Accuracy of maxillary full-arch digital impressions of tooth and implant models made by two intraoral scanners.

OBJECTIVES: Limited studies are available on the accuracy of intraoral scanners (IOSs) for full-arch implant and tooth models. This study aimed to assess the accuracy of maxillary full-arch digital impressions of tooth and implant models made by two IOSs. MATERIALS AND METHODS: This in vitro, experimental study was conducted on two maxillary dentiform models: one with six prepared natural teeth and the other with six implants at the site of canine, first premolar, and first molar teeth, bilaterally. A highly accurate industrial scanner was used for actual measurements on the models that served as the reference scan. TS (Trios3) and CO (CEREC Omnicam) IOSs were then used to scan each model 10 times according to the manufacturer's instructions. All scans were saved in STL format. The GOM Inspect software was used according to the best-fit algorithm to compare the accuracy of measurements in the groups with the reference scan. The trueness and precision were calculated. Statistical analyses were carried out using SPSS by one-way analysis of variance and t-test (α = .05). RESULTS: TS showed a significantly higher trueness than CO for both tooth and implant models (p < .05). TS also revealed significantly higher precision than CO for the tooth model; however, the difference in precision for the implant model was not significant between the two IOSs (p > .05). CONCLUSIONS: TS showed higher accuracy than CO in both tooth and implant models.

Reconstruction of Gingival Mask around CAD-CAM Bar and Ball Attachment in Implant-Retained Overdenture.

Gingival mask is a copy of the peri-implant tissue, which plays an important role in the fabrication of an optimal restoration. Losing the gingival mask is a clinical problem that complicates the process of restoration fabrication. Herein, a simple precise technique is described step by step to solve this problem in the patient with CAD/CAM milled bar and ball attachment treatment plan for a maxillary and a mandibular implant-supported overdenture, without the need to repeat the entire clinical and laboratory procedures.

Comparing the Surface Behavior of Conventional and CAD-CAM Feldspathic Porcelains in the Face of Laser-Assisted Bleaching and Post-bleach Polishing.

Introduction: The prevalence of using different esthetic methods increases the possibility of close contact between them with potential adverse interactions. This study aimed to compare the surface changes (microhardness and roughness) in two types of feldspathic porcelain after laser bleaching and post-bleach polishing. Methods: 12 standardized rectangular specimens were prepared for each porcelain group (conventionally layered and CAD-CAM milled). Vickers microhardness and roughness were evaluated before and after the bleaching procedure and after polishing. Data were statistically analyzed using repeated measures ANOVA and t test (P < 0.05). Results: The surface roughness of both groups increased significantly after laser bleaching (P < 0.001 for conventional and P=0.004 for CAD-CAM porcelains). The polishing process reduced the roughness of both groups; the reduction was significant in conventional specimens (P=0.020). The surface hardness values did not change significantly in the groups after bleaching and post-bleach polishing stages (P=0.142). Generally, the average surface roughness of CAD-CAM specimens was significantly lower (P < 0.001), and the surface microhardness of the CAD-CAM group was significantly higher than conventional porcelains (P=0.011). Conclusion: Laser bleaching significantly increased the surface roughness of feldspathic porcelains; however, it did not affect the surface microhardness significantly. Unlike CAD-CAM specimens, polishing significantly improved the surface smoothness of conventional porcelains.

Comparison of retention and fracture load of endocrowns made from zirconia and zirconium lithium silicate after aging: an in vitro study.

BACKGROUND: This study aimed to compare retention and fracture load in endocrowns made from translucent zirconia and zirconium lithium silicate. METHODS: Fifty-six intact human maxillary molars after being mounted in acrylic resin, were scanned to acquire biogeneric copies. Specimens underwent standard endodontic treatment and were prepared for endocrown up to 2 mm above the cementoenamel junction. The specimens were randomly divided into two groups of 28, and endocrowns were designed using biogeneric copies and milled from high-translucent zirconia disks (Zr) and zirconium lithium silicate blocks (ZLS). After cementation with dual-cure resin cement, all the specimens underwent thermomechanical aging, and pull-out retention test and compressive test were conducted (14 specimens were used for each test in each group, n = 14), and failure modes in both tests were evaluated. RESULTS: Independent samples t-test showed significant difference between the retention of Zr (271.5 N ± 114.31) and ZLS (654.67 N ± 223.17) groups (p value = 0.012). Compressive test results were also significantly different between Zr (7395.07 N ± 1947.42) and ZLS (1618.3 N ± 585) (p = 0.002). Failure mode of retention test was primarily adhesive failure at the cement-restoration interface in Zr group and cement-tooth interface in ZLS group. Failure modes of fracture test for Zr group were 7 non-restorable fractures and one restorable fracture while 6 specimens resisted compressive loads up to 8500 N without fracture. ZLS group showed 7 restorable and 7 non-restorable failures. CONCLUSIONS: Zr endocrowns showed significantly lower retention and higher fracture strength. Both materials seem to be suitable for fabrication of endocrown in clinical setup.

Evaluation of the effect of milling mode and margin definition on adaptation of chairside digitally designed and fabricated ceramic veneers.

AIM: The present study aimed to evaluate the effect of the milling mode and margin defining method on the marginal and internal adaptation of digitally designed and fabricated ceramic veneers. MATERIALS AND METHODS: Forty extracted central incisors were prepared for ceramic veneers. The veneers were categorized into four groups (n = 10) based on the milling mode (fine or extra-fine) and design (automatic or manual defining of cervical and incisal margins). The veneers were cemented to the teeth using resin cement and then polished. After cementation, the teeth were embedded in clear polyester resin, then cut into three sections. Absolute marginal gap at the cervical margins (AMGC), marginal gap at the incisal (MGI) and cervical (MGC) margins, and internal gap (IG) at the axial wall were evaluated using a scanning electron microscope. Two-way analysis of variance (ANOVA) and t tests were used (α = 0.05) for the statistical analysis. RESULTS: The margin defining method affected the adaptation of the internal and incisal margin; the automatic (software) margin defining method resulted in a smaller MGI (P = 0.038) and IG (P = 0.009) than the manual defining method. CONCLUSION: The type of milling mode did not affect the marginal gap. The margin defining method affected the marginal gap at the incisal margin and the internal gaps. (Int J Comput Dent 2022;25(3):277-285; doi: 10.3290/j.ijcd.b2588153).

Comparison of Marginal and Internal Adaptation in Endocrowns Milled from Translucent Zirconia and Zirconium Lithium Silicate.

PURPOSE: This study aimed to compare marginal and internal adaptation in endocrowns made from translucent zirconia and zirconium lithium silicate using CAD-CAM technology. MATERIALS AND METHODS: Twenty-eight freshly extracted upper molars were mounted in acrylic resin and underwent root canal therapy and endocrown preparation up to 2 mm above the cementoenamel junction. Endocrowns were CAD-CAM milled from zirconium lithium silicate (ZLS) and translucent zirconia (Zr). Internal and marginal adaptation was assessed by the replica technique before cementation. Marginal adaptation was evaluated by a stereomicroscope (×32) before and after cementation and also after thermomechanical aging. RESULTS: The ZLS group showed significantly higher internal adaptation compared to the Zr group (P = 0.028), while the marginal adaptation differences, at different times with different methods, were not statistically significant (P > 0.05). Axiomarginal angle had the highest and axiopulpal angle showed the lowest adaptation in both groups. The cementation process and thermomechanical aging increased the marginal gap in both groups significantly (P < 0.001). The marginal gap assessed by the replica technique before cementation was 7.11 µm higher than direct view under a stereomicroscope with intraclass correlation coefficient of 0.797. CONCLUSION: Zirconia seems to be an acceptable material for endocrown with comparable internal and marginal adaptation to ZLS. Cementation and thermomechanical aging had significantly negative effects on marginal gap. The marginal gap assessed by the replica technique was higher than direct view under the stereomicroscope technique.

Comparison of Fracture Resistance and Failure Mode in Digitally Milled Restorations with Rapid Layering by Indirect Composite Resin: An In Vitro Study.

PURPOSE: To evaluate the fracture resistance and failure mode of implant crowns made by polyether ether ketone (PEEK), zirconia, and chromium-cobalt frames, veneered by milled composite resin. MATERIALS AND METHODS: Thirty-six implant analogs were mounted in acrylic blocks, and solid abutments were secured (n = 12). Single-unit frameworks were milled from PEEK, zirconia, or chromium-cobalt, and cemented to indirect composite veneers fabricated by the rapid layering technique. After thermal cycling, the fracture resistance test was performed at a speed of 0.5 mm/min, and the results were statistically analyzed by one-way analysis of variance (ANOVA) and Tukey post hoc test (P < .05). The failure mode was evaluated by a stereomicroscope ('L10). Veneer failure without damage to other components was considered desirable (repairable). RESULTS: The mean fracture resistances of PEEK, zirconia, and chromium-cobalt specimens were 2,037.24, 2,567.05, and 2,032.10 N, respectively. The Tukey post hoc test showed no significant difference between the PEEK and chromium-cobalt groups (P = .99); however, the difference was significant between zirconia and PEEK or chromium-cobalt specimens (P = .001). Failure mode was desirable in all chromium-cobalt (12 specimens), 9 zirconia, and 7 PEEK-based specimens. CONCLUSION: Zirconia-composite implant crowns had significantly higher fracture resistance. Given the range of maximum occlusal forces, all the specimens had clinically acceptable results. The failure mode was more desirable in chromium-cobalt, followed by zirconia-based crowns.

Evaluation of the colour and translucency parameter of conventional and Computer-aided design and computer-aided manufacturing (CAD-CAM) feldspathic porcelains after staining and laser-assisted bleaching.

Aims: The present study aimed to evaluate the color and translucency changes of the feldspathic porcelain samples made using the conventional or computer-aided design/computer-aided manufacturing (CAD/CAM) methods after immersion in staining solutions and laser bleaching. Materials and Methods: A total of 72 samples of feldspathic porcelain were fabricated using the conventional (n = 36) or CAD/CAM (n = 36) methods. Afterward, each group was randomly divided into three subgroups (n = 12), which underwent exposure to coffee, orange juice, or distilled water for 6 weeks. Then, the samples underwent diode laser-assisted bleaching. A spectrophotometer assessed the samples' color and translucency preintervention, after staining, and after bleaching. Statistical Analysis Used: One-way and two-way analysis of variance and independent t-test were used. The significance level was 0.05. Results: Staining for 6 weeks significantly changed the color of both types of feldspathic porcelains. Furthermore, there were significant differences between the ceramics made using different methods and immersed in different staining solutions (P < 0.001). Furthermore, laser-assisted bleaching changed the color of immersed specimens significantly (P = 0.005). However, there were no significant translucency changes in all the subgroups after staining (P = 0.215) and laser bleaching (P = 0.325). Conclusions: The staining-induced discoloration of all the subgroups was in the clinically acceptable range (ΔΕ<3.3). In addition, bleaching could effectively remove the stains in both types of ceramics while not affecting the primary color. Moreover, the translucency of the ceramics was not affected by staining or laser-assisted bleaching.

Retention and Clinical Performance of Zirconia Crowns: A Comprehensive Review.

Zirconia has been used for rehabilitation of edentulous spaces approximately for a decade, and there have been several reports regarding the clinical performance and retention of zirconia crowns. Outstanding mechanical properties, biocompatibility, and excellent aesthetics make zirconia-based crowns as a popular crown among the current all-ceramic crowns in restorative dentistry. However, restoration with a zirconia crown is a challenging treatment. The goal of this study was to assess the current literature to summarize the studies reporting the effective risk factors on retention of zirconia crowns to provide clinicians with a useful point of view in the decision-making process for use of these restorations. Literature based-search was performed to find related articles until August 2020 using EMBASE, Google Scholar, and MEDLINE. Search terms used were "zirconia restorations properties," "zirconia crowns clinical performance," "zirconia crown survival," "biological complications," and "zirconia crown retention." Results were limited to papers available in English. The references of all related literature were also searched for further citations. Overall, although clinical long-term and follow-up studies are a vital requirement to conclude that zirconia has great reliability, it seems that zirconia crown restorations are both well tolerated and sufficiently resistant.

Comparison of Marginal Adaptation of Different Implant-Supported Metal-Free Frameworks Before and After Cementation.

PURPOSE: To compare marginal adaptation before and after cementation of implant-supported metal-free frameworks fabricated from zirconia, polyetheretherketone (PEEK), or composite. MATERIALS AND METHODS: Thirty-six CAD/CAM frameworks were constructed from zirconia, PEEK, or composite (n = 12 per material). Marginal gap was measured using a Video Measuring Machine (VMM) system, and repeated-measures analysis of variance was employed for data analysis (P < .05). RESULTS: Absolute marginal discrepancies of all frameworks decreased significantly after cementation (P < .05). Zirconia and composite frameworks' marginal gap values were clinically acceptable, while PEEK frameworks were judged as being on the borderline of acceptability. Zirconia demonstrated significantly better marginal adaptation than PEEK (P < .05). CONCLUSION: Zirconia showed the best marginal adaptation of the three tested metal-free frameworks.

The Effect of Flat Dual-Cure Stabilizer Occlusal Splint in Pain Relief of Individuals Suffering from Migraine Headaches.

BACKGROUND: No study on the effect of dual-cure stabilizer splint without canine ramp in migraine patients is present. OBJECTIVE: This study was conducted to determine the effects of maxillary flat dual-cure stabilizer occlusal splint on severity, frequency and episodes of headaches in individuals suffering from a migraine. METHODS: In this interventional clinical trial, 30 eligible patients were divided into 2 groups (case and control); each group consisted of 8 men and 7 women. Dual-cure stabilizer splint was made for patients in the case group and they used the adjusted splint 20 hours a day for 6 weeks. The severity, frequency and episodes of migraine attacks before and after using the splint were determined. For grading pain, severity visual analogue scale was used. The data were analyzed using SPSS 20 and Kolmogorov-Smirnov test and paired t-test. RESULTS: The severity, frequency, and episodes of migraine attacks before and after using the splint were reduced by 56%, 68%, and 72%, respectively. The reduction was statistically significant (p < 0.05). DISCUSSION: Despite the effect of occlusal devices on the migraine disorder is controversial, the most researchers agree that using these appliances can be effective in reducing headache in migraine patients. CONCLUSION: Given the favorable effects of dual-cure stabilizer splint on reducing the severity, frequency and episodes of migraine headaches, the device can be used as an effective alternative therapy besides common pain-relieving methods.

Comparing Retention and Internal Adaptation of Different Implant-Supported, Metal-Free Frameworks.

PURPOSE: This study was conducted to compare the fit and retention of implant-supported, metal-free copings fabricated from zirconia, polyetheretherketone (PEEK), or composite, as well as to evaluate the possible correlation between internal adaptation and retention. MATERIALS AND METHODS: A total of 36 copings were milled from zirconia, PEEK, or composite blanks (n = 12 in each group). Marginal and internal gap were evaluated by replica technique, and the pull-out test was used to evaluate retention. One-way analysis of variance, post hoc Tukey tests, and Pearson correlation coefficient test were used to analyze the data. RESULTS: Zirconia had significantly better marginal/internal adaptation (P < .05) than the other materials. There was no statistically significant difference in mean retention force between the different groups (P > .05). No correlation was found between internal adaptation and retention. CONCLUSION: In the metal-free copings tested, zirconia showed the best adaptation. The retention of copings was not influenced by internal fit or material type.

Comparative evaluation of the effect of impression materials and trays on the accuracy of angulated implants impressions.

BACKGROUND: Vinyl Polyether Siloxane is a newly introduced impression material and studies on that is scarce. Implant insertion in posterior mandible might be angulated due to anatomical considerations. The purpose of this study was to compare the dimensional and angular accuracy of impressions using full-arch versus sectional tray and Vinyl Polysiloxane versus Vinyl Polyether Siloxane in angulated implants. MATERIAL AND METHODS: Four implants were placed in dental areas #19, #21, #28 and #30 of a Kennedy class I mandibular acrylic model with 30° lingual angulation. Twenty sectional and 20 full-arch open trays were made on the primary cast. Impressions were taken using Vinyl Polysiloxane and Vinyl Polyether Siloxane (n=10 in 4 groups); and were poured with type IV dental stone. The coordinate measuring machine was used to measure displacements in the X, Y and Z axes and rotational discrepancies of implants. The data were analyzed using SPSS 22 and two-way ANOVA. RESULTS: Type of tray had no significant effect on the dimensional and angular accuracy of impressions (p >0.05). Type of impression material significantly affected linear displacement (∆r) (P <0.05); but it did not significantly affect the rotational displacement (P >0.05). CONCLUSIONS: Vinyl Polysiloxane yielded more accurate impressions of angulated implants. Key words:Dental implant, impression material, impression tray, vinyl polysiloxane, vinyl polyether silicone, coordinate measuring machine.

Effect of Sandblasting Angle and Distance on Biaxial Flexural Strength of Zirconia-based Ceramics.

AIM: Surface treatment is necessarily required for bonding of zirconia to the veneering porcelain and luting cements. Sandblasting is the most common and probably the most efficient surface treatment method. Sandblasting roughens the surface and may affect the flexural strength of zirconia. Different sandblasting protocols may yield variable results. This study sought to assess the effect of sandblasting angle and distance on the biaxial flexural strength of zirconia-based ceramics. MATERIALS AND METHODS: This in vitro experimental study was conducted on 50 zirconia discs measuring 1.2 ± 0.2 mm in thickness and 15 ± 0.2 mm in diameter, which were randomly divided into five groups (n = 10) of one control and four experimental groups subjected to sandblasting with 110 µm aluminum oxide particles under 2 bar pressure for 10 seconds at 15 and 25 mm distances and 45 and 90° angles (between the nozzle head and zirconia surface). Surface roughness was measured by a roughness tester and samples were subjected to thermocycling followed by biaxial flexural strength testing according to ISO6872. The data were analyzed using one-way analysis of variance (p < 0.05). RESULTS: No statistically significant difference was noted in the mean biaxial flexural strength of the five groups (p = 0.40). Different sandblasting protocols yielded significantly different surface roughness values (p < 0.001). The highest and the lowest mean surface roughness belonged to 15 mm/90° (0.51 µm) and control (0.001 µm) groups respectively. CONCLUSION: Change in sandblasting angle and distance had no significant effect on the biaxial flexural strength of zirconia-based ceramic, but surface roughness was significantly different in the study groups. Clinical significances: Regardless of sandblasting angle, increasing distance to 25 mm significantly decreases surface roughness that may negatively affect zirconia bond strength.

Effect of Repeated Firings on Microtensile Bond Strength of Bi-layered Lithium Disilicate Ceramics (e.max CAD and e.max Press).

AIM: To achieve acceptable contour, color, esthetics, and occlusal relations, the porcelain may be subjected to several firing cycles. This study sought to assess the effect of multiple firing cycles on the microtensile bond strength (MTBS) of lithium disilicate-based ceramics (e.max Press, e.max CAD). MATERIALS AND METHODS: IPS e.max computer aided design (CAD) cores were fabricated using CAD/(Computer Aided Manufacturing (CAM)) technology, and IPS e.max Press cores were fabricated using the heat-pressing technique (12 × 12 × 4 mm(3)). Cores in each group were divided into three subgroups based on the number of firing cycles (three, five, and seven cycles). After porcelain application, the samples were sectioned into microbars and a total of 20 sound microbars in each group were subjected to tensile load in a microtensile tester at a crosshead speed of 1 mm/minute. Microtensile bond strength of the core to the veneering porcelain was analyzed using one-way analysis of variance (ANOVA). Pairwise comparisons were made using the Tukey's test (p < 0.05). RESULTS: In the e.max CAD, the mean MTBS values were 22.07 ± 6.63, 34.68 ± 7.07, and 26.05 ± 10.29 MPa following three, five, and seven firing cycles respectively. These values for the e.max Press were 34.46 ± 9.28, 23.09 ± 5.02, and 31.26 ± 12.25 MPa respectively. There was significant difference in bond strength of e.max CAD (p < 0.003) and e.max Press (p < 0.002) based on the number of firing cycles. CONCLUSION: Increasing the number of porcelain firing cycles decreased the bond strength of the core to the veneering porcelain in both ceramics. CLINICAL SIGNIFICANCE: It is better to decrease the number of firing cycle as much as possible.

Full Mouth Reconstruction of a Bruxer with Severely Worn Dentition: A Clinical Report.

Tooth wear is attributed to several factors many of which often remain unidentified. Management of tooth wear is challenging in preventive and restorative dentistry. Correct assessment of occlusal vertical dimension, interocclusal rest space, and centric relation records are critical for successful treatment. In order to evaluate different treatment modalities and select the treatment of choice some information can be obtained from study casts and diagnostic wax-up. In order to achieve a predictable and desirable result, a systematic approach may be helpful. This paper describes the full mouth rehabilitation of a 36-year-old bruxer with severely worn dentition and other dental problems such as unfavorable restorations. A diagnostic work-up was performed and provisional restorations were made; then, they were clinically evaluated and adjusted based on the criteria dictating esthetics, phonetics, and vertical dimension. After endodontic therapy, clinical crown lengthening was performed. Two short implants were inserted in the posterior mandible. Custom-cast dowel cores and metal-ceramic restorations were fabricated and a full occlusal splint was used to protect the restorations. We ensured stable contacts on all teeth with equal intensity in centric relation and anterior guidance in accord with functional jaw movements.

Effect of storage time of extended-pour and conventional alginate impressions on dimensional accuracy of casts.

OBJECTIVES: Some manufacturers claim to have produced new irreversible hydro-colloids that are able to maintain their dimensional stability during storage. The present study evaluated the effect of storage time on dimensional stability of three alginates: Hydrogum 5, Tropicalgin and Alginoplast. MATERIALS AND METHODS: In this experimental in-vitro trial, a total of 90 alginate impressions were made from a Dentoform model using Hydrogum 5, Tropicalgin and Alginoplast alginates. The impressions were stored in a sealed plastic bag without a damp paper towel for 0, 24, 48, 72 and 120 hours and then poured with type III dental stone. Cross-arch (facial of 6 to facial of 6 on the opposite side) and antero-posterior (distal of right first molar to the ipsilateral central incisor) measurements were made with a digital caliper on the casts. Data were analyzed by two-way and one-way ANOVA and Tukey's post-hoc test (P<0.05). RESULTS: Alginate type and the pouring time significantly affected the dimensional stability of alginate impressions (both Ps<0.001). Pouring of Hydrogum 5 impressions can be delayed for up to 120 hours without significant dimensional changes. Alginoplast impressions may be poured after 72 hours, but Tropicalgin should be poured immediately and the storage time should not be more than 24 hours. CONCLUSION: Immediate pouring of alginate impressions provides the highest accuracy in reproducing the teeth and adjacent tissues; however, this study demonstrated that pouring may be delayed for up to five days using extended-pour (Hydrogum 5) alginates.

The effect of multiple firings on microtensile bond strength of core-veneer zirconia-based all-ceramic restorations.

PURPOSE: Differences in core and veneer coefficients of thermal expansion, firing shrinkage, and speed of increasing and decreasing the temperature may generate stress in veneered all-ceramic restorations. Given the necessity of performing multiple firing cycles to achieve improved contour, color, and esthetics, the purpose of this study was to determine the effect of multiple firing cycles on the microtensile bond strength (MTBS) of zirconia core to the porcelain veneer in zirconia-based all-ceramic restorations. MATERIALS AND METHODS: Thirty blocks (12 × 12 × 4 mm(3)) of semi-sintered zirconia were machined and sintered according to manufacturer's instruction. Specimens were placed in three groups based on the number of firing cycles (4, 6, 8) for the veneering process. After veneering, the specimens were sectioned into microbars with 8 mm length and 1 mm cross-section. Twenty sound microbars in each group were stressed to failure in a microtensile tester machine at 1 mm/min. Fractured specimens were surveyed under a scanning electron microscope and classified as cohesive in core, cohesive in veneer, and mixed. MTBS data were analyzed using one-way ANOVA and Tukey test (p < 0.05). RESULTS: The mean MTBS (MPa) after 4, 6, and 8 firing cycles were 30.33 ± 2.13, 27.43 ± 1.79, and 25.06 ± 1.76, respectively. There was a statistically significant difference between the bond strengths of each of the three groups (p < 0.001). CONCLUSION: Increase in firing cycles decreased MTBS. Most of the failures (90-95%) in all three groups were cohesive in the veneering porcelain and did not change as the number of firing cycles increased.

The effect of thermocycling on tensile bond strength of two soft liners.

OBJECTIVE: Failure of soft liners depends mostly on separation from the denture base resin; therefore measurement of the bond strength is very important. The purpose of this study was to compare the tensile bond strength of two soft liners (Acropars, Molloplast-B) to denture base resin before and after thermocycling. MATERIALS AND METHODS: Twenty specimens fromeach of the two different soft liners were processed according to the manufacturer's instructions between two polymethyl methacrylate (PMMA) sheets. Ten specimens in each group were maintained in 37°C water for 24 hours and 10 were thermocycled (5000 cycles) among baths of 5° and 55°C. The tensile bond strength was measured using a universal testing machine at a crosshead speed of 5 mm/min. Mode of failure was determined with SEM (magnification ×30). Two-way ANOVA was used to analyze the data. RESULTS: The mean and standard deviation of tensile bond strength of Acropars and Molloplast-B before thermocycling were 6.59±1.85 and1.51±0.22 MPa, respectively and 5.89±1.52 and1.37±0.18 MPa, respectively after thermocycling. There was no significant difference before and after thermocycling. Mode of failure in Acropars and Molloplast-B were adhesive and cohesive, respectivley. CONCLUSION: The bond strength of Acropars was significantly higher than Molloplast-B (P<0.05).