Outcome 7 - Assist with a fixed prosthodontic procedure Flashcards
Tooth preparation for a fixed prosthetic extends to…
extends to or slightly below the gingival margin of the tooth. The impression for laboratory frabrication of the prosthetic must extend into the sulcus for accurate replication of the margin.
Why must the free gingiva be retracted?
The free gingiva must be retracted and the sulcus widened to enable the impression material to flow around and beyond the margin of the tooth preparation.
What is the final impression also referred to?
The Master Impression
What are the ideal impression materials for fixed prosthetics? & Why?
Elastomers (as they are technically known) are the ideal impression materials for fixed prosthodontics because they can withstand being stretched and will snap back into original shape when the stress is removed.
Why are Elastomers are excellent materials for obtaining an impression of tooth or tissue?
Because they are extremely accurate and have an excellent flow in the fluid state, yet set sufficiently rigidly so they retain stability for accurate casting.
How many classes/types of elastomeric impression materials are manufactured?
4 types
Light Body
Regular Body
Heavy Body
Putty Material
Light Body Elastomeric Impression Material - Consistency, Preparation & Use
Consistency: Thin or Low viscosity
Preparation & Use:
-Placed into a syringe and ejected around the prepared tooth to record the fine or precise detail of the preparation
-May be supplied in an auto-mixer extruder gun for ease of delivery
Regular Body Elastomeric Impression Material - Consistency, Preparation & Use
Consistency: Medium viscosity
Preparation & Use:
-Placed into a tray to record an impression of an arch
-May be supplied in an auto-mixer extruder gun for ease of delivery
Heavy Body Elastomeric Impression Material - Consistency, Preparation & Use
Consistency: very thick viscosity
Preparation & Use:
-Placed into a tray to record an impression of an arch
-used in conjunction with the light body material to record the fine detail of prepared teeth and surrounding tissues
-Forms are specifically designed for recording occlusal relationships
-May be supplied in an auto-mixer extruder gun for ease of delivery
Putty Material Elastomeric Impression Material - Consistency, Preparation & Use
Consistency - Highest viscosity
Preparation & Use:
-Placed into a tray to record an impression of an arch
-May be used in the same manner as the heavy body material or to record an impression of an area prior to the tooth/teeth being prepared. In this case, it is then used as a custom tray in conjunction with the light body material to record the fine detail of the prepared tooth/teeth.
-May be supplied in an auto-mixer extruder gun for ease of delivery
Elastomeric impression materials can be one of three different chemical types:
- Polysulfide
- Polyether
- Silicone
*condensation silicone
*addition silicone
What is Polysulfide Impression Material?
Is a final impression material suitable for both hard and soft tissue replication where elasticity is a requirement.
-two-paste system consisting of low molecular weight polysulfide polymers with fillers including zinc sulfide, titanium dioxide and silica in the base paste. The catalyst paste has lead dioxide, sulfur, oils and stearic acid.
Recently, use of polysulfide rubber impression materials has declined because of the improvements made in silicone rubber materials.
What is Polyether Impression Material?
-can be used as final impressoin materials for crowns, bridges, inlays and partial dentures, but are more often used in removable prosthodontics as they are ideal for edentulous impressions for construction of complete dentures.
What is Silicone Impression Material?
3 types: Polysiloxane (Polyvinyl Siloxane) Impression Material, Condensation Reaction Type, Addition Reaction
- no objectionable taste or straining properties and, when properly used have acceptable accuracy.
- contain high molecular weight polydimethylsiloxane, an orthoalkysilicate, inorganic filler, metal organic ester and an oil diluent or thickening agent
Addition Reaction Silicone Impression Materials – Polyvinyl Siloxane
A significant improvement was made in silicone materials in the late 1970s. These new systems contain terminal vinyl groups in one paste and terminal hydrogen groups in the other paste. All of the silicone rubber impression materials used at SAIT are addition reaction silicones. These materials are usually referred to as polyvinyl siloxane impression materials.
Digital Impression
Vitrual impressions are becoming more common within the dental office. It is quick & easy way without the mess to obtain digital image. Within a couple of minutes, the scanner will create images of the teeth using digital imaging technology. The scanner is able to capture incredibly accurate digital impressoin. After scanning, he 3D model is created presenting the fine details of the area.
What is the main advantage of digital impressions?
The main advantage of digital impressions is the elimination of the distortion.
Steps of Creating a provisional/interim restoration (DA role)
-Create Template (Vacuum Form or Immediate)
-Determine Prosthetic Technique & Create
-Trimming of the Interim Prosthesis
-Fit & Assessment
-Occlusal Adjustment
-Polishing
-Temporary cementation, Final Adjustments and Post Op instructions
What can an interim prosthesis be made from?
Either Bis Acrylic or an Acrylic Polymer
Trimming of the Interim Prosthesis
Proper trimming of the prosthesis is important in order to achieve a functioning, aesthetically pleasing, interim prosthesis. There are slight variations to the technique depending on whether you are trimming a crown or a bridge.
What are Dental Cements classified as?
They are classified as “luting agents” due to their ability to adhere to the tooth structure
What should the selected temporary cement be able to provide?
Adequate strength to retain the temporary restoration for function.
This cement is referred to ZOE (Zinc Oxide Eugenol) and there are four types available. Only ZOE type is used as for a temporary cementation or provisional coverage.
Type I cement is supplied in:
Eugenol and Non-Eugenol form
Zinc Oxide-Eugenol is used on..
used on sensitive teeth as the material is soothing and has a sedative effect on the pulp.
It is within the Scope of Practice within the Province of Alberta for Dental Assistants to:
select or fabricate and fit provisional acrylic crowns, inlays, onlays and bridges intra-orally using self-curing or light curing materials, or prefabricated or custom fabricated acrylic shells, and remove excess material from occlusion or contour extra-orally with slow speed rotary handpiece
cement provisional crowns, inlays, onlays and bridges using temporary cement, and remove excess temporary cement with hand instruments
remove provisional crowns, inlays, onlays or bridges and cement with hand instruments
Dentist vs DA Role for Dental Cements ?
The dentist will determine the most suitable method of permanent cementation for the prosthesis, the DA will be asked to prepare and manipulate the materials involved.
Bonding Fixed Prosthetics
New products utilizing composite resin technology have been developed to bond to the prepared teeth. Bonding fixed prosthetics is complex and time consuming. Patient is typically booked for a longer appointment. Several bonding steps must be completed in order to successfully bond the restoration in place. Bonding kits are typically used with anterior teeth.
Common Components of a Bonding Kit
Shade guide - for colour matching to the tooth surface
Try-in Pastes - to ensure the colour chosen will be esthetically acceptable
Silane Primer - To prepare the restoration for the adhesion process
Acid etch - to create mechanical/chemical retention on the tooth surface
Primers 1, 2, & 3 - To prepare the tooth surface and/or restoration for the adhesion process
Base resins of various shades - Used alone for light-cured application in conjunction with catalyst for dual-cure application
Catalyst resin - to initiate chemical polymerization when required
Traditional cements composed of powder and liquid ingredients are also common. Example of paraments cements are:
-Zinc Phosphate
-Polycarboxylate Cement
-Glass Ionomer
-Composite Resin Cement/Bonding System
It is not within the Scope of Practice in AB for DAs to place and cement permanent resorations/casts intra oral. True or False?
TRUE - the dentist must do this
It is within the Scope of Practice within AB for DAs to take final impressions. True or False?
TRUE - note, the dentist should be evaluating final impressions obtained by a DA
It is within the Scope of Practice within the Province of Alberta for Dental Assistants “to place and remove gingival retraction cord with or without hemostatic agents (no epinephrine) in sulcus” . True or False?
TRUE
