Preoperative Planning

Proper treatment planning, as well as the selection of the proper implant length and diameter, are crucial to the longterm success of the implant and restoration. Before an implant can be selected, the anatomical foundation available to receive the implant must be carefully assessed. Several steps should be taken to complete the evaluation:

1. Clinical examination of the oral cavity can provide important information about the health of the soft tissue at the proposed implant site. Tissue tone and the state of the superficial tissues should be evaluated. In addition, the patient should demonstrate an adequate dimension of attached mucosa or keratinized tissue at the site selected for implantation. In partially edentulous cases, the periodontal status of the remaining dentition should be assessed and interaction between the implant restoration and the adjacent natural dentition should be considered.

 2. The bony foundation and ridge need to be clinically analyzed to ensure the presence of proper dimensions and the amount of bone for implant placement. At least one millimeter of bone should be present at the buccal and lingual aspects of the implant following placement. During the planning state, it is useful to measure the existing bone foundation.

Radiographic Marking Balls (RMB30)
The vertical height of the bone is best determined radiographically. Accurate measurement of the vertical dimension on the radiograph facilitates the selection of the appropriate implant length. This helps to avoid implant placement into the maxillary sinus, the floor of the nose or the mandibular canal and prevents perforation of the inferior aspect of the mandible. Measurements can be made directly on the panoramic radiograph using a millimeter ruler. Corrections should be made for the degree of enlargement produced by the particular radiographic equipment.

Radiographic marking balls of a known dimension can be embedded in a plastic template prior to radiographic examination. Once the radiograph is taken and the metal marking balls are visible on the image, measurements can be taken to determine the amount of bone available for implant placement.

To calculate the distortion factor, a simple formula can be utilized:
(5 ÷ A) x B = amount of actual bone available.

• Radiographic marking ball = 5mm in diameter.
• A = Size of marking ball image on radiograph.
• B = Length in millimeters on the radiograph of available bone between the crest of the ridge and the inferior alveolar nerve canal.

Example:
A = 6.5mm
B = 14mm Therefore: (5 ÷ 6.5) x 14 = 10.76mm
actual bone available

NOTE: A 2mm margin of safety, from the apical end of the implant to the adjacent vital structure, should be considered.

A. Marking Ball Image (6.5mm on this radiograph)
B. Inferior Alveolar Nerve Canal