Patient preference and operating time for digital versus conventional impressions: a network meta-analysis

Digital impression techniques have seen many advancements, with new hardware and software being developed each year. The technical advantages of these systems are real-time visualization, evaluation and archive, segmental capture, ease of recapture if necessary, economical in terms of no use of impression material or trays or disinfection, easy file transfer and communication with the laboratory. However patient satisfaction is one major factor that might influence the choice of impression technique. The aim of this network meta-analysis was to identify statistically the evidence on overall patient preferences relative to digital versus conventional impression techniques, in addition to the time taken in making these impressions.

Randomized or prospective clinical studies were identified based on the inclusion criteria in PUBMED, DARE and COCHRANE databases; subsequently pertinent data were extracted. Risk of bias of the included studies was assessed using the Cochrane risk of bias tool and Newcastle-Ottawa scale. Heterogeneity amongst the studies in direct comparison was assessed by Chi-square and I² tests using the Inverse variance heterogeneity model. Direct comparison estimates were derived by pooling the data from studies that compared the same intervention. Indirect comparison pooled estimates were derived by using the data amongst the studies, through a common comparator, using MetaXL software. Mean differences and Odds ratio at 95% confidence interval were used as the effect estimates, while inconsistencies were evaluated by H-statistics. GRADE working group approach was used to assess the quality of available evidence.

Fourteen studies were included. Results from 11 studies  on 471 patients (236-Digital; 235-conventional) were pooled for patient preference with 95% confidence interval. The Forest plot showed a pooled estimate of 31.23 [5.95, 163.87], showing a statistically significant number of patients favouring digital impressions. Results from 11 studies reported the time taken in 589 patients (278-digital; 311 conventional). The pooled estimate (2.72 [0.08, 5.32]) (95% confidence interval) showed a statistically significant increase in the time required to make digital impressions. The overall time taken in minutes for the interventions in the digital group in decreasing order were: LAVA Cos (8.14[3.64,12,26] (statistically significant); I tero (4.11[-1.02,9.24]; CEREC (0.34[-4.14,4.82]).

There was an overall preference for digital impressions, although the time required is longer. The factors related to the digital system, the operator and the patient were studied, with recommendations forming a basis for possible hardware and software upgrades of the digital systems that can produce significant improvement in the acceptance rate for both the patient and the clinician.