Endosseous blade implants 529

Fig. 11-213. This blade has been placed in the maxillary tuberosity in a buccopalatal direction. In some cases such an angle provides a greater mechanical advantage against lateral forces.

these regions would provide ample support (Fig. 11-210). Or perhaps there is bone only anterior to the sinus, with very little or none distally. In this situation, another type of blade can be placed into the tuberosity in a buccopalatal direction, providing the tuberosity is wide enough (Fig. 11-211) . There may indeed be a certain mechanical advantage in resisting lateral forces by setting one blade mesiodistally and the other buccopalatally.

Adequate amounts of bone may exist only in the maxillary tuberosity. If so, it must be determined whether or not the distance between the remaining cuspid and the tuberosity is too great to support a prosthesis. There is an even possibility of success if the distance is not exceptionally long (Fig. 11-212). Also, it might be more mechanically advantageous to set the blade into the tuberosity in a buccopalatal direction rather than in the usual mesiodistal direction (Fig. 11-213).

With the wide range of blade designs and possible insertion sites, it is rare when some type of blade cannot be used. One of the few remaining situations to be contraindicated for an endosseous implant intervention is one in which there is little or no bone menial or distal to a low-flaring sinus (Fig. 11-214).

THE FAILING BLADE

A correctly inserted blade should not fail. How-ever, occasionally one will. Failure of a blade type implant usually becomes evident from 2 to 4 weeks after its insertion, but a borderline case may take up to 6 months.

Fig. 11-214. There is not enough bone below, in front of, or behind the sinus for an endosseous implant of any kind.

Leading causes of failure

If a blade implant fails, it is usually a result of specific mistakes made by the operator. Most of these mistakes are made during implant insertion. The basic errors are listed here for emphasis; other causes of failure are extensively discussed in Chapter 13.

1. The groove may not be deep enough to al-low rapid, easy insertion of the implant so that the shoulder can be buried 1 to 2 mm. below the alveolar crest. If the groove is correct, no more than ten lightly tapped blows from the mallet should be required to properly bury the implant.

2. The groove may be too wide buccolingually. This means that the wedging action of the blade cannot be utilized. If the implant is not tight it should be removed. The mesiodistal length of the groove can be longer than the corresponding mesiodistal length of the blade because a tightly wedged blade will not slip or sink into the bone.

3. The shoulder may not have been adequately buried below the alveolar crest and wedged against the cortical plates of bone. This allows the epithelial tissue to invaginate and creep below the inferior border of the shoulder into the large openings in the body of the blade. Such invagination prevents the formation in that space of the desired fibrous tissue or bone.

Characteristics of a failing blade

Two main symptoms appear when a blade is failing: the patient complains of pain when chewing, and the implant becomes loose. At first the loosen-