This study was based on a sample of several thousand TDIs (n = 4909) from 2758 patients. The distribution of these traumatic injuries was found to be similar to other studies [1, 3, 12]. Moreover, this retrospective and cross-sectional analysis of patients, presenting at a German center, first and foremost, revealed a considerable gender discrepancy. Males outnumbered female patients by a factor of 1.65 and this distribution held true even when based only on the deciduous teeth. Perhaps, unsurprisingly, TDIs are well known to vary with gender and age. With regard to gender distribution, Petti et al. reported in a meta-analysis a global prevalence ratio of 1.43 and also suggested a 34 to 52% higher likelihood for males to experience dental trauma [3]. In other studies, male predominance has been found to range from 1.5 to 2.5 times [13,14,15,16,17] due to their statistically greater involvement in contact sports, fighting, occupational hazards and car accidents [12, 17,18,19,20]. Eslamipour et al. reported the prevalence of dental trauma to the permanent incisors as being 24% in 9- to 14-year-old patients, where the prevalence in girls was 18.8% compared to the significantly higher rate of 29.9% in boys [2].

The present study shows a continuous age gradient, with the first decade of life predominating and a clear majority of all patients (66.1%) being under 20 years old when the accidents occurred. The injury types differed for the permanent vs. the deciduous teeth and, with regard to the likelihood of sequelae, this notably included the extraction of teeth. There was a strong tendency for TDIs to entail implant treatment, while follow-up examinations revealed an 89.8% rate of tooth survival and a 60.2% rate of sequelae.

Consistent with a Chilean study where luxation trauma accounted for 70.4% of injuries to the deciduous teeth [14], in the present study the PDLs were twelve times more numerous than the DHT injuries to this dentition (Table 3). It has been noted that minor periodontal injuries may be underreported by going clinically unnoticed or due to parents not seeking a dentist in the absence of distinct symptoms or bleeding [21,22,23,24,25]. In a Turkish study, periodontal injuries were shown to account for 84.7% of injuries to the deciduous teeth, regardless of age or gender [26]. In the present study, 18.9% of the injured deciduous teeth were removed due to periodontal injuries. A series of retrospective cohort studies (follow-up ≥ 1 year) identified pulp necrosis, pulp canal obliteration, premature tooth loss and root resorption as the main sequelae of deciduous tooth trauma within 1 year [27,28,29].

Unlike the injury types (PDL versus DHT), the injury subtypes did not differ very much among the permanent and deciduous teeth. Notable exceptions included concussions (35.4% vs. 14.5% of PDL injuries) and fractures confined to the enamel (22.1% vs. 41.8% of DHT injuries) as opposed to enamel–dentin injuries (49.1% vs. 20.0%). PDL injuries to the permanent teeth were mainly found to include concussion (35.4%), lateral luxation (27.4%) and subluxation (22.0%). Cases of avulsion accounted for 7.4%. Regarding all injuries (to both permanent and deciduous teeth), trauma to the enamel or enamel–dentin fractures without pulp involvement accounted for 60% (22.6% plus 48.4%, respectively) of the DHT injuries. Hence, the latter (48.4%) were by far the most frequent subtype of hard-tissue injuries overall. Reviews from around the world (Nigeria, India, Canada and Chile) concluded that dental trauma mainly occurred to the enamel (63.7 to 80%), followed by enamel–dentin fractures (15.9 to 17.2%) or as uncomplicated crown fractures (32.9%) and subluxation (31.7%) [14, 30,31,32], whereas in a Brazilian study of all age groups, periodontal injuries were identified as the main type of dentoalveolar trauma [15, 33].

As the major findings of the present study concern sequelae, it is useful to provide a brief discussion of the mechanisms. Notable examples of complications following dental trauma would be pulp necrosis, apical periodontitis, clinical crown discoloration, fistula formation or inflammatory resorption. DHT injuries may facilitate bacterial colonization, inflammation and necrosis of the pulp [34,35,36,37]. Pulp survival has been reported to be 95 to 98% for uncomplicated crown fractures but only 63 to 94% for complicated crown fractures, however, after timely and correct treatment, long-term vitality may realistically be expected [37, 38]. After root fractures, pulp survival has been found in 60 to 80% of cases [39,40,41,42] and necrosis to be closely associated with the severity of the neurovascular supply disruption [43]. Therefore, while pulp necrosis is an unlikely scenario following isolated crown fractures if properly treated [44, 45], combined injuries (e.g., crown fracture plus subluxation) would weaken the pulp defense [33, 44] and increase the risk of necrosis by affecting not only the apical neurovascular bundle but also the periodontal fibers [44,45,46]. PDL injuries, which accounted for the majority of cases in the present study, may cause various forms of root resorption. Pulp necrosis is significantly more likely to occur in dislocated teeth with fully developed roots [47,48,49] and has been reported, depending on the severity of the trauma, to affect 17 to 100% of dislocated teeth [48, 50]. PDL injuries of the lateral-luxation, avulsion or intrusion type will often entail more serious complications such as external or replacement resorption, with lateral luxation resulting in soft-tissue damage and fracture of the vestibular bone lamella. Within the cross-sectional subsample reported here, only 175 of the 569 previously injured permanent teeth (30.8%) neither had sequelae nor required treatment. Conversely, 58 injured teeth (10.2%) were lost by the time of the follow-up examination; almost half of these losses (48.3%) occurred following PDL injuries. Informed on-site behavior and making the correct initial treatment decisions are essential to a favorable prognosis of traumatically injured teeth, which, as has been pointed out previously [43], will always depend on the type of trauma sustained, the length of time from the point of the accident to the emergency treatment, and the quality of the treatment.

The treatment of a TDI may be considered successful once healing of the pulp and periodontal soft tissue has been accomplished and the tooth is asymptomatic, exhibiting vitality, and appropriately positioned. In addition, the tooth should exhibit normal clinical and radiographic characteristics including an intact height of the alveolar bone as well as properly sealed root structures, with the root growth either completed or continuing. It is also a fact, however, that dental trauma can always entail sequelae which may vary in nature and severity; these often do not become manifest until months or, indeed, years after the event. Hence, early detection is the key to preventing long-term consequences; this can only be attained by conscientiously implementing and motivating patients to attend periodic recall visits in order to meticulously conduct all the required follow-up examinations.

Valuable information on the prognosis of TDIs was collected during the analysis. However, certain limitations were present due to the study design. Compared to retrospective studies, prospective studies can often collect more profound data. However, collecting the necessary data in the context of the initial treatment is questionable from an ethical point of view and difficult to integrate into the treatment process.

The data evaluated were taken from patient records, trauma documentation forms, radiographs and photographs. The evaluated TDIs were primarily treated by 23 different dentists or oral surgeons. Some of these practitioners were at the beginning of their professional careers, while others had several years of experience. Consequently, the prognosis of the affected teeth would be related to the clinical experience and competence of the individual dentist as it was they who had made the primary therapeutic decision.

The different treatment concepts applied, which have changed over the years due to current recommendations, may mean that there is a limit to the validity of the results. The TDIs that occurred during the period of 8 years were reexamined. The longer, historically, that the TDI had occurred, the less likely the patient would present for a recall examination in this study. Some patients presented regularly for a follow-up examination so that the necessary treatments could be performed early. Other follow-up patients presented for the first time after their primary care or had intermediate checkups and treatments performed by their dentists.