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