The long-term consequence of salivary contamination at various stages of adhesive application and clinically feasible remedies to decontaminate.

OBJECTIVE: To analyse the bond quality in dentine post-ageing after salivary contamination and decontamination at different stages of dental adhesive application. MATERIALS AND METHODS: A total of 1120 human dentine specimens were randomly allocated to 14 groups for four intervals (n = 20) to be treated with a self-etching (SE) and universal (U) adhesive. The saliva contamination and decontamination were implemented after surface preparation, after primer application (for SE) and after adhesive curing. The decontamination groups were either rinsed and air-dried or rinsed, air-dried and reapplied with adhesive. They were stored (37 °C, distilled water) for four intervals (1 week, 1 month, 3 months and 1 year) and subjected to shear bond strength (SBS) test at a crosshead speed of 0.5 mm/min. RESULT: One-way ANOVA with Tukey's test (α = 0.05) revealed significant reduction in SBS in all the groups in U adhesive compared with the control group at 1 week (p < 0.0001) and in SE when the contamination took place after primer application. However, decontamination improved the SBS in SE but not in U adhesive. The univariate analysis confirmed significant influences (p < 0.0001) seen by treatment procedure ([Formula: see text]=0.075), type of adhesive ([Formula: see text] = 0.328), ageing ([Formula: see text] = 0.13), experimental groups ([Formula: see text] = 0.518), and the stage of influence ([Formula: see text] = 0.60). CONCLUSION: Saliva contamination is detrimental after primer application in SE but, decontamination regained the SBS and maintained it over time. In U adhesive, SBS deteriorated over time irrespective of the contamination. CLINICAL RELEVANCE: Salivary contamination showed different influences on SBS at various stages of restoration with contemporary dental adhesives.

Sufficiency of curing in high-viscosity bulk-fill resin composites with enhanced opacity.

OBJECTIVES: The study aims analyzing if improved opacity in modern high-viscosity bulk-fill resin composites (BF-RBC) contradicts with the sufficiency of curing and to assess material's tolerance to less ideal curing conditions. MATERIALS AND METHODS: Simulated large cavities (10 × 6) mm were filled in one increment with three BF-RBCs (Filtek One, FO; Tetric Evo Ceram Bulk Fill, TEC-BF; SonicFill2, SF2). One central and two peripheral (4 mm apart from the center) micromechanical property line-profiles (HV, Vickers hardness; YHU, indentation modulus) were measured in 0.2-mm steps at 24 h post-polymerization (n = 6). Depth of cure (DOC) was calculated from the HV variation in depth. A scratch test (DOCscratch test) estimated the tolerance in polymerization when simulating clinically relevant curing conditions (exposure distance up to 7 mm; centered and with a 3-mm offset placement of the LCU). Irradiance and spectral distribution of the used light curing unit (LCU) were assessed at various curing conditions. RESULTS: DOC varied among 3.6 mm (SF2, peripheral) and 5.7 mm (FO, central). The BF-RBC influences DOC stronger (p < 0.001, ηP2 = 0.616) than the width (p < 0.001, ηP2 = 0.398). Significant lower DOC (t test) was measured peripheral compared to center in all materials. YHU was more sensitive to the varied parameters as HV. DOCscratch test varied among 2.4 mm (SF2, 3-mm offset, exposure distance 7 mm) and 3.9 mm (FO, center, 0 mm). CONCLUSIONS: Whether opacity competes with DOC is material dependent. BF-RBCs tolerate small variations in LCU's centricity better than variations in exposure distance. CLINICAL RELEVANCE: The upper incremental thickness threshold of 4 or 5 mm was not reached in all BF-RBCs under simulated clinically relevant curing conditions.

Mechanical properties of experimental composites containing bioactive glass after artificial aging in water and ethanol.

OBJECTIVES: To evaluate the effect of bioactive glass 45S5 (BG) in experimental composites on flexural strength (FS), flexural modulus (FM), modulus of resilience (MR), and material reliability after artificial aging in water for 1, 7, and 30 days, and an additional accelerated aging for 3 days in a 75 vol% ethanol-water solution. MATERIALS AND METHODS: Five experimental light-curable composites were prepared with 0-40 wt% of BG and a total filler load of 70 wt%. The resinous matrix was Bis-GMA/TEGDMA in 60:40 by weight. Mechanical properties were evaluated using a three-point bending test (ISO/DIN 4049:1998) with n = 20. Weibull statistics were used to assess material reliability. Additionally, the degree of conversion (DC) was assessed 24 h post-cure using FT-Raman spectroscopy. RESULTS: FS and FM decreased linearly as the amount of BG was increased. The ISO 4049 requirement for a minimum FS of 80 MPa was fulfilled in experimental composites with up to 20 wt% of BG. Degradation of FS and FM with artificial aging was more extensive in materials with higher BG amounts. MR decreased as a function of BG amount and artificial aging. Material reliability (Weibull modulus) was stable through aging for composites with up to 10 wt% of BG. DC was negatively influenced by the BG amount and ranged from 64 to 81%. CONCLUSION: Increasing the amount of unsilanized BG fillers from 0 to 40 wt% resulted in a progressive decline in mechanical properties and a more extensive degradation during artificial aging. CLINICAL RELEVANCE: Bioactive fillers diminished the mechanical properties in a dose-dependent manner.

Real-time curing characteristics of experimental resin composites containing amorphous calcium phosphate.

The real-time polymerization of light-curable experimental resin composites filled with amorphous calcium phosphate (ACP) was monitored. Experimental composites were based on a 2,2-bis[4-(2-ethoxy-3-methacryloyloxy propoxy)phenyl]propane (Bis-EMA)/triethyleneglycol dimethacrylate (TEGDMA)/2-hydroxyethyl methacrylate (HEMA) resin photoactivated by a camphorquinone/tertiary amine system. Four ACP composites were prepared, containing 40 wt% ACP and 0/10 wt% reinforcing fillers (barium glass and silica). Additionally, two control composites were prepared which contained only reinforcing fillers (40-50 wt%). The degree of conversion (DC) was monitored in real time using a Fourier-transform infrared (FTIR) spectrometer with an attenuated total reflectance accessory. During the light curing (1,219 mW cm-2 ) for either 20 or 40 s, infrared spectra were collected from the bottom of 2-mm-thick composite specimens at the rate of two spectra per second over 5 min. When cured for 40 s, the ACP composites attained a high DC (89.1%-92.4%), while the DC of control composites was significantly lower (53.5%-68.4%). All materials showed a lower DC for the shorter curing time (20 s) and various extents of 5-min postcure polymerization: 12.9%-21.5% for the ACP composites and 2.7%-5.2% for the control composites. The control composites reached the maximum reaction rate much earlier (4.1-4.3 s) and at lower DC (9.9%-10.4%) than did the ACP composites (17.4-22.0 s and 43.5%-49.3%, respectively).

Dentin Bond Strength of Experimental Composites Containing Bioactive Glass: Changes During Aging for up to 1 Year.

PURPOSE: To investigate dentin bond strength of experimental composites based on a bis-GMA/TEG-DMA composite filled with a varying amount (0 to 40 wt%) of bioactive glass 45S5 (BG) at a total filler content of 70 wt%. MATERIALS AND METHODS: Specimens for shear bond strength testing (diameter = 3.12 mm, height = 3 mm) were bonded to human dentin using a two-step self-etch adhesive and subjected to aging in water at 37°C for 1 week, 1 month, 3 months, 6 months, and 1 year. A total of 600 specimens were prepared (6 materials × 5 aging times × 20 specimens per experimental group). Bond strength was tested by loading specimens in a universal testing machine at a constant crosshead speed of 0.5 mm/min until fracture. Reliability analysis was performed using Weibull statistics. RESULTS: Experimental composites with a low BG content (up to 5 wt%) showed dentin bond strength and reliability comparable to those of the commercial reference composite. A further increase in the BG amount diminished both bond strength and reliability. The bond strength decline was linearly dependent on the amount of BG when observed within each aging time. One-year aging in water caused no deterioration of bond strength, but diminished bond reliability. The reliability after 1-year aging was similar among all composites, including the commercial reference composite. CONCLUSION: The variation in BG amount diminished the bond strength and reliability in a dose-dependent manner.

Transmitted irradiance through ceramics: effect on the mechanical properties of a luting resin cement.

OBJECTIVES: The study aims to characterise the curing behaviour of a light-curing luting composite (Variolink® Aesthetic LC, Ivoclar Vivadent) polymerised at different exposure times (10 s, 20 s) through different ceramics (IPS Empress CAD and IPS e.max CAD, Ivoclar Vivadent) and ceramic thicknesses (no ceramic, 0.5, 1, 1.5 and 2 mm). MATERIAL AND METHOD: Curing units' (Bluephase Style, Ivoclar Vivadent) variation in irradiance delivered up to 10-mm exposure distance as well as the incident and transmitted irradiance and radiant exposure up to 6-mm ceramic thickness were assessed on a laboratory-grade spectrometer. A total of 216 (18 groups, n = 12) thin and flat luting composite specimens of 500-µm thickness were prepared and stored after curing in a saturated vapour atmosphere for 24 h at 37 °C. Micro-mechanical properties (Vickers hardness, HV and indentation modulus, YHU) were determined by means of an automatic micro-hardness indenter. RESULTS: Within the study design, the radiant exposure received by the luting composite varied from 2.56 to 24.75 J/cm2, showing a high impact on the measured properties. Comparing the effect of the parameters exposure time, ceramic thickness and type, the highest influence on the micro-mechanical parameters was identified for exposure time, while this influence was stronger on HV (p < 0.001, η P2 = 0.452) than on YHU (p < 0.001, η P2 = 0.178). The influence of ceramic type was significant but low (η P2 = 0.161 on HV and 0.113 on YHU), while the influence of ceramic thickness was the lowest (η P2 = 0.04 and 0.05, respectively). CONCLUSIONS: Slightly higher irradiance values were transmitted through Empress CAD up to a ceramic thickness of 3 mm (p < 0.001), while being comparable with e.max for thicker slices. Differences in translucency between ceramics were reflected in the micro-mechanical properties of the luting composite. CLINICAL RELEVANCE: The radiant exposure reaching the luting composite is determined by the incident irradiance, exposure time, ceramic type and ceramic thickness. At the analysed incident irradiance, exposure time was the most consistent parameter affecting the micro-mechanical properties of the luting composite, and this effect was strongly reflected in the more translucent ceramic Empress CAD. Within the curing conditions, an exposure time of 20 s is recommended.

Shear bond strength and microleakage results for three experimental self-etching primer compositions for pit and fissure sealing.

OBJECTIVES: This in vitro study evaluated the shear bond strength (SBS) and microleakage of three experimental self-etching primers for pit and fissure sealing. MATERIALS AND METHODS: The material used three formulations of an experimental fissure primer (EFP) applied without phosphoric acid etching (EFP-1/EFP-2/EFP-3) and one control group with sealant application after 30 s of acid etching. Four groups of sealants (n = 40 specimens/group) were tested for SBS, and a failure analysis was conducted after 1-day water storage, 3-month water storage, and 5000-fold thermocycling. In addition, microleakage was tested. RESULTS: The SBSs of the EFPs (range 8.2 MPa (standard deviation 4.2) to 15.4 MPa (5.4)) were generally significantly lower than those of conventional fissure sealing (range 15.6 MPa (4.4) to 19.1 MPa (6.2)). The SBS of EFP-3 was better than that of the EFP-1 or EFP-2 formulations. Microleakage was significantly lower in the control group (1.1 %) than in the EFP-1 (3.8 %) and lower than in EFP-3 (7.7 %) group. In the (multiple) linear regression analysis, material and aging significantly influenced SBS. CONCLUSIONS: The SBS of EFP-3 was 15 to 32 % lower than it was for the corresponding controls. CLINICAL RELEVANCE: The SBS is lower, but the main potential benefit of this new approach is a reduced application time in clinical practice.

Adverse effects of salivary contamination for adhesives in restorative dentistry. A literature review.

PURPOSE: To review and critically analyze the literature concerning the influence of salivary contamination on the bond quality of adhesives used in restorative materials by comparing and contrasting the different adhesive materials. METHODS: A detailed search on PUBMED, Cochrane Library, Google Scholar and Web of Science was carried out to identify publications on salivary contamination and dental adhesive materials, from 1990-2017 (March) which resulted in a total of 6,202 web-identified publications. After screening titles/abstracts and de-duplicating, 54 publications were selected that matched the requirements for this review. The condition for selection was English literature concerning the effect of salivary contamination on the adhesives used in restorative dentistry. The obtained articles were systematically evaluated. RESULTS: Salivary contamination of adhesives during restorative procedures statistically (64.6%) showed an adverse effect on adhesives, occurring either at one or many stages of restoration. Methodological dissimilarities impeded the direct comparison of the selected studies. Nevertheless, the 2-step etch and rinse adhesives were relatively less vulnerable to salivary contamination than the others. 65% of the evaluated studies for decontamination achieved improved bonding when the contaminated surface was subjected to some kind of decontamination procedure. However, the duration and other specificities were not standard in all the evaluations and need further research to assess the course of action. It is necessary to do long term studies to evaluate the effectiveness of contaminated adhesive over time. CLINICAL SIGNIFICANCE: Salivary contamination is a potential cause for poor bond quality of adhesive systems during restorative procedures and to provide a successful treatment, proper care must be taken to ensure the operating area is free from contamination. Understanding the properties of the materials and its constituents as well as considering measures to manage the potential vulnerabilities due to salivary contamination in the area of bonding might help a clinician to produce better results.

Influence of extremely high irradiances on the micromechanical properties of a nano hybrid resin based composite.

PURPOSE: To investigate in vitro the effect of extremely high irradiance light-emitting diode (LED) light curing units (LCU) with different exposure distances and curing modes on the micromechanical properties of a nano hybrid resin based composite. METHODS: 72 resin based composite (RBC) (Kalore) specimens with 2 mm thickness were cured using two high irradiance LED LCUs (Bluephase 20i and FlashMax P3) at 0 and 7 mm exposure distances. The curing conditions were:a) Bluephase 20i - 10 seconds - High power; b) Bluephase 20i - 15 seconds - High power; c) Bluephase 20i - 5 seconds - Turbo; d) Bluephase 20i - 15 seconds - Soft start; e) FlashMax P3 - 4 mm tip cover - 3 seconds; f) FlashMax P3 - without tip cover - 3 seconds. The incident and transmitted irradiance and radiant exposure were evaluated in real time during curing, with a radiometer (MARC Resin Calibrator). The micromechanical properties (Vickers hardness, HV and indentation modulus, E) were measured with an automatic universal hardness indenter after storing specimens for 24 hours in distilled water. Data were analyzed with one- and two-way ANOVA tests followed by Tukey test and partial eta-square statistics (α= 0.05). RESULTS: For both LCUs, incident irradiance decreased progressively with increased exposure distance, reaching at 7 mm exposure distance less than 50% of the value measured when the LCU was applied directly on specimen's surface. In descending order of strength of their effects, the parameters incident irradiance (HV; η P2 =0.828, E; 0.693), LCU (HV, 0.257, E, 0.043) and exposure distance (HV, 0.031, E, 0.028) were significant factors affecting HV and E (P < 0.05). The localized radiant exposure (the incident and transmitted) as well as the position of HV and E measurements (top-bottom of the specimen) were additional factors affecting significantly only HV (P < 0.05), but not E (P > 0.05). CLINICAL SIGNIFICANCE: Extremely high irradiances were less efficient in adequate curing of the analyzed nano hybrid composite. Using a protection tip, as clinically indicated, reduces the irradiance of FlashMax P3 from 7,681.7 (160.53) mW/cm2; to 3052.5 (71.61) mW/cm2;.

Which Factors Influence the Shear Bond Strength of Sealant Materials?

PURPOSE: This study investigated the influence of several methodological details on the shear bond strength (SBS) testing of pit and fissure sealants. The following variables were considered: type of enamel surfaces, prismatic vs aprismatic enamel, etching time, and aging and shearing procedures. MATERIALS AND METHODS: The surfaces of 180 healthy human third molars were divided into 4 different sections (mesial, distal, buccal, and oral). After tooth separation, the specimens were randomly allocated to the following groups: 1) enamel preparation: prismatic vs aprismatic; 2) etching: 30 s vs 60 s; 3) aging: 1 day or 3 months vs 5000 thermocycles; 4) shearing: notched-edge method (ISO 29022:2013) vs knife-edge method. After following each protocol, SBS was determined using a universal testing machine, followed by failure mode analysis. Data were analysed using Mann-Whitney U-tests and regression analyses. RESULTS: In the aprismatic enamel group, the longer etching time resulted in slightly, not statistically significantly higher SBS. When aging sealants on aprismatic enamel with different procedures, significantly lower SBS was found for 5000 thermocycles. In the case of aprismatic enamel etched for 60 s and sheared with the notched-edge blade, there was no significant difference between the aging procedures. Failure mode analysis showed adhesive failures to be predominant. Simple linear regression revealed that all of the included factors significantly influenced SBS. In a multiple linear regression model, the variables "aprismatic enamel" and "distal surface" were associated with a higher SBS; "5000 thermocycles" reduced SBS significantly. CONCLUSION: Enamel grinding, aging method, and type of enamel surface significantly influenced the SBS.

Efficacy of four preventive measures against enamel demineralization at the bracket periphery-comparison of microhardness and confocal laser microscopy analysis.

OBJECTIVES: The aim of this in-vitro study was to investigate the efficacy of four preventive measures against enamel demineralization and to compare the suitability of microhardness (MH) measurements and confocal laser microscopy (CLSM). MATERIALS AND METHODS: A total of 80 teeth were randomly allocated into four groups. The effect against demineralization of two coating materials (group 1: resin-modified glass ionomer (RMGI) cement varnish (ClinproXT); group 2: composite sealant (ProSeal)) and that of two types of bracket-bonding material (group 3: amorphous calcium phosphate (ACP) composite (AegisOrtho); group 4: RMGI (FujiOrthoLC)) was compared after pH-cycling by MH and CLSM. Measurements were made at the edge of the coating/bracket as well as at 50, 100, 200, and 400 µm distance. The data were converted into values of mineralization (Vol%) and analyzed by parametric (ANOVA and Tukey's post hoc) or non-parametric (Kruskal-Wallis and Games-Howell post hoc) tests. RESULTS: ClinproXT and ProSeal were proved to protect the bracket periphery. However, the area next to them showed demineralizations. The mean area of lesion (CLSM-data) was significantly different between the groups (p < 0.0001). The smallest lesions were revealed for the RMGI-based materials. MH identified only for group 4 a significant difference between the area next to the bracket base and that at 200 and 400 µm distance. CONCLUSION: There was nearly no lesion under both coatings. A stagnation of demineralization was identified particularly for the RMGI. ProSeal showed an inferior protection of the untreated enamel. MH and CLSM analysis were suitable to detect subsurface lesions. CLINICAL RELEVANCE: A diverse efficacy of materials against enamel demineralization at bracket periphery has to be noticed.

Shear Bond Strength and Microleakage of a New Self-etching/Self-adhesive Pit and Fissure Sealant.

PURPOSE: To evaluate shear bond strength and microleakage of a new self-etching/self-adhesive fissure sealant on prismless enamel compared with conventional fissure sealing. MATERIALS AND METHODS: A total of 90 extracted third molars were assigned to 3 main groups: group 1: self-etching/self-adhesive sealant, without acid etching; group 2: self-etching/self-adhesive sealant, with prior acid etching; group 3: conventional fissure sealing (control group). After specimen preparation, each group was divided into 3 subgroups according to storage time (1-day water storage, 3-month water storage, and 1-day water storage followed by 5000x thermocycling). The shear bond strength was determined with a universal testing machine, according to ISO standard 29022. Afterwards, the failure mode was analyzed. An additional 24 third molars were used for microleakage assessment. The fissure pattern was sealed in strict accordance with the manufacturers' instructions. After thermocycling, the dye penetration was examined. Data were analyzed using the Mann-Whitney U-Test at a significance level of 0.05. RESULTS: The shear bond strength of the self-etching/self-adhesive fissure sealant without prior acid etching was significantly lower (4.3 MPa) than that of the self-etching/self-adhesive fissure sealant with prior acid etching (17.1 MPa) and the conventional fissure sealing (19.1 MPa). Microleakage was significantly lower in the control group (1.1%) and in the group with the self-etching/self-adhesive sealant with prior acid etching (0.8%) compared to the group that used the self-etching/self-adhesive material alone (49.4%). CONCLUSION: The self-etching/self-adhesive fissure sealant can be recommended for clinical use when enamel is etched with phosphoric acid. The self-etching/self-adhesive sealant without prior acid etching showed significantly inferior results.

Effect of different curing protocols on the mechanical properties of low-viscosity bulk-fill composites.

OBJECTIVES: This study aimed to assess the impact of curing conditions-exposure time, mode, energy density and exposure distance-on the efficiency of curing flowable bulk-fill resin-based composites (RBCs) at simulated clinical relevant filling depths. MATERIALS AND METHODS: Four flowable bulk-fill RBCs were investigated by assessing in 200 µm steps the variation in micro-mechanical properties (Vickers hardness (HV) and indentation modulus (E)) within simulated 6-mm-deep fillings (n = 5), considering 16 different curing modes/conditions. The exposure duration was 5, 20 and 40 s in the standard power mode; 3, 4 and 8 s in the high power mode; and 3 and 6 s in the plasma mode. Besides, the curing unit was placed at 0 and 7 mm distance away from the specimen's surface. Measurements were performed after 24 h of storage in distilled water at 37 °C. The depth of cure (DOC) was calculated as the 80 % hardness drop-off. The curing unit's irradiance at exposure distances up to 10 mm was monitored for all irradiation modes in 1 mm steps by means of a laboratory-grade spectrometer. RESULTS: Results were compared using one- and multiple way ANOVA and Tukey's honest significant difference (HSD) post hoc test (α = 0.05). A multivariate analysis (general linear model) assessed the effect strength of the parameters material, energy density reaching the specimen's surface (2.63 to 47.03 J/cm(2)), exposure distance and curing mode on HV, E and DOC. The effect of the parameter material was significant and strong on all measured properties (p < 0.05, partial eta-squared (η P (2)) = 0.683 for E, 0.724 for HV and 0.199 for DOC). Energy density exerted in all materials the strongest influence on the measured properties, while the influence of distance was strong on DOC and low or even not significant on HV and E. CONCLUSIONS: The susceptibility to variation in irradiance under the simulated clinical conditions was material dependent, while lower and upper energy density limits for curing the materials were defined. CLINICAL RELEVANCE: Materials react differently to the supplied irradiance. An exposure time of 20 s at moderate irradiance is recommended for all materials. The highest mechanical properties were reached not at the specimens' surface, but in deeper layers (0.4 to 3.1 mm).

Tensile bond strength of resin composite repair in vitro using different surface preparation conditionings to an aged CAD/CAM resin nanoceramic.

OBJECTIVES: This study was conducted in order to assess the pretreatment method (air abrasion, both wet and dry, and Al2O3 grinder), the conditioning method (comprised of different adhesive systems), the repair resin composite (low and high modulus of elasticity), the contamination of CoJet air-abraded surfaces with water, and the effect phosphoric acid on the macrotensile bond strength (TBS) to aged CAD/CAM resin nanoceramic (RNC). MATERIALS AND METHODS: Aged RNC substrates (LAVA Ultimate, 3M ESPE; N = 900; 10,000 cycles, 5 °C/55 °C) were air-abraded (CoJet 3M ESPE) with and without water contamination or treated with an Al2O3 grinder (Cimara, Voco). Immediately after pretreatment, half of the specimens were additionally cleaned with phosphoric acid, while the rest were only rinsed with water. Four intermediate agents (Futurabond U/VOCO, Scotchbond Universal/3M ESPE, One Coat Bond/Coltène Whaledent, visio.link/bredent) were selected for conditioning the surface, while no conditioned specimens acted as control groups. Specimens were thereafter repaired using two direct resin composites (Arabesk Top and GrandioSo, VOCO), stored for 24 h at 37 °C in H2O, and thermally aged for 10,000 cycles (5 °C/55 °C; n = 15/subgroup). TBS and failure types were determined and evaluated with four- and one-way ANOVA and χ (2) test (p < 0.05). RESULTS: The highest influence on TBS was exerted by the conditioning method (partial eta-squared (η P (2)) = 0.273, p < 0.05), followed by the resin composite repair (η P (2) = 0.07, p < 0.05) and the surface pretreatment method (η P (2) = 0.032, p < 0.05), while an acid contamination after surface pretreatment was insignificant (p = 0.154). CONCLUSIONS: Air abrasion produced superior TBS compared to grinding of the surface with Al2O3 prior to repair. The tested universal adhesives proved to be effective intermediate agents for repairing aged CAD/CAM RNC, while visio.link and Scotchbond Universal performed slightly better than Futurabond U. CLINICAL RELEVANCE: Phosphoric acid or water contamination of the air-abraded surface does not affect the repair bond strength.

Effects of ceramic shade and thickness on the micro-mechanical properties of a light-cured resin cement in different shades.

OBJECTIVE: The aim of this study was to evaluate the micro-mechanical properties of a light-cured resin cement in four different shades when polymerized through a leucite-reinforced glass-ceramic in different shades and thicknesses. MATERIALS AND METHODS: A light-cured resin cement in four different shades (HV+1, HV+3, LV-1 and LV-3) was selected for this study. The specimens were cured by using a LED-unit (Bluephase®, IvoclarVivadent) for 20 s under a leucite-reinforced glass-ceramic (IPS Empress® CAD, IvoclarVivadent) in two different shades (A1 and A3) of different thicknesses (1 and 2 mm). Specimens cured directly, without an intermediate ceramic, served as control. The specimens were stored after curing for 24 h at 37°C by maintaining moisture conditions with distilled water. Micro-mechanical properties (indentation modulus, E; Hardness, HV; creep, Cr) of the resin cements were measured with an automatic microhardness indenter (Fisherscope H100C, Germany). Twenty groups were included (n = 3), while 10 measurements were performed on each specimen. Data were statistically analyzed by using one-way ANOVA and Tukey's post-hoc test, as well as a multivariate analysis to test the influence of the study parameters. RESULTS: Significant differences were observed between the micromechanical properties of the tested resin cements (p < 0.05). The resin cement shade showed the highest effect on the micromechanical properties (Partial-eta squared (ηP(2))-E = 0.45, ηP(2)-HV = 0.59, ηP(2)-Cr = 0.29) of the resin cement, followed by ceramic thickness (ηP(2)-E = 0.38, ηP(2)-HV = 0.3, ηP(2)-Cr = 0.04) and ceramic shade (ηP(2)-E = 0.2, ηP(2)-HV = 0.26). CONCLUSIONS: Resin cement shade is an important factor influencing the mechanical properties of the material. Light shades of a resin cement express higher E and HV as well as lower Cr values compared with the darker ones.

Quantification of the amount of blue light passing through monolithic zirconia with respect to thickness and polymerization conditions.

STATEMENT OF PROBLEM: Dual-polymerized luting composite resin cements would benefit from enhanced irradiance transmitted through a ceramic restoration. A quantification of the amount of transmitted light through translucent zirconia is lacking. PURPOSE: The purpose of this study was to evaluate the amount of light (360 to 540 nm) passing through translucent and conventional zirconia and a glass ceramic with respect to material thickness and different polymerizing modes. MATERIAL AND METHODS: Six translucent and a conventional zirconia (negative control) and a glass ceramic (positive control) were considered. Ten specimens of each material and thickness (.5, 1, 1.5, 2, 2.5, 3 mm) were fabricated (n=480). Zirconia materials were sintered according to manufacturers' instructions. The irradiance passing the different ceramics and thicknesses was measured with a violet-blue LED polymerizing unit in 3 polymerizing modes (plasma, high, and standard power mode) with a USB4000 Spectrometer. The polymerizing unit was placed directly on the specimen's surface. Data were analyzed with one and multivariate analysis and the Pearson correlation analysis (α=.05). RESULTS: In all materials, the translucency and its rate decreased exponentially according to the specimen thickness. The highest influence on the measured irradiance passing through translucent zirconia was exerted by ceramic thickness (P<.05, partial eta squared [ηP²]=.998), closely followed by polymerizing mode (ηP²=.973), while the effect of the material (P=.03, ηP²=.06) and mean grain size (P=.029, ηP²=.027) was significant but low. CONCLUSIONS: Zirconia was less translucent than the glass ceramic, but the translucency decreased more slowly with material thickness, thus approaching the translucency of glass ceramics at a specimen thicknesses of 2.5 to 3 mm.

Translucency of esthetic dental restorative CAD/CAM materials and composite resins with respect to thickness and surface roughness.

STATEMENT OF PROBLEM: Little information is available about the translucency of monolithic CAD/CAM materials. PURPOSE: The purpose of this study was to evaluate the translucency of restorative CAD/CAM materials and direct composite resins with respect to thickness and surface roughness. MATERIALS AND METHODS: In total, 240 disk-shaped specimens (12×14×1 mm and 12×14×2 mm) of 3 different CAD/CAM glass ceramics (CELTRA Duo, IPS e.max CAD, IPS Empress CAD), a fine-structure feldspathic ceramic (VITA Mark II), a hybrid ceramic (VITA Enamic), a resin nanoceramic composite resin (LAVA Ultimate), an experimental (CAD/CAM nanohybrid composite resin), 2 interim materials (Telio CAD; VITA CAD-Temp), and 3 direct composite resins (Tetric EvoCeram; Filtek Supreme XTE; Tetric EvoCeram Bulk Fill) were fabricated (n=10). After 3 different surface pretreatments (polished, rough SiC P1200, or SiC P500), absolute translucency and surface roughness were measured using spectrophotometry and tactile profilometry. The influence of material type, thickness, and roughness on absolute translucency was analyzed using a multivariate analysis, 1-way ANOVA, and the Tukey HSD post hoc test (P<.05). Pearson correlations and statistical hypothesis tests were used to assess the results (P<.05). RESULTS: The effect of all tested parameters was significant among the materials (P<.05). The greatest influence on the measured translucency was thickness (partial eta squared ηP²=.988), closely followed by material (.982), and the pretreatment method (.835). The surface roughness was strongly influenced by the pretreatment method (.975) and type of material (.941). CONCLUSION: Thickness and surface roughness are major factors affecting the absolute translucency of adhesively luted restorations.

Polymerization kinetic calculations in dental composites: a method comparison analysis.

OBJECTIVES: This study aimed to describe the polymerization process and to quantify the parameters of influence in two bulk-fill resin-based composites by comparing two real-time methods: the Fourier transform infrared (FTIR) spectroscopy and the visible light transmission spectrometry. MATERIALS AND METHODS: The degree of conversion (DC) was recorded in real time for 5 min using the attenuated total reflectance FTIR spectroscopy (n = 6) on the lower surface of 2, 4, and 6 mm thick samples irradiated for 20 s. The variation in irradiance was recorded during material irradiation at the bottom of the samples (n = 5). Results were statistically analyzed using one-way and multiple-way ANOVAs with Tukey HSD post hoc test (α = 0.05), partial eta-squared statistics, and Pearson correlation. RESULTS: No significant difference was found in DC in any materials as a function of incremental thickness, whereas the irradiance passing the specimens differed consistently within both analyzed increments and materials. These data could be described by the superposition of two exponential functions, the first being attributed to the gel phase and the second to the glass phase, resulting in an exponential sum function. DC data were able to calculate the end of the gel phase and the beginning of the glass phase, whereas irradiance measurements were able to detect only the last phase. The polymerization kinetics in the glass phase was less material-dependent as in the gel phase. CONCLUSIONS: The irradiance measurements were more sensitive to variation in thickness, meaning that translucency is continuing to change as a function of thickness at a higher extent than DC. CLINICAL RELEVANCE: Knowing the impact of the modulation factors describing the calculated sum exponential function allows the manipulation of the polymerization process at different stages to tailor material properties.

Light transmittance and micro-mechanical properties of bulk fill vs. conventional resin based composites.

OBJECTIVES: The aim of this study was to quantify the blue light that passes through different incremental thicknesses of bulk fill in comparison to conventional resin-based composites (RBCs) and to relate it to the induced mechanical properties. MATERIALS AND METHODS: Seven bulk fill, five nanohybrid and two flowable RBCs were analysed. Specimens (n = 5) of three incremental thicknesses (2, 4 and 6 mm) were cured from the top for 20 s, while at the bottom, a spectrometer monitored in real time the transmitted irradiance. Micro-mechanical properties (Vickers hardness, HV, and indentation modulus, E) were measured at the top and bottom after 24 h of storage in distilled water at 37 °C. Electron microscope images were taken for assessing the filler distribution and size. RESULTS: Bulk fill RBCs (except SonicFill) were more translucent than conventional RBCs. Low-viscosity bulk fill materials showed the lowest mechanical properties. HV depends highly on the following parameters: material (ηp (2) = 0.952), incremental thickness (0.826), filler volume (0.747), filler weight (0.746) and transmitted irradiance (0.491). The bottom-to-top HV ratio (HVbt) was higher than 80 % in all materials in 2- and 4-mm increments (except for Premise), whereas in 6-mm increments, this is valid only in four bulk fill materials (Venus Bulk Fill, SDR, x-tra fil, Tetric EvoCeram Bulk Fill). CONCLUSIONS: The depth of cure is dependent on the RBC's translucency. Low-viscosity bulk fill RBCs have lower mechanical properties than all other types of analysed materials. All bulk fill RBCs (except SonicFill) are more translucent for blue light than conventional RBCs. SIGNIFICANCE: Although bulk fill RBCs are generally more translucent, the practitioner has to follow the manufacturer's recommendations on curing technique and maximum incremental thickness.

Effect of sonic-activated resin composites on the repair of aged substrates: an in vitro investigation.

OBJECTIVES: This study aimed to evaluate whether sonic-activated resin-based composites (RBCs) used as repair materials might improve the repair bond strength of aged RBC substrates. MATERIALS AND METHODS: Five RBCs were repaired by themselves and by all other materials. The repair was applied with and without sonic activation, resulting in 50 material application technique combinations (n = 15) and 750 specimens. The cohesive strength of the five materials was used as control (n = 15). Substrates were aged for 8 weeks in distilled water at 37 °C, roughened, cleaned with phosphoric acid, and repaired by using a silane primer and an adhesive as intermediate agents. The repair bond strength was assessed in a shear test. The modulus of elasticity (E) of the five RBCs was additionally evaluated in a three-point bending test. RESULTS: Results were compared using one- and multiple-way analyses of variance and Tukey's honestly significant difference post hoc test (α = 0.05), partial eta-square statistics, Pearson's correlation, and Weibull's analysis. No significant effect of sonic activation on the repair material was found in any material combination. The repair strength was 35.4-90.9 % of the cohesive strength of the original composites. E varied between 4.1 GPa (CLEARFIL MAJESTY Esthetic) and 9.7 GPa (CLEARFIL MAJESTY Posterior). The strongest influence on the shear bond strength was performed by E repair (η (2) P = 0.167), whereas the effect of E substrate was significant but low (η (2) P = 0.098). None of these parameters influenced the reliability of the repaired specimens (the Weibull parameter, m). The fracture pattern was mainly cohesive (93.3 %) in the control group and predominantly adhesive (89.2 %) in the repaired specimens. CONCLUSIONS: Except for the material with the highest modulus of elasticity used as a substrate material, it was not detrimental to combine different RBCs in terms of repair. CLINICAL RELEVANCE: If a substrate material is unknown, the recommendation for repairing would be in favor of a material with a high modulus of elasticity.