Dental Materials Exam 2

What are the characteristics of PFM crowns?

PFM crowns combine porcelain and metal, providing strength and durability, with a 5-year survival rate of 94%. Can be used as single-unit crowns or multi-unit bridges.

Before strong esthetic ceramics were developed, the most used esthetic restorations in crown and bridge procedures were combos of what?

Porcelain and Metal.

All of the following can cause porcelain/ceramic failure except:

• Occlusal loading

• Porcelain having more thermal expansion than the metal

• Compatible coefficients of thermal expansion of the porcelain and the metal

• Inadequate oxide layer at the interface of the porcelain and

Porcelain having more thermal expansion than the metal.

What are the advantages of PFM crowns?

Strength and durability provided by the fusion of oxides on the metal internal core and esthetic porcelain covering at high temp.

What type of polishing is recommended for ceramic restorations?

Fine diamond burs are recommended, starting with coarser ones and progressing to finer, using polishing pastes for a smooth surface.

What polishing pastes are typically used?

Aluminum oxide for safety, but some pastes are diamond paste if the objective is to produce luster or high shine.

How should polishing ceramic restorations be accomplished?

Light touch and low speed with water spray should be used when polishing.

What are the components of CAD/CAM systems?

An optical scanner, a computer with design software, and a milling device.

What does the optical scanner do?

It can make a digital impression of tooth preps, opposing teeth, and the bite.

What does the design software do?

It's used to design the restoration and get proper contacts, contours, and shapes. The design is sent to the milling machine, which cuts a ceramic block into the restoration.

CAD/CAM technology can be used to produce what?

Monolithic single-unit inlays, onlays, crowns, and veneers, and to make ceramic cores for crowns and bridges that are veneered with porcelain or other materials

How are porcelain restorations stained?

Stained by color modifiers containing metal oxides, applied to mimic natural imperfections and improve color. Glazes are used to give a shiny enamel appearance.

What causes fractures in PFM crowns?

Small cracks in porcelain from a single heavy load or repeated loads over time, poor bond of porcelain to metal due to inadequate or too thick oxide layer, and incompatibility of thermal expansion.

What is translucency?

Allow light to pass through into the body, but do not resemble tooth structure and pass in an unaltered path.

What is reflectance?

The surface of a ceramic reflects light that hits it. Some of the light is

reflected back.

What is opacity?

Opaque materials do not allow light to pass through; they either reflect or absorb it.

What is vitality?

A more lifelike appearance of a material, often seen in glass-based ceramics.

What are the advantages of ceramic restorations?

Esthetics, biocompatibility, wear resistance, color stability, and stain resistance.

What are the disadvantages of ceramic restorations?

Brittleness, wear on opposing enamel/restorations, difficult/unable to repair, needs 2 appointments, and difficult to polish in the mouth.

What is the process for placing amalgam?

Place t-matrix and wedge

Activate amalgam capsule in trituator

Place mixed amalgam in well, fill both ends of amalgam carrier

Place into prep and pack down amalgam with condenser

Continue to fill prep and after prep is overfilled burnish

Use the explorer tip to carve away excess amalgam

Remove matirc retainer and use interproximal carver to remove excess material

After amalgam is set floss contacts and check bite

Instruct patient to avoid chewing in that area until the next day.

What causes corrosion in amalgam restorations?

A chemical reaction between amalgam and substances in food and

saliva, resulting in oxidation. It also takes place within amalgam through interaction of its metal components.

What are the effects of corrosion?

It weakens amalgam over time, stains the surrounding tooth, and can deteriorate margins.

What is amalgam creep?

Gradual change in the shape of the restoration due to the compression of chewing and opposing teeth. High copper alloys exhibit far less creep.

What bonding agents are used under amalgams?

Adhesive resins are with method similar to that used in composites.

Which metal has the highest allergy incidence in base metals?

Nickel has the highest incidence of allergic response, with a rate of 9-12%.

What the metal can cause allergic reaction?

Beryllium is toxic and can cause chronic lung scarring and difficulty breathing and allergic reactions with skin rashes. Once exposed the individual is at a risk of lifetime exposure.

What are endodontic posts?

Dowels or rods placed in the canal space after RCT to retain core buildup for final restoration.

What is the difference between actives and passives in posts?

Actives engage the root canal surface with threads like a screw, and passives are cemented in without engaging the canal walls.

What are characteristics of parallel posts?

They transmit less stress than tapered posts.

What do tapered posts do?

Place a wedging force on the root having a higher risk of fracture.

What are characteristics of preformed posts?

They are are available from many commercial sources and are by far the most commonly used, can be used in most situations, are inexpensive, and can be placed in one appointment.

What are the characteristics of ortho wire?

A wrought metal that may be soft and easily shaped or it may resist bending and wires are currently mostly composed of base metals.

What is an arch wire?

A curved wire that approximates the general shape of the dental arches.

What is the difference between round and rectangular ortho wire?

Round wire is used for initial stages to move teeth, while rectangular wire provides more control in finalizing tooth position.

What is the strongest arch wire metal?

Stainless steel wire is readily formed or shaped, stiff, and the strong of archwire metals.

What are characteristics of Nickel-titanium arch wires?

It s very resilient, have the most springback or memory to return,

readily facilitates tooth movement, is hard to bend chairside, and prone to fracture if bent sharply.

What are characteristics of Beta-titanium arch wires?

Better springback and shapability compared to stainless steel, low

force, and slow movement of teeth to prevent root damage when movement is too fast.

What advancements have been made in dental implants?

Advancements include improved planning with CBCT and CAD software to help more accurately plan for and place implants.

Techniques like bone grafting and guided tissue regeneration to improve bone insights.

What is an acrylic surgical guide called?

Stent- Made ahead of time with holes drilled through it at the same angulation at which the implant should be positioned.

How is the guide placed by the surgeon?

The surgeon places the guide over the Ridge at the time of surgery and inserts a bone cutting Burr through the predetermined holes to cut the hole for the implant at the correct angulation.

When is the stent particularly helpful?

When the surgeon must place several implants that need to be parallel to each other for the purposes of the restoration that will be placed on the implants.

What is the purpose of a surgical guide during implant surgery?

To place the guide over the Ridge and insert a bone cutting Burr through predetermined holes for correct angulation.

What are endosseous implants?

Surgically placed into the bone, acting as a root substitute for missing teeth to support a crown or prosthesis.

What is the long-term survival rate of endosseous implants?

Very successful long term survival. 90% in maxilla and 95% in mandible.

What should not be used to polish titanium implants?

Prophylaxis paste with coarse or medium grit. Even very fine pace can produce some surface scratches on the implant.

What polishing paste can be used on titanium implants if necessary?

Tin oxide or other non-abrasive polishing paste in a rubber cup

applied with light pressure can be used.

What can air polishing devices do to implant surfaces?

Remove plaque and stain, but not calculus. Incorrect powders can scratch titanium implant surfaces and can injure surrounding soft tissues.

What are common causes of early implant failure?

Failure of bone to integrate with implant due to poor surgical technique, lack of infection control, excessive heat generated when drilled, infection, poor bone quality, or premature loading.

What typically causes later implant failure?

Bacterial infection of bone/supporting tissues or overloading forces.

What is the order of implant placement?

Implant fixture, cover screw (if used), healing abutment, custom abutment, crown/prosthesis.

What attaches to the implant abutment?

Abutments are attached to the fixture, and the crown/prosthesis is attached to the Abutment.

What is immediate loading of an implant?

Placing the abutment and provisional crown at the same time as the implant fixture.

When is immediate loading usually done?

When the implant is long and wide enough to engage sufficient bone in the socket and beyond to have a stable fixture.

When should implant patients return for recall?

3-4 months after initial placement. Subsequent recalls are then based on how well the patient's oral hygiene is.

What are synthetic polyglycolic acid sutures made from?

Biodegradable thermoplastic polymer.

What are Surgical gut sutures composed of?

Composed of purified collagen taken from the intestines of cattle, sheep, or goats.

What is chromic gut suture?

Collagen has been treated with chromic acid that almost doubles the length of time over plain gut before they absorb.

What are absorbable suture types?

Surgical gut, chromic gut, and synthetic polyglycolic acid.

What are non-absorbable suture types?

Surgical silk, Polyester, nylon.

How are implant crowns placed?

Screwed or cemented into the abutment.

How are screw retained crowns performed?

Need an access hole for the placement or removal of the screw. After the screw is tightened, soft materials are placed over the screw head to make retrieval easier, and then a restorative material, usually composite, is placed into the hole.

What are characteristics of cemented crowns?

More popular. Not likely be retrievable, but if it is cemented with a provisional submit, then retrievability is possible.

What is a downside of cementing implant crowns?

Crowns may come off unexpectedly. Cement remnants could cause peri implantitis and loss of the implant.

What causes denture irritation?

Bony or soft tissue undercuts, sharp bony edges to sockets, overextended borders, loose dentures, and uneven occlusion.

What are common symptoms of denture irritation?

Mild soreness when eating or placing and removing denture that can progress to pain and inflammation.

How can a broken denture be repaired?

Using chemical-cured or light-cured repair methods.

How is chemical cure repair accomplished?

Broken parts are repaired using sticky wax and plaster, with stone poured to create a stabilizing cast. After the cast sets, the fracture line is cut and surrounding surfaces are ground to prepare for bonding. Repair material is applied to the fracture, wet, and sprinkled with powder untiloverfilled. The cast is cured in a pressure pot with warm water for 20 minutes, after which excess material is removed, and the item is polished and disinfected before returning it to the patient.

How is light cure repair accomplished?

Different liquids are applied to fractured pieces to prevent an oxygen-inhibited layer development before repair material is used, as this layer complicates polishing. The prosthesis is then cured under intense blue light for 10 minutes, finished, polished, disinfected, and matched with color pigments to the base color before being given to the patient.

What is important for denture care?

Cleaning dentures to maintain tissue health and prevent infections. Improper home care can lead to fungal infections and/or damage to the dentures.

What are commonly used to clean dentures?

Denture brushes and soaks or cleaners as tablets or powders. Diluted bleach will remove some stains and have an antimicrobial effect but will remove the tissue color from the denture base over time.

What do plasticizers do in acrylic resins?

Oily liquids added to soften the acrylic plastics and make them more pliable.

What are modifiers in acrylic resins?

Used to change their physical and chemical properties. Rubbers may be added to increase the impact fracture resistance.

What is acrylic resin pliability like?

They have excellent flexibility/pliability.

How can dentures be customized?

They can be given characteristics to make them more life like. By matching the denture base acrylic to the patient's tissue and arranging teeth to recreate natural characteristics.

What are the options for arranging denture teeth?

Denture teeth can be arranged in ideal arch alignment or to recreate spaces, overlapping, or crooked teeth.

What colors can denture teeth be?

All one shade or can be selected to simulate the lighter and darker teeth that most people have in their mouths. Or custom shading with pigmented resins to simulate racial pigmentation.

What is the area of polymerization shrinkage in dentures?

Heat cured acrylic resin shrinks about 6% by volume and 0.2 to 0.5% linearly, particularly in the posterior palatal seal area.

What are the characteristics of acrylic denture teeth?

Tough, chemically bonded to the base, easy to grind and repolish, do not wear down opposing teeth, and are more resilient than porcelain. Wear readily and are softer.

What are the advantages of composite resin denture teeth?

Have improved properties compared to acrylic, a natural appearance, translucency, and better wear resistance.

What are the characteristics of porcelain denture teeth?

Porcelain teeth are brittle, prone to fracture, do not bond to the acrylic of the denture base, and can cause discomfort due to their abrasiveness.

When is porcelain not indicated?

Not indicated against natural dentition or other restorative materials because they are very abrasive and transmit heavier occlusal forces to the ridge and may be a factor in patient discomfort, denture sores, and accelerated ridge resorption.

What is the recommended daily care for dentures?

Clean dentures every day, ideally twice, using a denture brush and mild soap or non abrasive cleaning pads and remove food particles after meals.

What do you do with dentures after each meal?

Remove and rinse the dentures after each meal if you cannot brush them, but do not use hot water as it may warp the dentures once your mouth is well to remove food particles.

What do you do with dentures at bedtime?

Clean the tissues of the dentures, sit on and the and those surrounding

the dentures. Use a soft toothbrush and water to gently clean your gums, palette, tongue and lining of your cheeks.

When do you remove dentures and how often?

Remove the dentures overnight or at least 4 hours during the day to give the gums a rest. You can prepare a denture soak with commercial denture cleaning tablets and soak overnight.

How do you clean partial dentures?

The clasps can be cleaned with the pointed brush on the end of the denture brush. Gently clean the tissue bearing surfaces of dentures with soft liners using a soft toothbrush.

How should dentures be stored when not in use?

Store dentures in water to prevent drying and distortion. Hold them over a towel or put water in the sink so if you drop them they will not break.

What is the function of provisional restorations?

Provisional restorations promote biological health, protect prepped teeth, promote patient comfort, and allow for healing and communication with the lab.

How long can interim period be and what is it used for?

Two weeks or 6 to 15 months and used to: Make final diagnosis, develop treatment plan, allow healing, and communicate with lab for optimal success of the case.

What properties must provisional restorations have?

Must have sufficient compressive and tensile strength to resist forces of mastication, must be sufficient enough to resist abrasion and wear, should not produce any irritation, must have good color stability and stain resistance, and manipulability in difficult-to-access areas.

What are the uses of provisional restorations?

They are used in endodontic access, emergency care, in restorations of implant for long term provisional coverage, in restorations of primary teeth, when vitality of tooth is in question, and while awaiting permanent restorations.

What criteria should provisional restorations meet?

They should maintain function, protect hard and soft tissues, have esthetic qualities, not interfere with speech, good retention, and ensure patient comfort.

What are the advantages of custom provisional restorations?

More versatile and consistently meet success criteria.

What are the disadvantages of custom provisional restorations?

Require additional step of making template or matrix for final product.

What are the advantages of preformed provisional restorations?

Pre-made coming in many colors and sizes.

What are the disadvantages of preformed provisional restorations?

Metal typically only used posteriorly, preformed crowns may only be used for single crowns.

What is the direct technique in fabricating provisional restorations?

Provisional is fabricated directly in the mouth using provisional material inside of a template.

What is the indirect technique in fabricating provisional restorations?

Entire provisional is made outside of the mouth then tried in and adjusted as needed.

What is the indirect-direct technique in fabricating provisional restorations?

Provisional is fabricated using a pretreatment impressions and stone cast.

What is the advanced technique in fabricating provisional restorations?

Fabrication of provisionals for implants, inlays, onlays, long term provisionals.