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Year : 2023  |  Volume : 22  |  Issue : 3  |  Page : 327-332  

Prevalence and pattern of proximity of maxillary posterior teeth to maxillary sinus with mucosal thickening: A cone beam computed tomography based retrospective study

Department of Oral Medicine and Radiology, Government Dental College, Kottayam, Kerala, India

Date of Submission25-Apr-2022
Date of Decision28-Jan-2023
Date of Acceptance07-Feb-2023
Date of Web Publication4-Jul-2023

Correspondence Address:
Admaja K Nair
Department of Oral Medicine and Radiology, Government Dental College, Kottayam, Kerala
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/aam.aam_74_22

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Context: Odontogenic sinusitis is a prevalent but frequently unrecognized condition, and periapical pathologies of maxillary posterior teeth are accused as one of the main causative factors. Aim: This study aimed to evaluate the relationship between the periapical status of maxillary posterior teeth and its proximity to the maxillary sinus floor in the occurrence of incidental sinus pathologies using cone-beam computed tomography (CBCT). Methodology: CBCT scans of 118 patients of age range 18–77 years were evaluated retrospectively to determine the relationship of maxillary posterior teeth to sinus floor in which vertical relationship was assessed using modified Kwak's classification and periapical status using CBCT periapical index. Statistical analysis was performed using SPSS statistics software. Results: Of all 227 sinuses examined, 56.8% showed pathological changes, with mucosal thickening being the most common. More than 50% (50.2%) of sinuses were associated with periapical lesions of at least one maxillary posterior tooth based on evidence of pathological mucosal thickening. The presence of pathologic mucosal thickening was also significantly related (P < 0.05) to the presence of periapical pathologies. There was a significant association between tooth position and pathological sinus mucosal thickening, especially with second molars, first molars, and second premolars, respectively (P < 0.05). Second molar involvement was the most significant (P < 0.05). Conclusion: The present study established a positive association between periapical disease status of maxillary posteriors and maxillary sinus mucosal thickening. Maxillary second premolar and first and second molars pathologies can significantly affect the maxillary sinus compared to other maxillary posterior tooth. CBCT proved to be an efficient imaging modality in detecting these changes.
Contexte: La sinusite odontogène est une affection fréquente mais souvent méconnue, et les pathologies périapicales des dents postérieures maxillaires sont accusés comme l'un des principaux facteurs causals. Objectif: Cette étude visait à évaluer la relation entre le statut périapical du maxillaire dents postérieures et sa proximité avec le plancher du sinus maxillaire dans la survenue de pathologies sinusales accidentelles à l'aide du calcul par faisceau conique tomographie (CBCT). Méthodologie: Les scans CBCT de 118 patients âgés de 18 à 77 ans ont été évalués rétrospectivement pour déterminer la relation entre les dents postérieures maxillaires et le plancher sinusal dans laquelle la relation verticale a été évaluée à l'aide de la classification de Kwak modifiée et état périapical à l'aide de l'index périapical CBCT. L'analyse statistique a été réalisée à l'aide du logiciel de statistiques SPSS. Résultats: Sur les 227 sinus examinés, 56.8 % présentaient des modifications pathologiques, l'épaississement de la muqueuse étant le plus fréquent. Plus de 50 % (50.2 %) des sinus étaient associée à des lésions périapicales d'au moins une dent postérieure maxillaire sur la base de preuves d'un épaississement pathologique de la muqueuse. La presence d'épaississement muqueux pathologique était également significativement lié (P < 0.05) à la présence de pathologies périapicales. Il y avait un important association entre la position des dents et l'épaississement pathologique de la muqueuse des sinus, en particulier avec les deuxièmes molaires, les premières molaires et les deuxièmes prémolaires, respectivement (P < 0.05). L'atteinte de la deuxième molaire était la plus importante (P < 0.05). Conclusion: La présente étude a établi un bilan positif association entre l'état de la maladie périapicale des postérieurs maxillaires et l'épaississement de la muqueuse du sinus maxillaire. Deuxième prémolaire maxillaire et les pathologies des premières et deuxièmes molaires peuvent affecter de manière significative le sinus maxillaire par rapport aux autres dents postérieures maxillaires. Le CBCT s'est avéré être une modalité d'imagerie efficace pour détecter ces changements.
Mots-clés: Tomodensitométrie à faisceau conique, épaississement de la muqueuse du sinus maxillaire, sinusite odontogène, pathologie périapicale

Keywords: Cone-beam computed tomography, maxillary sinus mucosal thickening, odontogenic sinusitis, periapical pathology

How to cite this article:
Nair AK, Jose M, Sreela L S, Prasad TS, Mathew P. Prevalence and pattern of proximity of maxillary posterior teeth to maxillary sinus with mucosal thickening: A cone beam computed tomography based retrospective study. Ann Afr Med 2023;22:327-32

How to cite this URL:
Nair AK, Jose M, Sreela L S, Prasad TS, Mathew P. Prevalence and pattern of proximity of maxillary posterior teeth to maxillary sinus with mucosal thickening: A cone beam computed tomography based retrospective study. Ann Afr Med [serial online] 2023 [cited 2023 Sep 26];22:327-32. Available from:

   Introduction Top

Orofacial pain involving the maxillary sinus often causes a diagnostic dilemma for the clinician. The maxillary sinus located in the midface, has proximity to the alveolar process and can get incited by pathologies or therapeutic procedures or involving maxillary posterior teeth such as endodontic treatment, tooth extraction, implant procedures.[1] This connection may result in the spread of periodontal or periapical infections of maxillary molars and premolars into the sinus, causing sinusitis.[2] Asymptomatic sinus pathologies such as mucosal thickening, mucosal polyps, and retention cysts are very common in maxillary sinus which are detected on maxillofacial imaging done for purposes such as orthodontic treatment or implant procedures, of which flat mucosal thickening is most common one.[3] Mucosal thickening is the most frequently encountered pathology, with significant variations in prevalence among different reports ranging from 21.25%[4] to 66%.[3] Moreover, mucosal thickening is a recognized manifestation of otherwise asymptomatic maxillary sinusitis.[4]

Odontogenic sinusitis describes the presence of sinonasal disease where radiographic, microbiologic, and or clinical evidence indicates it is of a dental origin, and this condition is well described in the literature with a prevalence rate of 10%–40%.[5],[6] Approximately 10% to 12% of all maxillary sinusitis cases are caused by endodontic infection, aided by the proximity of the roots of the maxillary posterior teeth to the maxillary sinus cavities, mostly involving premolars and molars.[3],[5] This condition is predominantly unilateral, and is not responsive to conventional treatment modalities of chronic sinusitis without the removal of dental foci. Cone-beam computed tomography (CBCT) is the superior diagnostic aid for maxillary tooth as well as sinus pathologies compared to two-dimensional (2D) imaging modalities like panoramic imaging and is more accessible to oral diagnosticians compared to computed tomography.[7] This also delineates the exact vertical relationship between tooth and the maxillary sinus floor. Hence, we aimed to describe the prevalence and pattern and evaluate the association between the periapical status of maxillary posterior teeth and its proximity to the maxillary sinus floor in the occurrence of incidental mucosal thickening in maxillary sinuses among patients who presented for maxillofacial diagnostic purposes using maxillofacial CBCT.

   Methodology Top

This study was performed retrospectively on the CBCT data obtained from patients who were referred to the Department of Oral Medicine and Radiology, Government Dental College Kottayam, with different indications other than maxillary sinus pathologies during the period from June 2016 to November 2020. The Institutional Ethics Committee Clearance (IEC/M/22/2021/DCK) was obtained before starting the study.

Sample size calculation

Based on the reported prevalence rate of mucosal thickening[8] in patients with and without periapical changes, the sample size in each group was calculated using the formula:

n = (Zα + Zβ)2 pq2/d2 = 90

Inclusion criteria

  • Patients above the age of 18 years.

Exclusion criteria

  • Patients showing the following CBCT findings were not included:

  • Patients under 18 years old
  • Patients referred for radiographic evaluation of maxillary sinus pathologies/surgery
  • Patients with the edentulous maxillary molar region.

The selected CBCT images (obtained from the Planmeca ProMax 3D Mid CBCT unit (Planmeca Oy, Helsinki, Finland) were evaluated by two qualified oral radiologists who were not having any known previous exposure to the patient and in case of any disagreement in the interpretation of images, a consensus was reached after discussion between the two observers.

Evaluation of the anatomic relationship between the sinus floor and associated teeth

The vertical relationship between the inferior wall of the maxillary sinus and the maxillary premolars and molars was assessed using a modification of Kwak's classification.[9],[10] These vertical relationships were classified into five types based on the CBCT cross-sectional images [Figure 1]:
Figure 1: Vertical relationships between root and floor of maxillary sinus as seen in cone-beam computed tomography coronal section images. (a) Type I, (b) Type II, (c) Type III, (d) Type IV, (e) Type V

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Type I: Buccal and palatal root apices were not in contact with the inferior wall of the maxillary sinus.

Type II: Buccal and palatal root apices were in contact with the cortical borders of the inferior wall of the maxillary sinus.

Type III: Buccal root apices were projecting into the sinus cavity over the inferior wall of the maxillary sinus.

Type IV: Palatal root apices were projecting into the sinus cavity over the inferior wall of the maxillary sinus.

Type V: Buccal and palatal root apices were projecting into the sinus cavity over the inferior wall of the maxillary sinus.

For one-rooted teeth, the classification of the vertical relationship was used as follows:

  • Type I: The inferior wall of the maxillary sinus floor was located above the root apex
  • Type II: The root apex touches the inferior wall of the maxillary sinus
  • Type III: An apical protrusion of the root apex was observed over the inferior wall of the maxillary sinus.

Evaluation of periapical status

A periapical lesion was considered present when the lamina dura was invisible, and there was a periapical radiolucency around the root apex, indicating bone destruction. Apical periodontitis was assessed using the CBCT periapical index:[11]

0 Normal periapical structures

1 Periapical radiolucency 0.5–1 mm

2 Periapical radiolucency 1–2 mm

3 Periapical radiolucency 2–4 mm and

4 Periapical radiolucency 4–8 mm

5 Periapical radiolucency >8 mm.

Score (n) + E Expansion of cortical bone

Score (n) + D Destruction of periapical cortical bone

If the tooth had more than one periapical lesion that is associated with roots, the lesion with the most severe pathology was recorded.

Measurement of maxillary mucosal thickening

The criteria by Lu et al.[12] was used to assess mucosal thickening severity, in which the thickening of the mucosa beyond 2 mm will be considered pathological, identified from the sagittal view in CBCT images. Maxillary sinuses were divided into five classes according to the maximal mucosal thickening present in the exposed maxillary sinus: 1, normal (no mucosal thickening); 2, 0–2 mm; 3, 2–4 mm (mild maxillary sinus mucosal thickening); 4, 4 to 10 mm (moderate); and 5, >10 mm (severe) [Figure 2].
Figure 2: Mucosal thickening in maxillary sinus as seen in cone-beam computed tomography sagittal section images. (a) Normal (no mucosal thickening), (b) 0 to 2 mm, (c) 2 to 4 mm (mild maxillary sinus mucosal thickening), (d) 4 to 10 mm (moderate), and (e) >10 mm (severe)

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Statistical analysis was performed using SPSS Statistics software (version 22.0; IBM Corp, Armonk, NY, USA). Data were analyzed descriptively (frequencies, means, and standard deviations), and the associations among periapical lesions, and the proximity of the teeth to the floor of the maxillary sinus was assessed using the Chi-square test, and the results are presented as odds ratio and 95% confidence intervals.

   Results Top

CBCT scans of the total of 118 patients were included in the study. The patients were 18–77 years of age, with a mean age of 30.69 years. One hundred and eighteen right maxillary sinuses and 109 left maxillary sinuses (for 9 cases, only left side maxilla was considered for the study as right side posterior teeth were missing) were evaluated for the presence of pathologies. The most common indications for CBCT scans of the selected cases include mandibular fractures, evaluation of impacted or supernumerary tooth, temporomandibular joint pathologies, or implant placement. Mucosal thickening and sinus polyps were the pathologies encountered [Table 1]. Mucosal thickening was the most commonly encountered pathology in both the right and left maxillary sinuses. Mucosal thickening was observed in 54.1% of the total maxillary sinus scans analyzed. In terms of prevalence, the right side sinus was more affected than the left, with 66 (55.9%) and 58 (49.2%) cases, respectively. Out of the 124 cases which showed mucosal thickening, 58 (46.7%) belonged to Class 2, which was not pathological. A total of 65 sinuses showed the presence of pathological mucosal thickening, with 28.6% as the prevalence rate [Table 1]. Gender or age group was not found to have any association with the occurrence of pathological mucosal thickening in the sinus (P > 0.05).
Table 1: Base line characteristics of study sample

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Type I relation was the most common in the first premolar, whereas in all the other teeth, Type II was the most commonly encountered vertical relationship with the maxillary sinus. Type IV and V relations were seen only in molars and the second molar was found in the closest vicinity to the sinus floor [Table 2]. The distribution of periapical index scores in the study sample is described in [Table 3].
Table 2: Vertical relationship between maxillary posterior teeth and sinus floor

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Table 3: Distribution of periapical index scores

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There was a significant association between the presence of periapical pathology in any one maxillary posterior tooth and pathological mucosal thickening in the sinus (P < 0.05), with the risk of mucosal thickening four times more in sinuses associated with periapically involved maxillary posterior tooth [Table 4]. Second molars, first molars, and second premolars showed significant association (P < 0.05), with second molar involvement causing the most significant change [Table 5].
Table 4: Severity of mucosal thickening in patients with maxillary posterior tooth periapical pathologies

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Table 5: Association between periapical pathology of tooth type and sinus membrane thickening

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   Discussion Top

To the best of our knowledge, this study is the first to report that the prevalence of asymptomatic maxillary sinus membrane thickening in the Central Kerala population is 28.6% based on CBCT evaluation. Previous studies from other Indian states have reported a similar prevalence rate.[13],[14] Yet, there were critical differences in the prevalence rate of mucosal thickening, with reports having extremely low rates of around 12%[15] and a few with higher prevalence of around 48.5%–66%.[3],[16] In general, studies based on 2D imaging modalities reported lower prevalence compared to 3D modalities, which is explainable by the improved accuracy of the latter in detecting mucosal changes. Moreover, there is no common consensus regarding the diagnosis of pathologic mucosal thickening. Along with most authors, we also considered a thickening of more than 2 mm as pathological. In agreement with observations from Sakir and Ercalik Yalcinkaya,[8] we could not establish any evidence of the relationship between gender or age and the occurrence of pathological mucosal thickening. Many studies[3],[17],[18] have found that membrane thickening was associated with factors such as age and gender. A higher prevalence rate of sinus membrane thickening was found in males and older age groups (>50 years old) which is in contrast to our findings.

In 1974, Seldon described the term Endo-antral syndrome.[19] This refers to the spread of pulpal disease from the periapical region into the maxillary sinus. Previous reports have confirmed that periapical lesions in the posterior maxillary teeth were likely associated with pathological sinus mucosal thickening due to increased proximity roots to the sinus.[8],[20] The present study established a positive association between periapical disease status of maxillary posteriors and maxillary sinus mucosal thickening with evidence of 50.2% of the sinuses associated with teeth with periapical pathologies. Root proximity to the sinus floor shows significant variation among population, and in our study, the maxillary second molar was found close to the sinus compared to other posterior teeth, compatible with many other reports.[21],[22] However, several authors have reported as the maxillary first molar is in the closest proximity to the sinus,[23] which implies that ethnic as well as variations in measurement methods may influence the same. As the tooth apices closely approximated the sinus floor, periapical infections of the second molar were found to be most influential in causing sinus mucosal thickening with around five times more chance than normal counterparts. This study suggests that CBCT might be an ideal imaging modality in detecting teeth-sinus vertical relation as well as periapical pathologies.

However, this study had the limitations of a retrospective study design. In the future, studies involving clinical examinations of the patients and evaluations of pulpal disease activity, along with concurrent evaluation of sinus conditions, are needed for analyzing odontogenic sinusitis in detail.

   Conclusion Top

The current study demonstrated that odontogenic sinusitis is a prevalent condition in our population. The risk of overestimating the true significance of imaging findings can be reduced by taking incidental findings into account in the context of each patient's clinical indications and symptoms. The study recommends the wide availability of CBCT to increase the clinicians' recognition and ability to evaluate maxillary sinus more comprehensively.

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Conflicts of interest

There are no conflicts of interest.

   References Top

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  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]


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