The Journal of Adhesive Dentistry, 04/2010

In 2007, new clinical criteria were approved by the FDI World Dental Federation and simultaneously published in three dental journals. The criteria were categorized into three groups: esthetic parameters (four criteria), functional parameters (six criteria), and biological parameters (six criteria). Each criterion can be expressed with five scores, three for acceptable and two for non-acceptable (one for reparable and one for replacement). The criteria have been used in several clinical studies since 2007, and the resulting experience in their application has led to a requirement to modify some of the criteria and scores. The two major alterations involve staining and approximal contacts. As staining of the margins and the surface have different causes, both phenomena do not appear simultaneously. Thus, staining has been differentiated into marginal staining and surface staining. The approximal contact now appears under the name "approximal anatomic form" as the approximal contour is a specific, often non-esthetic issue that cannot be integrated into the criterion "esthetic anatomical form". In 2008, a web-based training and calibration tool called e-calib (www.e-calib.info) was made available. Clinical investigators and other research workers can train and calibrate themselves interactively by assessing clinical cases of posterior restorations, which are presented as high quality pictures. Currently, about 300 clinical cases are included in the database which is regularly updated. Training for 8 of the 16 clinical criteria is available in the program: "Surface luster"; "Staining (surface, margins)"; "Color match and translucency"; "Esthetic anatomical form"; "Fracture of material and retention"; "Marginal adaptation"; "Recurrence of caries, erosion, abfraction"; and "Tooth integrity (enamel cracks, tooth fractures)". Typical clinical cases are presented for each of these eight criteria and their corresponding five scores.

Purpose: The purpose of the study was to determine the microtensile bond strength of three different simplified adhesive systems to caries-affected dentin. Materials and Methods: Fifteen extracted human molars with primary carious lesions were ground flat until dentin was exposed. Soft caries-infected dentin was excavated with the help of caries detector dye. On the remaining hard dentin, a standardized smear layer was created by polishing with 600-grit SiC paper. Teeth were divided into three groups and treated with one of the three tested adhesives: Adper Scotchbond 1 XT (3M ESPE), a 2-step etch-andrinse adhesive, Clearfil S? Bond (Kuraray), a 1-step self-etching or all-in-one adhesive, and Clearfil SE Bond (Kuraray), a 2-step self-etching adhesive. Five-mm-thick composite buildups (Z-250, 3M ESPE) were built and light cured. After water storage for 24 h at 37°C, the bonded specimens were sectioned into bars (1.0 x 1.0 mm; n = 20 to 30). Microtensile bond strength of normal dentin specimens and caries-affected dentin specimens was measured in a universal testing machine (crosshead speed = 1 mm/min). Data were analyzed using two-way ANOVA and Tukey's post-hoc test (p < 0.05). Results: No significant differences in bond strength values to normal dentin between the three adhesives were found. Adper Scotchbond 1 XT and Clearfil S? Bond showed significantly lower bond strength values to caries-affected dentin. For Clearfil SE Bond, bond strength values to normal and caries-affected dentin were not significantly different. Conclusion: All the tested simplified adhesives showed similar bond strength values to normal dentin. For the tested 2-step etch-and-rinse adhesive and the all-in-one adhesive, the bond strength values to caries-affected dentin were lower than to normal dentin. Keywords: dentin bond strength test, adhesives, caries-affected dentin, microtensile bond strength test

Purpose: This study evaluated the marginal adaptation, fracture modes, and loads to failure of different mesio-occlusal- distal (MOD) restorations in root canal treated molars in vitro. Materials and Methods: Forty mandibular first molars were randomly assigned to five groups (n = 8): UTR= untreated, RCT-AM= root-canal treated (RCT)+amalgam filling; RCT-COM= RCT+direct composite resin restoration; RCTFRC= RCT+composite resin restoration with two layers of multidirectional woven glass fibers; RCT-CER= RCT+ceramic inlay. All teeth were subjected to thermocycling and mechanical loading (TCML) in a computer-controlled masticator (1,200,000 loads, 49 N, 1.7 Hz, 3000 temperature cycles of 5°C to 50°C). Marginal adaptation was evaluated before and after TCML by scanning electron microscopy at 200X at the tooth/restoration interfaces. After TCML, all specimens were loaded to failure in a universal testing machine at 0.5 mm/min. Failure types were analyzed and scored (reparable: modes 1 and 2; catastrophic: modes 3 to 5). Data were analyzed with ANOVA and Bonferroni correction. Results: Marginal adaptation decreased significantly after TCML in all groups. The highest decrease was observed in RCT-FRC (before: 89.9 ± 2.2%, after TCML: 49.8 ± 11.9%) and the lowest in RCT-CER (before TCML: 90.3 ± 2.6% after TCML 80.4 ± 9.0%). Loads to failure (in N) were in descending order as follows: UTR: 3048 ± 905; RCT-CER: 1853 ± 477; RCT-AM: 1447 ± 363; RCT-FRC: 1066 ± 306; RCT-COM 960 ± 228. While UTR resulted in statistically higher loads to failure than those of all other groups (p < 0.0001), RCT-CER showed significantly higher results than those of RCT-COM (p = 0.0014) and RCT-FRC (p = 0.0042). The UTR group showed exclusively reparable failures in the form of either superficial (mode 1) or complete cusp chipping (mode 2), but all restored teeth exhibited catastrophic failures involving fractures along or through the restoration (modes 3 to 5). Conclusion: None of the restored teeth in any group were able to bear the same load level as the natural teeth. With regard to marginal adaptation and fracture resistance, luted ceramic inlays were advantageous. The integration of FRC in the restoration had no positive effect on the fracture resistance. FRC application showed a negative effect on marginal adaptation of composite resin restorations. Keywords: ceramic, fiber reinforced composite, fracture resistance, inlay, intracoronal restoration, marginal adaptation, root canal treated teeth

Purpose: To evaluate marginal quality, fracture modes, and loads-to-failure of different overlay restorations in rootcanal treated molars in a laboratory setup. Materials and Methods: Thirty-two mandibular first molars were randomly assigned to four groups (n = 8): UTR= untreated (control), RCT-COM= root canal treated (RCT)+ lab-made composite overlay, RCT-FRC= RCT+composite resin overlay with two layers of multidirectional woven glass fibers; RCT-CER: RCT+ceramic overlay. The teeth in all groups were subjected to thermocycling and mechanical loading (TCML) in a computer-controlled masticator (1,200,000 loads, 49 N, 1.7 Hz, 3000 temperature cycles of 5°C to 50°C). Marginal adaptation was evaluated before and after TCML with scanning electron microscopy at 200X at the tooth-to-luting composite (IF1) and luting composite-to restoration (IF2) interfaces. After TCML, all specimens were loaded to failure in a universal testing machine at 0.5 mm/min. Data were analyzed with ANOVA and Bonferroni correction. Results: Marginal adaptation decreased from 93 ± 3.4 to 82 ± 6.5 % at IF1 after TCML (p > 0.001) but the decrease was not significant between the groups (p = 0.8130). At IF2, ceramic overlays showed about 10% lower marginal adaptation than composite overlays (p < 0.0001). Loads-to-failure (in N) were as follows in descending order: RCT-FRC: 3619 ± 520; UTR: 3048 ± 905; RCT-COM: 2770 ± 457; RCT-CER 2036 ± 319. RCT-FRC showed significantly higher results than those of RCT-COM (p = 0.0077) and RCT-CER (p < 0.0001). Only RCT-CER showed significantly lower results than that of the control (p = 0.0019). While the fractures in the UTR occurred exclusively above the cementoenamel junction (Mode 1 and Mode 2) and were rated reparable, RCT-COM and RCT-CER showed exclusively catastrophic failures in varying modes (nodes 3 to 5). Only in group RCT-FRC, half of the specimens fractured in a reparable fracture mode (modes 1 and 2) with veneering composite delamination from the glass-fiber weaver layer. Conclusion: As cusp-covering overlay restorations in root canal treated molars, composite resin overlays with and without fiber reinforcement performed similar to intact teeth with varying failure types. While intact teeth failed exclusively in reparable modes, all other restorations failed in a catastrophic manner, except half of the fiber reinforced composite group. Keywords: ceramic, composite resin, cusp-covering restoration, fiber reinforced composite, fracture resistance, marginal adaptation, overlay, root-canal treated teeth

Purpose: The aim of this study was to evaluate the microtensile bond strength of a resin composite bonded to two heat-pressed ceramics after performing different post-etching cleaning techniques. Materials and Methods: Resin composite specimens were bonded to IPS Empress Esthetic (EE) and IPS Empress 2 (E2) heat-pressed ceramic disks after etching with 10% HF, surface cleaning, silanization and application of an unfilled hydrophobic resin. Resin composite specimens were fabricated using 4-mm (height) Tygon tubes of 0.8 mm diameter and bonded according to the post-etching cleaning technique employed (n = 30): no cleaning (NC); air-water spray for 30 s (AWS); 37% phosphoric acid etching for 30 s (PA); ultrasonic bath in distilled water for 5 min (UB); PA + UB (PAUB); application of a self-etching silane/bonding system Clearfil Silane Kit (CSK). The resin composite specimens were subjected to tensile tension at a crosshead speed of 0.5 mm/min. SEM observation and EDX analysis were performed for each group to determine elemental distribution in the samples. Results: Two-way ANOVA with random effect showed statistically differences between subgroups for E2, in which E2NC only showed bond strength significantly lower than E2AWS and E2BU, as indicated by Student's t-test and a contrast method. For EE, subgroups EENC and EECSK groups showed statistically significant differences between each other and among the other post-etching cleaning technique groups (p < 0.05). Conclusion: Air-water spray may be used as a post-etching cleaning technique for both ceramics. The presence of residues did not significantly reduce the bond strength of resin composite to IPS Empress 2 ceramic. Keywords: ceramics, tensile strength, hydrofluoric acid

Purpose: The purpose of the current study was to evaluate the effect of acidic primers on the bond strength and durability of an acrylic resin luting agent to zirconia. Materials and Methods: Disk specimens were fabricated from zirconia partially stabilized with yttrium oxide (Katana, Noritake Dental Supply). The disks were treated with one of the following acidic primers: Acryl Bond (Shofu), All Bond II Primer B (Bisco), Alloy Primer (Kuraray), Estenia Opaque Primer (Kuraray), Eye Sight Opaque Primer (Kanebo), M.L. Primer (Shofu), MR. Bond (Tokuyama Dental), or Super-Bond Liquid (Sun Medical). Unprimed specimens served as the control. The disks were bonded with a tri-n-butylborane (TBB)-initiated acrylic resin. Shear bond strengths were determined both before and after 10,000 thermocycles (5°C and 55°C, 1 min dwell time each). Results: The pre-thermocycling bond strength ranged from 0.7 MPa to 30.8 MPa, whereas post-thermocycling bond strength varied from 0.3 MPa to 17.6 MPa. The significantly highest post-thermocycling bond strength was obtained when using the Alloy Primer and Estenia Opaque Primer agents. Conclusion: Within the limitations of the current experiment, it can be concluded that application of either the Alloy Primer or the Estenia Opaque Primer, both of which contain 10-methacryloyloxydecyl dihydrogen phosphate (MDP), is recommended for bonding the Katana zirconia material with TBB-initiated acrylic resin. Keywords: bonding, phosphate, primer, zirconia

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 porcelainfused- 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. Keywords: implant, restoration, integrated abutment crown, indirect composite, single unit

Purpose: This study evaluated the effect of water storage (WS) on the shear bond strength (SBS) and shear bond fatigue limit (SBFL) between denture base and reline resins. In addition, a possible correlation between SBS and SBFL was evaluated. Materials and Methods: Two denture base (Lucitone 550-L and Acron MC-AC) and two reline resins (Ufi Gel Hard- UGH and Tokuso Rebase Fast-TR) were selected. Cylinders (20 x 20 mm) of each denture base resin were processed, and the reline resins were packed on the bonding surfaces using a split mold (3.5 x 5.0 mm). Specimens of each denture base-reline resin combination were subjected to shear forces (0.5 mm/min) until fracture. A staircase approach was used to determine the SBFL. Specimens were submitted to either 10,000 cycles (5.0 Hz) or until fracture. For both SBS and SBFL, specimens were tested after relining (control) and after 30 days of WS. Data (MPa) were analyzed with 2-way ANOVA and Tukey's tests (α = 0.05). To test for a possible correlation between the SBS and SBFL, a linear regression analysis was performed. Results: WS significantly increased (p < 0.05) the SBS of AC-TR and AC-UGH and the SBFL of AC-TR, AC-UGH and LUGH. After WS, UGH produced higher (p < 0.05) SBS than TR, regardless of the denture base resin used. Regardless of the experimental groups and the denture base resins used, UGH produced higher (p < 0.05) SBFL than TR specimens. A strong positive linear correlation (r2 = 0.949) was observed between the SBS and SBFL. Conclusion: Overall, UGH promoted the highest SBS and SBFL. WS increased the SBS and SBFL of the AC relined specimens. A positive correlation was observed between the two variables. Keywords: shear strength, fatigue limit, water storage, adhesion, acrylic resins, reline resins