Effect of the C-factor and Dentin Preparation Method in the Bond Strength of a Mild Self-etch Adhesive

This study evaluated the effect of the C-factor and dentin preparation method (DPM) in the bond strength (BS) of a mild self-etch adhesive; the study also observed the SEM superficial aspects of the corresponding smear layer. For purposes of this study, 25 molars (n=5) were used in a bond strength test. The molars were divided into two parts (buccal and lingual): one part received a Class V cavity (C-factor=3) and the other received a flat surface (C-factor=0) with the same bur type (coarse diamond or carbide bur and fine diamond or carbide bur), both within the same dentin depth. Five teeth were prepared with wet 60-grit and 600-grit SiC papers. After restoration with Clearfil SE Bond, microtensile beans (0.8 mm(2)) were prepared and tested after 24 hours in a universal testing machine (0.5 mm/minute). An additional two teeth for each DPM were prepared for SEM evaluation of the smear layer superficial aspects. The BS values were submitted to one-way ANOVA, considering only the DPM (flat surfaces) and two-way ANOVA (C-Factor x DPM, considering only burs) with p=0.05. Although the DPM in the flat surfaces was not significant, the standard deviations of carbide bur-prepared specimens were markedly lower. The BS was significantly lower in cavities. The fine carbide bur presented the most favorable smear layer aspect. It was concluded that different dentin preparation methods could not prevent the adverse effect in bond strength of a high C-factor. A coarse cut carbide bur should be avoided prior to a mild self-etch adhesive, because it adversely affected bond strength. In contrast, a fine cut carbide bur provided the best combination: high bond strength with low variability, which suggests a more reliable bond strength performance.

Response of human dental pulp capped with MTA and calcium hydroxide powder

Objectives: To compare the response of human dental pulp capped with a mineral trioxide aggregate (MTA) and Ca(OH)(2) powder. Methods and Material: Pulp exposures were performed on the occlusal floor of 40 permanent premolars. The pulp was then capped with either Ca(OH)(2) powder (CH) or MTA and restored with resin composite. After 30 days (groups CH30 and MTA30) and 60 days (groups CH60 and MTA60), the teeth were extracted and processed for HE and categorized in a histological score system. The data were subjected to Kruskal-Wallis and Conover tests (alpha=0.05). Results: In regard to dentin bridge formation, CH30 showed a tendency towards superior performance compared to MTA30 (p>0.05), although the products showed comparable results at day 60. In the item ""Inflammation"" and ""General State of the Pulp"" (p>0.05), CH showed a tendency towards presenting a higher inflammatory response. In the item ""Other Pulpal Findings,"" MTA and Ca(OH)(2) showed equal and excellent performance after 30 and 60 days (p>0.05). Conclusion: After 30 days, Ca(OH)(2) powder covered with calcium hydroxide cement showed faster hard tissue bridge formation compared to MTA. After 60 days, Ca(OH)(2) powder or NITA materials showed a similar and excellent histological response with the formation of a hard tissue bridge in almost all cases with low inflammatory infiltrate.

Compromised Bond Strength after Root Dentin Deproteinization Reversed with Ascorbic Acid

Introduction: The present study evaluated the effect of a reducing agent on the bond strength of deproteinized root canal dentin surfaces when using a self-adhesive versus dual-cured cement. Regional differences were also evaluated. Methods: A total of 45 bovine incisor roots were divided into 3 groups: irrigation with physiologic solution (control), 10-minute deproteinization with 5% NaOCl, and 10-minute deproteinization with 5% NaOCl followed by 10 minutes of 10% ascorbic acid. Fiber posts were cemented with either RelyX 0100 or RelyX ARC (with SingleBond 2 or Clearfil SE Bond). The push-out bond strength was evaluated after 24 hours of storage. Data were submitted to three-way analyses of variance and Dunnett 13 tests (alpha = 0.05). Results: No differences between cements were observed within the testing conditions, regardless of the adhesive (P < .05). Deproteinization reduced bond strengths. Subsequent treatment with ascorbic acid was capable of reversing bond strength value changes to levels similar to those of controls. Regional radicular differences were also found, where coronal > middle > apical. Conclusions: The reducing agent was capable. of reversing the effect of dentin deproteinization, and RelyX U100 behaved similarly to RelyX ARC. (J Endod 2010;36:130-134)

Influence of glutaraldehyde priming on bond strength of an experimental adhesive system applied to wet and dry dentine

Objectives: This study tested the following null hypotheses: (1) there is no difference in resin-dentine bond strength when an experimental glutaraldehyde primer solution is added prior to bonding procedures and (2) there is no difference in resin-dentine bond strength when experimental glutaraldehyde/adhesive system is applied under dry or wet demineralized dentine conditions. Methods: Extracted human maxillary third molars were selected. Flat, mid-coronal dentine was exposed for bonding and four groups were formed. Two groups were designated for the dry and two for the wet dentine technique: DRY: (1) Group GD: acid etching + glutaraldehyde primer (primer A) + HEMA/ethanol primer (primer B)-under dried dentine + unfilled resin; (2) Group D: the same as GD, except for primer A application; WET: (3) Group GW: the same as GD, but primer B was applied under wet dentine condition; (4) Group W: the same as GW, except for primer A application. The bonding resin was light-cured and a resin core was built up on the adhesive layer. Teeth were then prepared for microtensile bond testing to evaluate bond strength. The data obtained were submitted to ANOVA and Tukey`s test (alpha = 0.05). Results: Glutaraldehyde primer application significantly improved resin-dentine bond strength. No significant difference was observed when the same experimental adhesive system was applied under either dry or wet dentine conditions. These results allow the first null hypothesis to be rejected and the second to be accepted. Conclusion: Glutaraldehyde may affect demineralized dentine properties leading to improved resin bonding to wet and dry substrates. (C) 2008 Elsevier Ltd. All rights reserved.

A Randomized Clinical Evaluation of a One- and Two-step Self-etch Adhesive Over 24 Months

Objective: To evaluate the performance of All Bond SE used in a one- or two-step protocol in a 24-month randomized clinical study. Methods: Thirty-three patients with two similarly sized non-carious cervical lesions participated in this study. A total of 66 restorations were placed, half using the one-step All Bond SE protocol (SE-1) and the other half using the two-step All Bond SE protocol (SE-2). The restorations were evaluated at baseline and after 6, 12 and 24 months following the modified USPHS criteria and analyzed by the McNemar`s test and Fisher`s exact test (alpha=0.05). Results: After 24 months, six SE-1 and four SE-2 restorations were rated as Bravo in marginal discoloration The retention rates for SE-1 and SE-2 were 84.8% and 90.9%, respectively, after 24 months. Compared to baseline, the retention rate for SE-1 was statistically lower. Conclusions: All Bond SE used in the one- or two-step protocol resulted in high retention rates after 24 months.

Fatigue life and failure modes of crowns systems with a modified framework design

Objectives: To evaluate the effect of framework design on the fatigue life and failure modes of metal ceramic (MC, Ni-Cr alloy core, VMK 95 porcelain veneer), glass-infiltrated alumina (ICA, In-Ceram Alumina/VM7), and veneered yttria-stabilized tetragonal zirconia polycrystals (Y-TZP, IPSe.max ZirCAD/IPS e.max,) crowns. Methods: Sixty composite resin tooth replicas of a prepared maxillary first molar were produced to receive crowns systems of a standard (MCs, ICAs, and Y-TZPs, n = 10 each) or a modified framework design (MCm, ICAm, and Y-TZPm, n = 10 each). Fatigue loading was delivered with a spherical steel indenter (3.18 mm radius) on the center of the occlusal surface using r-ratio fatigue (30-300 N) until completion of 10(6) cycles or failure. Fatigue was interrupted every 125,000 cycles for damage evaluation. Weibull distribution fits and contour plots were used for examining differences between groups. Failure mode was evaluated by light polarized and SEM microscopy. Results: Weibull analysis showed the highest fatigue life for MC crowns regardless of framework design. No significant difference (confidence bound overlaps) was observed between ICA and Y-TZP with or without framework design modification. Y-TZPm crowns presented fatigue life in the range of MC crowns. No porcelain veneer fracture was observed in the MC groups, whereas ICAs presented bulk fracture and ICAm failed mainly through the veneer. Y-TZP crowns failed through chipping within the veneer, without core fractures. Conclusions: Framework design modification did not improve the fatigue life of the crown systems investigated. Y-TZPm crowns showed comparable fatigue life to MC groups. Failure mode varied according to crown system. (C) 2010 Elsevier Ltd. All rights reserved.

Mechanical Testing of Indirect Composite Materials Directly Applied on Implant Abutments

Purpose: To test the strength to failure and fracture mode of three indirect composite materials directly applied onto Ti-6Al-4V implant abutments vs cemented standard porcelain-fused-to-metal (PFM) crowns. Materials and Methods: Sixty-four locking taper abutments were randomly allocated to four groups and were cleaned in ethanol in an ultrasonic bath for 5 min. After drying under ambient conditions, the abutments were grit blasted and a custom 4-cusp molar crown mold was utilized to produce identical crowns (n = 16 per group) of Tescera (Bisco), Ceramage (Shofu), and Diamond Crown (DRM) according to the manufacturer`s instructions. The porcelain-fused-to-metal crowns were fabricated by conventional means involving the construction and a wax pattern and casting of a metallic coping followed by sintering of increasing layers of porcelain. All crowns were loaded to failure by an indenter placed at one of the cusp tips at a 1 mm/min rate. Subsequently, fracture analysis was performed by means of stereomicroscopy and scanning electron microscopy. One-way ANOVA at 95% level of significance was utilized for statistical analysis. Results: The single load to failure (+/- SD) results were: Tescera (1130 +/- 239 N), Ceramage (1099 +/- 257 N), Diamond Crown (1155 +/- 284 N), and PFM (1081 +/- 243 N). Stereomicroscopy analysis showed two distinct failure modes, where the loaded cusp failed either with or without abutment/metallic coping exposure. SEM analysis of the fractures showed multiple crack propagation towards the cervical region of the crown below a region of plastic deformation at the indenter contact region. Conclusion: The three indirect composites and PFM systems fractured at loads higher than those typically associated with normal occlusal function. Although each material had a different composition and handling technique, no significant differences were found concerning their single load to fracture resistance among composite systems and PFM.

Image quality assessment and medical physics evaluation of different portable dental X-ray units

Introduction: Recently developed portable dental X-ray units increase the mobility of the forensic odontologists and allow more efficient X-ray work in a disaster field, especially when used in combination with digital sensors. This type of machines might also have potential for application in remote areas, military and humanitarian missions, dental care of patients with mobility limitation, as well as imaging in operating rooms. Objective: To evaluate radiographic image quality acquired by three portable X-ray devices in combination with four image receptors and to evaluate their medical physics parameters. Materials and methods: Images of five samples consisting of four teeth and one formalin-fixed mandible were acquired by one conventional wall-mounted X-ray unit, MinRay (R) 60/70 kVp, used as a clinical standard, and three portable dental X-ray devices: AnyRay (R) 60 kVp, Nomad (R) 60 kVp and Rextar (R) 70 kVp, in combination with a phosphor image plate (PSP), a CCD, or a CMOS sensor. Three observers evaluated images for standard image quality besides forensic diagnostic quality on a 4-point rating scale. Furthermore, all machines underwent tests for occupational as well as patient dosimetry. Results: Statistical analysis showed good quality imaging for all system, with the combination of Nomad (R) and PSP yielding the best score. A significant difference in image quality between the combination of the four X-ray devices and four sensors was established (p < 0.05). For patient safety, the exposure rate was determined and exit dose rates for MinRay (R) at 60 kVp, MinRay (R) at 70 kVp, AnyRay (R), Nomad (R) and Rextar (R) were 3.4 mGy/s, 4.5 mGy/s, 13.5 mGy/s, 3.8 mGy/s and 2.6 mGy/s respectively. The kVp of the AnyRay (R) system was the most stable, with a ripple of 3.7%. Short-term variations in the tube output of all the devices were less than 10%. AnyRay (R) presented higher estimated effective dose than other machines. Occupational dosimetry showed doses at the operator`s hand being lowest with protective shielding (Nomad (R): 0.1 mu Gy). It was also low while using remote control (distance > 1 m: Rextar (R) < 0.2 mu Gy, MinRay (R) < 0.1 mu Gy). Conclusions: The present study demonstrated the feasibility of three portable X-ray systems to be used for specific indications, based on acceptable image quality and sufficient accuracy of the machines and following the standard guidelines for radiation hygiene. (C) 2010 Elsevier Ireland Ltd. All rights reserved.

Finite Element Analysis of 2 Immediate Loading Systems in Edentulous Mandible: Rigid and Semirigid Splinting of Implants

Purpose: The objective of this study was to evaluate the stress on the cortical bone around single body dental implants supporting mandibular complete fixed denture with rigid (Neopronto System-Neodent) or semirigid splinting system (Barra Distal System-Neodent). Methods and Materials: Stress levels on several system components were analyzed through finite element analysis. Focusing on stress concentration at cortical bone around single body dental implants supporting mandibular complete fixed dentures with rigid ( Neopronto System-Neodent) or semirigid splinting system ( Barra Distal System-Neodent), after axial and oblique occlusal loading simulation, applied in the last cantilever element. Results: The results showed that semirigid implant splinting generated lower von Mises stress in the cortical bone under axial loading. Rigid implant splinting generated higher von Mises stress in the cortical bone under oblique loading. Conclusion: It was concluded that the use of a semirigid system for rehabilitation of edentulous mandibles by means of immediate implant-supported fixed complete denture is recommended, because it reduces stress concentration in the cortical bone. As a consequence, bone level is better preserved, and implant survival is improved. Nevertheless, for both situations the cortical bone integrity was protected, because the maximum stress level findings were lower than those pointed in the literature as being harmful. The maximum stress limit for cortical bone (167 MPa) represents the threshold between plastic and elastic state for a given material. Because any force is applied to an object, and there is no deformation, we can conclude that the elastic threshold was not surpassed, keeping its structural integrity. If the force is higher than the plastic threshold, the object will suffer permanent deformation. In cortical bone, this represents the beginning of bone resorption and/or remodeling processes, which, according to our simulated loading, would not occur. ( Implant Dent 2010; 19:39-49)

The influence of storage condition and duration on the resistance to fracture of different fiber post systems

Purpose: To evaluate the effects of storage condition and duration on the resistance to fracture of different fiber post systems (and to morphologically assess the post structure before and after storage. Methods: Three types of fiber posts (DT Light Post, GC Post, FRC Postect Plus) were divided in different groups (n=12) according to the storage condition (dry at 37 degrees C; saline water at 37 degrees C; mineral oil at 37 degrees C and storage inside the roots of extracted human teeth immersed in saline water at 37 degrees C and duration (6, 12 months). A universal testing machine loading at a 90 degrees angle was employed for the three-point bending test. The test was carried out until fracture of the post. A 3-way ANOVA and Tukey`s test (alpha= 0.05) were used to compare the effect of the experimental factors on the fracture strength. Two posts of each group were observed before and after the storage using a scanning electron microscope. Results: Storage condition and post type had a significant effect on post fracture strength (P< 0.05). The interaction between these factors was significant (P< 0.05). Water storage significantly decreased the fracture strength, regardless of the post type and the storage duration. Storage inside roots, in oil, and at dry conditions did not significantly affect post fracture strength. SEM micrographs revealed voids between fibers and resin matrix for posts stored in water. Posts stored under the other conditions showed a compact matrix without porosities. (Am J Dent 2009;22:366-370).

Microtensile vs Microshear Bond Strength of All-in-One Adhesives to Unground Enamel

Purpose To determine the bond strength to unground enamel of all in one adhesives in comparison with an etch and rinse system and to compare the reliability of microtensile and microshear methods in providing such measurements Materials and Methods The bonding procedure was performed on enamel of 64 extracted molars The tested all in one adhesives were Bond Force (Tokuyama), AdheSE One (Ivoclar Vivadent) and Xeno V (Dentsply) Prime&Bond NT (Dentsply) served as control Microtensile specimens were obtained from 4 teeth per group Twelve teeth per group were used for microshear testing Microtensile specimens that failed prior to testing were included in statistical calculations, they were assigned the lowest value measured in the respective group Failure modes were observed under light microscope and classified (cohesive within substrates, adhesive mixed) Statistically significant differences in bond strength were assessed among the adhesives within each testing method and between microshear and microtensile data for each adhesive Failure mode distributions were compared using the chi square test Results All in-one adhesives had similar microshear and microtensile bond strengths In both testing methods, the etch and rinse system achieved the strongest bond For all adhesives significantly higher bond strengths were measured with the microshear test In microtensile testing specimens bonded with the etch and rinse adhesive exhibited a significantly different distribution of failure modes The coefficients of variation were extremely high for microtensile bond strength data, particularly of all in one adhesives Conclusion The adhesive potential to intact enamel of recently introduced all in-one adhesives was inferior to that of an etch and rinse system When testing bond strength to enamel of all in one adhesives, microshear testing may be a more accurate method than microtensile

Interfacial evaluation of experimentally weakened roots restored with adhesive materials and fibre posts: An SEM analysis

Objectives: To evaluate the bonding interface in experimentally weakened roots reinforced with adhesive restorative materials and quartz fibre posts, varying the light-exposure time of the composite resin used for root reinforcement. Methods: Twelve extracted human maxillary incisors teeth were used. The crowns were removed and the roots were endodontically treated. After post space preparation, the roots were assigned to four groups. The thickness of the root dentine was reduced and adhesively restored with composite resin light-activated through a translucent fibre post for either 40 s (group 1), 80 s (group 2) or 120 s (group 3). In the case of control (group 4), the roots were not weakened. One day after post cementation, the specimens were sectioned transversally in three slices and processed for scanning electron microscopic analysis to observe bonding interface formation, quality of the hybrid layer and density of resin tags using a four-step scale method. Results: Formation of a hybrid layer and resin tags were evident in all groups. There was no statistically (p > 0.05) significant difference between the regions analysed in each group (Friedman test) and between groups in each section depth (Kruskal-Wallis test). Furthermore, comparison of the flared/reinforced groups showed that the different time;; used for composite resin cure did not affect the results significantly (Kruskal-Wallis test, p = 0.2139). Conclusions: Different light-exposure times used for composite resin polymerisation during root canal reinforcement did not affect significantly the formation and quality of the dentine/adhesive/composite resin bonding interface. (C) 2008 Elsevier Ltd. All rights reserved.

Bleaching Agents with Varying Concentrations of Carbamide and/or Hydrogen Peroxides: Effect on Dental Microhardness and Roughness

To evaluate the effect of low and highly concentrated bleaching agents on microhardness and surface roughness of bovine enamel and root dentin. According to a randomized complete block design, 100 specimens of each substrate were assigned into five groups to be treated with bleaching agents containing carbamide peroxide (CP) at 10% (CP10); hydrogen peroxide (HP) at 7.5% (HP7.5) or 38% (HP38), or the combination of 18% of HP and 22% of CP (HP18/CP22), for 3 weeks. The control group was left untreated. Specimens were immersed in artificial saliva between bleaching treatments. Knoop surface microhardness (SMH) and average surface roughness (Ra) were measured at baseline and post-bleaching conditions. For enamel, there were differences between bleaching treatments for both SMH and Ra measurements (p = 0.4009 and p = 0.7650, respectively). SMH significantly increased (p < 0.0001), whereas Ra decreased (p = 0.0207) from baseline to post-bleaching condition. For root dentin, the group treated with CP10 exhibited the significantly highest SMH value differing from those groups bleached with HP18/CP22, HP7.5, which did not differ from each other. Application of HP38 resulted in intermediate SMH values. No significant differences were found for Ra (p = 0.5975). Comparing the baseline and post-bleaching conditions, a decrease was observed in SMH (p < 0.0001) and an increase in Ra (p = 0.0063). Bleaching agents with varying concentrations of CP and/or HP are capable of causing mineral loss in root dentin. Enamel does not perform in such bleaching agent-dependent fashion when one considers either hardness or surface roughness evaluations. Bleaching did not alter the enamel microhardness and surface roughness, but in root dentin, microhardness seems to be dependent on the bleaching agent used.

Microtensile Bond Strength of Glass Fiber Posts Cemented with Self-adhesive and Self-etching Resin Cements

Purpose: To evaluate the bond strength of glass fiber posts to intraradicular dentin when cemented with self-etching and self-adhesive resin cements. Materials and Methods: Forty-eight single-rooted human teeth were decoronated, endodontically treated, post-space prepared and divided into 8 groups (n = 6). The glass fiber posts used were: Exacto (EA) (Angelus) and everStick (ES) (StichTeck), which were cemented with two self-adhesive resin cements: BisCem (BIS) (Bisco) and Rely-X Unicem (UNI) (3M/ESPE), and two self-etching resin cements: Esthetic Cementing System NAC100 (NAC) (Kuraray) and Panavia-F (PAN) (Kuraray). Specimens were thermocycled between 5 degrees C and 55 degrees C for 1000 cycles and stored in water at 37 degrees C for 1 month. Four 1-mm-thick (in cross section) rods were obtained from the cervical region of the roots. 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 (mu TBS) data were analyzed with two-way ANOVA and Tukey`s tests. Results: Means (and SD) of mu TBS (MPa) were: EA/PAN: 10.3 (4.1), EA/NAC: 14 (5.1) EA/BIS: 16.4 (4.8), EA/UNI: 19.8 (5.1), ES/PAN: 25.9 (6.1), ES/NAC: 29.1 (7), ES/BIS: 28.9 (6), ES/UNI: 30.5 (6.6). ANOVA indicated significant differences among the groups (p < 0.001). Mean mu TBS values obtained with ES post were significantly higher than those obtained with EA (p < 0.001). For EA, Tukey`s test indicated that higher mu TBS means were obtained with the self-adhesive resin cements (BIS and UNI), which were statistically significantly different (p < 0.05) from values obtained with the self-etching resin cements (PAN and NAC). Different cements had no significant effects on the bond strength values of ES post (p > 0.05). mu TBS values obtained with ES post were significantly higher than those obtained with EA post irrespective of the resin cement used. Conclusion: everStick posts resulted in the highest mean mu TBS values with all cements. Self-adhesive cements performed well in terms of bond strength.

Pulpal heat changes with newly developed resin photopolymerisation systems

Composite resin is a widely-used direct tooth coloured restorative material. Photoactivation of the polymerisation reaction can be achieved by visible blue light from a range of light sources, including halogen lamps, metal halide lamps, plasma arc lamps, and Light Emitting Diode (LED) lights. Concerns have been raised that curing lights may induce a temperature rise that could be detrimental to the vitality of the dental pulp during the act of photoactivation. The present study examined heat changes associated with standardised class V restorations on the buccal surface of extracted premolar teeth, using a curing time of 40 seconds. The independent effects of type of light source, resin shade and remaining tooth thickness were assessed using a matrix experimental design. When a conventional halogen lamp, a metal halide lamp and two different LED lights were compared, it was found that both LED lamps elicited minimal thermal changes at the level of the dental pulp, whereas the halogen lamp induced greater changes and the metal halide lamp caused the greatest thermal insult of all the light sources. These thermal changes were influenced by resin shade, with different patterns for LED versus halogen or halide sources. Thermal stress reduced as the remaining thickness of tooth structure between the pulp and the cavity floor increased. From these results, it is concluded that LED lights produce the least thermal insult during photopolymerisation of composite resins.