Adhesion of indirect ceramic and composite restorations: influence of chewing

Objective: The purpose of this study was to evaluate the influence of simulated chewing forces on bond strength of ceramic and composite disks luted to dentin with a simplified cement (Scotchbond Universal&RelyX Ultimate, 3M ESPE) or a multi-step cement (Variolink II, Ivoclar-Vivadent) ).

Methods: Eighty noncarious human molars were cut with a low speed diamond saw under water cooling and equally and randomly assigned to two main groups: CS (Chewing Simulation) and Controls (Static Conditions). Specimens were then divided in 4 different luting groups (N=20): Group1: Ceramic disks (Feldspathic Ceramic, Vita Mark II, Vita) luted with Scotchbond Universal & RelyX Ultimate ; Group2: Ceramic disks (Feldspathic Ceramic, Vita Mark II) luted with Variolink II ; Group3: Composite disks (Lava Ultimate, 3M ESPE) and Scotchbond Universal & RelyX Ultimate; Group4: Composite disks (Lava Ultimate) and Variolink II . Specimens were then either submitted to chewing simulation or stored in water and subsequently cut for microtensile bond strength analysis in accordance with the non-trimming technique. Sticks were stressed until failure with a simplified universal testing machine. Data were statistically analyzed by Student's T Test (p=0.05).

Results:  

Luted Material	Cement	Storage
		CS	Control
Ceramic	SU&RU	12.1 (4.4)a	14.3 (4.7)a,b,c
	VII	13.5 (4.7)a,b	16.1 (4.3)c,d
Composite	SU&RU	12.6 (4.7)a,b	13.2 (5.3)a,b
	VII	14.9 (5.3)b,c	17.8 (5.1)d

Table 1: Means and standard deviations (SD) of microtensile bond strength (MPa) obtained at luted material/dentin interface. Different superscript letters indicate statistical differences between the groups (p<0.05).

Conclusions: The simplified luting procedure (Scotchbond Universal&RelyX Ultimate) exhibited comparable bond strength values for both ceramic and composite irrespective from the aging conditions (both CS and Static). Albeit the strength values were slightly higher before chewing simulation, the multi-step cement (Variolink II) was significantly affected by chewing. Further studies are needed to clarify the role of occlusal forces on ceramic bond to dentin.

Supported, in part, by grants: FIRB RBAP1095CR and PRIN 2009SAN9K5 and 2009FXT3WL from MIUR, Italy.