that the sandblasting treatment improved SBS more effectively for SCA-treated specimens. Moreover, the effect of the SCA treatment was more material-dependent compared to that of the MCP treatment, which did not achieve a strong bond in all CBs but proved more effective than the SCA treatment, especially for non-sandblasted surfaces.

Effects of heated tobacco products and conventional cigarettes on dental implant wound healing: experimental research.

Smoking affects wound healing and is associated with dental implant failure. Heated tobacco products (HTPs) appear to be less harmful than conventional cigarettes (CCs); however, there is limited analytical data to support this claim. This study aimed to compare HTPs and CCs for their impact on wound healing using L929 mouse fibroblast cells and evaluate whether HTPs also lead to failure in implant therapy. Materials and methods: Cigarette smoke extract (CSE) was obtained from CCs (Marlboro, Philip Morris) and HTPs (Marlboro Heat Sticks Regular for IQOS, Philip Morris) and initiated a wound-healing assay with a cell-free area created in the centre of a titanium plate by sticking a 2-mm-width line tape. The L929 mouse fibroblast cells were exposed with 2.5 and 5% CSE from HTPs and CCs and then seeded in the titanium plate. A scratch wound-healing assay was initiated when all samples were at 80% confluence. The number of cells migrating to the wound site was counted after 12, 24, and 48 h. Results: Cell migration decreased after CSE exposure from both CCs and HTPs. At each time-point with 2.5% CSE, cell migration in the HTP group was less than that of the CC group. There were significant differences between the 2.5% CC and 2.5% HTP groups and the 5% CC and 5% HTP groups after 24 h. HTPs and CCs had similar effects in the wound-healing assay. Conclusion: Therefore, HTP use may be a risk factor for poor dental implant healing.

In vitro biocompatibility of dextrin: the addition of a low concentration of dextrin in the medium promotes the cell activity of L929 mouse fibroblasts.

To develop a bone substitute with shape-generating properties, we focused our attention on dextrin, which has a low viscosity. After considering methods of evaluation for research and development, we started by using cells that are widely used for safe biological evaluations in the field of dentistry and conducted in vitro evaluations. In this experiment, we variously added concentrations of 0.1, 1.0 and 10 mmol/l of dextrin to a culture medium in order to examine the effects on L929 mouse fibroblasts in vitro. As a result, the proliferative activity of the L929 cells was promoted during the culture period as the concentration of added dextrin became lower, and in particular, the 0.1 and 1 mmol/l addition group showed higher values than those of the control group. From the above results, it was revealed that the addition of a low concentration of dextrin in a medium promotes the cell proliferative activity.

Effect of degradation of filler elements on flexural strength for dental CAD/CAM resin composite materials in water.

Purpose This study aimed to evaluate the effects of degradation on the strength of computer-aided design/computer-aided manufacturing (CAD/CAM) resin composite blocks (RCBs) by subjecting them to accelerated degradation in water and conducting biaxial flexural strength tests.Methods Six commercial RCBs were tested. The RCBs were cut into disks, after which the disks were immersed in purified water. For the aging experiment, the samples were subjected to heat treatment at 37, 60, 70, and 80 °C, in a constant temperature oven and stored statically for 30 d. After the aging experiment, the elements released from the RCB fillers were measured by inductively coupled plasma atomic emission spectroscopy. In addition, the biaxial flexural strength of the RCB fillers was measured after accelerated degradation at 70 °C.Results Si (the main component of the filler) was detected in all the RCB solutions after the aging experiment; however, the type and amount of other elements differed considerably among the RCBs. The flexural strength of some of the RCBs decreased by approximately 20-40% after the accelerated degradation. For most materials, the Weibull coefficient decreased or remained unchanged after the test, whereas it increased in some materials.Conclusions The strength of all the RCBs decreased after the accelerated degradation tests; however, this behavior differed among the materials. In addition, the release of elements from the filler of some of the materials into the water correlated with the decrease in the strength of these materials. These findings indicate that the evaluation of the degradation behavior of RCBs in water is essential for their long-term usage.

Effect of self-cured acrylic resin added with an inorganic antibacterial agent on Streptococcus mutans.

In order to develop an self-cured acrylic resin having an antibacterial property, three types of commercially available inorganic antibacterial agents were added, at 1% each, to UNIFAST III to evaluate the antibacterial property. The antibacterial test evaluated the amount of Streptococcus mutans attached to UNIFAST III, the residual viable count of Streptococcus mutans cultured on UNIFAST III. And the color tone changes evaluated immediate and temporal color tone changes of UNIFAST III caused by the addition of antibacterial agents. As a result, compared to UNIFAST III without any added inorganic antibacterial agent, a significant decrease was observed in the attachment amount and the residual viable count of Streptococcus mutans. In addition, when adding NOVARON from among the added inorganic antibacterial agents, UNIFAST III exhibited little change in the temporal color tone. Thus, these results suggest that the addition of antibacterial agents to resins is effective first step toward developing self-cured acrylic resins having an antibacterial property.

Cell culture in vivo by means of diffusion chamber system.

In a diffusion chamber (DC) system, cells are cultured in vivo - hence making it possible to minimize infection and foreign material contamination. In view of this merit, we devised a technique to combine a DC system and a scaffold to the end of incubating sufficient host cells for grafting. In the present study, PLGA sponge and rat bone marrow cells were encapsulated inside a DC and then placed inside the abdominal cavities of rats. DCs were removed at two or four weeks after grafting. At four weeks after grafting, fibrous and calcified tissue matching the shape of the PLGA sponge was formed. These results suggested that the PLGA sponge was an effective scaffolding material in inducing three-dimensional tissue formation and that combination with a DC system resulted in a cell mass matching the scaffold shape. In addition, the cells were cultured in vivo - which meant that DC culturing did not require special incubation facilities or technologies after grafting.

Leaching behaviors of computer-aided design/computer-aided manufacturing composite resin component elements immersed in water.

PURPOSE: Immersion tests in purified water were conducted to evaluate the leaching behaviors of filler elements contained in computer-aided design/computer-aided manufacturing (CAD/CAM) composite resin. METHODS: Four commercial CAD/CAM resin composite blanks were tested: Shofu block HC 2 layer, Cerasmart, Katana Avencia block, and KZR-CAD HR Block 2. The specimens in the size of 10.0×12.0×2.0mm were immersed in a 50-mL conical tube containing 40mL of purified water, and then placed in a constant-temperature oven set at a temperature of 37, 60, 70, or 80°C and stored statically for 30 days. After storage, the concentrations of leached elements in the immersion solution were measured with an inductively coupled plasma atomic emission spectrometer. To characterize the surface of the specimen after the immersion test, secondary electron images were obtained. RESULTS: The immersion test resulted in the leaching of Si, the main component, from all materials tested. Some materials were found to have leached high amount of Ba or Sr in addition to Si, and remarkable surface degradation was observed. The amount of leached elements increased with increased immersion temperatures. CONCLUSIONS: Filler elements in CAD/CAM composite resins used in this study leached into purified water. The leached elements and its quantities greatly differed among materials and depend on the types of the oxides composing the filler. The amounts of leached elements varied in a temperature-dependent manner.

Second-Generation SYK Inhibitor Entospletinib Ameliorates Fully Established Inflammation and Bone Destruction in the Cherubism Mouse Model.

Cherubism is a craniofacial disorder characterized by maxillary and mandibular bone destruction. Gain-of-function mutations in the SH3-domain binding protein 2 (SH3BP2) are responsible for the excessive bone resorption caused by fibrous inflammatory lesions. A homozygous knock-in (KI) mouse model for cherubism (Sh3bp2KI/KI ) develops autoinflammation resulting in systemic bone destruction. Although administration of the TNF-α blocker etanercept to neonatal Sh3bp2KI/KI mice prevented the disease onset, this therapy was not effective for adult Sh3bp2KI/KI mice or human cherubism patients who already had lesions. Because genetic ablation of spleen tyrosine kinase (SYK) in myeloid cells rescues Sh3bp2KI/KI mice from inflammation, we examined whether SYK inhibitor administration can improve fully developed cherubism symptoms in adult Sh3bp2KI/KI mice. Entospletinib (GS-9973) was intraperitoneally injected into 10-week-old Sh3bp2KI/KI mice every day for 6 weeks. Treatment with GS-9973 improved facial swelling and histomorphometric analysis of lung and liver tissue showed that GS-9973 administration significantly reduced inflammatory infiltrates associated with decreased levels of serum TNF-α. Micro-computed tomography (µCT) analysis showed that GS-9973 treatment reduced bone erosion in mandibles, calvariae, and ankle and elbow joints of Sh3bp2KI/KI mice compared to Sh3bp2KI/KI mice treated with dimethyl sulfoxide (DMSO). Taken together, the results demonstrate that administration of the SYK inhibitor ameliorates an already established cherubism phenotype in mice, suggesting that pharmacological inhibition of SYK may be a treatment option for cherubism patients with active disease progression. © 2018 American Society for Bone and Mineral Research.

Rheological approach for determining yield stresses in flowable resin composites prior to setting.

The purpose of this study is to develop a method for quantifying the fluidity of flowable resin composites using determinations of yield stress. Five commercially available composites (AliteFlo LV, Flow-it ALC, Venus flow, Tetric N-flow, Revolution Formula2) were investigated. Yield stress values were obtained by plotting shear stresses for a range of shear rates, followed by fitting of Casson fluid models to flow curve data and extrapolation to the stress axis. To confirm that yield stress reflected fluidity, apparent viscosity at the lower shear rate (0.2 s-1) was calculated from flow curves. Yield stresses ranged from 5.4 to 43.1 Pa, and were found to capture differences in the fluidity of composites that were not captured by viscosity measurement at the low shear rate. Yield stress is directly proportional to fluidity, and could serve as a simple and precise indicator for selecting flowable resin composites for use in various clinical applications.

* Efficacy of a Self-Assembling Peptide Hydrogel, SPG-178-Gel, for Bone Regeneration and Three-Dimensional Osteogenic Induction of Dental Pulp Stem Cells.

The aim of this study was to assess the efficacy of a self-assembling peptide hydrogel as a scaffold for bone regeneration. We used a neutral and injectable self-assembling peptide hydrogel, SPG-178-Gel. Bone defects (5 mm in diameter) in rat calvarial bones were filled with a mixture of alpha-modified Eagle's medium and peptide hydrogel. Three weeks after surgery, soft X-ray and microcomputed tomography (micro-CT) images of the gel-treated bones showed new bone formations in the periphery and in central areas of the defects. Next, we evaluated the three-dimensional osteogenic induction of dental pulp stem cells (DPSCs), a type of mesenchymal stem cell, in SPG-178-Gel. We first confirmed that the osteogenic differentiation of DPSCs was significantly promoted by osteogenic induction medium containing recombinant human bone morphogenetic protein-4 (rhBMP-4) in a two-dimensional cell culture. Then, we verified DPSC proliferation and osteogenic differentiation in a three-dimensional cell culture using SPG-178-Gel. The gene expression levels of osteopontin, osteocalcin, and collagen type I were significantly increased when DPSCs were cultured in SPG-178-Gel with the osteogenic induction medium. Micro-CT observations showed the formation of widespread calcium deposition. In conclusion, SPG-178-Gel was adequately effective as a scaffold and can be a suitable tool for bone formation in vivo and in vitro. These findings suggest that the self-assembling peptide hydrogel, SPG-178-Gel, could be a promising tool for bone tissue engineering.

Global gene expression analyses of mouse fibroblast L929 cells exposed to IC50 MMA by DNA microarray and confirmation of four detoxification genes' expression by real-time PCR.

Methyl methacrylate (MMA) is the main component of methyl methacrylic resin, which is widely used in dentistry. Previous studies have investigated whether MMA has any adverse effects on growth and gene expression in mouse fibroblast L929 cells. The present study was designed to further understand the effects of MMA by focusing on cDNA microarray data after L929 cells were exposed to MMA. MMA was found to inhibit cell growth and induce detoxification response genes in L929 cells. One of the most highly up-regulated genes was glutathione S-transferase, alpha 1 (Ya) (Gsta1), which has recently been shown to participate in Nrf2 regulation and is considered to be related to detoxification response. Molecular biological data obtained in the present study may therefore provide useful insights into the effects of MMA on living tissue.

Influence of novel resin monomer on viability of L-929 mouse fibroblasts in vitro.

We have previously synthesized a novel acrylic resin monomer, methacryloyloxyethyl methyl succinate (TA). The aim of this in vitro study, therefore, was to examine its influence on cell viability using L-929 mouse fibroblasts and then compare the results with MMA, EMA, and LMA. Medium containing each monomer was changed every 15 minutes as some monomers were volatile. After one hour of exposure, these mediums were replaced with a normal medium and cells were further incubated for 72 hours. IC50 value for each monomer was determined, and chronological cell viability and cytomorphologic observation were evaluated. Viability was impaired in a dose-dependent manner. All monomers, except TA, tended to correlate between molecular weight and cell viability. On the other hand, TA showed excellent viability and did not impair growth abruptly. These results thus demonstrated that cellular damage by TA was much lower than that by other monomers.

Antimicrobial efficacy of gutta-percha supplemented with cetylpyridinium chloride.

To develop a root canal filling material with high antimicrobial activity, we prepared gutta-percha supplemented with the cationic surfactant cetylpyridinium chloride (CPC). Thermoplastic gutta-percha was supplemented with 0.05%, 0.2%, or 0.8% CPC. The gutta-percha containing CPC was tightly packed at the bottom of a 24-well plate. Its antimicrobial activity against eight representative endodontic pathogens-including gram-positive and gram-negative bacteria and fungi-was evaluated by adding 0.5 mL of liquid samples containing pathogens to the wells. After 24 h of cultivation under appropriate conditions, microbial growth was analyzed by counting colony-forming units (CFU). Gutta-percha alone (without CPC) partially inhibited microbial growth, probably through the antimicrobial effect of some of its components, such as zinc oxide. Addition of CPC dose-dependently increased the antimicrobial efficacy of gutta-percha. Addition of 0.05%, 0.2%, and 0.8% CPC reduced the viable microbial number to below the lower limit of detection (20 CFU/mL) for all tested pathogens except Pseudomonas aeruginosa, which was detected in 0.8% CPC-containing gutta-percha, although the viable number significantly decreased. Gutta-percha with CPC might be useful for preventing microbial infections during root canal therapy. (J Oral Sci 58, 277-282, 2016).