Interfacial micromorphology of three adhesive systems created in caries-affected dentin

Purpose: To investigate the morphology of the resin-dentin interface of three dentin adhesive systems (One Coat Bond, Clearfil SE Bond and One-Up Bond F) bonded to caries-affected dentin, exposed using either rotary instrumentation in conjunction with a caries detector dye or a chemo-mechanical caries removal system (Carisolv). Materials and Methods: 60 extracted human molars with occlusal caries were used. 30 teeth had carious dentin removed using slow-speed round steel burs after staining with the caries detector dye, and carious dentin from the remaining teeth was removed using Carisolv. The teeth from each caries removal technique were randomly divided into three groups, bonded with one of the three adhesive systems above according to the manufacturers' instructions, and a thin layer of resin-based composite applied. The teeth were sectioned parallel to the bonded surface to obtain a 3 mm thick bonded dentin disc. The specimens were assigned to one of two observation techniques: a fracture technique or an acid-base technique. Fracture technique: a shallow groove was prepared across the dentin surface of the specimen, fixed in 10% buffered formalin, dehydrated in an ascending ethanol series up to 100%, critical-point dried, and fractured along the prepared groove. Acid-base technique: the specimens were sectioned vertically across the bonded interface, fixed in 10% phosphate buffered formalin, polished with diamond paste down to 0.25-μm particle size, immersed in 10% orthophosphoric acid for 3-5 s and 5% sodium hypochlorite for 10 min. All specimens were gold sputter-coated and observed using FE-SEM. Results: All groups showed hybrid layer formation. However, the thickness varied depending on the adhesive system and the carious dentin removal technique used. One Coat Bond (a "one-bottle" system) showed the thickest hybrid layer (approximately 2 μm) in acid/base treated specimens when bonded to caries-affected dentin, whereas One-Up Bond F (an "all-in-one" system) bonded to normal dentin exhibited the thinnest hybrid layer (approximately 0.3 μm).link_to_subscribed_fulltex

Micromorphological study of resin-dentin interface of non-carious cervical lesions

This study examined the interfaces between two dentin adhesives, namely, One Coat Bond, Clearfil SE Bond and a resin-modified glass ionomer cement (Fuji II LC) and the dentin of non-carious cervical lesions (NCCLs) with FE-SEM, and compared them with the interfaces produced with "normal" dentin. Fifteen human premolars each with a buccal NCCL were used. Cervical cavities were prepared on the lingual surface of the same teeth for the normal (control) dentin. All lesions and prepared cavities were cleaned with a slurry of pumice and water. The teeth were randomly divided among the three products that were applied according to the manufacturers' instructions. For the resin-bonded specimens, the cavities were restored with resin composite. All specimens were stored in 37°C tap water. Resin-bonded specimens were observed using FE-SEM after treatment with 10% phosphoric acid, and 10% phosphoric acid and 5% sodium hypochlorite (NaOCl). The resin-modified glass ionomer cement (RM-GIC) specimens were observed after 10% phosphoric acid and 5% NaOCl treatment. The hybrid layer could be observed for the two adhesive systems in all specimens, but the thickness varied depending on the bonding system used and the dentin substrate. The results suggested that the hybrid layer produced in normal dentin was slightly thicker than that of NCCLs. Further, the hybrid layer thickness decreased in all specimens after NaOCl treatment.link_to_subscribed_fulltex

Raman spectroscopic study of noncarious cervical lesions

The surface of noncarious cervical lesions (NCCLs) consists of sclerosed dentin. This type of dentin may affect the ability of adhesive restorative materials to bond well to its surface, but little information exists on the chemical nature of this dentin surface and how it may be affected during acidic treatment. The inorganic part of normal dentin and dentin from NCCLs before and after acid conditioning with phosphoric acid or polyacrylic acid was investigated. Ten premolars with NCCLs and four human third molars (control) were used. Replicas of NCCLs were examined using scanning electron microscopy (SEM). Surfaces and longitudinal sections of four NCCLs and control dentin discs were analyzed using Raman spectroscopy. The discs and NCCLs were sectioned, and treated with 35% phosphoric acid or 20% polyacrylic acid/3% aluminum chloride, and Raman spectra obtained. The area under phosphate ν1 of the dentin spectrum was computed to obtain a ratio with the area under the second-order spectrum of a silicon phonon comparative standard. Mean phosphate ν1 and silicon phonon ratios from normal dentin and NCCLs were compared using a linear model with repeated measurements and Tukey's pairwise tests. Mean ratios from different locations of the NCCLs were compared using one-way analysis of variance (ANOVA) and Tukey's pairwise tests. SEM micrographs of NCCL surfaces showed variation from relatively smooth with no dentinal tubule openings to surfaces with occluded tubules. The mean phosphate ν1 and silicon phonon ratios for NCCLs were higher than those of normal dentin in all treatment groups (P < 0.05). Ratios from the untreated specimens were higher than those of the polyacrylic acid-treated specimens, and those for the phosphoric acid-treated group were the lowest (P < 0.05). The ratios obtained for the surfaces of NCCLs were higher than those halfway towards the pulp, and those adjacent to the pulp were the lowest (P < 0.05). © The Society of The Nippon Dental University 2005.link_to_subscribed_fulltex

Morphological study of demineralized dentine after caries removal using two different methods

Background: Caries-affected dentine is the usual substrate bonded to in everyday clinical practice. The first step for most of the current dentine adhesive systems is etching or conditioning. It is therefore important to understand the effect of etchant/conditioner on caries-affected dentine. Methods: Twelve extracted carious permanent molars were examined. Six teeth had caries removed using burs after staining with a caries detector dye, and caries from the other six was removed using Carisolv™. After caries removal, three teeth from each group were left untreated. The remaining teeth were sectioned to obtain two normal dentine samples and two caries-affected dentine samples from each tooth. One half of the normal dentine samples and one half of the caries-affected dentine samples were treated with 35 per cent phosphoric acid, and the remaining samples were treated with 20 per cent polyacrylic acid/3 per cent aluminium chloride. The samples were observed using field emission scanning electron microscopy (FE-SEM). Results: Phosphoric acid treated samples showed more obvious intertubular dentine microporosity and greater depth of demineralization in caries-affected dentine. Polyacrylic acid treated samples showed some residual smear layer. However, the peritubular and intertubular collagen network was easily observed in Carisolv™ treated dentine. The depth of demineralization was not as distinct as that of the phosphoric treated samples. Conclusions: From this study it was shown that etched 'normal' dentine and etched caries-affected dentine had different surface appearances. Furthermore, the two caries removal techniques resulted in different caries-affected dentine surfaces after acid treatment that may influence the longevity of bonds from adhesive restorative materials.link_to_subscribed_fulltex

Micromorphological investigation of noncarious cervical lesions treated with demineralizing agents

Purpose: The purpose of this study was to examine the micromorphology of noncarious cervical lesions (NCCL) and the change occurring after acid conditioning. Materials and Methods: Nine wedge-shaped lesions, 9 saucer-shaped lesions, and 5 third molars with prepared cervical cavities were used. All NCCLs exhibited a hard, smooth surface with no discoloration. The teeth were sectioned and divided into three groups, each containing the three lesion types. Teeth in Group I were not etched, and teeth in Groups II and III were etched with 35% phosphoric acid and 20% polyacrylic acidβ% aluminum chloride, respectively. Field emission SEM and atomic force microscopy were used to examine the lesion surfaces. Results: The surfaces of the prepared cervical (control) lesions were covered with a smear layer. Treatment with phosphoric acid and polyacrylic acid resulted in removal of the smear layer, although some residual smear layer was found on the surface treated with polyacrylic acid. The images of the untreated surfaces of NCCL showed highly mineralized dentin with complete obliteration of the dentinal tubules. After treatment with phosphoric and polyacrylic acids, the images revealed demineralization of the surface, which was more pronounced on those treated with phosphoric acid. Conclusion: The mineral deposits on the surface of NCCL decreased the effect of acid conditioning. Although there was no apparent difference between the two forms of NCCL used in this study, further work is needed to better understand these lesions.link_to_subscribed_fulltex

Microhardness and Ca:P ratio of carious and Carisolv™ treated caries-affected dentine using an ultra-micro-indentation system and energy dispersive analysis of x-rays - A pilot study

Background: This study aimed to evaluate microhardness and chemical analysis of carious and caries-affected dentine. The hypothesis tested was that calcium:phosphorous (Ca:P) ratios correlate with microhardness values. Methods: Four carious human third molars were sectioned through the caries lesion in the mesiodistal longitudinal plane. One half of each lesion underwent carious dentine removal using Carisolv™ gel. The cut surfaces were polished, microhardness tested using an Ultra-Micro-Indentation System (UMIS) and elemental analysis performed using energy dispersive analysis of x-rays (EDAX). Results: The microhardness of carious dentine decreased gradually towards the cavity floor, but that for caries-affected dentine showed more variation with depth, having a mean hardness of (0.63±0.18) GPa. Ca:P ratios of carious dentine varied among the four specimens. The mean Ca:P ratio of caries-affected dentine was 1:2.03±0.08. The hypothesis was accepted for active lesions. Conclusions: The use of Carisolv™ to excavate carious tissue can be as effective as rotary instrumentation.link_to_subscribed_fulltex