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2.2.2 Implant selection
Implant selection Implant selection Implant selection Implant selection Implant selection Implant selection Implant selection
 

To select an appropriate implant, it is important to obtain the patient’s medical history, examine them, and analyse their X-ray images. Selecting an implant, follow the rules specified below:

Assessing the optimal number of implants

Selecting an implant during preoperative planning, it is essential that you should determine their number, length and diameter.

If only one tooth is missing, it is clear that only one implant is required. If several teeth are missing, the optimal solution is to embed as many implants as there are missing teeth (if three teeth are missing, three implants should be inserted).

If the proposed solution is unfeasible, implants can be used for distal support of an implant-supported prosthesis 2.2.2-3. Remember that the greater is the distance between two adjacent implants, the bigger the implants should be.

If the previously mentioned solutions cannot be used, it may be necessary to use adjacent teeth to hold prostheses in place. The longevity of such constructions depends greatly on the number of supports and the fixation quality of prostheses.

If you register even a minute deviation from the standard procedure, you must inform the patient. The patient is entitled to make an informed choice! Later it will save you the headache of unnecessary explanations.
 
2.2.2-1 A classical situation: the absence of two incisors is compensated for by the insertion of two implants.
 
2.2.2-2 A free-end edentulous space. Three implants are inserted to support a denture which will not be connected with natural teeth.
 

This will provoke implant mobility and will result in connective tissue downgrowth on the surface of the endosseous implant or will eventually cause implant fracture.

Remember that even though it is not recommended to incorporate teeth in prostheses, it is still possible in cases when there are no other solutions 2.2.2-4. If you have to use adjacent teeth to hold prostheses in place, observe the following rules:

  • A prosthesis must have three or more supports (two implants and a tooth, two teeth and an implant). A prosthesis which is attached to one tooth and one implant cannot be considered a good solution. In a few years, due to natural micro-mobility of the natural tooth, the prosthesis will feel loose and will be held in place by the implant only.
  • Abutment teeth are subject to root canal therapy, which reduces periodontal blood circulation and eventually decreases tooth mobility.
  • Transocclusal screws are used to retain implant crowns.
For aesthetic reasons, transocclusal screws are often covered by composite filling material. Remember that a screw and a filling must be separated by a gasket to prevent cement from seeping into slots.

Deciding on implant size, remember that there are image distortions. It is easier to choose an implant if you use a transparency with implant silhouettes pictured in it.

4.2.2-3 A prosthetic denture consisting of three crowns attached to two implants.
 
4.2.2-4 A monolithic construction supported by non-removable implants and natural teeth.
 
4.2.2-5 If you plan to incorporate implants with natural teeth, the denture must have three or four supports.
 

As a rule, implant silhouettes are represented at a scale of 1:1 for focal images and at a scale of 1:25 (or 1:3) for orthopantomograms 2.2.2-6. Transparencies are easy to use. Overlay the implant silhouette (corresponding to the scale) onto the X-ray image to select the most appropriate implant.

Selecting an implant during the preoperative planning process, remember that wider implants resist vertical pressure more successfully, while longer implants are more resistant to lateral pressure. It is recommended to insert a great number of smaller implants rather than a small number of larger implants.

It is essential (especially during the first years of your clinical practice) that you should establish 2 mm security zones around implants to protect sinuses, nerves, and teeth. Remember that due to their geometry, drills cut holes which are 0.5 – 1.5 mm deeper, depending on their cutting diameter and point angle 2.2.2-7.

The loss of natural teeth results in the alveolar bone resorption accompanied by changes in bone architecture and reduced resistance to chewing pressure. There are sites (canine teeth, for example) that constantly experience excessive occlusal forces. It is highly recommended that the longest and the largest implants should be inserted in the sites. If for some reason it is impossible, an additional implant should be installed in the first premolar site. Occlusal correction is required to ensure implant longevity and effectiveness. Canine-protected occlusion should be avoided. It is recommended that you should promote multiple tooth contact in lateral gliding movements.

4.2.2-6Overlay a transparency with implant silhouettes at a scale of 1:1.25 onto an X-ray image to select an implant of appropriate length.
 
4.2.2-7Due to their geometry, drills cut holes which are 0.8 – 1.4 mm deeper than an implant can reach. In order to prevent complications, bear in mind the following distortions: drill Ø2.8 h1 = 0.8 mm, drill Ø 3.5 h2=1.0 mm, drill Ø 5.0 – 1.44 mm.
 

Sinus lift complications 4.7 Errors and Complications   
Sinus lift 2.8.3 Surgical Procedure   
Preoperative examination 2.2 Surgical Procedure   
Splitting an alveolar ridge 2.8.5 Surgical Procedure   
Problems of the prosthetic procedure 4.9 Errors and Complications   
Occlusal screw-retained crowns 3.4 Prosthetic procedure   
Other types of implant-supported prosthetic constructions 3.5 Prosthetic procedure   
Correction of dental-alveolar lengthening 2.8.1 Surgical Procedure   
Preoperative preparation 2.2.3 Surgical Procedure   
Specifics of making implant-supported single crowns 3.3 Prosthetic procedure