Positioning Maxillary Central Incisal Edges: Phonetics

In previous articles I discussed the role of positioning the incisal edges of maxillary central incisors using primarily visual cues. In this article I want to discuss a functional consideration when determining incisal edge position: phonetics. Any dentist who has done complete dentures, or who has restored anterior teeth, has experienced a patient who has returned with speech difficulties.

The key to understanding any changes in speech is to understand that the first thing necessary is to identify what “SOUND” the patient is struggling with. It’s also important to consider how much time the patient has had to adapt to the changes. The primary sounds that frequently change following alterations to anterior incisal edge position are: “F or V” sounds and “S” sounds.

“F or V” sounds are the easiest to understand as they relate directly to the positioning of the maxillary incisal edges and don’t involve the mandibular anterior teeth. As most of us were trained, when a patient says “55,” the incisal edges of the anterior teeth should lightly contact the wet-dry line, (vermillion border), of the lower lip. The incisal edges impinging into the lip would be an example of excess incisal edge length. The female patient in figure 1 is an example of a patient who is tending toward a skeletal Class II relationship and has over erupted central incisors. In this photo she is saying “55.” It is easy to see that the incisal edges are impinging into the lip, indicating they are over erupted and positioned too far to the facial.

 

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In my experience “S” sound problems are far more common than problems surrounding “F or V” sounds. I’ve found that “S” sound problems are also much more complicated. An “S” sound is the result of the maxillary anterior tooth position, mandibular anterior tooth position and the tongue interacting together. If a patient is having lisping problems following treatment, you need to assess how many teeth you altered to determine what is causing the problem. If you only altered the maxillary incisors, then the answer as to what produced the change is obvious, as it would be if you only treated the mandibular incisors.

Often a problem of lisping following treatment is produced because the anterior teeth are now making contact during the “S” sound. I would typically tell any patient that is having phonetic issues following treatment to wait at least four weeks to see if the issue resolves itself before making any major adjustments to incisal edge position.

If at the end of four weeks the problem still exists, I would bring the patient in and ask them to say “66,” watching their anterior teeth as they make the sound. Roughly 70 percent of patients will make their “S” sounds by positioning the mandible so the incisors are end-to-end, figure 2. The remaining 30 percent make their “S” sound with the mandibular incisors somewhere along the lingual contour of the maxillary anterior teeth, figure 3. If the patient makes their “S” sound along the lingual of the anterior teeth as seen in figure 3, it means your maxillary incisal edge position is not the problem. The relationship of the lingual of the maxillary anterior teeth against the mandibular anterior incisal edges is the problem.

Regardless of where the patient makes their “S” sound, the correction is virtually always the same. Use some very thin articulating ribbon, I use “accufilm,” hold it against the maxillary incisors and ask the patient to say “66.” I then look for any areas of contact indicating an interference in the “closest speaking space,” you will now have to adjust the teeth until there is no tooth contact during the “S” sound. The challenge is deciding where to adjust, the upper or lower anterior teeth.

The patient in figure 4 is in full upper and lower provisional restorations, he is saying “66” you can see his anterior teeth are contacting and he has a lisp that hasn’t gone away after four weeks. The question is where to adjust. If I shorten the maxillary incisal edges I can eliminate the lisp, but may alter the esthetics. If I alter the mandibular anterior teeth by shortening them, I can eliminate the lisp and maintain the esthetics. However, now when he goes back into his intercuspal position he may have lost anterior occlusal contact, risking secondary eruption and the redevelopment of the lisp.

In most patients with end-to-end “S” positions, as seen in figure 4, I choose to alter the mandibular anterior teeth to correct speech but maintain esthetics, I then check the intercuspal position for anterior occlusal contact; if contact is still present you are done. If the contact has been removed, you can regain it by adding to the lingual of the maxillary anterior teeth which won’t affect the “S” sounds in the end-to-end position, so the lisp won’t return.

If your patient developed the lisp but their “S” position is the same as figure 3, the solution is almost always to alter the lingual of the maxillary anterior teeth which will eliminate the lisp, leave the incisal edge position intact and rarely removes the intercuspal position contact.

The bottom line is when you alter maxillary incisal edges you will eventually create some phonetic issues. Understanding these concepts can help solve the problems if providing the patient time to adapt doesn’t.

Learn about techniques relating to treatment planning, as well as, occlusion and wear, esthetics and implants from Spear Digital Suite.
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Understanding Reduction Copings

 

The concept of a reduction coping is to create more space for the restoration after the laboratory receives the impression or cast of the prepared teeth. This additional space may be required to accomplish the goals of the case for esthetic or functional reasons.

The additional space allows for:

  • Adequate space to make the tooth morphology changes requested.
  • Increasing the thickness of the restorative material to improve its strength.

The coping can be fabricated out of:

  • Acrylic/resin
  • Cast metal

There can be a significant cost difference when a casting is made to due to the material and alloy expense, and the fabrication process. It may be worth considering the additional expense, as a cast metal coping will fit more precisely than one made from acrylic or resin.

Reduction copings are the most effective when the area of the tooth that needs to be reduced involves only the incisal edge, cusp tip, or one surface of the tooth. The modification of the preparation should never extend closer than 1mm to the finish line.

The coping is placed onto the tooth, and the amount of the tooth that extends through the opening is what will be reduced. A bur is used to reduce that portion of the tooth and slightly more, rounding all the edges and corners. This minimizes the chance that the restoration will not seat completely. Two examples where a reduction coping is most effective are:

  • When there is an inadequate tooth reduction in incisal length to achieve the goals of the case.
  • When the labial surface of one tooth protrudes further labial than the adjacent tooth or teeth, and the expectation is to have straight and aligned restorations. A reduction coping would be indicated for the protruded tooth in order to achieve the goal of the case, as the final outcome is significantly more predictable if all the restorations have a similar thickness.

The one surface on which it is difficult to use this process is the palatal aspect of the maxillary anterior teeth. It is difficult to replicate the palatal concavity that can be created in the laboratory using a reduction coping. If there is inadequate occlusal reduction, it may be necessary to re-prepare the teeth and take a new impression or modify the incisal edges of the mandibular anterior teeth to create more space.

Reduction copings can be used effectively in some cases to avoid rescheduling a patient to modify the preparations and re-impress. Consult your laboratory on a case-by-case basis to determine when it can be used to give the laboratory and clinician a more predictable outcome.

 

What is the Purpose of a Facebow?

All of us as dentists were issued a facebow in dental school in order to fulfill our requirements. For some reason a majority of dentists tend to forget about the facebow the second they get out of dental school and go into practice. I think one of the main reasons as to why this happens is because we were only taught the technique of the facebow as students, but we really weren’t taught what the actual purpose of a facebow was.

When we first got into practice, our initial thought of the facebow’s purpose was simply to aid in mounting models. We were taught in dental school that facebow only exists to help us mount the maxillary model on the articulator.

 

This thought process undoubtedly made us assume that we could simply perform this technique without using the facebow at all—we could tuck that facebow away and just pace the models in the middle of the articulator by hand or use things like a “stick bite.”

The purpose of the facebow is to transfer both esthetic and functional components from the patient to the articulator in a very efficient manner. The more accurately the models replicate those components, the more efficient we can be when we get back to the patient’s mouth. From an occlusal and esthetic standpoint, the more closely the models translate the function, the less occlusal adjustment we’ll have to do when we take the restoration back to the mouth or place our provisionals.

So, if you are not using a facebow, you must understand that the function and esthetic information of your mounted models may not be as accurate as you think it is. The effect of which will be noticed when you get back to the mouth and end up having to perform excessive adjustments for the occlusion and esthetics.


The concept of Facially Generated Treatment Planning can greatly simplify treatment planning for wear patients. You can find more information about treatment planning, esthetics and occlusion within Spear Digital Campus. Download the free resource:
The 8 Steps Checklist-Facially Generated Treatment Planning.

 

 

Yesterday’s Dentistry Belongs in the Past

We’ve all had the experience of looking through old photo albums of ourselves and laughing (and cringing) at the style choices we made back then. Those wide lapels, the shaggy long hair, the bell-bottom jeans. There we are, gathered around the 8-track player, feeling vital and modern. The thing is, of course we were—for that time. It’s the same no matter what era you grew up in and it will be the same for us again in later years: Today’s hot new trend is tomorrow’s quaint curiosity.

 

In dentistry we see this, too. You ask a patient to open wide and you see what I call a “museum of dentistry.” You see repairs and restorations of different vintages that represent the best professional standards at the time they were done, but are the oral care equivalent of 8-track technology in today’s world of high-performance digital dentistry.

I’m not suggesting that dentists should feel bad about the old-school dentistry they find in the mouths of longtime patients. The work that was done then was great for its time. You need to honor the past and acknowledge what you achieved with what you had, while at the same time always adjusting your sights to that ideal baseline as it stands today.

It’s not that you have to put a time limit on restorations, or suggest to patients that they overhaul their dental work every time something new emerges, but there comes a point when the functional and esthetic advantages of new procedures and materials are hard to ignore. You’re not rejecting your earlier standards as being wrong. You’re simply accepting that those standards were the best for that time, and that patients must be given the choice to engage with dentistry at the level of today’s possibilities.

 

 

Treatment Planning Paul – Part 4

Functional Concerns

A discussion of what to plan for and think about to ensure functionality: exams, wear patterns, patient history, functional occlusion, and equilibration.

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