GC Corporation Research Articles

Comparative Study Regarding the Surface Roughness of Highly Viscous Flowable Composites After Immersion in Acidic Drinks

The aim of the present study was to assess, by profilometry, the effect of different immersion regimes in Coca-Cola drink on the surface roughness of two highly viscous flowable composite resins. The studied materials were Gradia Direct LoFlo (GC Corporation,Tokyo, Japan) and Micro Esthetic flow-viscous (Bisico, Germany). Fifteen cylindrical samples having the of 5 mm and the thickness of 2 mm were made from each material using plastic molds placed on glass plates. The samples were light-cured for 40s on both sides through the glass plates, to ensure complete polymerization of the material. They were divided into two groups as follows: Group I. Gradia Direct LoFlo and Group II. Micro Esthetic flow-viscous. Specimens of each group were then randomly divided into 5 subgroups. In subgroup A (control group) 4 samples were kept only in artificial saliva. In subgroups B-E (each having 4 samples) the samples were immersed in Coca-Cola drink according to 4 different protocols. The mean values of roughness parameters, Ra, were calculated. The Kolmogorov-Smirnov normality test was used to determine the distribution of data in groups. ANOVA and Tukey post hoc statistical tests were used to compare the results from the groups. For both materials, the highest surface roughness was determined for the samples that were submerged 7 times/day in Coca Cola. The assessment of surface microstructure of the samples, after immersion, revealed for both materials a statistically significant increase of Ra values.

Characterization of Bioactive Restoration/Dentine Interface

Objectives: To characterize the bonding interfaces of a calcium silicate-based restorative material (Biodentine) and CPP/ACP-modified glass ionomer with dentine. Also, this study was designed to evaluate the influence of dentine-surface treatment with poly acrylic acid on the bonding of both materials to dentine.Methods: Sixty caries-free human molars were used in this study. Specimens were randomly divided into three groups according to type of restorative material used (n=20); calcium silicate-based (Biodentine, Septodont, France), conventional GIC Fuji VII-EP, GC Corporation, Tokyo, Japan) or CPP/ACP-modified glass ionomer (Fuji VII-EP, GC Corporation, Tokyo, Japan). Each group was divided into 2 sub-groups relative to the dentine surface treatment method (n=10); the dentine in control group was left without treatment, while the dentine surface in test groups was conditioned with poly acrylic acid (PAA) for 10s prior to the application of restorative. In each subgroup,5 specimens were double-labeled with fluorescein and rhodamine-B dyes then observed under a confocal laser scanning microscopy (CLSM). While the remaining 5 specimens were observed under scanning electron microscopy (SEM) then subjected to EDX elemental analysis.Results: CLSM micrographs showed that the mineral rich zone (MRZ) was obvious in non-conditioned Biodentine groups compared to conditioned groups. Both GICs groups exhibited obvious ion-exchange zones. In the non-conditioned Biodentine groups, polygonal crystal deposition was noticed beneath the hybrid layer. These findings were confirmed by the outcome of micromorphological analysis of restoration/tooth interface using SEM.Conclusions: Calcium silicate-based restorative material has a great affinity to exchange ions with tooth substrate and to bond chemically with dentine. The results of this study showed that calcium silicate-based restorative material (Biodentine) can be applied directly on dentine surface without any pre-surface treatment.

Assessing the effect of ceramic additives on the physical, rheological and mechanical properties of conventional glass ionomer luting cement – An in-vitro study

AimTo evaluate the effect of the addition of conventional ceramics on the physical, rheological and mechanical properties of conventional glass ionomer luting cement. Materials and methods5%, 10%, 15% and 20% (w/w) of Enamel and Body conventional ceramic additives (E44 Enamel and B96/c4 Body) were reinforced in the two commercially available glass ionomer luting cement – GC Fuji I (GC Corporation Tokyo, Japan) and Ketac Cem Radiopaque (3M ESPE AG). Setting time, film thickness and compressive strength of the cement was measured according to the American Dental Association Specification number 96 for luting cement. Enthalpy change of the cement reaction was measured with the help of Differential Scanning Calorimetry analysis. Compatibility between the sizes of powder particles was measured with the help of a particle size analyzer. Results5% of ceramic additive could not improve much of the compressive strength. Compressive strength increased significantly (p < 0.05) with the addition of 10% of ceramic additive, beyond which, there was a gradual decrease in strength. Although the setting time and film thickness were also shown to increase due to the additive, the former did not exceed the limit specified by the American Dental Association Specification number 96 (2–8 min for setting time and 25 microns for film thickness). ConclusionAddition of 10% of conventional ceramics resulted in a significant increase in the compressive strength of GIC Luting Cement without any significant compromise in its setting time. The substantial increase in film thickness is a major limitation. Use of ceramic additives with physical properties compatible with that of the glass ionomer cement may aid in increasing the compressive strength without compromising its setting time or film thickness.

An In-vitro Comparison of the Shear Bond Strength of Three Different Composite Materials with Three Different Etchants for the Bonding of Orthodontic Brackets.

IntroductionEsthetics, being the major concern of today’s treatments, has led to numerous innovations, including composites, for different treatment options. Esthetic orthodontics requires the use of composites for bonding orthodontic brackets to the teeth.AimsTo identify which combination of composites has the highest shear bond strength at the tooth-bracket interface.Materials and methodsThree different composite kits were selected for each group (n=42) and were further divided into three subgroups (n=14), where the bonding agents and/or primer were interchanged to find the best combination.ResultsSub-group B2 (Orthofix + Eazetch + Universal Bond) showed the highest shear bond strength (10.74 ± 3.45 MPa), which was highly significant at p =/<0.0001.ConclusionThe highest shear bond strength was found with the combination of 37% phosphoric acid (Eazetch), GC Universal Bond (GC Corporation, Tokyo, Japan), and Orthofix composite material (Anabond Stedman, Chennai, India). As this study is an in-vitro study, we need longitudinal in-vivo studies to establish the best combination for the bonding of orthodontic brackets.

Effect of different CAD-CAM materials on the marginal and internal adaptation of endocrown restorations: An in vitro study

Statement of problemRecent resin-based and ceramic-based computer-aided design and computer-aided manufacturing (CAD-CAM) materials have been used to restore endodontically treated teeth. Adaptation of the restoration is important for clinical success, but studies evaluating the effect of these materials on the adaptation of endocrowns are lacking. PurposeThe purpose of this in vitro study was to evaluate the effect of resin-based and ceramic-based materials on the marginal and internal adaptation of endocrowns. Material and methodsForty mandibular molars were divided into 4 groups (n=10); each group was restored with a different CAD-CAM material: group C: hybrid nanoceramic (Cerasmart; GC Corp), group T: fiber-composite material (Trilor; Bioloren Srl), group E: lithium disilicate glass-ceramic (IPS e.max CAD; Ivoclar Vivadent AG), and group V: zirconia-reinforced lithium silicate glass-ceramic (Vita Suprinity; VITA Zahnfabrik GmbH). A digital scan was made with an intraoral digital scanner (TRIOS 3; 3Shape A/S), and endocrowns were milled with a 5-axis milling machine (Coritec 250i; imes-icore GmbH). The replica technique and a stereomicroscope (×70) were used to measure the marginal and internal adaptation of the endocrowns at 32 points. All data were statistically analyzed using 1-way ANOVA and the Tukey honestly significant difference test (α=.05). ResultsStatistical tests showed significant differences among the tested groups (P<.001). The resin-based groups displayed larger discrepancies than the ceramic-based groups. The resin-based groups showed a mean marginal gap larger than the mean internal gap C (P=.009), T (P<.001), whereas the ceramic-based groups showed similar gaps, V (P=.396), E (P=.936). The largest gap was observed at the pulpal floor (P<.001). ConclusionsAll materials had clinically acceptable internal and marginal gaps (≤150 μm), except for the marginal gap of the Trilor group.

Vickers Micro-Hardness of New Restorative CAD/CAM Dental Materials: Evaluation and Comparison after Exposure to Acidic Drink.

CAD/CAM (computer-aided design/computer-aided manufacturing) for indirect restorative materials has been recently introduced in dentistry. The purpose of this study was to evaluate the change of the surface micro-hardness of different restorative CAD/CAM materials after exposure to a carbonated acidic drink (Coca-Cola, Coca-Cola Company, Milan, Italy). One hundred and eighty specimens of identical size (2 mm thickness) were obtained by sectioning each tested CAD/CAM block of four materials: a hybrid ceramic (CERASMART™, GC Corporation, Tokyo, Japan), a resin nano ceramic (Lava™ Ultimate, 3M, Monrovia, CA, USA), a nanohybrid composite (Grandio blocs, VOCO GmbH, Cuxhaven, Germany), and a zirconia-reinforced lithium silicate glass ceramic (VITA SUPRINITY® PC; VITA Zahnfabrik, Bad Sackingen, Germany). Forty-five specimens of each material were tested. Micro-hardness was measured at baseline, after 7 days and after 28 days. The data were analyzed. The micro-hardness of each material varied significantly after immersion in Coca-Cola. The nanohybrid composite had a high initial micro-hardness and the greatest percentage loss after acid exposure. The hybrid ceramic and the resin nano ceramic had similar percentage losses of micro-hardness values even if the second material had higher initial values. The zirconia-reinforced lithium silicate glass ceramic had the highest baseline values and the lowest percentage loss of micro-hardness. The different CAD/CAM materials presented different micro-hardness values before and after acid exposure.

Effect of Er,Cr:YSGG on Remineralization Using CPP - ACPF (MI - Paste Plus) after Enamel Erosion Caused by Carbonated Soft Drink in Primary Teeth: In-Vitro Study.

BACKGROUND:Erosion is a widespread phenomenon with higher predilection in primary dentition.AIM:The aim of the present study is to assess the remineralising effect of Er,Cr:YSGG laser application combined with CPP-ACPF after erosive demineralisation by Coca-Cola in primary teeth.METHODS:Fifty teeth (n = 10) were divided into; Group I: Artificial saliva, (Saliva natural, Medac, UK), Group II: CPP-ACPF (MI Paste Plus, GC Corp, USA), Group III: Er,Cr:YSGG (Waterlase iPlus, USA), Group IV: CPP-ACPF + Er,Cr:YSGG, Group V: Er,Cr:YSGG + CPP-ACPF. Teeth were immersed in Coca-Cola for 10 min, 5 times/day for 5 days. DIAGNOdent (DD) measurements were taken before and after the experiment.RESULTS:There was a significant increase in DD readings after erosive-treatment cycles in all test groups. The highest reading was in samples immersed in artificial saliva, and the lowest was in those subjected to combined CPP-ACPF and Er,Cr:YSGG laser application, regardless of the sequence used. There was no significant difference between samples immersed in artificial saliva, and after CPP-ACPF application. Similarly, there was no significant difference between samples treated by combined treatment of CPP-ACPF and Er,Cr:YSGG application. However, there was a significant difference between samples immersed in artificial saliva or treated with CPP-ACPF application and those subjected to combined treatment CPP-ACPF along with Er,Cr:YSGG.CONCLUSION:Combining Er,Cr:YSGG laser and CPP-ACPF paste significantly increased enamel remineralisation, regardless of the sequence implemented. Saliva naturally and CPP-ACPF application had a comparable effect on remineralisation.

Color Change of Different Dual-Cure Resin Cements After Thermocycling

The purpose of this study is to evaluate the effect of thermocycling on the color change of the amine-free dual-cure resin cements. IPS e.max CAD blocs were cut into specimens of 1 mm thickness (N=28) and cemented with one of the 4 different amine-free dual-cure resin cements (NX3 Nexus [NX], Kerr Dental; Variolink Esthetic DC [VE], Ivoclar Vivadent; Panavia V5 [PV], Kuraray Dental; G-CEM Linkforce [GC], GC Corporation) (n=7). A spectrophotometer was used for color measurements. Specimens were subjected to thermocycling (5°C and 55°C; 5000 and 10000 cycles). Normality of data distribution was tested by using the Kolmogorov-Smirnov test. Statistical analysis was performed using a two-way analysis of variance (ANOVA) and Tukey’s multiple comparison tests at a significance level of p&lt;0.05. ∆E values were significantly influenced by the resin cements and the cycle periods (p&lt;0.05). There were no significant differences between NX and VE groups after 5000 thermocycling, however after 10000 thermocycling VE group showed higher ∆E1 values than NX group (p&gt;0.05). There were no statistically significant differences between the ∆E0 and ∆E1 values of the GC group, however the other groups were affected after 10000 thermocycling (p&gt;0.05). Amine-free resin cements used for cementation showed color change after thermocycling except GC group. All resin cements were showed clinically acceptable color change after thermocycling (∆E &lt; 3.5).

Functional analyses to assess the effect of the curing process on the properties of light activated composites

Light activated composites are the most popular choice in the field of dental restoration. They generally show internal stress even after a prolonged time period. The knowledge of mechanical properties and residual stress should provide interesting information on the clinical performance of such materials. Accordingly, in the current research experimental analyses were carried out to assess the effect of the curing process on the properties of one of the most commonly employed light activated dental composites (Gradia Direct—GC Corporation, Japan). At 10 min, 1 h and 24 h after light curing, the bending modulus (4.7–6.2 GPa) as well as the punching performance (peak load of 12.1–17.5 N) were evaluated for the micro-hybrid composite. Scanning electron microscopy also allowed to analyze the fracture surface. Residual stresses ranging from 0.67 ± 0.15 MPa to 1.12 ± 0.17 MPa were measured by means of the thin-ring-slitting approach reported in the literature, according to measurement time and cutting time.

Flexural Properties and Elastic Modulus of Different Esthetic Restorative Materials: Evaluation after Exposure to Acidic Drink.

Background Acidic beverages, such as soft drinks, can produce erosion of resin composites. The purpose of the present study was to investigate mechanical properties of different esthetic restorative materials after exposure to acidic drink. Methods Nine different composites were tested: nanofilled (Filtek Supreme XTE, 3M ESPE), microfilled hybrid (G-ænial, GC Corporation), nanohybrid Ormocer (Admira Fusion, Voco), microfilled (Gradia Direct, GC Corporation), microfilled hybrid (Essentia, GC Corporation), nanoceramic (Ceram.X Universal, Dentsply De Trey), supranano spherical hybrid (Estelite Asteria, Tokuyama Dental Corporation), flowable microfilled hybrid (Gradia Direct Flo, GC Corporation), and bulk fill flowable (SureFil SDR flow, Dentsply De Trey). Thirty specimens of each esthetic restorative material were divided into 3 subgroups (n=10): specimens of subgroup 1 were used as control, specimens of subgroup 2 were immersed in 50 ml of Coca Cola for 1 week, and specimens of subgroup 3 were immersed in 50 ml of Coca Cola for 1 month. Flexural strength and elastic modulus were measured for each material with an Instron Universal Testing Machine. Data were submitted to statistical analysis. Results After distilled water immersion, nanofilled composite showed the highest value of both flexural strength and elastic modulus, but its flexural values decreased after acidic drink immersion. No significant differences were reported between distilled water and acidic drink immersion for all other materials tested both for flexural and for elastic modulus values. Conclusions Even if nanofilled composite showed highest results, acidic drink immersion significantly reduced flexural values.

Microleakage of high viscosity glass-ionomer and glass-carbomer with and without coating before and after hydrothermal aging

Objective: The objective of this study was to evaluate the microleakage patterns of GIC and GGC with and without their protective surface coatings on enamel and dentin margins before and after aging. Material and Methods: Two rectangular cavities (height: 2 mm; width: 3 mm; depth: 1.5 mm) were prepared on each tooth at the cemento-enamel junction were prepared on human permanent molars (N=56) and the teeth were randomly assigned to be restored with one of the following: a) high viscosity glass-ionomer cement (GIC) (EQUIA Fil, C Corp., Tokyo, Japan) (n=28), b) glass-carbomer cement (GCC) (Glass Carbomer Products, Leiden, The Netherlands) (n=28). Half of the teeth were further divided into two groups where one group received protective surface coating (SC) (G-Coat Plus, GC Corp) (n=14) and the other group did not (n=14). Half of the teeth were stored for 24 hours (n=7), and the other half was thermocycled (5000 cycles, 5-55°C) (n=7). For microleakage analysis, the teeth were immersed in 5% methylene blue dye for 24 hours, sectioned into two equal halves. Microleakage patterns were evaluated using stereomicroscope and scored on a scale of 0-3 (0: No dye penetration, 1: Dye penetration less than half of the axial wall, 2: Dye penetration more than half the axial wall, 3: Dye penetration spreading along the axial wall). Data were analyzed using Kruskal-Wallis tests at the significance level of 0.05. Results: Compared to 24 h storage, after thermocycling, surface coating on GIC decreased microleakage significantly compared to GCC (p=0.046) but not for GCC. In the thermocycled groups, coated GIC showed significantly less leakage at the enamel margin but no significant difference was found with both GIC and GCC in the dentin margins. Conclusion: The application of surface coating significantly reduced the microleakage scores of GIC but not GCC, within the enamel margins only.KeywordsGlass-carbomer; Glass-ionomer; Microleakage.

The Effect of Heating on Surface Microhardness of Resin-based Materials for Direct Restoration

The aim of this study was to evaluate and to compare the surface hardness of three types of resin-based materials used for direct restoration after heating at different temperatures. A giomer (Beautifil II, Shofu Dental), a compomer (Dyract eXtra, Dentsply Sirona) and a hybrid composite resin (Gaenial Posterior, GC Corporation) were selected for this study. Twenty disk-shaped specimens of each material were heated at room temperature (21�C), at 37�C, at 50�C and at 60�C. Vickers microhardness test was performed on top and bottom surfaces using digital microhardness tester (Micro-Vickers Hardness System CV- 400DMTM, CV Instruments Namicon). The top and bottom surfaces VHN was calculated as a mean value of five determinations. Also, the microhardness ratio was calculated by dividing the top mean VHN value by bottom mean VHN value. Increased mean hardness values were recorded after heating, irrespective of resin-based tested materials. The highest hardness values were recorded after heating all three materials at 60�C, followed by the hardness recorded at 50�C, 37�C and 21�C. For top surfaces, the lowest hardness value was recorded in Dyract eXtra group when samples were warmed at room temperature and the highest hardness value was obtained in Beautifil II group when samples where heated at 60�C. For the bottom surfaces, Dyract eXtra specimens heated at 21�C presented the lowest hardness values and Beautifil II samples heated at 60�C presented the highest hardness values. On top and on bottom surfaces Dyract eXtra showed the lowest hardness values, followed by G-aenial Posterior and Beautifil II, irrespective the heating temperature.

The Effectiveness of Remineralizing Agents on Dentinal Permeability.

The effectiveness of remineralizing agents in reducing dentine permeability by tubule occlusion using fluid filtration device functioning at 100 cmH2O (1.4 psi) pressure and SEM/EDX analysis were evaluated and compared. Seventy (n = 70) dentine discs of 1±0.2 mm width were prepared from sound permanent human molars. Fifty (n = 50) dentine discs were randomly divided into 5 groups (n = 10): Group 1: GC Tooth Mousse Plus (Recaldent GC Corporation Tokyo, Japan), Group 2: Clinpro™ White Varnish (3M ESPE, USA), Group 3: Duraphat® Varnish (Pharbil Waltrop GmbH, Germany), Group 4: Colgate Sensitive Pro-Relief™ dentifrice (Colgate Palmolive, Thailand), and Group 5: Biodentine™ (Septodont/UK). Dentine permeability was measured after treatment application at 10 minutes, artificial saliva immersion at 7 days, and citric acid challenge for 3 minutes. Data were analyzed by two-way repeated measures ANOVA. Dentine specimens (n = 20) were used for SEM/EDX analyses to obtain qualitative results on dentine morphology and surface deposits. Each treatment agent significantly reduced dentine permeability immediately after treatment application and created precipitates on treated dentine surfaces. All agents increased permeability values after 7 days of artificial saliva immersion except Clinpro White Varnish and Biodentine. Clinpro White Varnish exhibited significant resistance to acid challenge compared to others. Colgate Sensitive Pro-Relief dentifrice has a dual mechanism of action in reducing the dentine sensitivity.

An analysis on the potential of diode-pumped solid-state lasers for dental materials

Material structure-property relationship is strongly related to the employed process technology. Over the past years, laser processing of engineering materials has been proposed in many fields and different uses for diode lasers have been found in dentistry. In this contest, the potential of GaN- and InGaN-based laser diodes to cure dental materials was analysed. Two wavelengths of 405 nm and 445 nm were used as heat or light sources for warm condensation of gutta-percha, light transmission in dental posts and brackets or light curing of dental composites. Additive manufacturing approach was considered to fabricate 3D root analogues, suitable supports, positioning systems and moulds for optical measurements. A three-axis CAD/CAM system was implemented for positioning and aligning the laser beam.The ability of diode-pumped solid-state lasers to cure dental materials or to transmit light was compared to that of a traditional instrument. Temperature profile at the apex of an additive manufactured root canal sealed with gutta-percha, light transmission through translucent quartz fiber post or through aesthetic ceramic bracket, bending properties and morphological features of light cured dental composites (Gradia Direct - GC Corporation and Venus Diamond - Heraeus Kulzer) were measured. Results showed a very high potential of diode-pumped solid-state lasers to be used in endodontics, orthodontics and restorative dentistry.

Evaluation of Pre-heating Effects on Marginal Adaptation of Resin-based Materials

The aim of the study was to compare the marginal adaptation of three different resin-based materials used for direct restoration: hybrid composite resin (Gaenial Posterio, GC Corporation), a compomer (Dyract eXtra, Dentsply Sirona), and a giomer (Beautifil II, Shofu Dental) applied at room temperature or after preheated at preheating 50 and 60oC. Class II cavities were prepared on proximal surfaces of extracted teeth and randomly divided in 3 groups according to the material used for restoration. In each group five cavities were restored using the materials at room temperature (subgroup 1), five cavities were restored using preheated materials at 50şC (subgroup 2), and five cavities were restored using preheated materials at 60şC (subgroup 3). The teeth were stored in distilled water for 14 days and then were immersed in 2% methylene blue buffered dye solution (pH = 7) for 4 hours. The teeth were transversally cut and the sections were examined using optical microscope (Carl-Zeiss AXIO Imager A1m) at 50x magnification and the dye penetration was evaluated according to 4 scores. Decreased microleakage and fewer gap formation were recorded for all filling materials after they have been heated at 50 or 60oC. Pre-warming of resin-based materials improves the adaptation of these materials to tooth structures.

Clinical Evaluation of Fiber-Reinforced Composite Restorations in Posterior Teeth - Results of 2.5 Year Follow-up.

Objectives:The aim of this study was to evaluate the clinical performance of posterior composite restorations reinforced by bulk base of short-fiber composite (everX Posterior, GC Corporation).Methods:Thirty-six short fiber-reinforced composite restorations were placed in premolar and molar teeth of 33 patients. Eight of the teeth were vital and 28 were non-vital. Average follow up time of the restorations was 30.6 months (2.5 years), ranging from 16.2 to 51.3 months (1.3 - 4.3 years).Results:One restoration failed during the follow-up period due to secondary caries, at time point 39.5 months. Three fillings had minor fractures during the follow-up. The overall survival rate of the restorations was 97.2% and success rate (no maintenance needed) was 88.9%, respectively.Conclusion:Posterior composite restorations with a bulk base of short-fiber composite showed good clinical performance in the short term evaluation.

The Influence of Saliva on Gingival Marginal Microleakage of Class II Cavities when Using Universal Bonding Agent in Direct Composite Restoration

The aim of the study was to evaluate by microleakage assessment the effect of saliva contamination during bonding procedure when a universal bonding agent applied in two different strategies was used in direct restoration using composite resins.Standardized box-only Class II cavities were prepared on the mesial and distal surfaces of twenty extracted teeth. A hybrid composite resin (Gaenial Posterior, GC Corporation) and a universal bonding agent (G Premio Bond, GC Corporation) applied in two different strategies: etch-and-rinse and self-etch were used for restoration, with or without saliva contamination of the gingival margin of the cavity. Lower leakage was recorded in the cervical area apically than CEJ when universal bonding agent was applied in self etch strategy when compared to etch-and-rinse strategy. On enamel margins (1mm upper than CEJ) universal bonding agents applied in etch-and-rinse technique leaded to lower microleakage. Irrespective of etch-and-rinse or self-etch strategy of applying, the presence of saliva impaired the enamel or dentine leakage of universal bonding agents.

Does Shortened Application Time Affect Long-Term Bond Strength of Universal Adhesives to Dentin?

This study evaluated the effect of shortened application time on long-term bond strength with universal adhesives. Three universal adhesives were used: Clearfil Universal Bond (CU, Kuraray Noritake Dental Inc, Tokyo, Japan), Scotchbond Universal Adhesive (SB, 3M ESPE, St Paul, MN, USA) or G-Premio Bond (GP, GC Corp, Tokyo, Japan). Sixty molars were cut to expose midcoronal dentin and prepared with a regular diamond bur. Each adhesive was applied either according to the manufacturer's instruction or with shortened time. Specimens were stored in distilled water at 37°C for 24 hours and then cut into resin-dentin sticks. Microtensile bond strength (μTBS) was tested after either 24 hours or 1 year of water storage. Data were analyzed by the three-way ANOVA and Duncan tests ( α=0.05). Fracture modes were analyzed under a scanning electron microscope (SEM). One dentin stick per group was selected after fracture mode analysis and further observed using transmission electron microscopy (TEM). Six additional dentin discs were prepared and conditioned with each adhesive under the different application time to observe the adhesive-smear layer interaction by SEM. Shortened application time affected the μTBS ( p<0.001) while storage time did not affect bond strength ( p=0.187). A significant effect of shortened application time on μTBS was observed in the CU at 1 year and in the GP at both storage times. One-year storage time had no effect on the μTBS of universal adhesives to bur-cut dentin. The performance of universal adhesives can be compromised when applied using a shortened application time.

Microscopic evaluation of rotatory and handle caries removal on glass ionomer cement/dentin interface

Aim: This study evaluated the interface between glass ionomer cement (GIC) and dentin using the conventional and atraumatic restorative treatment (ART) techniques for removal of decayed tissue. Materials and Methods: After preparation of the cavities by the conventional (Group I – GI) and ART (Group II – GII) techniques, the specimens were divided into 3 subgroups according to the GIC used (n=10). The conventional GIC KETAC FILL (3M/ESPE) was used in the groups GI-1 and GII-1, the conventional GIC VIDRION R (SS WHITE) in the groups GI-2 and GII-2, and the modified GIC FUJI II LC (GC Corporation) in the groups GI-3 and GII-3. For the microscopic analysis, the teeth were decalcified in a solution containing equal portions of 50% formic acid and 20% sodium citrate, dehydrated and submitted to paraffin baths. The samples were sectioned (6mm in thickness), stained by the Brown and Brenn method, and evaluated in a light microscope. Results: The microscopic analysis revealed interaction between the material and dentin structure only with the FUJI II LC. In addition, the behavior was superior for the conventional technique in comparison to the ART technique. Conclusion: It was concluded that the technique used for carious dentin removal does not seem to be determinant for the bonding of ionomeric materials to the dental structure, except for the resin-modified GIC in which the formed hybrid layer was higher using the conventional technique.

Compressive strength of calcium silicate-based cement

Summary Introduction The aim of this study was to compare compressive strength (Cs) of new nanostructural calcium silicate based cement (nCS) with commercial calcium silicate cement and conventional GIC. Methods Four nanostructural materials were tested: nanostructural calcium silicate based cement (nCS) (Jokanović et al.), MTA Plus (Cerkamed, Poland), Fuji IX (GC Corporation, Japan) and Ketac Universal Aplicap (3M ESPE, USA). Five samples of each material were mixed in accordance with manifecturer’s guidelines and positioned in metal moulds (ϕ4mm and 6mm). Compressive strength (Cs) expressed in MPa was determined after 24 hours, 7 days and 28 days respectively. Measurements were performed on universal testing equipment (Tinius Olsen, USA) at a crosshead speed of 1mm/min. For processing the results one-way ANOVA and post-hoc test were used. Results The highest values of compressive strength after 24h was found in conventional GIC Fuji IX (mean 38.56±13.31) and Ketac Universal (mean 40.77±7.96). Calcium silicate cements after 24h showed low values of compressive strength (MTA Plus 5.91±0.28 MPa, nCS 1.35±0.36 MPa). After 7 days, FUJI IX 47.42±9.33 MPa and Ketac Universal 35.25±10.60 MPa showed higher value of compressive strength than MTA Plus (15.09±2.77 MPa) and nCS (11.06±0.88 MPa). After 28 days the Cs value for conventional GIC Fuji IX was 48.03±7.82 MPa and Ketac Universal 36.65±11.13 MPa while for calcium silicate cements it was 16.47±1.89 MPa and nCS 14.39±1.63 MPa. There was statistically significant difference (p&lt;0.05) in Cs between conventional GIC and CS cements after 24h, 7 and 28 days. Conclusions Calcium silicate cements initially showed lower values of compressive strength than conventional GIC that increased over time.