Download - impression procedures for removable partial dentures / academy of fixed orthodontics

Transcript
Page 1: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 2: impression procedures for removable partial dentures  / academy of fixed orthodontics

INDIAN DENTAL ACADEMYINDIAN DENTAL ACADEMY

Leader in continuing dental education Leader in continuing dental education www.indiandentalacademy.comwww.indiandentalacademy.com

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 3: impression procedures for removable partial dentures  / academy of fixed orthodontics

INTRODUCTIONINTRODUCTION IMPRESSIONIMPRESSION IMPRESSION TRAYSIMPRESSION TRAYS TRAYS USED IN RPD IMPRESSION TRAYS USED IN RPD IMPRESSION

PROCEDUREPROCEDURE FACTORS INFLUENCING THE CHOICE OF FACTORS INFLUENCING THE CHOICE OF

IMPRESSION MATERIALIMPRESSION MATERIAL IMPRESSION MATERIALS USED-OVERVIEWIMPRESSION MATERIALS USED-OVERVIEW

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 4: impression procedures for removable partial dentures  / academy of fixed orthodontics

RPD IMPRESSION Vs COMPLETE DENTURE IMPRESSION

PRIMARY IMPRESSION OBJECTIVES PROCEDURE PATIENT MANAGEMENT CONTROL OF SALIVA PRECAUTIONS TO BE TAKEN FOR “ GAGGERS ” EXAMINATION OF IMPRESSION REASONS FOR REJECTING AN IMPRESSION

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 5: impression procedures for removable partial dentures  / academy of fixed orthodontics

FINAL IMPRESSION METHODS McLEAN’S TECHNIQUE HINDEL’S TECHNIQUE SELECTIVE PRESSURE TECHNIQUE FUNCTIONAL RELINING TECHNIQUE FLUID WAX TECHNIQUE ALTERED CAST TECHNIQUE MODIFICATION REVIEW OF LITERATURE CONCLUSION REFERENCES

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 6: impression procedures for removable partial dentures  / academy of fixed orthodontics

INTRODUCTIONINTRODUCTION

Sensitive to technique and material procedures.Sensitive to technique and material procedures. Not a passive activity.Not a passive activity. Impression material accomplishes the task Impression material accomplishes the task operator is merely an observer. operator is merely an observer.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 7: impression procedures for removable partial dentures  / academy of fixed orthodontics

Combined effort event accomplished by:Combined effort event accomplished by:Operator Operator

basic fundamental knowledge of all aspects of basic fundamental knowledge of all aspects of the impression procedures the impression procedures

Intra oral condition of the patient.Intra oral condition of the patient.The position of the patient. The position of the patient. The size and position of the tray.The size and position of the tray.The selection of the material and technique.The selection of the material and technique.Patient’s actions and facial muscle activity.Patient’s actions and facial muscle activity.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 8: impression procedures for removable partial dentures  / academy of fixed orthodontics

Impression

A negative likeness or copy in reverse of the surface of an object ; imprint of teeth and adjacent structures for use in dentistry. GPT – 8

Partial denture impression

A negative likeness of a part or all of a partially edentulous arch - GPT – 8

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 9: impression procedures for removable partial dentures  / academy of fixed orthodontics

An impression of partially edentulous arch must record accurately the anatomic form of teeth and surrounding tissues. Unless the cast upon which the prosthesis is to be constructed is an exact replica of mouth, the prosthesis can’t be expected to fit. Properly made and accurate cast can be obtained only from an accurate impression.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 10: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 11: impression procedures for removable partial dentures  / academy of fixed orthodontics

Impression trays

A receptacle in to which suitable impression material is placed to make negative likeness

ORA device that is used to carry, confine and control

impression material while making an impression.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 12: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 13: impression procedures for removable partial dentures  / academy of fixed orthodontics

Impression trays can be classified broadly in to stock trays and custom trays

Stock trays for partially edentulous patients may be perforated to retain the impression material or they may be constructed with a rimlock for this purpose.

Another type of stock tray designed for the reversible type of hydrocolloid is water cooled trays. It contains tubes through which water can be circulated for purpose of cooling the tray.www.indiandentalacademy.comwww.indiandentalacademy.com

Page 14: impression procedures for removable partial dentures  / academy of fixed orthodontics

Modified stock tray (individual tray)Robert R Renner’s technique The stock tray can be modified with

modeling composition and with wax to create an accurately fitting tray.

This technique can be employed in class I and class II cases.

Technique: Softened modeling compound is placed in

the stock impression tray in such a way that it may capture the edentulous areas of mouth and include one or two teeth adjacent to the space. www.indiandentalacademy.comwww.indiandentalacademy.com

Page 15: impression procedures for removable partial dentures  / academy of fixed orthodontics

The tray is positioned in the mouth and compound is allowed to cool but it not permitted to harden completely, so that it is prevented from becoming hard when in contact with the adjacent teeth. When it is hardened sufficiently to contour it is removed from the mouth and thoroughly chilled.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 16: impression procedures for removable partial dentures  / academy of fixed orthodontics

The compound is trimmed so that it does not contact the adjacent teeth and surface of compound in the edentulous areas is scraped to a depth of 2 - 4 mm to provide space for a uniform layer of impression material.

In maxillary impression the compound should cover the edentulous ridges and the palate and should accurately fit to post dam area.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 17: impression procedures for removable partial dentures  / academy of fixed orthodontics

Modification of the tray to make it adhesive

If Impression material to be used is either alginate or agar, we can heat surface of compound with a flame.

An alternate method Is to paint the surface of compound with a solvent such an chloroform to make it tacky and then to embed cotton fibers in it, the impression material will become enmeshed in cotton fiber. And if rubber base material is to be employed rubber adhesive is painted on the compound

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 18: impression procedures for removable partial dentures  / academy of fixed orthodontics

Advantages over custom tray:1. Impression can be accomplished in one

appointment.2. Can be used inpatient with tendency to gag.

Advantages over conventional use of stock stray: Especially useful for mouth that is either

exceptionally large or small or the one with anomalous contour which cannot be accurately fitted with conventional stock tray.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 19: impression procedures for removable partial dentures  / academy of fixed orthodontics

Disadvantages: STOCK TRAY

a. The peripheral borders cannot be accurately recorded.

b. Considerably more bulkier than a custom tray.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 20: impression procedures for removable partial dentures  / academy of fixed orthodontics

Custom impression trays:

a. Peripheral borders can be precisely recorded in the impression

b. Thickness of impression material can be controlled. This is important consideration when using rubber base type material, which should not exceed thickness of 2-4 mm because a section thicker than this is subject to distortion.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 21: impression procedures for removable partial dentures  / academy of fixed orthodontics

C. Well fitted tray will better support the impression in the palate, then avoiding even present danger of material slumping in vital areas.

Custom trays are sometimes needed for mouths that are abnormally or of unusual configuration.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 22: impression procedures for removable partial dentures  / academy of fixed orthodontics

Impression MaterialsImpression Materials

www.indiandentalacademy.com

Page 23: impression procedures for removable partial dentures  / academy of fixed orthodontics

Factors that influence the selection of impression materials are:

Convenience of use Time of manipulation and set Cost Need for special trays Operator training and preference

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 24: impression procedures for removable partial dentures  / academy of fixed orthodontics

Impression Materials• Non-elastic• Elastic

– Aqueous hydrocolloids• Agar• Alginate

– Non-aqueous elastomers• Polysulfide• Silicones

– Condensation– Addition

• Polyether

www.indiandentalacademy.com

Page 25: impression procedures for removable partial dentures  / academy of fixed orthodontics

Impr

essi

on

Mat

eria

lsNon-elastic

Elastic

Aqueous Hydrocolloids

Non-aqueous Elastomers

Polysulfide

Silicones

Polyether

Condensation

Addition

Agar (reversible)

Alginate (irreversible)

Plaster

Compound

ZnO - Eugenol

Waxes

O’Brien Dental Materials & their Selection 1997

www.indiandentalacademy.com

Page 26: impression procedures for removable partial dentures  / academy of fixed orthodontics

Reversible Hydrocolloid (Agar)

• Indications– crown and bridge

• high accuracy

• Example– Slate Hydrocolloid (Van R)

www.indiandentalacademy.com

Page 27: impression procedures for removable partial dentures  / academy of fixed orthodontics

Composition• Agar

– complex polysaccharide

• seaweed

– gelling agent• Borax

– strength

• Potassium sulfate– improves gypsum

surface• Water (85%)

agar hydrocolloid (hot) agar hydrocolloid (cold)

(sol) (gel)

cool to 43 C

heat to 100 C

O’Brien Dental Materials & their Selection 1997

www.indiandentalacademy.com

Page 28: impression procedures for removable partial dentures  / academy of fixed orthodontics

Manipulation

• Gel in tubes– syringe and tray material

www.indiandentalacademy.com

Page 29: impression procedures for removable partial dentures  / academy of fixed orthodontics

Manipulation• 3 chamber conditioning unit

– (1) liquefy at 100C for 10 minutes

• converts gel to sol– (2) store at 65C– place in tray– (3) temper at 46C for 3 minutes– seat tray– cool with water at 13C for 3 minutes

• converts sol to gelO’Brien Dental Materials & their Selection 1997

www.indiandentalacademy.com

Page 30: impression procedures for removable partial dentures  / academy of fixed orthodontics

Advantages

• Dimensionally accurate• Hydrophilic

– displace moisture, blood, fluids• Inexpensive

– after initial equipment• No custom tray or adhesives• Pleasant• No mixing required

Phillip’s Science of Dental Materials 1996

www.indiandentalacademy.com

Page 31: impression procedures for removable partial dentures  / academy of fixed orthodontics

Disadvantages

• Initial expense– special equipment

• Material prepared in advance• Tears easily• Dimensionally unstable

– immediate pour– single cast

• Difficult to disinfect

Phillip’s Science of Dental Materials 1996

www.indiandentalacademy.com

Page 32: impression procedures for removable partial dentures  / academy of fixed orthodontics

Irreversible Hydrocolloid (Alginate)

• Most widely used impression material

• Indications– study models– removable fixed partial dentures

• framework

• Examples– Jeltrate (Dentsply/Caulk)– Coe Alginate (GC America)

Phillip’s Science of Dental Materials 1996

www.indiandentalacademy.com

Page 33: impression procedures for removable partial dentures  / academy of fixed orthodontics

Composition• Sodium alginate

– salt of alginic acid• mucous extraction of

seaweed (algae)

• Calcium sulfate– reactor

• Sodium phosphate– retarder

• Filler• Potassium fluoride

– improves gypsum surface

2 Na3PO4 + 3 CaSO4 Ca3(PO4)2 + 3 Na2SO4

Na alginate + CaSO4 Ca alginate + Na2SO4

(powder) (gel)

H2O

O’Brien Dental Materials & their Selection 1997

www.indiandentalacademy.com

Page 34: impression procedures for removable partial dentures  / academy of fixed orthodontics

Manipulation

• Weigh powder• Powder added to water

– rubber bowl– vacuum mixer

• Mixed for 45 sec to 1 min• Place tray• Remove 2 to 3 minutes

– after gelation (loss of tackiness)

Caswell JADA 1986

www.indiandentalacademy.com

Page 35: impression procedures for removable partial dentures  / academy of fixed orthodontics

Advantages

• Inexpensive• Easy to use• Hydrophilic

– displace moisture, blood, fluids• Stock trays

Phillip’s Science of Dental Materials 1996

www.indiandentalacademy.com

Page 36: impression procedures for removable partial dentures  / academy of fixed orthodontics

Disadvantages• Tears easily• Dimensionally unstable

– immediate pour – single cast

• Lower detail reproduction– unacceptable for fixed prosthodontics

• High permanent deformation• Difficult to disinfect

Phillip’s Science of Dental Materials 1996

www.indiandentalacademy.com

Page 37: impression procedures for removable partial dentures  / academy of fixed orthodontics

RPD IMPRESSION Vs COMPLETE DENTURE

The complete denture impression records the edentulous mucosa with underlying bone only, whereas partial denture impression records not only relative soft yielding tissues (the oral mucosa) as well as a hard unyielding substance (the remaining teeth).

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 38: impression procedures for removable partial dentures  / academy of fixed orthodontics

Removable partial denture impression need to record the teeth that are irregular in contour as well as varying in their vertical relations to occlusal plane. The chosen impression material must be capable of recording the tissue contours as accurately as possible without distortion, which occurs as impression is withdrawn.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 39: impression procedures for removable partial dentures  / academy of fixed orthodontics

PRIMARY IMPRESSION

Objectives: To obtain an impression of all the standing

teeth and denture - supporting tissues of each jaw from which study casts may be prepared.

The purpose of the study casts are:

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 40: impression procedures for removable partial dentures  / academy of fixed orthodontics

To enable special trays and occlusion rims to be constructed if necessary.To examine the occlusion in detail on an articulator.By use of a surveyor, to plan the path of insertion of the proposed denture, arrive at a tentative design and plan any mouth preparation.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 41: impression procedures for removable partial dentures  / academy of fixed orthodontics

Checking Maxillary Tray For Correct Size

Checking Mandibular Tray for Correct Size

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 42: impression procedures for removable partial dentures  / academy of fixed orthodontics

Control of Gagging

It is usually a mistake to make too big an issue over the making of impressions. The dentist definitely should not bring up the subject of gagging. The dentist should ask whether the patient has had impression made previously. If this is to be the patient‘s first experience a brief description of the procedure should be given.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 43: impression procedures for removable partial dentures  / academy of fixed orthodontics

That the material to be used has the consistency of thick whipped cream and that is sets up to a rubber consistency in several minutes, is usually all the explanation that is necessary. The dentist should proceed in confident, efficient manner. Dentist usually encounter more problems with gagging when they are in initial stages of dental practice and approach the making the impressions with unsure and nervous demeanor.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 44: impression procedures for removable partial dentures  / academy of fixed orthodontics

Procedures that will help prevent Gagging

Seating the patient in an upright position with the occlusal plane with the floor

correcting the maxillary tray with modeling plastic and leaving sufficient unrelieved modeling plastic at the posterior borders that positive contact can be maintained against the posterior palate during the setting of the alginate.

Not overfilling the tray with alginate.www.indiandentalacademy.comwww.indiandentalacademy.com

Page 45: impression procedures for removable partial dentures  / academy of fixed orthodontics

Seating the posterior part of the tray first and then rotating the tray into position thereby forcing excess alginate in an anterior direction rather than out of the posterior border of the tray.

Asking the patient to keep the eyes open during the impression procedure This usually reduces the patient tension.

Asking the patient to breath through the nose.

Asking the patient to keep eyes focused on some small object.

Giving all instructions to the patient in a firm controlled manner.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 46: impression procedures for removable partial dentures  / academy of fixed orthodontics

Having the patient use astringent mouth rinse and cold water rinses before the impression is made. The use of an anesthetic spray is usually contraindicated because it will cause numbness of the tongue and palate and may contribute to the urge to gag.

Most gagging problems are psychologic rather than physical, and confidence in the dentist will help eliminate many of them.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 47: impression procedures for removable partial dentures  / academy of fixed orthodontics

Control of Saliva

Alginate has a tendency to stick to teeth that are too dry. Therefore the teeth should not be air dried before making an impression. However, excessive amounts of saliva, particularly of the thick mucous type, will displace the alginate impression material and will contribute to an inaccurate impression.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 48: impression procedures for removable partial dentures  / academy of fixed orthodontics

The saliva can be controlled for most

patients by having the patient rinse cold water and then packing the mouth with 2x2 inch gauze that has been unfolded to form a strip of 2-inch gauze. In the maxillary arch one gauze strip is placed in the right buccal vestibule and another in the left vestibule.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 49: impression procedures for removable partial dentures  / academy of fixed orthodontics

The patient can be asked to lightly hold a third piece of gauze in the palate. Because too much force by the patient may displace the tissue to be recorded in the impression, the dentist may prefer to wipe the palatal area just before making the impression.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 50: impression procedures for removable partial dentures  / academy of fixed orthodontics

In the mandibular arch one gauze strip is placed in each of the buccal vestibules and another is placed in the linguoalveolar sulcus by having the patient raise the tongue, placing the gauze in the sulcus, and then having the patient relax the tongue to hold the gauze in position. The gauze is removed immediately before the impression is made.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 51: impression procedures for removable partial dentures  / academy of fixed orthodontics

A few patients secrete an excessive amount of thick mucinous saliva from the palatal salivary glands. This heavy saliva displaces the alginate and results in an inaccurate and rough surface to the impression.

These patients should be instructed to rinse with an astringent mouth rinse. The 2x2 inch sponges dampened in warm water should be used to place pressure over the posterior palate in an attempt to milk the glands.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 52: impression procedures for removable partial dentures  / academy of fixed orthodontics

This is followed by an ice water rinse immediately before the impression is made.

In rare instances the patient will secrete such copious amounts of saliva that impression making becomes extremely difficult if not impossible.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 53: impression procedures for removable partial dentures  / academy of fixed orthodontics

The use of an antisialagogues in combination with mouth rinse and gauze packs effectively controls this salivation. A 15 mg propantheline bromide (pro-banthine) tablet taken 30 minutes before the impression appointment will also help control the excessive salivation.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 54: impression procedures for removable partial dentures  / academy of fixed orthodontics

These drugs should never be prescribed in the presence of medical contraindications such as glaucoma, cardiac conditions in which any increase in the heart rate is to be avoided.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 55: impression procedures for removable partial dentures  / academy of fixed orthodontics

Mixing Impression Material

Alginate may be mixed by hand spatulation, mechanical spatulation, or mechanical spatulation under vacuum.

The objective is to obtain a smooth, bubble- free mix of alginate. In hand spatulation a measured amount of distilled water at approximately 22 °C is placed in a rubber mixing bowl The pre-weighed alginate powder is sifted from its container into the water. www.indiandentalacademy.comwww.indiandentalacademy.com

Page 56: impression procedures for removable partial dentures  / academy of fixed orthodontics

The mixing should begin slowly using a stiff, broad - bladed spatula.When the powder is thoroughly wet, the speed of the spatulation should be increased The spatula should crush the material against the sides of the bowl to ensure that the material is completely mixed. The spatulation should continue for a minimum of 45 seconds.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 57: impression procedures for removable partial dentures  / academy of fixed orthodontics

The strength of the gel can be reduced to 50 % if the mixing is not complete. Insufficient spatulation can result in failure of the ingredients to dissolve sufficiently. Then the chemical reaction of changing from sol to gel will not proceed uniformly throughout the mass of alginate. An incompletely spatulated mix will appear lumpy and granular and will have numerous areas of trapped air.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 58: impression procedures for removable partial dentures  / academy of fixed orthodontics

Complete spatulation will result in a smooth, creamy mixture. The mixing should be completed by wiping the alginate against the side of the bowl with the spatula to remove any trapped air. The most consistent method of making a smooth, bubble- free mix is mechanical spatulation under vacuum.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 59: impression procedures for removable partial dentures  / academy of fixed orthodontics

The pre-weighed powder is added to the pre-measured water in the mechanical mixing bowl .The powder is thoroughly incorporated into water by hand spatulation. The mix is then mechanically spatulated under 20 pounds of vacuum for 15 seconds.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 60: impression procedures for removable partial dentures  / academy of fixed orthodontics

Longer spatulation will result in a greatly reduced setting time of the alginate and could affect the strength of the gel.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 61: impression procedures for removable partial dentures  / academy of fixed orthodontics

Loading the Impression Tray

Small increments of the impression material should be placed in the tray and forced under the rim lock. Placing too large a portion of alginate at one time increases the possibility of trapping air The tray should be filled to the level with the flanges of the tray.

Overfilling should be avoided.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 62: impression procedures for removable partial dentures  / academy of fixed orthodontics

Making the Impression

The mandibular impression is made first because it usually entails less patient discomfort Patient confidence is increased when an impression has been successfully completed while holding the tray with the left hand the dentist uses the right hand to remove the gauze pads from the patient’s mouth.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 63: impression procedures for removable partial dentures  / academy of fixed orthodontics

The syringe is used to inject the impression material over the occlusal surface of the teeth and into the vestibular and alveolingual sulcus areas. The impression material will remain in place if the tissues are fairly dry. A tendency for the alginate to form a ball and not remain where placed indicates that the tissues are too moist and that voids are likely to be present in the impression.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 64: impression procedures for removable partial dentures  / academy of fixed orthodontics

There is not enough time to repack the mouth before gelation begins, so the impression procedure should be completed. The impression should be carefully inspected and if voids are present in critical areas, the impression procedure should be repeated. Packing the mouth with more or larger gauze pads and avoiding removal of the gauze until ready to apply the alginate will usually prevent this problem.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 65: impression procedures for removable partial dentures  / academy of fixed orthodontics

The layer of alginate applied with the syringe should be 3 to 4 mm thick; If it is too thin, the heat of the tissues of the oral cavity may cause the material to set before the tray is seated, resulting in a layered impression.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 66: impression procedures for removable partial dentures  / academy of fixed orthodontics

The fingers of the left hand that are retracting the right cheeks should depress the lower lip to provide good visibility. When the tray is correctly lined up over the teeth, the patient is asked to protrude the tongue. The tray is carefully seated so that its flanges are below the gingival margins of the teeth.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 67: impression procedures for removable partial dentures  / academy of fixed orthodontics

The tray should not be over seated because this could result in the cusps of the teeth contacting the tray, causing an inaccurate impression. Great care must be exercised in seating the tray if the patient has mandibular tori or other exostoses, or the making of this impression can be a very painful experience for the patient.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 68: impression procedures for removable partial dentures  / academy of fixed orthodontics

As the tray is being seated, the cheeks are pulled out to prevent the trapping of buccal tissues under the tray. The patient is asked to keep the tip of the tongue in contact with the upper surface of the tray during the gelation of the impression material.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 69: impression procedures for removable partial dentures  / academy of fixed orthodontics

The dentist must maintain the position of the tray during the entire gelation period. This can be accomplished most conveniently and effectively by placing the forefinger of each hand on the top of the tray in the premolar area and by placing the thumbs under the patient ‘s chin.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 70: impression procedures for removable partial dentures  / academy of fixed orthodontics

The dentist through tactile sense can maintain an even amount of pressure on the tray even if the patient swallows or opens or closes the mouth. Any movement of the tray during the gelation period will result in an inaccurate impression.

Allowing the patient or the assistant to hold the

tray or leaving the patient unattended must be avoided.

Within 3 to 4 minutes the alginate should be set.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 71: impression procedures for removable partial dentures  / academy of fixed orthodontics

For maxillary impression, the patients is prepared by using the rinses and placing the gauzes pads described for making the mandibular impression. While holding the loaded tray with the left hand the dentist uses the right hand to remove the gauze pads.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 72: impression procedures for removable partial dentures  / academy of fixed orthodontics

Alginate is injected onto the occlusal surfaces and in all vestibular areas as for the mandibular arch. In addition, a fairly large amount should be wiped onto the palate. Failure to accomplish this step will usually result in an impression with a large void in the palatal area.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 73: impression procedures for removable partial dentures  / academy of fixed orthodontics

The loaded maxillary tray is grasped by the thumb and forefinger of the right hand. As the right posterior flange of the impression tray stretches the right corner of the mouth, the dentist ‘s left arm should be behind the patient’s head and headrest so that the thumb and index finger may grasp the left corner of the mouth and distend it slightly to allow the impression tray to enter the mouth in a straight line.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 74: impression procedures for removable partial dentures  / academy of fixed orthodontics

No attempt should be made to seat the tray until the tray is in its correct anteroposterior position. Once the tray is in the mouth, the thumb and forefinger of the left hand should raise the upper lip to allow the dentist to see the relationship between the labial flange of the tray and the anterior teeth or the residual ridge.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 75: impression procedures for removable partial dentures  / academy of fixed orthodontics

The tray must be centered and properly aligned. This position can best be verified by looking at the patient ‘s face from above and observing the position of the handle of the tray.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 76: impression procedures for removable partial dentures  / academy of fixed orthodontics

It should protrude straight from the center of the mouth. After the proper position has been verified the tray is seated by using the fingers of both hands over the premolar areas. As the tray is being seated the cheeks must be lifted outward and upward to prevent the buccal tissues from being trapped under the flanges of the tray.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 77: impression procedures for removable partial dentures  / academy of fixed orthodontics

The lip must also be lifted up and out to allow good visibility and to avoid trapping the lip between the flanges of the tray and the anterior teeth. Care must be taken not to over seat the tray to avoid. contact between the tray and cusp tips of incisal edge of the teeth.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 78: impression procedures for removable partial dentures  / academy of fixed orthodontics

The tray should be stabilized throughout the set of the impression material by keeping light pressure over the premolar areas on both sides of the arch The alginate should set in 3 to 4 minutes.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 79: impression procedures for removable partial dentures  / academy of fixed orthodontics

Effect of movement of tray:

Gelation of alginate occurs by a chemical reaction. When mixed with water, the sodium alginate and calcium sulfate in the powder react to form a lattice work of fibrils of insoluble calcium alginate. The heat of the oral tissues accelerates the chemical reaction, causing the alginate next to the tissues to gel first .

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 80: impression procedures for removable partial dentures  / academy of fixed orthodontics

If the dentist exerts pressure or allows the tray to move during gelation of the remainder of the alginate, internal stresses are created that can distort the impression as it is removed from the mouth.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 81: impression procedures for removable partial dentures  / academy of fixed orthodontics

Removal of Impression from Mouth:

Clinically, the initial set of alginates is determined by a loss of surface tackiness. The impression should be left in the mouth for an additional 2 to 3 minutes to allow the development of additional strength. Early removal of the weak alginate may lead to unnecessary tearing of the impression.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 82: impression procedures for removable partial dentures  / academy of fixed orthodontics

The gel strength doubles during the first 4- minutes after initial gelation. No further strengthening is found after that time. In fact, Impression is left in the mouth for 5 minutes rather than the recommended 2 to 3 minutes after initial gelation exhibits definite distortion.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 83: impression procedures for removable partial dentures  / academy of fixed orthodontics

Most alginates improve their elasticity with time, providing a better opportunity for accurate reproduction of undercuts. Impressions removed too early after initial gelation produce a rough surface of the poured cast. These data indicate the alginate impressions should not be removed from the mouth for at least 2 to 3 minutes after initial gelation.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 84: impression procedures for removable partial dentures  / academy of fixed orthodontics

There are two reliable methods of determining thecorrect time for removal of the impression

1. A timer can be used to measure the 2 to 3 minute period after initial gelation or

2. A small mound of the original mix of alginate can be placed on a glass or metal surface; when this alginate will fracture cleanly with finger pressure, the impression is ready to be removed from the mouth.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 85: impression procedures for removable partial dentures  / academy of fixed orthodontics

Reasons for Rejecting Impression

The following are specific reasons for rejecting andrepeating an impression:

1. Bubbles or voids in and around rest preparations.

2. Contact of cusp with the tray, especially when the teeth are involved in the frame work design.

3. Show through between teeth and modeling plastic or modeling plastic and hard palate (if the tray has been modified for an alginate impression)

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 86: impression procedures for removable partial dentures  / academy of fixed orthodontics

4. Voids or bubbles in palatal vault when palatal major 4. Voids or bubbles in palatal vault when palatal major connectors are to be constructed.connectors are to be constructed.

5. Peripheral underextension when a denture base has been 5. Peripheral underextension when a denture base has been designed and a corrected cast impression is not planned.designed and a corrected cast impression is not planned.

6. Interproximal tearing of the impression material when 6. Interproximal tearing of the impression material when coverage of those teeth has been designed.coverage of those teeth has been designed.

7. Lack of detail on the impression surface.7. Lack of detail on the impression surface.

8. Any doubt as to the accuracy of the impression.8. Any doubt as to the accuracy of the impression.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 87: impression procedures for removable partial dentures  / academy of fixed orthodontics

Impression Methods:

There are basically two dual impression techniques. The physiologic, or functional, impression technique records the ridge portion by placing an occlusal load on the impression tray as the impression is being made.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 88: impression procedures for removable partial dentures  / academy of fixed orthodontics

The underlying s tissues will be displaced because displacement will normally occur under function.

The physiologic impression techniques that discussed are as follows: Mc Lean’s and Hindel’s methods, the functional relining method, and the fluid wax method.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 89: impression procedures for removable partial dentures  / academy of fixed orthodontics

The selected pressure impression technique not only equalizes the support between the abutment teeth and the soft tissue, but has the added advantage of directing the force to the portions of the ridge that are most capable of withstanding the force.

This is accomplished by providing relief in the impression tray in selected areas and permitting the impression to be recorded.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 90: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 91: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 92: impression procedures for removable partial dentures  / academy of fixed orthodontics

In those areas of the tray where relief was not provided (the buccal shelf of the mandibular ridge and the buccal slope and crest of the maxillary ridge), greater displacement of the underlying mucosa will occur.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 93: impression procedures for removable partial dentures  / academy of fixed orthodontics

In both the fluid wax functional impression technique and the selected pressure technique an impression of the displaced edentulous ridge is made by using an impression tray attached to the frame work, and the master cast is altered to accommodate the new ridge impression.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 94: impression procedures for removable partial dentures  / academy of fixed orthodontics

For this reason the technique is often referred to as the “Altered cast impression technique” or the “corrected cast impression technique”.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 95: impression procedures for removable partial dentures  / academy of fixed orthodontics

The advantage of the difference in The advantage of the difference in terminology is doubtful, and the descriptive terminology is doubtful, and the descriptive terms minimally displaced refer to the terms minimally displaced refer to the situation that has responded favorably and situation that has responded favorably and excessively “displaced” to that which excessively “displaced” to that which responds unfavorably are used.responds unfavorably are used.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 96: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 97: impression procedures for removable partial dentures  / academy of fixed orthodontics

The need for physiologic impressions was first recognized by McLean and others

They realized the need of recording the tissues of the residual ridge that would eventually support a distal extension denture base in the functional or supporting form and then relating this functional impression to the remainder of the arch by means of a second impression.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 98: impression procedures for removable partial dentures  / academy of fixed orthodontics

For this dual impression a custom impression tray was constructed over a preliminary cast of the arch, a function impression of the distal extension ridge was made, and then hydrocolloid impression was made with the first impression held in its functional position with finger pressure.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 99: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 100: impression procedures for removable partial dentures  / academy of fixed orthodontics

The greatest weakness of the technique was that finger pressure could not produce the same functional displacement of the tissue that biting force produced. The apparent advantage of the technique was lost with this weakness.

Many variations of this technique have been developed and advocated, but all require some form of finger loading pressure as the second impression is made.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 101: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 102: impression procedures for removable partial dentures  / academy of fixed orthodontics

Hindels and other developed irreversible Hindels and other developed irreversible hydrocolloid trays for the second impression that hydrocolloid trays for the second impression that were provided with holes so that finger pressure were provided with holes so that finger pressure could be applied through the tray as the could be applied through the tray as the hydrocolloid impression was made. hydrocolloid impression was made.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 103: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 104: impression procedures for removable partial dentures  / academy of fixed orthodontics

The main change that Hindels introduced The main change that Hindels introduced to McLean ‘s original technique was that to McLean ‘s original technique was that the impression of the edentulous ridge the impression of the edentulous ridge was not made under pressure but was an was not made under pressure but was an anatomic impression of the ridge at rest anatomic impression of the ridge at rest made with a free flowing zinc oxide made with a free flowing zinc oxide eugenol paste. eugenol paste.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 105: impression procedures for removable partial dentures  / academy of fixed orthodontics

As the hydrocolloid second impression As the hydrocolloid second impression was being made, however, finger pressure was being made, however, finger pressure was applied through the holes in the tray was applied through the holes in the tray to the anatomic impression. The pressure to the anatomic impression. The pressure had to be maintained until the alginate was had to be maintained until the alginate was completely set. The two were related to completely set. The two were related to each other, however, as if masticating each other, however, as if masticating forces were taking place on the denture forces were taking place on the denture base.base.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 106: impression procedures for removable partial dentures  / academy of fixed orthodontics

The main purpose of these techniques was to relate an impression of the edentulous ridge to the teeth under a form of functional loading.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 107: impression procedures for removable partial dentures  / academy of fixed orthodontics

A disadvantage of these techniques was that if the action of the retentive clasps of the partial denture is sufficient to maintain the denture base in relation to the soft tissues in the displaced or functional form, interruption of blood circulation would ensue, with possible adverse soft tissue reaction and resorption of the underlying bone.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 108: impression procedures for removable partial dentures  / academy of fixed orthodontics

If the action of the retentive clasps was not sufficient to maintain that functional relationship of the denture base to the soft tissue, when the partial denture was in the mouth at rest, the partial denture would be slightly occlusal to the position it would assume when occlusal force was applied.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 109: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 110: impression procedures for removable partial dentures  / academy of fixed orthodontics

This means that each time the patient ‘s teeth came together, the remaining natural teeth should contact only after the mucosa had been displaced to the position at which the impression was made. This early or premature contact of the artificial teeth is objectionable to many patients.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 111: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 112: impression procedures for removable partial dentures  / academy of fixed orthodontics

Most methods of obtaining a physiologic Most methods of obtaining a physiologic impression for support of a distal extension impression for support of a distal extension denture base accomplish the impression denture base accomplish the impression procedure before completion of the denture, procedure before completion of the denture, usually following the construction of the usually following the construction of the framework. framework.

It is possible, however, to obtain the same It is possible, however, to obtain the same results after the partial denture has been results after the partial denture has been completed. completed.

The technique is referred to as a functional The technique is referred to as a functional reline. It consists of adding a new surface to the reline. It consists of adding a new surface to the inner, or tissue, side of the denture base.inner, or tissue, side of the denture base.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 113: impression procedures for removable partial dentures  / academy of fixed orthodontics

The procedure may be accomplished The procedure may be accomplished before the insertion of the partial denture, before the insertion of the partial denture, or it may be done at a later date f because or it may be done at a later date f because of bone resorption, the denture base no of bone resorption, the denture base no longer fits the ridge adequately.longer fits the ridge adequately.

Although the functional reline has many Although the functional reline has many advantages, and fir correcting the fit of advantages, and fir correcting the fit of denture base that has been worn for a denture base that has been worn for a period of time is essential, it does present period of time is essential, it does present many difficulties. many difficulties.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 114: impression procedures for removable partial dentures  / academy of fixed orthodontics

The main problems that arise are caused by The main problems that arise are caused by failure to maintain the correct relationship failure to maintain the correct relationship between the framework and the abutment teeth between the framework and the abutment teeth during the impression procedure and failure to during the impression procedure and failure to maintain accurate occlusal contact following the maintain accurate occlusal contact following the reline.reline.

The procedures for relining and rebasing an The procedures for relining and rebasing an existing removable partial denture are discussed existing removable partial denture are discussed in detail. in detail.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 115: impression procedures for removable partial dentures  / academy of fixed orthodontics

The functional reline discussed here is that done The functional reline discussed here is that done to a completed partial denture before initial to a completed partial denture before initial insertion for the purpose of perfecting the fit of insertion for the purpose of perfecting the fit of the denture base to the residual ridge.the denture base to the residual ridge.

The partial denture is constructed on the cast The partial denture is constructed on the cast made from a single impression, usually with made from a single impression, usually with irreversible hydrocolloid. This is an anatomic irreversible hydrocolloid. This is an anatomic impression, and no attempt is made to alter it or impression, and no attempt is made to alter it or produce a functional impression of the produce a functional impression of the edentulous ridge.edentulous ridge.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 116: impression procedures for removable partial dentures  / academy of fixed orthodontics

To allow room for the impression material between the denture base and the ridge, space must be provided. One of the most accurate methods of ensuring uniform space for the impression is to adapt a soft metal spacer over the ridge on the cast before processing the denture base. After processing, the metal is removed leaving an even space between the base and the edentulous ridge.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 117: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 118: impression procedures for removable partial dentures  / academy of fixed orthodontics

The portion of the technique that introduces the The portion of the technique that introduces the greatest hazard is the making of the reline greatest hazard is the making of the reline impression. The patient must maintain the mouth in impression. The patient must maintain the mouth in a partially open position while the border molding a partially open position while the border molding and impression are being accomplished because:and impression are being accomplished because:

1.The border tissues, cheek, and tongue are thus 1.The border tissues, cheek, and tongue are thus best controlled andbest controlled and

2.The relationship between the partial denture frame 2.The relationship between the partial denture frame work and the teeth must be observed.work and the teeth must be observed.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 119: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 120: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 121: impression procedures for removable partial dentures  / academy of fixed orthodontics

The functional reline method of improving The functional reline method of improving the fit of the denture base to the residual the fit of the denture base to the residual ridge, although fraught with potential ridge, although fraught with potential danger, has the advantage that the danger, has the advantage that the amount of soft tissue displacement can be amount of soft tissue displacement can be controlled by the amount of relief given to controlled by the amount of relief given to the modeling plastic before the final the modeling plastic before the final impression is made. The greater the relief impression is made. The greater the relief the less will be the tissue displacement.the less will be the tissue displacement.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 122: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 123: impression procedures for removable partial dentures  / academy of fixed orthodontics

The fluid wax impression may be used to The fluid wax impression may be used to make a reline impression for an existing make a reline impression for an existing partial denture or to correct the distal partial denture or to correct the distal extension edentulous ridge portion of the extension edentulous ridge portion of the original master cast.original master cast.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 124: impression procedures for removable partial dentures  / academy of fixed orthodontics

OBJECTIVES

To obtain maximum extension of the peripheral borders of the denture base while not interfering with the function of movable border tissues.

To record the stress bearing areas of the ridges in their functional form.

To record non pressure bearing areas in their anatomic form.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 125: impression procedures for removable partial dentures  / academy of fixed orthodontics

The fluid wax impression is made with the The fluid wax impression is made with the open mouth technique so that there is less open mouth technique so that there is less danger of over displacement of ridge danger of over displacement of ridge tissue by occlusal or vertical forces.tissue by occlusal or vertical forces.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 126: impression procedures for removable partial dentures  / academy of fixed orthodontics

The term fluid wax is used to denote The term fluid wax is used to denote waxes that are firm at room temperature waxes that are firm at room temperature and have the ability to flow at mouth and have the ability to flow at mouth temperature. temperature.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 127: impression procedures for removable partial dentures  / academy of fixed orthodontics

The most frequently used fluid waxes are Iowa wax, developed by Dr.Smith at the University of Iowa, and Korrecta Wax no 4, developed by Dr. 0. C. and S. G Applegate at the Universities of Michigan and Detroit, respectively.

Korrecta wax no. 4 is slightly more fluid than Iowa wax.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 128: impression procedures for removable partial dentures  / academy of fixed orthodontics

The key to the use of fluid wax lies in two areas: space and time.

Space refers to the amount of relief provided

between the impression tray and the edentulous ridge. :1 to 2 mm is desired.

Each time the tray is introduced into the mouth, it must remain in place 5 to 7 minutes to allow the wax to flow and to prevent buildup of pressure under the tray with resulting distortion or displacement of the tissue.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 129: impression procedures for removable partial dentures  / academy of fixed orthodontics

The clinical technique for the use of the fluid The clinical technique for the use of the fluid wax calls for the water bath maintained at wax calls for the water bath maintained at 51° to 54° C into which a container of the 51° to 54° C into which a container of the wax is placed. At this temperature the wax wax is placed. At this temperature the wax becomes fluid. The wax is painted on the becomes fluid. The wax is painted on the tissue side of the impression tray with a tissue side of the impression tray with a brush. brush.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 130: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 131: impression procedures for removable partial dentures  / academy of fixed orthodontics

The peripheral extension of the The peripheral extension of the impression tray is critical. The borders impression tray is critical. The borders must be short of all movable tissue, but not must be short of all movable tissue, but not more than 2 mm short because the fluid more than 2 mm short because the fluid wax does not have sufficient strength to wax does not have sufficient strength to support itself beyond that distance.support itself beyond that distance.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 132: impression procedures for removable partial dentures  / academy of fixed orthodontics

Inaccuracies will develop if the wax is Inaccuracies will develop if the wax is extended beyond that length. Originally a extended beyond that length. Originally a harder wax, Korrecta Wax no:1 was used harder wax, Korrecta Wax no:1 was used to support the softer No.4 wax if to support the softer No.4 wax if extension beyond that length was extension beyond that length was needed. The no.1 wax however, is no needed. The no.1 wax however, is no longer available.longer available.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 133: impression procedures for removable partial dentures  / academy of fixed orthodontics

The wax is painted on the surface of the tray to a The wax is painted on the surface of the tray to a depth slightly greater than the amount of relief depth slightly greater than the amount of relief provided. The tray is seated in the mouth. The provided. The tray is seated in the mouth. The patients must remain with the mouth patients must remain with the mouth approximately half open for about 5 minutes. The approximately half open for about 5 minutes. The tray is removed, and the wax examined for tray is removed, and the wax examined for evidence of tissue contact. Where tissue contact evidence of tissue contact. Where tissue contact is present the wax surface will be dull. is present the wax surface will be dull.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 134: impression procedures for removable partial dentures  / academy of fixed orthodontics

If needed additional wax is painted on those areas If needed additional wax is painted on those areas not in contact with the tissue. The tray must remain not in contact with the tissue. The tray must remain in the mouth a minimum of 5 minutes after each in the mouth a minimum of 5 minutes after each addition of wax. The peripheral extensions are addition of wax. The peripheral extensions are developed by tissue movements by the patient. For developed by tissue movements by the patient. For the buccal and distobuccal extension in a the buccal and distobuccal extension in a mandibular impression the patient must move to a mandibular impression the patient must move to a wide- open-mouth position. This will activate the wide- open-mouth position. This will activate the buccinator muscle and pterygomandibular raphe buccinator muscle and pterygomandibular raphe and produce the desired border anatomy. and produce the desired border anatomy.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 135: impression procedures for removable partial dentures  / academy of fixed orthodontics

For the proper lingual extension for a mandibular For the proper lingual extension for a mandibular impression the patient must thrust the tongue into impression the patient must thrust the tongue into the cheek opposite the side of the arch being border the cheek opposite the side of the arch being border molded. The distolingual extension is obtained by molded. The distolingual extension is obtained by having the patient press the tongue forward against having the patient press the tongue forward against the lingual surface of the anterior teeth.the lingual surface of the anterior teeth.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 136: impression procedures for removable partial dentures  / academy of fixed orthodontics

These movements must be repeated a These movements must be repeated a number of times after the impression has number of times after the impression has been in the mouth long enough for the wax been in the mouth long enough for the wax to have softened sufficiently to flow.to have softened sufficiently to flow.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 137: impression procedures for removable partial dentures  / academy of fixed orthodontics

When the impression evidences complete tissue When the impression evidences complete tissue contact and when the anatomy of the limiting contact and when the anatomy of the limiting border structure is evident, the impression should border structure is evident, the impression should be replaced in the mouth for 12 minutes. This final be replaced in the mouth for 12 minutes. This final time to be certain that the wax has completely time to be certain that the wax has completely flowed and released any pressure that may be flowed and released any pressure that may be present.present.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 138: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 139: impression procedures for removable partial dentures  / academy of fixed orthodontics

The finished impression must be handled The finished impression must be handled carefully and the new cast poured as soon carefully and the new cast poured as soon as possible because the wax is fragile and as possible because the wax is fragile and subject to distortion.subject to distortion.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 140: impression procedures for removable partial dentures  / academy of fixed orthodontics

The fluid wax impression technique can produce an accurate impression if the technique is properly executed The procedure is time consuming, but if the time periods are not followed accurately, an impression with excessive tissue displacement will result.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 141: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 142: impression procedures for removable partial dentures  / academy of fixed orthodontics

Corrected castCorrected cast

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 143: impression procedures for removable partial dentures  / academy of fixed orthodontics

Technique

1. Fashioning custom acrylic resin impression tray 1. Fashioning custom acrylic resin impression tray to retention lattice work of removable partial to retention lattice work of removable partial denture.denture.

2. Developing denture base impression on these 2. Developing denture base impression on these trays.trays.

3. Removing edentulous ridge from master cast.3. Removing edentulous ridge from master cast.4. Securing framework with developed bases to 4. Securing framework with developed bases to

master cast.master cast.5. Pouring the impression with dental stone.5. Pouring the impression with dental stone.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 144: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 145: impression procedures for removable partial dentures  / academy of fixed orthodontics

Modifications:Variation of altered cast technique by Robert. P

Renner After the fit of framework has been refined intra

orally, the border of residual ridge are outlined on master cast. A small residual ridge are outlined on master cast. A small segment of bone plate wax is warmed over Bunsen burner and adapted to penciled outline. The wax will act as shim / space between residual ridge and custom tray.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 146: impression procedures for removable partial dentures  / academy of fixed orthodontics

Retention latticework of removable partial denture framework is warmed over a frame and framework is seated back on master cast. It should be freed in one or two areas so that the auto polymerizing acrylic resin tray will be adapted to it.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 147: impression procedures for removable partial dentures  / academy of fixed orthodontics

Apply separating medium, allow it to dry and auto dry and auto polymerizing acrylic resin material is mixed and polymerizing acrylic resin material is mixed and adapted to edentulous area of master cast, any adapted to edentulous area of master cast, any excess material is trimmed.excess material is trimmed.

When acrylic material is polymerized, assembly is When acrylic material is polymerized, assembly is placed in warm slurry water to soften and remove placed in warm slurry water to soften and remove wax spacer. Border molding is done. Vent holes wax spacer. Border molding is done. Vent holes are placed in order to reduce hydrostatic pressure are placed in order to reduce hydrostatic pressure developed between tray and tissues. Final developed between tray and tissues. Final impression is accomplished using metallic oxide impression is accomplished using metallic oxide paste or rubber base impression material.paste or rubber base impression material.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 148: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 149: impression procedures for removable partial dentures  / academy of fixed orthodontics

Procedure

11. A metallic paste impression is received in the laboratory. Remove impression material from the framework in areas that contact the teeth.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 150: impression procedures for removable partial dentures  / academy of fixed orthodontics

2. Trim the master cast so that the functional impression can be poured in correct relationship to the remaining teeth.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 151: impression procedures for removable partial dentures  / academy of fixed orthodontics

3. Seat the framework on the cast, and inspect it for contact between the functional impression and the cast. If contact

is present, the cast must be trimmed until clearance is present.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 152: impression procedures for removable partial dentures  / academy of fixed orthodontics

4. Cut retention grooves into the areas of the cast that will be corrected when the functional impression is poured

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 153: impression procedures for removable partial dentures  / academy of fixed orthodontics

5. Adapt and seal beading wax 2 to 3 mm above the borders of the functional impression

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 154: impression procedures for removable partial dentures  / academy of fixed orthodontics

6. Seat the framework on the cast, and secure it in position with sticky wax

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 155: impression procedures for removable partial dentures  / academy of fixed orthodontics

7. 7. Seal the leading edge of the impression to the cast to prevent dental stone from flowing onto the teeth when the cast is poured.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 156: impression procedures for removable partial dentures  / academy of fixed orthodontics

8. Use strips of base plate wax to compete the boxing of the impression on the buccal and lingual aspects

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 157: impression procedures for removable partial dentures  / academy of fixed orthodontics

9. A tight seal of beading and boxing wax is critical in this pouring method and is difficult to attain. Test the completeness of the seal by pouring clear slurry water into the boxed impression. A difficult area to seal is the relief area under the major connector.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 158: impression procedures for removable partial dentures  / academy of fixed orthodontics

10. Place the cast and impression in clear slurry water to soak for 4 to 5 minutes in preparation for pouring the corrected cast.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 159: impression procedures for removable partial dentures  / academy of fixed orthodontics

11. Measure and mix the improved dental stone. Pour the boxed impression by adding small increments of stone and using light vibration. Sufficient stone must be used to support the heel of the cast.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 160: impression procedures for removable partial dentures  / academy of fixed orthodontics

12. Remove the boxing and luting materials from the corrected cast. Shape the cast on a model trimmer.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 161: impression procedures for removable partial dentures  / academy of fixed orthodontics

13. 13. Soften the impressionSoften the impression material in warm water, and material in warm water, and remove the framework and impression tray from the remove the framework and impression tray from the corrected cast.corrected cast.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 162: impression procedures for removable partial dentures  / academy of fixed orthodontics

14. Burn the impression tray off the framework and place it on the cast. Smooth the land area of the cast, and the corrected cast procedures is complete.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 163: impression procedures for removable partial dentures  / academy of fixed orthodontics

AN ALTERED CAST PROCEDURE TO IMPROVE TISSUE SUPPORT FOR

REMOVABLE PARTIAL DENTURES- R J. LEUPOLD, F J. KRATOCHVIL : JPD 1965(15), 4, 672- 678

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 164: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 165: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 166: impression procedures for removable partial dentures  / academy of fixed orthodontics

SINGLE- TRAY DUAL- IMPRESSION TECHNIQUE FOR DISTAL EXTENSION PARTIAL DENTURES

JOSEPH A. R- JPD 1970(24,1,41-46)

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 167: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 168: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 169: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 170: impression procedures for removable partial dentures  / academy of fixed orthodontics

IMPRESSION TECHNIQUE FOR MAXILLARY REMOVABLE PARTIAL DENTURES

- C D. LEACH & T E. DONOVAN JPD 1983 (50)2,283-285

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 171: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 172: impression procedures for removable partial dentures  / academy of fixed orthodontics

AN ALTERED CAST IMPRESSION TECHNIQUE THAT ELIMINATES CONVENTIONAL CAST DISSECTING & IMPRESSSION BOXING

-M S. CHEN AND et al - JPD 1987 (57) 4, 471-474

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 173: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 174: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 175: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 176: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 177: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 178: impression procedures for removable partial dentures  / academy of fixed orthodontics

A MODIFICATION OF THE ALTERED CAST TECHNIQUE-RICHARD BAUMAN & JAMES .D B – JPD 1982(47) 2, 212-213

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 179: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 180: impression procedures for removable partial dentures  / academy of fixed orthodontics

AN IMPRESSION TECHNIQUE TO MAKE NEW MASTER CAST FOR AN EXISTING REMOVABLE PARTIAL DENTURE

-PHILIP J. R - JPD 1992 (67) 4, 488-490

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 181: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 182: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 183: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 184: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 185: impression procedures for removable partial dentures  / academy of fixed orthodontics

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 186: impression procedures for removable partial dentures  / academy of fixed orthodontics

For the production of accurate master cast the impression technique far out weights the selection of the impression material.

No available knowledge of the person making the impression material will produce results greater than the skill and knowledge of the person making the impression.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 187: impression procedures for removable partial dentures  / academy of fixed orthodontics

“ “ Good technique pays off ” is not merely a motto to hang on a wall but these are words of wisdom. Good technique will indeed result in better treatment and improved patient care.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 188: impression procedures for removable partial dentures  / academy of fixed orthodontics

1. Glossary of Prosthodontic Terms -8 th Edn, 2005.1. Glossary of Prosthodontic Terms -8 th Edn, 2005.

2. 2. Stewart, Rudd, KuebkerStewart, Rudd, Kuebker : Clinical Removable Partial : Clinical Removable Partial Prosthodontics.Prosthodontics.

3.3. McGivney GP, Alan B Carr David T BrownMcGivney GP, Alan B Carr David T Brown : : McCracken’s Removable Partial Dentures-11 th Edn.McCracken’s Removable Partial Dentures-11 th Edn.

4.4. Joseph E. Grasso, Ernest L. MillerJoseph E. Grasso, Ernest L. Miller : Removable Partial : Removable Partial Prosthodontics.Prosthodontics.

5.5. Alan A. Grant, Wesley JohnsonAlan A. Grant, Wesley Johnson : Removable Partial : Removable Partial Dentures. Dentures.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 189: impression procedures for removable partial dentures  / academy of fixed orthodontics

6. 6. F. James KratochvilF. James Kratochvil : Partial Removable Prosthodontics. : Partial Removable Prosthodontics.

8. 8. Robert P. Renner, Louis J. BoucherRobert P. Renner, Louis J. Boucher : Removable Partial : Removable Partial Dentures. Dentures.

9. 9. Kenneth D Rudd, MorrowKenneth D Rudd, Morrow: Dental Lab, Procedure for : Dental Lab, Procedure for Removable Partial Dentures.Removable Partial Dentures.

10. 10. DavenportDavenport: Color Atlas of Removable Partial Dentures.: Color Atlas of Removable Partial Dentures.

11. 11. BatesBates: Removable Denture Construction.: Removable Denture Construction.

12. 12. OsborneOsborne: Partial Dentures.: Partial Dentures.

www.indiandentalacademy.comwww.indiandentalacademy.com

Page 190: impression procedures for removable partial dentures  / academy of fixed orthodontics

AN ALTERED CAST PROCEDURETO IMPROVE TISSUE SUPPORT FOR REMOVABLE PARTIAL DENTURES- R J. LEUPOLD, F J. KRATOCHVIL : JPD 1965(15), 4, 672- 678

SINGLE- TRAY DUAL- IMPRESSION TECHNIQUE FOR DISTAL EXTENSION PARTIAL DENTURESJOSEPH A. R- JPD 1970(24,1,41-46)

IMPRESSION TECHNIQUE FOR MAXILLARY REMOVABLE PARTIAL DENTURES- C D. LEACH & T E. DONOVAN JPD 1983 (50)2,283-285

AN ALTERED CAST IMPRESSION TECHNIQUE THAT ELIMINATES CONVENTIONAL CAST DISSECTING & IMPRESSSION BOXING-M S. CHEN AND et al - JPD 1987 (57) 4, 471-474

A MODIFICATION OF THE ALTERED CAST TECHNIQUE-RICHARD BAUMAN & JAMES .D B – JPD 1982(47) 2, 212-213

AN IMPRESSION TECHNIQUE TO MAKE NEW MASTER CAST FOR AN EXISTING REMOVABLE PARTIAL DENTURE-PHILIP J. R - JPD 1992 (67) 4, 488-490www.indiandentalacademy.comwww.indiandentalacademy.com

Page 191: impression procedures for removable partial dentures  / academy of fixed orthodontics

For more details please visit For more details please visit www.indiandentalacademy.comwww.indiandentalacademy.com

www.indiandentalacademy.comwww.indiandentalacademy.com