Nihan Gönülol

The effects of finishing and polishing techniques on surface roughness and color stability of nanocomposites

OBJECTIVESnThe aim of this in vitro study was to evaluate the effects of different finishing and polishing techniques on the surface roughness and color stability of nanocomposites.nnnMETHODSnTwo nanohybrid (Grandio, Aelite Aesthetic Enamel), two nanofill (Filtek Supreme XT Dentin and Translucent), and a microhybrid (Filtek Z250) composites were used. Two hundred and eighty disc-shaped specimens were cured under a mylar strip. Seven specimens of each resin composite were randomly assigned to one of the seven polishing systems. A profilometer was used for assessing surface roughness. ΔE was calculated with a colorimeter at baseline and 48 h after storage in a coffee solution. The results were analysed by two-way ANOVA and Tukeys HSD test (α=0.05). Regression analysis was used to examine the correlation between surface roughness and color stability (α=0.01).nnnRESULTSnThere was no significant difference in R(a) values between mylar strips and Sof-Lex polishing discs (p>0.05). The highest ΔE and R(a) values were obtained from Grandio (p<0.05), and Aelite Aesthetic Enamel had the lowest ΔE values (p<0.05). The Enhance system showed the lowest color differences among all the finishing systems. The highest ΔE values were found in the composite resin groups under mylar strips and finished with diamond burs (p<0.05).nnnCONCLUSIONSnWhile the Sof-Lex discs provided the lowest surface roughness, the Enhance Polishing system provided the most stain-resistant groups. Grandio presented the highest surface roughness and staining susceptibility after storage in coffee solution. Aelite Aesthetic Enamel, which did not include TEGDMA in its composition, showed the least discoloration.nnnCLINICAL SIGNIFICANCEnThe composites with smaller filler size did not necessarily show low surface roughness and discoloration. Staining of composite resins was dependent on monomer structure, as well as surface irregularities.

Deformation and fracture of Mtwo rotary nickel-titanium instruments after clinical use.

INTRODUCTIONnIn recent years, a number of rotary nickel titanium (NiTi) systems have been developed to provide better, faster, and easier cleaning and shaping of the root canal system. Although the NiTi instruments are more flexible than the stainless steel files, the main problem with the rotary NiTi instruments is the failure of the instruments. The aim of this study was to evaluate the deformation and fracture rate of Mtwo rotary nickel-titanium instruments (VDW, Munich, Germany) discarded after routine clinical use.nnnMETHODSnA total of 593 Mtwo rotary NiTi instruments were collected after clinical use from the clinic of endodontics over 12 months. The length of the files was measured using a digital caliper to determine any fracture, and then all the files were evaluated under a stereomicroscope for defects such as unwinding, curving, or bending and fracture. The fracture faces of separated files were also evaluated under a scanning electron microscope. The data were analyzed using a chi-square and z test.nnnRESULTSnA percentage of all files (25.80%) showed defects, and the major defect was fracture (16.02%). The most frequently fractured file was #10.04 (30.39%). Deformations without fracture were mostly observed on #15.05 files (25.47%).nnnCONCLUSIONSnA higher rate of deformation was observed for #10.04 and #15.05 files. Therefore, these files should be considered as single-use instruments. Because cyclic fatigue was the cause of 71.58% of the instrument fractures, it is also important not to exceed the maximum number of usage recommended by the manufacturer and discard the instruments on a regular basis.

Effect of sodium ascorbate on the bond strength of silorane and methacrylate composites after vital bleaching

We investigated the effect of sodium ascorbate (SA) on the microtensile bond strengths (MTBSs) of different composites to bovine enamel after vital bleaching with hydrogen peroxide (HP) or carbamide peroxide (CP). Thirty bovine incisors were randomly divided into five groups and treated with no bleaching application (control), 35% HP alone, 35% HP+10% SA for 10 minutes (HP+SA), 16% CP alone, or 16% CP+10% SA for 10 minutes (CP+SA). Specimens were restored with Silorane adhesive and Filtek Silorane composite (designated as S/group) or with Clearfil SE bond and Filtek Supreme XT (designated as F/group). Composite build-up was created on the enamel. Sectioned specimens (n=10 per group; 1 mm2; cross-sectional area) were created and stressed in a universal testing machine at 1 mm/min crosshead speed. The application of 10% SA immediately after bleaching with 16% CP or 35% HP increased the enamel MTBS, regardless of the adhesive/composite resin used. The resulting MTBS values were similar to those of the control groups. Use of 16% CP and 35% HP alone decreased the enamel MTBS, regardless of the adhesive/composite resin used, with F/CP+SA=F/HP+SA=F/CP=S/CP+SA=S/HP+SA=S/C>S/CP=S/HP=F/CP=F/HP (p<0.05). We concluded that the application of SA for 10 minutes immediately after vital bleaching increases the enamel BS for dimethacrylate- and silorane-based composites.

Endodontic treatment of a taurodontic premolar with five canals.

Taurodontism is a morpho-anatomical abnormality in the shape of a tooth. An enlarged pulp chamber, apical displacement of the pulpal floor and no constriction at the level of the cemento-enamel junction are the characteristic features. Special care is required in all aspects of endodontic treatment of a taurodontal tooth, including identifying the orifice, canal exploration, cleaning, shaping and obturation of the root canal. This case report describes the successful endodontic treatment of a taurodontic mandibular second premolar with five root canals.

Bond strengths of silorane- and methacrylate-based composites to various underlying materials.

Objective. To evaluate shear bond strength (SBS) values of a methacrylate (FZ 250) and a silorane-based (FS) resin composite to various underlying materials. Materials and Methods. A total of 80 samples were prepared with four different underlying materials; a flowable (FLC) and a bulk-fill flowable composite (BFC), and a conventional (CGIC) and resin modified glass-ionomer cement (RMGIC). These underlying materials were laminated plus to methacrylate or silorane-based resin composites (n = 10). To evaluate the specimens SBS values were evaluated with a universal testing machine (cross-head speed; 1.0u2009mm/min). Statistical comparisons were carried out using two-way ANOVA and Tukeys post hoc test with a significance level of P < 0.05. Results. SBS values for FZ250 were significantly higher than for FS for all of the underlying materials tested (P < 0.05). SBS values of FZ250 to BFC were significantly higher than to all other materials (P < 0.05), whereas SBS values of FS did not vary significantly according to underlying material (P > 0.05). Conclusion. The use of FS in conjunction with any of the tested materials showed lower SBS than the FZ 250. Also, new low elastic modulus liner BFC presented slightly good interfacial adhesion so, the usage of BFC as an underlying material may be preferable for FZ 250.

Effect of a third-generation LED LCU on microhardness of tooth-colored restorative materials.

OBJECTIVEnTo assess the effects of different modes of a third-generation light-curing unit (LCU) (VALO) on the microhardness of restorative materials.nnnDESIGNnA microhybrid composite resin (Filtek(™) Z550), a giomer (Beautifil II), a compomer (Dyract eXtra) and a RMGIC (Photac(™) Fil) were used in the study. Three different modes of VALO were tested and a second-generation LCU (Elipar S10) was used as a control. The microhardness (VHN) was measured using a Vickers Hardness tester. Data were analyzed using two-way anova and post hoc Tukeys test (P < 0.05).nnnRESULTSnThe Filtek Z550 group had the highest VHN values followed by Photac Fil, Beautifil II and the Dyract eXtra at both top and bottom surfaces, however the difference between Filtek Z550 and Photac Fil was not statistically significant for the bottom surfaces (P > 0.05). Of the different curing protocols tested, the VALO LCU in Mode 3 resulted in the lowest VHN values at both top and bottom surfaces (P < 0.05).nnnCONCLUSIONnBased on the results of this study, it can be concluded that the high-power mode of the VALO LCU can be recommended for clinical applications especially in pediatric patients, as it can shorten the time required to adequately polymerize resin-based tooth-colored restorative materials.

Water Sorption, Solubility, and Color Stability of Giomer Restoratives

OBJECTIVESnThis study compared the color stability, water sorption, and solubility of a giomer composite and two nanohybrid composite resins.nnnMATERIALS AND METHODSnDisc-shaped specimens (1-mm thicknessu2009×u200915-mm diameter) of a giomer (Beautifil II, Shofu, Kyoto, Japan) and two nanohybrid (Filtek Z550, 3M ESPE, St. Paul, MN, USA; Tetric N-Ceram, Ivoclar Vivadent, Schaan, Liechtenstein) composites (Nu2009=u200910) were prepared. Baseline color measurements were taken, and specimens were immersed in water for 28 days. Following immersion, color values were remeasured, and color-change values (ΔE) were calculated. Water sorption and solubility were assessed by mass gain or loss after storage in water for 28 days. Data were analyzed with one-way analysis of variance and Tukeys post-hoc tests (pu2009=u20090.05). Pearsons correlation test was used to assess possible correlations between water sorption and solubility, water sorption and color stability, and solubility and color stability (pu2009=u20090.05).nnnRESULTSnWater sorbtion (%) and color change (ΔE) varied significantly among groups, with Beautifil II exhibiting the highest values (pu2009<u20090.001). No statistically significant differences were observed in water solubility values among the groups (pu2009=u20090.661); however, a linear, positive correlation was detected between solubility and discoloration (ru2009=u20090.368, pu2009=u20090.046).nnnCONCLUSIONnWater sorption and discoloration values of the giomer composite group were significantly higher than those of the nanohybrids tested.nnnCLINICAL SIGNIFICANCEnThe high levels of water sorption and discoloration of giomer composites are likely to have an adverse effect on esthetic restorations.

Effect of propolis as a root canal irrigant on bond strength to dentin

Purpose The purpose of this in vitro study was to evaluate the effect of propolis on bond strength to dentin of a self-etch adhesive when used as a final irrigant. Methods 126 human third molars were sectioned 3 mm below the occlusal level and then randomly divided into 7 groups (n = 18). The exposed dentin surfaces were treated with irrigation solutions as follows: Group 1: 5.25% NaOCl; Group 2: 5.25% NaOCl followed by 17% EDTA; Group 3: 5.25% NaOCl followed by Tubulicid Plus (Temrex, Freeport, NY, USA); Group 4: 5.25% NaOCl followed by MTAD; Group 5: 5.25% NaOCl followed by 20% propolis; Group 6: 5.25% NaOCl followed by 2% CHX; Group 7: distilled water (control). Irrigated specimens were bonded using Clearfil SE Bond (Kuraray, Osaka, Japan) with Tygon (Saint-Gobain, Saint-Gobain Performance Plastics, France), tubes for microshear bond strength testing. Data was analyzed using a one-way ANOVA and Tukey test. Results Among the tested groups, although the lowest bond strength values were detected in Group 1 (11.25 ± 1.97), a significant statistical difference was detected only between this group and Group 4 (18.70 ± 1.82) and Group 5 (16.75 ± 3.70) (p = 0.0012). Conclusions 20% propolis solution as a final irrigant was found to have a favorable effect on the dentin bond strength of the tested self-etch adhesive to coronal dentin when compared with other irrigation solutions.

Clinical evaluation of a low-shrinkage resin composite in endodontically treated premolars: 3-year follow-up

ObjectivesThis study compared the 3-year clinical performance of a low-shrinkage silorane-based composite material with that of a methacrylate-based composite material in the restoration of endodontically treated premolar teeth.Materials and methodsA total of 70 patients requiring a Class II composite-resin restoration of a premolar tooth following root-canal treatment participated in the study. Cavities were restored with either a silorane-based restorative (Filtek Siloraneu2009+u2009Silorane System Adhesive) or a methacrylate-based restorative (Filtek Z250u2009+u2009Clearfil SE Bond) system applied according to the manufacturer’s instructions. Restorations were evaluated by two blinded observers at five different time intervals (baseline; 6xa0months; 1, 2, and 3xa0years) according to modified USPHS criteria. Pearson’s chi-square tests were used to examine differences in the clinical performance of the materials (retention, color match, marginal discoloration, secondary caries, anatomical form, marginal adaptation, and surface roughness), and Friedman and Wilcoxon tests were used to compare changes between baseline and each recall time, with a level of 0.05 considered statistically significant.ResultsAfter 3xa0years, no statistically significant differences in clinical performance were observed between the two materials (pu2009>u20090.05). Intra-system comparisons revealed a statistically significant deterioration in color match, marginal discoloration, anatomical form, marginal adaptation, and surface roughness scores after 3xa0years for both systems. Although the difference was not significant at 3xa0years of follow-up, the level of deterioration in marginal adaptation and surface roughness was greater for the Filtek Silorane restoration than for the Filtek Z250 restoration at the 1xa0year follow-up (pu2009>u20090.05).ConclusionRestorations of both materials were clinically acceptable after 3xa0years. The Filtek Silorane system did not appear to offer any clinical advantages over the methacrylate-based system when used in the restoration of Class II cavities in endodontically treated premolars.Clinical relevanceThe restoration of endodontically treated premolars with minor or moderate loss of tooth structure can be directly performed either with silorane or methacrylate-based composite resins.

Farklı polimerizasyon protokolleri ve yüzey uygulama metodlarının iki farklı fissür örtücünün makaslama bağlanma dayanım kuvveti üzerine etkisi

AMAC: Iki farkli rezin esasli fissur ortucunun [BeautiSealant (BS), UltraSeal XT hydro (UH)], fosforik asit (Ultra-Etch asit) veya primer (BeautiSealant Primer) uygulanarak, 3. nesil bir light emitting diode (LED) isik cihazinin iki farkli moduyla (Standart mod; 10 sn veya Xtra power mod; 3 sn) polimerizasyonu sonrasinda mineye makaslama baglanma dayanim kuvvetini in vitro olarak degerlendirmektir. GEREC VE YONTEM: Cekilmis 40 adet insan 3. molar disinden 80 adet mine ornegi elde edildi. Ornekler yuzey uygulama metodlarina, fissur ortucu tipine ve polimerizasyon protokollerine gore rastgele 8 alt gruba ayrildi (n=10). Gruplar; Grup 1: Asit + BS + Xtra power mod, Grup 2: Primer + BS + Xtra power mod, Grup 3: Asit + BS + Standart mod, Grup 4: Primer + BS + Standart mod, Grup 5: Asit + UH + Xtra power mod, Grup 6: Primer + UH + Xtra power mod, Grup 7: Asit + UH + Standart mod, Grup 8: Primer + UH + Standart mod seklinde idi. Orneklerin makaslama baglanma dayanim kuvveti (MBDK) degerleri Instron cihazi kullanilarak (1.0 mm/dk) olculdu. Elde edilen verilerin istatistiksel analizleri tek yonlu ANOVA ve Tukey’s testleri kullanilarak yapildi (p<0.05). BULGULAR: Gruplar arasinda istatistiksel olarak anlamli farkliliklar saptandi (p<0.05). BS grubunun tum alt gruplarinda MBDK degerleri UH grubunun tum alt gruplarindan dusuktu (p<0.05). Tum gruplar arasinda en yuksek MBDK degeri Grup 5’te, en dusuk Grup 1’de elde edildi. SONUC: Fissur ortuculerin MBDK degerleri, yuzey uygulama islemleri ve polimerizasyon protokollerinden etkilenebilmektedir.