Clinical evaluation of zirconia crowns cemented with two different resin cements: A retrospective study.

BACKGROUND: Self-adhesive resin cement has been used extensively with zirconia crowns. Several in vitro studies showed that adhesive resin cementation may increase zirconia crowns' retention and their fatigue resistance. OBJECTIVES: This retrospective study aimed to evaluate the clinical performance, survival and success rates and complications encountered with zirconia crowns cemented with two different self-adhesive resin cements. METHODS: A total of 112 patients who received 176 monolithic zirconia crowns were evaluated. Crowns were cemented with RelyX Unicem 2 (n = 74) and Panavia SA (n = 102) self-adhesive resin cements. Clinical assessments of the crowns and supporting periodontal structures were performed following the modified California Dental Association (CDA) criteria. Intraoral photographs and periapical and bitewing radiographs were obtained for further assessment by two evaluators. Descriptive statistics, McNemar, t-test, log rank (Mantel-Cox) tests and Kaplan-Meier survival analyses were performed (a = .05). RESULTS: The 5-year survival and success rates were 100% and 96.4%, respectively. The complications encountered were recurrent caries (2.2%) and the need for endodontic treatment (0.5%). No technical complications, such as fracture or loss of retention, were observed. The type of cement and patient-related factors did not influence the survival and success rates of the crowns. CONCLUSIONS: Survival rate of zirconia crowns cemented with two different self-adhesive resin cements was 100% after 5 years.

Stress Distribution of Monolithic and Veneered 3-unit Zirconia FDPs - Finite Element Analysis.

PURPOSE: To evaluate the effect of restoration design on fracture resistance and stress distribution of veneered and monolithic 3-unit zirconia fixed partial dentures (FDPs) using finite element analysis (FEA). MATERIALS AND METHODS: Identical epoxy resin replicas of mandibular second premolar and second molar (to serve as abutment for the 3-unit bridge) were divided into four groups (n = 10): monolithic zirconia (MZ) restorations; conventional layering veneering technique (ZL), heat-pressed technique (ZP), or CAD/CAM lithium disilicate glass ceramic (CAD-on). Specimens were subjected to compressive cyclic loading on the mesio-buccal cusp of the pontic (load range 50 to 600 N; aqueous environment; 500,000 cycles) in a universal testing machine. Data were statistically analyzed at 5% significance level with Fisher exact test and Kaplan-Meier survival analysis. 3D models were constructed in accordance with experimental groups. The stress distribution in each model was analyzed and evaluated according to the location and magnitude of the maximum principal stresses (MPS) using ANSYS software. RESULTS: Specimens from ZL and ZP groups failed at different stages of the 500,000 cycles fatigue, while CAD-on and MZ restorations survived fatigue test. Statistically, there was a significant difference between the groups (P < .001). The MPS were located under the mesial connector in both monolithic and bilayered 3-unit zirconia FDPs. These stresses were found to be higher in monolithic geometries compared to bilayered zirconia FDPs. CONCLUSION: Monolithic 3-unit zirconia and CAD-on zirconia frameworks resulted in superior fracture resistance. Restoration design significantly affected the stress distribution of 3-unit zirconia FDPs.

Six-year clinical performance of lithium disilicate glass-ceramic CAD-CAM versus metal-ceramic crowns.

PURPOSE: To assess the clinical performance of monolithic CAD-CAM lithium disilicate glass-ceramic (LDGC) crowns and metal-ceramic (MC) crowns provided by predoctoral students. This study also assessed the effects of patient and provider-related factors on their clinical performance as well as patient preference for these types of crowns. MATERIALS AND METHODS: Twenty-five patients who received 50 crowns (25 LDGC CAD-CAM and 25 MC) provided by predoctoral students were retrospectively examined. LDGC CAD-CAM crowns were milled in-house using the CEREC Bluecam system and cemented with either RelyX Unicem or Calibra Esthetic resin cements. MC crowns were cemented with RelyX Unicem cement. Clinical assessment of the crowns and the supporting periodontal structures were performed following the modified California Dental Association (CDA) criteria. Patients' preference was recorded using a visual analog scale (VAS). The results were statistically analyzed using log-rank test, Pearson Chi-squared test and Kaplan-Meier survival analysis. RESULTS: Twelve complications were observed in the MC crown group (9-esthetic, 2-technical and 1-biological). In comparison, 2 complications in the LDGC CAD-CAM crown group were observed (1-technical and 1-esthetic). The 6-year cumulative survival rates for MC crowns and LDGC CAD-CAM were 90.8% and 96%, respectively, whereas the success rates were 83.4% and 96%, respectively. Overall, patients preferred the esthetic outcomes of LDGC CAD-CAM crowns over MC crowns. CONCLUSION: The high survival and success rates, low number of complications, and the high level of patients' acceptance of monolithic LDGC CAD-CAM crowns lend them well as predictable and viable alternatives to the "gold standard" MC crowns.

Clinical performance of CAD-CAM crowns provided by predoctoral students at the University of Toronto.

STATEMENT OF PROBLEM: The clinical success of monolithic lithium disilicate glass-ceramic (LDGC) crowns manufactured with computer-aided design and computer-aided manufacturing (CAD-CAM) technology provided by predoctoral students has not been fully investigated. PURPOSE: The purpose of this retrospective clinical study was to evaluate the performance of laboratory-fabricated monolithic posterior LDGC CAD-CAM crowns provided by predoctoral students at the University of Toronto. Specific patient- and provider-related factors were also investigated. MATERIAL AND METHODS: A sample of posterior LDGC CAD-CAM crowns (IPS e.max) provided by predoctoral students was evaluated. Crown preparations were made according to specific criteria, and crowns were milled in an in-house laboratory by using the CEREC Bluecam system. The crowns were cemented with Rely-X Unicem (3M ESPE) and Calibra Universal (Dentsply Sirona) resin cements. Clinical assessments of the crowns and supporting periodontal structures were performed following the modified California Dental Association (CDA) criteria. Intraoral photographs and periapical and bitewing radiographs were obtained for further assessment by 2 evaluators. Descriptive statistics, McNemar, t test, log rank (Mantel-Cox) tests, Pearson chi-squared tests, simple logistic regression, odds ratios, and Kaplan Meier survival analyses were performed (α=.05). RESULTS: A total of 189 patients receiving 210 crowns (108 premolar and 102 molar) were examined with a follow-up period of up to 6 years. Altogether, 28 complications were observed (12 technical, 11 biological, and 5 esthetic). No significant association was found between patient age, sex, periodontal condition, tooth type, tooth vitality, cement type, and crown longevity. However, significantly lower survival and success rates were found for mandibular crowns than for maxillary crowns (P=.029). The provider's experience had no significant effect on the clinical performance of LDGC CAD-CAM crowns. The 6-year cumulative survival rate was 93.0%, and the success rate was 86.4%. CONCLUSIONS: The ease of use of the CAD-CAM system and clinical performance of LDGC suggest that this technology should be used in the dental school setting by predoctoral students.

Hardness of Resin Cements Polymerized through Glass-Ceramic Veneers.

(1) Background: The aim of this study is to evaluate the hardness of resin cements polymerized through ceramic disks under different process factors (ceramic type and thickness, light-polymerization units and polymerization time); (2) Method: Three types of ceramic blocks were used (IPS e.max CAD; Celtra Duo; VITABLOCS). Ceramic disks measuring 0.5 mm, 1.0 mm and 1.5 mm were cut from commercial blocks. Two resin cements (Rely X Veneer and Variolink Esthetic) were polymerized through the ceramic specimens using distinct light-polymerization units (Deep-cure; Blue-phase) and time intervals (10 and 20 s). Hardness of cement specimens was measured using microhardness tester with a Knoop indenter. Data were statistically analyzed using factorial ANOVA (α = 5%); (3) Results: Mean microhardness of Rely X Veneer cement was significantly higher than that of Variolink Esthetic. Deep-cure resulted in higher mean microhardness values compared to Blue-phase at 0.5- and 1-mm specimen thicknesses. Moreover, a direct correlation was found between polymerization time and hardness of resin cement; (4) Conclusions: Surface hardness was affected by resin cement type and ceramic thickness, and not affected by ceramic types, within evaluated conditions. Increasing light-polymerization time significantly increased the hardness of the cement.

Radiant-exposure attenuation through Class-2 proximal slots.

PURPOSE: To determine the extent of radiant exposure (RE) attenuation of three LED light-polymerization units (LPUs), and their beam-profile, at the bottom of the Class-2 slot, using MARC-PS. METHODS: 10 seconds RE was delivered to MARC-PS' anterior sensor by Bluephase-Style, Demi-Plus, and Deep-Cure-S. Two ivorine lower first-molars received Class-2 proximal box preparations: (3×2×4 mm and 4×4×4 mm) and were sectioned horizontally above the cementoenamel junction. Tofflemire matrix-retainer was placed around each tooth and secured with a low-fusing compound. Each LPU tested delivered 10 seconds RE to MARC-PS through proximal slots. Mean RE of three readings per group was obtained. Data were analyzed using Pearson correlation, mixed ANOVAs with a pre-set alpha of 0.05. RESULTS: RE attenuation ratio calculated from the baseline to 4× 4×4/3×2×4 Class-2 boxes were: 58.25/80.03 Bluephase-Style; 49.36/80.25 Demi-Plus; 32.8/77.43 Deep-Cure-S. A significant and strong correlation (r= 0.86, P< 0.001) between the reduction in aperture size and RE was found. The beam profile of LED-LPUs tested decreased RE values at the bottom of a proximal box. More than 80% RE value reduction from the baseline to the smallest Class-2 cavity 3×2×4 aperture was observed. CLINICAL SIGNIFICANCE: Polymerization of resin-composites at the bottom of the Class-2 box is challenging due to the small aperture size, depth, and hard-to-reach location. Inadequate polymerization at the bottom of the Class-2 proximal box is a causative factor for secondary caries and, ultimately, restoration failure.

Clinical outcomes of lithium disilicate glass-ceramic crowns fabricated with CAD/CAM technology: A systematic review.

The use of ceramic materials and the computer-aided design/computer-aided manufacturing (CAD/CAM) technology for the fabrication of complete-coverage restorations has significantly increased in the last decade. The aim of this study was to evaluate the survival rate of anterior and posterior monolithic and bilayered lithium disilicate glass-ceramic (LDGC) CAD/CAM crowns, and to identify the types of complications associated with the main clinical outcomes reported in clinical trials. MEDLINE/PubMed, Embase, Scopus, Web of Science, Cochrane Library, and ClinicalTrials.gov were searched by 2 independent reviewers for clinical studies published between 2006 and 2019, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The electronic search was supplemented by a hand search. Quality assessment for the included studies was performed. Qualitative and quantitative data was extracted from each study. Out of 219 studies, 6 studies that evaluated LDGC CAD/CAM crowns were identified and used for data extraction. The included studies had 154 participants, who received 204 crowns. The shortto medium-term survival and success rates were high. Biological complications occurred more frequently than technical complications. No esthetic complications were reported. This review indicated that the medium-term survival rate of LDGC CAD/CAM crowns was high. Further multicenter studies with longer follow-ups and larger sample sizes are needed in order to augment the data already in existence.

Convergence Angle of Preparations for Lithium Disilicate Glass-Ceramic Crowns by Dental Students and Its Effect on Crown Retention.

The aims of this study were to determine the convergence angles of posterior teeth prepared by dental students at the University of Toronto for lithium disilicate glass-ceramic (LDGC) CAD/CAM crowns and to investigate their effect on loss of retention rate. A total of 280 preparations for posterior monolithic LDGC CAD/CAM crowns were performed on 270 patients (169 women and 101 men). Crowns were cemented with RelyX Unicem and Calibra Universal resin cements. Mesial, distal, and angle of convergence were measured on the bitewing radiographs. Cemented crowns were followed for up to six years. Data were analyzed for tooth type and location and for operator experience. The results showed the majority of convergence angles were greater than the recommended guidelines but fell within a clinically acceptable range (20 to 24 degrees). However, angles of convergence for mandibular molar preparations were highest (28.06±5.50 degrees), while maxillary premolars exhibited the lowest values (24.72±6.59 degrees). No significant difference was found between the results of dental students and foreign-trained dentists. Over a six-year observation period, only two crowns lost retention. The findings of this study indicated that ideal taper angles were impractical and difficult to achieve in clinical education settings.

Clinical performance of chairside monolithic lithium disilicate glass-ceramic CAD-CAM crowns.

OBJECTIVES: To evaluate the clinical performance and the effect of various patient and provider-related factors on the longevity of chairside monolithic posterior lithium disilicate glass-ceramic (LDGC) computer-aided design (CAD)-computer-aided manufacturing (CAM) crowns provided by predoctoral students. MATERIALS AND METHODS: A sample of posterior LDGC CAD-CAM crowns was evaluated. Crown preparations were milled chairside using the CEREC Omnicam system and cemented with Rely-X Unicem or Calibra Universal resin cements. Clinical assessment of the crowns and supporting periodontal structures was performed using the modified California Dental Association (CDA) criteria. Intraoral photographs as well as radiographs were taken for further assessment by two evaluators. Kaplan-Meier survival analysis was performed. RESULTS: A total of 40 crowns were inserted in 32 patients and evaluated for 4 years. Three complications were observed (two-technical and one-biological). No chipping or fracture of crowns was observed. No significant association was found between age, sex, periodontal condition, tooth type, tooth vitality, cement type, and longevity. The 4-year cumulative survival and success rates were 95.0 and 92.3%, respectively. CONCLUSION: Chairside LDGC CAD-CAM crowns exhibited a high survival rate after 4 years in function and were shown to be a viable and reliable treatment option for posterior teeth. CLINICAL SIGNIFICANCE: The high survival rate of chairside CAD-CAM crowns observed in this study suggests the likelihood of predictable performance in the predoctoral setup.

Porcelain veneers: An update.

New glass-ceramic restorative materials have been developed over the last few years, with enhanced strength characteristics along with desirable optical properties that make them ideal for the fabrication of esthetic crowns and veneers. The purpose of this paper was to provide an overview of the current state of the art of porcelain veneers as a viable option for the esthetic treatment of anterior teeth, and to illustrate the potential of the newly-developed glass-ceramics. Some historical background about the development of the porcelain veneer concept is provided. A list of indications and contraindications for porcelain veneers is followed by their preparation designs, with emphasis on the importance of maintaining the preparation boundaries within the enamel. Impression-taking procedures, provisional restoration fabrication, the choice of porcelain materials and their intaglio surface treatment are all discussed. A case where veneers made with a lithium-disilicate glass-ceramic were used to improve the appearance of maxillary anterior teeth is included. Several studies reporting on the longevity of porcelain veneers up to 12 years are discussed.

Influence of crown design and material on chipping-resistance of all-ceramic molar crowns: An in vitro study.

BACKGROUND: All-ceramic restorations have become popular and the trend is ongoing. However, the incidence of chipping within the veneering layer has been a commonly reported failure in clinical practice. OBJECTIVES: The aim of this in vitro study was to evaluate the effect of ceramic crown design (monolithic vs bi-layered) and material on the chipping resistance of molar crowns submitted to compressive cyclic loading. MATERIAL AND METHODS: Fifty identical epoxy resin replicas of a mandibular first molar with crown preparation were divided into 5 groups (n = 10) as follows: the MLD group - monolithic CAD/CAM lithium-disilicate glass-ceramic (LDGC) crowns; 30 zirconia cores were veneered with either feldspathic porcelain by hand-layering technique (ZHL) or by heat-pressing technique (ZVP), or with milled LDGC veneers and subsequently fused to the cores (ZLD); 10 porcelain-fused-to-metal (PFM) crowns acted as a control group. All crowns were cemented using Panavia® F2.0 resin cement (Kuraray Dental, Tokyo, Japan). After storage in water at 37°C for 1 week, the specimens were subjected to compressive cyclic loading at the mesiobuccal cusp which was tilted at 30°. A load cycle of 50-450 N was used and specimens were maintained in an aqueous environment throughout 500,000 cycles in a universal testing machine (Instron, Norwood, USA). The data was statistically analyzed at 5% significant level with Fisher's exact test and Kaplan-Meier survival analysis. RESULTS: Significant differences in survival rates of the specimens used in the groups (p < 0.001) were found. Specimens of the PFM, ZHL and ZVP groups underwent failures at different stages of the 500,000 fatigue cycles, while specimens of the MLD and ZLD groups survived the entire fatigue test. ZHL and ZVP crowns had the worst chipping-resistance, while PFM crowns performed slightly better. The Kaplan-Meier test revealed significantly higher survival rates for the MLD and ZLD specimens compared to the other 3 groups. CONCLUSIONS: The use of LDGC as a monolithic molar crown and as a veneer over a zirconia core resulted in superior resistance to cuspal chipping.

Gingival microleakage of class II bulk-fill composite resin restorations.

BACKGROUND: Bulk-fill composites were developed to simplify composite placement and minimize polymerization shrinkage stresses, which can improve gingival marginal adaptation in deep class II cavities. OBJECTIVES: The objective of this study was to compare the gingival microleakage of class II cavities restored with bulk-fill composites to that of incrementally restored ones with a conventional composite at 2 storage periods. MATERIAL AND METHODS: Forty freshly extracted intact molars were employed. Two standardized class II slot cavities, 3-millimeter-wide buccolingually, with the gingival floor 0.5 mm below the cementoenamel junction (CEJ) and the axial wall depth of 1.3 mm were prepared in each tooth (80 cavity preparations). The prepared teeth were divided equally into 3 bulk-fill groups (Tetric EvoCeram® Bulk Fill, X-tra Fil® and QuiXX®) and 1 control group (TPH Spectra® HV). Each group was subdivided into 2 equal subgroups (n = 10) according to the storage period in distilled water (24 h and 6 months). The Adper® Single Bond Plus adhesive was used with all the restorative materials. The cavities in the experimental groups were restored with 4-millimeter bulk-fill composites in 1 increment, while the cavities in the control group were restored with 2 increments of the thickness of 2 mm. The polymerization light was applied from the occlusal surfaces. The teeth were then immersed in 2% procion red dye solution, sectioned and examined under a stereomicroscope to determine the extent of dye penetration. The data was statistically analyzed using the Kruskal-Wallis test and the Mann-Whitney U test. RESULTS: The Kruskal-Wallis test revealed no significant differences in the mean microleakage scores among all the groups after 24-hour and 6-month storage (p = 0.945 and p = 0.928, respectively). The Mann-Whitney U test revealed an increase in the mean microleakage scores in all the groups after 6-month storage; however, the scores were not significantly different from the means obtained after 24 h (p = 0.259 for Tetric EvoCeram Bulk Fill; p = 0.205 for X-tra Fil; p = 0.166 for QuiXX; p = 0.155 for TPH Spectra HV). CONCLUSIONS: Gingival microleakage of bulk-fill composites in class II cavities was not significantly different from that of incrementally restored ones with a conventional composite. The increase in the mean gingival microleakage of the specimens stored for 6 months was not statistically significantly different in comparison to the values obtained after the 24-hour storage period for each composite.

Radiopacity of Resin Cements Using Digital Radiography.

STATEMENT OF PROBLEM: Monitoring performance of glass-ceramic based indirect restorations using radiographic imaging might be difficult due to their low radiopacity. Therefore, materials used for their cementation must possess adequate radiopacity. PURPOSE: This study determined radiopacity of a group of resin-cements used for adhesive-cementation of glass-ceramic-based restorations using digital radiography. METHODS: Two specimens were prepared from a group of resin cements (VariolinkII-opaque, VariolinkII-opaque (base), VariolinkII-Transparent, VariolinkII-Transparent (base), Nexus, RelyX Unicem, RelyX ultimate, Duolink, Monocem and Resinomer) and longitudinal sections of same thickness were obtained from molar and premolar. Specimens were assigned to two groups one had molar section with 10 specimens whereas other had premolar with remaining 10 specimens. Each group was placed on digital radiograph sensor (Schick CDR, size 2) together with aluminum step-wedge. Sensor was exposed to X-ray using standard technique. Two images were obtained for each group. Pixel measurements were made using NIH Image-J software. Mean pixel measurements were converted into aluminum thickness equivalents. Data were statistically-analyzed using one-way ANOVA and Tukey's tests. RESULTS: ANOVA revealed significant difference in mean pixel values among cements (p < 0.001). VariolinkII-opaque showed highest mean aluminum equivalent (4.6 mm Al/1 mm) followed by VariolinkII-opaque-Base (4.5 mm Al/1 mm), VariolinkII-transparent (4.45 mm Al/1 mm), VariolinkII-transparent-Base (4.45 mm Al/1 mm), Nexus (2.95 mm Al/1 mm), Duolink (2.7 mm Al/1 mm), RelyX Unicem (2.2 mm Al/1 mm) and finally RelyX ultimate (2 mm Al/1 mm). All cements had mean radiopacity values higher than that of enamel whereas Monocem (1.25 mm Al/1 mm) and Resinomer (1.2 mm Al/1 mm) had means between those of enamel and dentin. CONCLUSIONS: All tested resin-cements showed radiopacity values higher than that of dentin which is adequate for diagnostic purposes according to ISO recommendation. CLINICAL SIGNIFICANCE: The use of resin cement with adequate radiopacity for adhesive cementation of glass-ceramic based restorations enables their radiographic monitoring. (J Esthet Restor Dent 29:215-221, 2017).

Microtensile bond strength between a UDMA fiber post and different resin cements: Effect of pre-surface treatment.

During a fiber post cementation, bonding failure often occurs at the junction between the fiber-post and resin-cement. Because this failure requires better characterization, we evaluated if different post surface treatment can affect the bond strength of urethane dimethacrylate (UDMA) fiber-posts with resin-cements. Three groups were created: G1: no treatment/silane; G2: ethyl alcohol (96° GL)/silane; G3: 24% H2O2/silane and further divided into four subgroups: I-Unicem/3MESPE; II-BisCem/Bisco; III-Panavia SA/Kuraray and IV-DuoLink/Bisco. Blocks of cured resin cements and posts placed in the center were serially cut into bar-shaped specimens and loaded into a micro tensile testing machine. ANOVA indicated no significant differences among post surface treatments (p>0.05), however, significant within the resin cements (p<0.05) and the interaction of both (p<0.05). The G3/IV showed the highest bond strength values. SEM showed that surface treatments on UDMA fiber posts presented no benefits in terms of surface roughness, thus, should not be performed.

Fracture toughness of chairside CAD/CAM materials - Alternative loading approach for compact tension test.

OBJECTIVE: This in-vitro study determined plane-strain fracture toughness (KIC) of five different chairside CAD/CAM materials used for crown fabrication, following alternative innovative loading approach of compact tension test specimens. METHODS: Rectangular-shaped specimens were cut from CAD/CAM blocks (n=10): Vita Mark II (Vident) (VMII); Lava-Ultimate (3M/ESPE) (LU); Vita Enamic (Vident) (VE); IPS e.max CAD (Ivoclar Vivadent); crystallized and un-crystallized (E-max and E-max-U, respectively); and Celtra Duo (Dentsply) fired and unfired (CD and CD-U, respectively). Specimens were notched with thin diamond disk prior to testing. Instead of applying tensile loading through drilled holes, a specially-made wedge-shaped steel loading-bar was used to apply compressive load at the notch area in Instron universal testing machine. The bar engaged the top » of the notch before compressive load was applied at a cross-head speed of 0.5mm/min. Fracture load was recorded and KIC calculated. Data was statistically-analyzed with one-way ANOVA at 95% confidence level and Tukey's tests. RESULTS: Means and SDs of KIC in MPam(1/2) for VMII, LU, VE, E-max, E-max-U, CD and CD-U were: 0.73 (0.13), 0.85 (0.21), 1.02 (0.19), 1.88 (0.62), 0.81 (0.25), 2.65 (0.32) and 1.01 (0.15), respectively. ANOVA revealed significant difference among the groups (p<0.001). CD and E-max had significantly highest mean KIC values. SIGNIFICANCE: Mean KIC values of the tested materials varied considerably, however, none of them reached mean KIC of dentin (3.08MPam(1/2)) previously reported. For E-max and CD, specimens firing significantly increased mean KIC. The modified test arrangement was found to be easy to follow and simplified specimen preparation process.

Radiopacity of Nonmetallic CAD/CAM Restorative Blocks.

PURPOSE: This study determined the radiopacity of a group of computer-aided design/computer-assisted manufacture blocks using digital radiography and pixel monitoring. MATERIALS AND METHODS: Specimens 2.0 ± 0.05-mm thick were cut from nine different blocks. Longitudinal sections of the same thickness were obtained from molar and premolar. Specimens were assigned to one of two groups, and each group was placed on a digital radiograph sensor together with an aluminum step wedge. Following standardized technique, the sensor was exposed and two images were obtained from each group. Images were analyzed using ImageJ software to determine the number of pixels at five different locations for each specimen. Means and standard deviations were calculated and the data statistically analyzed. Radiopacity values were expressed as equivalent of aluminum thickness. RESULTS: Analysis of variance revealed significant difference in mean pixels among the blocks (P < .001). CONCLUSION: The majority of blocks had radiopacity values that were higher than that of dentin.

Cuspal Deflection of Premolars Restored with Bulk-Fill Composite Resins.

OBJECTIVE: This in vitro study compared cuspal deflection of premolars restored with three bulk-fill composite resins to that of incrementally-restored ones with a low-shrinkage silorane-based restorative material. MATERIALS AND METHODS: Forty freshly-extracted intact human upper premolars were used. Reference points at buccal and palatal cusp tips were acid-etched and composite rods were horizontally bonded to them (TPH-Spectra-HV, Dentsply). Two acrylic resin guiding paths were made for each premolar to guide beaks of a digital micrometer used for cuspal deflection measurements. Standardized MOD cavities, 3 mm wide bucco-lingually and 3.5 mm deep, were prepared on each premolar. Prepared teeth were then equally divided into four groups (n = 10) and each group was assigned to one of four composite resin (QuiXX, Dentsply; X-tra fil, Voco; Tetric EvoCeram Bulk Fill, Ivoclar Vivadent; low-shrinkage Filtek LS, 3M/ESPE). Adper Single Bond-Plus, 3M/ESPE was used with all bulk-fill restoratives. LS-System Adhesive, 3M/ESPE was used with Filtek LS. For each prepared premolar, cuspal deflection was measured in microns as the difference between two readings between reference points before and after restoration completion. Means and SDs were calculated and data statistically-analyzed using One-way ANOVA and Tukey's test. RESULTS: Filtek LS showed the lowest mean cuspal deflection value 6.4(0.84)µm followed by Tetric EvoCeram Bulk Fill 10.1(1.2) µm and X-tra fil 12.4(1.35)µm, while QuiXX showed the highest mean 13(1.05)µm. ANOVA indicated significant difference among mean values of groups (p < 0.001). Tukey's test indicated no significant difference in mean values between QuiXX and X-tra fil (p = 0.637). CONCLUSIONS: Tetric EvoCeram Bulk Fill had significantly lower mean cuspal deflection compared with the two other bulk-fill composite resins tested. Filtek LS had the lowest significant mean cuspal deflection in comparison to all tested bulk-fill restoratives. CLINICAL SIGNIFICANCE: The use of Tetric EvoCeram Bulk fill composite resin restorative for class II MOD cavities resulted in reduced cuspal deflection in comparison to the two other bulk-fill composite resins tested. The silorane-based Filtek LS restorative resulted in the least cuspal deflection in comparison to all tested bulk-fill composite restoratives.

The Effect of Self-adhesive and Self-etching Resin Cements on the Bond Strength of Nonmetallic Posts in Different Root Thirds.

PURPOSE: The purpose of this study was to evaluate the effect of self-adhesive and self-etching resin cements on the bond strength of nonmetallic posts in different root regions. MATERIALS AND METHODS: Sixty single-rooted human teeth were decoronated, endodontically treated, post-space prepared, and divided into six groups. Glass-fiber (GF) posts (Exacto, Angelus) and fiber-reinforced composite (FRC) posts (EverStick, StickTeck) were cemented with self-adhesive resin cement (Breeze) (SA) (Pentral Clinical) and self-etching resin cement (Panavia-F) (SE) (Kuraray). Six 1-mm-thick rods were obtained from the cervical (C), middle (M), and apical (A) regions of the roots. The specimens were then subjected to microtensile testing in a special machine (BISCO; Schaumburg, IL, USA) at a crosshead speed of 0.5 mm/min. Microtensile bond strength data were analyzed with two-way ANOVA and Tukey's tests. RESULTS: Means (and SD) of the MPa were: GF/SA/C: 14.32 (2.84), GF/SA/M: 10.69 (2.72), GF/SA/A: 6.77 (2.17), GF/SE/C: 11.56 (4.13), GF/SE/M: 6.49 (2.54), GF/SE/A: 3.60 (1.29), FRC/SA/C: 16.89 (2.66), FRC/SA/M: 13.18 (2.19), FRC/SA/A: 8.45 (1.77), FRC/SE/C: 13.69 (3.26), FRC/SE/M: 9.58 (2.23), FRC/SE/A: 5.62 (2.12). The difference among the regions was statistically significant for all groups (p < 0.05). The self-adhesive resin cement showed better results than the self-etching resin cement when compared to each post (p < 0.05). No statistically significant differences in bond strengths of the resin cements when comparable to each post (p > 0.05). CONCLUSION: The bond strength values were significantly affected by the resin cement and the highest values were found for self-adhesive resin cement.