Outcome 2 - Take an Accurate Preliminary Impression Flashcards
What are preliminary impressions?
Preliminary impressions record details of the teeth and surrounding tissues. The impression produces an accurate three dimensional duplicate of the patient’s oral anatamoy.
What is a negative reproduction?
Which when poured in stone to form models which can be used as diagnostic aids, for the fabrication of dental appliances and as a pre-treatment and post-treatment records.
General Armamentarium to record preliminary impression:
- Impression trays
- Small saliva ejector, air/water syringe tip, mouth mirror (optional)
- Alginate mixing bowls: clean, dry, flexible rubber or plastic with smooth, unscratched surface
- Alginate mixing spatulas: clean, dry, with a wide blade end that will reach every part of the bowl without scraping or cutting the surface
- Dental materials:
-alginate - measuring scoop and calibrated water measure
-room temp water
-utility wax (as per patient oral cavity conditions)
What IPC must be followed for impression trays?
- multiple use trays must be sterile, and free of any debris
-single use trays must be disenfected, and free of any debris
For maximum visibility when assessing tray size:
patient chair should be placed in supine position, however, placement of patient in upright seating position is also acceptable. Clinical observation must be preformed prior to tray selection.
These intra-oral conditions must be considered when choosing the tray size:
Presence of..
-tori
-high palate
-crowded or rotated teeth
-lesions
-mobile teeth
What to consider for tray width?
-must allow for adequate thickness of impression material on the facial and lingual of each tooth to provide strength and rigidity to the impression
- tray flanges may be spread to accomodate extra width in the molar regions, particularly lingual to the mandibular molars in the mylohyoid region.
- when a tooth is prominent labio-, bucco-, or linguoversion, a minimum thickenss of 1/4 inches is suggested, but even then, the fragitlity of the impression material in that area is increased.
What to consider for tray length?
- must allow for coverage of the retromolar area of the mandible and the tuberosity of the maxilla
-on the anterior, there should be at least 2-5mm clearance labial to the most protruded incisor without impingement on the lingual gingiva
Operator Position for Mandibular Tray Try-in?
Right handed: 7 to 9 o’clock
Left handed: 3 to 5 o’clock
Operator Position for Maxillary Tray Try-in?
For the best outcome, tray is tried from two different positions
Right handed: 9 and 12 o’clock
Left handed: 3 and 12 o’clock
How to evaluate the size of hte tray..
Gently lower the front of the tray while holding the posterior border in place and examine the relationship of the posterior border to the most posterior molars and the tuberosity areas to determine whether there will be ample coverage. By moving the tray up and down it is possible to observe the relation to the facial surface of all teeth, mal-aligned teeth, protuberances and other features to assess the space allowed for impression material.
Re-select larger and smaller trays as indicated and repeat try-in; when in double the LARGER TRAY is used, rather than smaller.
Patient management techniques for impression tray placement
- Approach ith confidence to reassure the patient
-Work as quickly and efficiently as possible
-Use topical anesethetic:
*cold water or an ice cube held in the mouth has some anesthetic effect.
*Salt (1/4 tsp) on the tongue to swallow just before the tray is to be insterted may releive tissue retractions
-Topical anesthetic may be applied to posterior palatal area, or patient may rinse with a commercial topical agent. A spray topical prepartion is contraindicated because of the proximity to throat, where coughing may be initiated.
-Technique considerations:
*avoid excessive impression material in the tray
*seat the maxillary tray from posterior to anterior
-instruct patient to breathe deeply through his nose before tray is inserted and to continue after insertion, bring head forward.
When may tray adaption be required?
May be required to accommodate various intra oral patient anatomy, prevent or minimize patient gag reflex, create palatal seal with high palate or minimize discomfort during impression taking during presence of tori.
What may be used to extend the impression tray during impression taking?
Dental Wax
Dental waxes are categorized into 3 classifications:
- Pattern waxes
- Processing waxes
- Impression Waxes
Example of impression waxes are:
Utility Wax (Rope strips)
Occlusal registration wax: Baseplate wax
How to load the impression tray
- Do not overload; fill to a level just below the edge of the rim
- Wet your index finger with water and pass lightly over the surface of the impression material.
Factors relating to the impression material that contribute to a satisfactory impression:
-Powder
-Water
-Strength and Quality
The alginate material (powder) deteriorates on standing, particularly at higher temperatures and humididty. Do the following:
-keep container tightly closed; store in cool place
-Use individually sealed packages except when large numbers of impressions are made regularly
-Refrigerate indivudual packages in hot weather, provided the powder is used immediately upon opening. If left exposed, water condenses on the powder. The bulk container cannot be refrigerated for that reason.
Ideal water for impressions:
-temperature controls gelation time
-room temperature provides adequate working time
-colder water will prolong mixing and setting time. Control in hot, humid weather; use cooler water and refrigerate the bowl and spatula.
The strength and quality of the finished impression depend on the following factors:
- powder to water ratio accurately weighed and measured
-firm spatulation will allow chemical reactions to proceed uniformly
-holding the impression material in position for an optimum period. Distortion can result when the impression is left in the mouth too long or removed prior to setting of material.
What steps are involved in order to record dental impressions?
-Prepare armamentarium as per patient appointment
- Communicate and explain procedure to the patient
-Clinical Observation: access patient oral conditions, determine tray size required
-Impression Tray Size Fitting: try mandibular tray first, try maxillary tray second, consider tray modification if required (adding utilty wax for tray extension, patient comfort)
-Mixing and Loading Impression Material
-Recording Mandibular Impression First
-Recording Maxillary Impression Second
- Outcome
- IPC / Safety Procedures
- Charting
Steps for Mixing & Loading Impression Material
- Follow manufacture instructions for product mixing
-Mix impression material to smooth consistency
-Spread the alginate against the side of the bowl with the spatula while turning in the palm of your hand
*For mandibular: load tray from lingual and/or buccal rims and press material down into base, load more material anterior
*For maxilllary: Load tray from posterior to anterior, press material down into base, load more material anterior
- Smooth the surface of the alginate by wiping a moistened finger along the surface
How to Record the Mandibular Impression?
Done 1st
-Support tray evenly with index fingers around premolar areas on both sides until impression is set
- Ensure patient is seated at the dental assistant height for correct ergonomics
- Attend to patient needs before examining and evaluating the impression
How to Record the Maxilary Impression
Done 2nd
-Support tray evenly with index finger around premolar areas on both sides until impression is set
- Ensure patient is seated lower as the impression is taken from 11-12 for right handed operators & 12-1 for left handed operators.
- attend to patient needs before examining & evaluating the impression
How to evaluate an impression?
Observe presence of surface details, proper extension over retromolar area or tuberosity, and the peripheral roll (rounded border of the impression) generally.
- Repeat the impression if required. Correct mistakes, rather than be satisfied with substandard impression.
IPC / Safety for Impression Taken
- Rinse impression under running cool tap water to remove saliva and/or debris. Disinfect and rinse impression again to prevent disinfection chemical from distorting the impression.
-Ensure moisture is removed before wrapping impression in moist paper towel.
Criteria required for Mandibular Impression
- There must be retromolar area included in the impression
-The impression should be centered in the tray
-The tray size must provide an adequate peripheral roll both facial, and lingual.
-The impression must be free of voids & tears (except interproximal)
-Anatomical detail must be sharp & clear
-Bone height must be visible throughout
Tray must be fully seated.
Criteria Required for Maxillary Impression
- The hard palate and maxillary tuberosity area must be included in the impression
-The impression must be centered in the tray
-The tray size must provide an adequate peripheral roll into the facial vestibules
-The impression must be free of void & tears (Except interproximal)
-Anatomical detail must be sharp & clear
-Bone height must be visible throughout
-Tray must be fully seated
What are bite registrations or occlusal records?
In order for the prosthesis to fit and function properly in the mouth, an accurate record of the patient’s bite must be obtained. These are often called bite registrations or occlusal records. There are various materials and different procedures that can be used depending on the extent of the treatment and the number of teeth involved.
What is the purpose of bite registration/ occlusal records?
- To relate the maxillary and mandibular cast correctly
-To place between the cast during trimming and storage to prevent breakage of teeth
-To provide an indication for a special need, when there are problems such as open bite, cross bite, edentulous areas, end-to-end, or edge-to-edge relations
What is a facebow?
A facebow is a dental tool that measures the relationship between a patient’s teeth and jaw, and transfers that information to a dental articulator.
What is an articulator?
Once the facebow transfer is taken, the casts can be mounted on an articulator. The articulator is a device that simulates the movements of a patient’s jaw. The dental lab will often use these devices to achieve an accurate fit for the prostheses. They can be simple devices with hinges that simulate only up and down motions, or more complex where they simulate side to side motions as well.
How to use a face bow & articulator?
Each manufacturer of facebow/articulator models will have specific set of instructions to follow.
How to chart impressions?
The procedure must be entered on the Services Rendered portion of the patient’s chart. When entering services rendered, document procedure steps/materials by order of use.
What should be included in Services Rendered for Impressions?
-the reason the impression was taken
-impression tray(s) size used
-brand name of the product used
-wax type if used and reason
-setting time of the material used: fast set or regular set?
-flavour if available
-include any additional comments such as: patient had strong gag reflex, etc.
IPC Safety For Impression Taking?
DA role is to understand, implement, and maintain infection control during patient appointment. During impression taking, patient may experience gag reflex and/or coughing. This can produce large particles of spatter containing saliva, blood and other debris. Spatter can travel far and land on upper surfaces of the wrist and forearms, upper arms, and chest of the operator. Best work practices will minimize spatter such as: ensure the impression material is not placed heavy along the posterior tray as this will minimize patient gag reflex.
Standard IPC protocols must be maintained prior, during and after patient dental appointment.
Disposable impression trays or any heat sensitive or single used items must be disinfected with the high -level disinfectant and rinsed prior use, multiple use impression trays must be sterilized after each patient use.
According to Spaulding Classification, impression trays are classified as…
Semi-Critical as they come in contact with mucous membranes or non-intact skin
Prior to impression, how to explain the procedure to patient?
- what to expect during impression recording: sensation, drooling
-Identify approx. time impression stays in the mouth: as per manufacture instructions
- Ask patient to follow directions closely during impression taking
- Explain briefly purpose of tray size fitting
During impression taking, how to maintain patient safety and comfort?
-Ask patient to lift tounge when asked (during mandibular tray seating)
-Ask patient to breath through nose (during maxillary tray seating)
-ask patient to lean forward when advised
After impression is taken, how to maintain patient safety and comfort?
-instruct patient to rinse with water to remove any excess alginate
-provide patient with tissue to clean impression debris from around the face
-use of floss may be required to remove alginate
-patient can eat and drink right away
