Outcome 4 - Fabricating Functioning Diagnostic Casts Flashcards
A dental study model consists of two parts:
-The anatomic portion (created from the alginate impression)
- The art portion (the base of the model)
What is the anatomic portion of a finished study model
The teeth and gingival attachment
What is the art portion of a finished study model?
The base - 1 / 3 of the overall height of model
Characteristics of a Finished Study Model?
-The occlusal plane of the related models is parallel with both bases which are parallel with eachother.
- Side cuts are equally angled to the posterior borders and are of equal length right to left and maxillary to mandibular
- Heel cuts are symmetrical from right to left and maxillary to mandibular
Characterists of Anterior Cuts of a Finished Study Model?
-Mandibular is rounded
-Maxillary is in a point
-the Maxillary and mandibular cuts start at the same point from the right canine to the left canine.
What is model trimming equipment used for?
Model trimming equipment is used to trim, shape gypsum products such as stone or plaster. Model trimmers use electric bench motors with large abrasive disc (course sanding disc). Equipment is typically mounted permanently to the surface (counter). When in use, additional water line must be installed.
In order to operate model trimmer complete the following:
- Turn Trimmer power on
-Open and check water flow. Water should be adequate to keep the abrasive wheel clean when in use
Maintenance of a Model Trimmer?
In order to have fully functional equipment, the DA should clean and maintain the equipment after each use. Water must be used when using the model trimmer. Trimming wheel/disc may need to be sprayed and/or brushed to remove any built-up gypsum sludge.
What is recommended to do with a model/cast before trimming?
It is recommended to soak the art portion (Base) of the model in a bowl of water for atleast 5 minutes. This will produce softer model/cast which will make trimming easier. Do not over soak as model/casts could break during trimming
Steps to trimming a model/cast.
- Trim maxillary model/cast first.
-trim base
-trim posterior borders
-trim lateral sides
-trim heel cuts
-trim anterior borders (cut is angled from the right canine to left canine) - Trim the mandibular model / cast second.
-occlude the mandi model with the maxillary model, use the wax bite is recommended as the wax will keep accurate occlusion during trimming.
-trim base until even with max model
-trim lateral cuts
-trim heel cuts
-trim anterior borders (cut is angled from the right canine to left canine) This part is trimmed by itself - Finishing & Polishing
What are the steps of Finishing & Polishig of study cast/model?
To remove any lumps and bumps, laboratory knife or laboratory handpiece can be used to trim rough edges and margins of both models/casts.
To fill in any voids on the art portion, small amount of gypsum us mixed to produce” slurry paste” like consistency of gypsum.
Voids are not repaired on the tooth anatomy (anatomic portion)
Allow models to dry if polishing paste is available. The paste is used to achieve a glossy appearance. Follow manufacturer’s instructions.
Label both models/casts accordingly: Print patient first and last name, date impressions were taken, use permanent marker.
Safety & IPC for Model Trimmer
- No eating or drinking is permitted
-Wear PPE: safety glasses/face shields, mask, and lab coat
-Do not wear gloves during trimming (watch your fingers)
-Keep hair pulled back
-Report all accidents immediately
-Follow the manufacturer’s instructions for equipment operation and care
-Clean the work area after every procedure
-Maintain chemical safety when handling corrosive materials
-Maintain biohazard safety when handling contaminated materials (disinfect impressions prior to entering lab)
Dental assistant role is to evaluate articulated study models prior final patient presentation. Below criteria should be met:
Did you accidentally remove any anatomy? Place each model base down on the counter. Look at each cut. Did you remove any vestibular anatomy such as maxillary tuberosity or retromolar pad or frenum?
Did you accidentally remove any portion of a tooth or any other anatomy (tori)?
Did you use bite registration to correctly articulate the maxillary and mandibular study models? (When in occlusion, the bases of the models should be parallel to the occlusal plane)
Are both model bilaterally symmetrical? (in occlusion, look at the models from directly above.) Are the angle and the length of the heel cuts equal on both sides of the model? Do they match the opposing model? Are the side cuts equal? The anterior cuts?
Set the two models, still in occlusion, on their posterior borders. Do the teeth stay in occlusion?
Is the model/cast functional and usable as a diagnostic aid requested by the dentist?
Is this model/cast usable for fabricating a dental device requested by the dentist?
Did you label both models/cast?
Did you include the month/day/ year impression was taken?
Did you include patient first and last name?
Is the information clear to read?
Is the information PRINTED with the p
