The Impact Of Different Root Canal Preparation Instrument For The Occurrence Of Micro Cracks On Root Tube Wall

Objective:To compare the impact of different taper, working speed,the number and position of cross section contacting whit root tube wall of the root canal preparation instrument for the occurrence of micro cracks on root tube wall.Methods:One hundred and eighty simple root whit straight root canal premolars were selected. The crowns were removed 2 mm above the proximal cementoenamel junction, Using autopolymer resin and alginate membrane materials for embedding, root crown exposure 2 mm, apex exposed to 3 mm. Twenty teeth were left unprepared and served as a negative control; another One hundred and sixty teeth were randomly divided into eight groups,20 cases in each group. The eight groups include stainless steel K-files group、Protaper Ni-Ti hand files group、Protaper Ni-Ti machine files group、ProtaperNext Ni-Ti machine files group 、Mtwo Ni-Ti machine files group 、S3 Ni-Ti machine files group、 TF Ni-Ti machine files group 、WaveOne Ni-Ti machine files group. The stainless steel K-files group prepare root canal up to number 25, The Protaper Ni-Ti hand files group and Protaper Ni-Ti machine files group prepare root canal up to size F2,The Protaper Next Ni-Ti machine files group prepare root canal up to size X2,The Mtwo Ni-Ti machine files group prepare root canal up to number #25/06, The S3 Ni-Ti machine files group prepare root canal up to size 2S,The TF Ni-Ti machine files group prepare root canal up to number #25/0.06, The WaveOne Ni-Ti machine files group prepare root canal up to primary reciprocating files(#25/0.06). After root canal preparation, all of the roots were sectioned perpendicular to the long axis at 3, 6, and 9mm from the apex, and the sections were then observed under a stereomicroscope. The absence of cracks was recorded, and the data were analyzed with a chi-square test. The significance level was set at P=0.05. Results:1. No cracks were observed in the stainless steel K-files group, The incidence rate of the ProTaper Ni-Ti hand files group micro cracks on root tube wall is10%,micro cracks produced in 6mm section from the apex; The incidence rate of the ProTaper Ni-Ti machine files group micro cracks on root tube wall is50%, micro cracks produced in 3mm、6mm section from the apex;The incidence rate of The Mtwo Ni-Ti machine files group micro cracks on root tube wall is30%,micro cracks produced in 3mm、6mm section from the apex; The incidence rate of The TF Ni-Ti machine files group micro cracks on root tube wall is20%,micro cracks produced in 3mm、6mm section from the apex; The incidence rate of The S3 Ni-Ti machine files group micro cracks on root tube wall is10%,micro cracks produced in 3mm section from the apex; The incidence rate of The ProtaperNext Ni-Ti machine files group micro cracks on root tube wall is5%,micro cracks produced in 3mm section from the apex; The incidence rate of The WaveOne Ni-Ti machine files group micro cracks on root tube wall respectively is 20%,micro cracks produced in 3mm、6mm section from the apex; there were significant differences among the incidence rate of above. No cracks were observed in The negative control group.2. The group A:No cracks were observed in the stainless steel K-files group, The incidence rate of the ProTaper Ni-Ti hand files group micro cracks on root tube wall is 10%, there were significant differences between The incidence rate of the stainless steel K-files group and the ProTaper Ni-Ti hand files group.3. The group B :The incidence rate of the ProTaper Ni-Ti hand files group micro cracks on root tube wall is 10%, The incidence rate of the ProTaper Ni-Ti machine files group micro cracks on root tube wall is 50%, there were significant differences between The incidence rate of the ProTaper Ni-Ti hand files group and the ProTaper Ni-Ti machine files group.4. The group C:The incidence rate of The Mtwo Ni-Ti machine files group micro cracks on root tube wall is 30%, The incidence rate of The S3 Ni-Ti machine files group micro cracks on root tube wall is 10%,The incidence rate of The TF Ni-Ti machine files group micro cracks on root tube wall is 20%, there were no significant differences among The incidence rate of The Mtwo Ni-Ti machine files group 、The S3 Ni-Ti machine files group and The TF Ni-Ti machine files group.5. The group D :The incidence rate of The ProtaperNext Ni-Ti machine files group micro cracks on root tube wall is 5%, The incidence rate of The Mtwo Ni-Ti machine files group micro cracks on root tube wall is 30%, there were significant differences between The incidence rate of The Protaper Next Ni-Ti machine files group and The Mtwo Ni-Ti machine files group.6. The group E :The incidence rate of the Protaper Ni-Ti machine files group micro cracks on root tube wall is 50%,The incidence rate of The WaveOne Ni-Ti machine files group micro cracks on root tube wall is 20%, there were significant differences between The incidence rate of the Protaper Ni-Ti machine files group and The WaveOne Ni-Ti machine files group. Conclusions:1. There were differences in occurrence of micro cracks on root tube wall among the Stainless steel k files group 、the ProTaper Ni-Ti hand file group、The Mtwo Ni-Ti machine files group、The TF Ni-Ti machine files group、The S3 Ni-Ti machine files group、The ProtaperNext Ni-Ti machine files group、The WaveOne Ni-Ti machine files group.2. There were differences in occurrence of micro cracks on root tube wall between the Stainless steel k files group and the ProTaper Ni-Ti hand file group. The taper of Ni-Ti root canal preparation instrument has correlation with the occurrence of micro cracks on root tube wall,The lager of taper,the greater possibility of the occurrence of micro cracks on root tube wall.3. There were differences in occurrence of micro cracks on root tube wall between the ProTaper Ni-Ti hand files group and the ProTaper Ni-Ti machine files group, The work speed of Ni-Ti root canal preparation instrument has correlation with the occurrence of micro cracks on root tube wall,The lager of work speed,the greater possibility of the occurrence of micro cracks on root tube wall.4. The number of rotary Ni-Ti root canal preparation equipment contacting with root canal has correlation with the occurrence of micro cracks on root tube wall.But there were no differences in occurrence of micro cracks on root tube wall among The Mtwo Ni-Ti machine files group 、The S3 Ni-Ti machine files group and The TF Ni-Ti machine files group. When the points of the Ni-Ti root canal preparation Instru-ment cross section contacting whit root tube wall is 2,3,4, there were no significant differences in occurrence of micro cracks on root tube wall.5. There were differences in occurrence of micro cracks on root tube wall between The Protaper Next Ni-Ti machine files group and The Mtwo Ni-Ti machine files group. the position of the Ni-Ti root canal preparation instrument cross section contacting whit root tube wall has correlation with the occurrence of micro cracks on root tube wall.6. There were differences in occurrence of micro cracks on root tube wall between the Protaper Ni-Ti machine files group and The WaveOne Ni-Ti machine files group. The Ni-Ti root canal preparation instrument working in the form of rotary motion has a greater possibility of the occurrence of micro cracks on root tube wall than in the form of reciprocating motion of the occurrence of micro cracks on root tube wall.