Clinical diagnostic tools
1) Diagnostic Models
Diagnostic study models help in evaluation of the:
- Amount of interocclusal space
- Arch relationship
- Hard and soft tissue contours
- Opposing dentition
- Proposed implant site
- Position of implant
- Planning of the final restoration
The specific objectives of preprosthetic imaging are:
1) Identify disease
2) Determine bone quality
3) Determine bone density
4) Identify critical structures at the proposed implant regions
5) Determine the optimum position of the implant placement relative to the occlusal loads
2) Radiographic assessment may include:
a) Periapical radiograph
Periapical radiographs are valuable for disclosing any periapical pathology and establishing interdental bone levels. It also provides an idea of the available bone height beyond the apex, the mesio distal dimensions of the roots and the space available between the adjacent roots. They also indicate the mesio distal orientation of the roots. (Iacono V.J. 2000)
b) Orthopantomograph (OPG)/ Digital Panoramic Tomograph (DPT) (Iacono V.J. 2000)
Panoramic radiographs provide an excellent overview of the jaws, confirming the information obtained from periapical radiographs, in particular the availability of bone beyond the apex.
The advantages include:
• The opposing landmarks are easily identified
• Vertical height of the bone can be easily assessed.
• The procedure is performed with convenience, ease and speed in most dental offices.
• Gross anatomy of the jaws and any related pathologic findings can be evaluated.
c) Computed Tomography (CT) scans (Iacono V.J. 2000)
These provide very useful three dimensional information regarding the spatial position of the root in relation to the ridge. The orientation of the root in the bucco-lingual plane enables the direction of the projected osteotomy to be determined accurately.
The cross sections provide valuable information regarding the integrity of the labial and lingual plates of bone. It also provides a method to measure the bone density in Hounsfield units.
A minimum of 4–5 mm of bone width at the alveolar crest, and at least 10 mm bone length from the alveolar crest to a safe distance above the mandibular canal are recommended.
Sufficient distance must also be available to the maxillary sinus and the floor of the nose. A satisfactory esthetic result in the esthetic zone requires the interproximal bone height to be 5 mm or less, when measured from the contact point of the adjacent tooth.
As the distance from the contact point to the interproximal bone increases, samewise retention of the interproximal papillae after implant placement diminishes. Patients must be made aware of potential esthetic shortcomings if implants are placed in compromised esthetic zones.
Bone quality and bone volume influence successful outcomes. Lower success rates are associated with cancellous than with cortical bone.
The volume density of bone matrix in cortical bone is about 80 to 90% and in cancellous bone about 20% to 25%.
Therefore, cortical bone contributes to greater implant-bone contact and implant fixation.
Once a patient is considered a candidate for immediate implant, a surgical guide should be used to assure proper implant placement.
A temporary appliance should be available for insertion after implant placement with an ovate pontic.