STATEMENT OF PROBLEM: Dual-arch impression trays often are used for addition silicone final impressions of fixed prosthodontic preparations, but concerns about distortion of the impression are common because such trays lack rigidity. PURPOSE: This in vitro pilot study was designed to determine the accuracy of addition silicone impressions made with custom trays or made with either passive or stressed dual-arch trays. MATERIAL AND METHODS: Complete crown preparations of a mandibular molar, premolar, and incisor were made on a dentoform. These tooth preparations received flat, parallel indexes on the facial and lingual axial walls for accurate and reproducible positioning of a digital caliper. Gypsum dies were produced with an addition silicone impression material in either custom trays or dual-arch trays seated passively or with induced flexure (3 dies per tray group). The facio-lingual dimensions of the dies were measured with a digital caliper accurate to +/-5 microm and compared to the dimensions of the original preparations. Flexure in the latter group was induced by contact of the tray with a simulated torus, made of resin, in the lingual vestibule of the dentoform. Data were analyzed with 2-way analysis of variance and Tukey's multiple comparison test (alpha=.05). RESULTS: Dies fabricated with either the custom or passive dual-arch tray reproduced the facio-lingual dimensions of the preparations within a -27 to +13 microm range. Dies fabricated with the flexed dual-arch tray exhibited greater discrepancy, in the range of -47 to -67 microm relative to the preparations. Tray type was a significant factor (P=.002): the flexed tray group was significantly different than the other 2 groups, which did not differ from each other. CONCLUSION: Within the limitations of this pilot study, dual-arch impressions were comparable in accuracy to impressions made with custom trays. Accuracy was reduced, however, when the trays were flexed during closure of the arches.
STATEMENT OF PROBLEM: Dual-arch impression trays often are used for addition silicone final impressions of fixed prosthodontic preparations, but concerns about distortion of the impression are common because such trays lack rigidity. PURPOSE: This in vitro pilot study was designed to determine the accuracy of addition silicone impressions made with custom trays or made with either passive or stressed dual-arch trays. MATERIAL AND METHODS: Complete crown preparations of a mandibular molar, premolar, and incisor were made on a dentoform. These tooth preparations received flat, parallel indexes on the facial and lingual axial walls for accurate and reproducible positioning of a digital caliper. Gypsum dies were produced with an addition silicone impression material in either custom trays or dual-arch trays seated passively or with induced flexure (3 dies per tray group). The facio-lingual dimensions of the dies were measured with a digital caliper accurate to +/-5 microm and compared to the dimensions of the original preparations. Flexure in the latter group was induced by contact of the tray with a simulated torus, made of resin, in the lingual vestibule of the dentoform. Data were analyzed with 2-way analysis of variance and Tukey's multiple comparison test (alpha=.05). RESULTS: Dies fabricated with either the custom or passive dual-arch tray reproduced the facio-lingual dimensions of the preparations within a -27 to +13 microm range. Dies fabricated with the flexed dual-arch tray exhibited greater discrepancy, in the range of -47 to -67 microm relative to the preparations. Tray type was a significant factor (P=.002): the flexed tray group was significantly different than the other 2 groups, which did not differ from each other. CONCLUSION: Within the limitations of this pilot study, dual-arch impressions were comparable in accuracy to impressions made with custom trays. Accuracy was reduced, however, when the trays were flexed during closure of the arches.
Authors: Michael S McCracken; David R Louis; Mark S Litaker; Helena M Minyé; Thomas Oates; Valeria V Gordan; Don G Marshall; Cyril Meyerowitz; Gregg H Gilbert Journal: J Prosthodont Date: 2017-01-11 Impact factor: 2.752
Authors: Luciana Martinelli Santayana de Lima; Gilberto Antonio Borges; Luiz Henrique Burnett Junior; Ana Maria Spohr Journal: J Int Oral Health Date: 2014-06-26
Authors: Michael S McCracken; Mark S Litaker; Ashley J George; Scott Durand; Sepideh Malekpour; Don G Marshall; Cyril Meyerowitz; Lauren Carter; Valeria V Gordan; Gregg H Gilbert Journal: J Am Dent Assoc Date: 2017-08-16 Impact factor: 3.634
Authors: Nathaniel C Lawson; Mark S Litaker; Ellen Sowell; Valeria V Gordan; Rahma Mungia; Kenneth R Ronzo; Ba T Lam; Gregg H Gilbert; Michael S McCracken Journal: J Prosthet Dent Date: 2019-10-04 Impact factor: 3.426