A comparative retrospective study on the prevalence and therapeutic treatment of dental agenesis between healthy children and children with systemic disease or congenital malformation

In the present study, a selected patient population was examined in the period from January 2015 to December 2020. Thus, a period of six years was considered, enabling a comparison with similar studies in the literature [9, 13].

The American Dental Association [14] has established guidelines for radiographs, recommending panoramic radiographs to ensure the growth and development of dentofacial structures. Based on these considerations, the present study was limited to existing panoramic radiographs. The justifying indications for this included the assessment of tooth development or tooth germs, tooth malpositions, structural disorders of the tooth structure, or trauma. Thus, no new radiological findings were made, which would have entailed additional radiation exposure for the patients and would not have been ethically justified. Assessment of missing teeth in the permanent dentition could be retrospectively misdiagnosed if teeth were lost due to caries, trauma, or extraction caused by an orthodontic indication. These possible sources of error could be reduced by using several panoramic radiographs over a period of time along with clinical photographs.

Based on the data collected at a dental clinic, it is possible that the study sample features more missing permanent tooth structures or teeth than the general population. There is also a potential tendency for a higher percentage of oligodontia and anodontia due to the patient population attending a university dental facility. The study population may also be somewhat skewed because dentists in private practice often refer patients with complex cases to the university for care. However, the panoramic shift sample included over 60% of children not taking any medication, suggesting that referrals were due to children’s behavioural problems rather than the complexity of the dental procedures.

A strength of this study was the availability of up-to-date panoramic radiographs. The sample size provided an adequate representation of the patient population at the Department of Paediatric Dentistry. In most cases, parents with children suffering from systemic disease or a congenital malformation visit a highly specialised dental clinic or are referred directly by the general dental practice. The close cooperation with the in-house polyclinic for orthodontics additionally facilitated the documentation of therapy approaches.

Within the patient population, 12.9% were found to suffer from DA. Depending on the study design and population group, a prevalence range of 1.6–12.6% has been described in the literature [9, 13]. Thus, our results are slightly higher than the upper range in previous literature. The wide range in the prevalence of non-congenital cases could be attributed to differences in sampling methods and sample size, as well as variations in origin [15]. In addition, most studies excluded children and adolescents with general diseases. The available data from healthy patients with missing teeth showed a frequency of 9.7%, which is in agreement with other authors [13, 16].

In addition, some authors do not present the severity of missing teeth and thus hypodontia, oligodontia, and anodontia are not differentiated more precisely [16]. With regard to the subdivision of the severity of DA, our study was consistent with a previous study by Behr et al. [9] that reported 12% hypodontia and 2% oligodontia in children at a University Hospital (our results were 10.5% hypodontia, 2.1% oligodontia, and 0.1% anodontia). In comparison, children with systemic diseases more often presented missing teeth in the form of hypodontia (15.9%), oligodontia (3.7%), or anodontia (0.3%). Due to the scarcity of studies on children with systemic diseases, no comparison can be made.

Looking at the different patient groups, patients with ectodermal dysplasia (6 out of 6 patients), Down syndrome (11 out of 14 patients), or cleft lip and palate (6 out of 8 patients) showed more missing teeth. ED, in particular, was associated with oligodontia (83.3%) or anodontia (16.7%), as confirmed by other studies showing an association of these diseases with hypodontia [17, 18]. Patients with DS commonly suffer from congenital heart defects. Reuland-Bosma et al. [19] also found that congenital heart defects and hypothyroidism in children with DS are parameters for DA.

One limitation here is that no calibration took place due to the retrospective data collection. However, since the practitioners underwent the same training in their studies, as well as postgraduate training at the department, this factor is likely negligible.

Our results showed that agenesis of the second lower premolars was most common, followed by agenesis of the upper lateral incisors, upper second premolars, and lower central incisors. Most previous studies have confirmed these results [15, 20]. In a sample of 5127 patients, agenesis of the maxillary lateral incisors occurred with a frequency of 2.2% and agenesis of the second premolar with a frequency of 3.4% [21]. In turn, other authors highlighted the maxillary lateral incisor as the most frequently affected tooth [22]. It was also observed that the terminal tooth in a row of teeth (incisors, premolars, and molars) is the most frequently missing [23]. In the evolutionary process, these teeth did not provide a selective advantage to the species and were, therefore, lost [24]. Kaer [25] described the location of tooth agenesis based on neural developmental fields in the jaw (incisor field, canine/premolar, and molar field). The region within a single field where innervation occurs last was more likely to show DA. However, these data were limited to children and adolescents without general diseases.

Among patients with DS, primarily the second upper incisors were absent in the present study. This was also confirmed through a meta-analysis by Palaska et al. [17], who investigated the frequency of missing teeth in children with DS. Russel et al. [26] also reported that children with DS were ten times more likely to suffer from missing teeth compared to healthy children.

ED showed a relatively even distribution of affected missing teeth. However, due to the rarity of ED, the number of cases was not very large and involved only six patients. A comparison with the literature is also difficult because there are few studies on the missing teeth patterns of affected children; mostly, such studies are individual case reports.

Patients with CLP were affected by agenesis of the incisors and premolars in both the maxilla and mandible. Again, the case number of six patients is very small and should be confirmed by further studies. Due to the cleft formation in the upper jaw, malformations and missing teeth can certainly occur in regions of the incisors [27].

As in the patients without SD/CM, the lower second premolar was the most frequently found missing in developmentally delayed patients, followed by the second upper premolar. Currently, there are no studies reporting missing teeth in children with developmental delays.

Therapeutic approaches are described in the literature mainly from an orthodontic perspective. Therefore, a comparison with paediatric dentistry is hardly possible. Our results clarified that affected patients are not exclusively treated in orthodontic practice but that therapeutic measures in paediatric dentistry are also important. Among the total patient population, 71.9% underwent therapy through paediatric dentistry. The present study, therefore, focused on the care measures of paediatric dentistry for DA. Due to the age, no therapy for definitive prosthetic measures or implant therapy could be considered.

For up to 37.7% of the affected patients, no orthodontic therapy was possible. In healthy patients, only 4% could not be treated with orthodontics. Many children with general illness have cognitive limitations, and the resulting lack of cooperation makes chairside treatment and thus orthodontic therapy impossible. Therefore, mainly children with DS were affected by the therapeutic decision of “no treatment”. The mental abilities of people with DS vary widely. Thus, the literature contains rare information about the prosthetic rehabilitation of patients with DS and tends to consist of individual case reports [28]. In addition, the patient’s cooperation may be reduced and there may be an increased risk of root resorption during orthodontic therapy [29]. Early involvement of patients in dental care with DS/ID could possibly lead to achieving habituation and cooperation for necessary dental therapy and in addition, in order to achieve a fast and therapeutically satisfactory treatment result orthodontic treatment should be carried out simple and realistic.

The types of restorations in paediatric dentistry were mainly a decision between “primary tooth preservation” and “primary tooth extraction” in diseased children. More complex types of restoration, such as cantilever resin-bonded fixed dental prostheses, were performed exclusively in healthy patients. Only children with ED could be fitted with paediatric dentures. This result is also related to the young age of the children presented firstly with an average of 4.9 years. Due to the multiple DA, functional and esthetic rehabilitation should be performed early and in appropriate cooperation, which is only possible through the use of paediatric dentures which is why these results of therapy seem unsurprising. The prosthetic rehabilitation of these patients with paediatric prostheses was confirmed by individual case reports [30, 31]. The limitations mentioned above also apply here, as the known distribution patterns of non-unions in, e.g., ectodermal dysplasia may have led to a distortion of the therapeutic approaches.