Purpose: Mechanical interlocking is the key to improve bond strength of computer-aided design and computer-aided manufacturing (CAD-CAM) resin-based materials. The purpose of this study was to evaluate the effect of air abrasion with a newly developed variable pressure chair-side particle abrader on bond strengths of a resin luting agent to a CAD-CAM resin material.

Methods: A CAD-CAM resin block (Katana Avencia) was abraded with either a conventional Miniblaster (MIN) or Adprep (ADP) at an air pressure of either 0.2 or 0.4 MPa. The CAD-CAM resin block was bonded with a dual cure resin luting agent (Panavia V5) and light cured. After 24 h storage in water, specimens were divided into two groups; one group remained in water (thermal cycling [TC] 0), while the second group was subjected to thermal stress (5-55°C) for 10,000 cycles (TC10,000). Following this, microtensile bond strength (µTBS) testing was performed. The surface morphology of the CAD-CAM resin block specimens after air abrasion was observed by a confocal laser scanning microscopy (CLSM). The µTBS data were statistically analyzed using a t-test (Welch’s method) with Bonferroni's correction (α = 0.05).

Results: The µTBS to the CAD-CAM resin blocks significantly increased using 0.4 MPa pressure compared with 0.2 MPa pressure. The µTBSs significantly decreased after TC stress, except for MIN at 0.2 MPa. From the CLSM observations, air abrasion with MIN at 0.4 MPa showed deeper surface concavities on the surface compared with ADP.

Conclusion: The current results suggest the performance of ADP could be acceptable as a chair-side particle abrader.

Purpose: The aim of the current study is to evaluate the influence of ultrasonic vibration on bond strength of four luting agents joined to particle abraded base metal alloy.

Methods: Cast disc specimens made of nickel-chromium (Ni-Cr) were airborne-particle abraded with alumina and bonded with four luting agents. The specimens were stored in water, and subsequently vibrated with an ultrasonic generator for up to 5 min. Shear bond strength was determined with universal testing device.

Results: Bond strength in MPa without vibration (baseline, BL) was 51.8 for composite luting agent, 25.1 for glass ionomer cement (GIC), 12.9 for zinc polycarboxylate cement (PCC), and 6.1 MPa for zinc phosphate cement (ZPC). The specimens cemented with ZPC were detached within 1 minute during application of ultrasound, whereas 1-min/BL bond strength ratio was 102 for PCC, 87 for GIC, and 88 for composite luting agent.

Conclusion: Ultrasonic vibration effectively reduced bond strength to Ni-Cr alloy of ZPC. Reduction in bond strength was not apparent up to 2-min vibration for PCC, 3-min vibration for GIC, and 1-min vibration for composite luting agent. Care must be taken in the application of ultrasound for removing cast restorations seated with PCC, GIC, and composite resin luting agent.

Purpose: The aim of the present study was to evaluate the irradiance of light-emitting diode (LED) light bulbs seated around the abrasive grinding disc of a wet laboratory cast trimmer for the enhancement of environmental brightness.

Methods: A total of 12 LED light bulbs were set up along the inner framework of a rotary cast trimmer. The irradiance of the bulbs was determined with a spectral radiometer.

Results: The spectral irradiance mean of 12 LED light bulbs in the cast trimmer was 37.3 µW/cm² and the value was significantly greater than that of the control. The irradiance median of the 9787 LED light bulb varied from 640.3 µW/cm² for 0 mm distance to 79.4 µW/cm² for 200 mm distance. Analysis revealed that irradiance was not statistically affected by the bulb-sensor vertical distances within 50 mm.

Conclusion: The working environment, especially brightness, around a dental stone cast placed on the trimmer stage can be improved considerably through the use of the LED light bulbs.