Subperiosteal implants Types, Procedure and Surgical Stages

Subperiosteal Implants

Implants placed on top of resorbed alveolar ridges are called sub-periosteal.

Subperiosteal implants Types: Total or full subperiosteal implants. They can be non-coated or coated with hydroxyapatite. Materials for subperiosteal implants are surgical valium, titanium, or titanium alloy, zirconium, biennium, and nickel-free cobalt-chromium alloy.

Subperiosteal implants Parts of subperiosteal Implants

The part below the periosteum is called the substructure.

Subperiosteal implants consists of:

1. Primary struts consist of peripheral (lay on extended areas of cortical bone) and abutment struts (connects labial, lingual struts and vertical per mucosal post on the crest of the ridge).
2. Secondary struts help to distribute forces from primary abutment struts.
3. Permucosal attachment acts as a prosthetic retainer. The part of the implant above the tissue is called the mesostructure.

Read And Learn More: Complete Dentures Question and Answers

Subperiosteal implants consists of:

1. Mesobar
2. Superstructure which attaches to mesostructure.

Subperiosteal implants Procedure

• An impression of the residual maxilla or mandible with a bone-bite registered at centric relation and the proper vertical dimension is made. A cast is then made and the implant is designed and fabricated.
• A more extended two-stage procedure, where the implant is inserted 20-30 days after the initial bone impression with the help of a CAT-scan bone model.

Subperiosteal Implants Technique Of Subperiosteal Implants

Subperiosteal implants Preliminary

1. The normal prosthetic procedure for constructing complete upper and lower dentures is carried out until the dentures have reached the trial stage.
2. The lower denture is retained in the wax stage.
3. The first molars and the canines are removed from the wax lower denture and an instrument pushed through the wax in the areas occupied by these teeth until it penetrates the surface of the ridge of the cast.
4. These marks on the cast locate the positions of the abutments of the implant. A template is replaced on the cast and holes are drilled through it in the areas marked for future abutments.
5. Two impression trays are made on the cast and they will be used to take the impression of the bone surface when the mucoperiosteum has been reflected.
6. An acrylic record block is also constructed to occlude with the finished upper denture. Rims
   are only built in the premolar and molar regions and wire staples are inserted into the acrylic in the premolar regions to facilitate its manipulation.
7. This record block will be used lined with gutta-percha to record the jaw relationship when the mucosa has been reflected to enable the cast of the bone impression to be correctly related to the upper denture.

Subperiosteal Implants Two Surgical Stages

• The first consists of the reflection of the mucoperiosteum, two impressions of the surface of the bone, and the recording of the occlusion taken with the record block fitting the bone.
• The second stage, about three to six weeks after the first, consists of the reflection of the mucoperiosteum and the insertion of the implant substructure after completing the lab procedures.
• In the lab procedures, care should be taken to prepare the abutment posts with a neck of 2.5 to 3 mm diameter and with a depth slightly greater than the thickness of the mucosa.
• The diameter of the base of the abutment posts should be about 4 mm in the canine regions and 6 mm in the molar regions and each post should have a 5° taper.
• The casting of the pattern is made with a nickel-free cobalt-chromium alloy. The implant is positioned on the cast, thimbles waxed to the abutment posts and joined by wax bars. The whole wax pattern is cast in cobalt-chromium to form the superstructure.
• The cast superstructure is seated on the abutment posts and the lower denture waxed around it.

Subperiosteal implants Reasons For Failures Are:

1. The inaccurate fit of the cast framework.
2. Incorrect outline and inadequate extension of the substructure.
3. Uneven pressure.
4. Careless surgical technique.
5. The compromised general health of the patient and careless oral hygiene.