Glossary: Dentures

Dentures, or, more accurately, removable complete dentures are full-mouth false teeth, which are used when a patient has no teeth left on either the mandibular arch, the maxillary arch, or both. Patients can become entirely edentulous (without teeth) either due to ineffective oral hygiene or trauma. Removable complete dentures, can help give the edentulous patient better masticatory (chewing) abilities, as well as enhance the esthetic appeal of their lips in specific and their entire face in general. Removable partial dentures are for patients who are missing only some of their teeth on a particular arch. Fixed partial dentures, better known as crowns and bridges, are also for patients missing only some of their teeth, but these are more expensive than removable appliances, and they are contraindicated in certain instances. Sets of dentures have been found dating from the 15th century and probably existed before that time. Carved from bone or ivory, or made up of teeth from dead or living donors, these dentures were uncomfortable and rotted after extended use. The first porcelain dentures were made around 1770 by Alexis Duch?teau. In 1791 the first British patent was granted to Nicholas Dubois De Chemant, previously assistant to Duchateau, for De Chemant's Specification, "a composition for the purpose of making of artificial teeth either single double or in rows or in compleat setts and also springs for fastening or affixing the same in a more easy and effectual manner than any hitherto discovered which said teeth may be made of any shade or colour, which they will retain for any length of time and will consequently more prefectly resemble the natural teeth." He began selling his wares in 1792 with most of his porcelain paste supplied by Wedgwood. Single teeth in porcelain were made from 1808. Later dentures were made of vulcanite and then, in the 20th century, acrylic resin and other plastics. In Britian in 1968 79% of those aged 65-74 had no natural teeth, by 1998 this proportion had fallen to 36%. [edit] Problems associated with Complete Dentures

Problems with dentures include the fact that patients are not used to having something in their mouth that is not food. The brain senses this appliance as "food" and sends messages to the salivary glands to produce more saliva and to secrete it at a higher rate. New dentures will also be the inevitable cause of sore spots as they rub and press on the mucosa. A few denture adjustments for the weeks following insertion of the dentures can take care of this issue. Another problem with dentures is keeping them in place. There are three rules governing the existance of removable oral appliances, and they are support, stability and retention. Support is the principle that describes how well the underlying mucosa (oral tissues, including gums and the vestibules} keeps the denture from moving in the vertical plane towards the arch in question, and thus being excessively depressed and moving deeper into the arch. For the mandibular arch, this function is provided by the gingiva (gums) and the buccal vestibule (valley region between the gums and the lip), whereas in the maxillary arch, the palate joins in to help support the denture. The larger the denture flanges (part of the denture that extends into the vestibule), the better the support. More recently, there has been a move to increase denture stability with implants. When pressure is applied to alveolar bone bereft of teeth (alveolar bone is the bone in which teeth normally reside), the bone reacts to this pressure by resorbing. After many years of denture wearing, the ridges upon which the dentures rest deteriorate and can easily all but disappear. The insertion of implants into the bone below the dentures can help to seriously combat this unfortunate occurrence. The implants are strategically placed to bear the brunt of the pressure when the denture is used for chewing, keeping the bone from melting away. When implants are integrated into treatment, the denture is now referred to as being an implant supported overdenture and the implants are referred to as overdenture abutments. Stability is the principle that describes how well the denture base is prevented from moving in the horizontal plane, and thus from sliding side to side or front and back. The more the denture base (pink material) runs in smooth and continuous contact with the edentulous ridge (the hill upon which the teeth used to reside, but now consists of only residual alveolar bone with overlying mucosa), the better the stability. Of course, the higher and broader the ridge, the better the stability will be, but this is usually just a result of patient anatomy, barring surgical intervention (bone grafts, etc.). Retention is the principle that describes how well the denture is prevented from moving in the vertical plane in the opposite direction of insertion. The better the topographical mimicry of the intaglio (interior) surface of the denture base to the surface of the underlying mucosa, the better the retention will be (in removable partial dentures, the clasps are a big time provider of retention), as surface tension, suction and just plain old friction will aid in keeping the denture base from breaking intimate contact with the mucosal surface. As mentioned above, implant technology can vastly improve the patient's denture-wearing experience by increasing stability and saving his or her bone from wearing away. Implant can also help with the retention factor. Instead of merely placing the implants to serve as blocking mechanism against the denture pushing on the alveolar bone, small retentive appliances can be attached to the implants that can then snap into a modified denture base to allow for tremendously increased retention. Options available include a metal Hader bar or precision balls attachments, among other things. As can be expected with any removable appliance placed in the mouth, there will be some problems (in respect to the three principles mentioned above) with dentures no matter how well they are made. This is because the best the dentist can do is fabricate the upper denture to work in harmony with the lower denture when the patient is at rest. If the only variables in the equation are the patient's edentulous ridges and the two dentures, the dentist can set the teeth in certain ways to help prevent dislodgement during opening, closing and swallowing. Once food enters into the picture, though, the stability of the denture bases is not impervious to disruption. During chewing, the denture bases will sometimes act as class 1 levers, and when the patient bites down on the anterior, or front, teeth, the posterior, or rear, teeth are bound to move away from the ridge. Although the ideals of denture design will have it that the intaglio surface is in perfect, intimate contact with the ridge and the margins of the denture base will create a perfect suction seal (the seal is actually only on the maxillary denture), ideals are rarely if ever met in this imperfect world, and thus some movement is to be expected. Denture adhesive can then be utilized to compete against the forces trying to pull the denture base away from the mucosa. In a perfect world, a patient with a perfect edentulous ridge with a perfectly fitting denture would require no adhesive, as the actual form of the denture base should work in tandem with the three principles mentioned above, thus precluding movement in any way, shape or form. [edit] Mini implants Mini dental implants are ultra-small diameter (1.8 millimeter width), biocompatible titanium alloy implant screws, conceived and designed over 20 years ago by a dentist, Victor I. Sendax, DDS. He created this unique dental product as a transitional device to help support fixed bridge replacements for lost teeth. His novel theory was that mini implants could function free standing by themselves or in combination with natural tooth supports and/or larger conventional type dental implants. This was a revolutionary concept in dental science. link Mini-implant Illustration In 1997, Dr. Sendax collaborated about his mini implant theory and design concepts with a colleague, Dr. Ronald A. Bulard. Dr. Bulard had previously formed a dental implant company, IMTEC Corporation, which was at the time manufacturing and marketing standard sized dental implants, abutments, and other dental products. Convinced they were on to something special, the two implantologists spent countless hours studying and refining Dr. Sendax's original creative design, resulting in a more efficient top and collar to the mini dental implants. Combining this now re-designed mini implant with Dr. Sendax's original insertion protocol resulted in a successful breakthrough. IMTEC Corporation now offers this innovation under the brand name IMTEC Sendax MDI (mini dental implant). The innovative system and procedure was thereafter formally introduced to the United States dental community at an implant conference in Orlando, Florida in April, 1999. It was an instant success and now represents one of the fastest growing segments of the dental product industry.