Simone F. M. Janner Characteristics and dimensions of the Marco D. Caversaccio Patrick Dubach Schneiderian membrane: a radiographic Pedram Sendi analysis using cone beam computed Daniel Buser Michael M. Bornstein tomography in patients referred for dental implant surgery in the posterior maxilla Authors’ affiliations: Key words: cone beam computed tomography, dental implants, mucosal thickness, posterior Simone F. M. Janner, Daniel Buser, Michael M. maxilla, Schneiderian membrane, sinus floor elevation, volume tomography Bornstein, Department of Oral Surgery and Stomatology, School of Dental Medicine, University of Bern, Bern, Switzerland Abstract Marco D. Caversaccio, Patrick Dubach,ClinicforEar, Objectives: To determine the dimensions of the Schneiderian membrane using limited cone beam Nose and Throat Diseases, Head and Neck Surgery, Bern University Hospital, University of Bern, Bern, computed tomography (CBCT) in individuals referred for dental implant surgery, and to determine Switzerland factors influencing the mucosal thickness. Pedram Sendi, Institute for Clinical Epidemiology & Material and methods: The study included 143 consecutive patients referred for dental implant Biostatistics, Basel University Hospital, Basel, Switzerland placement in the posterior maxilla. A total of 168 CBCT images were taken using a limited field of view of 4 Â 4cm,6 Â 6 cm, or 8 Â 8 cm. Reformatted coronal CBCT slices were analyzed with regard to the Corresponding author: thickness and characteristics of the Schneiderian membrane in nine standardized points of reference. PD Dr Michael M. Bornstein Department of Oral Surgery and Stomatology Factors such as age, gender, or status of the remaining dentition that could influence the dimensions School of Dental Medicine of the Schneiderian membrane were evaluated using univariate and multivariate linear regression University of Bern Freiburgstrasse 7 models. 3010 Bern Results: The thickness of the Schneiderian membrane exhibited a wide range, with a minimum value Switzerland of 0.16 mm and a maximum value of 34.61 mm. The highest mean values, ranging from 2.16 to Tel.: þ 41 31 632 25 45/66 Fax: þ 41 31 632 09 14 3.11 mm, were found for the mucosa located in the mid-sagittal regions of the maxillary sinus. The e-mail: [email protected] most frequent mucosal findings diagnosed were flat thickenings of the Schneiderian membrane (62 positive findings, 37%). For the multivariate linear regression model, only gender had a statistically significant influence on the mean overall and mid-sagittal thickness of the sinus mucosa. Conclusion: There is great interindividual variability in the thickness of the Schneiderian membrane. Gender seems to be the most important parameter influencing mucosal thickness in asymptomatic patients. Future studies are needed to assess the therapeutic and prognostic consequences of mucosal alterations in the maxillary sinus. Since the first description in 1998 (Mozzo et al. pekar et al. 2008), CBCT imaging is becoming 1998), cone beam computed tomography (CBCT) more popular (Ziegler et al. 2002; Bremke et al. has become a popular and important technique 2008). for diagnosis and treatment planning in dental The placement of endosseous dental implants medicine (Ziegler et al. 2002; Bremke et al. has become an established and very common 2008). It has already become an established surgical procedure in dentistry over the past three diagnostic tool for some indications, such as decades. In the posterior maxilla, reduced bone endodontics (Lofthag-Hansen et al. 2007; Patel height and low bone density are the most com- 2009), dental traumatology (Bornstein et al. mon limitations for implant placement (Jemt & 2009), apical surgery (Rigolone et al. 2003; Low Lekholm 1995). Sinus floor elevation (SFE) pro- et al. 2008; Bornstein et al. 2010), challenging cedures have been documented as predictable Date: Accepted 7 December 2010 periodontal bone defects (Misch et al. 2006; Kasaj surgical options to overcome this obstacle (Born- & Willershausen 2007), preoperative planning of stein et al. 2008). Radiographic findings that To cite this article: Janner SFM, Caversaccio MD, Dubach P, Sendi P, Buser D, furcation surgery (Walter et al. 2009), and dental sometimes may pose problems for the surgeon Bornstein MM. Characteristics and dimensions of the implant surgery (Guerrero et al. 2006). Even for planning an SFE procedure with or without Schneiderian membrane: a radiographic analysis using cone beam computed tomography in patients referred for dental visualization of the paranasal sinuses, for which simultaneous dental implant placement are the implant surgery in the posterior maxilla. conventional computed tomography (CT) is con- presence of bony septa (Naitoh et al. 2009), Clin. Oral Impl. Res. xx, 2011; 000–000. doi: 10.1111/j.1600-0501.2010.02140.x sidered the diagnostic method of choice (Fatter- thickening of the Schneiderian membrane, prior c 2011 John Wiley & Sons A/S 1 Janner et al Á Characteristics and dimensions of the Schneiderian membrane destructive maxillary sinus surgery (e.g., Cald- well-Luc operation), and manifest pathology such as acute rhinosinusitis or neoplastic processes (van den Bergh et al. 2000). There is only limited knowledge of the mean thickness and the dimen- sion of the Schneiderian membrane, and there are no guidelines for assessment and classifica- tion of mucosal findings in the maxillary sinus before SFE. The objective of the present study was to analyze the thickness and the anatomic charac- teristics of the Schneiderian membrane using limited CBCT in patients referred for dental implant placement in the posterior maxilla. Ad- ditionally, the influence of age, gender, smoking habits, periodontal and endodontic findings, and thetimeperiodelapsedsincethelasttooth Fig. 1. Location of the measurement regions in the sagittal cone beam computed tomography slices: anterior region (a; PM1, removal in the region of interest on the dimen- first premolar; PM2, second premolar), middle region (m; M1, first molar), and posterior region (p; M2, second molar; M3, third molar). Patient with a distal extension situation in the left posterior maxilla (a); patient with a single tooth gap in the left sions and morphology of the maxillary sinus posterior maxilla (b). mucosa were evaluated. Evaluation of the images selected anterior slice of the maxillary sinus The CBCT images were evaluated by an experi- floor corresponds to the region between the root Material and methods enced graduate student not directly involved in tips of the maxillary premolars in a dentate the treatment and follow-up of the patients (S. J.). Patient selection patient (Fig. 1). The following anatomic land- For knowledge and diagnostic skills of maxillary For the present study, all partially edentulous marks in the coronal CBCT slices were selected sinus pathologies, the graduate student was in- patients scheduled for limited CBCT imaging for for standardized measurements at each position structed by two ENT specialists. For calibration further radiographic evaluation of a future im- (Fig. 2a–c): and evaluation of intraexaminer reliability, 10 plant insertion site in the posterior maxilla (first randomly selected cases were measured twice (1) The onset of the zygomatic process for the premolar to second molar) were consecutively on two different days, resulting in a mean differ- lateral measurement ( ¼ alat). enrolled. All patients had been referred by their ence of 0.18 mm per image (range of 0–0.33 mm). (2) The deepest point of the sinus floor in the private dentist to the Department of Oral Surgery For the further study, each measurement was coronal CBCT slice for the mid-sagittal and Stomatology at the University of Bern for repeated, and the mean value was calculated. measurement ( ¼ amid). implant therapy. The CBCT image taking oc- When the difference between two values was (3) The ipsilateral bony floor of the nose for the curred in the period between January 1, 2008 and 0.2 mm, a third measurement was performed medial measurement ( ¼ amed). December 31, 2008. Patients with a history of (Bornstein et al. 2010). CBCT images were ana- previous dental implant placement or bone graft- lyzed using a Dell 380 Precision workstation ing in the posterior maxilla, reduced sinus visi- In cases where the sinus floor was located more (Dell SA, Geneva, Switzerland) and a 19 in. bility in the CBCT scan volume (less than the cranial than the onset of the zygomatic process, Eizo Flexscan monitor with a resolution of region of the anterior maxillary sinus border to or than the bony floor of the nose, the lateral (lat) 1280 Â 1024 pixels (Eizo Nanao AG, Wa¨dens- the second molar in the sagittal slices; floor of the – respectively, the medial (med) – measurements wil, Switzerland). The analyses and measure- nose and/or onset of the zygomatic process not were performed at the height of the onset of the ments described below were performed using a visible in the coronal slices), or with evident ipsilateral inferior nasal choncha. These three specialized computer software (i-Dixel Version artifacts due to movement during image taking measurements were repeated in 1.8, Morita). were excluded from the present study. the middle region (Fig. 1, see marking m), corre- Atthetimeoftheretrospectivedataanalysis, sponding to the apex of the first maxillary molar (mlat, mmid, mmed), and in the posterior region the implant therapy planning, and in most cases, Measurements to determine the thickness of the the implant surgery had already been performed. Schneiderian membrane (Fig. 1, see marking p), corresponding to the The CBCT slices were first reformatted to region between the apex of the second and the place the posterior maxillary segment (first third maxillary molars in dentate patients (plat, Imaging procedure premolar to second molar) of the alveolar pmid, pmed). In edentulous posterior sites, dis- The CBCT images were obtained with a 3D bone crest in a vertical position in the axial tances between premolar roots were set at 7 mm, Accuitomo XYZ Slice View Tomograph (Morita, slices, and the palate/floor of the nose in a and distances between molar roots at 8 mm. Kyoto, Japan) with a voxel size of 0.08 mm.