Tri-channel platform evaluation by computerized microtomography and its mechanical properties after insertion torque, fatigue and fracture

Author(s)

Renata Costa de Morais

• Document type: Doctoral Thesis
• Press: Ribeirão Preto.
• Institution: Universidade de São Paulo (USP). Faculdade de Odontologia de Ribeirão Preto (PCARP/BC)
• Defense date: 2018-10-26

Examining board members

Ricardo Faria Ribeiro; Gelson Luiz Adabo; Rossana Pereira de Almeida; Carlos José Soares

• Advisor: Ricardo Faria Ribeiro; Renata Cristina Silveira Rodrigues Ferracioli

Abstract

To investigate the physical-mechanical properties of Dérigs tri-channel implants, regarding the 0.25 mm addition in 3.75 NP implant structure (in relation to 3.5 NP as control) and the influence of platform switching (in equal diameters of 4.3 mm and different platforms - Narrow and Regular), this study related the resistance to insertion torque (microgap evaluation between implant and abutment - bi and tridimensional measurements), computerized microtomography (CT); resistance to fracture and fatigue. For the resistance to insertion torque, the samples were randomly divided into four subgroups (n=10), according to the torque applied: GT45: 45 N.cm; GT80: 80 N.cm; GT120: 120 N.cm; GT150: 150 N.cm. The implant/abutment/screw assemblies were taken to bi and tridimensional deformation analyzes in CT. For the fracture strength test, the implant/abutment assemblies were taken to the universal test machine until failure and then to optical and scanning electron microscopes. For the fracture resistance, the sets (n=12) were subjected to a cyclic test (5 Hz, 5° - 55° C, loads in 80, 120, 160, 200, 240, 280 and 320 N, maximum of 2x104 cycles) and loaded to failure (or maximum of 14x104 cycles) (Life Table Survival Analysis). For mechanical aging, the sets (n=12) were submitted to 106 cycles (2 Hz, 120 N, 5º - 55º C) and, again, to microscopic analysis. After statistical analysis (2-way ANOVA, Bonferroni, p<0.05), there were statistical differences (p<0.05) in all comparisons for the bi and three-dimensional deformation percentages of the insertion torques in CT, except between 4.3 NP x 4.3 RP (45N). The microtomographies evidenced microgaps in new sets and a qualitative increase of the same sets in diameters and smaller platforms. The linear comparison with new sets showed significant differences (p<0.05) in 3.5 NP and 3.75 NP (all torques) and 4.3 NP (120 and 150 N.cm). As for the fracture resistance test (1-way ANOVA, Tukey B, p<0.05), 4.3NP had a higher maximum deformation force (p<0.05) than 3.75 NP and 3.5NP (p=0.004), but there was no significant differences between 4.3 RP, 3.5 NP and 3.75 NP (p>0.05). Regarding the fatigue strength tests, the mechanical aging led to the screw loosening of all groups analyzed, and by the exception of 3.75 NP, there were significant differences (p<0.05) between initial and final torque applied; for the accelerated fatigue, both groups of 4.3 mm (NP and RP) survived at the end of the test, with fractures in all 3.5 NP samples. Finally, regarding the survival rate, there was a significant difference (p<0.05) between 3.5 NP and 3.75 NP, with a 92% rate for this last one. It could be concluded that the diameter 4.3 mm is stronger than 3.5 mm; 4.3 NP presented higher fracture resistance; the mechanical aging leads to screw loosening; the accelerated mechanical fatigue has influence in smaller diameters and the methodology in CT is valid for bi and three-dimensional analyzes (AU)

• FAPESP's process: 15/13199-5 - "Evaluation of the effect of diameter on the insertion torque and resistance to fracture of tri-channel implants".
• Grantee: Renata Costa de Morais
• Support Opportunities: Scholarships in Brazil - Doctorate