Comparison Of Effects On Root Surface From Different Angles Of Magnetostrictive Working Tip And Mechanical Polishing Applied On Human Periodontities Teeth

Objective:To evaluate the effects of different working angles of magnetostrictive working tip and mechanical polishing methods on the root surface roughness and surface morphology of periodontitis,in order to provide experimental basis for clinical treatment of periodontitis.Methods:The first part: 60 root surfaces of 10 isolated teeth(Incisor/premolars)with severe periodontitis were randomly divided into 6 groups according to different types of treatment: G1(Hand scaling),G2(Magnetostrictive work tip-0 °),G3(Magnetostrictive working tip-15 °),G4(Magnetostrictive working tip-30 °),G5(Magnetostrictive working tip-45 °),G6(Magnetostrictive working tip-60 °),Scale the root surface of the teeth until the calculus is removed absolutely.After scaling,measuring the roughness of root,scanning electron microscope and tissue section were used to observe the surface of the root.The second part: another 50 proximal and distal root surfaces of 25 isolated teeth(incisor/premolars)which could not be remained duing to severe periodontitis were scaled by manual curettage.Then,the tooth were randomly divided into group A(Silicon particle polishing),group B(Rubber cup polishing),group C(Super-snap disc polishing)and group D(Glycine aie polishing).After scaling,measuring the roughness of root,and the root surface was observed by scanning electron microscope and tissue section.Result:1.Manual curettage will produce the minimum roughness on the root surface of periodontitis(Ra: 1.73 ±0.38 μ m).When the magnetostrictive working tip angle is 0 °,it has the least influence on the root surface roughness comparing with other angles(Ra value: 1.83 ±0.53 μ m).Compared with the manual curettage group,the difference is not significant(P<0.05).2.The maximum roughness of the root surface will be produced when the magnetostrictive work tip angle is 45 °(Ra value: 4.93 ±1.20 μ m),and the differ ence is significant between the groups(P ≤ 0.05).3.With the use of scanning electron microscope,it was found that there were almost no residual dental calculi on the root surface when the magnetostrictive working tip angle was 0 °,and the cementum was preserved completely,whichshowed the existence of "fish scale" cementum.When the angle of the magnetostrictive working tip increases to 15 °,the original structure of the root surface disappears,and the existence of small cracks and film debris can be seen,Small cracks,pits and residual debris also can be seen when the angle of the magnetostrictive working tip is 30 ° or 60 °,but the pits will be more obvious when the working tip is 60 °.When the angle of working tip increases to 45 °,the cementum is fall off partly and the surface will become rougher.4.By tissue section and HE staining,showing that cementum exfoliation will occurre when the working tip increased to 45 °.When working tip increases to60 °,the cementum on the root surface is worn seriously.5.Compared with the rubber cup polishing technology,silicon particle polishing will make the root surface more smooth,but tissue sections and HE staining show that silicon particles may increase the root’s wearness.6.The traditional polishing methods(rubber cup and silicon particle polishing)are difficult to achieve the ideal roughness of the root surface.The new type of polishing disc(Super-snap polishing disc)can achieve the smoothest root surface to less than 0.2 μ m,and there is significant difference between the each oher group.The results of scanning electron microscope showed that the root surface of the polishing disc group was smooth withour wear caused by polishing.7.Glycine air polising will increase the root surface roughness(Ra’: 3.73 ±0.32 μ m),the difference is significant.The scanning electron microscope showed that the root surface was covered with tiny tips,which was related to the increase of its roughness.Conclusion:1.When using the magnetostrictive ultrasonic scaler,the working tip should be kept parallel to the root surface as far as possible in order to reduce the influence on the root surface,especially to avoid the excessive angle between the working tip and the root surface so as to reduce the damage to the root as much as possible.2.Silicon particle polishing will increase the wear of root surface,whetherit is suitable for root surface polishing needs further study.3.Traditional mechanical polishing is difficult to make the root surface completely smooth.The use of new polishing discs can reduce the roughness to less than 0.2μm,so that the root surface can reach the ideal roughness.4.Although glycine air polising is helpful to the removal of plaque and pigment,it will lead to the increasing of root surface roughness,so the indication should be treated strictly.