Basic Informations

C.V

Name: Mohamed mostafa radwan
address: 5 a bassem elkateb - messaha
Email: m.mostafa@dent.bsu.edu.eg

Master Title

The Effect of Different Superstructure Materials on the Stress Distribution of Implant Supported Restorations.

Master Abstract

Successful long-term results of dental implants have led to an increase in their usage in many clinical situations. Since the introduction of osseo-integrated implants for the rehabilitation of the partially edentulous patient, a tremendous awareness and subsequent demand have arisen in the field resulting in implant supported fixed prosthesis being widely accepted as an alternative to conventional removable prosthesis. However, some clinical studies have reported variable rates of failure. Biomechanical factors and stress distribution around implant supported FPDs are some of the prime factors leading to failure of implant supported FPDs. The current study evaluated the effect of different superstructure materials mainly all ceramic, ceramo-metallic and temporary resin bridge on the stress distribution of implant supported restorations .The relative effect of the three different materials were compared using mechanical loading test together with strain gauge analysis. The following materials were used in the current study: 1. Zimmer Dental Implant fixture. 2. Zimmer Dental Implant abutment. 3. Vita In-Ceram YZ blocks. 4. Vita VM9 veneering material. 5. Base Metal alloy ( Ni-Cr alloy). 6. Vita VMK95 3-D master veneering material. 7. Voco Structure Premium Temporary resin bridge. 8. Provicol C temporary cement. 9. Epoxy resin model. 10. Electrical resistance strain gauges. Six implants were fixed in three anatomically correct epoxy resin models in order to stimulate restoring posterior missing second premolar, first molar and second molar. The six implant abutments were fixed in place over their fixture and the fifteen superstruchere were fabricated as follow: a. Five All ceramic FPDs . b. Five Ceramo-metallic FPDs . c. Five Temporary resin FPDs . Strain gauges were bonded on the buccal, lingual and distal for the anterior abutment (second premolar) the buccal, lingual and mesial for the posterior abutment (second molar).The remaining strain gauge (seventh) was placed on the center of the buccal surface of pontic. Zirconia core all ceramic FPDs were milled using Cerec Inlab system and veneered using (Vita VM9) veneering material. Metallic core of the ceramo metallic FPDs were cast from Ni-Cr alloy and veneered with the (Vita VMK95) veneering material. Standardization between zirconia core and the metallic core was achieved by the use of silicone index. A second silicone index was also used for the standardization of the thickness of the ceramic veneering material of both zirconia core and the metallic core. Using a third silicone index of the finished veneered FPD was used to fabricate temporary composite resin bridges using Voco Structure Premium temporary resin bridge material. For the mechanical testing: All strain gauges were set to zero the FPDs were temporary cemented using Provicol C temporary cement over their corresponding abutments. At the beginning of the cementing procedure, a defined force of 200 N was applied to the pontic by a universal testing machine. After 30 seconds, the force was reduced to 100 N and applied for 3 minutes. Then the force was removed and the cement was allowed to set for another 2 minutes. The final strain values were recorded after 6 minutes of cement seating. The philosophy of this study was based on preventing micromotion of implants and on fair distribution of the functional loads within a rigid suprastructure for the success of the implant-supported restoration. Results showed that none of the FPDs exhibited a true passive fit with the strain gauges showing zero microstrain. Regarding the stress induced within the superstructure restoration itself, the temporary resin bridge recorded the highest microstrains .Whereas regarding the stress induced within the supporting structures, the temporary resin bridge recorded least microstrain in the supporting structures.

PHD Title

The effect of different abutment materials on the fracture resistance and stress distribution of implant supported fixed partial denture

PHD Abstract

Successful long-term results of dental implants have led to an increase in their usage in many clinical situations. Since the introduction of osseo-integrated implants for the rehabilitation of the partially edentulous patient, a tremendous awareness and subsequent demand have arisen in the field resulting in implant supported fixed prosthesis being widely accepted as an alternative to conventional removable prosthesis. However, some clinical studies have reported variable rates of failure. Biomechanical factors and stress distribution around implant supported FPDs are some of the prime factors leading to failure of implant supported FPDs. The current study evaluated the effect of different abutment materials titanium and zirconia with different bone density (D2 & D3) on the stress distribution and fracture resistance of implant supported FPD. The relative effect of the two different abutment materials were compared using mechanical loading test together with strain gauge analysis. The following materials were used in the current study: 1. Zimmer Dental Implant fixture. 2. Zimmer Dental Implant abutment.(titanium & zirconia) 3. inCoris TZI medi block 4. Provicol C temporary cement. 5. Unsaturated Epoxy resin (cancellous bone). 6. Saturated epoxy resin (compact bone). 7. Electrical resistance strain gauges. Eight implants were fixed in four anatomically correct D2 and D3 bone density models in order to stimulate restoring posterior missing second premolar, first molar and second molar. The eight implant abutments were fixed in place over their fixture and the twenty Full anatomical zirconia FPD were fabricated as follow: 1. D2 bone density with titanium abutment 2. D2 bone density with zirconia abutment 3. D3 bone density with titanium abutment 4. D3 bone density with zirconia abutment Strain gauges were bonded on the buccal, lingual , mesial and distal for the both implant abutment ( 2nd premolar & 2nd molar ) Full anatomical Zirconia FPDs were milled using Cerec Inlab system. A cementing device is used to cement the FPD to its corresponding abutment using temporary cement. For the mechanical testing: All strain gauges were set to zero the FPDs were temporary cemented using Provicol C temporary cement over their corresponding abutments. At the beginning of the cementing procedure, a defined force of 200 N was applied to the pontic by a universal testing machine. After 30 seconds, the force was reduced to 100 N and applied for 3 minutes. Then the force was removed and the cement was allowed to set for another 2 minutes. The final strain values were recorded after 6 minutes of cement seating. The philosophy of this study was based on preventing micromotion of implants / abutment and on fair distribution of the functional loads within a rigid suprastructure for the success of the implant-supported restoration. Results showed that none of the abutment materials exhibited a true passive fit with the strain gauges showing zero microstrain. Regarding the stress induced within D2 & D3 bone density zirconia abutment show higher stress distribution than titanium abutment. Whereas regarding fracture resistance zirconia abutment show higher resistance to fracture than titanium Within the limitations of this study, the following conclusions were drawn as follows: 1- Different abutment materials affect the stress pattern induced around dental implants. 2- Zirconia abutments had a favorable effect on the stress distribution when compared with titanium abutments regarding different bone density ( D2 & D3 ). 3- Fracture resistance of the zirconia and titanium abutments might be affected by the strength properties and modulus of elasticity of the material. 4- Both Zirconia and titanium abutments could withstand the functional loads developed during physiologic chewing in the molar area. Consequently, zirconia abutments could be a valid alternative to titanium abutments in high forces demanding areas.