Evaluation of two techniques to measure the available space in the mandibular dental arch using the method error

purpose: to evaluate the influence of errors when two methods for assessing the available space in the dental arch are used. methods: a single investigator measured the available space in 30 plaster models by using two techniques: 1) with a digital caliper; and 2) by contouring the arch with a brass wire and subsequently straightening and measuring this wire with a millimeter ruler. fifteen days later, data were collected using both methods with duplicate measurements, so that each method was used twice for each model. the random and systematic errors of each method under the conditions of repeatability and reproducibility were calculated. results: for method reproducibility, systematic errors were statistically significant (p<0.05) only when the brass wire method was used. the random errors were less than 1 mm under both conditions. with the brass wire, random errors were not significant for repeatability; however, for reproducibility, the mean value was 1.69 mm. conclusion: in the digital caliper method, systematic and random errors were considered acceptable. the brass wire measurement method did not present errors under the condition of repeatability; for reproducibility, however, the systematic error was significant and the random error indicates that this method should be considered inappropriate to measure space in the dental arch.