الفهرس 
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Abstract
Twenty one 3-units all ceramic veneer retained fixed dental prostheses were fabricated to replace a missing maxillary lateral incisor. The prostheses were divided into three groups. group “A” Seven all ceramic labial veneer retained fixed dental prosthesis (VRFPD) were fabricated. group “B” Seven all ceramic labial veneer retained fixed dental prosthesis (VRFPD) were fabricated with additional preparation that included shallow proximal groove at the pontic side. group “C” Seven all ceramic palatal veneer retained resin bonded fixed dental prosthesis that acted as control.
Preparations were done on teeth number 21, 23 of a typodont model for groups (A & C), fourteen epoxy resin models were duplicated for both groups. For group “B”, the modified labial design were added on a duplicated epoxy resin model and further reproduced in to seven epoxy resin models. All preparations were finished on a milling machine surveyor. All ceramic fixed dental prostheses were designed using a CAD software and constructed using heat pressed technique. Then the prostheses were bonded to their corresponding epoxy resin model using dual cure resin cement according to their manufacturer instructions.
Fracture resistance test were performed on all specimens after aging with thermocycling of 1000 cycles (5 -55oC) in distilled water and 150,000 mechanical fatigue cycles of 50 N load. Failure were examined through digital image to determine the mode of failure, and microscopically through SEM to locate origin of fracture and direction of crack propagation. Data were collected, tabulated and statistically analyzed through one way ANOVA, t-test and Chi square test.
The results of the study revealed that that the highest mean values were recorded by Palatal group (547.52±94.914 N) followed by Modified labial group (462.601±90.029 N) while the lowest mean values were recorded by Labial group (418.377±39.177 N). The difference between the groups was statistically non-significant as indicated by ANOVA test (F= 2.477, p value = 0.1121> 0.05)
The fracture site located for Labial group after chewing simulation occurred predominantly at the mesial connector and central retainer (3(42.857%) for both). For Modified labial group the fracture site located predominantly at pontic (4(57.143%)) and for Palatal group the fracture site located predominantly at mesial connector (4(57.143%)). The difference between groups was statistically significant as indicated by chi square test (chi= 274.25, p value = 0.0001< 0.05)
Within the limitations of this in-vitro study, the following could be concluded:
1. All designs performed the same. This is due to the fact that the fracture test measurement after thermo-mechanical aging exceeded the bite forces in the oral environment reported in the literature between 155-200N for the anterior zone. Nevertheless patient selection for a VRFDP is restricted to patient with normal occlusion with absence of any parafunctional habits where the pontic is placed out of occlusion in all centric and eccentric movements.
2. Palatal VRFDP remains the standard choice when resin bonded prosthesis is indicated.
3. Modified labial VRFDP showed a favorable failure mode (mid pontic), compared to the labial VRFDP showed as deflecting the failure from the connector site which is the weakest point in all ceramic bridge.
In this study expansion boundaries of minimally invasive dentistry through labial VRFDP has been probed, however, long-term studies and clinical follow-ups may be a prerequisite to accept this line of treatment in everyday dental practice. In addition, it represents a viable conservative treatment option till full growth is attained.