The Effects of a Novel Nanohydroxyapatite Gel and Er: YAG Laser Treatment on Dentin Hypersensitivity.

PURPOSE: This study evaluates the effects of a novel nanohydroxyapatite gel and Er: YAG laser on the surface roughness, surface morphology, and elemental content after dentin hypersensitivity treatments. METHODS: Dentin discs (2 × 3 × 3 mm3) were prepared from 75 human molars. Out of 75 human molars, 50 were used to evaluate surface roughness and randomly divided into five groups: Group ID (intact dentin), Group DD (demineralized dentin), Group BF (fluoride varnish/Bifluorid 10), Group Lsr (Er: YAG laser-50 mJ, 0.50 W, 10 Hz), and Group NHA (nanohydroxyapatite-containing gel). Dentin hypersensitivity was stimulated by 35% phosphoric acid for 1 min (except Group ID). The surface roughness (Ra, µm) was measured via contact profilometry (n = 10). Out of the 75 sound human molars, 25 were used to evaluate the surface morphology and elemental content using scanning electron microscopy and energy-dispersive X-ray spectroscopy (n = 5). The data were statistically analyzed using Welsch ANOVA, Games-Howell, Kruskal-Wallis, and Dunn tests (p < 0.05). RESULTS: Group Lsr showed significantly lower surface roughness than Group NHA and Group BF (p < 0.05). The SEM analysis indicated that most of the dentinal tubules were obliterated for Group NHA. Precipitant plugs with partially occluded dentinal tubules were observed for Group BF, while partially or completely occluded tubules with a melting appearance were detected for Group Lsr. The EDS analysis revealed that Group NHA and Group Lsr presented similar calcium and phosphorus amounts to Group ID. All dentin hypersensitivity treatment methods could provide promising results in terms of tubular occlusion efficiency. However, laser treatment resulted in smoother surfaces, which could help prevent dental plaque accumulation.

Comparison of a Nanofiber-Reinforced Composite with Different Types of Composite Resins.

The aim of this study was a comprehensive evaluation and comparison of the physical and mechanical properties of a newly developed nano-sized hydroxyapatite fiber-reinforced composite with other fiber-reinforced and particle-filled composites. Commercially available eight composite resins (3 fiber-reinforced and 5 particle-filled) were used: Fiber-reinforced composites: (1) NovaPro Fill (Nanova): newly developed nano-sized hydroxyapatite fiber-reinforced composite (nHAFC-NF); (2) Alert (Pentron): micrometer-scale glass fiber-reinforced composite (µmGFC-AL); (3) Ever X Posterior (GC Corp): millimeter-scale glass fiber-reinforced composite (mmGFC-EX); Particle-filled composites: (4) SDR Plus (Dentsply) low-viscosity bulk-fill (LVBF-SDR); (5) Estelite Bulk Fill (Tokuyama Corp.) low-viscosity bulk-fill (LVBF-EBF); (6) Filtek Bulk Fill Flow (3M ESPE) low-viscosity bulk-fill (LVBF-FBFF); (7) Filtek Bulk Fill (3M ESPE) high-viscosity bulk-fill (HVBF-FBF); and (8) Filtek Z250 (3M ESPE): microhybrid composite (µH-FZ). For Vickers microhardness, cylindrical-shaped specimens (diameter: 4 mm, height: 2 mm) were fabricated (n = 10). For the three-point bending test, bar-shaped (2 × 2 × 25 mm) specimens were fabricated (n = 10). Flexural strength and modulus elasticity were calculated. AcuVol, a video image device, was used for volumetric polymerization shrinkage (VPS) evaluations (n = 6). The polymerization degree of conversion (DC) was measured on the top and bottom surfaces with Fourier Transform Near-Infrared Spectroscopy (FTIR; n = 5). The data were statistically analyzed using one-way ANOVA, Tukey HSD, Welsch ANOVA, and Games-Howell tests (p < 0.05). Pearson coefficient correlation was used to determine the linear correlation. Group µH-FZ displayed the highest microhardness, flexural strength, and modulus elasticity, while Group HVBF-FBF exhibited significantly lower VPS than other composites. When comparing the fiber-reinforced composites, Group mmGFC-EX showed significantly higher microhardness, flexural strength, modulus elasticity, and lower VPS than Group nHAFC-NF but similar DC. A strong correlation was determined between microhardness, VPS and inorganic filler by wt% and vol% (r = 0.572-0.877). Fiber type and length could affect the physical and mechanical properties of fibers containing composite resins.

Repair Bond Strength to Hybrid CAD/CAM Materials after Silane Heat Treatment with Laser.

PURPOSE: This study investigated the effect of different surface treatments and the effect of silane heat treatment with laser on the shear bond strength (SBS) of a nanoceramic composite to repaired hybrid CAD/CAM blocks. MATERIALS AND METHODS: 60 hybrid CAD/CAM specimens (Cerasmart, GC) were prepared and randomly divided into six groups according to the different surface treatments (n = 10): group ER: Er:YAG laser+silane (Monobond Plus, Ivoclar Vivadent); group ER+SHT: Er:YAG laser+silane heat treatment; group B: bur+silane; group B+SHT: bur+silane heat treatment; group HF: hydrofluoric acid+silane; group HF+SHT: hydrofluoric acid+silane heat treatment. Afterwards, a universal adhesive (Universal Bond Quick, Kuraray) was applied, and nanoceramic resin composite (Zenit, President) cylinders were bonded to the Cerasmart specimens. They were thermocycled for 10,000 cycles (5-55°C) and subjected to SBS testing using a universal testing machine. Failure modes were examined with a stereomicroscope (15X). Scanning electron microscopy (SEM) was used to evaluate the surface topography (n = 2). The data were statistically analyzed using the Mann-Whitney U-test and the Kruskal-Wallis test (p < 0.05). RESULTS: Regarding the surface treatments, group ER showed significantly lower SBS than groups B and HF (p < 0.05). Regarding the presence of silane heat treatment by laser, groups ER+SHT and B+SHT showed significantly lower SBS than group HF+SHT(p < 0.05). In addition, group B+SHT showed significantly lower SBS than did group B (p < 0.05). CONCLUSION: Er:YAG laser treatment for repairing hybrid CAD/CAM blocks was not as effective as bur roughening or hydrofluoric acid etching. Silane heated by Er:YAG laser was incapable of significantly increasing the bond strength to repaired hybrid CAD/CAM blocks.

The effect of curing modes and times of Third-Generation led LCU on the mechanical properties of nanocomposites / Efecto del modo y tiempo de fotocurado de la lámpara LCU Led de tercera generación en las propiedades mecánicas de los nanocompuestos

Abstract This study evaluates the effect of curing modes and times on the mechanical properties of nanocomposites. Two nanocomposite resins were investigated: suprananohybrid (Estelite Posterior Quick; EP) and nanohybrid (Solare X; SX). They were polymerized with a light-emitting diode light-curing units (LED LCU, Valo) as follows: standard mode for 20s (ST20), high power mode for 12s (HP12), high power mode for 20s (HP20), extra power mode for 6s (XP6), and extra power mode for 20s (XP20). For Vickers microhardness (HV), disc-shaped specimens were fabricated (n=10). For the three-point bending test, bar-shaped specimens were fabricated (n=10). Flexural strength and resilience modulus were calculated. The fractured surfaces and specimen surfaces of composites were observed using scanning electron microscopy. The data were analyzed with repeated measures ANOVA, two-way variance, and Bonferroni tests (p<0.05). On the top and bottom surfaces of the EP nanocomposite resin, ST20 and HP12 revealed statistically higher HV than with XP6. Moreover, HP20 and XP20 had statistically higher HV than HP12 and XP6. For the SX nanocomposite resin, HP20 had statistically higher HV than HP12. For EP and SX, there were no significant differences in flexural strength and resilience modulus regarding the curing modes and times. Furthermore, SX demonstrated lower mechanical properties than EP. Scanning electron microscopy indicated that both nanocomposites had similar surface appearances. However, with all curing modes and times, SX exhibited layered fractures and more crack formations than EP. Different curing modes and times could influence the microhardness of nanocomposites.

Resumen Este estudio evalúa el efecto del modo y tiempo de fotocurado sobre las propiedades mecánicas de los nanocompuestos. Se investigaron dos resinas nanocompuestas: supra-nanohíbrida (Estelite Posterior Quick; EP) y nanohíbrida (Solare X; SX). Se polimerizaron con unidades de fotopolimerización de diodos emisores de luz (LED LCU, Valo) de la siguiente manera: modo estándar durante 20s (ST20), modo de alta potencia durante 12s (HP12), modo de alta potencia durante 20s (HP20) , modo extra power durante 6s (XP6) y modo extra power durante 20s (XP20). Para la microdureza Vickers (HV), se fabricaron especímenes en forma de disco (n=10). Para el ensayo de flexión de tres puntos, se fabricaron probetas en forma de barra (n=10). Se calcularon la resistencia a la flexión y el módulo de resistencia. Las superficies fracturadas se observaron mediante microscopía electrónica de barrido. Los datos se analizaron con ANOVA varianza de dos vías y pruebas de Bonferroni (p<0,05). En las superficies superior e inferior de la resina nanocompuesta EP, ST20 y HP12 revelaron un HV estadísticamente mayor que con XP6. Además, HP20 y XP20 tenían un HV estadísticamente más alto que HP12 y XP6. Para la resina nanocompuesta SX, HP20 tenía un HV estadísticamente más alto que HP12. Para EP y SX, no hubo diferencias significativas en la resistencia a la flexión y el módulo de resistencia con respecto al modo y tiempo de fotocurado. Además, SX demostró propiedades mecánicas inferiores que EP. La microscopía electrónica de barrido indicó que ambos nanocompuestos son similares en la superficie. Sin embargo, SX exhibió fracturas en capas y más formaciones de grietas que EP. Diferentes modos y tiempos de fotocurado podrían influir en la microdureza de los nanocompuestos.

The effect of fiber insertion on fracture strength and fracture modes in endocrown and overlay restorations.

Aim of this study was to determine the fracture strength and modes of endocrown and overlay restorations with/without fiber reinforcement on endodontically treated teeth. Sixty-five molar teeth were used: Group IN (intact teeth), Group E (endocrown), Group ER (endocrown + ribbond), Group O (overlay), Group OR (overlay + ribbond; n = 13). Ribbond (Seattle, WA) was inserted at the base of pulp chamber in Group ER and OR. All restorations were designed and produced by using computer-aided design and computer-aided manufacturing (Sirona Dental Systems, Bensheim, Germany) and Cerasmart (GC Corp. Kasugai, Aichi, Japan). All teeth were subjected to thermomechanical aging and fractured in a universal test device. Fractured surfaces were analyzed with a stereomicroscope (SMZ1000, Nikon, Japan). Data were analyzed with Welch's analysis of variance and Games-Howell test (p < .001). Group E showed significantly lower fracture strength values than other groups(p < .05). No statistically significant differences were found among the other groups(p > .05). Most of the unfavorable fractures were seen in Groups E and O. Overlay restorations showed higher fracture strength values than endocrown restorations. Although fiber insertion did not improve the fracture strength of the indirect restorations, it reduced the frequency of irreparable fracture mode. Overlay restorations and fiber application are more advantageous in preserving the durability of the endodontically treated teeth.

How does antiseptic mouthwashes against SARS-COV-2 affect the bond strength of universal adhesive to enamel?

This study compares the effect of different mouthwashes that have been recommended during the Coronavirus disease 2019 (COVID-19) pandemic on shear bond strength (SBS) of universal adhesive to enamel in regards to self-etch (SE) and etch-and-rinse (ER) modes. Flat enamel surfaces were obtained from 100 sound human maxillary central incisors. They were randomly allocated to five groups according to the different mouthwashes (no mouthwash/control [Ctrl], 0.2% chlorhexidine 1.5% hydrogen peroxide [H2 O2 ], 0.2% povidone-iodine [PVP-I], Listerine [L]), and adhesive application modes (ER and SE) (n = 10). After the application of a universal adhesive (single bond universal), composite resin (Filtek Z250) was bonded by a cylinder-shaped mold (height: 2 mm, diameter: 2.4 mm). They were subjected to SBS test using a universal testing machine (AGS-X, Shimadzu Corp.) (crosshead speed: 1 mm/min). The resin-enamel interfaces were observed with a scanning electron microscope (SEM). The semiquantitative chemical microanalyses were performed with energy-dispersive spectroscopy (EDS). The data were statistically analyzed by two-way analysis of variance and Bonferroni test (p < .05). In SE mode, Group Ctrl revealed significantly higher SBS than all mouthwash groups (p < .05). In ER mode, Group Ctrl showed significantly higher SBS than H2 O2 and PVP-I groups (p < .05). ER mode caused significantly higher SBS than SE mode in all mouthwash groups (p < .05). The SEM observations highlighted that Group Ctrl had a regular and intact hybrid layer with resin tag formation while the H2 O2 and PVP-I groups exhibited a thin hybrid layer in both modes. EDS analysis indicated that in SE mode, all mouthwash groups presented increased O content compared to Group Ctrl. H2 O2 and PVP-I that were suggested for preprocedural use during the COVID-19 pandemic, reduced the enamel bond strength of the universal adhesive in ER mode.

Can Fiber Application Affect the Fracture Strength of Endodontically Treated Teeth Restored with a Low Viscosity Bulk-Fill Composite?

OBJECTIVE: The aim of this study is to evaluate the effects of different fiber insertion techniques and thermomechanical aging on the fracture resistance of endodontically treated mandibular premolar teeth restored using bulk-fill composites. MATERIALS AND METHODS: Eighty human mandibular premolar teeth were randomly divided into eight groups: Group IN, Group BF, Group PRF1, Group PRF2, Group IN-TMA, Group BF-TMA, Group PRF1-TMA ,and Group PRF2-TMA. Group IN (intact) and Group IN-TMA (intact but subjected to thermomechanical aging) served as control groups. In the other six groups, endodontic treatment was performed and standardized mesio-occluso-distal (MOD) cavities were prepared. In BF, PRF1, and PRF2, the cavities were restored with bulk-fill composite only, bulk-fill/Ribbond, and bulk-fill/additional Ribbond, respectively. In BF-TMA, PRF1-TMA, and PRF2-TMA, the teeth were subjected to thermomechanical aging after the restorations. All of the teeth were fractured on the universal testing machine. Fracture surfaces were analyzed with a stereomicroscope. RESULTS: Control groups showed significantly higher fracture strengths than tested groups (P<0.05). No statistically significant difference was observed among the tested groups (P>0.05). Most of the favorable fractures were seen in PRF1, PRF2, and PRF2-TMA. Most of the unfavorable fractures were seen in BF-TMA. CONCLUSIONS: Although fiber insertion with different techniques did not increase the fracture strength of teeth restored with bulk-fill composites, it increased the favorable fracture modes. Thermomechanical aging did not change the fracture strength of the groups.

Microhardness and water solubility of expired and non-expired shelf-life composites.

BACKGROUND:: The aim of this study was to determine the Vickers hardness and water solubility of expired and non-expired shelf-life bulk-fill and conventional dental composite material. METHODS:: Four different expired (E) (after 6 months) and non-expired (N) shelf-life composite resin materials (Clearfil Majesty ES-2 Enamel, Clearfil Majesty ES-2 Dentin, Tetric N-Ceram Bulk-Fill, and Tetric N-Ceram) were used. For each tested material, seven specimens were prepared and polymerized with a light curing unit. Vickers hardness measurements were made on the top and bottom surfaces. For the water sorption test, initially all specimens were weighted, the thickness and diameter of each specimen were measured, and the average volume of specimen was calculated. Then, each specimen was immersed in distilled water and kept in an incubator for 7 days and finally weighed again. RESULTS:: There was not any statistically significant difference between the microhardness results of expired and non-expired shelf-life composites on the top and bottom surfaces (p > 0.05). No significant difference was determined between the non-expired shelf-life composite materials on the top surfaces (p > 0.05). Non-expired Clearfil Majesty ES-2 Dentin showed lower microhardness than non-expired Tetric N-Ceram Bulk-Fill and non-expired Tetric N-Ceram on the bottom surface (p < 0.05). Expired Clearfil Majesty ES-2 Dentin showed lower microhardness results than expired Tetric N-Ceram Bulk-Fill on the top and bottom surfaces (p < 0.05). There was not any significant difference between the water sorption results of expired and non-expired shelf-life composites (p > 0.05). Expired Clearfil Majesty ES-2 Dentin showed higher water sorption than expired Tetric N-Ceram E-TN (p < 0.05). CONCLUSION:: Expiration date did not affect the microhardness and water sorption of bulk-fill and conventional composites. The hardness and water sorption of the composite materials varied depending on the type of composites.

Use of Artificial Neural Network in Determination of Shade, Light Curing Unit, and Composite Parameters' Effect on Bottom/Top Vickers Hardness Ratio of Composites.

OBJECTIVE: To assess the influence of light emitting diode (LED) and quartz tungsten halogen (QTH) light curing unit (LCU) on the bottom/top (B/T) Vickers Hardness Number (VHN) ratio of different composites with different shades and determination of the most significant effect on B/T VHN ratio of composites by shade, light curing unit, and composite parameters using artificial neural network. METHOD: Three composite resin materials [Clearfil Majesty Esthetic (CME), Tetric N Ceram (TNC), and Tetric Evo Ceram (TEC)] in different shades (HO, A2, B2, Bleach L, Bleach M) were used. The composites were polymerized with three different LED LCUs (Elipar S10, Bluephase 20i, Valo) and halogen LCU (Hilux). Vickers hardness measurements were made at a load of 100 g for 10 sec on the top and bottom surfaces and B/T VHN ratio calculated. The data were statistically analyzed with three-way ANOVA and Tukey test at a significance level of 0.05. The obtained measurements and data were then fed to a neural network to establish the correlation between the inputs and outputs. RESULTS: There were no significant differences between the B/T VHN ratio of LCUs for the HO and B shades of CME (p>0.05), but there were significant differences between the B/T VHN ratio of LCUs for shade A2 (p<0.05). No significant difference was determined between the B/T VHN ratio of LCUs for all shades of TNC (p>0.05). For TEC, there was no significant difference between the B/T VHN ratio of halogen and LED LCUs (p>0.05), but a significant difference was determined among the LED LCUs (p<0.05). The artificial neural network results showed that a combination of the curing light and composite parameter had the most significant effect on the B/T VHN ratio of composites. Shade has the lowest effect on the B/T VHN ratio of composites. CONCLUSION: The B/T VHN ratio values of different resin-based composite materials may vary depending on the light curing device. In addition, the artificial neural network results showed that the LCU and composite parameter had the most significant effect on the B/T VHN ratio of the composites. Shade has the lowest effect on the B/T VHN ratio of composites.

Influence of powdered dentin on the shear bond strength of dentin bonding systems.

This study evaluated the effect of different amounts of dentin powder (DP) mixed in Clearfil SE Bond (CSB) or Single Bond (SB) on adhesion to dentin. Human third molars (n=96) were sectioned to expose the mid-coronal dentin and divided into eight experimental groups (n=12 per group), namely, Group 1: CSB, Group 2: CSB+1.5 mg DP, Group 3: CSB+3 mg DP, Group 4: CSB+4.5 mg DP, Group 5: SB, Group 6: SB+1.5 mg DP, Group 7: SB+3 mg DP, and Group 8: SB+4.5 mg DP. Filtek Z250 composite was bonded onto dentin, and all specimens were subjected to shear bond strength test at a crosshead speed of 1 mm/min. Highest bond strength was obtained in Groups 1, 2, and 3 (15.1, 13.5, and 16.4 MPa respectively; p>0.05) and the lowest in Groups 6, 7, and 8 (5.5, 5.6, 4 MPa; p>0.05). DP addition, regardless of amount, adversely affected the bond strength of SB. Bond strength of CSB was not affected when 1.5 or 3 mg of DP was added.

Two-year clinical evaluation of three adhesive systems in non-carious cervical lesions.

OBJECTIVES: Adhesive systems are continuously being introduced to Dentistry, unfortunately often without sufficient clinical validation. The aim of this study was to evaluate the clinical performance of cervical restorations done with three different adhesive systems. MATERIAL AND METHODS: 158 non-carious cervical lesions of 23 patients were restored with a nanofilled composite resin (Filtek Supreme, 3M/ESPE) combined with Single Bond (3M/ESPE, group SI), Clearfil SE (Kuraray Medical Inc., group CL) and Xeno III (De Trey Dentsply, group XE). In groups SI-B, CL-B and XE-B, the outer surface of the sclerotic dentin was removed by roughening with a diamond bur before application of the respective adhesive systems. In groups CL-BP and XE-BP, after removal of the outer surface of the sclerotic dentin with the bur, the remaining dentin was etched with 37% phosphoric acid and the self-etch adhesive systems Clearfil SE and Xeno III were applied, respectively. Lesions were evaluated at baseline, and restorations after 3 months, 1 year and 2 years using modified USPHS criteria. RESULTS: After 2 years, no significant difference was found between the retention rates of the groups (p >0.05). Although groups CL and SI showed significantly better marginal adaptation than group XE (p<0.05) at 2 years, no significant difference was found between the marginal adaptation of the groups SI-B, CL-B and XE-B (p>0.05). After 2 years no significant difference was observed among the marginal staining results of all groups (p>0.05). CONCLUSION: Although all adhesive systems showed similar retention rates, Clearfil SE and Single Bond showed better marginal adaptation than Xeno III after 2 years of follow-up.