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TRY-IN

Try-in procedure in Complete denutre prosthodontics refers to the insertion of Trial waxed denture in the mouth of the patient for assessing the success of treatment plan and for verification of jaw relation records made during the treatment procedure. Try-in procedure offers the operator yet one more chance for communication with the patient and at the same time mistakes that may have happened during clinical procedures would be better understood.

A trial denture is defined as a prelimenary arrangement of teeth that has been prepared for placement into patients mouth to evaluate esthetics and maxillomandibular relationship.(GPT)

OBJECTIVES OF TRY-IN PROCEDURE

1. To observe the appearance and reaction of the patient in respect of selected teeth for their size, shape and arrangement.

2. To examine the contours of trial denture in relation to surrounding tissues.

3. To evaluate the location; plane of occlusion and to verify the established vertical dimension of occlusion and free way space.

4. To check centric and eccentric occlusion.

5. To make any additional inter occlusion records for further adjustments to the articulator if required.Try-in appointment consists of three parts

1. Perfection and verification of jaw relation records.

a. Vertical jaw relation (dimension)

b. Centric jaw relation

2. Centric jaw relation records, articulator and cast adjustment, establishing the posterior palatal seal.

3. Creating facial and functional harmony with anterior teeth.

PROCEDURE FOR LOWER DENTURE

After the placement of the lower denture in mouth.

Peripheral outline is checked to ensure that it is within the functional limit.

A. BUCCAL & LABIAL PERIPHERY

1. Particular attention to buccal frena is given and ensure that adequate allowance is given for its movement.

2. The bulk and shape of buccal aspect of the denture is checked. It should take form of gentle convexity in molar region and concave in the premolar region in order that the buccinator muscle as it contracts forces the cheeks in an inward direction and presses the denture downwards. Thus may assist in the retention of the denture.

B. THE LINGUAL PERPHERY

1. The denture is held in place with light pressure and the patient is asked to protrude his tongue sufficiently to moisten his lips. If the denture lifts at the back, it is beyond the functional limit in the region of lingual pouch.

2. Then ask the patient to place the tip of his tongue as far back on his palate as possible, if the denture lifts in front it is most possibly that lingual frenum is not given adequate allowance. This should be corrected.

C. POSTERIOR EXTENSION

This is from the base of the retromolar pad till 1/3 of it. This is the posterior limit.

D. UNDER EXTENSION

a. If the denture is found to be not extending upto functional limit in any part of the periphery as shown by the presence of gap between it and the functional position of the surrounding mucous membrane functional impression can be made to record those areas.

E. STABILITY UNDER OCCLUSAL LOAD

This is used to determine if occlusal stresses will be transmitted unfavourably. Apply pressure lighly with finger in the premolar and molar regions of each side alternately, this pressure must be directed at right angles to the occlusal surface. If pressure on one side causes the denture to tilt and rise from the ridge on the other side, it indicates that the teeth on the side on which pressure is applied are set too far outside the ridge. It may also indicate lack of adaptation of the base on the side being loaded or the flanges on the side which rises are not extending upto functional limit.

F. TONGUE SPACE

1. If the tongue is cramped by the denture, lateral pressure will be exerted, producing instability when the tongue moves.

2. Test for lack of tongue space is done by asking the patient to relax the tongue, make sure that the denture is seated on the ridge and then request him to raise the tongue. If the tongue is cramped, the denture will begin to rise immediately the tongue moves. The causes of tongue cramping:a. Posterior teeth set inside the ridge.b. Molar teeth which are too broad buccolingaully. Such teeth should be replaced by smaller ones or their width reduced by grinding.c. Molar teeth leaning inwards. This will not always cause cramping of the tongue but should never be allowed to occur as it interferes with the free vertical movements of the tongue. If this inward inclination is necessary to obtain occlusion, it is best to finish the denture and then grind away the lingual cusps.G. HEIGHT OF THE OCCLUSAL PLANE

1. The denture must be examined to see if the tongue when relaxed lies above or below the occlusal plane.

2. It should be at the level of occlusal plane specially the junction of Dorsal and ventral surface of tongue.To obtain maximum stability of a lower denture, the occlusal plane of the lower teeth should be very slightly below the bulk of the tongue, so that the tongue performs the majority of its movements above the denture and thus tends to keep the denture down.

The denture must therefore be examined to see if the tongue, when relaxed, lies above or below the occlusal plane. Ask the patient to relax and place the tip of the tongue comfortably and without strain behind the lower front teeth, which is the normal relaxed position of the tongue, and then open his mouth without moving his tongue. If the height of the occlusal plane is correct, the tongue will be seen to lie on top of the lingual cusps.

If the lower denture still tends to rise unduly after the lingual periphery has been trimmed, and as much lateral space as possible for the tongue has been allowed, it may be necessary to re-set the case completely, lowering the occlusal plane.

The height of the occlusal plane is also of importance for the following reason: the greater the height of the lower denture, the longer will be the lower front teeth and the greater therefore the surface exposed to the pressure of the lower lip.

This concludes the examination of the lower denture alone, and it should be removed from the mouth and placed in a basin of cold water.

PROCEDURE FOR UPPER DENTURE1) Peripheral outlinea) The buccal and labial periphery is checked as for lower denture

b) The posterior extention in an area where the tissue can be placed without interfering with the function.

2) Stability

a) Stability under occlusal load may be carried out as for the lower denture but is intended to check the closeness of adaptation of the base against the mucosa and the future support of the denture in those cases where the mucosa is unevenly displaceable.3) Retention

a) Retention is checked by seating the denture with a finger on the vault of the palate and then attempting to remove the denture at right angles to the occlusal plane.

b) Load is then applied upwards and outwards in one canine region to check the retention force in the contra lateral corner of the denture i.e., in the region of tuberosity vestibular space and pterygomaxillary notch then check the other side in the same way.

BOTH DENTURES TOGETHER

I. Check the vertical height (Vertical Jaw Relation)1) An over closed vertical height will be associated with a large free way space, and when the teeth are in occlusion the lips will be seen to be pressed too firmly together with some loss of the vermilion border.

2) Ask the patient to speak S determination of closet speaking space.

3) Varity the VDO once again comparing with the earlier one.

II. Check for horizontal relation (centric relation)1) If the registration is accurate, the teeth will interdigitate in the mouth in exactly the same manner as they do on the articulator but if the registration is wrong, the teeth will not interdigitate correctly and may even occlude cusp to cusp on one or both sides.

2) The clinician must make quite certain that occlusion in the mouth is not due to movement of the dentures on the ridges, tilting of either denture or dropping of the upper denture.

3) When errors of occlusion are noted at this trial stage they must be corrected by re-recording the position of occlusion.Re-Recording Of Horizontal Relation (Centric Relation)

1) The dentures are seated on the casts on the articulator and the posterior teeth removed from one of the dentures and replaced by wax which should be trimmed to occlude with the posterior teeth of the other denture without altering the vertical dimension as set on the articulator.

2) The position of occlusion is recorded by adding a little of softened base plate wax to the chilled blocks, placing the dentures in mouth and asking the patient to close on the back teeth thus impressing the cusps of the opposing teeth into the wax without effecting vertical height.

III. Evenness of Occlusal ContactProvided the horizontal and vertical relationship are correct, the evenness of the occlusion is next checked.

As the teeth close, they should occlude evenly and with equally distributed pressure all around.

To Test unevenness of occlusal pressure

Place two pieces of thin celluloid strip between the teeth in the molar region, one on each side. Request the patient to close and then endeavour to remove the celluloid strips simultaneously, holding one with each hand, by pulling them out between the closed teeth. Any difference in the force required to remove the strips will be readily appreciated, and if this force is interpreted in terms of occlusal pressure, an assessment may be made of whether or not it is even. Repeat the test in the premolar regions.

If the unevenness of contact is very slight, soften the wax supporting the teeth on one of the dentures on the offending side. Replace the denture in the mouth and holding the lower firmly in place, request the patient to close. The teeth on the side of heavy pressure will sink slightly into the softened wax until the occlusion of the teeth on the opposite side arrests them thus evening the occlusal pressure. If the unevenness is more than very slight, this technique is not advisable as the initial contact on one side will either compress the supporting mucosa on that side or cause deviations of the mandible as the first tooth contact acts as a pivot. Complete retaking of the retruded contact position (RCP), record with builtup wax blocks is the only solution.

1V. Balanced occlusion and articulationThe first check is for centric occlusion, which, if found to be incorrect, necessitates the removal of the lower posterior teeth and the recording of the correct position on the wax blocks replacing them. The lower model is then removed from the articulator and re-set according to the new position, thus keeping the upper model in the same position as it was set by means of the face-bow. When the centric position is found to be correct, the testing of the waxed-up denture continues in the following manner:

Check for evenness of occlusal pressure in the centric position with celluloid strips and then test for balance with gentle lateral and protrusive movements. With the teeth in a lateral position of occlusion, insert the point of a wax knife between the teeth on the balancing side, and attempt to separate them; if they do separate, it shows that the occlusion of the teeth on tat side is apparent only and is resulting from the displacement of the denture bases from the ridges. The cause of this error may be due either to an incorrect face-bow reading, or to an incorrect condylar path registration. When the error is considerable, these registrations must be taken again, the models re-mounted on the articulator and the teeth re-set; but if the error is only slight, it ay be corrected by grinding the occlusal surfaces of the teeth when the dentures are finished. Minor errors of cuspal interference may be eliminated at this stage, or when the dentures have been finished and fitted, by careful grinding of the teeth concerned.V. Appearance

This aspect of the trial stage is a matter more for individual judgement and sometimes the patients ideas.

(a) Center Line: (Clinical midline)

Stand in front of the patient, some distance away and checked. Minor may be corrected by adjusting the maxillary anterior teeth at the chair side but if the error is more than 1mm then the teeth are rearranged.

(b) Anterior Plane:

This is also observed from the same position and any tendency for this plane to slope markedly up or down should be noted and corrected. The incisal edges of the maxillary incisors lying parallel to the smiling lower lip, produces a pleasing appearance.

(c) Shape Of The Teeth:

Compare the selected teeth form with the patients facial type.

(d) Size Of The Teeth:

Slight irregularities during tooth arrangement such as mesially rotated lateral tooth will affect the apparent size of the tooth i.e., canine and which looks larger than small first premolar. But this is subtle and may look more natural in some cases.(e) Shade And Blend Of The Teeth:

The shade in affected by the colour and density of the surrounding wax which is entirely different environment than the acrylic in the finished denture.

(f) Profile And Lip Form:

Observe the patients profile and if the lips are either excessively distended or unduly sunken.

(g) Amount Of Tooth Visible:

The patient is asked to speak as the dentist observes. In this connection remember that a smiling person usually only shows the upper teeth, if much of the lower incisors are visible, or only these teeth show, examine the amount of over lap and if excessive reduce it by altering the lower teeth.(h) Approval Of The Apperance By The Patient:

It is always wise for the dentist to obtain the patients approval of the appearance of the trial dentures. It is also recommended that the patient should bring his or her relative for the approval of the appearance.

VI. PhoneticsThe use of the fricatives fa and va when arranging anterior teeth, as suggested by landa, is an aid in determining the proper position of the maxillary incisors. Normally the lower lip contacts the incisal edges of these teeth in pronouncing these sounds. The pronunciation of words ending in s to establish the closet speaking space in determining proper vertical dimension as advocated by silver man.

VII Stabilization of Denture Base (if required)Can be reinforced with:

1) Zinc Oxide Eugenol Impression paste

2) Rubber base impression material

3) Self cure acrylic

4) Soft linear and tissue conditioners

Permanent and stable denture base

5) Heat cure acrylic

6) Metallic denture base

VIII. Recording of posterior palatal seal area if required

1) Conventional approach

2) Fluid wax method

IX. Approval of appearance by the patient

It is always wise for the operator to obtain the patients approval of the appearance of the waxed up dentures before they are passed to the technician for completion, as this enables the operator to make necessary adjustments.

Some patients are quite prepared to leave the question of appearance to the operator, whilst others are extremely fussy over the smallest detail. When dealing with the former class, the operator should insist that they consider the matter of their appearance, otherwise when the dentures are finished they may react unfavourably. In the case of the fussy patient, much time and trouble must be spent on getting the shade, shape and set-up of the teeth just as the patient wishes. (It is very important to obtain his final approval before finishing the case.) In this connexion the operator often needs to use his restraining influence to avoid extremely bad errors of aesthetics, and a waste of time. It should be remembered that other people will see more of a patients dentures than he will, and if they are not aesthetically pleasing in the opinion of his relations and friends he will usually become dissatisfied with them. It is, therefore, advisable to ask the patient to bring a relation or candid friend with him at the time of trying-in the dentures, and the approval or criticism of this second individual should be sought as well as that of the patient himself.

S components for trial denture assessment

Summary of components for trial denture assessment

Dentists role Ensure that the trial dentures fit the master casts and that the bases are stable.

Verify the vertical, sagittal and coronal intermaxillary relations.

Verify the stability of the bases in the mouth.

Verify the selection of anterior and posterior teeth, their colour and that the occlusal planes are correct.

Verify that speech is lucid.

Verify that the waxwork is aesthetic and functional.

Patients role To record their wishes and expectations.

Informed consent agreed and that the patient approves of any alteration in form from the previous dentures.

The patient, and any accompanying person, should agree on the acceptability of the trial dentures and that the patient is happy to proceed to completion.

Technicians role To have replicated the registration records faithfully.

To place teeth according to prosthodontic norms.

To provide stable bases.

To ensure that balanced occlusion/articulation is provided, according to the prescription by the clinician.

To have articulated casts appropriately and to have set condylar angles to any prescription given.

To ensure waxwork is complementary to the age and personality of the patient.