Objective: The purpose of the study was to compare the wear resistance of a composite material light-cured with either a pulse-delay cure (PC) technique or by normal cure (NC). Methods: Cylindrical-shaped preparations (6mm diameter by 4mm deep) were prepared in custom acrylic fixtures. The preparations were slightly overfilled with Z100 (A3.5) composite and light polymerized as described below. The first increment was 2mm thick and the second 2.5mm. For the PC group the second increment was cured for 3 seconds at 200mW/cm2, polished flat to remove excess and cured at 500mW/cm2 for 20 seconds. For the NC group the second increment was given a single cure at 500mW/cm2 for 20 seconds and then polished flat. Specimens were stored in water at 23°C for 24 hours. Knoop hardness measurements (KHN) were obtained on the surface prior to wear testing. Wear testing was conducted using a Leinfelder wear simulator for 100,000 cycles with a conical-shaped steel stylus to simulate contact area wear. Wear was determined using a MTS 3D profiliometer and Ansur 3D software. KHN values were also determined after wear testing and after repolishing. Results:The results are presented in the following table:
|
|
Wear – 100,000 Cycles |
KHN |
|||
|
|
Vol Loss (mm3) |
Max Depth (mm) |
24 Hr |
Post Wear |
Repolish |
|
PC |
0.011 (0.003) |
67.35 (9.00) |
68.4 (3.8) |
72.1 (2.8) |
95.6 (2.0) |
|
NC |
0.012 (0.004) |
70.01 (11.01) |
78.3 (2.3) |
79.7 (2.5) |
95.8 (2.0) |
|
Sig (p=0.05) |
NS |
NS |
S |
S |
NS |
Conclusions: Contact area wear was similar for both curing methods despite initial surface KHN being different. Repolished surfaces had a greater and essentially identical KHN suggesting that initial values were the result of polishing at an incomplete stage of polymerization.