Grand Rapids Dentures- Bone Loss Treatment - Best Choice Dental Implant and Denture Center

Grand Rapids Dental Implants - Best Choice Dental Implant Center - Dr. Timothy Moore

Facts about Dentures and Bone Loss

Why do dentures get loose?

The simple answer is BONE LOSS!

Many patients contemplating the extraction of their teeth, as well as many long time denture wearers are surprised to learn that once the teeth are removed the bone starts to shrink.

After a few years, the teeth become less visible and the dentures start to slip, skid and pinch the gum. Many just think the dentures are wearing out and getting loose. Actually, it is not the dentures that get loose. The dentures do not change much over the years. It is the patient that is getting “loose”, because the supporting bone is shrinking from underneath the dentures.

Why do you lose bone after the extraction of the teeth?

The bone around the teeth is called “alveolar bone”, and it’s only purpose is to support the roots of the teeth. The common term for alveolar bone is the “ridge” (Fig. 1 & 4). The body starts to resorb or dissolve the ridge immediately after the teeth are removed.


Fig. 1 The ridge a week after extraction of the teeth.	Fig. 2 The ridge 5-10 years later. The bone is narrowing, and often becomes knife-edge. The bone may be replaced by soft gum tissue.	Fig. 3 10 or more years after extraction of the teeth. The ridge may be flat, like the model, or it may be knife-edge covered with soft mobile gum tissue. It provides very poor denture support.

Fig. 4 Excellent upper ridge. Firm bone and gum. Very good denture support.	Fig. 5 Ridge similar to Fig. 2. The bone is "knife-edge" under the gum. It may hurt to bite.	Fig. 6 The bone is flat or knife- edge. The gum is soft and mobile. The probe easily displaces the soft ridge tissue.

How quickly do you lose bone?

The most rapid ridge loss occurs the first 12 months after the teeth are removed. It is not unusual to lose 30%-40% of the height and width of the ridge in the first year.

After the first year, on average, the ridge will lose about one millimeter (about 1/25th of an inch) per year (Fig. 2 & 5). That does not seem like a lot of bone, but over a 15 or 20 year period, that is most of the bone forming the ridge(Fig. 3 & 6). In fact, so much bone can be lost in the lower jaw that the main nerve trunk supplying the lower teeth can be exposed. This can be a very painful problem. In rare instances, so much bone can be lost that the lower jaw will fracture.

Is the pattern and rate of bone loss the same for everyone?

No, bone loss is different for everyone.

Most of the time the ridge will get narrow and shorter at the same time. In some individuals the ridge will get narrow first, creating what is called a “knife- edge" ridge (Fig. 13 & 16), and then it starts to get short. A narrow, knife-edge ridge makes biting with dentures very uncomfortable, because the sharp ridge is “biting” the gum from the inside out.

On average, enough bone will be lost in 3 to 5 years so that the denture will need to be relined, because it no longer fits the bone. Wearing a denture that fits the gum, but not the bone will bruise the soft tissue and contribute to more rapid bone loss.

Can I chew as well with dentures as I did when I had all my own teeth?

No.

The average tooth can support a biting pressure of about 100 to 150 pounds per square inch. Once the teeth are removed, the biting muscles can still generate the same amount of power. Unfortunately, the gums can only take about 10 and 15 pounds of pressure per square inch before they start to hurt. When wearing dentures, the gum is literally caught between and a rock (the bone) and a hard place (the denture base).

How much chewing function is lost with dentures compared to natural teeth?

Clinical studies have shown that denture wearers with well made dentures on good ridges lose about 90% of their chewing power and efficiency compared to people with natural teeth. This does not mean that denture wearers cannot chew, because they can. It just means it will take longer to pulverize the food enough to swallow.

Why do denture wearers complain about their lower denture more than their upper?

There are four main reasons why the lower denture is more of a problem than the upper denture. First, the lower jaw is smaller Fig. 1 & 7). Second, the tissue covering the ridge deteriorates over time (Fig. 6 & 14). Third, the bone loss is uneven (Fig. 7 & 16), and fourth, it is often not possible to obtain good retention (suction) with the lower denture.

The “ridge” is where most of the force of the denture is directed when chewing. As a rule, the wider and taller the ridge, the more stable is the denture, and the more comfortable is the chewing.
Because the upper denture uses the entire roof of the mouth (palatal bone) for support, the upper denture covers about four times as much bone as the lower denture (Fig. 1, 4, 7 & 11), Like a snowshoe covering more area makes it possible to walk on top of the snow. The upper denture is like the snow shoe. It covers a large area and puts less pressure on the gum and the bone, making chewing more comfortable.

The first reason people complain about their lower denture is because the lower denture covers only about ¼ of the surface area of the upper denture (Fig. 7 & 11). The lower denture sinks into the lower gum and bone just like a regular shoe sinks into the snow. Less surface area covered means more force on the lower ridge. The force delivered to the lower ridge is magnified three to four times. More stress means faster bone loss. In fact, the lower ridge will often shrink four times faster than the upper ridge in the same individual.

The second problem for lower denture wearers is the quality of the gum covering the lower ridge deteriorates (Fig. 10 & 14).

When the teeth are first removed, the ridge is covered with “attached gingiva” (Fig. 11). This is the type of gum that is around the neck of natural teeth. It is bound down to the underlying bone, so it does not move. It is thick, tough and abrasion resistant (that is why you can brush your teeth without hurting your gums).

After a few years of bone loss, the attached gingiva disappears and is replaced with “unattached gingiva” or “mucosa” (Fig. 13 & 14). Mucosa is like the lining of your cheeks. It is thin. It is not bound down to the underlying bone, so it moves. It’s not very tough and cannot take much abrasion or pressure. This makes for very poor quality denture bearing tissue.


Fig. 7 Lower ridge. Teeth on the front and right side of model were removed 6 months before. Note teeth on left side were missing for longer, and the ridge is narrower.	Fig. 8 Same patient as Fig. 7, three years later. Note narrowing of the ridge on both sides	Fig. 9 Same patient as Fig. 7, six years later. Ridge ia almost flat on the left side. Two implants were placed in the front to stabilize the denture.	Fig. 10 Model from patient who had been wearing a denture for over 30 years. The ridge is gone.

Fig. 11 Lower ridge with good bone and firm soft tissue.	Fig. 12 The ridge is narrowing.	Fig. 13 Knife-edge ridge. Most of the tough gum tissue has been replaced by mucosa. Denture function and comfort are poor.	Fig. 14 The ridge is gone, and the tough gum tissue has been replaced with soft mucosa. The denture will pinch the nerve in the lower jaw, making chewing painful.

Fig. 15
The bone under the gum in Fig. 12 may look like this, round and smooth.

Fig. 16
The bone under the gum in Fig. 13 may look like this. Narrower and ragged

Fig. 17
This model is similar to the patient in Fig. 14. notice the openings for the lower nerve (dark spots) are on top of the ridge.

The third reason lower dentures are difficult to wear is the contour of the ridge as the bone shrinks. In most people the tooth extraction sockets will fill in with bone and the ridge will round off to a smooth “U” shape in two or three years (Fig. 11,12 & 15). However, as bone loss progresses, the ridge starts to resorb or shrink very unevenly. The bone under the gum starts to take on the appearance of very small peaks and valleys, almost like a row of sharp little teeth (Fig. 13, 14, 16 & 17)). At the same time the quality of the gum covering the ridge is deteriorating. Patients with this type of bone loss are in constant discomfort, because the gum is thin, the denture is slipping, and the little bone spikes are poking into the gum when chewing.

The fourth common complaint with lower dentures is, “It doesn't stay in place like my upper denture.”

The upper denture usually has good retention, because the roof of the mouth does not move and a prosthodontist can usually achieve good “suction” with the upper denture. With the lower denture, good suction is almost impossible to achieve. As you swallow, speak and chew, the floor of the mouth is constantly moving up and down with the tongue. This constant movement allows air to get under the lower denture and break the suction. When the suction is lost the lower denture will move or float.

Does bone loss affect the appearance of the face and the smile?

Emphatically yes, and it’s not good.


Fig. 18 Denture wearer. Lips together, jaw at rest, and teeth apart.	Fig. 19 Same patient with denture teeth together. The bite is "overclosed". Notice how the lips thin out, and the corners of the mouth turn down.

Fig. 20 Same patient. Profile view.	Fig. 21 Same patient as Fig. 20 with denture teeth together. Note how lips "disappear", the corners of mouth turn down and the chin hinges forward, making the jowls more prominent.

As the bone shrinks the upper denture starts to move up and back, and the lower denture moves down and back. The lower 1/3 of the face starts to collapse. The lower jaw hinges forward and the chin comes too close to the nose (fig. 19 & 21). Frequently, the lower front teeth will move in front of the upper front teeth.

As the facial support collapses, the lips thin out and recede, the corners of the mouth turn down, and saliva starts to leak out. Often the corners of the mouth develop cracks or sores from a fungal infection (angular cheilitis) (Fig. 22 and 23) which many denture wearers mistake for dry lips. Women may notice that their lips are not as full as they used to be, and there is “less lip” on which to put lipstick.


Fig. 22 Denture wearer with bone loss and overclosed bite. Corners of the mouth have turned down, and saliva is leaking out. Sores are developing at corners of mouth.	Fig. 23 Same patient as Fig. # 22. The sore at the corner of the mouth (angular cheilitis) is caused by a fungus (Candida Albicans). This is a common problem for denture wearers as the bone shrinks and the bite and lower 1/3 of the face "collapse"

In many patient who have been wearing the same set of dentures for more than 10 or 15 years, the upper teeth have moved above the upper lip and the lower teeth have moved down to the point where you cannot even tell the patient is wearing their dentures.

As the dentures settle, the lower 1/3 of the face starts to recede (Fig. 19 & 21). This makes the nose and chin appear more prominent. The lines around the nose and the mouth become deeper and the skin bags below the jaws, contributing to jowls. This is a very old look.

Prosthodontists call this cascade of events, being “overclosed”.

Why do new dentures not “work” as well as my old ones?

Prosthodontists have a great deal of experience and knowledge making dentures that fit well and look great. We can restore the dimensions of the face, often taking years off the appearance of the face and the smile. However, we have to rest the dentures on the existing bone.

As you have read above, the bone is constantly shrinking. As a result, each new denture becomes less functional than the previous denture, not because we cannot make a denture that fits…we do an excellent job at fitting the gum and bone that remains. It is just that the foundation is getting worse and worse.

As the bone shrinks up and back on the upper ridge, and down and back on the lower ridge, the new dentures have to replace the missing bone with the plastic denture base to get the teeth back to their original position. As a result the denture base of each new denture gets thicker and thicker, and the replacement teeth get further and further away from the supporting bone. The further the denture teeth are away from the bone, the more tippy and unstable the dentures become. Each successive well made denture will become less satisfactory and less functional than the denture that preceded it.

Can lost bone be replaced?

Yes, lost bone can be replaced with bone grafting. However, bone grafting can be expensive, and grafted bone will shrink even faster than regular bone unless dental implants are placed to preserve the bone and give the bone a reason to stay.

Can bone loss be stopped?

Yes. Dental implants can be placed to preserve bone and provide a solid foundation of support for individual crowns, fixed bridgework or fixed or removable dentures.