Choosing an implant for the lower jaw

The choice of an implant involves the choice of the material from which it is made, as well as the choice of the shape needed to improve the patient's appearance. The ideal material for implantation in the mandible and cheekbone area should have the necessary consistency, flexibility and density; it should be non-reactive, resistant to infection, stable, accessible for removal and replacement, easy to manufacture and safe for surrounding tissues. The only alloplastic material that meets virtually all of these requirements is monolithic silicone elastomer rubber (Silastic).

Silastic is made of a polymer whose consistency can be changed to select softness and flexibility. The body accepts this material, forming a fibrous capsule around it, without deforming the implant itself. Implants with holes are additionally stabilized by the ingrowth of connective tissue. The material can be industrially manufactured into implants of various sizes and shapes using computer modeling. They can be adjusted by changing the shape in the operating room, cutting with conventional instruments and blades.

Choosing one of the many Silastic mandibular implants available can be challenging. The first decision to make is whether to choose an extended mandibular implant over a central chin implant. The three most studied and commonly used extended mandibular implants are the extended mandibular implant (four sizes), the various Flowers chin implants (standard, vertical, anteriorly tapered, or posteriorly tapered), and the Mittelman anterior mandibular implants (four sizes). All three implant types have different configurations and approaches to placement, but produce very good results. The extended mandibular implant provides varying amounts of chin augmentation depending on the patient’s needs, but the amount of implant that falls below the mental foramen is approximately the same regardless of how much augmentation is given to the chin itself. In other words, the augmentation in the anterior sulcus remains the same regardless of the amount of augmentation given to the chin. The Flowers mandibular implant is characterized by a different inclination in the central, chin part and a conical continuation along the lower jaw under the mental foramen.

The Mittelman anterior maxillary implants offer four options for chin augmentation, combined with four comparable options for the placement of these implants in the anterior maxillary groove. They are designed to provide varying degrees of correction of the anterior maxillary groove while simultaneously augmenting the chin. In addition, there is an extended mandibular implant that does not augment the chin itself, but corrects the anterior maxillary groove. It becomes an extremely important adjunct to facelifts in patients who have an adequate chin, which is so often combined with the presence of an anterior maxillary groove. There is a modification of the extended chin implant proposed by Terino. It has a more square chin protrusion, thereby creating a more forward-looking chin.

The Silastic implants described here come in a variety of densities. The softer monolithic implants are more flexible and easier to place through smaller incisions. They conform more to the mandible and contribute less to bone resorption. For mandibular augmentation, we use Silastic implants with a durometer of 10. Most extension mandibular implants and all anterior mandibular implants have multiple holes that facilitate anchoring the implants to the periosteum or soft tissue of the chin. The surgeon may also make holes with a biopsy instrument. There is no standard for implant sizes (for example, average sizes vary from manufacturer to manufacturer). However, there is some consistency among the different implant configurations made by a single manufacturer. The choice of the practitioner is made easier by the availability of "calibrators" supplied by the implant manufacturers. The calibrators can be inserted into the created pocket until the surgeon is satisfied with the result. The calibrator is then removed and an implant of the same size is inserted.

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