Real-time atomic force microscopy of root dentine during demineralization when subjected to chelating agents

A critical analysis of research methods and experimental models to study irrigants and irrigation systems

Irrigation plays an essential role in root canal treatment. The purpose of this narrative review was to critically appraise the experimental methods and models used to study irrigants and irrigation systems and to provide directions for future research. Studies on the antimicrobial effect of irrigants should use mature multispecies biofilms grown on dentine or inside root canals and should combine at least two complementary evaluation methods. Dissolution of pulp tissue remnants should be examined in the presence of dentine and, preferably, inside human root canals. Micro-computed tomography is currently the method of choice for the assessment of accumulated dentine debris and their removal. A combination of experiments in transparent root canals and numerical modeling is needed to address irrigant penetration. Finally, models to evaluate irrigant extrusion through the apical foramen should simulate the periapical tissues and provide quantitative data on the amount of extruded irrigant. Mimicking the in vivo conditions as close as possible and standardization of the specimens and experimental protocols are universal requirements irrespective of the surrogate endpoint studied. Obsolete and unrealistic models must be abandoned in favour of more appropriate and valid ones that have more direct application and translation to clinical Endodontics.

Comparative evaluation of decalcifying agents for dissolution of pulp stones: An in vitro study

Background:

Despite constant advances in science, obscurity remains in the efficient removal of pulp stones to aid in successful root canal treatment. In this context, chemical means of dissolving pulp stones were explored.

Aim:

The aim of this study is to evaluate and to compare the efficacy of decalcifying agents on the dissolution of pulp stones.

Materials and Methods:

The study was divided into two groups for pulp stone analysis (21 samples) and dentin analysis (54 samples). Twenty-one pulp stones from patients aged 18–70 who underwent root canal treatment were collected and divided into three subgroups (n = 7) randomly. They were subjected to chemical treatment in a labeled glass container with 5 ml of the respective chemical agents, such as 17% ethylenediaminetetraacetic acid solution (positive control), no treatment (negative control), and newly developed Physiological Simulated Decalcifying Agent (PSDA). At the end of the study period (24 h), the samples were removed, rinsed with deionized water, and subjected to physical analysis, scanning electron microscopy (SEM), and Energy –dispersive X-ray spectroscopy (EDS) analysis. Under dentin analysis, 54 maxillary premolars scheduled for orthodontic extraction without caries or extensive restorations were selected, following which 2-mm thick transverse dentinal sections at the cementoenamel junction level were obtained and randomly divided into two groups for SEM (n = 21) and microhardness analysis (n = 33). The samples were subjected to respective chemical treatment groups similar to pulp stones for 24 h and analyzed using SEM, EDS, and microhardness analysis.

Results:

Postchemical treatment with the newly developed decalcifying solution, the pulp stones showed the absence of nodular crystallites and surface softening under SEM and a decrease in the calcium level under EDS analysis. Concerning the microhardness of dentin, no significant changes could be observed.

Conclusion:

The newly explored PSDA was found to be efficacious in the decalcification of pulp stones at a clinically relevant time of 24 h, without significantly affecting the structural integrity and the hardness values of dentin.

Real-time co-site optical microscopy study on the morphological changes of the dentine's surface after citric acid and sodium hypochlorite: a single-tooth model

BACKGROUND

To this day, the effects of sodium hypochlorite and chelating agents on the smear layer and on the dentine's surface, remain not fully examined. The study is aimed to analyze the dentine's surface treated with 40% citric acid and 5.25% sodium hypochlorite according to two irrigation protocols.

MATERIALS AND METHODS

The study employed a computer-controlled Nikon Eclipse LV100 optical microscope. Ten roots split longitudinally with canals prepared mechanically using the MTwo system to a size of 40/04 were observed. The root halves were divided into two study groups, one half in each of the groups. According to two irrigation protocols, the dentine's surface was irrigated with 40% citric acid and 5.25% sodium hypochlorite, separated with water. Dentine surface was observed in a fixed place and photographed in 500 × magnification after each irrigation stage. The obtained images were then analyzed using computer software (NIS-Elements AR, GIMP-2.6, ImageJ 1.45s).

RESULTS

Various speed of removal of the smear layer and varied morphological changes of the dentine's surface were observed in both examined groups. Double irrigation of the dentine with citric acid for 30 s resulted in complete removal of the smear layer, and double irrigation for 60 s resulted in increased mean diameter of the dentine tubules (degradation of the dentine's surface).

CONCLUSIONS

Double alternating irrigation with citric acid and sodium hypochlorite for 30 s yielded satisfactory results, while double irrigation for 60 s resulted in increased mean diameter of the dentine tubules. A real time assessment of the dentine's surface changes after both tested solutions can improve understanding of the phenomena that occur during the irrigation and as a result it might help to improve clinical outcomes in root canal treatment.

A Review of Single-Cell Adhesion Force Kinetics and Applications

Cells exert, sense, and respond to the different physical forces through diverse mechanisms and translating them into biochemical signals. The adhesion of cells is crucial in various developmental functions, such as to maintain tissue morphogenesis and homeostasis and activate critical signaling pathways regulating survival, migration, gene expression, and differentiation. More importantly, any mutations of adhesion receptors can lead to developmental disorders and diseases. Thus, it is essential to understand the regulation of cell adhesion during development and its contribution to various conditions with the help of quantitative methods. The techniques involved in offering different functionalities such as surface imaging to detect forces present at the cell-matrix and deliver quantitative parameters will help characterize the changes for various diseases. Here, we have briefly reviewed single-cell mechanical properties for mechanotransduction studies using standard and recently developed techniques. This is used to functionalize from the measurement of cellular deformability to the quantification of the interaction forces generated by a cell and exerted on its surroundings at single-cell with attachment and detachment events. The adhesive force measurement for single-cell microorganisms and single-molecules is emphasized as well. This focused review should be useful in laying out experiments which would bring the method to a broader range of research in the future.

Efficacy of glycolic acid for the removal of calcium hydroxide from simulated internal Resorption cavities

OBJECTIVES

This study evaluated the efficacy of 5% and 10% glycolic acid solutions for the removal of calcium hydroxide medicament from artificial internal resorption cavities.

MATERIALS AND METHODS

A total of 170 human maxillary premolars were selected and artificial internal resorption cavities were prepared using round burs and 37% orthophosphoric acid in the apical third of the root halves. Entire canal and resorption cavity were filled with calcium hydroxide paste. Then, the specimens were assigned to 2 control groups or ten experimental groups according to the irrigating solutions used for medicament removal with and without activation with ultrasonic energy as following: 5% glycolic acid, 10% glycolic acid, 17% EDTA, and 10% citric acid and distilled water. The resorption cavities were examined under different magnifications using stereomicroscopy and scanning electron microscopy (SEM). The calcium hydroxide remnants in the resorption cavity were scored by 2 evaluators using a 4-scoring scale. The data were analyzed with Kruskal-Wallis H tests with 5% significance threshold.

RESULTS

There was no significant difference regarding the distribution of removal scores among non-activated solutions (P > 0.05). In activated groups, 10% glycolic acid irrigation removed significantly more amount of calcium hydroxide than EDTA and distilled water (P < 0.05). No significant difference was found between the efficacy of 10% glycolic and citric acid (P > 0.05). Citric acid, 5% glycolic acid, and EDTA showed similar removal scores (P > 0.05). Passive ultrasonic irrigation significantly improved calcium hydroxide removal scores in 10% glycolic acid, citric acid, and EDTA groups (P < 0.05). The SEM examination revealed that the specimens that were scored 0 are not entirely free of calcium hydroxide remnants.

CONCLUSION

Concentration of 10% glycolic acid removed significantly more calcium hydroxide paste from resorption cavities than EDTA when used with passive ultrasonic irrigation. Although passive ultrasonic irrigation favored medicament removal in all irrigating solutions, complete elimination of medicament remnants was unattainable.

CLINICAL RELEVANCE

This study showed the improved efficacy of ultrasonically activated 10% glycolic acid in removing the calcium hydroxide medicament from the internal resorption cavity.

Scanning electron microscopy evaluation of chitosan and carboxymethyl chitosan as retrograde smear layer removing agents

Background:

The smear layer acts as a physical barrier against penetration of root canal medicaments and sealers, thus compromising the seal leading to microleakage.

Objectives:

This study was conducted to evaluate the efficacy of 17% ethylenediaminetetraacetic acid (EDTA), 0.2% chitosan solution, and 0.2% carboxymethyl chitosan (CMC) used as smear layer removing agents in retrograde root canal preparation using scanning electron microscopy (SEM).

Materials and Methodology:

Eighty single-rooted teeth extracted for periodontal reasons were collected for the study. Root canals were prepared and obturated with gutta-percha coated with AH plus resin sealer. Apical 3 mm of each root resected and Class I retrograde preparation carried out using ultrasonic handpiece and ultrasonic retro tips to a depth of 3 mm along the root long axis. In Group 1 (control), normal saline solution alone was used for smear layer removal. In Group II, 17% EDTA, Group III and IV were treated with 5 ml of 0.2% chitosan and 0.2% carboxyl methyl chitosan, respectively, for 3 min. Blinded evaluation of specimens using SEM was performed independently by two operators who registered the amount of the smear layer present on the surface of the canal walls based on the score described by Hülsmann et al.

Results:

Group I (saline) was least efficient in the removal of the smear layer. Group II (17% EDTA), Group III (0.2% Chitosan), and Group IV (0.2% CMC) efficiently removed the smear layer from the retrograde cavity with mean scores 1.35, 1.60, and 1.35, respectively. Statistically, no significant difference found in Group II (17% EDTA), Group III (0.2% Chitosan), and Group IV (0.2% CMC).

Conclusions:

About 0.2% CMC and 0.2% chitosan can be better alternatives to 17% EDTA for smear layer removal due to their biological advantages.

Dentine decalcification and smear layer removal by different ethylenediaminetetraacetic acid and 1-hydroxyethane-1,1-diphosphonic acid species

AIM

To compare solutions of di- and tetrasodium ethylenediaminetetraacetic acid (EDTA) and 1-hydroxyethane-1,1-diphosphonic acid (HEDP) regarding their ability to solubilize calcium from dentine and remove smear layer.

METHODOLOGY

Solutions with a molarity corresponding to that of 17% Na₂ EDTA (pH adjusted to 8.5) were prepared by dissolving Na₂ and Na₄ salts of HEDP (etidronate), or Na₄ EDTA in deionized water. Standardized root dentine discs covered by a smear layer were prepared from human third molars. These discs (n = 10 per group) were immersed in test solutions or phosphate-buffered saline for 1 min. The dissolved Ca²⁺ was determined by atomic absorption spectroscopy, apparently opened dentinal tubules by laser scanning microscopy and automated image analysis. Ca²⁺ values were compared between groups by parametric, tubular areas by nonparametric methods, α = 0.05.

RESULTS

Solutions prepared from the tetrasodium salts were alkaline (pH 11.3-11.4), whilst counterparts made from the disodium salts were acidic. The EDTA solutions dissolved more calcium than the HEDP counterparts (P < 0.05); solutions prepared with the disodium salts dissolved more calcium than those made from the tetrasodium salts (P < 0.05). There was a high correlation between dissolved calcium and the apparently opened tubular areas (Spearman's ρ = 0.81). Differences between groups regarding opened tubules were similar to those observed regarding the Ca²⁺ values, with a slightly reduced discerning power due to high variance.

CONCLUSION

Calcium chelation and thus smear layer removal by EDTA and HEDP are influenced by pH.

Scanning Electron Microscopic Evaluation of Efficacy of 17% Ethylenediaminetetraacetic Acid and Chitosan for Smear Layer Removal with Ultrasonics: An In vitro Study

Introduction:

The main aim of root canal treatment is cleaning, shaping and then obturating three dimensionally to prevent reinfection. This includes chemicomechanical cleansing by instrumentation and the use of irrigating solutions. Therefore, the purpose of this study was to compare the smear layer removal from root canal dentine subjected to two root canal irrigants, 17% EDTA and 0.2% Chitosan, a new irrigant using Scanning Electron Microscope.

Methodology:

40 single rooted premolars were decoronated followed by instrumentation with I Race files and intermediate irrigation with 3% sodium hypochlorite and activation with ultrasonics. Then the samples were longitudinally sectioned and place in the respective test solutions and their controls for 5 minutes. Scanning Electron Microscopic evaluation was further carried out.

Results:

The results of the present study indicates that the Chitosan which was proved effective in removing smear layer.

Conclusion:

A moderate concentration of 0.2% chitosan removes the smear layer with greater efficiency.

Comparative Analysis of Dentinal Erosion after Passive Ultrasonic Irrigation versus Irrigation with Reciprocating Activation: An Environmental Scanning Electron Study

INTRODUCTION

The aim of this study was to assess ex vivo the erosive effects of passive ultrasonic irrigation versus irrigation with reciprocating activation on the dentinal surface of the root canal at 3 predetermined levels using environmental scanning electron microscopy.

METHODS

Ten roots of mandibular premolars were prepared using the ProTaper Universal system (Dentsply Maillefer, Ballaigues, Switzerland). The specimens were embedded in flasks cleaved longitudinally, and indentations were made 3.0, 6.0, and 9.0 mm from the apex. The specimens in the control group (n = 10) were cleaned in an ultrasonic bath containing 2.5% sodium hypochlorite and 17% EDTA and then dried. Then, environmental scanning electron microscopic images were obtained at magnification × 800. The specimens were then reassembled in their flasks, and the NaOCl and EDTA solutions were activated according to the conditions established for the experimental groups (ie, the passive ultrasonic irrigation group [n = 5] and the EasyClean (Easy Equipamentos Odontológicos, Belo Horizonte, MG, Brazil) group, irrigation with reciprocating activation with the EasyClean instrument [n = 5]). The specimens of both experimental groups were analyzed in the same manner as in the control group. Analysis of the dentinal surface topography was conducted using the 3D Roughness Reconstruction program (Phenom-World BV, Eindhoven, the Netherlands) as a means for assessing erosion. The data were evaluated by means of the Kruskal-Wallis, Student-Newman-Keuls, and Mann-Whitney tests.

RESULTS

In the EasyClean group, the degree of dentinal erosion at 3.0 mm was significantly higher than at 9.0 mm. In the other comparisons, there was no statistically significant difference (P < .05).

CONCLUSIONS

The final irrigation techniques tested were equivalent in relation to the degree of erosion caused to the dentinal surface.

Prenatally administered HMB modifies the enamel surface roughness in spiny mice offspring: An atomic force microscopy study

OBJECTIVE

The aim of this research was to check the effect of the prenatally administered β-hydroxy β-methylbutyrate (HMB) on the development of enamel surface of the spiny mice offspring.

DESIGN

The spiny mice dams were randomly assigned into three groups: control group (not supplemented with HMB) and two experimental groups in which powdered HMB was given at the daily dosage of 0.2g/kg of body weight (group I) and 0.02g/kg of body weight (group II) during the last period of gestation. Newborn pups were euthanized by CO₂ inhalation. The morphology of incisor teeth was analysed using atomic force microscopy (AFM) in semi-contact mode in the height, magnitude and phase domains. Height images became a basis for determination of surface roughness parameters.

RESULTS

Conducted study indicated that maternal HMB administration markedly influences enamel development. Enamel of offspring's teeth in both experimental groups was characterized by significantly smaller values of indices describing surface roughness and profile. HMB supplementation influenced the calculated parameters regardless of the diet type and offspring sex, however higher dose of HMB caused stronger changes in enamel surface's physical properties and could be observed in higher intensity in the male group.

CONCLUSIONS

HMB administration caused reduction in the irregularities of enamel surface, thereby possibly reducing the probability of bacteria adhesion and caries development. These observations may serve to improve nutrition and supplementation of animals and could be a lead for further research.

Efficacy of etidronic acid, BioPure MTAD and SmearClear in removing calcium ions from the root canal: An in vitro study

OBJECTIVE

The purpose of this study was to quantify the amount of calcium ions removed from the root canal by etidronic acid (HEBP), BioPure MTAD, and SmearClear using atomic absorption spectrophotometer.

MATERIALS AND METHODS

Fifty (n = 50) freshly extracted human mandibular premolar teeth were collected and decoronated at the cementoenamel junction. The canals were prepared in a crown down fashion using the rotary system and copiously irrigated with 1.0% sodium hypochlorite. All specimens were rinsed with the deionized water. Based on the type of chelating agent used, the samples (n = 10) were randomly divided into five (four test and one negative control) groups. Accordingly, Group I - 9% HEBP, Group II - 18% HEBP, Group III - SmearClear, Group IV - BioPure MTAD, and Group V - normal Saline. Subsequent to irrigation, the solution was collected in a test tube and subjected to atomic absorption spectrophotometer for the quantification of calcium ions removed from the root canal.

RESULTS

The mean concentration of calcium ions removed from the root canal (mean ± standard deviation) in all groups (I-V) were 13.32 ± 0.54 μg/ml, 16.36 ± 0.27 μg/ml, 20.04 ± 0.24 μg/ml, 18.15 ± 0.39 μg/ml, and 8.74 ± 0.49 μg/ml, respectively.

CONCLUSIONS

SmearClear was the most effective agent for the removal of calcium ions from the root canal. Hence, its combined use with an organic solvent can be recommended for efficient smear layer removal.

Preventive effect of different toothpastes on enamel erosion: AFM and SEM studies

The aim of the present in vitro study was the evaluation of new formulation toothpastes on preventing enamel erosion produced by a soft drink (Coca Cola), using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Fifty enamel specimens were assigned to 10 groups of 5 specimens each. 1: intact enamel, 2: enamel + soft drink, 3: intact enamel + BioRepair Plus-Sensitive Teeth, 4: enamel + soft drink + BioRepair Plus-Sensitive Teeth, 5: intact enamel + BioRepair Plus-Total Protection, 6: enamel + soft drink + BioRepair Plus-Total Protection, group 7: intact enamel + Sensodyne Repair & Protect, 8: dentin + soft drink + Sensodyne Repair & Protect, 9: intact dentin + Colgate Sensitive Pro Relief, 10: dentin + soft drink + Colgate Sensitive Pro Relief. The surface of each specimen was imaged by AFM and SEM. The root mean-square roughness (Rrms ) was obtained from the AFM images and the differences in the averaged values among the groups were analyzed by ANOVA test. Comparing groups 4, 6, 8, 10 (soft drink + toothpastes) Colgate Sensitive Pro Relief promoted enamel remineralization, while BioRepair Plus-Sensitive Teeth, Biorepair Plus-Total Protection and Sensodyne Repair & Protect provided lower effectiveness in protecting enamel against erosion.

SIGNIFICANCE

the use of new formulation toothpastes can prevent enamel demineralization.

The role of different toothpastes on preventing dentin erosion: an SEM and AFM study®

The aim of the present in vitro study was the evaluation of new formulation toothpastes on preventing dentin erosion produced by a soft drink (Coca Cola®), using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Fifty dentin specimens were divided in treatment and control halves and were than assigned to 5 groups of 10 specimens each: group 1a: intact dentin, group 1b: dentin + soft drink, group 2a: intact dentin + Biorepair Plus-Sensitive Teeth®, group 2b: dentin + soft drink + Biorepair Plus-Sensitive Teeth®, group 3a: intact dentin + Biorepair Plus-Total Protection®, group 3b: dentin + soft drink + Biorepair Plus-Total Protection®, group 4a: intact dentin + Sensodyne Repair & Protect®, group 4b: dentin + soft drink + Sensodyne Repair & Protect®, group 5a: intact dentin + Colgate Sensitive Pro Relief®, group 5b: dentin + soft drink + Colgate Sensitive Pro Relief®. The surface of each specimen was imaged by AFM and SEM. Comparing specimens of group a and b (no demineralization and demineralization), a statistically significant difference (p < 0.01) in Rrms values was registered. Comparing b groups, all the analyzed toothpastes tended to remineralize the dentine surface in different extent. Biorepair Plus-Total Protection® and Sensodyne Repair & Protect® provided higher protective effect against dentin demineralization.

Etidronate from medicine to endodontics: effects of different irrigation regimes on root dentin roughness

An increase in dentin roughness, associated with surface composition, contributes to bacterial adherence in recontaminations. Surface roughness is also important for micromechanical interlocking of dental materials to dentin, and understanding the characteristics of the surface is essential to obtain the adhesion of root canal sealers that have different physico-chemical characteristics.

OBJECTIVES

To evaluate the effects of sodium hypochlorite (NaOCl), ethylenediaminetetraacetic (EDTA), etidronic (HEBP), and citric acid (CA) associated with different irrigation regimens on root dentin roughness.

MATERIAL AND METHODS

Forty-five root halves of anterior teeth were used. The root parts were sectioned in thirds, embedded in acrylic resin and polished to a standard surface roughness. Initially, the samples of each third were randomly assigned into 3 groups and treated as follows: G1 - saline solution (control); G2 - 5% NaOCl+18% HEBP mixed in equal parts; and G3 - 2.5% NaOCl. After initial measuments, the G3 samples were distributed into subgroups G4, G5 and G6, which were subjected to 17% EDTA, 10% CA and 9% HEBP, respectively. Following the new measuments, these groups received a final flush with 2.5% NaOCl, producing G7, G8 and G9. The dentin surface roughness (Ra) was determined before and after treatments using a profilometer. The Wilcoxon test (α<0.05) was used to compare the values before and after treatments, and the Friedman test (α<0.05) to detect any differences among root thirds.

RESULTS

(i) NaOCl did not affect the surface roughness; (ii) there was a significant increase in roughness after the use of chelating agents (P<0.01); and (iii) only the G3 group showed a difference in surface roughness between apical third and other thirds of the teeth (P<0.0043).

CONCLUSION

Only the irrigation regimens that used chelating agents altered the roughness of root dentin.

Influence of tip wear of piezoelectric ultrasonic scalers on root surface roughness at different working parameters. A profilometric and atomic force microscopy study

Roughness on tooth surfaces is reported to facilitate the reestablishment of microbial dental plaque. Hence, the main goal of dental scaling is to remove bacterial plaque and obtain smoother tooth surfaces. This study was aimed to assess the influence of tip wear of ultrasonic scaler inserts on root surface roughness at different working parameters. Twenty piezoelectric ultrasonic scaler inserts (10 worn/10 new) were selected to examine the erosion ratio (ER) on the scaler tips and to assess the influence of tip wear on root surface roughness. Erosion on the tip surfaces was evaluated under atomic force microscopy (AFM). Root samples were prepared and instrumented by new (Group I) and worn (Group II) inserts at different working parameters. Roughness change (Rc) on root surfaces after instrumentation was examined under profilometer and compared between and within the groups. Statistically significant differences were found between the mean ERs of new and worn tips (P < 0.01). The results of this study showed that tip angulation and instrument power strongly influenced the Rc values on instrumented samples (P < 0.05). It was also revealed that tip wear influenced the Rc values on root surfaces especially at 45° tip angulation (P < 0.05). Therefore, tip wear should also be considered as much as the other parameters to minimize the surface roughness during ultrasonic treatment.

Failure of fiber posts after cementation with different adhesives with or without silanization investigated by pullout tests and scanning electron microscopy

INTRODUCTION

The aim of the study was to test retentive forces of different adhesive systems after cementation of glass-fiber posts with or without prior silanization of the post by using a pullout test and scanning electron microscope (SEM) observation to detect the mode of failure.

METHODS

Fifty-six roots were randomly divided into 6 experimental and 2 control groups: ParaCore (PAR), Paracore + silane (PAR-SIL), RelyX Unicem (RXU), RelyX Unicem + silane (RXU-SIL), RelyX ARC (RXA), RelyX ARC + silane (RXA-SIL), negative control (NEG-CON), and positive control (POS-CON). ParaCore posts were placed in the experimental groups (each n = 8) by using an adhesive resin with or without prior silanization. NEG-CON received uncemented posts (n = 4); POS-CON received an active screw post with an adhesive (n = 4). All samples were subjected to a pullout test in a universal mechanical testing machine for pullout tests and SEM to assess the fiber posts and the roots after the tests.

RESULTS

Mean failure load values for each ground were PAR 247.4 ± 59.3 N, PAR-SIL 240.5 ± 68.8 N, RXU 102.3 ± 22.8 N, RXU-SIL 106.4 ± 19.8 N, RXA 119.8 ± 27.3 N, RXA-SIL 125.8 ± 28.3 N, NEG-CON 0 ± 0 N, and POS-CON 412.9 ± 27.4 N. There was a statistically significant difference between the 3 experimental adhesive systems (P < .001) and between each experimental group and NEG-CON and POS-CON (P < .05). PAR was significantly different from RXU and RXA (P < .05). No statistically significant differences existed between RXU and RXA and between the use of silanization or not. Representative samples for SEM showed cohesive failure as the principal fracture mode for PAR and mainly adhesive failure for RXU and RXA.

CONCLUSIONS

The results indicated that silanization of fiber posts does not make a difference to prevent dislocation of a post. Full-etching systems demonstrated significantly higher retentive forces than self-etching systems.

Nanofork for single cells adhesion measurement via ESEM-nanomanipulator system

In this paper, single cells adhesion force was measured using a nanofork. The nanofork was used to pick up a single cell on a line array substrate inside an environmental scanning electron microscope (ESEM). The line array substrate was used to provide small gaps between the single cells and the substrate. Therefore, the nanofork could be inserted through these gaps in order to successfully pick up a single cell. Adhesion force was measured during the cell pick-up process from the deflection of the cantilever beam. The nanofork was fabricated using focused ion beam (FIB) etching process while the line array substrate was fabricated using nanoimprinting technology. As to investigate the effect of contact area on the strength of the adhesion force, two sizes of gap distance of line array substrate were used, i.e., 1 μm and 2 μm. Results showed that cells attached on the 1 μm gap line array substrate required more force to be released as compared to the cells attached on the 1 μm gap line array substrate.

Effects of chelating agents on the mineral content of root canal dentin

OBJECTIVE

The objective of this in vitro study was to assess the effect of several chelating agents on the mineral content of root dentin.

STUDY DESIGN

Extracted human mandibular incisor roots were prepared and divided into groups according to the following irrigation protocols: 1) 17% ethylenediaminetetraacetic acid (EDTA); 2) 10% citric acid solution; 3) 18% etidronate; 4) 2.25% peracetic acid; 5) and deionized water (control). Dentin chips were obtained (Gates-Glidden nos. 3, 4, and 5). The levels of different minerals were analyzed with the use of inductively coupled plasma-atomic emission spectrometry (ICP-AES).

RESULTS

1) Peracetic acid significantly decreased P, K, Mg, Na, and S levels compared with the other groups (P < .05). 2) S decreased by different levels in all of the chelating solutions (P < .05), and the greatest decrease was observed in peracetic acid. 3) Ca levels significantly decreased in peracetic acid, citric acid, and EDTA (P < .05). 4) Mn levels significantly decreased in the citric acid and peracetic acid groups (P < .05). 5) Na and Zn levels significantly decreased in the peracetic acid, citric acid, and etidronate groups (P < .05).

CONCLUSIONS

The chelation agents can create different effects on mineral contents of root dentin, so it is important to know what effects each solution will have on root dentin before their clinical use. In addition, according to the results of this in vitro study, it might be recommended that peracetic acid, in particular, should be used with caution.

Critical appraisal of published smear layer-removal studies: methodological issues

The smear layer phenomenon has been extensively addressed over the past 3 decades. However, there still are unanswered questions on this issue and the main responsible factor is the qualitative and nonreproducible character of most in vitro smear layer removal studies. The methodological reasons that led to the current lack of reliable conclusions on procedures aiming to remove the smear layer are comprehensively addressed. The limitations and outcomes related to different assessment methods are discussed as well. General speaking, the results by score-based conventional SEM studies are not trustworthy and reproducible. Computational routines able to automatically extract quantitative data of dentin morphology are necessary to minimize the human bias. An ideal experimental model should have a longitudinal observational character, in which a given dentin area can be observed at different times. The use of flat dentin samples should be avoided because of the influence of gravity as well as root canal anatomy on the final result of the chelating process. The experimental model also needs to take into consideration the amount and distribution of sclerotic dentin and irregular secondary dentin, otherwise the final results can be compromised. Inasmuch as there is a clear lack of scientific standard, simple comparative SEM evaluations are pointless at the present moment. The ideal experimental model to assess smear layer removal is not currently available. Therefore, further research efforts should be directed to the development of and testing of new methodological approaches to be used in the smear layer removal studies. The improvement of the experimental models is a requirement to draw up optimized clinical guidelines for the chemical treatment of the root dentin.

Interfacial adaptation of the Epiphany self-adhesive sealer to root dentin

OBJECTIVE

The present study was designed to investigate interfacial quality between both Epiphany and Epiphany SE and the surrounding dentin having conventional gutta-percha/AH plus root filling as reference for comparison.

STUDY DESIGN

A sample of 36 human maxillary canines was prepared and assigned to experimental groups of 12 teeth each, designated as G1, Resilon/Epiphany; G2, Resilon/Epiphany SE; and G3, gutta-percha/AH Plus. After the filling procedures, each specimen was horizontally sectioned at 3, 6, and 8 mm from the apex and a metallographic preparation was performed to enable the evaluation under Confocal Laser Scanning Microscopy (CLSM). The integrity of the interface was determined by calculating the ratio between the total sealer/dentin interface and the sealer/dentin interface that presented gap-containing regions. Additionally, the width of each gap was measured and pooled per each specimen for comparison. Statistical analysis was performed using nonparametric methods.

RESULTS

Nonbonding AH Plus/gutta-percha root fillings showed a significantly higher amount of gap-free regions (P < .05). In the same way, nonbonding AH plus root fillings displayed significantly narrower gaps compared with the 2 adhesive root-filling groups (P < .05).

CONCLUSIONS

Under the present in vitro conditions, the quality of the interfacial adaptation of the current adhesive root fillings is compromised even when teeth with simple anatomic features were obturated under well-monitored laboratory conditions.

Impact of two toothpastes on repairing enamel erosion produced by a soft drink: an AFM in vitro study

OBJECTIVES

The aim of the present in vitro study was the evaluation of two toothpastes (Sensodyne Pronamel and Biorepair Plus on repairing enamel erosion produced by a soft drink (Coca Cola), using Atomic Force Microscopy (AFM).

METHODS

Fifty extracted human central incisors free of caries were selected and divided in a treatment and a control half; they were kept in artificial saliva during whole experimentation. The treatment halves were divided into five groups; group 1: demineralization with soft drink; group 2: demineralization with soft drink + Pronamel; group 3: demineralization with soft drink + Biorepair Plus; group 4: intact enamel + Pronamel; group 5: intact enamel + Biorepair Plus. Specimen demineralization was carried on in 4 intervals of 2 min. In groups 2, 3, 4, and 5 the toothpastes were applied for 3 min at 0, 8, 24 and 36 h. The surface of each specimen was imaged by AFM and R(rms), root-mean-square roughness, and Maximum Depth of the cavities were registered.

RESULTS

Amongst treatment specimens of groups 1, 2, and 3 a statistically significant difference (P<0.01) in R(rms) and Maximum Depth values was registered: the toothpastes reduced enamel demineralization. No statistical differences in R(rms) values were registered between the two toothpastes.

CONCLUSIONS

The toothpastes tested (Pronamel and BioRepair Plus) offer a degree of protection from erosive drinks.

A comparative study of smear layer removal and erosion in apical intraradicular dentine with three irrigating solutions: a scanning electron microscopy evaluation

INTRODUCTION

This study compared the efficacy of BioPure MTAD (Dentsply Tulsa, Tulsa, OK), 17% EDTA, and 42% citric acid in endodontic smear layer removal and degree of erosion in the apical third of endodontic canals.

METHODS

Ninety-six extracted single-rooted human teeth were randomized into four groups (n = 24) and instrumented using System GT nickel-titanium rotary instruments (Dentsply Tulsa, Tulsa, OK). Each canal was irrigated with one of the following solutions: BioPure MTAD, 17% EDTA, 42% citric acid, or 5.25% NaOCl (control). Next, all specimens were irrigated with 5.25% NaOCl.

RESULTS

Evaluation by scanning electron microscopy showed no significant differences among test irrigants in removing the smear layer. However, the efficacy of BioPure MTAD and 17% EDTA in removing the smear layer was significantly greater than 5.25% NaOCl (control). The erosive effects of irrigating solutions could not be evaluated.

CONCLUSIONS

In conclusion, the protocols used in this study were not sufficient to completely remove the smear layer in the apical third of prepared root canals.

Protective effect on enamel demineralization of a CPP-ACP paste: an AFM in vitro study

OBJECTIVES

The aim of the present in vitro study was the evaluation of a CPP-ACP paste (Tooth Mousse) on preventing dental erosion produced by a soft drink (Coca Cola), using Atomic Force Microscopy (AFM).

METHODS

Thirty extracted human central incisors free of caries were selected and divided in a treatment and a control half. The treatment halves were divided in three groups-group 1: demineralization with soft drink (4 intervals of 2 min); group 2: demineralization with soft drink (4 intervals of 2 min) plus Tooth Mousse; group 3: intact enamel plus Tooth Mousse. In groups 2 and 3 Tooth Mousse was applied for 3 min at 0, 8, 24 and 36 h. The surface of each specimen was imaged by AFM and R(rms) values were registered.

RESULTS

Among treatment specimens of groups 1 and 2, a statistically significant difference (P<0.01) in R(rms) values was registered: treatment of the specimens with CPP-ACP paste had a protective effect on enamel demineralization. In group 3 no statistically significant difference was registered between exposed and not exposed halves of the specimens.

CONCLUSIONS

The use of a CPP-ACP paste had a protective effect on enamel demineralization in an in vitro model.

Bactericidal activity of phosphoric acid, citric acid, and EDTA solutions against Enterococcus faecalis

OBJECTIVES

The objectives of this study were to evaluate the minimal bactericidal concentration (MBC) for Enterococcus faecalis of phosphoric acid, citric acid, and ethylenediaminetetraacetic acid (EDTA) solutions, and to determine the contact time required for 2.5% and 5% phosphoric acid, 10% and 25% citric acid, and 17% EDTA to exert bactericidal activity.

STUDY DESIGN

Bactericidal activity was tested by means of the dilution neutralization method in accordance with BS-EN-1040:2005 norm, using contact times of 0.5 to 60 minutes.

RESULTS

The MBCs of citric and phosphoric acid were 20% and 2.5%, respectively. EDTA solution lacks bactericidal activity, even after 60 minutes of contact. The 2.5% and 5% phosphoric acid solutions required 5- and 3-minute contact times, and the 10% and 25% citric acid solutions required 10- and 3-minute contact times, respectively.

CONCLUSIONS

Phosphoric acid revealed bactericidal activity against E. faecalis and required less time than citric acid to exert its activity.

Co-site digital optical microscopy and image analysis: an approach to evaluate the process of dentine demineralization

AIM

To introduce and explore the potential of digital optical co-site microscopy and image analysis for the observation of changes in dentine surfaces during demineralization. The effect of ethylenediamine tetraacetic acid (EDTA) was evaluated quantitatively and longitudinally.

METHODOLOGY

Three maxillary human molars were sectioned transversely at the cemento-enamel junction, and the crowns discarded. Subsequently, discs approximately 3 mm thick were cut in the cervical third of the root and a standardized smear layer produced. Co-site image sequences of the dentine surface subjected to 17% EDTA were obtained over the experimental period (15, 30, 60, 180 and 300 s). Sixteen images were obtained in each dentine sample for each experimental time, thus, a total of 48 image fields were obtained. For each field, an image analysis routine automatically discriminated open dentine tubules and measured their number, area fraction and minimum diameter, thus allowing the quantification of the demineralization process. The Student t-test was used to analyse the data.

RESULTS

The number of open tubules remained essentially constant during the demineralization process. The area fraction increased from 9% to 32%. Tubule minimum diameter increased from 1.5 to 3.0 microm. The changes over time for the area fraction and minimum diameter were significant for comparison between all experimental times (P<0.05).

CONCLUSIONS

The methodology developed for longitudinal observation of dentinal surfaces was fast, robust and reproducible. It could be easily extended to other chelating substances, thus contributing to the understanding of the demineralization process and in establishing an optimal time-effect relationship in the clinical application.