How does GIC bond to dentin?
The chemical adhesion of GIC to enamel and dentin is achieved by reaction of phosphate ions in the dental tissue with carboxylate groups from the polyacrylic acid. Electro-neutrality is maintained by the displacement of calcium ions with the phosphate ions [64]. The glass-ionomer cements bond to dentin with values of tensile bond strength reported between 1 and 3 MPa [18]. These low values were observed due to the sensitivity of GIC to moisture during setting. The bond strength has been improved to 11 MPa by treatment of the dentin with a polycarboxylic acid cleaning agent [7,10]. Chemical adhesion of GIC to the hard tissue of teeth through the combination of polycarboxylic acids with hydroxyapatite has been cited as the most important advantage of the GIC. The ionic bonding mechanism between the acid and the hydroxyapatite is supported by observations that bond strength to enamel is greater than those to dentin, in correspondence with the relative amounts of hydroxyapatite in the two dental hard tissues [65]. It has been proposed that bonding results in polyacrylate ions replacing phosphate ions in the surface structure of hydroxyapatite. Although the exact mechanism is still unknown, it seems likely that it involves good wetting of the GIC and the subsequent formation of ionic bonds [66]. GIC bond directly to dentin and enamel, even in the presence of a smear layer. However, surface conditioners, such as polycarboxylic, citric or phosphoric acids, have been found to improve bond strength [67]. The conditioner acts as an etching agent which removes the smear layer from the dentin tubuli. The acids demineralise and penetrate a dentin surface layer to a depth of approximately 1 µm [68] and prepare for a chemical bonding.
What are the different types of direct restorative materials?
Different types of direct restorative materials are used in daily dental practice. The most common, next to amalgam, are resin composites, and glass-ionomer cements (GICs). Amalgam, with its long clinical history, is inexpensive and easy to handle. However, the possible toxicity caused by mercury and poor esthetics are disadvantages [2]. Resin composites are the most esthetically accepted material with satisfactory physical properties [5]. They show their drawbacks in a being a highly expensive, time-consuming and technique-sensitive adhesive procedure [6,7]. Glass-ionomer cements may be used in a wide range of clinical applications due to the ability to modify their physical properties by changing the powder/liquid ratio or chemical formulation [8]. The glass-ionomer cements are esthetically more attractive than metallic restorations [9]. In addition, by incorporating fluorine, they exhibit an anticariogenic potential, and they have good biocompatibility and chemical adhesion to mineralized tissue [10]. On the other hand, poor mechanical properties, such as low fracture strength, toughness and wear, limit their extensive use in dentistry as a filling material in stress-bearing areas [11,12]. In the posterior dental region, glass-ionomer cements are mostly used as a temporary filling material [13]. The requirement to strengthen those cements has lead to an increasing research effort into reinforcement concepts. Several former approaches dealt with incorporation of second phase ceramic or glass fibers or with metal particles [14]. Encouraging results were also obtained by compounding reactive glass fibers [15,16].
How does fluoride help prevent caries?
It is common knowledge that fluoride is the most effective agent in caries prevention [69]. Fluorides may act in different ways: The metabolism of the bacteria that cause caries is inhibited and the resistance of enamel and dentin is increased due to the remineralization of porous or softened enamel and dentin. Usually fluoride is applied as a solution, paste or varnish covering the whole dentition. The clinical experience of the anticariogenic effect indicates the benefits from fluoride releasing restorative materials [70]. However, a sustained, long-term fluoride release especially in marginal gaps between filling material and tooth help prevent secondary caries of the dental tissues [14]. For conventional GIC, an initial release of up to 10 ppm and a constant long-term release of 1 to 3 ppm over 100 months was reported [70]. This release (measured in vitroin distilled water) was evidenced to be capable of secondary caries prevention. In contrast, resin composite and compomer materials exhibit a reduced release between 0 and 1 ppm within the first seven days of water storage [71].
Is GIC a good material for dental?
GIC are clinically attractive dental materials and have certain unique properties that make them useful as restorative and adhesive materials. This includes adhesion to moist tooth structure and base metals, anticariogenic properties due to the release of fluoride, thermal compatibility with tooth enamel, biocompatibility and low toxicity. However, limitations in their applications may result from the low mechanical strength and toughness [40].
What is the cheek shake technique?
The cheek shake isn’t necessarily a common practice. Only a handful of dentists use this method, but the ones who do often swear by it. By shaking your cheek, the dentist is giving your brain a distraction from the pain of the anesthesia shot.
Does the cheek shake work?
So, does the cheek shake technique work? Yes and no. Yes, it works to minimize some of the pain. However, consider our earlier example. When you hit your hand on a corner and you start to shake your hand, does the pain immediately subside? You’re distracted, but the pain is still there for a few minutes.
How do you stop the pain from a dental injection?
As is the case with many things today, technology has offered us an alternative to the cheek shake technique that is much more effective. The DentalVibe Comfort Injection System is an FDA-approved device that helps dentists deliver pain-free injections. The DentalVibe is a cordless, rechargeable, handheld device.