The Sealing Effect Of Phenoaldehyde Resin On Root Canal Wall

Objectives: The permeability of root canal wall was increased after shaping and cleaning plus periodontal scaling and root planning in cases of periodontal-endodontic combined lesions. In order to improve the prostecdtive efficacy of periodontal-endodontic combined lesions, we investigate the sealing effect of phenoaldehyde resin on the root canal wall.Methods:1 Effect of cementum to the permeability of root canal wall140 anterior teeth, 140 premolars, 140 molars were randomly divided into 2 groups, respectively. Each group have 70 teeth. These groups were named as group A to group F. In order to expose the dentin, the cementum located between 4 mm and 10 mm from root apex in group A, group B and group C were scaled thoroughly with hand-held hoe. The cementum of teeth in group D, group E and group F did not treated to keep the cementum integrity. All in vitro teeth root apex 4 mm area were evenly coated with two layers of nail polish. Then these teeth root apex 10 mm area were immersed into 2% methylene blue solution in eppendorf tube with root apex downward. These teeth were observed once every 24 hours. The continuous observation lasted for 7 days. 10 teeth of each group were taken out from the 2% methylene blue solution everyday. These teeth were splitted along the longitudinal axis of observed root. The status of methylene blue permeation were observed under stereoscopic microscope.2 The sealing effect of phenoaldehyde resin for root canal wall20 anterior teeth, 20 premolars, 20 molars were divided into 2 groups randomly and respectively. These teeth were merged into group A, which root canal wall were sealed with phenoaldehyde resin, and group B without phenoaldehyde resin sealing, 30 in each group.In order to expose the dentin, the cementum located between 4mm and 10 mm from root apex in group A and group B were scaled thoroughly with hand-held hoe. The crown was cut down at enamel-cemental junction. Reserved root length is greater than or equal to 12 mm. Canal shaping and cleaning was performed according to crown-down technique with hand-held Pro Taper root canal file, and combined with chemical preparation and sonic oscillation. Phenoaldehyde resin was used in group A to seal the root canal wall. Phenoaldehyde resin did not used in group B. All in vitro teeth root apex 4 mm area were evenly coated with two layers of nail polish.Dry cotton twist was inserted into the root canal of all in vitro teeth till the stop. Then these teeth root apex 10 mm area were immersed into 2% methylene blue solution in eppendorf tube with root apex downward. The inserted cotton twist was taken out every 24 hours to observe whether there is the blue dye. The continuous observation lasted for 7 days.2 teeth of group A and 2 teeth of group B prepared according to upper description were splited and observed under stereoscopic microscope and scanning electron microscope(SEM). The status of phenoaldehyde resin infiltration and sealing effect for the root canal wall was observed and recored with photographs.Results: 1 Effect of cementum to the permeability on root canal wall 1.1 Morphological observation of methylene blue solution penetration into root canal wallIn group A, B, C, methylene blue penetration could be seen in the dentin at the first day. Penetration distance limited outer 1/3 layer and middle 1/3 layer of dentin of the root canal. Methylene blue penetration could be seen in the inner 1/3 layer of dentin at the third day. At the forth day, methylene blue penetration into root canal could be seen in these group, nearly. Only a small amount of infiltration are visible in group D, E, F. Penetration distance limited outer 1/3 layer and middle 1/3 layer of dentin even at the seventh day. One case of group B, a striga-like penetration into root canal was seen at the first day, which indicated that this was a lateral root canal. 1.2 Scores of methylene blue solution penetration into root canal wallThe scores of corresponding groups such as anterior teeth without cementum(group A) and with cementum(group D), premolars without cementum(group B) and with cementum(group E), molars without cementum(group C) and with cementum(group F), were compared everyday. Statistical analysis of upper data showed P<0.05 in every comparison, which means that the scores of methylene blue penetration between corresponding groups were different significantly. These results indicated that the penetration of root canal wall increased significently when cementum was scaled thoroughly. 2 The sealing effect of phenoaldehyde resin on root canal wall 2.1 Morphological observation of infiltration of phenoaldehyde resin into dentinal tubulesAfter routine root canal shaping and cleaning, the light irradiated on the root canal wall diffused irregularly when observed under stereoscopic microscope. After routine root canal shaping and cleaning and treated with phenoaldehyde resin, the light irradiated on the root canal wall reflected directedly to eyes, like irradiated on a mirror. When observed with SEM, the orifices of dentinal tubules were open after routine root canal shaping and cleaning, and the longitudinal section of dentinal tubules showed which were empty. After routine root canal shaping and cleaning and treated with phenoaldehyde resin, the orifices of dentinal tubules were sealed, and the longitudinal section of dentinal tubules showed which were blocked with infiltrated phenoaldehyde resin. 2.2 The leakage situation of methylene blue into root canal after treated with phenoaldehyde resinThere were no methylene blue leaked into root canal space at the first day and the second day. The leakage of methylene blue between blocked group and unblocked group had no significant difference(P>0.05). Since the third day, the leakage of methylene blue in unblocked group was obvious, and the leakage of methylene blue between blocked group and unblocked group had significant difference(P<0.05).Conclusions:1 Permeability of the root canal wall increased significantly after cementum have been destroied. Leakage oriented from peridontal tissue to pulp could be found.2 Phenoaldehyde resin have favourable sealing effect on root canal wall, because which can infiltrated into dentinal tubules.