Microhybrid Composite Resin Research Articles

Impact of a novel polishing method on the surface roughness and micromorphology of nanofilled and microhybrid composite resins

ObjectiveThis study aimed to evaluate the effects of different finishing and polishing techniques, including a novel polishing method (silicon carbide brush), on the surface roughness and morphology of nanofilled (Filtek Z350XT) and microhybrid (Filtek Z250) composite resins. MethodsThirty-five specimens of each resin were fabricated and assigned randomly to receive the following finishing/polishing treatments (n = 5 per group): none (control), Sof-Lex Pop-On discs (POP), Praxis discs (PRA), POP + felt discs with diamond paste, POP + silicon carbide brush, PRA + felt discs with diamond paste, and PRA + silicon carbide brush. Average roughness (Ra) in μm was evaluated using a 3D profilometer. Scanning electron microscopic images were also obtained and descriptively analyzed. Two-way analysis of variance and Tukey's test (p < 0.05) were used to evaluate the effects of resin type, finishing/polishing system, and interactions between these two variables on Ra values. ResultsFor the microhybrid resin, greater surface smoothness was obtained using POP or PRA + silicon carbide brush. For the nanofilled resin, the smoothest surface was obtained with POP + felt discs with diamond paste or silicon carbide brush. ConclusionThe surface roughness of a composite resin depends on its composition and finishing and polishing technique used.

Evaluation Of Color Change After Polymerisation Of Esthetic Restoratives With Different Composition

Objective: The aim of this study is to evaluate color change after polymerisation of seven restorative materials with different composition. Methods: Nanofill, nano-hybrid and micro-hybrid composite resin, silorane composite resin, compomer, ormocer and giomer were tested in this study. Ten millimeters in diameter and 2 mm in thickness cylindrical teflon mold was used for specimen preparation. Color measurements were performed before and after polymerisation using non-contact type spectrophotometer and changes in color parameters were calculated by using CIE L*a*b* color system. The data were statistically analysed using one-way ANOVA and Tukey’s multiple comparison test. Results: One-way ANOVA revealed that colors of restorative materials were significantly affected after polymerisation (p ≤ 0.05). The ∆E values were ranged from 3,37 to 13,76. The highest color change was observed in silorane composite and the least change was observed in nano-hybrid composite. While ∆L* and ∆b* values decreased after polymerisation for all groups, ∆a* values increased (p ≤ 0.05). Conclusion: Clinically unacceptable color change of restorative materials after polymerisation may lead to failure regarding color mismatch of restoration. Therefore, especially before a restoration in the esthetic zone, it is suggested that clinician should be aware of color characteristics of resin-based restoratives after polymerisation and perform shade-matching of restoratives based on polymerised shades.

In situ evaluation of micro and nanofilled load on biofilm retention of composite resins submitted to different surface treatments

Introduction: Finishing and polishing materials did not develop as the composites improved in these last years. The nanometric load particles were firstly and only incorporated in the polishing pastes formulation in this in vitro and in situ study. Objective: This study evaluated the biofilm retention of two different composite resins - Vit-l-escence™ (microhybrid) and Filtek™ Z350 XT (Nanofilled) after finishing and polishing technique, quantification and in situ comparison of the polishing pastes effectiveness with micrometric loads (Enamelize™ and Diamond Polish Paste™) and Nanofilled load - Lummina-E (Alumina and Diamond). Materials and Methods: Ten volunteers were selected for the in situ biofilm evaluation, a palatal device made of acrylic resin was confectioned, and each intra-oral device had fixed six specimens from each experimental group. After exposition to 20% sacarosis, the biofilm from each specimen was extracted in NaOH 1.0 M and quantified by absorbance spectrophotometer. The data were submitted to analysis of variance, followed for multiple comparisons of averages for the ad hoc de Dunn test, both at 1% significance level. Results: Vit-l-escence™ resin showed lower biofilm retention than Filtek Z350™ XT in all the tested groups. The lowest biofilm retention was after aluminum oxide paste (Lummina-E - Alumina) polishing. Conclusion: The Vit-l-escence™ (microhybrid) composite resin exhibited lower biofilm retention than Filtek™ Z350 XT (nanofilled) resin among all the tested groups. The lowest in situ biofilm retention occurred at the surfaces treated with Lummina - E Alumina (folder-based aluminum oxide) nanometric prototype.

Effect of finishing and polishing on the color stability of a composite resin immersed in staining solutions

Objective: To evaluate the influence of finishing/polishing methods and staining solutions using different immersion periods on the color stability of a microhybrid composite resin. Materials and Methods: Ninety specimens were fabricated using a stainless steel mold and polyester strips. The samples were randomly divided into five groups according to the finishing and polishing performed: Control group (no surface treatment was performed), Diamond Pro group, Diamond burs group, Enhance group, and SiC paper group. After finishing and polishing, six samples from each group were immersed in coffee, red wine, or water for 30 days. The color measurements were obtained using digital photography before immersion and after 7, 15, and 30 days of immersion. The red, green, and blue values provided by the Adobe Photoshop software were converted into CIELab values. A three-way analysis of variance and Tukey's test were used for statistical analysis (P ≤ 0.05). Results: The finishing and polishing methods, staining solutions, immersion times, and their interaction had statistically significant effects on the color change (P = 0.00). Coffee and red wine caused intense staining. Among the polishing methods, the highest color change value was observed in the control group (P < 0.05) and the Diamond Pro disks provided the most stain-resistant surfaces (P ≤ 0.05). Conclusion: The finishing and polishing method, staining solution, and immersion time influences the color stability. Finishing and polishing should be applied to obtain a more stain-resistant surface.

Retrospective evaluation of posterior direct composite restorations: 10-Year findings

ObjectivesThis 10-year retrospective study investigated the differences in the changes and the longevity of Class II restorations using 4 similar microhybrid resin composites (Filtek Z250, Herculite XR, Gradia Direct Posterior, Renew). MethodsData were collected from patient records. Those patients who received posterior restoration between 2001 and 2003, and who still visited the clinical practice for regular check-up visits were selected. A total of 225 adult patients (86 males, 139 females) with 701 restorations were evaluated by 2 operators using the USPHS criteria. Data were analyzed with Fisher's Exact Test, Pearson's Chi-Square Test and Kaplan–Meier analysis (p<0.05). ResultsA failure rate of 2.1% was detected. The reasons of failures included restoration fracture, secondary caries and endodontic treatment. Similar survival rates for Gradia Direct Posterior (91.25%) and Renew (92.19%) were observed; better performance was observed with the Filtek Z250 (99.1%) and Herculite XR (98.64%). There was a higher probability of failure in 3 surface (n=10) than in 2 surface (n=5) restorations (p<0.001), and this rate was similar when molars (n=8) and premolars (n=7) were compared. The most frequent but clinically acceptable deficiency was the marginal discoloration. SignificanceAll four microhybrid resin composites showed acceptable clinical durability in Class II restorations during the 10-year follow-up period, with an overall survival rate of >97.8%. Higher rates of failures and deficiencies were observed with the Renew (fracture) and Gradia Direct Posterior (color match), respectively.

Impact of intracoronal dentin treatment prior to bleaching on bond strength of restorative materials.

Surface treatment of dentin before the bleaching procedure may affect its permeability and influence the bond strength of restorative materials. This study evaluated the influence of surface treatment before the bleaching on shear bond strength (SBT) of restorative materials to intracoronal dentin. Dentin slabs were subjected to surface treatment: no bleaching (control - CON), no surface treatment + bleaching (HP), 37% phosphoric acid + bleaching (PA) and Er:YAG laser + bleaching (L). After the bleaching procedure, specimens (n=10) were restored with: microhybrid composite resin (MH), flowable composite resin (F), and resin-modified glass-ionomer cement (RMGIC). The shear test was carried out. ANOVA and Tukey's test (α=0.05) showed significant difference for surface treatment and restorative materials (p<0.05). CON presented higher STB and was statistically different from HP (p<0.05). PA and L showed intermediate values and were statistically similar to CON and HP (p>0.05). STB for MH and F were higher than RMGIC (p<0.05), and did not differ from each other (p>0.05). The surface treatments with phosphoric acid and Er:YAG laser before the bleaching procedure provided shear bond strength at the same level of unbleached dentin and the composite resins presented superior bond strength to the intracoronal dentin.

The Effect of Addition of Titanium Oxide Nanofillers on The Water Sorption and Solubility of Resin Based Composite (An In Vitro Study)

Background and Objectives: The aim of this study was to measure the water sorption (Wsp) and water solubility (Wsl) of modified microhybrid composite resins by adding Titanium oxide nanofillers in four concentration 0.5% , 1%, 3% and 5% and comparing them to unmodified microhybrid composite resins and to nanofilled composite resin. Methods: For water sorption (Wsp) and solubility (Wsl), ten disk-shaped specimens of each resin composite were made for each group and stored in desiccators until constant mass was achieved. Specimens were then stored in water for 7 days, and the mass of each specimen was measured. The specimens were dried again and weighed. The Wsp and Wsl were calculated from these measurements. Data analyzed by one-way ANOVA. Results: The results showed there were significant differences among the groups in the Wsp mean values which ranged from 20.2120 to 28.4680 μg/ mm³, while the Wsl mean values were ranged from 1.1060 to 5.6800 μg/ mm³. Conclusion: The addition of TiO2 nanofillers to microhybrid composite increased the Wsp and Wsl values compared to the control group but still lower than the value established by the ISO 4049 standard

Usefulness of Composite Restoration in Direct Esthetic Closure of Midline Gap

Abstract Introduction. Midline gap (diastema) is a space between two teeth, commonly between two incisors. The treatment can be provided by orthodontic, conservative (restorative) or prosthetic methods. Aim. The aim of the study was an assessment of using direct composite restoration in aesthetic closing of diastema. Material and methods. The space correction between teeth was performed among female and male adult patients with diastema of 3 to 6 mm. The microhybrid resin composite was used for the composite build-ups with a help of celluloid or silicon matrix due to its good handling properties and shade matching, and polishability properties. Results. Depending on the size of diastema, the partial or total closing was done to achieve the cosmetic effect. The obtained clinical results were highly assessed both by dentists and patients. It was possible to obtain optimal aesthetic results with resin composite restorations only. Conclusions. The simple closure of diastema with direct composite reconstructions can result in successful outcome and patient's satisfaction.

A randomized clinical trial of the effect of low-level laser therapy before composite placement on postoperative sensitivity in class V restorations.

This study aimed to investigate the efficacy of low-level laser irradiation when applied just before placement of resin composite on reducing postoperative sensitivity of class V lesions. In this randomized clinical trial, 31 patients with 62 class V cavities were included (two teeth in each participant). The teeth were randomly assigned into laser and placebo groups. After cavity preparation, the teeth in the experimental group were subjected to irradiation from a low-power red laser (630 nm, 28 mW, continuous wave, 60 s, 1.68 J), which was applied for 1 min on the axial wall of the cavity. In the control group, the same procedure was performed but with laser simulation. Then, a self-etch adhesive was applied and the cavities were restored with a microhybrid resin composite. Before treatment and on days 1, 14, and 30 after treatment, tooth sensitivity to a cold stimulus was recorded using a visual analogue scale. Data were analyzed by Friedman and Wilcoxon signed-rank tests (p < 0.05). Pain scores after restorative procedures were significantly lower in the laser group compared to the placebo application (p < 0.05). Although both groups experienced a significant improvement in pain and discomfort throughout the follow-up periods (p < 0.001), the changes in visual analogue scale (VAS) scores between baseline and each follow-up examination were significantly greater in the laser than the placebo group (p < 0.05). Low-level laser therapy (LLLT) before placement of resin composite could be suggested as a suitable approach to reduce postoperative sensitivity in class V restorations.

Microhardness of light- and dual-polymerizable luting resins polymerized through 7.5-mm-thick endocrowns

The complete polymerization of luting resins through thick indirect restorations is still questioned. The purpose of this study was to evaluate the degree of polymerization of light- and dual-polymerizable luting resins under thick indirect composite resin and ceramic endocrowns by means of Vickers microhardness measurements. The Vickers microhardness measurements of a light-polymerizable microhybrid composite resin and a dual-polymerizable luting cement directly polymerized in a natural tooth mold for 40 seconds with a high-power light-emitting diode lamp (control) were compared with measurements after indirect irradiation through 7.5-mm-thick composite resin and ceramic endocrowns for 3 × 90 seconds. A test-to-control microhardness values ratio of 0.80 at a depth of 0.5 mm below the surface was assumed as the criterion for adequate conversion. For the Vickers microhardness measurements of a dual-polymerizable luting cement, no differences (P>.05) were found between Vickers microhardness control values and values reported after polymerization through composite resin and ceramic endocrowns. For The Vickers microhardness measurements (±SD) of a light-polymerizable microhybrid composite resin, control values were significantly (P<.05) higher (111 ±3.3) than those reported after polymerization through composite resin (100.5 ±3.8) and ceramic (99.7 ±2.3) endocrowns. However, the hardness values of The Vickers microhardness measurements of a light-polymerizable microhybrid composite resin polymerized through the endocrowns were approximately 10% to 12% lower than those of the control values. Two-way ANOVA showed the influence of the luting material on the Vickers microhardness values (P<.05). The effect of endocrown material was not significant (P>.05). Under the conditions of this in vitro study, Vickers microhardness values of the dual-polymerizable resin cement and the light-polymerizable restorative composite resin irradiated for 3 × 90 seconds with a high irradiance light-emitting diode lamp through 7.5-mm-thick endocrowns reached at least 80% of the control Vickers microhardness values, which means that both materials can be adequately polymerized when they are used for luting thick indirect restorations.

Effect of polishing systems on stain susceptibility and surface roughness of nanocomposite resin material

Different polishing systems vary in their effect on reducing surface roughness and stain susceptibility of dental composite resin materials. The purpose of this study was to compare the effect of 3 polishing systems on the stain susceptibility and surface roughness of 2 nanocomposite resins and a microhybrid composite resin. Forty-five disks (2×10 mm) each were fabricated of 2 nanocomposite resins (Filtek Supreme XT and Tetric EvoCeram) and 1 microhybrid composite resin (Z250). Both sides of the disks were wet finished, and 1 side was polished with PoGo, Astropol, or Hi-Shine (n=5). Unpolished surfaces served as controls. The average roughness (Ra, μm) was measured with a profilometer, and the baseline color was recorded with a spectrophotometer. All specimens were incubated while soaking in a staining solution of coffee, green tea, and berry juice for 3 weeks. The color was recorded again, and the data were analyzed with 2-way ANOVA at α=.05 and Tukey multiple comparison tests. All polishing systems improved the staining resistance of Filtek Supreme XT and Z250 but did not affect that of Tetric EvoCeram. The surface color of Filtek Supreme XT was changed significantly and was the smoothest after polishing with PoGo, whereas Hi-Shine produced significantly rougher surfaces but with the lowest color change. Hi-Shine produced the highest color change in Z250. The surface roughness did not differ significantly between the other polishing systems. Tetric EvoCeram showed no significant differences in color change or surface roughness. Staining susceptibility and surface roughness depend mainly on material composition and on the polishing procedures. Polishing improves the staining resistance of composite resins. Nanocomposite resins did not exhibit better staining resistance or surface roughness than microhybrid composite resin.

Effect of finishing and polishing on surface roughness of composite resins after bleaching

Aim: To evaluate the influence of finishing and polishing techniques on the surface roughness of two composite resins (CRs) subjected to bleaching procedure. Methods: Forty-eight CR specimens were divided into six groups (n=8). For G1 to G3, a microhybrid CR (Opallis; FGM) was used, and G4 to G6, received a nanohybrid CR (Brilliant NewLine; Coltene/Whaledent). All specimens were subjected to bleaching procedure with 35% hydrogen peroxide (two 45-min applications, with a 5-day interval). The surface roughness of all specimens was evaluated before and after the bleaching and/or finishing/polishing (Ra parameter) by a roughness meter. After bleaching, the groups were subjected to finishing and polishing procedures: G2 and G5 - felt discs + diamond pastes; and G3 and G6 - silicon rubber tips. The control groups (G1 and G4) had no finishing or polishing treatment after bleaching. Data were analyzed by ANOVA and Tukey’s posttest, and t test for paired samples (α=0.05). Results: bleaching treatment increased Ra values for the nanohybrid CR specimens, but both finishing/polishing techniques were able to reduce these values; for the microhybrid specimens, only finishing/polishing with silicon rubber tips decreased the roughness values. Conclusions: For both microhybrid and nanohybrid CRs, the silicon rubber tips were effective to reduce the surface roughness after bleaching procedure.

Evaluation of the microleakage of different class V cavities prepared by using Er:YAG laser, ultrasonic device, and conventional rotary instruments with two dentin bonding systems (an in vitro study)

This study aimed to evaluate the extent of microleakage in class V cavities prepared with bur, Er:YAG laser, and ultrasonic, hybridized with two different bonding agents ("Single bonding" solvent-free bonding agent and "Swiss TEC SL bond" alcohol-based solvent). Thirty freshly extracted human premolars were divided into three groups (n = 10), on each tooth, two cavities were prepared on the buccal and the lingual surfaces, and each group was subdivided into two subgroups (n = 5). Group 1: 20 cavities were prepared by using Er:YAG laser (500 mJ, 10 Hz, 63.69 J/cm(2)) (subgroup1a: Single bonding was used with 10 cavities; subgroup 1b: Swiss TEC SL bond was used with 10 cavities). Group 2: 20 cavities were prepared by using ultrasonic (subgroup 2a: Single bonding was used with 10 cavities; subgroup 2b: Swiss TEC SL bond was used with 10 cavities). Group 3: 20 cavities were prepared by using burs (subgroup 3a: Single bonding was used with 10 cavities; subgroup 3b: Swiss TEC SL bond was used with 10 cavities). Cavities were restored with a micro-hybrid composite resin. After thermocycling, the specimens were immersed in 2 % methylene blue solution for 4 h and then sectioned in the bucco-lingual direction. Dye penetration was scored based upon the extent of the dye using a stereomicroscope. The two-way ANOVA test and paired t-test revealed no statistically significant differences among the methods of preparation (conventional, laser, and ultrasonic). However, statistical differences were found between the adhesives tested: the "Single bonding", which represented the solvent-free bonding agent, had lower microleakage values than "Swiss TEC SL bond", which represented the alcohol-based bonding agent. Based on the results of this study, it can be concluded that the Erbium:Yttrium-Aluminum Garnet (Er:YAG) laser and ultrasonic are as effective as the conventional method for preparing cavities and the extent of microleakage depends on the type of the bonding agents.

An in vitro evaluation of effect of eugenol exposure time on the shear bond strength of two-step and one-step self-etching adhesives to dentin.

Objectives:To evaluate the effect of the eugenol exposure time of an eugenol-based provisional restorative material on the shear bond strength of two-step and one-step self-etching adhesives to dentin, at three different time intervals of 24 h, 7 days, and 14 days.Materials and Methods:Forty extracted human posterior teeth were sectioned mesiodistally to obtain two halves and the resulting 80 halves were randomly assigned into four groups of 20 specimens each (Group-I, -II, -III, and -IV). Cavities of specified dimensions were prepared to expose dentin surface. In Group-I, temporarization was carried out with noneugenol cement (Orafil-G) for 24 h (control group). In Group-II, -III, and -IV, temporarization was carried out with eugenol cement (intermediate restorative material (IRM)) for 24 h, 7 days, and 14 days, respectively. Each group was further divided into two subgroups of 10 teeth each for two-step (Adper SE Plus) and one-step (Adper Easy One) self-etch adhesive systems, respectively. A plastic tube loaded with microhybrid composite resin (Filtek Z-350, 3M) was placed over the dentin surface and light cured. The specimens were subjected to shear stress in universal testing machine.Results:Group-II yielded low shear bond strength values compared with Group-III, -IV, and Group-I, which was statistically significant.Conclusions:The prior use of eugenol containing temporary restorative material reduced the bond strength of self-etch adhesive systems at 24-h period. No reduction in bond strength at 7 or 14 days exposure was observed with either two-step or one-step self-etch adhesive.

Joint-design and welding effect on flexural strength of Ti-6Al-4V bars

Purpose: The aim of this study was to microbiologically compare the surface of class V restorations performed with microhybrid composite resin or flowable composite resin, over 48 months, in order to determine an increased risk of secondary caries. Methods & Materials: 36 class V restorations were performed according to a standardized method, in order to asses if the different composite materials had changed the microbiological pattern on the restoration’s surface. Samples were collected over 48 months from the execution of the restoration, to evaluate the incidence of time on the growth of S. mutans, in correspondence of four different composite resins (two microhybrid and two flowable composite resins). Samples were managed with sterile paper points, withdrawing localized plaque on the margin of the restoration, then kept frozen in saline solution. For each tooth with class V restoration a control sample was taken from an healthy element, to analyze the relationship between presence of S. mutans and restoration. Samples were processed according to the method of PCR-Realtime, to find and quantify S. mutans. For restorations were used 2microhybrid composite resins, Venus Diamond (Heraeus Kulzer) and Ceram-x (Dentsply) and 2 flowable resins,Tetric Evoflow (Ivoclar Vivadent) and Venus Diamond flow (Heraeus Kulzer). Results: Flowable composite resins show an increased capability of creating a suitable substrate to bacterial growth, probably because of the surface porosity that this resin develops in time, caused by imbibitions of the organic matrix. The highest quantity of bacterial flora was found on restorations performed with flowable resin; also the highest relative quantity of S. mutans was found on the same kind of restoration. Conclusion: Flowable composite resins seem to offer a better substrate to bacterial growth in general; data obtained can state that there’s an increased growth of S. mutans in correspondence of restorations performedwith flowable composite resin.

Comparative Evaluation of the Effects of Light Intensities and Curing Cycles of QTH, and LED Lights on Microleakage of Class V Composite Restorations.

The purpose of this study was to evaluate the effects of light intensity and curing cycles of QTH and LED lights on the microleakage of Class V composite restorations. Eighty freshly extracted human maxillary premolars were used for this study. Standardized Class V cavities were prepared and they were restored with microhybrid resin composite. According to the curing protocol, the teeth were then divided into 4 groups (n=20): QTH curing (standard and soft start modes), and LED (standard and soft start modes) irradiations. Microleakage was evaluated by immersion of the samples in 50% silver nitrate solution. The samples were then sectioned, evaluated under a stereomicroscope, and scored for microleakage. The results of the present in-vitro study showed mean dye leakage scores of 1.9, 1.2, 1.45 and 0.90 for Group I (QTH-Standard mode), Group II (QTH-Soft Start mode), Group III (LED-Standard mode) and Group IV (LED-Soft Start mode) respectively. It was thus concluded that the soft start polymerization showed a highly significant difference as compared to the standard curing modes of QTH and LED lights, respectively.

Effect of acidic solutions on the surface degradation of a micro-hybrid composite resin.

Composite resins may undergo wear by the action of chemical substances (e.g., saliva, alcohol, bacterial acids) of the oral environment, which may affect the material's structure and surface properties. This study evaluated the effect of acidic substances on the surface properties of a micro-hybrid composite resin (Filtek Z-250). Eighty specimens were prepared, and baseline hardness and surface roughness (KMN0 and Ra0, respectively) were measured. The specimens were subjected to sorption (SO) and solubility (SL) tests according to ISO 4049:2009, but using different storage solutions: deionized water; 75/25 vol% ethanol/water solution; lactic acid; propionic acid; and acetic acid. The acids were used in two concentrations: PA and 0.02 N. pH was measured for all solutions and final hardness (KMN1) and surface roughness (Ra1) were measured. Data were analyzed with paired t-tests and one-way ANOVA and Tukey's test (a=5%). All solutions decreased hardness and increased the Ra values, except for the specimens stored in water and 0.02 N lactic acid, which maintained the hardness. All solutions produced similar SO and SL phenomena, except for the 0.02 N lactic acid, which caused lower solubility than the other solutions. Ethanol showed the highest pH (6.6) and the 0.02 N lactic acid the lowest one (2.5). The solutions affected negatively the surface properties of the composite resin; in addition, an acidic pH did not seem to be a significant factor that intensifies the surface degradation phenomena.

Influence of softening test and light-activation protocols on resin composite polymer structure.

Objective:This study analyzed the influences of the light-activation protocol and softening test on the degree of conversion (DC) and Knoop Hardness (KHN) of a microhybrid resin composite.Materials and Methods:Filtek Z250 (3M ESPE) was light-activated with a third-generation light-emitting diode (Valo Ultradent) by three protocols – standard, high power, and plasma emulation – or with a quartz-tungsten halogen XL 3000 (3M ESPE) in conventional mode. All modes were set to deliver 19 J/cm2. The DC (N = 20) was determined by Fourier transform infrared spectrometry on the top (T) and bottom (B) surfaces. For the KHN test, samples were subdivided in four groups (n = 5 each) according to the storage media: absolute ethanol, 75% ethanol, distilled water, and air (control group). The KHN values were evaluated on T and B before and 24 h after immersion in the storage media. Data were analyzed by split-plot analysis of variance (ANOVA; for DC) or repeated-measures split-plot ANOVA (for KHN), followed by Tukey's test (α = 0.05).Results:For the DC, the light-activation protocol did not influence the results and there was no difference between T and B. For the KHN test, the light-activation protocol did not influence the results and T showed higher microhardness values than B for all experimental conditions. There were significant differences in KHN depending on the storage media. Samples immersed in absolute ethanol generally presented lower KHN values, with no differences compared to samples in 75% ethanol.Conclusion:The storage media affected the outcomes of the softening test.

Effect of Toothbrushing-mouthrinse-cycling on Surface Roughness and Topography of Nanofilled, Microfilled, and Microhybrid Resin Composites

The purpose of this study was to evaluate the influence of toothbrushing-mouthrinse-cycling (TMC) on the surface roughness and topography of three resin composites with different filler particle systems (Z350, nanofilled [Nf]; Durafill, microfilled [Mf], and Empress Direct, microhybrid [Mh]). Twenty specimens of each resin composite (8.0 mm diameter and 2 mm height) were randomly divided into four groups (n=5) according to the mouthrinses: alcohol-free (Plax--P) and alcohol-containing (Listerine--L and Plax Fresh Mint--PM) and artificial saliva (control--AS). The specimens were submitted to TMC for nine weeks. A surface roughness tester and a three-dimensional profilometer were used to measure the roughness (Ra) and the topography (Sa) before and after TMC. The data were analyzed by multifactor analysis of variance and Tukey post hoc test (α=0.05). In all media, Mh presented greater roughness than Mf (p<0.05). The highest value of roughness was presented by Mh immersed in L (p<0.05). The lowest values of roughness were presented by Mf (p<0.05). The three resin composites presented the highest roughness after immersion in mouthrinses containing alcohol (PM and L) (p<0.05). For the three resin composites, the increase in roughness was noticeable after the fifth week. Topographic analysis showed that the smoothest surfaces were present after immersion in AS.

Randomized clinical evaluation of the effect of chlorhexidine on postoperative sensitivity of posterior composite resin restorations.

Evaluation of postoperative sensitivity in posterior teeth restored with etchand- rinse adhesive and composite resin after application of 2% chlorhexidine solution. Thirty participants with similar dental caries on both sides of the jaws were selected. After cavity preparation, each tooth was randomized to one of the following restoration methods. Teeth in the control group were restored using etch-and-rinse resin adhesive (Single Bond, 3M ESPE) and universal microhybrid composite resin (Filtek Z250, 3M ESPE). Restoration of teeth in the experimental group was similar to the control group except that 2% chlorhexidine solution (Concepsis, Ultradent) was applied on the etched dentin for 60 seconds. Subjects were recalled for evaluation of postoperative sensitivity at 1 day, 1 week, 1 month, and 6 months. Data were analyzed by Fisher exact test (α = .05). The experimental group showed significantly less postoperative sensitivity (8 teeth) compared with the control group (20 teeth) at the 1-day recall (P < .05; Fisher exact test). Conventional restorations were comparable to teeth treated with chlorhexidine at other recall times (P > .05). Chlorhexidine significantly decreased immediate postoperative sensitivity of posterior teeth restored by composite resin.