Intro to Direct and Indirect Restorations Flashcards
What are the basic principles of a restoration?
- Retention of the material with the tooth structure (within harsh environment)
- Ability to maintain function and protect from further mechanical failure (needs to maintain function of original tooth)
- Prevent formation of recurrent caries
- Perform under occlusal load
- Aesthetics
What do we need to think about when selecting a material?
Analyse problems, think of requirements for that resotation based on location, think of available materials
What 3 things vary significantly in the oral environment?
- Temp (due to food taken in, exposure of environment to these temp, changes are transient and large) usually between 32-37 but hot drink can go up to 56
- pH (due to what is eaten, difference in individuals)
- Cyclic stresses (have to pick which material based on compressive and tensile forces)
What can materials replace?
Can replace lost or damaged tooth tissue. They are used to maintain or improve quality of life through replacement or alteration of tooth structure.
What are the main types of material?
Temporary, intermediate and permanent.
Direct and indirect.
What are some details on direct restorations?
All such procedures involve chairside treatment.
The materials must adhere to the tooth structure and be able to flow. The materials must be set in a desired time post placement in the oral environment.
The need for restoration may arise due to trauma, dental caries, abrasion or dietary habits.
Restoration may vary in size, shape and location in the mouth - choice of material is governed by this.
Some materials may set in a moist environment and other may not.
What are some details of indirect restorations?
Procedures carried out in the dental laboratory.
Fabrication can be done at a higher temperatures and or high pressure.
It is essential that these fixtures are then bonded to the tooth structure.
Indirect - carried out in lab, fixture are made in the lab but instructions are given by clinician.
Material will be prepared as for requirement under specific conditions
What are the requirements for direct filling materials?
- Durability of a restoration governs the success of a restorative material
- Durability depends on: physical, mechanical and biological properties
Any material should not undergo any changes due to these factors.
What are the 3 main requirements for dental materials in general?
- Stable in the oral environment
- Withstand masticatory forces
- Aesthetics
Give some differences in properties between permanent and temporary fillings
Permanent:
- Biocompatible
- Adequate strength for mechanical function and durable over a long period of time
- Bond permanently to tooth structure
- Match the natural appearance of tooth structure and other visible tissues
- Exhibit properties similar to those of tooth tissues (enamel and dentine)
- Initiate tissue repair or regeneration of missing or damaged tissues
Temporary:
- Biocompatible
- Adequate strength to last a few weeks, but weak enough to be dislodged easily
- Easy to place and remove
- Provide adequate sealing
- Possess antibacterial properties
- Therapeutic effects such as pain relief, healing.
- Cariostatic properties
What are the 4 main types of material in dentistry?
- Glasses
- Composites
- Metals
- Porcelain and resin
What properties of materials do we use to characterise them?
- Storage
- Setting
- Mixing
- Properties of material
What do we need to be away of during mixing and setting?
- Method of dispensation (mixing of pastes, automixing)
- Rate of set (working and setting time)
- Viscosity (flow properties)
- Temp rise on setting
- Dimensional changes
(If setting time Is too long, the material can deform and the patient will have their mouth open for a long time. Should set quickly.
Viscosity affects flow, too viscous = difficult to place, little viscosity = splashing everywhere.
Material undergo reactions when setting = temperature increase, leads to the temperature increase in pulp or soft tissue which causes damage.
Can undergo changes in dimension, may expand or shrink.)
What do we need to be aware of with set material?
- Mechanical properties
- Physical properties
- Thermal properties
- Chemical properties
- Biological properties
- Adhesion
(Physical - interacting with oral environment, changes when subjected to oral fluids
Thermal - expand/contact with temp change
Chemical - what happens when interaction with oral fluids, any reactions occurring
Biological - compatible with tissues, no release of chemicals that could be toxic
Adhesion - for retention of the material)
What are the ideal requirements for chemical and thermal properties?
Chemical - filling material should be resistant to the hostile oral environment and withstand dissolution, degradation and erosion
Thermal - filling materials should be good insulators protecting the pulp from hot/cold. They should ideally match the thermal expansion/contraction of enamel and dentine.
What are the ideal requirements for mechanical and biological properties>
Mechanical - good abrasion resistance, resist plastic deformation, high modulus of elasticity is beneficial
Biological - should be harmless to both patients and operator, dentine tubules are capable of transporting chemicals to pulp so any products released should be non toxic and non irritable
What materials are avaliable?
Amalgams (metal metallic components)
Composites and compomers (of polymers and ceramics), composers are no longer used
Glass-isomer and resin modified glass-isomer cements (adhesive to tooth so additional adhesive not needed)
Give some direct and indirect materials that can be used for a filling for class 1 or 2 cavity
Direct - high copper dental amalgam, hybrid composites
Indirect - ceramic inlay, composite inlay, type 2 gold inlay
What direct materials would be used for a direct filling in a class 3 or 4 cavity?
Hybrid composite
Glass isomer cement
Resin modified glass isomer cement
(direct fillings used here due to low stress)
Give some details on indirect restorations (stages of it)
Restoration of teeth with rigid materials.
The materials being rigid are fabricated outside the mouth.
A model replica of the tooth needs to be constructed.
First stage is to record an accurate impression, followed by casting, investment od the pattern to a mould and then construction of appliance.
Current developments include digital imaging which may eventually decrease or eliminate impression taking.
What are the advantages of indirect restorations?
Used when there is less natural tooth remaining.
Shows less intraoral shinkage.
Greater morphology control.
Allows use of machined or pressed ceramics.
Higher degrees of polymerisation.
What materials tend to be used for direct and indirect restorations?
Rigid materials (resist high stress without distortion)
Ceramics
Pure gold
Where are metals used in dentistry?
Direct fillings e.g. silver alloys mixed with mercury.
Crowns or bridges using titanium or gold alloys.
Partial denture framework: cobalt-chromium alloys
Dental Instruments: stainless steels
Implants: pure titanium
Do alloys or pure metal have more strength?
Alloys
What is an alloy?
An alloy is a partial or complete solid solution of one or more elements in a metallic matrix.
Partial solid solution - give two or more phases that may be homogenous in distribution depending on thermal treatment
Complete solid solution: alloys give single solid phase microstructure
Give some examples of noble and base metal alloys
Noble - gold, platinum, rhodium, iridium
Base - cobalt-chromium, titanium
What are cast alloys and when are they used?
They are alloys that can be heated to a melt.
The molten metal is poured into a mould to solidify.
What are wrought alloys?
They are relatively ductile and amenable to hot or cold working during fabrication.
They do not get melted.
What materials are used for implants and why?
Titanium or titanium-aluminium.
Alloys are used as they have good mechanical properties and can osseointegrate.
What are ceramics and how are they used?
They are non-metallic, inorganic material that can vary on clay, silicate or advanced ceramics.
Ceramics contain ionic and covalent bonds and the combination leaves good rigidity, hardness and chemical stability.
They have an ordered arrangement, aesthetic, hard and resistant to chemical attack.
They do shrink during processing however.
They are usually used for fillings, crowns, veneers, implants and orthodontic brackets.
What are many filling materials made from?
Polymer/ceramic composites.
The matrix is a polymerisable monomer and the filler is usually a ceramic.
What are veneers usually made from?
Porcelain that is bonded onto the front surface of the tooth to improve aesthetics.
They are translucent and correct crowding or replace composite bonding. They are resistant to staining but are very expensive.
What are tooth coloured crowns usually made of?
Porcelain.
We use a ceramic crown core so that the black metal does not show when light is on the tooth.
