Effect of bleaching agents on bonding to pulp chamber dentine.

AIM: To determine the effect of intracoronal bleaching agents on adhesion of bonding agents to pulp chamber dentine. METHODOLOGY: Forty extracted human maxillary anterior teeth were randomly divided into four groups of 10 teeth each. Bleaching agents were sealed in pulp chambers for 7 days, as in clinical use. Group 1 (control): distilled water, group 2: 35% hydrogen peroxide, group 3: sodium perborate mixed with water, and group 4: sodium perborate mixed with 35% hydrogen peroxide. Teeth were stored in saline at 37 degrees C for 7 days. After the bleaching agent was removed, teeth were leached in water for a further 7 days prior to bonding. The crown was cut vertically from mesial to distal and the labial pulp chamber dentine was prepared for bonding with Clearfil SE-Bond and filled with resin composite (Clearfil AP-X). The bonded specimens were kept moist at 37 degrees C for 24 h. Microtensile bond strengths were determined using a universal testing machine. Additional teeth were prepared using the same bleaching procedures to investigate the scanning electron microscopic appearance of the dentine surface. RESULTS: Mean values (+/-SD) of microtensile bond strength for the experimental groups were: group 1: 5.29 +/- 2.21 MPa, group 2: 5.99 +/- 1.51 MPa, group 3: 9.17 +/- 1.65 MPa and group 4: 3.99 +/- 1.31 MPa. Dentine treated with sodium perborate in water (group 3) had significantly higher mean bond strength when compared with the other three groups (P < 0.05, Tukey's test). Mean bond strength was lowest when dentine was treated with sodium perborate plus hydrogen peroxide (group 4). CONCLUSIONS: In terms of subsequent bond strength during restoration, sodium perborate mixed with distilled water appears to be the best intracoronal bleaching agent.

Micro-tensile bond strengths of bonding agents to pulpal floor dentine.

AIM: The purpose of this study was to characterize the dentine surface of the pulpal floor and to determine the micro-tensile bond strengths of two dentine adhesive systems used in conjunction with a resin composite core material to pulpal floor dentine. METHODOLOGY: Thirty-six extracted human molars were cut horizontally with a slow-speed diamond saw to expose the pulp chamber and the pulp tissue was removed. Eight teeth were used to investigate characteristics of untreated and etched dentine surfaces of the pulpal floor using SEM. Twenty-eight teeth were randomly allocated to two groups, each of 14 teeth. In group 1, a 'one-bottle' system (Prime & Bond NT) was used as dentine bonding agent and in group 2, a self-etching-priming system (Clearfil SE Bond) was applied. Pulp chambers of both groups were then filled with resin composite core buildup (FluoroCore) and kept moist in tap water at 37 degrees C for 24 h. Samples were prepared for micro-tensile bond testing by sectioning each tooth vertically in the mid-pulpal floor region and shaped to an hour-glass form of 1 +/- 0.2 mm(2) area at the bonded interface. Micro-tensile bond strengths were determined using a universal testing machine at a crosshead speed of 1 mm min-1. Fractured surfaces were examined by SEM. RESULTS: The intact pulpal floor showed numerous calcospherites with variable tubule density and few accessory canals. Etching the pulpal floor with 34% phosphoric acid gel resulted in an irregular surface with patent dentinal tubules and the dome-shaped calcospherites mostly lost. With self-etching primer, the superficial dentine surface was less demineralized and little peritubular dentine matrix was removed. Mean bond strength for the self-etching-priming (Clearfil SE Bond) specimens was significantly greater than for 'one-bottle' (Prime & Bond NT) specimens (P< 0.05, Student's t-test). The fracture mode of Clearfil SE Bond specimens was mostly partial cohesive failure within dentine, whilst Prime & Bond NT specimens mostly showed partial cohesive failure in bonding resin/composite. CONCLUSIONS: Despite an irregular surface morphology and absence of a smear layer, bonding to pulpal floor dentine was weaker than previously reported for cut coronal dentine. The self-etching-priming system bonded more strongly than the 'one-bottle' system.

Effect of removal of the smear layer on apical microleakage.

It has been shown previously that the smear layer created during instrumentation of the root canal promotes apical microleakage. The purpose of the present study was to investigate the effect of removal of the smear layer on apical microleakage, using the fluid filtration method. Thirty-six single-rooted human premolar teeth were used. Six of the teeth were selected randomly as controls, and the remaining 30 teeth were randomly divided into two groups of 15 teeth each. For the first group (group 1) teeth were irrigated with NaOCl only (smear layer not removed). In the second group (group 2) the teeth were irrigated with 15% EDTA, followed by NaOCl to remove the smear layer. Both groups were filled with thermoplasticized gutta-percha (Obtura II) using glass-ionomer cement as sealer. All teeth were stored at 37 degrees C and 100% humidity for 2 days. Apical microleakage of the filled root canal was measured by the fluid filtration technique. Hydraulic conductance was measured by the movement of an air bubble in a capillary tube after a pressure of 200 mm Hg was applied to the system. The mean microleakage rate of group 1 and group 2 were 13.0 (SD +/- 5.1) and 16.9 (SD +/- 15.3) nl/s, respectively. Removal of the smear layer caused significantly more apical microleakage (p < 0.05, Student's t test) than when the smear layer was left intact.

Adhesion of a glass-ionomer root canal sealer to the root canal wall.

Glass-ionomer root canal sealer is commonly used because of its chemical bonding and favorable physical characteristics when bonding to dentin. This study was designed to determine the tensile bond strength of a glass-ionomer sealer (Ketac Endo, Espe, Seefeld, Germany) on root canal walls after pretreatment with different conditioners. Flat inner surfaces of root canal specimens were prepared. The specimens were divided into five groups of 10 teeth, and the groups were conditioned with one of the following smear layer removal solutions: 15% EDTA/NaOCl, 10% polyacrylic acid, 35% phosphoric acid, 6% citric acid, and 5.25% NaOCl as a control. Then the exposed root canal areas were coated with Ketac-Endo. Tensile bonding was measured using a universal testing machine until ultimate failure was obtained. The groups that were treated with phosphoric acid and citric acid showed significantly higher bond strengths than the groups that were treated with 15% EDTA and polyacrylic acid (p < 0.05). Bonding to dentin without smear layer removal (NaOCl group) was too low to be measured in the testing apparatus. Scanning electron microscopy confirmed that phosphoric and citric acids were more effective in removing smear layer than EDTA or polyacrylic acid. The result supported the view that pretreatment with phosphoric acid or citric acid should be used in association with glass-ionomer root canal sealer to achieve the most effective removal of the smear layer and to provide better adhesion.

Bacterial coronal leakage after obturation with three root canal sealers.

The purpose of this study was to compare the bacterial leakage of root canals obturated with three root canal sealers, using Endodontalis faecalis as a microbial tracer to determine the length of time for bacteria to penetrate through the obturated root canal to the root apex. Seventy-five, single-rooted teeth with straight root canals had the crown cut off at the cementoenamel junction. Root canals were instrumented by a step-back technique. The prepared teeth were randomly divided into 3 groups of 19 teeth each and another 2 groups as positive and negative controls (9 teeth each). The experimental groups were dependent on the sealer used: AH-Plus, Apexit, and Ketac-Endo. The root canals were obturated using a lateral condensation technique. After 24 h the teeth were attached to microcentrifuge tubes with 2 mm of the root apex submerged in Brain Heart Infusion broth in glass test tubes. The coronal portions of the root canal filling materials were placed in contact with E. faecalis. The teeth were observed for bacterial leakage daily for 30 and 60 days. With the chi2 test for comparing pairs of groups at the 0.05 level (p < 0.05), there was no statistical difference between Ketac-Endo and AH-Plus (p > 0.06), but Apexit had significantly higher leakage (p < 0.05) at 30 days. After 60 days there was no statistical difference between Ketac-Endo and Apexit (p > 0.05), but Apexit leaked more than AH-Plus. The conclusion drawn from this experiment was that epoxy resin root canal sealer was found to be more adaptable to the root canal wall and filling material than a calcium hydroxide sealer when bacterial coronal leakage was studied.

Apical sealing ability of glass ionomer sealer with and without smear layer.

The effect of two different root canal cements and removal of the smear layer on the apical seal in roots obturated with Thermafil obturators was tested. Thirty extracted human mandibular first molars with 60 canals (mesial roots) were instrumented with the use of a step-back technique. Teeth were placed into 6 groups of 10 canals each. The first three groups had the smear layer removed with EDTA and NaOCl, and the other three groups were irrigated with NaOCl only. Canals were obturated using Thermafil without sealer cement or Thermafil with Ketac-Endo or Thermafil with zinc oxide-eugenol cement. All roots were placed in India ink for 4 days. The roots were cleared, and the degree of linear dye penetration was measured. The study showed that root canal cement significantly improved the apical seal of the Thermafil obturation technique (p < 0.05), whether the smear layer was removed or not. The apical seal exhibited by Ketac-Endo was not significantly different from that provided by zinc oxide-eugenol cement (p > 0.05), regardless of the presence or absence of a smear layer.

The effect of an anticalculus dentifrice on calculus formation and gingival recession in Thai children and teenagers: one-year study. Study #2. An anticalculus dentifrice containing 1.3% soluble pyrophosphate and 1.5% of a copolymer.

A one-year, double-blind clinical study was conducted on a population of Thai children and teenagers to determine the effect of the twice daily use of an anticalculus dentifrice on supragingival calculus formation and gingival recession, as compared to the use of a placebo dentifrice and the continuation of customary oral hygiene procedures. The subjects were initially evaluated for calculus using the Volpe-Manhold procedure and for gingival recession using the GRT procedure of Volpe, Triratana, and Rustogi. All subjects received an oral prophylaxis and were assigned to the use of the following: (1) a placebo dentifrice containing 0.243% sodium fluoride in a silica base, (2) an anticalculus dentifrice containing 1.3% soluble pyrophosphate and 1.5% Gantrez copolymer in a 0.243% sodium fluoride/silica base, or (3) continuation of customary oral hygiene procedures. After six months, the subjects using the anticalculus dentifrice had 35.93% less supragingival calculus than the placebo dentifrice subjects, and 52.74% less supragingival calculus than the subjects who continued their regular/customary oral hygiene procedures. After one year, the subjects using the anticalculus dentifrice had 39.76% less supragingival calculus and 18.33% less gingival recession than the subjects using the placebo dentifrice. Also, after one year, the subjects using the anticalculus dentifrice had 57.86% less supragingival calculus and 16.55% less gingival recession than the subjects who continued their customary oral hygiene procedures. All reductions were statistically significant at the 99% level of confidence.

[Endodontic therapy in irradiated patient].

Endodontic treatment should be the treatment of choice in irradiated patients in order to avoid extraction or to postpone it to a less threatening post irradiation period. Regressive changes in the irradiated area supplied by these damaged vessels appear so far to be of a nutritional nature. Endodontic procedures should be accomplished with judicious precision and gentle. The tooth should never leave "open for drainage" in an irradiated patient. Shorter lengths during instrumentation of the root canals would appear to be more desirable than over extended lengths. Canal obturation with gutta percha by means of lateral condensation is effective. This report demonstrated multiple endodontic treatments in two patients after cancericidal radiation to the head and neck area. The successful treatment had been followed up after 2 years.

[Successful endodontic treatment of dens in dente].

The dens in dente is a developmental variation which is thought to arise as a result of an invagination in the surface of a tooth crown before calcification has occurred. This report is a case which documents the successful non surgical endodontic treatment permanent tooth with dens in dente by periodical dressing the intracanal space with calcium hydroxide for a year and follow up after permanent filling-for one and a half years. After a sign of repair around the periapical area had occurred, the canal was filled with warm gutta percha technique. The importance of early and corrected diagnosis, the possible significance of even a small and noncarious dens in dente, and the treatment of anomaly were emphasized.

[Antibacterial effects of CMCP, Cresophene, and formocresol as root canal medications].

This clinical and laboratory study was to compare the antimicrobial effects of camphorated monoparachlorophenol, Cresophene and formocresol. Root canals of anterior teeth with 3-5 mm. rarefied area were instrumented and irrigated until they were ready to be filled. The patients returned every 7 days. Intracanal medicaments were changed until negative culture was obtained. The number of visits was recorded. The comparative effectiveness of the three medicaments were analysed. Results showed no statistical differences of the three medicaments (p greater than 0.1). The antimicrobial activity against bacteria from positive root canal culture of these three antiseptics were assayed by disc diffusion method. The inhibition zone of camphorated mono-parachlorophenol and Cresophene were nearly the same size, but that of formocresol had greater diameter. Using Gram's staining procedure, the majority of bacteria obtained from root canals was identified as gram positive cocci (94.74%).

An in vitro study of the comparative effectiveness of obturating curved root canals with gutta-percha cones, silver cones, and stainless steel files.

The quality of apical seal obtained with gutta-percha cones, silver cones, and stainless steel files was assessed in 120 freshly extracted teeth with moderately or severely curved root canals. Teeth were coated with wax, except in the apical foramen area, and immersed in 2 percent methylene blue solution for 48 hours. Apical leakage was quantitated by a linear measurement of the distance that the dye penetrated along the root canal and by a volumetric measurement of the quantity of dye within the root. There was a highly significant (p less than 0.001) correlation between the two measurements. Root canals filled with silver cones showed significantly less apical leakage than those filled with gutta-percha or stainless steel files, regardless of degree of curvature. For both silver cones and stainless steel files, leakage was less in severely curved roots than in moderately curved roots.