Axial Triangle of the Maxillary Sinus, and its Surgical Implication With the Position of Maxillary Sinus Septa During Sinus Floor Elevation: A CBCT Analysis
The aim of this study was to measure the convexity of the lateral wall of the maxillary (Mx) sinus and identify the locational distribution of antral septa in relation to the zygomaticomaxillary buttress (ZMB), in order to suggest another anatomical consideration and surgical modification of sinus floor elevation procedures. This study was designed as a cross-sectional study, and a total of 134 patients and 161 sinuses containing edentulous alveolar ridges were analyzed. The angle between the anterior and lateral walls of the Mx sinus (lateral sinus angle [LSA]), and the angle between the midpalatal line and the anterior sinus wall (anterior sinus angle [ASA]) were measured. Mean LSAs and ASAs were 105.9° ± 9.86° and 58.4° ± 6.43°, respectively. No significant difference between left and right sides was found (LSA, P = .420; right = 105.5° ± 9.27°; left = 105.5° ± 9.27° and ASA, P = .564; right = 57.9° ± 6.80°; left = 58.8° ± 6.02°). The prevalence of septa was 37.3%, and it was most frequently noted in the second molar region (32.8%), followed by the first molar (20.9%), retromolar (16.4%), and second premolar regions (14.9%). Septa were most frequently located posterior to the ZMB (49.2%), while ZMB was mostly located in the first molar region (66.4%). Narrow LSAs may complicate the surgical approach to the posterior maxilla, especially when sinus elevation should be used in the second molar region. Considering the occasional presence of antral septa, membrane elevation may be complicated when a septum is encountered during the procedure. These results suggest that 3-dimensional examination of the convexity of the Mx sinus should be performed preoperatively to choose proper surgical techniques and minimize surgical complications.
The lateral wall for sinus floor elevation can be divided into 2 surfaces, bordered by the zygomaticomaxillary buttress. The anterior part is easily accessible, whereas the posterior part can occasionally present limited access. The easily accessible anterior part is called the “bright side,” and the less visible posterior part is called the “dark side.” It is easy to make a window on the bright side, which can be extended to the posterior part, if necessary.
The Frankfort horizontal plane was set to make axial images of the maxilla (a): the angle between the anterior and lateral sinus walls (lateral sinus angle [LSA]) is marked “a”; the angle between the anterior sinus wall and the midpalatal line (anterior sinus angle [ASA]) is marked “b”; a bony septum, marked “c”. Measurement of the position of zygomaticomaxillary buttress. (b) Medical image processing software was used to create a 3-dimensionally rendered image of the maxilla, Position of the zygomaticomaxillary buttress (black arrow) was then estimated.
Figure 3. Distribution of the lateral sinus angle (angle between the anterior and lateral walls of the maxillary sinus). Figure 4. Distribution of anterior sinus angle (angle between the anterior sinus wall and midpalatal line). Figure 5. Position and prevalence of maxillary sinus septa. ASA indicates anterior sinus angle; LSA, lateral sinus angle; P1, the first premolar; P2, the second premolar; M1, the first molar; and M2, the second molar.
Figure 6. A sinus septum bisecting the cavity into 2 compartments was observed, and the placement of 2 dental implants with sinus floor elevation was planned. Two separate lateral windows were initially designed for the graft. Creating a posterior window sinus floor elevation beyond zygomaticomaxillary buttress is predicted to be clinically difficult. Figure 7. A schematic drawing of the septum resection to facilitate the grafting procedure. (a) After revealing the septum, a small gutter can be formed to securely place an osteotome. (b) The osteotome can be gently tapped on the back. The concave side of the osteotome should be inferiorly directed.
Clinical application of the technique. (a) Initially, 2 separate windows were prepared. (b) The septum was osteotomized following the technique explained in Figure 7. (c and d) After resecting the septum, a single cavity was prepared for the graft, and the cavity was filled with demineralized bovine bone.
Postoperative cone beam computerized tomography scans of the patient. Healing was uneventful.
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