Tooth Retention: Analysis of Prevalence Among Patients Receiving Orthodontic Treatment

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Introduction

Tooth eruption is a complex process that can be условно divided into two stages. The first stage involves intraosseous movement of the tooth from the bony crypt to the corresponding site in the dental arch [1]. During this stage, an interaction occurs between the dental follicle and bone structures, triggering bone resorption — this allows the tooth to occupy its proper position by the time two‑thirds of its root has formed. The second stage consists of the tooth erupting through the gingiva into the oral cavity [2]. A tooth is considered impacted if its crown remains embedded in the bone beyond the physiological eruption time, with no communication between the periodontium and the oral cavity [3].

The problem of impacted permanent teeth is among the most common anomalies encountered in dental practice. According to experts, tooth impaction is a multifactorial phenomenon caused by certain local or systemic factors. The main etiological factors include: abnormal position of impacted teeth within the jawbone; abnormalities in tooth shape and size; ankylosis; presence of supernumerary teeth; odontomas or other obstacles along the eruption path of a regular tooth; insufficient space in the dental arch; premature extraction of primary teeth with partial or complete closure of the post‑extraction space [5, 6, 7].

Ectopic positioning of tooth germs — frequently observed in maxillary canines and first permanent molars — is a significant factor contributing to impaction. This condition is often due to genetic predisposition, abnormal tooth morphology, or insufficient length of the dental arch [8].

Multiple tooth impactions are relatively rare anomalies. According to literature, systemic diseases play a leading role in generalized impaction, including: endocrine disorders (hypothyroidism, endemic goiter, pseudohypoparathyroidism, idiopathic hypoparathyroidism, Froehlich’s disease, cerebral‑pituitary dwarfism); infectious and inflammatory diseases [9, 10].

Analysis of both domestic and international studies shows that permanent tooth impaction is quite common in dental practice, with prevalence rates ranging from 2.9 % to 13.7 %. There is considerable heterogeneity in prevalence across different populations and geographic regions [11, 12].

Most frequently impacted teeth include third molars, canines, premolars, and central incisors. Existing scientific literature primarily focuses on maxillary canine impaction, though most studies have relatively small sample sizes and lack comprehensive analysis of other tooth groups. Nevertheless, available data indicate significant variability in permanent tooth impaction rates [13, 14].

Aim of the study
To analyze the prevalence of eruption anomalies in the maxilla and mandible among patients, and to determine the significance of local etiological factors in orthodontic patients during the period 2020–2025.

Materials and Methods

The study was conducted at clinical bases of the Department of Pediatric Dentistry and Orthodontics, Samara State Medical University. It involved a retrospective evaluation of archival data from 3 905 patients aged 18–29 years who sought dental care between 2020 and 2 Newton. Patient histories, orthopantomograms, and diagnostic models were reviewed. From the total sample, a representative group of 717 patients with diagnosed tooth impaction was formed.

Inclusion criteria:

age 18–29 years (permanent dentition, no primary teeth); no prior orthodontic treatment; absence of congenital maxillofacial anomalies; no systemic medical conditions; written consent; availability of orthopantomogram, lateral teleroentgenogram, and diagnostic plaster models of jaws.

Exclusion criteria:

patients younger than 18 or older than 29; prior extraction of permanent teeth; history of orthodontic treatment;congenital maxillofacial anomalies; systemic medical conditions;lack of informed consent; insufficient or missing diagnostic materials.

To determine causes of impaction, we analyzed the following potential etiological factors: ankylosis; premature tooth extraction with partial or complete closure of post‑extraction space; supernumerary teeth; odontogenic tumors; traumatic injuries; ectopic eruption path; cases with unidentified etiology.

Third molar impaction was excluded from this study.

Statistical analysis was performed using the «Statistica» software package (StatSoft).

Results and Discussion

A retrospective review of medical records of 3 905 patients was conducted. Among the 717 included in the study, 360 (50.21 %) were women with a mean age of 21.93 ± 4.08, and 357 (49.79 %) were men with a mean age of 22.77 ± 4.32. During the study, each patient was found to have at least one impacted tooth based on their medical history, radiographs, and diagnostic models. The total number of impaction cases in the sample was 782. The overall percentage of permanent tooth impaction in the study group was 20.03 %.

The distribution of tooth impaction prevalence on the maxilla and mandible relative to gender and age, according to the retrospective analysis, is systematized and presented in Tables 1, 2, 3, 4. These tables illustrate the results concerning the frequency of impaction on the maxilla and mandible, as well as the percentage of each tooth type relative to the studied jaw and to the total number of impacted teeth.

Table 1. Frequency of maxillary tooth impaction in women stratified by age.

Table 2. Frequency of mandibular tooth impaction in females stratified by age.

Table 3. Frequency of maxillary tooth impaction in males stratified by age.

Table 4. Frequency of mandibular tooth impaction in males stratified by age.

During clinical examination and analysis of orthopantomograms in 717 patients, 782 impacted teeth were identified, of which 514 (65.73 %) were located in the maxilla and 268 (34.27 %) in the mandible. According to the tables, maxillary canines are the most frequently impacted teeth in the maxilla: their frequency is 17.52 % in women and 15.47 % in men. Premolar impaction in the maxilla is observed in 12.92 % of women and 14.69 % of men. In the mandible, premolars are the most common impacted teeth, occurring in 11.25 % of men and 10.49 % of women.

Regarding second molars in the mandible, their impaction is significantly higher, amounting to 5.88 % in men and 4.47 % in women. Impacted incisors in the maxilla occur in 1.54 % of women and 2.05 % of men; in the mandible this percentage is lower — 0.64 % in women and 0.38 % in men. The prevalence of canine impaction in the mandible is 0.64 % in women and 0.51 % in men.

The study found more than one impaction per patient in 32 cases. Among these: 11 cases had bilateral maxillary canine impaction; 7 cases had bilateral maxillary premolar impaction; 6 cases had bilateral mandibular premolar impaction; 3 cases had combined maxillary canine and premolar impaction; 2 cases had bilateral canine and second molar impaction; 1 case had bilateral mandibular second molar impaction.

Additionally, cases of incisor and canine impaction, as well as combined impaction of two molars and a second mandibular premolar, were recorded.

Analysis of the topography of retention also demonstrates significant differences. In Gasyumova's study, canines were the most frequently retained teeth in the upper jaw (2.29–2.44%), while second premolars (1.85–2.20%) and third molars (2.27–2.50%) were the most common in the lower jaw. In our study, where third molars were not included, canine retention in the upper jaw was 15.47% in men and 17.52% in women, while retention of premolars was found at 12.92% to 14.69%. In the absence of third molars in the lower jaw, premolar retention was noted at higher rates (11.25% in men, 10.49% in women), and second molars were recorded less frequently (5.88% in men, 4.47% in women).

In a study involving 14,774 orthodontic patients from 10 university dental clinics in Korea (2020–2022), the overall prevalence of retained teeth (excluding third molars) was found to be 13.6% (2,014 cases), with 24.5% (1,614 cases) among child patients. The most frequently diagnosed retained tooth was the upper canine (50.1%), followed by the lower second molar (11.7%) and the upper second premolar (9.6%). These data correlate with findings indicating that retention of upper jaw canines is the most common; however, our study shows a significantly higher frequency of retention of premolars in the upper jaw (12.92% in women and 14.69% in men).

Analyzing the results of a Greek study (1,400 patients, Siotou et al., 2022) alongside our data (717 patients) reveals several key observations. Both studies noted a predominance of retention in the upper jaw: 71.52% in the Greek sample and 65.73% in ours. The frequency of upper jaw canine retention was also similar—32.28% in Greece and about 33% in our findings.

However, the overall prevalence of retention differs significantly: in the Greek population, 15.14% of patients had at least one case of retention, whereas in our sample, each patient had, on average, more than one retained tooth (782 cases among 717 individuals).

A difference in the frequency of retention in the lower jaw should also be noted. In the Greek study, second molars and premolars were observed with almost equal frequency (11.39% and 11.08%, respectively), while in our data, premolars predominated (11.25% in men and 10.49% in women), with molars being less common (5.88% in men).

Thus, the results of this study confirm the importance of further analysis of the causes of tooth retention. In this context, a retrospective study led to the analysis of the etiological factors of permanent tooth retention, the results of which are organized in Table 5, reflecting the frequency of local causes contributing to the formation of tooth retention.

Table 5. Frequency of local etiological factors contributing to the retention of permanent teeth.

The analysis of etiological factors revealed their heterogeneous prevalence and specific impact on different tooth groups:

The analysis of the etiological factors of tooth retention revealed their heterogeneous distribution and specificity of impact on various tooth groups. The most significant factor was the premature extraction of primary teeth, accounting for 39.13% (n = 306), primarily influencing the retention of canines and premolars in the upper jaw, highlighting the necessity of installing orthodontic rings to maintain space in the dental arch or orthopaedic rehabilitation. Ectopic pathways of eruption were recorded in 27.88% (n = 218), predominantly affecting upper jaw canines and second molars in both jaws. Ankylosis was comparatively less frequently registered (5.63%, n = 44), and supernumerary teeth were found in 2.43% (n = 19), mainly localized in the frontal segment of the upper jaw, contributing to the retention of central incisors. Odontogenic tumors (2.56%, n = 20) were usually identified in the lateral sections of the jaws, as well as traumatic injuries (4.22%, n = 33) primarily affecting upper jaw incisors. The group of cases with unidentified etiologies of retention comprised 144 observations (18.41% of the total). It is noteworthy that in the complete absence of identifiable causative factors (such as injuries, ankylosis, supernumerary teeth, etc.), this group showed a clear topographical selectivity: predominantly affecting the incisors and canines of the lower jaw, demonstrating the need for further research into the pathogenesis.

Conclusion

Based on the conducted research, it can be concluded that the retention of permanent teeth represents a significant clinical problem in modern dentistry, characterized by a multifactorial nature of occurrence and substantial variability in manifestations.

The analysis of archival data from 3,905 patients, with the formation of a representative group of 717 individuals aged 18 to 29 years, established that the prevalence of retention in the studied group was 20.03%. The most commonly observed cases were retention of upper jaw canines (17.52% in women and 15.47% in men), upper jaw premolars (12.92% in women and 14.69% in men), and lower jaw premolars (11.25% in men and 10.49% in women). Moreover, an increase in the frequency of premolar retention was noted compared to previous studies.

The analysis of etiological factors confirmed that the premature extraction of primary teeth is the primary cause of retention formation. This underscores the necessity to implement preventive measures such as the installation of orthodontic rings to maintain space in the dental arch and orthopedic rehabilitation. Additionally, the prevention of caries in primary teeth is crucial, as it significantly reduces the likelihood of their premature extraction.

Furthermore, the identified differences in the frequency of retention between men and women, as well as the variety of accompanying etiological factors, including ankylosis, the presence of supernumerary teeth, and trauma, indicate the need for further research to gain a detailed understanding of the pathogenesis of this condition.

The results of this study highlight the importance of early diagnosis and a comprehensive approach to the treatment of retained teeth. This can significantly improve the quality of dental care and reduce the complications associated with eruption anomalies.

About the authors

Irina Shchukina

Samara State Medical University

Author for correspondence.
Email: i.ju.schukina@samsmu.ru
ORCID iD: 0009-0003-7299-8340

Ассистент кафедры стоматологии детского возраста и ортодонтии

Russian Federation

Nikolai Vladimirovich Popov

Email: studmfc@samsmu.ru

Ekaterina Aleksandrovna Ishchenko

Email: kateishch@gmail.com

References

Supplementary files