Basic Research Of The Piezoelectricity For The Electret Of Modified Denture Base Resins

Reduction of residual ridges(RRR) occures after extraction of teeth which leads to gradual absorption of alveolar bone and difficulty in prosthesis of the denture.Bone is the first identifed bioelectret. Electrical fields aid bone healing at the areas of fracture,which inhance the growth rate of bone.The study aims to synthesize a new denture base material to complemete the electret of teeth-extracted alveolar bone and stimulate bone growth towards the denture base when masticating and inhibit or rimit the RRR.The experiment investigated the piezoelectic property of the modified polymethylmethacrylate(PMMA) and the composite of PMMA and barium titanate(BaTiO₃, BT) in different polarizing conditions. Favorable polarizing conditions were identified which established the foundation for further research.The study was divided into two parts:Part one: The study of piezoelectricity of denture base resin electret(PMMA).Round plate samples was made by heat curing . Surficial potential and piezoelectric constant d₃3 was measured after thermal polarization.The results are under present polarizing conditions, no piezoelectricity revealed in the samples..Part two: The study of polarizing temperature and trend of d₃3 attenuation for the composite of PMMA/BT.The best BT volume and polarizing temperature was selected according toorthogonal experimental design in which the field intensity was fixed at 12kV/mm, the polarizing time was 25 mins,BT volume ranged from 80% to 90% with a span of 2.5% and polarizing temperature ranged from 90°C to 130°C with a span of 10°C.Methods of manufacturing, polarizing and measuring samples were same as part one. Thepiezoelectric constant was measured again at 1 â– > 3> 7> 12-. 20-. 30 days after polarization.The results are as follows:1) The best polaring conditions of PMMA/BT are: BT volum equals 87.5% and the polarizing temperature is 120°C.2) The trend of d33 attenuation in each group is similar,which is slightly quicker in the first few days and then arrives at a stabilization nearly after a week.3) Curve estimation of the dr> attenuation in the composite of PMMA/BT with BT volume equaling 87.5% and polarizing temperature eaqualing 120°C was made using SPSS 11.5 for windows.The best curve equation was Y=8.2625— 0.4511X+0.01X2 (X represented time whose unit was day,Y represented piezoelectric constant dj3 whose unit was 10"6C/N).To summarize the preceding work, the experiment investigated the piezoelectic property of the modified PMMA and the composite of PMMA /BT in different polarizing conditions. Favorable polarizing conditions were identified which established the foundation for further research.