dental implant guidelines for treatment planning therapy in the edentulous mandible are designed to improve the success of both the implants and the prosthesis. The "rules" govern the biology and amount of bone necessary for the size of implants sufficient to support chewing forces. The "rules" also specify the distribution of the implants to control the forces they must withstand and the amount of space necessary to fabricate a prosthesis with enough structural integrity to withstand these forces.
Implant tissue bar/overdenture and implant supported/fixed (hybrid) prostheses:
The first rule is that the lower jaw must allow for implants at least 10mm in length--that the mandible's inferior/superior dimension be at least 10mm. Evidence in the literature supports the conclusion that 10mm implants in the anterior mandible have an equally high survival rate than longer implants.
The second rule is that the vertical (restorative) dimension must be at least 10mm from ridge crest to the occlusal plane. Using a "top down" approach (the teeth are designed first), the average height of the mandibular anterior teeth is 10mm, and there must be room for acrylic attachment, a rigid framework, abutment height and biologic width. This allows for a prosthesis with structural integrity and permits establishment of proper contours in support of comfort, mastication and speech.
The third rule is that the anterior/posterior distribution of implants be at least 10mm for the hybrid. This allows the lever arm from the anterior implants to the posterior implants to be sufficient for the counter leverage necessary to support 15mm of cantilevered teeth back to the first molar.
Cone-Beam technology required
Applying these rules requires using cone-beam computed technology for a volumetric assessment of the mandible. It means determining final anterior and posterior tooth position prior to planning and execution implant placement and presurgical correlation of the anatomy of the mandible with the location of the planned prosthetic teeth.
Robert G. Tupac, DDS, FACP, Inc.,
Diplomate, American Board of Prosthodontics
(661) 325-1275 | www.drtupac.com
5060 California Ave., #170, Bakersfield, CA 93309