Evaluating the Relation of Maxillary Posterior Roots to the Floor of Maxillary Sinus in Southern Iraqi Patients, a CBCT Study

Background: This present study aims to evaluate the type of relationship between roots of maxillary posterior teeth and maxillary sinus. Methods: Cone beam computed tomography images for 148 patients were evaluated (62 males Vs 86 females). A total of 1052 teeth were examined (518 maxillary premolars and 534 maxillary molars). The relation between roots tips and maxillary sinus oor were classied into four types: type 0, type 1, type 2 and type 3, vertical linear distance was measured and distribution of type of relationship in different age groups were evaluated. Results: Most of single rooted maxillary premolars showed (type 0) relationship with maxillary sinus oor (98.1%) for maxillary rst premolars and (69.5%) for maxillary second premolars. In buccal roots of double rooted maxillary rst premolars, (type 0) represented (98.7%). While for maxillary second premolars occurred in (50%). Type 0 still the most common appearing type in palatal roots of maxillary rst premolars (92%) and in maxillary second premolars it appeared in (45.8%). The Conclusions: Most maxillary roots of maxillary second molars were in contact with the sinus oor (type1).


Introduction
The maxillary sinus (MS) is the largest air sinus which is located in the body of the maxilla. It varies in shape, size and position in different individuals and also in different sides of the same individual. The dimensions of the MS can also be different according to the gender and ethnicity. The inferior wall of the MS is curved and extended between the adjacent roots in about half of the population. 1 The size of MS varies between patients with the oor of the sinus extending between adjacent teeth or between individual roots in about 50% percent of the population. 2 Dentists who conduct clinical procedures in the area of posterior maxilla should be aware to the amount of protrusion of teeth roots into the oor of the sinus. The percentage of teeth approaching or penetrating into the sinus varies to a large extent according to the examined sample and the community where these studies were performed 3 .

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The root tips of the maxillary molars (MM) in general are closer to the sinus oor than those of the premolars. An inverse relationship is found between the thickness of bone buccolingually and that of the bone lying superior to the apices of the teeth. 4 Conventional radiographic techniques have been used in the study of the relationship between maxillary posterior teeth and maxillary sinus oor (MSF). Most of these techniques have limitations that may affect this analysis. The limitation results from the fact that two-dimensional images prevents the correct interpretation of the periapical relation of roots apices to the MSF .The clinical introduction of cone beam computed tomography (CBCT) for use in the diagnosis and planning has contributed to improve treatment approaches .5 Studies that used computed tomography(CT) scan have shown to be even more accurate than cadaveric studies 1 .
When compared with medical CT, CBCT has lower radiation, higher resolution in shorter scanning time. CBCT can produce high-resolution 3D images of oral and maxillofacial region and help to evaluate the relationship between apices of the maxillary roots and MS clearly. 6 When the roots projects laterally or medially over the sinus, using panoramic images will lead to misinterpretation, and the root will appear to be in the sinus so ordering a CBCT should be considered for assessment of risk associated with oral surgery in maxillary posterior teeth area 7 .
Most abnormalities of the MS were found to be associated with at least one of the maxillary posterior tooth with a periapical lesion. . 8 Sinusitis may result from the spread of either a periapical or periodontal infection to the MS or from iatrogenic perforation of the sinus 9 Therefore, the assessment of the relationship between roots of posterior teeth and maxillary sinus oor( MSF) is crucial before planning of any dental treatment procedure in posterior maxilla to avoid procedural complications. 10 Few studies have evaluated relationship between maxillary posterior teeth and MS in Iraqi population 8 ' [11][12] with no study made for southern Iraqi patients, so the present study aims to analyze the vertical relationship and vertical linear measurements(VLM) between roots tips of maxillary posterior teeth and MS in a sample of population from Basrah city in south of Iraq.

Patients
This study was approved by Ethical Review Committee at College of Dentistry, university of Basrah. All methods were carried out in accordance with relevant guidelines and regulations. CBCT images for 148 patients (62 males Vs 86 females) were evaluated, these images have been requested for many clinical purposes including oral surgery, orthodontics, endodontics and implants in the time period from 15/6/2018 to 1/2/2020. The sample of population had an age range between 18-63 years (average age 32.1 years). This study was approved by Ethical Review Committee at College of Dentistry, university of Basrah. All methods were carried out in accordance with relevant guidelines and regulations. 1052 teeth were examined in this study including 518 maxillary premolars (262 maxillary rst premolar (MFP) Vs 256 maxillary second premolar (MSP)) and 534 maxillary molars (254 maxillary rst molar (MFM) Vs 280 maxillary second molar (MSM)).
The exclusion criteria were as follow: history of trauma/orthodontic treatment to the maxillary arch, pathology affecting size, shape and/or appearance of MS, history of surgical procedures in posterior maxilla, presence of radiographic sign/signs of periapical pathology around one or more of the apices of the included teeth, maxillary posterior teeth with developmental anomalies that could interfere with interpretation of CBCT image, presence of root canal lling, root resorption, fracture or open apex in any of the included teeth and images with artifacts related to technique that affect interpretation.

Radiographic technique
The CBCT images were obtained using a Gendex (GXDP -7000) CBCT machine (Germany) operating at 90 kV and 10 mA, and the scan time was 13 seconds. The image dimension used was 400.400.300 IJK, image size ( eld of view) was 80.0* 80.0 *60.0 mm, while image resolution was 0.20 *0.20 *0.20 mm. The minimum slice thickness was 0.5 mm with slice interval 1 mm. The detector resolution was 200µm. Scan's procedures were done according to the manufacturer's instructions protocol. All CBCT examinations were carried out by an oral radiologist with more than 12 years' experience with obligation to ALARA principle.

Evaluation of the images
The CBCT images were analyzed using an inbuilt software (GxPicture TM ) (Invivo5 dental viewer application, version 2.0.1) running in a 64-bit Windows 10 system. All the images were analyzed using Lenovo LCD screen (17 inch) with a resolution of (1920 × 1080) pixels in a dark room. Contrast and brightness of images was adjusted during examination using the software's image processing tools to get the optimal visualization condition. To determine the exact positions of roots apices and oor of maxillary antrum, the examiners were scrolling through the axial, coronal and sagittal views. The CBCT images were evaluated by a professional oral radiologist, a maxillofacial surgeon and an endodontist separately. The obtained data were compared, and the incompatible data were rechecked and reassessed by the examiners at the same time to obtain consensus in their radiographic ndings. A second reading was done after one month using approximately 20% of the images selected randomly to assess intraobserver reliability.
The included teeth were evaluated on axial, coronal and sagittal sections for the relation between roots apices and MSF, decision was reported according to coronal section, this relation was classi ed according to Jung and Cho classi cation 13 into four types as shown in gure 1: Linear measurements for the vertical distance between the roots' apices and the inferior wall of MS was obtained using linear measurement tool built in (Invivo5 dental viewer) software as seen on coronal and sagittal sections, when the measured distance was different between the two planes (coronal and sagittal), the shortest value was depended. The measurement was de ned positive when the root apex lies away from or below the inferior wall of MS ( g.3 a), while measurement was de ned negative when root apex protruded into or above the inferior wall of MS ( g.3 b).

Statistical analysis:
Statistics were recorded for the type of relation between maxillary posterior roots apices and inferior wall of maxillary sinus on both sides of maxilla, patient's gender and age. The sinus relation types among different age groups were assessed using Chi-squared t test. Intra-observer reliability was analyzed with Cohen's Kappa tests. The SPSS for Windows software (ver. 22.0) was used to conduct the statistical analysis tests.

Results
The kappa values for the intra-examiner agreements of each examiner were 0.91, while for inter-examiner agreement, the kappa values were 0.821 and 0.852 for the rst and second assessments, respectively. There was a good intra-examiner and inter-examiner agreement.
As seen in table1 and gure 4, the vast majority of MFP roots in case of single rooted teeth, their apices were classi ed to have (type 0) relationship with MSF (98.1%). While for MSP, type 0 still representing the most appearing type but in slightly less ratio (69.5%). In case of buccal roots of double rooted MFP, (type 0) represented (98.7%). While for MSP, type 0 accounted for only (50%). Type 0 still the most common appearing type in palatal roots of MFP (92%) and MSP with a ratio of (45.8%). Table 2 shows that for single rooted MSM, the most common appearing type of relationship was type 1 that appeared in 45.6% of the cases. For MBR in multirooted MM, type 0 was the most commonly seen type in MFM (41.4%) while for MSM type 1 was the dominant type (45.5%). In DBR, type 0 was also the most common type in MFM (39.8%), while type 1 was seen more in MSM (48.1%).
For PR, type 0 was the most common type in both rst and second molars (38.3% Vs 37.9%) ( gure 5).
In table 3 it was noticed that in double rooted MSM, type 0 and type 1 only occurred with equal distribution (50%Vs 50%). Table 4 showed that type 0 is also the most common appearing type in almost all age groups in maxillary rst and second premolars.
In table 5 we can notice that type 0 is appearing in a larger ratio in older age group (>45 years) in MFM and also in MSM but in a lesser extent. In double rooted MSM, BR were closest to the MSF than PR.

Discussion
The apices of the maxillary posterior teeth lie in close proximity to, or within, the sinus. So, both surgical and nonsurgical endodontic procedures in this area could lead to perforation of the inferior recess of a MS [4].
It is so important to evaluate the relationship between the roots of maxillary posterior teeth and MSF when planning any dental or surgical procedure to avoid related procedural complication [14].
Using CBCT could improve accuracy in diagnosing protruding roots into the sinus as was reported by Roque- The relationship between the root apices and the MSF could be interpreted differently between coronal and sagittal planes on CBCT, so a root may be seen to be protruded inside the sinus on one plane, but it is seen either in contact with or away from the sinus, so a root will be only be classi ed to be protruded into the sinus when it shows protrusion in all planes of CBCT images [16]. However, even though a root could be seen to be protruded into the sinus in only one plane, it should be classi ed as high-risk factor for evoking odontogenic sinus infection and/or sinus oor perforation during surgical procedures. Similarly, the mean distance between the root apex and the MSF was not similar when measured on coronal and sagittal planes. So, the distance between the root apex and the MSF should be measured on both coronal and sagittal CBCT planes and the shortest value would be selected as the nal measurement [16][17]. This fact was depended when making VLM in the present study.
In the present study, most of the MP roots were observed to be separated from the oor of MS (type 0) as seen in (table 1) According to the measurements recorded in the present study, it looks logical to state that Type 0, when root apex was below the MSF, is relatively safe to perform dental procedure as nonsurgical endodontic treatment The results of the present study could help to conduct a research base for relation of maxillary posterior teeth to the MS with VLM between roots and MSF in southern Iraqi population that might be of clinical value for dentistry practitioners and dental surgeons.

Conclusions
Most of MP roots was seen to be separated from MS (type 0). The same nding but in less ratio was reported for MFM. Most of the MBR and DBR of MSM were in contact with the sinus oor (type1), while most of PR was separated from MS (type 0). The shortest VLM were reported in MBR of MSM.

Patents
None Declarations -Ethics approval and consent to participate: This study was approved by Ethical Review Committee at College of Dentistry, university of Basrah. All methods were carried out in accordance with relevant guidelines and regulations. Informed consent was obtained from all participants -Consent for publication Publisher has the permission of the Author to publish this work.
-Availability of data and materials All data related to this work could be obtained by asking the corresponding author (aqeel.lazim@uobasrah.edu.iq) -Competing interests: The authors declare no con icts of interest.         Figure 1 classi cation of vertical relationship of maxillary sinus oor and maxillary posterior teeth13 Type 0: In which the root is separated from (below) inferior wall of MS ( g.2 a). Type 1: In which the root is in contact inferior wall of MS ( g.2 b). Type 2: In which the root is projected laterally (tangential) to the inferior wall of MS without protrusion into the sinus ( g.2 c). Type 3: In which the root is protruded into the inferior wall of MS ( g 2 d).
Page 18/20 Frequency of type of relationship between roots apices of maxillary premolars and maxillary sinus oor Frequency of type of relationship between roots apices of single and multirooted maxillary molars and maxillary sinus oor