Influence of dentin and core porcelain thickness on the color of fully sintered zirconia ceramic restorations.

STATEMENT OF PROBLEM: The influence of the thickness of dentin and core porcelain, and the glazing procedure on the color of computer-aided design and computer-aided manufacturing ceramic restorations has not been investigated. PURPOSE: This study evaluated the influence of the thickness of dentin and core porcelain and glazing on the color of fully sintered zirconia ceramic restorations. MATERIAL AND METHODS: Fully sintered zirconia core material was cut into 90 specimens of 0.3 mm (n=30, group ZC1), 0.4 mm (n=30, group ZC2), and 0.5-mm thickness (n=30, group ZC3). On a dentin disk obtained from an extracted molar, the L*, a*, b* values of the specimens were measured at different steps in the laboratory procedures (Zirconia core, Effect Bonder, Effect Liner, dentin porcelain, glazing) with a spectrophotometer. One millimeter dentin porcelain was applied on half of the specimens of each group and 1.5-mm dentin porcelain on the rest. To assess the ability of porcelain substructures to mask the underlying dark colored tooth structure, color difference (ΔE) values between the steps were calculated. Results were statistically analyzed with ANOVA. RESULTS: Glazing caused a decrease in the L* values and an increase in the a* and b* values (P<.05). Increasing the thickness of dentin porcelain decreased the L*, a*, and b* values (P<.05). Increasing the zirconia core thickness resulted in an increase in the L* values and a decrease in the a* and b* values (P<.05). Increasing the dentin porcelain thickness from 1 mm to 1.5 mm resulted in a color change below the perceptibility threshold (ΔE<2.6). In the ZC1 group, glazing resulted in a color change perceptible to 50% of observers, whereas, in the ZC2 and ZC3 groups with 1-mm dentin porcelain, the ΔE value was higher than 5.5. However, the color change was perceptible to 50% of the observers in all of the groups with 1.5-mm dentin porcelain. CONCLUSIONS: Although the thicknesses of the dentin and core porcelain did not influence the final shade of the restoration, glazing resulted in a perceptible color difference.

Evaluating the ability of dental technician students and graduate dentists to match tooth color.

STATEMENT OF PROBLEM: The ability of dental technician students to match tooth shade with the Vita 3D-Master shade guide and Toothguide Training Box has not been investigated. PURPOSE: The purpose of this study was to evaluate and compare the shade-matching ability of dental technician students and graduate dentists using the Vita 3D-Master shade guide. MATERIAL AND METHODS: Twenty-nine dental technician students (DTS group) and 30 graduate dentists (GD group) participated in this study. The Toothguide Training Box (TTB) was used to train the participants and test their shade-matching abilities. Shade-matching ability was evaluated with 3 exercises and a final test, all of which are components of the TTB. The number of mistakes for each participant for value (L), chroma (c), and hue (h) were recorded during the exercises and the final test, and the mistake ratios were calculated. Color difference (ΔE) values for each shade were calculated from the L*, a*, and b* values of the Vita 3D-Master shade guide for each participant in both groups. The Mann-Whitney U test was used to determine statistically significant differences between the L, c, and h mistake ratios of the 2 groups, and the Student t test was used to determine statistically significant differences between the final test scores and the ΔE values of the groups (α=.05). RESULTS: The mistake ratio for L in the GD group was significantly higher than that of the DTS group (P<.05), whereas the mistake ratio for h in the DTS group was higher (P<.001). No significant differences were observed between the groups regarding the mistake ratios for c (P>.05). With regard to the final test scores and the ΔE values, no significant differences were found between the groups (P<.001), and the DTS group received higher scores than the GD group (912 and 851). The mean ΔE values for the DTS and GD groups were 1.72 and 2.92. CONCLUSIONS: DTSs made more mistakes in the h parameter than GDs, and GDs made more mistakes in the L parameter than DTSs. With regard to the final test scores and the ΔE values, DTSs were more successful in shade matching than GDs.

Effect of an Effervescent Multivitamin on Color and Surface Roughness of Micro-Hybrid Dental Resin Composites.

The use of multivitamins has become widespread globally, yet there is a scarcity of studies investigating their impact on resin composite restorations. This study aimed to evaluate the effect of an effervescent multivitamin tablet on micro-hybrid dental resin composites' surface roughness and color. Fifty disc-shaped samples (8 × 2 mm, shade A2; n = 10) were prepared and polished using five different micro-hybrid resin composites (Pergamon, Dentac, Turkey; Estelite Posterior, Tokuyama, Japan; Geanial Anterior, GC, Japan; Charisma Opal, Kulzer, Germany; Beautifil II, Shofu, USA). Samples were immersed in 200 mL water to one effervescent multivitamin tablet (Redoxon Triple Action, Bayer) at 24 °C for 2 min a day in 24 h intervals for 30 days. All samples' surface roughness (Ra) and ΔE(L*a*b) measurements were recorded at the beginning and end of the 30 days. The Wald chi-square and a two-way ANOVA were used for statistical analysis (significance level p < 0.05). The resin composite type and exposure to the multivitamin had a statistically significant effect on Ra values (p < 0.05). The resin composite type had a statistically significant effect on ΔE values, likely due to the higher mean value of BII (p = 0.040). The surface roughness and color of resin composites can be affected by multivitamins with a pH value of 3.0. Therefore, it is important to consider the patient's routine vitamin intake during resin composite selection. Additional research is required to explore the properties of different dental restorative materials.

In-vitro evaluation of wear characteristics, microhardness and color stability of dental restorative CAD/CAM materials.

The aim of this study was to demonstrate the vertical and volumetric wear characteristics of CAD/CAM materials. The microhardness and color stability were evaluated. A polymer infiltrated ceramic network CAD/CAM block, resin nanoceramic CAD/CAM blocks, a resin composite, and enamel tissue were investigated. Samples were loaded in a chewing simulator. Other samples were aged and immersed in coffee. Color change was evaluated using the digital image analysis and a spectrophotometer. The data were analyzed using Kolmogorov-Smirnov, Kruskal Wallis, Mann Whitney U, Friedman, Spearman's rho tests (p<0.05). The lowest level of wear was obtained in enamel tissue group 0.20 (Q1:0.14; Q3:0.27µm). Resin composite group 2.48 (Q1:2.12; Q3:2.92) showed lower level of discoloration. No agreement was obtained between the digital image analysis and spectrophotometer data (Spearman's rho -0.314, p=0.014). Similar wear rate to the natural enamel tissue was obtained for Vita Enamic. Digital image analysis was considered a promising technique for monitoring the color change.

Radiological assessment of alveolar bone loss associated with overhanging restorations: A retrospective cone beam computed tomography study.

Background/purpose: Studies suggested that presence and size of overhanging restoration margins play role in alveolar bone loss. The aim of this study was to determine the prevalence and distribution of overhanging approximal restorations, to evaluate the effect of presence and size of overhang on bone loss using cone beam computed tomography (CBCT) reformatted panoramic images, and to encourage the use of CBCT in retrospective studies on restorative dentistry. Materials and methods: CBCT images of 382 patients with approximal restorations were included in the study. On CBCT images, alveolar bone loss adjacent to each restored surface was determined and compared to the control tooth. The overhang size was measured and categorized as small, medium, or large. Data obtained were evaluated statistically using Kruskal Wallis, Mann Whitney U, chi-square, and one-sample chi-square tests with a significance level set at P < 0.05. Results: A total of 216 (32.4%) surfaces with overhanging restorations were detected in CBCT images. The number of overhanging surfaces with alveolar bone loss (71.3%) was higher than the control surfaces with bone loss (49.1%) (P < 0.05). The amount of bone loss adjacent to overhanging surfaces (2.28 ± 1.69 mm) was significantly higher compared to control surfaces (1.53 ± 1.73 mm) (P < 0.05). However, the same trend applied to the surfaces without overhang and their controls. The amount of bone loss was not correlated with the overhang size (P > 0.05). Conclusion: Approximal restorations with and without overhanging margins may often result in alveolar bone loss, the amount of which is not always correlated with the overhang size.

Evaluation of shade matching in the repair of indirect restorative materials with universal shade composites.

Purpose: To evaluate color differences in repair of indirect ceramic and resin nanoceramic CAD/CAM blocks with two universal shade composites after different surface preparations. Materials and methods: 120 samples were prepared from IPS Empress and GC Cerasmart270 CAD/ CAM blocks and thermocycled (5000 cycles, 5°C-55°C). Initial colors of sample surfaces were measured using a spectrophotometer. Rectangular prism-shaped cavities were prepared and repaired with Tokuyama Universal Bond/Omnichroma and G-Multiprimer/G-Premio/Essentia Universal following surface preparation with aluminum oxide, Cojet, and bioactive glass (Sylc). Repaired samples were thermocycled (5000 cycles) and color measurement was performed. Color coordinates L*a*b* were recorded, and color differences were calculated using the CIELab formula. Color differences between pre-and post-repair (ΔE1) and between post-repair and post-aging (ΔE2) were determined. Data were analyzed using Three-way ANOVA with a significance level set at p<0.05. Results: ΔE1 values in all subgroups exceeded the threshold of 3.3. No significant difference was found between the surface preparation processes regarding ΔE1 values. There was no significant difference between the composites and bonding agents in ΔE1 values, except for Cerasmart/Sylc and Empress/Sylc groups. No statistically significant difference was detected in ΔE2 values between the surface preparation treatments in all groups. (p >0.05). Conclusion: Color match of the universal shade composites, which are preferred to increase the esthetic satisfaction and to simplify repair procedures, were found above the acceptable threshold. Post-aging color stability of universal shade composites was below the acceptable threshold.

Microleakage and Marginal Integrity of Ormocer/Methacrylate-Based Bulk-Fill Resin Restorations in MOD Cavities: SEM and Stereomicroscopic Evaluation.

This in vitro study aimed to compare the microleakage and marginal integrity of methacrylate/ormocer-based bulk-fill composite (BFC) restorations used in cervical marginal relocation with two different layering thicknesses in mesio-occlusal-distal (MOD) cavities exposed to thermo-mechanical loading. Standard MOD cavities were prepared in 60 mandibular molars and assigned into three groups: x-tra fil/AF + x-tra base/XB, Tetric N-Ceram Bulk Fill/TNB + Tetric N-Flow Bulk Fill/TFB, and Admira Fusion x-tra/AFX + Admira Fusion x-base/AFB. Each group was further divided into two subgroups (2 mm and 4 mm) based on the thickness of flowable BFCs (n = 10). The specimens were subjected to thermo-mechanical loading (240,000 cycles) and immersed in 0.2% methylene blue. Following mesiodistal sectioning, the specimens were examined under stereomicroscope (×25) and scored (0-3) for microleakage. Marginal integrity was examined using a scanning electron microscope (SEM). Descriptive statistical methods and the chi-square test were used to evaluate the data (p < 0.05). While there was no statistically significant difference in gingival cement microleakage in the XB and AFB specimens with a 4 mm thickness, microleakage was significantly increased in the TFB specimen (p = 0.604, 0.481, 0.018 respectively). A significantly higher amount of score 0 coronal microleakage was detected in the AFX2 mm + AFB4 mm compared to the TNB2 mm + TFB4 mm (p = 0.039). The SEM examination demonstrated better marginal integrity in groups with 2 mm thick flowable BFCs. Ormocer and methacrylate-based materials can be used in marginal relocation with thin layers.

Assessment of Micro-Hardness, Degree of Conversion, and Flexural Strength for Single-Shade Universal Resin Composites.

Single-shade universal resin composites (SsURC) are preferred in clinical practice to reduce time for shade selection and obtain good esthetic results. In this study, the static mechanical properties of seven new SsURCs were investigated, their spectral analyzes were performed and scanning electron microscopy (SEM) evaluations were presented. Charisma Diamond One/DO, Admira Fusion x-tra/AFX, Omnichroma/OC, OptiShade/OS, Essentia Universal/EU, Zenchroma/ZC, Vittra APS Unique/VU were used in a three-point bending test to determine flexural strength (FS) and elastic modulus (EM); Vickers micro-hardness (VHN) and hardness-ratio (HR) were performed with a micro-hardness tester from top/bottom after 24-h/15-days of storage in distilled water at 37 °C (±1 °C). The degree of conversion (DC) was assessed by using Fourier transform infrared spectroscopy (FTIR). The structure of the resin matrix and filler content were assessed by SEM. Data were analyzed using IBM SPSS V23 and the R program and the significance level was taken as p < 0.05. The main effect of the tested SsURCs was found to be statistically significant on FS, EM, VHN, and DC values (p < 0.001). Bis-GMA free SsURCs (AFX, DO, VU) showed better DC and HR except for OC. All seven tested SsURCs conform to the requirements of ISO standards for dental resin composites for all tested categories.

Cross-contamination and infection control in intraoral digital imaging: a comprehensive review.

Dental health care workers are subjected to various infectious disease agents that are present in patients' saliva and blood which make infection control and universal prevention methods indispensable to the dental practice given that some of these diseases cause loss of work and time for dental staff and patients; some of them cause serious morbidity; and some of them currently have a poor prognosis and no effective treatments. Although dental radiographic procedures are not invasive, and there are no incidents such as injuries caused by dental instruments, they are a potential infection source because of contamination with saliva and blood, and comprehensive infection control procedures also apply to the radiology clinic. In addition, contact with a large number of patients in dental schools and clinics in a short period of time, and the fact that radiographic procedures are performed in the same environment as other dental procedures in dental offices increase the significance of infection control in dental radiology. Major advances in computer technology have enabled digital imaging systems to develop rapidly and to become common in dental practice as an alternative to conventional film-based imaging. The use of digital sensors in dental radiology introduced unique infection control challenges and required the revision and modification of existing infection control techniques. In this review, studies concerning the risk of cross-contamination and challenges of infection control with digital image sensors are comprehensively reviewed and infection control protocols that should be followed in intraoral digital imaging using both direct and indirect systems are thoroughly examined.

Effect of Modeling Resins on Microhardness of Resin Composites.

OBJECTIVES: This study was aimed to determine the effects of modeling resins on the surface microhardness of composites. MATERIALS AND METHODS: Six resin-based composites (Charisma Smart, Estellite Asteria, CeramX-One SphereTEC, Admira Fusion, Filtek Ultimate, and Clearfil Majesty Es-2) and three wetting agents (Modeling Liquid, Composite Primer, and Modeling Resin) were investigated. In all, 240 specimens were prepared, and wetting agents were applied prior to light curing in the experimental groups. After 24 hours, specimens were polished and Vickers microhardness (VHN) values were measured. STATISTICAL ANALYSIS: Shapiro-Wilk and two-way analysis of variance (ANOVA) were used for analyses (p < 0.05). RESULTS: Both modeling resin and composites were determined to be effective factors (p < 0.001). The control group showed the highest VHN (70.37 ± 7.94), followed by Modeling Liquid (64.68 ± 12.07), Composite Primer (59.84 ± 6.33), and Modeling Resin (58 ± 3.52b; p < 0.001). Filtek Ultimate showed the highest VHN (76.62 ± 9.78c), whereas Charisma Smart (58.87 ± 7.95), and Clearfil Majesty (67.27 ± 2.58) showed the lowest (p < 0.001). Clearfil Majesty-Modeling Liquid (46.62 ± 5.33) and Charisma Smart-Composite Primer (50.81 ± 0.39) combinations showed the lowest VHN, whereas Filtek Ultimate-control (87.15 ± 2.12) and Filtek Ultimate-Modeling Liquid (84.24 ± 3.11) showed the highest (p < 0.001). CONCLUSION: All tested modeling resins decreased VHN value, and the amount of reduction varied among composites and wetting agents. It might be safer not to use wetting agents unless they are necessary.

Comparison of apical extrusion of sodium hypochlorite using 4 different root canal irrigation techniques.

INTRODUCTION: We compared the apical extrusion of sodium hypochlorite delivered with a 27-G needle, self-adjusting file (SAF), passive ultrasonic irrigation, or the EndoVac system (SybronEndo, Orange, CA) during the instrumentation and final irrigation of root canals. METHODS: Matched paired single-canal teeth were divided into 8 groups. The experimental groups were needle irrigation size #30 (NI30) and #50 (NI50), SAF size #30 (SAF30) and #50 (SAF50), passive ultrasonic irrigation size #30 (PUI30) and #50 (PUI50), and EndoVac size #30 (EV30) and #50 (EV50). Teeth were embedded in 0.2% agarose gel (pH = 7.4) containing 1 mL 0.1% m-Cresol purple (Sigma-Aldrich, St Louis, MO), which changes color at a pH level of 9.0. Root canals were irrigated with sodium hypochlorite and EDTA using 4 different techniques, and the amount of irrigant was controlled. Standardized digital photographs were taken 20 minutes after the first irrigant was used and were analyzed to determine the amount of extrusion (expressed as a percentage of total pixels). RESULTS: The amounts of apical extrusion obtained in the NI30, NI50, SAF30, SAF50, PUI30, PUI50, EV30, and EV50 groups were 30% (3/10), 50% (5/10), 20% (2/10), 70% (7/10), 40% (4/10), 40% (4/10), 10% (1/10), and 10% (1/10), respectively. The overall extrusion frequency, regardless of the apical preparation size, was 40% (8/20) for needle, 45% (9/20) for SAF, 40% (8/20) for ultrasonic irrigation, and 10% (2/20) for EndoVac. Although the SAF group showed more extrusion, the percentage of pixels was significantly higher in the needle irrigation group (P < .01). The EndoVac group showed significantly lower extrusion values than the other techniques in terms of the number of teeth and pixels (P < .05 and P < .01, respectively). CONCLUSIONS: The risk of apical extrusion is significantly lower with the EndoVac in comparison with the 3 other techniques.

The effect of zirconia thickness on the biaxial flexural strength of zirconiaceramic bilayered discs.

The aim of this study was to assess the effect of zirconia core thickness on the biaxial flexural strength values of zirconia-porcelain bilayered discs. A total of 60 discs with 0.3, 0.4, and 0.5 mm thickness were obtained from a fully sintered zirconia block. A 1.5-mm thick layer of veneer porcelain was fired on the zirconia specimens and biaxial flexural strength tests were performed on the bilayered discs. In each group, the loading surface was the veneer porcelain in half of the specimens (core in tension) and the zirconia core surface in the other half (core in compression). The zirconia core thickness had no effect on the biaxial flexural strength of zirconiaporcelain bilayered discs when the core was in tension (p>0.05). Whereas, when the core was in compression, an increase in the zirconia core thickness resulted in an increase in the biaxial flexural strength (p<0.05).

Radiologic Assessment of Periapical Health: Comparison of 3 Different Index Systems.

INTRODUCTION: The aim of this study was to evaluate observer variations and observer reproducibility in the interpretation of periapical health using the Strindberg system, the periapical index (PAI), and the probability index for radiologic assessment of periapical health. METHODS: Four observers read digital periapical images to evaluate the periapical health of 200 root-filled teeth. Each observer evaluated a tooth twice by using the Strindberg system, twice by using the PAI, and twice by using the probability index. Each observation session was held at 1-month intervals. Three scores were used for the evaluations conducted by using the Strindberg system. Both the PAI and the probability index were considered on 5-point scales and were also dichotomized. SPSS for Windows 15.0 software (SPSS Inc, Chicago, IL) was used for data analysis, and intra- and interobserver agreements were described by using kappa statistics. RESULTS: The average kappa values of intra- and interobserver agreement calculated for the Strindberg system were 0.53 and 0.36, respectively. The corresponding average kappa values were calculated as 0.48 and 0.39 for the PAI and 0.45 and 0.30 for the probability index. The highest mean proportion values of intra- and interobserver agreement were observed for the dichotomization of the PAI (88.9% and 87.0%, respectively) followed by the dichotomization of the probability index (86.8% and 82.9%, respectively). CONCLUSIONS: The Strindberg system has lower intraobserver variation compared with the PAI and the probability index, whereas PAI has lower interobserver variation compared with the Strindberg system and the probability index. The dichotomization of the PAI and the probability index provided higher intra- and interobserver agreement values in the radiologic assessment of periapical health.

Tensile bond strength of dentin adhesives on acid- and laser-etched dentin surfaces.

OBJECTIVE: To evaluate tensile bond strengths of 2 dentin bonding agents containing solvents on Nd:YAG and Er,Cr:YSGG laser-etched dentin surface. METHOD AND MATERIALS: Occlusal enamel of 146 molars was removed, and exposed surfaces were ground with a diamond bur to produce bur-cut dentin surfaces. Of those teeth, 120 were assigned to 3 groups of 40 samples in which dentin was conditioned with Er,Cr:YSGG laser, Nd:YAG laser, and 37% orthophosphoric acid (control). Each group was further divided into 2 subgroups, acetone- and ethanol-containing bonding agents, and 4-mm-long x 4-mm-wide composite rods were bonded to all specimens using a Plexiglas mold. Tensile bond strength testing of 120 samples was performed at a crosshead speed of 0.5 mm/min using a 50-kgf load cell. The remaining 26 samples were examined under SEM to evaluate the adaptation/penetration of the bonding materials and the alterations in mineral content. Data were analyzed using 1-way ANOVA and Kruskal-Wallis tests; P < .05 was considered statistically significant. RESULTS: The difference between the mean tensile bond strength values obtained with bonding agents was statistically significant in the control group. The bond strength values of the acetone-containing agent in this group were found to be higher than the ethanol-containing agent (P < .001). When compared with Nd:YAG laser, bond strength values obtained with Er,Cr:YSGG laser were higher (P < .001). The bond strength values obtained in the acid-etched group were highest for both bonding agents and demonstrated statistical significance (P < .001). CONCLUSION: Although in this study laser etching is more influential than the solvent type on bond strengths of dentin bonding agents, it cannot be considered as an alternative to conventional acid etching.