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DENTURES

The standard denture

As you can see from the picture below, the back of a standard denture ends just behind the hard bone in the roof of the mouth.  They do this because they require as much surface area as possible to maximize retention and stability.  In the case of people who gag, the back of the denture can be cut forward making the denture base look more and more like an arch.  However, the more it is cut back, the less stable and retentive it will be!

Standard dentures are made for people who are already missing all their teeth. The top denture relies on "suction" to retain it, and the hardness of the underlying tissues for its stability.  It generally takes 4 or sometimes more appointments to make a set of standard dentures. 

The first appointment consists of an oral examination, sometimes X-Rays, and a set of impressions of the upper and lower edentulous (toothless) ridges (gums). These impressions are poured with plaster to form accurate models of the shape of the edentulous ridges. Other parameters are determined such as the shade, size and shape of the teeth that will be placed on the new dentures. 
Upon occasion, the dentist will recommend surgical alteration of the ridges to remove flabby tissue which will interfere with the stability of the denture, and sometimes to alter the shape of the underlying bone allowing for a better fit. In most cases, such surgery is not essential, but can create the conditions for a MUCH more satisfactory final denture. Alterations like this are generally money well spent!  In some offices, the first set of impressions are used to make custom fitting impression trays for a second, more accurate impression. In this case, there will be one extra appointment in addition to the standard 4 mentioned above.

The second appointment consists of deciding how "long" to make the teeth, determining the plane of the tooth setup (when you smile, the teeth should be parallel to a line between the pupils of your eyes), and the correct relationship of the upper and lower teeth so that when you bite together, the upper and lower teeth line up correctly.  This is done using a loose fitting denture base and a rim of wax to approximate the position of the teeth. 

Both upper and lower wax rims are adjusted to fit correctly in the patient's mouth so he can speak correctly without the wax rims "clicking" together, and so that the upper and lower rims fit together evenly.  Ideally, the wax rim should be visible slightly below the patient's lip when the lip is at rest.  When the patient smiles, the position of the lip is marked in the wax to help the lab decide which set of teeth are appropriate for this patient.  Once these relationships are correct, the rims  are sent to the lab where they are used to fabricate the wax-try-in. 

The third appointment is called the "wax try-in".  The lab returns the loosely fitting tray from the second appointment with the actual final plastic teeth lined up along the outer edge of the wax rim.  The wax try-in looks just like a real denture, except that the base fits loosely on the gums, and the teeth are embedded in wax instead of plastic.

This gives us the opportunity to see how the denture looks and works before we are committed to the setup.  At this point, if something is wrong, it can be changed.  If the teeth look too long, or the patient clicks when talking, or the midline is wrong, we can send the denture back to the lab where a technician can melt the wax and reset the teeth to specification

We try the denture in as many times as necessary until the teeth look and function like we want them to. What you see is what you get!  When everything is perfect, the denture is sent back to the lab to be processed and finished.  The old lose fitting base and all the wax are discarded, and replaced by a tightly fitting plastic denture base.

The fourth appointment is the insertion date when the patient walks out of the office with new dentures.  The plastic tends to shrink while being processed, so some adjustment is usually necessary before they will get the suction that you might associate with a new denture. How stable the denture is depends upon the condition of the ridges.

Immediate dentures

Immediate dentures(sometimes called temporary dentures) are actually made BEFORE the natural teeth are extracted.  The patient walks into the office with natural teeth, and walks out with false teeth.  The teeth are extracted, and a prefabricated denture is inserted directly over the bleeding sockets.  The patient is still numb from the extractions, and nothing hurts until you get home.  Generally, most patients do not complain of much pain after their teeth are extracted and the immediate denture is inserted.  The denture acts like a band aid and reduces pain.  

The construction of an immediate denture requires only one or two preliminary appointments before the insertion date, depending on how many natural teeth the patient has left.  They usually work out reasonably well.  When the patient leaves, he looks much better than when he walked into the office.  The bone that supported the original teeth is still intact, and the gum tissue is firm.  For the first week or so, the denture remains stable and reasonably retained. 

In a majority of cases, immediate dentures become permanent dentures, but there are a number of problems associated with immediate dentures than may cause the patient to want new dentures made after their gums have healed, in about a year.  These problems account for the alternate name; "temporary dentures":

1. If the patient has more than one or two remaining front top teeth, it is usually impossible to do a wax try in.  The denture teeth are placed in about the same position as the natural teeth before extraction.  Even though the denture teeth will be straight, and clean, their position may not be ideal because there is no way to preview them as we do with a standard denture.  For this reason, not everyone will be happy with the final appearance of their immediate denture, and may wish to invest in a new one at the end of about a year when most of the healing has taken place.

2. After the natural teeth are extracted and the immediate denture is inserted, there is a relatively fast loss of the bone that used to hold the natural teeth in place.  By the end of three weeks, enough bone has been lost that there is a LOT of space between parts of the denture and the healing gums.  This leads to rapidly increasing looseness and sore spots which must be removed frequently.  We can include a temporary "soft" reline at about one month after the extraction/insertion date.  This is a simple way to tighten the denture against the gums, and since the material is a bit rubbery, it makes the denture much more comfortable until enough healing has taken place to do a permanent "hard" reline.  

3. At the end of 4 to 6 months, the immediate denture must be relined with the same acrylic that the denture base was made from originally.  The longer you wait, (no more than 6 months), the longer you can expect the denture to remain tight before another reline is needed.  The hard reline is a separate procedure and the cost is NOT generally included in the original price of the immediate denture.  Thus the immediate denture ends up costing a bit more than the standard denture when the cost of the reline is taken into account. The hard reline marks the official transition of the immediate denture into a standard denture.

Implant retained dentures 

Implants, as mentioned elsewhere, are quite expensive (generally about $2000 apiece, not counting the tooth replacement that goes on top of them), but quite effective in retaining an otherwise non retentive denture.  A titanium "screw" is actually placed into a hole drilled into the bone to approximate the position of teeth.  After several months, the titanium has integrated (attached) into the bone, and the implant is then uncovered and a post which "pokes" through the gums into the mouth is attached to the implant.  This post may support a porcelain tooth, or it may support an attachment for a denture.  If the patient has NO teeth at all in any given arch (upper or lower), a full mouth of individual implants attached to porcelain teeth and bridges could cost about what an expensive automobile costs.  

On the other hand, a minimum of 2 implants can maintain a lower denture which would not otherwise be tolerated by that patient.  More than two implants are needed for upper implant retained dentures.  Although the dentures that fit over implants are considerably more expensive than standard dentures, they offer the added advantage of allowing upper dentures to be built in the shape of an arch instead of having to cover the entire palate. This is of special significance to people who otherwise cannot wear full dentures because they make them gag.  

Implant retained dentures have special significance for people who cannot wear lower dentures. As an edentulous (toothless) person ages, and the bone continues to resorb away, lower ridges frequently disappear entirely.  Thus there is no vertical bone underlying the gums to stabilize a lower denture.  These people frequently cannot wear a lower denture at all.  The addition of two implants in the front of the lower jaw can make it possible to retain a lower denture which would otherwise be impossible for the patient to tolerate. The image on the left below shows a pair of ball attachments on implants, and the denture that fits over them is shown in the image on the right.

PARTIALS
 

If you are missing only a few teeth scattered over either arch (upper or lower teeth), or even if you have a minimum of two teeth on both sides of the arch, then you can most inexpensively replace the missing teeth with a removable partial denture.  There are several types of removable partial dentures.  All of them use standard plastic denture teeth as replacements for the missing natural teeth.  The differences between them are the materials that are used to support the denture teeth and retain the removable partial denuture in the mouth.

Cu-Sil partial dentures

There are a number of drawbacks associated with full dentures, and not everyone can successfully wear them.  In many instances, false teeth are not especially useful because of retention or stability problems.  For this reason, even a single healthy tooth left in place can stabilize an otherwise unstable full denture.   

Only recently has it become possible to build a denture leaving a hole here and there to allow a few remaining teeth to poke through without ruining the suction which generally holds the denture in the mouth.  The Cu-Sil partial denture has holes for natural teeth.  These holes are surrounded by a gasket of stable silicone rubber which hugs the natural teeth and allows the rest of the denture to rest against the gums giving the benefit of suction in addition to the mechanical stability offered by the immobility of the natural teeth. These are especially useful in situations in which the remaining teeth are on the same side or area of the arch as in the example below.  Even a single remaining tooth in the arch can increase the stability of the entire denture several hundred percent over a completely edentulous (no teeth) arch.  

Cu-sil partial dentures are not the best solution for people with numerous, evenly distributed, stable natural teeth.  They are advertised mostly as "transitional" dentures meaning that they are especially recommended when the remaining teeth are likely to be lost (eventually) for any reason, or in cases where stable teeth are poorly distributed about the dental arch (as in the case below).  A Cu-sil partial denture can stabilize loose teeth and, with care, can extend their lives.  It is also easy to replace lost natural teeth on the Cu-sil * denture, and the denture can be relined like any other standard denture.  In other words, the Cu-sil denture can eventually be transformed into a regular full denture if the patient loses all the natural teeth.  I have found them to be especially useful for upper dentures, but more of a problem for lowers.  Lower Cu-Sil*partial dentures are prone to breakage if the patient is a heavy bruxer (grinder), especially if the remaining natural teeth are located in the front of the arch.  This is because the holes that allow the penetration of the natural teeth weaken the architecture of a lower denture.   

An additional problem with Cu-sil Partial dentures is a longer wait to get them relined.  We work with a local lab which can return a relined standard denture within 6-8 hours. 

If there are many stable natural teeth remaining, and they are distributed on both sides of the arch with some in front and some in back to lend support, a partial denture may be as good or even better solution.  Partial dentures have the added advantage of not having to cover the entire roof of the mouth.

The Treatment Partial Denture “flippers”

Affectionately known in dentistry as a "flipper", this is the least expensive of all the removable partial dentures.  The one pictured on the right replaces 4 missing teeth, leaving spaces for 7 natural teeth.  Two of the natural teeth are clasped with wrought wire clasps which are cured into the structure of the denture base.   

The pink plastic of the denture base is brittle acrylic, the same material used to make standard full dentures.  The largest single advantage to this type of removable partial denture is that new teeth and new denture base can easily be added to an existing treatment removable partial denture.  These are frequently fabricated even if the remaining teeth have existing decay or periodontal disease and their prognosis is doubtful.  If later in the course of treatment some of the existing natural teeth are extracted for any reason, new false teeth can be added quickly to the partial, maintaining the patient's appearance.  This partial is considered temporary just to get you by without missing teeth until your final treatment is finished.

Flippers do have a number of disadvantages, however.  

The acrylic denture base is somewhat brittle, and due to their irregular shape, these partials tend to break frequently, especially those made for the lower arch.  (Full dentures are more regular in shape and tend to be fairly strong as a result.) 

In order to counteract their tendency to break, the acrylic is usually built fairly thick which can take some "getting used to".  

As the gums resorb, the false teeth tend to sink below their original level making it necessary to reline them frequently, and sometimes even to reset the teeth which adds to their expense.

Flippers are most frequently retained with wire clasps.  These are frequently unsightly due to the limitations that pertain to their placement (they can't interfere with the way you bite).

Cast Metal Removable Partial Denture

Removable Partial Dentures with cast metal frameworks are probably one of the oldest forms of dentistry.  Originally, were made out of wrought (hammered) silver.  One of the most famous American dentists was Paul Revere who was a silversmith when he wasn't fighting redcoats.

This type of partial denture offers numerous advantages over the “flipper” described above. Since they sit on the teeth, as well as being attached to them, they are extremely stable and retentive.  The teeth have been altered slightly beforehand in order that the partial denture can rest upon them without interfering with the way the patient bites the teeth together.

The metal framework does not contact the gums.  Thus, as the gums resorb, this type of partial does not sink with them and rarely requires relines.  Because the teeth are altered by the dentist beforehand, there are fewer limitations in the placement of clasps, and they are less likely to be seen than the wrought wire clasps of the treatment partial. Modern frameworks are cast from an extremely strong alloy called chrome cobalt which can be cast very thin and are much less likely to break than the all plastic variety.  They are also much less noticeable to the tongue.

The largest single advantage that cast metal framework partial dentures have over the newer flexible framework partials (covered below) is that sore spots are less likely since neither the framework, nor the plastic extensions contact the soft oral tissues with any force!  Patients who exhibit the symptoms of TMJ, or who are known bruxers are much better off with cast metal partials than with flexible framework partials.  

The Flexible Framework Removable Partial Denture

The most recent advance in dental materials has been the application of nylon-like materials to the fabrication of dental appliances.  Nylon generally replaces the metal, and the pink acrylic denture material used to build the framework for standard removable partial dentures. Nylon is similar to the material used to build those fluorescent orange traffic cones you sometimes see on highways. It is nearly unbreakable, is colored pink like the gums, can be built quite thin, and can form not only the denture base, but the clasps as well.  Since the clasps are built to curl around the necks of the teeth, they are practically indistinguishable from the gums that normally surround the teeth.

Even though this type of denture does not rest on the natural teeth like the metal framework variety, the clasps rest on the gums surrounding the natural teeth.   This tissue, unlike the gums over extraction sites, is stable and changes very little over time which keeps these removable partial dentures stable and unchanging similar to the cast metal variety.  The clasps can be seen if you look hard. This type of partial denture is extremely stable and retentive, and the elasticity of the flexible plastic clasps keeps them that way indefinitely.

The Cast/Flexible Partial Denture

A good alternative to the all-nylon partial denture is one made with a combination cast metal framework with nylon clasps.  This has the advantage of being tooth supported (like the cast metal framework partial denture discussed above) and also having gum colored plastic clasps like the nylon partial.  This combination of metal framework and plastic clasp eliminates most of the difficulty of recurrent sore spots, since the framework resists movement and pressure from the clasps, while having the benefit of nearly invisible clasps.