Evaluation of Implant Site

Evaluation of Implant Site 

Evaluation of the planned site begins with a thorough clinical examination. Visual inspection and palpation ‘will allow the detection of flabby excess tissue, narrow bony ridges, and sharp underlying ridges and undercuts
that may limit implant placement. Clinical inspection alone may not be adequate if the thick overlying soft tissue is dense, immobile, fibrous tissue (Fig. 14-29). Radiographic evaluation is also necessary, with the best initial film being a panoramic radiograph. Because variations in magnification from 5% to 35% may occur (Fig. 14-30), a small radiopaque reference object of known size placed at the area of the proposed implant placement
allows correction for any magnification. A ball bearing placed in wax on a denture base plate or within polyvinylsiloxane putty adapted to the ridge works well (Fig. 14-31). – Bone width not revealed on panoramic films can be evaluated in the anterior maxilla and mandible with a lateral cephalometric film. Width of the posterior mandible and maxilla are primarily determined by clinical examination. Specialized computerized tomography (CT) scans are useful to determine tbe location of the
inferior’alveolar canal and maxillary sinus and to evaluate ridge form (Fig. 14-32). These should be viewed as adjunctive tools. Their routine use is not required and has pot been demonstrated to improve outcome or
decrase mortdtty.

TABLE 14-1

Anatomic Limitations to Implant Placement

Strudure –
Buccal plate
Lingual plate
Maxillary sinus
Nasal cavity
Incisive canal
Interim plant distance
Inferior alveolar canal.
Mental nerve
Adjacent natural tooth
Minimum _equl..-
Distance aetween IIIIJIIMt
and Indk.tH Structure •
0.5 mm
” mm
, mm
Avoid midline maxilla
3 rnrn between outer edge
of implants
2 mm from superior aspect
of bony canal
5 mm from anterior or bony
, mm
0.5 mm

.implant success when compared ‘with thinner cortical bone and loose cancellous mairow (i.e., posterior maxil-  Ia). Bone quality has been classified as type I-rf (Fig. 14-33). In type ,I-III bone, implant success, regardless of length, is predictably high. However, in type IV bone,
short implants « 10 mm) have significantly higher failure rates. To maximize the chance for success, there must be adequatebone width to allow 1 mm of bone on the lingual aspect and 0.5 mm on the facial aspect of the implant. There should also be adequate space between the implants. The minimal distance between implants varies slightly among implant systems, but is generally accepted as 3’mm. This minimal space is necessary .to ensure bone  viability between the implants and to allow adequate oral
hygiene once the restorative dentistry is complete. Specific limitations as a result of anatomic variations between different areas of the jaws must also be considered. Implant length, diameter, proximity to adjacent
structures, and  time required to achieve integration v~ries in areas within the jaws. The anterior maxilla, posterior maxilla, anterior mandible, and posterior mandible each require special consideration when placing implants. Some common guidelines ‘for implant placement are summarized in Table 14-1. . After tooth loss, resorption of the ridge follows a patterlt
that results in crestal bone thinning and changes in angulation of the residual ridge (Fig. 14-34), which is most often a problem in ‘the anterior mandible and rnax- ‘lIa. The altered anatomy of the residual ridge may lead to intraoperative problems of achieving ideal implant angulation or lack of adequate bone along the labial aspect of the implant. This is a particular problem in the esthetic zone. Techniques for intraoperative management of these problems are discussed later, but the potential for such problems must be anticipated in the preoperative phase to allow-adequate management should they arise

The anterior maxilla must be evaluated for proximity , of the nasal cavity. A minimumof 1 mm of bone should be left between the apical end of the implant and the nasal cavity. The incisive foramen may be iocated near
the residual ridg  as a result of resorption ‘of anterior maxillary bone. This is especially true in patients in whom the edentulous maxilla has been allowed to function against natural mandibular anterior dentition. Anterior
maxillary implants should be located slightly off midline on either side of the incisive foramen. Implant placement in the posterior maxilla poses two
specific concerns: First, ·’as previously discussed, the quality of the hone in the maxilla, particularly the posterior maxilla, is poorer than mandibular bone. Larger marrow spaces and thinner, less dense cortical bone that affecttreatment planning exist, because increased time must be allowed for integration of implants. Generally a minimum of 6 months fs necessary for adequate integration of implants placed in the maxilla (Table 14-2):The second concern is that the maxillary sinus is in close proximity to the edentulous ridge in the posterior , maxilla. Frequently as’ a result of resorption of bone and increased pneumatization of the sinus, only a few millimeters of bone are found between the ..ridge and the’ sinus (Fig. 14-35). In treatment planning of implants in the posterior maxilla, the surgeon should plan to leave 1  mm of bone between the floor of the sinus and the
implant. This allows the implant to be anchored apically into the cortical bone of the sinus floor. Adequate bone height for implant stability can usually be found in the area between the nasal cavity and maxillary sinus (Fig. 14-36). If inadequate bone exists fer implant placement and support, bony augmentation through the sinus may be performed as discussed in the section on advanced surgical techniques. The posterior mandible poses some limitations on implant- placement. The inferior alveolar nerve 11t

TABLE 14-2

Minimum Integration Times

Minimum Integration
3 months
4 months
6 months
6 months
6 to 9 months
Anterior mandible
Posterior mandible
Anterior maxilla
Posterior maxilla
Into bone graft

of -implant length must allow for a 2-mm margin from the apical end of the implant to the superior aspect of the inferior alveolar canal (Fig. 14-37), which is an inviolable guideline to avoid damaging the inferior alveolar nerve and causing numbness of the lower lip. If inadequate length is present for even the shortest available implant, nerve repositioning, grafting, Of a. conventional nonimplant- borne prosthesis can be considered. These procedures are discussed further in the section on advanced surgical techniques. Implants placed in the posterior mandible are usually shorter, do not engage cortical bone inferiorly, and must support increased blomechanical occlusal force once loaded. As a result, slightly increased time for integration may be beneficial. Additionally if short implants (8 to 10 mm)are used, it is advisable to “over engineer,” and place more implants than usual, to withstand the occlusal load. The width of the residual ridge must also be carefully evaluated in the posterior mandible. Attachment of the mylohyoid’ muscle may maintain bony width along the superior aspect of the ridge, although a deep lingual depression forms immediately below (Fig. 14-38). This area should be palpated at the time of evaluation and
visualized at surgery. The anterior mandible is usually the most straightforward area for treatment planning, with respect to anatomic ,limitations. The mandible is usually wide enough and tall enoug  to provide adequate bone for implant placement. The bone quality is usually excellent, which makes this the area of the jaw that requires the least time for integration to occur. In the premolar area, care must be taken
to ensure that the implan t is placed antertor to the mental foramen. The inferior alveolar nerve usually courses ‘anterior to the mental foramen before turning posteriorly and superiorly ‘to exit the mental foramen. Because the nerve may be as much as:~ mm anterior to the foramen, the most posterior extent (If. the implant should be a minimum of 5
mrn anterior to the mental foramen (Fig. 14-39).








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