Serious childhood respiratory infections and asthma in adult life. A population based study. ECRHS Italy. European Community Respiratory Health Survey

BACKGROUND

A number of epidemiologic studies have tried to establish whether respiratory tract infections in early childhood cause obstructive pulmonary disease in adult life.

OBJECTIVE

To determine whether reported serious respiratory infection before the age of 5 years (SRI) is a significant risk factor for subsequent development of bronchial asthma and/or bronchial hyperresponsiveness in adults.

METHODS

We investigated a random population sample of 1,104 subjects (aged 20 to 40 years), participating in the European Respiratory Health Survey in Italy. Bronchial response to methacholine and answers to a standardized questionnaire were analyzed.

RESULTS

The prevalence of SRI (ie, a positive response to the question "Have you ever had a serious respiratory infection before the age of 5 years?") was significantly higher in the subjects with a positive family history of allergic diseases than in those with a negative one (O.R. 1.89; 95% C.I. 1.24 to 2.87, P < .01). No relationship was found between SRI and current adult asthma; however, asthma in the past was found in 20.5% of the SRI positive subjects and in 9.1% of SRI negative subjects (O.R. 2.47; 95% C.I. 1.47 to 4.15, P < .05). No difference in the response to methacholine and in FEV1, FEV1/FVC values was found between SRI positive and SRI negative subjects.

CONCLUSIONS

We suggest that a positive family history of atopy is associated with a significantly higher prevalence of SRI. Furthermore our results indicate that exposure to SRI is a risk factor for asthma in the past (ie, asthma in childhood and adolescence) but not for adult asthma or for the development of bronchial impairment in adult life.

Myocardial region (right or left ventricle) and aetiology of heart failure can influence the inotropic effect of ouabain in failing human myocardium

AIMS

To investigate whether the inotropic effect of ouabain in failing human myocardium varies according to the heart chamber tested (right or left ventricle) or the aetiology of the heart disease, i.e. ischaemic or idiopathic.

METHODS

The inotropic effect of ouabain was measured, as the percentage change in baseline tension, in myocardial strips isolated from right (RV; n=21) and left ventricles (LV; n=21) of hearts explanted from patients with idiopathic (IDC; n=11) and ischaemic cardiomyopathy (CAD; n=10). Concentration-effect curves obtained with ouabain (0.05-1.6 micromol l-1 ) were analysed using the Emax sigmoidal model, and the following parameters were calculated: Emax, EC50, n and EC10 (threshold concentration). The influence of ventricular chamber and heart failure aetiology on these parameters was evaluated by means of a two-way anova.

RESULTS

Age and baseline haemodynamic parameters did not differ between IDC and CAD patients. Baseline strip contractility was highly variable (range: 0.48-10.0 mN), but neither ventricular chamber nor aetiology could explain such variability. A two-way anova showed that EC10 was greater in CAD than in IDC preparations (0.097+/-0.013 micromol l-1 vs 0.059+/-0. 009 micromol l-1; 95% C.I. for difference 0.043, 0.071) and Emax was lower in RV than in LV (121+/-21% vs 250+/-38%; 95% C.I. -221, -36), while EC50 and n were not significantly different between groups.

CONCLUSIONS

The inotropic effect of ouabain in human myocardium may vary according to aetiology of heart failure and the ventricle being tested. Although our results do not support the hypothesis of increased sensitivity to cardiac glycosides in CAD patients, they may explain the diminished effect observed in patients with RV failure.

Genetics and molecular biology of the GHRH-GH-IGF-I axis

In this paper, the genetics and molecular biology of the GHRH-GH-IGF-I (Growth Hormone Releasing hormone-Growth Hormone-Insulin like Growth Factor I) axis involved in the pathogenesis of short stature are reviewed. Short stature associated with GH deficiency is estimated to occur in about 1/4000-10,000 live births; 3-30% of cases affect first-degree relatives, suggesting a genetic aetiology. Identification of such molecular defects is very recent and dependent on new findings on the physiology of GHRH-GH-IGF-I axis: for example the pituitary-specific transcription factors and their mutations have only been described in the last few years. The epidemiological importance of the identified molecular defect depends on the level of the axis involved, but the prevalence of some of these genetic defects is probably underestimated. Time will tell what the practical relevance of these findings is and what the clinical features of the new mutations are; we will probably learn something more about the GHRH-GH-IGF-I axis: to date, no mutations have been reported regarding the GHRH gene or the IGF-I receptor.

External jugular vein hemangioma occurring as a lateral neck mass

Hemangioma is an extremely frequent tumor, accounting for 7% of all benign neoplasms. In contrast, hemangioma arising in blood vessels is rare and should be differentiated from other neoplasms of vascular origin, such as hemangioendothelioma, hemangiopericytoma, hemangiosarcoma, and leiomyosarcoma. The case we report has the peculiarity of occurring as a lateral neck mass in which color-coded duplex sonography contributed significantly to diagnosis.

Detection of rifampin resistance in Mycobacterium tuberculosis by double gradient-denaturing gradient gel electrophoresis

We applied double gradient-denaturing gradient gel electrophoresis (DG-DGGE) for the rapid detection of rifampin (RMP) resistance from rpoB PCR products of Mycobacterium tuberculosis isolates and clinical samples. The results of this method were fully concordant with those of DNA sequencing and susceptibility testing analyses. DG-DGGE is a valid alternative to the other methods of detecting mutations for predicting RMP resistance.

Clinical evaluation of a one-bottle bonding system for desensitizing exposed roots

PURPOSE

To evaluate the effectiveness of a one-bottle adhesive system as a desensitizing treatment, with or without a prior phosphoric acid-etch step.

MATERIALS AND METHODS

Two different clinical procedures using a one-bottle adhesive bonding system were tested for its efficacy on desensitizing exposed roots. Thirty subjects with a history of dentin hypersensitivity were selected and 60 exposed sensitive teeth were divided into two groups (n = 30). In Group 1 samples, Scotchbond 1 bonding system (Single Bond in USA) was applied without a prior acid-etching, while in those of Group 2, the exposed sensitive roots were acid-etched with 35% phosphoric acid for 15 seconds, prior to application of bonding agents. The sensitivity was evaluated at 0, 1, 2, 4 weeks and 3 months using cold air blast stimuli, and recorded using a visual-analogue scale. The scores were analyzed as non-parametric data by means of the Mann-Whitney and Sign tests. Five samples from each group were randomly selected in order to make scanning electron microscope observations of the sensitive dentin surfaces at baseline and at each recall using the replica technique.

RESULTS

At baseline, after both desensitizing procedures all the patients reported distinct reductions in dentin sensitivity. At 1- and 2-week recalls, 20 teeth of Group 1 and 17 teeth in Group 2 exhibited a return of sensitivity, and in five teeth in each group, the sensitivity score was between 5-8. During the first recall (1-2 weeks), the sensitive teeth were retreated and showed an immediate reduction of sensitivity. At the 1-month recall, eight teeth in Group 1 and four teeth in Group 2 showed a return of some sensitivity, and in six teeth in Group 1 and in three teeth in Group 2, old amalgam restorations were replaced and this procedure almost completely resolved the sensitivity. At the 3-month recall, only five teeth from each group showed residual mild sensitivity (score 1-2). For both Groups 1 and 2 there was a statistically significant (P < 0.0005) reduction in sensitivity levels between the baseline pain scores and immediately after treatment, and between the first recall pre-treatment pain scores and the last recall pain scores. Overall, the two methods of treatment demonstrated a general decrease in sensitivity in both groups over the 3-month study period, adequately solving the clinical and patients' perception of the discomfort of sensitivity. The SEM observations of the replicas showed a progressive loss of the adhesive resin from the treated surfaces. This fact was more evident in the non-etched samples (Group 2) than in those in Group 1. The results of this study showed that exposed root dentin sealed with Scotchbond 1, with or without prior acid-etching, did not show spontaneous sensitivity after 3 months.

Radiation protection in radioguided surgery of breast cancer

The protocols for sentinel lymph node biopsy and radioguided occult lesion localization could potentially be of great value in the management of breast cancer patients. Both involve the injection of a 99Tcm-labelled radiopharmaceutical close to or into the lesion, localization of the sentinel lymph node or occult lesion by scintigraphy, and surgical removal with the aid of a hand-held gamma-ray detector. We present dosimetric data on patients and hospital personnel involved in these procedures. For evaluation of radiation protection, we measured the absorbed dose and air kerma rate. Activity levels in excised tissues and surgical instruments were also determined. For patients, the mean absorbed dose to the abdomen was 0.45 mGy, which is low compared to doses received from other diagnostic examinations. For surgeons after 100 operations, the mean absorbed dose to the hands was 0.45 mGy and the mean effective dose 0.09 mSv. Absorbed doses to all hospital personnel involved in the procedures were very low compared to recommended annual limits stipulated by the International Commission on Radiological Protection. We conclude that these procedures, performed according to protocols laid down by the European Institute of Oncology, Milan, are safe from the point of view of radiological protection and that only routine precautions are necessary.

Biokinetics and dosimetry in patients administered with (111)In-DOTA-Tyr(3)-octreotide: implications for internal radiotherapy with (90)Y-DOTATOC

Recent advances in receptor-mediated tumour imaging have resulted in the development of a new somatostatin analogue, DOTA-dPhe(1)-Tyr(3)-octreotide. This new compound, named DOTATOC, has shown high affinity for somatostatin receptors, ease of labelling and stability with yttrium-90 and favourable biodistribution in animal models. The aim of this work was to evaluate the biodistribution and dosimetry of DOTATOC radiolabelled with indium-111, in anticipation of therapy trials with (90)Y-DOTATOC in patients. Eighteen patients were injected with DOTATOC (10 microg), labelled with 150-185 MBq of (111)In. Blood and urine samples were collected throughout the duration of the study (0-2 days). Planar and single-photon emission tomography images were acquired at 0.5, 3-4, 24 and 48 h and time-activity curves were obtained for organs and tumours. A compartmental model was used to determine the kinetic parameters for each organ. Dose calculations were performed according to the MIRD formalism. Specific activities of >37 GBq/ micromol were routinely achieved. Patients showed no acute or delayed adverse reactions. The residence time for (111)In-DOTATOC in blood was 0.9+/-0.4 h. The injected activity excreted in the urine in the first 24 h was 73%+/-11%. The agent localized primarily in spleen, kidneys and liver. The residence times in source organs were: 2.2+/-1.8 h in spleen, 1.7+/-1.2 h in kidneys, 2.4+/-1.9 h in liver, 1.5+/-0.3 h in urinary bladder and 9. 4+/-5.5 h in the remainder of the body; the mean residence time in tumour was 0.47 h (range: 0.03-6.50 h). Based on our findings, the predicted absorbed doses for (90)Y-DOTATOC would be 7.6+/-6.3 (spleen), 3.3+/-2.2 (kidneys), 0.7+/-0.6 (liver), 2.2+/-0.3 (bladder), 0.03+/-0.01 (red marrow) and 10.1 (range: 1.4-31.0) (tumour) mGy/MBq. These results indicate that high activities of (90)Y-DOTATOC can be administered with low risk of myelotoxicity, although with potentially high radiation doses to the spleen and kidneys. Tumour doses were high enough in most cases to make it likely that the desired therapeutic response desired would be obtained.

A new CACNA1A gene mutation in acetazolamide-responsive familial hemiplegic migraine and ataxia

OBJECTIVE

To search for mutations in the calcium channel gene CACNA1A and to study the genotype-phenotype correlation in a family with a severe familial hemiplegic migraine (FHM) phenotype and a slowly progressive cerebellar ataxia.

BACKGROUND

CACNA1A gene mutations on chromosome 19 are involved in approximately 50% of FHM families. The association of FHM and cerebellar ataxia has been reported in a small number of FHM families, all linked to chromosome 19.

METHODS

The proband, in addition to typical hemiplegic migraine attacks, experienced severe episodes during which hemiplegia was associated with acutely altered consciousness and fever lasting several days. She, as well as her affected sister, developed a permanent, late-onset cerebellar ataxia and cerebellar atrophy evident on MRI. Linkage analysis was performed and the whole CACNA1A gene, 47 exon-intron boundaries, was analyzed by double gradient-denaturing gradient gel electrophoresis (DG-DGGE).

RESULTS

Genetic studies suggested linkage to chromosome 19p13, and DG-DGGE analysis detected a heteroduplex fragment in exon 13 of the CACNA1A gene. By direct sequencing, a G-to-A substitution resulting in an arginine to glutamine change at codon 583 in the second putative voltage sensor domain of the channel alpha1A-subunit, was identified, possibly representing the disease-causing mutation. The proband and her affected sister were treated with acetazolamide, reporting freedom from new FHM attacks but no benefit in the progression of ataxia.

CONCLUSIONS

The combination of episodic dysfunction and permanent deficit could depend on the variety of functions of calcium channels and their distribution in the nervous system.

Genetic heterogeneity in Italian families with familial hemiplegic migraine

OBJECTIVE

To verify linkage to chromosome 19p13, to detect mutations in the CACNA1A gene, and to correlate genetic results to their clinical phenotypes in Italian families with familial hemiplegic migraine (FHM).

BACKGROUND

FHM is an autosomal dominant disease, classified as a subtype of migraine with aura. Only a proportion of FHM patients have been associated with chromosome 19p13. Among these, four missense mutations within the CACNA1A gene in five unrelated families have been described.

METHODS

A linkage study was performed in 19 patients affected by FHM from five families by studying microsatellite markers associated with the 19p13 region. All familial and seven additional sporadic patients with FHM were analyzed to search for mutations within the CACNA1A gene by applying the double gradient-denaturant gradient electrophoresis technique.

RESULTS

Lod score values did not establish significantly linkage to chromosome 19. However, seven new genetic variants were detected: six were new polymorphisms. The seventh was a missense mutation present in family 1, and it was associated with a hemiplegic migraine phenotype without unconsciousness and cerebellar ataxia. Because this missense mutation is absent in the general population and cosegregates with the disease, it may be a pathologic mutation.

CONCLUSIONS

Genetic heterogeneity of FHM has been shown in familial and sporadic FHM patients of Italian origin. The new missense mutation-G4644T-is associated with milder clinical features compared with typical FHM.

The rationale for a study on HIV-1 reverse transcriptase mutations and outcome of antiretroviral therapy with two nucleoside analogs

The development of resistance to antiretroviral drugs has been recognized as an important cause of treatment failure in HIV-1-infected patients; however the correlation between emergence of resistance and treatment failure has not been yet clearly defined. The high rate of viral replication, together with the lack of proof reading activity of HIV-1 reverse transcriptase, accounts for the rapid establishment of extensive genotypic variation, resulting in the emergence of viral mutants showing primary or secondary resistance to antiretroviral drugs. In this regard, phenotyping and genotyping allow the detection of drug resistance. Both tests have advantages and limitations compared to each other. The complete suppression of viral replication seems to be the best way to avoid occurrence of drug resistance, and viral loads below the limit of detection can be usually achieved by a combination of 3 antiretroviral drugs. In this scenario, the proportion of HIV-1-infected patients on dual therapy is still relevant in Italy. We believe that the study of this subset of individuals is very important, as resistance to nucleoside analogues may impair the outcome of a future triple therapy. In addition, this study could contribute to define the role of resistance assays in the management of HIV-1-infected patients.

Blood lactate accumulation and muscle deoxygenation during incremental exercise

Near-infrared spectroscopy (NIRS) could allow insights into controversial issues related to blood lactate concentration ([La](b)) increases at submaximal workloads (). We combined, on five well-trained subjects [mountain climbers; peak O(2) consumption (VO(2peak)), 51.0 +/- 4.2 (SD) ml. kg(-1). min(-1)] performing incremental exercise on a cycle ergometer (30 W added every 4 min up to voluntary exhaustion), measurements of pulmonary gas exchange and earlobe [La](b) with determinations of concentration changes of oxygenated Hb (Delta[O(2)Hb]) and deoxygenated Hb (Delta[HHb]) in the vastus lateralis muscle, by continuous-wave NIRS. A "point of inflection" of [La](b) vs. was arbitrarily identified at the lowest [La](b) value which was >0.5 mM lower than that obtained at the following. Total Hb volume (Delta[O(2)Hb + HHb]) in the muscle region of interest increased as a function of up to 60-65% of VO(2 peak), after which it remained unchanged. The oxygenation index (Delta[O(2)Hb - HHb]) showed an accelerated decrease from 60- 65% of VO(2 peak). In the presence of a constant total Hb volume, the observed Delta[O(2)Hb - HHb] decrease indicates muscle deoxygenation (i.e., mainly capillary-venular Hb desaturation). The onset of muscle deoxygenation was significantly correlated (r(2) = 0.95; P < 0.01) with the point of inflection of [La](b) vs., i.e., with the onset of blood lactate accumulation. Previous studies showed relatively constant femoral venous PO(2) levels at higher than approximately 60% of maximal O(2) consumption. Thus muscle deoxygenation observed in the present study from 60-65% of VO(2 peak) could be attributed to capillary-venular Hb desaturation in the presence of relatively constant capillary-venular PO(2) levels, as a consequence of a rightward shift of the O(2)Hb dissociation curve determined by the onset of lactic acidosis.

New immunosuppressive drug PNU156804 blocks IL-2-dependent proliferation and NF-kappa B and AP-1 activation

We had previously shown that the drug undecylprodigiosin (UP) blocks human lymphocyte proliferation in vitro. We have now investigated the mechanism of action of a new analogue of UP, PNU156804, which shows a more favorable activity profile than UP in mice. We demonstrate here that the biological effect of PNU156804 in vitro is indistinguishable from UP: PNU156804 blocks human T cell proliferation in mid-late G1, as determined by cell cycle analysis, expression of cyclins, and cyclin-dependent kinases and retinoblastoma phosphorylation. In addition, we show that PNU156804 does not block significantly the induction of either IL-2 or IL-2R alpha- and gamma-chains but inhibits IL-2-dependent T cell proliferation. We have investigated several molecular pathways that are known to be activated by IL-2 in T cells. We show that PNU156804 does not inhibit c-myc and bcl-2 mRNA induction. On the other hand, PNU156804 efficiently inhibits the activation of the NF-kappa B and AP-1 transcription factors. PNU156804 inhibition of NF-kappa B activation is due to the inhibition of the degradation of I kappa B-alpha and I kappa B-beta. PNU156804 action is restricted to some signaling pathways; it does not affect NF-kappa B activation by PMA in T cells but blocks that induced by CD40 cross-linking in B lymphocytes. We conclude that the prodigiosin family of immunosuppressants is a new family of molecules that show a novel target specificity clearly distinct from that of other immunosuppressive drugs such as cyclosporin A, FK506, and rapamycin.

Influence of tissue characteristics at margins on leakage of Class II indirect porcelain restorations

PURPOSE

To evaluate the sealing ability of Class II porcelain inlays with margins placed in cementum-dentin and enamel, luted by two new different cementing materials.

MATERIALS AND METHODS

Thirty extracted molars, free from caries and restorations, were selected. The sample cavities were prepared in a standardized manner and then were divided in three groups (n = 10) at random. Group 1: The cervical margin was located 1 mm below the CEJ and the inlays were luted with EBS Multi (Espe) bonding system in combination with Compolute 1.0 Aplicap (CLA 1.0, Espe) experimental resin cement. Group 2: The cervical margin was placed 1 mm below the CEJ and Syntac bonding system (Vivadent) and Variolink II resin cement (Vivadent) were used. Group 3: The cervical margin was placed 0.5 mm above the CEJ and the same materials selected for Group 1 were used. IPS-Empress (Ivoclar) inlays were made following manufacturer's instructions. After luting procedures and 2500 thermal cycles (5 degrees and 55 degrees C), the samples were processed and evaluated for marginal leakage at cervical and occlusal site. Samples of Group 3 were first sectioned in the center of the restorations as in Group 1 and 2 and scored (Group 3A) and then two other cuts were made along the buccal and lingual areas (Group 3B) and also scored. After scoring dye penetration of Group 1 and 2 samples, half of the sections were randomly selected to evaluate: (1) resin cement thickness, (2) Hybrid layer formation at the interface between adhesive material and dental substrate and (3) to observe the morphology of the Class II cavity margins. The leakage data were statistically evaluated with the Mann-Whitney U test (P < 0.5).

RESULTS

Statistically significant differences were found between Groups 3A and 3B at the occlusal site, and not at the cervical site. Samples of Group 1 showed a cement thickness of 92 microns, and 68 microns in Group 2. Hybrid layer and resin tag formation was evident in Group 1. In Group 2 samples, the hybrid layer formation was less evident and thinner than in Group 1. At cervical margins, an outer layer, not identifiable as sound dentin, of 200-300 microns thick, was noted. This layer was present in all three groups between outer margin and sound dentin. The margins located both cervically and axially in enamel mainly showed prisms cut along their long axis and a low level of structured etch pattern.

Determinants of stent restenosis in chronic coronary occlusions assessed by intracoronary ultrasound

Chronic coronary occlusions have a high recurrence rate that can be reduced by stenting, but this rate remains higher than in nonocclusive lesions. To analyze possible determinants of restenosis in these lesions, intracoronary ultrasound was performed during the recanalization procedure. A chronic coronary occlusion of > or = 1 month duration (range 1 to 33 months; median 3.3) was successfully recanalized in 41 patients. Quantitative ultrasound analysis was performed before and after stent placement, with measurement of the luminal area, the extent of the plaque burden at the site proximal and distal to the occlusion, and within the occlusion and the subsequent stent. The degree of compensatory enlargement of the coronary artery within the occlusion was determined by comparing the average of the total vessel area of the proximal and distal reference with the lesion site. Early reocclusion (subacute stent thrombosis) was observed in 1 patient (2.4%). The angiographic control after 6 months showed restenosis in 9 patients with 1 late reocclusion. The overall recurrence rate was 24%. There was no difference in clinical and procedural characteristics between lesions with restenosis and without restenosis. The latter had a larger minimum stent area (7.59 +/- 1.96 mm2 vs 5.71 +/- 0.90 mm2; p <0.01), and there was evidence for more compensatory vessel enlargement in lesions without restenosis. Thus, intracoronary ultrasound showed that a smaller minimum stent area was a major predictor of angiographic restenosis, and it occurred more often in occlusions without compensatory vessel enlargement.

Endogenous catecholamine synthesis, metabolism, storage and uptake in human neutrophils

Evidence is presented that human neutrophils contain catecholamines and several of their metabolites. In vitro, incubation with alpha-methyl-p-tyrosine or pargyline affects intracellular dopamine, norepinephrine and their metabolites, suggesting catecholamine synthesis and degradation by these cells. Reserpine reduces intracellular dopamine and norepinephrine and desipramine reduces intracellular norepinephrine, suggesting the presence of storage and uptake mechanism. In view of the ability of catecholamines to affect neutrophil function, the present results support the hypothesis that autoregulatory adrenergic mechanisms may exist in these cells.

Effect of leisure time and working activity on principal risk factors and relative interactions in active middle-aged men

DESIGN

This study was designed to evaluate, in a cohort of 1039 middle-aged men, the interaction between the duration and intensity of physical activity performed either during leisure time (competitive sports, walking, cycling) or work, and principal coronary disease risk factors.

METHOD

A cohort of subjects aged 45-64 years were recruited in 1993. Subjects included both individuals who were physically active and those who were sedentary, and were age-matched.

RESULTS

Leisure time physical activity was inversely related to levels of total cholesterol, triglycerides, and fibrinogen, and to diastolic and systolic blood pressure. High-density lipoprotein cholesterol level was directly related to leisure time activity. Working activity, even if strenuous, was not related to risk profile. Leisure time activity did not favorably influence lipid levels in smokers, obese subjects or those with known dyslipidemia.

CONCLUSIONS

This study further reinforces the use of continuous diet and drug treatment in dyslipidemic subjects and in smokers, who have to refrain from smoking if they are to benefit fully from the effects of physical activity.

[Emergency myocardial revascularization of the beating heart after angioplasty failure]

Occlusion of the left anterior descending coronary artery during angioplasty has a high mortality rate despite emergent myocardial revascularization. We describe two cases of coronary artery bypass grafting on beating heart without extracorporeal circulation to perform emergency operations after failed angioplasty.

Standardized microscopic evaluation of the bonding mechanism of NRC/Prime & Bond NT

PURPOSE

To investigate the in vitro formation of hybrid layer, resin tags and adhesive lateral branches, when using Prime & Bond NT (PBNT) "one-bottle" enamel-dentin bonding system on conditioned and unconditioned human dental substrates.

MATERIALS AND METHODS

The enamel dentin adhesive was tested on 18 dentin and 18 enamel flat preparations made on facial and occlusal surfaces, respectively, of extracted posterior teeth. Each experimental tooth substrates were randomly divided in six groups of six samples each: Group 1: PBNT on conditioned dentin (CD) with 36% phosphoric acid (PA), Group 2: PBNT on etched enamel (EE) with 36% PA, Group 3: PBNT on CD with NRC non-rinse conditioning (NRC); Group 4: PBNT on EE with NRC, Group 5: PBNT on dentin without any conditioning (UD), Group 6: PBNT on enamel without any conditioning (UE). In the experimental groups, PBNT was applied following the manufacturer's instructions. Over the PBNT, a layer of Dyract AP was placed and light-cured for 20 seconds. All samples were split-fractured along their long axis. One half of each sample was deproteinized and decalcified at the interface in order to visualize the hybrid layer and the other was completely dissolved in order to observe the morphology of resin tags with a scanning electron microscope.

RESULTS

Groups 1, 2: The tested samples showed a micromechanical bonding mechanism to CD and EE with phosphoric acid. PBNT formed hybrid layer, resin tags and adhesive lateral branches on dentin. In the dentin samples of the first group, characteristic reverse cone-shaped tags with their corresponding adhesive lateral branches were evident. At the enamel site, traditional pattern of etch enamel was always observed with resin tags formation. Groups 3, 4: When the bonding system was applied on dentin conditioned with NRC, a thin hybrid layer was formed, resin tags were also noted but their shape was narrower than that observed in Group 1. At the enamel site, the conditioned surface showed presence of an etched pattern and of resin tags. Groups 5, 6: When PBNT was applied without any previous conditioning, the hybrid layer and resin tags formation were not evident on dentin, and no bonding mechanism was developed with unetched enamel.

Dye leakage and SEM study of roots obturated with Thermafill and dentin bonding agent

The apical seal of roots obturated with a dentin bonding agent and Thermafill with and without the use of sodium hypochlorite as an irrigating solution was compared by a dye leakage test. Roots obturated with Thermafill and a zinc oxide eugenol sealer were used as controls. Thirty-eight roots were prepared chemomechanically and divided into three experimental groups. The teeth of group 1 were filled with Thermafill and the dentin bonding agent using sodium hypochlorite as the irrigant. The teeth of group 2 were filled in the same way, but saline solution was used as the irrigant. Before the root canal was filled the smear layer was removed from the root canal walls of both groups by rinsing the root canal with a 17% EDTA solution. The teeth of group 3 were filled with Thermafill and a zinc oxide eugenol sealer. The teeth were immersed in 2% methylene blue solution. The root fillings of groups 1 and 2 leaked significantly more than those of group 3. The resin-dentin-guttapercha interface of group 1 was observed by scanning electron microscopy and showed a typical hybrid layer. An intimate contact between resin and dentin was present in group 2, but a resin-dentin interdiffusion zone was only occasionally observed. The use of dental adhesives and the hybrid layer formation did not improve the seal of Thermafill root canal fillings.