Some edentulous patients simply cannot tolerate complete denture. It must be accepted that many patient who wear complete denture will experience considerable difficulty adapting to their prostheses. These situations are very frustrating for both patient and the dentist and means were identified to treat the maladaptive denture behavior.

Maladaptive denture behavior:

Maladaptive problem was initially thought to be resulting mainly from adverse anatomic changes in the denture bearing surface e.g. flat ridges, sharp ridges or thin mucosal tissues. However, clinical experience and some research have confirmed that there are physiologic as well as psychologic contributions to such behavior. For such patients who are unfit to accept the removable dentures because of anatomic, physiologic or psychologic reasons, dental implants are the alternative.

Dental implant: -

A dental implant is a foreign object inserted within or over the bones of maxilla or mandibular to support a fixed or removable prostheses for restoration of function lost with the loss of natural teeth.

Overdenture
An over denture is a complete or partial denture supported by mucoperiosteum and prepared teeth or roots.

Implant supported overdenture

It is a complete or partial denture supported by mucoperiosteum and by means of inserted implants.

Prime complaints regarding conventional complete denture

1. Instability of mandibular denture
2. Low retention
3. Oral discomfort
4. Migrating pain

Indications of implant supported overdenture: -

1. Grossly resorbed ridge
2. Poor oral muscular coordination
3. Low tolerance of the mucosal tissues
4. Parafunctional habits leading to recurrent soreness and instability of the prosthesis
5. Knife edged ridges, sharp mylohyoid projection or superficial placement of mental nerve.
6. Unrealistic prosthodontic expectations
7. Active or hyperactive gag reflex elicited by a removable prosthesis.
8. Psychologic inability to wear a denture, even if adequate denture retention or stability is present.

Contraindications for dental implants:-

1. Patients with all systemic problems where surgery is contraindicated.
2. Patients with hypersensitive to implant components.
3. Patients who lack maintenance of good oral hygiene.
4. Patients with deliberating or uncontrolled diseased and epileptic patients.
5. Lack of exposure on the part of the dentist.

Advantages of using implant supported overdenture

1. Retention security
2. Hygiene access
3. Lip support
4. Minimal contact with sensitive mucosa
5. Removable flanged prostheses

 
Insertion  of implants
 

A two stage surgical procedure is required to bring about osseointegration. Both stages are performed under strict surgical and sterilization protocol, with a 4-6 month healing period in between. During the interval between stages the patient?s old prosthesis is modified for use with tissue conditioners.

1. In the first stage, the following steps are needed to prepare the site for a titanium root analogue: -
   • A template is formed to locate and identify the position of implant in the jaw bone.
   • Flap preparation and gradual widening of the fixture site. Two to four implants are placed into the marked location in the bone after raising a mucoperiosteal flap using various drills.
   • Placement of a cover screw under the mucoperiosteal flap.
2.  In the second stage, approximately four months later, the following steps are needed for the abutment connection. This stage involves reopening the mucosa over each implant and placing a temporary healing screw into each implant. This screw will protrude through the mucosa provide easy access to the implants while new denture is being made.

The ball and socket attachments are screwed into the respective implants after removing the healing screws. The female component (sockets) is fixed into the marked and relieved locations in the fitting surface of the lower denture by means of cold cure acrylic resin. 

Criteria for success of implants:-

1. The individual unattached implant remains immobile when tested clinically.
2. No evidence of radiolucency around the implant is found on undistorted radiographs.
3. The mean vertical bone loss around the implant does not exceed 0.2mm annually after the first year of service.
4. No persistent pain or discomfort is attributable to the implant.
5. The implant design does not preclude placement of a prosthesis that is esthetically satisfactory to both patient and dentist.
6. In the context of the foregoing criteria, an individual implant success rate of 85% at the end of a 5year observation period and of 80% at the end of a 10 year period is the minimum level for success.