الفهرس 
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Abstract
The purpose of this study was to determine the effect of different surface pretreatments on the shear bond strength of two glass-ionomer cements to two different tooth substrates (enamel and dentin) at two different time elapsed between cement application and shear bond strength testing.
Assesement of failure mode followed shear bond strength testing was done using a modified ARI and finally a relation was done between the amount of cement remained, mode of failure, the effect of time elapsed and calcium content of tooth substrates after different surface pretreatments with shear bond strength of the two glass-ionomer cements used.
A total of 360 intact human molar teeth were used in this study. A 320 of those previously selected teeth were randomly used for shear bond strength testing, while the remaining 40 teeth were used for calcium content measurements.
For shear bond strength testing, the 320 teeth were divided into two main groups (of 160 teeth each) according to the type of restorative material used, namely M1 for group of teeth received conventional glass-ionomer cements, M2 for group of teeth received resin-modified glass-ionomer cements. Each of the previously mentioned group was subdivided into two sub-groups (of 80 teeth each) according to tooth substrate, A1 for enamel and A2 for dentin. Each of the two subgroups was further divided into four divisions (20 each), representing different surface pretreatments, normal saline (T1), 10% polyacrylic acid (T2), 35% phosphoric acid (T3) and non-rinse conditioner (T4).
After that, each of the four divisions was subdivided into two subdivisions (10 each) according to the time elapsed between cement application and shear bond strength testing namely S1 (10 minutes after material application) and S2 ( 48 hours after material application).
Assessment of shear bond strength was done using a universal testing machine. An occlusogingival load was then applied to the bonded restoration producing a shear force at the restoration-tooth interface until failure occurred.
After the shear bond strength test was completed, the debonded surfaces for each group were evaluated in a random sequence for the amount of cement remained on the surface using stereomicroscope under a magnification of 20X. The images were subjected to image analysis and then modified ARI were categorized as 0 to 5 scores.
The results revealed that the different surface pretreatments significantly affects the shear bond strength of the two glass-ionomer cements bonded to enamel as well as dentin at the different tested time elapsed. Also, there was significant difference for the effect of the material, different time elapsed and tooth substrates on the shear bond strength.
ARI results partially proved the results obtained for shear bond strength testing especially for the effect of different surface pretreatments. For calcium content measurements, a total of 40 of the previously selected teeth were divided into two main groups (of 20 teeth each) according to tooth substrates used (enamel and dentin). Each group was subdivided into four sub-groups (of 5 teeth each) according to the type of surface pretreatment used.
Calcium content measurements were done using energy dispersive X-ray analysis (EDAX) before and after surface pretreatment for each sample.
Calcium content measurement results showed that the highest mean difference in calcium content value was recorded by the phosphoric acid surface pretreatment for both enamel and dentin, while the lowest value was recorded by normal saline.
Under the circumstances of this study, the following conclusions were drawn:
1- Surface pretreatment improved shear bond strength for both types of glass-ionomer cements bonded to enamel and dentin.
2- ARI is not the parameter of choice for the confirmation of the shear bond strength results of conventional or resin-modified glass-ionomer cements to enamel and dentin especially when evaluating the effect of time elapsed, the different materials and the tooth substrates.
3- Mixed adhesive cohesive failure was the predominant mode of failure for both types of glass-ionomer cements bonded to enamel and dentin after different surface pretreatments..
4- The increasing in elapsed times before shear bond strength testing increased the shear bond strength of the two glass-ionomer cements bonded to enamel and dentin substrates.
5- The different surface pretreatments decreased the calcium content of both enamel and dentin.
Under the circumstances of this study, the followings could be recommended:
1- Phosphoric acid (35%) is the pretreatment of choice for enamel and dentin when resin-modified glass-ionomer cements are to be used.
2- The tested time elapsed of 10 minutes for shear bond strength measurement of glass-ionomer cements is a valuable method to determine the immediate shear bond strength to tooth substrates when finishing and polishing procedures are to be performed or when occlusal adjustments must be made.
3- Studying the change in calcium content of tooth substrates after different surface pretreatments was not a valuable method to determine the shear bond strength of glass ionomer cements bonded to tooth substrates.
4- Further studies using SEM, TEM and FEESEM sould be done to evaluate the nature of bonding as well as the characters of the interface of glass-ionomer cements bonded to different tooth substrates.