Bleaching Effect of Ozonized Substances on Resin Composite: A New Potentiality for Ozone Therapy in Dentistry

Composite resins are commonly used in dentistry for direct restorations. The color stability of these materials still represents a major concern for both the clinician and the patient. In recent years, ozone therapy has been extensively used in dentistry to manage wounds healing, dental caries, oral lichen planus, gingivitis and periodontitis, halitosis, osteonecrosis of the jaw, post-surgical pain, plaque and biofilms, root canal treatment, dentin hypersensitivity, temporomandibular joint disorders, and teeth whitening. To date, several studies have evaluated the bleaching effect exerted by ozone on natural teeth, but no studies have been conducted to determine the effect on the color of composite resins. The aim of the present study is to determine whether ozonized oils/gels could determine a color change on composite resin. A total of 40 discs of an A3 shade restorative composite were divided into two groups, respectively exposed to a pigmentation treatment consisting of 10 applications of 10 min each of a 1% chlorhexidine-based gel (trial group) and to storage into physiological solution (control group). The samples of both groups were respectively subdivided into four subgroups which underwent four different protocols, three of which were based on the exposure to different ozonized products and the latter representing the control. A colorimetric analysis with the CIELAB method was conducted with the following timing: after 24 h of storage in physiological solution (before the experimental procedures) (T0), after the subdivision into groups A and B (corresponding to the pigmentation for samples of group A and storage in physiological solution for samples of group B) (T1), and after subdivision into subgroups 1–4 (corresponding to the application of the ozonized products vs. control) (T2). No statistically significant difference was found between the samples at T0. The 20 samples of group A, exposed to the colorant agent, underwent a color change from T0 to T1, whereas the 20 samples exposed to the physiologic solution did not undergo any significant color change. A positive but moderate influence was assessed for E and L values, whereas no significant change occurred for A and B values. Therefore, dental ozonized oils/gels could be valuable in restorative dentistry as bleaching agents of resin composites exposed to discoloration, an alternative to the traditional hydrogen peroxide and carbamide peroxide, but further studies are required to confirm these findings.

Cytotoxicity of Different Composite Resins on Human Gingival Fibroblast Cell Lines

The aim of the present study was to evaluate and compare the cytotoxic effects of eight composite resins on immortalized human gingival fibroblasts. Composite resins were eluted in cell culture medium for 48 or 72 h at 37 °C. Immortalized human gingival fibroblast-1 (HGF-1) cell lines were seeded in 96-well (1 × 10⁴) plates and incubated for 24 h at 37 °C with the obtained extraction medium. The percentage of viable cells in each well (MTT test) was calculated relative to control cells, which were set to 100%. Data observed were not normally distributed, and nonparametric statistical methods were used for statistical analysis. The Wilcoxon test was used for intragroup comparison, and the Kruskal–Wallis test was used for intergroup multiple comparisons. Significance value was set as p < 0.05. All materials tested showed cytotoxic effects on gingival fibroblasts, recordable as noncytotoxic, mildly cytotoxic or severely cytotoxic, depending on the percentage of cell viability. The Wilcoxon test for intragroup comparison showed that the percentage of viable cells decreased significantly for extracts, for all composite resins tested. The composite resins contained monomers that displayed cytotoxic properties. BisGMA, TEGDMA and UDMA had inhibitory effects and induced apoptotic proteins in pulp fibroblast. Composite resins that contained lower percentages of unbound free monomers—and that released less ions—possessed superior biocompatibility in vitro.

Effect of different surface finishing/polishing procedures on color stability of esthetic restorative materials: A spectrophotometric evaluation

Objective:

To evaluate the color stability of different esthetic restorative materials after surface finishing/polishing with different procedures.

Materials and Methods:

All materials were polymerized into silicone rubber rings to obtain specimens identical in size. Samples were randomly assigned into four groups (10 specimens of each composite for each group), and they were finished with different procedures: Control group (Group 1), three or two polishers interspersed with diamond grit (Groups 3 and 2, respectively), and one tungsten carbide bur + one polisher interspersed with diamond grit (Group 4). After staining process in coffee, a colorimetric evaluation according to the CIE L*a*b* system was performed by a blind trained operator at 7, 14, 21, and 28 days. Shapiro–Wilk test and Kruskal–Wallis analysis of variance were applied to assess significant differences among restorative materials. Means of the different polishing/finishing groups were compared with Scheffe's multiple comparison test at the 0.05 level of significance.

Results:

In control group, significant lower discolorations were recorded for Essentia, Admira Fusion, and Estelite. After finishing, Filtek Supreme XTE and Ceram.X Universal showed a significantly lower degree of staining. The finishing technique used for Group 4 produced higher color changes.

Conclusions:

Tungsten carbide burs produced the higher color variations; after finishing, the nanofilled composites showed lower discoloration than nanohybrid ones, and the time of exposure to the staining agent and the polishing/finishing technique influenced the color change.

Discoloration of different esthetic restorative materials: A spectrophotometric evaluation

Objective:

A crucial property of esthetic restorative materials is their long-term color stability. The aim of this in vitro study was to evaluate the color stability of esthetic restorative materials (one microfilled flowable composite, one nanofilled composite, one nanoybrid composite, one microfilled composite, and one nanoybrid ormocer-based composite) after surface roughening with cola and exposure to different staining solutions (coffee and red wine).

Materials and Methods:

All materials were polymerized into silicone rubber rings (2 mm × 6 mm × 8 mm) to obtain 150 specimens identical in size. Seventy-five specimens of Group A were first exposed to cola for 24 h, and then samples were immersed in coffee or red wine over a 28-day test period. A colorimetric evaluation, according to the CIE L*a*b* system, was performed at 7, 14, 21, 28 days. Shapiro–Wilk test and Kruskal–Wallis analysis of variance were applied to assess significant differences among restorative materials. Means were compared with Scheffe's multiple comparison test at the 0.05 level of significance.

Results:

Specimens of Group A showed higher variations when compared with Group B's specimens (P < 0.05). After 28 days, the immersion protocols caused a clinically perceivable color change for all materials tested (P < 0.05). CeramX Universal and Admira Fusion showed the lowest ΔE variations (P < 0.05).

Conclusions:

Staining beverages caused significant discolorations for all the materials tested. The first exposure to cola enhanced the subsequent staining with coffee or red wine. Nanohybrid composites reported the lowest color variations.

Shear bond strength of one-step self-etch adhesives to dentin: Evaluation of NaOCl pretreatment

Background

The aim of this study was to evaluate the influence of dentin pretreatment with NaOCl on shear bond strength of four one-step self-etch adhesives with different pH values.

Material and Methods

Bovine permanent incisors were used. Four one-step self-etch adhesives were tested: Adper™ Easy Bond, Futurabond NR, G-aenial Bond, Clearfil S3 Bond. One two-step self-etch adhesive (Clearfil SE Bond) was used as control. Group 1- no pretreatment; group 2- pretratment with 5,25 % NaOCl; group 3- pretreatment with 37 % H3PO4 etching and 5,25 % NaOCl. A hybrid composite resin was inserted into the dentin surface. The specimens were tested in a universal testing machine. The examiners evaluated the fractured surfaces in optical microscope to determine failure modes, quantified with adhesive remnant index (ARI).

Results

Dentin pretreatment variably influenced bond strength values of the different adhesive systems. When no dentin pretreatment was applied, no significant differences were found (P >.05) among four adhesives tested. No significant differences were recorded when comparing NaOCl pretreatment with H3PO4 + NaOCl pretreatment for all adhesive tested (P >.05) except Clearfil S3 Bond that showed higher shear bond strength values when H3PO4 was applied. Frequencies of ARI scores were calculated.

Conclusions

The influence of dentin pretreatment with NaOCl depends on the composition of each adhesive system used. There was no difference in bond strength values among self-etch adhesives with different pH values.

Key words:Dentin, pretreatment, self-etch adhesives.

Effect of different finishing/polishing procedures on surface roughness of Ormocer-based and different resin composites

BACKGROUND

The aim of this study was to evaluate and compare the surface roughness of six esthetic restorative materials (Gradia Direct Anterior, GC Corporation, Tokyo, Japan; Filtek Supreme XTE, 3M ESPE, St. Paul, MN, USA; Ceram.X Universal, Dentsply DeTrey, Konstanz, Germany; Essentia enamel, GC Corporation, Tokyo, Japan; Admira Fusion, Voco, Cuxhaven, Germany; and Estelite, Tokuyama Dental corporation, Taitou-ku, Tokyo, Japan) achieved using three different finishing and polishing techniques.

MATERIALS AND METHODS

In this in vitro study Forty specimens of each material (6 mm in diameter, 2 mm high) were created and divided into four groups, one per each finishing and polishing procedure and a control group, only cured and not polished. All specimen preparation and finishing and polishing procedures were performed by the same investigator, to reduce variability, following strictly the manufacturer's instructions. Specimens were analyzed using a profilometer to measure the mean surface roughness (Ra, μm), and microscopy images were taken during the measurements through the microscope of the profilometer. Two-way ANOVA test was applied to determine significant differences with respect to material, finishing/polishing technique, and interaction between both variables. Post hoc comparison was done using Tukey's honestly significant difference test. Significance for statistical tests was predetermined at P < 0.05.

RESULTS

Finishing and polishing procedure using tungsten carbide burs provided the best values in terms of surface roughness. All materials of this study treated with this method have provided superimposable values, and no material can be considered more performing than the others. Similar values were also found in the control group.

CONCLUSION

This study demonstrated that the finishing technique with carbide burs produced an excellent surface smoothness, even if the best surface smoothness is achieved curing the restorative material under a polyester matrix.

Comparison of apical extrusion of intracanal bacteria by various glide-path establishing systems: an in vitro study

OBJECTIVES

This study compared the amount of apically extruded bacteria during the glide-path preparation by using multi-file and single-file glide-path establishing nickel-titanium (NiTi) rotary systems.

MATERIALS AND METHODS

Sixty mandibular first molar teeth were used to prepare the test apparatus. They were decoronated, blocked into glass vials, sterilized in ethylene oxide gas, infected with a pure culture of Enterococcus faecalis, randomly assigned to 5 experimental groups, and then prepared using manual stainless-steel files (group KF) and glide-path establishing NiTi rotary files (group PF with PathFiles, group GF with G-Files, group PG with ProGlider, and group OG with One G). At the end of canal preparation, 0.01 mL NaCl solution was taken from the experimental vials. The suspension was plated on brain heart infusion agar and colonies of bacteria were counted, and the results were given as number of colony-forming units (CFU).

RESULTS

The manual instrumentation technique tested in group KF extruded the highest number of bacteria compared to the other 4 groups (p < 0.05). The 4 groups using rotary glide-path establishing instruments extruded similar amounts of bacteria.

CONCLUSIONS

All glide-path establishment instrument systems tested caused a measurable apical extrusion of bacteria. The manual glide-path preparation showed the highest number of bacteria extruded compared to the other NiTi glide-path establishing instruments.

Color stability of CAD/CAM Zirconia ceramics following exposure to acidic and staining drinks

Background

The aim of this in vitro study was to evaluate the color stability of CAD/CAM Zirconia ceramics following exposure to acidic drink (Coca Cola) and after exposure to staining solution (coffee).

Material and Methods

All the samples were immersed in different staining solutions over a 28-day test period. A colorimetric evaluation according to the CIE L*a*b* system was performed by a blind trained operator at 7, 14, 21, 28 days of the staining process. Shapiro Wilk test and Kruskal-Wallis ANOVA were applied to assess significant differences among restorative materials. Paired t-test was applied to test which CIE L*a*b* parameters significantly changed after immersion in staining solutions.

Results

One week immersion in acidic drink did not cause a perceivable discoloration for all restorative materials (ΔE < 3.3). Subsequent immersion in coffee affected color stability of all Zirconia samples, even if Kruskal-Wallis ANOVA found significant differences among the various restorative materials.

Conclusions

The ∆Es of CAD/CAM Zirconia ceramics after immersion in coffee varied among the products, but color integrity is not affected by contact with acidic drinks.

Key words:CAD/CAM restorative materials, CIE Lab, Zirconia ceramics.

Color Stability of New Esthetic Restorative Materials: A Spectrophotometric Analysis

The aim of this in vitro study was to evaluate and compare the color stability of different esthetic restorative materials (one microfilled composite, one nanofilled composite, one nanoceramic composite, one microfilled hybrid composite, one microfilled hybrid composite, one nanohybrid Ormocer based composite and one supra-nano spherical hybrid composite) after exposure to different staining solutions (physiological saline, red wine, coffee). All materials were prepared and polymerized into silicon rings (2 mm × 6 mm × 8 mm) to obtain specimens identical in size. Thirty cylindrical specimens of each material were prepared. Specimens were immersed in staining solutions (physiological saline, coffee and red wine) over a 28-day test period. A colorimetric evaluation according to the CIE L*a*b* system was performed by a blind trained operator at 7, 14, 21, 28 days of the staining process. The Shapiro–Wilk test and ANOVA were applied to assess significant differences among restorative materials. A paired t-test was applied to test which CIE L*a*b* parameters significantly changed after immersion in staining solutions. All restorative materials showed significant color differences after immersion in coffee. Coffee caused a significant color change in all types of tested composite resins. Only Filtek Supreme XTE demonstrated a staining susceptibility to red wine; no other significant differences among the materials were demonstrated. Long-term exposure to some food dyes (coffee in particular) can significantly affect the color stability of modern esthetic restorative materials regardless of materials’ different compositions.

Color stability of esthetic restorative materials: a spectrophotometric analysis

Objective: The aim of this in vitro study was to evaluate the color stability of different restorative materials (one microfilled composite, one nanofilled composite, one nanohybrid composite and one Ormocer-based composite) after exposure to different staining solutions (coffee, coca-cola and red wine).

Material and methods: All materials were polymerized into silicon rings (2 mm ×6 mm ×8 mm) to obtain specimens identical in size. Thirty cylindrical specimens of each material were prepared. They were immersed in staining solutions over a 28-day test period. A colorimetric evaluation according to the CIE L*a*b* system was performed by a blind trained operator at 7, 14, 21, 28 days of the staining process. The Shapiro–Wilk test and Kruskal–Wallis ANOVA were applied to assess significant differences among restorative materials. The paired t-test was applied to test which CIE L*a*b* parameters significantly changed after immersion in staining solutions.

Results: All restorative materials showed clinically perceptible color differences after immersion in coffee. L* and b* values showed the highest variability. Coca cola and red wine did not influence the color stability for all restorative materials except for Filtek Supreme XTE.

Conclusions: Coffee caused a significant color change in all types of tested composite resins. Filtek Supreme XTE demonstrated alone a staining susceptibility to red wine; no other significant differences among the materials were demonstrated. Long-term exposure to some food dyes (coffee in particular) can significantly affect the color stability of modern esthetic restorative materials regardless of materials’ different composition.

Influence of dentin pretreatment on bond strength of universal adhesives

Objective: The purpose of the present study was to compare bond strength of different universal adhesives under three different testing conditions: when no pretreatment was applied, after 37% phosphoric acid etching and after glycine application. Materials and methods: One hundred and fifty bovine permanent mandibular incisors were used as a substitute for human teeth. Five different universal adhesives were tested: Futurabond M+, Scotchbond Universal, Clearfil Universal Bond, G-Premio BOND, Peak Universal Bond. The adhesive systems were applied following each manufacturer's instructions. The teeth were randomly assigned to three different dentin surface pretreatments: no pretreatment agent (control), 37% phosphoric acid etching, glycine pretreatment. The specimens were placed in a universal testing machine in order to measure and compare bond strength values. Results: The Kruskal-Wallis analysis of variance and the Mann-Whitney test were applied to assess significant differences among the groups. Dentin pretreatments provided different bond strength values for the adhesives tested, while similar values were registered in groups without dentin pretreatment. Conclusions: In the present report, dentin surface pretreatment did not provide significant differences in shear bond strength values of almost all groups. Acid pretreatment lowered bond strength values of Futurabond and Peak Universal Adhesives, whereas glycine pretreatment increased bond strength values of G Praemio Bond adhesive system.

Resin infiltrant for non-cavitated caries lesions: evaluation of color stability

BACKGROUND

The objective of this in vitro study was to evaluate the over time color stability of one resin infiltrant (Icon) upon exposure to staining solutions (coffee and wine) compared with one nano-hybrid sealant (Grandio Seal), one transparent fissure sealant with fluoride (Control Seal) and one nanofilled composite (Filtek Supreme XTE).

MATERIAL AND METHODS

All materials were polymerized according to manufacturers' instructions into silicon rings (height 1 mm; internal diameter 6 mm; external diameter 8 mm) to obtain specimens identical in size. The specimens were immersed in staining solutions at room temperature over a 28-day test period. The control samples have not been subjected to the staining process. A colorimetric evaluation according to the CIE L*a*b* system was performed by a blind trained operator at 7, 14, 21, 28 days of the staining process. Shapiro Wilk test and Kruskal Wallis ANOVA were applied to assess significant differences among different materials. Means were compared with Scheffe's multiple-comparison test at the 0.05 level of significance.

RESULTS

In the case of all materials, immersion in solutions resulted in clinically perceivable color changes after 1 week (∆E < 3.3). Lowest CIE L* variation was registered for Control Seal and Grandio Seal both after 1 week and after 1 month, while Icon showed significantly higher variation (P < 0.05). Color coordinate CIE a* varied significantly more for Icon samples (P > 0.05). Color coordinate CIE b* varied similarly for all materials tested (P > 0.05).

CONCLUSIONS

Immersion in coffee or red wine resulted in clinically perceivable color changes for all materials tested. Icon showed the highest color variations both after 1 week and 1 month. Icon can fix the initial esthetic problem associated with white spot lesions, but the resin may become more discolored than other materials over time. Key words:CIE Lab, color stability, resin infiltrant.

Differences between panoramic and Cone Beam-CT in the surgical evaluation of lower third molars

Background

The aim of this study was to evaluate the ability to identify the contiguity between the root of the mandibular third molar and the mandibular canal (MC) in panoramic radiographs compared with Cone Beam-CT.

Material and Methods

Panoramic radiographs of 326 third molars and CBCT radiographs of 86 cases indicated for surgery and considered at risk were evaluated. The following signs were assessed in panoramic radiographs as risk factors: radiolucent band, loss of MC border, change in MC direction, MC narrowing, root narrowing, root deviation, bifid apex, superimposition, and contact between the root third molar and the MC.

Results

Radiographic signs associated with absence of MC cortical bone are: radiolucent band, loss of MC border, change in MC direction, and superimposition. The number of risk factors was significantly increased with an increasing depth of inclusion. CBCT revealed a significant association between the absence of MC cortical bone and a lingual or interradicular position of the MC.

Conclusions

In cases in which panoramic radiographs do not exclude contiguity between the MC and tooth, careful assessment the signs and risks on CBCT radiographs is indicated for proper identification of the relationships between anatomic structures.

Key words:Panoramic radiography, Cone-Beam computed tomography, third molar, mandibular nerve.

Protective effects of a zinc-hydroxyapatite toothpaste on enamel erosion: SEM study

AIM

The aim of the present in vitro study was to evaluate the protective effects of a zinc-hydroxyapatite toothpaste against an erosive challenge produced by a soft drink (Coca-Cola) using Scanning Electron Microscopy (SEM).

METHODS

Forty specimens were assigned to 4 groups of 10 specimens each (group 1: no erosive challenge, no toothpaste treatment, group 2: erosive challenge, no toothpaste treatment, group 3: erosive challenge, fluoride toothpaste treatment, group 4: erosive challenge, zinc-hydroxyapatite toothpaste treatment). The surface of each specimen was imaged by SEM. A visual rating system was used to evaluate the condition of the enamel surface; results were analyzed by nonparametric statistical methods.

RESULTS

Statistically significant differences were found between the samples untreated and those immersed in Coca-Cola (group 1, 2); the highest grade of damage was found in group 2, while the lowest grade was recorded in the samples of group 4. Comparing the groups, the two analyzed toothpaste tended to protect in different extend.

CONCLUSIONS

In this study treatment of erosively challenged enamel with Zn-Hap toothpaste showed a clear protective effect. This was greater than the effect observed for a normal fluoride toothpaste and confirmed the potential benefit the Zn-HAP technology can provide in protecting enamel from erosive acid challenges.

Radiographic technical quality of root canal treatment performed by a new rotary single-file system

AIM

The aim of the present study was to evaluate radiographically the technical quality of root canal filling performed by postgraduate students with a new single-file Nickel-Titanium System (F6 Skytaper Komet) in clinical practice.

METHODS

Records of 74 patients who had received endodontic treatment by postgraduate students at the School of Dentistry, Faculty of Medicine, University of Pavia in the period between September 2015 and April 2016 were collected and examined: the final sample consisted 114 teeth and 204 root canals. The quality of endodontic treatment was evaluated by examining the length of the filling in relation to the radiographic apex, the density of the obturation according to the presence of voids and the taper of root canal filling. Chi-squared analysis was used to determine statistically significant differences between the technical quality of root fillings according to tooth's type, position and curvature.

RESULTS

The results showed that 75,49%, 82,84% and 90,69% of root filled canals had adequate length, density and taper respectively.

CONCLUSIONS

Overall, the technical quality of root canal fillings performed by postgraduates students was acceptable in 60,78% of the cases.

Remineralizing effect of a zinc-hydroxyapatite toothpaste on enamel erosion caused by soft drinks: Ultrastructural analysis

Background

Material and Methods

Results

Conclusions

Debris Evaluation after Root Canal Shaping with Rotating and Reciprocating Single-File Systems

This study evaluated the root canal dentine surface by scanning electron microscope (SEM) after shaping with two reciprocating single-file NiTi systems and two rotating single-file NiTi systems, in order to verify the presence/absence of the smear layer and the presence/absence of open tubules along the walls of each sample; Forty-eight single-rooted teeth were divided into four groups and shaped with OneShape (OS), F6 SkyTaper (F6), WaveOne (WO) and Reciproc and irrigated using 5.25% NaOCl and 17% EDTA. Root canal walls were analyzed by SEM at a standard magnification of 2500×. The presence/absence of the smear layer and the presence/absence of open tubules at the coronal, middle, and apical third of each canal were estimated using a five-step scale for scores. Numeric data were analyzed using Kruskal-Wallis and Mann-Whitney U statistical tests and significance was predetermined at P < 0.05; The Kruskal-Wallis ANOVA for debris score showed significant differences among the NiTi systems (P < 0.05). The Mann-Whitney test confirmed that reciprocating systems presented significantly higher score values than rotating files. The same results were assessed considering the smear layer scores. ANOVA confirmed that the apical third of the canal maintained a higher quantity of debris and smear layer after preparation of all the samples; Single-use NiTi systems used in continuous rotation appeared to be more effective than reciprocating instruments in leaving clean walls. The reciprocating systems produced more debris and smear layer than rotating instruments.

Antimicrobial Effect and Surface Tension of Some Chelating Solutions with Added Surfactants

Abstract This study assessed the antimicrobial efficacy and surface tension of established irrigating solutions with a new experimental chelating solution in infected dentin tubes. Twenty-five specimens were randomly assigned to each of the irrigating solutions. Twenty specimens were used as negative and positive controls. After 21 days of contamination with E. faecalis, the irrigating solutions MTAD, QMiX and Tetraclean NA were delivered into each infected root canal. The solutions were removed and dentin samples were withdrawn from the root canals with sterile low-speed round burs with increasing ISO diameters. The dentin powder samples obtained with each bur were immediately collected in separate test tubes containing 3 mL of BHI broth. After that, 100 μL from each test tube was cultured on blood agar. The grown colonies were counted and recorded as colony-forming units (CFU). The surface tension of the irrigants was measured using a Cahn DCA-322 Dynamic Contact Angle Analyzer. A Kruskal Wallis nonparametric ANOVA and a Friedman test were used (p<0.05). Tetraclean NA showed lower surface tension and CFU values than MTAD and QMiX. Better antibacterial action and low surface tension were observed for Tetraclean NA, probably due to the improved penetration into the root canal and dentinal tubes

Fluoride release and uptake abilities of different fissure sealants

Background

The long-term capability of resin sealants and glass ionomer cements to release fluoride is associated to a reduction in pit and fissure caries. The regular use of fluoride varnishes/toothpastes can result in the absorption of fluoride into the sealant. The objective of the present study was to assess the fluoride release/uptake capacities of different fissure sealants.

Material and Methods

Three different fissure sealants (Fuji Triage/GC, Fissurit FX/Voco and Grandio Seal/Voco) were examined. Ten discs of each material were prepared. Each disc was incubated with distilled water and then the solution analyzed for diluted for fluoride concentration, using a combination of fluoride electrode (OrionGP 1 S/N 13824, Orion Research Inc, Boston, MA, USA) connected to an expandable ion analyzer (Orion 720A, Orion Research Inc, Boston, MA, USA). Standard curves between 1 and 100 ppm F- were used to calibrate the electrode. Cumulative fluoride release was measured on days 1, 2, 3, 5, 7, 21, 35 and 49, then two different fluoride varnishes/pastes (Profluorid Varnish/Voco, MI Paste Plus/GC), were applied to the sealants tested, and fluoride release (after reuptake) was measured on days 56, 70 and 84.

Results

Kruskal Wallis test confirmed significant differences in fluoride release between Fuji Triage/GC and Fissurit FX/Voco and Grandio Seal/Voco from day 1 (P < 0.001). The application of fluoride varnish Profluorid Varnish enhanced the fluoride release for all sealants (P < 0.05). MI Paste Plus enhanced the fluoride release for all sealants except for Fuji Triage/GC (P > 0.05).

Conclusions

The GIC-based sealant (Fuji Triage/GC) released significantly more fluoride than the resin sealants tested. The exposure to the fluoridated varnish (Profluorid Varnish) significantly recharged the sealants tested more than the CPP-ACPF toothpaste (MI Paste Plus).

Key words:Fissure sealants, fluoride release, fluoride uptake, glass ionomer cements.

Effect of self-assembling peptide P11 -4 on enamel erosion: AFM and SEM studies

The aim of the present in vitro study was to evaluate the protective effect of self-assembling peptide P11 -4 (Curodont™ Protect/Credentis) on enamel erosion produced by a soft-drink, by using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Thirty human incisors were equally and randomly assigned to 6 groups. Group 1: intact enamel, group 2: soft drink, group 3: Curodont(™) Protect applied, group 4: Curodont(™) Protect applied + soft drink, group 5: soft drink + Curodont(™) Protect applied, group 6: soft drink + Curodont(™) Protect applied + soft drink. Specimens were observed through atomic force microscopy (AFM). 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 Shapiro-Wilk test in order to assess the normality of the distribution. Parametric ANOVA and post hoc Tuckey test were performed to assess the differences between the different groups. After demineralization process, enamel demonstrated a high degree of surface porosity. This morphological aspect was reflected in the increase of Rrms values. No significant differences (p > 0.05) were reported between intact enamel and enamel only treated with P11 -4 and between eroded enamel and enamel treated with P11 -4 and then demineralized. However significant differences (p < 0.05) were recorded when comparing softened enamel with softened enamel further remineralized with biomimetic self-assembling peptides and enamel treated with the protective paste between two acid attacks. The use of P11 -4 remineralizing may offer a degree of protection from enamel erosion. SCANNING 38:344-351, 2016. © 2015 Wiley Periodicals, Inc.

Ultrastructural evaluation of enamel surface morphology after tooth bleaching followed by the application of protective pastes

The aim of the present in vitro study was to evaluate the morphology of bleached enamel surface followed by the application of different protective pastes. Specimens were prepared from 50 human incisors free of caries and defects. The bleaching procedure was performed with 35% hydrogen peroxide (Perfect Bleach Office+). For the remineralization treatment, different protective pastes (Tooth Mousse, MI Paste Plus, Remin Pro, and Profluorid Varnish) were evaluated. Specimens were randomly assigned to 10 groups of 5 specimens each. The specimens were analyzed under scanning electron microscopy. The superficial morphology of enamel was examined and scored as follows: 0, enamel with smooth surface morphology; 1, enamel with slight irregularities; 2, enamel with moderate irregularities; 3, enamel with accentuated irregularities. The photomicrographs were evaluated in a double-blind manner by three examiners, previously calibrated. Results were analyzed by a Kruskal-Wallis nonparametric test, at the significance level of 0.05. Dunn method posttest was applied for multiple comparisons. A different superficial morphology was observed among control group specimens and specimens treated with bleaching agent and protective pastes (p < 0.05). Enamel bleached showed pronounced surface changes and irregularities, significantly different from other groups except for groups 8 (enamel + Perfect Bleach Office+ + Remin Pro) and 10 (enamel + Perfect Bleach Office+ + Profluorid Varnish) (p > 0.05). The application of the tested pastes after bleaching is effective on repairing enamel surface morphology, demonstrating a higher efficacy for the CPP-ACP products compared to fluoridated ones. SCANNING 38:221-226, 2016. © 2015 Wiley Periodicals, Inc.

Effect of glycine pretreatment on the shear bond strength of a CAD/CAM resin nano ceramic material to dentin

Background

The purpose of this study was to evaluate the effect of glycine pretreatment on the shear bond strength between dentin and a CAD/CAM resin nano ceramic material (LavaTM Ultimate Restorative), bonded together with adhesive cements using three different luting protocols (total-etch; self-etch; self-adhesive).

Material and Methods

Thirty cylinders were milled from resin nano ceramic blocks with CAD/CAM technology. The cylinders were subsequently cemented to the exposed dentin of 30 bovine permanent mandibular incisors. The specimens were assigned into six groups of five teeth each according to luting procedure and dentin pretreatment. In the first two groups (A1, A2) 10 cylinders were cemented using a total-etch protocol; in groups B1 and B2, 10 cylinders were cemented using a self-etch protocol; in groups C1 and C2, 10 cylinders were cemented using a self-adhesive protocol; in groups A1, B1 and C1 the dentinal surface was also treated with glycine powder. All cemented specimens were submitted to a shear bond strength test. Statistical analysis was performed with Stata 9.0 software.

Results

ANOVA showed the presence of significant differences among the various groups (P <0.0001).

Conclusions

Glycine did not change the different bond strength demonstrated by the various luting protocols tested. Conventional resin composite cements used together with a self-etch adhesive reported the highest values. However the use of glycine seems to increase the bond strength of self-adhesive resin cements.

Key words:Adhesive cements, CAD/CAM, glycine, luting system, resin nano ceramic, shear bond strength.

F360 and F6 Skytaper: SEM evaluation of cleaning efficiency

AIM

Root canal preparation may produce a large quantity of smear layer that covers canal walls. Single-file systems have recently appeared, with the aim of reducing the number of steps and files to reach a correct endodontic treatment. The purpose of this study was to evaluate by SEM the root canal walls after instrumentation with F360 (Komet, Brasseler GmbH & Co., Lemgo, Germany) and F6 Skytaper (Komet, Brasseler GmbH & Co., Lemgo, Germany), in order to evaluate the presence/absence of smear layer and the presence/absence of open tubules on the root canal walls at coronal, middle, and apical third of each sample.

METHODS

Twenty single-rooted freshly extracted teeth were selected and divided into 2 groups. For each group root canals were shaped with F360 (Komet, Brasseler GmbH & Co., Lemgo, Germany) and F6 Skytaper (Komet, Brasseler GmbH & Co., Lemgo, Germany) instruments under irrigation with 5,25% NaOCl and 17% EDTA. Specimens were fractured longitudinally and analyzed by SEM at standard magnification of 5000x. The presence/absence of smear layer and the presence/absence of open tubules at the coronal, middle, and apical third of each canal were evaluated using a 5-step scale for scores. Numeric data were analyzed using Kruskall-Wallis and Mann-Whitney U statistical tests and significance was predetermined at P <0.05.

RESULTS

This study did not reveal differences among two groups at the coronal and apical third. The apical third showed the highest values of scores for all Ni-Ti systems used. Significant differences in smear layer scores were recorded among the Ni-Ti systems at middle canal level (P < 0.05), where F6 Skytaper showed significantly lower scores than F360.

CONCLUSIONS

Within the limitation of this study, F360 and F6 Skytaper rotary instruments seem to be effective in shaping root canals with good debridement from canal walls, without significant differences between the two systems as it regards the coronal third and the apical third, the area where more debris is still visible. Instead, in the middle third F6 Skytaper seems to be more effective than F360, with statistically significative differences between the two systems.

Influence of Temperature on the Antibacterial Activity of Sodium Hypochlorite

Abstract The aim of this study was to compare the antimicrobial activity of 5.25% NaOCl, Hypoclean and Chlor-Xtra at 20 °C and 45 °C in bovine root dentin. One-hundred-and-seventy dentin tubes prepared from bovine maxillary incisors were infected for 21 days with Enterococcus faecalis. The specimens were divided into the following groups: 1. 5.25% NaOCl 20 °C; 2. Hypoclean 20 °C; 3. Chlor-Xtra 20 °C; 4. 5.25% % NaOCl 45 °C; 5. Hypoclean 45 °C; 6. Chlor-Xtra 45 °C; 7. positive control; 8. negative control. Dentin chips were collected with round burs into Brain Heart Infusion (BHI) broth. After culturing, the number of colony-forming units (CFU) was counted. Statistical analyses were performed using descriptive statistics (mean, standard deviation, median), Shapiro-Wilk test, ANOVA and Tukey test. Significance level was set at p<0.05. In all experimental groups, CFU was minimum after treatment (day 0) and the obtained results were significantly different from each other at any period (p<0.05). After treatment, the Hypoclean and Chlor-Xtra showed the lowest numbers of CFU at 20 °C and 45 °C, whereas 5.25% NaOCl showed the highest number of CFU at both temperatures. In each group, the number of CFUs increased significantly with time (p<0.05). The antibacterial activity of Hypoclean and Chlor-Xtra at 45 °C were significantly greater than other tested solutions.

Influence of different luting protocols on shear bond strength of computer aided design/computer aided manufacturing resin nanoceramic material to dentin

Background:

Materials and Methods:

Results:

Conclusion:

In vitro antibacterial activity of different pulp capping materials

Background

Direct pulp capping involves the application of a dental material to seal communications between the exposed pulp and the oral cavity (mechanical and carious pulp exposures) in an attempt to act as a barrier, protect the dental pulp complex and preserve its vitality. The aim of this study was to evaluate and compare, by the agar disc diffusion test, the antimicrobial activity of six different pulp-capping materials: Dycal (Dentsply), Calcicur (Voco), Calcimol LC (Voco), TheraCal LC (Bisco), MTA Angelus (Angelus), Biodentine (Septodont).

Material and Methods

Streptococcus salivarius, Streptococcus sanguis and Streptococcus mutans strains were selected to evaluate the antimicrobial activity by the agar disc diffusion test of different pulp capping materials. Paper disks were impregnated whit each pulp capping materials and placed onto culture agar-plates pre-adsorbed with bacterial cells and further incubated for 24 h at 37°C. The growth inhibition zones around each pulp capping materials were recorded and compared for each bacterial strain.

Results

For the investigation of the antibacterial properties the ANOVA showed the presence of significant differences among the various materials. Tukey test showed that MTA-based materials induced lower growth inhibition zones.

Conclusions

MTA-based products show a discrete antibacterial activity varying from calcium hydroxide-based materials which present an higher antibacterial activity.

Key words:Agar disc diffusion test, antimicrobial activity, calcium hydroxide, MTA, pulp capping materials.

Viscosity of endodontic irrigants: Influence of temperature

BACKGROUND

The aim of this study was to assess the influence of temperature on the viscosity of different endodontic irrigants.

MATERIALS AND METHODS

The measurements of viscosity of 3% hydrogen peroxide, 0.9% sodium chloride, aqueous solution of 0.2% chlorhexidine (CHX) and 0.2% cetrimide, 5% sodium hypochlorite (NaOCl) and 17% ethylenediaminetetraacetic acid (EDTA) at different temperatures (22°C, 30°C, 40°C, 50°C and 60°C) were obtained using Mohr balance and Ostwald viscometer. The Shapiro-Wilk test and Mann-Whitney U-tests were used for the statistical analysis. (α = 0.05).

RESULTS

No significant differences were recorded at each temperature among 3% hydrogen peroxide, 0.9% sodium chloride and aqueous solution of 0.2% CHX and 0.2% cetrimide. 5% NaOCl and 17% EDTA showed the higher values. Viscosity statistically decreased with increasing temperature.

CONCLUSION

Within the limitations of this study, 5% NaOCl and 17% EDTA are significantly viscous at room temperature and their viscosity reduces with elevating temperature.

In vitro cytotoxicity evaluation of different pulp capping materials: a comparative study

Direct pulp capping covers the exposed surface of the pulp to maintain its vitality and preserve its functional and biologic activity. The aim of the present study was to compare the biocompatibility effects of seven different pulp-capping materials in vitro: Dycal®, Calcicur®, Calcimol LC®, TheraCal LC®, ProRoot MTA®, MTA-Angelus®, and Biodentine®. Using the Transwell insert methodology by Alamar blue test, we evaluated the cytocompatibility of the above mentioned materials towards murine odontoblasts cells (MDPC-23) at three different times (24, 48, and 72 h). For additional control, the cell viability at 72 hours was also assessed by MTT assay. Morphological analysis of murine odontoblasts was assessed by Confocal Laser Scanning Microscope. The results indicate significantly different biocompatibility among materials with different composition. Biodentine® and mineral trioxide aggregate (MTA)-based products showed lower cytotoxicity, varying from calcium hydroxide-based materials, which exhibited higher cytotoxicity. Although our findings are limited to in vitro conditions, the observation that Biodentine® caused a cytotoxic effect similar to MTA suggests that it may be considered an alternative in pulp-capping treatment, as calcium hydroxide-based materials present higher cytotoxic effects.

Protective effect of casein phosphopeptide-amorphous calcium phosphate on enamel erosion: Atomic force microscopy studies

The aim of this study was to investigate the in vitro effect of a casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste (GC Tooth Mousse- TM, GC Corporation, Tokyo, Japan) on preventing enamel erosion, by using Atomic Force Microscopy (AFM). 30 human incisors, were equally assigned to 6 groups: intact enamel, enamel + soft drink, enamel + TM, enamel + TM + soft drink, enamel + soft drink + TM, enamel + soft drink + TM + soft drink. Specimens were observed through atomic force microscopy (AFM). The most common topographical parameters were determined, such as the surface roughness (Rrms ). The use of soft drink on intact enamel has roughened the surface of the sample. The application of the CPP-ACP paste on non-treated enamel made the surface smoother. A significant decrease in roughness was seen after remineralization with CPP-ACP paste. Significant differences were recorded when comparing softened enamel with softened enamel remineralized with CPP-ACP paste. Comparing eroded enamel with demineralized/remineralized specimens, the application of a CPP-ACP paste leads to a significant reduction in roughness values. AFM images of enamel surface treated with CPP-ACP resulted in less morphological changes of the tooth substrate when compared with the only eroded enamel surface morphology; thus, indicating that CPP-ACP paste promoted remineralization. Specimens' surface roughness remained similar regardless that the protective agent is used before or after exposure to coke or between two demineralizing cycles. The results confirmed the effectiveness of the CPP-ACP paste on preventing enamel erosion produced by soft drinks.

Decalcifying capability of irrigating solutions on root canal dentin mineral content

BACKGROUND

Chelating agents are believed to aid root canal irrigation and to be able to remove the inorganic smear layer.

AIMS

The purpose of the present study was to evaluate and to compare the decalcifying capability of different irrigating solutions (Tubuliclean, Largal Ultra, ethylenediaminetetraacetic acid 17%, Tetraclean, Tetraclean NA).

MATERIALS AND METHODS

Sixty maxillary central incisors were used. Root canals were instrumented and irrigated. From each root, four comparable slices of cervical dentin were obtained. At three successive 5-min interval immersion times, the concentration of calcium extracted from root canal dentin was assessed with an inductively coupled plasma-atomic emission spectrometer.

STATISTICAL ANALYSIS USED

Data were analyzed by means of Kruskal Wallis and Mann-Whitney tests. Significance was predetermined at P < 0.05.

RESULTS AND CONCLUSIONS

For all irrigating solutions, the maximum amount of Ca(2+) extracted from root canal dentin samples was reached after 10 min contact time except for citric acid-based agents (Tetraclean and Tetraclean NA) which induced a higher and still increasing calcium release even after 10 min contact time. In order to obtain an efficient decalcifying action on dentin and to facilitate the biomechanical procedures, citric acid-based irrigants can be applied.

Biological and chemical-physical properties of root-end filling materials: A comparative study

AIM

The purpose of the study is to evaluate and compare the biological and chemical-physical properties of four different root-end filling materials.

MATERIALS AND METHODS

Cytotoxicity towards murine odontoblasts cells (MDPC-23) was evaluated using the Transwell insert methodology by Alamar blue test. Streptococcus salivarius, S. sanguis, and S. mutans strains were selected to evaluate the antimicrobial activity by agar disc diffusion test. Solubility was determined after 24 h and 2 months. pH values were measured after 3 and 24 h. To evaluate radiopacity, all materials were scanned on a GE Healthcare Lunar Prodigy.

RESULTS

Excellent percentage of vitality were obtained by mineral trioxide aggregate (MTA)-based materials and Biodentine. MTA-Angelus, ProRoot MTA, and Intermediate Restorative Material (IRM) showed the highest values for the inhibition zones when tested for S. mutans, while Biodentine showed the largest inhibition zone when tested for S. sanguis. All the materials fulfilled the requirements of the International Standard 6876, demonstrating low solubility with a weight loss of less than 3%. No significant reduction in pH value was demonstrated after 24 h. ProRoot MTA and MTA-Angelus showed the highest values of radiographic density.

CONCLUSIONS

The differences showed by the root-end filling materials tested do not cover completely the ideal clinical requests.

Shear bond strength of one-step self-etch adhesives: pH influence

BACKGROUND

The aim of this study was to compare the shear bond strength of four one-step self-etch adhesives with different pH values to enamel and dentin.

MATERIALS AND METHODS

In this in vitro study, 200 bovine permanent mandibular incisors were used. Four one-step self-etch adhesives with different pH values were tested both on enamel and on dentin: Adper™ Easy Bond Self-Etch Adhesive (pH = 0.8-1), Futurabond NR (pH=2), G-aenial Bond (pH = 1.5), Clearfil S(3) Bond (pH = 2.7). After adhesive systems application, a nanohybrid composite resin was inserted into the bonded surface. The specimens were placed in a universal testing machine. The shear bond strength was performed at a cross-head speed of 1 mm/min until the sample rupture. The shear bond strength values (MPa) of the different groups were compared with analysis of variance after that Kolmogorov and Smirnov tests were applied to assess normality of distributions. P < 0.05 was considered as significant.

RESULTS

In enamel shear bond strength, the highest shear bond strength values were reported with Futurabond NR (P < 0.01); however, no significant differences were found with Clearfil S(3) Bond. The others adhesive systems showed lower shear bond strength values with significant differences between them (P < 0.05). When comparing the dentin shear bond strength, the lowest shear bond strength values were reported with Clearfil S(3) Bond (P < 0.05), while there were no significant differences among the other three products (P > 0.05).

CONCLUSION

The pH values of adhesive systems did not influence significantly their shear bond strength to enamel or dentin.

Scattering properties of a composite resin: Influence on color perception

Background:

The properties of the composite materials and the clinical expertise while layering them carry many esthetic implications in restorative dentistry.

Aims:

The aim of the present study is to assess the influence of scattering properties of G-aenial A2 shade on color perception when used in esthetic restorations.

Materials and Methods:

Two composite resins were evaluated in this study: Gradia Direct (shade A3) and G-aenial (shade A2). A colorimetric evaluation according to the CIE L*a*b* system, relative to standard illuminant A against a white background, was performed to assess the referred chameleonic properties of G-aenial when used in simulated clinical situations.

Statistical Analysis Used:

The differences in color change between the test group G-aenial and the test Group Gradia Direct were considered clinically not perceptible (ΔE* <3.3). Differently, the differences in color change were considered clinically perceptible (ΔE* >3.3) between the control group G-aenial and the control group Gradia Direct and between the test group G-aenial and the control specimens obtained with G-aenial. The CIE Lab parameters which brought to ΔE were investigated using t-test (P < 0.05).

Results and Conclusions:

Color harmonization in simulated clinical conditions depends on different factors related to dentine and to composite resins. In this study dentine variables were dropped in order to analyze the influence of thickness and of the composition of the composite resin.

Ultrastructural analysis of the root canal walls after preparation with two rotary nickel-titanium endodontic instruments

Background:

Root canal preparation may produce a large quantity of smear layer that covers canal walls.

Aims:

The aim of this study was to evaluate by Scanning Electron Microscope (SEM) the root canal dentine after instrumentation with nickel-titanium rotary files, in order to evaluate the presence/absence of smear layer and the presence/absence of open tubules on the root canal walls at the coronal, middle, and apical third of each sample.

Materials and Methods:

A total of 20 single-rooted freshly extracted teeth were selected and divided into two groups. For each group, root canals were shaped with Mtwo and Revo-S instruments under irrigation with Sodium hypochlorite and 17% ethylenediaminetetraacetic acid. Specimens were fractured longitudinally and SEM analyzed at standard magnification of ×1000 and ×5000. The presence/absence of smear layer and the presence/absence of open tubules at the coronal, middle, and apical third of each canal were evaluated using a three-step scale for scores.

Statistical Analysis Used:

Numeric data were analyzed using the Kruskall-Wallis and Mann-Whitney U-Statistical tests and significance was pre-determined at P < 0.05.

Results and Conclusions:

This study did not reveal differences among the two groups. Mtwo and Revo-S showed no significant difference between them and both presented very low smear layer scores and open tubules scores, with no significant difference among coronal, middle, and apical third. Mtwo and Revo-S rotary instruments seem to be effective in removing smear layer from canal walls.

Atomic force microscopy study of enamel remineralization

AIM

The aim of the present in vitro study was the evaluation of two products: a CPP-ACP paste (GC Tooth Mousse, GC Corp.) and a desensitizing toothpaste (Colgate Sensitive Pro Relief, Colgate-Palmolive) on preventing enamel erosion produced by a soft drink (Coca Cola) by using Atomic Force Microscopy (AFM).

METHODS

Thirty enamel specimens were assigned to 6 groups of 5 specimens each. 1: intact enamel, 2: enamel + soft drink, 3: intact enamel + Colgate Sensitive Pro Relief, 4: enamel + soft drink + Colgate Sensitive Pro Relief, 5: intact enamel + GC Tooth Mousse, 6: enamel + soft drink + GC Tooth Mousse. The surface of each specimen was imaged by AFM. 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.

RESULTS

Comparing groups 4 and 6 (soft drink + toothpastes) with group 2 (eroded enamel) a statistical difference (P<0.05) was registered, suggesting effectiveness in protecting enamel against erosion of the products investigated.

CONCLUSIONS

The use of new formulation toothpastes can prevent enamel demineralization.

Cyclic fatigue resistance of OneShape, Reciproc, and WaveOne: An in vitro comparative study

Aims:

The aim of this in vitro study was to evaluate the cyclic fatigue resistance of three single-use nickel–titanium (NiTi) instruments.

Materials and Methods:

Forty files each of OneShape (OS), Reciproc R25 (R25), WaveOne Primary (WO) file, and ProTaper (PT) F2 (as control) were tested in four curved artificial canals with different angles and radii of curvature. The number of cycles to fracture (NCF) was determined and the data were compared for differences by using two-way analysis of variance (P < 0.05).

Results:

In general, all single-use instruments were more resistant than traditional rotary instrument used as control. R25 showed the highest cyclic fatigue resistance. One Shape and WO files showed similar cyclic fatigue resistance values, higher than PT F2.

Conclusions:

Within the limitations of this study, it can be concluded that R25 was the most fatigue resistant. OS rotary instruments seem to have good mechanical resistance, similar to NiTi files developed for reciprocating motion.

Biocompatibility of a new pulp capping cement

AIM

THE AIM OF THE PRESENT STUDY WAS TO EVALUATE THE BIOCOMPATIBILITY OF A NEW PULP CAPPING MATERIAL (BIODENTINE, SEPTODONT) COMPARED WITH REFERENCE PULP CAPPING MATERIALS: Dycal (Dentsply), ProRoot MTA (Dentsply) and MTA-Angelus (Angelus) by using murine odontoblast cell line and Alamar blue and MTT cytotoxicity tests.

METHODS

The citocompatibility of murine odontoblasts cells (MDPC-23) were evaluated at different times using a 24 Transwell culture plate by Alamar blue test and MTT assay.

RESULTS

The results were significantly different among the pulp capping materials tested. Biocompatibility was significant different among materials with different composition.

CONCLUSIONS

Biodentine and MTA-based products show lower cytotoxicity varying from calcium hydroxide-based material which present higher citotoxicity.

Effects of dentin surface treatments on shear bond strength of glass-ionomer cements

AIM

The aim of this in vitro study was to evaluate the effect of different surface treatments on shear bond strength of a conventional glass-ionomer cement (GIC) and a resin-modified glass-ionomer cement (RMGIC) to dentin.

MATERIALS AND METHODS

80 bovine permanent incisors were used. 40 cylindrical specimens of a GIC (Fuji IX GP Extra) and 40 cylindrical specimens of a RMGIC (Fuji II LC) were attached to the dentin. The teeth were then randomly assigned to 8 groups of equal size (n=10), 4 for every type of glass-ionomer cement, corresponding to type of dentin surface treatments. Group 1: GC Cavity Conditioner; Group 2: 37% phosphoric acid gel; Group 3: Clearfil SE Bond; Group 4: no dentin conditioning (control). The specimens were placed in a universal testing machine (Model 3343, Instron Corp., Canton, Mass., USA) and subsequently tested for shear bond strength (MPa).

RESULTS

ANOVA showed the presence of significant differences among the various groups. Post hoc Tukey test showed different values of shear bond strength for Fuji IX GP Extra and for Fuji II LC. The different conditioners variably influence the adhesion of the glass-ionomer cements tested. Conclusions. RMGIC shear bond to dentin was higher than GIC. The use of a Self-etch adhesive system improved the shear bond strength values of RMGIC and lowered the shear bond strength values of GIC significantly.

Surface discoloration of composite resins: Effects of staining and bleaching

Background:

The purpose of this in vitro study was to evaluate surface discoloration of three microhybrid composite resins (Esthet•X HD, Clearfil AP-X, Gradia Direct) and five nanohybrid composite resins (Ceram•X, GC Kalore, G-aenial, Grandio, GrandioSO), after staining and bleaching procedures.

Materials and Methods:

The composite resins were polymerized with a curing light (Celalux II, Voco, Cuxhaven, Germany) into 160 silicon molds (6,4 mm in diameter and 2 mm in thickness) to obtain identical specimens. Twenty samples for each composite resin were prepared. The specimens were polished using an automated polishing machine with the sequence of 600-, 800-, 1000-grit abrasive paper under water irrigation. The specimens were immersed in tea and distilled water: the specimens were dipped for 20 min, once a day (every 24 h), for 14 days into the drinks. The specimens were then bleached with carbamide peroxide at 17% (Perfect Bleach-Voco). The color of specimens was measured with a spectrophotometer according to the CIE L^*a^*b^* system after light-polymerization of composite resin specimens, after 7 days, after 14 days, and after bleaching. The color difference h index (DEab^*) between each measurement was calculated. Statistical analysis was made using analysis of variance (ANOVA).

Results:

All specimens showed a significant increase in staining with a similar trend and no significant differences between microhybrid and nanohybrid composite resins. After whitening procedures, materials tested showed both significant and unsignificant differences of the h index.

Conclusions:

Microhybrid and nanohybrid composite resins had similar in vitro surface discoloration in tea. After bleaching, discoloration was removed from some composite resins tested.