Push-out bond strength of CAD/CAM-ceramic luted to dentin with self-adhesive resin cements

OBJECTIVES: This study evaluated the initial and the artificially aged push-out bond strength between ceramic and dentin produced by one of five resin cements. METHODS: Two-hundred direct ceramic restorations (IPS Empress CAD) were luted to standardized Class I cavities in extracted human molars using one of four self-adhesive cements (SpeedCEM, RelyX Unicem Aplicap, SmartCem2 and iCEM) or a reference etch-and-rinse resin cement (Syntac/Variolink II) (n=40/cement). Push-out bond strength (PBS) was measured (1) after 24h water storage (non-aged group; n=20/cement) or (2) after artificial ageing with 5000 thermal cycles followed by 6 months humid storage (aged group; n=20/cement). Nonparametrical ANOVA and pairwise Wilcoxon rank-sum tests with Bonferroni-Holm adjustment were applied for statistical analysis. The significance level was set at alpha=0.05. In addition, failure mode and fracture pattern were analyzed by stereomicroscope and scanning electron microscopy. RESULTS: Whereas no statistically significant effect of storage condition was found (p=0.441), there was a significant effect of resin cement (p<0.0001): RelyX Unicem showed significantly higher PBS than the other cements. Syntac/Variolink II showed significantly higher PBS than SmartCEM2 (p<0.001). No significant differences were found between SpeedCEM, SmartCem2, and iCEM. The predominant failure mode was adhesive failure of cements at the dentin interface except for RelyX Unicem which in most cases showed cohesive failure in ceramic. SIGNIFICANCE: The resin cements showed marked differences in push-out bond strength when used for luting ceramic restorations to dentin. Variolink II with the etch-and-rinse adhesive Syntac did not perform better than three of the four self-adhesive resin cements tested.

Clinical results with two different methods of root-end preparation and filling in apical surgery: mineral trioxide aggregate and adhesive resin composite

INTRODUCTION: The aim of apical surgery is to hermetically seal the root canal system after root-end resection, thereby enabling periradicular healing. The objective of this nonrandomized prospective clinical study was to report results of 2 different root-end preparation and filling methods, ie, mineral trioxide aggregate (MTA) and an adhesive resin composite (Retroplast). METHODS: The study included 353 consecutive cases with endodontic lesions limited to the periapical area. Root-end cavities were prepared with sonic microtips and filled with MTA (n = 178), or alternatively, a shallow concavity was prepared in the cut root face, with subsequent placement of an adhesive resin composite (Retroplast) (n = 175). Patients were recalled after 1 year. Cases were defined as healed when no clinical signs or symptoms were present and radiographs demonstrated complete or incomplete (scar tissue) healing of previous radiolucencies. RESULTS: The overall rate of healed cases was 85.5%. MTA-treated teeth demonstrated a significantly (P = .003) higher rate of healed cases (91.3%) compared with Retroplast-treated teeth (79.5%). Within the MTA group, 89.5%-100% of cases were classified as healed, depending on the type of treated tooth. In contrast, more variable rates ranging from 66.7%-100% were found in the Retroplast group. In particular, mandibular premolars and molars demonstrated considerably lower rates of healed cases when treated with Retroplast. CONCLUSIONS: MTA can be recommended for root-end filling in apical surgery, irrespective of the type of treated tooth. Retroplast should be used with caution for root-end sealing in apical surgery of mandibular premolars and molars.

Influence of curing rate on softening in ethanol, degree of conversion, and wear of resin composite

PURPOSE: To investigate the effect of curing rate on softening in ethanol, degree of conversion, and wear of resin composites. METHOD: With a given energy density and for each of two different light-curing units (QTH or LED), the curing rate was reduced by modulating the curing mode. Thus, the irradiation of resin composite specimens (Filtek Z250, Tetric Ceram, Esthet-X) was performed in a continuous curing mode and in a pulse-delay curing mode. Wallace hardness was used to determine the softening of resin composite after storage in ethanol. Degree of conversion was determined by infrared spectroscopy (FTIR). Wear was assessed by a three-body test. Data were submitted to Levene's test, one and three-way ANOVA, and Tukey HSD test (alpha = 0.05). Results: Immersion in ethanol, curing mode, and material all had significant effects on Wallace hardness. After ethanol storage, resin composites exposed to the pulse-delay curing mode were softer than resin composites exposed to continuous cure (P< 0.0001). Tetric Ceram was the softest material followed by Esthet-X and Filtek Z250 (P< 0.001). Only the restorative material had a significant effect on degree of conversion (P< 0.001): Esthet-X had the lowest degree of conversion followed by Filtek Z250 and Tetric Ceram. Curing mode (P= 0.007) and material (P< 0.001) had significant effect on wear. Higher wear resulted from the pulse-delay curing mode when compared to continuous curing, and Filtek Z250 showed the lowest wear followed by Esthet-X and Tetric Ceram.

Halogen lamp and led activation of resin-modified glass ionomer restorative material. In vitro microhardness after long term storage

AIM: The purpose of this study was to evaluate the activation of resin-modified glass ionomer restorative material (RMGI, Vitremer-3M-ESPE, A3) by halogen lamp (QTH) or light-emitting diode (LED) by Knoop microhardness (KHN) in two storage conditions: 24hrs and 6 months and in two depths (0 and 2 mm). MATERIALS AND METHODS: The specimens were randomly divided into 3 experimental groups (n=10) according to activation form and evaluated in depth after 24h and after 6 months of storage. Activation was performed with QTH for 40s (700 mW/cm2) and for 40 or 20 s with LED (1,200 mW/scm2). After 24 hrs and 6 months of storage at 37°C in relative humidity in lightproof container, the Knoop microhardness test was performed. Statistics Data were analysed by three-way ANOVA and Tukey post-tests (p<0.05). RESULTS: All evaluated factors showed significant differences (p<0.05). After 24 hrs there were no differences within the experimental groups. KHN at 0 mm was significantly higher than 2 mm. After 6 months, there was an increase of microhardness values for all groups, being the ones activated by LED higher than the ones activated by QTH. CONCLUSION: Light-activation with LED positively influenced the KHN for RMGI evaluated after 6 months.

A systematic review of the survival and complication rates of resin-bonded bridges after an observation period of at least 5 years

OBJECTIVES: The objectives of this systematic review were to assess the 5-year survival of resin-bonded bridges (RBBs) and to describe the incidence of technical and biological complications. METHODS: An electronic Medline search complemented by manual searching was conducted to identify prospective and retrospective cohort studies on RBBs with a mean follow-up time of at least 5 years. Patients had to have been examined clinically at the follow-up visit. Assessment of the identified studies and data extraction were performed independently by two reviewers. Failure and complication rates were analyzed using random-effects Poissons regression models to obtain summary estimates of 5-year proportions. RESULTS: The search provided 6110 titles and 214 abstracts. Full-text analysis was performed for 93 articles, resulting in 17 studies that met the inclusion criteria. Meta-analysis of these studies indicated an estimated survival of RBBs of 87.7% (95% confidence interval (CI): 81.6-91.9%) after 5 years. The most frequent complication was debonding (loss of retention), which occurred in 19.2% (95% CI: 13.8-26.3%) of RBBs over an observation period of 5 years. The annual debonding rate for RBBs placed on posterior teeth (5.03%) tended to be higher than that for anterior-placed RBBs (3.05%). This difference, however, did not reach statistical significance (P=0.157). Biological complications, like caries on abutments and RBBs lost due to periodontitis, occurred in 1.5% of abutments and 2.1% of RBBs, respectively. CONCLUSION: Despite the high survival rate of RBBs, technical complications like debonding are frequent. This in turn means that a substantial amount of extra chair time may be needed following the incorporation of RBBs. There is thus an urgent need for studies with a follow-up time of 10 years or more, to evaluate the long-term outcomes.

Influence of beveling and ultrasound application on marginal adaptation of box-only Class II (slot) resin composite restorations

A laboratory study was performed to assess the influence of beveling the margins of cavities and the effects on marginal adaptation of the application of ultrasound during setting and initial light curing. After minimal access cavities had been prepared with an 80 microm diamond bur, 80 box-only Class II cavities were prepared mesially and distally in 40 extracted human molars using four different oscillating diamond coated instruments: (A) a U-shaped PCS insert as the non-beveled control (EMS), (B) Bevelshape (Intensiv), (C) SonicSys (KaVo) and (D) SuperPrep (KaVo). In groups B-D, the time taken for additional bevel finishing was measured. The cavities were filled with a hybrid composite material in three increments. Ultrasound was also applied to one cavity per tooth before and during initial light curing (10 seconds). The specimens were subjected to thermomechanical stress in a computer-controlled masticator device. Marginal quality was assessed by scanning electron microscopy and the results were compared statistically. The additional time required for finishing was B > D > C (p < or = 0.05). In all groups, thermomechanical loading resulted in a decrease in marginal quality. Beveling resulted in higher values for "continuous" margins compared with that of the unbeveled controls. The latter showed better marginal quality at the axial walls when ultrasound was used. Beveling seems essential for good marginal adaptation but requires more preparation time. The use of ultrasonic vibrations may improve the marginal quality of unbeveled fillings and warrants further investigation.

Determination of caries risk at resin composite margins

PURPOSE: To design an artificial mouth in order to evaluate if a new diagnostic tool (Clinpro Cario Diagnosis) can be used for early detection of secondary caries at resin composite margins in vitro. METHODS: 32 intact human third molars received standardized Class-V resin composite restorations (Tetric Ceram bonded with Syntac SC). After storage for 4 weeks at 37 degrees C, teeth were subjected to 5,000 or 10,000 thermocycles (+/- 5 degrees C and +/- 55 degrees C) and polysiloxane impressions were taken. Streptococcus mutans 10449 (SM) was used in a nutrition medium to initiate a secondary caries process. Daily, the teeth were incubated for 2 x 2.5 hours in SM containing nutrition medium followed by 2 x 9.5 hours incubation in artificial saliva. Teeth were investigated after total incubation periods of 4, 6, and 8 weeks. After the different incubation protocols, the restoration margins were evaluated for infection and secondary caries processes in using Clinpro Cario Diagnosis which measures site-specifically the lactic acid production of SM in response to a sucrose challenge. The color signal was read 5 minutes after removal of the diagnostic impression. After thermocycling and biological load cycling, precision polysiloxane impressions were taken and replicas were investigated under a light microscope for gap widths at enamel and dentin margins. Demineralization was evaluated by fluorescence microscopy in using a special FITC filter. The demineralization depths at the cavity margin were calculated with Xpert for Windows using a pixel distance of 5 microm. RESULTS: After the different thermocycling protocols, no differences in gap widths and demineralization depths were found (P > 0.05). After SM incubation, gap widths and demineralization depths were significantly dependent on SM incubation time and previous number of thermocycles (P < 0.05). Lactic acid formations of SM were detectable by Clinpro Cario Diagnosis at dentin cavosurface margins formed after 6 weeks of incubation with SM (P < 0.05).

Shear bond strength of resin cements to human dentin

OBJECTIVES: The objectives of this in vitro study were (1) to assess the bond strength of the universal cement RelyX Unicem to dentin and to compare it with three conventional resin cements, (2) to test the influence of aging on their bonding capacity and (3) to test the influence of the operator on bonding quality by performing the same test in two different centers. METHODS: 160 third molars, divided into 80 for tests at the University of Zurich (Z) and 80 for tests at the University of Berne (B), were assigned to 2 x 8 subgroups of 10 teeth each. The specimens were prepared with the corresponding bonding agents and acrylic rods were luted either with RelyX Unicem (U), RelyX ARC (A), Multilink (M) or Panavia 21 (P). All specimens were stored in water for 24h (W) and half of the specimens were subjected to 1500 cycles of thermocycling (5 degrees C and 55 degrees C) (T). Bond strength was measured by means of a shear test. RESULTS: After water storage RelyX Unicem exhibited lowest bond strength (UWZ: 9.2+/-1.6 MPa, UWB: 9.9+/-1.2 MPa, AWZ: 15.3+/-6.0 MPa, AWB: 12.2+/-4.3 MPa, MWZ: 15.6+/-3.3 MPa, MWB: 12.4 MPa+/-2.4, PWZ: 13.4+/-2.9 MPa, PWB: 14.9+/-2.6 MPa). Thermocycling affected the bonding performance of all four cements. However, bond strength of RelyX Unicem was least influenced by thermocycling (UTZ: 9.4+/-2.9 MPa, UTB: 8.6+/-1.3 MPa, ATZ: 11.4+/-6.3 MPa, ATB: 13.3+/-3.7 MPa, MTZ: 15.4+/-3.1 MPa, MTB: 10.3+/-2.4 MPa, PTZ: 11.1+/-2.8 MPa, PTB: 11.3+/-2.8 MPa). SIGNIFICANCE: Although the bond strength of RelyX Unicem to dentin was lower in comparison to RelyX ARC, Multilink and Panavia 21, its bond strength was less sensitive to variations in handling and aging.

Resin composites: Modulus of elasticity and marginal quality

OBJECTIVE To investigate how the modulus of elasticity of resin composites influences marginal quality in restorations submitted to thermocyclic and mechanical loading. METHODS Charisma, Filtek Supreme XTE and Grandio were selected as they were found to possess different moduli of elasticity but quite similar polymerization contraction. MOD cavities (n=30) were prepared in extracted premolars, restored and then subjected to thermocyclic and mechanical loading. Marginal quality of the restorations before and after loading was analyzed on epoxy replicas under a scanning electron microscope. The percentage of gap-free margins and occurrence of paramarginal fractures were registered. Modulus of elasticity and polymerization contraction were analyzed with parametric and margins with nonparametric ANOVA and post hoc Tukey HSD or Wilcoxon rank-sum tests, respectively. The number of paramarginal fractures was analyzed with exact Fisher tests (α=0.05). RESULTS Grandio demonstrated significantly more gap-free enamel margins than Charisma and Filtek Supreme XTE, before and after loading (p<0.01), whereas there was no difference between Charisma and Filtek Supreme XTE (p>0.05). No significant effect of resin composite (p=0.81) on the quality of dentine margins was observed, before or after loading. Deterioration of all margins was evident after loading (p<0.0001). More paramarginal enamel fractures were observed after loading in teeth restored with Grandio when compared to Charisma (p=0.008). CONCLUSIONS The resin composite with the highest modulus of elasticity resulted in the highest number of gap-free enamel margins but with an increased incidence of paramarginal enamel fractures. CLINICAL SIGNIFICANCE The results from this study suggest that the marginal quality of restorations can be improved by the selection of a resin composite with modulus of elasticity close to that of dentine, although an increase in paramarginal enamel fractures can result as a consequence.

Influence of increment thickness on microhardness and dentin bond strength of bulk fill resin composites

OBJECTIVES To investigate the influence of increment thickness on Vickers microhardness (HV) and shear bond strength (SBS) to dentin of a conventional and four bulk fill resin composites. METHODS HV and SBS were determined on specimens of the conventional resin composite Filtek Supreme XTE (XTE) and the bulk fill resin composites SDR (SDR), Filtek Bulk Fill (FBF), x-tra fil (XFIL), and Tetric EvoCeram Bulk Fill (TEBF) after 24h storage. HV was measured either as profiles at depths up to 6mm or at the bottom of 2mm/4mm/6mm thick resin composite specimens. SBS of 2mm/4mm/6mm thick resin composite increments was measured to dentin surfaces of extracted human molars treated with the adhesive system OptiBond FL, and the failure mode was stereomicroscopically determined at 40× magnification. HV profiles and failure modes were descriptively analysed whereas HV at the bottom of resin composite specimens and SBS were statistically analysed with nonparametric ANOVA followed by Wilcoxon rank sum tests (α=0.05). RESULTS HV profiles (medians at 2mm/4mm/6mm): XTE 105.6/88.8/38.3, SDR 34.0/35.5/36.9, FBF 36.4/38.7/37.1, XFIL 103.4/103.9/101.9, TEBF 63.5/59.7/51.9. HV at the bottom of resin composite specimens (medians at 2mm/4mm/6mm): XTE (p<0.0001) 105.5>85.5>31.1, SDR (p=0.10) 25.8=21.9=26.0, FBF (p=0.16) 26.6=25.3=28.9, XFIL (p=0.18) 110.5=107.2=101.9, TEBF (p<0.0001) 63.0>54.9>48.2. SBS (MPa, medians at 2mm/4mm/6mm): XTE (p<0.0001) 23.9>18.9=16.7, SDR (p=0.26) 24.6=22.7=23.4, FBF (p=0.11) 21.4=20.3=22.0, x-tra fil (p=0.55) 27.0=24.0=23.6, TEBF (p=0.11) 21.0=20.7=19.0. The predominant SBS failure mode was cohesive failure in dentin. SIGNIFICANCE At increasing increment thickness, HV and SBS decreased for the conventional resin composite but generally remained constant for the bulk fill resin composites.

5-year results comparing mineral trioxide aggregate and adhesive resin composite for root-end sealing in apical surgery

INTRODUCTION Recent meta-analyses of the outcome of apical surgery using modern techniques including microsurgical principles and high-power magnification have yielded higher rates of healing. However, the information is mainly based on 1- to 2-year follow-up data. The present prospective study was designed to re-examine a large sample of teeth treated with apical surgery after 5 years. METHODS Patients were recalled 5 years after apical surgery, and treated teeth were classified as healed or not healed based on clinical and radiographic examination. (The latter was performed independently by 3 observers). Two different methods of root-end preparation and filling (primary study parameters) were to be compared (mineral trioxide aggregate [MTA] vs adhesive resin composite [COMP]) without randomization. RESULTS A total of 271 patients and teeth from a 1-year follow-up sample of 339 could be re-examined after 5 years (dropout rate = 20.1%). The overall rate of healed cases was 84.5% with a significant difference (P = .0003) when comparing MTA (92.5%) and COMP (76.6%). The evaluation of secondary study parameters yielded no significant difference for healing outcome when comparing subcategories (ie, sex, age, type of tooth treated, post/screw, type of surgery). CONCLUSIONS The results from this prospective nonrandomized clinical study with a 5-year follow-up of 271 teeth indicate that MTA exhibited a higher healing rate than COMP in the longitudinal prognosis of root-end sealing.

Bond Strength of Resin Composite to Dentin with Different Adhesive Systems: Influence of Relative Humidity and Application Time.

PURPOSE To investigate the influence of relative humidity and application time on bond strength to dentin of different classes of adhesive systems. MATERIALS AND METHODS A total of 360 extracted human molars were ground to mid-coronal dentin. The dentin specimens were treated with one of six adhesive systems (Syntac Classic, OptiBond FL, Clearfil SE Bond, AdheSE, Xeno Select, or Scotchbond Universal), and resin composite (Filtek Z250) was applied to the treated dentin surface under four experimental conditions (45% relative humidity/application time according to manufacturers' instructions; 45% relative humidity/reduced application time; 85% relative humidity/application time according to manufacturers' instructions; 85% relative humidity/reduced application time). After storage (37°C, 100% humidity, 24 h), shear bond strength (SBS) was measured and data analyzed with nonparametric ANOVA followed by Kruskal-Wallis tests and Mann-Whitney U-tests with Bonferroni-Holm correction for multiple testing (level of significance: α = 0.05). RESULTS Increased relative humidity and reduced application time had no effect on SBS for Clearfil SE Bond and Scotchbond Universal (p = 1.00). For Syntac Classic, OptiBond FL, AdheSE, and Xeno Select there was no effect on SBS of reduced application time of the adhesive system (p ≥ 0.403). However, increased relative humidity significantly reduced SBS for Syntac Classic, OptiBond FL, and Xeno Select irrespective of application time (p ≤ 0.003), whereas for AdheSE, increased relative humidity significantly reduced SBS at recommended application time only (p = 0.002). CONCLUSION Generally, increased relative humidity had a detrimental effect on SBS to dentin, but reduced application time had no effect.