| ObjectiveCurrently,when preparing root canal with rotary nickel titanium flies,there was no steps of flushing the rotary nickel titanium flies with liquids.Early experiment has proved that flushing the rotary nickel titanium flies with water during preparing root canal can prepare more number of root canals and improve efficiency.And this study will further research the influence of " flushing the file with different kinds of fluids outside the root canal during root canal preparation on the diameter of laser-labled sites and fracture length,exploring to rotate nickel-titanium instrument prepared root canal irrigation condition.MethodsThis experiment brought in 100 rotating nickel titanium files of ProTaper Universal(PTU)F1,and Fiber laser marked flies from the needle tip 6 mm,9 mm,12 mm,15 mm line,according to the different conditions of liquid were randomly divided into 5 groups,There were 20 in each groupeach group of 20,respectively,the control group,0.2% chlorhexidine group,1% sodium hypochlorite,and 5% sodium hypochlorite group.Each group of PTU F1 file perparing root canals on the standardization of transparent resin bending module with a constant stress,and immediately lifting out of file when reaching a fixed torque,at the same time flushing the file with different kinds of fluids outside the root canal during root canal preparation.We recorded diameter of the difererent Laser-labeled sites,and the fracture length each group before or after PTU F1 broke,observing the location of the broken files in root canals.Results 1.The change of different diameter of the Laser-labeled sites:Under the different conditions of liquid preparation,from the tops of file 6 mm diameter respectively before and after the broken: distilled water group(0.5075±0.0117 and 0.0117±0.0138)mm and normal saline group(0.4936±0.0082 and 0.0082±0.0115)mm,0.2% chlorhexidine acetate(0.4825±0.0103 and 0.0103±0.0141)mm,1% sodium hypochlorite group(0.4958±0.0107 and 0.0107 ± 0.0134)mm,5% sodium hypochlorite group(0.4831 ± 0.0137 and 0.4935±0.0145)mm.The first four groups before and after the break were no significant change(P>0.05)in diameter,5% sodium hypochlorite group diameter changes before and after the broken had statistical difference(P<0.05).Under the different conditions of liquid preparation,from the file pointed to 9 mm in diameter respectively before and after the broken: distilled water group(0.6517±0.0146 and 0.0146±0.0143)mm and normal saline group(0.6336±0.0167 and 0.0167±0.0147)mm,0.2% chlorhexidine acetate(0.6244±0.0179 and 0.0179±0.0157)mm,1% sodium hypochlorite group(0.6314±0.0157 and 0.0157 ± 0.0140)mm,5% sodium hypochlorite group(0.6337 ± 0.0167 and 0.0167±0.0156)mm.Diameter before and after the equipment brokenof five group were no significant(P > 0.05).Under the different conditions of liquid preparation,from the tops of file 12 mm diameter respectively before and after the broken: distilled water group(0.7564±0.0174 and 0.0174±0.0211)mm and normal saline group(0.7560±0.0200 and 0.0200±0.0193)mm,0.2% chlorhexidine acetate(0.7568±0.0153 and 0.0153±0.0161)mm,1% sodium hypochlorite group(0.7523±0.0141 and 0.0141 ± 0.0180)mm,5% sodium hypochlorite group(0.7544 ± 0.0181 and 0.0181±0.0171)mm.Diameter before and after the equipment broken of five group were no significant(P > 0.05).Under the different conditions of liquid preparation,from the tops of file 15 mm diameter respectively before and after the broken: distilled water group(0.9124±0.0206 and 0.0206±0.0149)mm and normal saline group(0.9209±0.0128 and 0.0128±0.0193)mm,0.2% chlorhexidine acetate(0.9138±0.0208 and 0.0208±0.0248)mm,1% sodium hypochlorite group(0.9129±0.0244 and 0.0244 ± 0.0233)mm,5% sodium hypochlorite group(0.9006 ± 0.0262 and 0.0262±0.0217)mm.Diameter before and after the equipment broken of five group were no significant(P > 0.05).2.Fracture length and the location of the broken files in root canals:The actual fracture length of five groups of preparation method respectively as follows: distilled water group(2.5260±0.4429)mm;0.9% normal saline group(2.6006±0.5452)mm;0.2% chlorhexidine set group(2.6216±0.5541)mm;1% sodium hypochlorite group(2.8875 ± 0.7429)mm;5% sodium hypochlorite group(2.8012±0.9822)mm.5 groups broken preparation method of the relative length respectively as follows: distilled water group(2.5358±0.4157)mm;0.9% normal saline group(2.5052 ± 0.5905)mm;0.2% chlorhexidine set group(2.5908±0.5494)mm;1% sodium hypochlorite group(2.9040±0.7286)mm;5% sodium hypochlorite group(2.5884±1.0555)mm.The actual fracture lengths were no difference between 5 groups(P > 0.05),the relative lengths of broken were no difference between 5 groups(P > 0.05),the first four groups of actual fracture lengths and relative lengths of broken were no difference(P>0.05),5% sodium hypochlorite group had statistical differences between the actual fracture length and relative fracture length(P < 0.05).This study found that groups of PTU F1 file in prepared root canal module straight road(8-18 mm from apical foramen)when no the phenomenon of break off,all instrument fracture occurred in the curved segment(0-8 mm from apical foramen).In the first four groups the area of 0-1.5 mm from apical foramen broken instrument has the highest frequency,followed by 1.5-3 mm area,root hole distance,the more the greater the frequency of broken occur near region;But for 5% sodium hypochlorite group,from the root hole area break the highest frequency of 3-5.5 mm,and in the 0-1.5 m device was not found broken.ConclusionsFlushing the rotary nickel titanium file during root canal preparation with different kinds of fluids,which were 1% sodium hypochlorite solution,0.2% chlorhexidine and distilled water and 0.9% saline.There were no effect on the diameter of the the laser-labeled sites before and after the broke.Using 5% sodium hypochlorite caused the broken file surface abrasion and distortion,the diameter of 6 mm laser-labeled site of the nickel titanium file changed before and after file broken,but no difference between the diameter changes of the 9mm,12 mm,15 mm laser-labeled sites.Flushing the rotary nickel titanium file during root canal preparation with different kinds of fluids,the actual fracture length of five groups had no difference,the relative fracture length of five groups had no difference.there were no no difference between actual fracture length and relative fracture length respectively in the first four groups.But actual fracture length was greater than relative fracture length in 5% sodium hypochlorite group,there were statistical difference.The broken part of nickel titanium file was mainly stretching deformation.The instrument mainly boke in the bent section of root canal of 1/3,and the probability of fracture was highest within 1/12 of the root tip.The distance nearer apical foramen,root preparation will be more difficulty.The instrument broken rate of is higher. |
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