Impact of Endodontic Treatments on the Rigidity of the Root

The destabilizing effect of endodontic treatment upon teeth is still controversial. The purpose of this study was to investigate the effects of different steps of endodontic treatments upon the rigidity of teeth. Extracted untreated central maxillary anterior teeth were loaded (3.75 N), and deformations of the root were assessed by Speckle pattern interferometry. The following treatments (with subsequent determination of deformability) were conducted sequentially: access preparation, manual instrumentation (Kerr files ISO-40, ISO-60, ISO-80, ISO-110), and tapered and parallel-sided post preparation. It was found that the teeth were increasingly destabilized by any treatment. While the increased deformability was not significant with the manual enlargement (p > 0.05), we found a significant destabilization after access preparation and post preparation (p < 0.05). A corresponding difference was found after conversion of the post preparation from tapered to parallel-sided (p < 0.05). Both substance loss and modifications of the natural root canal geometry play an important role in tooth rigidity.

The Influence of One-step Polishing Systems on the Surface Roughness and Microhardness of Nanocomposites

One-step polishing systems exhibited similar or better surface roughness values when compared to multi-step polishing systems. In all groups, mylar-strip created surfaces showed lower microhardness values than polished surfaces. Different polishing procedures did not effect the microhardness of nanocomposites. One-step polishing systems may be a good choice for polishing nanocomposites, resulting in reduced chair time.

Healing of onlay mandibular bone grafts covered with collagen membrane or bovine bone substitutes: a microscopical and immunohistochemical study in the sheep

The objective of this study was to evaluate the role of collagen membrane and Bio-Oss coverage in healing of an onlay graft to the mandible. Twelve adult sheep each received an onlay bone graft (experiment 1), bone graft+Bio-Gide (experiment 2), and bone graft+Bio-Oss/Bio-Gide (experiment 3) on the lateral surface of the mandible. The animals were euthanized at 4, 8, 12 or 16 weeks after surgery, and findings were analysed by routine microscopy and immunohistochemistry for proliferation (Ki67) and apoptotic (Caspase-3) markers. Grafts were fully incorporated in all specimens. Pronounced resorption was observed in experiment 1. Minimal loss of graft volume was seen in experiment 2 specimens without membrane displacement. A remarkable increase in the augmented region of the mandible was observed in experiment 3. A high number of osteoclasts were expressed within the grafts during the early healing period, and thereafter declined markedly. Osteoblasts within the grafts expressed a moderate level of Ki67 at 8 weeks, which thereafter declined markedly. The strongest expression of Caspase-3 on the bone surface was observed after 16 weeks. In conclusion, the effect of collagen membrane coverage on bone graft volume maintenance was dependent on membrane stability during healing. An autogenous bone graft covered with Bio-Oss particles resulted in a remarkable increase in augmented lateral surface of the mandible. The late stage of bone graft healing was associated with a high apoptotic induction pathway of osteoblasts lining the surfaces of the new bone, demonstrated by strong positive Caspase-3 immunoreactivity.

Chemical Analysis of Enamel and Dentin Following the Application of Three Different At-home Bleaching Systems

Purpose

To determine the change in the chemical composition of enamel and dentin as well as to evaluate the differences in surface texture of the same dental hard tissues following three at-home bleaching systems in vitro.

Methods

Sixty extracted intact human anterior teeth were used in this study. Thirty teeth were used as samples for enamel, and the buccal surfaces of the remaining 30 teeth were abraded and used as dentin samples. Prior to bleaching treatments, calcium (Ca), phosphorus (P), potassium (K), sodium (Na), magnesium (Mg), fluoride (F), and oxygen (O) levels of each sample were measured using an energy dispersive spectrometer. The teeth were then randomly allocated into three groups according to the bleaching system used, as follows: GI, 10% carbamide peroxide (CP); GII, 20% CP; GIII, and 35% CP. Following the bleaching treatments, Ca, P, K, Na, Mg, F, and O measurements were repeated. The surface configurations were examined using scanning electron microscopy (SEM). The data were analyzed using Wilcoxon signed rank and Kruskal-Wallis tests followed by the Dunn test.

Results

All three bleaching systems tested caused similar changes in the chemical composition of enamel and dentin. Bleaching systems decreased Ca and K, while F and O levels increased in enamel. In dentin, Ca, P, and K levels decreased; however, Na, F, and O levels increased. SEM observations revealed no deleterious effect on enamel and dentin.

Conclusion

The use of home bleaching agents could affect the chemical composition of dental hard tissues, whereas the change in the chemical composition of enamel and dentin was not affected by the CP concentration of the bleaching systems used.

Shear bond strength of orthodontic brackets with 3 self-etch adhesives

INTRODUCTION

The purpose of this study was to compare shear bond strength and mode of failure of brackets bonded with 3 self-etching products.

METHODS

The products tested were (1) a recently developed, modified self-etching, 1-step adhesive system (Adper Prompt L-Pop Self Etch Adhesive, 3M, St Paul, Minn); (2) a new fluoride-releasing, antibacterial, self-etching adhesive system (Clearfil Protect Bond, Kuraray, Osaka, Japan); and (3) a fluoride-releasing, self-etching adhesive system (Transbond Plus Self Etching Primer, 3M). Thirty-six defect-free premolars were randomly divided into 3 groups (n = 12 each), and metal brackets were bonded according to the manufacturer's instructions. Brackets were debonded in shear on a universal testing machine with a crosshead speed of 1 mm per minute.

RESULTS

One-way ANOVA showed a statistically significant (P < .001) difference between groups. Group 2 had the highest shear bond strength. The difference between groups 1 and 3 was not statistically significant. The Kruskal-Wallis test showed no significant differences in the ARI scores (P = .595; P < .05).

CONCLUSIONS

The fluoride-releasing, antibacterial, self-etching adhesive system, Clearfil Protect Bond, produced greater shear bond strength than the other 2 products tested and could be considered for clinical use.

Effect of adhesives and thermocycling on the shear bond strength of a nano-composite to coronal and root dentin

OBJECTIVES

To evaluate the effects of "etch & rinse" vs "self-etch" adhesives and thermocycling on the shear bond strength (SBS) of a nano-composite to coronal and root dentin.

MATERIALS AND METHODS

FIFTY-SIX EXTRACTED HUMAN MOLARS WERE mounted and ground to expose coronal and root dentin surfaces and were randomly divided into two groups according to adhesive system: SE--a two-step self-etch adhesive (Adper SE Plus, 3M ESPE) and ER-an etch & rinse adhesive (Adper Single Bond 2, 3M ESPE). The adhesives were applied to the coronal and root dentin of the mounted teeth. A nano-composite (Filtek Supreme XT, 3M ESPE) was applied to both dentin surfaces. The bonded specimens were stored in distilled water at 37 degrees C for 24 hours. Half of the bonded specimens were tested for SBS in a universal testing machine without thermocycling. The remaining specimens were thermocycled (500 cycles between 5 degrees C and 55 degrees C) prior to SBS testing. Two specimens from each group were kept for Scanning Electron Microscope evaluations of the adhesive interfaces. Failure modes were determined under a stereomicroscope. The mean SBS value of each group was calculated, and the results were subjected to ANOVA, Duncan test and Paired samples t-test (p = 0.05).

RESULTS

Thermocycling did not affect the SBS of coronal dentin for either adhesive. However, it affected the SBS of SE in root dentin (p < 0.05). The two different dentin substrates did not exhibit a significant difference except for higher values in root dentin with the SE group without thermocycling. The greatest number of cohesive failures was observed in root dentin with SE adhesive; however, the failure modes were mainly adhesive for the other groups.

CONCLUSION

The SE adhesive exhibited higher SBS values than the ER adhesive in root dentin. Thermocycling did not affect the SBS in coronal dentin for either adhesive but it decreased the SBS of SE in root dentin.

Irreversible inflammation is associated with decreased levels of the alpha1-, beta1-, and alpha2-subunits of sGC in human odontoblasts

The nitric oxide (NO) receptor enzyme soluble guanylate cyclase (sGC) contains one prosthetic heme group as an αβ heterodimer, and two heterodimer isoforms (α(1)β(1), α(2)β(1)) were characterized to have enzyme activity. To test the irreversible inflammation-dependent regulation of sGC in odontoblasts, we incubated decalcified frozen sections of healthy and inflamed human third molars with antibodies against β-actin, nitrotyrosine, inducible nitric oxide synthase (iNOS), α(1)-, β(1)-, and α(2)-subunits of sGC and analyzed them at protein levels by quantitative immunohistochemistry. The irreversible inflammation induced an increase in the signal intensities for nitrotyrosine and iNOS and a decrease for the α(1)-, β(1)-, and α(2)-subunits of sGC in odontoblasts. Inflammatory mediators, reactive oxygen, and nitrogen species may impair the expression of the α(1)-, β(1)-, and α(2)-subunits in odontoblasts. The decrease of sGC at the protein level in inflamed odontoblasts is compatible with a critical role for sGC to mediate biological effects of NO in health.

Shear Bond Strength of Orthodontic Brackets Bonded using Conventional vs One and Two Step Self-etching/adhesive Systems

OBJECTIVE

To assess and compare the effects of one- and two-step self-etching primer and adhesive with conventional acid-etching and bonding system on the shear bond strength of orthodontic brackets.

MATERIALS AND METHODS

The one-step self-etching primer and adhesive used was Clearfil tri-S bond, the two-step fluoride-releasing antibacterial self-etching primer and adhesive was Clearfil Protect Bond, and the fluoride-releasing conventional acid-etching and bonding system was Kurasper F Bond. Brackets were bonded to defect-free human premolars (n = 14 per group) according to each manufacturer's recommendations by using light-cured bracket adhesive Kurasper F Paste with a light-emitting diode of a light-curing unit. The specimens were stored in deionized water at 37 degrees C for 48 hours and then tested in shear with a universal testing machine at a crosshead speed of 5 mm/min until the brackets debonded. The mode of failure of the brackets was determined by a modified adhesive remnant index.

RESULTS

Mean shear bond strength values were 9.00 MPa for Kurasper F Bond, 9.55 MPa for Clearfil Protect Bond, and 9.48 MPa for Clearfil tri-S Bond. One-way analysis of variance detected no statistically significant difference among groups (P = .98, P > .05). The predominant failure for the three groups was at the bracket-adhesive interface leaving less than 25% of the adhesive on the bracket base.

CONCLUSIONS

One-step self-etching adhesive and two-step fluoride-releasing antibacterial self-etching adhesive have sufficient mechanical properties for the bonding of orthodontic brackets.

Influence of different conditioning methods on the shear bond strength of novel light-curing nano-ionomer restorative to enamel and dentin

The purpose of this study was to investigate shear bond strength (SBS) between a light-curing nano-ionomer restorative and enamel or dentin after acid etching, after erbium:yttrium-aluminum-garnet (Er:YAG) laser etching, or after combined treatment. Forty third molars were selected, the crowns were sectioned, and 80 tooth slabs were obtained. The specimens were assigned to two groups, which were divided into four subgroups(n = 10). Group 1 [enamel (e)], treated with 37% phosphoric acid (A) + Ketac nano-primer (K); group 2 [dentin (d)], (A) + (K); group 3(e), Er:YAG laser etching (L) + (A) + (K); group 4(d), (L) + (A) + (K); group 5(e), (L) + (K); group 6(d), (L) + (K); group 7(e), (K); group 8(d), (K). The SBS of the specimens was measured with a universal test machine (1 mm/min). Data were analyzed by independent samples t-test, one-way analysis of variance (ANOVA) and a post-hoc Duncan test (p < 0.05). No difference was determined between groups 3 and 5 (p > 0.05). Group 7 exhibited higher SBS values than those of groups 3 and 5 (p < 0.05). Group 1 showed higher SBSs than those of groups 3, 5 and 7 (p < 0.05). There was no significant difference between groups 4 and 6 (p > 0.05). No difference was observed between groups 2 and 4 (p > 0.05). However, group 2 presented higher SBSs than did group 6 (p < 0.05). Group 8 exhibited the highest SBS values when compared with groups 2, 4 and 6 (p < 0.05). Er:YAG laser adversely affected the adhesion of the light-curing nano-ionomer restorative to both enamel and dentin.

Shear bond strength of three different nano-restorative materials to dentin

OBJECTIVES

To evaluate the shear bond strength (SBS) of a nano-composite, a flowable nano-composite and a nano glass ionomer to dentin in vitro.

MATERIALS AND METHODS

Sixty human molars were ground flat, exposing the dentin surfaces, and they were randomly divided into five groups according to the restorative materials and adhesive systems used (n = 12/group). The restoratives were applied to all dentin surfaces according to the manufacturer's instructions, using a special jig (Ultradent) in the following manner: Group 1: a nano-composite (NC) (Filtek Supreme XT-3M ESPE) was applied with a two-step self-etch adhesive (SE) (Adper SE Plus-3M ESPE); Group 2: NC was applied with an etch&rinse adhesive (SB) (Adper Single Bond 2-3M ESPE); Group 3: a flowable nano-composite (FNC, Filtek Supreme XT Flow-3M ESPE) was applied with SE; Group 4: FNC was applied with SB and Group 5: a nanofilled resin-modified glass ionomer (Ketac N100-3M ESPE) was applied with Ketac Nano Primer (3M ESPE). The bonded specimens were stored in distilled water (37 degrees C, 24 hours) and tested for SBS in a universal testing machine (1 mm/minute). Two specimens from each group were subjected to SEM evaluations of the adhesive interfaces. Failure modes were determined using a stereomicroscope. The mean SBS values were calculated and the data were analyzed with the Kruskal Wallis and Mann-Whitney-U tests (p < 0.05).

RESULTS

Mean SBS values (MPa) for the groups were 13.64; 7.83; 11.20; 4.12 and 0.64 for Groups 1, 2, 3, 4 and 5, respectively. Group 1 exhibited a significantly higher value than all the other groups; whereas, Group 5 had the lowest value (p < 0.05). The SE adhesive yielded higher bond values than the SB adhesive with NC and FNC restorative materials. Failure modes in all the groups were primarily adhesive.

CONCLUSION

The results demonstrate the capacity of the current two-step self-etch adhesive to outperform the etch&rinse adhesive in conjunction with the two nano-restoratives tested.

NO-cGMP signaling molecules in cells of the rat molar dentin-pulp complex

By the formation of cyclic guanosine 3',5'-monophosphate (cGMP), nitric oxide (NO)-sensitive enzyme-soluble guanylate cyclase (sGC) plays a receptor role for NO within the NO-cGMP signaling cascade, which is involved in vasodilatation and neurotransmission. The hypothesis that NO-cGMP signaling molecules modulate cells of the dentin-pulp complex was investigated in rat molars by histochemical, immunohistochemical, immuno-ultrastructural, and organ bath techniques. NO synthase (NOS) I-III, the sGC alpha(2)-subunit/beta(1)-subunit, and cGMP were detected in odontoblasts and blood vessels. NOS I, sGC alpha(2), and cGMP were identified in nerve fibers. Treatment of rat molars with the NO donor NONOate (10(-5) M) increased cGMP staining intensities in blood vessels and odontoblasts, while NO synthase inhibitor L-NAME (10(-4) M) attenuated intensity of the reaction products for cGMP, suggesting an effect of endogenous NO on sGC. These correlations of patterns and alterations of cGMP staining intensities after treatment with the NO donor or NO inhibitor might represent an NO-sGC-cGMP signaling-dependent modulation of odontoblasts, blood vessels, and nerve fibers in the dentin-pulp complex.

Comparison of shear bond strengths of orthodontic brackets bonded with flowable composites

This study evaluated the shear bond strengths of orthodontic brackets bonded to human premolars using five different combinations of flowable composites and one-step self-etching adhesives (n=12): (1) Adper Easy Bond+Filtek Supreme XT Flow; (2) Futurabond NR+Grandio Flow; (3) Clearfil S3 Bond+Clearfil Majesty Flow; (4) AdheSE One+Tetric EvoFlow; and (5) Transbond Plus Self Etching Primer+Transbond XT Light Cure Adhesive. After shear bond strength testing, adhesive remnant index (ARI) scores were given according to the amount of adhesive and resin remaining on the brackets. On shear bond strength, there were no statistically significant differences between Groups 2 and 4 and between Groups 3 and 5 (p>0.05). On ARI scores, the predominant ARI scores in Groups 1, 2, 3, and 5 were 4, 2, 5, and 4 respectively; in Group 4, they were 0 and 4. Results showed that some combinations of flowable composites and self-etching adhesives might not be suitable for orthodontic use due to their low shear bond strengths and high ARI scores -with the latter signaling the risk of damaging the enamel surface during debonding.

The effects of ozone application on genotoxic damage and wound healing in bisphosphonate-applied human gingival fibroblast cells

OBJECTIVES

Medication-related osteonecrosis of the jaws (MRONJ) is an extremely therapy-resistant disease involving the jaws especially following bisphosphonate treatment. Bisphosphonates accumulate in bone in concentrations sufficient to be directly toxic to the oral epithelium. Current therapeutic options are inadequate for the prevention and treatment of MRONJ. The aim of this study was to investigate effects of ozone gas plasma therapy on wound healing in bisphosphonate-applied human fibroblasts.

MATERIAL AND METHODS

Human primary gingival fibroblasts were cultured. Cytotoxic concentrations (IC50) of bisphosphonates (pamidronate (PAM), alendronate (ALN), and zoledronate (ZOL)) were determined by MTT test. A 60 μg/μl for 30 s of ozone gas plasma application was performed to all experimental culture flasks after drug treatment at 24-h intervals as 3 s/cm². Genotoxic damages were evaluated by comet assay and wound healing was determined by in vitro scratch assay.

RESULTS

PAM, ALN, and ZOL applications caused genotoxic damage on primary human gingival fibroblast DNA. Ozone gas plasma therapy significantly decreased the genotoxic damage (p < 0.05), and this application provided 25, 29, and 27% less genotoxic damage in order of ALN, PAM, and ZOL groups. Ozone gas plasma therapy significantly increased wound healing rates both in postsurgical 24th and 48th hours for all doses of experimental drug groups (p < 0.05).

CONCLUSION

The ozone gas plasma application decreased genotoxic damage effect of bisphosphonate usage while improved the wound closure rate on human gingival fibroblasts.

CLINICAL RELEVANCE

Ozone gas plasma therapy may be helpful in prevention of gingival healing delay in MRONJ pathogenesis especially when applied simultaneously with surgical intervention.

Sealant and composite bond strength to enamel with antibacterial/self-etching adhesives

INTRODUCTION

The enamel in pits and fissures undergoing preventive or ultraconservative resin restorations may be affected by secondary caries. An antibacterial adhesive bond may be a useful choice to prevent and reduce demineralization.

OBJECTIVES

The purpose of this study was to determine the shear bond strength of an experimental antibacterial bond, a self-etch bond, and an ormocer-based adhesive bond using an ormocer-based fissure sealant and a composite resin on intact enamel.

METHODS

Twenty-four extracted human molars were sectioned bucco-lingually to obtain two flat and sound enamel surfaces. Forty-eight specimens were randomly assigned into four groups. The groups were prepared to receive the following treatments: (1) Admira Bond + Admira Seal (n = 10); (2) ABF Bond + Admira Seal (n = 11); (3) Clearfil SE Bond + Clearfil AP-X (n = 12); and (4) ABF Bond + Clearfil AP-X (n = 11). A cylindrical mould was placed over the bonded surface, and both materials were applied according to the instructions. The teeth were thermocycled 500 cycles between 5 and 55 degrees with a dwell time of 30 s. For shear bond strength testing, the load was applied vertically to the base of the mould. The cross-head speed was 5 mm min(-1).

RESULTS

The maximum load that a specimen can withstand until failure was determined and shear bond strength was calculated by dividing the load at failure by the surface area of the mould. The results (median, minimum and maximum, respectively) for the four groups were: (1) 7.9, 4.2 and 13.6 MPa; (2) 8.6, 2.6 and 15.9 MPa; (3) 5.9, 5.3 and 8.2 MPa; and (4) 8.8, 3.0 and 19.2 MPa. Kruskal-Wallis and Mann-Whitney U-tests were performed for the statistical analysis. Groups 3 and 4 were statistically significantly different (P = 0.005; P < 0.05). There was no statistically significant difference between the sealant and composite groups for ABF (P = 0.375). Fracture sites were viewed by microscope under x 16 magnification to determine if the mode of failure was adhesive or cohesive. The results (number of adhesive failed specimens and number of cohesive failed specimens, respectively) for the four groups were: (1) 7 and 3; (2) 3 and 8; (3) 2 and 9; and (4) 8 and 3.

CONCLUSION

The ABF bond has sufficiently physical qualities to be used under fissure sealant and composite resin on uncut enamel, its antibacterial efficiency notwithstanding.

Bradykinin Mediates Phosphorylation of eNOS in Odontoblasts

While the activation of eNOS by Akt/PKB-dependent phosphorylation, leading to NO release, and the inhibition of enzyme activity by bradykinin (BK)-mediated phosphorylation of eNOS in endothelial cells are established, the phosphorylation of eNOS in odontoblasts is unknown. To clarify the regulation of eNOS in odontoblasts by BK, we examined the phosphorylation of eNOS, Akt/PKB, and ERK1/2 in odontoblasts of rat molars. BK (10−7 M) transiently induced the phosphorylation of eNOS at Ser1177, Akt/PKB in odontoblasts, while it induced the phosphorylation of eNOS at Thr495 throughout the entire period of BK treatment. BK receptor 2 antagonist HOE 140 (10−6 M) significantly reduced signal intensities of phosphorylated-eNOS at Ser1177, Thr495, and phosphorylated-Akt/PKB. These results suggest that BK has dual effects on the activation of eNOS in odontoblasts, the Akt/PKB-dependent up-regulation of eNOS by the transient phosphorylation at Ser1177, and the ERK1/2-independent down-regulation of eNOS by the phosphorylation at Thr495.

Effect of Antibacterial Varnishes Applied to Root Dentin on Shear Bond Strength of Tooth-colored Restorative Materials

The application of antibacterial varnish affects the shear bond strength of tooth-colored restorative materials after six months.

Microleakage of class V cavities with different adhesive systems prepared by a diamond instrument and different parameters of Er:YAG laser irradiation

OBJECTIVE

The aim of this study was to evaluate the microleakage of composite resin restorations using two different dentine adhesive systems prepared with a diamond instrument and different parameters of Er:YAG laser irradiation.

BACKGROUND DATA

Information on this topic with regard to preparing class V cavities with different parameters of Er:YAG laser irradiation and adhesive systems is scarce.

MATERIALS AND METHODS

Two hundred class V cavities were assigned to ten groups (n = 20 each): group 1: Er:YAG laser (5 Hz, 600 mJ) + phosphoric acid (PA) + Adper Single Bond 2 (ASB2); group 2: Er:YAG laser (10 Hz, 300 mJ) + PA + ASB2; group 3: Er:YAG laser (15 Hz, 200 mJ) + PA + ASB2; group 4: Er:YAG laser (20 Hz, 150 mJ) + PA + ASB2; group 5: diamond instrument + PA + ASB2; group 6: Er:YAG laser (5 Hz, 600 mJ) + Adper Prompt L-Pop (APLP); group 7: Er:YAG laser (10 Hz, 300 mJ) + APLP; group 8: Er:YAG laser (15 Hz, 200 mJ) + APLP; group 9: Er:YAG laser (20 Hz, 150 mJ) + APLP; and group 10: diamond instrument + APLP. Cavities were restored with a nanofill composite (Filtek Supreme XT Body). After thermocycling, the specimens were stained with 0.5% aqueous basic fuchsin dye and sectioned bucco-lingually. Dye penetration was then scored. The data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests with Bonferroni correction. The Wilcoxon signed ranks test was used to compare occlusal and gingival scores.

RESULTS

Leakage was seen in all groups at both the occlusal and gingival margins. The Kruskal-Wallis test showed statistically significant differences among the 10 groups (p < 0.001). The gingival margins had more microleakage than the occlusal margins (p < 0.001). Pairwise analysis by the Mann-Whitney U test showed that statistically significant differences (p < 0.05) in microleakage were found between groups 3 and 5 (3 > 5), 5 and 7 (7 > 5), and 7 and 8 (7 > 8) at the gingival margin, and between groups 3 and 6 (6 > 3), 3 and 7 (7 > 3), 4 and 6 (6 > 4), and 4 and 7 (7 > 4) at the occlusal margin.

CONCLUSION

We concluded that for all groups, microleakage values were higher at the gingival margins. The use of the Er:YAG laser for cavity preparation with different parameters and different dentine adhesive systems influenced the marginal sealing of composite resin restorations.

Downregulation of the α1- and β1-subunit of sGC in Arterial Smooth Muscle Cells of OPSCC Is HPV-Independent

The nitric oxide (NO)-sensitive soluble guanylyl cyclase (sGC) is a heterodimeric enzyme with an α and β subunit. NO binds to heme of the β₁-subunit of sGC, activates the enzyme in the reduced heme iron state in vascular smooth muscle cells (VSMCs), and generates cGMP-inducing vasodilatation and suppression of VSMC proliferation. In the complex tumor milieu with higher levels of reactive oxygen species (ROS), sGC heme iron may become oxidized and insensitive to NO. To change sGC from an NO-insensitive to NO-sensitive state or NO-independent manner, protein expression of sGC in VSMC is required. Whether sGCα₁β₁ exists at the protein level in arterial VSMCs of oropharyngeal squamous cell carcinoma (OPSCC) is unknown. In addition, whether differences in the genetic profile between human papillomavirus (HPV)-positive and HPV-negative OPSCC contributes to the regulation of sGCα₁β₁ is unclear. Therefore, we compared the effects of HPV-positive and HPV-negative OPSCC on the expression of sGCα₁β₁ in arterial VSMCs from tumor-free and tumor-containing regions of human tissue sections using quantitative immunohistochemistry. In comparison to the tumor-free region, we found a decrease in expression of both α₁- and β₁-subunits in the arterial VSMC layer of the tumor-containing areas. The OPSCC-induced significant downregulation of the α₁- and β₁-subunits of sGC in arterial VSMC was HPV-independent. We conclude that the response of sGC to NO in tumor arterial VSMCs may be impaired by oxidation of the heme of the β₁-subunit, and thus, α₁- and β₁-subunits of sGC could be targeted to degradation under oxidative stress in OPSCC in an HPV-independent manner. The degradation of sGCα₁β₁ in VSMCs may result in increased proliferation of VSMCs, promoting tumor arteriogenesis in OPSCC. This can be interrupted by preserving the active heterodimer sGCα₁β₁ in arterial VSMCs.

Shear bond strength of orthodontic brackets with newly developed antibacterial self-etch adhesive

Because the enamel adjacent to brackets may be affected by microorganisms, an antibacterial adhesive may be a useful choice to prevent and reduce demineralization. The purpose of this in vitro study was to determine the (1) shear bond strength of a self-etch and an antibacterial self-etch adhesive for orthodontic metal brackets and (2) bond failure interface of a self-etch and an antibacterial self-etch adhesive using a modified adhesive remnant index (ARI). Twenty-four defect-free premolars were randomly assigned into two groups. The teeth received the following treatments-group 1: Transbond Plus Self-Etching Primer + Transbond XT; group 2: antibacterial dentin bonding system (ABF) + Transbond XT. All samples were stored in deionized water at 37 degrees C for 48 hours. Shear debonding tests were performed at a crosshead speed of five mm/min. The results in megapascals were (median, minimum, maximum) group 1: 8.53, 4.59, 12.63; group 2: 9.79, 4.01, 22.10, respectively. Mann-Whitney test revealed that the difference between the groups was not statistically significant (P = .2, P > .05). Failed brackets were examined by an optical microscope at 16x magnification to determine the bond failure interface using a modified ARI. The predominant mode of failure for both groups was at the bracket-adhesive interface. ABF may have sufficient mechanical properties and also an antibacterial effect that makes it a good choice for orthodontic bonding.

Time-dependent Activation of ERK1/2 in Nerve Terminals of the Dentin-Pulp Complex following Bradykinin Treatment

The extracellular signal-regulated kinases 1 and 2 (ERK1/2) have been implicated in the inflammation-dependent sensitization of nociceptors, and the inflammatory mediator bradykinin (BK) led to a reduced threshold in the nociceptor terminals, activating intracellular signaling by phosphorylating receptors and ion channels. The effects of BK on the non-transcriptional modulation of the ERK1/2 in the peripheral nociceptor terminals, including in nerve endings of the dentin-pulp complex, are unknown. The time-dependent effects of BK (10−7 M) on the ERK1/2 phosphorylation in nerve terminals of the dentin-pulp complex were investigated by quantitative and double immunolabeling with organ bath experiments. In nerve terminals, total and p-ERK1/2 were detected. In comparison with the controls, the numbers of p-ERK1/2-positive nerve endings increased after 1 and 3 min and decreased after 10 min of BK treatment. Analysis of the data indicates that BK induces phosphorylation-mediated local activation of ERK1/2 in nerve terminals modulating nociception in the dentin-pulp complex.

Sealing capacity of a flowable composite, as a protective base, with different conditioning methods in nonvital bleaching

OBJECTIVE

The purpose of this in vitro study was to determine the microleakage of a nano-flowable composite used as a protective base, applied with different conditioning methods in nonvital bleaching.

MATERIALS AND METHODS

Forty root-filled teeth were divided into four treatment groups (n = 10 per group): group 1--Er:YAG laser etching + Adper Single Bond 2; group 2-37% phosphoric acid + Adper Single Bond 2; group 3--Adper Prompt L-Pop; and group 4--No treatment. A nano-flowable composite (Filtek Supreme Flow) base was used in each group. For a 24-h period, 40% hydrogen peroxide solution was applied to the pulp chambers, and they were subsequently subjected to a dye (silver nitrate) challenge for 4 h. After the dye was washed out with water, each tooth was cut in half and both halves were exposed to sunlight for 2 h to promote oxidation of the dye, turning it black. Finally the sections were examined under 4x magnification to determine the degree of leakage as assessed with a four-point scale. Statistical analysis was performed with the Mann-Whitney U test.

RESULTS

There were no significant differences between groups 1, 2, and 3 (p > 0.05), but the teeth in group 4 had significantly higher microleakage scores than the teeth in the other groups (p < 0.05).

CONCLUSION

Self-etching adhesive application, Er:YAG laser etching, and phosphoric acid etching combined with an adhesive system all showed similar microleakge scores when a nano-flowable composite was applied as a protective base in nonvital bleaching.