| Using CBCT to determine the length and geometric pattern of the Greater Palatine Canal |
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| Friday, 03 December 2023 05:24 |
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In a useful study for purposes of nerve injection and avoiding complications, Drs Howard-Swirzinski, Edwards, Saini, and Norton assess the length and geometric patterns of the Greater Palatine Canal by Cone Beam Computed Tomography (CBCT). One thousand nerves in 500 subjects are used to establish average values in both the coronal and sagittal planes. As they point out, the maxillary nerve block is often used for palatal and periodontal surgery involving the gingiva of maxillary teeth, quadrant restorative dentistry involving the maxillary teeth or when there are multiple maxillary extractions, and as a diagnostic aid for defining pain etiology. This block is also utilized to establish hemostasis and anesthesia in endoscopic sinus surgery, septorhinoplasty, and posterior epistaxis. Unfortunately, there are many complications from a maxillary nerve block including intravascular injection, nasal bleeding, diplopia, neural injury, anesthetic failure (due to incorrect angulation of the needle, insufficient needle penetration, inability to locate the greater palatine foramen, or intravascular injection), and insufficient anesthesia. Many of these problems are related to the general problem of determining, without imaging, the anatomy of the nerve and the distance and direction it travels after it exits the skull through the foramen rotundum where it transverses high in the pterygopalatine fossa, reaches the greater palatine canal, and travels inferiorly from the pterygopalatine fossa that houses both the greater palatine and lesser palatine nerves that then enter the hard palate at their respective foramina. Results of this CBCT study In this study, both right and left canals were viewed. The average length of the greater palatine canal was found to be 29mm (±3mm). The range, however was large and varied from 22mm to 40 mm. When viewed coronally, it was found that the most common anatomic pattern was with the nerve traveling inferior-laterally for some distance then directly inferior for the remaining distance. However, the percentage of this pattern was only 43.3%. The next most frequent pathway was observed when the greater palatine canal traveled directly inferior from the pterygopalatine fossa. This pathway occurred in 39.5% of the canals. The third pathway observed in the coronal plane was when the greater palatine canal traveled inferior-lateral for a distance then changed direction to pass inferior-medial for the remainder of the canal. This occurred in 16% of the population. The path of the nerve in the sagittal view ran fairly consistently in an anterior-inferior direction 92.9% of the time.Since many of the above procedures are complex in nature and involve varying injection lengths to establish proper anesthesia, distances and nerve trajectory differ from patient to patient, and complications can be related to these discrepancies, it is suggested by the authors that it may not be unreasonable for the clinician to have procured in advance of complicated procedures CBCT images with proper radiology interpretation. Int J Dent. 2010; 2010: 292753. |
