Root canal therapy combined with endoscopic sinus surgery for odontogenic sinusitis: Efficacy comparison in a cohort study

Abstract

BACKGROUND

Odontogenic maxillary sinusitis, often triggered by dental issues like periapical periodontitis, significantly contributes to chronic sinusitis, mainly affecting adults around 50 years old, emphasizing the need for a multidisciplinary diagnostic and treatment approach.

AIM

To investigate the therapeutic effect and clinical value of root canal therapy combined with nasal endoscopic surgery compared with simple root canal therapy in the treatment of severe odontogenic maxillary sinusitis caused by periapical periodontitis.

METHODS

The clinical data, diagnosis, and treatment of 200 patients with severe odontogenic maxillary sinusitis caused by periapical periodontitis from October 2020 to October 2021 were analyzed retrospectively. Among them, 63 patients were treated with simple root canal therapy as the control group, and 137 patients were treated with root canal therapy combined with nasal endoscopic surgery as the observation group. The therapeutic effect, Lund-Kennedy endoscopic score, paranasal sinus Lund-Mackay score, complication rate, recurrence rate, and patient satisfaction were compared between the two groups.

RESULTS

First, we compared the effective rates: 23 cases were cured, 22 were improved, and 8 were ineffective in the control group, yielding a total effective rate of 84.90%. Meanwhile, 97 cases were cured, 34 improved, and 6 were ineffective in the observation group, resulting in a total effective rate of 95.62%. The observation group had a higher total effective rate compared with the control group (P < 0.05). Second, we compared the Lund–Kennedy endoscopic score. Before treatment, no significant difference (P > 0.05) was observed in this score between the two groups. After treatment, the Lund–Kennedy endoscopic score decreased in both groups. The Lund–Kennedy endoscopic score of the observation group at 3 and 6 mo after treatment was lower compared to that of the control group (P < 0.05). Third, we compared the Lund–Mackay score of paranasal sinuses. Before treatment, there was no significant difference in this score between the two groups (P > 0.05). After treatment, the Lund–Mackay scores of paranasal sinuses decreased in both groups. The Lund–Mackay scores of paranasal sinuses in the observation group at 3 and 6 mo after treatment were lower compared to those of the control group (P < 0.05). Fourth, we compared the incidence and recurrence rate of complications. Three months after treatment, no significant difference was found in the incidence and recurrence rate of complications between the observation group (6.56%) and the control group (9.52%) (P > 0.05). However, 6 mo after treatment, the incidence and recurrence rate of complications in the observation group (2.91%) was significantly higher compared to that of the control group (12.69%) (P < 0.05). Fifth, we compared patient satisfaction. Six months after treatment, the patient satisfaction of the observation group (93.43%) was significantly better than that of the control group (84.12%) (P < 0.05).

CONCLUSION

Root canal therapy combined with nasal endoscopic surgery has a good therapeutic effect on severe odontogenic maxillary sinusitis caused by periapical periodontitis, and it can reduce the injury of maxillary sinus mucosa and bone, and significantly reduce the incidence of complications and recurrence rate. Meanwhile, it has high patient satisfaction and remarkable therapeutic effect, which is suggested to be popularized and applied in clinic.

Key Words: Root canal therapy; Nasal endoscopic surgery; Periapical periodontitis; Odontogenic maxillary sinusitis; Therapeutic effect; Clinical value

Core Tip: Combining root canal therapy with nasal endoscopic surgery significantly improves treatment outcomes for severe odontogenic maxillary sinusitis caused by periapical periodontitis, compared to root canal therapy alone. This combination approach not only enhances the total effective rate but also reduces the scores of Lund-Kennedy and Lund-Mackay, indicating a reduction in maxillary sinus mucosa and bone injury. Moreover, it significantly lowers the incidence of complications and recurrence rates, while increasing patient satisfaction. These findings support the broader clinical adoption of this combined treatment strategy.

INTRODUCTION

Odontogenic maxillary sinusitis refers to maxillary sinusitis caused by tooth-related factors, accounting for about 10% of maxillary sinusitis[1]. In recent years, studies have suggested that more than 40% of cases of chronic bacterial maxillary sinusitis are caused by odontogenic factors, which is much higher compared to the previously reported incidence of 10%. Earlier studies have suggested that adults between the ages of 30 and 40 are at risk for the disease. In a recent data analysis, it was found that odontogenic sinusitis was more common in adults around the age of 50 and slightly predisposed to women[2]. It is usually induced by maxillary tooth infection, trauma, maxillary lesions, and maxillary sinus mucosal perforation during maxillary surgery and dental implant, in which periapical periodontitis of maxillary teeth is the most important contributing factor. It is also one of the causes of odontogenic maxillary sinusitis[3]. Periapical periodontitis is caused by bacterial infection in the root canal and can lead to the destruction of the apical alveolar bone. The root tips of the maxillary premolars and molars are adjacent to the bottom wall of the maxillary sinus and sometimes only separated from the mucosa of the maxillary sinus. About 50% of cases of periapical periodontitis are 65% likely to bring about changes of the maxillary sinus mucosa, including mucositis, periostitis, and maxillary sinusitis[4]. Maxillary sinus mucositis is characterized by localized mucosal thickening caused by inflammatory stimulation. And further development can lead to maxillary sinusitis. Odontogenic maxillary sinusitis is more likely to be caused by odontogenic maxillary sinusitis in patients with no previous history of sinusitis and unilateral nasal cavity or paranasal sinus lesions[5]. In addition, odontogenic maxillary sinusitis should be differentiated from unilateral hemorrhagic necrotizing polyps, fungal maxillary sinusitis, early maxillary sinus carcinoma, and maxillary malignant tumor based on the patient's characteristic clinical symptoms, signs, and imaging examinations. For example, the malignant tumor invades the infraorbital nerve and causes numbness in the infraorbital region, and invasion of the orbital contents leads to changes in exophthalmos vision[6]. Fungal masses in the maxillary sinus caused by fungal sinusitis can lead to uneven density in the maxillary sinus on computed tomography (CT), which can help to differentiate. Early lesions or atypical symptoms often rely on pathological examination. Odontogenic maxillary sinusitis caused by periapical periodontitis is a refractory disease in clinic, which may lead to tooth loss[7]. Meanwhile, odontogenic infection is a slow and gradual process, which may lead to a high rate of missed diagnosis. Some typical symptoms of odontogenic maxillary sinusitis are mainly nasal and sinus symptoms, including nasal congestion and runny nose, with or without odor. Oral symptoms such as toothache and tooth sensitivity are not the exact causes of odontogenic maxillary sinusitis[8]. In clinic, odontogenic maxillary sinusitis can be diagnosed according to unilateral maxillary sinus disease, affected side maxillary diseased teeth, and CT finding of increased density of maxillary sinus lumen or mucosal thickening[9]. After surgical treatment of affected teeth and maxillary sinus lesions, the patient's disease can be further diagnosed if the symptoms are relieved. Odontogenic maxillary sinusitis usually requires the cooperation of multidisciplinary doctors to make a clear diagnosis and complete the operation, which demonstrates that multidisciplinary cooperation plays a very important role in the diagnosis and treatment of odontogenic maxillary sinusitis.

The principles for the treatment of odontogenic maxillary sinusitis are removal of etiology, establishment of drainage, control of infection, and prevention of complications[10]. In the acute stage, systemic application of antibiotics to treat pathogenic teeth; improvement and maintenance of ventilation and drainage of paranasal sinuses or early establishment of drainage; and management of severe odontogenic infection and its complications are recommended in the literature for 3-4 wk. In addition, it also includes 2-3 d of systemic or local application of nasal decongestants. Odontogenic maxillary sinusitis is a mixed infection of aerobes and anaerobes. The most commonly isolated bacteria include streptococci, Gram-negative bacilli, and enterobacteria[11]. Most of the literature recommends cephalosporins, sulfamethoxazole, gentamicin, penicillin, B-lactam, and metronidazole, to which bacteria in the paranasal sinuses and oral cavity are sensitive. In the chronic phase, application of vasoconstrictor in nasal cavity to maintain unobstructed drainage, or maxillary sinus lavage; and treatment or extraction of diseased teeth to remove lesions are recommended. Radical maxillary sinus surgery was performed for those who could not be cured by local and systemic treatment after extraction of the affected teeth[12]. In patients with oral maxillary sinus fistula, oral maxillary sinus repair was performed after inflammation was controlled. The fistula above 5 mm should be repaired after the maxillary sinus inflammation has been controlled, and the fistula should be repaired by peeling off the local mucoperiosteal flap. It has also been reported that bone slices are repaired and fixed with biological glue, and the effect is good[13]. Some scholars believe that as long as the treatment of dental diseases, maxillary sinusitis cannot be treated, while some scholars believe that sinusitis should be treated or can be completely cured, otherwise the disease can be delayed or difficult to cure[14]. On the question of whether or not to remove the pathogenic teeth, many scholars hold a positive opinion that the extraction of the diseased original teeth should be based on the specific conditions of the patient, and should not be generalized, and the residual roots need to be removed, otherwise root canal therapy should be performed. When extracting teeth, the alveolar fossa should be scratched thoroughly, granulation tissue and necrotic bone should be removed, and the sinus orifice should be closed[15]. Radical maxillary sinus surgery should be carried out 6 mo after tooth extraction to observe the cure of maxillary sinusitis after tooth extraction in order to determine whether it is necessary to carry out radical maxillary sinus surgery, and to observe whether the alveolar fossa has completely healed to avoid the occurrence of oral maxillary sinus fistula, which is helpful to the success of radical operation. Odontogenic maxillary sinusitis has even formed maxillary sinus alveolar fistula or oral fistula[16]. Due to periosteal infection at the bottom of the sinus, surgery is needed to completely remove the lesion and seal the fistula. It has been reported that a right premolar protruding into the maxillary sinus causes recurrent maxillary sinusitis with purulent nose and other symptoms. After Caldwell-Luc resection, the symptoms disappear[17]. Postoperative semi-recumbent position, local cold compress, semi-fluid diet, and oral care can reduce the pain of the patients and shorten the course of the disease.

The surgical treatment of odontogenic maxillary sinusitis includes the treatment of dental diseases, such as tooth extraction and root canal therapy, and the treatment of maxillary sinus and nasal cavity lesions[18]. At present, there is no standardized treatment plan for the treatment of odontogenic maxillary sinusitis. This study retrospectively analyzed the clinical data, diagnosis, and treatment of 200 patients with severe odontogenic maxillary sinusitis caused by periapical periodontitis in Wuhan No. 9 Hospital from October 2020 to October 2021 to investigate the therapeutic effect and clinical value of root canal therapy combined with nasal endoscopic surgery compared with simple root canal therapy alone in the treatment of severe odontogenic maxillary sinusitis caused by periapical periodontitis.

MATERIALS AND METHODS

General information

The clinical data, diagnosis, and treatment of 200 patients with severe odontogenic maxillary sinusitis caused by periapical periodontitis from October 2020 to October 2021 were analyzed retrospectively. Among them, 137 patients were treated with simple root canal therapy alone as the control group, and 63 patients were treated with root canal therapy combined with nasal endoscopic surgery as the observation group. In the control group, there were 53 males and 84 females, and their age was 18-74 years old, with an average of 46.92 ± 3.65 years, while in the observation group, there were 25 males and 38 females, and their age was 19-72 years old, with an average of 47.25 ± 3.84 years. There was no significant difference in age, sex ratio, or other general clinical data between the two groups (P < 0.05). This study was approved by the Medical Ethics Council of Wuhan No. 9 Hospital, and all the patients included in this study signed an informed consent form.

The inclusion criteria were: (1) Unilateral maxillary sinus disease; (2) Clinical detection of related maxillary diseased teeth; (3) CT examination showed moderate density shadow in the coronal maxillary sinus cavity, and some patients with ectopic teeth showed low tooth shadow and floor mucosal thickening in the sinus; (4) Symptom relief after treatment; (5) No previous history of cognitive impairment and mental illness; and (6) Providing informed consent.

The exclusion criteria were: (1) Patients with myocardial infarction or complicated with severe hepatorenal dysfunction, severe infection, severe diabetes, etc.; (2) Pregnancy or lactation; (3) Patients with malignant tumor; and (4) Patients with a previous history of mental illness and cognitive impairment or suspected cognitive impairment.

Treatment methods

The control group was treated with simple root canal therapy: The teeth in the study were routinely photographed via apical films and cone beam computed tomography (CBCT) before treatment. For the first visit, the teeth underwent treatment with a rubber barrier, routine pulp opening, pulp extraction, root canal dredging to 15 mm by balance force method, root canal flushing with 3% sodium hypochlorite solution, calcium phosphate cotton balls in the pulp cavity, and temporary glass ionomer sealing. On the second visit, the affected teeth were insulated with a rubber barrier, 17% ethylenediaminetetraacetic acid gel combined with Ni-Ti instruments was used to prepare the root canal, 3% sodium hypochlorite solution was adopted to rinse the root canal, calcium hydroxide paste was utilized to seal the root canal, and glass ionomer was used for temporary sealing. On the third revisit, if there were no obvious symptoms, the affected teeth were insulated with a rubber barrier, and root canals were washed with 3% sodium hypochlorite solution and ultrasonic wave. The affected teeth were filled with iRoot SP plus root canal paste and gutta percha, and the treatment was completed after three times of treatment.

The observation group was treated with root canal therapy combined with nasal endoscopic surgery: Root canal therapy was the same as that for the control group, and nasal endoscopic surgery was performed under general anesthesia after root canal therapy. After anesthesia, the maxillary sinus was punctured with a 5 mm cannula in the canine fossa, and if necessary, one bone hole was adopted for nasal endoscopy, and the other was used to attract and remove lesions. The uncinate process was resected through the nasal cavity to open the ethmoid chamber in the anterior and middle group, enlarge the natural opening of the maxillary sinus to reach a diameter above 10 mm as far as possible, drill holes alternately through the natural opening of the middle nasal meatus and the canine fossa, place the nasal endoscope, observe the condition of the maxillary sinus comprehensively, and complete the clearance of the lesion through the nasal endoscope. While clearing the lesion, the inflammatory and hypertrophic mucosa should be preserved as far as possible, especially the mucous membrane around the orifice of the sinus. After resecting the lesion, several side holes were made at one end of the 4 mm diameter rubber tube through which the casing needle was left for 3-5 d to facilitate flushing. A small piece of iodine spinning yarn can be filled into the sinus orifice to deal with the resection of part of the mucosa.

Observation indexes

Therapeutic effect: Therapeutic effect was classified as cure, improvement, and ineffectiveness. Recovery was defined as the disappearance of clinical symptoms, good opening of the sinus orifice, no purulent secretion. and epithelialization of the sinus mucosa. Improvement was regarded when most of the clinical symptoms disappeared, the sinus orifice opened better, and the sinus mucosa had no purulent secretion. Ineffectiveness was deemed when clinical symptoms were not improved, and there were bean dregs or purulent secretions in the nasal cavity.

Lund-Kennedy endoscopic score: The Lund-Kennedy endoscopic score scale was adopted to evaluate the five dimensions of nasal polyp, edema, secretion, scar, and scab on both sides of the nasal cavity before and 3 and 6 mo after treatment. The score ranges from 0-20. The higher the score, the worse the result of nasal endoscopy.

Paranasal sinus Lund-Mackay scoring: The bilateral maxillary sinus, anterior ethmoid sinus, posterior ethmoid sinus, sphenoid sinus, frontal sinus, and ostiomeatal complex were evaluated using the Lund-Mackay scale before and 3 and 6 mo after treatment. The score ranges from 0-24. The higher the score, the worse the result of sinus examination.

Rates of complications and recurrence: The rates of complications and recurrence were calculated after 6 mo of treatment. The complications included maxillary toothache, facial numbness, facial swelling, dry scab of the nasal cavity, and thickening of the nasal mucosa.

Patient satisfaction with treatment: After 6 mo of treatment, the patients' treatment satisfaction was subjectively evaluated by the patients as satisfaction, fairness, and dissatisfaction.

Statistical analysis

The data were analyzed with SPSS 21.0 statistical software. Measurement data are expressed as the mean ± SD; independent samples t-test was adopted for comparison between groups, and paired t-test was employed for comparison before and after treatment. Counting data are expressed as n (%), and χ² test was adopted for comparisons. P-values < 0.05 were considered statistically significant.

RESULTS

Effective rate

In the control group, 27 cases was cured, 26 were improved, and 10 were ineffective, yielding a total effective rate of 84.13%; in the observation group, 68 cases were cured, 62 were improved, and 7 were ineffective, resulting in a total effective rate of 94.89%. The total effective rate of the observation group was significantly higher than that of the control group (P < 0.05) (Table 1).

Table 1 Comparison of total effective rate between two groups of patients.

Group	n	Cured	Improved	Ineffective	Effective rate
Control	63	27	26	10	84.13%
Observation	137	68	62	7	94.89%
χ2		6.455			6.165
P value		0.040			0.013

Lund-Kennedy endoscopic score

Before treatment, there was no significant difference in the Lund-Kennedy endoscopic score between the two groups (P > 0.05). After treatment, the Lund-Kennedy endoscopic score decreased. The Lund-Kennedy endoscopic score at 3 and 6 mo after treatment was significantly lower in the observation group than in the control group (P < 0.05) (Table 2).

Table 2 Lund-Kennedy endoscopic score comparison (mean ± SD, points).

Group	n	Treatment	3 mo after treatment	6 mo after treatment
Control	63	5.84 ± 2.13	2.42 ± 1.51	1.98 ± 0.84
Observation	137	5.73 ± 2.05	1.57 ± 0.78	1.35 ± 0.71
t		0.348	5.249	5.495
P value		0.728	< 0.01	< 0.01

Lund-Mackay score of paranasal sinuses

Before treatment, there was no significant difference in the Lund-Mackay score of paranasal sinuses between the two groups (P > 0.05). After treatment, the Lund-Mackay score of paranasal sinuses decreased. The Lund-Mackay scores of paranasal sinuses at 3 and 6 mo after treatment were significantly lower in the observation group than in the control group (P < 0.05) (Table 3).

Table 3 Paranasal sinus Lund-Mackay score comparison (mean ± SD, points).

Group	n	Before treatment	3 mo after treatment	6 mo after treatment
Control	63	4.93 ± 2.32	2.16 ± 1.84	1.82 ± 0.91
Observation	137	4.75 ± 2.36	1.54 ± 0.72	1.37 ± 0.64
t		0.504	3.422	4.02
P value		0.613	< 0.01	< 0.01

Complication and recurrence rates

Six months after treatment, there was no significant difference in the rate of complications between the observation group (6.56%) and the control group (9.52%; P > 0.05). Six months after treatment, the rate of complications in the observation group (2.91%) was significantly lower than that of the control group (12.69%; P < 0.05) (Table 4).

Table 4 Comparison of rates of complications and recurrence between two groups.

Group	n	Maxillary tooth ache	Facial numbness	Facial swelling	Dry and scabbed nasal cavity	Nasal mucosa thickening	Rate of complications	Recurrence rate
Control	63	4	0	1	1	0	9.52%	12.69%
Observation	137	3	1	4	0	1	6.56%	2.91%
χ2							0.592	6.650
P value							0.441	0.009

Patient satisfaction

Six months after treatment, the patient satisfaction of the observation group (93.43%) was significantly higher than that of the control group (84.12%; P < 0.05) (Figure 1).

Figure 1  Comparison of patient satisfaction between two groups.

DISCUSSION

The maxillary sinus is located between the nasal cavity and the oral cavity, and the pathogenic bacteria can invade into the sinus through the opening of the nasal meatus and the oral cavity[19]. The lower wall of the maxillary sinus is the alveolar process of the maxilla, which covers the root tip of the maxillary second bicuspid and the maxillary molars from front to back. Sometimes the position of the sinus bottom wall is low and the root or tip of the tooth protrudes into the maxillary sinus, resulting in only a thin layer of bone between the second bicuspid teeth, the maxillary molars, and the sinus floor[20]. Even, the missing bone fragments are separated by only one layer of mucous membrane. The development of the maxillary sinus mostly begins in the 4th month of the embryo, protruding from the epithelium of the nasal meatus under the outer turbinate to the outside, and gradually eroding the adjacent bone through the interaction between osteoblasts and osteoclasts, thus forming a small cavity to become the sinus[21]. The maxillary sinus volume usually reaches its maximum value at about 30 years old for men and 20 years old for women. The overdevelopment of the maxillary sinus can lead to bone thinning of the alveolar process, which may be one of the reasons why odontogenic infection tends to cause maxillary sinusitis through local spread[21,22]. It can be noticed that the degree of gasification development of the maxillary sinus is closely related to the pathogenesis of odontogenic maxillary sinusitis. Most previous studies believe that although there are ethnic and gender differences in the development of the maxillary sinus, there are no obvious lateral differences, which cannot explain the clinical characteristics and etiology of odontogenic maxillary sinusitis[22]. Odontogenic maxillary sinusitis is caused by periapical inflammation or periodontitis, maxillary odontogenic cyst or tumor, iatrogenic factors, etc., accounting for about 10% of all maxillary sinusitis cases. Clinically, odontogenic maxillary sinusitis can be classified into acute and chronic forms. Odontogenic maxillary sinusitis usually demonstrates a long course of disease, unilateral onset, and atypical clinical symptoms in addition to the general clinical manifestations of chronic maxillary sinusitis, such as nasal odor, toothache and periodontal swelling, and periodic pain in the maxillary sinus[23]. The diagnostic criteria for odontogenic maxillary sinus mucositis are different. By reviewing the relevant literature, this study adopted mucosal thickness > 3 mm as the standard advocated by most scholars. This study found that the incidence of maxillary sinus mucositis caused by periapical periodontitis of maxillary posterior teeth was 61%, which was basically consistent with the incidence of 50%-65% reported in the literature. It is suggested that odontogenic maxillary sinus mucositis should be further examined when patients are found to have periapical periodontitis[24].

At present, root canal therapy is the most effective method for the treatment of periapical periodontitis, but there is no report on the success rate of this treatment for maxillary sinus mucositis caused by periapical periodontitis in China[23,24]. It has been reported that the occurrence of maxillary sinus lesions has no correlation with the size of periapical periodontitis, but has a positive correlation with the distance between the lesions and the floor of the maxillary sinus[25]. Clinical examination includes maxillary sinus examination and oral examination. When tapping in the facial maxillary sinus area, acute maxillary sinusitis can be significantly sensitive to percussion. Acute maxillary sinusitis can also cause toothache, usually radiating to all the posterior teeth in the quadrant. The teeth are sensitive to palpation and percussion, but the pulp vitality test is within the normal range[24,25]. In addition, cotton swabs containing 5% lidocaine can be placed in the nostrils of the affected side for 20 s. If the pain is caused by maxillary sinusitis, it would be changed or eliminated in 1-2 min. Oral examination should include pulp vitality in the posterior area, periodontal health, and the integrity of the entire oral mucosa. Imaging examinations recommended included CT and CBCT. CBCT can obtain high-quality three-dimensional images with lower radiation dose and cost, and better display tooth, root canal system, periodontal tissue, and maxillofacial bone structure, but it often fails to observe the entire maxillary sinus, and may not be able to evaluate the degree of maxillary sinus inflammation and the patency of the maxillary sinus orifice[26]. It is recommended to reduce the resolution to obtain a larger field of view. The normal maxillary sinus is filled with air and demonstrates a transmissive and well-defined appearance on imaging. Chronic maxillary sinusitis has different degrees of mucosal thickening, and active maxillary sinusitis demonstrates an increase in the air-liquid interface or complete density of the maxillary sinus[27]. Clinical treatments usually include systemic use of antibiotics, diseased dental surgery (including root canal therapy, apical surgery, and tooth extraction), and maxillary sinus surgery[28]. Both dental surgery and maxillary sinus surgery are effective in the treatment of odontogenic maxillary sinusitis, but their sequence and timing are uncertain. For odontogenic maxillary sinusitis caused by periapical periodontitis, pulp and periapical infection is the exact source of infection, so pulp and periapical infection must be managed first. If the root canal treatment is not successful, it is recommended to remove the affected teeth.

Root canal therapy is mainly through the use of paste to fill the root canal of the affected teeth, which can restore the smooth surface of the tooth, remove the inflammatory infection in the root canal, and help to reduce the periapical inflammatory reaction[29]. The core of root canal therapy is to control root canal infection and root canal filling. In the past, root canal therapy was often used for many times, and the course of treatment was long. Patients need to revisit the clinic many times, the treatment cost is high, and thus the probability of root canal infection will be increased. As a result, the therapeutic effect for the patients was affected[28,29]. Strict filling is the key to the success of root canal therapy. Nasal endoscopic surgery is widely adopted at present. Nasal endoscope has the advantages of high visualization in the opening of maxillary sinus orifice or cleaning of the maxillary sinus cavity, good preservation of normal tissue structure, and reduction of tooth extraction rate. It has the advantages of reducing operation-related complications, restoring nasal sinus ventilation and drainage, and shortening hospitalization time. The treatment under nasal endoscope advocates that the lesion teeth should be preserved as far as possible, and the normal physiological function and morphological structure should be preserved as far as possible while removing the lesions in the paranasal sinus[30]. The structure and function of the nasal mucosa and maxillary sinus mucosa can gradually return to normal after operation. Radical maxillary sinus surgery should be performed when there is dead bone or broken root in the paranasal sinus. The dead bone and obvious irreversible mucous membrane should be removed completely during the operation. Radical maxillary sinus surgery should be carried out 6 mo after tooth extraction[29,30]. One is to observe the cure of maxillary sinusitis after tooth extraction in order to determine whether radical maxillary sinus surgery is necessary. Second, the alveolar fossa has completely healed, which avoids the occurrence of oral maxillary sinus fistula and contributes to the success of radical surgery[31]. Once the oral maxillary sinus fistula occurs, if the fistula is smaller than 5 mm, the fistula can usually be formed by clot, and the mucosa can be crawled and healed by itself. If the defect is larger than 5 mm, it is difficult to seal the fistula. After the local symptoms of the whole body and maxillary sinus are controlled, the fistula should be repaired successfully by peeling off the local mucoperiosteum flap and bone patch repair. Nasal endoscopic surgery is based on the pathology and physiology of the paranasal sinus mucosa. Through the implementation of nasal endoscopic surgery, it can not only effectively clear the sinus lesions, but also restore and reconstruct the function of sinus drainage and ventilation[31,32]. Water and fasting should be prohibited within 6 h after nasal minimally invasive endoscopic surgery to prevent asphyxiation caused by vomiting; after removing nasal gauze, diet can return to normal, but taboo of irritating food is needed; during the period of gauze filling the nasal cavity, it is appropriate to supplement warm boiled water for many times and a small amount; cough, sneezing, cough, etc. should be avoided after operation, and nasal gauze should not be removed to avoid active bleeding of the nasal cavity. In order to help the recovery of nasal function after operation, bad living habits such as alcoholism and smoking should be avoided, nasal irrigation or local medication should be performed in accordance with the doctor's advice, and regular reexamination should be carried out[33]. In order to better prevent the recurrence of the disease, as long as the self-protective function is restored, it can effectively resist the external pathogenic factors. By indwelling a rubber tube and lavaging the maxillary sinus, the hospitalization time can be greatly shortened, and the patients can recover quickly. Thus, this treatment has the characteristics of small reaction after operation, less bleeding, and minor surgical trauma. This retrospective study was subject to potential biases including missing data bias and confounding bias. Data loss may occur, potentially leading to biased interpretations of the study results. This study still has limitations. The sample size of this study is small. We plan to conduct a multi-center study in the future to further expand the sample size and increase the follow-up time.

CONCLUSION

In summary, root canal therapy combined with nasal endoscopic surgery is effective in the treatment of severe odontogenic maxillary sinusitis caused by periapical periodontitis, with less damage to the maxillary sinus mucosa and bone, and a significant reduction in the rates of complications and recurrence. Meanwhile, it has high patient satisfaction and remarkable treatment effects.