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 »  Home  »  Endodontic Articles 2  »  Endodontic implications of the maxillary sinus: a review
Endodontic implications of the maxillary sinus: a review
Diagnostic evaluation of the maxillary sinus.

Radiographic examination of the maxillary sinus may be accomplished with a wide variety of exposures readily available in the dental surgery or radiology clinic (Peterson 1993). These include periapical, occlusal, panoramic and facial views, which may provide adequate information to either confirm or rule out pathology. On periapical radiographs, the borders of the maxillary sinus appear as a thin, delicate tenuous radiopaque line (actually a thin layer of cortical bone) (White & Pharoah 2000). In the absence of disease it appears continuous, but on close examination it can be seen to have small interruptions in its smoothness or density. In adults the sinuses are normally seen to extend from the distal aspect of the canine to the posterior wall of the maxilla above the tuberosity. The floors of the sinus and the nasal cavity are seen at approximately the same level at puberty. In older individuals the sinus floor may extend further into the alveolar process and may appear considerably below the level of the floor of the nasal cavity. Anteriorly each sinus is restricted by the canine fossa and is usually seen to sweep superiorly, crossing the level of the floor of the nasal cavity in the premolar or canine region. The roots of the molars usually lie in close apposition to the maxillary sinus. Root apices may project into the floor of the sinus, causing small elevations or prominences. The thin layer of bone covering the root is seen as a fusion of the lamina dura and the floor of the sinus (White & Pharoah 2000). A periapical radiograph may fail to show lamina dura covering the root apex in areas with defective bony covering.
Panoramic radiography provides an extensive overview of the sinus floor and its relationship with the tooth roots. It allows determination of the size of periapical lesions and cysts as well as radiodense foreign bodies. Matilla (1965) demonstrated that stereo-orthopantomography is a reliable mode of examination when distance between periapical lesions and the mucous membrane of the sinus, as well as interdistances of dental roots and the floor of the sinus have to be clarified. In orthopantomography the central radius goes almost straight toward the longitudinal axis of the molars resulting in minimal projection error ( Jung 1964). Furthermore, local swelling of the sinus membrane and opacities can be diagnozed.
Additional information can be obtained with the help of specialized skull views (White & Pharoah 2000). The occipito-mental or Water’s projection is optimal for visualization of the paranasal sinuses including the maxillary sinuses. Taken at varying angles (15 , 30 and 35 ) a comparison of internal anatomy, bony continuity and defects, as well as sinus pathology or foreign objects is possible (Gonty 1994). Other images that may be included are the submentovertex, posteroanterior and lateral skull views. The lateral skull view allows examination of all four pairs of paranasal sinuses, but with each member of a pair superimposed on the other.
Computerized tomography (CT) and magnetic resonance imageing (MRI) have become increasingly important for the evaluation of sinus disease and have virtually replaced conventional tomography (White & Pharoah 2000). These modalities provide multiple sections through the sinuses at different planes and therefore contribute to the final diagnosis and the determination of the extent of the disease. High-resolution axial and coronal CT and MRI examinations are the most revealing noninvasive techniques for the paranasal sinuses and adjacent structures and areas (Perez & Farman 1988, White & Pharoah 2000). Tomographic systems that have been developed specifically for oral surgical purposes facilitate three-dimensional evaluation of the sinus. Because coronal sections through dental fillings, crowns and metallic restorations can result in artefacts, axial sectioning is carried out. Considering the fact that the use of threedimensional methods, such as conventional tomography and computed tomography, is almost compulsory for presurgical diagnosis in implant surgery, the use of these diagnostic techniques also seems to be justified in conservative dentistry (Tachibana & Matsumoto 1990).
A-mode ultrasound is a safe, quick, noninvasive technique that has been introduced as a diagnostic screening tool for sinus pathology (Landman 1986). The ultrasonic waves are generated by a probe that contains a piezoelectric crystal stimulated by an alternating current oscillator (Landman 1986). When applied to portions of human anatomy, these waves are transmitted, reflected and scattered depending on the physical properties of the tissues. In normal sinus scans an initial reflected echo is seen at the probe/skin interface and the second echo at the bone/air interface. With mucosal thickening an echo will be obtained from the mucosa/air interface as well as the bone/mucosa interface. A back wall echo is obtained when fluid or a large polyp carries ultrasound to the posterior bony wall, which reflects an echo. The accuracy of ultrasound in detecting fluid has been well documented. Mann et al . (1977) compared A-scan results with sinus irrigations and found that 93% of cases with back wall echoes had fluid confirmed by irrigation. Revonta (1980) compared ultrasound with radiography in the detection of secretions in sinuses as confirmed by trephination or sinus puncture. In adults, ultrasound was 90% and radiography 82% accurate; in children ultrasound was 94% and radiography was 75% accurate in detecting fluid. Revonta & Suonpaa (1982) later showed that disappearance of ultrasonic signs of sinusitis correlated better with clinical resolution than did the disappearance of radiological signs. Ultrasound provides an excellent method of screening for sinus pathology at a cost about 25% that of conventional radiographs (Landman 1986) and may be helpful in following the resolution of acute suppurative sinusitis instead of repeated radiographs (Pinheiro et al . 1998). If the scan is abnormal, ultrasound is not a replacement for radiographic studies, which are necessary to differentiate fluid, polyps, thick mucosa or tumours (Landman 1986).
Diagnostic endoscopy (Kennedy et al . 1985, Kennedy 1985) allows direct optical evaluation of processes of unknown origin in the antral floor region. It is an optimal method especially for the assessment of foreign bodies (such as root filling materials and root tips) that have penetrated into the maxillary sinus. The following paths of access can be used: transoral access via the canine fossa, transalveolar access via an already existing connection between the oral cavity and the antrum (e.g. when the antrum is artificially exposed during apicectomy) and access via the inferior meatus of the nose.
The 30 and 70 endoscope has been used as an adjunct to endodontic surgery involving maxillary and mandibular molars (Held et al . 1996). This instrument has been found to allow visualization in previously inaccessible areas such as maxillary molar roots that are often positioned behind the distobuccal root of the maxillary first molar. In cases in which maxillary roots have been found to penetrate into the maxillary sinus, this instrument has aided the operator in identification and treatment of these diseased root apices following entry into the sinus (Held et al . 1996).