• Restorative Dentistry and Endodontics
• /
• v.24 no.1
• /
• pp.166-179
• /
• 1999

Apical sealing is essential for the success of surgical endodontic treatment. Root-end cavity is apt to be contaminated with moisture or blood, and is not always easy to be dried completely. The purpose of this study was to evaluate the influence of dry methods of retrocavity on the apical seal in endodontic surgery. Apical seal was investigated through the evaluation of apical leakage and adaptation of filling material over the cavity wall. To investigate the influence of various dry methods on the apical leakage, 125 palatal roots of extracted human maxillary molar teeth were used. The clinical crown of each tooth was removed at 10 mm from the root apex using a slow-speed diamond saw and water spray. Root canals of the all the specimens were prepared with step-back technique and filled with gutta-percha by lateral condensation method. After removing of the coronal 2 mm of filling material, the access cavities were closed with Cavit$^{(R)}$. Two coats of nail polish were applied to the external surface of each root. Apical three millimeters of each root was resected perpendicular to the long axis of the root with a diamond saw. Class I retrograde cavities were prepared with ultrasonic instruments. Retrocavities were washed with physiologic saline solution and dried with various methods or contaminated with human blood. Retrocavities were filled either with IRM, Super EBA or composite resin. All the specimens were immersed in 2% methylene blue solution for 7 days in an incubator at $37^{\circ}C$. The teeth were dissolved in 14 ml of 35% nitric acid solution and the dye present within the root canal system was returned to solution. The leakage of dye was quantitatively measured via spectrophotometric method. The obtained data were analysed statistically using one-way ANOVA and Duncan's Multiple Range Test. To evaluate the influence of various dry methods on the adaptation of filling material over the cavity wall, 12 palatal roots of extracted human maxillary molar teeth were used. After all the roots were prepared and filled, and retrograde cavities were made and filled as above, roots were sectioned longitudinally. Filling-dentin interface of cut surfaces were examined by scanning electron microscope. The results were as follows: 1. Cavities dried with paper point or compressed air showed less leakage than those dried with cotton pellet in Super EBA filled cavity (p<0.05). However, there was no difference between paper point- and compressed air-dried cavities. 2. When cavities were dried with compressed air, dentin-bonded composite resin-filled cavities showed less apical leakage than IRM- or Super EBA-filled ones (p<0.05). 3. Regardless of the filling material, cavities contaminated with human blood showed significantly more apical leakage than those dried with compressed air after saline irrigation (p<0.05). 4. Outer half of the cavity showed larger dentin-filling interface gap than inner half did when cavities were filled with IRM or Super EBA. 5. In all the filling material groups, cavities contaminated with blood or dried with cotton pellets only showed larger defects at the base of the cavity than ones dried with paper points or compressed air.

• Restorative Dentistry and Endodontics
• /
• v.22 no.2
• /
• pp.536-545
• /
• 1997

The purposes of this study were to evaluate the degree of cavity cleanliness and to observe cavity wall morphology when root-end retrograde cavity preparation was done with ultrasonics. Root resections were done on 20 extracted human maxillary central incisors after canal filling with gutta-percha, and retrocavities were prepared using a slow-speed round bur as a control, and stainless steel ultrasonic tips of power settings of 2 and 6 ($Miniendo^{TM}$, EIE, SA, USA) as experimentals. The degree of the remaining cavity debris and smear layer, and wall morphology were evaluated under the scanning electron microscope. The results were as follows : Cavity prepared with ultrasonics of either power setting showed significantly less smear layer than did slow-speed preparations (p<0.01). However, there was no significant difference in canal debris (p<0.05). Cavity prepared with ultrasonics showed hatcheted appearance of wall, while slow-speed preparation showed relatively plain one.

• Restorative Dentistry and Endodontics
• /
• v.23 no.1
• /
• pp.515-524
• /
• 1998

The purposes of this study were to observe the cavity wall morphology and to evaluate the degree of cavity cleanliness when root-end retrograde cavity preparation was done with ultrasonic diamond instruments. To observe the morphology of retrocavity and to evaluate the degree of cavity cleanliness. root-end resections were done on 20 palatal roots of extracted maxillary first molars after canal filling with gutta-percha. Retrocavities were prepared using either ultrasonic diamond instruments or stainless steel ones of medium power setting of level 6 ($Miniendo^{TM}$, EIE, CA, U.S.A.). Morphology of the cavity. degrees of the remaining canal debris and smear layer were evaluated under the scanning electron microscope. The results were as follows: Cavities prepared with ultrasonic diamond instruments showed scratched appearance of wall, while ultrasonic stainless steel preparation showed hatcheted appearance. Ultrasonic diamond instruments induced more smear layer than stainless steel ones did (p<0.01) in the cavity. However, there was no significant difference in canal debris (p>0.05).

• Restorative Dentistry and Endodontics
• /
• v.23 no.1
• /
• pp.54-67
• /
• 1998

The purposes of this study were to evaluate the efficiency of dentin cutting and root-end cavity preparation, and to determine the incidence of tooth crack when root-end retrograde cavity preparation was done with. ultrasonic diamond instruments. To evaluate the efficiency of dentin cutting, ultrasonic diamond and stainless steel instruments were applied to 20 exposed bovine dentin surfaces perpendicularly or parallely at the low, and medium power settings for 1 minute ($Miniendo^{TM}$, EIE, CA, U.S.A.). The resultant cavity depth was measured. To evaluate the efficiency of cavity preparation and to investigate the incidence of tooth crack, 165 mesiobuccal, distobuccal and palatal root-ends of extracted human maxillary first molars were resected by 3 mm perpendicularly to the long axis of tooth using a slow speed diamond saw after root canal preparation and filling. Retrocavities were prepared using a ultrasonic diamond instrument or a stainless steel one of the low- or medium power settings of 2 or 6. Time consumed and the number of strokes used for the cavity preparation were measured and the incidence of tooth cracks was evaluated under a stereomicroscope. The results were as follows: Both at the low and medium power settings, and both with perpendicularly- and parallely applied tips to dentin, diamond instruments showed higher dentin cutting efficiency than stainless steel ones did (p<0.01). When tips were applied to dentin perpendicularly, both diamond instrument and stainless steel one showed higher cutting efficiency with medium power setting than with low power one (p<0.01). Both at the low- and medium power settings, both diamond instrument and stainless steel one showed higher cutting efficiency when tips were applied perpendicularly to dentin surface than applied parallely (p<0.01). At the medium power setting, the number of stroke and time consumed were less with diamond instrument than with stainless steel one (p<0.05) for the retrograde cavity preparation. At the low power setting, diamond instrument induced less tooth cracks than stainless steel one did (p<0.01).