The Measurement Of Properties Of Supra-Gingival Dental Calculus

Objective:we have developed robot system for periodontal scaling based on the force feedback.To cater for the clinical need,the mechanical properties of supra-gingival dental calculus needs to be measured to modify the current force feedback system.In this paper,the interface shear strength between dental calculus and tooth were evaluated and elastic modulus and hardness of supra-gingival dental calculus were measured the to provide basis for force feedback of dental roboticsMethods:(1)Specimens of supra-gingival dental calculus were obtained from 5 patients with periodontal disease.The cross-section view,4 mm × 10 mm × 10 mm in size was prepared in a dental base resin mount and polished.Nanoindentation method was used to survey elastic modulus and hardness of supra-gingival calculus.(2)Specimens of teeth with supra-gingival dental calculus were obtained from patients with periodontal disease.The sample was fixed to the glass plane.The interface shear strength between dental calculus and tooth was evaluated by using a digital push pull tester.Results:(1)Among the 10 specimens,a total of 100 indentation curves were harvested and 95 can be calculated(excluding error and unable fitted curves).(2)The elastic modulus is ranging from 7.27 GPa to 53.60GPa with the average of 25.22 GPa;the hardness is ranging from 0.11 GPa to 2.25 GPa and the average is 0.67 GPa.(3)Among the 10 specimens,10 sets of data about the interface shear strength were obtained.(4)Interface shear strength between dental calculus and tooth is ranging from 6.4 N to 45.5 N with the average of 27.38 N.Conclusion(1)Distinct variances presented in different dental calculus and tooth of a particular individual and also among different cases.(2)Using a nano-indentor to measure elastic modulus and hardness of supra-gingival calculus and using digital push pull tester to evaluate interface shear strength between dental calculus and tooth is practicable.(3)Dental base resin is a recommendable method which can fix tooth and dental calculus.(4)In the future experiment,a larger sample size is needed to ensure the homogeneity of the sample.