A Novel In Vitro Model for Detail Reproduction of Elastomers

OBJECTIVES: To develop a new bovine in vitro test model to simulate in vivo detail reproduction of enamel and dentin. The null hypothesis was that a bovine in vitro model will not differ from the standard ANSI/ ADA stainless steel die in terms of mean widths of its inscribed horizontal lines.

METHODS: Bovine enamel and dentin models were fabricated with similar indenting technology and dimensions recommended in ANSI/ADA Specification 19 for the stainless steel detail reproduction die. The three horizontal lines of 20um, 50um and 75um widths on bovine models and stainless steel die were scanned on a non-contact surface profilometer (Proscan 2000, Scantron, UK). Mean line-widths among the three models were compared using the GLIMMIX procedure followed by Tukey's post-hoc comparisons.

RESULTS:

	Mean Line-widths (um)
	Line 1	Line 2	Line 3
ADA specs.	50	20	75
Stainless steel die	48	26.67	70
Bovine enamel	80	151.25	213.75
Bovine dentin	72.5	42.5	140.83

In spite of similar machining of lines on all models, the bovine models showed significantly wider lines than those on stainless steel die and ADA specifications (p<0.0001). Bovine enamel registered higher widths than bovine dentin suggesting that although being densely mineralized and stiffer than dentin, it is brittle whereas dentin is very tough and resilient.

CONCLUSIONS: Stainless steel provides calibrated surfaces for precise measurements but its moisture content and surface energy differs significantly from teeth making metal a difficult material to be used for predicting clinical success of impression materials. Similarities between bovine teeth and human teeth in microstructure and composition support our results. Thus, bovine teeth are the closest biological tissue to human teeth that can be employed in defining a new standard/protocol for in vitro testing of detail reproduction of elastomeric impression materials.