[show abstract][hide abstract] ABSTRACT: This study evaluated the effect of adding diphenyliodonium hexafluorphosphate (DPI) as a third component of the free-radical photoinitiator system of model resin cements on their photopolymerization kinetics/stress and fundamental properties.
A model resin cement containing a 1:1 mass ratio of 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane and triethyleneglycol dimethacrylate was obtained. Camphorquinone (1mol%) and 2-(dimethylamino)ethyl methacrylate (2mol%) were added to monomer blend. Six mixtures were obtained by incorporation of 0 (control), 0.25, 0.5, 1, 2, or 4mol% of DPI. The cements were loaded with a 60% mass fraction of silanated glass fillers. Polymerization kinetics (using Fourier-transform near-infrared spectroscopy), flexural strength and modulus, water uptake/solubility, and polymerization stress were assessed. Data were statistically analyzed using one-way ANOVA and Student-Newman-Keuls' test (P≤0.05).
In the DPI-modified materials, the onset of autodeceleration occurred earlier and at higher conversion compared with the control cement. The addition of DPI also led to a more active early-stage polymerization. The flexural modulus was generally higher for DPI-containing materials. Water uptake and solubility were generally lower for materials with DPI fractions ≥0.5%. Significant increase of polymerization stress was observed only in the group with 1mol% of DPI compared with the control cement.
The effect of DPI on the photopolymerization reactivity of the cement is concentration-dependent; the use of DPI could result in better polymerization efficiency of resin-based cements.
Dental materials: official publication of the Academy of Dental Materials 10/2013; · 2.88 Impact Factor
[show abstract][hide abstract] ABSTRACT: Background/purposePolymerization contraction stress is an undesirable and inevitable characteristic of adhesive restorations. It is important to understand the stress distribution to improve the clinical effectiveness of resin composite restoration. The aim of this study was to evaluate the polymerization shrinkage stress created in tooth photoelastic models using different filling techniques.Materials and methodsTwenty Class II tooth models were obtained. They were distributed into four experimental groups (n = 5) according to the following restorative techniques: resin composite with horizontal insertion, resin composite with oblique insertion, flowable composite + resin composite with horizontal insertion, and flowable composite + resin composite with oblique insertion restoration. Restored photoelastic models were analyzed using a plane polariscope. The stress along seven points of adhesive interface was analyzed from images of each insertion, at the baseline (immediately) and 24 hours after polymerization. Maximum shear stress data were obtained and submitted to two-way ANOVA analysis followed by Tukey's posthoc test at P = 0.05.ResultsHorizontal and oblique techniques have shown differences in stress patterns. No difference between stress values of horizontal and oblique techniques was found. Groups restored with flow composite showed significant higher stress levels than those restored only with universal composite.Conclusion
The use of flow composite created higher polymerization stress effects on the class II restoration than does the conventional restoration technique.
[show abstract][hide abstract] ABSTRACT: The type IV dental stone is widely used for the fabrication of dyes and master casts for fixed and removable partial prostheses. It is typically normal to wait at least 24 hours for the casts to dry prior to beginning the laboratory procedures. The waiting time has been shown to be greatly reduced by using microwave drying.
This study evaluated the influence of drying techniques at room temperature and microwave oven on the linear dimensional change, compressive strength and detail reproduction in type IV dental stones.
Three type IV dental stone brands were selected; elite Rock, Shera Premium and Durone IV. Two different drying protocols were tested in 4 groups (n=10); G1 - room temperature (25±4ºC) dried for 2 hours; G2 - room temperature dried for 24 hours; G3 - room temperature dried for 7 days and G4 - microwave oven dried at 800 W for 5 minutes and after 2 hours at room temperature. After drying, the samples were assayed for dimensional charges. The sample surface was submitted to the ImageTool 3.0 software for compressive strength in a universal testing machine with a cell load of 50 KN at a crosshead speed of 0.5 mm/minutes and the detail reproduction was analyzed with a stereomicroscope at 25x magnification. The statistical analysis of the linear dimensional change and compressive strength data were conducted by the ANOVA test followed by the Tukey test (p<0.05). Detailed reproduction values were reported in percentages.
For the compressive strength test, Elite Rock and Durone IV did not present significant differences between G2 and G4, while Shera Premium did not present differences between G3 and G4. The best reproduction levels were observed for G3.
Dental stone microwave oven drying showed a linear dimensional change similar to after room temperature drying for 24 hours and 7 days. The compressive strength of the stone dried in the microwave oven was similar to those dried at room temperature for 24 hours, with the exception of Shera Premium, which had similar results for microwave and room temperature drying for 7 days. For the microwave drying method the detail reproduction levels for samples dried at room temperature for 24 hours and 7 days were similar, except for the Durone IV.
Journal of applied oral science: revista FOB 10/2012; 20(5):588-93. · 0.39 Impact Factor
[show abstract][hide abstract] ABSTRACT: Objectives
To evaluate the effects of four different light-curing protocols on the microtensile bond strength (μTBS), ultimate tensile strength (UTS), Knoop micro-hardness (KH) and cross-link density (CLD) of a nano-filled resin composite.
Filtek Supreme XT (3M-ESPE) was used for the entire experiments following four light-curing approaches: ST) Standard irradiance; HI) High irradiance; PD) Pulse delay: SS) Soft Start. The specimens were submitted to different storage periods (24 h or 6 months), cut into match-sticks and subsequently submitted to μTBS testing. Hourglass specimens were also prepared for UTS and KH. Cylindrical specimens were prepared for the CLD evaluation after absolute ethanol challenge. The results were statistically analyzed with a two-way ANOVA and Tukey's test (α=0.05).
For UTS and KH, continuous irradiance (PD and SS) induced statistically higher results (p < 0.05) both after 24 h and 6 months of water storage compared to ST and HI groups. However, a drop in UTS and KH was obtained after 6 months in all groups. The μTBS was not affected by the different light-curing approaches and, no statistical differences (p > 0.05) were observed between 24 h and 6 months storage. The CLD evaluation showed a statistical drop in KH after 24 h of ethanol storage for PD and SS (step-curing protocols) compared to those attained in continuous mode (ST and HI).
The soft-start mode may improve the UTS and KH of nano-filled resin composites without compromising the resin-dentin μTBS. However, both the step-curing protocols may reduce the cross-link density of the composite polymeric network.
High irradiances photo-polymerization may be adequate for direct aesthetic restorations such as veneers and onlays. Meanwhile, the soft start protocol would seem more appropriate for the photo-polymerization of high c-factors class I and II restorations.
Journal of Dentistry 06/2012; · 3.20 Impact Factor
[show abstract][hide abstract] ABSTRACT: To evaluate the effects of four different light-curing protocols on the microtensile bond strength (μTBS), ultimate tensile strength (UTS), Knoop micro-hardness (KH) and cross-link density (CLD) of a nano-filled resin composite.
Filtek Supreme XT (3M-ESPE) was used for the entire experiments following four light-curing approaches: ST, standard irradiance; HI, high irradiance; PD, pulse delay; SS, soft start. The specimens were submitted to different storage periods (24h or 6 months), cut into match-sticks and subsequently submitted to μTBS testing. Hourglass specimens were also prepared for UTS and KH. Cylindrical specimens were prepared for the CLD evaluation after absolute ethanol challenge. The results were statistically analyzed with a two-way ANOVA and Tukey's test (α=0.05).
For UTS and KH, continuous irradiance (PD and SS) induced statistically higher results (p<0.05) both after 24h and 6 months of water storage compared to ST and HI groups. However, a drop in UTS and KH was obtained after 6 months in all groups. The μTBS was not affected by the different light-curing approaches and, no statistical differences (p>0.05) were observed between 24h and 6 months storage. The CLD evaluation showed a statistical drop in KH after 24h of ethanol storage for PD and SS (step-curing protocols) compared to those attained in continuous mode (ST and HI).
The soft-start mode may improve the UTS and KH of nano-filled resin composites without compromising the resin-dentine μTBS. However, both the step-curing protocols may reduce the cross-link density of the composite polymeric network.
High irradiances photo-polymerization may be adequate for direct aesthetic restorations such as veneers and onlays. Meanwhile, the soft start protocol would seem more appropriate for the photo-polymerization of high c-factors class I and II restorations.
Journal of dentistry 06/2012; 40(10):802-9. · 2.00 Impact Factor
[show abstract][hide abstract] ABSTRACT: We compared polymerization stress in two commercial composites and three experimental composites made using camphorquinone (CQ) and/or phenylpropanedione (PPD) as photoinitiators. The internal surfaces of photoelastic resin discs with cylindrical cavities were roughened and treated with adhesive. Composites were divided into five groups: two commercial composites (Filtek Silorane and Filtek Z250) and three experimental composites with CQ/amine, CQ/PPD/amine, and PPD/amine. Composites were photopolymerized inside cavities, and subjected to photoelastic analysis immediately and at 24 hours and 7 days later using a plane polariscope. Stress created by Silorane (3.08 ± 0.09 MPa) was similar to that of Z250 (3.19 ± 0.13 MPa) immediately after photopolymerization (p > 0.05). After 24 hours and 7 days, Z250 (3.53 ± 0.15 and 3.69 ± 0.10 MPa, respectively) showed higher stress than Silorane (3.19 ± 0.10 and 3.16 ± 0.10 MPa, respectively). Qualitative analysis immediately after photopolymerization showed composite/CQ promoted higher stress than PPD, but stress levels at other evaluated times were statistically similar, varying between 3.45 ± 0.11 MPa and 3.92 ± 0.13 MPa. At 24 hours and 7 days, Silorane created the lowest stress. All photoinitiators created comparable tensions during polymerization.
[show abstract][hide abstract] ABSTRACT: OBJECTIVE: This study evaluated the mechanical characteristics and stress distribution of the hybrid technique fixation of the sagittal split ramus osteotomy. STUDY DESIGN: In the mechanical test, 10 polyurethane replicas of human hemimandibles of each group were submitted to linear loading test. For the photoelastic evaluation, 3 hemimandible replicas of photoelastic resin were subjected to photoelastic analysis. In the finite element analysis, 3 computer models simulated the displacement and the results of maximum principal stress were analyzed. RESULTS: The results of this study demonstrated that the fixation technique with 3 bicortical screws presented better mechanical resistance and stress distribution pattern when compared with the hybrid technique that, on the other hand, presents better results in comparison with a miniplate and monocortical screws. CONCLUSIONS: The results suggest that the hybrid technique increased the resistance and improved stress distribution of miniplate/monocortical screw fixation, maintaining most of the advantages of this technique.
[show abstract][hide abstract] ABSTRACT: The mismatch of thermal expansion and contraction between restorative materials and tooth may cause stresses at their interface, which may lead to microleakage. The present work compared the coefficient of thermal expansion (CTE) with the thermomechanical behavior of human and bovine teeth and determined if the CTE is a suitable parameter to describe tooth behavior. Fifteen human third molar and 15 bovine incisor tooth slices (6×5×2 mm) were allocated to 3 groups according to the test environment: G1 - room condition, G2 - 100% humidity, G3 - desiccated and tested in dry condition. Each specimen was weighed, heated from 20 to 70ºC at 10ºC min-1 and reweighed. The CTE was measured between 20 and 50ºC. Fresh dentin (human -0.49% ± 0.27, bovine -0.22% ± 0.16) contracted on heating under dry condition. Under wet conditions, only human teeth (-0.05% ± 0.04) showed contraction (bovine 0.00% ± 0.03) accompanied by a significantly lower (p<0.05) weight loss than in dry specimens (human 0.35% ± 0.15, bovine 0.45% ± 0.20). The desiccated dentin expanded on heating without obvious weight changes (0.00% ± 0.00). The CTE found was, respectively, in dry, wet and dissected conditions in ºC(-1): human (-66.03×10(-6), -6.82×10(-6), 5.52×10(-6)) and bovine (-33.71×10(-6), 5.47×10(-6), 4.31×10(-6)). According to its wet condition, the dentin showed different CTEs. The thermal expansion behavior of human and bovine dentin was similar. A simple evaluation of the thermal expansion behavior of tooth structure by its CTE value may not be appropriate as a meaningful consideration of the effects on the tooth-material interface.
[show abstract][hide abstract] ABSTRACT: The aim of this study was to evaluate the polymerization stress and degree of conversion of a composite submitted to different photoactivation protocols. The composite Filtek Z350 was placed in the central perforation of a photoelastic disc and polymerized using a LED-based curing unit (BluePhase II--Ivoclar Vivadent) with energy density of 12, 24 or 36 J/cm2 using the following photopolymerization protocols: continuous high intensity (HI: 1200 mW/cm2 during 10, 20 or 30s), continuous low intensity (LI: 650 mW/cmz during 18, 36 or 54s) and soft-start (SS: 150 mW/cm2 during 5 s + 1200 mW/cm2 during 9, 19 or 29s) (n = 5). Photoelastic analysis was used to evaluate polymerization shrinkage stress and FTIR was performed to determine the degree of conversion of the composite. ANOVA 3-way procedure was used to determine the significance of the main effects and their interactions followed by two-way ANOVA for each time was performed (p < 0.05). Shrinkage stress increased with higher values of energy. No statistically significant differences on polymerization shrinkage stress were found between high and low intensity activation modes. Soft-start method generated stresses that were statistically lower than continuous modes except when 12 J/cm2 was applied. Similar degree of conversion was observed for photoactivation modes used, except for soft-start mode with 12, 24 and 36J/cm2 that showed lowest levels of conversion. Energy density and activation mode influenced polymerization shrinkage stress, but no benefit on degree of conversion was observed.
[show abstract][hide abstract] ABSTRACT: This study evaluated the temperature change into the pulp chamber during the light curing of composite resin by direct (bovine tooth) and indirect (matrix) methods.
Direct method: fifty standardized cavities (2x2x2 mm) were prepared in bovine incisors, which were randomly assigned to evaluation of the temperature changes in the pulp chamber. Indirect method: temperature changes were evaluated through a dentine slice of 1.0 mm thickness in a elastomer cubic mold (2x2x2 mm). Filtek Z250 composite resin (3M/ESPE) was photo-activated using three light curing units: quartz-tungsten-halogen (QTH) by continuous, soft-start or intermittent light modulations; light emitting diode (LED); and plasma arc-curing (PAC). Ten groups (N.=10) were established according to technique evaluation and photo-activation methods. All experiments were carried out in a controlled environment (37 °C and 50 ± 10% relative humidity). The temperature changes were recorded using a digital thermometer attached to a type-K thermocouple in contact with the dentin slice (indirect method) or in contact with the axial wall (dentin) of pulp chamber (direct method). The results were submitted to ANOVA and Tukey's test (α=0.05).
Temperature changes were statistically higher for the matrix indirect method (2.56 ºC) than bovine teeth direct method (1.17ºC). The change temperature was statistically higher for the PAC (1.77 ºC) when compared to other photo-activation modes in bovine teeth direct method.
The two methods of temperature evaluation were different, however indirect method detected the higher temperature increase. Higher energy density arising from the light curing units and polymerization techniques promoted higher temperature increase.
[show abstract][hide abstract] ABSTRACT: This study investigated the influence of both room temperature storage and water storage on tooth displacement in complete dentures. Thirty maxillary dentures were manufactured and processed using 3 different curing cycles; long, short conventional and microwaved. Distances between fixed points on teeth were measured and the dentures stored at room temperature for 24 weeks. After storage, the distances were measured again and the dentures then stored in water at 37 degrees C for 24 weeks, when the distances were re-evaluated. Anteroposterior distances demonstrated contraction in all acrylic resins. Incisor-incisor (air = -8.5% and water = -7.0%) and molar-molar (room = -1.8% and water = -1.1%) distance changes were greater in the Onda-Cryl resin (p < 0.05), whereas the premolar-premolar (room = -2.2% and water = -1.7%) distance was higher in the QC-20 resin (p < 0.05).
The European journal of prosthodontics and restorative dentistry 09/2011; 19(3):105-10.
[show abstract][hide abstract] ABSTRACT: O uso constante de restaurações estéticas na Odontologia tem promovido cada vez mais o desenvolvimento e o aperfeiçoamento de materiais que atendam a estes requisitos. As restaurações em cerâmica promoveram uma nova era na Odontologia estética, e embora, este material restaurador tenha uma história antiga, a sua utilização clínica ainda é controversa. O avanço tecnológico, tanto no surgimento de novos materiais como no desenvolvimento de novas técnicas para a obtenção de resultados mais compatíveis com a dentição natural, tem estimulado cada vez mais o uso destes materiais. As cerâmicas odontológicas têm sido uma alternativa viável de tratamento protético tanto em áreas com perda de apenas um elemento dentário, quanto em áreas com espaços anodônticos mais amplos. Esta revisão de literatura teve por objetivo realizar uma análise crítica a respeito dos diversos tipos de cerâmicas odontológicas utilizadas na confecção de restaurações protéticas indiretas, já que, cada vez mais novos materiais cerâmicos têm sido introduzidos no mercado durante as duas últimas décadas.
[show abstract][hide abstract] ABSTRACT: The purpose of this study was to evaluate the bleaching agent action on color stability, surface roughness and microhardness of composites (Charisma, Filtek Supreme and Heliomolar - A2) submitted to accelerated artificial aging (AAA).
A Teflon matrix (12 x 2 mm) was used to fabricate 18 specimens (n=6) which, after polishing (Sof-Lex), were submitted to initial color reading (ΔE), Knoop microhardness (KHN) (50 g/15 s load) and roughness (R(a)) (cut-off 0.25 mm) tests. Afterwards, the samples were submitted to AAA for 384 hours and new color, microhardness and roughness readings were performed. After this, the samples were submitted to daily application (4 weeks) of 16% Carbamide Peroxide (NiteWhite ACP) for 8 hours and kept in artificial saliva for 16 hours. New color, microhardness and roughness readings were made at the end of the cycle, and 15 days after bleaching.
Comparison of the ΔE means (2-way ANOVA, Bonferroni, P<.05) indicated clinically unacceptable color alteration for all composites after AAA, but without significant difference. Statistically significant increase in the KHN values after AAA was observed, but without significant alterations 15 days after bleaching. For R(a) there was no statistically significant difference after AAA and 15 days after bleaching.
The alterations promoted by the bleaching agent and AAA are material dependent.
European journal of dentistry. 04/2011; 5(2):143-9.
[show abstract][hide abstract] ABSTRACT: The aim of the study was to verify the influence of surface sealants on the surface roughness of resin composite restorations before and after mechanical toothbrushing, and evaluate the superficial topography using atomic force microscope. Five surface sealers were used: Single Bond, Opti Bond Solo Plus, Fortify, Fortify Plus and control, without any sealer agent. The lowest values of surface roughness were obtained for control, Single Bond and Fortify groups before toothbrushing. Fortify and Fortify Plus were the sealer agents that support the abrasive action caused by the toothbrushing although Fortify Plus group remained with high values of surface roughness. The application of specific surface sealants could be a useful clinical procedure to maintain the quality of resin-based composite restorations.
Journal of the mechanical behavior of biomedical materials. 04/2011; 4(3):433-9.
[show abstract][hide abstract] ABSTRACT: The purpose of the study was to verify the linear displacement of teeth in maxillary complete dentures influenced by different monomer-polymer ratios - according to the manufacturer's instructions, with 25% excess or 25% less monomer content - in the conventional and microwaved polymerization techniques. Wax base plates and wax planes were made on edentulous maxillary stone casts according to traditional method. The set was assembled in semi-adjustable articulator with a lower toothed stone cast as guide to mounting of the maxillary artificial teeth. Impressions were taken from this tooth arrangement with silicone and the mold was used to standardize the mounting of the teeth of all dentures. Referential points were made on the artificial teeth for linear measurements with optical microscope before processing of the dentures and after deflasking. Denture bases were conventionally packed with acrylic resin according to the monomer-polymer ratio protocol. Tooth displacement data were submitted to ANOVA and Tukey test (α=0.05). There were no statistically significant differences (p>0.05) between the group with monomer content recommended by the manufacturer and groups with 25% more and 25% less monomer, in both conventional and microwaved polymerizations. Excess or less monomer in the monomer-polymer ratio and polymerization types did not change the linear distance between teeth.
[show abstract][hide abstract] ABSTRACT: This study investigated the influence of different composite resin organic matrix (methacrylate - Filtek Z350 XT and silorane - Filtek P90) on light energy transmission through the composite and bottom/top rate.
A light-emitting diode (New Blue Phase), light-curing unit was used with different photoactivation protocols (high-continuous mode - HCM, 1400 mW/cm2 for 20 seconds; low-continuous mode - LCM , 700 mW/cm2 for 40 seconds; and soft-start mode - SSM, 140 mW/cm2 for 5s followed by 39 seconds for 700 mW/cm2). Twenty specimens were prepared for each composite. The light energy transmission through the composite was calculated (n=10). The bottom/top rate of the same specimen was calculated (n=10). The data were compared by Tukey's test in different tests (light energy transmission through the composite and bottom/top rate).
The light energy transmission through the Filtek Z350 XT composite (HCM - 576 mW/cm2, LCM - 238 mW/cm2, SSM - 232 mW/cm2) did not show statistical difference when compared with Filtek P90 composite (HCM - 572 mW/cm2, LCM - 233 mW/cm2, SSM - 230 mW/cm2). The bottom/top rate of the Filtek Z350 XT composite (HCM - 88.98%, LCM - 90.94%, SSM - 89.92%) was statistically higher than that of the Filtek P90 composite (HCM-77.29%, LCM-77.51%, SSM- 77.79%).
Light energy transmission through the composite was not influenced by the use of different dental composite restoratives. However, the bottom/top rate of the composites was influenced by the use of different dental composite restoratives.
Insufficiently polymerized composite resin may present a large number of problems. For this reason, dental composite resins should have the similar deep surface polymerization as the top surface in dental restorations.
The journal of contemporary dental practice 01/2011; 12(5):361-7.
[show abstract][hide abstract] ABSTRACT: The aim of this study was to evaluate the influence of artificial accelerated aging on dimensional stability of two types of acrylic resins (thermally and chemically activated) submitted to different protocols of storage.
One hundred specimens were made using a Teflon matrix (1.5 cm x 0.5 mm) with four imprint marks, following the lost-wax casting method. The specimens were divided into ten groups, according to the type of acrylic resin, aging procedure, and storage protocol (30 days). GI: acrylic resins thermally activated, aging, storage in artificial saliva for 16 hours, distilled water for 8 hours; GII: thermal, aging, artificial saliva for 16 hours, dry for 8 hours; GIII: thermal, no aging, artificial saliva for 16 hours, distilled water for 8 hours, GIV: thermal, no aging, artificial saliva for 16 hours, dry for 8 hours; GV: acrylic resins chemically activated, aging, artificial saliva for 16 hours, distilled water for 8 hours; GVI: chemical, aging, artificial saliva for 16 hours, dry for 8 hours; GVII: chemical, no aging, artificial saliva for 16 hours, distilled water for 8 hours; GVIII: chemical, no aging, artificial saliva for 16 hours, dry for 8 hours GIX: thermal, dry for 24 hours; and GX: chemical, dry for 24 hours. All specimens were photographed before and after treatment, and the images were evaluated by software (UTHSCSA - Image Tool) that made distance measurements between the marks in the specimens (mm), calculating the dimensional stability. Data were submitted to statistical analysis (two-way ANOVA, Tukey test, p= 0.05).
Statistical analysis showed that the specimens submitted to storage in water presented the largest distance between both axes (major and minor), statistically different (p < 0.05) from control groups.
All acrylic resins presented dimensional changes, and the artificial accelerated aging and storage period influenced these alterations.
Journal of Prosthodontics 08/2010; 19(6):432-7. · 0.68 Impact Factor
[show abstract][hide abstract] ABSTRACT: The study evaluated the influence of accelerated artificial aging on colour stability, opacity and cross-link density of resin-based composites (RBCs). Seven specimens were obtained of five RBCs (Heliomolar, 4 Seasons, Tetric Evo Ceram, SR Adoro), which were submitted to colour stability and opacity analysis and cross-link density evaluation. All tests were performed before and after aging. After statistical analysis (one-way ANOVA; Tukey; p<0.05), it was observed that QuiXfil and SR Adoro presented colour alteration values above those that are clinically acceptable (deltaE=5.77 and 4.34 respectively) and the variation in opacity was lowest for SR Adoro. There was an increase in the cross-link density of all studied materials after aging.
The European journal of prosthodontics and restorative dentistry 06/2010; 18(2):89-93.
[show abstract][hide abstract] ABSTRACT: To assess the bond strength of Rely-X Unicem (RX), in comparison with Cement-Post (CP), to the cervical, middle and apical thirds of root canal dentin irradiated with a 980-nm diode laser.
Forty maxillary canines were separated into four equal groups according to the cement used and the laser surface treatment: RX/laser irradiation (LI) group; RX/no irradiation (NI) group; CP/LI group; and CP/NI group. Two slices (2-mm thick) of each root third were submitted to a push-out test to assess the bond strength of the cement to the root canal dentin. The data obtained were submitted to two-way ANOVA and fracture analysis was performed by scanning electron microscopy.
The type of cement as well as 980-nm LI at the different root canal thirds significantly affected the bond strength values (p < 0.05). LI promoted an increase in bond strength of RX in all root thirds (p < 0.05). For all groups, bond strength to the cervical third was highest, followed by the middle and apical thirds (p < 0.05). When the cements were compared, RX always presented the highest bond strength in comparison with CP, irrespective of the laser application (p < 0.05). Fracture analysis showed a predominance of mixed failures for RX and of adhesive failure between dentin and cement for CP, irrespective of the laser application.
The 980-nm LI promoted an increase in bond strength of the self-adhesive resinous cement to root dentin.