Consequences of Tooth Loss
Effect on the Jaw Bone
The bone in the body acts very similar to a muscle. When muscles are exercised, they grow strong and larger. When bone is exercised or stimulated, it also becomes stronger. For example when an arm is broken and placed in a cast for six weeks, you can see the arm is smaller after this time frame, since the muscles have started to shrink or atrophy. In addition, if you evaluate the bone protected by the cast, it also becomes less dense and weaker in this 6-week period. Similarly, the bone of the jaw can only be stimulated by a tooth or by an implant. The connections between a tooth, or an implant, create and preserve the size and shape of the bone. Bone needs the stimulation of the tooth roots to maintain its form, density, and strength. Scientific studies have proven that the normal chewing forces that are transmitted from the teeth to the bone of the jaw are what preserves the bone and keeps it strong.
This close relationship between the tooth and the bone continues throughout life. When a tooth is lost, the lack of stimulation to the surrounding bone results in a decrease in the density and dimensions of the bone. This means that there is a loss of width and height of the bone. In a 25-year study of patients with no teeth, x-rays demonstrated continued bone loss of the jaws during this entire time span. Therefore, a tooth is necessary both to the development of the bone around the tooth, and is also necessary for the stimulation of this bone to maintain its strength, density and shape. The loss of all of the teeth slowly, but eventually leads to jaws with almost complete bone loss. A lower jaw, which starts out two inches in height, can be reduced to less than 1/4 inch by atrophy over time. That is one reason why modern dentistry is so excited about implants to replace missing teeth.
 Patients wearing dentures don’t realize they are losing bone. Over time, the misfit and poor function of the denture is often thought to be due to its age, weight loss by the patient, or wear of the denture’s teeth. The rate and amount of bone loss may be influenced by gender (females lose more bone), hormones (lack of estrogen causes more bone loss), metabolism, medications, parafunction (grinding the teeth) and poorly fitting dentures. Despite this, almost 40% of denture wearers have been wearing the same denture for more than 10 years. Although the fact that wearing dentures day and night places greater forces on the bone and gum, and accelerates bone loss, 80% of dentures are worn both day and night.
Consider the following:
The issue of bone loss after tooth loss has been ignored in the past by traditional dentistry. This is so because dentistry had no treatment to stop or prevent the process of bone loss and its consequences. As a result, doctors had to ignore the inevitable bone loss after tooth extraction.
Today, the profession knows about bone loss and implants can stop bone loss because implants stimulate the bone, similar to the way the tooth did prior to its loss.
Jaws with bone loss are associated with problems (Table 1-1 below), which often impair the predictable results of traditional dentures. The loss of bone first results in decreased bone width. There is a 25 percent decrease in width of bone during the first year after tooth loss and an overall _-inch decrease in height during the first year following extractions of several teeth. The remaining narrow bone often causes discomfort when the thin overlying gum tissues are loaded under a complete or partial denture. In the lower jaw, the continued bone loss eventually results in prominent bony projections covered by thin, movable, unattached gum tissue. As the remaining bone on the front of the jaw continues to disappear, the bony projection under the tongue rises to sit on the top of ridge. This results in pain as the denture sits atop the sharp bony projection. In addition, there is little to prevent the denture from moving forward against the lower lip during function or speech. The problems are further compounded by the upwards movement of the back of the denture during contraction of the muscles during speech and function. The resultant incline (slope) of the now deformed lower jaw compared with that of the upper jaw also creates instability and movement of the lower denture.
Loss of bone in the upper and lower jaw is not limited to the bone around the teeth; portions of the skeletal bone also may be lost especially in the back parts of the lower jaw where the patient may lose more than 80% of the bone. The nerves of the lower jaw which were surrounded by and protected by bone eventually become exposed and sit on the top of the ridge directly under the denture. As a result, acute pain and/or temporary to permanent loss of sensation or feeling of the areas supplied by the nerve is possible. The bone loss in the upper jaw may cause pain and an increase in upper denture movement during eating. The forces from eating with an ill-fitting denture are transferred directly to the surface only and not the internal structure of the bone since there are no roots. Therefore, these forces do not stimulate and maintain the bone, but instead actually decrease blood supply and increased the rate of the bone loss. Chewing forces generated by short facial types can be 3 or 4 times that of long facial types. These patients are at even greater risk to develop severe bone loss.
Many of these conditions that have been described for patients without any teeth also exist for patients where only back teeth are missing and they are wearing a removable partial denture. The above problems focus on the damage to the bone. The remaining natural teeth are also subjected to substantial damage. The teeth must support the partial denture by connections called clasps. The clasps grab onto the teeth, and by design, transfer lateral or sideward forces to the teeth, which weaken them and cause tooth loss. Since these teeth often become compromised by loss of bone due to these forces, many partial dentures are then designed to minimize the forces applied upon these teeth. The net result is an increase in movement of the removable denture, and greater pressures on the soft gum tissue over the bone. This results in more bone loss. These conditions can protect the remaining teeth, but then accelerate the bone loss in the regions without teeth.
Effect on Soft TissueAs bone continues to lose width, then height, then more width and height, the gum tissues gradually decrease. A very thin gum usually lies over the advanced bone loss of the lower jaw. The gum is prone to sore spots caused by the overlaying denture. In addition, unfavorable high muscle attachments and loose tissue often complicates the situation.
The tongue of the patient with no teeth often enlarges to accommodate the increase in space formerly occupied by teeth. At the same time, the tongue is used to limit the movements of the removable denture, and takes a more active role in the chewing of food. As a result, the removable denture decreases in stability. The decrease in muscular control, often associated with aging, further compounds the problems of traditional removable dentures. The ability to wear a denture successfully may be largely a learned, skilled performance. The aged patient who recently loses their teeth may lack the motor skills needed to accommodate to the new conditions. This often results in food that is not adequately chewed and digestion and nutrition problems follow. (See “Health Effects of Tooth Loss” below)
Effects of Bone Loss on Facial Appearance
Facial changes naturally occur in relation to the aging process. When the teeth are lost this process is grossly accelerated with more rapid facial aging. The loss of teeth can add 10 or more years to a persons face. A decrease in face height occurs as a result of the collapse of bone height when teeth are lost. This results in several facial changes. The decrease in the angle next to the lips and deepening of vertical lines on the lips create a harsher appearance. As the vertical bone loss progressively and rapidly increases, the bite relationship deteriorates. As a result, the chin rotates forward and gives a poorer facial appearance. These conditions result in a decrease in the angle at the corner of the lips, and the patient appears unhappy when the mouth is at rest. Short facial types have higher bite forces, greater bone loss and more facial changes with tooth loss, compared to others. A thinning of the upper lip results from the poor lip support provided by the denture. And, there is a loss of tonicity of the muscles. Women often use one of two techniques to hide this cosmetically undesirable appearance: either no lipstick and minimum make-up, so that little attention is brought to this area of the face or lipstick is drawn over the border of the lips to give the appearance of fuller lips.
The upper lip naturally becomes longer with age as a result of gravity and loss of muscle tone. The loss of muscle tone is accelerated in a patient with no teeth hence the lengthening of the lip occurs at a younger age. Men often grow a moustache to minimize this effect. This has a tendency to “age” the smile, because the younger the patient the more the teeth show in relation to the upper lip at rest or when smiling. A deepening of the groove next to the nose and an increase in the depth of other vertical lines are made worse by the bone loss in the upper front jaw. This usually is accompanied by an increase in the angle under the nose. This can make the nose appear larger. The attachments of the muscles to the jaw also are affected by bone loss. The tissue sags along the lower jaw with bone loss, producing “jowls” or a “witch’s chin.” This effect is additive because of the loss of muscle tone along with the loss of teeth.
Patients are unaware that these bone, gum and facial changes are due to the loss of teeth. Instead, they blame these problems on aging, weight loss, or the dentist for making a poor denture. (Table 2 below)
Health Effects of Tooth Loss
A study of 367 denture wearers (158 men and 209 women) found that 47% exhibited a low chewing performance. Lower intakes of fruit and vegetables and vitamin A were noted in this group. These patients took significantly more drugs (37%) compared to those with superior chewing ability (20%), and 28% were taking medications for stomach or intestinal disorders. The reduced consumption of high fiber foods could therefore induce stomach or intestinal problems in patients without teeth with deficient chewing performance. In addition, as the coarser food is chewed it may impair proper digestive and nutrient extraction functions. The literature provides several reports that suggest that compromised dental function results in poor swallowing and chewing performance which in turn may negatively affect overall health and favor illness, debilitation, and shortened life expectancy.
Several reports in the literature correlate patients’ health and life span to their dental health. After conventional risk factors for stroke and heart attacks were accounted for, there was a significant relationship between dental disease and heart or blood vessel disease, still the major cause of death. It is legitimate to believe that restoring the mouth of patients to a more normal function may indeed enhance the quality and length of the life.
Psychological Aspects of Tooth Loss
The psychological effects of total tooth loss are complex and varied, and range from very minimal to a state of neuroticism. Although complete dentures are able to satisfy the appearance needs of many patients, there are many who feel their social life is significantly affected. They are concerned with kissing and romantic situations, especially if a new relationship is unaware of their oral handicap. A past dental health survey indicates that only 80% of the population without teeth is able to wear both upper and lower dentures all of the time. Some patients wear only one of the dentures, usually the upper; others are able to wear their dentures only for short periods. In addition, approximately 7% of denture wearers are not able to wear them at all, and become dental cripples or “oral invalids.” They rarely leave their home environment, and when they feel forced to “venture out”, the thought of meeting and talking to people while not wearing teeth is unsettling.
A study of 104 patients missing all of their teeth and seeking treatment was performed by Misch and Misch. Eighty eight percent of the patients claimed difficulty with speech, with one-fourth having very difficult problems. It is easy to correlate the reported increase in concern relative to social activities. Movement of the lower denture was reported by 62.5% of these patients. The upper denture “stayed in place” at almost the same percentage. Lower jaw discomfort was listed with equal frequency as movement (63.5%), and 16.5% stated they never wear the lower denture. The psychological effects of the inability to eat in public can be correlated to these findings. In comparison, the upper denture was uncomfortable half as often (32.6%), and only 0.9% were seldom able to wear the denture. Function was the fourth problem reported. Half of the patients avoided many foods, and 17% claimed they were able to chew more effectively without the denture.
The psychological needs of the patient without teeth is expressed in many forms. For example, in 1982 more than 5 million Americans used denture adhesives. A recent report showed that in the United States more than $147 million is spent each year on denture adhesives, representing 45 million units sold. The patient is willing to accept the unpleasant taste, need for recurrent application, inconsistent denture fit, embarrassing circumstances, and continued expense for the sole benefit of increased retention of the denture.
In contrast, eighty percent of the patients treated with implant-supported prostheses judged their overall psychological health improved compared with their previous state wearing traditional, removable dentures, and perceived the implant-supported prosthesis (denture) as an integral part of their body. Clearly, the lack of retention and psychological risk of embarrassment in the denture wearer is a concern the dental profession must address.
Decreased Performance of Removable Dentures
The difference in maximum bite forces recorded in a person with natural teeth and one who is completely without teeth is dramatic. In the first molar region of a person with teeth, the average force has been measured at 150 to 250 pounds per square inch (psi). A patient who grinds or clenches the teeth may exert a force that approaches 1,000 psi since their muscles get stronger with the increase in exercise. The maximum bite force in the patient without teeth is reduced to less than 50 psi since they now must chew on the softer gums. The longer the patient is without teeth the more the muscles atrophy and the less force they are able to generate. Patients wearing complete dentures for more than 15 years may have a maximum bite force of 5.6 psi because the muscles decrease in strength and tone.
As a result of decreased bite force and the instability of the denture, chewing efficiency also is decreased with tooth loss. Within the same time frame, 90% of the food chewed with natural teeth fits through a no. 12 sieve; this is reduced to 58% in the patient wearing complete dentures. The 10-fold decrease in force and the 30% decrease in efficiency affects the patient’s ability to chew. 29% of persons with dentures are able to eat only soft or mashed foods; 50% avoid many foods; and 17% claim they eat more efficiently without the denture.
Removable partial dentures have one of the lowest patient acceptance rates in dentistry. A Scandinavian 4 year study revealed that only 80% of patients who received partial dentures were wearing them after one year. The number further decreased to only 60% percent after four years. Reports of removable partial dentures indicate the health of the remaining teeth and surrounding gum tissues could deteriorate. In a study that evaluated the need for repair of a tooth as the indicator of failure of the partial denture, the survival rate of conventional removable partial dentures was 40% at 5 years and 20% at 10 years. The patients wearing the partial dentures often exhibit greater mobility of the teeth, greater bacterial plaque retention, increased bleeding around the teeth, more incidence of decay and accelerated bone loss in the regions with no teeth. Therefore, alternative therapies which improve the oral conditions and maintain bone are often more desirable. The 5-year survival rates of partial dentures based upon tolerance and use of the dentures is approximately 60% when replacing molars and 80% for partials completely supported by teeth. This is reduced to 35% and 60% at 10 years respectively. In another study, few partial dentures survived more than 6 years. Although one out of 5 US adults has had a removable denture of some type, 60% reported at least one problem with it.
| | Table 1.
| Bone Problems and Consequences Associated With Tooth Loss
| Decreased width of supporting bone
| Prominent bony ridges
| Decreases height of supporting bone
| Progressive decrease in gum tissues
| Elevation of denture with contraction of muscles of speech or function
| | Forward movement of denture from anatomic inclination | Thinning of gum, with sensitivity to abrasion and sore spots
| Loss of skeletal bone
| Loss of nerve sensation or feeling exposed nerves after bone loss
| Increase in size of tongue
| More active role of tongue in chewing
| Decrease of muscular control with aging
| Effect of bone loss on esthetic appearance of lower 1/3 of face
|
Table 2
| Cosmetic Consequences of Complete Tooth Loss
| Lower jaw protrudes out farther than upper jaw
| Angle of corner of mouth decrease in frown-like appearance
| Thinning of lips (especially the upper)
| Deepening of grooves in the skin over the lips
| Increased depth of associated vertical lines in the skin over the lips
| Increase in angle under the nose (makes nose look larger)
| Sagging of muscles (“jowls” and/or “witch’s chin”)
| Decrease in overall height of the face
| Loss of tone in muscles of facial expression
| Increased length of maxillary lip
| Less teeth show at rest position of jaw and lower high lip line position during smiling (aged smile)
|
Advantages Of Implant-Supported Replacement Teeth
The use of dental implants to provide support for replacement teeth offers a multitude of advantages compared with the use of removable dentures. These advantages include:
- The maintenance of bone and vertical dimension of the face.
- Teeth positioned for proper appearance.
- Improved psychological health.
- Increased success rates compared to conventional prostheses.
- Establishment of a proper bite.
- Increased bite force.
- Improved chewing performance.
- Increased stability and retention of removable dentures.
- Improved speech.
- Reduced palate or flanges compared to a removable denture
- Improved health.
1. Maintain Bone
A primary reason to consider dental implants to replace missing teeth is the maintenance of bone. The dental implant placed into the bone serves not only as an anchor for the replacement teeth, but also as one of the better preventive maintenance procedures in dentistry. Stress may be applied to the bone surrounding the implant. There is an increase in bone strength and density when the dental implant is inserted and functioning. The overall volume of bone is also maintained with a dental implant. An implant can dramatically slow the bone loss and maintain bone width and height as long as the implant remains healthy. Bone loss around an implant may represent more than a 20-fold improvement in lost bone structure compared with the bone loss occurring with removable replacement teeth.
The features of the lower third of the face are closely related to the supporting skeleton. When vertical bone is lost, the dentures act as “oral wigs” to improve the contours of the face. The dentures become bulkier as the bone disappears, making it more difficult to control function, stability, and retention. With implant supported teeth the vertical dimension of the face may be restored similar to that with natural teeth. The facial profile may be improved for the long term with implants, rather than deteriorating over the years.
2. Teeth Positioned for Esthetics
A lower denture often moves when the muscles contract during speech or function. The teeth are often positioned for denture stability, rather than where natural teeth usually reside. With implants, the teeth may be positioned to enhance esthetics rather than in the places dictated by traditional denture techniques to improve the stability of a denture.
3. Increased Success Rates
The success rate of implant replacement teeth is highly variable, depending on a host of factors that vary for each patient. However, compared with traditional methods of tooth replacement, the implant replacement teeth offers increased longevity, improved function, bone preservation, and better psychological results. Ten-year survival surveys of crowns on natural teeth indicate decay as the most frequent reason for replacement, and survival rates after 10 years are approximately 75 percent. Survival rates for bridges are far less. In the patient missing teeth, independent tooth replacement with implants may preserve intact adjacent natural teeth, which may further limit complications such as decay, porcelain fracture of the crown and poorer esthetics, which are the most common causes of failure. A major advantage of the implant supported replacement teeth is they cannot decay. The implant and related replacement teeth can attain a greater than 10-year survival of greater than 90 percent with proper hygiene and follow-up care. It is possible that the implants may last a lifetime. However, if removable teeth are attached to the implants, the replacement teeth may need periodic replacement.
4. Increased Bite Force
The maximum bite force of a traditional denture wearer ranges from 5 to 50 lb. Patients with implant-supported replacement teeth may increase their maximal bite force by 85 percent within 2 months after the completion of treatment. After 3 years the mean force may reach 300 percent greater, compared with pretreatment values. As a result, patients with implants may illustrate a force similar to natural teeth.
5. Proper Bite
Occlusion (the bite) is difficult to establish and stabilize with a completely soft tissue-supported denture. Since the lower denture may move as much as 1 inch or more during eating, proper bite contacts occur by chance, not by design. On the other hand, an implant-supported restoration is stable. The patient can more consistently return to the proper bite rather than adopt variable positions as dictated by the denture instability. As a result of improved bite awareness and stability, the patient functions in a more consistent range. With implant-supported replacement teeth, the direction of the bite loads are controlled by the dentist. On removable dentures, the uncontrolled horizontal forces accelerate bone loss, decrease denture stability, and increase sore spots on the gums. Therefore, the decrease in horizontal forces which are applied to implanted teeth improve the local conditions and help preserve the underlying bone and gum tissues. (Click here to see x-rays of a patient with collapsed bite that was restored to proper function)
6. Improved Chewing Performance
Chewing efficiency with implant replacement teeth is greatly improved compared with that of a soft tissue-borne denture. The chewing performance of dentures versus natural teeth were evaluated by Rissin, et al. The traditional denture showed a 30 percent decrease in chewing efficiency, and other reports indicate a denture wearer has less than 60 percent of the function of people with natural teeth.
7. Improved Stability and Retention
Implants can also be used to provide support, stability and retention for a removable denture. The stability and retention of implant-supported replacement teeth are greatly improved over soft tissue-borne dentures. Mechanical means of implant retention are far superior to the soft tissue retention provided by dentures or adhesives and cause fewer associated problems. The implant support of the final teeth is variable, depending on the number and position of implants; yet all treatment options demonstrate significant improvement.
8. Improved Speech
Speech may be impaired by the instability of a conventional denture. The muscles may flex and propel the back portion of the denture upward, causing clicking. As a result, a patient in whom the bone has collapsed 10 to 20 mm. (1/2 to 1 inch) may produce clicking sounds during speech. The tongue of the denture wearer often is flattened in the back areas to hold the denture in position. The lower jaw muscles of facial expression may be tightened to prevent the lower denture from sliding forward. In contrast, implant replacement teeth are stable and retentive and do not require these facial muscle maneuvers.
9. Reduced Size of Prosthesis
The implant restoration allows a reduced size of the denture. This is of benefit especially to the new denture wearer, who often reports discomfort with the bulk of the denture. The extended gum tissue coverage also affects the taste of food, and the gum tissue may be tender in the extended regions. The palate of an upper denture may cause gagging in some patients, and this portion of the denture may be eliminated in implant supported replacement teeth.
10. Improved Health
As reviewed earlier, denture wearers have experienced detrimental effects on their health. Implant patients report increased health effects with fixed teeth because they can chew properly and improve their diets. They can decrease the fat, cholesterol, and carbohydrate food groups and now eat more solid and nutritious foods.
Dental Profession Response
From 1982 to 1987, the numbers of practitioners who performed implant therapy increased 10-fold. Over 300,000 dental implants were inserted in the United States in 1992 and the number of implants inserted each year has continued to increase steadily through 1996. Over 90 percent of oral surgeons, periodontists (gum specialist) and prosthodontists (specialist of dentures and bridges) currently provide at least some aspect of dental implant treatment in their practices, and more than 65 percent of general dentists have used implants for supporting fixed and removable replacement teeth. All American dental schools now provide some education in implants.
Implanted teeth often offer a more predictable treatment course than traditional treatments. Thus, the profession and the public are becoming increasingly aware of this dental discipline. Almost every professional journal now carries articles about implants. Implant dentistry finally has been accepted by organized dentistry around the world. The current trend to expand the use of implant dentistry will continue until every dental practice uses this modality for support of both fixed and removable dentures. |
