Related Experiment Video
Updated: Sep 27, 2026
Measuring the Complete-arch Distortion of an Optical Dental Impression
Published on: May 30, 2019
A clinical trial to compare double-arch and complete-arch impression techniques in the provision of indirect
D Andrew Lane1, Rosalind C Randall, Natalie S Lane
1Unit of Operative Dentistry and Odontology, University Dental Hospital of Manchester, Manchester, United Kingdom. lane@vtsurvey.com
Statement Of Problem:
Anecdotal reports of use of double-arch impressions for indirect restorations suggest time and materials savings, but there is little clinical evidence to support their use.
Purpose:
To establish whether a double-arch impression technique could produce restorations comparable with those produced by use of the complete-arch technique and to investigate reported time and material savings.
Material And Methods:
Five practitioners each recruited 10 adult patients requiring a single complete veneer crown into the study. Two sets of impressions, 1 complete-arch in a stock metal tray, and 1 double-arch in a plastic double-arch tray were made for each patient in addition-polymerized silicones in a random order. The time taken for each impression was recorded along with patient's assessment of comfort, taste, and overall acceptability. One technician, who selected the impressions for the fabrication of each crown according to a predetermined scheme of randomization, fabricated all crowns. Equal numbers of crowns were made from the complete and double-arch impressions. At the time of crown placement, the accuracy of fit, occlusal harmony, and the time taken for try-in were also recorded. The weight of impression material used was measured for each impression. Data were analyzed by use of computerized statistical software (t test for equality of means) at a significance level of 95%.
Results:
The double-arch technique was faster (222 seconds [SD, 57 seconds] vs 445 seconds [SD, 87 seconds], P=.000), more comfortable (P=.025), better tasting (P=.001), and preferred by 80% of the patients (P=.000). No significant differences were found between the 2 groups for accuracy of fit, occlusion, or time taken for try-in of the restorations. The mean weight of impression material used was 39 g (SD, 10 g) for complete-arch and 20 g (SD, 7 g) for double-arch impressions, a mean difference of 19 g (P=.000).
Conclusion:
Within the limitations of this study, double-arch impressions were found to take less time, to use less material, and to be preferred by patients. Under the conditions of this study, the resulting restorations were no less accurate than those made from complete-arch impressions.
