Evaluation of enamel wear by 3 occlusal splint materials: An in vitro study.

STATEMENT OF PROBLEM: Occlusal devices used to manage bruxism have been commonly fabricated from polymethyl methacrylate with the powder-liquid technique. More recently, Vertex ThermoSens (VTS) and the biocompatible high-performance polymer (BioHPP), an optimized material having polyetheretherketone (PEEK) as its basis, have been used, but little is known about the wear of these materials on human enamel. PURPOSE: The purpose of this in vitro study was to assess via a mastication simulation test how 3 occlusal device materials affected the wear and roughness of enamel antagonists. MATERIAL AND METHODS: A noncontact 3D optical profilometer was used to measure the enamel surface roughness (Ra) against 3 occlusal device materials: vertex regular, VTS, and PEEK high-performance polymer (BioHPP). A dual-axis mastication simulator was used to perform a 2-body wear test on specimens from each group. The test consisted of 10 000 cycles with a 70-N force and 5 to 55 °C thermocycling. Following simulated mastication, the weight of each specimen and the Ra change were compared with the Kolmogorov-Smirnov test, paired specimens t test, Wilcoxon signed-rank test, and 1-way analysis of variance (α=.05). RESULTS: The polyamide group caused the lowest amount of enamel wear (P<.05), while the heat-polymerized acrylic resin group induced the largest amount of enamel wear (P<.05). For polyamide and PEEK, the change in enamel surface roughness exhibited a smooth texture, whereas it found a rougher surface for the heat-polymerized acrylic resin. CONCLUSIONS: According to this study, surface roughness and wear on human enamel were not correlated. PEEK is a promising material for the fabrication of occlusal devices.

Risk Factors with Porcelain Laminate Veneers Experienced during Cementation: A Review.

The clinical success of porcelain laminate veneers (PLVs) depends on many clinical and technical factors, from planning to execution, among which adhesive cementation is of significant importance. This procedure carries many risk factors if not optimally executed. The objective of this study was to document the clinical parameters affecting successful cementation procedures with a focus on the adhesive strength, integrity, and esthetics of the PLVs. A literature search was conducted through MEDLINE, complemented by a hand search using predefined keywords. Articles published in English between 1995 and 2023 were selected. According to this review, the success and longevity of PLVs rely in great part on the implementation of a precise cementation technique, starting from field isolation, adequate materials selection for adhesion, proper manipulation of the materials, the seating of the veneers, polymerization, and elimination of the excess cement. Several clinical steps performed before cementation, including treatment planning, preparation, impression, and adequate choice of the restorative material, could affect the quality of cementation. Scientific evidence suggests careful implementation of this process to achieve predictable outcomes with PLVs. The short- and long-term clinical success of adhesively luted PLVs is tributary to a deep understanding of the materials used and the implementation of clinical protocols. It is also contingent upon all the previous steps from case selection, treatment planning, and execution until and after the cementation.

Simulating mandibular movements and articulator design.

Establishing new dentition and occlusal schemes requires a thorough understanding of the principles of occlusion, mandibular movements, phonetics, and esthetics. This presentation is designed to help understand the dynamics of mandibular movements, form and function of the dentition, occlusal schemes, patient simulation, and the interaction of those factors on occlusal rehabilitation. Special emphasis is laid upon articulator design and the current innovations utilizing digital technology in the development of this instrument from an articulator to a patient simulator.

The patient-specific anatomical articulator.

Currently available dental articulators have limitations for reproducing human mandibular movements. The present article describes an innovative device that is a true patient-specific anatomical articulator that accurately simulates patient anatomy and eliminates all technique-sensitive mounting procedures, thus substantially diminishing potential errors in mounting and articulator settings. By using three-dimensional (3D) printing technology, patient cone beam computed tomography (CBCT) data are used to print 3D replicas of the condylar fossae, as well as the actual condyles, at the correct intercondylar distance. The maxilla (maxillary teeth and edentulous ridge) is printed with the correct spatial relationship to the condylar complexes and the Frankfort horizontal plane (FHP). Those printed structures are then premounted onto a modified articulator frame to render it "anatomic." This new custom anatomical articulator, which accurately mimics patient anatomical movements rather than relying on average values, represents the first truly fully adjustable articulator that is more precise than can be generated by a pantographic tracing. It saves money, time, and effort by eliminating earbow transfers and mounting errors in complex prosthodontic treatment.

Radiographic Appearance of Interocclusal Record Materials for Cone Beam Computed Tomography-Guided Implant Surgeries.

PURPOSE: To select an ideal interocclusal record material for cone beam computed tomography (CBCT)-guided implant surgery based on the material's radiodensity on the scan. MATERIALS AND METHODS: Twelve commonly used interocclusal record materials were used for this investigation: two were waxes, one was polyether, and nine were polyvinyl-siloxane-type materials. A scan template was fabricated by duplicating existing dentures in Ortho-Jet acrylic resin mixed with 30% barium powder for the teeth and 10% barium powder for the denture base between the teeth and the tissue. An interocclusal record was fabricated with each material, and the same template was used to obtain a CBCT scan with an ICAT machine (Imaging Sciences International) at 0.3 voxel and 14-bit depth settings. Twelve CBCT scans were obtained and analyzed. The radiopacity of the barium teeth was used as a control and was compared with the opacity of the 12 materials using a paired t test. A post hoc analysis of variance (ANOVA) test was used to compare the densities of the various materials with each other. RESULTS: There was a statistically significant difference between the radiopacity of barium teeth (gray value: 1,959.475) and that of Modelling Wax (gray value: 750; P = .0026), Aluwax (gray value: 795.22; P = .0022), Blu-Bite CT (gray value: 1,105; P = .005), Ramitec (gray value: 1,105.3; P = .08), Memosil 2 (gray value: 1,202; P = .01) followed by Reprosil (gray value: 1,407.73; P = .01). Compared with the barium teeth, there was no statistically significant difference between the densities of Futar D (gray value: 1,866.5; P = .51), Jet Bite (gray value: 1,660.04; P = .08), Lab-Putty (gray value: 1,402.14; P = .19), and Memoreg 2 (gray value: 1,754.72; P = .1). The highest radiodensity was seen with Blu-Mousse (gray value: 2,949; P = .007) and Take 1 (gray value: 2,229.85; P = .025), which were also significantly different from the density of the barium teeth but in the opposite direction, making them more opaque. CONCLUSION: Within the limitations of this in vitro study, the most radiolucent appearance of Modelling Wax, Aluwax, Memosil 2, Blu-Bite CT, and Ramitec made them the suitable materials of choice of those tested, as the interocclusal registration record during CBCT scanning allowed clear visualization of barium teeth.

Radiographic Blind Test of Curvature of the Posterior Border of the Mandibular Ramus as a Morphological Indicator of Gender.

PURPOSE: Curvature of the posterior border of the mandibular ramus at the occlusal plane has been described as a morphological trait for males. Controversy over the accuracy of this method remains among researchers; studies employing similar methods report accuracy rates for successful gender identification ranging from 59% to 99%. This blind study assessed evaluators' ability to determine gender based on the presence or absence of curvature of the posterior margin of the mandibular ramus through panoramic radiographs. MATERIALS AND METHODS: Randomly selected panoramic radiographs were obtained from The Ohio State University College of Dentistry for 413 adult male (M) and female (F) subjects. Two evaluators separately assigned ratings using a similar method to the Loth and Henenberg methodology to each subject on the right and left sides of mandibular rami. The ratings were based upon three criteria: (1) presence of curvature at the occlusal plane (M), (2) presence of curvature but not at the occlusal plane (F), and (3) lack of curvature (F). Pearson exact chi-squared test was used to evaluate the statistical strength of the ratings. RESULTS: The evaluators were only in agreement for both the right and left rami in roughly two-thirds (66.8%) of cases when there was no excessive tooth loss (ETL); however, the inter-observer agreement improved to 82.1% for those rami associated with ETL. Inter-observer agreement occurred in 72.9% of female rami and in only 64.4% of male rami. CONCLUSION: The results of this study indicated that assessment of posterior border curvature of  mandibular rami through panoramic radiographs was not a reliable indicator of gender and was further plagued by unacceptably high levels of inter-observer disagreement.

Mandibular function after Myorelaxation Therapy in temporomandibular disorders.

PURPOSE: The aim of this study was to analyze the efficacy of Myorelaxation Therapy in temporomandibular disorders on the basis of mandibular movement measurements, reported functional impairment and clinical findings. MATERIAL/METHODS: To ascertain the mandibular movements 78 women were investigated. The first group consisted of 32 consecutive patients (23.3±4.8 years) suffering from muscle disorder and disk displacement with a reduction serving as a treated group. The second group was formed from 46 volunteers, as a healthy group (20.1±1.3 years). Jaw-tracking records (K7, Myotronics-Noromed Inc.) were performed including the measurements of opening, lateral and protrusive movement range, maximal and average velocity of opening/closing. Reported impairment and clinical data were collected. The treatment involved nocturnally applied a non-occluding sublingual relaxation splint combined with daily performed stretching exercises. Measurements were taken before treatment, after 4 weeks with no interventions (control period) and after 3 weeks, 3 and 6 months. RESULTS: After the treatment mandibular opening range increased by 8mm (19%, p<0.05), lateral movement by 2.1mm (36%, p<0.05) while protrusive movement decreased by 0.5mm (p>0.05). Maximal and average velocity parameters significantly increased (p>0.05). These results were supported by the decrease in reported impairment and clinical pain occurrence (p<0.05). Only joint clicking change was non-significant (p>0.05). CONCLUSIONS: Myorelaxation Therapy was effective in the treatment of our group of patients. A significant improvement in the opening and lateral movement range, as well as opening/closing velocity was obtained after 6 months of treatment. This method can be easily managed by general practitioner, especially in muscles-related TMD types.

Kinematic Modeling of Normal Voluntary Mandibular Opening and Closing Velocity-Initial Study.

PURPOSE: Determination and quantification of voluntary mandibular velocity movement has not been a thoroughly studied parameter of masticatory movement. This study attempted to objectively define kinematics of mandibular movement based on numerical (digital) analysis of the relations and interactions of velocity diagram records in healthy female individuals. MATERIALS AND METHODS: Using a computerized mandibular scanner (K7 Evaluation Software), 72 diagrams of voluntary mandibular velocity movements (36 for opening, 36 for closing) for women with clinically normal motor and functional activities of the masticatory system were recorded. Multiple measurements were analyzed focusing on the curve for maximum velocity records. For each movement, the loop of temporary velocities was determined. The diagram was then entered into AutoCad calculation software where movement analysis was performed. The real maximum velocity values on opening (Vmax ), closing (V0 ), and average velocity values (Vav ) as well as movement accelerations (a) were recorded. Additionally, functional (A1-A2) and geometric (P1-P4) analysis of loop constituent phases were performed, and the relations between the obtained areas were defined. Velocity means and correlation coefficient values for various velocity phases were calculated. RESULTS: The Wilcoxon test produced the following maximum and average velocity results: Vmax = 394 ± 102, Vav = 222 ± 61 for opening, and Vmax = 409 ± 94, Vav = 225 ± 55 mm/s for closing. Both mandibular movement range and velocity change showed significant variability achieving the highest velocity in P2 phase. CONCLUSIONS: Voluntary mandibular velocity presents significant variations between healthy individuals. Maximum velocity is obtained when incisal separation is between 12.8 and 13.5 mm. An improved understanding of the patterns of normal mandibular movements may provide an invaluable diagnostic aid to pathological changes within the masticatory system.

Porcelain thickness and cement shade effects on the colour and translucency of porcelain veneering materials.

OBJECTIVE: Purposes of this in vitro study include evaluating colour changes in combinations of feldspathic porcelain and cement resulting from different thicknesses of porcelain and different shades of composite luting agent, and evaluating relative translucency parameter (RTP) values. MATERIALS AND METHODS: Porcelain discs of shade A1 at nominal thicknesses of 0.5 and 1.0mm were bonded to cements of three shades in a factorial design. Colours were calculated for CIE D65 Illuminant and Standard Human Observer on black, grey and white backings. A colour difference (CD) was calculated of each possible pair of different porcelain thickness values for the same cement shade and each possible pair of different cement shades for the same porcelain thickness. RTP was analyzed by ANOVA and selected pairwise comparisons. RESULTS: All mean CDs studied were perceptible and most were at or greater than the clinical acceptability threshold, with the notable exception that the mean CDs and their confidence limits were below the clinical acceptability threshold for a change in porcelain thickness when utilizing the Clear cement shade. Variation in the shade of the resin luting cement will result in CDs which are near or beyond clinical acceptability. A decrease in porcelain thickness did significantly increase RTP when bonded to the resin cement shades studied. CONCLUSION: Changes in porcelain thickness or cement shade may adversely affect basic aesthetic properties of these materials. Development of methods for analyzing aesthetic effects over greater ranges of thickness for these materials would improve the prognosis for using these materials.

Optical characteristics of contemporary dental composite resin materials.

OBJECTIVES: Optical and physical properties of dental restorative composite materials are affected by composition. Basic optical absorption and scattering properties have been derived through the use of a corrected reflectance model, but practical and important optical properties are not easily derived from these basic spectral characteristics. The purposes of this study are to derive and compare colour and translucency characteristics of two cured contemporary nanohybrid composites being marketed as universal composites, and to evaluate colour difference between each composite material and published shade guide data. METHODS: Previously derived optical scattering and absorption coefficients for five diverse shades of these composite materials were used to calculate the CIE colour parameters of L*, a* and b* at infinite thickness under various illuminants and to derive ideal translucency parameters at various thicknesses using two colour difference formulae. RESULTS: Differences were found in the inherent colour parameters and in the translucency parameters between the brands for some of the shades studied. The colour differences of the inherent colours from published shade guide data were always higher than the perceptibility limit, and often higher than the acceptability limit. CONCLUSIONS: Inherent colours and ideal translucency parameters may be calculated from optical coefficients for a variety of illuminants. Different inherent colour parameters of composite materials marked for the same shade indicate the influence of compositional differences between these materials. CLINICAL SIGNIFICANCE: Since patients are seen under various illuminations, the ability to assess appearance matching characteristics under diverse illuminants will help assure an optimum match for the patient.

Accuracy of Kubelka-Munk reflectance theory for dental resin composite material.

OBJECTIVE: The objective of this study is to determine the effect of interfacial reflection correction (IRC) on the accuracy of this reflectance model for contemporary dental resin composite materials. METHODS: Visible reflectance spectra were obtained for varying thicknesses (∼0.3-1.2mm) of five shades of each of two brands (Herculite Ultra and Kalore) of dental resin composite materials on black, gray and white backings. For each shade and brand, K-M theory was fit (SAS non-linear fit) for each of three IRC methods: (1) no IRC (No), (2) an IRC method which uses a theoretical value of the internal reflection for translucent materials (Tr), and (3) an IRC method which uses a derived value of the internal reflection for opaque materials (Op). The errors were subjected to repeated measures analysis of variance and Bonferroni corrections were applied to selected pairwise comparisons. RESULTS: The Op method had a statistically lower error than the No method at wavelengths from 460 to 560nm, and the Tr method had this lower error at wavelengths from 440 to 780nm. SIGNIFICANCE: Corrected K-M reflectance theory may be used to accurately quantify the optical K-M absorption and scattering coefficients for contemporary dental resin composite materials, and this theory may be used to calculate accurately the reflectance spectrum for a clinically relevant thickness value and for a backing that is low, mid-range or high in lightness. Both color and translucency information of resin composite materials may be accurately predicted using corrected Kubelka-Munk reflectance model.

Effect of bleaching on tooth discolouration from food colourant in vitro.

OBJECTIVES: The purpose of this study was to evaluate the effect of bleaching on tooth discolouration from neutral food colourant media (NFCM). METHODS: Freshly extracted human molar teeth (n = 32) were divided into four groups (n = 8): non-bleached treatment-NBT, non-bleached control-NBC, bleached treatment-BT and bleached control-BC. Bleached teeth specimens were subjected to 20% carbamide peroxide bleaching agent for 10h. Colour measurements (pre-test) were done using a non-contact spectroradiometer. The teeth specimens were immersed in a neutral buffer solution. NBT and BT groups had 0.025% red food colour (Red 40) added to the buffer solution. The immersed specimens were incubated for 4h at 37°C. Colour was again measured after immersion/incubation (post-test) and after subsequent polishing using plain-pumice slurry (post-polish). Differences in CIE a* (redness parameter) were analysed by repeated measures ANOVA with Bonferroni-corrected t-tests for the pairwise comparisons of interest. RESULTS: Tooth discolouration was measured as total stain (mean difference in a* between post-test minus pre-test), extrinsic stain (mean difference in a* post-polish minus post-test) and intrinsic stain (mean difference in a* post-polish minus pre-test) A statistically significant difference in the mean Δa* was observed (P = 0.009) between staining treatment for bleached and non-bleached teeth. Also, a statistically significant difference (P < 0.001) was noted between control and treatment groups of bleached teeth that were subjected to staining. CONCLUSIONS: Bleaching resulted in total and extrinsic tooth discolouration by the NFCM. CLINICAL SIGNIFICANCE: It might be beneficial to avoid highly pigmented foods immediately following bleaching in order to optimize the effects of tooth whitening.

Effect of substrate shades on the color of ceramic laminate veneers.

STATEMENT OF PROBLEM: Ceramic laminate veneers are generally fabricated with varying thicknesses ranging from 0.3 to 1 mm, depending on the need to mask discolored teeth or slightly correct the contour of malpositioned teeth. Clinical color reproduction poses a challenge because of color interaction with the underlying substrate, whether tooth structure or esthetic restorative material. PURPOSE: The purpose of this in vitro investigation was to measure the effect of color change resulting from applying 2 shades of ceramic material, translucent (T1) and opaque (O2), to 2 shades of composite resin substrate material, light (A3) and dark (C4), on the overall color of ceramic laminates. MATERIAL AND METHODS: Forty disks were fabricated. Twenty disks (15 × 0.5 mm) were cut from pressed ceramic, 10 disks for each shade (translucent and opaque). Additionally, 20 disks (15 × 4.0 mm) were fabricated from light-polymerized composite resin material, 10 disks for each shade (light and dark). The ceramic disks were bonded to the composite resin disks with clear resin cement. The specimen combinations were divided into 4 groups (n=5). Color measurements were done with a colorimeter (Minolta Chroma Meter CR-200b) configured with diffuse illumination/0-degree viewing geometry. Mean CIE lightness (L*), chroma (C*(ab)), and hue angle (h(ab)) values were obtained. A 2-way analysis of variance (ANOVA) was used to compare the means and standard deviations between the different color combinations (α=.05), followed by Tukey's HSD post hoc test for significant interactions. RESULTS: The 2-way ANOVA showed significant differences (P<.001) in L*, C*(ab), and h(ab) for a change in the composite resin substrate, regardless of the ceramic material shade. There was significant color change from dark to light substrate (P=.044). The mean h(ab) (SD) of dark substrate/opaque veneer was 89.62 (1.5), while the mean h(ab) of light substrate/translucent veneer was 81.23 (1.7). CONCLUSIONS: Within the limitations of this study, the selected color of a 0.5 mm ceramic laminate veneer was significantly affected by the change in color of the supporting substrate.

Effect of pH on tooth discoloration from food colorant in vitro.

OBJECTIVES: The purpose of this study was to evaluate the effect of acidic, neutral and alkaline food colorant media (FCM) on tooth discoloration in vitro. METHODS: Treatment (n=24) and control (n=24) sterile, hydrated human molars were prepared in individual, impervious holders and their color measured (pretest) using a non-contact spectroradiometer system. Specimens were randomly assigned to and immersed in one of the three buffer solutions (pH 2, pH 7 or pH 12). Red food color (Red 40) was added to the treatment buffer solutions at 0.025%. Immersed specimens were incubated for 4h at 37°C. Color was also measured after immersion/incubation (posttest) and again after subsequent 2-min of polish using plain-pumice slurry with a slow-speed handpiece (post-polish). Differences in CIE a* (redness parameter) were analyzed by repeated measures ANOVA with Bonferroni-corrected t-tests for the pairwise comparisons of interest. RESULTS: Tooth discoloration was measured as total stain (mean difference in a* between posttest minus pretest), extrinsic stain (mean difference in a* post-polish minus posttest) and intrinsic stain (mean difference in a* post-polish minus pretest). No significant change in color was observed between the control and treatment groups for neutral and alkaline FCM. However, acidic FCM caused reddish tooth discoloration posttest minus pretest, post-polish minus pretest and post-polish minus posttest compared to neutral and alkaline treatment and control groups. CONCLUSIONS: The degree and type of tooth discoloration are influenced by both the low pH and food color rather than the dietary pigment alone.

A simplified technique for creating a customized gingival emergence profile for implant-supported crowns.

A successful implant restoration is one that will allow adequate function and esthetics. Soft-tissue management around implant-supported restorations continues to present a considerable challenge for the restoring dentist as well as the laboratory technician while fabricating the final prosthesis. This article presents a simplified and economical technique to direct gingival tissue healing, as well as create a removable gingival replica of the customized gingival emergence profile. The created profile can then be used in the dental laboratory to achieve a superior and predictable esthetic outcome for implant-supported fixed restorations.

Effect of home bleaching systems on enamel nanohardness and elastic modulus.

OBJECTIVES: The purpose of this study was to evaluate the nanohardness and elastic modulus of human enamel after treatment with tray and strip bleaching systems. METHODS: Fifty-five human enamel samples were exposed to five different bleaching agents. Nanoindentations were made before and after bleaching treatments following the manufacturer's directions using a Nanoindenter XP (MTS Systems Corporation, Oak Ridge, TN, USA). Nanohardness and elastic modulus measurements were obtained and the results were statistically analyzed using a repeated measures analysis of variance with a post-hoc Tukey-Kramer multiple comparison test. RESULTS: Nanohardness and elastic modulus measurements showed decrease of mean values for each group except the control which remained the same. There were significant differences due to time (before and after treatment) and material effects in nanohardness (P<0.0001) and elastic modulus (P=0.0241). Measurements after treatment showed significant decrease in nanohardness between all groups and the control group. There was a significant difference in hardness between CP and TO after treatment. Additionally, there were significant differences in elastic modulus between the control group when compared to OB and TO after treatment. While there were significant changes in the elastic modulus due to treatment for both CP and TO, there were no significant differences between any of the groups after treatment. CONCLUSIONS: Nanohardness and elastic modulus of human enamel were significantly decreased after the application of home-bleaching systems.

Effect of mixing methods on the physical properties of dental stones.

OBJECTIVES: This in vitro comparative study evaluated the effect of different stone mixing methods on material properties of four dental stones. Two ADA type IV stones (Silky-Rock and Snap-Stone), one type V high expansion stone (Die Keen), and one recently introduced type V specialty stone (HandiMix) were chosen for this study. METHODS: Forty cylindrical specimens (25 mm x 12.5 mm) were cast for each of the nine stone sub-groups and bench dried at 23+/-2 degrees C for 1 and 24h. Specimens were then tested in an Instron in tensile and compression modes at crosshead speeds of 0.5 and 1.0 mm/min, respectively. Four rectangular-shaped specimens (30 mm x 15 mm x 15 mm) of each stone type were cast and bench dried for 48 h. Knoop microhardness measurements were obtained from defined areas on each specimen for surface hardness testing using 200 g load and 20s dwell time. A 12.6 mm(2) area was then delimited in the center of two sides of each specimen and photographed under low power magnification (40x). The average pore number per area was then determined for each specimen for surface porosity testing. The setting time and setting expansion for each stone type was recorded as well. RESULTS: ANOVA (P<0.001) and Ryan-Einot-Gabriel-Welsh test (P<0.05) showed significant differences between diametral tensile strengths and pore numbers for both stone types and mixing methods. CONCLUSION: Within the limitations of this study, the newly introduced mixing method did not appear to have an effect on the physical properties of HandiMix stone.

Comparative study of the transverse strength of three denture base materials.

OBJECTIVES: Fracture resistance of recently introduced denture base resins has not been compared to traditional denture base materials. This study compared the transverse strength of three denture base materials, namely, Lucitone 199, Triad VLC, and the newly introduced Eclipse. MATERIALS AND METHODS: A total of 30 specimens (50mmx25mmx2.5mm) were fabricated, 10 from each material. The specimens were loaded until failure on an Instron universal testing machine using a three point flexural test. One-way analysis of variance (ANOVA) was used to compare the mean transverse strength between the three materials tested. RESULTS: The transverse strength values showed significant differences between the three denture base materials (P<0.0001). The mean transverse strength and standard deviations (MPa) were as follows: Eclipse 116.13+/-17.7, Lucitone 87.12+/-8.1, and Triad VLC 57.96+/-7.3. CONCLUSIONS: Within the limitations of this study, Eclipse showed the highest transverse strength among the materials tested. Eclipse denture base material may provide a stronger alternative to traditional denture base resins.

Bond strengths of one- and two-step self-etch adhesive systems.

STATEMENT OF PROBLEM: One-bottle self-etching adhesives have been introduced that combine the etchant, primer, and adhesive into a single bottle in an effort to reduce the number of bonding steps. Limited research has been conducted comparing the efficacy of 1-bottle and 2-bottle self-etching adhesives. PURPOSE: This investigation evaluated the microtensile bond strength (MTBS) of 3 one-step self-etching adhesives, 2 two-step self-etching adhesives, and a total-etch adhesive. A secondary objective was to evaluate the effect of an intermediary layer of elastic resin on the MTBS of 2 of the self-etching adhesives. MATERIAL AND METHODS: The MTBS of 3 one-step self-etching adhesives (G-Bond, iBond, and Clearfil S(3)), 2 two-step self-etching adhesives (Clearfil SE and Optibond Solo Plus Self-Etch), and a total-etch adhesive (Prime & Bond NT) was evaluated. Microtensile bond strength (MPa) was determined using composite resin (Herculite XRV) cylinders bonded to the dentin surface of human third molars (n=24) using 6 bonding agents. Each bonded tooth specimen was longitudinally sectioned to produce bar-shaped specimens with a square cross-sectional nominal bond area of 1.4 mm(2) (n=20). Bonded specimens were stored in distilled water at 37 degrees C +/- 2 degrees C for 72 hours, during which time they were subjected to thermal cycling (1500 cycles, in water baths of 5 degrees C and 55 degrees C, for a dwell time of 30 seconds). Testing was performed on a universal testing machine at a crosshead speed of 1.0 mm/min. One-way ANOVA, Ryan-Einot-Gabriel-Welsh multiple range test, and Wald chi square test, each using an overall alpha=.05, were performed on all data. Low-power (x20) microscopic examination of the bond failure was observed for each specimen. RESULTS: The 1-way ANOVA (P<.001) and Ryan-Einot-Gabriel-Welsh multiple range test (P<.05) showed significant differences between the mean MTBS values for several of the bonding agents tested. The Wald chi square test of the Weibull distribution showed significant differences between adhesives (P<.001). CONCLUSION: Of the bonding agents tested, significantly higher MTBS was obtained with the total-etch 2-stage adhesive. The results of this study suggest that there are similar bond strengths between the 1- and 2-bottle self-etch adhesives.