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To increase the success of the edentulous restoration services you offer your patients, it is vital to know, apply, and master the fundamentals of complete denture fabrication. These fundamentals are relevant for fabrication of all tissue-supported complete dentures, tissue-supported/implant-retained complete dentures, and All-on-4,6 restorations.
This article highlights important fundamentals of:
the records step,
the wax try in,
denture processing,
delivery of the new dentures, and
follow-up adjustments.
It is also significant for the dentist, dental assistants, and dental laboratory technicians to work together as a harmonious team. Each step should be carried out diligently to enhance the restorative results and decrease the chances of an unsuccessful treatment outcome.
The Records (See figure 1)
For edentulous restoration fabrication, it is extremely important to (1) determine within acceptable limits and record vertical dimension of occlusion (VDO) and tooth positions, and (2) to precisely record centric relation (CR). For predictably successful restorations, the goal in most cases is to determine and record as closely as possible the position of the patient’s natural teeth before extraction and potentially improve tooth positioning, if appropriate.
The term verti-centric is used for the simultaneous recording of the VDO with the jaws in CR. If the verti-centric record is inaccurate, this leads to unpredictability of the denture service and a higher likelihood of failure of the restorations. In the past, verti-centric has been recorded with wax rims, but accuracy and consistency are difficult to achieve when using this method. A more reliably accurate and easier way to make a verti-centric record is with the gothic arch tracing device. Learning and mastering this technique is well worth it.
Determining VDO
The VDO is a vertical facial measurement indicating the relationship of the mandible and the maxilla when the mandible is in its most closed position and the teeth are occluding in maximum intercuspation.
The muscle length of the mandibular elevator muscles determines the patient’s VDO by guiding the eruption of the patient’s natural teeth.
The VDO can be determined by measuring the distance between two reference points: one on the fixed member of the face (tip of nose) and one on the movable member (chin), when the mandible is at the VDO in relation to the maxilla. This distance is maintained by the occlusion of the teeth — either natural or denture. Since the natural teeth are missing in an edentulous person, the VDO must be re-established. Care must be taken to not increase/ open the VDO (not increase the distance between the mandible and the maxilla) when fabricating edentulous restorations because this can cause soreness of the denture supporting tissues, malfunction of the stomatognathic system, and possibly failure of the edentulous restorations.
There are various clinical methods of determining the VDO including:
Measurement of the distance between the two aforementioned reference points when evaluating mandibular movement during speech. The vertical dimension of speech is the most closed position of the mandible during speech. It is the distance measured between the two selected points when the maxillary and mandibular teeth are in their closest proximity during speech — when making “s” or sibilant sounds — and this is the preferred method to use to determine the patient’s VDO. The VDO must be “more closed” than the vertical dimension of speech so the teeth do not make contact while speaking.
Evaluating facial appearance.
Measurement of the distance between the two reference points when evaluating the vertical dimension of rest, which is the position of the mandible when the mandibular elevator muscles are in a state of minimal contractual activity or when the patient says “Emma”. The VDO must be more closed than the vertical dimension of rest. Using the vertical dimension of rest is not a consistently reliable method of determining VDO, but sometimes it may be helpful.
Measuring VDO of former denture restorations and deciding if VDO should be increased or decreased or remain the same.
Asking the patient where the jaw feels comfortable and measurement of the distance between the two reference points.
Measurements of these various methods can be compared when determining an appropriate VDO for the edentulous patient. There is no one method that works in all patients and sometimes determining the VDO is a “best guess”. In this case, the VDO should be verified and adjusted at the wax try-in step.
Centric relation
CR is the relationship of mandible to maxilla when the right and left mandibular condyles are properly positioned on the articular discs in the glenoid fossae. The gothic arch tracing device is a relatively easy and accurate way to determine and record CR, a critically important element for setting the denture teeth to centric relation occlusion.
Using the gothic arch tracing device (see figure 2) versus wax rims for accurate verti-centric records makes the following tasks easier:
seating and maintaining the baseplates on the alveolar ridges during recording of verti-centric, because the vertical forces of the tracing pin to opposing tracing plate seats the baseplates and keeps them stable,
adjusting for and recording VDO,
locating and recording CR,
confidently and accurately guiding the patient to CR at the VDO for the verti-centric record, and
placing bite recording material.
Each denture fabrication step must be done carefully and accurately including mounting the master casts on the articulator with an accurate verti-centric record.
Determining/recording tooth positions using an esthetic maxillary wax rim
So the esthetic wax rim will require the least amount of contouring clinically, it is important for the laboratory to:
Construct a well-fitting comfortable maxillary baseplate with a carefully contoured esthetic wax rim to be adjusted clinically.
Contour the wax rim close to the anticipated positions of the denture teeth on the final restoration. If the wax rim is constructed with the labial surface of the central incisor area 10 mm anterior to the center of the incisive papilla (use the Alma Gauge to measure this) and the length of the wax rim in the lateral incisor area 20 mm vertically below the anticipated final border of the denture (use a Boley Gauge to measure this), the wax rim will usually need minimal adjusting clinically. Contouring the occlusal plane of the esthetic wax rim by the dental lab using a Swissedent wax rim former will create an occlusal plane parallel to the horizon (and the interpupillary line) and anteroposteriorly to the ala-tragus line.
Clinically, the contours of the wax rim should be refined to indicate the labial surfaces and incisal edge positions of the maxillary six (6) anterior teeth and the occlusal plane.
The Wax Try-in
The purpose of the wax try in appointment is:
The dentist to ensure that the restoration has:
good esthetics (evaluate the shapes, shade, and positions the teeth, and the occlusal plane),
an adequate VDO, and
contact of all posterior denture teeth in centric relation occlusion.
To show the patient the set up in their mouth after the dentist has approved it.
To obtain patient approval of tooth shape, shade, positions, and esthetics. Be sure that the patient understands these elements cannot be changed without redoing the restorations at additional fees. Suggest that the patient bring trusted family members and friends to the wax try in appointment (or consider the patient taking the set up home to show others for their approval).
To create a feeling of excitement and acceptance for the new restorations.
Denture Processing
Acrylic resin shrinks approximately 7% during polymerization, so this must be controlled for predictably successful dentures. If the denture base undergoes dimensional changes (shrinking and warping) during processing, this can cause problems, including denture fit, retention, stability, and occlusion. Shrinkage of the denture base acrylic resin during polymerization can be reduced with injection processing (as with the IvoBase Injection Processing System by Ivoclar Vivadent, Inc.), thus creating improved physical properties of the denture bases versus conventional packing processing. It is recommended to not use conventional packing processing for fabrication of tissue-supported dentures.
Denture Delivery
Delivery of new dentures:
Place dentures in the patient’s mouth and be sure they are comfortable. Use a pressure indicator paste and acrylic burs to detect and adjust areas where denture bases are placing excessive pressure on the tissues.
Have the patient bite firmly on two cotton rolls for five minutes for complete seating of the denture bases to detect areas which may become sore in the future as dentures “settle”. Also, this is an essential step before adjusting the occlusion. If the dentures continue to seat after the occlusal adjustment, the occlusion will change requiring further occlusal refinement.
Occlusal adjustments can be done by remounting dentures on an articulator or using Kerr Occlusal Indicator Wax intra-orally. It is recommended to not use articulating paper, ribbon, or film intra-orally to adjust the denture occlusion because the dentures move on the soft supporting tissues, so precise adjustment of occlusion cannot be made.
Post-Delivery Adjustments
Many of the post-delivery problems with discomfort are from occlusal interferences causing movement of the denture bases resulting in sore areas.
If a sore area is from occlusal problems, grinding on the denture base in the sore area can cause a poor fit of the denture base to the tissues and does not treat the cause of the denture base movement. Again, occlusion should be adjusted by remounting dentures or using Kerr Occlusal Indicator Wax.
Hopefully, the patient understands that many elements of their new dentures cannot be changed, and you have previously discussed how you will address problems with: esthetics, function, TMD, phonetics, occlusion/bite, comfort, retention, stability, biting cheeks and lips, and unhealthy tissues.
If the patient has problems with comfort, retention, or stability of the dentures, consider doing a laboratory reline. A general rule is to only reline a denture if the posterior denture teeth have even occlusal contacts in centric relation occlusion and the denture base has complete coverage of the proper denture supporting tissues with maximum extension without muscle impingement.
Conclusion
By using these methods, you can develop a workflow in your office that incorporates the fundamentals of complete denture fabrication and improves your edentulous restoration service. Only some of the fundamentals have been emphasized and considered here. Dental team members are encouraged to further study each step of denture fabrication, master the fundamentals, and consider adding other services to improve edentulous restorations.
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