The buccal and lingual extents of the outlines of the two neutral zones were measured for each segment thrice by three observers.
In the mandibular anterior segment on right and left buccal sides both neutral zones coincided in almost equal numbers amongst previous denture wearers and non denture wearers.
The objective of the study was to evaluate the effect of previous denture wearing on the morphology of two neutral zones recorded with a similar material.
Considering the limitations of the study increased sample size may give a definitive result about the influence of previous dentures over existing neutral zones. It is suggested that further research in the field with a dynamic imaging record may be helpful in observing the influence of musculature with or without dentures.
The influence of previous denture on the comparative shapes of phonetic and swallowing neutral zone may not be prominent.
Key Words: Edentulous Denture Neutral zone Phonetics Muscles.
Neutral zone outlines the zone of minimal conflict where the forces of tongue and cheek musculature can be neutralized during static and dynamic conditions.
Stresses [[sigma].sub.R] in straight pipe  of normal direction of outer layer is 1.35 times less than in pipe elbow in neutral zone outer layer.
In the neutral zone middle layer stress is 2.85 times more than in compression zone inner layer.
Stresses [[sigma].sub.R] in straight pipe  of tangential direction of outer layer is 1.18 times less than in pipe elbow in neutral zone outer layer.