الفهرس 
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Abstract
The current study is an in vitro study to investigate water sorption and leakage behavior in conventionally heat cured acrylic hollowed obturator and thermoplastic hollowed obturator. A model was constructed from a properly extended final impression of patient with class I maxillary defect.
The final impression was poured with extra hard stone and the cast was duplicated by silicone duplicating material twenty times.
Two materials were tested; conventionally heat cured acrylic resin and thermoplastic resin. 10 casts (group 1) were used to construct acrylic obturators. Another 10 casts (group 2) were used to construct thermoplastic resin obturators.
The lid part of obturators was unified using specially constructed metallic lid which was used in construction of all lids.
The obturators were subjected to desiccation cycle and were weighed then were put in distilled water for seven days and were weighed again . Then the obturators were desiccated again.
Separate lid was drilled in the center and was weighed. Same hole was made in the center of lid in the obturator to help in detection of leakage.
Then the water sorption was calculated using equation:
• Absorption %=(W2-W3) g / (W1) g x 100
• where
• W1= initial weight
• W2=weight after absorption
• W3=final weight after desiccation
Data were collected and tabulated and tested for statistically significance.
The results showed that:
The water sorption mean value of control group was 3.44±0.28 and mean value of test group was 1.35±0.21. Acrylic group showed statistically significantly higher mean water sorption than Thermoplastic group.
The leakage mean value of control group was (0.0026) and mean value of test group was (0.0355), So Thermoplastic group showed statistically significantly higher leakage values than that of acrylic group.