Effect of artificial saliva on permeability of dentin treated with phosphate containing desensitizer measured by digital flow meter.

The aim of this study was to investigate the effects of artificial saliva on permeability measured using a highly sensitive digital flow meter of dentin discs treated with a phosphate containing desensitizer compound (Teethmate desensitizer; TD). Four random groups (n=10) were treated either with TD or distilled water (DW), then stored in artificial saliva (AS) or DW for 1 day, 1 week and 1 month. Flow rates under 2 kPa pressure were calculated as percentage reduction (PR%) from the baseline. The PR% of TD/AS group was significantly lower after 1 day and 1 week, but the PR%s of 1 month groups among TD/AS, TD/DW and DW/AS were not significantly different. The SEM photograph of TD/AS group displayed that the dentin surface was densely covered with mineral deposits. Ca and phosphate ions from the artificial saliva could penetrate into the tubules and precipitate as hydroxyapatite, resulting in the reduction in permeability.

Novel treatment of in-office tooth bleaching sensitivity: A randomized, placebo-controlled clinical study.

OBJECTIVES: Aim of this clinical trial was to investigate the effect of a calcium phosphate based desensitizer paste applied prior to in-office tooth whitening on bleaching sensitivity (BS). METHODS: This crossover study was designed as randomized double-blinded, placebo-controlled trial. The desensitizer paste Teethmate AP (TAP) contains tetracalcium phosphate and dicalcium phosphate anhydrous in glycerol and polyethylene glycol, whereas placebo (PLA) is a calcium phosphate free analog. Fifty patients with sound maxillary incisors and canines were enrolled. Tooth shades were determined with a Vitapan Classic Shade guide. Randomly, TAP and PLA were applied to the left or to the right anterior teeth. After rinsing and air-drying the bleaching gel (Opalescence Boost PF 40%) was applied and left on the labial surfaces for 15 minutes. Sensitivity was recorded using a 10 cm visual analog scale (VAS) before, at 5, 10, and 15 minutes during, and at 1 hour, 1, 2, and 7 days after bleaching. Tooth whitening was determined with the shade guide after 1 day and 1 week. RESULTS: Prebleaching desensitization with TAP reduced BS significantly when compared with PLA. Between 1 and 7 days the average sensitivity scores were close to zero, whereas the average scores for PLA were significantly higher during this time interval. Independent from the desensitizing treatment after 1 and 7 days the medians of the shades were between 5 and 3.5 units brighter. CONCLUSIONS: Prebleaching desensitization with TAP was effective in reducing BS during and after tooth whitening treatment and had no adverse effect on the bleaching result. CLINICAL SIGNIFICANCE: Prebleaching topical application of a calcium phosphate containing compound reduced significantly bleaching sensitivity during a single 15 minutes treatment and up to one week with a 40% hydrogen peroxide containing gel without compromising tooth whitening.

Discoloration of various CAD/CAM blocks after immersion in coffee.

OBJECTIVES: This study evaluated color differences (ΔEs) and translucency parameter changes (ΔTPs) of various computer-aided design/computer-aided manufacturing (CAD/CAM) blocks after immersion in coffee. MATERIALS AND METHODS: Eight CAD/CAM blocks and four restorative composite resins were evaluated. The CIE L*a*b* values of 2.0 mm thick disk-shaped specimens were measured using the spectrophotometer on white and black backgrounds (n = 6). The ΔEs and ΔTPs of one day, one week, and one month immersion in coffee or water were calculated. The values of each material were analyzed by two-way ANOVA and Tukey's multiple comparisons (α = 0.05). The ΔEs after prophylaxis paste polishing of 1 month coffee immersion specimens, water sorption and solubility were also evaluated. RESULTS: After one month in coffee, ΔEs of CAD/CAM composite resin blocks and restorative composites ranged from 1.6 to 3.7 and from 2.1 to 7.9, respectively, and ΔTPs decreased. The ANOVA of ΔEs and ΔTPs revealed significant differences in two main factors, immersion periods and media, and their interaction except for ΔEs of TEL (Telio CAD, Ivoclar Vivadent). The ΔEs significantly decreased after prophylaxis polishing except GRA (Gradia Block, GC). There was no significant correlation between ΔEs and water sorption or solubility in water. CONCLUSIONS: The ΔEs of CAD/CAM blocks after immersion in coffee varied among products and were comparable to those of restorative composite resins. The discoloration of CAD/CAM composite resin blocks could be effectively removed with prophylaxis paste polishing, while that of some restorative composites could not be removed.

Effect of two desensitizing agents on dentin permeability in vitro.

OBJECTIVE: The aim of this in vitro study was to investigate the effect of two desensitizing agents and water on hydraulic conductance in human dentin. MATERIAL AND METHODS: GLUMA Desensitizer PowerGel (GLU) contains glutaraldehyde (GA) and 2-hydroxyethyl methacrylate (HEMA), and Teethmate Desensitizer (TD) is a powder comprising tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA) that is mixed with water. Deionized water was used as a negative control (CTR). Thirty discs with a thickness of 1.2 mm were cut from the coronal dentin of the third molars and cleaned with 0.5 M EDTA (pH 7.4). After being mounted in a split-chamber device, the discs were pressurized with water at 1 kPa and 3 kPa in order to measure flow rates with a highly sensitive micro-flow sensor and to calculate hydraulic conductance as a baseline value (BL). Following the application of GLU, TD, and CTR (n=10), hydraulic conductance was remeasured with intermittent storage in water after 15 min, 1 d, 1 w, and 1 m. Reduction in permeability (PR%) was calculated from hydraulic conductance. Data were statistically analyzed using nonparametric methods (α<0.05). Representative discs were inspected by SEM. RESULTS: PR% for GLU and TD were 30-50% 15 min and 1 m after their application. Post hoc tests indicated that PR% of CTR was significantly greater than those of GLU and TD at all time points tested. The PR% of GLU and TD were not significantly different. SEM examinations showed noncollapsed collagen meshes at the tubular entrances after GLU, and crystalline precipitates occluding the tubular orifices after TD, whereas CTR specimens showed typical patterns of etched dentin. CONCLUSIONS: The present study on hydraulic conductance in dentin discs treated with two chemically different desensitizing agents and water as a control demonstrated that both products may be characterized as effective.

Effect of two desensitizing agents on dentin permeability in vitro

Abstract Objective The aim of this in vitro study was to investigate the effect of two desensitizing agents and water on hydraulic conductance in human dentin. Material and Methods GLUMA Desensitizer PowerGel (GLU) contains glutaraldehyde (GA) and 2-hydroxyethyl methacrylate (HEMA), and Teethmate Desensitizer (TD) is a powder comprising tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA) that is mixed with water. Deionized water was used as a negative control (CTR). Thirty discs with a thickness of 1.2 mm were cut from the coronal dentin of the third molars and cleaned with 0.5 M EDTA (pH 7.4). After being mounted in a split-chamber device, the discs were pressurized with water at 1 kPa and 3 kPa in order to measure flow rates with a highly sensitive micro-flow sensor and to calculate hydraulic conductance as a baseline value (BL). Following the application of GLU, TD, and CTR (n=10), hydraulic conductance was remeasured with intermittent storage in water after 15 min, 1 d, 1 w, and 1 m. Reduction in permeability (PR%) was calculated from hydraulic conductance. Data were statistically analyzed using nonparametric methods (α<0.05). Representative discs were inspected by SEM. Results PR% for GLU and TD were 30-50% 15 min and 1 m after their application. Post hoc tests indicated that PR% of CTR was significantly greater than those of GLU and TD at all time points tested. The PR% of GLU and TD were not significantly different. SEM examinations showed noncollapsed collagen meshes at the tubular entrances after GLU, and crystalline precipitates occluding the tubular orifices after TD, whereas CTR specimens showed typical patterns of etched dentin. Conclusions The present study on hydraulic conductance in dentin discs treated with two chemically different desensitizing agents and water as a control demonstrated that both products may be characterized as effective.

Effect of a Calcium Phosphate Desensitizer on Pre- and Postcementation Sensitivity of Teeth Prepared for Full-Coverage Restorations: A Randomized, Placebo-Controlled Clinical Study.

PURPOSE: The aim of this study was to investigate the effect of Teethmate Desensitizer (TD), an aqueous slurry of calcium phosphates, on the pre- and postcementation sensitivity of contralateral premolars prepared for full-coverage restorations. MATERIALS AND METHODS: In this clinical study, using a split-mouth design, 20 patients were allocated and two contralateral vital premolars per patient were randomly assigned to treatment with TD and placebo (PLA; distilled water). One day after preparation and temporization, sensitivity (PRE) upon air blast (AB) and probe scratch (PS) was determined using a 10-cm-long visual analog scale (VAS). The trial was double-blinded; neither the patient nor the investigator knew the treatment performed. Sensitivity was assessed immediately after treatment, before seating the final crowns after 1 week, and 1 month after cementation. Statistical data analysis was performed with one-way analysis of variance followed by Tukey post hoc test and two-sided paired t test. Statistical significance was determined at α < .05. RESULTS: VAS scores upon stimulation with AB and PS were significantly lower at POST and 1 week, and with AB after 1 month. TD-treated teeth showed significantly less sensitivity than PLA. At the postcementation recall, TD and PLA were not significantly different and the average pain scores were almost 0. CONCLUSION: Treatment of teeth prepared for full crown restorations with TD can significantly reduce pre- and postcementation sensitivity.

Randomized, placebo-controlled study of the efficacy of a calcium phosphate containing paste on dentin hypersensitivity.

OBJECTIVE: Hypersensitivity of non-carious cervical lesions (DH) is a frequently encountered disease. This randomized, controlled, single-blind crossover study evaluated the effectiveness of a calcium phosphate containing desensitizer paste (TAP) on DH in comparison to water as placebo (PLA). METHODS: In this clinical trial 35 patients were randomly assigned to the test and the negative control group. Using a 10cm long VAS (visual analog scale) patients should respond with DH score >6 on one tooth in each of two quadrants for allocation. Pain stimuli were a 2-seconds air blast (AB) and probe scratching (PS) of the exposed dentin. VAS scores were determined pre-operatively (PRE), immediately after treatment (POST), at 1 week, 1, 3 and finally after 6 months. RESULTS: Both TAP and PLA applications decreased DH significantly at POST and throughout the 6-months recalls (p<0.001). Pain reductions upon AB stimulation of TAP treated teeth, assessed at POST and 6 months were 35 and 55%, upon PS stimuli 21 and 54%, respectively. PLA treated lesions responded to AB at POST and after 6 months with 20 and 36% pain reduction, to PS with 11 and 30% pain reduction, respectively. Differences between TAP and PLA pain scores were statistically significant at all recalls (p<0.05). SIGNIFICANCE: TAP paste reduced DH successfully during this 6-months trial. The calcium phosphate crystallites included in the paste and the presumed hydroxyapatite precipitates upon exposure to saliva were hypothetically able to occlude open dentinal tubules, at least to some extent. TAP is considered a biocompatible desensitizer paste.

In vitro evaluation of the wear resistance of composite resin blocks for CAD/CAM.

UNLABELLED: The aim of the study was to investigate two- and three-body wear of CAD/CAM blocks. Four composite resins, one hybrid ceramic and one feldspar ceramic block material were examined. Six specimens each were tested in a ball-on-disc wear device fitted with a zirconia ball (50 N load, 1.2 Hz, 50 k cycles) in water for two-body and in poppy seed slurry for three-body wear evaluation. Volume loss after each 10 k cycle was quantified using a digital CCD microscope. STATISTICAL ANALYSIS: ANOVA and Tukey's multiple comparisons (α=0.05). Two-body wear for composite resin blocks was small, hybrid ceramic and ceramic blocks showed larger volume loss. Threebody wear was very low for all materials. All CAD/CAM block materials investigated displayed low wear compared to previous data for direct posterior composites carrying out the same wear test. The block materials are considered suitable for fabrication of single full crown restorations on premolar teeth.

Polishing and toothbrushing alters the surface roughness and gloss of composite resins.

This study aimed to investigate the surface roughness and gloss of composite resins after using two polishing systems and toothbrushing. Six composite resins (Durafill VS, Filtek Z250, Filtek Z350 XT, Kalore, Venus Diamond, and Venus Pearl) were evaluated after polishing with two polishing systems (Sof-Lex, Venus Supra) and after toothbrushing up to 40,000 cycles. Surface roughness (Ra) and gloss were determined for each composite resin group (n=6) after silicon carbide paper grinding, polishing, and toothbrushing. Two-way ANOVA indicated significant differences in both Ra and gloss between measuring stages for the composite resins tested, except Venus Pearl, which showed significant differences only in gloss. After polishing, the Filtek Z350 XT, Kalore, and Venus Diamond showed significant increases in Ra, while all composite resin groups except the Filtek Z350 XT and Durafill VS with Sof-Lex showed increases in gloss. After toothbrushing, all composite resin demonstrated increases in Ra and decreases in gloss.

Mechanical properties of composite resin blocks for CAD/CAM.

This study compared commercial composite resin blocks with one ceramic block for use in computer-aided design/computer aided manufacturing (CAD/CAM). Four composite resins, one composite ceramic, and one feldspar-ceramic block were investigated. Flexural strength (FS), flexural modulus (FM), and Vickers hardness (VH) were determined under three conditions: dry storage; immersion in water at 37°C for 7 days; and immersion in water at 37°C for 7 days followed by 10,000 thermocycles. After dry storage, FS ranged from 127 to 242 MPa, FM from 9.6 to 51.5 GPa, and VH from 64 to 455. Two-way ANOVA was performed for FS, FM and VH followed by Tukey's multiple comparison (α<0.05). Results demonstrated that the materials degraded after water immersion and thermocycling, but their properties were within the acceptable range for fabrication of single restorations according to the ISO standard for ceramics (ISO 6872:2008).

In vitro and in vivo evaluation of the effectiveness of three dentin desensitizing treatment regimens.

PURPOSE: To evaluate the in vitro and in vivo effects of three treatment regimens on dentin permeability and reduction of dentin hypersensitivity (DH). METHODS: The desensitization treatments were: Gluma Desensitizer PowerGel (GLU), MS Coat One (MSC), and dentin burnishing with fiber-resin burs (STB). A split-chamber device was used to determine the permeability of dentin slices cut from human molars in vitro. Fluid flow through dentin was recorded with a photochemical method after EDTA cleaning, albumin soaking and desensitization treatment (n = 10). 61 study participants with three severely hypersensitive teeth each were enrolled. Sensitivity was determined with an air stimulus before, immediately after treatment, and after 1, 3 and 6 months, using a verbal rating scale. RESULTS: From the 61 study participants enrolled, 52 completed the trial. Permeability at baseline and after albumin soaking was not significantly different. All treatments produced reduced fluid flow through dentin (P > 0.05). All treatments reduced DH significantly (no or moderate sensitivity). Statistical results revealed significant differences among the treatments (P = 0.03). Mann-Whitney comparisons showed GLU, STB < MSC.

Texture of composite resins exposed to two- and three-body wear in vitro.

PURPOSE: To analyze on scanning electron microscopy (SEM) pictures from eight composite resins, taken in the centers of the initial, the middle and the terminal thirds of in vitro produced wear tracks morphological features to explain causative mechanisms for the material wear observed under two- and three-body wear. MATERIALS AND METHODS: In vitro wear behavior of eight composite resins, three conventional and five nanofiller containing marketed products was evaluated using a custom-made Zr-ball-on-disk sliding device. The composite specimens were subjected to 50,000 one-way sliding cycles (1.2 Hz, 50 N load), either simulating two-body wear with water as the intermediate medium or three-body wear using aqueous suspensions of polymethyl methacrylate (PMMA) beads and poppy seeds, respectively. Volume loss of the materials was determined in previous study. Representative specimens were selected for inspection by scanning electron microscopy at 500-fold magnification. From each of the 24 wear tracks microphotographs were taken in the central deepest parts of the initial, middle and terminal thirds of the tracks. RESULTS: For most materials morphological differences were detected depending on the location within the wear track. As a rule, the surface deterioration found increased toward the final part of the wear scar. According to common classification in tribology abrasive wear and fatigue wear, or a combination of both mechanisms were found for all materials tested. Wear was dependent both on the testing mode and on the composition of the individual composite resin material. CONCLUSION: The morphological assessment of wear tracks refects the nature of the abrasive and reveals insight into the mechanism generating wear patterns. Morphological details confirmed abrasive and fatigue-related wear as main failure mechanisms. Selection of food-like slurries as third-body media, such as poppy seed suspension is mandatory to simulate wear of composite restorations in occlusal cavities where three-body wear is the dominating determinant of loss of substance and surface deterioration.

Randomized controlled clinical trial on the efficacy of dentin desensitizing agents.

OBJECTIVE: To investigate the effects of four dentin desensitizers on pain reduction in hypersensitive cervical dentin lesions. MATERIALS AND METHODS: The trial was designed as a randomized, controlled, four-arm, single-masked study. Fifty subjects with at least one hypersensitive lesion in each of the four quadrants were allocated. The requested pre-operative pain, determined as a response to 2-s air-blast (AB) and probe scratching (PS), was ≥5 on a VAS scale, 0 = no through to 10 = worst pain. Randomly each subject received each of the four treatments: MS Coat One F (MSC, Sun Medical, Japan), Nanoseal (NAN, Nishin, Japan), Teethmate Desensitizer (TMD, Kuraray Noritake, Japan) and Gluma Desensitizer PowerGel (GLU, HeraeusKulzer, Germany). The investigator assessed blindly the pain response using the two stimuli and recorded the patients' VAS scores before and immediately after application, after 1 week and after 1, 3 and 6 months. STATISTICAL DATA TREATMENT: ANOVA and post-hoc testing (p ≤ 0.05). RESULTS: Forty-nine subjects completed the trial. Pre-operative dentin hypersensitivity (DH) for the groups was not significantly different. All desensitizers reduced DH significantly throughout the 6-months observation. ANOVA revealed significant differences among VAS scores, obtained with the desensitizing agents (p < 0.001). Ranking by post-hoc testing was: MSC > NAN > TMD > GLU (p < 0.05). Upon PS NAN and TMD showed slight but significant regain of sensitivity after 6 months. For GLU PS scores immediately after application and after 6 months were not significantly different, whereas recalls after 1 week, 1 month and 3 months revealed significantly lower scores. CONCLUSION: The calcium phosphate-based TMD and GLU proved highly effective in reducing sensitivity.

Quantitative wear and wear damage analysis of composite resins in vitro.

The aim of this study was to investigate volume loss and worn surfaces' morphologies of eight composite resins: Durafill VS (DUR), Clearfil AP-X (APX), Filtek Z250 (Z250), Filtek Supreme XT (FIL), Kalore (KAL), MI Flow (MFL), Venus Diamond (VED) and Venus Pearl (VEP). Disc-shaped specimens were fabricated and mounted in a ball-on-disc wear testing machine and abraded in water or with the third-body media, poppy seed slurry and polymethyl methacrylate (PMMA) slurry. Volume loss (n=5) was determined after 50k sliding cycles, and analyzed using two-way ANOVA (α=0.05). The worn surfaces were examined with SEM. Two-way ANOVA suggested significant interaction between composite and wear condition. DUR, KAL and MFL showed low wear in water. DUR, Z250 and FIL showed moderate wear with PMMA slurry, whereas APX, KAL and MFL were deeper abraded. Under the action of poppy seed slurry DUR proved high volume loss. SEM showed that Z250, FIL and MFL were uniformly abraded in water. KAL and MFL with poppy seed were heavily destructed, whereas VED and VEP appeared very smooth. KAL and MFL abraded with PMMA slurry showed many cracks, but VEP remained crack-free and smooth. Volume loss and worn surfaces' morphologies varied with type of composite and third-body media used.

Clinical trial of tooth desensitization prior to in-office bleaching.

The aim of this clinical trial was to compare tooth sensitivity during and after bleaching with hydrogen peroxide gel following application of GLUMA Desensitizer PowerGel or placebo. Forty-six subjects with sound maxillary incisors and canines were enrolled. Tooth shades were determined by comparison with a Vitapan Classic Shade guide. GLUMA Desensitizer PowerGel and placebo were randomly applied to the labial surfaces of the left or right anterior teeth for 1 min, which were then rinsed and dried. Then, Opalescence Boost PF 40% gel was applied onto labial enamel for 15 min. Sensitivity scores [recorded on a 10-point visual-analog scale (VAS)] were determined before, at 5, 10, and 15 min during, and 1, 24, 48 h and 1 wk after, the bleaching treatment. Shades were determined postbleaching and after 1 wk. Prebleaching application of GLUMA Desensitizer PowerGel significantly reduced tooth sensitivity during and after bleaching when compared with treatment with placebo. The whitening effects immediately and 1 wk after bleaching were significant when compared with the prebleaching shades. In conclusion, tooth pretreatment with GLUMA Desensitizer PowerGel for 1 min prior to 15 min of in-office bleaching with 40% hydrogen peroxide gel was highly effective in reducing tooth sensitivity during and after bleaching.

Effects of the space for wash materials on sulcus depth reproduction with addition-curing silicone using two-step putty-wash technique.

Aim of this study was to investigate effects of space thickness and consistency of wash materials on sulcus depth reproduction with silicone impressions, low (L), medium (M), and very high consistency (VH), using two-step putty-wash technique. Impressions were taken from truncated cones with 50-, 100-, or 200-µm-wide sulci, using the combinations L+VH or M+VH and different space thickness for wash materials: 2 mm (ST2), 1 mm (ST1), and approximately 25 µm (ST0.025). Sulcus depth reproduction tended to increase with increasing sulcus width. Sulcus reproduction of ST0.025 was deeper than those of the other groups. At 100- and 200-µm sulcus widths, sulcus reproductions of ST1 and ST2 with L+HV were deeper than with M+HV. Regardless of consistency, the thin spacer produced deep reproduction. Adequate 0.5 mm sulcus reproductions were obtained with 100 and 200 µm wide sulci and 1- and 2-mm spacer widths, combined with low consistency impression material.

Effects of toothbrush hardness on in vitro wear and roughness of composite resins.

AIM: To investigate and compare the effects of toothbrushes with different hardness on abrasion and surface roughness of composite resins. MATERIALS AND METHODS: Toothbrushes (DENT. EX Slimhead II 33, Lion Dental Products Co. Ltd., Tokyo, Japan) marked as soft, medium and hard, were used to brush 10 beam-shaped specimens of each of three composites resins (Venus [VEN], Venus Diamond [VED] and Venus Pearl [VEP]; HeraeusKulzer) with standardized calcium carbonate slurry in a multistation testing machine (2N load, 60 Hz). After each of five cycles with 10k brushing strokes the wear depth and surface roughness of the specimens were determined. After completion of 50k strokes representative samples were inspected by SEM. Data were treated with ANOVA and regression analyses (p < 0.05). RESULTS: Abrasion of the composite resins increased linearly with increasing number of brushing cycles (r² > 0.9). Highest wear was recorded for VEN, lowest for VED. Hard brushes produced significantly higher wear on VEN and VEP, whereas no difference in wear by toothbrush type was detected for VED. Significantly highest surface roughness was found on VED specimens (Ra > 1.5 µm), the lowest one on VEN (Ra < 0.3 µm). VEN specimens showed increased numbers of pinhole defects when brushed with hard toothbrushes, surfaces of VEP were uniformly abraded without level differences between the prepolymerized fillers and the glass filler-loaded matrix, VED showed large glass fillers protruding over the main filler-loaded matrix portion under each condition. CONCLUSION: Abrasion and surface roughness of composite resins produced by toothbrushing with dentifrice depend mainly on the type of restorative resin. Hardness grades of toothbrushes have minor effects only on abrasion and surface roughness of composite resins. No relationship was found between abrasion and surface roughness. CLINICAL SIGNIFICANCE: The grade of the toothbrush used has minor effect on wear, texture and roughness of the composite resin.

Effects of two topical desensitizing agents and placebo on dentin hypersensitivity.

PURPOSE: To evaluate the efficacy of two commercial desensitizing agents in subjects with moderate to severe dentin hypersensitivity for a period of 6 months and to compare the results with topical application of water as negative control. METHODS: BisBlock (BIS; oxalate) and Gluma Desensitizer PowerGel (GLU; glutaraldehyde/HEMA) were tested. 50 subjects, average age 32.4 years, with at least one cervical hypersensitive incisor, canine or premolar tooth area and pre-operative pain score > or = 6 on VAS from 0 to 10 in each of three quadrants were included. Prior to application of the desensitizing agents or placebo (PLA; water) the sensitive areas were cleaned with prophy paste. Desensitizers were applied according to manufacturers' instructions, the placebo was left for 60 seconds dwell, rinsed off and dried. Pain scores were determined using both evaporative and tactile stimuli immediately after treatment, after 1 day, 1 week, 1, 3 and 6 months. Statistical analyses of the findings were performed using ANOVA and pot-hoc tests with a significance set at P < or = 0.05. RESULTS: All subjects completed the trial. Both the two desensitizing agents and placebo showed significant reduction in sensitivity at baseline and throughout the 6-month evaluation. The effects of the three treatments were significantly different. Pain reduction with GLU was consistently highest, followed by PLA that was significantly greater than BIS. VAS scores for the evaporative stimulus were moderately, but significantly lower than for tactile stimulation.

Two- and three-body wear of composite resins.

OBJECTIVE: The aim of the present study was to investigate two- and three-body wear of microfilled, micro-hybrid and nano-hybrid composite resins using a ball-on-disc sliding device. METHODS: One microfilled (Durafill VS), one micro-hybrid (Filtek Z250), one hybrid (Clearfil AP-X), one nanofilled (Filtek Supreme XT), and two nano-hybrid (MI Flow, Venus Diamond) composite resins were examined. The composites were filled in a cylindrical cavity, and light polymerized. After storage in 37°C distilled water for 7days, all specimens were tested with a custom-made ball-on-disc sliding device with a zirconia ball as antagonist (50N loads, 1.2Hz, 10,000 cycles) immersed in water, poppy seed slurry and polymethyl methacrylate slurry, respectively. Maximum wear depth and volume loss of worn surfaces were quantified by a digital CCD microscope and analyzed with two-way analysis of variance. RESULTS: The interactions between composite resin and condition of their maximum wear depth and volume loss were significant (p<0.01). The abrasive wear produced at three-body loading with poppy seed slurry was very large for the microfilled composite, and small for all other composites tested. In contrast, two-body wear of the microfilled composite, and one nano-hybrid composite was very low. SIGNIFICANCE: The ball-on-disc sliding device used is considered suitable to simulate sliding of an antagonist cusp on an opposing occlusal composite restoration, either in the two- or the three-body wear mode. All tested materials except for the microfilled composite showed low surface wear when exposed to poppy seed as the third-body medium.

Comparative evaluation of mechanical characteristics of nanofiller containing resin composites.

PURPOSE: To determine basic mechanical characteristics of six commercially available nanofiller containing resin composites compared to a microhybrid and a microfilled reference material. The tested hypothesis was that there are no differences in mechanical properties between the materials. METHODS: Durafill VS (DUR) and Filtek Z250 (Z250) were used as microfilled and microhybrid references. The nanofiller containing products were: Filtek Supreme XT (FIL), Grandio (GRA), Kalore (KAL), MI Flow (MIF), Tetric EvoCeram (TET), and Venus Diamond (VED). The following material characteristics were determined after 24 hours water storage (n = 6): Flexural strength and modulus (FM), yield stress (0.02%), tensile strength and modulus (TM), diametral tensile strength, Knoop hardness (KHN), and fracture toughness (KIC). RESULTS: The microfilled composite DUR consistently showed the lowest values for each property investigated. The group of nanofiller containing products could be subdivided into two groups: the nanohybrid products GRA and VED and the nanofilled FIL with higher values, on the one hand, and the flowable MIF, and the prepolymer containing composites KAL and TET, on the other. The mechanical performance of the microhybrid reference material Z250 was overall slightly better or in line with the nanohybrid and nanofilled materials. Stringent linear relationships were found between KHN and the moduli FM and TM, respectively (r > 0.95). Linear relations between the other materialvalues investigated were moderate to high.