| Root canal therapy(RCT)is the first choice for treatment of pulpitis and periapical periodontitis. It is a method to promote the healing of root lesions or prevent the occurence of periapical disease. The process of this treatment are: first, clean the root canal inflammation of the pulp, necrotic tissue, bacteria and their metabolic products compltely, second, extend the root canal space and shape it, then after disinfected, fill the root canal up with special materials very tightly. Root canal preparation includes the first two steps stated above, i. e. root canal shaping and cleaning, Equipment is needed for both of them. With the development of science and technology, the research of root canal preparation equipment is becoming more and more important.The purpose of this study is to compare the shaping and cleaning ability of two different nickel-titanium instruments in the resin curved root canals and extracted teeth. Part 1.Shaping ability of nickel-titanium instruments in curved root canals. Objective:Apply Reciproc and Pro Taper preparation system on both of 3D simulated resin teeth and extacted teeth respectively. By combinative using Micro-CT and 3D reconstruction technology, evalute the canal root shaping capability of different instruments through analying the root canal volumn, surfacearea and the amount of deviation degree change before and after root canal preparation. Expermental data for clinical work is expected. Methods:40 3D simulated resin maxillary second molar teeth with 50° bending mesial buccal root canals were prepared for the experiment. The apical diameter is 0.20 mm and the root canal total length is 15 mm. Divide those 3D simulated resin teeth into 2 groups evenly and randomly, i.e. 20 teeth for each group, and number each of them sequentially. Then, fix every one 3D simulated resin teeth at an individual location and apply Micro-CT on all of them. After that, apply Reciproc preparation on one group and Pro Taper on the other one. Meanwhile, record the preparation time. Place each of them at the exact position as before and apply Micro-CTagain. 3D reconstruction technology was used to analyze and compare the before- and afterpreparation root canal morphology parameters(volume, surface, area and straightening) obtained from Micro-CT scanning. With SPSS 17.0 statistical analysis, then, the shaping capability of the two different kinds of instruments could be evaluated. Also, with SPSS 17.0 statistical analysis for the recorded preparation time, the effectiveness of the two different kinds of instruments could be evaluated.20 extracted mandibular first molar teeth were prepared for the experiment. After being treated with 2.5% sodium hypochlorite solution and removing the foreign bodies, those 20 extracted teeth were placed at 0.02% chlorhexidine solution and stored at room temperature. Selection of those 20 extracted teeth follows the requirements:(1) apical completely developed,(2) no calcification around the buccal and lingual unblocked root canal,(3) root canal major apice file is less than #15K,(4) the root canal bending is larger than 15°(determined by X-ray film). Divide those selected extracted teeth into 2 groups evenly and randomly, i.e. 10 teeth for each group, and number each of them sequentially. Open the pulp in regular way with special high-speed handsaw and build the straight path. Cut off the dental crown at cemento-enamel junction(CEJ) and determine the reference point and working length.Check and dredge the root canal with K grater. Clean the root canal with 5ml 0.5% sodium hypochlorite solution and rinse it with 5ml distilled water and dry it. Then, fix every one 3D simulated resin teeth at an individual location and apply Micro-CT on all of them. After that, apply Reciproc preparation on one group and Pro Taper on the other one. Meanwhile, record the preparation time. Place each of them at the exact position as before and apply Micro-CT again. 3D reconstruction technology was used to analyze and compare the before- and after- preparation root canal morphology parameters(volume, surface, area and straightening) obtained from Micro-CT scanning. With SPSS 17.0 statistical analysis, then, the shaping capability of the two different kinds of instruments could be evaluated. Also, with SPSS 17.0 statistical analysis for the recorded preparation time, the effectiveness of the two different kinds of instruments could be evaluated Reasult:The two groups of 3D simulated resin teeth are tagged as Group 1(prepared by Reciproc system) and Group 2(prepared by Pro Taper system). The root canal volume change is compared between Group 1 and Group 2 at root crown 1/3 point, root middle 1/3 point and root apical 1/3 point. No statistically significant difference between them. The root canal surface area change is compared between Group 1 and Group 2 at root crown 1/3 point, root middle 1/3 point and root tip 1/3 point. No statistically significant difference between them at root crown 1/3 point, root middle 1/3 point. But, obvious statistical difference occurs at root apical 1/3 point. For the root canal deviation, Group 1 is less than Group 2. Reciproc preparation has a better shaping capability than Pro Taper preparation for the bending resin root canal. Also, significant statistical difference exist between Group 1 and Group 2 for the preparation time. Reciproc system has a higher effectiveness than Pro Taper system for those 3D simulated resin teeth.The two groups of extracted teeth are tagged as Group 3(prepared by Reciproc system) and Group 4(prepared by Pro Taper system).The root canal volume change is compared between Group 3 and Group 4 at root crown 1/3 point, root middle 1/3 point and root apical 1/3 point.No statistically significant difference between them at root crown 1/3 point, root middle 1/3 point. But, obvious statistical difference occurs at root apical 1/3 point.The root canal surface area change is compared between Group 3 and Group 4 at root crown 1/3 point, root middle 1/3 point and root apical 1/3 point. No statistically significant difference between them at root crown 1/3 point, root middle 1/3 point. Again, obvious statistical difference occurs at root apical 1/3 point. The root canal deviation of Group 3 is less than Group 4. Reciproc preparation has a better shaping capability than Pro Taper preparation for the root canal of extracted teeth.Also, significant statistical difference exist between Group 3 and Group 4 for the preparation time. Reciproc system has a higher effectiveness than Pro Taper system for the extracted teeth Conclusion:Between Reciprocand Pro Taperpreparation system, the former one has the better capability to keep the original shape of the bending root canal. With the great centering ability and the small deviation of root canal caused by it, Reciproc preparation system behave the excellent ability root canal shaping capability. Besides, Reciproc preparation system has higher clinical work effectiveness than Pro Taper due to the less required preparation time.. Part 2 Cleaning ability of nickel-titanium instruments in curved root canals.Objective:Treat extracted teeth root canal with Reciproc and Pro Taper preparation system respectively. Observe the root canal inner wall under Scanning Electron Microscope(SEM). Evaluate the smear layer and debris and compare the cleaning capability of those two preparation system. Experiment data for clinical work is expected. Methods:20 extracted mandibular first molar teeth were selected for the experiment. The selection of those 20 extracted teeth follows the requirements:(1) apical completely developed,(2) no calcification around the buccal and lingual unblocked root canal,(3)) root canal major apice file is less than #15K,(4) the root canal bending is larger than 15°(determined by X-ray film). Divide those selected extracted teeth into 2 groups evenly and randomly, i.e. 10 teeth for each group. Open the pulp in regular way with special high-speed handsaw and build the straight path.Check and dredge the root canal with K grater. Treat those two groups with Reciproc and Pro Taper preparation system respectively and rinse and dry the root canal. Longitudinal section the dental root along the long axis of it with bone hammer or bone chisel. 18 samples are for each group and mark root crown(from the apical 5-7mm), central root(from apical 3-5mm) and root tip(from apical 1-3mm) for each sample. Treat the samples with 2.5% glutaraldehyde for 48 hrs and graded ethanol dehydration drying. Fix the samples at the stage. Observe the inner wall morphology of the root canal with SEM(JEOL JSM-6700F). Under 1000 x magnification, take images at 4 randomly selected different areas for each part of the root canals based on single-blind method. Then, evaluate the smear layer and debris condition according to the M.Hülsmann5-point scoring standard and compare the result according to the Mann-Whitney U Test. At last, the cleaning capability of the instruments could be evaluated. Results:The two groups in this experiment are tagged as Group 5(prepared with Reciproc system) and Group 6(prepared with Pro Taper system). For the debris cleaning capability, no significant statistical difference of the score exist between those two systems at root crown 1/3 point and root apical 1/3 point. But at central root 1/3 point, the evaluated debris score of Group 5 is less than Group 6. The debris cleaning capability of Reciproc system is better than Pro Taper system. For the smear layer evaluation, no significant statistical difference of the score exist between those two systems at root crown 1/3 point and central root 1/3 point. But at root apical 1/3 point, the evaluated score of Group 5 is less than Group 6. Reciproc system has a better smear layer cleaning capability than the Pro Taper system.. Conclusion:At the root crown area, the cleaning capability of Reciproc and Pro Taper preparation system are approximately the same. However, at central root 1/3 point and root apical 1/3 point, Reciproc system has a better smear layer and debris cleaning capability than the Pro Taper system. |
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