A conventional over-denture rests over some healthy natural tooth roots.
An overview of theJaw
Maintaining a denture on the jaw bone ridge (called alveolar ridge) isessential to preventing it from becoming loose during eating, speaking andother activities.
Preserving the alveolar ridge facilitates denture stability
The body tends to conserve energy and nutrients by maintaining onlystructures with apparent immediate value. A typical example is the bulkreduction of a broken leg held immobile by a full leg cast for a month or more.
The body "recognizes" the only one purpose for alveolar boneis to hold tooth roots.
Alveolar bone no longer supporting a tooth root is removed, or literallydissolved away by the body. This is called resorption or simply shrinkage.
Resorption progresses at varying rates in the same person at differenttimes and at different rates between different people. Resorption progressesrapidly within the first year of loosing a tooth after which time the rateprogresses at a slower pace.
Preserving the Jawbone
IF the maximum amount of bone is to be maintained then preserving themaximum number of healthy tooth roots should achieve that end.
Preserving thesensation of having teeth
Studies demonstrate that even though only roots are preserved, and theyare covered by a denture, a patient still has sensory input sensations similarto that experienced with teeth, as opposed to individuals with conventionaldentures and no preserved roots. Over-denture patients also appear to have amore natural perceived directional sense in their chewing activities. In otherwords, many patients relate that they still feel like they have teeth - - apositive comment.
Why anover-denture?
If a patient is treatment planned to have a denture, and the roots ofsome remaining teeth are supported in healthy alveolar bone - - then aconventional over-denture is a viable consideration.
However, only a licensed dental professional can determine if a conventionalover-denture is a suitable consideration for a certain person, after acomprehensive examination.
Somecharacteristics of a conventional over-denture
- Most of atooth crown (that part of the tooth above the gums) is removed. This oftennecessitates root canal therapy if not already done.
- Remainingtooth, projecting above the gum, is rounded and usually covered with asimilarly shaped artificial crown-like covering.
- Variousconfigurations and extensions may be built onto some retained roots. In thosecases, that portion of the denture overlying these configurations is modifiedto contain attachments that clip onto a framework or receive the individualextensions. In addition to preserving alveolar bone and sensory input, thedenture is securely held in place, but may be comfortably and easily removed forcleaning.
Advantages of aconventional over-denture
- Feelsmore like having teeth
- Moreretentive in many cases
- Helpsreduce shrinkage of surrounding bone
- Reducespressure to portions of the alveolar ridge
- Positive psychological advantage of still having teeth
Disadvantages of aconventional over-denture
- Scrupulousoral hygiene is essential in order prevent decay and gum disease.
- Theover-denture may feel bulkier than a conventional denture.
- Frequentmaintenance examinations are necessary.
- Generallythis is a more expensive approach than a conventional denture.
ImplantOver-Denture
An implantover-denture connects to cylinder-like configurations (called implants) thathave been surgically implanted into jaw bone.
The denture appearslike a traditional prosthesis. However, that part of the denture overlying implantsis modified to retain various semi-rigid attachments that receive implantextensions projecting above the gum. This arrangement helps keep a denturesecurely in place while eating, speaking and during other oral activities, butstill allows easy self-removal of the denture for cleaning purposes.
There are two phasesto this process. The first is a surgical phase consisting of two stages, andthe second is a prosthetic phase (making the implant denture).
The surgical phase
Surgical insertionstage
Implants arecompletely inserted into precise preparations in jaw bone. While there arevarious implant configurations, they are essentially cylindrical in shape andmade of pure titanium metal. After implants are inserted into jaw bone, gumtissue over the implant is closed with sutures in most cases.
While a minimum of twoimplants may be inserted for an acceptable outcome, a person may be treatment plannedto receive three or more - - depending upon individual needs and anatomicallimitations. More implants will give additional support and retention to theimplant denture.
Healing andsurgical exposure stage
During healing, anexisting or temporary denture may continue to be worn after adjustments havebeen made to adapt to the surgerized site. If the existing denture cannot bealtered sufficiently, a provisional prosthesis should be fabricated.
Implants are leftundisturbed beneath gum tissue for at least several months as determined by thedental professional. During this time bone reorganizes and grows around theimplant surface, anchoring it securely into the jaw (this is calledosseointegration).
At the end of thehealing stage, the top of the implant is exposed by removing gum tissuedirectly over it.
An extension that isthen screwed into the exposed implant projects slightly above the gum tissue. Afteradjustments, an existing denture can be worn over an implant extension whilethe gum heals.
However, the denturemust be reshaped to conform to surgical site contours in order to avoid unnecessarypressure areas on the newly surgerized site.
The prostheticphase (making the implant denture)
A precisionsuperstructure is fabricated that is screwed into the implant extensions. Thissuperstructure may have various interface configurations ranging from interconnectingmetal bars to specially shaped singular extensions.
A denture isfabricated with special provisions on the inside surface to receive varioustypes of attachments (interlocks). Depending on the attachment, they interactin various ways with the superstructure. For example, a metal or plasticattachment may clip onto metal superstructure bars, a nylon receptacle mayreceive a specially configured implant extension, and so forth.
Theattachment/superstructure configuration helps to securely maintain a denturewhile eating and speaking, and still allows a person to comfortably and easilyremove the prosthesis for cleaning purposes.
Essentialmaintenance needs
As might be expected,exemplary oral hygiene is essential to helping prevent the development ofdisease around implants that could cause their failure.
Implants,superstructure, attachments and the over-denture must be checked andprofessionally maintained by a licensed dental professional on a regular basis.Attachments often need periodic adjustment or replacement due to wear.
While the implantover-denture approach is complex and expensive, the value received by anindividual usually far exceeds monetary considerations.
How long willimplant over-dentures last?
An implant may lastfor a lifetime (current reports show many implants lasting twenty years) ordeteriorate in a few years - manyfactors are involved that reduce the life expectancy of implants, such as oral hygiene,general health, habits such as smoking, grinding, and so forth. The superstructureor implant extensions may need to be replaced after five years. Depending onthe implant system used, some parts may need to be replaced annually, orsooner, because of wear or deterioration. These time frames are generalities.The dental profession continues to strive for long-term durability.
