Effect of light- and chemical-cured composites on microtensile bond strength of simplified-step adhesives

Abstract no. 66published_or_final_versio

Van der Woude Syndrome: A report of two cases

Van der Woude syndrome is a rare autosomal dominant condition with high penetrance and variable expression. It consists of a cleft lip and/or palate pits on the vermilion of the lower lip, and hypodontia. Two cases of congenital lip pits with cleft lip and alveolus and an isolated cleft palate are described to illustrate the variable presentation of the clinical features and the importance of early recognition of Van der Woude syndrome because of the genetic implications.link_to_subscribed_fulltex

Chewing gum as a medium for the delivery of anticariogenic therapetuic agents: a review

Objectives. To consider the e"ects of chewing gum on dental plaque and saliva, and to discuss the value of chewing gum as a means of delivering anticariogenic agents. Methods. Literature and data from 1940 to 2007 related to chewing gum and anticariogenic therapeutic agents were sourced using PubMed and hand searches. Results. Chewing of gum increases salivary production and salivary #ow rate. With the increase in salivary #ow, the concentration of bicarbonate and phosphate is higher in stimulated saliva. The resultant increase in plaque pH and salivary bu"ering capacity prevents demineralization of tooth structure. The chewing action also results in the physical removal of plaque and food debris, which assists in cleansing the occlusal surfaces of the teeth. Because gum is repetitively chewed it has a longer period of exposure to the surfaces of teeth than a dentifrice or mouthrinse; thus, it can be a useful adjunct in maintaining oral health, especially if it contains a therapeutic agent that is e"ective topically. Agents that have been added to chewing gum to speci$cally prevent dental caries include: polyols such as xylitol and sorbitol, #uoride, calcium phosphate, carbamide (urea), enzymes, and granules. Conclusions. There is insu!cient published evidence, especially for carbamide, enzymes, and granules, to support the notion that these addictives have a therapeutic role when added to chewing gum. Further investigations are required to justify the anticariogenic claims when chewing gum is the medium of delivery

Factors contributing to the incompatibility between simplified-step adhesives and chemically-cured or dual-cured composites. Part I. Single-step self-etching adhesive

Purpose: To determine if adverse chemical interaction and adhesive permeability are both responsible for the incompatibility between a single-step, self-etching adhesive and chemically-cured or dual-cured composites. Materials and Methods: Bonding was performed with Xeno CF Bond (Dentsply-Sankin), on either hydrated (H) or dehydrated (DH) human dentin. For microtensile bond strength evaluation, a dual-cured hybrid composite (Bis-Core) was activated using: (1) the light-cured (L) mode (base syringe only), (2) delayed light activation (DL) (base syringe left on top of cured adhesive in the dark for 20 min before activation), and 3) the chemically-cured (C) mode (base and catalyst syringes in the dark). A chemical co-initiator (B; BondLink) was also applied to the cured adhesive before coupling with the composite in chemically-cured mode. This resulted in seven experimental groups: (1) L-H (control); (2) DL-H; (3) DL-DH; (4) C-H; (5) C-DH; (6) C-B-H; and (7) C-B-DH. For transmission electron microscopy, the dual-cured composite in the seven groups was replaced with a light-cured microfilled composite (Metafil CX) and an experimental chemically-cured microfilled composite of the same composition. Specimens were immersed in ammoniacal silver nitrate for 24 h. After reduction of the diamine silver ions to silver, undemineralized and unstained sections were examined for nanoleakage within the resin-dentin interfaces of the seven groups. Results: For the light-cured modes, bond strengths fell substantially in DL-H but not in DL-DH. For the chemically-cured modes, bond strengths were lowest in C-H and only increased slightly in C-DH. The use of a chemical co-initiator with the adhesive further improved the bond strength in C-B-H. Only C-B-DH was not significantly different from the control light-cured mode L-H. Two abnormal modes of silver deposition were observed in resin-dentin interfaces. A continuous layer of silver was observed when the chemically-cured composite was applied to the cured adhesive in the absence of the chemical co-initiator (C-H; C-DH). Silver-impregnated water blisters were identified when the chemically-cured composite was coupled to bonded hydrated dentin (C-H; C-B-H). Similar water blisters were seen in DL-H in which adverse chemical interaction should not occur. Conclusion: Adverse chemical interaction between catalytic components of chemically-cured composite and the tested single-step, self-etching adhesive was the major cause of reductions in bond strength, while adhesive permeability was a minor cause of bond strength reduction. The combination of these two factors accounts for the substantial reduction in bond strength when chemically-cured or dual-cured composites were coupled to bonded hydrated dentin.link_to_subscribed_fulltex

Adverse surface interactions between one-bottle light-cured adhesives and chemical-cured composites

Objectives: This study examined the effect of one-bottle adhesives with different acidities on bonding to chemical-cured and light-cured resin composites. Methods: Twenty-four non-carious human third molars were divided into eight groups. A flat dentin surface was created for each tooth. Acid-conditioned dentin surfaces were bonded with Prime&Bond NT (Dentsply), OptiBond SOLO (Kerr), Single Bond (3M) or One-Step (Bisco). Each adhesive group was covered with composite buildups, using either a light-cured (Z100, 3M) or a chemical-cured composite (BisFil 2, Bisco). Specimens were vertically sectioned into 0.9 × 0.9 mm beams. Microtensile bond strengths were recorded and failure modes were classified using a stereoscopical microscope. Four representative beams from each group were further prepared for SEM examination. Results: Two-way ANOVA showed that the effect of adhesive types, composite curing modes and their interaction were statistically significant (P 0.05). However, they were significantly lower when used with the chemical-cured composite (P < 0.01). A positive correlation was observed between the acidity of adhesives and the bond strengths of the chemical-cured composite. Failure occurred predominantly along the composite-adhesive interface, with microporosities on the adhesive surface and voids within the chemical-cured composite. Significance: Air incorporated during mixing of chemical-cured composites only contributed partially to the decreased bond strength observed in simplified-step adhesives. Ultrastructural observations suggested the presence of a surface interaction between the uncured, acidic resin monomers from the oxygen inhibition layer of the adhesive and the initiator components in the chemical-cured composite. © 2001 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved.link_to_subscribed_fulltex

Chemical-cured composite weakens bonding of adhesives by surface interaction

The run-out report for a compressor rotor showed an almost continuous bow between the two bearings, with the maximum run-out of 0.03 mm (0.0012 in)at the inlet to the fourth stage impeller. It had been run in service, and removed for normal maintenance, when the bow was observed. The seven stage compressor rotor was made of 34 Cr Ni Mo 6 steel, which is approximately a 4340 steel. It was just over 3 m in length, with diameters of approximately 265 mm at the disk mounting areas (Fig. 1). Each of the compressor stages was mounted on the rotor at the time of the stress measurement. An evaluation of the residual stress at these locations in the shaft was performed using a nondestructive technique involving critically refracted longitudinal, LCR, ultrasonic waves. The LCR stress measurement data showed compressive stress on the bowed side of the rotor, supporting the conclusion that residual stress is the cause of the bow. At the time that the data were taken, the rotor was horizontal, resting on two stands at the bearing ends. The following is a brief report of the test and the results. Ref. 1 should be consulted for additional detail