Methodology for the Absolute Configuration Determination of Epoxythymols Using the Constituents of Piptothrix areolare.

Since epoxythymols occur in Nature either as scalemic mixtures or as pure enantiomers, the knowledge of their chiral composition and of the absolute configuration (AC) of the dominant enantiomer turns out to be mandatory. This task has already been faced using 1,1-bis-2-naphthol (BINOL), as a chiral solvating agent in accurate 1H NMR quantifications to determine the enantiomeric ratio, and vibrational circular dichroism (VCD) to evidence the AC of the dominant enantiomer. We now explore the use of electronic circular dichroism (ECD) to determine the AC of an epoxythymol for which time-expensive DFT calculations would be required unless the AC of a related molecule is already known, from either VCD studies or single-crystal X-ray diffraction analysis, since one could correlate the ECD Cotton effect with the AC because in ECD only chromophores and their neighborhoods are evidenced. This method is now applied by using the epoxythymols from Piptothrix areolare. Known areolal (1) and 10-cinnamoyloxy-8,9-epoxythymol isobutyrate (2) were isolated from the roots, while known 7-acetoxy-10-cinnamoyloxy-8,9-epoxythymol isobutyrate (3) and 10-cinnamoyloxy-7-hydroxy-8,9-epoxythymol isobutyrate (4), as well as the new enantiopure 7-acetoxy-10-cinnamoyloxy-6-hydroxy-8,9-epoxythymol isobutyrate (5) and 10-cinnamoyloxy-8,9-epoxy-6-hydroxy-7-northymol isobutyrate (6), were obtained from the extract of the flowers. Chemical correlation of epoxythymols 1 and 3 was achieved. Compounds 1-4 were obtained as scalemic mixtures, and 5 and 6 as the pure (8S) enantiomers. In addition, the new 10-cinnamoyloxy-7-oxo-8,9-dehydrothymol isobutyrate (7) was isolated from the roots. The structures of 5-7 followed from NMR and HRMS data, while enantiomeric compositions of 1-6 were determined by 1H NMR-BINOL measurements. The AC determination for 2-6 was done by ECD using a sample of 1 to reference the ECD Cotton effect. In turn, the AC of 1 was determined by VCD and extensive DFT calculations. The ECD-BINOL methodology turned out to be some 500 times more sensitive than that combining VCD and 1H NMR-BINOL.

Correction to: Microleakage in class V composite and compomer restorations following exposure to a colutory prescribed for the treatment of xerostomy.

In the original publication of the article, one of the author names was published incorrectly as José L. Calvo. The correct name is José L. Calvo-Guirado.

Correction to: Metallic ion content and damage to the DNA in oral mucosa cells of children with fixed orthodontic appliances.

Due to an unfortunate turn of events, the surname of the fourth author appeared incorrectly in the original publication and should have read Calvo Guirado.

Time-dependent ligand-receptor binding kinetics and functionality in a heterodimeric receptor model.

GPCRs heteromerize both in CNS and non-CNS regions. The cell uses receptor heteromerization to modulate receptor functionality and to provide fine tuning of receptor signaling. In order for pharmacologists to explore these mechanisms for therapeutic purposes, quantitative receptor models are needed. We have developed a time-dependent model of the binding kinetics and functionality of a preformed heterodimeric receptor involving two drugs. Two cases were considered: both or only one of the drugs are in excess with respect to the total concentration of the receptor. The latter case can be applied to those situations in which a drug causes unwanted side effects that need to be reduced by decreasing its concentration. The required efficacy can be maintained by the allosteric effects mutually exerted by the two drugs in the two-drug combination system. We discuss this concept assuming that the drug causing unwanted side effects is an opioid and that analgesia is the therapeutic effect. As additional points, allosteric modulation by endogenous compounds and synthetic bivalent ligands was included in the study. Receptor heteromerization offers a mechanistic understanding and quantification of the pharmacological effects elicited by combinations of two drugs at different doses and with different efficacies and cooperativity effects, thus providing a conceptual framework for drug combination therapy.

Nontoxic effects of thymol, carvacrol, cinnamaldehyde, and garlic oil on dung beetles: A potential alternative to ecotoxic anthelmintics.

The sustainability of the traditional extensive livestock sector will only be possible if healthy dung-decomposing insect communities are preserved. However, many current pharmaceutical anthelmintics are harmful to dung beetles, their presence can have a negative impact on biological systems. Phytochemical anthelmintics are an alternative to ecotoxic synthetic pharmaceutical anthelmintics, although ecotoxicological tests of their possible indirect effects on dung beetles are required to demonstrate their viability. In this study, the potential ecotoxicity of thymol, carvacrol, cinnamaldehyde and garlic oil (diallyl disulfide and diallyl trisulfide) were tested for the first time. Inhibition of antennal response was measured as a relevant parameter by obtaining relevant toxicity thresholds derived from concentration‒response curves, such as the IC50. All phytochemical compounds tested were demonstrated to be suitable alternative candidates to the highly ecotoxic compound ivermectin, considering their non-toxicity to nontarget organisms. Residues of the phytochemical antiparasitics found in cattle droppings were extremely low, even undetectable in the case of diallyl disulfide and diallyl trisulfide. Furthermore, our results showed that none of the phytochemical compounds have ecotoxic effects, even at extremely high concentrations, including those almost 1000 times higher than what is most likely to be found in dung susceptible to ingestion by dung beetles in the field. We can conclude that the four selected phytochemical compounds meet the requirements to be considered reliable alternatives to ecotoxic veterinary medicinal products, such as ivermectin.

Metallic ion content and damage to the DNA in oral mucosa cells of children with fixed orthodontic appliances.

Although the metal devices used in orthodontic treatments are manufactured highly resistance to corrosion, they may still suffer some localized corrosion resulting from the oral cavity conditions. The corrosion causes the release of metals from the alloys used for their manufacture. In this report, we evaluated the in vivo metal ions release of three alloys (stainless steel, titanium and nickel-free) usually used in the orthodontics treatments and its genotoxicity. We applied to 15 patients, between 12 and 16 years, 4 tubes and 20 brackets. Samples from oral mucosa were taken before the treatment and 30 days later. The concentration of the titanium, chromium, manganese, cobalt, nickel, molybdenum and iron were detected using inductively coupled plasma mass spectrometry (ICP-MS). The genotoxicity was measured with a comet assay (Olive moment). The oral mucosa cells in contact with the stainless steel alloy displayed the greatest titanium and manganese concentrations and those in contact with the nickel-free alloy presented the greatest concentration of chromium and iron. Both alloys, stainless steel and nickel-free, induced a higher DNA damage in the oral mucosa cells than the titanium alloy, in which the Olive moment was similar to controls. Based on the results of our study, we can conclude that titanium brackets and tubes are the most biocompatible of the three alloys.

Microleakage in Class V composite and compomer restorations following exposure to a colutory prescribed for the treatment of xerostomy.

The purpose of this study was to evaluate the effect of a colutory (XeroLacer, Lacer), prescribed for the treatment of xerostomy, on microleakage into class V cavities filled with a composite (Z100, 3M ESPE) or a compomer (F2000, 3M ESPE) in combination with either a two-step etch-and-rinse adhesive (Adper Scotchbond 1XT, 3M ESPE) or a self-etching adhesive (Adper Prompt L-Pop, 3M ESPE). Class V cavities were made in the buccal surfaces of 80 bovine lower incisors which were randomly divided into four groups (n = 20): (1) Adper Scotchbond 1XT/Z100; (2) Adper Scotchbond 1XT/F2000; (3) Adper Prompt L-Pop/Z100; and (4) Adper PLP/F2000. All specimens were immersed in distilled water for 3 months and ten specimens of each group were immersed and vibrated in XeroLacer for 2 min three times a day. The specimens were dyed with 1% methylene blue for 24 h. Longitudinal sections were made and percentages of microleakage were determined by image analysis. In distilled water, microleakage with the Adper Scotchbond 1XT/F2000 combination was significantly greater than with Adper Scotchbond 1XT/Z100 or Adper Prompt L-Pop/Z100, and microleakage with Adper Prompt L-Pop/F2000 was significantly greater than that with Adper Prompt L-Pop/Z100. No significant differences were detected among the groups exposed to XeroLacer. However microleakage was significantly less with Adper Scotchbond 1XT/F2000 after exposure to XeroLacer than after immersion in distilled water only. In conclusion, exposure to XeroLacer decreased microleakage into cavities restored with the compomer.

The effects of two soft drinks on bond strength, bracket microleakage, and adhesive remnant on intact and sealed enamel.

The purpose of this study was to evaluate the effects of Coca-Cola and Schweppes Limón on bond strength, adhesive remnant, and microleakage beneath brackets. One hundred and twenty upper central incisor brackets were bonded to bovine incisors and divided into three groups: (1) Control, (2) Coca-Cola, and (3) Schweppes Limón. The teeth were submerged in the drinks three times a day for 15 minutes over a 15 day period. Shear bond strength (SBS) was measured with a universal testing machine, and adhesive remnant evaluated using image analysis equipment. Microleakage at the enamel-adhesive and adhesive-bracket interfaces was determined using methylene blue. One hundred and eight teeth were used for scanning electron microscopy to determine the effect of the drinks on intact and sealed enamel. SBS and adhesive remnant data were analysed using the Kruskal-Wallis test (P < 0.05) and microleakage using the Kruskal-Wallis and Mann-Whitney tests applying Bonferroni correction (P < 0.017). No significant differences were found in SBS and adhesive remnant between the groups (P > 0.05). Microleakage at the enamel-adhesive interface for groups 2 and 3 was significantly greater than for group 1 (P < 0.017). At the adhesive-bracket interface, microleakage was significantly greater in group 2 than in group 1 (P < 0.017) while microleakage in group 3 did not differ significantly from either group 1 or 2 (P < 0.017). The drinks produced enamel erosion, loss of adhesive and microleakage. Coca-Cola and Schweppes Limón did not affect the SBS of brackets or the adhesive remnant.

Biomagnification and body distribution of ivermectin in dung beetles.

A terrestrial test system to investigate the biomagnification potential and tissue-specific distribution of ivermectin, a widely used parasiticide, in the non-target dung beetle Thorectes lusitanicus (Jekel) was developed and validated. Biomagnification kinetics of ivermectin in T. lusitanicus was investigated by following uptake, elimination, and distribution of the compound in dung beetles feeding on contaminated faeces. Results showed that ivermectin was biomagnified in adults of T. lusitanicus when exposed to non-lethal doses via food uptake. Ivermectin was quickly transferred from the gut to the haemolymph, generating a biomagnification factor (BMFk) three times higher in the haemolymph than in the gut after an uptake period of 12 days. The fat body appeared to exert a major role on the biomagnification of ivermectin in the insect body, showing a BMFk 1.6 times higher than in the haemolymph. The results of this study highlight that the biomagnification of ivermectin should be investigated from a global dung-based food web perspective and that the use of these antiparasitic substances should be monitored and controlled on a precautionary basis. Thus, we suggest that an additional effort be made in the development of standardised regulatory recommendations to guide biomagnification studies in terrestrial organisms, but also that it is necessary to adapt existing methods to assess the effects of such veterinary medical products.

Microleakage beneath brackets bonded with flowable materials: effect of thermocycling.

The purpose of this study was to evaluate the effects of thermocycling on microleakage beneath brackets bonded with an orthodontic composite and different flowable materials. Brackets were bonded to 200 bovine incisors divided into five groups: (1) Transbond XT, (2) X-Flow, (3) Dyract-Flow, (4) Admira-Flow, and (5) Beautiful-Flow. Half the teeth in each group were thermocycled. The specimens were dyed with 1 per cent methylene blue for 24 hours to determine the percentage of microleakage into the enamel-adhesive and adhesive-bracket interfaces using image analysis equipment. Data were analysed using the Kruskal-Wallis and Mann-Whitney U-tests (P < 0.05), applying Bonferroni correction when required (P < 0.005). Without thermocycling, microleakage at the enamel-adhesive interface was significantly greater for Admira-Flow than for X-Flow (P < 0.005). At the adhesive-bracket interface, there were no significant differences (P > 0.005). After thermocycling, microleakage of Beautiful-Flow at the enamel-adhesive interface was significantly less than for the other materials tested (P < 0.005), while at the adhesive-bracket interface, Admira-Flow and X-Flow showed significantly more microleakage than Beautiful-Flow and Transbond XT (P < 0.005). Analysis of the effect of thermocycling on each material showed that microleakage increased significantly at the enamel-adhesive interface with Transbond XT (P < 0.05), decreased with Beautiful-Flow (P < 0.05), increased significantly at both interfaces with X-Flow, but not to a statistically significant level with Dyract-Flow and Admira-Flow (P > 0.05). The giomer, Beautiful-Flow, demonstrated the best performance after thermocycling, while composite resins and, in particular, the flowables showed a poorer performance.

Author Correction: First assessment of the comparative toxicity of ivermectin and moxidectin in adult dung beetles: Sub-lethal symptoms and pre-lethal consequences.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Effects of chronic L-NAME on nitrotyrosine expression and renal vascular reactivity in rats with chronic bile-duct ligation.

In liver cirrhosis, elevated levels of NO and ROS (reactive oxygen species) might greatly favour the generation of peroxynitrite. Peroxynitrite is a highly reactive oxidant and it can potentially alter the vascular reactivity and the function of different organs. In the present study, we evaluated whether peroxynitrite levels are related to the progression of renal vascular and excretory dysfunction during experimental cirrhosis induced by chronic BDL (bile-duct ligation) in rats. Experiments were performed at 7, 15 and 21 days after BDL in rats and in rats 21 days post-BDL chronically treated with L-NAME (N(G)-nitro-L-arginine methyl ester). Sodium balance, BP (blood pressure), basal RPP (renal perfusion pressure) and the renal vascular response to PHE (phenylephrine) and ACh (acetylcholine) in isolated perfused kidneys were measured. NO levels were calculated as 24-h urinary excretion of nitrites, ROS as TBARS (thiobarbituric acid-reacting substances), and peroxynitrite formation as the renal expression of nitrotyrosine. BDL rats had progressive sodium retention, and decreased BP, RPP and renal vascular responses to PHE and ACh in the time following BDL. They also had increasing levels of NO and ROS, and renal nitrotyrosine accumulation,especially in the medulla. All of these changes were either prevented or significantly decreased by chronic L-NAME administration. In conclusion, these results suggest that the increasing levels of peroxynitrite might contribute to the altered renal vascular response and sodium retention in the development of the experimental biliary cirrhosis. Moreover, the beneficial effects of decreasing NO synthesis are, at least in part, mediated by anti-peroxinitrite-related effects.

First assessment of the comparative toxicity of ivermectin and moxidectin in adult dung beetles: Sub-lethal symptoms and pre-lethal consequences.

Among macrocyclic lactones (ML), ivermectin (IVM) and moxidectin (MOX) potentially affect all Ecdysozoan species, with dung beetles being particularly sensitive. The comparative effects of IVM and MOX on adult dung beetles were assessed for the first time to determine both the physiological sub-lethal symptoms and pre-lethal consequences. Inhibition of antennal response and ataxia were tested as two intuitive and ecologically relevant parameters by obtaining the lowest observed effect concentration (LOEC) values and interpolating other relevant toxicity thresholds derived from concentration-response curves (IC50, as the concentration of each ML where the antennal response is inhibited by half; and pLC50, as the quantity of ingested ML where partial paralysis was observed by half of treated individuals) from concentration-response curves. Both sub-lethal and pre-lethal symptoms obtained in this study coincided in that IVM was six times more toxic than MOX for adult dung beetles. Values of LOEC, IC50 and pLC50 obtained for IVM and MOX evaluated in an environmental context indicate that MOX, despite needing more time for tis elimination in the faeces, would be twice as harmful to dung beetles as IVM. This approach will be valuable to clarify the real impact of MLs on dung beetle health and to avoid the subsequent environmental consequences.

Ivermectin residues disrupt dung beetle diversity, soil properties and ecosystem functioning: An interdisciplinary field study.

Ivermectin is the most common endectocide used to control parasites affecting livestock. Short-term physiological and behavioural effects of ivermectin on dung beetles may have long-term consequences for beetle populations and ecosystem functioning. Long-term effects of the use of ivermectin can be estimated by comparing dung assemblages and ecosystem functions in areas with conventional ivermectin-treated livestock and environmentally similar areas in which livestock are not treated with veterinary medical products (organic farming). In this study, we investigated both short-term and long-term effects of the administration of ivermectin on the characteristics of dung beetle assemblages and the services they provided in a protected area (Doñana National Park, SW Spain). We examined short-term dung colonization, dwelling, relocation, and disaggregation rates and the associations between these processes and the key assemblage parameters of species richness, abundance, biomass and functional diversity. Furthermore, we analysed changes in soil physical-chemical properties and processes. Short-term differences were observed in the total amount of dung relocated by dung beetles at different colonization vs. emigration stages, suggesting that dung beetles in this area were affected by the recent treatments of livestock with ivermectin. Moreover, short-term effects could also be responsible for the significant differences in dung spreading rates between sites. Conventional use of ivermectin disrupted ecosystem functioning by affecting species richness, abundance and biomass. The decrease in diversity parameters was related to a reduction in the functional efficiency, which resulted in the long-term accumulation of dung on the ground and considerable changes in soil functionality.

Isolation and determination of ivermectin in post-mortem and in vivo tissues of dung beetles using a continuous solid phase extraction method followed by LC-ESI+-MS/MS.

A new analytical method based on solvent extraction, followed by continuous solid-phase extraction (SPE) clean-up using a polymeric sorbent, was demonstrated to be applicable for the detection of ivermectin in complex biological matrices of dung beetles (hemolymph, excreta or dry tissues) using liquid chromatography combined with positive electrospray ionization tandem mass spectrometry (LC/ESI+-MS/MS). Using a signal-to-noise ratio of 3:1, the limit of detection (LOD) in the insect matrices at trace levels was 0.01 ng g-1 and the limit of quantification (LOQ) was 0.1 ng g-1. The proposed method was successfully used to quantitatively determine the levels of ivermectin in the analysis of small samples in in vivo and post mortem samples, demonstrating the usefulness for quantitative analyses that are focused on future pharmacokinetic and bioavailability studies in insects and the establishment of a new protocol to study the impact of ivermectin on non-target arthropods such as dung beetles and other insects that are related with the "dung community". Because satisfactory precision and accuracy values were obtained in both in vivo matrices, we suggest that the method can be consistently used for quantitative determinations that are focused on future pharmacokinetic and bioavailability studies in insects. Furthermore, this new analytical method was successfully applied to biological samples of dead dung beetles from the field suggesting that the method can be used to establish a new routine analysis of ivermectin residues in insect carcasses that is applied to complement typical mortality tests.

Identification and evaluation of semiochemicals for the biological control of the beetle Omorgus suberosus (F.) (Coleoptera: Trogidae), a facultative predator of eggs of the sea turtle Lepidochelys olivacea (Eschscholtz).

The beetle Omorgus suberosus (F.) is a facultative predator of eggs of the olive ridley turtle Lepidochelys olivacea (Eschscholtz). Laboratory and field investigations were conducted in order to characterize volatile attractants of O. suberosus and to explore the potential for application of these volatiles in a selective mass trapping method. Headspace sorptive extraction (HSSE) coupled to thermo-desorption gas chromatography-mass spectrometry (TD-GC-MS) analysis of the volatile constituents from beetles or turtle nests revealed 24 potential compounds. However, electroantennographic (EAG) measurements revealed antennal sensitivity only to indole, linoleic acid, trimethylamine, dimethyl sulphide, dimethyl disulphide and ammonia. Behavioural tests showed that these compounds are highly attractive to O. suberosus. Field trapping experiments revealed that indole and ammonia were more attractive than the other volatile compounds and showed similar attractiveness to that produced by conventional baits (chicken feathers). The use of a combined bait of indole and NH3 would therefore be the most effective trap design. The data presented are the first to demonstrate effective massive capture of O. suberosus using an attractant-based trapping method. These findings have potential for the development of an efficient mass trapping method for control of this beetle as part of efforts towards conservation of L. olivacea at La Escobilla in Oaxaca, Mexico.

Effects of 3 adhesion promoters on the shear bond strength of orthodontic brackets: an in-vitro study.

INTRODUCTION: The objectives of this study were to (1) determine the effect of 3 adhesion promoters on shear bond strength and the amount of remnant adhesive on the teeth after debonding and (2) learn whether 1 promoter is material-specific, as stated by the manufacturer. METHODS: The promoters tested were OrthoSolo (Ormco, Orange, Calif), All-Bond 2 (Bisco, Schaumburg, Ill), and Enhance L.C. (Reliance, Itasca, Ill). Two adhesives were used: Transbond XT (3M Unitek, Monrovia, Calif) and Light Bond (Reliance). One hundred fifty premolars were divided into 6 groups of 25, and brackets were bonded according to the manufacturers' instructions: (1) Transbond XT, (2) Transbond XT plus All-Bond 2, (3) Transbond XT plus OrthoSolo, (4) Transbond XT plus Enhance L.C., (5) Light Bond, and (6) Light Bond plus Enhance L.C. Bond strength was tested on a universal testing machine, and remnant adhesive was quantified with image analysis equipment. RESULTS: The highest bond strength values were obtained when brackets were bonded with Light Bond plus Enhance L.C. These values were significantly higher than those achieved with Transbond XT, Transbond XT plus Enhance L.C., or Transbond XT plus All-Bond 2. Of the groups bonded with Transbond XT, the group that included OrthoSolo had the best results. CONCLUSIONS: None of the adhesion promoters significantly increased bond strength or the amount of adhesive remaining on the tooth after debonding. Enhance L.C. produced the greatest bond strength when used with the material-specific product Light Bond.

Drugs related to the etiology of molar incisor hypomineralization: A systematic review.

BACKGROUND: Molar incisor hypomineralization (MIH) is an idiopathic syndrome that has been associated with several etiologic factors. The authors' objective was to systematically review studies in which the investigators had studied how the etiology of MIH was related to medication intake. TYPES OF STUDIES REVIEWED: The search covered a period from January 1, 1965, to September 29, 2014. The search revealed 1,042 articles, to which the authors applied eligibility criteria and selected 20 studies for review. The authors considered 9 of the 20 studies to be high quality. The drugs used in these studies were chemotherapeutic drugs, antibiotics, asthma drugs, antiepileptic drugs, antiviral drugs, antifungal drugs, and antiparasitic drugs. RESULTS: Two reviewers independently performed risk-of-bias assessment and data extraction. The investigators of all of the studies had reported enamel defects, but only 2 sets of investigators had used the term "molar incisor hypomineralization." Owing to the different methodologies used by the investigators of the selected studies, the authors could not perform a meta-analysis of the study results. CONCLUSIONS: More well-designed prospective studies are needed to clarify the relationship between MIH and medication. PRACTICAL IMPLICATIONS: It would be convenient to establish a preventive protocol in patients with a potential risk of developing MIH to avoid the complications that are characteristic of this disease.

Adhesion promoters: effects on the bond strength of brackets.

PURPOSE: To evaluate the effect of two adhesion promoters on shear bond strength and remnant adhesive of brackets cemented with a light-cured orthodontic adhesive resin system. METHODS: The two adhesion promoters tested were OrthoSolo and All-Bond 2 Primer. Seventy-five upper premolars were divided into three groups of 25. A control group was established using Transbond-XT adhesive system and two experimental groups: Transbond-XT/OrthoSolo and Transbond-XT/All-Bond 2. Shear bond strength was measured using a universal testing machine and adhesive remnant was quantified using an image analysis equipment. RESULTS: The application of Orthosolo significantly increased bond strength for Transbond-XT adhesive system (P< 0.017). All-Bond 2 primer did not significantly increase the bond strength of Transbond-XT (P> 0.017). The Adhesive Remnant Index results and the analysis of the percentage of area of tooth occupied by adhesive indicated that adhesive remnant after debonding did not increase significantly (P> 0.05) with the use of either of the promoters.

Shear bond strength of orthodontic brackets bonded with self-etching primers.

PURPOSE: To evaluate the effectiveness of two self-etching primers for bonding brackets in comparison with the conventional acid-etch technique. METHODS: The brackets were bonded to extracted human premolars using the resin orthodontic adhesive system, Transbond XT. This procedure was carried out in accordance with one of the following three protocols of enamel conditioning: (1) 37% phosphoric acid etching, (2) Transbond Plus Self Etching Primer (TSEP), and (3) Adper Prompt L-Pop (Adper PLP). Shear bond strength was measured with a universal test machine. The adhesive remnant on the tooth after debonding was quantified using image analysis equipment. Scanning electron microscopy (SEM) was used to observe the effects of conditioning of each product on the enamel. RESULTS: No significant differences were observed in bond strengths of the three groups evaluated (P> 0.05). Self-etching primers left significantly less adhesive on the tooth than the conventional acid-etch technique and, among them, Adper PLP left significantly less adhesive than TSEP (P< 0.017). SEM observations showed that the etching effect of self-etching primers approximated to the etching effect of phosphoric acid.