Does Shortened Application Time Affect Long-Term Bond Strength of Universal Adhesives to Dentin?

OBJECTIVE: This study evaluated the effect of shortened application time on long-term bond strength with universal adhesives. METHODS AND MATERIALS: Three universal adhesives were used: Clearfil Universal Bond (CU, Kuraray Noritake Dental Inc, Tokyo, Japan), Scotchbond Universal Adhesive (SB, 3M ESPE, St Paul, MN, USA) or G-Premio Bond (GP, GC Corp, Tokyo, Japan). Sixty molars were cut to expose midcoronal dentin and prepared with a regular diamond bur. Each adhesive was applied either according to the manufacturer's instruction or with shortened time. Specimens were stored in distilled water at 37°C for 24 hours and then cut into resin-dentin sticks. Microtensile bond strength (µTBS) was tested after either 24 hours or 1 year of water storage. Data were analyzed by the three-way ANOVA and Duncan tests ( α=0.05). Fracture modes were analyzed under a scanning electron microscope (SEM). One dentin stick per group was selected after fracture mode analysis and further observed using transmission electron microscopy (TEM). Six additional dentin discs were prepared and conditioned with each adhesive under the different application time to observe the adhesive-smear layer interaction by SEM. RESULTS: Shortened application time affected the µTBS ( p<0.001) while storage time did not affect bond strength ( p=0.187). A significant effect of shortened application time on µTBS was observed in the CU at 1 year and in the GP at both storage times. CONCLUSIONS: One-year storage time had no effect on the µTBS of universal adhesives to bur-cut dentin. The performance of universal adhesives can be compromised when applied using a shortened application time.

The potential effect of ultra-long insulin degludec on glycemic variability.

Despite the therapeutic advances in the treatment of diabetes, metabolic control instability due to glycemic variability (GV) is frequently observed in patients with diabetes on intensive insulin therapy and is associated with hyperglycemic peaks and hypoglycemic episodes. Hyperglycemia associated with GV has been implicated in the development of chronic complications due to its pro-oxidative consequences. On the other hand, hypoglycemia can be associated with increased cardiovascular risk secondarily to adrenergic activation. The ultra-long-acting insulin analogue, insulin degludec (IDeg), presents a flat and stable glucose-lowering effect both in Type 1 and Type 2 diabetes patients. In pharmacodynamic studies, IDeg has been associated with a lower variability in its insulin action than other alternatives for basal insulin, which might have clinical advantages for the stability of the glycemic control. The main objective of this review is to present pharmacological and clinical data regarding the efficacy and safety of IDeg for the treatment of diabetes focusing on its effects on GV and on hypoglycemia frequency.

Effects of Temperature and Aging on Working/Setting Time of Dual-cured Resin Cements.

OBJECTIVES: To evaluate the effects of aging and temperature on working time (WT) and setting time (ST) of several dual-cured resin cements. METHODS: WT and ST were determined with a thermo-controlled stage oscillating rheometer. New cement kits were used for the study. Cements were mixed according to instructions and dispensed on the oscillating stage that was preset at 22°C or 37°C. Rheologic charts were generated from the beginning of mixing until no further oscillation was detected. After initial measurements, cement kits were aged at 37°C for 12 weeks, and WT/ST was determined again at both temperatures. Five samples were read for each material and condition. Data were analyzed with repeated measures analysis of variance and a Tukey test at α=5% for each individual material. RESULTS: The WT and ST of all cements were significantly affected by temperature and aging (p<0.05). In general, higher temperature accelerated WT/ST, but aging effects were material dependent. Some materials presented reduced WT/ST, whereas others showed increased WT/ST, regardless of the temperature. CONCLUSIONS: The WT and ST were significantly affected by temperature variation and aging condition. Although temperature changes appeared to affect all materials similarly, aging effects were material dependent.

What constitutes an ideal dental restorative material?

Intense environmental concerns recently have prompted dentistry to evaluate the performance and environmental impact of existing restoration materials. Doing so entices us to explore the 'what if?' innovation in materials science to create more ideal restorative materials. Articulating a specification for our design and evaluation methods is proving to be more complicated than originally anticipated. Challenges exist not only in specifying how the material should be manipulated and perform clinically but also in understanding and incorporating implications of the skill of the operator placing the restoration, economic considerations, expectations patients have for their investment, cost-effectiveness, influences of the health care system on how and for whom restorations are to be placed, and global challenges that limit the types of materials available in different areas of the world. The quandary is to find ways to actively engage multiple stakeholders to agree on priorities and future actions to focus future directions on the creation of more ideal restorative materials that can be available throughout the world.

The importance of size-exclusion characteristics of type I collagen in bonding to dentin matrices.

The mineral phase of dentin is located primarily within collagen fibrils. During development, bone or dentin collagen fibrils are formed first and then water within the fibril is replaced with apatite crystallites. Mineralized collagen contains very little water. During dentin bonding, acid-etching of mineralized dentin solubilizes the mineral crystallites and replaces them with water. During the infiltration phase of dentin bonding, adhesive comonomers are supposed to replace all of the collagen water with adhesive monomers that are then polymerized into copolymers. The authors of a recently published review suggested that dental monomers were too large to enter and displace water from collagen fibrils. If that were true, the endogenous proteases bound to dentin collagen could be responsible for unimpeded collagen degradation that is responsible for the poor durability of resin-dentin bonds. The current work studied the size-exclusion characteristics of dentin collagen, using a gel-filtration-like column chromatography technique, using dentin powder instead of Sephadex. The elution volumes of test molecules, including adhesive monomers, revealed that adhesive monomers smaller than ∼1000 Da can freely diffuse into collagen water, while molecules of 10,000 Da begin to be excluded, and bovine serum albumin (66,000 Da) was fully excluded. These results validate the concept that dental monomers can permeate between collagen molecules during infiltration by etch-and-rinse adhesives in water-saturated matrices.

Effects of potassium oxalate on knoop hardness of etch-and-rinse adhesives.

The objective of this study was to determine whether the hardness of etch-and-rinse adhesives may be affected by the pretreatment of acid-etched dentin with potassium oxalate desensitizer. Unerupted human third molars were cut into crown segments by removing the occlusal enamel and roots. The pulp chamber of these crown segments was connected to a syringe barrel filled with phosphate-buffered saline so that the moisture of dentin was maintained during the bonding procedures. Three etch-and-rinse adhesives-two two-step systems (Adper Single Bond 2 [SB], One-Step [OS]) and one three-step system (Adper Scotchbond Multi-Purpose [MP])-were applied to acid-etched dentin that had been treated (experimental groups) or not (control groups) with potassium oxalate (BisBlock). The Knoop hardness (KHN) of adhesives was taken at different sites of the outer surface of the adhesive-bonded dentin. The KHN of the three tested adhesives applied to acid-etched dentin treated with potassium oxalate was significantly lower than that exhibited by the respective controls (not treated with oxalate; p<0.05). Regardless of the adhesive, the treatment with potassium oxalate reduced the adhesives' KHN (p<0.05), with the OS system exhibiting the lowest KHN compared with the MP and SB systems.

Yellow fever vaccination in organ transplanted patients: is it safe? A multicenter study.

BACKGROUND: Yellow fever (YF) may be very serious, with mortality reaching 50%. Live attenuated virus YF vaccine (YFV) is effective, but may present, although rare, life-threatening side effects and is contraindicated in immunocompromised patients. However, some transplant patients may inadvertently receive the vaccine. METHODS: A questionnaire was sent to all associated doctors to the Brazilian Organ Transplantation Association through its website, calling for reports of organ transplanted patients who have been vaccinated against YF. RESULTS: Twelve doctors reported 19 cases. None had important side effects. Only one had slight reaction at the site of YFV injection. Eleven patients were male. Organs received were 14 kidneys, 3 hearts, and 2 livers. Twelve patients received organs from deceased donors. Mean age at YFV was 45.6 ± 13.6 years old (range 11-69); creatinine: 1.46 ± 0.62 mg/dL (range 0.8-3.4); post-transplant time: 65 ± 83.9 months (range 3-340); and time from YFV at the time of survey: 45 ± 51 months (range 3-241). Immunosuppression varied widely with different drug combinations: azathioprine (7 patients), cyclosporine (8), deflazacort (1), mycophenolate (10), prednisone (11), sirolimus (3), and tacrolimus (4). CONCLUSIONS: YFV showed no important side effects in this cohort of solid organ transplanted patients. However, owing to the small number of studied patients, it is not possible to extend these findings to the rest of the transplanted population, assuring safety. Therefore, these data are not strong enough to safely recommend YFV in organ transplanted recipients, as severe, even life-threatening side effects may occur.

Methods used by Dental Practice-based Research Network (DPBRN) dentists to diagnose dental caries.

OBJECTIVES: To (1) identify the methods that dentists in The Dental Practice-Based Research Network (DPBRN) use to diagnose dental caries; (2) quantify their frequency of use and (3) test the hypothesis that certain dentist and dental practice characteristics are significantly associated with their use. METHODS: A questionnaire about methods used for caries diagnosis was sent to DPBRN dentists who reported doing some restorative dentistry; 522 dentists participated. Questions included the use of dental radiographs, the dental explorer, laser fluorescence, air-drying and fiber-optic devices and magnification as used when diagnosing primary, secondary/recurrent or non-specific caries lesions. Variations on the frequency of their use were tested using multivariate analysis and Bonferroni tests. RESULTS: Overall, the dental explorer was the instrument most commonly used to detect primary occlusal caries and caries at the margins of existing restorations. In contrast, laser fluorescence was rarely used to help diagnose occlusal primary caries. For proximal caries, radiographs were used to help diagnose 75%­100% of lesions by 96% of the DPBRN dentists. Dentists who use radiographs most often to assess proximal surfaces of posterior teeth were significantly more likely to also report providing a higher percentage of patients with individualized caries prevention (p=.040) and seeing a higher percentage of pediatric patients (p=.001). CONCLUSION: The use of specific diagnostic methods varied substantially. The dental explorer and radiographs are still the most commonly used diagnostic methods..

Utilização do óleo de alho e da amoxilina, metronidazol e omeprazol no controle de Helicobacter spp. em cães / Use of garlic oil and amoxicillin, metronidazole, and omeprazol in the control of Helicobacter spp. in dogs

Avaliaram-se a eficácia do óleo de alho e da terapia tripla (amoxicilina, metronidazol e omeprazol) no tratamento de 21 cães infectados por Helicobacter spp., que apresentavam alterações histológicas nas biopsias endoscópicas da mucosa gástrica e reação positiva ao teste de urease. Os animais foram distribuídos, aleatoriamente, em três grupos de sete cães, os quais receberam os seguintes tratamentos: grupo 1 - cápsulas vazias; grupo 2 - 500mg de óleo de alho em cápsulas, diariamente, por um período de 30 dias; grupo 3 - amoxicilina, metronidazol e omeprazol, respectivamente, nas doses de 20mg/kg a cada 12 horas, 25mg/kg e 20mg/kg a cada 24 horas, durante 15 dias. Ao final dos tratamentos, os cães foram submetidos à endoscopia com realização de biopsias da mucosa gástrica. O tratamento com amoxicilina, metronidazol e omeprazol resultou em erradicação de Helicobacter spp. tanto na região fúndica quanto na pilórica. No grupo 2, houve redução da degeneração glandular na região fúndica em dois animais e em outros dois na pilórica. O tratamento com óleo de alho não foi eficaz em erradicar Helicobacter spp., apenas reduziu a sua colonização em quatro dos animais tratados.

The efficacy of garlic oil and triple therapy (amoxicillin, metronidazole, and omeprazol) were evaluated in the treatment of 21 dogs infected by Helicobacter spp., which presented histological alterations of the gastric mucosa according to endoscopic biopsies and positive reaction to urease test. The animals were randomly distributed into three groups of seven dogs each, and received the following treatment, group 1 - empty capsules; group 2 - 500mg of garlic oil capsules daily for a period of 30 days; and group 3 - amoxicillin, metronidazole, and omeprazol, in doses of 20mg/kg every 12 hours, 25mg/kg and 20mg/kg every 24 hours, respectively, for 15 days. By the end of the treatment, the dogs were subjected to new endoscopic procedure with gastric mucosa biopsies. Treatment with amoxicillin, metronidazole, and omeprazol resulted in eradication of Helicobacter spp. both in fundic and pyloric regions. The garlic oil treatment reduced glandular degeneration in the fundic region in two animals and in the pylorus region in two other animals, and it was inefficient in eradicating Helicobacter spp. in dogs as it only reduced the colonization in some of the treated animals.

Classificação da função motora e do desempenho funcional de crianças com paralisia cerebral / Classification of motor function and functional performance in children with cerebral palsy

OBJETIVOS: Classificar crianças com paralisia cerebral (PC) utilizando sistemas de classificação de mobilidade e de função manual; comparar os grupos de crianças com PC nos desfechos de função motora grossa e de desempenho funcional; avaliar a associação entre as classificações funcionais e os escores obtidos nos desfechos investigados. MATERIAL E MÉTODOS: Trinta crianças com PC foram classificadas pelos sistemas Gross Motor Function Classification System (GMFCS) e Manual Abilities Classification System (MACS) e divididas em três grupos, de acordo com a sua classificação em cada um destes sistemas em leve, moderado e grave. A função motora grossa foi documentada pelo teste Gross Motor Function Measure (GMFM-66), e as habilidades funcionais e assistência do cuidador em autocuidado e em mobilidade, pelo teste Pediatric Evaluation of Disability Inventory (PEDI). RESULTADOS: O teste one-way ANOVA demonstrou diferenças significativas entre os grupos nos resultados do GMFM-66 e do teste PEDI. Testes de comparação post-hoc (Scheffé) revelaram que crianças com comprometimento moderado (GMFCS) apresentaram habilidades funcionais e receberam assistência do cuidador semelhantes às crianças leves. Entretanto, crianças moderadas (MACS) assemelharam-se às graves. Índices de correlação de Spearman rank demonstraram associação inversa, significativa e de magnitude forte entre as classificações funcionais e os resultados dos testes PEDI e GMFM-66. CONCLUSÕES: Os resultados sugerem que as classificações funcionais MACS e GMFCS são bons indicadores da função manual e da mobilidade de crianças com PC, podendo ser úteis nos processos de avaliação e planejamento de intervenção.

OBJECTIVE: To classify children with cerebral palsy (CP) using classification systems for mobility and manual function; to compare groups of children with CP regarding gross motor function and functional performance outcomes; and to evaluate associations between the functional classifications and the scores obtained in the outcomes that were investigated. METHODS: Thirty children with CP were classified using the Gross Motor Function Classification System (GMFCS) and the Manual Abilities Classification System (MACS), and were divided into three groups, based on their classification (mild, moderate or severe) in each of these systems. Gross motor function was documented using the Gross Motor Function Measure (GMFM-66) test, while functional abilities and the caregiver's assistance regarding self-care and mobility were documented using the Pediatric Evaluation of Disability Inventory (PEDI). RESULTS: One-way ANOVA showed that the groups were significantly different regarding the GMFM-66 and PEDI results. Post-hoc comparison tests (Scheffé) revealed that the children with moderate impairment (GMFCS) had functional abilities and caregiver support that were similar to those of the mildly impaired children. However, the moderate children (MACS) were not different from the severe children. Spearman rank correlations showed strong and significant inverse associations between the functional classifications and the results from the PEDI and GMFM-66 tests. CONCLUSIONS: The results suggest that the MACS and GMFCS functional classifications are good indicators of the manual function and mobility of children with CP. These classifications may be useful in the processes of evaluation and intervention planning.

In vivo preservation of the hybrid layer by chlorhexidine.

Host-derived proteases have been reported to degrade the collagen matrix of incompletely-resin-infiltrated dentin. This study tested the hypothesis that interfacial degradation of resin-dentin bonds may be prevented or delayed by the application of chlorhexidine (CHX), a matrix metalloproteinase inhibitor, to dentin after phosphoric acid-etching. Contralateral pairs of resin-bonded Class I restorations in non-carious third molars were kept under intra-oral function for 14 months. Preservation of resin-dentin bonds was assessed by microtensile bond strength tests and TEM examination. In vivo bond strength remained stable in the CHX-treated specimens, while bond strength decreased significantly in control teeth. Resin-infiltrated dentin in CHX-treated specimens exhibited normal structural integrity of the collagen network. Conversely, progressive disintegration of the fibrillar network was identified in control specimens. Auto-degradation of collagen matrices can occur in resin-infiltrated dentin, but may be prevented by the application of a synthetic protease inhibitor, such as chlorhexidine.

Chlorhexidine preserves dentin bond in vitro.

Loss of hybrid layer integrity compromises resin-dentin bond stability. Matrix metalloproteinases (MMPs) may be partially responsible for hybrid layer degradation. Since chlorhexidine inhibits MMPs, we hypothesized that chlorhexidine would decelerate the loss of resin-dentin bonds. Class I preparations in extracted third molars were sectioned into two halves. One half was customarily restored (etch-and-rinse adhesive/resin composite), and the other was treated with 2% chlorhexidine after being acid-etched before restoration. Specimens were stored in artificial saliva with/without protease inhibitors. Microtensile bond strengths and failure mode distribution under SEM were analyzed immediately after specimens' preparation and 6 months later. With chlorhexidine, significantly better preservation of bond strength was observed after 6 months; protease inhibitors in the storage medium had no effect. Failure analysis showed significantly less failure in the hybrid layer with chlorhexidine, compared with controls after 6 months. In conclusion, this in vitro study suggests that chlorhexidine might be useful for the preservation of dentin bond strength.

Evaluation of a self-limiting concept in dentinal caries removal.

The mechanical removal of dentinal caries traditionally involves the use of tactile sensation and/or caries-indicating dyes. This study tested the hypothesis that self-limiting polymer burs are as effective as conventional carbide burs in creating substrates for dentin bonding. Carious dentin from extracted human molars was removed with carbide or polymer burs, with dental explorer hardness as the end-point for caries removal. Dentin substrates were bonded with etch-and-rinse or self-etch adhesives and prepared for microtensile bond testing and transmission electron microscopy. For each bur type, there was no difference in bond strength between adhesives. However, the polymer bur surface exhibited significantly lower bond strengths than the carbide bur, and both were lower than flat, non-carious dentin controls. TEM revealed areas of incompletely removed, denatured caries-infected dentin in the polymer bur specimens. These first-generation polymer burs might best be utilized for deep caries removal where pulpal exposure is a concern.

Incompatibility of oxalate desensitizers with acidic, fluoride-containing total-etch adhesives.

The use of oxalate desensitizers on acid-etched dentin prior to adhesive application can result in subsurface tubular occlusion by calcium oxalate crystals. However, the solubility of calcium oxalate increases in acidic solution. We hypothesized that total-etch adhesives can, depending upon their pH, interact with oxalate-desensitizer-treated dentin in an adverse manner. Acid-etched human dentin treated with 2 oxalate desensitizers (BisBlock and Super Seal) was bonded with 4 simplified total-etch adhesives: One-Step (OS), Single Bond (SB), OptiBond Solo Plus (OB), and Prime&Bond NT (PB). Composite-dentin beams were examined by SEM and TEM, both of which revealed numerous spherical globules on OB- and PB-bonded, desensitizer-treated dentin, but not in OS or SB samples. Bond strengths produced by OB and PB were significantly lower in oxalate-treated specimens than those produced by OS or SB. These surface globules may have interfered with hybridization of demineralized dentin with OB and PB resins and caused compromised bond strengths.

A laparoscopic approach to allograft nephrectomy and bilateral native nephrectomy: a case report.

INTRODUCTION: Laparoscopic surgery is rapidly emerging as the standard of care for a variety of urological conditions, even among patients who have undergone prior renal transplantation. We describe the technique of bilateral native nephrectomy and allograft nephrectomy by laparoscopy. CASE REPORT: A 32-year-old man with end-stage renal disease who had undergone a cadaveric renal transplant presented with chronic graft dysfunction. He had received a living donor kidney transplant with a postoperative course complicated by persistent proteinuria and refractory hypertension. Our nephrology service indicated the need for bilateral native nephrectomy and allograft nephrectomy for better blood pressure control following a second transplant. Bilateral native nephrectomy was performed following the previous reported techniques for pure laparoscopic nephrectomy. Allograft nephrectomy started by dissection of the iliac vessels to identify the vascular anastomosis. The hilum of the transplanted kidney was accessed. The renal vessels were clipped and transected. The ureter was identified and clipped. All three kidneys were removed from the abdominal cavity through a 3-cm skin incision. RESULTS: The left nephrectomy took 25 minutes and the right nephrectomy, 40 minutes. The estimated blood loss was 300 mL and the total operative time was 210 minutes. The patient had an uneventful postoperative course and was discharged on the third postoperative day. CONCLUSIONS: We demonstrate the feasibility of laparoscopic allograft nephrectomy and bilateral native nephrectomy in a transplant recipient.

Single-bottle adhesives behave as permeable membranes after polymerization. I. In vivo evidence.

OBJECTIVES: This study tested the hypothesis that single-bottle total-etch adhesives are effective in reducing dentine permeability under in vivo conditions. METHODS: Crown preparations on vital human teeth were performed under local analgesia as part of the treatment plan for prosthetic rehabilitation. Four single-bottle adhesives (Single Bond, 3M ESPE; Excite DSC, Ivoclar Vivadent; Prime and Bond NT Dual-Cure, Dentsply DeTrey and One-Step, Bisco Inc.) were applied to the cut dentine after acid-etching. Polyvinyl siloxane impressions were taken, using an ultra-low viscosity impression material, of the smear layer-covered dentine before applying the adhesives to deep vital dentine, and after adhesive placement. Additional impressions were taken of the adhesive-sealed dentine following the removal of the provisional prostheses after a 7-10 day period. Epoxy resin replicas of the crown preparations were examined with scanning electron microscopy to evaluate the extent of dentinal fluid transudation during pre-bonded, immediately bonded and post-bonded periods. RESULTS: Dentinal fluid transudation from localised areas that were close to the dental pulp was universally observed from all epoxy resin replicas, irrespective of the adhesive employed. The transudation of dentinal fluid from the control smear layer-covered dentine of each crown preparation was comparatively mild when compared to the extent that was observed after total-etching and application of the single-bottle adhesive. Dentinal fluid droplets were specifically located over the surface of the adhesive layer. Continuous transudation of dentinal fluid occurred even after the removal of the provisional prostheses, and was considerably more profuse in subjects who opted for the fitting of the permanent prostheses without the use of a local anaesthetic solution. CONCLUSION: Single-bottle adhesives, because of their lack of a comparatively more hydrophobic bonding resin layer, behave as permeable membranes after polymerisation. They permit the continuous transudation of dentinal fluid and do not provide a hermetic seal in vital deep dentine. Although the relatively slow rate of diffusion of dentinal fluid is unlikely to result in post-operative cold sensitivity, it may interfere with the optimal polymerisation of dual-cured or auto-cured composites or resin cements in both direct and indirect restorations.

Interaction of resin-modified glass-ionomer cements with moist dentine.

OBJECTIVES: The objective of this study was to report on a novel phenomenon that occurs when resin-modified glass-ionomer cements (RMGICs) are bonded to moist human dentine. METHODS: Dentine surfaces from extracted third molars were abraded with 180-grit SiC paper. Ten teeth were prepared for each of the two RMGICs tested (Fuji II LC, GC Corp. and Photac-Fil Quick, 3M ESPE). RMGIC buildups were made according to the manufacturers' instructions. After storage at 37 degrees C, 100% humidity for 24 h, the bonded specimens were cut occlusogingivally into 0.9 x 0.9 mm beams. Dentine surfaces bonded with the two RMGICs were examined along the fractured RMGIC/dentine interfaces. Additional beams fractured within the RMGICS and at 3 mm away from the interfaces were used as controls. The fractured beams were examined using scanning electron microscopy (SEM), field emission-environmental SEM (FE-ESEM) and transmission electron microscopy (TEM). RESULTS: SEM and FE-ESEM revealed numerous solid spherical bodies along the RMGIC/dentine interfaces. By contrast, no spherical bodies could be identified within the RMGIC fractured 3 mm distant from the bonded interface. TEM and energy dispersive X-ray analyses performed on carbon-coated ultrathin sections showed that these solid spherical bodies consisted of a thin aluminum and silicon-rich periphery and an amorphous hydrocarbon core within the air voids of the original resin matrix. CONCLUSION: The spherical bodies probably represent a continuation of GI reaction and poly(HEMA) hydrogel formation that results from water diffusion from the underlying moist dentine. Their existence provides evidence for the permeation of water through RMGIC/dentine interfaces.

Aggressiveness of self-etch adhesives on unground enamel.

Manufacturers of mild self-etch adhesives advocate the adjunctive use of phosphoric acid etching when bonding to unground enamel. This study tested the null hypothesis that there is no difference between the recently introduced, more aggressive self-etch adhesives and a total-etch adhesive in bonding to unground enamel. The ultrastructure and microtensile bond strengths (microTBS) of Xeno III (Dentsply) and Simplicity (Apex Dental Materials), bonded to unground enamel, were examined after thermocycling. Clearfil SE Bond (Kuraray), a mild self-etch adhesive, was used as the negative control, and One-Step (BISCO), a total-etch adhesive bonded to phosphoric acid-etched unground enamel, was used as the positive control. Differences in the thickness of enamel hybrid layers were observed and the aggressiveness of apatite dissolution in the four adhesives.

Effect of resin hydrophilicity and water storage on resin strength.

This study evaluated the change in the ultimate tensile strength (UTS) of five polymerised resin blends of increasing hydrophilicity, after ageing in distilled water or silicon oil. Resin blocks were prepared from each resin blend by dispensing the uncured resin into a flexible, embedding mould, containing multiple cavities. The resins were polymerised in the moulds under nitrogen at 551.6 kPa and light-activated at 125 degrees C for 10 min. After dry ageing for 24 h at 37 degrees C, the middle third of each resin specimen was trimmed into an 'I' shape. Fifteen control specimens were randomly selected from each resin blend for baseline UTS evaluation. The UTS of the experimental specimens were determined after 1, 3, 6 and 12 months of ageing in water or oil. The UTS of each group of resins at different storage periods in water or oil were analysed using the Friedman multiple ANOVA on ranks and Dunn's multiple comparison tests at 95% confidence level. Significant reduction (p < 0.01) in UTS was observed in Groups II-V resins after 12-month storage in water, while the most hydrophobic Group I resin showed no significant change (p > 0.05) in the same period. The percentage reduction in UTS increased with the hydrophilicity of the resin blends. Long-term water storage of hydrophilic resin blends such as those employed in dentine adhesives, resulted in a marked reduction in their mechanical strength that may compromise the durability of resin-dentine bonds.