OBJECTIVE:The aim of this research was to assess the efficiency of 4 restorative glass ionomer cements (GICs): Fuji IX (GC), ChemFil Rock (DENSPLY), Riva Self-Cure (SDI), and Ketac Nano (3M ESPE).MATERIALS AND METHODS:The 4 restorative glass ionomers' diametral tensile and compressive strengths were evaluated at room temperature for 24 hours and then stored in distilled water. The universal testing machine (INSTRON 5566A) was used to record the maximum load necessary to fracture specimens. Surface wear, diametral tensile strength, and compressive strength against dental ceramic were compared using analysis of variance followed by the Bonferroni method at a significance level of 0.05.RESULTS:Ketac Nano and ChemFil Rock were found to have better diametral tensile strength than Riva Self-Cure and Fuji IX. The significant difference between ChemFil Rock and Fuji IX (P ≤ .005) and ChemFil Rock with Riva Self-Cure (P ≤ .005) was shown by post hoc analysis. Ketac Nano had better tensile strength than Riva Self-Cure and Fuji IX. Fuji IX showed the lowest material loss of the GICs as revealed by wear against VITABLOCS Mark II (VITA Zahnfabrik).CONCLUSIONS:This study indicated a significant difference in the compressive strengths of ChemFil Rock and Riva Self-Cure. ChemFil Rock had the highest tensile strength. The diameter tensile strength of all 4 materials was statistically insignificant. Finally, Fuji IX had the least amount of material loss. ChemFil Rock was proven to be more effective than Fuji IX.

Background: A variety of veneering options to zirconia frameworks are now available. The purpose of this study is to evaluate the effect of veneer materials, veneering methods, cement materials, and aging on the failure load of bilayered veneer zirconia. Material and methods: Zirconia bars (20 × 4 × 1 mm) were veneered to 2 mm total thickness (n = 10/group). Veneering method groups included: 1. Hand-layered feldsparthic porcelain (VM = Vita VM9, Vident) and fluorapatite glass–ceramic (CR = IPS e.max Ceram, IvoclarVivadent); 2. Pressed feldspathic porcelain (PM = Vita PM9, Vident) and fluorapatite glass–ceramic (ZP = IPS e.max ZirPress, IvoclarVivadent); 3. CAD-/CAM-milled feldspathic ceramic (TF = Vitablocs Triluxe Forte, Vident) and lithium-disilicate glass–ceramic (CAD = IPS e.max CAD, IvoclarVivadent). CAD/CAM veneers were either cemented with resin cements (P = Panavia21, KurarayDental), (R = RelyX Ultimate, 3M ESPE), (M = Multilink Automix, Ivoclar Vivadent) or fused with fusion glass–ceramic (C = CrystalConnect, IvoclarVivadent). A three-point bending test (15 mm span, zirconia on tension side) was performed on Instron universal testing machine (ISO 6872) recording load-to-failure (LTF) of first veneer cracks or catastrophic failure. For group VM, PM, TF-M, TF-C, CAD-M, CAD-C, ten more bars were prepared and aged with cyclic loading (100,000 cycles, 50% LTF) and thermocycling (2000 cycles) before testing. Data were analyzed by ANOVA, Tukey HSD post hoc tests, and t-test (α = 0.05). Zirconia veneered with IPS e.max CAD by fusing had significantly higher failure load compared with zirconia veneered with other veneering materials. (p ≤ 0.05). For cemented veneers, the cement type had a significant effect on the failure load of the veneer zirconia specimens. Specimens cemented with Panavia 21 had a lower resistance to loading than other cements. The aging experiment revealed a significant difference in failure load between non-aged and aged bars in groups VM and PM, but not in the groups with CAD-/CAM-milled veneers. In conclusion, veneer materials, veneering methods, and cement materials have a significant effect on the failure load of bilayered veneer zirconia. CAD-/CAM-milled veneer zirconia is not susceptible to aging performed in this study.

Purpose: To evaluate whether the composite cement tensile bond strength is affected by different firing cycles or etching conditions on zirconium-incorporated lithium-silicate glass ceramics. Materials and Methods: Specimens (N=53) were prepared from blocks of zirconium-incorporated lithium-silicate glass ceramic (ZLS, Dentsply Sirona) with specimen dimensions of 12.5 x 14 x 2 mm (L x W x H, respectively). The specimens were subjected to different firing cycles and etching conditions. They were subsequently cemented onto titanium rods (grade V Ti-alloy, 4.8 mm in diameter, and 25.4 mm in length) with self-adhesive composite cement (TheraCem, Bisco), and then tested for tensile bond strength (TBS). The least-square means linear regression model was used to analyze the effects on TBS using JMP Pro 14 (SAS) and the post-hoc Tukey test with α = 0.05. Results: The TBS was significantly affected by etching duration (p < 0.001) and firing cycles (p < 0.001), but was not significantly affected by etchant concentration (p = 0.31). The highest TBS peak (4.83 MPa) on the fit curve was observed at 45 s of etching time. The lowest TBS was observed at 20 s (3.02 ± 0.28 MPa) etching time. In terms of firing cycles, 1 firing cycle (4.00 ± 0.71 MPa) provided the highest TBS. In contrast, the lowest TBS was observed for as-machined ZLS specimens but without a firing step (3.29 ± 0.53 MPa). Conclusions: Changing the etching time and firing conditions of the specimens had a significant effect on the composite cement tensile bond strength to zirconium-incorporated lithium-silicate glass ceramic. In contrast, etching the specimens with different acid concentrations, 5% or 9.6% of HF, did not significantly change the composite cement tensile bond strength.

Fluoride is considered to be an important caries-preventive agent as it decreases the solubility of tooth minerals. The aim of the present study was to investigate the amount of fluoride ion released, over a 9 day period, from four restorative glass ionomer cements (GIC). Elemental analysis, for O, F, Na, Mg, Al, Si, P, S, Ca, Sr, Zn, and Zr, was performed on three conventional glass ionomers [ChemFil ROCK (Dentsply), Fuji IX (GC), and Riva self-cure (SDI)] and one resin-modified glass ionomer, Ketac Nano (3M ESPE) using Energy Dispersive Spectrometry (EDS). A digital caliper was used to measure the length and diameter of each sample. The fluoride release, in mu g/cm(2), from the samples in deionized water was measured for 9 days using a fluoride ion selective electrode and analyzed using the SPSS. The release of fluoride on day 1 from Fuji IX was significantly higher (6.19 +/- 1.04 mu g/cm(2)) than that from Ketac Nano (3.88 +/- 0.13 mu g/cm(2)), Riva self-cure (3.19 +/- 0.66 mu g/cm(2)), and ChemFil ROCK (1.68 +/- 0.08 mu g/cm(2)). The value found for Fuji IX was comparable to that found in various other experimental settings. The difference in fluoride release on day 1 between Ketac Nano and Riva self-cure was not significant. The fluoride release from day 5 to day 9 stabilized at a lower level for all the ionomers and no statistically significant difference in the level of release was present between them during that period. I concluded that there is a wide range in the release of the fluoride ion among restorative glass ionomer cements with the highest level of release on day 1 being observed in Fuji IX, followed by Ketac Nano, Riva self-cure, and ChemFil ROCK.

Objective. This study evaluated the effect of ceramic surface treatments on bond strength of metal brackets to machinable ceramics and veneering porcelain using different adhesive resins. Materials and methods. Machined ceramic specimens (10 × 10 × 2 mm) were prepared from Vitablocs mark II (Vita) and IPS e.max® CAD (Ivoclar). Layered porcelain fused to metal (IPS d.Sign®, Ivoclar) was used to fabricate PFM specimens (n = 60/group). Half of specimens were etched (9.6% HF, 15 sec), and the rest were nonetched. Three resin bonding systems were used for attaching metal brackets (Victory series™ APC II, 3M) to each group (n = 10): Transbond™ XT (3M), Light Bond™ (Reliance), or Blugloo™ (Ormco), all cured with LED curing unit (Bluephase G1600, Vivadent) for 50 s each. Specimens were immersed in deionized water at 37°C for 24 hours prior to shear bond testing (Instron) at crosshead speed of 0.5 mm/min. Debond surface of ceramic and bracket base was examined for failure mode (FM), Ceramic Damage Index (CDI), and Adhesive Remnant Index (ARI). ANOVA and post hoc multiple comparisons were used to analyze the differences in bond strength. The chi-squared test was used to determine significance effect of FM, CDI, and ARI. Results. Significant differences in shear bond strength among group were found (p≤0.05) related to ceramic, surface treatment, and resin cement. Conclusion. Bond strength of bracket to ceramic is affected by type of ceramic, resin cement, and ceramic surface conditioning. Etching ceramic surface enhanced ceramic-bracket bond strength. However, bond strengths in nontreated ceramic surface groups were still higher than bond strength required for bonding in orthodontic treatment.

Statement of problem: Current techniques for repairing porcelain-chipped restorations have several limitations. With advances in CAD/CAM technology, the combination of resin cements and high-strength ceramic materials might offer new options for repairing the chipping of veneering ceramic. Purpose: The purpose of this study is to compare the load-to-failure of veneered zirconia crowns repaired by different materials. Material and Methods: Veneered zirconia crowns were made on aluminum dies (n = 10/group). Feldspathic porcelain (Vita VM9, Vident) was applied to the zirconia coping (Vita In-Ceram YZ, Vident) in a cylindrical shape (Ø 10.5 mm, height 7.5 mm). A bevel cut on the porcelain veneer (45 degree, 3 mm width) was made at one side of each crown to simulate porcelain chipping. The crowns were then divided into four different groups according to the repair materials: 1. Conventional resin composite (A; Tetric EvoCeram, Ivoclar Vivadent); 2. Flowable resin composite (B; G-aenial Universal Flo, GC america); 3. CAD/CAM milled feldspathic ceramic (C; Vita Trilux Forte, Vident); 4. CAD/CAM milled lithium disilicate glass-ceramic (D; IPS e.max CAD, Ivoclar Vivadent). Resin cement (Multilink Automix, Ivoclar Vivadent) was used to cement the CAD/CAM ceramic materials to the beveled crowns. Each crown underwent 5000 cycles of thermocycling. The strength test was performed on an Instron universal testing machine by loading force on the center of repaired part to record load-to-failure. Data were analyzed by ANOVA and Tukey HSD post-hoc tests (α = 0.05). Results: Mean loads-to-failure (in Newton +/− SD) of repaired veneered zirconia crowns were: Gr. A: 660.0 ± 200.5; Gr. B: 681.7 ± 175.9; Gr. C: 1236.0 ± 188.8; Gr. D: 1536.3 ± 286.1. Catastrophic failure was the most dominant failure mode in every group. Few specimens exhibited cohesive failure. Only one specimen in group D had adhesive failure. Conclusions: Within the limitation of the study, veneered zirconia crowns repaired with CAD/CAM ceramic materials have significantly higher load-to-failure than veneered crowns repaired with resin composite (p ≤ 0.05). Clinical Implications: Traditionally, porcelain-chipped restorations are often repaired with resin composite and bonding technique. Repairing chipped porcelain with CAD/CAM ceramics fitting the fractured parts can be alternative option with potential advantages. More well-designed studies are necessary to justify this novel repair technique.

Statement of problem. Estimating the width of the maxillary anterior teeth when creating an esthetic smile can be challenging. Valid metrics to assist in this process are needed. Purpose. The purpose of this systematic review was to evaluate the validity of interalar distance and inner canthal distance with the golden proportion, golden mean, and recurring esthetic dental proportion in predicting intercanine distance and the combined width of central incisors to potentially provide a guide for tooth restoration. Material and methods. A literature search was conducted using PubMed, Medline, Google Scholar, EMBASE, CNKI, Web of Science, and the Cochrane Collaboration, identifying English- and non-English-language articles reporting on interalar width, inner canthal width, and maxillary anterior tooth width. Additional studies were identified by searching reference lists of the articles identified. Only studies that fulfilled inclusion criteria were included. Two examiners independently performed the literature search and data extraction. Using a meta-analysis software program, data extracted from each selected study were statistically combined using the random-effects model. Weighted mean differences, 95% confidence intervals, and heterogeneity were calculated for each measurement. Results. The search strategy resulted in a total of 282 articles, but only 41 articles fulfilling the inclusion criteria were included in the meta-analysis. The interalar distance was found to be significantly larger than intercanine distance, and the inner canthal distance was found to be substantially smaller than the intercanine distance. When predicting the central incisors combined width by interalar distance, both the golden proportion and golden mean predicted value were larger than the combined width of the central incisors. Only the recurring esthetic dental proportion (70%) predicted value showed no significant difference from the combined width of central incisors. When predicting the central incisors combined width by inner canthal distance, the golden proportion predicted value was larger than the combined width of central incisors, whereas both the golden mean and recurring esthetic dental proportion (70%) predicted value were found to be significantly smaller than the combined width of central incisors. Conclusions. By analyzing the data from the literature, only the recurring esthetic dental proportion (70%) with interalar distance could be an accurate method for predicting the combined width of central incisors. Neither interalar distance nor inner canthal distance could directly be used to predict the intercanine distance.

Objective The purpose of this study was to evaluate the effect of glazing on flexural strength of highly translucent zirconia materials. Materials and Methods Specimens of three brands of zirconia bars (Prettau Zirconia, Zirkonzahn; inCoris TZI, Sirona; and Zirlux FC, Pentron Ceramics) were prepared and polished according to manufacturers' instructions. Final specimen dimensions were 20 × 4 × 2 mm. The specimens from each brand were divided into 3 groups (N = 10): control, heat-treated, and glazed. Heat-treated specimens were fired without the application of the glaze material. The glaze material was applied to the glazed specimens before being fired. A three-point bending test (15 mm span) was performed in an Instron universal testing machine (ISO 6872). Data were analyzed by ANOVA and Tukey's HSD post hoc test (α = 0.05). Results Two-way ANOVA showed a significant influence of surface treatments on flexural strength of zirconia materials (P ≤ 0.05). There was no significant difference in flexural strength among the different brands of highly translucent zirconia (P ≥ 0.05). Tukey's HSD post hoc test showed that specimens in the “glazed” group had significantly lower flexural strength than the control and heat-treated groups (P ≤ 0.05). Conclusion Within the limitations of the study, external glazing decreased the flexural strength of highly translucent zirconia.

Statement of problem. Data on the retention of individually formed fiber-reinforced composite posts (ever Stick) cemented with self-adhesive cement are lacking. Purpose The purpose of this in vitro study was to investigate the pull-out strength of 2 different fiber-reinforced composite posts (prefabricated and individually formed) cemented into extracted teeth with self-adhesive resin cement. Material and Methods. Thirty extracted single-rooted human teeth were decoronated, endodontically treated, and prepared with post spaces of equal length. Prepared specimens were divided into 2 groups (n=15 each) based on the type of post: commercially prefabricated fiber posts (GC) and individually formed resin posts (using GC reinforcing fibers). Self-adhesive resin cement (G-CEM LinkAce; GC) was used to cement all posts. Each post was held with moderate pressure, and root surfaces were light polymerized for 20 seconds (650 mW/cm(2)). After cementation, the specimens were stored in saline solution for 30 days. Treated teeth were kept in water for 24 hours before pull-out testing parallel to the longitudinal axis of the posts. Data were analyzed using the Student t test (alpha=.05) and the coefficient of variance as the ratio of the standard deviation to the mean. Results. The mean pull-out retention strength was 185.7 +/- 61.2 N for the prefabricated fiber posts and 98.9 +/- 56.5 N for the individually formed fiber posts (P=.026). Conclusions. The prefabricated fiber posts exhibited significantly higher retention forces than the individually formed posts.

PurposeRepeated tightening and loosening of the abutment screw may alter its mechanical and physical properties affecting the optimal torque and ultimate reliability of an implant/abutment connection. The purpose of this study was to evaluate the effect of repeated tightening and loosening of implant/abutment screws on the loosening torque of implant/abutment connections of commercially available implant systems. Materials and methodsSeven different implant/abutment connections and their modifications were tested. The screws of each system were tightened according to the manufacturer's specifications. After 20 minutes the screws were loosened. This procedure was repeated ten times, and the differences between the 1st and 10th cycle were expressed as a percentage change RTq(%) and correlated with initial torque, the number of threads, the length of shank, and thread surface area employing Spearman's analysis. ResultsAll systems showed significant differences in residual torque (RTq) value (p < 0.05) between the 1st and 10th cycle except groups 6 and 11 (p > 0.05). All connections but group 3 (p = 1.000) showed a significant change from the initial torque (ITq) to the RTq values. The first successive RTq values increased in two connection groups 1 and 2. The remaining connections showed reduced RTq values ranging from -1.2 % (group 5) to -23.5% (group 6). The RTq values declined gradually with every repeated tightening in groups 1, 2, 3, 8, 9, 11, 12. In group 2, after the tenth tightening the RTq was still above the ITq value. Only length of shank demonstrated a correlation with the RTq(%) change over the successive tightening loosening cycles (p < 0.05). ConclusionRepeated tightening and loosening of implant/abutment screws caused varying torque level changes among the different systems. These observations can probably be attributed to connection design. Clinical Implications: Limiting the number of tightening/loosening cycles in clinical and laboratory procedures is advisable for most of the implant systems tested.

STATEMENT OF PROBLEM:The translucency and opacity of ceramics play a significant role in emulating the natural color of teeth, but studies of the masking properties and limitations of dental ceramics when used as monolayer restorations are lacking. PURPOSE:The purpose of this in vitro study was to determine the translucency of 6 materials used for veneer restorations by assessing their translucency parameters (TPs), contrast ratios (CRs), and potential to mask dark tooth colors. MATERIAL AND METHODS:Ten square- or disk-shaped specimens (0.5-mm thickness, shade A2) were fabricated from Vitablocks Mark II (VMII; Vita Zahnfabrik), IPS e.max CAD LT (EMXC LT; Ivoclar Vivadent AG), IPS e.max CAD HT (EMXC HT; Ivoclar Vivadent AG), IPS Empress CAD LT (EMP LT; Ivoclar Vivadent AG), IPS e.max Press LT (EMXP LT; Ivoclar Vivadent AG), and CZR (CZR; Kuraray Noritake Dental Inc). Their luminance (Y) values over black and over white tiles were measured, followed by their color (CIELab) over black tiles and white tiles and shaded A2 (control group), A3.5, A4, and B4 acrylic resin blocks. All measurements were performed using a spectrophotometer in 2 different areas on each specimen. Then CRs, TPs, and color differences (over shaded backgrounds) were determined. Data were subjected to 1-way and 2-way ANOVA (α=.05) for analysis. RESULTS:Mean CR values of EMXP LT were significantly higher than those of the other tested materials, whereas VMII and EMXC HT had the lowest values (P<.001). Mean TP values over black and over white backgrounds of VMII and EMXC HT were significantly higher than those of the other tested materials, while EMXP LT and EMXC LT revealed the lowest values (P<.001). Background shade A4 displayed the highest mean effect (expressed in ΔE* values) on the color of the ceramic materials, whereas shade B4 demonstrated the lowest mean background effect (P<.001). CONCLUSIONS:Significant differences in translucency among the tested ceramics were revealed (P<.001). The EMXC LT and EMXP LT groups were the least translucent under the conditions of this study (P<.001). All tested ceramics exhibited poor masking properties against the A4 background. The color differences of most tested ceramics were more acceptable when tested against the B4 background (ΔE*≤3.3).

Objectives: The aim of this study was to evaluate the effect of photon induced photoacoustic streaming (PIPS) technique in combination with EDTA on bond strength of gutta-percha/AH Plus and Resilon/RealSeal SE root canal fillings to root dentine.Materials and Methods: Forty freshly extracted human maxillary anterior teeth with intact straight roots, were instrumented endodontically with rotating ProTaper instruments and randomly divided into two experimental groups. In group 1 (n = 20), root canals were rinsed for 1 minute with 2 ml of 17% EDTA. In group 2 (n = 20), Er: YAG laser, with a 14 mm long 400 mu diameter tapered PIPS tip, was used for 1 minute with 2ml of 17% EDTA. The laser parameters used were: 20 mJ per pulse, 15 Hz, 50 microsecond. In each experimental group, half of the root canals (n = 10) were obturated with gutta-percha/AH Plus and other half (n = 10) with Resilon/RealSeal SE. A micropush-out test was performed on sectiond specimens of the filled roots using a universal testing machine and resistance to failure plus failure modes were determined.Results: Both gutta-percha/AH Plus groups had higher bond strength to root dentin than the Resilon/RealSeal SE groups (P<0.05). The smear layer removal protocol, with EDTA only or combining PIPS technique with EDTA, had no influence on bond strength of either gutta-percha/AH Plus, or Resilon/RealSeal SE (P>0.05).Conclusion: Within the limitations of this study, it was found that the application of the PIPS technique did not have an affect on the push-out bond strength of Resilon/RealSeal SE root canal filling to dentin nor on the gutta-percha/AH Plus. A significant difference in bond strength was noted between the two root canal filling materials. (C) 2016 Wiley Periodicals, Inc.

Objective: The primary objective of this study was to compare the dentin ablation volume and ablation rate of quantum square pulse (QSP), using two different pulse energy settings plus a new digitally controlled dental laser handpiece (X-Runner), with those of variable square pulse (VSP), using three different pulse durations. The secondary objective was to examine, by scanning electron microscopy (SEM), the surface effects of ablation with the different Er:YAG laser modes on the dentin surfaces. Background data: The available literature has limited data on the efficiency of different operating modes, pulse durations, and the new digitally controlled handpiece of the Er:YAG laser on human dentin. Materials and methods: Freshly extracted human molars (n=72) were divided into two experimental groups (n=36 each): (1) QSP group, and (2) VSP group. Each group was randomly divided into three subgroups (n=12 each). In the QSP group, preparations in dentin were performed using 250 and 500mJ of pulse energy with the conventional handpiece, and with the X-Runner handpiece set at 250mJ pulse energy. In the VSP group, cavity preparations were performed using three pulse variables: super short pulse (SSP), micro short pulse (MSP), and short pulse (SP). Cavity preparations were made in dentin at time intervals of 1, 2, and 5sec. A laser triangulation profilometer was used to determine cavity volumes. Surface analysis of the ablated dentin specimens was performed by SEM. Results: For time intervals of 1 and 2sec, ablated volume and ablation rate for QSP-500mJ were significantly higher than for all other groups (p<0.0001). For the 5-sec time interval, X-Runner and QSP-500mJ were the most efficient in dentin ablation (p<0.0001). Dentin surfaces were free of smear layer in all groups. Conclusions: The most efficient modes of dentin ablation in the study were the QSP-500mJ and X-Runner groups. Dentin surfaces were free of smear layer in all groups.

: Magnetic attachments are being increasingly used for removable dental prostheses, mainly because they are relatively simpler to use than other attachments, and they show good retention and stability. However, this approach poses some problems. In patients undergoing magnetic resonance imaging （ MRI ） procedures, the presence of magnetic structures and keepers may cause artifacts that hinder the diagnosis. We therefore aimed to develop a technique that could reduce the damage caused to dental roots and root caps during removal of the magnetic keepers. A modified keeper tray and custom-made metallic guide bar were used for root cap fabrication. The retrieval hole of the root caps was made from the bottom of the keeper tray to the labial side of the root. A special crown remover was then inserted into the retrieval hole and rotated to facilitate removal of the magnetic keepers through the hole without causing damage to the root caps. Conclusion : This study describes a new technique that uses a keeper tray along with magnetic attachments for overdentures to enable simple removal of the keeper without causing damage.

Statement of problem. The recent development of polymer-based computer-aided design and computer-aided manufactured (CAD/CAM) milling blocks and the limited availability of independent studies on these materials make it pertinent to evaluate their properties and identify potential strengths and limitations.Purpose. The purpose of this in vitro study was to determine and compare mechanical properties (flexural strength, flexural modulus, modulus of resilience) and compare the margin edge quality of recently introduced polymer-based CAD/CAM materials with some of their commercially available composite resin and ceramic counterparts.Material and methods. The materials studied were Lava Ultimate Restorative (LVU; 3M ESPE), Enamic (ENA; Vita Zahnfabrik), Cerasmart (CES; GC Dental Products), IPS Empress CAD (EMP; lvoclar Vivadent AG), Vitablocs Mark II (VM2; Vita Zahnfabrik), and Paradigm MZ100 Block (MZ1; 3M ESPE). Polished 4x1x13.5 mm bars (n=25) were prepared from standard-sized milling blocks of each tested material. The bars were subjected to a 3-point flexural test on a 10-mm span with a crosshead speed of 0.5 mm/min. In addition, 42 conventional monolithic crowns (7 per material) were milled. Margin edge quality was observed by means of macrophotography and optical microscopy, providing a qualitative visual assessment and a measurement of existing roughness. The results were analyzed by ANOVA followed by the Tukey HSD test (alpha=.05).Results. The mean flexural strength of the tested materials ranged from 105 +/- 9 MPa (VM2) to 219 +/- 20 MPa (CES). The mean flexural modulus ranged from 8 +/- 0.25 GPa (CES) to 32 +/- 1.9 GPa (EMP). The mean modulus of resilience ranged from 0.21 +/- 0.02 MPa (VM2) to 3.07 +/- 0.45 MPa (CES). The qualitative assessment of margin edge roughness revealed visible differences among the tested materials, with mean roughness measurements ranging from 60 +/- 16 mu m (CES) to 190 +/- 15 mu m (EMP).The material factor had a significant effect on the mean flexural strength (P<.001), flexural modulus (P<.001), modulus of resilience (P<.001), and margin edge roughness (P<.001) of the tested specimens.Conclusions. The new-generation polymer-based materials tested in this study exhibited significantly higher flexural strength and modulus of resilience, along with lower flexural modulus values compared with the tested ceramic or hybrid materials. Crowns milled from the new resin-based blocks seemed to exhibit visibly smoother margins compared with the ceramic materials studied.

Objective: The purpose of this study was to determine the effectiveness of laser-activated irrigation by photon-induced photoacoustic streaming (PIPS) using Er:YAG laser energy in decontaminating heavily colonized root canal systems in vitro. Materialsand methods: Extracted single-rooted human teeth (n=60) were mechanically and chemically prepared, sterilized, inoculated with Enterococcus faecalis for 3 weeks, and randomly assigned to four groups (n=15): Group I (control, no decontamination), Group II (PIPS+6% NaOCl), Group III (PIPS+saline), and Group IV (6% NaOCl). PIPS settings were all preset to 50 μsec pulse, 20 mJ, 15 Hz, for an average power of 0.3 W. After decontamination, the remaining live microbes from all specimens were collected and recovered via plate counting of the colony-forming units (CFUs). Randomized root canal surfaces were examined with scanning electron microscopy and confocal laser microscopy. Mean variance and Dunnett's t test (post-hoc test) comparisons were used to compare mean scores for the three groups with the control group. Results: The CFU analysis showed the following measurements (mean±SE): Group I (control), 336.8±1.8; Group II (PIPS+NaOCl), 0.27±0.21; Group III (PIPS+saline), 225.0±21; and Group IV (NaOCl), 46.9±20.29. Group II had significantly lower CFUs than any other groups (p<0.05). Both imaging analyses confirmed levels of remaining bacteria on examined root surfaces. Conclusions: The use of the PIPS system along with NaOCl showed the most efficient eradication of the bacterial biofilm. It appears that laser-activated irrigation (LAI) utilizing PIPS may enhance the disinfection of the root canal system.

BACKGROUND:Fracture of restored endodontically treated teeth is a common complication. The mechanical properties of post systems may play a role in the incidence of tooth fracture.AIM:The purpose of this study was to evaluate in vitro the fracture resistance and pattern of fracture of endodontically treated teeth restored with three different post systems.MATERIAL AND METHODS:Posts used were fiber-reinforced composite resin posts (FRC post), custom cast silver-palladium, and nickel-chromium posts and cores. A 3-point bending test was performed to calculate flexural strengths and elastic moduli of the specimens. Sixty extracted human maxillary canines were endodontically treated and divided into three groups (n = 20). All-ceramic crowns were fabricated and cemented with Variolink II resin cement. Ten specimens of each group were subjected to a constantly increasing load until fracture. The other 10 specimens were fatigued for 106 cycles in a custom-made fatigue machine. Recorded failure loads and modes were statistically compared with one-way anova and Tukey-HSD tests (α = 0.05).RESULTS:The resistance to fracture of teeth restored with FRC posts, composite resin cores, and Empress II crowns was similar to that of teeth restored with cast posts and cores (P = 0.162). Supracrestal (above root/level of acrylic resin base) oblique fracture was the predominant mode of fracture associated with teeth restored with FRC posts (70%), while vertical root fractures were more common with teeth restored with cast posts and cores.CONCLUSIONS:Teeth restored with the FRC post system did not exhibit vertical root fractures and were less likely to show root fracture. Sixty to 80% of teeth restored with both types of cast posts and cores showed vertical and subcrestal root fractures.