Fiber-Reinforced Framework in Conjunction with Porcelain Veneers for the Esthetic Replacement of a Congenitally Missing Maxillary Lateral Incisor: A Case Study

This article presents a case of a congenitally missing right maxillary lateral incisor and the contralateral incisor with discolored composite resin restorations. The technique of fiber reinforcement in conjunction with porcelain veneers was used to provide a satisfactory outcome for the patient. The key learning points of the article are the following: proper diagnosis, treatment plan and appropriate utilization of materials are mandatory for a successful result.

Inhibition of human platelet aggregation by nitric oxide donor drugs: relative contribution of cGMP-independent mechanisms

Inhibition of platelet activation by nitric oxide (NO) is not exclusively cGMP-dependent. Here, we tested whether inhibition of platelet aggregation by structurally distinct NO donors is mediated by different mechanisms, partly determined by the site of NO release. Glyceryl trinitrate (GTN), sodium nitroprusside (SNP), S-nitrosoglutathione (GSNO), diethylamine diazeniumdiolate (DEA/NO), and a novel S-nitrosothiol, RIG200, were examined in ADP (8 microM)- and collagen (2.5 microgram/ml)-activated human platelet rich plasma. GTN was a poor inhibitor of aggregation whilst the other NO donors inhibited aggregation, irrespective of agonist. These effects were abolished by the NO scavenger, hemoglobin (Hb; 10 microM, P < 0.05, n = 6), except with high concentrations of DEA/NO, when NO concentrations exceeded the capacity of Hb. However, experiments with the soluble guanylate cyclase inhibitor, ODQ (100 microM), indicated that only SNP-mediated inhibition was exclusively cGMP-dependent. Furthermore, the cGMP-independent effects of S-nitrosothiols were distinct from those of DEA/NO, suggesting that different NO-related mediators (e.g., nitrosonium and peroxynitrite, respectively) are responsible for their actions.

Selective modifiers of glutathione biosynthesis and 'repriming' of vascular smooth muscle photorelaxation

Photorelaxation of vascular smooth muscle (VSM) is caused by the release of nitric oxide (NO) from a finite molecular store that can be depleted by irradiating pre-contracted arteries with visible light. The ability of an 'exhausted' vessel to respond to a further period of illumination is lost temporarily but then recovers slowly as the photosensitive store is reconstituted in the dark. The recovery process, termed repriming, displays an absolute requirement for endothelium-derived NO and is inhibited by pre-treating arteries with ethacrynic acid, a thiol-alkylating agent. Here we demonstrate that agents that up- or down-regulate glutathione (GSH) biosynthesis influence the extent to which the store is regenerated in the dark. Isolated rat tail arteries (RTAs) were perfused internally with Krebs solution containing phenylephrine (PE; mean [PE] +/- s.e.mean: 5. 78+/-0.46 microM) and periodically exposed to laser light (lambda=514.5 nm, 6.3 mW cm(-2) for 6 min). Photorelaxations of control RTAs were compared with those from either (a) vessels taken from animals previously injected i.p. with buthionine sulphoximine (BSO), an inhibitor of gamma-glutamylcysteine synthetase (three injections, 100 mg kg(-1) at 8 h intervals); or (b) isolated RTAs that were perfused ex vivo with oxothiazolidine (OXO), a precursor of cysteine (10(-4) M OXO for 60 min). RTAs from BSO-treated animals exhibited attenuated photorelaxations: the mean (+/-s.e.mean) amplitude of the response recorded after 72 min recovery in the dark was 12.4+/-1.6% versus 21.4+/-2.9% for control arteries (n=5; P<0. 01). Conversely RTAs treated with OXO and allowed to recover for a similar period showed enhanced photorelaxations, 32.6+/-6.3% as compared to 21.4+/-2.9% for control arteries (n=5; P<0.01). A hyperbolic curve fit to repriming curves for BSO-treated and control arteries returned asymptote values (maximum photorelaxations) of (mean +/- s.e.mean) 24.2+/-3.2% and 55.2+/-8.5%, respectively. The level of GSH in RTA extracts was measured by high-pressure liquid chromatography (HPLC). Injecting animals with BSO decreased GSH to 85% of control levels (P<0.05) while treatment of isolated vessels with OXO resulted in a 31% increase above control levels (P<0.05). Thus, drug-induced changes in RTA GSH levels were positively correlated with altered photorelaxations. The results lead us to postulate that the photosensitive store in VSM is generated, at least in part, from intracellular GSH which becomes converted to S-nitrosoglutathione (GSNO) by nitrosating species that are formed ultimately from endothelium-derived NO. The possible physiological significance of a photolabile store of NO in VSM is discussed briefly.

Caries diagnosis: the necessity for a new standard of care

Conclusive research has called for the elimination of the explorer as a means of diagnosing pit and fissure caries. It has been shown to be not only unreliable, but capable of spreading caries and damaging enamel. This technique, however, is still in use in most dental offices and is still taught in our dental schools. The well-intentioned placing of sealants on undiagnosed caries further exacerbates the problem. New technology has provided the means for reliably and conservatively dealing with this problem. These new modalities should become the standard in diagnosis and treatment. Video examination of all pits, fissures, and grooves for changes in light transmission, color, or staining. Microabrasion of all suspect areas at low pressure with 27 mu medical grade alpha alumina. Exposing and staining carious tooth structure with a propylene glycol caries indicator. Removal of decay using microabrasion. Restoration with a bonded composite.