Comparison of microtensile bond strength and resin–dentin interfaces of two self‐adhesive flowable composite resins by using different universal adhesives: Scanning electron microscope study

The aim of this in‐vitro study was to evaluate microtensile bond strength (μTBS) of two different self‐adhesive composites (SACs) on the permanent dentin by applying five different universal adhesive systems. In this study, two different SACs [Vertise Flow (VF), Fusio Liquid Dentin (FLD)] and five different bonding systems [Clearfil Universal Bond Quick (CUB), Single Bond Universal (SBU), All Bond Universal (ABU), Prime Bond Universal (PBU), Futurabond U (FBU)] were used. A total of 22 groups were created in which SACs were applied without adhesive and with five different universal bonding agents in total‐etch (TE) and self‐etch (SE) modes. Two hundred and forty test sticks were obtained using 48 healthy human molar teeth in total with groups having 10 samples each. The μTBS test was applied to each sample in the Universal test device and the data obtained were analyzed statistically by variance analysis and Tukey HSD test. In addition, the resin–dentin interface and fractures modes in the groups were examined by SEM. Upon examining the μTBS results, the highest values were seen in the use of SBU adhesive in TE mode in VF group, while the lowest values were seen in the FLD control group. The difference between the control and experimental groups was found statistically significant (p < .05). Upon comparing the control groups with each other, it was seen that VF group had higher μTBS values than FLD group and the difference between the groups was found statistically significant (p < .05). The μTBS results and SEM images of the study showed that the use of SACs with universal adhesive systems provides a more effective bond strength.     

Effect of dentin pretreatment with potassium oxalate: A 6‐year follow‐up

Oxalate‐based products are effective against dentine sensitivity and have been studied as an option to improve long‐term adhesive bonding strength. Our aim was to evaluate the effect of potassium oxalate on the microtensile bond strength (µTBS) of the dentin/resin interface after 24 h, 1, and 6 years. Dentin on the occlusal surface of 16 human premolars was exposed and etched with 35% phosphoric acid. The teeth were divided into four groups. Two groups received 3% monohydrated potassium oxalate and the following adhesive systems and composites: Adper Scotchbond Multipurpose + FiltekZ350 (3M/ESPE) and Prime & Bond NT + Esthet‐X (Dentsply). Two control groups did not receive potassium oxalate. Teeth were cut into sticks and kept in distilled water at 37°C for 24 h, 1, and 6 years. The sticks underwent µTBS testing after storage. ANOVA, Tukey's post hoc test, and paired t test were used to compare storage times (α = 0.05). The fracture mode of the specimens was classified under a stereomicroscope (40×). Morphology of the hybrid layer and the fracture pattern were observed with scanning electronic microscopy (SEM). Mean µTBS was high at 24 h and decreased after 1 and 6 years. After 6 years, the mean µTBS values were similar with no statistically significant difference between the groups (p = .121). SEM images showed proper dentin hybridization. Dentin pretreatment with potassium oxalate did not affect hybrid layer formation, but bond strength decreased over time after 24 h. Therefore, the clinical use of potassium oxalate to increase dentin bond durability is not indicated.     

Effects of sodium hypochlorite as dentin deproteinizing agent and aging media on bond strength of two conventional adhesives

This study evaluated the effect of 10% sodium hypochlorite (NaOCl) as deproteinizing agent and storage media on bond strength (BS) of two etch‐and‐rinse adhesive systems to dentin. Twenty‐eight sound extracted human third molars were divided in four groups (n = 7), according to dentin treatment (conventional etching or etching followed by 10% NaOCl application) and adhesive systems (GB—Gluma 2Bond and OS—One‐Step). After dentin treatments and adhesive application, a composite block was built‐up on dentin surface and teeth were serially sectioned to obtain bonded sticks specimens. The sticks were submitted to three aging conditions: (24H) 24 hr in water (immediate), (SH) 3 hr of NaOCl accelerated‐aging or (1Y) 1 year of water storage. Afterward, submitted to microtensile bond strength test (μTBS), failure modes and adhesive interfaces analyzes. Data were analyzed by two‐way analysis of variance (ANOVA) and Tukey's test (α = .05). Dentin deproteinization before bonding significantly reduced μTBS for GB‐treated group (p < .05), regardless the aging conditions. Water storage for 1 year (1Y) and NaOCl accelerated‐aging (SH) decreased μTBS for both adhesives. Yet, the groups stored in NaOCl (SH) exhibited the lowest BS results (p < .05). Bond strength of deproteinized dentin was dependent on the adhesive system composition and NaOCl accelerated‐aging promoted decreased bond strength and further degradation than water storage for 1 year.     

Resin-tooth interfacial morphology and sealing ability of one-step self-etch adhesives: microleakage and SEM study

OBJECTIVES: To compare microleakage of three self‐etch adhesives and to analyze enamel surface morphology and interfacial morphology of resin–enamel and resin–dentin interface under scanning electron microscope (SEM). EXPERIMENTAL DESIGN: Study was conducted in 65 extracted human premolars. Class V cavities were prepared in 45 teeth and assigned to three groups (n = 15) according to three self‐etch adhesives (OptiBond All‐in‐One, iBond, and Adper Prompt L‐Pop). After restoration, 10 samples from each group were used to assess microleakage at enamel and dentin margin. Five samples from each group were used for analysis of interfacial morphology at resin–enamel and resin–dentin interface under SEM. Remaining 20 teeth were used to prepare flat enamel buccal surfaces to analyze the difference in surface morphology after treatment with three adhesives (n = 5 each) and 36% phosphoric acid treatment (n = 5). PRINCIPAL OBSERVATIONS: At enamel margin, Prompt L‐Pop depicted least leakage of all the three adhesives and also showed best interfacial adaptation under SEM. At dentin margin, OptiBond All‐in‐One showed significant less leakage than iBond and Prompt L‐Pop. On flat enamel surface, phosphoric acid produced the most retentive etching pattern when compared with the three adhesives. CONCLUSION: Prompt L‐Pop showed the best bonding effectiveness in enamel, whereas OptiBond All‐in‐One performed significantly better in dentin. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.     

Long‐term chlorhexidine effect on bond strength to Er:YAG laser irradiated‐dentin

This study evaluates the bond strength of dentin prepared with Er:YAG laser or bur, after rewetting with chlorhexidine on long‐term artificial saliva storage and thermocycling. One hundred and twenty human third molars were sectioned in order to expose the dentin surface (n = 10). The specimens were randomly divided in 12 groups according to treatment and aging: Er:YAG laser rewetting with deionized water (LW) and 24 h storage in artificial saliva (WC); LW and 6 months of artificial saliva storage + 12.000 thermocycling (6M), LW and 12 months of artificial saliva storage + 24.000 thermocycling (12M), Er:YAG laser rewetting with 2% chlorhexidine (LC) and WC, LC and 6M, LC and 12M, bur on high‐speed turbine rewetting with deionized water (TW) and WC, TW6M, TW12M, bur on high‐speed turbine + 2% chlorhexidine (TC) and WC, TC and 6M, TC and12M. The specimens were etched with 35% phosphoric acid, washed, and dried with air. Single Bond 2 adhesive was applied and the samples were restored with a composite. Each tooth was sectioned in order to obtain 4 sticks, which were submitted to microtensile bond strength test (µTBS). The two‐way ANOVA, showed no significant differences for the interaction between the factors and for the aging factor. Tukey 5% showed that the LC group had the lowest µTBS. The rewetting with chlorhexidine negatively influenced the bond strength of the preparation with the Er:YAG laser. The artificial saliva aging and thermocycling did not interfere with dentin bond strength. Microsc. Res. Tech. 77:37–43, 2014. © 2013 Wiley Periodicals, Inc.     

Surface roughness and filler particles characterization of resin‐based composites

The purpose of this study was to evaluate the surface roughness (Ra), and the morphology and composition of filler particles of different composites submitted to toothbrushing and water storage. Disc‐shaped specimens (15 mm × 2 mm) were made from five composites: two conventional (Z100?, and Filtek? Supreme Ultra Universal, 3M), one “quick‐cure” (Estelite ∑ Quick, Tokuyama), one fluoride‐releasing (Beautiful II, Shofu), and one self‐adhering (Vertise Flow, Kerr) composite. Samples were finished/polished using aluminum oxide discs (Sof‐Lex, 3M), and their surfaces were analyzed by profilometry (n = 5) and scanning electron microscopy (SEM; n = 3) at 1 week and after 30,000 toothbrushing cycles and 6‐month water storage. Ra data were analyzed by two‐way analysis of variance and Tukey's test (α = 0.05). Filler particles morphology and composition were analyzed by SEM and X‐ray dispersive energy spectroscopy, respectively. Finishing/polishing resulted in similar Ra for all the composites, while toothbrushing and water storage increased the Ra of all the tested materials, also changing their surface morphology. Beautifil II and Vertise Flow presented the highest Ra after toothbrushing and water storage. Filler particles were mainly composed of silicon, zirconium, aluminum, barium, and ytterbium. Size and morphology of fillers, and composition of the tested composites influenced their Ra when samples were submitted to toothbrushing and water storage.     

Effect of laser preparation on adhesion of a self‐adhesive flowable composite resin to primary teeth

The aim of the study was to evaluate the adhesion of a self‐adhering flowable composite resin to primary tooth enamel and dentin after silicon carbide paper (SiC) and laser pretreatment. Adhesive properties were evaluated as shear bond strength (SBS) and scanning electron microscopic (SEM) characteristics. A total 120 primary canine teeth were randomly divided into two groups to study enamel and dentin. Each group was divided into 6 subgroups (n = 10) according to type of surface preparation (SiC or Er:YAG laser) of enamel or dentin. Three methods were used to build cylinders of restoration on tooth surface: OptiBond All‐In‐One + Premise Flowable composite, OptiBond All‐In‐One + Vertise Flow and Vertise flow. After restoration, samples were tested for SBS and failure mode. Twenty eight samples were examined by SEM. The results of the study showed SBS of Vertise Flow was lower than others in enamel and dentin samples pretreated with SiC and in dentin samples pretreated with laser (P < 0.001). Compared to SiC pretreatment, laser pretreatment led to a significantly higher SBS with Vertise Flow on enamel (P < 0.001). Vertise Flow associated with the adhesive led to a higher SBS in enamel and dentin compared to Vertise Flow alone. Adhesive and mixed failure modes were observed more frequently in Vertise Flow groups. SEM images showed that Vertise Flow led to more irregularities on enamel and more open dentinal tubules after laser ablation compared SiC pretreatment. Microsc. Res. Tech. 79:334–341, 2016. © 2016 Wiley Periodicals, Inc.     

Osseointegration of hydroxyapatite and remodeling‐resorption of tricalciumphosphate ceramics

Background: Cancellous bone defects surrounded by still intact bone structures never heal. Ceramics offer a solution providing osteoconductive scaffolds. Purpose: The purpose of the study is to evaluate whether structured β‐TCP and HA implants can reconstruct cancellous bone defects, which role micro‐ and macro‐porosity, stiffness and surface area play; finally the indication for both materials based on its resorbability. Material & Methods: 10 German Shepard dogs were operated on both tibial heads implanting shell‐like fully interconnected ceramic cylinders, using a wet grinding hollow drill coated with diamonds. β‐TCP was compared with HA. A polychromatic sequential labelling with 4 different fluorochromes controlled bone formation dynamics. Non‐decalcifying histology after perfusion fixation and vessel casting was performed. μ‐CT was combined with high resolution microradiography and histology on thin ground crossections. The stages after 6 weeks, 2, 3, 4 months and 15 months were evaluated. Results: In spite of osseointegration of HA and β‐TCP, the osseointegration of both materials was completely different. Both shell‐like bone void fillers were osseointegrated in a sandwich‐like manner. HA yielded primarily a reinforcement of the recipient's cancellous‐bone bed and full osseointegration after 4 months, whereas β‐TCP‐implants were fully osseointegrated after 6 weeks. HA did not show signs of resorption. The resorption of the β‐TCP resulted during remodelling. The final stage showed restitution “ad integrum” of the β‐TCP defects with a physiological architecture, whereas HA was integrated in the cancellous bone construction providing 600 μm measuring macropores showing osteoinductive properties. Microsc. Res. Tech. 76:370–380, 2013. © 2013 Wiley Periodicals, Inc.     

X‐ray microdiffraction,TEM characterization and texture analysis of human dentin and enamel

Human tooth is a complex bioceramic composite, which consists of enamel, dentin and the interface, the dentin–enamel junction (DEJ). The crystal properties and ultrastructure of the inorganic phase through the thickness of healthy human molar teeth were investigated using X‐ray microdiffraction (μXRD), electron diffraction and transmission electron microscopy (TEM) techniques. The XRD data were analysed using the Le Bail profile fitting approach. The size and the texture of the crystallites forming enamel and dentin in the crown part of teeth were measured using both techniques and then compared. Results showed that the thickness of dentin crystallites was found to decrease towards the DEJ, whereas the thickness of the enamel crystallites increased from the DEJ towards the outer layers. It was demonstrated that enamel exhibited an increase of texture in 002 lattice planes from the DEJ towards the outer layers. Texture was also detected in 102 lattice planes. The texture effect in 002 planes at the scale of less than 1 μm was also demonstrated in dentin. The variation of lattice parameters as a function of the position within the thickness of dentin and enamel was also observed. The values of the nonuniform microstrain in the dentin and enamel crystallites were from 1.40 × 10^?6% to 4.44 × 10^?5%. The good correlation between XRD and TEM indicated that μXRD is a useful technique to study crystallography and microstructure of heterogeneous enamel and dentin. The observed gradient characteristics of texture and crystallite size in enamel and dentin maybe an evolutionary outcome to resist wear and fracture, thereby contributing to the excellent mechanical properties of teeth.     

Effects of Er,Cr:YSGG laser parameters on dentin bond strength and interface morphology

Previous studies have shown the effects of Er,Cr:YSGG laser irradiation on the dentin bond strength; but there are few reports that show the significance of the irradiation with different laser parameters on dentin bond strength and interface morphology. This in‐vitro study attempted to evaluate the microtensile bond strength (μTBS) and interface morphology of resin‐dentin interfaces, either followed by treatment with Er,Cr:YSGG laser irradiation with different parameters or not. The flattened dentin samples of 35 bovine teeth were embedded into acrylic blocks and randomly divided into seven groups according to surface treatments using Er,Cr:YSGG lasers with different parameters: 3 W/20 Hz, 3 W/35 Hz, 3 W/50 Hz, 1.5 W/20 Hz, 1.5 W/35 Hz, 1.5 W/50 Hz, or no laser treatment (n = 5). Composite buildups were done over bonded surfaces and stored in water (24 hours at 37°C). Specimens were sectioned into sticks that were subjected to μTBS testing and observed under FE‐SEM. Control groups (27.70 ± 7.0) showed statistically higher values than laser‐irradiated groups. There were no significant differences among laser groups. Despite that, increasing the pulse frequency yielded slightly higher bond strength. Depending on laser settings, Er,Cr:YSGG laser irradiation caused interfacial gaps and resin tags with wings morphology. With the parameters used in this study, Er,Cr:YSGG laser irradiation promoted morphological changes within resin‐dentin interfaces and negatively influenced the bond strength of adhesive systems. Microsc. Res. Tech. 78:1104–1111, 2015. © 2015 Wiley Periodicals, Inc.     

Interfacial ultramorphology evaluation of resin luting cements to dentin: A correlative scanning electron microscopy and transmission electron microscopy analysis

The objective of this study was to analyze the dentin‐resin cements interfacial ultramorphologies using two different methods: scanning (SEM) and transmission electron microscopy (TEM). Four commercial products were evaluated: two conventional cementing system (RelyX ARC/Adper? Scotchbond? Multi‐Purpose Plus, 3M ESPE and Clearfil Esthetic Cement/DC Bond, Kuraray) and two self‐adhesive resin cements (RelyX Unicem, 3M ESPE and Clearfil SA Cement, Kuraray). Prepolymerized resin disks (Sinfony, 3M ESPE) were cemented on oclusal dentin surfaces of 24 third human molars, simulating the indirect restorations. After 24 h, teeth were sectioned into 0.9‐mm thick slabs and processed for microscopy analyses (SEM or TEM/ n = 3). Qualitative characterization of dentin‐resin cement interface was performed. Hybrid layer formation with long and dense resin tags was observed only for RelyX ARC cementing system. Clearfil Esthetic Cement/DC Bond system revealed few and short resin tags formation, whereas no hybridization and resin tags were detected for self‐adhesive resin cements. Some interfacial regions exhibited that the self‐adhesive resin cements were not bonded to dentin, presenting bubbles or voids at the interfaces. In conclusion, TEM and SEM bonding interface analyses showed ultramorphological variations among resin cements, which are directly related to dental bonding strategies used for each resin cement tested. Microsc. Res. Tech. 76:1234–1239, 2013. © 2013 Wiley Periodicals, Inc.     

Investigation of mineral content of root canal dentin after the application of various antibiotic paste using energy‐dispersive X‐ray detector

The purpose of this study was to evaluate mineral content of root canal dentin after treatment with different antibiotic pastes including the mixture of metronidazole, ciprofloxacin, doxycycline, cefaclor, amoxicillin, or minocycline. Fifty extracted maxillary canine teeth were randomly divided into five groups (n = 10 teeth for each group). Root canals were prepared Reciproc rotary files. Canals were irrigated using 5 ml 5% NaOCl and 1 ml 15% EDTA. Each tooth in all groups were longitudinally splitted into two pieces as a control and experimental samples. Each experimental group received following antibiotic paste; double antibiotic paste (DAP) and triple antibiotic paste with doxycycline (TAPd), TAP with cefaclor (TAPc), TAP with amoxicillin (TAPa), and TAP with minocycline (TAPm) for 21 days. The Ca, P, Mg, Ca, and K levels, and the Ca/P ratio was analyzed by a scanning electron microscope (SEM) equipped using a Bruker energy‐dispersive X‐Ray (EDX) detector. Data were analyzed with independent samples t‐test, one‐way anova, and Duncan tests. Ca and Ca/P ratio showed a statistically significant increase TAP with amoxicillin and cefaclor (p < .05). DAP, TAPd, and TAPm did not change the mineral levels (p > .05). TAPa and TAPc with increased the Ca level and Ca/P ratio of the root canal dentin which consequently positively influences the revascularization process.     

Effects of ultramorphological changes on adhesion to lased dentin-Scanning electron microscopy and transmission electron microscopy analysis

Dentin irradiation with erbium lasers has been reported to alter the composite resin bond to this treated surface. There is still a lack of studies reporting the effect of erbium lasers on dentin organic content and elucidating how laser treatment could interfere in the quality of the resin-dentin interface. This study aimed to evaluate the effect of erbium laser irradiation on dentin morphology and microtensile bond strength (μTBS) of an adhesive to dentin. Seventy-two dentin disks were divided into nine groups (n = 8): G1-Control (600-grit SiC paper); Er:YAG groups: G2- 250 mJ/4 Hz; G3- 200 mJ/4 Hz; G4- 180 mJ/10 Hz; G5- 160 mJ/10 Hz; Er,Cr:YSGG groups: G6- 2 W/20 Hz; G7- 2.5 W/20 Hz; G8- 3 W/20 Hz; G9- 4 W/20 Hz. Specimens were processed for cross-sectional analysis by scanning electron microscopy (SEM) (n = 3), transmission electron microscopy (TEM) (n = 2), and adhesive interface (n = 3). Forty-five dentin samples (n = 5) were restored and submitted to μTBS testing. ANOVA (α = 5%) revealed that G1 presented the highest μTBS values and irradiated groups did not differ from each other. TEM micrographs showed a superficial layer of denatured collagen fibrils. For SEM micrographs, it was possible to verify the laser effects extending to dentin subsurface presenting a rough aspect. Cross-sectional dentin micrographs of this hybridized surface revealed a pattern of modified tags with ringlike structures around it. This in vitro study showed that erbium laser irradiation interacts with the dental hard tissue resulting in a specific morphological pattern of dentin and collagen fibrils that negatively affected the bond strength to composite resin.     

Investigation of properties of electrochemically synthesizediron oxide nano‐powders

Nano‐sized powders of iron oxides have been synthesized electrochemically at temperatures in the range of 295–361 K, and current densities in the range of 200–1000 mA dm^?2. The structure and morphology of the powders were investigated by X‐ray diffraction and scanning electron and transmission electron microscopy techniques. Their infrared absorption spectra, specific heat C_p(T) and magnetic susceptibility χ(T) temperature dependences are also determined. The obtained powders consist of two phases, each possessing distinguished characteristics: the one formed of large plates and the other of whiskers. By appropriate adjustment of the synthesis conditions, it is possible to change features and relative abundances of the two phases, and that way to control morphology and other powder properties. Relaxation and transformation of the phases under external influences was also investigated, and the optimal procedure for preparation and stabilization of iron oxide nano‐sized powders with desired characteristics was established.     

Polymerization shrinkage and porosity profile of dual cure dental resin cements with different adhesion to dentin mechanisms

This research aims to probe the porosity profile and polymerization shrinkage of two different dual cure resin cements with different dentin bonding systems. The self‐adhesive resin cement RelyX U200 (named RU) and the conventional Allcem Core (named AC) were analyzed by x‐ray microtomography (μCT) and Scanning Electron Microscopy (SEM). Each cement was divided into two groups (n = 5): dual‐cured (RUD and ACD) and self‐cured (RUC and ACC). μCT demonstrated that the method of polymerization does not influence the porosity profile but the polymerization shrinkage. Fewer concentration of pores was observed for the conventional resin cement (AC), independently the method used for curing the sample. In addition, SEM showed that AC has more uniform surface and smaller particle size. The method of polymerization influenced the polymerization shrinkage, since no contraction for both RUC and ACC was observed, in contrast with results from dual‐cured samples. For RUD and ACD the polymerization shrinkage was greater in the lower third of the sample and minor in the upper third. This mechanical behavior is attributed to the polymerization toward the light. µCT showed to be a reliable technique to probe porosity and contraction due to polymerization of dental cements.     

Effect of different irrigation protocols on the radicular dentin interface and bond strength with a metacrylate‐based endodontic sealer

This study assessed the influence of different endodontic chemical substances on the adhesion of the Epiphany SE/Resilon system (with and without resinous solvent) to radicular dentin walls, using the push‐out test and scanning electron microscopy (SEM). Forty‐eight root canals of human canines were prepared biomechanically with ProTaper rotary files (crown‐down technique) and the radicular dentin was treated with either 17% EDTA, 2% chlorhexidine gel (CHX) or 2.5% NaOCl (control). The root canals were filled with Resilon cones and Epiphany SE sealer with and without resinous solvent. Six groups of eight canals each had their roots sectioned transversally to obtain 1‐mm thick slices. Data were subjected to statistical analysis by ANOVA and Tukey's tests. The specimens treated with 17% EDTA (1.59 ± 0.91) presented higher bond strength (P < 0.05) than those treated with 2.5% NaOCl (0.93 ± 0.27) and 2% CHX (0.92 ± 0.22). Significantly higher bond strength (P < 0.05) was observed when the Epiphany SE was prepared with (1.37 ± 0.78) than without (0.92 ± 0.33) solvent. Adhesive failures were predominant in all groups. SEM analysis showed greater homogeneity of the filling mass when the solvent was added to the sealer. Treatment of root canal walls with 17% EDTA, and addition of a resinous solvent to Epiphany SE produced the highest adhesion to radicular dentin. Microsc. Res. Tech. 77:446–452, 2014. © 2014 Wiley Periodicals, Inc.     

Fine structure of tooth enamel in the yellowing human teeth: SEM and HRTEM studies

Objective : The aim of this study was to clarify an influence of the fine structure of human tooth enamel to the yellowing teeth. Materials and methods : Sound maxillary first premolars of 15–50‐year‐old females that were extracted for the orthodontic treatment were used as the test samples. The tooth enamel sections of these teeth that prepared by ion polishing were observed by scanning electron microscopy (SEM). Furthermore, the fine structure of substance filling the inter‐rod spaces was analyzed by high resolution transmission electron microscopy (HRTEM). Results : In white tooth, the inter‐rod spaces were observed at the width of about 0.1 μm, while in yellow tooth, the inter‐rod spaces were not clearly observed by SEM. HRTEM observations revealed for the first time that the inter‐rod spaces were filled with fine particles of poorly crystallized hydroxyapatite in the yellow tooth. In yellow tooth, it was considered that the color of the inner dentin was recognized due to the decrease of light scattering by filling the tooth enamel inter‐rod spaces. The generation of particles in the tooth enamel inter‐rod spaces was considered to be caused by the long‐time progression of calcification. Conclusions : These results suggested that the change in fine structure, filling in inter‐rod spaces of tooth enamel, was related to progression of calcification in the inter‐rod spaces with advancing age and one of the factors of yellowness of human tooth. Microsc. Res. Tech. 79:14–22, 2016. © 2015 Wiley Periodicals, Inc.     

Effects of chemical agents on physical properties and structure of primary pulp chamber dentin

This study evaluated the effects of chemical agents on the physical properties and structure of primary pulp chamber dentin using surface roughness, microhardness tests, and scanning electron microscopy (SEM). Twenty‐five primary teeth were sectioned exposing the pulp chamber and were divided into five groups (n = 5): NT, no treatment; SH1, 1% sodium hypochlorite (NaOCl); SH1U, 1% NaOCl + Endo‐PTC^®; SH1E, 1% NaOCl + 17% EDTA; and E, 17% EDTA. After dentin treatment, the specimens were submitted to roughness, microhardness testing, and SEM analysis. Roughness and microhardness data were submitted to one‐way ANOVA and Tukey's test (P < 0.05). The SH1E group showed the highest roughness, followed by the E group (P < 0.05) when compared with the NT, SH1, and SH1U groups. Microhardness values of SH1 and SH1U showed no significant difference as compared to the NT (control) group (P > 0.05). Microhardness values could not be obtained in the EDTA groups (SH1E and E). The presence of intertubular dentin with opened dentin tubules was observed in the NT, SH1, and SH1U groups. SH1E showed eroded and disorganized dentin with few opened tubules and the intertubular/peritubular dentin was partially removed. Considering the physical and structural approaches and the chemical agents studied, it can be concluded that NaOCl and NaOCl associated with Endo‐PTC^® were the agents that promoted the smallest changes in surface roughness, microhardness, and structure of the pulp chamber dentin of primary teeth. Microsc. Res. Tech. 77:52–56, 2014. © 2013 Wiley Periodicals, Inc.     

Analysis of efficacy of the self‐assembling peptide‐based remineralization agent on artificial enamel lesions

The objective of this in vitro study was to analyze and compare the biomimetic remineralizing efficacy of the self‐assembling peptide (P11‐4) with agents containing casein phoshopeptide‐amorhous calcium phosphate fluoride (CPP‐ACFP) and sodium fluoride (NaF) on artificial caries lesions using DIAGNOdent and micro‐computed tomography (μCT). Artificial enamel lesions were prepared on extracted impacted sound mandibular third molars. The samples were randomly allocated to four groups (n = 8): Group 1, P11‐4 (Curodont Repair, Credentis AG, Switzerland); Group 2, CPP‐ACFP (MI Varnish, GCCo., Japan); Group3, NaF (Duraphat Varnish, Colgate, Colgate‐Palmolive, NY, USA); Group 4, artificial saliva (control). The agents were applied to demineralized surfaces according to manufacturers' instructions; all specimens were stored in artificial saliva for 1 month. Demineralization and remineralization on enamel surfaces were analyzed and quantified by DIAGNOdent (KaVo, Germany) and μCT (SkyScan1174, Belgium) for lesion depth/area/volume/mineral density (MD). The remineralization efficacy of the agents was evaluated by DIAGNOdent on 1st, 7th, 30th days and by μCT on 30th day. Data were statistically analyzed by ANOVA, Kruskal–Wallis, T test, and Wilxocon tests. The highest remineralization efficacy findings in all periods were determined in Group 1, followed by Groups 2, 3, and 4. The remineralization findings for fluorescence, MD, lesion depth in Group 1 were found significantly higher (p < 0.01) than Group 3; and no significant differences (p > 0.05) were found between Groups 1–2 and Groups 2–3. The area and volume change values in Groups 1, 2, and 3 have shown no significancy (p > 0.05). A significant correlation (p < 0.01) was found between μCT and DIAGNOdent methods. The data of this study have demonstrated that P11‐4 has showed the best remineralization efficacy, followed by CPP‐ACFP and NaF. It is concluded that self‐assembling peptide‐based remineralization agent can be used successfully for biomimetic remineralization of enamel subsurface lesions.     

In vivo response to HA-polyhydroxybutyrate/polyhydroxyvalerate composite

This study examined the morphological and compositional structure of bone–implant interfaces after in vivo implantation into the tibias of rabbits. The implants were composed of biodegradable polyhydroxybutyrate/polyhydroxyvalerate copolymer reinforced with synthetic hydroxyapatite (HA) particles. Optical and scanning electron microscopy techniques were used, including energy‐dispersive X‐ray analysis. The interface was found to be morphologically, biologically and chemically active throughout the period of study. There was a strong tendency to rebuild the bone structure at the interface after implantation, independent of the composition of the implant, but direct bone bonding with the implant depended on the bioactive nature of the interface, as represented by the HA particles. At all implantation times, lamellar bone formed at the interface and replaced degrading polymer matrix, while engulfing HA filler particles. In regions about 50–100 from the interface, the bone region displayed an osteon organization. Osteoblasts and osteocytes were identified throughout the interface region. The thickness of the newly formed bone significantly increased over the period of the experiment from about 130 µm at 1 month to about 770 µm at 6 months. Materials that behave in this manner may be useful in some bone replacement therapies.