For complete dentures

Dr. Ahmad Rabah

• It is a very important stage in denture construction which follows the setting up of teeth and waxing up stages

• To Check all the details in dentures because it is difficult and sometimes impossible to do alteration in a finished denture

Procedures of try-in

I- Extra-oral examination of trial denture: - The articulator - The master cast - The trial denture bases - The teeth

II- Intra-oral examination of the trial denture: - Upper denture - Lower denture - Both upper and lower together

III- Patient Approval IV- Protrusive records

1. The articulator: * VDO: * Mounting rings * Smooth movement * Locked in centric no other movement

2. The master cast: Free from scratches, air bubbles, wax debris 3. Denture base: stable, borders smooth, round, 4. Artificial teeth: shade, form, size, arrangement, relation to

ridge

Check the upper denture alone 1. Extension, stability, retention 2. Neutral zone and tongue space. 3. Occlusal plane height and orientation

Check the lower denture alone 1. Extension, stability and retention. 2. Neutral zone and tongue space. 3. Occlusal plane height and orientation

Check both dentures 1. Vertical dimension 2. Centric occlusion 3. Evenness of occlusal pressure. 4. Evaluation of esthetics 5. Evaluation of phonetics

1- Extensions

• All the peripheries of the denture should be in the vestibule

• Over extended denture will move away from the tissues due to

direct muscle action on the peripheries

• Under extended denture won’t remain in place when the

patient opens his mouth due to lack of peripheral seal

• This is done by visualization, palpation or testing paste

2- Retention

When the patient opens and closes his mouth the denture must stay in it’s place and considerable force needed to remove it.

We have to check the retention of the denture in the following areas:

a. The anterior part of the denture (labially) by pulling the anterior teeth gently

b. In the posterior palatal seal area (post dam area) by applying outward pressure on the palatal surfaces of upper anterior teeth

c. Tuberosity region in the upper denture by applying outward pressure on the palatal surface of each canine and check for opposite side

d. The retromolar pad area in the lower denture by applying pressure on the lingual surface of the anterior teeth outward and downward

3- Stability

• Checking of the stability is done by applying alternating vertical pressure on one side of the denture if it rise from the other side this means that the teeth are outside the ridge in side of the applied pressure.

• If the denture teeters in the middle it indicates that the denture is warped in the middle or the relief area isn’t done properly.

Causes of denture instability: 1- The teeth set outside (more buccally) the ridge 2- Warpage of the denture base 3- Unrelieved hard area.

Setting up of the lower teeth, and shape of the polished surface should allow proper tongue function (in the neutral zone area) and to avoid the cramped tongue (lack of tongue space) leading to tongue biting

Causes of cramped tongue: 1. Posterior teeth are set lingual to the neutral zone 2. Posterior teeth are tilted more lingually 3. Posterior teeth are too broad bucco-lingually

A combination of methods to evaluate the vertical dimension of occlusion would likely give a more accurate evaluation after teeth arrangement. These methods include: • Facial measurements • Phonetics • Esthetics • Patient’s proprioception

When the mandible is in the rest position there should be an interocclusal space of at least 2mm at the first premolar but sometimes in some patients may require more than 2mm

The free way space

FACIAL MEASUREMENTS • Ask the patient to wet his lips, swallow and then allow his

mandible to rest then ask him to maintain this position. Part his lips to see whether his teeth are touching or there is adequate space between his teeth.

• If the teeth are in contact at rest; the VDO is high so needs a new VDO record.

PHONETICS • It is difficult to locate speech problems at the try-in stage due to

different reaction of the tongue and lips to wax than the finished and polished denture surface, however, series of test is to be carried out

• Ask the patient to say S, S, S or count from 60 to 70; if there is clicking sound of teeth then the VDO is high and if there is whistling then the VDO is low.

• Instruct the patient to say “f” or “v” to evaluate the anterior

and posterior teeth positions also low or high position of

maxillary teeth

• If the incisal edges of the upper anteriors contact the lingual

side of the lower lip, then either the upper anteriors are set too

far lingually or the lower anteriors are set too far labially

• Difficulty in making contact between the lower lip and upper

teeth usually indicates that the maxillary anteriors must be

moved downward

• If the upper teeth are placed too far anteriorly, there will be

depression to the lower lip during “f” or “v” sounds

Looking at the facial form shows: • If the appearance of the patient from front and lateral views

is like old man (approximation of nose and chin), then VDO is low

• If they show stretching of muscles then VDO is high

Ask the patient if he feels that the teeth are touching earlier to mouth closure which indicates high VDO, late indicating low VDO or about the right time which indicates correct VDO

ESTHETICS

PATIENT PROPRIOCEPTION

In case of too much teeth showing (which indicates high vertical dimension) then all teeth will have to be removed and a new jaw relationship recorded. Wax rims can be added to the dentures bases and then trimmed to the desired level.

Remounting

When the complaint that too little teeth are visible (low vertical dimension) wax can be added to the occlusal surfaces of the teeth until a satisfactory amount of wax is visible. Anew centric relation record should be made and then removing and re-setting of the teeth to this new position

Remounting

• Corrections to the wrong VDO

Ask the patient to relax and try to touch the back of the

upper denture with the tip of the tongue and slowly close the

teeth together, making sure the bases are stable

Note if the teeth interdigitate accurately exactly like they do

on the articulator

This test gives correct information ,when the try in is made

with well adapted base plates

The trial dentures should remain in place while the teeth

interdigitate

Faulty centric occluding relation

• Due to an error either in the registration or mounting the

articulator

• Trial dentures moved from their places due to poor retention

and stability

If centric occluding relation is found wrong in the patient’s

mouth a new mouth record of centric occluding relation is

obtained. Mandibular cast is detached and remounted

according to the new record

Even occlusal pressure:

As the teeth come together, they should occlude evenly with equal

pressure.

Testing:

a. Place two thin celluloid strips between the posterior teeth and check

for any difference in force of withdrawal

b. Placing the blade of wax knife between occlusal surfaces

c. Using articulating check paper and look for deep pressure areas

Causes of uneven occlusal pressure: • Unequal pressure during Jaw relation recording (softening of the

wax) • Errors in seating record blocks on their respective casts either due

to warpage, wax debris or touching record bases at heal • Errors in mounting and/or interferences at posterior parts of cast

Correction of uneven occluding pressure

• If it is very slight, it can be corrected by grinding the teeth after the denture is processed.

• If the unevenness is more than slight, it is better to take a new centric relation record at this stage. Remove the lower posterior teeth, replace by softened wax and record a new jaw relations then remount the lower cast.