Objectives: To evaluate the hypothesis that dentin bond strengths may be affected by flaws resulting from solvent evaporation, the remaining acetone content (RAC) and degree of conversion (DC) of dried and cured single-solution bonding agents with increasing initial acetone content (IAC) were interpreted in comparison to Weibull statistics of previously reported microtensile bond strength (MTBS) data (Cho&Dickens AADR, 2001).

Methods: Experimental dentin bonding agents with (27, 37, 47, 57, or 67) mass fraction % IAC were dispersed on KBr crystals, dried for 10 s and covered with another KBr crystal. RAC and DC were determined on thin films by a mid-IR technique using the C=C absorption at 1637 cm^-1 and the -CO-CH₃ absorption at 530 cm^-1, respectively. MTBS data were subjected to Weibull analysis.

Results:

IAC	MTBS					RAC (%) n = 4	DC (%) n = 4
	n	Mean (±sd; MPa)	m	s0 (90% C.I.; MPa)	R2
27 %	39	53.0±12.8 b	4.60	58.0 {30.4-73.7}	0.989	7.7±1.4 a	29.8±1.5 a
37 %	27	63.5±13.4 a	5.72	68.3 {40.6-82.7}	0.976	8.6±1.4 a,b	29.7±7.9 a
47 %	25	52.7±11.9 b	5.05	57.4 {31.9-71.3}	0.981	7.3±2.9 a,b	26.4±6.1 a
57 %	23	47.5±15.3 b	3.43	52.7 {22.2-72.6}	0.973	5.3±2.2 a,b	16.5±8.5 a
67 %	29	38.2±15.8 c	2.72	43.2 {14.5-64.6}	0.993	3.5±1.7 b	25.4±14.9 a

Conclusions: DC did not seem to affect MTBS. However, greater loss of solvent (i.e. lower RAC) in higher IAC formulations may have caused a large number of pores within the bonded interfaces of acetone-rich formulations. Since RAC correlated extremely well with MTBS (r= 0.958, p=0.01) and the Weibull parameter 'm' as an indirect measure of the flaw population (r=0.970, p=0.006), the flaws within the adhesive layer are suggested as a critical factor in the resulting MTBS. Supported by NIDCR Grant No. DE13298, ADAHF and NIST.

Back to the Dental Materials: II - Adhesion-Other Program
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