Direct pulp capping is the placement of a dental material directly over exposed pulp to prevent dental pulp from dying and avoid the need for root canal treatments. Calcium hydroxide and calcium silicates/mineral trioxide aggregates (MTA) have been commonly used for direct pulp capping with great success clinically. In recent years, resin-modified calcium hydroxide and calcium silicates have been developed with the advantages of precise placement, command set, and superior physical strength. As pulp capping materials would be in direct contact with the pulp, the cytotoxicity and biocompatibility is of particular importance in order to avoid pulp irritation and maintain pulp vitality. Therefore, this review article will summarize the cytotoxicity and biocompatibility of direct pulp capping materials, particularly resin-modified materials.
Calcium silicate-based cements have superior sealing ability, bioactivity, and marginal adaptation, which make them suitable for different dental treatment applications. However, they exhibit some drawbacks such as long setting time and poor handling characteristics. To overcome these limitations calcium silicates are engineered with various constituents to improve specific characteristics of the base material, and are the focus of this review. An electronic search of the PubMed, MEDLINE, and EMBASE via OVID databases using appropriate terms and keywords related to the use, application, and properties of calcium silicate-based cements was conducted. Two independent reviewers obtained and analyzed the full texts of the selected articles. Although the effects of various constituents and additives to the base Portland cement-like materials have been investigated, there is no one particular ingredient that stands out as being most important. Applying nanotechnology and new synthesis methods for powders most positively affected the cement properties.
This study aimed to evaluate the effect of surface preparation on bond strength of a tri-n-butylborane initiated resin (MMA-TBB) bonded to zirconia. Zirconia disks were either airborne-particle abraded with alumina or silica-coated. The disks were thereafter primed with one of the following materials: phosphate-silane (Clearfil Ceramic Primer), phosphate (Alloy Primer), or silane (ESPE Sil). The specimens were bonded with the MMA-TBB. Shear bond strength was determined both before and after thermocycling. Bond strength of unprimed zirconia (control) was not affected by the surface roughness of each adherend. Priming with phosphate was effective for bonding alumina-blasted zirconia. Priming with silane was effective for bonding silica-coated zirconia. Priming effect of the phosphate-silane was superior to that of silane alone for bonding silica-coated zirconia. Bond strength to zirconia of the MMATBB is significantly influenced by a combination of the specific functional monomer and the surface modification performed rather than the material surface roughness.
The aims of this study were to evaluate the feasibility of 70% reduced inlay and 4-unit bridge models of International Standard (ISO 12836) assessing the accuracy of laboratory scanners to measure the accuracy of intraoral scanner. Four intraoral scanners (CS3500, Trios, Omnicam, and Bluecam) and one laboratory scanner (Ceramill MAP400) were used in this study. The height, depth, length, and angle of the models were measured from thirty scanned stereolithography (STL) images. There were no statistically significant mean deviations in distance accuracy and precision values of scanned images, except the angulation values of the inlay and 4-unit bridge models. The relative errors of inlay model and 4-unit bridge models quantifying the accuracy and precision of obtained mean deviations were less than 0.023 and 0.021, respectively. Thus, inlay and 4-unit bridge models suggested by this study is expected to be feasible tools for testing intraoral scanners.
The blending effect (BE) plays an important role in esthetics of the composite resin. The objective of this study was to determine the extents to which filler size and content affect the BE. Three types of fillers (0.7, 1.0, and 1.5 µm) were mixed at weight contents of 60, 70, 75, and 80%. This study simulated clinical class 3 or 4 cavities and quantitatively measured the color diffusion of the objects next to the cavities based on the CIELab color space. For each filler size, there was a trend of increasing BE as the filler content was increased. The translucency parameter (TP) exhibited the opposite trend of decreasing (p<0.05) with increases in filler content. The filler size did not affect the BE, and the different filler sizes produced statistically non-significant results in this study. Increases in filler content elevated the opacity of the composite resin and significantly influenced the BE.
The aim of this study was to compare the biocompatibility of Endocem Zr® and ProRoot MTA® by histopathologic analysis in a canine model of pulpotomy. This study utilized 39 teeth of two beagle dogs. The exposed pulp tissues were treated by pulpotomy using ProRoot MTA (n=19) or Endocem Zr (n=20). After 8 weeks, the teeth were extracted and processed with hematoxylin-eosin staining for histologic evaluation. Most of the specimens in both groups developed a calcific barrier at the pulp amputation site and formed an odontoblast layer. However, some of the Endocem Zr specimens showed less calcific barrier formation with a greater inflammatory response and less odontoblast layer formation when compared with the ProRoot MTA specimens. ProRoot MTA and Endocem Zr specimens developed a calcific barrier; however, ProRoot MTA was more biocompatible than Endocem Zr.
This study aimed to evaluate the susceptibility of cut and uncut enamel surfaces to an erosive challenge and to examine the resultant characteristics/morphological changes. Ten extracted human incisors were used for preparation of enamel samples, and samples were immersed in citric acid. After 3 (total 3 min) and 6 cycles (total 6 min) of erosive challenges, surface loss (SL) and morphological changes were measured using scanning microscopy and FIB-TEM. Ca release (CA) and surface hardness (SH) were measured using a calcium-sensitive electrode and hardness tester respectively. Mean values of all measurements were statistically analyzed by using a t-test. Uncut enamel samples had significantly lower SL and greater SH than cut enamel (p<0.01). Cut enamel samples after 3 cycles showed higher CA compared with those from uncut enamel samples (p<0.05). Cut enamel was shown to be more susceptible to acidic dissolution and deeper acid penetration than uncut enamel after erosive demineralization.
This study aimed to assess the effect of bioglass and silica coating of zirconia substrate on its bond strength to resin cement. A total of 120 specimens were used in this in-vitro, experimental study. Zirconia discs measuring 10×7×2 mm were cut from Y-TZP zirconia blocks, sintered, cleaned and received different surface treatments of sandblasting, bioglass powder coating+etching, bioglass powder coating+etching+silanization, bioglass slurry coating+etching, bioglass slurry coating+etching+silanization, silica coating+silanization, silica coating+etching+silanization and no treatment group (control). Then the microshear bond strength testing and scanning electron microscope (SEM) analysis were done. Data were analyzed using the Mann Whitney U and the Kruskal Wallis tests. Significant differences existed in bond strength of different groups (p<0.001). The sandblasted and bioglass coated groups showed higher and the colloidal silica-coated groups showed lower bond strength compared to the control group.
This study used an ultrasonic measurement device to monitor the setting behavior of silicone elastomeric impression materials, and the influence of temperature on setting behavior was determined. The ultrasonic device consisted of a pulser-receiver, transducers, and an oscilloscope. The two-way transit time through the mixing material was divided by two to account for the down-and-back travel path; then it was multiplied by the sonic velocity. Analysis of variance and the Tukey honest significant difference test were used. In the early stages of the setting process, most of the ultrasonic energy was absorbed by the elastomers and the second echoes were relatively weak. As the elastomers hardened, the sonic velocities increased until they plateaued. The changes in sonic velocities varied among the elastomers tested, and were affected by temperature conditions. The ultrasonic method used in this study has considerable potential for determining the setting processes of elastomeric impression materials.
The purpose of the present study was to evaluate the efficacy of pretreatment on the bonding durability between titanium casting and two acrylic adhesives. Cast titanium disk specimens treated with four polymer-metal bonding systems as follow: 1) air-abraded with 50–70 μm alumina, 2) 1)+Alloy Primer, 3) 1)+M.L. Primer and 4) tribochemical silica/silane coating system (Rocatec System). The specimens were bonded with M bond or Super-bond C&B adhesive. The shear bond strengths were determined before and after thermocycling (20,000 cycles). The surface characteristics after polishing, and for the 1) and 4) preparations were determined. The bond strengths for all combinations significantly decreased after thermocycling. The combination of Super-bond C&B adhesive and 2) led to significantly higher bond strength than the other preparations after thermocycling. The maximum height of the profile parameters for the polishing group was lower than other preparations.
Phosphatidylserine (PS) is known to enhance biomineralization due to the ability to accumulate calcium ions. In this study, the effects of PS on odontogenic differentiation and mineralization of human dental pulp cells (HDPCs) were investigated using phosphatidylserine-containing liposomes (PSLs). PSL was slightly cytotoxic at 125 µM in growth medium, and ALP activity was up-regulated in the PSL-treated HDPCs at non-cytotoxic concentrations. Mineralization was also enhanced by PSL, while mRNA expressions of DSPP and OCN genes were slightly attenuated. The mRNA expression of Runx2 was not altered by PSL. It is thus likely that PSL selectively affected odontogenic differentiation processes of HDPC. Finally, the interaction between PSL and HDPC was investigated by staining with annexin V-FITC in PSL-treated HDPC. It was found that PS was gradually incorporated into HDPC cytoplasm for several days. The results of this study suggest that PSL is able to stimulate dentin formation in dental pulps.
Previous reports have demonstrated that ions released from dental alloys might cause cytotoxicity. However, how dental alloys influence the organism has not been extensively studied. In order to make it clear, the cytotoxic effect of four dental alloys on L929 cells was evaluated by flow cytometry (FCM) and Real-time quantitative PCR assay (Real-time qPCR) to identify the cell death mode and its biological mechanism. The cells were treated with the leach liquors of cobalt-chromium (Co-Cr), commercially pure titanium (CP-Ti), palladium-based (Pd-based) and gold-platinum (Au-Pt) alloys for 48 and 72 h. FCM results indicated, apart from Au-Pt alloy, the major cell death of dental alloys was time-dependent early apoptosis rather than necrosis/late apoptosis. Caspase 3 and Caspase 9 mRNA expression were determined by Real-time qPCR, and shared the same trend in each group over time. Hence, except for Au-Pt alloy, dental alloys might cause time-dependent early apoptosis via the intrinsic pathway.
Composite resin blocks for computer-aided design/computer-aided manufacturing (CAD/CAM) applications have recently become available. However, CAD/CAM composite resins have lower wear resistance and accumulate more plaque than CAD/CAM ceramic materials. We assessed the effects of SiO2-nanocomposite film coating of four types of CAD/CAM composite resin blocks: Cerasmart, Katana Avencia block, Lava Ultimate, and Block HC on surface hardness and bacterial attachment. All composite blocks with coating demonstrated significantly greater Vickers hardness, reduced surface roughness, and greater hydrophobicity than those without coating. Adhesion of Streptococcus mutans to the coated specimens was significantly less than those for the uncoated specimens. These reduced levels of bacterial adherence on the coated surface were still evident after treatment with saliva. Surface modification by SiO2-nanocomposite film coating has potential to improve wear resistance and susceptibility to plaque accumulation of CAD/CAM composite resin restorations.
This study aimed to investigate shear stress distributions in resin built-up teeth using resin composites of varying elastic moduli (E), with or without fiber posts. Three-dimensional mathematical models of a root-filled mandibular premolar tooth were constructed. Resin post and cores were built-up with resin composites of three different E: 12,000, 18,000 and 24,000 MPa, with or without fiber posts. Finite element linear analysis was performed to calculate shear stress distributions at bonding interface between resin core and dentin. Regardless of fiber post insertion, the shear stress on the cervical surface of resin core decreased as the E of resin composites increased. Insertion of fiber posts increased the shear stress on the post surface of resin core, with increases in the E of resin composites. In conclusion, using resin core materials with higher E decreased the shear stress at cervical interface between resin core and dentin regardless of fiber post insertion.
In the present report, we have generated osteoblast-like cells derived from mouse induced-pluripotent stem (iPS) cells on PLGA with osteoinduction medium in vitro and in vivo. The cell culture period was 2 weeks. At 2 weeks, mRNA level of type I collagen was significantly higher than at 1 week. Osteocalcin mRNA level at 2 weeks was tendency to increase compared with at 1 week. And the cells cultured on PLGA were positive for immunofluorescent staining of osteocalcin and alizarin red S staining. The scaffold and osteogenic-like cells induced in vitro were implanted subcutaneously into SCID mice. In resected teratoma, hard tissues resembling bone were observed mixed with other tissues on the scaffold. The sum of these findings suggests that PLGA does not disturb the osteogenesis of iPS cells.
Experimental silane primers and a urethane dimethacrylate resin were prepared to resin titanium bonding. Commercially pure 2 Ti coupons were pretreated and randomly assigned into groups: group-SM (ESPE Sil™+Multilink® Speed), group-SE (ESPE Sil™+experimental resin), group-AM (1.0 vol% 3-acryloxypropyltrimethoxysilane+Multilink® Speed), group-AE (1.0 vol% 3-acryloxypropyltrimethoxysilane+experimental resin), group-BM (1.0 vol% 3-acryloxypropyltrimethoxysilane+0.5 vol% bis-(1,2-triethoxysilyl)ethane+Multilink® Speed), and group-BE (1.0 vol% 3-acryloxypropyltrimethoxysilane+0.5 vol% bis-(1,2-triethoxysilyl) ethane+experimental resin). Specimens were stored in a desiccator for 24 h, and artificially aged by thermo-cycling (6,000 and 12,000 cycles). According to ANOVA and the Tukey’s test (n=10, α=0.05), the mean enclosed mold shear bond strength after 24 h was highest in group-AE (26.2±4.0 MPa). After 12,000 thermo-cycles, the group-BM exhibited the highest adhesion strength (13.4±3.2 MPa). This study suggests that a silane primer (3-acryloxypropyltrimethoxysilane+0.5 vol% bis-(1,2-triethoxysilyl)ethane) might enhance adhesion strength.