Resin-based Cements Research Articles

Mechanical stability of zirconia meso-abutments bonded to titanium bases restored with different monolithic all-ceramic crowns.

To evaluate the bending moments and failure modes of zirconia meso-abutments bonded to titanium bases restored with different monolithic all-ceramic crowns after aging, and to compare them to titanium abutments restored with all-ceramic crowns. Forty-eight internal conical connection implants (Conelog, Camlog 4.3 mm diameter) were restored with four different computer-aided design/computed-aided manufacturing (CAD/CAM) abutment-crown combinations (n = 12). Thirty-six customized zirconia meso-abutments were bonded to titanium bases (Conelog Titanium Base CAD/CAM crown, Camlog) and divided into three groups according to the different crown materials: (T1) monolithic lithium-disilicate (e-max CAD, Ivoclar), (T2) monolithic PICN (polymer-infiltrated ceramic network [Enamic, Vita]), and (T3) monolithic zirconia (Lava Plus, 3M ESPE). Twelve titanium customized abutments restored with monolithic lithium-disilicate (e-max CAD, Ivoclar) crowns served as the control group (C). The crowns were equal maxillary central incisors and were adhesively bonded with a resin-based cement (Panavia 21, Kuraray). All samples were embedded in acrylic holders. After aging (1,200,000 cycles, 49 N, 1.67 Hz, 5°C to 50°C, 120 seconds), static load was applied until failure. Bending moments were calculated for comparison of the groups. Data were statistically treated with one-way analysis of variance (ANOVA) followed by Tukey post hoc test (P < .05). Failure modes were analyzed descriptively. The means of the bending moments were 356.4 ± 20.8 Ncm (T1), 357.7 ± 26.3 Ncm (T2), 385.5 ± 21.2 Ncm (T3), and 358.8 ± 25.3 Ncm (C). Group T3 revealed significantly higher mean bending moments than the other groups (P < .05). No differences were found between zirconia meso-abutments supported by titanium bases and customized titanium abutments when lithium-disilicate crowns were used (P > .05). No failures were identified during and after aging. After static load, failures occurred due to fracture of the abutment in the internal connection in all the groups. Zirconia meso-abutments bonded to titanium bases showed similar mechanical stability compared with customized titanium abutments. Regarding the crown material, all three tested ceramics (lithium-disilicate, PICN, and zirconia) revealed very good stability when used in the monolithic state.

Shear bond strength of PEEK and PEEK-30GF cemented to zirconia or titanium substrates

Objectives: The aim of this study was to evaluate the use of dual-cure resin cement to promote the bonding between a veneering PEEK and zirconia or titanium surfaces.Materials and methods: The surface of titanium and sintered zirconia disks were gritblasted, ultra-sonically cleaned in distilled water, and dryed by oil-free air. Then, a adhesive system was applied on the clean and dry surfaces. Disks of PEEK or 30% glass-reinforced PEEK were cut from a rod and their surface were acid etched and therefore the PEEK roughness was analysed using a contact profilometer. A resin cement was then applied between the substrates and the veneering PEEK and light cured for 4 Shear bond strength tests were performed on PEEK-cement to zirconia or titanium interfaces. Scanning electron microscopy (SEM) analyses were performed to evaluate the samples surface, interface and failure mode.Results: Surface treatment with acid etching decreased the average roughness of PEEK-based surfaces. oMicroscopic analyses by SEM revealed morphological aspects of a poor bonding between the resin-based cement and PEEK. Those aspects could be confirmed by the low mean values in shear bond strength. The fracture analysis showed that the main failure mode was adhesive, which explain the low values of shear bond strength.Conclusion: PEEK is a promising material for dental applications. However, significant improvements on surface modifications and in chemical composition of the cement are still required for dental applications involving cementation of PEEK or PEEK-30GF to zirconia or titanium concerning a desirable long-term clinical performance of prosthetic structures.

Dental practice in the UK in 2015/2016. Part 3: aspects of indirect restorations and fixed prosthodontics.

This paper reports data which helps identify changes and trends in the provision of indirect fixed prostheses in general dental practice in the UK. To determine by means of an anonymous, self-report questionnaire, the current trend in the provision of fixed prosthodontic treatments, with a special emphasis on the choice of treatment modalities, techniques and materials. The data presented were extracted from the data obtained from a validated,121-question questionnaire distributed at random to general dental practitioners in the UK attending postgraduate meetings in 2015/2016, with a wide distribution of locations. A response rate exceeding 66% was achieved. Amalgam and light-cured composite were the preferred material for core build-up of vital teeth for around 62% of the respondents. Dentine pins were still being used by 66% of the respondents. The vast majority of respondents (92%) used a post and core to restore root-treated teeth. Fibre posts were the most commonly used (63%) type of preformed post among the respondents. Using the opposing and adjacent teeth as a reference to control tooth structure reduction during vital tooth preparation was the most common method, used by 42% of the respondents. Addition-cured silicone impression materials were the most frequently used impression material (78%). The surveyed practitioners were equally split between precious and non-precious metals as the substructure for indirect restorations. Glass-ionomer luting cements (47%) and resin-based cements (52%) were the most commonly used to cement porcelain fused to metal and zirconia indirect restorations, respectively. Laboratory made aesthetic veneers were prescribed by half of the respondents, while a third of them preferred direct resin composite as a veneer material. Within the limitations of the study, it was concluded that there has been an increase in the use of adhesive bonding and metal-free restorations. Amalgam and dentine pinscontinued to be used, contrary to international trends. Studies of the type reported are considered important in investigating trends and developments in dentistry.

Influence of interim cements on the optical properties of interim restorations

Statement of problemEven if the appropriate resin shade is selected for an interim restoration, how the optical characteristics of the interim cement affect the esthetics of the interim restoration is unclear. PurposeThe purpose of this in vitro study was to evaluate the effects of interim cements on the optical properties of interim restorations. Material and methodsTwenty dentin disks (6×1 mm) were obtained from the labial surface of bovine incisors. Disks of acrylic and bis-acrylic resins (n=20) with the same dimensions were prepared and cemented over the dentin using the following cements: Bifix Temp (resin-based; VOCO), ClearTemp LC (resin-based; Ultradent Products, Inc), Provicol (VOCO), TempCem NE (Coltène). The same dentin and resin disks were used for all cements. After cementation, the color difference (ΔE00), translucency parameter (TP), and fluorescence of the dentin/cement/resin combinations were compared with each other and with a control group (C), in which a transparent liquid (polyethylene glycol 400; LabSynth) was applied. Color and translucency were evaluated with a spectrophotometer (CM-2600; Konica Minolta) and fluorescence with a spectrofluorophotometer (RF-5301PC; Shimadzu). ΔE00 and TP data were analyzed using 2-way ANOVA. For fluorescence, 1-way ANOVA was used. The Tukey test was used for multiple comparisons (α=.05). ResultsΔE00 values were significantly influenced by the interim material (P<.001) and the interim cement (P<.001). Bifix Temp showed the lowest significant ΔE00 values (P<.001). The highest ΔE00 values were observed for TempCem NE. No differences were observed between the interim resins with respect to TP (P=.318). The lowest translucency values were measured for TempCem NE, followed by Provicol, ClearTemp LC, Bifix Temp, and the control group (P<.001), with no significant differences among the interim resin-based cements. Among the cements, Bifix Temp and TempCem NE yielded fluorescence similar to that of the natural tooth for both interim resins. A similar result was found for bis-acrylic resin combined with Provicol. ConclusionsCementation with interim resin-based cements resulted in better esthetics. However, the high fluorescence of the ClearTemp LC may reduce the esthetics of interim restorations in environments with predominantly UV light.

The Effect of CAD/CAM Crown Material and Cement Type on Retention to Implant Abutments.

To evaluate the pullout resistance of CAD/CAM implant-supported crowns cemented with provisional and definitive cements on Ti-base implant abutments. Sixty crowns were milled for use in Ti-base implant abutments and divided (n = 15/group) according to material, as follows: (a) [Pr] Temporary acrylic resin; (b) [Co-Cr] Cobalt-Chromium alloy; (c) [Zr] polycrystalline zirconia; and (d) [Ti] titanium. The cementation was performed with RelyX Temp NE (RxT) cement or RelyX U200 self-etching resin cement, under a 50 N (5 kg) load for 10 minutes. Twenty-four hours after cementation, the crowns were subjected to the pullout test in a universal test machine, at a 1.0 mm/min crosshead speed. The tests were performed first without cement to evaluate frictional resistance (Baseline), then with provisional cement (RelyX Temp NE without cement again (Baseline After RxT), and finally with resin cement (U200). The results were analyzed by ANOVA and Tukey test (p < 0.05). Data evaluation as a function of cement type demonstrated the superiority of resin-based cements relative to provisional and baseline groups (p < 0.01). While Co-Cr crowns presented the highest pullout strength values, Pr showed the lowest values (data collapsed over cement) (p < 0.001). Retentiveness data as a function of both factors demonstrated similar pullout resistance between groups without cement (p < 0.001), except Zr baseline. Also, Co-Cr presented higher pullout strength compared to other materials. Self-adhesive resin cement exhibited superior retention compared to temporary cement, regardless of crown material. Co-Cr and titanium presented higher levels of retention to Ti-base abutment after being cemented.

Cementation of Full Coverage Metal Crowns in Dogs

This step-by-step article describes the technique for cementation of a full metal prosthodontic crown on the maxillary fourth premolar tooth of a dog using a common resin-based cement.

The effect of Z-primer on the shear bond strength of zirconia ceramic to dentin: in vitro.

BackgroundOne of the major limitations of zirconia ceramic is the difficulty to adhere to dental. Said adhesion improves the marginal sealing of the restoration, minimizing microleakage. According to the limitation of zirconia ceramic bonding, zirconia primer enhances bond strengths to Zirconia, Alumina and Metal substrates. Purpose: the aim of the current study was to determine effect of Z-primer on the shear bond strength of zirconia ceramic to dentin.Material and Methods28 newly extracted intact premolars and divided into 4 groups (n=7). In group 1, resin-based (Duo-link; Bisco, Schaumburg, IL) cement was used without applying Z-primer. In group 2, resin-based (Duo-link; Bisco, Schaumburg, IL) cement was used with applying Z-primer. In group 3, resin-based cement (Panavia F2; Kurary, Japan) was used without Z-primer. In group 4, resin- based cement (Panavia F2) with Z-primer was used. Zirconia ceramic blocks (4×4×2mm) without sandblasting were applied onto the surface of dentin then cured from 3 dimensions for 20S. Shear bond strength test was carried out after 24h. Stereo microscope was used to evaluate the zirconia ceramic and dentin topography and failure mode.ResultsAccording to the data, significant difference detected on after application of the Z-primer compared to the other groups (p<0.001). No significant difference detected between 2 types of resin cements (p>0.05). However, the highest SBS observed in second group (Duo-link(+)Zprimer) while lowest detected in first group (Duo-link(-)Zprimer).ConclusionsThese results suggested application of the Z-primer increased shear bond strength between zirconia ceramic and dentin. Key words:Flexural strength, monolithic zirconia, sintering temperature, sintered-holding time.

Effect of CAD/CAM Abutment Height and Cement Type on the Retention of Zirconia Crowns

To evaluate Ti-Base abutment height and cement type on the retentiveness of zirconia-based restorations. Four millimeter (tall) and 2.5-mm-height (short) abutments along with temporary (provisional), glass ionomer (Meron), self-adhesive (U200), and conventional resin cement (Ultimate) were evaluated using pull-out testing (n = 10 crowns/group). Tall and short abutments demonstrated similar retention for all within cement comparisons, except U200 (P = 0.032). Resin cements exhibited superior retentiveness than others (P < 0.01). Although no significant difference was evidenced between resin cements for short abutments, Ultimate evidenced higher retention than U200 for tall abutments (P = 0.043). Although Ti-Base abutment height has not influenced zirconia superstructures' retentiveness, resin-based cements significantly evidenced higher retention than glass ionomer and temporary cements.

Effect of Fiber Post Cementation Timing on the Bond Strength of Resin Cements in Epoxy Resin-Obturated Canals.

This study evaluated the influence of timing after endodontic treatment and type of resin cement used on the bond strength of fiber posts to epoxy resin-obturated canals. A total of 80 bovine incisor roots were divided into four groups (n = 20). Glass fiber posts were cemented at two different times, immediately or 7 days after endodontic treatment, using either a dual-curing resin cement (RelyX ARC, 3M ESPE) or a self-adhesive resin cement (RelyX U200, 3M ESPE). Following post cementation, the samples were cross-sectioned into slices containing root dentin, cement, and fiber post at the cervical, mid, and apical root thirds. The push-out test was performed on a universal testing machine. Three-way analysis of variance for randomized blocks showed no significant effect within the triple interaction (P = .394) or between the double interactions cement-timing (P = .395), cement-root thirds (P = .996), and timing-root thirds (P = .331). The main factor cement revealed a significant effect, showing that regardless of the timing and root third, RelyX ARC provided significantly higher bond strength values than U200. Regardless of root third and timing, the dual-curing resin cement showed higher bond strength to root dentin when the canals were filled with epoxy resin-based cement.

Using glass-graded zirconia to increase delamination growth resistance in porcelain/zirconia dental structures

ObjectivePorcelain fused to zirconia (PFZ) restorations are widely used in prosthetic dentistry. However, their tendency to delaminate along the P/Z interface remains a practical problem so that assessing and improving the interfacial strength are important design aspects. This work examines the effect of modifying the zirconia veneering surface with an in-house felspathic glass on the interfacial fracture resistance of fused P/Z. MethodsThree material systems are studied: porcelain fused to zirconia (control) and porcelain fused to glass-graded zirconia with and without the presence of a glass interlayer. The specimens were loaded in a four-point-bend fixture with the porcelain veneer in tension. The evolution of damage is followed with the aid of a video camera. The interfacial fracture energy GC was determined with the aid of a FEA, taking into account the stress shielding effects due to the presence of adjacent channel cracks. ResultsSimilarly to a previous study on PFZ specimens, the fracture sequence consisted of unstable growth of channel cracks in the veneer followed by stable cracking along the P/Z interface. However, the value of GC for the graded zirconia was approximately 3 times that of the control zirconia, which is due to the good adhesion between porcelain and the glass network structure on the zirconia surface. SignificanceCombined with its improved bonding to resin-based cements, increased resistance to surface damage and good esthetic quality, graded zirconia emerges as a viable material concept for dental restorations.

Effect of different endodontic sealers and time of cementation on push-out bond strength of fiber posts.

This study aims to evaluate the effect of different endodontic sealers (epoxy resin, eugenol, and bioceramic/calcium silicate-based) and the time of cementation (immediately or 7days after canal obturation) on the bond strength of a fiberglass post cemented with RelyX™ ARC. Eighty-four premolars were instrumented and divided into groups (n=12) according to the sealer and the time of post cementation: Endofill (EN), Endosequence BC Sealer (BC), and AH Plus (AH) had immediately fiber post cementation; EN7, BC7, and AH7 had post cementation after 7days; and control group (C) had fiber post cementation without endodontic sealer. Each post space of the root was cut into slices and submitted to push-out test. Failure mode was assessed. Two-way ANOVA, Tukey's, and Dunnett's tests were used for statistical analysis (α=5%). The type of endodontic sealer (p<0.001), the time of post cementation (p=0.038), and the interaction sealer time (p=0.002) had negative influence on bond strength of fiberglass posts cemented with RelyX™ ARC. AH promoted the highest bond strength mean values (21.20MPa immediately and 15.54MPa at 7days). EN (9.75MPa immediately and 13.15MPa at 7days) and BC (10.43MPa immediately and 5.73MPa at 7days) had lower bond strength than AH, regardless the time of cementation. AH was the best sealer to obturate the root canal when fiberglass cementation with resin-based cement is planned. The correct choice of an endodontic sealer and the adequate time of post cementation may avoid post dislocation caused by low bond strength to dentin.

Mechanical properties of resin-based cements with different dispensing and mixing methods

Statement of problemResin-based cements are frequently used in clinical practice. To reduce time and technique sensitivity, manufacturers have introduced the same brand of cement with different dispensing methods. The effect of this change on properties of the cement is unknown. PurposeThe purpose of this in vitro study was to evaluate the mechanical properties of resin-based cements with different dispensing systems. Material and methodsSpecimens of resin-based cements (n=14) PANAVIA SA Cement Plus Handmix, PANAVIA SA Cement Plus Automix, RelyX Unicem Handmix, RelyX Unicem 2 Automix, G-CEM Capsule Automix, G-CEM LinkAce Automix, Variolink II Handmix, and Variolink Esthetic Automix were prepared for each mechanical test. They were examined after thermocycling (n=7/subgroup) for 20000 cycles as to fracture toughness (FT) (ISO standard 6872; single-edge V-notched beam method), compressive strength (CS) (ISO 9917-1), and diametral tensile strength (DTS). The specimens were mounted and loaded at a crosshead rate of 1 mm/min (0.5 mm/min for FT) with a universal testing machine until failure occurred. The 2-and 1-way ANOVA followed by the Tukey HSD post hoc test were used to analyze data for statistical significance (α=05). ResultsThermocycling had a significant effect in reducing the FT property of all resin-based cements except RelyX Unicem 2 and G-CEM LinkAce (P<.05). Variolink II and G-CEM LinkAce showed better FT properties than their automixed counterparts (P<.05). The overall CS of all automixed resin-based cements was better than that of their hand-mixed counterpart, except for Variolink II. PANAVIA SA Automixed and G-CEM LinkAce had higher DTS than their hand-mixed counterparts (P<.05). ConclusionsChanging the dispensing method alters the mechanical properties of resin-based cements. The clinical significance of these results is yet to be determined.

Favorable residual stress induction by resin-cementation on dental porcelain

ObjectivesDespite developments in polycrystalline ceramics, glassy dental-ceramic materials provide the optimum cosmetic option in most clinical situations to mimic the natural dentition. The clinical success of glassy dental-ceramic materials is often attributed to resin-adhesive bonding techniques. In this study we explore whether shrinkage stresses generated on photo-polymerisation of the resin-cement are sufficient to induce ceramic surface defect stabilization, and we quantify the transient nature of the induced stresses. MethodsStress-induced changes in a feldspathic ceramic over a range of thicknesses (0.5–2.0mm: n=20 per thickness) were measured using a profilometric technique at baseline for each disc-shaped specimen (mean of the maximum deflection (δbaseline)) and again following polymerisation of a controlled resin-cement thickness on the contra-lateral surface. Measurements were repeated at 30, 60, 90 and 1440min following photo-polymerization (δ30, δ60, δ90 and δ1440, respectively) before bi-axial flexure strength (BFS) determination at 24h. ResultsA repeated measures ANOVA and post-hoc Bonferroni tests determined that δ1440 was significantly different from δbaseline (p=0.02), δ30 (p<0.01) and δ60 (p<0.01) but not δ90 (p=0.61). Data exploration revealed that there were differences in directionality of the independent variable (mean of the maximum deflection (δ)) with a proportion of specimens increasing in deflection and others reducing. The directionality of the effect strongly correlated with the BFS values. Where δ1440-δbaseline was low and/or negative, BFS values were also low. High BFS values were observed when δ1440-δbaseline was large and positive (indirectly inferring high shrinkage-stress-induced-deformation). SignificanceA link between shrinkage stresses associated with the photo-polymerization of dental resin-based cements and the reinforcement of dental porcelain has clearly been established.

Influence of curing protocols on water sorption and solubility of a self-adhesive resin-cement

Aim: To evaluate the effect of different activation protocols on the polymerization of a self-adhesive dual cured resin-based cement. Methods: Thirty disc-shaped specimens were prepared with the resin cement RelyX U200 (3M ESPE) and divided according to three protocols: immediate light-activation for 40 s, delayed light-activation (10 min after manipulation, for 40 s) or self-curing without light-activation. The specimens were desiccated, kept in water at 37 °C for 7 days and desiccated again to calculate water sorption, solubility and mass variation. Data were analyzed by Shapiro-Wilk Test and Wilcoxon tests (α=0.05). Images after the specimens’ final desiccation were also made. Results: The Wilcoxon test revealed a significant difference for sorption and mass variation (p&lt;0.05) and the highest value was observed in self-curing or chemical activation group (CA), followed by delayed light-activation (DL) and immediate light-activation (IL). Besides the water sorption parameters, there were also microvoids on the discs from the delayed and no light-activation groups. Conclusions: The light-activation immediately after manipulation is recommended for the evaluated resin cement.

Effect of time interval between core preparation and post cementation on pushout bond strength of glass fiber-reinforced posts.

Introduction:The aim of this study was to investigate the effect of timing of coronal preparation on the pushout bond strength of fiber postluted with resin cement in the root canal.Materials and Methods:In this experimental study, 48 mandibular human premolars were selected in a 3-week range. After root canal treatment and postspace preparation, a post #2(Angelus, Brazil) was cemented into the canal by a resin-based cement (Bifix SE, VOCO, Germany). Cylindrical resin composite cores were built on the posts. Then, the specimens were divided into 4 groups of 12 specimens each: one control group without core preparation and 3 experimental groups with core preparation that was done 15 min, 1 h, and 24 h after postcementation. One day after postcementation, each root was sectioned into 3 segments. Each slice was connected to universal testing machine. The load was applied at the speed of 0.5 mm/min till failure happened. The collected data were analyzed (SPSS/PC 20.0; SPSS Inc., Chicago, IL, USA) using two-way ANOVA and post hoc Tukey test at P < 0.05 level of significance.Results:Mean shear bond strength differences among interventional groups were not statistically significant (P > 0.05). Nevertheless, there were significant differences among root regions (P < 0.001).Conclusion:It was concluded that core preparation and its timing does not affect adversely retention of fiber post and bond strength is higher in the cervical segment.

A Comparative Study of Ion Diffusion from Calcium Hydroxide with Various Herbal Pastes through Dentin.

AimThe aim of this study was to evaluate the diffusion ability of ions through dentinal tubules of different nonalcoholic calcium hydroxide-containing herbal pastes and compare it with the calcium hydroxide paste prepared with saline.Materials and methodsA total of 36 single-rooted premolar teeth were used in this study. The tooth crowns were removed and the root canals were prepared. Depending on the vehicle to be used for preparing calcium hydroxide pastes, six groups were made: Group I: Ca(OH)2 saline paste (control group), group II: Ca(OH)2 papaya latex paste, group III: Ca(OH)2 coconut water paste, group IV: Ca(OH)2 Ashwagandha (Withania somnifera) paste, group V: Ca(OH)2 Tulsi (Ocimum tenuiflorum) paste, and group VI: Ca(OH)2 garlic (Allium sativum) paste. After biomechanical preparation, calcium hydroxide herbal paste dressings were applied and sealed with resin-based cement. The teeth were placed in containers with deionized water, and the pH of the water was measured at regular intervals over 3, 24, 72, and 168 hours.ResultsWe observed that all herbal pastes allowed the diffusion of ions, but pastes prepared with Ashwagandha and papaya latex showed more ion diffusion after 168 hours and marked increase in pH, depicting better support for calcium hydroxide action.ConclusionWe conclude that Ashwagandha and papaya latex allow better diffusion of calcium hydroxide through den-tinal tubules, thus enhancing its action, and advise its use as a vehicle for placing intracanal medicament.How to cite this articleDausage P, Dhirawani RB, Marya J, Dhirawani V, Kumar V. A Comparative Study of Ion Diffusion from Calcium Hydroxide with Various Herbal Pastes through Dentin. Int J Clin Pediatr Dent 2017;10(1):41-44.

Effect of Storage Medium and Aging Duration on Mechanical Properties of Self-Adhesive Resin-Based Cements

The aim of this study was to investigate the effects of storage medium and aging duration on Martens hardness (HM) and indentation modulus (EIT) of self-adhesive resin-based cements (SARCs). A total of 416 discs were fabricated from 8 SARCs (n = 52 per SARC): (i) BeautyCem (BEA), (ii) Bifix SE (BIF), (iii) Clearfil SA Cement Automix (CLE), (iv) RelyX Unicem2 Automix (RXU), (v) SeT (SET), (vi) SmartCem 2 (SMC), (vii) SoloCem (SOC) and (viii) SpeedCEM (SPC). The specimens were ground and stored in (a) physiological saliva, (b) artificial saliva, (c) sodium chloride and (d) distilled water, at 37°C for 1, 7, 14, 28, 90 and 180 days. Non-aged specimens (3 hours after photo-initiation) of each SARC acted as control groups. HM and EIT were assessed using a universal hardness testing machine. Data were analyzed using Kolmogorov-Smirnov and Kruskal-Wallis tests and paired t-test, and 3-, 2- and 1-way ANOVA with post hoc Scheffé test (p<0.05). SARC materials exerted the highest influence on HM and EIT values (p<0.001, partial eta squared [ηP²] = 0.753 and 0.433, respectively), closely followed by aging duration (p<0.001, ηP² = 0.516 and 0.255) and storage medium (p<0.001, ηP² = 0.043 and 0.033). The interaction effect of the combinations of the 3 independent parameters was also significant (p<0.001, ηP² = 0.163 and 0.133). The lowest initial HM and EIT was presented by CLE, followed by SET and SPC; highest HM was for BIF, followed by RXU and SMC. SET gave a greater HM and EIT percentage decrease than SOC, SPC, BEA, SMC, RXU or CLE. Aging duration is a major factor affecting the micromechanical properties of SARCs, while storage medium was shown to have a significant but minor role.

Coronal Microleakage Of Enterococcus Faecalis In Three Types Of Endodontic Filling (Warm Vertical Compaction, Lateral Compaction, And Single Cone)

Introduction: the adequate sealing of endodontic fillings is critical for a successful treatment, as it prevents the entry of microorganisms and/or their growth in case they persist within the root system. The purpose of this study was to determine bacterial microleakage time in root canals filled with the lateral compaction, warm vertical compaction, and single cone techniques. Methods: 30 single-rooted teeth extracted from humans were randomly distributed into three experimental groups (n = 8); positive and negative controls were also used (n = 6). Teeth were prepared with the corono-apical ProTaper Universal technique and obturations were performed using lateral compaction, warm vertical compaction (System B – Obtura II) and single cone. Top Seal resin-based cement was used in the three groups. Enterococcus faecalis (E. faecalis ) microleakage was assessed every 24 hours for 30 days using the dual chamber model, with the lower chamber containing a pH indicator in the culture medium, which showed bacterial microleakage time. The data were statistically analyzed using one-way Anova test and Bonferroni and Tukey’s post-tests. Results: The single-cone technique showed the highest level of bacterial microleakage of E. faecalis as a function of time, while lateral compaction and warm vertical compaction showed better results, with no statistically significant differences between them, being the techniques with the best sealing results against E. faecalis microleakage. Conclusions: Under the conditions of this study, it can be concluded that the single-cone technique is not suitable for root canal sealing, as it does not prevent bacterial microleakage of E. faecalis compared to the other two techniques

The effects of cavity-margin-angles and bolus stiffness on the mechanical behavior of indirect resin composite class II restorations

ObjectiveTo study the influence of the different class II mesio-occlusal-distal (MOD) cavity shape on the stress and strain distributions in adhesive indirect restorations, using numerical finite element analysis (FEA). To investigate the relationship between restored teeth failure and stiffness of food, three values of Young’s modulus were used for the food. MethodsA 3D model of a sound lower molar and three class II MOD cavities with different shape were created. Slide-type contact elements were used between tooth surface and food. An adhesive resin-based cement, modeled with fixed-type contact elements, and a single restorative filling materials were considered. To simulate polymerization shrinkage effect, which is basically restricted to the thin composite cement layer, shell elements were employed and the thermal expansion approach was used. A vertical occlusal load of 600N was applied, while assigning fixed zero-displacements on the cutting surfaces below the crevices. All the materials were assumed to be isotropic and elastic. A static linear analysis was carried out. ResultsIn the lingual cusp, the displacements increased as the values of the stiffness food increased. In the restored teeth, the stress near the restoration-tooth interface was strongly dependent on the MOD cavity shape. The stress peaks were mainly located along the enamel–dentin interface at the lingual side; wedge-shaped MOD cavity with a low angle, in combination with the lowest food stiffness provided the best results. SignificanceA more complex load application on the occlusal surfaces was introduced. Food stiffness slightly affected the stress distribution of the restored and sound teeth. Teeth with adhesive class II MOD indirect resin composite restorations were potentially more susceptible to damage if the class II MOD cavity-margin-angle was higher than 95°. Restored teeth with a higher cavity-margin-angle led to considerable stress concentration in the lingual cusp along the enamel–dentin interface. These models were more susceptible to fracture in the lingual cusps when compared to the buccal ones.

Polymer infiltrated ceramic network structures for resistance to fatigue fracture and wear

ObjectiveTo investigate fatigue fracture resistance and wear behavior of a polymer infiltrated ceramic network (PICN) material (ENAMIC, Vita Zahnfabrik). MethodsAnatomically shaped ENAMIC monolithic crowns were milled using a CAD/CAM system. The crowns were cemented on aged dentin-like composite abutments (Z100, 3M ESPE) with resin-based cement (Vita DUO Cement, Vita). The specimens were subjected to 2 types of fatigue and wear tests: (1) accelerated sliding-contact mouth-motion step-stress fatigue test (n=24) in water; and (2) long-term sliding-contact mouth-motion fatigue/wear test using a clinically relevant load (P=200N, n=8) in water. Failure was designated as chip-off or bulk fracture. Optical and scanning electron microscopes were used to examine the occlusal surface and subsurface damage, as well as to reveal the material’s microstructure. In addition, wear volume and depth were measured by X-ray micro-computed tomography. ResultsFor accelerated mouth-motion step-stress fatigue testing, 3 out of the 24 ENAMIC crowns fractured following cyclic loading up to 1700N. Minor occlusal damage and contact-induced cone cracks were observed in all surviving specimens, but no flexural radial cracks were seen. For long-term mouth-motion fatigue/wear testing under a 200N load in water, a small wear scar without significant cracks was observed in all 8 tested ENAMIC crowns. SignificanceMonolithic CAD/CAM ENAMIC crowns showed superior resistance to sliding-contact fatigue fracture and wear.