Effect of artificial toothbrushing and water storage on the surface roughness and micromechanical properties of tooth-colored CAD-CAM materials.
BACKGROUND
Because of the different composition of resin-ceramic computer-aided design and computer-aided manufacturing (CAD-CAM) materials, their polishability and their micromechanical properties vary. Moreover, depending on the composition of the materials, their surface roughness and micromechanical properties are likely to change with time.


OBJECTIVE
The purpose of this in vitro study was to investigate the effect of artificial toothbrushing and water storage on the surface roughness (Ra and Rz) and the micromechanical properties, surface hardness (Vickers [VHN]) and indentation modulus (EIT), of 5 different tooth-colored CAD-CAM materials when polished with 2 different polishing systems.


METHODS
Specimens (n=40 per material) were cut from a composite resin (Paradigm MZ100; 3M ESPE), a feldspathic ceramic (Vitablocs Mark II; Vita Zahnfabrik), a resin nanoceramic (Lava Ultimate; 3M ESPE), a hybrid dental ceramic (Vita Enamic; Vita Zahnfabrik), and a nanocomposite resin (Ambarino High-Class; Creamed). All specimens were roughened in a standardized manner and polished either with Sof-Lex XT discs or the Vita Polishing Set Clinical. Surface roughness, VHN, and EITwere measured after polishing and after storage for 6 months (tap water, 37°C) with periodic, artificial toothbrushing. The surface roughness, VHN, and EITresults were analyzed with a nonparametric ANOVA followed by Kruskal-Wallis and exact Wilcoxon rank sum tests (α=.05).


RESULTS
Irrespective of polishing system and of artificial toothbrushing and storage, Lava Ultimate generally showed the lowest surface roughness and Vitablocs Mark II the highest. As regards micromechanical properties, the following ranking of the CAD-CAM materials was found (from highest VHN/EITto lowest VHN/EIT): Vitablocs Mark II > Vita Enamic > Paradigm MZ100 > Lava Ultimate > Ambarino High-Class. Irrespective of material and of artificial toothbrushing and storage, polishing with Sof-Lex XT discs resulted in lower surface roughness than the Vita Polishing Set Clinical (P≤.016). However, the polishing system generally had no influence on the micromechanical properties (P>.05). The effect of artificial toothbrushing and storage on surface roughness depended on the material and the polishing system: Ambarino High-Class was most sensitive to storage, Lava Ultimate and Vita Enamic were least sensitive. Artificial toothbrushing and storage generally resulted in a decrease in VHN and EITfor Paradigm MZ100, Lava Ultimate, and Ambarino High-Class but not for Vita Enamic and Vitablocs Mark II.


CONCLUSIONS
Tooth-colored CAD-CAM materials with lower VHN and EITgenerally showed better polishability. However, these materials were more prone to degradation by artificial toothbrushing and water storage than materials with higher VHN and EIT.
Research Associate, Department of Preventive, Restorative, and Pediatric Dentistry, School of Dental Medicine, University of Bern, Bern, Switzerland. Electronic address: simon.flury@zmk.unibe.ch.
Simon
S
Flury
Private practice, Bern, Switzerland.
Elisabeth
E
Diebold
Senior Researcher, Department of Preventive, Restorative, and Pediatric Dentistry, School of Dental Medicine, University of Bern, Bern, Switzerland.
Anne
A
Peutzfeldt
Professor, Head of Department, Department of Preventive, Restorative, and Pediatric Dentistry, School of Dental Medicine, University of Bern, Bern, Switzerland.
Adrian
A
Lussi
D002516:Ceramics / Q000627:therapeutic use; D003188:Composite Resins / Q000627:therapeutic use; D017076:Computer-Aided Design; D003775:Dental Polishing / Q000009:adverse effects / Q000379:methods; D017266:Dental Prosthesis / Q000009:adverse effects / Q000379:methods; D017267:Dental Prosthesis Design; D006244:Hardness; D006801:Humans; D066298:In Vitro Techniques; D017797:Prosthesis Coloring / Q000379:methods; D013499:Surface Properties; D014099:Toothbrushing / Q000009:adverse effects*; D014867:Water
D003188:Composite Resins; D014867:Water