MDA Chapter 47 Flashcards

Questions and Answers

What are safety precautions that should be taken in the dental laboratory?

No eating, drinking, or smoking permitted

Keep all cosmetics away from the area

Wear personal protective equipment

All of the above (correct)

Where would the dental laboratory be located in a dental office?

Separate area of the dental office, away from the patient treatment area.

What specialty practices might have a more extensive laboratory set up?

Pediatric dentistry, orthodontics, and fixed and removable postorthodontics.

What is an example of a contaminated item in the dental laboratory?

Impressions and other items brought into the lab. Signup and view all the answers

What are wall-mounted bins used for?

To store bulk supplies of plaster, stone, and investment material. Signup and view all the answers

What are work pans?

Open plastic containers with identification labels used to hold the laboratory work in progress for an individual patient. Signup and view all the answers

Why might the work pans be color coded?

To indicate the type of procedure to be performed. Signup and view all the answers

Why is a heat source required in the dental lab?

To heat wax or other materials. Signup and view all the answers

What can be used to heat the wax?

A propane or butane torch. Signup and view all the answers

When can we use the Bunsen burner?

If a gas line has been installed in the laboratory. Signup and view all the answers

Why is it important to fully turn the gas on or off?

Any loose turn can let gas escape. Signup and view all the answers

What is a model trimmer?

A machine that is used to trim stone or plaster models. Signup and view all the answers

What is a vacuum former?

A small electric appliance used to construct custom trays for bleaching, mouth guards, and positioners for orthodontics. Signup and view all the answers

How does a vacuum former work?

The upper part of the unit is a heating element that warms and softens a sheet of thermoplastic resin. Signup and view all the answers

What is a vibrator used for?

To remove air from the mix of plaster or stone and to aid in the flow of material when a diagnostic model is poured up. Signup and view all the answers

What handpiece is required in the dental laboratory?

A low-speed handpiece. Signup and view all the answers

What is a sandblaster?

A hand-held unit that sprays at a high rate of speed, creating etching or pitting on metal, porcelain, or acrylic surfaces. Signup and view all the answers

What is an articulator used for?

To hold maxillary and mandibular dental models in relation to aid in reproduction of the mandible. Signup and view all the answers

What does the articulator allow the dentist to do?

To fabricate removable dentures, fix bridges, crowns, inlays and onlays. Signup and view all the answers

What is the face bow?

The first step the dentist takes to determine the positional relationship of the maxillary arch to the temporomandibular joints. Signup and view all the answers

What is the centric relation?

A measurement of where the teeth are positioned when the joints are aligned correctly. Signup and view all the answers

What is the dental lathe used for?

To polish or trim custom trays, provisional, dentures, and indirect restorations. Signup and view all the answers

When is pumice used?

During polishing. Signup and view all the answers

What is a wax spatula used for?

A double-ended instrument used in waxing a pattern. Signup and view all the answers

What determines the mixing spatula you have to use?

The strength of the dental material being mixed. Signup and view all the answers

What are rubber bowls used for?

For mixing of alginate in the treatment area and for mixing of stone or plaster in the lab setting. Signup and view all the answers

What piece of equipment is used to grind away plaster or stone?

The model trimmer. Signup and view all the answers

What piece of equipment does the dentist use to determine centric relation on a diagnostic model?

The face bow. Signup and view all the answers

What is the most common wax spatula size used in the lab?

The #7 wax spatula. Signup and view all the answers

What are dental models used for?

Diagnosis for planning prosthetic devices, orthodontic treatment, visual presentation, production of custom trays. Signup and view all the answers

What are gypsum products used for?

To make dental models. Signup and view all the answers

What are the chemical properties of gypsum?

Dehydrate and hemihydrate. Signup and view all the answers

What is the setting reaction of gypsum?

When mixing gypsum powder with water, hemihydrate crystals dissolve to form clusters. Signup and view all the answers

What are the clusters that form when mixing gypsum with water called?

Nuclei of crystallization. Signup and view all the answers

What are the three forms of gypsum products used in pouring models?

Model plaster, dental stone, and high-strength stone. Signup and view all the answers

What is model plaster used for?

Primarily for pouring up preliminary impressions for diagnostic models. Signup and view all the answers

What is dental stone used for?

Used when a more durable diagnostic cast or working model is needed. Signup and view all the answers

What is high strength stone?

Densite or improved dental stone used for fabrication of wax patterns. Signup and view all the answers

What happens when too little water is used when mixing gypsum?

The mix will dry, providing a short working time. Signup and view all the answers

What happens when too much water is used when mixing gypsum?

The mix will be thin and runny and will take longer to set. Signup and view all the answers

What is another term for dental model?

Study casts. Signup and view all the answers

What are the two parts of a dental model?

The anatomical portion and the art portion. Signup and view all the answers

What is the anatomical portion created from?

The alginate impression. Signup and view all the answers

What does the art portion form?

The base of the cast. Signup and view all the answers

What are the three different types of pouring methods?

Double pour method, box-and-pour method, and inverted pour method. Signup and view all the answers

What is the double pour method?

The anatomical portion of the cast is poured first, then the art portion is prepared. Signup and view all the answers

What is the box and pour method?

The impression is surrounded by a box made from boxing wax. Signup and view all the answers

How much should the completed box in a box pour method extend?

At least 1/2 inch above the palatal area of the maxillary impression. Signup and view all the answers

What is the inverted pour method?

Consists of pouring up the impression first then placing a base of material. Signup and view all the answers

What is the most common way of pouring up?

Inverted pour method. Signup and view all the answers

How long should you wait before you separate the model from the impression?

Wait 46-60 minutes after the impression has been poured. Signup and view all the answers

Which of the two models do you begin measuring and trimming first?

Maxillary. Signup and view all the answers

Study Notes

Safety Precautions in the Dental Laboratory

No eating, drinking, or smoking allowed in the lab.
Cosmetics should be kept away to prevent contamination.
Personal protective equipment (PPE) is mandatory for safety.
Hair must be secured to avoid interference during procedures.
Any accidents must be reported to the dentist without delay.
Always adhere to manufacturer instructions for equipment usage.
Clean the work area before and after procedures to maintain hygiene.

Location and Setup of Dental Laboratory

Dental laboratories are usually separate from patient treatment areas in dental offices.

Specialty Practices with Extensive Laboratories

Pediatric dentistry, orthodontics, and fixed/removable prosthodontics require more extensive laboratory setups due to higher lab work demand.

Contaminated Items in the Lab

Impressions can be contaminated with blood or saliva, necessitating disinfection before and after use.

Storage in the Dental Laboratory

Wall-mounted bins are utilized to store plaster, stone, and investment materials, protecting them from moisture.

Work Pans

Open plastic containers used to hold ongoing laboratory work for individual patients, typically labeled for identification.

Color Coding Work Pans

Color coding indicates the type of procedure being performed.

Heat Sources in the Dental Laboratory

A heat source is essential for heating wax and other materials used in dental procedures.

Heating Wax

Propane or butane torches are effective for heating wax and other lab materials.

Use of Bunsen Burner

A Bunsen burner can be utilized if a gas line is installed in the laboratory.

Gas Safety

It is crucial to fully turn the gas on or off to prevent leakage from loose connections.

Model Trimmer

A device for trimming stone or plaster models in the dental lab.

Vacuum Former

An appliance used for constructing custom trays, mouth guards, and orthodontic positioners.

Operation of Vacuum Former

The heating element softens thermoplastic resin, while a vacuum shapes the plastic around models.

Purpose of Vibrator in Lab

A vibrator removes air from plaster or stone mixtures, aiding the material's flow when pouring diagnostic models.

Low-Speed Handpiece

Essential for trimming custom trays, adjusting dentures, and polishing indirect restorations.

Sandblaster

A handheld tool that creates etching on metals, porcelain, or acrylic.

Articulator

A mechanical device for holding dental models, aiding in reproducing mandible-maxilla relationships.

Functions of the Articulator

Used in the fabrication of dentures, bridges, crowns, inlays, and onlays.

Face Bow

Instrument for determining maxillary arch position relative to temporomandibular joints.

Centric Relation

Measurement aligning teeth when joints are accurately positioned before contact.

Dental Lathe

Used for polishing or trimming custom trays, provisional units, and indirect restorations.

Pumice in Polishing

Pumice and polishing agents are used under a protective pan to manage spatter.

Wax Spatula

A double-ended instrument used primarily in waxing patterns in the lab.

Choosing a Mixing Spatula

Selection depends on the dental material's strength being mixed.

Rubber Bowls

Used for mixing alginate and other dental materials in labs and treatment areas.

Grinding Equipment

Model trimmer is utilized for grinding away plaster or stone.

Diagnostic Model Relation

The face bow is the tool for assessing centric relation on diagnostic models.

Common Size of Wax Spatula

The #7 wax spatula is predominantly used in laboratory settings.

Study Casts

Dental models are accurate reproductions of maxillary and mandibular arches and soft tissues.

Uses for Dental Models

Aid in diagnosis and planning for prosthetics, orthodontic treatment, presentations, custom trays, and mouthguards.

Gypsum Products

Evaluations include model plaster, dental stone, and high-strength stone for creating dental models.

Chemical Properties of Gypsum

Exist in two forms: dehydrate and hemihydrate.

Setting Reaction of Gypsum

Mixing gypsum powder with water forms clusters of hemihydrate crystals.

Crystallization in Gypsum

Clusters formed during the mixing process are known as nuclei of crystallization.

Gypsum Mixing Ratios

Model plaster: 100g with 45-50ml water.
Dental stone: 100g with 30-32ml water.
High-strength stone: 100g with 19-24ml water.

Effects of Water on Gypsum Mix

Too little water results in a short working time and rapid drying.
Excess water leads to weaker, thinned models with prolonged setting time.

Two Parts of a Dental Model

Comprises an anatomical portion from alginate impressions and an art portion forming the base.

Pouring Methods for Models

Various methods include double pour, box-and-pour, and inverted pour techniques.

Double Pour Method

The anatomical part is poured first, followed by a second mix for the art portion.

Box-and-Pour Method

Involves surrounding the impression with a wax box for pouring.

Inverted Pour Method

A single-step method where a large mixture is poured into the impression upside down.

Separating Models from Impressions

Wait 46-60 minutes post-pour before separating the model from the impression.

Measuring and Trimming Models

Begin with trimming and measuring the maxillary model first.

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Description

Test your knowledge on laboratory materials and safety procedures from MDA Chapter 47. These flashcards cover essential safety precautions every dental professional must follow in the workplace. Perfect for preparing for exams or refreshing your understanding of dental lab safety.