The Prevalence of Maxillary and Mandibular Exostosis in the Mississippi Population: A Retrospective Study

Abstract

Purpose: The objective of this study was to determine the prevalence of exostosis in the Mississippi population. Methods: The patient archives of the UMMC School of Dentistry between January 2018 and May 2021 were examined. Patients with exostosis were included in the study based on the findings from intraoral photographs, full-moth series (FMS), panoramic radiographs, and cone-beam computerized tomography (CBCT) images of the patients. Patients were excluded from the study if they did not have maxillary or mandibular exostosis. In addition, each patient’s age, gender, and ethnic origins, such as Caucasian, African-American, or Asian, were recorded. All data regarding exostosis were evaluated and categorized according to age, gender, and ethnicity. Multiple logistic regression analysis was performed for more detailed statistical analysis. Results: A total of 1242 patients were examined for the presence of maxillary and mandibular tori. In total, 303 patients were diagnosed with maxillary and/or mandibular tori among the Mississippi population, with a prevalence rate of 24.4%. Exostosis was seen more in females (57.4%) compared to males (42.6%). The highest prevalence of exostosis was seen in Caucasians (71.3%), followed by African-Americans (23.8%) and Asians (5%). Conclusions: High prevalence of exostosis was seen in the Mississippi population. Our findings will help clinicians to be more aware of these bony protuberances and, thus, better at diagnosing them. This may specifically help oral surgeons, periodontists, and prosthodontists in pre-prosthodontic surgery and denture fabrication.

1. Introduction

Tori (exostosis) are non-pathological, usually asymptomatic, benign growths of the cortical portion of the bone [1,2,3]. They are named according to their localization in jaw bones [2,4]. The most common form of growth, which occurs in the palatal bone in the midline of the maxilla, is called torus palatinus [2,5]. The form that is located in the lingual regions of the mandibular premolar and canine teeth and is mostly bilateral is called torus mandibularis [2,5,6]. Apart from these two common forms, tori can be observed in the vestibule, buccal, or palatal regions of the jaws [7]. These bony protuberances are classified according to their size (palpable, visible, or large) and shape (flat, nodular, spindle-shaped, or lobular) [1,8].

The etiology of oral tori, including torus palatinus, remains unclear; however, various theories suggest that autosomal dominant inheritance and genetic factors may play a significant role in their formation. Although torus palatinus has been associated with chromosomal anomalies and Mendelian syndromes, its inheritance is primarily believed to follow an autosomal dominant pattern, largely based on observational evidence [9]. However, it has been associated with conditions such as tooth clenching, bruxism, and tooth deficiency, which may cause excessive occlusal force or unbalanced occlusal force distribution [10]. In addition, the effects of environmental factors such as vitamin deficiency or a calcium-rich diet on its etiology have also been examined [1,3]. Although their etiology is still not fully known, it has been reported that the frequency of oral tori may vary depending on conditions such as ethnic origin, gender, and age, according to academic studies [11,12,13,14].

Oral tori are not considered pathology [4]. Tori are benign, slow-growing bony formations primarily composed of compact bone. Microscopically, these structures consist of dense cortical bone, typically well-demarcated from surrounding tissues. They may occasionally contain trabecular bone, but are predominantly made up of cortical bone and generally lack significant vascularity or signs of infection [1,2,3,15]. These tori can be beneficial in some cases; for instance, there are reports of related growths being surgically removed for regenerative purposes and used as a donor site for an autogenous bone graft [4,14]. However, in some cases, this anatomical formation creates problems for the patient and the physician [14]. It is known that these bone growths may hinder the successful oral hygiene practices of patients, and that chewing trauma to the tori region may predispose patients to conditions such as ulceration in the soft tissue [1,16]. Additionally, they can present challenges for oral surgeons and prosthodontists in terms of surgery and prosthetic treatment [14,17]. For example, recovery after gingivectomy operations in the region of the mandibular torus may not proceed as expected, leading to restricted flap movement and complicating dental surgical procedures [1,14]. In such cases, surgical removal of the oral tori may be necessary [18]. Therefore, general dentists, oral and maxillofacial surgeons, periodontists, and prosthodontists should remain vigilant towards these anatomical formations and consider them carefully during treatment planning.

This study aimed to determine the prevalence of tori in the Mississippi population to provide dental health providers in Mississippi with the most up-to-date and accurate data. There are large discrepancies in statistics regarding the prevalence of maxillary and mandibular tori from across the globe. One goal of this research project was to gather more data, specifically from the Mississippi population, to produce more accurate figures regarding tori in this region of the world.

2. Material and Methods

The study plan was approved by the Institutional Review Board of The University of Mississippi Medical Center (IRB file number—2021V0588). All stages of the study were carried out as per the Helsinki Declaration Guidelines.

The University of Mississippi Medical Center School of Dentistry (UMMC SOD) patient archives were used in this retrospective study. Intraoral photographs, full-mouth series (FMS), panoramic radiographs, and cone-beam computerized tomography (CBCT) images from the clinic’s database of patients treated at UMMC SOD between January 2018 and May 2021 were examined in detail. Patients older than 18 years of age and with oral tori findings were included in the study (Figure 1 and Figure 2). A code in EPIC was also used to find patients with tori in the patient database. Intraoral photographs typically show the presence of bony growths along the palatal or mandibular areas, appearing as well-defined nodular or sessile projections. On panoramic radiographs, oral tori are identified as radiopaque, well-defined masses located in the maxillary or mandibular arches. The presence of these masses on CBCT scans provides further detail, revealing the exact location, size, and shape of the tori, which helps differentiate them from other bony lesions or exostoses. Radiographically, tori are characterized by dense cortical bone, often without significant trabecular involvement, and are seen as non-expansile, stable structures. Patients showing these findings through the various imaging modalities were included for evaluation in the study. The age, gender, and ethnic origins (Caucasian, African-American, or Asian) of the patients included in the study were recorded. In addition, the localization of the anatomical formations was evaluated, including the jaw in which the relevant anatomical formation was localized (localized only in the maxilla, only in the mandible, or in both). All protected health information was anonymized before the data were compiled.

The data were analyzed with IBM SPSS V 23 (IBM SPSS Statistics for Windows, Version 23.0 Armonk, 2015, NY: USA). Multiple logistic regression analysis was used for the evaluations and the significance level was established as p < 0.05.

3. Results

A total of 1242 patients were examined for the presence of maxillary and mandibular exostosis. In total, 303 patients were diagnosed with maxillary and/or mandibular tori among the Mississippi population, with a prevalence rate of 24.4%. The ages of the patients with exostosis ranged between 18 and 93. The mean age of the patients was 56 ± 16.2. Exostosis was seen more in females (n = 174, 57.4%) compared to males (n = 129, 42.6%). A higher prevalence of exostosis was seen in Caucasians (n = 216, 71.3%) than African-Americans (n = 72, 23.8%) and Asians (n = 15, 5%). The number of patients with oral tori in the maxilla only was 30 (9.9%), the number of patients with oral tori in the mandible only was 195 (64.4%), and the number with oral tori in both the maxilla and mandible was 78 (25.7%).

Out of 300 patients diagnosed with tori, 216 were Caucasian. Of these, 126 (n = 126, 58.3%) were female and 90 (41.7%) were male. Oral tori were present only in the maxilla in 18 of these patients (8.3%), only in the mandible in 138 patients (63.9%), and in both jaws in 60 patients (27.8%). The mean age of the Caucasian patients was 54.8 ± 15.2 years. There were 72 African-American patients in the study. Of these, 39 (n = 39, 54.2%) were female and 33 (45.8%) were male. Oral tori were present only in the maxilla in 12 of these patients (16.7%), only in the mandible in 45 patients (62.5%), and in both jaws in 15 of them (20.8%). The mean age of the African-American patients was 48.2 ± 16.9 years. There were 15 Asian patients in the study. Of these, 9 (n = 9, 60%) were female and 6 (40%) were male. Oral tori were present only in the maxilla in none of these patients, only in the mandible in 12 (80%), and in both jaws in 3 of them (20%). The mean age of the Asian patients was 51.4 ± 23.5 years (

Table 1. Distribution of patients according to ethnicity.

Parameters		Ethnicity
		Caucasian	African-American	Asian
Gender	Female	n = 126 58.3%	n = 39 54.2%	n = 9 60%
	Male	n = 90 41.7%	n = 33 45.8%	n = 6 40%
Localization	Only maxillary	n = 18 8.3%	n = 12 16.7%	n = 0 0%
	Only mandibulary	n = 138 63.9%	n = 45 62.5%	n = 12 80%
	Both	n = 60 27.8%	n = 15 20.8%	n = 3 20%
Age	Median (min–max)	56 (18–93)	52 (20–75)	51 (24–90)
	Mean ± sd	54.8 ± 15.2	48.2 ± 16.9	51.4 ± 23.5

).

Oral tori were present only in the maxilla in 30 patients, of whom 27 (90%) were female and 3 (10%) were male. A total of 18 of the patients (60%) with tori in the maxilla were Caucasian and 12 of them (40%) were African-American. The mean age of the patients with oral tori in only the maxilla was 51.9 ± 12.4 years. The number of patients with oral tori only in the mandible was 195, of whom 99 (50.8%) were female and 96 (49.2%) were male. In addition, 138 of these patients (70.8%) were Caucasian, 45 of them (23.1%) were African-American, and 12 of them (6.1%) were Asian. The mean age of these patients was 54.1 ± 16.6. Oral tori were present in both jaws of 78 patients, of whom 48 patients (61.5%) were female and 30 (38.5%) were male. Of the patients with oral tori in both jaws, 60 of them (77%) were Caucasian, 15 of them (19.2%) were African-American, and 3 of them (3.8%) were Asian. The mean age of the patients with oral tori in both jaws was 51.1 ± 16.9 years (

Table 2. Distribution of patients according to localization of oral tori.

Parameters		Localization
		Only Maxillary	Only Mandibulary	Both Jaws
Gender	Female	n = 27, 90%	n = 99 50.8%	n = 48 61.5%
	Male	n = 3 10%	n = 96 49.2%	n = 30 38.5%
Ethnicity	Caucasian	n = 18 60%	n = 138 70.8%	n = 60 77%
	African-American	n = 12 40%	n = 45 23.1%	n = 15 19.2%
	Asian	n = 0 0%	n = 12 6.1%	n = 3 3.8%
Age	Median (min–max)	50 (29–67)	58 (20–93)	51.5 (18–87)
	Mean ± sd	51.9 ± 12.4	54.1 ± 16.6	51.1 ± 16.9

).

Multiple logistic regression showed that the probability of a patient having tori in the mandible was not dependent on patient age (p = 0.59) or Asian heritage (p = 0.99), but it was dependent on patient gender (p < 0.001) and Black heritage (p = 0.04). The best predictor of mandibular exostosis was the following model:

$$logit\left(P\right)=\mathrm{l}\mathrm{o}\mathrm{g}\left({\displaystyle \frac{P}{1-P}}\right)=4.091-2.113\times female-0.989\times black$$

where P is the probability of a patient having tori, and female and black are both dichotomous observational variables (0 = false or 1 = true). This model had a predictive accuracy of 90%.

Multiple logistic regression showed that the probability of a patient having tori in the maxilla was not dependent on patient age (p = 0.08), Asian heritage (p = 0.18), or Black heritage (p = 0.98), but it was dependent on patient gender (p < 0.001). The best predictor of maxillary exostosis was the following model:

$$logit\left(P\right)=\mathrm{l}\mathrm{o}\mathrm{g}\left({\displaystyle \frac{P}{1-P}}\right)=-1.068+0.79\times female$$

where P is the probability of a patient having tori and female is a dichotomous observational variable (0 = false or 1 = true). This model had a predictive accuracy of 64%.

4. Discussion

In this retrospective study, we aimed to assess the prevalence of oral tori within the Mississippi population, focusing on their correlation with ethnicity, age, and gender. Our findings reveal that both maxillary and mandibular exostosis are more prevalent in females, with a notably higher occurrence among Caucasians in this population. These results provide valuable insights into the demographic factors influencing the prevalence of this unique anatomical feature, shedding light on patterns that could guide future clinical and epidemiological research. The clinical significance of these findings is that tori are easily diagnosed through routine imaging, and their higher prevalence in Mississippi may require heightened awareness among dental professionals, particularly when planning prosthetic treatments. If tori are indeed more common in this region compared to other populations, it could impact treatment protocols and necessitate a more tailored approach to managing patients with these bony growths.

There are similar studies in the literature evaluating the prevalence of oral tori in different populations [5,7,10,12,19,20,21,22,23,24,25,26,27,28]. When these studies were examined, it was seen that the frequency of these bone growths differs from population to population. Although many studies show that populations such as Jordan [10], Japan [19,20], Turkey [12], Taiwan [21], Morocco [22], Romania [23], Nigeria [24], Malaysia [25], Thailand [5,7], Norway [27], and Ghana [28] are affected by oral tori, the number of studies conducted on the US population is very low. In one of these studies, Austin et al. (1965) reported that 19.5% of African-Americans in the USA had palatal tori [18,29]. In another study, Woo (1950) found that the prevalence of palatal tori was 37% in African-Americans, 45% in White Americans, and 47% in Mongolians in the USA [18,30]. In the current study, not only palatal tori, but also all oral tori in the oral region were evaluated, and it was reported that oral tori were observed in 24.4% of the population in Mississippi. In another study conducted in the USA, Sonnier et al. (1999) analyzed 328 modern American skulls and recorded the presence of mandibular tori, palatal tori, and palatal tubers [14]. It was reported that of 254 Caucasian skulls, 63 (24.8%) mandibular tori and 58 (22.8%) palatal tori were observed [14]. In the same study, 25 of 74 African-American skulls had mandibular tori (33.8%) and 9 of them had palatal tori (12.2%) [14]. The prevalence of oral tori, the etiology of which depends on genetic and environmental factors, is already expected to be higher in certain populations and ethnic groups [11,12,13,14]. As per our knowledge, the current study is the only study conducted on this subject that focuses on the Mississippi population. In this respect, it will shed light on the literature and increase the awareness of clinicians regarding this issue.

In the current study, it can be seen that the percentages of oral tori are quite different in different ethnicities. These results suggest that ethnic origin is an important factor in this anatomical formation. Similarly, El Sergani et al. (2020) evaluated 625 individuals of European ancestry, 377 of West African ancestry, and 100 of East Asian ancestry, that is, a total population of 1102 individuals, in terms of torus palatinus prevalence in their study [18]. Although the same population was not evaluated in the current study, Sergani et al. (2020) reported that the prevalence of torus palatinus is higher in East Asian females [18]. This result supports the idea that not only ethnicity, but also gender may affect the prevalence. Sergeni et al. (2020) found in their study that torus palatinus had higher prevalence in females, which is consistent with the current study [18]. Similar to these findings, it has been reported that palatal tori localized in the maxilla have a higher prevalence in females in many studies examining populations of European, African, and Asian origins. Haugen et al. (1992) examined palatal tori during a study conducted on Norwegians and found that they were observed at a rate of 11.2% in females and 6.7% in males, that is, they had a higher prevalence in females [31]. There is evidence that this anatomical formation is more common in Black American [18,29], Thai [5], and Ghanaian [28] females, i.e., similar results have been reported. Although torus palatinus was not directly examined in the current study, it can be said that the prevalence of tori in the maxilla is similar to these studies in that it was found to be higher in females.

Many similar studies support the idea that the incidence of oral tori may vary in different populations. For example, Kumar Singh et al. (2017) examined the prevalence of oral tori in Malaysia in another study [4]. In that study, three different types of oral tori were examined: torus palatinus, torus mandibularis, and exostosis [4]. The authors reported that oral tori were observed at a rate of 33% in the population they examined [4]. They found that torus palatinus was most common in females, and torus mandibularis and exositos were more common in males [4]. Torus palatinus is most common in females, which is consistent with the other mentioned studies and the current study [4,5,18,29]. In addition, in the present study, it was observed that the prevalence of torus palatinus was higher in Malawian patients than in Chinese and Indian patients [4]. Kumar Singh et al. (2017) reported that a high rate of oral tori was observed in their study groups and that physicians should be mindful of these anatomical formations in cases such as prosthesis planning.

In another study, the prevalence of buccal and palatal tori was examined in the Thai population [7]. Similar to the current study, bone growths in the maxilla and mandible were evaluated separately. Bone growths, or tori, were observed in 26.9% of the 960 individuals studied. The percentage of oral tori in the Mississippi population was also recorded as 24.4%, a very similar result [7]. It has been found that tori localized in the mandible are more common, and their prevalence in both the maxilla and mandible is higher in males [7]. We think that the contradictory results on this subject in the literature may vary depending on the population studied. In the aforementioned study conducted on the Thai population, it was seen that the possibility of tori increases with age [7]. On the other hand, in a study conducted in Jordan by Sawair et al. (2019), it was similarly observed that the prevalence of oral tori increases with age, and it appears most often in people in their 50s [17]. In the present study, the presence of oral tori was examined in a wide age group aged between 18 and 91 years, and similarly, it was observed that there was a higher prevalence in older ages. The mean age of the people with tori was found to be 56 ± 16.2. There are also studies that conflict with these findings. For example, Jainkittivong et al., 2007, reported that both mandibular and palatal tori appear most frequently in the third decade of life in their study of the Thai population [26]. In the study conducted by Telag et al. in Malaysia, it was reported that tori were mostly seen in people between the ages of 20–29 [25].

The present study has similar results to many studies in the literature and presents the prevalence of oral tori in the Mississippi population, but it has some limitations. The most important of these is the diagnosis through retrospective clinical records rather than clinical examination. Although retrospective studies are carried out more easily and in a shorter time, and at the same time allow the scanning of larger archives, there is a risk that some dental conditions, such as oral tori, that should be diagnosed with clinical findings are overlooked in these studies. For example, in some studies, oral tori have been classified according to their size, and it can be seen in these studies that there are smaller sizes of oral tori that can be diagnosed only by palpation [1,8]. It is very difficult to diagnose oral tori retrospectively only using photography and radiography. We think this tori size may have been overlooked in the current study. The second biggest limitation is the evaluation of the tori by classifying them as only maxillary or mandibular. In terms of a more comprehensive interpretation of the study, it would be more accurate to evaluate them as palatal tori, mandibular tori, or buccal/labial-lingual/palatal exocytosis, as in many studies in the literature [2,4]. In the current study, the classification as only upper or lower jaw tori may have caused deviations in some prevalences. Additionally, genetic and pathological examinations were not conducted, which limits our understanding of the underlying factors contributing to the formation of tori. Moreover, in this retrospective study, we were unable to assess patients’ hormonal imbalances, vitamin D levels, autoimmune diseases, and potential metabolic disorders, which may have further influenced the development of oral tori. Despite all these limitations, the current study is the first study conducted in the Mississippi population as far as we know, and is very valuable in this respect. In similar studies to be conducted in the future, larger patient populations should be included and these should be evaluated through clinical examination. In addition, while evaluating different races, it would be beneficial to comment on the prevalence in this respect by screening a similar number of patients from all races as much as possible.

5. Conclusions

A high prevalence of oral tori was observed in the Mississippi population. These findings emphasize the importance of raising awareness among clinicians about these bony growths, enabling better diagnosis and management. This is particularly relevant for oral surgeons, periodontists, and prosthodontists involved in pre-prosthetic surgery and denture fabrication. Furthermore, this study paves the way for future research exploring the underlying factors contributing to bone growth in the maxillofacial region, which could ultimately lead to a better understanding of the causes of oral tori.