Effect of desensitizing agents on the microtensile bond strength of two‐step etch‐and‐rinse adhesives to dentin

Desensitizers can be used to control postoperative sensitivity in adhesive restorations. The aim of this study was to evaluate the effect of desensitizing agents on the bond strength of two‐step etch‐and‐rinse adhesive systems to dentin. Forty‐two human molars were sectioned to obtain 3‐mm‐thick dentin discs. The discs were divided into three groups (n = 14 in each) – no‐treatment control group (CT), and oxalic acid [BisBlock (BB)] and calcium phosphate [Desensibilize Nano‐P (NP)] desensitizers – before the application of two adhesive systems [Adper Single Bond Plus (SB) and One‐Step Plus (OSP)]. A nanoparticle composite resin was used to create a 3‐mm‐thick build‐up. The specimens were stored in distilled water for 24 h before a microtensile bond‐strength test was performed. The failure modes were determined using a stereomicroscope at 100 × magnification. Specimens were sectioned perpendicular to the interface for scanning electron microscopy analyses. The CT‐SB group exhibited the highest bond strength, differing significantly from BB‐SB and BB‐OSP groups. Mixed failures were prevalent for all groups. Scanning electron microscopy revealed a continuous hybrid layer and resin tags in all groups. Dentin bond strength of etch‐and‐rinse adhesive systems was reduced by an oxalic acid desensitizer but was not affected by a calcium phosphate‐containing desensitizer.     

Fiber‐post bond strength in canals obturated with a cross‐linked gutta‐percha core obturator

The aim of this in‐vitro study was to evaluate the bond strength of fiber posts cemented in a root canal filled using various root‐canal obturation techniques. A total of 33 monoradicular samples, treated endodontically, were randomly assigned to three groups according to the root‐canal obturation technique: group 1, continuous‐wave technique; group 2, plastic‐obturator‐core technique; and group 3, cross‐linked gutta‐percha obturator‐core technique. Fiber posts were luted in each sample and each was sectioned perpendicular to the post axis. The push‐out test was performed using a universal machine and the maximum failure load was recorded in MPa mm^?2. Several samples were randomly chosen for scanning electron microscopy evaluation. The mean debris and dentinal tubule‐opening scores were calculated separately in the coronal and apical portions. Bond strength was significantly higher in group 1 than in groups 2 and 3. Debris scores were significantly higher in the apical portion of groups 2 and 3 than in group 1. Within the limitations of this study it can be affirmed that thermoplasticized alpha gutta‐percha seemed to worsen the cleaning of post‐space walls and hence reduced fiber‐post bond strength.     

Enamel and dental anomalies in latent‐transforming growth factor beta‐binding protein 3 mutant mice

Latent‐transforming growth factor beta‐binding protein 3 (LTBP‐3) is important for craniofacial morphogenesis and hard tissue mineralization, as it is essential for activation of transforming growth factor‐β (TGF‐β). To investigate the role of LTBP‐3 in tooth formation we performed micro‐computed tomography (micro‐CT), histology, and scanning electron microscopy analyses of adult Ltbp3‐/‐ mice. The Ltbp3‐/‐ mutants presented with unique craniofacial malformations and reductions in enamel formation that began at the matrix formation stage. Organization of maturation‐stage ameloblasts was severely disrupted. The lateral side of the incisor was affected most. Reduced enamel mineralization, modification of the enamel prism pattern, and enamel nodules were observed throughout the incisors, as revealed by scanning electron microscopy. Molar roots had internal irregular bulbous‐like formations. The cementum thickness was reduced, and microscopic dentinal tubules showed minor nanostructural changes. Thus, LTBP‐3 is required for ameloblast differentiation and for the formation of decussating enamel prisms, to prevent enamel nodule formation, and for proper root morphogenesis. Also, and consistent with the role of TGF‐β signaling during mineralization, almost all craniofacial bone components were affected in Ltbp3‐/‐ mice, especially those involving the upper jaw and snout. This mouse model demonstrates phenotypic overlap with Verloes Bourguignon syndrome, also caused by mutation of LTBP3, which is hallmarked by craniofacial anomalies and amelogenesis imperfecta phenotypes.     

Non‐carious cervical lesions: a scanning electron microscopic study

Background: Examining non‐carious cervical lesions using scanning electron microscopy (SEM) provides an opportunity to clarify their complex aetiology. This study aimed to examine the morphological forms of non‐carious cervical lesions found within a sample of extracted human permanent anterior teeth using scanning electron microscopy. Methods: Five examples of non‐carious cervical lesions from each of eight different morphologic categories were replicated and examined using scanning electron microscopy. Results: In total, 40 non‐carious cervical lesions were examined at magnifications ranging from 10× to 2605× magnification. Qualitative ultrastructural features evident in the lesions were described and classified according to their appearance. A total of 13 different qualitative features were observed throughout the sample of NCCLs. Conclusions: SEM highlighted a broad range of microscopic features of NCCLs, providing valuable insights into their complex, multifactorial aetiology.     

Effect of two storage solutions on surface topography of two root‐end fillings

The effect of different storage solutions on surface topography of mineral trioxide aggregate (MTA) and new experimental cement (NEC) as root‐end fillings was investigated. Twenty‐four single‐rooted teeth were cleaned, shaped and obturated in a same manner. After root‐end resection, 3‐mm deep root‐end cavities were ultrasonically prepared. Samples were randomly divided into four test groups (A1‐A2‐B1‐B2, n = 6). Root‐end cavities in groups A and B were filled with MTA and NEC, respectively, and were then stored in 100% humidity for 24 h. The samples of groups 1 and 2 were, respectively, immersed in normal saline (NS) and phosphate buffer saline solutions for 1 week. The samples were imaged under stereomicroscope before and after immersion and were then investigated and analysed by scanning electron microscopy (SEM) and energy dispersive X‐ray analysis (EDXA). Results showed significant difference among studied groups. Surface topography of all samples was altered by crystal formation and precipitation on root‐end fillings except for group A1 (MTA–NS). SEM and EDXA results showed that the composition and structure of precipitated crystals were comparable with that of standard hydroxyapatite. It was concluded that biocompatibility, sealing ability, and cementogenic activity of MTA and probably NEC may be attributed to this fundamental bioactive reaction.     

Mechanism of action of tin‐containing fluoride solutions as anti‐erosive agents in dentine – an in vitro tin‐uptake,tissue loss,and scanning electron microscopy study

Ganss C, Hardt M, Lussi A, Cocks A‐K, Klimek J, Schlueter N. Mechanism of action of tin‐containing fluoride solutions as anti‐erosive agents in dentine – an in vitro tin‐uptake, tissue loss, and scanning electron microscopy study. Eur J Oral Sci 2010; 118: 376–384. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci Solutions containing tin and fluoride exhibit remarkable anti‐erosive properties with tin ions as a major agent. To elucidate its mechanism of action in dentine, the tin uptake on and in the tissue was investigated and related to histological findings and substance loss. Samples were treated twice daily, each treatment lasting for 2 min, with fluoride solutions [pH 4.5; 1,500 parts per million (p.p.m.) F] containing 2,100, 1,400, or 400 p.p.m. Sn as SnCl₂. In experiments 1 and 2, samples were eroded with citric acid (pH 2.3) six times each day, each treatment lasting for 5 min; in experiment 2, the demineralized organic matrix was continuously digested by collagenase; in experiment 3, no erosive challenges were performed. Sample surfaces and cross‐sections were investigated using energy dispersive X‐ray spectroscopy, scanning electron microscopy, and profilometry. Surface retention of tin was found in almost all treatment groups and was highest in experiment 2. On cross‐sections, tin was retained within the organic matrix; in mineralized areas, tin was found mainly within a depth of 10 μm. Test solutions inhibited substance loss significantly; in experiment 2, the effect was dose‐dependent. Erosion inhibition seemed to depend mainly on the incorporation of tin in the mineralized dentine when the organic portion was preserved, but on surface precipitation when the organic portion was continuously digested.     

Distribution and structure of the initial dental enamel formed in incisors of young wild‐type and Tabby mice

Mouse incisor enamel can be divided into four layers: an inner prism‐free layer; an inner enamel with prism decussation; outer enamel with parallel prisms; and a superficial prism‐free layer. We wanted to study how this complex structural organization is established in the very first enamel formed in wild‐type mice and also in Tabby mice where enamel coverage varies considerably. Unworn incisors from young female wild‐type and Tabby mice were ground, etched, and analyzed using scanning electron microscopy. In both wild‐type and Tabby mice, establishment of the enamel structural characteristics in the initially formed enamel proceeded as follows, going from the incisal tip in an apical direction: (i) a zone with prism‐free enamel, (ii) a zone with occasional prisms most often inclined incisally, and (iii) a zone where prism decussation was gradually established in the inner enamel. The distribution of enamel in Tabby mice exhibited considerable variability. The sequence of initial enamel formation in mouse incisors mimics development from a primitive (prism‐free) structure to an evolved structure. It is suggested that genes controlling enamel distribution are not associated with genes controlling enamel structure. The control of ameloblast configuration, life span, organization in transverse rows, and movement is important for establishing the characteristic mature pattern of mouse incisor enamel.     

Clinical and scanning electron microscopy evaluation of the Er,Cr:YSGG laser therapy for treating dentine hypersensitivity: short‐term,randomised, controlled study

Er,Cr:YSGG laser is a rising treatment option for dentine hypersensitivity (DH). However, there is no data available concerning the scanning electron microscope (SEM) evaluation of the clinical application of Er,Cr:YSGG laser in the treatment of DH. The aim of this study was to evaluate and compare the desensitising and tubule occlusion effects of Er,Cr:YSGG laser with different power settings. Twenty patients (60 teeth) participated in this study. For each patient, teeth were randomised to 3 groups. In groups 1 and 2, patients were treated with Er,Cr:YSGG laser at 0·25 and 0·5 W, respectively. In control group, same laser was applied without laser emission. DH was assessed for all groups with a visual analogue scale (VAS). When compared with the baseline data and control group, in both active treatment groups laser irradiation provided a desensitising effect immediately after treatment (P < 0·001). In group 2, VAS scores were significantly lower than group 1. The tubule diameters in the both laser groups were significantly smaller than the control group (P < 0·01). When group 1 compared with group 2, group 2 showed significantly smaller tubule diameters (P < 0·001). Both 0·25 and 0·5 W laser irradiation were effective for the treatment of DH; however, 0·5 W laser irradiation showed best results for the decrease in VAS scores. The SEM findings of the reduction in number/patency of dentine tubules seem to be related to the clinical findings, which were associated with improvement in treatment efficacy.     

Promotion of adhesive penetration and resin bond strength to dentin using non‐thermal atmospheric pressure plasma

Non‐thermal atmospheric pressure plasmas (NT‐APPs) have been shown to improve the bond strength of resin composites to demineralized dentin surfaces. Based on a wet‐bonding philosophy, it is believed that a rewetting procedure is necessary after treatment with NT‐APP because of its air‐drying effect. This study investigated the effect of ‘plasma‐drying’ on the bond strength of an etch‐and‐rinse adhesive to dentin by comparison with the wet‐bonding technique. Dentin surfaces of human third molars were acid‐etched and divided into four groups according to the adhesion procedure: wet bonding, plasma‐drying, plasma‐drying/rewetting, and dry bonding. In plasma treatment groups, the demineralized dentin surfaces were treated with a plasma plume generated using a pencil‐type low‐power plasma torch. After the adhesion procedures, resin composite/dentin‐bonded specimens were subjected to a microtensile bond‐strength test. The hybrid layer formation was characterized by micro‐Raman spectroscopy and scanning electron microscopy. The plasma‐drying group presented significantly higher bond strength than the wet‐bonding and dry‐bonding groups. Micro‐Raman spectral analysis indicated that plasma‐drying improved the penetration and polymerization efficacy of the adhesive. Plasma‐drying could be a promising method to control the moisture of demineralized dentin surfaces and improve the penetration of adhesive and the mechanical property of the adhesive/dentin interface.     

Micro-shear bond strength and surface micromorphology of a feldspathic ceramic treated with different cleaning methods after hydrofluoric acid etching

Objective

The aim of this study was to evaluate the effect of feldspathic ceramic surface cleaning on micro-shear bond strength and ceramic surface morphology.

Material and Methods

Forty discs of feldspathic ceramic were prepared and etched with 10% hydrofluoric acid for 2 minutes. The discs were randomly distributed into five groups (n=8): C: no treatment, S: water spray + air drying for 1 minute, US: immersion in ultrasonic bath for 5 minutes, F: etching with 37% phosphoric acid for 1 minute, followed by 1-minute rinse, F+US: etching with 37% phosphoric acid for 1 minute, 1-minute rinse and ultrasonic bath for 5 minutes. Composite cylinders were bonded to the discs following application of silane and hydrophobic adhesive for micro-shear bond strength testing in a universal testing machine at 0.5 mm/min crosshead speed until failure. Stereomicroscopy was used to classify failure type. Surface micromorphology of each treatment type was evaluated by scanning electron microscopy at 500 and 2,500 times magnification.

Results

One-way ANOVA test showed no significant difference between treatments (p=0.3197) and the most common failure types were cohesive resin cohesion followed by adhesive failure. Micro-shear bond strength of the feldspathic ceramic substrate to the adhesive system was not influenced by the different surface cleaning techniques. Absence of or less residue was observed after etching with hydrofluoric acid for the groups US and F+US.

Conclusions

Combining ceramic cleaning techniques with hydrofluoric acid etching did not affect ceramic bond strength, whereas, when cleaning was associated with ultrasound, less residue was observed.     

Structure of the bone‐titanium interface in retrieved clinical oral implants

7 clinically stable, "osseointegrated", titanium implants, inserted in human jaws for l–16 years, were retrieved for morphological analysis of the bone‐titanium interface, using 3 different preparation techniques. The bone‐titanium interface varied as judged from light microscopy of ground sections. The threads of the implants were well filled 79–95% with dense lamellar bone as quantified with morphometry. A large fraction of the implant surface (56–85%) appeared to be in direct contact with the mineralized bone. In general, the non‐boric areas consisted of pockets with osteocytes, bone marrow tissue and/or vessels. Sections were prepared for light microscopy and transmission electron microscopy using a fracture technique. where the implant was separated from the embedded tissue before sectioning, and an electropolishing technique, where the bulk part of the implant was electrochemically removed. In areas judged as direct mineralized bone‐titanium contact in the light microscope. the interfacial structure varied at the ultrastructural level. In areas along the interface, unmineralized tissue was present either as a narrow 0.5–l μm wide zone containing collagen fibril or as deeper pockets containing osteocytes or vessels. In areas with mineralized bone contact. an amorphous granular layer (100–400 nm wide) with no mineral was observed in the innermost interface bordering the mineralized bone, with an electron‐dense lamina limitans‐like line (approximately 50 nm thick). It is concluded that the bone‐titanium interface of the 7 clinically retrieved titanium oral implants examined in the present study bone was heterogenous. In areas of a direct mineralized bone‐titanium contact at the ultrastructural level. mineralized bone reached close to the implant surface, but was separated by an amorphous layer. 1 being 100–400 nm thick.