Evaluation of the relationship between the maxillary sinus floor and the root apices of the maxillary posterior teeth using cone-beam computed tomographic scanning.

BACKGROUND: The relationship between the maxillary sinus (MS) and the root apices of the posterior teeth is of clinical relevance in diagnosing and treatment planning in the posterior area of the maxilla. This study aimed to assess the relationship between the MS floor and the root apices of the posterior teeth using cone-beam computed tomography (CBCT) scanning.
MATERIALS AND METHODS: 325 CBCT scans of patients aged 20-70 years were analyzed. Patients were divided into three age groups: young group (20-44 years), middle age group (45-59 years), and elderly group (60-70). The distance from the MS floor and the root apices of posterior teeth was measured in each group. The relationship between the MS and the posterior roots was also recorded according to Kwak classification. The results were analyzed by IBM statistic SPSS.
RESULTS: Type II was most commonly seen in the first and second molars. For premolars, Type I was often observed. The shortest distance to the floor of MS was recorded for the mesiobuccal root of the second molar and the longest distance for the palatal root of the first and second molars. No statistical differences were found between age groups (P > 0.01).
CONCLUSION: The anatomical relationship between the MS and the root apices of the posterior teeth is of clinical importance and should be taken into consideration during surgical or endodontic treatment.

INTRODUCTION

The maxillary sinus (MS) is the largest pyramid-shaped bilateral air sinus located in the body of the maxilla. It varies in size, shape, and position not only in different individuals but also in different sides of the same individual.[1] The dimensions of the MS can also be different among the gender and ethnic groups.[1] The anatomical variability could be explained by its relation to the maxillary posterior teeth and the size and degree of pneumatization of the MS.[2] The inferior wall of the MS is curved and extended between the adjacent teeth or roots in about half of the population, creating elevations in the antral surface or protrusions of the root apices into the sinus cavity.[3]

The relationship between the MS and the root apices of the posterior teeth is of clinical relevance in diagnosing and treatment planning in the posterior area. The periodontal or periapical infections of maxillary molars and premolars can spread to the MS and cause sinusitis.[4] The pathological influence of dental diseases in the formation of sinusitis in the MS is well documented in the dental literature.[56] Maillet et al. reviewed 82 cone-beam computed tomography (CBCT) scans with signs of maxillary sinusitis for evidence of a dental pathology and concluded that over 50% of these cases were of dental etiology.[7]

In addition, tooth extraction or endodontic surgery can lead to perforation, formation of oroantral fistula, or root displacement into the MS in a case of presenting tooth root protrusion in the MS.[8] Therefore, accurate evaluation of the anatomic relationship of MS and posterior teeth is crucial in the clinical practice in diagnosing maxillofacial pathologies and preoperative treatment planning.

Many studies have used panoramic radiograph and computed tomography or CBCT scans in assessing the relationship between the MS and the maxillary posterior roots among different populations.[91011] Using panoramic radiograph allows visualization of anatomical features at low cost and low radiation dose. The disadvantage of panoramic radiograph is the two-dimensional image, which cannot be reliable for determining the relationship between the MS and posterior teeth. While CBCT has the advantage of three-dimensional (3D) images and accurate cross-sectional slices that could identify this relationship precisely.[12]

This study aimed to determine the relationship between the MS and the root apices of maxillary teeth using CBCT.

MATERIALS AND METHODS

This cross-sectional study included patients from those who attended the radiologic diagnostic center for CBCT investigation at the period between October 2017 and May 2018. All patients signed written consent. The study protocol was approved by the ethics committee in the university.

CBCT scans were obtained with a 3D eXam (Kavo, Biberach, Germany) with standard exposure settings (23 cm × 17 cm field of view, 0.3 mm voxel size, 110 kv, 1.6–20 s) and were analyzed by two endodontic examiners in a semidark room using the I-CAT viewer software (Version 10, Hatfield, England). Inclusion criteria were (1) patients aged from 20 to 70 years, (2) patients with no history of orthodontic treatment or any surgical procedures involving the MS, (3) patients with no diseases or pathological conditions involving this area, and (4) presence of at least one maxillary premolar and one molar especially in older patients.

From 693 patients, 325 were selected according to the inclusion criteria, and they were divided into three age groups: 165 – young group (20–44 years), 120 – middle age (45–59 years), and 40 – elderly (60–70 years).

To determine the vertical relationships between the root apices of the maxillary premolars and the maxillary molars, the classification of Kwak et al.[13] was used as follows [Figure 1]:

Figure 1

The vertical relationship between the inferior wall of the maxillary sinus and the roots of the maxillary molars[13]

Type I: The inferior wall of the MS floor is located above the root apex of the buccal and palatal roots

Type II: The inferior wall of the MS is located below the level connecting the buccal and palatal root apices without an apical protrusion over the MS

Type III: An apical protrusion of the buccal root apex is observed over the inferior wall of the MS

Type IV: An apical protrusion of the palatal root apex is observed over the inferior wall of the MS

Type V: Apical protrusions of the buccal and palatal root apices are observed over the inferior wall of the MS.

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

Type I: The inferior wall of the MS floor is located above the root apex

Type II: The root apex touches the inferior wall of the MS

Type III: An apical protrusion of the root apex is observed over the inferior wall of the MS.

The types of the vertical relationship were observed in cross-sectional images and recorded in both sides; the distance between the root apices of the maxillary molars and premolars was measured for each root.

For statistical analysis, IBM SPSS Statistics v 22.0 licensed package (IBM, Chicago, IL, USA) was used. The method of descriptive statistics was used for statistical processing of the received data. For analysis and comparison of the left and right sides, a paired t-test was done. For comparison between the vertical relationship among age groups, Kruskal–Wallis test was used.

RESULTS

325 CBCT scans for patients with mean age 44 years were analyzed to study the relationship between the MS and the root apices of posterior teeth. A total of 487 first premolars, 502 second premolars, 498 first molars, 454 second molars, and 267 third molars were recorded. By analyzing the classification of the vertical relationship for each tooth, it was observed that Type I was most commonly seen in the first and second premolars [Table 1]. Whereas, Type II was more often found in the first and second molars in each age group [Table 2]. Type II was also revealed in maxillary third molars [Table 3]. For one-rooted teeth, Type I was more often to be found in the first and second premolars [Table 1]. The longest mean distance from the MS to the root apices can be seen for the palatal root of molars and the buccal root of premolars [Table 4]. The difference in the relationship between the MS and root apices for both right and left sides was not statistically significant (P > 0.01). The difference in the relationship between diverse types among age groups was also not statistically significant (P > 0.01).

Table 1

Vertical relationship between root apices of maxillary premolars and maxillary sinus

Teeth	Age groups	Type I (%)	Type II (%)	Type III (%)	Type IV (%)	Type V (%)
First premolar (2 roots)	Young group	154 (92.2)	9 (5.4)	-	1 (0.6)	3 (1.8)
	Middle group	126 (87.5)	18 (12.5)	-	-	-
	Elderly	56 (84.8)	10 (15.2)	-	-	-
Total		336 (89.1)	37 (9.8)	-	1 (0.3)	3 (0.8)
Second premolar (2 roots)	Young group	41 (53.2)	36 (46.8)	-	-	-
	Middle group	28 (50.9)	27 (49.1)	-	-	-
	Elderly	3 (75)	1 (25)	-	-	-
Total		72 (52.9)	64 (47.1)	-	-	-
First premolar (1 root)	Young group	34 (63)	20 (37)	-	-	-
	Middle group	21 (61.8)	13 (38.2)	-	-	-
	Elderly	20 (90.9)	2 (9.1)	-	-	-
Total		75 (68.2)	35 (31.8)	-	-	-
Second premolar (1 root)	Young group	82 (46.1)	86 (48.3)	10 (5.6)	-	-
	Middle group	76 (55.5)	61 (44.5)	-	-	-
	Elderly	20 (47.6)	22 (52.4)	-	-	-
Total		178 (49.9)	169 (47.3)	10 (2.8)		-

Table 2

Vertical relationship between root apices of maxillary first and second molars and maxillary sinus

Types	Maxillary first molar (%)			Total (%)	Maxillary second molar (%)			Total (%)
	Young	Middle	Elderly		Young	Middle	Elderly
Type I	45 (20.9)	46 (23.2)	27 (35.5)	118 (24.1)	35 (16.9)	38 (21)	26 (39.4)	99 (21.8)
Type II	126 (58.6)	141 (71.2)	49 (64.5)	316 (64.6)	124 (59.9)	116 (64.1)	40 (60.6)	280 (61.7)
Type III	9 (4.2)	-	-	9 (1.9)	28 (13.5)	17 (9.4)	-	45 (9.9)
Type IV	22 (10.2)	4 (2)	-	26 (5.3)	4 (1.9)	1 (0.6)	-	5 (1.1)
Type V	13 (6)	7 (3.5)	-	20 (4.1)	16 (7.7)	9 (5)	-	25 (5.5)

Table 3

Vertical relationship between root apices of maxillary third molars and maxillary sinus

Types	Maxillary third molar (%)			Total (%)	Maxillary third molar one root (%)			Total (%)
	Young	Middle	Elderly		Young	Middle	Elderly
Type I	10 (28.6)	5 (22.7)	1 (50)	16 (27.1)	23 (18.9)	26 (41.3)	10 (43.5)	59 (28.4)
Type II	23 (65.7)	17 (77.3)	1 (50)	41 (69.5)	94 (77)	33 (52.4)	13 (56.5)	208 (67.3)
Type III	-	-	-	-	5 (4.1)	4 (6.3)	-	9 (4.3)
Type IV	1 (2.9)	-	-	1 (1.7)	-	-	-	-
Type V	1 (2.9)	-	-	1 (1.7)	-	-	-	-

Table 4

The mean distance from root apices of posterior teeth and the floor of maxillary sinus

Teeth	Root	Distance
Maxillary third molar	MB	0.55±1.07
	DB	0.58±1.08
	P	0.78±1.36
	One root	0.53±1.00
Maxillary second molar	MB	0.54±1.19
	DB	0.55±1.14
	P	0.69±1.22
Maxillary first molar	MB	0.86±1.54
	DB	0.87±1.53
	P	0.87±1.65
Second premolar	B	1.15±1.19
	P	1.11±1.12
	One root	1.12±1.32
First premolar	B	4.60±2.87
	P	3.78±2.33
	One root	3.86±2.49

B: Buccal, P: Palatal root, MB: Mesiobuccal, DB: Distobuccal

DISCUSSION

The relationship between the MS and the root apices of the posterior teeth has a significant effect on the planning of surgical and endodontic treatment, especially if the apices are located in proximity to the MS. Errors during endodontic treatment frequently occur, for example, there is a high risk of perforation the MS floor with endodontic instruments when the root apices are in contact or protrude the sinus floor.[14] In addition, in these cases, the inflammatory response after the endodontic treatment may involve the sinus mucosa and cause sinusitis.[15] Hence, it is crucial to pay attention not to extrude the instruments or medicaments during the endodontic treatment and to assess the relationship between the root apices of the posterior teeth and the MS. This relationship also has a role in periodontal surgery; Huang and Brunsvold reported a case of periodontal pockets and bony defects of the maxillary first molar and these periodontal defects resulted in maxillary sinusitis.[16]

Many studies were conducted to investigate this relationship using panoramic or CT scans. A study by Lopes et al.[9] compared the panoramic and CBCT in assessing the root protrusion into the sinus and found that CBCT can predict the root protrusion. Roque-Torres et al.[10] demonstrated a high level of correlation between the data of CBCT and panoramic radiograph when roots are below the MS floor. Ali et al.[17] demonstrated that CT scan is essential to provide information about the relation to the MS when there is a protrusion detected in panoramic images. Mattar et al.[18] used panoramic radiographs to study the relationship between MS floor and roots of posterior teeth in Saudi patients; they found that 1st and 2nd maxillary molars were in a very close position to the MS.

Many studies determined the relationship by measuring the distance between the MS and the root apices of the maxillary posterior teeth. A study by Kilic et al.,[11] was conducted to analyze 92 CBCT scans and it was observed that the distance between sinus floor and root tip was longest for the first premolar and shortest for the second molar distobuccal root. Another study by Estrela et al.[19] in a subpopulation of the Brazilian central region found that the shortest distances between MS and root apices were found in the mesiobuccal root of the 2nd molar (0.36 mm) and the palatal root of the 1st molar (0.45 mm). Chand et al.[20] reported that maxillary 2nd molars were the closest to the sinus floor and the palatal root was the closest root to MS floor.

Other studies used the classification by Kwak et al.,[13] or Jung and Cho[21] to determine the relationship between the MS and the posterior teeth. A study by Shokri et al.[8] analyzed 110 CBCT scans and revealed that Type 0 was mostly observed in the first and second premolars with 95.3% and 67.6% prevalence, respectively. Type 3 was common in the first and molar with 34.5% and 40% prevalence, respectively.

Another study by Jung and Cho[4] used the Jung classification to evaluate the relationship between MS and maxillary molars and found that Type 3 was commonly observed in 32.5% and 36.7% for 1st and 2nd molars, respectively. The results also showed that the shortest distance was for the mesiobuccal root of the 2nd molar. Eberhardt et al.[22] and Georgescu et al.[23] reported that the mesiobuccal roots of 2nd molar were the closest to the sinus floor.

Fry et al.[24] found in their study that Type 0 was commonly seen in 1st and 2nd premolars, whereas Type 1 was seen in the 1st and 2nd molars. They also measured the distance between MS and root apices, and the mean distance was the longest for the palatal root of molars and the buccal root of 1st premolar.

In this study, we aimed to identify this relationship according to Kwak classification and by measuring the distance between MS and root apices comparing between three age groups. The results of our studies showed: type II was seen commonly in the first, second, and third molars among different age groups with 64.6%, 61.7%, and 67.3%, respectively. Type V, characterized by the root protrusion into the MS, was observed in 5.5% for the second molar. Type II was observed for the second one-rooted premolars in 47.3%. The shortest distance to the MS was recorded for the mesiobuccal root of the maxillary second molar and for the palatal root of maxillary premolars [Figure 2]. These findings are correlating with previous studies.[4222324]

Figure 2

Cone-beam computed tomography cross-sectional images, 5 types of vertical relationship between the maxillary sinus and root apices of posterior teeth (a) Type I. (b) Type II. (c) Type III. (d) Type IV. (e) Type V. (f) Type II for second premolar one rooted

Knowledge of this relationship can guide clinicians in preparing an optimal treatment plan and help avoiding the complications during surgical and endodontic procedures.

CONCLUSION

Within the limitations of this study, most of the root apices of the maxillary molars contact the floor of the MS in different age groups. Therefore, this anatomical relationship between the MS and the posterior teeth should be taken into consideration when performing surgical or endodontic treatment in this area.

Financial support and sponsorship

The publication has been prepared with the support of the «RUDN University Program 5–100».

Conflicts of interest

There are no conflicts of interest.