RESEARCH
Open Acce
Masafumi Oda ¹ , Shinji Yoshii², Nao Wakasugi-Sato ¹ , Shinobu Matsumoto-Takeda ¹ , Ikuko Nishida ³ , Shun Nishimura¹, Susumu Nishina¹, Manabu Habu ⁴ , Daigo Yoshiga ⁵ , Masaaki Sasaguri ⁴ and Yasuhiro Morimoto 1*
Abstract
Background  Very recently, a significant relationship between tonsilloliths and dental plaque-related pathologies was reported using digital panoramic radiographs. Their dynamics over time suggest that tonsilloliths may be in a per- manently active phase that functions to remove foreign matter. The aim of the study was to evaluate the relationship between the occurrence of tonsilloliths and the extent of periodontitis. Methods  A total of 608 patients who underwent both CT and panoramic radiographs were included in the study. Both of two imaging were retrospectively and independently assessed with respect to the presence of tonsilloliths detected on CT and panoramic radiographs, and bone defects caused by periodontitis detected on panoramic radiographs. The type of retrospective study is case-control. Then, the differences between age groups were evalu- ated with respect to the degree of bone resorption and its correlation with the presence of tonsilloliths. The relation- ships between categorical variables were assessed using Pearson's correlation coefficient or Spearman's correlation coefficient. Results  There was a significant relationship between tonsilloliths on CT and the extent of the bone defect on pano- ramic radiographs (Spearman's correlation coefficient, r = 0.648, p = 0.043). In addition, there was a significant dif- ference in the extent of the bone defect caused by periodontitis between subjects with and without tonsilloliths in the 60 to 69-year-old group (Mann-Whitney U test, p =0.025), 70 to 79-year-old group (Mann-Whitney U test, p =0.002), and 80 to 89-year-old group (Mann-Whitney U test, p =0.022), but not in other age groups (Mann-Whitney U test: under 9-year-old group, ρ = 1.000; 10 to 19-year-old group, ρ = 1.000; 20 to 29-year-old group, ρ = 0.854; 30 to 39-year-old group, p = 0.191, 40 to 49-year-old group, p = 0.749; 50 to 59-year-old group, p = 0.627; ≥90-year-old group, p = 1.000). Conclusions  The presence of tonsilloliths was related to the extent of periodontitis because the structures were responding dynamically. Keywords  Tonsilloliths, CT, Periodontitis, Panoramic radiographs *Correspondence: Yasuhiro Morimoto rad-mori@kyu-dent.ac.jp Full list of author information is available at the end of the article © The Author(s) 2023. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the articles Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecom- mons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.
Background
Tonsilloliths are oropharyngeal concretions that form within the palatine tonsillar crypt in reaction to a for- eign nidus such as bacteria or organic debris [ 1 ]. It has been suggested that tonsilloliths may be correlated with halitosis and tonsillar abscess [ 2 – 9 ]. Tonsilloliths have very high detection rates on computed tomography (CT), such as nearly 50% in some reports [ 2 , 10 – 14 ]. A recent longitudinal study of changes in tonsilloliths found dynamic fluctuation of the calcification levels of all ton- silloliths with time [ 10 ]. It was hypothesized that their dynamics over time suggest that tonsilloliths may be in a permanently active phase that functions to remove for- eign matter [10]. Very recently, a significant relationship between ton- silloliths and dental plaque-related pathologies was reported buy Gurbiuz et al. using digital panoramic radiographs [ 15 ]. In addition, some of the bacteria as a foreign nidus in tonsilloliths are periodontal disease- related bacteria, such as Actinomyces, Eubacterium, Fuso- bacterium, Megasphaera, Porphyromonas, Prevotella, Selenomonas, and Tannerella spp. [ 16 – 18 ]. These results seem reasonable because tonsilloliths may be involved in continuously dental plaque-related pathologies such as periodontal disease and active alteration of calcifications, which are correlated to the surrounding environment [ 10 , 15 ]. However, the report by Gurbuz et al. was relatively limited because the presence or absence of tonsilloliths was judged by panoramic radiographs in that study [ 15 ]. The detection rate of tonsilloliths by panoramic radio- graphs was only about 13%, not approaching the nearly 50% seen on CT [ 2 , 10 , 15 ]. Therefore, it was thought that it necessary to evaluate patients’ tonsilloliths using CT in order to investigate the relationship between tonsilloliths and periodontal disease more precisely. en it was retrospectively hypothesized that analyzing the relationship between the presence or absence of tonsilloliths on CT and bone loss due to perio- dontal disease on panoramic radiographs would be effec- tive in clarifying the relationship between the two.
Methods
A total of 608 patients who underwent both pre-treat- ment CT including the palatine tonsils and panoramic radiographs were included in the retrospective study. The type of retrospective study is case-control. No CT or panoramic radiographs were performed for this study. The examination was performed at the Division of Oral and Maxillofacial Radiology of Kyushu Dental Univer- sity between 2020 and 2022. Patients who underwent CT including the palatine tonsils and panoramic radiographs had maxillary and mandibular disease such as inflam- mation, cysts, tumors, and etc. of the soft tissues of the maxilla, mandible, and head and neck, and required both examinations clinically. Patients who had no remain- ing teeth and patients without pre-treatment CT and panoramic radiographs, low quality panoramic radio- graph and low quality CT image due to metal artifact to calculate the presence of tonsillolith were excluded. In addition, CBCT and panoramic radiographs together were not used is that CBCT cannot adequately evaluate the tonsilloliths. Patients involved in this study were 237 male and 371 female patients. Patients ranged in age from 5 to 94 years, with a mean of 50.3 years. e present study was approved by the institutional review board (IRB) of Kyushu Dental University (No. 20–16). This study is ret- rospective, and the Kyushu Dental University the IRB has indicated that informed consent from patients for this study is not required. Panoramic radiographs were acquired using a pano- ramic AUTO-1000 EX system (Asahi Roentgen Ind. Co., Ltd., Kyoto, Japan). Images were taken in the inci- sive occlusion position with the head held by head sup- ports with the FH plane parallel to the ground. CT was performed using an Activion 16 (Toshiba, Tokyo, Japan) scanner. Contiguous axial images with slice thickness of 3mm were obtained using standard algorithms and viewed with soft-tissue windows. The presence of tonsilloliths was evaluated indepen- dently on both panoramic radiographs and CT. Using the differential diagnosis of tonsilloliths on panoramic radiographs reported by Ram et al., a radiopaque nodular mass or masses piled up on the mandibular ramus and soft palate were defined as tonsilloliths [ 2 , 19 ]. Tonsillo- lith pathology was diagnosed based on the system of Oda et al., as follows [ 2 ] (Fig. 1 ). Tonsilloliths were defined as structures of CT density > 100 Hounsfield units (HU). The numbers and long axes of the tonsilloliths were cal- culated on CT images. e calcification levels of the tonsilloliths were calculated as CT values. If the subject had multiple tonsilloliths, the size and calcification lev¬ els of the largest calculus were analyzed. Analysis of ton- sillolith on 608 pairs of panoramic radiographs and CT images were assessed by a single oral and maxillofacial radiologist with 15 years of experience (M. O.). To reduce sources of bias, the investigator for tonsilloliths was a sin- gle experienced oral and maxillofacial radiologist familiar with the study. Alveolar bone defects caused by periodontitis were assessed using panoramic radiographs, which were commonly used to evaluate bone loss due to periodon- tal disease, that included all teeth. Implants, supernu- merary teeth, and third molars were excluded from the number of teeth. Residual roots without a cap for an overdenture were also excluded. Teeth with car- ies or periapical lesions were not excluded. Bone loss was considered when the alveolar crest was found to be 2mm or more from the cemento-enamel junction according to Gurbuz et al. [ 15 ]. Alveolar bone defects caused by periodontitis were assessed on panoramic radiographs by measuring the distance between the cement-enamel junction and the alveolar crest and between the cement-enamel junction and the root apex at two sites (mesial and distal) on each tooth (Fig. 2 ) [20]. The apex was defined as the most apically located point of the root. e alveolar bone defect caused by periodontitis of each subject was calculated as the average of the cement-enamel junction-alveolar crest/ cement-enamel junction-apex of all teeth [ 21 ]. The points of cement-enamel junction, alveolar crest and apex of teeth on panoramic radiograph were assessed by an oral and maxillofacial radiologist with 15years of experience (M. O.) and a conservative dentist with 14 years of experience (S. Y.). e measurement point was determined by agreement between the two inves- tigators. To reduce sources of bias, those assessing for alveolar bone defects on panoramic radiographs were performed by experts of radiologists and conservative dentist. In addition, CT and panoramic radiographs were evaluated independently and randomly. The essential null hypothesis of this study is that the presence of tonsilloliths on CT is not related to alveo- lar bone loss on panoramic radiographs. On the other hand, the alternative hypothesis is that there is a rela- tionship between the two. Sample size was calculated with using G*Power version 3.1.9.6 (Franz Faul, Uni- versity of Kiel, Germany). Input parameters and sample sizes were as follows: tails, two; effect size, 0.3; alpha error, 0.05; power (1-Beta error): 0.95; allocation ratio N2/N1, 1.2. And 586 was calculated as the sample size. All statistical analyses were performed using IBM SPSS Statistics version 26 statistical software (SPSS, Chi- cago, IL, USA). Categorical variables were compared using Fisher's exact test or the Mann-Whitney U test. The relationships between categorical variables were assessed using Pearson's correlation coefficient or Spearman's correlation coefficient. Results were con- sidered significant at p < 0.05. The sample size was con- sulted with a statistician to ensure that it was sufficient for this study.

Results
Detection of tonsilloliths on CT and panoramic
radiographs
Of the 608 individuals, 278 (45.7%) were considered to have tonsilloliths on CT scans, with only 64 (10.5%) on panoramic radiographs. The 278 patients with tonsillo- liths on CT consisted of 107 males and 171 females, with no difference in the tonsillolith detection rate by sex on CT (Fisher's exact test, p =0.867) and on panoramic radiographs (Fisher's exact test, p = 0.685). A significant correlation was found between age and the tonsillolith detection rate on CT (Spearman's correlation coeffi- cient, r=0.894, p<0.001) (Table 1 ). As the subjects aged, the detection rate increased gradually. In particular, a significant difference in the tonsillolith detection rate was found between the under and over 40-year-old age groups (Fisher's exact test, p < 0.001). Overall, 105 patients had one calculus, 48 had two, 39 had three, 23 had four, 18 had five, and so on (Table 2 ), up to a maximum of 36. With respect to the sizes of the ton- silloliths, 76 were less than 2mm, 188 were greater than 2 mm and less than 5 mm, 14 were greater than 5 mm, and none was greater than 8mm (Table 3 ). The calcification levels of tonsilloliths on CT images were greater than 100 HU and less than 300 HU in 115, greater than 300 HU and less than 500 HU in 77, greater than 500 HU and less than 1000 HU in 66, and greater than 1000 HU in 20 (Table 4 ). Relationship between the detection of tonsilloliths on CT and the extent of the bone defect caused by periodontitis on panoramic radiographs A significant difference in the extent of the bone defect caused by periodontitis was seen between subjects with and without tonsilloliths (Mann-Whitney U test, p<0.001) (Table 1). A strong correlation was found between the tonsillolith detection rate on CT and the extent of the bone defect caused by periodontitis (Spearman's correlation coefficient, r =0.648, p =0.043) (Table 5 ) (Fig. 3 ). As the extent of the bone defect caused by periodontitis increased, the detection rate increased gradually. There was a significant difference in the extent of the bone defect caused by periodontitis between sub- jects with and without tonsilloliths in the 60 to 69-year- old group (Mann-Whitney U test, p =0.025) (Fig. 3), 70 to 79-year-old group (Mann-Whitney U test, p = 0.002),
and 80 to 89-year-old group (Mann-Whitney U test, p = 0.022), but not in other age groups (Mann-Whitney U test: under 9-year-old group, p = 1.000; 10 to 19-year-old group, p = 1.000; 20s, p = 0.854; 30 to 39-year-old group, p=0.191 (Fig. 4 ), 40 to 49-year-old group, p=0.749; 50 to 59-year-old group, p =0.627; ≥90-year-old group, p = 1.000) (Table 1 ). e number of tonsilloliths on CT was weakly related to the bone defect caused by peri- odontitis (Spearman's correlation coefficient, r = 0.235, p<0.001) (Table 2). No significant correlations were found between the extent of the bone defect caused by periodontitis on panoramic radiographs and the size of tonsilloliths (Pearson's correlation coefficient, r=0.45, p=0.458) (Table 3 ) or HU number (Pearson's correlation coefficient, r =0.020, p =0.746) (Table 4 ).

Discussion
It was retrospectively hypothesized that there is a rela- tionship between the presence of tonsilloliths and the extent of periodontitis. The relationships between the detection rate of tonsilloliths on CT and the extent of the bone defect caused by periodontitis on panoramic radiographs were evaluated by age group. It was found that there was a significant relationship between the detection rate of tonsilloliths on CT and the extent of the bone defect caused by periodontitis on panoramic radio- graphs. In particular, one of the most interesting results of the present study was that there was a significant cor- relation between the detection rate of tonsilloliths and the extent of the bone defect caused by periodontitis on panoramic radiographs in the relatively older age group. In the previous reports, tonsilloliths were shown to form within the palatine tonsillar crypt in reaction to a foreign nidus such as bacteria or organic debris. Some of the bacteria as a foreign nidus are periodontal dis- ease-related bacteria, such as Actinomyces, Eubacte- rium, Fusobacterium, Megasphaera, Porphyromonas, Prevotella, Selenomonas, and Tannerella spp. [ 16 , 17 ]. Oral bacteria in secretions in contact with tonsillar epi- thelium may adhere to the mucosal surface and may stimulate cytokine production by mucosal epithelium [22]. In a clinical study, it was shown that the preva¬ lence of periodontal disease is increased in patients with peritonsillar abscess [ 23 ]. The aforementioned studies emphasized the possibility of a causal relationship for these pathologies. In addition, it was reported that there were dynamic fluctuations of the calcification levels of all tonsilloliths, as well as a tendency for the tonsilloliths to be excreted from the body with increasing tonsillo- lith size [10]. The active dynamics of tonsilloliths func- tion to remove foreign matter from the body [10]. Together with the present results and previous reports, our hypothesis seems. The status of periodontitis might be related to the occurrence of tonsilloliths in older age groups. It was very recently reported that there was a significant relationship between tonsilloliths and dental plaque-related pathologies on digital panoramic radio- graphs [ 15 ]. As the subjects aged, the detection rate of tonsilloliths and the rate of dental plaque-related pathologies increased gradually [ 15 ]. Therefore, the result could not be negated by confounding factors with aging. However, the present study showed that there was a significant correlation between the detection rate of tonsilloliths and the extent of the bone defect on panoramic radiographs in the relatively older age group. The present results mean that there may be a direct rela- tionship between the presence of tonsilloliths and the occurrence of periodontitis, without confounding due to aging. At the same time, on one side, the results support the relationship between the occurrence of halitosis and the presence of tonsilloliths through periodontitis. Tonsilloliths, also known as smelly balls, have a strong odor that might induce halitosis. So far, there have been some reports of previous studies about the relationship between the occurrence of halitosis and the presence of tonsilloliths [ 7 , 16 , 19 , 24 , 25 ], but there is no consen- sus. Since the relationship between the presence of ton- silloliths and the extent of periodontitis was elucidated in the present study, the results support the relationship between the occurrence of halitosis and the presence of tonsilloliths. However, tonsilloliths with a strong odor might not necessarily induce halitosis directly, and the periodontitis coexisting with tonsilloliths might be par- tially responsible. The limitations of the recent previous study of the rela- tionship between tonsilloliths and dental plaque-related pathologies might be related to sampling [ 15 ]. The detec- tion rate of tonsilloliths was 46.1% on CT scans, but only 7.3% on panoramic radiographs [ 2 ]; the main causes for the discrepancy were the calcification levels (CT value < 300 HU) and the sizes (< 5mm) of the tonsilloliths in the report [ 2 ]. Another interesting result was that there was no sig- nificant correlation between the detection rate of ton- silloliths and the extent of the bone defect caused by periodontitis on panoramic radiographs in younger and middle-aged groups, but not in the older age group. This result suggests that the extent of the bone defect caused by periodontitis might be partially related to the detec- tion rate of tonsilloliths, but not directly or completely. Dynamic changes of calcification levels of almost all tonsilloliths occur [ 10 ]. Therefore, as the rate of various kinds of periodontitis-related bacteria may be increas- ing, the formation and the growth of tonsilloliths should be affected. An unknown mechanism in addition to hormone concentrations and pH in saliva might affect the dynamic changes in tonsilloliths. Further studies are needed to clarify the reasons for the relationship between the presence of tonsilloliths and the extent of periodontitis. The major limitations of the present study are that the status of periodontitis was assessed only by the extent of bone defects on panoramic radiographs. e plaque index, the numbers of bleeding on probing, mobility, red- ness, swelling by inspection, etc. should be examined to determine the status of periodontitis. Because the present study was retrospective, it failed to assess confounding factors that should be considered, even though periodon- titis is a multifactorial disease. In particular, the clinical attachment loss and other radiologic examination, which is fundamental to the diagnosis of periodontal disease, were unable to do. However, it is not considered this limi- tation to be decisive for the validity of the study results. In the future, it is believed that the possible relationship between tonsil stones and periodontitis will be further elucidated by using PCR to examine the relationship between periodontal bacterial strains and those in tonsil stones and by examining the role of nanobacteria in den- tal calculus and tonsilloliths. In addition, the data were obtained from subjects with diseases mainly involving the oropharyngeal area, rather than the oral and maxil- lofacial region. The present results should be interpreted as being relevant to relatively healthy, active populations. A further limitation is that only Japanese subjects were examined.
Conclusions
e aim of the study was to evaluate the relationship between the occurrence of tonsilloliths and the extent of periodontitis. A total of 608 pairs of CT and panoramic radiographs were retrospectively assessed for the pres- ence of tonsilloliths and bone defects caused by peri¬ odontitis. ere was a significant relationship between tonsilloliths on CT and the extent of the bone defect caused by periodontitis on panoramic radiographs. At the same time, there was a significant correlation between the presence of tonsilloliths and the extent of the bone defect caused by periodontitis on panoramic radiographs in the relatively older age group, but not in the younger or middle-aged population. e presence of tonsilloliths might be partially related to the extent of periodontitis, because the structures might be responding dynamically to a foreign nidus such as bacteria in the body.
Acknowledgements
Not applicable.
Authors' contributions
Funding
Declarations
Ethics approval and consent to participate
Competing interests
Author details
Abbreviations CT Computed tomography HU Hounsfield units 3. Takahashi A, Sugawara C, Kudoh T, Ohe G, Takamaru N, Tamatani T, Nagai H, Miyamoto Y. Prevalence and imaging characteristics of palatine tonsilloliths evaluated on 2244 pairs of panoramic radiographs and CT images. Clin Oral Investig. 2017;21:85–91. https://doi.org/10.1007/ s00784-016-1752-0. 4. Kim MJ, Kim JE, Huh KH, Yi WJ, Heo MS, Lee SS, Choi S. Multidetector computed tomography imaging characteristics of asymptomatic palatine tonsilloliths: a retrospective study on 3886 examinations. Oral Surg Oral Med Oral Pathol Oral Radiol. 2018;125:693–8. https://doi.org/10.1016/j. 0000.2018.01.014. S. Missias EM, Nascimento E, Pontual M, Pontual AA, Freitas DQ, Perez D, Ramos-Perez F. Prevalence of soft tissue calcifications in the maxillofacial region detected by cone beam CT. Oral Dis. 2018;24:628–37. https://doi. org/10.1111/odi.12815 . 6. Takahashi A, Sugawara C, Kudoh K, Yamamura Y, Ohe G, Tamatani T, Miyamoto Y. Lingual tonsillolith: prevalence and imaging characteristics evaluated on 2244 pairs of panoramic radiographs and CT images. Dentomaxillofac Radiol. 2018;47:20170251. https://doi.org/10.1259/dmfr. 20170251. 7. Rio AC, Franchi-Teixeira AR, Nicola EM. Relationship between the pres- ence of tonsilloliths and halitosis in patients with chronic caseous tonsil- litis. Br Dent J. 2008;204:E4. https://doi.org/10.1038/bdj.2007.1106. ad Caldas MP, Neves EG, Manzi FR, de Almeida SM, Bóscolo FN, Haiter-Neto F. Tonsillolith--report of an unusual case. Br Dent J. 2007;202:265-7. https:// doi.org/10.1038/bdj.2007.175 . 9. Ansai T, Takehara T. Tonsillolith as a halitosis-inducing factor. Br Dent J. 2005;198:263–4. https://doi.org/10.1038/sj.bdj.4812116. 10.   Yamashita K, Oda M, Tanaka T, Nishida I, Wakasugi-Sato N, Matsumoto- Takeda S, Habu M, Sago T, Takahashi O, Tsurushima H, Tabe S, Otani T, Yoshiga D, Sasaguri M, Joujima T, Miyamura Y, Morimoto Y. Changes in tonsillolith characteristics detected in a follow-up CT study. BMC Oral Health. 2021;21:72. https://doi.org/10.1186/s12903-021-01426-1 . 11. Mesolella M, Cimmino M, Di Martino M, Criscuoli G, Albanese L, Galli V. Tonsillolith. Case report and review of the literature. Acta Otorhinolaryn- gol Ital. 2004;24:302–7. 12. Weller CV. The incidence and pathogenesis of tonsillar concretions. Ann Otol Rhinol Laryngol. 1924;33:79–119. 13. Aspestrand F, Kolbenstvedt A. Calcifications of the palatine tonsillary region: CT demonstration. Radiology. 1987;165:479–80. https://doi.org/ 10.1148/radiology.165.2.3659369. 14. Fauroux MA, Mas C, Tramini P, Torres JH. Prevalence of palatine ton- silloliths: a retrospective study on 150 consecutive CT examinations. Dentomaxillofac Radiol. 2013;42:20120429. https://doi.org/10.1259/dmfr. 20120429. 15.   Gurbuz E, Gungor M, Hatipoglu H. Radiographic detection of the relation- ship between Tonsilloliths and dental plaque-related pathologies in a series of digital panoramic radiographs. Med Princ Pract. 2022;31:149–55. https://doi.org/10.1159/000521687 . 16. Tsuneishi M, Yamamoto T, Kokeguchi S, Tamaki N, Fukui K, Watanabe T. Composition of the bacterial flora in tonsilloliths. Microbes Infect. 2006;8:2384–9. https://doi.org/10.1016/j.micinf.2006.04.023 . 17.   Arvisais-Anhalt S, Quinn A, Bishop JA, Wang CS, Mitchell RB, Johnson RF, Schultz B, Day AT. Palatine Tonsilloliths and Actinomyces: a multi-insti- tutional study of adult patients undergoing tonsillectomy. Otolaryngol Head Neck Surg. 2020;163:743–9. https://doi.org/10.1177/0194599820 921392. 18. Hajishengallis G. Periodontitis: from microbial immune subversion to systemic inflammation. Nat Rev Immunol. 2015;15:30–44. https://doi.org/ 10.1038/nri3785 . 19. Ram S, Siar CH, Ismail SM, Prepageran N. Pseudo bilateral tonsilloliths: a case report and review of the literature. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2004;98:110–4. https://doi.org/10.1016/j.tripleo.2003.11.015. 20.   Kim TS, Obst C, Zehaczek S, Geenen C. Detection of bone loss with different X-ray techniques in periodontal patients. J Periodontol. 2008;79:1141–9. https://doi.org/10.1902/jop.2008.070578 . 21. Bassiouny MA, Grant AA. The accuracy of the Schei ruler: a laboratory investigation. J Periodontol. 1975;46:748–52. https://doi.org/10.1902/jop. 1975.46.12.748 . 22. Scannapieco FA. Role of oral bacteria in respiratory infection. J Periodon- tol. 1999;70:793–802. https://doi.org/10.1902/jop.1999.70.7.793 . All listed authors participated meaningfully in the study, and they have seen and approved the submission of this manuscript. MO participated in the performance of the research, data collection, data analysis, and drafted the initial manuscript. SY participated in the performance of the research, data collection, and participated in data analysis. NW and MS participated in the performance of the research, data analysis, and critically reviewed the manuscript. SM and SN designed the study and participated in data analysis. IN and MH participated in the performance of the research, data collection, and participated in data analysis. SN and DY participated in interpretation of data and critically reviewed the manuscript. YM conceptualized the study and drafted the initial manuscript. In this study, the production of study design, the collection, analysis and interpretation of subject's data, and writing the manuscript is nothing to use the funding. Availability of data and materials All data generated or analysed during this study are included in this pub- lished article. The institutional review board at Kyushu Dental University approved this study (No. 20–16; Oct. 26, 2020). All methods were carried out following Helsinki declaration guidelines and regulations. Informed consent was obtained from all patients for the panoramic tomography and CT clinical examinations. The patients’informed consent in this retrospective study was not required by the institutional review board at Kyushu Dental University (No. 20–16; Oct. 26, 2020). Consent for publication Not applicable. The authors declare no competing interests. 1 Division of Oral and Maxillofacial Radiology, Kyushu Dental University, 2-6-1 Manazuru, Kitakyushu, Kokurakita-ku 803-8580, Japan. ²Division of Promot- ing Learning Design Education, Kyushu Dental University, Kitakyushu, Japan. 3Division of Developmental Stomatognathic Function Science, Kyushu Dental University, Kitakyushu, Japan. 4Division of Maxillofacial Surgery, Kyushu Dental University, Kitakyushu, Japan. 5 Division of Oral Medicine, Kyushu Dental University, Kitakyushu, Japan. Received: 7 March 2023   Accepted: 12 December 2023 Published online: 03 January 2024 Mandel L. Multiple bilateral tonsilloliths: case report. J Oral Maxillofac 1. Surg. 2008;66:148–50. https://doi.org/10.1016/j.joms.2006.05.047 . 2. Oda M, Kito S, Tanaka T, Nishida I, Awano S, Fujita Y, Saeki K, Matsumoto- Takeda S, Wakasugi-Sato N, Habu M, Kokuryo S, Kodama M, Kaneuji T, Yoshiga D, Miyamoto I, Nishimura S, Yamashita Y, Maki K, Tominaga K, Yoshioka I, Ansai T, Morimoto Y. Prevalence and imaging characteristics of detectable tonsilloliths on 482 pairs of consecutive CT and panoramic radiographs. BMC Oral Health. 2013;13:54. https://doi.org/10.1186/ 1472-6831-13-54. 23.   Georgalas C, Kanagalingam J, Zainal A, Ahmed H, Singh A, Patel KS. The association between periodontal disease and peritonsillar infection: a prospective study. Otolaryngol Head Neck Surg. 2002;126:91-4. https://doi.org/10.1067/mhn.2002.121318. 24. Lo RH, Chang KP, Chu ST. Upper airway obstruction caused by bilateral giant tonsilloliths. J Chin Med Assoc. 2011;74:329–31. https://doi.org/10. 1016/j.jcma.2011.05.011. 25. Stoodley P, Debeer D, Longwell M, Nistico L, Hall-Stoodley L, Wenig B, Krespi YP. Tonsillolith: not just a stone but a living biofilm. Otolaryngol Head Neck Surg. 2009;141:316–21. https://doi.org/10.1016/j.otohns.2009. 05.019. Springer Nature remains neutral with regard to jurisdictional claims in pub- lished maps and institutional affiliations.