A fluid filtration and clearing technique to assess microleakage associated with three dentine bonding systems

Comparison of the effect of post space preparation time on the apical seal of two different sealers

BACKGROUND

The present study compared the effect of post space preparation time on the apical seal of two different sealers.

METHODS

In the in vitro study, 94 central incisors were used. After the samples' root canal preparation, they were randomly assigned to four experimental groups (n = 21). The samples in groups 1 and 2 were obturated with AH Plus sealer, gutta-percha, and in groups 3 and 4 with Endoseal MTA bioceramic sealer and single cone technique. The post spaces in groups 1 and 3 were prepared immediately and in groups 2 and 4 with a delay. The samples were evaluated at 7-, 30-, and 90-day intervals for apical microleakage using the fluid filtration technique. The data were analyzed with SPSS 25, using three-way ANOVA and independent t-test.

RESULTS

The apical microleakage in groups 3 and 4, obturated with Endoseal MTA bioceramic sealer and prepared immediately and after a delay, respectively, was not significantly different between the interval times. In group 2, obturated with AH Plus sealer and prepared for post space with a delay, the apical microleakage was significantly less than all the other groups. Group 1, obturated with AH Plus sealer and prepared for post space immediately, exhibited the least microleakage after seven days, but its microleakage increased over time to reach the level of groups 3 and 4.

CONCLUSION

According to the results, the apical microleakage in the AH + sealer group and the delayed post-space preparation method, was significantly less than all the other groups over time.

In vitro Interrelationship between Apical Fill and Apical Leakage Using Three Different Obturation Techniques

AIM AND OBJECTIVES

To evaluate the apical fill in relation to apical leakage using three different obturating techniques - Single Cone, Ultrafil 3D, and lateral condensation.

MATERIALS AND METHODS

Sixty-six mandibular single-rooted premolar teeth were selected and were randomly assigned into three different groups of obturating techniques. The canals were prepared using 0.4/25 HyFlex CM (Coltene Endo) rotary system file and obturated with corresponding HyFlex CM Single Cone, Ultrafil 3D injectable technique, and lateral condensation. AH Plus (Dentsply, Detrey) has been used as the sealer. Twenty teeth each were assigned to the three experimental groups, and six teeth were used as positive and negative controls (3 in each group). Fluid filtration technique was used to determine the amount of apical leakage. The evaluation was done for 8 min at the interval of every 2 min. The same teeth were sectioned and a spectroscopic examination was done at 2 mm and 4 mm distance from the apices. The obtained data were statistically analyzed using analysis of variance test followed by post hoc turkeys test for multiple comparisons.

RESULTS

The mean apical leakage was maximum for lateral condensation when compared to the Single Cone and Ultrafil 3D. The amount of apical fill at 2 mm and at 4 mm was found to be more in the Single Cone than the other two techniques.

CONCLUSION

The present study concluded that Single Cone obturation technique exhibited more gutta-percha filled area in the canal which led to decreased apical leakage than Ultrafil 3D and lateral condensation techniques, proving to be more effective in achieving a complete three-dimensional apical seal.

Effect of Calcium Hydroxide Based Intracanal Medicaments on the Apical Sealing Ability of Resin Based Sealer and Guttapercha Obturated Root Canals

INTRODUCTION

Calcium Hydroxide (CH) is one of the most commonly used intracanal medicaments which can be used with various vehicles.

AIM

The aim of this in vitro study was to evaluate the effect of three CH based intracanal medicaments on the apical sealing ability of AH Plus - guttapercha obturation.

MATERIALS AND METHODS

Crowns of 100 extracted single rooted human teeth were sectioned at the Cemento-Enamel Junction (CEJ) to a standardized length. The root canals were instrumented upto ISO size 40 using step back technique and the specimens were randomly divided into two control and four experimental groups. The control groups were not medicated. Specimens in positive control group (Group I) were obturated with guttapercha without placing sealer and in negative control group (Group II) were obturated with guttapercha and AH Plus sealer. Among the experimental groups, specimens of Group III were not medicated while groups IV, V and VI were medicated with CH-saline, CH-2% Chlorhexidine (CHX) and Vitapex respectively for a period of 14 days. The medicaments were removed from the specimens and the teeth were obturated with AH Plus sealer and guttapercha using lateral compaction technique. The specimens were immersed in India ink dye, demineralized and diphanized. The extent of dye penetration was assessed using a 10X stereomicroscope. Data obtained was statistically analyzed by one-way ANOVA (p<0.05) followed by Post-hoc Tukey test.

RESULTS

Amongst the three CH medicaments, CH-2% CHX when used as an intracanal medicament showed a significantly higher microleakage as compared to the other groups with p<0.001. The microleakage values between the remaining groups were not statistically significant.

CONCLUSION

Under the conditions of this study it was concluded that all groups with or without intracanal medicament showed apical leakage. The vehicle used to carry CH may significantly influence the apical sealing ability of guttapercha - AH Plus obturated canals.

Effect of different gingival margin restorations of class II cavities on microleakage: an in-vitro study

Introduction

Microleakage is one of the important contributing factors in the failure of resin restorations. The aim of this study was to determine the effect of the location of the gingival margin (enamel, dentin, or cementum) on nanohybrid composite resin on the microleakage of Class II posterior restoration.

Methods

This was an in vitro study done at Al-Farabi College of Dentistry and Nursing in Jeddah (Saudi Arabia). Eighty-one previously extracted human molars were taken from clinics at Al-Farabi College and divided into three main groups (27 each) according to the location of the gingival margin. Group 1: the location of the gingival margin was in the enamel. Group 2: at the cemento-enamel junction. Group 3: in the cementum. Each main group was divided into three subgroups (9 each) according to storage time. Subgroup A: storage time was 24 hours. Subgroup B: storage time was one month. Subgroup C: storage time was three months. Class II cavity was prepared in one proximal surface for each molar following the general principles of cavity preparation. All samples were restored by nanohybridresin composite (TetricEvoCeram). The specimens were stored in distilled water at 37°C and a humidity of 100% in an incubator for one day, one month, and three months, respectively, according to the subgroups. After sealing, the samples were stained with 2.5% methylene blue dye. Each sample was examined microscopically by a stereomicroscope using a computerized image analyzing system. Statistical analysis was done by two-way ANOVA test comparing dye penetration mean values (μm).

Results

The value of dye penetration increased remarkably from enamel, Cemento-enamel junction [CEJ] to cementum, and this was statistically significant (p < 0.001).

Conclusion

None of the materials tested was able to completely eliminate marginal microleakage at different gingival margins. The least dye penetration was detected at the enamel gingival margin followed by CEJ and then cementum. The least microleakage was observed at the gingival margin located in the enamel.

On the interfacial fracture resistance of resin-bonded zirconia and glass-infiltrated graded zirconia

OBJECTIVE

A major limiting factor for the widespread use of zirconia in prosthetic dentistry is its poor resin-cement bonding capabilities. We show that this deficiency can be overcome by infiltrating the zirconia cementation surface with glass. Current methods for assessing the fracture resistance of resin-ceramic bonds are marred by uneven stress distribution at the interface, which may result in erroneous interfacial fracture resistance values. We have applied a wedge-loaded double-cantilever-beam testing approach to accurately measure the interfacial fracture resistance of adhesively bonded zirconia-based restorative materials.

METHODS

The interfacial fracture energy GC was determined for adhesively bonded zirconia, graded zirconia and feldspathic ceramic bars. The bonding surfaces were subjected to sandblasting or acid etching treatments. Baseline GC was measured for bonded specimens subjected to 7 days hydration at 37°C. Long-term GC was determined for specimens exposed to 20,000 thermal cycles between 5 and 55°C followed by 2-month aging at 37°C in water. The test data were interpreted with the aid of a 2D finite element fracture analysis.

RESULTS

The baseline and long-term GC for graded zirconia was 2-3 and 8 times greater than that for zirconia, respectively. More significantly, both the baseline and long-term GC of graded zirconia were similar to those for feldspathic ceramic.

SIGNIFICANCE

The interfacial fracture energy of feldspathic ceramic and graded zirconia was controlled by the fracture energy of the resin cement while that of zirconia by the interface. GC for the graded zirconia was as large as for feldspathic ceramic, making it an attractive material for use in dentistry.

Microleakage of teeth restored with different adhesive dowel systems: an in vitro study

PURPOSE

Commercial fiber-reinforced dowel systems are marketed as having better adhesion and sealing ability than conventional metallic dowel systems. The aim of this in vitro study was to evaluate the microleakage of teeth restored with nine dowel systems.

MATERIALS AND METHODS

Ninety mandibular second premolar teeth were decoronated, and nine homogenous groups were composed of ten teeth each. Root canal and dowel space preparations were made, and eight fiber-reinforced composite dowel systems and one stainless steel dowel system were used to fabricate dowel restorations. Microleakage measurements of the restored teeth were made with a modified fluid filtration method, and data were collected. One sample Kolmogorov-Smirnov, one-way ANOVA, and Tukey-HSD tests were performed on the relative microleakage data of the groups.

RESULTS

Microleakage values were reported relative to those for teeth with unfilled canals. The highest and lowest relative microleakage values were recorded for the metallic Parapost (7.06 × 10(-4) %) and fiber-reinforced Everstick (3.55 × 10(-4) %) groups, respectively. Significant differences in relative microleakage between the fiber-reinforced dowels and stainless steel dowels were observed. Significant differences among the fiber-reinforced dowel groups were observed as well.

CONCLUSIONS

The sealing ability of all fiber-reinforced composite dowels is not better than that of stainless steel dowels, and there are significant differences among different fiber-reinforced dowel systems as well. Differences among commercial dowel systems must be taken into consideration when making a selection.

The effect of topical fluoride therapy on microleakage of tooth colored restorations

AIM

The aim of this study was to evaluate the effect of pre and post fluoride therapy on the microleakage of composite resin and glass ionomer restorations.

MATERIALS AND METHODS

Class V cavities were prepared on the buccal surfaces of sixty extracted human third molars. Based on the restorative materials the samples were assigned into two essential groups of thirty and each of them divided into three subgroups regarding the mode of Acidulate Phosphate Fluoride (APF) gel usage. Fluoride therapy was applied pre and post restoration whether OptiBond Solo Plus as a total-etch adhesive system with Herculite XRV as a light cured composite resin or Fuji II LC glass ionomer as an restoration. Each essential group contained a control group without fluoride therapy. Thermo cycling was done, and then the rate of microleakage was evaluated by the fluid filtration method.

RESULTS

There were no significant differences by pre and post-treatment with APF on microleakage of composite resin restorations. A significant difference was found on microleakage of glass ionomer restorations based on different APF therapy.

CONCLUSIONS

In contrast to composite resin restoration which had not influenced by fluoride therapy, after glass ionomer placement, the gel of fluoride led to significantly increase the microleakage of the restoration.

Effect of a new desensitizing material on human dentin permeability

OBJECTIVES

Resin-modified glass ionomers (RMGI) have demonstrated clinical success providing immediate and long-term relief from root sensitivity. RMGIs have been recently introduced as paste-liquid systems for convenience of clinical usage. The objective of this study was to measure the ability of a new paste-liquid RMGI to reduce fluid flow through human dentin, compared to an established single-bottle nanofilled total etch resin adhesive indicated for root desensitization.

METHODS

Dentin permeability was measured on human crown sections on etched dentin, presenting a model for the exposed tubules typical of root sensitivity, and permitting measurement of the maximum permeability. In the first two groups, the etched dentin was coated with either the RMGI or adhesive, and permeability measured on the coated dentin. In a third group, a smear layer was created on the dentin with sandpaper, then the specimens were coated with the RMGI; permeability was measured on the smeared and coated dentin. Specimens from each group were sectioned and examined via scanning electron microscopy (SEM).

RESULTS

Both the resin adhesive and the new paste-liquid RMGI protective material significantly reduced fluid flow through dentin, and exhibited excellent seal on dentin with either open tubules or smear-layer occluded tubules. The RMGI infiltrated the smear layer with resin during placement, penetrated dentin tubules, and formed resin tags.

SIGNIFICANCE

The RMGI was equivalent to the adhesive in its ability to reduce fluid flow and seal dentin. It is therefore concluded that the new RMGI and the adhesive show the potential to offer excellent sensitivity relief on exposed root dentin.

Effect of a new liner/base on human dentin permeability

OBJECTIVES

Resin-modified glass ionomers (RMGI) have demonstrated clinical success in their ability to minimize post-operative sensitivity of restorations. RMGIs have been recently introduced as paste-liquid systems for convenience of clinical usage. The objective of this study was to measure the ability of a new paste-liquid RMGI liner/base to reduce fluid flow through human dentin.

METHODS

Dentin permeability was measured on human crown sections on etched dentin, using etched dentin as a model for the exposed tubules typical of root sensitivity, and permitting measurement of the maximum permeability. In the one group, the etched dentin was coated with the RMGI, and pre- and post-treatment permeability was measured on the coated dentin. In the second group, a smear layer was created on the dentin with sandpaper, then the samples were coated with the RMGI; permeability was measured on the smeared and coated dentin. Samples from each group were sectioned and examined via scanning electron microscopy (SEM).

RESULTS

The new paste-liquid RMGI liner/base significantly reduced fluid flow through dentin, and exhibited excellent seal on dentin with either a smear layer or open tubules. SEM images show evidence that the RMGI infiltrated the smear layer with resin during placement, penetrated dentin tubules, and formed resin tags in acid-etched dentin.

CONCLUSIONS

Based on these results, combined with previous research on adhesion and microleakage, it is concluded that the new RMGI liner/base should minimize post-operative sensitivity in restorations.

In vitro evaluation of dentin permeability of fluorotic primary teeth with a new electronic hydraulic conductance measurement system with photosensors

OBJECTIVES

The permeability characteristics of dentin have been used in many in vitro studies to evaluate longitudinally the efficacy of various restorative and preventative procedures. The easiest way to evaluate dentin permeability is to calculate its hydraulic conductance (Lp) by fluid filtration method. There are researches on electronic hydraulic conductance measurement systems which can give more precise and reliable results of permeability of dentine than the classical system. To the authors' knowledge, there are no studies on bonding properties of restoratives to fluorotic primary teeth and dentin permeability of those teeth in the literature. The aim of this in vitro study was to determine the dentin permeability of fluorotic primary molars precisely with a new 'electronic hydraulic conductance measurement system with photosensors' and to compare the data with healthy primary molars.

METHODS

A total of 40 fluorotic and healthy primary second molar teeth with 1/3 root resorption, which were extracted for orthodontic purpose and with no caries, restoration, fracture or crack were selected and used in this study. Teeth were classified according to the modified form of dental fluorosis index of Thylstrup&Fejerskov. Dentin discs were placed in the electronic hydraulic conductance measurement system with photosensors which was designed for the measurement of dentin permeability. The amount of distilled water passed through each dentin disk (muL/min) under a constant pressure was determined. Dentin permeability data of the fluorotic and healthy teeth were recorded and analysed statistically.

RESULTS

It was observed that dentin permeability decreases, while dental fluorosis severity increases in primary teeth.

Effect of Pulp Pressure on the Micropermeability and Sealing Ability of Etch & Rinse and Self-etching Adhesives

Etch & rinse adhesives are much more micropermeable and affected by pulp fluid compared with self-etching adhesives. Pulp pressure reduces dentin sealing with etch & rinse adhesives but not with self-etching adhesives. Pulp pressure has no effect on enamel sealing, which is lower when self-etching adhesive is used.

Methodologies for assessment of apical and coronal leakage of endodontic filling materials: a critical review

Apical leakage continues to be a topic of great interest, because in spite of the advances in Endodontics, clinical failures still occur. Most failures are probably attributed to the proliferation of bacteria that remain viable after chemical-mechanical preparation and cause periapical tissue irritation. Coronal leakage has aroused researchers' interest over the last few years, since canals may be re-contaminated after loss of coronal sealing or fracture of the remaining tooth. In this review, the various methodologies used for assessing root canal sealing capacity are critically analyzed, as they are not standardized, which makes it difficult to compare the results obtained when different methodologies are used, even though the same substrate is being assessed.

Apical Leakage of Resin Based Root Canal Sealers with a New Computerized Fluid Filtration Meter

In this in vitro study, the apical leakage of three root-canal sealers: AH Plus, Diaket, and EndoREZ was evaluated using a new computerized fluid filtration meter. Forty-five extracted human premolar teeth with single root and canal were used. The coronal part of each tooth was removed and the root canals were prepared using GT Rotary files and crown-down technique. The roots were randomly divided into three groups of 15 samples, filled with one of the test materials and gutta-percha cones by the cold lateral condensation technique and were stored at 37 degrees C and 100% humidity for 7 days. One-week later, apical parts of roots of 10 +/- 0.05 mm were attached to computerized fluid filtration meter. Apical leakage quantity was determined as microl/cmH(2)O/min(-1). Statistical analysis indicated that root fillings with Diaket in combination with cold lateral condensation technique showed lower apical leakage than the others (p < 0.05). In addition, this new computerized fluid filtration meter allowed quantitative measurement of leakage easily. As it is a newly developed device to measure apical leakage of endodontic sealers, the reliability of it needed to be tested.

Microleakage of glass-ionomer cement placed in association with non-setting calcium hydroxide

The purpose of this investigation was to determine whether non-setting calcium hydroxide [Ca (OH)2] cement placed in the root canal system of premolar teeth would affect the subsequent microleakage of a glass-ionomer restoration (GIC). Following selection, 62 human premolar teeth extracted for orthodontic reasons were accessed and root canals prepared according to a standardized procedure. The specimens were then allocated randomly into two major groups each of 30 teeth. Two other teeth were used as a positive and a negative control. The control group was restored with glass-ionomer cement following drying of the canal and placement of a cotton wool pledget. The test group had all canals dressed with non-setting Ca(OH)2 and then was subdivided, one set (n = 22) being restored following conditioning of the access cavity margins, the other (n = 8) having the margins cleaned with a hand excavator. Samples were assessed for microleakage using a two-point scoring system (leakage or no leakage) in conjunction with a clearing technique using AgNO3. Using Fisher's exact test, a statistically significant difference was found between the control and test groups (P < 0.05) but there was no significant difference between the excavated and conditioned cavities (P=0.55). It is concluded that contamination of access cavity margins with Ca(OH)2 during medication of a root canal interferes with the bond of GIC, resulting in increased microleakage in vitro.

Root apex sealing with different filling materials photopolymerized with fiber optic-delivered argon laser light

The present study evaluates the seal quality in the apex delta of uniradicular teeth filled with light-cured materials (calcium hydroxide, glass ionomer, and Flow-Fill Magic composite). A total of 45 roots prepared by the endo PTC/Dakin technique were used. All sample restorations were light-cured with 488-nm argon laser light. A 200-microm optical fiber introduced into the root canal delivered 100 mW of light power to the filler material. The fiber tip was positioned 5 mm away from the apex. Light was applied for 20 s. After curing, the samples were immersed in a methylene blue solution for 24 h. Then the samples were cut longitudinally and analyzed under a stereoscopic microscope for dye infiltration. For the sake of comparison, an additional group of ten samples submitted to conventional treatment with EndoREZ root canal sealer was also analyzed. The samples sealed with calcium hydroxide or with the glass ionomer presented less dye infiltration, as compared to those sealed with the Flow-Fill Magic composite. All products activated by fiber optic-delivered light showed superior sealing quality when compared with the self-activated EndoREZ sealer.

In vitro dentine permeability: the relative effect of a dentine bonding agent on crown preparations

OBJECTIVE

The aim of this study was to determine whether a dentine bonding agent (DBA) had an effect in reducing fluid filtration under cemented provisional crowns.

METHODS

Crown preparations on 34 premolars, randomly allocated to two equal-sized test and control groups, were assessed for dentine permeability by a fluid filtration technique. In the test group, prepared crowns were acid-etched and then treated with a DBA (Prime & Bond NT). In the control group, no such DBA was applied. Provisional crowns were cemented on both groups of teeth using non-eugenol zinc oxide cement. Fluid filtration rates were measured repeatedly after crown preparation, at cementation, 1 h, 1 day, 1 week and 3 weeks following crown cementation for both groups. Filtration rates were also measured after acid-etching and dentine bonding for the test group.

RESULTS

There was insufficient evidence to suggest any statistically significant differences either between the two groups or, on average, across the five time points in each group in terms of the relative percentage of fluid filtration.

CONCLUSION

The DBA used did not seal dentinal tubules any more than did the smear layer and provisional crowns luted with a non-eugenol ZnO cement.

Effect of dentin perfusion on the sealing ability and microtensile bond strengths of a total-etch versus an all-in-one adhesive

OBJECTIVES

To test the null hypothesis that perfusion of dentin has no effect on the sealing or bond strength in Class V resin composite restorations using a two-step total-etch (Scotchbond 1), or a one-step self-etch (all-in-one) (Prompt L-Pop) adhesive.

METHODS

Dentin permeability in Class V cavity preparations cut into extracted human third molars was measured in a fluid transport setup. Resin composites were placed using either Scotchbond 1, or Prompt L-Pop with or without dentin perfusion at 1.47 kPa. Permeability was re-measured, and the reduction in permeability was calculated as a percentage of the initial value. Additionally, microtensile bond strength (microTBS) to dentin was measured.

RESULTS

Whereas the ability of Scotchbond 1 to seal dentin was significantly decreased due to dentin perfusion (p = 0.00025), that of Prompt L-Pop was not affected (p = 0.099). Scotchbond 1 produced significantly less dentinal seal than Prompt L-Pop only in the restorations carried out with perfusion (p = 0.0003), in the absence of perfusion, however, the difference was not significant (p = 0.343). Dentin perfusion significantly decreased the microTBS of Scotchbond 1 to dentin (p = 0.001). Due to excessive premature failure during sectioning, microTBS test could not be performed with Prompt L-Pop.

SIGNIFICANCE

Dentinal fluid flow may have detrimental effects on the sealing ability of dental adhesives depending on the type of adhesive used. Studies aiming to rank adhesives in relation to their sealing ability in vitro should not disregard dentin perfusion.

Anin vitrocomparison of adhesive systems to seal pulp chamber walls

AIM

To compare in vitro the sealing properties of five different dentine adhesive materials (Prime&Bond NT (PBNT); Prompt L-Pop (PLP); Clearfil SE Bond (CSEB); Scotchbond Multi Purpose Plus (SMPP); EBS-Multi (EBSM)) inside the pulp chamber.

METHODOLOGY

Seventy-five recently extracted human molar teeth were used. The roof of the pulp chambers and roots were removed under water cooling. Pulp tissue was removed, and the canal orifices were sealed. The pulp chambers were then treated with 5% sodium hypochlorite (NaOCl) for 1 min. The teeth were randomly divided into five groups of 15 teeth each. Adhesive systems were applied to the pulp chamber walls according to the manufacturers' instructions. The samples were connected to Plexiglass plates, and a fluid filtration method was used for quantitative evaluation of leakage. Measurements of fluid movement were made at 2-min intervals for 8 min. The quality of seal of each specimen was measured immediately, after 24 h, 1 week and 1 month. The data were statistically analysed by repeated-measurements multivariate anova, Friedman test, Wilcoxon signed rank test, Kruskal-Wallis of one-way anova and Mann-Whitney U-tests. The pulp chamber wall with and without NaOCl and resin-dentine interfaces of specimens were observed under a scanning electron microscope (SEM).

RESULTS

The leakage values of the materials were significantly different at different measurement periods. In all groups, leakage values decreased with time (P < 0.05). PBNT and PLP had the least leakage during immediate measurements (P < 0.05). After 1 month, leakage of all adhesive systems was not significantly different (P < 0.05). SEM observation of pulp chamber walls demonstrated that the irregular dentine surface without smear layer was present in the nontreated group. However, NaOCl application removed the collagen fibrils leaving the dentine surface smooth. At resin-dentine interfaces of specimens, no hybridization zone was observed.

CONCLUSIONS

None of the materials had created a perfect seal to the pulp chamber walls. PBNT and PLP had better sealing over the short term, but over the long term, there were no differences between the materials.

Comparison of two methods to measure permeability of dentin

Dentin permeability was measured alternatively with two methods: a 10-microl capillary method with visual evaluation (PC) and a motorized automatic measuring device (Flodec, FD), both interposed in a simulated perfusion system. Eight human third molar coronal fragments were connected to systems, and their permeability to distilled water measured at 0, 5, 10, 15, 20, 25, and 29 cm H(2)O pressure. Resultant permeabilities (in microl/s) for both techniques were interrelated with the use of the Passing and Bablok nonparametric method, which gives information about the range of constant and proportional errors and their 95% confidence intervals (95CI). The relationship between the methods is described by the regression formula: FD = -0.0003 + 0.945.PC, with 95CI for constant (-0.0015-0.0009) and for slope (0.738-1.168), indicating that both methods are interchangeable, although not identical.

The effect of thermocycling regimens on the nanoleakage of dentin bonding systems

OBJECTIVES

The purpose of this study was to compare nanoleakage associated with polished and fractured specimens, and evaluate the effects of thermocycling on nanoleakage.

METHODS

The dentin bonding systems used in this study were PermaQuik and Prime and Bond NT (PBNT). Flat occlusal dentin surfaces and class V cavities from extracted human molars were bonded with one of the dentin bonding systems. With or without thermocycling, samples were immersed in a 50% w/v solution of silver nitrate for 24h, and exposed to photodeveloping solution for 8h. The specimens were cut or fractured, and mounted on stubs, carbon coated and observed in a Field Emission-SEM using backscattered electron mode.

RESULTS

Polished and fractured specimens showed similar nanoleakage patterns for both dentin-bonding systems. Thermocycling with regimens of different temperatures and number of cycles did not result in different nanoleakage patterns and leakage lengths in controls and thermocycled groups. PBNT combined with non-rinse conditioner (NRC) produced no significant difference in nanoleakage length, but a somewhat different nanoleakage pattern, compared with PBNT and 34% phosphoric acid.

SIGNIFICANCE

Thermocycling does not have an effect on nanoleakage of dentin bonding systems. The smearing effect from sectioning and polishing procedures does not affect the nanoleakage result.

The effects of post-extraction time on the hydraulic conductance of human dentine in vitro

The permeability characteristics of dentine have been used in many in vitro studies to evaluate longitudinally the efficacy of various restorative and preventative procedures. However, the permeability of human dentine increases over time after tooth extraction. The aim here was to determine if there is a steady phase in dentine permeability in vitro over time. The convective permeability of dentine discs cut from extracted human third molars to 0.8% albumin solution was measured initially on day 7 after extraction using a fluid-transport model and the hydraulic conductance was calculated. The permeability of each disc was then re-measured de- and re-mounting the split-chamber 1h after the initial measurement as well as on days 8, 9, and 37 after extraction. No significant difference was found between the initial and 1h hydraulic conductances. A significant increase in hydraulic conductance was seen from day 7 to 9, but there was no significant difference between the hydraulic conductances on days 9 and 37. These results suggest that the measurements were reproducible and that a steady phase of dentine permeability is established 9 days after extraction under these study conditions in vitro.

The influence of resin composite and bonded amalgam restorations on dentine permeability in Class II cavities in vitro

OBJECTIVES

This study was conducted to measure and compare dentine permeability reduction in Class II preparations, after restoration with resin composite or bonded amalgam, using either a multi-step or one-bottle dental adhesive system.

METHODS

An in vitro fluid transport model was used to measure initial dentine permeability in Class II cavities with an intact smear layer in crown segments from extracted human premolars. One week and 3 months after restoration with resin composite or bonded amalgam, using either multi-step or one-bottle dental adhesive system, the measurements were repeated and the reduction in permeability was calculated as a percentage of the initial values. The data were analyzed statistically using a one-way ANOVA and Least Significant Difference tests.

RESULTS

After 1 week the resin composite with one-bottle dental adhesive system provided the highest reduction in dentine permeability, whereas after 3 months the bonded amalgam caused the highest reduction. At both time intervals the resin composite with multi-step adhesive system provided the lowest reduction. (P=0.036 at 1 week, P=0.016 at 3 months). After 3-months storage in water a significant increase in dentine permeability reduction was found in the bonded amalgam group only (P=0.017). The reduction in dentine permeability provided by resin composite with one-bottle dental adhesive system and bonded amalgam in Class II cavities was similar at both time intervals. (P=0.182 at 1 week, P=0.750 at 3 months).

SIGNIFICANCE

The results of this study indicated that on the basis of reducing dentine permeability in vitro, resin composite restorations with the investigated one-bottle adhesive system was superior to its multi-step equivalent and bonded amalgam can also be preferred in Class II restorations.