https://acawiki.org/api.php?action=feedcontributions&user=Ddg42&feedformat=atomAcaWiki - User contributions [en]2024-03-29T10:46:12ZUser contributionsMediaWiki 1.31.12https://acawiki.org/index.php?title=Material_Selection_for_Direct_Posterior_Restoratives&diff=8746Material Selection for Direct Posterior Restoratives2012-11-30T11:57:45Z<p>Ddg42: Created page with "{{Summary |title=Material Selection for Direct Posterior Restoratives |authors=John O. Burgess, Deniz Cakir |url=http://www.ineedce.com/courses/2067/PDF/1108cei_dentsply_Restorat..."</p>
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<div>{{Summary<br />
|title=Material Selection for Direct Posterior Restoratives<br />
|authors=John O. Burgess, Deniz Cakir<br />
|url=http://www.ineedce.com/courses/2067/PDF/1108cei_dentsply_Restoratives.pdf<br />
|summary=Material Selection for Direct Posterior Restoratives (Summary/Outline)<br />
Dominique Gnatowski<br />
<br />
http://www.ineedce.com/courses/2067/PDF/1108cei_dentsply_Restoratives.pdf<br />
<br />
Abstract <br />
• type of material selected for posterior restoration (filling of molars) depends on patient/individual situation – new technological advances have been made<br />
o types of fillings – amalgam (alloy of silver and mercury) or resin (many different varieties of polymers that vary in chemical composition)<br />
o amalgam – used for long time; successful; however not esthetically pleasing, which has become a high demand<br />
o esthetic restorations – glass ionomers, compomers, composite resin (all types of resins that just vary in chemical composition)<br />
o desirable attributes in material - fluoride release (fluoride – strengthens tooth); wear resistance; low polymerization shrinkage (sometimes after filling is completed, the material shrinks allowing bacteria to enter the cavity again); low polymerization stress (the more a material is resistant to stress, the less likely polymerization shrinkage will occur<br />
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Introduction<br />
• material selection for posterior teeth restoration depends on: patient’s age, caries (cavity) risk, esthetic requirements, how well the tooth can be isolated, and functional demands of the restoration – each material has certain pros and cons in their usage<br />
o compomers, glass ionomers, composite resins – pros: bond to tooth structure chemically; may reinforce tooth; long-lasting; non-invasive procedure; esthetic; good thermal insulators; have fluoride release – cons: clinical limitations (requires more attention to detail during adhesive placement; longer time; more difficult procedure in comparison to an amalgam filling); postoperatively – polymerization shrinkage possible as a result of difficult procedure where there can be poor adhesive placement, all of which lead to possible leakages at the tooth surface<br />
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Posterior Amalgam Restorations<br />
• history of clinical success<br />
o good moisture tolerance since it does not bond to tooth structure chemically – not necessary to keep the tooth isolated and in dry conditions like in resin restorations<br />
o wear resistance – metal alloy – malleable so easily formed into shape of tooth but also strong and durable<br />
o limitations: galvanism (battery effect occurs because of amalgams composition of two metals, usually silver and mercury, in a liquid medium, saliva – produces electric current which leads to break down of amalgam and corrosion) high thermal conductivity, poor esthetics <br />
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• in resin fillings – bonding material must be applied before the resin in order to form a chemical bond between the tooth surface and the resin<br />
o amalgam does not require a bonding material, but one has been developed called the bonded amalgam technique using adhesives (most successful called “4-META-based Amalgambond Plus (Parkell)”<br />
o a bonding agent bonds to dentin (second layer of the tooth from outside in; after the enamel which forms the crown visible on the outside) with a hybrid layer <br />
o bonding resin to amalgam attachment is still mostly mechanical, not chemical <br />
o amalgam use criticized especially in children and decreased in popularity because it contains mercury – however, after many studies and tests, there have been no significant signs of mercury having a negative affect on health<br />
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Fluoride-releasing Materials<br />
• types:<br />
o glass ionomers – useful as liner/base so for deep cavities <br />
• release high levels of fluoride <br />
• low bond strength <br />
• conditioner or primer is needed to improve bond of ionomer to tooth surface – usually weak inorganic acids – clean tooth surface before bonding<br />
• low overall strength – paste/paste resin easier to mix and place but these lower the strength of the system (weaker bonding than powder/liquid resin) <br />
• low wear resistance<br />
• medium fluoride recharge (ability of tooth to uptake fluoride from the environment and incorporate in the tooth structure)<br />
o high-viscosity glass ionomers <br />
• release high levels of fluoride<br />
• medium bond strength<br />
• medium overall strength<br />
• medium wear resistance <br />
• medium fluoride recharge<br />
o resin-modified glass ionomers -> nanofillers added – reduce particle size – smoother, more esthetic appearance<br />
• release high levels of fluoride – increases long-term survival; good for high caries risk patient<br />
• medium bond strength<br />
• low overall strength – not ideal for posterior restorative (on molars)<br />
• low-medium wear resistance – cannot be used if cavity is located at the occlusal surface of the tooth (top surface) because it receives the most stress<br />
• high fluoride recharge – increases long-term survival; good for high caries risk patient<br />
o compomers – blends of resin composite and glass ionomer<br />
• release medium levels of fluoride – between resin composites and glass ionomers – successful on use for children’s teeth – bonding system uses adhesive which blocks fluoride uptake in dentin, thus only releasing fluoride onto the outer tooth surface<br />
• high bond strength<br />
• medium overall strength<br />
• medium wear resistance – ideal for children’s teeth<br />
• medium fluoride recharge <br />
o fluoride releasing composites <br />
• release low levels of fluoride – not good for high caries risk patients<br />
• high bond strength<br />
• high overall strength<br />
• high wear resistance – best of any fluoride-releasing material<br />
• low fluoride recharge – not good for high caries risk patients<br />
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Composite Resin<br />
• pro: improved wear resistance – gaining popularity in usage for posterior restorations as opposed to solely bicuspids (frontal teeth)<br />
• con: composite resin shrinkage during polymerization – causes eventual breakdown and thermal sensitivity<br />
o visible light cured composite is placed in prepared cavity and light cured in 2mm incredments– photoinitiators in the resin (camphoroquinone, usually in the presence of an amine accelerator/catalyst) are activated (more chemistry detail to analyze here)<br />
o combo of photoinitiator types may cause problems because they need to absorb different wavelengths of light for their reactivity <br />
o usually LED lights are used but quartz-tungsten-halogen or plasma arc curing lights polymerize all photoinitiators <br />
o often the wrong type of light is used leading to low wear resistance in the final cured product <br />
• soft-curing lights – decrease polymerization stress – unproven results<br />
o slows rate of polymerization with initial low intensity or short pulses of light – allows for polymer chain movement – provides stress relief <br />
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Flowable Composites<br />
• composite resins but with a lower viscosity because of lower filler load which allows them to better adhere to the cavity surface – may reduce polymerization stress (no clear consensus based on numerous studies has been reached)<br />
o con: lower filler load may reduce wear resistance - however percentage of filler may be chosen relative to type of tooth in concern<br />
• even though they have higher polymerization shrinkage than composite resins – flowables are more elastic – provide stress relief - debate is still continued<br />
o main use: cavity adaptation<br />
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Composite Resin Shrinkage and Stress<br />
• in composite resins, polymerization shrinkage 3.7%-0.9%<br />
o new resin monomers developed to reduce polymerization shrinkage stress<br />
• Filtek LS –> silorane ring-opening chemistry 0.7%-0.9%<br />
• N’Durance -> dimer chemistry 1.2%<br />
• Thiolene polymers (thiolene/thiol epoxy hybrid networks) – not available commercially – 90% less stress than in control dimethacrylate resin<br />
• C-factor (shape of preparation) – ratio of bonded surfaces to unbounded surface in final restoration – more stress at the margins (cavities located on frontal teeth or near gums) – no ideal solutions<br />
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Low stress Composite<br />
• Stress Decreasing Resin (SDR) Technology – reduces internal stress from polymerization shrinkage – instead of 2mm increments of polymerization it uses 4mm increments <br />
o Polymerization modulator embedded chemically in the resin backbone <br />
• interacts with the photoinitiator to regulate a slow modulus development while at the same time still allowing a steady rate of polymerization or conversion of the material <br />
• modulator allows more linear and branching chain propagations and conversions in the polymerization – slower modulus development without increasing cross-linking density – decreases stress <br />
• SDR highly translucent – high light transmission allows for bulk polymerization<br />
o Used as a base or filler up until enamel layer of tooth - cannot be used on the surface of the tooth because of its low wear resistance (high shrinkage) – highly filled material should be placed on top surface<br />
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<br />
Case study<br />
• Procedure with photographs of a restoration using SDR technology<br />
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<br />
Summary<br />
• Each material has pros and cons to its usage - should be personalized to each clinical situation and needs of the patient; there have been many new developments in esthetic composite resins that cause low polymerization shrinkage and low stress, allowing for even more options and therefore accuracy in restorations<br />
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|journal=Dental CE Digest (PennWell Publications)<br />
|pub_date=2011<br />
|subject=Chemistry<br />
}}</div>Ddg42https://acawiki.org/index.php?title=User:Ddg42&diff=8745User:Ddg422012-11-30T11:40:32Z<p>Ddg42: Created page with "{{User |name=Dominique Gnatowski }}"</p>
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<div>{{User<br />
|name=Dominique Gnatowski<br />
}}</div>Ddg42