RESUMO
Objective: To examine the effect, on the depth of mandibular alveolo-buccal vestibule, of mouth remaining open or closed at the impression recording stage
Methodology: In the first place, in each of the 5 dentate subjects, with their teeth in light occlusion and no biting force, 5 recordings of the alveolo-buccal vestibule were obtained by injecting a cartridge type VPS impression material [Exahiflex, GC, Corp, Tokyo, Japan]. Impressions were made in controlled manner with the subjects performing a standard lip protrusion and retrusion exercise three time to shape the material accordingly. The procedure was then repeated in the same manner except the subjects keeping their opposing teeth apart by 10mm using a custom made bite-block fitting the central incisor teeth. For each subject, a mandibular arch stone-cast was also prepared from an alginate impression [Aroma Fine Mixer Type, GC, Corp, Tokyo, Japan]. The vestibular impressions were modified by removing the portion above the gum margins so as to leave the occlusal surfaces and the coronal third of teeth uncovered when adapted to their stone-casts. Subsequently, each of the impression on its cast was carefully sectioned between reference lines drawn on the cast to connect selected points on the occlusal surfaces of second molar [M2], first molar [Ml], second premolar [P2] and first premolar [PI] teeth with a corresponding point at the peripheral land around the sulcus. In all cases, these lines crossed the deepest part of the gum margin around the teeth and were made parallel to each other. After cutting, the mesial face of each impression section was scanned with Twain 32, Epson Twain Pro Version 1.5, at 400 resolution against a mm ruler. Using the Photo-Editor Software [Microsoft Co, USA] in an IBM compatible computer, the depth of the alveolo-buccal vestibule at the selected locations was determined between the deepest part of the gum margin and the peripheral-most outline of the impression section representing the sulcus. The data obtained were analyzed statistically, for significance of the within and between subjects variations, using student t-test and paired t-test respectively
Results: In the results, the depth of the alveolo-buccal vestibule was significantly less with the close-mouth method than that with the open-mouth method. In general, a depth reduction, ranging between 11.5 to 18.6%, was observed with the highest amounts of reduction between the first molar and second molar [M2-M1] region
Conclusions: Decreased vestibulor depth will be recorded when using an open-mouth impression technique