Principles of Attachment Selection for Implant Supported Overdentures
| Principles of Attachment Selection for Implant Supported Overdentures | Hamid Shafie, DDS* and George Obeid, DDS** |
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Distance Between Implants As a general rule, if a single bar is utilized, the ideal length would be 20 mm to |
22 mm to accommodate two clips or riders. This will place the centers of the implants 24 mm to 26 mm apart if standard diameter 4 mm implants are being used. (Fig. 11A, 11B) If two implants are too close together a short bar cannot provide enough retention and stability for the overdenture. (Fig. 11C) Factors influencing the distance between implants are listed in Table 6. If the implants are placed too far distally, not only will a long straight-line bar interfere with the tongue space and create problems in fabricating the prosthesis, but it will also be at risk of bending. (Figs. 11D, 11E) If the bar is positioned diagonally, it will not allow friction-free anterior hinge movement of the prosthesis. This condition creates excessive torsional loading on the supporting implants. (Fig. 11F) As a general rule, the bar should be perpendicular to the line that bisects the angle formed by the two posterior mandibular arch segments. (Fig. 11G) Vertical Relationship of Bar to the Alveolar Ridge A wide gap of 2 mm or more between the bottom of the bar and the soft tissue will allow easy passage of saliva and food particles as well as cleaning tools. (Fig. 12A) Hygiene maintenance in this situation is very easy. A small gap of 1 mm or less between the bottom of the bar and the soft tissue will cause plaque and calculus accumulation, |
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Volume 19.6 |