Replica technique remain most commonly used technique for
measuring the marginal fit in the medical literature, the silicone
rubber addition is considered most accurate and least changing
dimensions.
Aim of study to compare the accuracy and simpl
icity of traditional
replica technique and modified replica technique to measure
marginal fit of zirconium posterior bridges manufactured by
CAD\CAM. After removal of first lower molar from TYPODENT
(Frasco, Tettnang, Germany), the second lower molar and premolar
neighboring were prepared commensurate with full ceramic
restoration. Final impression of this bridge was taken by silicone
rubber addition (Zhermack Elite HD+) with the aid of custom tray.
The impression was condensed with amalgam to make the main
metal cast. Fifteen custom acrylic resin trays were used for fabricate
fifteen impressions of main metal cast that were used for fabricate
15 zirconium bridges by CAD\CAM technique According to the
manufacturer's instructions. Tow rubber thicknesses were taken for
the marginal fit of each bridge over its cast gypsum by used light
silicone rubber addition. Then the first rubber thickness was treated
by developed replica technique to form the Group (A) of the study
and the second rubber thickness was treated by replica technique to
form the group (B) of the study. Depending on T-test, no significant
difference between two techniques was detected. We conclude that
developed replica technique reliable technique to study and measure the marginal gap of bridge and crown, and it is statistically more accurate than the traditional technique.