In the present study, we demonstrated that OTUL can occur in patients of any age and gender. It is widely recognized that oral mucosal disorders, such as OLP, oral leukoplakia (OLK), burning mouth syndrome (BMS), and RAS, exhibit significant associations with both age and gender [7, 9,10,11]. However, the clinical study regarding the correlation between gender, age, and OTUL is still lacking. In the present study, after analyzing 1543 patients, we found that the clinical characteristics of OTUL, including duration, pain intensity, the composition of lesion sites were all significantly correlated with age and gender. To the best of our knowledge, the present study might be the first to demonstrate that the clinical characteristics of OTUL vary significantly across age and gender groups. Comprehensive research on this condition is essential, offering valuable insights for dental clinicians.

Research on the clinical characteristics of OTUL requires a detailed investigation into its underlying pathogenic factors. Based on the duration, OTUL can be classified into acute and chronic forms [2, 5, 8]. The acute form, often resulting from accidental biting or hot food, is marked by a sudden onset, pronounced pain and short duration. It typically displays a white or yellowish central clear area with erythematous halo [2, 8]. In contrast, the chronic form, commonly associated with sharp tooth edges and ill-fitting dentures, typically presents with a gradual onset or slow progression [2]. It is characterized by a shallow or deep disruption of the epithelium, often accompanied by peripheral keratosis, and may be either symptomatic or asymptomatic [2]. However, existing studies might be somewhat limited in depth and warrant more thorough investigation [4, 9, 12,13,14]. Given the larger sample size, our study more comprehensively demonstrated the diversity and complexity of traumatic injuries in the oral cavity. Abnormal tooth position is acknowledged as a potential factor in periodontitis [15], yet few studies have revealed the traumatic impact of third molars on the oral mucosa. Our study demonstrated that impacted, malpositioned, or elongated third molars, which are often overlooked in clinical practice, were among the most commonly prevalent traumatic factors in the oral cavity. The necessity for extraction of third molars is still under debate [16,17,18]. When making the decision whether or not to remove third molars, clinicians generally give priority to the needs of orthodontic, periodontal or prosthetic treatment, and the prevention of caries and root resorption in second molars [18]. However, based on our research, we advocate that the potential traumatic consequences of third molars on the oral mucosa should not be disregarded. Prophylactic removal of impacted, malpositioned, or elongated third molars may prove beneficial in preventing mucosal trauma.

A clear definition and classification of self-inflicted injuries to the oral cavity have not been established [19,20,21]. In this study, we found that self-inflicted behaviors mainly referred to conscious or compulsive repetitive injuries to an existing oral ulcer or normal-appearing mucosa, which is usually achieved through biting with the teeth or friction and could seriously interfere with healing. A previous study on 19 patients showed that oral ulcerative lesions caused by self-inflicted behaviors were mainly on the lips and tongue, with only one case on the cheek [19]. After analyzing 27 literature cases with oral self-inflicted injuries, a report found that 25 of 27 cases had gingival lesions, and the gingiva was the most frequently affected site [22]. By contrast, in our present study of 174 patients having self-inflicted injuries, the tongue was the most affected site (nearly 60%), followed by the cheek (24.71%) and the lip (9.20%). The percentage affecting the gingiva was only 4.60%. Mounting evidence indicates that children and adolescents with attention deficit and hyperactivity disorder (ADHD) or subsyndromal ADHD have a significantly increased risk of self-inflicted injury [23,24,25]. A previous study also found that self-mutilation of the oral cavity is very common in mentally retarded children [26]. Routine inspection of the oral cavity was recommended in these children and those receiving neuroleptic and anti-epileptic drug therapy [26]. Based on our clinical experience, we suggest that it might be helpful for dental clinicians and psychologists to perform psychological assessment on patients with repetitive self-inflicted injuries. When possible, multidisciplinary collaboration should be implemented to avoid or stop self-mutilation of the oral cavity.

In addition to the chronic types, we also showed several common acute or transient types of traumas, including inadvertent bite during chewing, accidental abrasion or knock, thermal injury, chemical irritation, and iatrogenic injury. The findings of our study could be very useful for clinical practice and prevention. Nevertheless, traumatic factors might still have been underestimated. First, the clinical presentations of traumatic lesions in the oral cavity are various, including not only ulcerative lesions but also others, such as irritational fibroma and keratosis, which were not included in the present study [2]. Second, our study was performed with patients who were seeking treatment in a hospital and all patients had oral mucosal lesions as their chief complaint. More patients with milder symptoms might self-medicate instead of seeking medical care. Third, some specific forms of trauma, such as oral electrical burn resulting from sucking a live wire, were not found in this study. In the future, multi-center clinical or epidemiological studies on oral trauma should be conducted.

The large sample size allowed us to analyze traumatic factors in more detail. Recognizing that these factors may vary among individuals of different ages and genders holds significance for clinical practitioners. Self-inflicted injury emerged as the predominant traumatic factor across both children and adolescents. Furthermore, it is noteworthy that males exhibited a significant prevalence of self-inflicted injuries compared to females, with nearly 70% of observed ulcerative lesions manifesting chronically. As a result, it is imperative for dental clinicians to be especially attentive to young male patients who exhibit chronic oral ulcers, as this may indicate underlying self-injurious tendencies. With advancing age and eruption of the third molars, the most common traumatic factor in young adults changed to impacted, malpositioned, or elongated third molars, which has not been reported previously. In the adult population, ranging from 19 to 74 years of age, inadvertent biting during chewing emerged as the predominant cause of oral trauma, regardless of gender. However, other factors, including residual crowns or roots, sharp teeth and tooth edges, and ill-fitting removable dentures became increasingly more common with increasing age. This phenomenon is explicable as these traumatic elements, often associated with tooth wear and loss, are notably more frequent among older adults in contrast to young adults. Furthermore, these factors exhibit variance between genders. A recent study has recommended the implementation of gender-specific oral health literacy education to promote oral health within older adults [27]. Therefore, customizing strategies based on age and gender considerations becomes imperative for decreasing oral trauma and optimizing oral health outcomes.

Owing to the varying degrees of pain or discomfort, OTUL may impede the oral health-dependent quality of life, cause difficulty in speaking or swallowing, and hinder oral hygiene. Prompt and accurate diagnosis is of utmost importance. Thorough medical history taking and physical examination are required. Considering the limited diagnostic utility of laboratory tests in trauma cases, it is imperative for clinicians to demonstrate considerable patience in the acquisition of pertinent diagnostic information. In particular, the sequence of trauma and lesions should be determined and the lesions need to be consistent with their traumatic origin. Nevertheless, it should be noted that, even if some patients, such as children and the elderly, fail to confirm a history of trauma, the diagnosis of a traumatic lesion cannot be easily ruled out. Dental clinicians should continuously improve the understanding of the clinical characteristics of oral traumatic lesions and corresponding traumatic factors. Once the causal relationship is established, proper management should focus on the elimination of the causative factor and then enhancing the healing of the ulcerative lesion [1]. If ulcerative lesions persist after the elimination of the suspected causative factor within a reasonable time limit (2–4 weeks), a biopsy should be considered to confirm the diagnosis [1, 2].

Given the inherent weaknesses of retrospective studies, several limitations of this study need to be highlighted. First, the data collected from medical records might not fully describe the traumatic factors in the oral cavity. The traumatic lesions of some patients may represent the synergistic effect of two or more factors [1]. Since the occlusal relationship was not routinely described in the medical records of our study, we believe that trauma stemming from malocclusion may have been underestimated or potentially overlooked. Second, potential influencing factors, such as educational background, family income, systemic disorders, psychological factors and daily habits were not assessed in this study due to insufficient information available in the medical records. For future studies on oral trauma, it is essential to take these factors into consideration for a more comprehensive analysis.