Preheating and "snow-plow" composite application technique affect double bond conversion but not bond strength to dentine.

OBJECTIVE: To measure degree of conversion (DC) of a flowable composite, microtensile bond strength (MTBS) to dentine in the snow-plow technique with/without preheating and temperature in the preheated composite. MATERIALS AND METHODS: For DC, snow-plow specimens of Filtek Ultimate Flowable (Flow) and Filtek Bulk Fill (Bulk) (3M) were prepared by light-curing composites simultaneously in standardized molds while in control groups light-curing was separate. DC of Flow was measured using micro-Raman spectroscopy. For MTBS, specimens were prepared on dentine of human extracted molars by simultaneous (snow-plow) or separate (control) light-curing. MTBS was measured using a universal testing machine after 24 h and 6 months. Data were analyzed using ANOVA with Tukey's post hoc (α = 0.05). RESULTS: Increased curing time significantly increased DC in snow-plow from 13.4% ± 11.6% (10 s) to 31.8% ± 4.4% (40 s) albeit significantly lower than controls (p < 0.05). Preheated Bulk improved conversion in snow-plow (44.3% ± 1.7%) and control (50.5% ± 2.6%) (p < 0.05). No significant differences occurred in MTBS between groups (p > 0.05). MTBS values ranged between 66.7 ± 8.4 MPa (snow-plow group_21°C_baseline) and 54.1 ± 15.8 MPa (control_21°C_long-term). Temperature in the preheated Bulk dropped to ~38°C after 30 s. CONCLUSIONS: Snow-plow technique, irrespective of preheating, resulted in lower DC of Flow than separate light-curing of composite increments. Snow-plow, irrespective of preheating, resulted in similar initial and long-term MTBS to dentine. CLINICAL SIGNIFICANCE: Clinicians with preference for flowable composite liners in Class II restorations should be aware that the snow-plow technique of simultaneous light-curing of flowable and bulk-fill composite increments affects monomer-to-polymer conversion, albeit no effect on immediate, and long-term bonding to dentine was detected. Preheating sculptable bulk-fill composite improves conversion of the flowable liner in the snow-plow technique but has no detectable effect on bond strength to dentine.

Hydroxyapatite-based dental inserts: Microstructure, mechanical properties, bonding efficiency and fracture resistance of molars with occlusal restorations.

This study aimed to (1) comparatively analyze properties of Sr- and Mg-substituted hydroxyapatite (HAP)-based dental inserts; (2) evaluate insert bonding to restorative materials, and (3) evaluate the effect of doped HAP inserts on fracture resistance (FR) of human molars with large occlusal restorations. By ion-doping with Sr or Mg, 3 insert types were obtained and characterized using XRD, SEM, Vickers hardness and fracture toughness. Shear bond strength (SBS) was determined between acid etched or unetched inserts and following materials: Maxcem cement (Kerr); Filtek Z250 (3M) bonded with Single Bond Universal (SBU; 3M) or Clearfil Universal (Cf; Kuraray). Modified Class I cavities were prepared in 16 intact molars and restored using insert + composite or composite only (control) (n = 8/group). FR of restored molars was determined by static load until fracture upon thermal cycling. Fracture toughness was similar between Sr/Mg-doped inserts (0.94-1.04 MPam-1/2 p = .429). Mg-doped inserts showed greater hardness (range 4.78-5.15 GPa) than Sr6 inserts (3.74 ± 0.31 GPa; p < .05). SBS for SBU and Cf adhesives (range 7.19-15.93 MPa) was higher than for Maxcem (range 3.07-5.95 MPa) (p < .05). There was no significant difference in FR between molars restored with insert-containing and control restorations (3.00 ± 0.30 kN and 3.22 ± 0.42 kN, respectively; p > .05). HAP-based inserts doped with Mg/Sr had different composition and mechanical properties. Adhesive bonding to inserts resulted in greater bond strength than cementation, which may be improved by insert acid-etching. Ion-doped HAP inserts did not affect FR of restored molars. In conclusion, HAP-based dental inserts may potentially replace dentin in large cavities, without affecting fracture resistance of restored teeth.

Clinical longevity of direct and indirect posterior resin composite restorations: An updated systematic review and meta-analysis.

OBJECTIVES: To answer the PICO(S) question: Is there a difference in clinical longevity between direct and indirect resin composite restorations placed on permanent posterior teeth? DATA: Randomized controlled clinical trials (RCTs) investigating direct and indirect resin composite restorations in posterior permanent teeth were considered. SOURCES: Several electronic databases were searched, with no language or date restrictions. The revised Cochrane Collaboration's tool for assessing risk of bias (RoB-2) was used to analyze the studies; meta-analyses were run and the certainty of evidence was assessed by the GRADE tool. A subgroup meta-analysis was performed for resin composite restorations placed on posterior worn dentition. STUDY SELECTION: Twenty-three articles were included in qualitative synthesis, while 8 studies were used for meta-analyses. According to the RoB-2 tool, 5 studies were ranked as "low risk", 7 had "some concerns", while 11 papers were rated as "high risk" of bias. There were no statistically significant differences in short-term (p = 0.27; RR=1.54, 95% CI [0.72, 3.33]), medium-term (p = 0.27; RR=1.87, 95% CI [0.61, 5.72]) and long-term longevity (p = 0.86; RR=0.95, 95% CI [0.57, 1.59]). The choice of restorative technique had no influence on short-term survival of resin composite restorations placed on worn dentition (p = 0.13; RR=0.46, 95% CI [0.17, 1.25]). The certainty of evidence was rated as "very low". CONCLUSIONS: Direct and indirect resin composite restorations may show similar clinical longevity in posterior region, regardless of the observation period or substrate (wear-affected and non-affected dentition). The very low quality of evidence suggests that more long-term RCTs are needed to confirm our results.

Melatonin Mitigates iNOS-Related Effects of HEMA and Camphorquinone in Human Dental Pulp Cells: Relevance for Postoperative Sensitivity Mechanism in Type 2 Diabetes.

High elution and diffusion of 2-hydroxylethyl methacrylate (HEMA) and camphorquinone (CQ) through dentinal tubules may induce pulp injury and postoperative sensitivity. We aimed to investigate the melatonin protective effect in HEMA- and CQ-treated human dental pulp cells (hDPCs) as well as its relevance in a mechanism for postoperative sensitivity in diabetic patients. hDPCs were exposed to HEMA (5 mM) and/or CQ (1 mM) in the absence and presence of melatonin (MEL) (0.1 mM and 1 mM). Heme oxygenase-1 (HMOX1), NADPH oxidase-4 (NOX4), BCL-2-associated X-protein (BAX), B-cell lymphoma-2 (BCL-2) and caspase-3 (CASP3) gene expression levels, and superoxide dismutase (SOD) activity were measured in hDPCs while inducible nitric oxide synthase (iNOS) and melatonin protein expression were measured in human dental pulp as well, by RT-PCR, by ELISA, and spectrophotometrically. Bioinformatic analyses were performed by using the ShinyGO (v.0.75) application. Type 2 diabetic patients showed a higher incidence of postoperative sensitivity and lower melatonin and higher iNOS content in dental pulp tissue compared with non-diabetic patients. Melatonin, when co-added in hDPC culture, reverses HEMA and CQ cytotoxic effects via anti-apoptotic and anti-inflammatory/antioxidant iNOS-related effects. Enrichment analyses showed that genes/proteins, altered by HEMA and CQ and normalized by melatonin, are the most prominently overrepresented in type 2 diabetes mellitus pathways and that they share subcellular localization in different oligomeric protein complexes consisting of anti- and pro-apoptotic regulators. This is the first evidence of the ability of melatonin to counteract iNOS-mediated inflammatory and stress effects in HEMA- and CQ-treated hDPCs, which could be of significance for the modulation of presently observed immediate postoperative sensitivity after composite restoration in type 2 diabetic patients.

IN VITRO EVIDENCE INDICATES SILVER DIAMINE FLUORIDE PRETREATMENT OF DENTINE MAY REDUCE BOND STRENGTH OF DENTAL ADHESIVES, BUT NOT OF GLASS IONOMER CEMENTS.

ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION: Bonding of Glass-Ionomer Cement and Adhesives to Silver Diamine Fluoride-treated Dentin: An Updated Systematic Review and Meta-Analysis. Fröhlich TT, Botton G, Rocha RO. J Adhes Dent. 2022;24(1):29-38. SOURCE OF FUNDING: Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001. TYPE OF STUDY/DESIGN: Systematic review with meta-analysis of data.

Effects of staining and artificial aging on optical properties of gingiva-colored resin-based restorative materials.

OBJECTIVES: To evaluate CIEDE2000/CIELAB differences in color (ΔE00/ΔEab), and translucency parameter (ΔTP00/ΔTPab), and gloss of gingiva-colored resin-based restorative materials upon staining/aging. MATERIALS AND METHODS: Disc-shaped, 10 mm in diameter, and 2-mm-thick samples (n = 5/group) were made from giomer (Beautifil II gingiva), oligomer-based (crea.lign GUM gel), CAD/CAM polymethyl-methacrylate-based (IvoBase CAD), PMMA-based (ProBase Hot), and dimethacrylate-based (SR Nexco Paste Gingiva). Color and gloss were recording using a benchtop spectrophotometer and gloss meter, respectively, at baseline (T0), and upon staining in coffee or red wine for 60 (T1) and 120 h (T2), or artificial aging of 150 kJ/m2 (T1) and 300 kJ/m2 (T2). Three-way analysis of variance (materials x staining conditions x time intervals), Tukey's test (α = 0.05), and Pearson's correlation test were used in analytical statistics. RESULTS: CIEDE2000 color differences ranged from 1.0 to 4.4 (coffee), 1.5 to 5.3 (wine), and 0.9 to 2.0 after artificial aging, with ΔE00 values being significantly higher for Beautifil than other materials (p < 0.05). ΔTP00 values ranged from 0.2 to 0.7 and were statistically higher upon staining in wine compared to artificial aging (p < 0.05). Gloss values at T0 were 76.7-87.0. Beautifil exhibited the lowest gloss retention (50.8-60.2%) after staining, compared to > 90% of other materials (p < 0.05). ΔE00/ΔEab and ΔTP00/ΔTPab were positively correlated (p < 0.0001). CONCLUSIONS: Color, translucency, and gloss changes of gingiva-colored restorative materials were material- and staining/aging-dependent. Generally, wine caused greatest changes in color (with IvoBase CAD being the most color stable) and translucency parameter. All materials except Beautifil gingiva II exhibited staining- and aging-dependent gloss retention greater than 90% for all compared time intervals. CLINICAL RELEVANCE: Optical properties of resin-based gingiva-colored restorative materials depend on material, staining/aging conditions, and exposure time. Certain materials should be avoided in individuals with high consumption of red wine and coffee.

Effects of bioflavonoid-containing mouth rinses on optical properties of tooth-coloured dental restorative materials.

This study investigated differences in colour (ΔE00) and translucency parameter (ΔTP00) of nanofilled/microhybrid composites and a glass-ionomer cement following immersion in bioflavonoid (Citrox)- or chlorhexidine-based mouth rinses. Sixty disc-shaped specimens (N = 5/group) of Filtek Supreme (3M), Gradia Anterior (GC) and Fuji IX (GC) were exposed to Citrox/0.2%CHX (Perio+0.2, Curaprox), Citrox/0.09%CHX (Perio+0.09, Curaprox), 0.2%CHX (Savacol, Colgate-Palmolive) or distilled water by 2-min agitation daily for 28 days in an orbital shaker at 200 rpm at 37 °C. Colour recordings were performed using a clinical spectrophometer to obtain CIELab coordinates. General linear model, ANOVA, Tukey test (α = 0.05) and Pearson correlation test were used to analyse data. ΔE00 ranged between 0.33 (Gradia_Savacol_T28) and 6.35 (Fuji_Savacol_T28) (p < 0.001). ΔTP00 ranged between 0.36 (Fuji_ Perio+0.2) and 1.73 (Fuji_Savacol) (p < 0.05). Savacol resulted in higher ΔE00 of Filtek and Fuji and ΔTP00 of Filtek than Perio+0.09 and Perio+0.2 (p = 0.005). Perio+0.09 and Perio+0.2 resulted in higher ΔE00 at T7 than T28 (p < 0.05). There was no correlation between ΔTP00 and ΔE00 (r = 0.445, p = 0.147). Generally, Perio+0.2 and Perio+0.09 mouth rinses produced similar or lower ΔE00 and ΔTP00 than Savacol. GIC Fuji showed higher ΔE00 and similar or higher ΔTP00 than composites Filtek and Gradia. ΔE00 in all materials decreased in Perio+0.2 and Perio+0.09 over time.

A Retrospective Clinical Study on Factors Influencing the Failure of NCCL Restorations.

Objectives: This retrospective study evaluated the factors influencing the clinical failure of noncarious cervical lesion (NCCL) restorations. Methods: Patients were routinely treated by undergraduate or postgraduate students and randomly received a clinical recall evaluation. A retrospective study was performed with two experienced calibrated examiners to evaluate NCCL restorations, including the critical parameters of retention, caries, marginal discoloration, and marginal integrity. The factors related to the restoration included gender, age, arch site, tooth position, the presence of occlusal wear facets, caries risk, operator, adhesive strategy, and composite. The clinical failure comparison between the parameters and factors was performed using the binary logistic regression analysis. Results: A total of 460 cervical restorations from 96 patients were evaluated. The adhesive strategy and the presence of occlusal wear facets were the most important factors influencing the parameter failure. Therefore, the highest failure was marginal integrity, in which the gingival marginal integrity failure was 50.7%, and the occlusal marginal integrity failure was 42.4%. Conclusions: The main factors influencing clinical failure for partial loss, marginal discoloration, and marginal integrity were the adhesive strategy and the presence of occlusal wear facets. Therefore, marginal integrity was the most frequent failure parameter.

Effect of the Degree of Conversion on Mechanical Properties and Monomer Elution from Self-, Dual- and Light-Cured Core Composites.

The objective of this work was to measure and correlate the degree of conversion (DC), mechanical properties and monomer elution from self-, dual- and light-cured core composites. Five samples of each of the following materials were prepared for each test: Clearfil (Core, Photo Core, Automix), Bisco (Core-Flo, Light-Core and Bis-Core). DC was determined using FTIR, compressive and flexural strength and modulus of elasticity using a universal testing machine and microhardness using Vickers hardness. Elution was measured using HPLC. One-way ANOVA with Tukey's post-test and Pearson's correlation were used to statistically analyze the data. DC of Clearfil-Dual (70.1%) and Clerafil-Photo (66.8%) were higher than Clearfil-Self (55.4%) and all Bisco materials (51.4-55.3%). Flexural strength of Clearfilwas higher than that of Bisco composites. The Microhardness of Clearfil-Dual (119.8VHN) and Clearfil-Photo (118.0VHN) were higher compared to other materials. The greatest elution was detected from self-cured materials. DC positively correlated to microhardness and compressive/flexural strength and negatively to BisGMA elution. Clearfil-Photo and Automix showed higher conversion, lower monomer elution and, generally, better mechanical properties. Self-cured composites should not be recommended for routine clinical use as their performance was inferior to dual- and light-cured composites. Microhardness may be used as an indicator of elution.

The effect of COVID-19 pandemic on final year dental students' self-confidence level in performing clinical procedures.

BACKGROUND: The outbreak of COVID-19 pandemic in 2020 has dramatically changed teaching approach in dental schools due to the switch to distance learning and the lack of practice training in direct contact with patients with possible impact on clinical skills of students. The aim of the study was to assess the level of the 2020 final year dental students' self-confidence in performing different dental procedures through specially designed questionnaire and compare it to self-confidence of the 2019 final year students. MATERIALS AND METHODS: An anonymous questionnaire consisting of 40 questions regarding self-confidence level in performing 40 different dental procedures and based on five points Likert-like scale was distributed during November 2020 to final year dental students whose studies were disrupted by the COVID-19 pandemic lockdown in one semester. The study group comprised their answers. The comparison was done with the control group that consisted of students' answers on the same questionnaire from previous 2019 year conducted as a part of regular internal educational evaluation. RESULTS: Response rate was 74.2% in study group and 89.3% in control group. Mean level of self-confidence reported by 115 students in study group was significantly lower than that reported by 100 students in control group (3.28±1.08 vs. 3.58±0.88, respectively) and the distribution of self-confidence scores were different in observed groups. Graduates from study group felt less confident than those from control in 8 clinical skills. CONCLUSION: Abrupt changes in teaching modalities caused by COVID-19 pandemic had significant impact on final year dental students' self-confidence indicating additional educational needs in postgraduate period.

Effects of non-thermal atmospheric plasma on dentin wetting and adhesive bonding efficiency: Systematic review and meta-analysis.

OBJECTIVES: This systematic review and meta-analysis evaluated the effects of non-thermal atmospheric plasma (NTAP) treatment on dentin wetting and adhesive-dentin bond strength. DATA/SOURCES: This report followed the PRISMA 2020 statement. Two reviewers conducted literature search of MEDLINE, Web of Science and Scopus databases up to the end of November 2020. Included in vitro studies compared the effect of NTAP on treated dentin of non-carious, intact, extracted human third molar teeth with different control groups. Studies with no adequate methods, missing data, lack of control group, or those using animal teeth were excluded. The random effects model was used to summarize the treatment effect with standardized mean difference (SMD) and 95% CI. Risk of bias was assessed using the custom Cochrane Collaboration's tool. STUDY SELECTION/RESULTS: Seventeen studies met inclusion criteria. The effects on dentin wetting were reported in favor of NTAP (SMD -5.38; 95% CI [-6.97, -3.78]; p<0.00001; I2=81%). Regarding adhesive-dentin bond strength, statistically significant differences between the NTAP and control group were in favor of NTAP in the short-term (SMD 1.92; 95%CI [1.35, 2.50]; p<0.00001; I2=97%), and long-term (SMD 3.28; 95%CI [2.46, 4.09]; p<0.00001; I2=97%). A limitation of meta-analysis is moderate heterogeneity caused by methodological differences and lack of data, which was evaluated through risk of bias and sensitivity analysis. CONCLUSIONS: NTAP substantially improves dentin wetting and adhesive-dentin bond strength with 30 seconds exposure time and up to 10 mm tip-to-surface distances being sufficient for positive NTAP effects on bonding efficiency. FUNDING: ON172207 and III41008 from the Ministry of Education, Science and Technological Development, Republic of Serbia. NP is funded by MESTD grant number 451-03-68/2020-14/200024. CLINICAL SIGNIFICANCE: This systematic review and meta-analysis substantiate potential applicability of NTAP treatment of dentin in improving adhesive bonding clinically. Further research should be based on the optimized parameters such as time and distance with additional refinement of NTAP power.

Effects of whitening gels on color and surface properties of a microhybrid and nanohybrid composite.

The aim of this study was to compare color changes, surface roughness and gloss of a microhybrid and nanohybrid composite whitened in a simulated in-office or at-home procedure using 40% hydrogen peroxide or 16% carbamide peroxide, respectively. CIELab coordinates were measured before, during and after treatment using VITA EasyShade V (VITA) and ∆E00 calculated. Surface roughness was measured using a surface roughness tester (SJ210; Mitutoyo). Gloss was measured using a gloss checker (IG-331; Horiba). At-home whitening resulted in ∆E00 of 1.23±0.49 (microhybrid) and 1.01±0.76 (nanohybrid). In-office exposure resulted in ∆E00 of 0.69±0.38 (microhybrid) and 0.72±0.50 (nanohybrid). There were no significant differences in ∆E00, surface roughness and gloss between whitening protocols (p>0.05). Color changes of a microhybrid and nanohybrid composite following simulated in-office or at-home whitening reached CIEDE2000 50:50% perceptibility but not acceptability threshold. Surface roughness and gloss of the microhybrid and nanohybrid composite were not affected by whitening.

Multifactorial analysis of optical properties, sorption, and solubility of sculptable universal composites for enamel layering upon staining in colored beverages.

OBJECTIVE: To analyze the effects of factors 'composite,' 'medium,' and 'time' on color, translucency, and sorption/solubility of sculptable universal composites for enamel layering upon immersion in colored beverages. MATERIALS AND METHODS: Disk-shaped specimens, 10 mm in diameter and 2 mm thick (n = 5/group), of ultrafine, hybrid composite Essentia (GC), microhybrid Gaenial Anterior (GC), nanofilled Filtek Ultimate Enamel and Body ( 3M ESPE) were immersed in red wine, coffee, or distilled water for 15 days. CIELab color coordinates were measured and CIEDE2000 (∆E00 ) and Translucency Parameter differences (∆TP00 ) were calculated. Sorption and solubility were determined according to ISO 4049:2009. Data were analyzed using the analyses of variance and Tukey's post-hoc test (α = 0.05). RESULTS: Essentia and Gaenial exhibited the lowest and the highest staining-dependent color differences, with mean ∆E00 range of 1.7-6.1 and 5.1-11.3, respectively (p < 0.05). ∆TP00 was more pronounced in wine than in coffee (p < 0.05). Sorption and solubility varied between 9.8 and 15.3 µg/mm3 and -1.6 and -5.4 µg/mm3 , respectively, with positive correlation between ∆TP00 and sorption (p = 0.005). CONCLUSIONS: Total color and translucency differences of sculptable composites for enamel layering were material-, time- and medium-dependent. Translucency differences positively correlated with sorption. Overall, the ultrafine, hybrid composite exhibited the best results in terms of color stability, sorption and solubility. CLINICAL SIGNIFICANCE: Clinicians should be aware of differences in color stability of sculptable composites for enamel layering as these are directly exposed to discoloration in the oral environment and are directly related to patients' long-term satisfaction and restoration longevity. Ultrafine, hybrid composite may be preferred due to better color stability, lower sorption and solubility compared to nanofilled and microhybrid composites evaluated in this study.

Immediate and Long-Term Porosity of Calcium Silicate-Based Sealers.

INTRODUCTION: Open pores between endodontic sealer and root canal walls present potential niches for bacterial growth and migration pathways. The aim was to assess the internal and external porosity of calcium silicate-based sealers and to ascertain the long-term effect of storage in simulated body fluid on sealer porosity. METHODS: Sixteen single-rooted teeth were filled with gutta-percha and 1 of 4 root canal sealers: BioRoot RCS, EndoSequence BC, MTA Fillapex, or AH Plus. Obturated roots, stored in Hank's balanced salt solution, were scanned after 7 days and after 6 months by using micro-computed tomography at an isotropic resolution of 9.9 µm. Total, open, and closed porosity were calculated in the coronal, middle, and apical thirds. Data were statistically analyzed by using general linear model and paired t test (α = 0.05). RESULTS: Significantly higher percentage of open than closed porosity was found in all groups. Initially, significantly greater open and total porosity were found for MTA Fillapex than for AH Plus. After 6 months, the percentage of open and total porosity increased in BioRoot RCS and MTA Fillapex and decreased in AH Plus and EndoSequence BC. Both initially and after storage, coronal region of all sealers had significantly greater total porosity than middle and apical regions, which were comparable. CONCLUSIONS: None of the root fillings were void-free, with predominant open porosity persisting after long-term storage.

Dissimilar sintered calcium phosphate dental inserts as dentine substitutes: Shear bond strength to restorative materials.

The application of sintered calcium phosphate dental inserts in the central part of tooth cavities can reduce amount of embedded dental composite and polymerization shrinkage of final dental fillings. The aim of this study was to analyze comparatively physico-chemical and mechanical properties of dental inserts and shear bond strength (SBS) between three dissimilar hydroxyapatite-based dental inserts and different restorative materials, after application of different clinical protocols. Starting from two different hydroxyapatite nano powders and nanostructured stabilized zirconia (YSZ), monophasic two-step sintered dense HAp inserts (TSSHAp), biphasic single-step sintered controlled porous inserts (HAp/TCp), and single-step sintered reinforced HAp/YSZ inserts were processed and characterized. Obvious differences in the microstructure of inserts surface were visualized after etching with 37% phosphoric acid. Fracture toughness of sintered inserts was ranged between 1.01 and 1.85 MPam1/2 (maximum value in the case of HAp/YSZ), while hardness values were in the range of 3.71-5.22 GPa (maximum value in the case of TSSHAp). Acid etching before application improved SBS between inserts and Maxcem compared to direct cement application. TSSHAp and HAP/TCp inserts showed comparable and relatively high SBS values, certainly higher compared to HAp/YSZ inserts. Slightly higher SBS values were measured in the case of TSSHAp insert group, and the highest mean SBS value of 18.51 MPa was determined between TSSHAp inserts and Filtek Z250_SBU following the "self-etch" protocol.

Color stability of bulk-fill and universal composite restorations with dissimilar dentin replacement materials.

OBJECTIVE: To determine color changes in bulk-fill composite and universal composite restorations with dissimilar dentin replacement materials in extracted teeth after staining in red wine. MATERIALS AND METHODS: Cylindrical, 4 mm deep, class I cavities were prepared in 140 human molars. Bottom 2 mm was restored with Biodentine (Septodont), everX posterior (GC) or experimental HAP inserts. Each dentin replacement material was covered with a 2-mm layer of a universal composite Filtek Z250 or Z550 (3M ESPE) or Gradia Posterior (GC). Groups combining top composite layer and the underlying dentin replacement were designated as "composite_dentin replacement." Filtek Bulk Fill (3M ESPE) and Tetric EvoCeram Bulk Fill (Ivoclar Vivadent) were placed as a single 4-mm layer. Color measurements were performed using Vita Easyshade 4.0 (Vita Zahnfabrik) initially and after 48-hours storage in red wine at 37°C. RESULTS: Color differences (ΔEoo ) ranged between 2.1 ± 0.7 (Z250_HAP) and 7.8 ± 1.1 (Z550_everX). EverX resulted in higher ΔEoo of the overlying composite than HAP (P < .001) and Biodentine (P = .006). Generally, ΔEoo was affected more by decreasing lightness (ΔL') than changes in chroma (ΔC'). CONCLUSIONS: EverX resulted in higher ΔEoo of the restoration than Biodentine and experimental HAP after staining in red wine. No significant differences in ΔEoo may be expected in different composites with the same underlying dentin replacement material. The same was generally true for bulk-fill and universal composites. CLINICAL SIGNIFICANCE: Similar extent of color changes may be expected in bulk-fill and universal composites. Highly translucent everX might exhibit greater color differences irrespective of the capping composite than non-translucent materials. Clinicians have a wider choice of composite materials to cover a particular dentin replacement material, for example, everX or Biodentine, as similar color differences may be expected in various overlying composite brands.

Effects of non-thermal atmospheric plasma treatment on dentin wetting and surface free energy for application of universal adhesives.

OBJECTIVES: The study aims to evaluate the effects of non-thermal atmospheric plasma (NTAP) treatments on dentin wetting and surface free energy (SFE) and compare the effects of NTAP treatment, etch-and-rinse, and self-etch protocols for application of universal adhesives. MATERIALS AND METHODS: Mid-coronal dentin of intact third molars was used to measure contact angles of distilled water, ethylene-glycol, and diiodomethane and calculate SFE following different NTAP preset treatments (feeding gas consisting of pure He, He + 1% O2, He + 1.5% O2), power input (1 or 3 W), and tip-to-surface distance (2, 4, or 8 mm). Contact angles of reference liquids and SFE of dentin following He + 1.5% O2 at 3-W and 4-mm treatment was compared to phosphoric acid etching. Contact angles of Single Bond Universal (SBU; 3M ESPE) and Clearfil Universal Bond (CUB; Kuraray Noritake) were measured following NTAP, etch-and-rinse, and self-etch protocols. RESULTS: NTAP significantly reduced contact angles of reference liquids and increased dentin SFE compared to untreated dentin (p < 0.05). O2 intensified the effect of He NTAP (p < 0.05). NTAP and phosphoric acid increased dentin polarity and Lewis base surface characteristics. Phosphoric acid increased contact angles of adhesives compared to the self-etch protocol (p < 0.05). NTAP resulted in lower adhesive contact angles than phosphoric acid, the difference being statistically significant for CUB (p < 0.05). Compared to the self-etch protocol, NTAP slightly reduced CUB contact angle but not that of SBU (p > 0.05). CONCLUSIONS: He NTAP with and without O2 increased dentin wetting and SFE, surpassing the effect of phosphoric acid and lowering adhesive contact angles. NTAP produced no apparent micro-morphological changes on dentin surface comparable to acid etching. CLINICAL SIGNIFICANCE: NTAP treatment of dentin prior to adhesive application increases dentin wetting and surface free energy facilitating better adhesive distribution on dentin surface compared to phosphoric acid etching and similar to the "self-etch" application protocol.

Optical properties of composite restorations influenced by dissimilar dentin restoratives.

OBJECTIVES: To evaluate optical properties (color and translucency) of 'sandwich' restorations of resin-based composites and esthetically unfavorable dentin restoratives. METHODS: Cylindrical 'dentin' specimens (8mm in diameter and 2mm thick, N=5/group) were prepared using EverX Posterior (GC), Biodentine (Septodont), experimental hydroxyapatite (HAP) or conventional composites (Gradia Direct Posterior, GC; Filtek Z250 and Filtek Z500, 3M ESPE). Capping 'enamel' layers were prepared using composites (Gradia Direct Posterior, Filtek Z250 or Z550) of A1 or A3 shade and the following thickness: 0.6, 1 or 2mm. Color (ΔE) and translucency parameter (TP) were determined using a spectrophotometer (VITA Easyshade Advance 4.0, VITA Zahnfabrik). Data were statistically analyzed using analysis of variance with Tukey's post-hoc tests (α=0.05). RESULTS: TP was greatly affected by layer thickness, whilst ΔE depended on shade and layer thickness of the capping composite. HAP and Biodentine showed significantly lower TP and higher ΔE (deviation from 'ideal white') than composites (p<0.05). Greater TP was seen in EverX_composite groups than in corresponding control groups of the same shade and thickness. TP of composites combined with Biodentine or HAP was below 2, lower than the corresponding control groups (p<0.05). Within-group differences of ΔE were greatest in HAP_composite groups. EverX_Gradia and EverX_FiltekZ250 combinations showed the most comparable ΔE with the control groups. SIGNIFICANCE: A 2mm thick layer of composite covering dentin restoratives with unfavorable esthetics is recommended for a final 'sandwich' restoration that is esthetically comparable to a conventional, mono-composite control restoration.

Microtensile bond strength of universal adhesives to flat versus Class I cavity dentin with pulpal pressure simulation.

OBJECTIVES: The aim of this study was to test long-term microtensile bond strength (µTBS) of 2 universal adhesives applied to dentin following "total-etch" (TE) or "self-etch" (SE) protocols and aged by direct or indirect water exposure using simulated pulpal pressure. MATERIALS AND METHODS: Single Bond Universal (SBU, 3M ESPE) or Ipera Bond (IP, Itena) were applied to mid-coronal dentin ("flat dentin") or Class I cavity ("cavity dentin") following TE or SE protocols in 112 extracted human third molars. Sixteen groups (n = 7 per group) were prepared, 8 groups for µTBS measurements after 24 hours, and further 8 groups for measurements after 6 months storage. "Cavity dentin" groups were subjected to simulated hydrostatic pulpal pressure of 15 cm H2 O using a custom-made device before cutting 1 × 1 mm sticks while "flat dentin" groups were cut into sticks and directly exposed to deionized water. RESULTS: Generally, the TE protocol resulted in highest µTBS values on flat dentin initially for both adhesives (general linear model, P < .05). Long-term storage resulted in significantly lower µTBS values for the TE protocol (P < .05) while the SE protocol showed comparable values after 6 months (P > .05). "Cavity dentin" with simulated pulpal pressure resulted in lower µTBS than "flat dentin" (P < .05). For both adhesives, µTBS was in the range of 19-42 MPa initially and 16-36 MPa after 6 months storage. CONCLUSIONS: µTBS to dentin of universal adhesives is more stable in the long term following the SE than TE protocol. Simulated pulpal pressure and cavity-type sample preparation may be recommended for µTBS testing as a more clinically relevant strategy. CLINICAL SIGNIFICANCE: Microtensile bond strength to dentin of universal adhesives appears more stable following the "self-etch" than "total-etch" protocol after long-term degradation. More clinically relevant data may be obtained using simulated pulpal pressure and cavity-type sample preparation in the study design.

Cytotoxicity and genotoxicity of a low-shrinkage monomer and monoacylphosphine oxide photoinitiator: Comparative analyses of individual toxicity and combination effects in mixtures.

OBJECTIVE: To compare cytotoxicity and genotoxicity of novel urethane-based monomer FIT-852 and monoacylphosphine oxide photoinitiator (Lucirin TPO) with conventional Bisphenol A-glycidyl-methacrylate (BisGMA) and triethylene glycol dimethacrylate (TEGDMA) monomers and camphorquinone (CQ)/amine photoinitiator system, respectively. Moreover, we quantified and analyzed the combinatorial effects of individual substances in resin-based mixtures concerning the nature of the combinatorial effects. METHODS: Cytotoxic and genotoxic effects of BisGMA, FIT, TEGDMA, CQ, DMAEMA and TPO and their combined toxicity in four clinically relevant mixtures (FIT/TPO, FIT/CQ, BisGMA/TPO, BisGMA/CQ) were tested on human fetal lung fibroblasts MRC-5 using MTT and Comet assays. We assessed combination effects of monomers and photoinitiators on overall toxicity from the measured concentration-effect relationships. Combination index (CI) was calculated on the basis of the median-effect equation derived from the mass-action law principle. RESULTS: Individual substances showed decreasing cytotoxic effects in the following order: BisGMA>TPO>FIT>CQ>DMAEMA>TEGDMA. Experimental mixtures showed decreasing cytotoxic effects in the order BisGMA/TPO>BisGMA/CQ>FIT/CQ>FIT/TPO. FIT-based mixtures exhibited antagonistic cytotoxic effects between components while BisGMA-based mixtures demonstrated synergistic effects at ED50. TPO amplified both antagonistic and synergistic cytotoxic effects in mixtures. Pure substances showed genotoxicity in the following order: TPO>BisGMA>FIT>CQ>TEGDMA. We did not detect the genotoxic potential of DMAEMA. The rank of genotoxic concentrations of the mixtures was: BisGMA/TPO>BisGMA/CQ>FIT/CQ>FIT/TPO. SIGNIFICANCE: Lower cytotoxicity and genotoxicity of FIT than BisGMA suggests its greater biocompatibility. Conversely, photoinitiator TPO was significantly more cytotoxic and genotoxic than both CQ and DMAEMA. CI values showed that components of FIT-based mixtures exhibit an antagonistic cytotoxic effect, while compontents of BisGMA-based mixtures show synergism.