An in vitro study of the debridement of isthmuses in mandibular first molars

doi:10.3877/cma.j.issn.1674-1366.2008.05.008

Abstract

Abstract:

Objective

To histologically evaluate the efficacy of sodium hypochlorite（NaOCl） in combination with ultrasonic irrigation and/or calcium hydroxide （Ca （OH）₂） in dissolving necrotic tissue and cleaning root canals as well as canal isthmuses in mesial roots of mandibular first molars.

Methods

45 freshly extracted human mandibular first molars were randomly assigned to three groups. Each group consisted of 15 mesial roots. They were instrumented by using ProTaper hand files and subsequently subjected to three different irrigation regimens as followed： Group A—a 1 min of ultrasonic irrigation with 5.25% NaOCl， group B—a 1 min of ultrasonic irrigation with 0.5% NaOCl after pretreatment with Ca （OH）₂ paste for 24 h，and group C—irrigation with 15ml of 5.25% NaOCl using disposable syringes after pretreatment with Ca （OH）₂ paste for 24 h. After histological preparation and staining， 4 μm cross-sections from the 1- to 3-mm apical levels were evaluated for percentage of tissue removal.

Results

Nonparametric analysis revealed that mean percentage of canal and isthmus cleanliness values were significantly higher in group A and B at all levels evaluated， except one （P ＜0.05）.

Conclusion

0.5% NaOCl ultrasonic irrigation in combination with Ca（OH）₂ pretreatment can be used safely and effectively in root canal irrigation instead of 5.25% NaOCl.

Key words: Mandibular first molar, Isthmus, Organic debris, Ultrasonic irrigation

Li-sha GU, Jun-qi LING, Xiang-ya HUANG, Xi WEI, Qiong XU. An in vitro study of the debridement of isthmuses in mandibular first molars[J]. Chinese Journal of Stomatological Research(Electronic Edition), 2008, 02(05): 476-484.

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Figures/Tables 7

References 26

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组别	n	根管化学预备方法
A组	15	5.25% NaOCl超声冲洗1 min
B组	15	Ca（OH）₂糊剂24 h加0.5% NaOCl超声冲洗1 min
C组	15	Ca（OH）₂糊剂24 h加0.5% NaOCl注射器冲洗15 ml

组别	n	根管化学预备方法
A组	15	5.25% NaOCl超声冲洗1 min
B组	15	Ca（OH）₂糊剂24 h加0.5% NaOCl超声冲洗1 min
C组	15	Ca（OH）₂糊剂24 h加0.5% NaOCl注射器冲洗15 ml

距根尖水平（mm）	根管清洁度		管间峡区清洁度
距根尖水平（mm）	n	清洁度（%）	n	清洁度（%）
3.0	10	5.78±1.85	1	1.07
2.5	10	4.88±1.62	1	1.62
2.0	10	4.59±1.43	1	0
1.5	10	3.84±1.71	0	-
1.0	10	3.68±1.30	0	-

距根尖水平（mm）	根管清洁度		管间峡区清洁度
距根尖水平（mm）	n	清洁度（%）	n	清洁度（%）
3.0	10	5.78±1.85	1	1.07
2.5	10	4.88±1.62	1	1.62
2.0	10	4.59±1.43	1	0
1.5	10	3.84±1.71	0	-
1.0	10	3.68±1.30	0	-

距根尖水平（mm）	A组		B组		C组
距根尖水平（mm）	n	清洁度（%）	n	清洁度（%）	n	清洁度（%）
3.0	15	99.79±0.31	15	99.92±0.11	15	99.73±0.52
2.5	15	99.26±0.64	15	99.84±0.17	15	97.80±2.11
2.0	15	99.21±0.34	15	99.82±0.19	15	96.42±1.83
1.5	15	99.49±4.67	15	99.21±1.57	15	89.03±6.57
1.0	15	98.96±3.80	15	98.41±1.83	15	85.41±9.83

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