The collapsed dental bite is a serious condition, which affects functioning of the teeth in chewing and speaking, and the appearance as well. When the teeth are flattened out, basically ground down to 50% of their normal height, serious effects occur, and it is very expensive to recover normal function and appearance.
This loss of the vertical dimension of occlusion – basically the height of the teeth from bottom gumline to top gumline – is discussed in Wikipedia with a couple of useful references.
Organization of this Chapter
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The Collapsed Dental Bite: Basics
A Full Mouth Rehabilitation Example
Important Issues during Full Mouth Rehabilitation
Basic Steps in Full Mouth Rehabilitation
Variations
Bottom Line for Full Mouth Rehabilitation
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Collapsed Dental Bite: Basics – Definitions and Determinants
The difference between this kind of case and when the dentist rebuilds the patients entire mouth with an implant-borne prosthesis, is that here most of the teeth are still left. The difference between this kind of case and when the dentist creates a removable partial denture that replaces most of the teeth, is that here the appliance is not removable, and, second, the level of the bite – the occlusal plane and vertical dimension of the bite – is not being changed with an RPD.
In general, full mouth rehab or reconstruction is done when there are plenty of teeth but they have been worn down so far that the bite has collapsed – that is the nose and chin have become too close together. This could and often IS true of a completely edentulous person that has been wearing dentures for a long time and the bone has resorbed more and more, and fixed restoration on implants brings the mouth open again – but in that case the TEETH are not being restored – just the vertical height of occlusion.
When you see someone whose lips seem pursed or sticking out a little too far for their face, and the lips are turned a little outward so the inner portion shows that normally wouldn’t be seen, AND you notice when they smile that it is hard to see the incisal edges of their teeth, but when you can they are very flat from one side to the other – they are a likely candidate for full mouth rehabilitation.
A Full Mouth Rehabilitation Example
As a dental student I was tremendously lucky to do my first full mouth rehab case. I was at a school that had no graduate Prosthodontics department at the time, so when this gentleman came to the school for help, an undergraduate would need to do the work. I fought hard to be allowed to tackle this case, and the deal with the Dean was that I would take classes outside of the school to learn about how to do it responsibly. There were such classes at the time being given by Dr. Robert Lee in just the next town. He even invented the Panadent articulator to make it easier for dentists to do such cases well. And, during the entire process, a faculty mentor was appointed so I could run every step past him.
In the case of my patient, he had ground down his teeth and had the appearance I described above. He was missing lower first molars and the second molars were tilted considerably toward the front of the mouth, to get into the space of the teeth that had been missing for a long time. His opposing teeth to the second molar were still present and healthy. He did not have significant periodontal issues. By measurement at the front of the mouth, the wear on his front teeth had shortened the height of his bite by approximately 6 mm. The front teeth had all been ground down about half way, and a similar story was true for the back teeth.
He was keenly interested in getting things fixed up so he could look normal again. As a pastor in the public eye a lot, he was aware that the appearance given to him by the wear he had inflicted on his teeth was a disadvantage.
I ended up taking 2 1/2 years to complete this case, spending every one of the three calendar years the maximum that his insurance would cover – and they eventually covered everything!
Casts when first Examined:
These Casts are for the case described above.
Note the second molars highly tilted toward the front of the mouth, while there is a premolar and molar missing on the right side and the molar is missing on the left, and the second premolar is worn off to the gumline.
Splint Worn to Open Bite
The splint below was worn by the patient to get him used to having his bite more open. It was adjusted so that he could eat with it and bite down on it. It was modified over a period of months so that he bit on it evenly, while the joint was positioned ideally.
Restoration of Upper Arch
On the right side only the first molar was crowned. On the left side both the first and second molars were crowned. These crowns were made first.
After that all of the front teeth on the top were prepared for crowns and the crowns made according to the wax models of what the lower teeth will look like and how the occlusion was planned.
Restoration of the Lower Arch
The first two slides show the results of orthodontic treatment designed to upright the second molars so that a bridge CAN be made which connects them to the more anterior teeth.
Final Casts
Unfortunately, I do not have final pictures of the smiling patient – and these are the only casts I have showing the final restorations – and the casts are not fully in occlusion. Nonetheless, you can get an idea how the teeth look for both the upper and lower arches.
This patient found he had a good bite for the first time in many years, he looked presentable, his joint was comfortable, and he did not have to worry about his oral condition continuing to deteriorate, as it had for many years.
Important Issues during Full Mouth Rehabilitation
The main thing is that the patient has gotten so used to biting down, closing more, than is natural for their jaw structure. We need to OPEN UP THE BITE – and it may require some “getting used to”. In fact, we’re not really sure from the start IF the patient will tolerate a higher bite anymore.
AND – another major issue, is what is happening to their TMJ.
The TMJ is used to the mouth closing more than it should, and there is the possibility that the joint has reorganized somewhat, at least at the disc level – to say nothing of what the muscles are used to now. And – we need to insure that as we do open the mouth back up for a higher vertical dimension the TMJ is happy in this new position as well.
Now – the entire occlusal plane of the mouth is being rebuilt. It is not really a plane, but is designed to have some curvature from front to back, and is also tiled somewhat toward the center. These curves are so that when the jaw moves from side to side, and from back to front, the relationship between opposing teeth remains fairly constant.
Also, as the jaw moves away from center in any direction, the TMJ moves as well, as we’ve discussed in Chapters II.4 and III.6. The entire complex, including the TMJ and the occlusal surfaces of all of the teeth in opposing relationship, must move HARMONIOUSLY, and every component must be comfortable. In the new configuration the joint should always feel comfortable and the teeth should bite exactly where they should and all together at the same time, and the teeth should move away from centric in a harmonious way as well.
This means that as we do such a case we must be totally aware of the joint as well as the level of the teeth as we restore EVERY tooth, AND that as the teeth bite down into their most comfortable position at EXACTLY that point, the joint is in its most comfortable position.
The Basic Steps in Full Mouth Rehabilitation
First – realize that this restoration will require crowning virtually every tooth in the mouth. So, many of these may need dental treatment first – including building up vital teeth or performing root canal therapy and rebuilding the core for a crown. Periodontal health and home care must be totally under control.
Second – we need to take records of how the patient’s jaw moves. This involves tracing the movement of the TMJ to see WHERE the condyle of the joint hinges – the hinge axis – relative to the tooth positions. We actually connect a frame to the upper teeth that holds a little piece of graph paper near the patient’s ears, and a frame to the lower teeth that holds a pencil. As the jaw is opened and closed, the pencil draws out the movement of the joint, rotating and sliding as well down the slope of the joint – and, most importantly, we find the exact HINGE AXIS of the TMJ RELATIVE to the teeth. We need to mount casts of the patients teeth on a mechanical device which will SIMULATE THE MOVEMENT of the jaws in relation to each other – and to do this accurately enough for full mouth reconstruction, the casts must be positioned at the correct distance from the part which simulates the joint.
Third – the dentist must build an appliance which helps the patient re-learn what it is like to have their mouth more open at rest. This SPLINT will often fit on their upper teeth and allow the lower teeth to contact it (as I learned) first in the front. This leaves the back teeth a little open at first. In order for the back teeth to close the condyle of the TMJ needs to shift into a new, more stable, position that is different from where it was – likely more upward and forward. Why was it not there before? Probably because there was some inflammation and swelling the the TMJ tissues before which displaced the condyle from its ideal place when the teeth are occluding.
Fourth – the splint will be adjusted over a period of weeks and then months until the condyle is settled into a comfortable position and the lower teeth (that are left) are all in occlusion with the splint. And, since this splint is designed to put the patient at the correct vertical height for their bite – we know that the patient will be comfortable “opened up”.
Fifth – with the articulator set to mimic the relative movement of the patient’s jaws AT the desired vertical dimension – there will be space between the upper and lower teeth on the casts. Now the dentist or laboratory will rebuild EVERY tooth in the mouth with wax, on the cast, in the ideal way that is desired for the final configuration for that patient. This “wax up” is used to guide the laboratory, as they MAKE each of the crowns, and from the waxup we will also make provisional, temporary crowns. As each tooth is prepared for a crown, the crown must be made TO the exact height of the occlusal plane for the CHANGED occlusion.
Sixth – thinking about this for a minute – as the crowns are made, something else needs to be there to HOLD the patient in the open position so that the new crowns are not “hitting high” – it would REALLY be high. At the earlier stages the crowns can be made and the splint can still be used to keep the mouth at the correct position. As more crowns are made, the splint is removed and provisional restorations on teeth without crowns are used to keep the patient’s bite the way we want. So, basically, there will be both final crowns cemented, AND temporary crowns in place – all of which create the new vertical dimension and anatomy desired.
Seventh – the PATTERN of making the crowns varies from case to case, but often the posterior crowns are made first and the anterior last. So at some point the bite is resting on the posterior crowns while the anterior, front, teeth are plastic temporaries. So the final appearance, so importantly involving the front teeth from canines to canines – is worked out at the end of the case. It will often be the case that the lab will make TWELVE crowns at once as the last step. They can be made to match each other perfectly, and to have exactly the anatomy initially decided based on the wax-up. It is a great day when these last 12 crowns are cemented in the last visit!
Variations
The basic outline of steps above is pretty much adhered to by anyone working to build the case with everything being considered – occlusal plane, excursive movements and TMJ position.
The exact TYPE of restorations will vary from case to case, or course. It may be that missing teeth are replaced with bridges or implants, depending on the situation. Since the mouth is being opened, there will be plenty of height available for making a bridge. Since ALL of the teeth in the mouth are being crowned, an implant will NOT save the expense of crowning the adjacent teeth as would be required for a bridge. Implants would more likely used in situations where the dentist wants to get the occlusion back in the mouth more than is possible to support on teeth, because there are not teeth there. For example, if there are NO molars and it is desired to get good function back to the first molar, it will need to be made on an implant.
When jaw relationships deviate a lot from “normal”, as in crossbite or overbite or underbite – decisions need to be made as to how much can be altered as the jaws open more. It might even seem that the patient is in cross bite as they come in, but as the mouth is opened the occlusal relationship seems more normal and can be built that way.
The Collapsed Dental Bite: Bottom Line
Full mouth rehabilitation is a tremendous service that the dentist can offer the patient, when it is done responsibly. There are dentists that attempt a case they should not and it doesn’t work out well for the patient. When I studied with Dr. Robert Lee he often told of patients he had that went through occlusal rehabilitation with another dentist, only to need for it to be done over.
A graduate prosthodontist may have done a case or two over the years, but there are practitioners out there that do these cases on a regular basis, and have all the experience to manage more challenging situations. If the dentist or prosthodontist has studied with a great mentor and has done a score of cases, probably they can serve your needs well.