Dental Tech Quiz 2 PDF

Intro to dental tech quiz 2 Types of waxes (10) Baseplate wax Border wax Box wax Card wax Corrective impression wax Inlay pattern wax Occlusal registration wax Resin wax Amorphous materials with high molecular weight and low surface energy Wax low thermal...

Intro to dental tech quiz 2 Types of waxes (10) Baseplate wax Border wax Box wax Card wax Corrective impression wax Inlay pattern wax Occlusal registration wax Resin wax Amorphous materials with high molecular weight and low surface energy Wax low thermal conductivity High heat capacity Insoluble in water Dental wax Made up of 2 or more different waxes with other additives (natural and synthetic ) ○ Gums ○ fat ○ Fatty acids ○ oils ○ Resins ○ Pigments Used for ○ for casts ○ Construction of non metallic denture bases ○ Registering jaw relations ○ Lab work Natural waxes Organic compounds Melting range since they are not pure compound May have variable properties due to impurities Carnauba: Hard High melting Type: plant based (forms as flakes on leaves) Beeswax:  Brittle Moderate melting point Type : Insect Paraffin: Soft Low melting point Petroleum based Not really natural wax Synthetic waxes Controlled production = uniform quality Properties without impurities Melting point not melting range Designed and produced for specific use Classes of wax 1. Impression waxes Originally impression wax Does not work well with undercuts Soft waxes can be used in the mouth Peripheral waxes used on stock trays with alginate ○ To improve peripheral border molding ○ Aid in comfort ○ Red ,blue clear ○ Pliable can be used without heating 2. Pattern waxes Used to form object patterns for lost wax casting technique ○ Crown and bridges ○ Partial dentures Lost wax technique : eliminate wax and is replaced with acrylic or ceramic, used a lot. First intro was in 1907 Direct technique - wax molded in the patient's mouth. Wax used to restore something for an impression Indirect technique- wax formed on a model in lab aka everything techs do Inlay casting wax (functional anat waxes) ○ paraffin , gum dammar, carnauba ○ Must be strong and stable ○ Must produce fine detail, easily carved without flaking and cracking, burnout cleanly (leave no residue) Partial denture wax patterns  ○ Complex shapes made regular with required contours and tapers for flexibility ○ Most use patterns today for clasps and bars ○ Sheet wax used for relief or exact thickness ○ acrylic/ saddled retention grids ○ Veined wax for palates gives tactile sensation for tongue for framework ○ Pattern wax for surface of maxillary major connectors 3. Processing wax Used to facilitate lab work , not part of final prosthetic ○ Boxing ,Utility, Beading Util - white (base plate), border for sprinkling beading-red, comes in strips Pliable and sticky Easily formed and applied with little to no heat Used for isolating surfaces ○ Sticky Beeswax, paraffin and resins. Brittle, ridgid and high melting point, does not clean off well Used for temp luting (crazy glue) Toffee coloured, sticks and chunks ○ Sprue channels for metal, ceramics or acrylic to enter mold: tube like ○ undercut/ blockout wax Very hard High melting point Beeswax, resin Landing area: utility (beading wax), has lots of accuracy. Needs to be sealed otherwise gypsum will flow through or leads to porosity Set up wax is hard, able to be used in the mouth without softening or distortion Wax in digital Waxes used in digital processing are synthetic blends to control properties Resins added to allow chemical hardening Wax can be printed to build designed restoration  Incisive papillae has lots of nerves, patient can feel burning sensation if it is compressed. Also allergy to monomer can lead to burning sensation Patients that have some to most teeth, bite blocks will use wax Full set of teeth don't require bite block, teeth will fit together like puzzle pieces unless patient has irregular bite Polymers High molecular weight, chain like molecule, repeating group of atoms derived from small molecules ( monomers) to build chain Polymethyl Methacrylate Acrylic (PMMA) First used as a glass sub ( pixie glass) 1928 Used as a thermoplastic ( pressed or injected while it's hot) 1937 became a denture base material As a denture base: more resistant, prevents teeth and bone from resorption Mer Chem unit, large substrate of a macromolecule Made up of O,H,C Monomer is basic unit of pmma Low molecular weight Cross Linking Joining polymers together by covalent bonds Adds strength and stiffness Copolymer- type of polymer produced by polymerization Flat teeth = smooth surface, hard to chew food which results in stomach working Overtime , stomach will hurt A polymer made by reaction of two monomers with units of more than one kind Alternating, random and block  Different mer change to pro Molecular weight Measured in Daltons Different molecules of the same compounds may have different weights Weight is higher in longer chains Weight changes the characteristics of acrylic Higher mole weight Brittle More crosslinking harder/stiffer Higher softening temp More brittle Low mol weight Less crosslinking Weaker/softer Lower softening temp Less brittle Polymerization- low molecular weight are converted into chains of polymer with a high molecular weight 1. Condensation polymerization Change in the mers during curing Atoms are split off to form smaller molecules during reaction ○ Byproduct is water or alcohol Final mers are smaller than original Dimension change: shrinkage Polysiloxane 2. Addition polymerization All atoms are used in final product No byproduct (mers are unchanged) Little shrinkage upon curing Acrylics, polyether Polymerization steps: Initiation ○ external initiator (heat light chemical) creates an active site where other mers can join. ○ Requires an activator ○ initiator = starts , activator = turn on Propogation (multiplying) ○ Monomers or repeating units attach to the mol chain, propagating the chain length ○ Continues with no added energy Termination ○ Growth is terminated through neutralization of the reactive center ○ Process continues until all are gone ○ In freshly cured acrylic, residual monomers remain ( sticky feeling on light cure). Can cause allergies ○ Dehydration will shrink denture Types of acrylic (6) 1. Heat cure 2. Auto-polymerization (cold cure) 3. Tinting resin 4. Tooth shade 5. Soft liner 6. Vinyl resin and polysterenes Methods of of curing (3) Heat ○ Used for most denture bases ○ Processed under heat and pressure ○ Heat starts starts reaction , activating the initiator Benzoyl peroxide (BPO) Cold cure/auto-polymerization/self-cure ○ Chemical activator (dimethyl-p-toluidine) starts reaction, activates initiator BPO ○ Used to repair acrylic,ortho,fluid resin, soft denture liners  ○ More dimensionally stable because less temp stress ○ Less strength than heat cured ○ Placed in pressure pot to reduce bubbles (acrylic palate) Light polymerizing ○ Activator is camphoroquinine ○ Custom trays, occlusal rims, blockout resin ○ Cures faster in well lit rooms Thermoplastics- comfortable Polymer that can be softened by heat and pressure then cooled without any chemical change (night guard) Will revert back to cured place Thermosetting- mouth guard Polymers that solidify during fabrication and cannot be softened by heat without altering chemical comp Crosslinked polymers Softer material Duolaminate - inside thermoplastics, outside hard acrylic. Used to prevent sleep apnea and clenching Warpage - curing shrinkage (polymerization or thermal) Bubbles caused by: Temp too high Cure too quick Acrylic too soft Not enough pressure Impuriteies