Mechanical Degradation of Different Classes of Composite Resins Aged in Water, Air, and Oil.

A significant deterioration of the properties can drastically compromise the survival rate of restorative materials. The aim of this study was to assess flexural strength and hardness of three composite classes: hybrid composite resin (HCR), nanoparticulate composite resin (NCR), and silorane-based composite resin (SBCR). One hundred specimens were prepared for hardness testing by using a split metallic mold measuring 10 mm in diameter and 2 mm deep.

Pre-heating mitigates composite degradation.

Dental composites cured at high temperatures show improved properties and higher degrees of conversion; however, there is no information available about the effect of pre-heating on material degradation. Objectives This study evaluated the effect of pre-heating on the degradation of composites, based on the analysis of radiopacity and silver penetration using scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS). Material and Methods Thirty specimens were fabricated using a metallic matrix (2x8 mm) and the composites Durafill VS (Heraeus Kulzer), Z-250 (3M/ESPE), and Z-350 (3M/ESPE), cured at 25°C (no pre-heating) or 60°C (pre-heating).

Time reduction of light curing: Influence on conversion degree and microhardness of orthodontic composites.

Introduction: The aim of this study was to assess the influence of curing time and power on the degree of conversion and surface microhardness of 3 orthodontic composites.

Methods: One hundred eighty discs, 6 mm in diameter, were divided into 3 groups of 60 samples according to the composite used-Transbond XT (3M Unitek, Monrovia, Calif), Opal Bond MV (Ultradent, South Jordan, Utah), and Transbond Plus Color Change (3M Unitek)- and each group was further divided into 3 subgroups (n = 20). Five samples were used to measure conversion, and 15 were used to measure microhardness.

Effect of carbamide peroxide bleaching gel on composite resin flexural strength and microhardness.

This study investigated the effect of 16% carbamide peroxide (Whiteness Perfect/FGM) on the Vickers microhardness and flexural strength of the restorative composites Filtek Z100 (hybrid), Filtek Z350 (nanofill), Brilliant (micro-hybrid) and Opallis (micro-hybrid). Disc-shaped (4x2 mm; n=5) and bar-shaped (12x2x1 mm; n=10) specimens of each restorative material were randomly divided into 2 groups: (G1) 16 weeks stored in distilled water; (G2) 16 weeks stored in distilled water, with 16% carbamide peroxide application during 6 h per day for the last 4 weeks. The mechanical properties were evaluated using a Vickers microhardness tester and a mechanical testing machine.

Effect of different airborne-particle abrasion/bonding agent combinations on the bond strength of a resin cement to a base metal alloy.

Statement Of Problem: Investigation of surface treatments to improve the bond of resin cements to metals may contribute to the longevity of metal ceramic restorations.

Purpose: The purpose of this study was to evaluate the efficacy of surface treatments on the shear bond strength (SBS) of a resin cement to nickel-chromium (NiCr) alloy.

Material And Methods: Eighty cast NiCr alloy disks (9 × 3 mm) were divided into 8 groups (n=10), which received 1 of the following surface treatments: 1) 50 µm Al(2)O(3) particles + silane; 2) 120 µm Al(2)O(3) + silane; 3) 30 µm silica-modified Al(2)O(3) (Cojet Sand) + silane; 4) 120 µm Al(2)O(3) followed by 110 µm silica-modified Al(2)O(3) (Rocatec) + silane; 5) 50 µm Al(2)O(3) + metal primer; 6) 120 µm Al(2)O(3) + metal primer; 7) 30 µm silica-modified Al(2)O(3) (Cojet Sand) + metal primer; and 8) 120 µm Al(2)O(3) followed by 110 µm silica-modified Al(2)O(3) (Rocatec) + metal primer.

Shear bond strength of different repair systems to titanium after water aging.

This study evaluated the shear bond strength (SBS) and stability of commercially pure titanium (CP Ti)/repair material interfaces promoted by different repair systems. One hundred CP Ti cast discs were divided into five repair system groups: 1) Epricord (EP); 2) Bistite II DC (BT); 3) Cojet (CJ); 4) Scotchbond Multi-Purpose Plus (SB) (control group); and 5) Cojet Sand plus Scotchbond Multi-Purpose Plus (CJSB). The specimens were stored in distilled water for 24 hours at 37°C, thermal cycled (5000 cycles, 5°-55°C) and stored under the same conditions for either 24 hours or six months (n=10).

Shear bond strength of metal-ceramic repair systems.

This study evaluated the shear bond strength of different repair systems to nickel-chromium (NiCr) alloy after storage in water for either 24 hours or six months. One hundred cylindrical specimens (3 mm thick x 9 mm diameter) were fabricated using an NiCr alloy and embedded in a PVC ring, where they received one of five bonding and resin composite repair treatments (n = 20): Clearfil SE Bond/Clearfil AP-X (Group 1), Bistite II DC/Palfique (Group 2), CoJet/Z100 (Group 3), Scotchbond Multi-Purpose Plus/Z100 (Group 4; reference group), and CoJet Sand plus Scotchbond Multi-Purpose Plus/Z100 (Group 5). The specimens were stored in distilled water for 24 hours at 37 degrees C, thermocycled for 1,000 cycles in two baths (at 5 degrees C and 55 degrees C) with a dwell time of 30 seconds for each bath, and stored in distilled water at 37 degrees C for either 24 hours or six months.

Shear bond strength of metal-ceramic repair systems.

Statement Of Problem: When clinical fractures of the ceramic veneer on metal-ceramic prostheses can be repaired, the need for remake may be eliminated or postponed. Many different ceramic repair materials are available, and bond strength data are necessary for predicting the success of a given repair system.

Purpose: This study evaluated the shear bond strength of different repair systems for metal-ceramic restorations applied on metal and porcelain.

The influence of chemical activation on hardness of dual-curing resin cements.

During the cementation of metallic restorations, the polymerization of dual-curing resin cements depends exclusively on chemical activation. This study evaluated the influence of chemical activation compared with dual-curing (chemical and light activation), on the hardness of four dual-curing resin cements. In a darkened environment, equal weight proportions of base and catalyst pastes of the cements Scotchbond Resin Cement, Variolink II, Enforce and Panavia F were mixed and inserted into moulds with cavities of 4 mm in diameter and 2 mm in height.

The volumetric fraction of inorganic particles and the flexural strength of composites for posterior teeth.

Objective: To evaluate the content of inorganic particles and the flexural strength of new condensable composites for posterior teeth in comparison to hybrid conventional composites.

Method: The determination of the content of inorganic particles was performed by mass weighing of a polymerized composite before and after the elimination of the organic phase. The volumetric particle content was determined by a practical method based on Archimedes' principle, which calculates the volume of the composite and their particles by differential mass measured in the air and in water.