BDS Tutorial – 23 August 2012
Overdentures
Definition and types of overdentures
A tooth supported overdenture (TSO), is a complete or partial removable denture supported by
retained roots to provide improved support, stability, and *tactile and *proprioceptive sensation.
Since the introduction of implants, implant- supported overdentures (ISO) have also been
introduced which are overdentures that are supported by and attached to implants. Implants can
preserve alveolar bone provided they are placed before loss of bone height.
Maintaining a denture on the alveolar ridge is essential to preventing it from becoming loose during
eating, speaking and other activities. Alveolar bone resorbs post-extraction. This is perpetuated by
placing a conventional denture in an edentulous patient, especially in the mandible. Overdentures
are known for preserving the alveolar ridge thus facilitating denture stability.
*Tactile sensation – the sensation produced by pressure receptors in the skin.
*Proprioceptive sensation - Awareness of posture, balance or position due to the reception of stimuli, produced within the
organism, which stimulate receptors (called proprioceptors) located within muscles, tendons, joints and the vestibular apparatus
of the inner ear.
Indications
Proper patient evaluation and treatment planning (see Zarb et al, pp 293) are of grave importance.
These include evaluation of patient’s oral hygiene, reasons for tooth loss, remaining alveolar bone,
position of nerves especially the mental nerve for patient selection. The most important factors
however are:
Supporting alveolar architecture
 Healthy roots and supporting structures
 Patients with exceptional oral hygiene.
Location of the teeth within the arch
 Retained roots should preferably be on both quadrants in the jaw, strategically distributed
(first molar or second premolar with canines)
Complexity of the root structure
 Determine if root canal therapy is feasible and whether or not it is required, depending on
the height of crown resection.
In the case of ISO the patient must have adequate alveolar bone height.
Tooth supported overdentures
When all the teeth have been lost the alveolar bone resorbs. By leaving some of the roots of the
teeth in place we can significantly reduce bone loss and provide the patient with a more stable
denture. The remaining roots also help anchor the denture.
Remove the portion of the teeth above the gingival margin. Most of a tooth crown is removed.
This often necessitates root canal therapy.
Fig. 1 tooth preparation for overdenture
The retained roots can support retentive elements (see figures 2,3,4). The remaining tooth,
projecting above the gingiva, can be rounded and covered with a similarly shaped artificial crownlike coping (see fig. 2).
Fig. 2 Gold crown covering root
Various configurations and extensions may be built onto some retained roots. In those cases, that
portion of the denture overlying these configurations is modified to contain attachments that clip
into a framework or receive the individual extensions. In addition to preserving alveolar bone and
sensory input, the denture is securely held in place, but may be comfortably and easily removed for
cleaning.
Fig. 3 Retentive elements in overdentures
Fig. 4 “Female" cement into the root
“Male" incorporated in the denture
Implant supported overdentures
An implant-supported overdenture (ISO) is a type of overdenture that is supported by and attached
to implants. There has to be sufficient alveolar bone to support the implant.
An ISO had special attachments that snap onto attachments on the implants.
They are usually made for the lower jaw because regular dentures tend to be less stable there.
Usually, a conventional denture made to fit an upper jaw is quite stable on its own and doesn't need
the extra support offered by implants. However, they are not uncommon in the maxilla.
An implant-supported denture should be removed daily to clean the denture, gingiva and implants.
Just as with conventional dentures, you should not sleep with the implant-supported dentures at
night.
At least two implants are needed for support.
There are two types of implant-supported dentures: bar-retained and ball-retained
Fig. 5 Bar-retained dentures — a thin metal bar that follows the curve of your jaw is attached to two to five implants that have
been placed in your jawbone. Clips or other types of attachments are fitted to the bar, the denture or both. The denture fits over
the bar and is securely clipped into place by the attachments.
Fig. 6 Ball-retained dentures (stud-attachment dentures) — Each implant in the jawbone holds a metal attachment that fits
into another attachment on the denture. In most cases, the attachments on the implants are ball-shaped ("male" attachments),
and they fit into sockets ("female" attachments) on the denture. In some cases, the denture holds the male attachments and the
implants hold the female ones
“How the implants maintain/keep bone height”
See process called osseointegration . See Implantology
Advantages and disadvantages
Advantages
TSO
The patient still has sensory input sensations
similar to that experienced with teeth
Provides better retention, support and stability
to regular dentures
Helps reduce alveolar bone resorption.
ISO
Provides superior retention, support and stability
regular dentures and TSO
Helps reduce alveolar bone resorption.
Positive psychological advantage of still having
teeth.
Psychological advantage because of very
retentive prosthesis
Prevent combinations Syndrome
Prevent combinations Syndrome
Disadvantages
TSO
Caries and periodontal disease may cause
mobility of underlying teeth
ISO
Perimplant disease may cause mobility of
underlying implants.
The over-denture may feel bulkier than a
conventional denture.
The over-denture may feel bulkier than a
conventional denture.
Frequent maintenance examinations are
necessary.
Frequent maintenance examinations are
necessary.
Generally this is a more expensive approach than
Generally this is a more expensive approach than
a conventional denture root canal treatment,
copings etc depending on the patient’s needs.
a conventional denture, the surgery, and
implants.
Failure due to failed root canal.
Maintenance demands are high and meticulous
oral hygiene is necessary.
Time because of root canal phase and tooth
preparation.
Failure due to poorly placed implants.
Maintenance is costly
Time between surgical phase/s of implant
placement and overdenture placement
Maintenance
Meticulous oral hygiene practice is essential in preventing caries and periodontitis/ peri- implatitis.
Antibacterial agents, topical fluoride and routine oral hygiene practices should be adhered to daily.
Frequent professional visits must be kept up.
Implant’s superstructure and attachments and the over-denture must be checked and clinically, and
should be maintained on a regular basis. Attachments often need periodic adjustment or
replacement due to wear.
The retentive elements for TSO need to be monitored and may need to be replaced from time to
time.