The foundation of a beautiful smile lies in a good set of teeth. Nothing distorts a smile more than the unsightly gaps left behind by missing teeth.
Missing teeth not only disrupt the harmony of the face, but a 2008 study also found that people with missing teeth are viewed more negatively for traits such as attractiveness, health status, education level, aggressiveness, intelligence and trustworthiness.
A more practical (and perhaps more important) aspect of missing teeth is that it can affect our chewing and speaking. Without teeth, the severely and completely edentulous (toothless) amongst us are restricted to a soft diet.
Sounds such as “f”, “v”, “ph” and “th” rely on the interplay between teeth, tongue and lips. The loss of our upper and lower incisors may affect the clarity of these sounds due to the resultant lisp.
Teeth also provide contours to the face, especially around the mouth and cheeks. Lips and cheeks start to sag, giving one an aged appearance, when teeth are lost. In addition, the resulting malalignment caused by teeth drifting into their neighbouring vacant spaces (left by missing teeth) interferes with biting and appearance.
It is no wonder then for eons, humans have gone through great lengths (and great pains) to find ways and means to replace missing teeth. From implants made of precious metal or seashells hammered into jawbones to dentures or bridges made from human and animal teeth, our forefathers certainly pushed the boundaries of creativity, ingenuity and pain.
Thankfully, these tooth replacements have undergone massive improvements since their somewhat barbaric beginnings. Currently, the three main options for tooth replacement are bridges, implants and dentures. Dentures are traditionally thought of as removable prostheses, i.e. appliances that can be removed and reinserted into the mouth by the wearer.
However, with the advent of dental implants, dentures can also be made into fixed prostheses. Fixed prostheses (including bridges) are appliances that are anchored onto structures in the mouth (i.e. teeth or implants).
Removable replacement teeth
Modern dentures are classified according to the number of teeth they replace. A partial denture replaces one or more missing teeth, while a complete denture replaces the entire upper or lower row of missing teeth.
Complete dentures rely on the underlying jawbone and soft tissue for support, while partial dentures rely on these, as well as the still-existing teeth for support.
The process of constructing a denture may involve several visits to the dentist. During these visits, impressions of the remaining teeth and surrounding mouth are made to produce accurate representative moulds of the jaws.
Measurements are then taken to determine the position of teeth before the final processing is done in the laboratory. A few minor adjustments are made after processing before the final product is fitted on the patient.
The main concerns with dentures are their appearance, comfort and stability. Current dentures are made from acrylic, which can be stained to resemble the natural appearance of gums and teeth. However, acrylic is also brittle, making dentures prone to breakage.
Sometimes, partial dentures are constructed with acrylic on a metal base (cobalt chromium alloy) and this greatly improves their strength without adding much weight. Complete dentures however, are usually constructed using only acrylic, as they rely on bulk to improve stability and resist breakage.
This may take some getting used to, as an upper denture may cover the palate, while the lower denture may encroach into the tongue space, affecting speech and swallowing. After a period of adjustment, most people are able to get used to having dentures in their mouth.
The stability of a denture, which is its ability to resist displacing forces in the mouth while chewing, is perhaps the greatest concern of most wearers. Stability depends on the quality and quantity of the remaining jawbone ridge.
Severely resorbed ridges (ridges that have thinned due to bone loss) may not be suitable for dentures or any prostheses for that matter, unless some surgical intervention is undertaken.
Dentures may also become loose over time as the underlying bone shrinks with age and may require replacement after several years. The use of denture adhesives can sometimes help improve denture stability, but a poorly-made denture is beyond help.
Whether replacing a single tooth, multiple missing teeth or all the person’s teeth, dentures remain a viable option, especially when cost is taken into consideration.
Just like real teeth
Contrary to removable prostheses, fixed prostheses are permanently fixed in the mouth. There are essentially two types of fixed prostheses:
• Dental bridge
A traditional bridge is made up of crowns cemented onto teeth at either side of the gap left by missing teeth. These supporting teeth are known as abutment teeth. These abutments act as anchors for the false tooth/teeth that will fill the space left behind by the missing tooth/teeth.
Implants can also act as abutments, with the constructed bridge either cemented or screwed onto the implants.
A bridge can be fabricated from tooth-coloured ceramics (porcelain) or zirconia, and are almost impossible to distinguish from natural teeth when done well. These types of bridges are known as all-ceramic bridges.
The porcelain teeth can also be fused to metal for added strength, and such bridges are called porcelain fused to metal bridges. The cost of a bridge varies depending on the number of teeth involved and the material used.
The main disadvantage of dental bridges is that some sacrifice of healthy tooth structure is required before it can be cemented on the abutment teeth. The abutments are also meant to do their fair share of biting duty, which can be detrimental to the tooth if the bridge is not well constructed.
• Dental implants
Dental implants have been around since ancient times. The ancient Chinese used bamboo pegs as implants, while the ancient Egyptians and Celts used precious metal, ivory, and even human teeth (from someone else).
The skeletal remains of a Mayan woman from the sixth century had seashells implanted into her jaw to replace her missing teeth. What was more surprising was that bone had formed around these seashells to hold them in place, much like modern implants.
The game changer in modern implantology came in 1952 through a discovery made by Dr Per-Ingvar Brånemark, a Swedish orthopaedic surgeon.
While studying blood flow in rabbit bone, he discovered that the titanium chambers implanted during the study could not be removed as they had become so completely integrated with the surrounding bone.
Dr Brånemark called this phenomena osseointegration, where bone forms directly over the surface of a metal implant such as titanium. He placed the first titanium dental implant in a human in 1965. However, it was only in the 1980s when his work became widely acknowledged.
A dental implant is basically a titanium screw that is surgically inserted into the jawbone. Crowns, bridges or dentures can then be placed onto these implants to replace missing teeth. Placement of an implant involves a minor surgical procedure, usually done under local anaesthesia.
During the procedure, a gum flap is raised to expose the alveolar bone beneath. The implant is then surgically inserted directly into the bone and covered by the gum flap, which is then stitched into place over the implants.
The implants are usually left undisturbed for about three months to allow it to osseointegrate with the surrounding bone. The patient then returns for a second minor procedure where part of the implant is exposed to begin the process of fitting a prosthesis.
However, there are some implants that allow a prosthesis to be fitted at the same as the insertion of the implant, allowing the procedure to be completed in one sitting. The success of implants rests on osseointegration, which will provide the support and stability that allows the implant to withstand biting forces.
Implants are the closest we have come to replacing natural teeth. It would be useful to bear in mind that, just like natural teeth, adequate bone levels are necessary to ensure the stability of an implant.
In cases where bone resorption or loss has occurred after tooth loss, additional procedures such as bone grafting are required prior to implant placement to ensure adequate bone height and width. Conditions that affect bone healing or make it susceptible to infections can affect the stability of an implant.
Poor oral hygiene and smoking can also have a detrimental effect. A condition known as peri-implantitis, causes bone loss around an implant the same way that periodontitis affects natural teeth.
This may result in an unsightly exposure of the underlying metal implant, movement of the implant, and worse, loss of the entire implant.
Much like natural teeth, good oral hygiene and regular dental check-ups are necessary once implants are placed. The main limitation of implants is their high cost and the wariness of most people towards implants. However, the high success rates, as seen in many studies, should placate their worries.
Although some may argue that almost everyone can have implant therapy, those who may have compromised bone quality – such as those who have had previous radiotherapy in the head and neck region, patients on intravenous bisphosphonates or those with bleeding disorders – need to be carefully reviewed before the decision for treatment is made.
It is important for the attending clinician to assess each patient’s medical condition and to weigh the risks and benefits of implant placement before a treatment plan is formulated.
In conclusion, for those who wish to replace missing teeth, there are many options to choose from. Choices should be made after discussion with your dentist on the prognosis of each treatment and the financial and biological costs, as well as the potential longevity of the prostheses.
We should also remember that all fitted prostheses require maintenance and we are advised to visit our dentist regularly to ensure the continuous function of these prostheses.