INTRODUCTION
There is a large body of evidence that supports the success of dental implants. The dental literature also contains many clinical procedures that were developed to facilitate implant placement. In addition, clinicians have contributed, via discussion or lecture, ideas and techniques to manage diverse situations. Many of these concepts that can make clinical practice easier are not universally known, and others have not been published.
DIAGNOSTIC PROCEDURES
Diagnostic Probing
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| Figure 1. The correct probing force is 25 gm. This force when applied with a probe causes blanching of the nail bed. |
Diagnostic probing should be done with a 25-gm force (the pressure it takes to blanch a nail bed with a probe) (Figure 1). Deeper than usual probing depths around an implant may not reflect peri-implantitis, since an implant that is placed subgingivally can result in a deep sulcus.
Contributing to this finding is the fact that connective fibers adhere to, but are not attached to, an implant as they are to teeth. Therefore, they do not impede probe tip penetration. Nevertheless, it is valuable to monitor probing depths after insertion of an implant, because subsequent changes in measurements may reflect disease progression. Relative attachment levels also can be recorded using a fixed reference point on the restoration (eg, measurement from crown margin to base of the pocket). Probing assessments do not adversely affect the epithelial attachment to an implant, because the junctional epithelium usually heals within 7 days. Furthermore, probing assessments can help avoid frequent x-rays to detect alterations in bone levels.
RADIOGRAPHS
Radiographs are the best way to assess support around implants and ought to be obtained every 24 to 36 months for routine monitoring. They should be taken more frequently if probing or attachment level alterations are detected, or if swelling or pain exists.
X-Ray Interpretations—Several radiographic findings of diagnostic and clinical interest are addressed. Clear depiction of implant threads on an x-ray reflects good radiographic angulation. When threads are clear on one side of the implant and not apparent on the other side, the radiographic angle is incorrect by 10º; if both sides are unclear, the film is undiagnostic. A perpendicular orientation of the radiographic beam is important when assessing the connection between an implant and an abutment. If the angulation of an x-ray is inaccurate by more than 10º, superior-inferiorly, implant parts may appear mated when they are separated. In this regard, bite-wings provide greater diagnostic accuracy than periapical films.
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Figure 2. Thick radiopaque crest reflects ridge resorption. |
Figure 3. Endodontic Rinn holder used with guide pin. |
Another radiographic finding with clinical implications are small, vertical, white lines in the sinus area. They represent full (underwood septa) or partial septa that are usually located adjacent to the medial wall of the antrum. These septa are a concern if an osteotome sinus floor elevation procedure is planned, because it is difficult to infracture the subantral floor under them.
Periapical Films of Direction Indicators—When guide pins are inserted into an osteotomy in an edentulous area, it is not possible for a patient to bite down on a regular bite tab or Rinn holder. A special Rinn holder employed for endodontic instruments can be used to take a radiograph with a direction indicator in place (Figure 3). Another method for radiographic assessments involves shortening guide pins or purchasing ones that are reduced in size (Gelb radiographic depth gauge), so that they could be used with a standard Rinn holder. If no radiographic aids are available, a regular direction indicator can be inserted into the osteotomy and a hemostat should be utilized to position the film. Place the hemostat horizontally across the inferior border of the film, and have the patient hold the hemostat during the x-ray exposure.
| Table. Distortion on Radiographs | ||||||||||||
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Accounting for Radiographic Distortion—Table lists mean linear radiographic errors with respect to different x-ray techniques when locating the mandibular canal. The numbers in the table represent mean errors, and they can be incorrect by even larger amounts. These inaccuracies need to be taken into account when creating an osteotomy in sensitive areas. For example, if a sinus elevation is planned and the periapical film indicates there is 5 mm of bone subantrally, do not drill to 4 mm, because if there is a 20% radiographic error, the twist drill can penetrate the sinus, and the ability to elevate the Schneiderian membrane will be compromised. Go a little shorter and verify the drill’s position with a periapical film. To avoid misinterpretation of linear measurements on radiographs, clinicians can use markers of known dimension when taking an x-ray (eg, 5 mm diameter ball bearing) or obtain a computed tomography (CT) scan for more accurate measurements.
Detecting the Inferior Alveolar Nerve
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Figure 4. Inferior alveolar nerve next to apex of a tooth. Usually it is several millimeters away from the apex of the mandibular first and second molars. |
Prior to developing an osteotomy over the inferior alveolar nerve, its position must be detected radiographically. A combination of periapical and panoramic film should provide a good estimate of the nerve canal’s apicocoronal position. On average, the distance from the apex of the mandibular first and second molars to the inferior alveolar nerve varies from 3.5 mm to 5.4 mm. However, the nerve’s position can fluctuate from being many millimeters away from the apex of a mandibular first molar to being adjacent to it (Figure 4). If the nerve’s position is not clear, then a CT scan should be ordered. Similarly, if the mandibular canal is 10 mm or less from alveolar crest, consider ordering a CT scan. A good general rule to follow dictates that if you are wondering if you need a CT scan, then order one. Without a clear depiction of the nerve’s position before initiating an osteotomy, clinicians are at risk of causing a parasthesia.