Establish anterior tooth position on the maxillary rim, select the appropriate artificial teeth (shade and mold), then set teeth 6-11 in the wax.
Calculate and establish vertical dimension of occlusion (VDO).
Mount the maxillary cast with a face bow record.
Mount the mandibular cast at the desired VDO with a centric relation record
Wax spatulas, #31 and #7
Green handled knife
Acrylic adjustment burs
Alginate mixing bowl
Air/water syringe tip
Thompson marker stick
Medicine cup with Vaseline
(2) Sheets of pink baseplate wax
Red handled knife and blade
Slow speed straight handpiece
(2) Wooden tongue blades
2x2 gauze and cotton rolls
Hotplate or large flat metal spatula
Regisil with mixing tip and gun
(2) Sheets of Aluwax
The esthetic aspects and anterior tooth placement of new dentures is greatly simplified if the patient has an existing maxillary denture that has been in service for a number of years, the patient is well adapted to the denture, and the denture has reasonable appearance and form. In these cases, it is the clinician's responsibility to copy the dimensions and esthetic aspects of the original denture very closely.
The maxillary rim is adjusted first and exclusively, to establish upper lip support, incisal length, midline, occlusal plane orientation, symmetry and arch form.
The incisal length varies with gender, age and upper lip contour, with young women displaying up to 5mm of maxillary incisor below an active and bow-shaped upper lip, and older men with flaccid and long lip displaying none of the incisal edge. The incisal length of an existing maxillary denture can be measured with a ruler, when the denture is in place, between incisal edge and the under-surface of the nose (don't compare flange-to-tooth measurements between old denture and new rim, because of variation in flange length).
The incisal length can be confirmed by fricative speech patterns ("f" and "v" sounds), during which the lower lip brushes the maxillary incisal edges (in this situation, the wax rim).
The midline mark on the rim is aligned with the center of the face; dental landmarks, such as incisive papilla, labial frenum, and/or philtrum may not be within the mid-plane of the face. Instead, hold dental floss vertically at arm's length in front of the patient's face, and position it from right to left until the floss seems to be centered in the face. Transfer the floss midline onto the rim.
The occlusal plane of the upper wax rim is adjusted so that it is horizontal, aligned anteroposteriorly with the ala-tragus, or Camper's line, and parallel with the interpupillary line when viewed from the frontal view.
The symmetry of the anterior arch curve is best viewed from behind the patient, looking down over the nose at the wax rim contour. The wax should be recontoured so that the right and left aspects of the midline mark are mirror images. The contour of the upper lip should also be observed at this time, and wax is added or removed accordingly. This contouring may also involve shortening or thinning the labial flange of the record base.
The arch form is also considered at this time, based on gender and facial contours. The arch form of the residual ridge may be of limited usefulness, because of bone resorption and unknown original tooth position. It is usual practice to reflect the facial form (rounded, square,tapering) in the maxillary anterior arch, and a round-tapering contour favors women while the square form is appropriate for men.
When the maxillary rim contours are appropriate, place ala marks (vertical lines, indicating central pillars of the maxillary canines) and a high upper lip line (suggests how much of the maxillary arch will display when the patient smiles broadly).
Artificial tooth selection requires the clinician to determine shade and mold in cooperation with the patient. Shade selection is based on patient preference, and the dentist can assist the patient by showing a few shade tabs at a time (a notorious approach is to hand the patient the entire array of 16 shades). A typical adult tooth shade is A-3 or C-2, but there is no right or wrong decision by the patient. In the clinic all the Vita shades are used and bleach shades are available (special request). Gold teeth in various forms and sizes are also available for an extra fee. Anterior and posterior tooth sizes are generally related to arch size, with small, medium and large categories. Maxillary anterior molds are available in square, ovoid and tapering, andshould mimic facial form and gender criteria, (see arch form discussion above). Generally an anatomical posterior mold is preferred (better appearance and balanced occlusion), but there are many situations when a flat posterior tooth is indicated: resorbed residual ridge, poor jaw coordination, severe retro- and prognathic jaw relations, including posterior cross-bite, and history of flat or severely worn occlusal plane.
When the teeth have been selected, obtain an instructor's signature on a laboratory prescription requesting artificial teeth and pick up the teeth at Laboratory Services. The maxillary anterior teeth (6-11) are set in the wax rim, then tried in the patient's mouth to confirm tooth selection and position. A considerable advantage of the early anterior try-in is that it initiates the important process of patient participation and approval, and demonstrates to the patient that progress is being made.
After completing the maxillary rim, the VDO is established next, using the patient's rest dimension as a reference point. Customarily, the patient's existing maxillary denture or the maxillary rim is in the mouth, to provide adequate support for the upper lip during restdetermination. Have the patient sit upright without head support, or have the patient stand. With the lips together and the jaw relaxed, the patient is measured for vertical dimension of rest (VDR) by means of ruler, Boley gauge, or Verticorder.
The ruler and Boley gauge require 2 dots to be placed, one on the chin and one on the tip of thenose.
The Verticorder has a chin cup, which is held in place by the thumb and forefinger of thedominant hand, with a light inward pressure. There is an adjustable vertical arm, which isadjusted up or down until the end of the device points at the tip of the nose. Pressure indicatingspray is applied to the end of the device; when the Verticorder is pivoted toward the face, the pressure indicating powder is transferred to the nose, creating a VDR mark. Preserve this markon the nose; do not allow the patient to wipe away the mark or to disturb it. It is a criticallyimportant reference mark for the VDO determination.
With any of the measurement devices, the clinician should interrupt the patient's posturalposition several times, re-establish rest position, and then re-measure VDR. Typical interruptionactivities are to open the mouth halfway, lick the lips, recite words or phrases with "m" sounds,or to swallow, each time returning to the "lips together, jaw relaxed" position. These activitieswill demonstrate the reproducibility of the rest position.
If the patient is unable to demonstrate a consistent rest posture, or there is a wide range of VDRmeasurements, the clinician must use judgment to decide which position is most appropriate.
One option is to use speech to measure a habitual position of the jaw. Have the patient countfrom 60 to 70, which creates repeating "s" sounds, while holding the Verticorder lightly in place. The pressure spray on the end of the instrument will make a "speech zone" mark on the nose,and the most superior edge of the mark will be the "closest speaking" position, which in manypatients is close to the rest position.
Now the mandibular rim is placed in the mouth and the patient is guided into a centric closureuntil the upper and lower rims touch. Measure the VDO and if greater than the VDR, which isusually the case, melt wax from the lower rim occluding surface to reduce the distance betweenthe jaws. The important sole purpose of this exercise is to create a physiologic freeway spacefor the denture patient, or, in other words, a VDO that is 3-5mm less than the patient's VDR, asmeasured between the patient's chin and nose.
The measurement of VDO using a ruler or Boley gauge, and the comparison with the previouslydetermined VDR, is straightforward. Beware the variation in measurement because of skinmovement, particularly on the chin; a tense or erratic patient can cause many problems with theVDO step by contracting the mentalis muscle. The clinician should also understand that apatient with dense beard presents difficulties in locating a measurable point on or near the chin.
The measurement of VDO using the Verticorder is also straightforward for most patients, as longas the clinician understands that the instrument is not changed or re-adjusted after the restposition is marked. Rather the instrument remains at a fixed setting or length, and the end ofthe instrument touches the nose in a position relative to the mark created during the restposture. The optimal VDO is achieved when the Verticorder end is 3-5mm above the restposition mark on the nose, indicating that the mandible is closed, or that the chin is closer to thenose, compared with the patient's rest position. If the VDO is indicated below the rest positionon the tip of the nose, this means that the VDO is open and that more wax should be removedfrom the lower rim. This explanation is offered to help novices understand the simplemechanics involved in measuring and verifying this important parameter in denture prosthetics.
Finally, because it is important and because it is routinely misjudged in clinical practice, the VDOcan be checked by several other means:
Speech – With both rims in place, the patient is asked to count from 60 to 70, and the enunciation of "s" sounds creates the "closest speaking space." The clinician willobserve that the rims come close together, but should not collide, during "s" sounds. Precaution is advised when using speech with occlusal rims, which may be loose andalways have considerable bulk in areas of tongue activity when compared with actualdentures or an empty mouth. Speech analysis at the occlusal rim stage, in a patient whohas never worn any denture, may be a frustrating exercise for all involved.
Swallow – The patient should be able to swallow without restriction with rims in place. Difficulty swallowing is an early symptom of open VDO.
Facial Contour – Problems with profile of the lower half of the face are particularlytelling of significant opening or collapse of VDO. If the patient has a lip-protrudingappearance, especially if the lips cannot be closed, it is likely that the VDO is muchgreater than VDR and/or that the wax rims are too bulky facially. On the other hand,collapsed appearance of the lips, with large folds in the commissures, indicates greatlyreduced VDO or facial under-contour of the wax rims.
As the wax rims approach a physiologic VDO, a common finding is lack of space betweenposterior aspects of the wax rims/record bases. The clinician should assess the proximitybetween the opposing rims as the patient closes. Premature contact of the heels will result inmovement of one or both record bases, and the patient may move the jaw (typically in aprotrusive direction). If the clinician is not sure of the situation, it is recommended that theheels of the mandibular record base be reduced to create visible space between the recordbases. It is appropriate to emphasize here that, while lack of posterior space and collision ofposterior record bases are very common in clinical situations, it is quite difficult for the clinicianto see or judge ahead of time that this problem is occurring.
Ultimately, if the problem is not resolved as it is happening, it shows up later after the centricrelation record, when the rims are removed from the mouth and reassembled in the hand. Then the clinician will be able to see if there is contact between the posterior aspects of therecord bases; if this is the case, then the offending wax rim or plastic base must be removed,and the centric relation record repeated.
The centric relation record is next. By this time in the appointment the clinician and the patientshould have rehearsed the centric relation (retruded) closure multiple times.
The maxillary rim is prepared by carving 3 posterior occlusal grooves in each side; the groovesare 5mm deep and wide, have 45 degree walls with sharp definition, and form a "z" patternwhen viewed from above the occlusal plane. Smear Vaseline in the grooves and over the flatocclusal plane, then place the upper rim in the mouth.
The lower rim is prepared by softening an end of Aluwax over the Bunsen burner, folding,heating, folding repeatedly to form a cylinder of softened wax, then pressing 1/3 to 1/2 of thecylinder onto the posterior base of the lower rim. Sear the warm Aluwax to the plastic baseusing a hot wax spatula (so that the Aluwax will not separate later from the lower base).
Flame the surface of the Aluwax with a Hanau torch (the optimal wax consistency is described as"dead soft") then place in the mouth without disturbing the warm wax. Now the patientcooperation part of the centric relation record begins.
Ideally, the record bases are retentive and stable, and the clinician can retrude and close thecompletely relaxed mandible as the soft Aluwax records centric relation. In reality, few of theseideal conditions exist; the rims may be loose and unstable, the patient may not cooperate andoften resists the clinician's efforts, and the result may be a record of a completely random jawposition.
The following are some tips for obtaining a satisfactory centric relation record:
If the upper rim is not self-retentive, use denture adhesive to secure it. If this is not effective,get a partner or faculty member to hold the upper rim in position (typically with a single fingeron the incisal edge of the rim). Do not proceed if the upper rim is floating or falling down; youwill not be able to control both rims during the record.
The patient posture should be reclining, with the spine 45 degrees to horizontal; this allowsgravity to assist in distalizing the mandible.
The clinician holds the lower rim with its soft Aluwax in place and the mandible is manipulatedwith a "bimanual" grasp (forefingers bilaterally on the buccal shelf of the rim and thumbscontacting under the inferior border of the mandible).
It is possible for the clinician to do the entire closure into the softened wax for patients who areable to completely relax the jaw muscles. However, this is rarely the case, and it is moreappropriate to think of the centric relation record as a cooperative venture, with the patienthelping the dentist achieve a proper result. In addition to coaching the patient to "relax," theclinician should suggest that the patient keep a posterior and elevated position of the tongue,and if muscular resistance is encountered during the closure, ask the patient to "close straightup slowly and gently." If the patient is using her/his own muscles to close into the wax record,inform the patient ahead of time that the closure must stop on your command, to avoid over-closing the wax rims and causing shunting of the rims or jaw.
The clinician's role in the procedure is to guide patient actions and to provide firm butunstrained retruding and closing energy during the record.
The retruded closure of the jaw should stop just short of anterior rim contact, to ensure that therecord is completely passive.
Have the patient hold still at the end of the record and chill the Aluwax intra-orally with airspray. If possible, remove the rims from the mouth in one mass without disturbing the waxrecord.
Stream cold water over the Aluwax to chill it thoroughly, then separate the rims and inspect therecord for detail; the upper posterior orientation grooves must be plainly visible, and the lowerrecord should lock into the upper rim in a single position without rocking.
Trim away any interfering excess Aluwax, and return the rims to the mouth to visually check theaccuracy of the centric relation record. Repeat the retruded closure and look for the rims andwax record to key together exactly. If there is a shunt, or if multiple new patterns are made inthe Aluwax, the clinician should repeat the centric relation record by stripping away the chilledAluwax and starting over with a new sheet of Aluwax (do not attempt to reheat and modify anexisting record).
With uncooperative patients, or extremely unstable record bases, it may be unwise orimpossible to double check the accuracy of the record in the mouth. In these situations, the riskfor error is increased, and then the try-in appointment becomes critical as a final quality controlmeasure before the dentures are completed.
Autopolymerizing resilient bite registration materials (such as Regisil) are also used for thecentric relation record. There is little tactile feedback to the patient through the unset materialduring closure (this can be an advantage and a disadvantage), and the jaw must be held inposition as the material sets. A situation that recommends a Regisil bite is the patient whoconstantly closes in a protruded position. The clinician, by hook or crook, positions the patientin centric relation with no material between the rims, asks the patient to hold the position, theninjects Regisil into the space between the posterior rims. This requires index grooves on bothupper and lower surfaces, because the Regisil material does not adhere to wax. This approach isa "static" technique, in which the jaw is positioned before the record is made and is not movingduring the record (closing the jaw into a recording material is a "dynamic" technique).
The centric relation record is regarded as a precision step in prosthetics, with acceptabletolerances measured in tenths of millimeters. Repetition, skillful patient management, and adiscerning nature are useful to acquire competence in this area of prosthetic dentistry.
The face bow record completes the occlusal records appointment. The fork is placed on thecountertop and 3-4 Regisil dots are injected onto the fork, then the upper rim is immediatelyplaced over the dots to index the rim on the fork. Note that denture patients do not "bite" onthe fork, as dentate patients are able to do. If the upper rim with the fork attached is not self-retentive in the mouth, then the patient is asked to hold the rim/fork assembly in the mouthwith a finger during the face bow procedure.
Rinse the rims, remove denture adhesive with a brush and soapy water, then spray withdisinfectant and place the rims in a zip-lock baggie, for transport to the lab.
Make sure the rims seat completely in their respective master casts. Be aware that small tracesof wax or debris from the records appointment may be present on the intaglio (impression)surface of the rims and this can have disastrous effects on the accuracy of the articulation if thematerial is not removed and full seating of rim to cast is inhibited.
The maxillary cast is positioned in the articulator with the face bow record. There should be 3large triangular index grooves in the base of the master cast, and the base of the cast (includingthe grooves) should be lightly smeared with Vaseline as a separating agent between cast andmounting stone. Remember to leave the center area of the cast (circumference of a quarter) bare, with no Vaseline coating, to create nominal retention for the mounting stone. Mount themaxillary cast, and then remove the face bow jig.
The mandibular cast is seated in its rim and the centric record should key together passivelywith the mounted upper rim. There should be no contact between the posterior record basesand the posterior stone casts. If posterior contact exists, there is 100% certainty that themounting will be wrong, and that a significant amount of appointment time will be repeatedlater on because of this error.
Make sure the base of the mandibular cast has mounting index grooves. Position and hold theupper and lower casts in the best fit position in the centric relation record, then attach rigid objects, such as straight hand piece burs or wooden sticks, to the bases of the upper and lower casts with a glue gun or sticky wax. Both adhesive materials work best on dry, not wet, gypsum(the casts should be dry). There should be a minimum of 3 anchor points on each cast, and thecast position should be rigidly and positively held in the centric relation position. This step hashigh merit because it eliminates mounting error, which is the second most frequent cause ofremounting at the try-in appointment (most frequent problem at Pacific is centric relationrecord error). Smear Vaseline on the base of the cast, leaving the center bare, then mount thelower cast on the articulator. Set-up the artificial teeth.