Clinical Relevance Tribochemical treatment of existing composite surfaces is highly effective for composite repair. When repairing an old composite restoration, the clinician should try to use the same composite originally used for the restoration. If the information about the original restoration is not known, a composite with strong mechanical properties should be used for the repair restoration. SUMMARY This study evaluated the effect of tribochemical coating on composite-to-composite repair interfacial fracture toughness (iFT). Sixty beam-shaped specimens (21×4×3 ± 0.2 mm) were prepared with a nanofill composite (Filtek Supreme Ultra [FSU]) and a nanohybrid composite (Clearfil Majesty ES-2 [CME]) and aged for 50,000 thermocycles (5°C-55°C, 20-second dwell time) and then sectioned in half. The resulting 120 hemispecimens (60 for each composite) were randomly assigned to different repair methods (n=10): universal adhesive (Clearfil Universal Bond Quick [CUB]), sand-blasting followed by CUB, or tribochemical coating (CoJet, CoJet sand, Espe-Sil, and Visio-Bond). The repair surface was prepared with a diamond bur (Midwest #471271), rinsed, and dried. Each aged composite brand (FSU, CME) was repaired with either the same composite or the opposite composite. All adhesives and composites were light cured with a high-irradiance LED curing light (Elipar DeepCure-S). After postrepair storage in 100% humidity and at 37°C for 24 hours, iFT was measured as K Ic (MPa m ½ ). Data were analyzed for statistical significance using two-way analysis of variance (ANOVA) and the Tukey honest significant difference post hoc test (α=0.05). Regardless of the substrate composite, ANOVA showed significant differences for surface treatment ( p <0.0001) and repair composite ( p <0.0001). Mean iFT values (SD) ranged from 0.91 (0.10) MPa·m ½ to 2.68 (0.12) MPa·m ½ . Repairs made with FSU after CoJet resulted in significantly higher iFT (FSU: 2.68 MPa·m ½ ; CME: 2.21 MPa·m ½ ) when compared to the other experimental groups. The repair iFT was higher with CoJet treatment and when the nanofill composite FSU was used as the repair composite.
SUMMARY Objective: To evaluate the composite-to-composite repair interfacial fracture toughness (iFT) as a function of adhesive and composite repair material. Methods and Materials: Beam-shaped composite specimens (21×4×3±0.2 mm) were prepared for each substrate material (Filtek Supreme Ultra [FSU] or Clearfil Majesty ES-2 [CME]) and artificially aged for 50,000 thermocycles (5-55°C, 20-second dwell time). Aged specimens were sectioned in half, and the resulting hemispecimens were randomly assigned to one of the different repair methods (n=10) based on the following variables: type of substrate composite (FSU or CME), acid etch (yes or no), adhesive type (Scotchbond Universal or Clearfil SE Bond 2), and type of repair composite (FSU or CME). The repair surface was prepared with a course diamond bur (Midwest #471271). When used, 37% phosphoric acid was applied for 20 seconds, rinsed, and dried. All adhesives and composites were applied according to manufacturers' instructions. After postrepair storage (100% humidity, 37°C, 24 hours), iFT was measured and expressed as MPa. Data were analyzed for statistical significance using a three-way analysis of variance and Tukey post hoc tests (α=0.05). Results: iFT values ranged from 0.64 ± 0.19 MPa to 1.28 ± 013 MPa. Significantly higher iFT values were achieved when FSU was used as the repair composite resin regardless of the substrate composite resin ( p <0.001). Clearfil SE Bond 2 adhesive was associated with significantly higher iFT values for FSU substrate ( p <0.001). The etching procedure had no significant effect on the iFT values of the repair procedures ( p >0.05). Conclusions: Composite repair strength is adhesive and composite dependent. Repair strength appears to be higher when FSU is the repair composite regardless of the adhesive used.
SUMMARY Statement of the Problem: Resin-modified glass ionomer cements (RMGIs) are often used for luting indirect restorations. Hand-mixing traditional cements demands significant time and may be technique sensitive. Efforts have been made by manufacturers to introduce the same cement using different dispensing/mixing methods. It is not known what effects these changes may have on the mechanical properties of the dental cement. Purpose: The purpose of this study was to evaluate the mechanical properties (diametral tensile strength [DTS], compressive strength [CS], and fracture toughness [FT]) of RMGIs with different dispensing/mixing systems. Methods and Materials: The RMGI specimens (n=14)—RelyX Luting (hand mix), RelyX Luting Plus (clicker–hand mix), RelyX Luting Plus (automix) (3M ESPE), GC Fuji PLUS (capsule-automix), and GC FujiCEM 2 (automix) (GC)—were prepared for each mechanical test and examined after thermocycling (n=7/subgroup) for 20,000 cycles to the following: DTS, CS (ISO 9917-1) and FT (ISO standard 6872; Single-edge V-notched beam method). Specimens were mounted and loaded with a universal testing machine until failure occurred. Two-/one-way analysis of variance followed by Tukey honestly significantly different post hoc test was used to analyze data for statistical significance ( p <0.05). Results: The interaction effect of both dispensing/mixing method and thermocycling was significant only for the CS test of the GC group ( p <0.05). The different dispensing/mixing methods had no effect on the DTS of the tested cements. The CS of GC Fuji PLUS was significantly higher than that of the automix version ( p <0.05). The FT decreased significantly when switching from RelyX (hand mix) to RelyX Luting Plus (clicker–hand mix) and to RelyX Luting Plus (automix) ( p <0.05). Except in the case of the DTS of the GC group and the CS of GC Fuji PLUS, thermocycling had a significant effect reducing the mechanical properties of the RMGI cements ( p <0.05). Conclusions: Introducing alternative dispensing/mixing methods for mixing RMGIs to reduce time and technique sensitivity may affect mechanical properties and is brand dependent.