Evaluation of pre-alginate impression preparation methods in the surface accuracy of dental cast

The aim of this study was to investigate the influence of pre-preparation technique (finger smearing and saliva ejection) of alginate impressions on the quality and accuracy of dental casts.

Twenty mandibular impressions from 20 patients (10 males, 10 females) with an age range of 20-40 years were recorded using stock trays. A standard impression and pre-preparation technique for alginate were employed. This included removal of saliva with saliva ejector, smearing of alginate on occlusal surfaces of posterior teeth and smoothing of the material in the tray (Group-1: Test) and no drying and smearing or smoothing of the material prior to impression (Group-2: Control). Standardized disinfection, storage, pouring and removal from die stone techniques were used for all samples. Surface defects (nodules/blebs) on the occlusal surface of casts as examined with digital microscope, were classified according to their sizes and surface area into; Type-A (<500); Type-B (>500 <100); Type-C (>1000) in micrometers (μm). Data was tabulated and analyzed by SPSS using Anova and Tukey's test.

Defects were significantly higher (p < 0.01) in samples in Group-2 (1225.51 ± 823.44 μm) as compared to Group-1 (783.68 ± 501.41 μm). All types of defects (Types A, B and C) were significantly higher in samples from Group-2 as compared to Group-1.

Use of pre-preparation technique of finger smearing and saliva ejector prior to alginate impressions resulted in significant reduction of surface nodules/blebs and enhanced the quality and accuracy of fabricated casts. Therefore, the use of saliva ejector, finger smearing on the occlusal surface of teeth and smoothening of alginate impression, immediately prior to intra-oral placement is clinically recommended.