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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This research investigated the effects of wet and dry conditions of phosphoric acid etched dentin on resin bonding and determined the optimum moisture condition for resin bonding using an ethanol-based one-bottle adhesive system. Bovine dentin surfaces were etched with 35% phosphoric acid and rinsed with water. Under four wet and dry conditions (overwet, blot dry, one-second dry and desiccated), resin composite was bonded using Single Bond. Tensile bond strength was measured and the results analyzed by one-way ANOVA and Fisher's PLSD test at the 5% level. The resin-dentin interfaces of bonded specimens were observed with SEM. The bond strength of overwet, blot dry, one-second dry and desiccated groups were 5.2 MPa, 12.6 MPa, 11.9 MPa and 4.4 Mpa, respectively. The blot dry group and one-second dry groups revealed significantly higher bond strengths than the desiccated and overwet groups (p < 0.05). The formation of hybrid layers approximately 5 microm thick (overwet and blot dry), 2 microm (one-second dry) and 3 microm (desiccated) were observed. The coefficient of variation in the blot dry group was very high, even though a higher mean was observed. In the one-second dry group, the moisture content of the collagen network was possibly too low, such that hybrid layer formation was not as good even though the bond strength was high.
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PMID:Effect of residual water on dentin bond strength and hybridization of a one-bottle adhesive system. 1241 20

Questions over the use of self-etching primers with composite resin adhesives in the bonding of orthodontic brackets remain unsolved. In addition, there are no previous reports on the efficacy of self-etching primers with resin-modified glass ionomer cements for bonding orthodontic brackets in orthodontic dentistry. The purpose of this study was to determine the shear bond strengths of orthodontic brackets bonded with one of four protocols: (1) a composite resin adhesive used with 40% phosphoric acid, (2) the same composite resin used with Megabond self-etching primer, (3) a resin-modified glass ionomer cement adhesive used with 10% polyacrylic acid enamel conditioner, and (4) the same resin-modified glass ionomer cement used with Megabond self-etching primer. The appearance of the tooth surfaces after acid etching or priming was observed with a field-emission scanning electron microscope (FE-SEM). When used with resin-modified glass ionomer cement, Megabond self-etching primer gave no significantly different shear bond strength compared with polyacrylic acid etching. But when used with composite resin adhesive, Megabond self-etching primer gave significantly lower shear bond strength than phosphoric acid etching. However, the shear bond strength of orthodontic brackets bonded with composite resin adhesive after Megabond priming was almost the same as that of brackets bonded with resin-modified glass ionomer cement after polyacrylic acid etching. FE-SEM observation revealed that Megabond self-etching primer produced less dissolution of enamel surface than did phosphoric acid and polyacrylic acid etching. Megabond self-etching primer may be a candidate for bonding orthodontic brackets using the resin-modified glass ionomer cement for minimizing the amount of enamel loss.
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PMID:Effect of using self-etching primer for bonding orthodontic brackets. 1282 28

Sixty-seven extracted molars were selected (134 samples). Dentin and enamel samples were prepared by buccal and lingual surface sectioning to expose a planar enamel or dentin surface. For the roughness study, 80 samples were randomly assigned to eight groups. Enamel and dentin surfaces were etched with a 37% phosphoric acid solution, irradiated with an Er:YAG laser or irradiated with a Nd:YAP laser. Samples were then observed in SEM using BSE. For the free-surface energy study, 54 samples received the same treatment as above. Two contact angle measurements were made on each surface using a goniometer. Data were analyzed by a non-parametric statistical test. Morphological changes on enamel and dentin were greater with acid-etch and Er:YAG laser than with Nd:YAP laser. Free surface energy was significantly greater with acid-etch or Er:YAG laser than with Nd:YAP laser (p < 0.001).
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PMID:Effects of Er:YAG and Nd:YAP laser irradiation on the surface roughness and free surface energy of enamel and dentin: an in vitro study. 1254 Jan 21

Hybridization of dentine is identified as a basic bonding mechanism between resin and dentine, hence studying the micro morphology of hybrid layer may explain lower bond strength that has been observed in primary teeth. The aim of the present study was to compare the thickness and micromorphology of Hybrid layer formed in primary and permanent teeth for 3 different durations of dentine etching time (5, 10 and 15 sec) with 10% phosphoric acid as etchant. Thickness and micromorphology of hybrid layer was observed on SEM photographs obtained at 750X. Results indicated that primary teeth presented with a significantly thicker hybrid layer compared to permanent teeth at 10 sec (P<0.05) and 15 sec (P<0.01) of dentine etching. It was concluded that owing to the high reactivity of primary teeth to etchants, the etchants be applied for shorter period on primary dentine compared to permanent dentine for better performance of composite restoration in primary dentition.
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PMID:Comparison of resin-dentine interface in primary and permanent teeth for three different durations of dentine etching. 1258 47

The aim of this study was to analyze the etching effect of a new dental adhesive system that uses an antibacterial and self-etching primer agent. Non-carious primary human molars were divided into three groups: 35% phosphoric acid etching (3M-ESPE), self-etching primer (Clearfil SE Bond--Kuraray) and antibacterial self-etching primer (ABF experimental system--Kuraray) for SEM evaluation of surface, resin replicas and interface. Both self-etching primers produced shallow grooves and no defined etching morphologies. Phosphoric acid produced definite etching patterns at the enamel surface.
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PMID:Antibacterial and conventional self-etching primer system: morphological evaluation of intact primary enamel. 1273 86

Recently several long-term studies have reported evidence of the hydrolytic degradation of collagen fibrils based on fractured surface observations after bond testing. Those studies suggested that one cause of the decline in the bond strength was the degradation of the collagen fibrils within the bonds. However, one concern has been raised that the dentinal collagen fibrils may be stable in water that does not contain oral bacteria or enzymes. Therefore, the present study aimed to clarify the micromorphological change in naked collagen fibrils after 500 days of water storage. To prepare exposed collagen fibrils, sectioned and polished human dentin surfaces were acid conditioned for 15 s with the use of two commercially available acid conditioners: All-Etch (10% phosphoric acid) and Uni-Etch (32% phosphoric acid) (Bisco, Inc.). Those specimens were stored in distilled water at 37 degrees C for 1 day (control) for 500 days. After the storage periods, the samples were examined with the use of SEM and TEM. Under SEM and TEM examination, micromorphological alterations (disarrangement of collagen web, widening the interfibrillar space, and the thinning diameter of collagen fibrils) were found in the specimens after 500 days in water.
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PMID:SEM and TEM analysis of water degradation of human dentinal collagen. 1280 86

This in vitro study verifies whether there are differences between bonding to hypermineralized dentin and normal dentin and if longer acid etching can improve the bond strength to this modified substrate without damaging the bond to normal dentin. Forty-two extracted human molars with chronic occlusal caries were transversally cut with a diamond saw under refrigeration. The occlusal surfaces were ground until the carious lesion was removed, exposing the sclerotic dentin in the center and polished to 600/grid. A 35% phosphoric acid (3M) was applied for 15 seconds in 15 specimens. SingleBond (3M) adhesive system was applied and a hybrid resin composite (Filtek Z250, 3M) was inserted in four 1-mm increments and light-cured. The remaining 15 molars were prepared in the same manner, but with an acid etching time of 30 seconds. After 24 hours in water, the specimens were cut in two perpendicular directions to obtain a cross section of approximately 0.7 mm2 (n=25). A visual examination was conducted to select sticks between the two groups: sclerotic dentin (G15S or G30S) and normal dentin (G15N or G30N). Sticks without 100% sclerotic dentin (translucent area) or those with normal areas were not tested. Two-way ANOVA computed the mu-TBS data taking into consideration dentin type and acid etching time. The dentin Knoop hardness number (KHN) of the sticks was verified. A t-test compared the KHN data between sclerotic and normal dentin. Twelve additional molars (n=6) were prepared to observe the interface under a SEM. The mean (+/- SD) microtensile bond strengths (mu-TBS) were: G15S=56.4(+/- 14.9), G15N=69.7(+/- 17.2), G30S=63.2(+/- 15.6) and G30N=67.7(+/- 13.3). Two-way ANOVA showed higher mu-TBS to normal dentin than sclerotic dentin. Duncan's Post Hoc showed G15N had higher mean mu-TBS than G15S. Other comparisons were not significantly different. The t-test showed statistically higher microhardness in sclerotic dentin than in normal dentin (p<0.0001). The hybrid layer (HL) formation was observed in all specimens without gap formation in any region. In sclerotic dentin (G15S), the HL was very thin, with minimal resin tags in the dentinal tubules and, when present, they were shorter. Doubling the etching time (G30S) resulted in more resin tags with an HL formation on peritubular dentin. The HL on normal dentin was thicker when it was acid etched for 30 seconds (G30N). Numerous resin tags were present with both etching times. The results suggest that the higher mineral amount in sclerotic dentin makes it difficult to bond to this substrate, resulting in a lower mu-TBS. However, doubling the etching time resulted in mu-TBS similar to normal dentin.
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PMID:Dentin bonding: effect of degree of mineralization and acid etching time. 1287 29

The aim of the study was the morphological analysis of coronal dentin caries and the modifications induced by different pretreatments with phosphoric acid or sodium hypochlorite. Carious dentin specimens were obtained from human molars affected by carious lesions. Specimens were divided in four groups and submitted to: (1) untreated; (2) 35% phosphoric acid for 15 s; (3) 35% phosphoric acid for 15 s and 5% sodium hypochlorite for 2 min; (4) sodium hypochlorite for 5 min. Specimens were observed under high-resolution SEM. Different areas were identified within the carious lesion: a deeper, inner region revealing closed highly mineralized tubules, and a more superficial outer layer showing an increasing demineralization rate toward the surface of the lesion. Phosphoric acid followed by NaOCl treatment removed all collagen fibrils from greatly altered carious outer-dentin layer. The 5-min treatment with sodium hypochlorite affected both inner and outer dentin, removing all collagen fibrils and increasing the porosities of deeper intertubular hypermineralized dentin. FEISEM analysis confirmed that only inner carious dentin after phosphoric acid treatment may be considered a suitable substrate for dentinal bonding system. On the contrary, the outer dentin is an unstable substrate for any type of bonding systems and must be avoided/removed from any surface before conditioner application.
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PMID:Effect of dentinal pretreatments on coronal dentin primary carious lesions: a field emission SEM study. 1292 Jun 10

The hypothesis tested in this study is that the application of phosphoric acid prevents collagen fibrils (CF) from maintaining their structural morphology, as assessed by their immunochemical antigenicity. Dentin was conditioned with EDTA and with 35% H3PO4 for 15, 30, and 60 s. For a control there was no treatment. A pre-embedding immunohistochemical procedure was evaluated under high-resolution SEM and a postembedding immunolocalization technique was performed on ultrathin sections at TEM level. Conditioning with EDTA resulted in a weaker labeling signal than for dentin conditioned with H3PO4. The most intense labeling was observed after dentin had been etched with H3PO4 for 15 s. The least intensive labeling was evident when the acid was applied for 30 s or for 60 s. A very weak signal was detected on the untreated dentin surface. These results provide evidence that a 15-s application of 35% H3PO4 causes mineral dissolution of the crystals enveloping the superficial CF without damaging the ultrastructure of the CF while longer applications of 35% H3PO4 cause alterations in the CF that decrease their antigenicity.
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PMID:Immunocytochemical identification of type I collagen in acid-etched dentin. 1292 27

This study investigated the factors that could influence microleakage, penetration ability and the formation of resin tags of different sealants used in routine oral health care. One hundred and two caries-free extracted molars were divided into 34 groups of three teeth each. A questionnaire and three teeth were submitted to 34 dentists participating in the study. They completed the questionnaire anonymously based on their own clinical procedures. The teeth were then treated, corresponding to the questionnaires. The types of sealants were categorized into three groups: classical sealant, flowable composite and flowable compomer. The molars were thermocycled in water (5,000 cycles between 5 degrees C and 55 degrees C), then stained with 5% methylene blue for 24 hours. Each tooth was then sectioned longitudinally at three sites. Fissure type, microleakage and penetration ability of the sealants was evaluated with a computer-linked light microscope (25x magnification). Formation of resin tags at the enamel-sealant interfaces was examined using SEM. Variables thought to influence performance of the sealants were analyzed by multiple regression analyses. Classical sealants showed significantly lower microleakage than flowable composites and flowable compomers. Conventional etching with phosphoric acid was critical for sealant success. Agitating the etchant could improve the quality of sealing by decreasing microleakage significantly. In addition, the fissure types had a significant effect on the penetration ability of sealants.
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PMID:Variables contributing to the quality of fissure sealants used by general dental practitioners. 1465 91


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