Repair of siloranes dependent on surface pretreatment in vitro

Objectives:

Aim of the study was the in-vitro-investigation of the repairability of a dental silorane (Filtek Silorane, 3M Espe, Seefeld, Germany) after different surface pretreatments.

Methods:

54 silorane specimens (5x5x5 mm) were fabricated and stored in saline solution (24h/ 37°C). Their surface was polished with abrasive paper (600grit), etched with phosphoric acid (10 sec) and rinsed with water (30 sec). Afterwards, repair was performed with a silorane due to one of the 9 treatment protocols (each n=6): no additional treatment (NT) , silorane primer (P) and silorane bond (B), B only, sandblasting (SB), SB plus P/B,  SB plus B, Cojet and silane (CJ), CJ plus P/B, CJ plus B. Whole silorane specimens (5x5x10 mm) with no repair served as positive control. Specimens were sectioned and microtensile bond strength (MTBS) was measured (30 beams per group, surface area 1.2 mm²) with crosshead-speed of 1 mm/min, statistical analysis (ANOVA, Dunnett, p<0.05) was performed.

Results:

	Control	NT	B	P/B	SB	SB/B	SB/P/B	CJ	CJ/B	CJ/P/B
Mean (MPa)	59.3a,b	19.3e	38.6d	42.0c,d	42.7c,d	55.7a,b,c	44.2c,d	46.4b,c,d	63.7a	36.6d
SD	10.5	5.3	17.9	14.1	13.3	6.7	14.4	15.2	12.0	9.4

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            

MTBS of the specimens was affected by either surface roughing or adhesive procedure (p<0.05). Higher MTBS values were determined after SB or CJ pretreatment compared to NT (p<0.001). The  groups NT and CJ benefit from further treatment with B (p<0.01), for SB, no significant differences were detected. After treatment with SB/B, CJ and CJ/B, the MTBS values of the repaired groups did not differ from the control. The additional use of P did not improve MTBS, but was detrimental for the CJ groups (p<0.001).

Conclusions:

Due to data after 24h water storage, siloranes can be  repaired with either SB and CJ in combination with a silorane bond, the additional use of silorane primer is disadvantageous.                                                                                                                                                                                                                                                                                                          

The silorane and the silorane adhesives were provided by 3M Espe, Seefeld, Germany.