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Prevalence of Dental Anomalies in Orthodontic Patients

Aim The aim of this retrospective study was to determine the frequency of hypodontia, hyperdontia, invagination, impaction, dilacerations, peg-shaped lateral incisors, taurodontism and short or blunt and narrow or pipette-shaped roots in Croatian orthodontic patients. Material and methods 506 orthopantomographs and study casts from 12-16 year-old orthodontic patients treated at the Department of Orthodontics, School of Dental Medicine University of Zagreb were analyzed. Results At least one dental anomaly was present in 24.1% of patients, and more than anomaly in 1.2% of them. The frequency was not significantly different between genders. Hypodontia was the most frequent anomaly with the incidence of 7.5%, followed by teeth impaction with the incidence of 6.3%. Conclusion The distribution and the prevalence of anomalies were similar to those described in the general Croatian population.


Introduction
Dental anomalies are abnormalities of teeth structure, form, number, location and size. They can be caused by genetic, systemic, traumatic and local factors (1). They are divided in genetic and acquired. Genetic and environmental factors cause dental anomalies mostly during histodifferentation and morphodifferentiation of teeth (2,3) They occur more frequently in the context of certain syndromes; e.g. their incidence is five times higher in patients with Down's syndrome than in the general population (4). The study of Jukić et al (5) showed that hypodontia is significantly more frequent in children with developmental disturbances than in healthy children. Oral-facial-digital syndrome 1 (OFDS1) is related to hyperdontia, hypodontia and peg-shaped lateral incisors (6,7).
Dental anomalies are most frequently diagnosed by clinical examinations and panoramic radiographs (8). Recently, cone beam computerized tomography (CBCT) has been used more frequently. This technique is, because of its ability to generate three-dimensional representations, more precise, especially in overlapping structures (9). A disadvantage of CBCT is an exposure of the patient to relatively high doses of radiation, even more important because of the fact that children constitute the majority of patients with dental anomalies. Magnetic resonance imaging (MRI) is an alter-native, producing three-dimensional representation of structures, without the use of ionizing radiation (10).
Dental anomalies can lead to abnormal positioning of other teeth in the dental arch. Fixed orthodontic appliances are most frequently used to treat patients with hypodontia (11), because the precise and controlled tooth movements are needed (12) In patients with hyperdontia, especially in mesiodens cases, which can be functional as well as esthetical problems (13), extraction therapy followed by fixed orthodontic appliance is often indicated. Therapeutic options for treating dental anomalies include implantoprosthetic replacements (14), dental bridges and orthodontic tractions; in cases in which the anomaly is neither a functional nor an aesthetic problem, treatment is occasionally not needed (11).
Dental anomalies could result in changed length of the maxilla and mandible resulting in occlusal disturbances which complicate and prolong orthodontic therapy (15). The frequency of impaction in patients with orthodontic anomalies Class II division1 as well as short or blunt roots in patients with anomalies Class II division 2 is increased compared to eugnathic patients (16).
Understanding the influence of dentofacial genetics on the diagnosis and planning of orthodontic treatment has become an integral part of modern dental care (17). This study focused on the prevalence of dental anomalies in a sample of orthodontic patients in Croatian population.

Material and methods
This study was performed on a sample of 506 orthopantomographs and study casts of orthodontic patients obtained from the archives of the Department of Orthodontics at School of Dental Medicine University of Zagreb. Inclusion criteria were: 1. No history of permanent teeth extraction before the start of orthodontic treatment 2. No history of endodontic therapy or tooth trauma before the start of orthodontic treatment 3. Orthopantomograms were obtained by standardized method using the same X-ray device (Siemens, Orthopos, average voltage 69 kV, constant current strength of 16 mA/s and time of exposition of 16 s).
The study was performed on a sample of 12-16 year-old children with permanent dentition. Based on orthopantomograms and study casts the following teeth anomalies were studied: hypodontia, hyperdontia, invagination, impaction, dilacerations, the presence of peg-shaped lateral incisors, short or blunt roots, thin or pipette-shaped roots and taurodontism. Data were collected and analyzed regarding the incidence, sex, distribution and type of teeth affected by the anomaly. Statistical analysis was performed using the STA-TISTICA 9.1 program. The research procedures were carried out following the decision of the Ethics Committee of the School of Dental Medicine University of Zagreb. Participation in the research was voluntary, whereas the participants were guaranteed anonymity and confidentiality.

Results
Out of a total of the 506 studied orthopantomographs and study casts, 278 (54.9%) of them were female and 228 (45.1% ) of male patients. There were no statistically significant differences in the frequency of studied anomalies between sexes (p>0.05), hence further statistical analysis could be performed. The results are presented in Figure 1.

Rezultati
Od pregledanih 506 ortopantomograma i modela čeljusti, 278 (54,9 %) bilo je od pacijentica, a 228 (45,1 %) od pacijenata. Od 506 ispitanika, kod njih 122 (24,1 %) zabilježena je barem jedna anomalija. Između spolova nije bilo statistički značajne razlike u učestalosti ispitivanih anomalija. Rezultati istraživanja prikazani su na slici 1.   At least one anomaly was found in 122 (24.1%) patients. In 6 (1.2 %) cases, more than 1 anomaly was noted. Five anomalies were combinations of hypodontia with another anomaly. In two cases, hypodontia coexisted with pegshaped lateral incisors and taurodontism, and in one it coexisted with short or blunt roots. Impaction coexisted with thin or pipette-shaped roots in one patient. Hypodontia of the left upper lateral incisor was most frequent (24%), followed by the left lower second premolar (21%), right upper lateral incisor (18%) and left and right upper premolar (16% and 13% of cases) (Tables 1 & 2). In 30 patients (79%), hypodontia was present on only one tooth, and in 8 (21%) in more than one teeth. Mesiodens was found in three patients (60%) and an additional tooth was found in the molar area in two patients (40%). Invagination occurred most frequently on the upper lateral incisors (4 patients), single, or in combination with other teeth. It occurred on one tooth in six patients (75%), and on more than one in two patients (25%). In all cases, invagination occurred in the upper jaw. Impaction most frequently affected the upper right canine (15 patients), and the upper left canine (11 patients). One tooth was affected in 23 (72%), and more than one in 9 patients (28%). It occurred much more frequently in the upper than lower jaw (23 vs. 8 patients); in one patient (3%), both, the upper and lower jaw, were affected. Dilaceration occurred on the right upper lateral incisor in 3 (30%), and on the right upper central incisor and right upper second premolar in 2 patients (20%) each. In all 10 patients, dilacerations occurred on only one tooth, in 8 patients it occurred in the upper and in 2 patients in the lower jaw. Peg-shaped lateral incisors occurred on one side in 7 (64%), and on both sides in 4 patients (36%); on the left side in 9 patients, and on the right side in 6 patients. Short and blunt roots occurred most frequently on upper median and upper lateral incisors; on one tooth in 2 patients (20%), and on more than one in 8patients (80%). Maxillary teeth were affected in all cases. Thin or pipette-shaped roots were found in 9 patients, most frequently on lower incisors (67%). In 5 patients, they were present on one (56%), and in 4 patients on more than one tooth (44%). They were located in the lower jaw in eight patients (89%), and in the upper jaw in one patient (11%). Taurodontism was noted in six patients. It occurred most frequently on the first upper right molar, in 4patients (67%) on single tooth or in combination with other teeth. Taurodontism was noted on one tooth in 5 patients (83%), and on more than one in one patient (17%). It occurred in the upper jaw in 4 patients (67%), and in the lower in 2 patients (33%).

Rasprava
Dosad objavljeni radovi znatno se razlikuju kad je riječ o učestalosti dentalnih anomalija. Tako je u istraživanju Altuga Ataca i Erdema (18) (11) with 28.4 %. The latter result is very similar to ours; we found at least one dental anomaly in 24.1% of patients. The reason for such big differences is not completely clear; they might result from real differences in frequency of dental anomalies in different races and populations, but also from differences in indications for orthodontic treatment or diagnostic procedures and criteria for diagnosing dental anomalies. All other studies obtained the results very similar to ours. They failed to find differences in dental anomalies between sexes (21). Only in the study of Thongudomporn et al. were invagination and short or blunt roots somewhat more prevalent in females (19). Hypodontia was the most frequent anomaly in our study, followed by teeth impaction. These two anomalies were also most frequent in all other published studies. Apart from third molars, which were excluded from due to their variability, lateral incisors and second premolars were most frequently missing teeth. This finding is in agreement with Bolk's theory of terminal reduction according to which, in cases of hypodontia of up to 4 teeth, last teeth in a group are most frequently missing: lateral incisors, second premolars and third molars (22). This finding is explained by the fact that embryonal joining of the maxilla with the medial nasal process occurs in the area of maxillary lateral incisors, while mandibular second premolars are located on the genetically unstable area at the end of the dental lamina (23). Hypodontia is usually treated with orthodontic therapy, prosthetic appliance or multidisciplinary -by combining orthodontics and prosthetics (24). Impacted teeth were the second most frequently found anomaly. Likewise, they were most frequent anomaly in studies by Sella Tunis (25), Roslan (11) and Lagan (26). The frequency of patients with impaction in the study of Prskalo et al. (27) -4.71%, performed on the general Croatian population, was very similar to our results. Peg-shaped lateral incisors are by definition the teeth that have the mesio-distal diameter in the incisal part bigger than that in the cervical part (28). The frequency of this anomaly in our study corresponds to published results in orthodontic patients: 1.9% -2.7 % (29). It seems that this anomaly is more frequent in patients of Asian ancestry and least frequent in the USA Caucasian population (29). The frequency of dilacerations, defined as deviations of the linear relationship of the crown relative to the root (30), was in our study as expected higher than in the study of Malčić et al. (31) performed on the general Croatian population (1.2%). Dilaceration was most frequent anomaly in the study of Ezoddini et al. on the Iranian population -even 15% (32). Approximation of root length is an indispensable part of prosthetic, orthodontic and periodontal therapy. Root length anomalies are thought to be caused by trauma to the area of affected teeth during their development (33). Root morphology abnormalities increase the probability of its resorption during orthodontic therapy (34). The incidence of short and blunt roots varies from 2.7% in Caucasian (35) even to 10 % in Asian (36). Our results are similar to the results of the studies that obtained 2%. Tooth invagination is an anomaly in which one tooth develops in- (19)  Ovaj posljednji rezultat vrlo je sličan našemu -mi smo našli barem jednu dentalnu anomaliju kod 122 od 506 ispitanika (24,1 %). Razlozi za tako velike razlike nisu posve jasni, možda su posljedica stvarne razlike u učestalosti dentalnih anomalija kod pripadnika različitih rasa ili populacija, ali i razlika u indikacijama za upućivanje na ortodontsko liječenje ili u dijagnostičkim postupcima i kriterijima za dijagnozu dentalnih anomalija. Kao ni u našoj, tako ni u jednoj drugoj studiji nije zabilježena razliku u sveukupnoj učestalosti dentalnih anomalija između spolova (21). Jedino je u studiji Thongudomporna i suradnika istaknuto da su invaginacija i kratki i tupi korijeni nešto češći kod žena Na ispitivanom uzorku najčešća je anomalija bila hipodoncija, a slijedi impakcija. Te dvije anomalije bile su najčešće i u svim ostalim istraživanjima. Osim trećih molara, koje smo zbog varijabilnosti pojave izostavili iz istraživanja, najčešće su nedostajali lateralni sjekutići i drugi pretkutnjaci. Taj se nalaz uklapa u Bolkovu teoriju terminalne redukcije u kojoj su, u slučaju hipodoncije četiri ili manje zuba, zubi koji nedostaju uglavnom oni zadnji u skupini: lateralni sjekutići, drugi premolari i treći kutnjaci (22). To se objašnjava činjenicom da se u području maksilarnih lateralnih sjekutića događa embrionalno spajanje maksile s medijalnim nosnim nastavkom, a mandibularni drugi molari nalaze se na genetski nestabilnom području kraja dentalne lamine (23). Hipodoncija se obično liječi ortodontskom terapijom, protetičkim nadomjestkom ili multidisciplinarno -kombinacijom ortodoncije i protetike (24). Impaktirani zubi kod nas su bili druga najčešća anomalija, a u istraživanjima Sella Tunisa (25), Roslana (11) te Lagana (26) najučestalija. U istraživanju Prskalo i suradnika (27) u hrvatskoj općoj populaciji nađen je vrlo sličan udio pacijenata s impakcijom kao i u ovom istraživanju -4,1 %. Pandžasti konični lateralni sjekutić onaj je kod kojega je meziodistalni promjer u incizalnom dijelu veći nego u cervikalnome (28). Rezultati našeg istraživanja o udjelu pacijenata s tom anomalijom uklapaju se u raspon rezultata dosadašnjih studija na ortodontskim pacijentima koji iznosi između 1,9 % i 2,7 % (29). Uočeno je da se ta anomalija češće pojavljuje kod pacijenata žute rase, a najrjeđa je kod bijelaca u SAD-u (29). Učestalost dilaceracije, definirane kao odstupanje linearnoga odnosa krune prema korijenu (30), u našem je istraživanju očekivano nešto veća nego u istraživanju Malčić i suradnika (31) provedenom na hrvatskoj općoj populaciji u kojoj iznosi 1,2 %. Najveća učestalost pacijenata s dilaceracijom zabilježena je među iranskom populacijom u istraživanju Ezoddinia i suradnika (32) -čak 15 %. Procjena dužine korijena neizostavan je dio protetičke, ortodontske i parodontološke terapije. Pretpostavlja se da je uzrok anomalijama u dužini korijena trauma u području zuba tijekom njegova razvoja (33). Abnormalnosti morfologije korijena povećavaju vjerojatnost njegove resorpcije tijekom ortodontske terapije (34). Učestalost kratkih i tupih korijena varira od 2,7 % kod bijelaca (35) do čak 10 % kod pripadnika žute rase (36). U skladu s tim su i naši rezultati (2 %). Invaginacija zuba anomalija je u kojoj se jedan zub razvija u drugome. Smatra se da nastaje zbog prodiranja side another. It is thought to result from penetration of one enamel organ of one tooth into the area of dental pulp of another (37). Teeth affected by this anomaly have a higher risk of developing caries and dental pulp diseases, and their endodontic treatment is difficult because of atypical morphology of their root channels (38). The prevalence of permanent teeth affected by this anomaly is between 0.3% and 10%; our findings are consistent with such results. Taurodontism is a morphologic anomaly of teeth characterized by apicoocclusal prolongation of the tooth crown and pulp chamber with shortened roots. It is most frequently an incidental finding discovered during X-ray evaluation, because teeth appear to be the same as normal (39). The prevalence of this anomaly is highest in Inuits, persons with Down's syndrome and the Central European population (40,41). The larger pulp chamber increases the risk of pulp exposure during therapeutic procedures, thus making planning of orthodontic and prosthetic therapies difficult (42). The prevalence of taurodontism was 1.2% in our patients, similar to findings of the study by Brkić et al. (43) on the general Croatian population (2.65%) and Blumberg et al (44) and Witkop et al (45) on American Caucasians (2.5 and 2.6%). Hyperdontia is defined as an increase in the number of teeth in dental arches. Most frequently, the additional tooth is located between maxillary incisors and called mesiodens (46). If the additional tooth is next to premolars, it is called a parapremolar, and if it is located distally from the third molar, a distomolar (47). If the additional tooth resembles morphologically its normal counterparts, it is called a supplementary tooth, and if it does not, it is called an atypical or accessory tooth (48). Mesiodens is not always clinically visible. It can be impacted and cause diastema between incisors, thus making orthodontic therapy more complicated (49). Similar to our results, some previously published studies reported the prevalence of hyperdontia between 0.2% and 3% (50).

Conclusion
The results of our study on dental anomalies in Croatian orthodontic patients suggest: 24.1% of patients had at least one examined anomaly; Hypodontia was the most frequent anomaly, followed by teeth impaction. The prevalence of investigated dental anomalies was not significantly different between males and females; 1.2% of patients had more than one anomaly. The prevalence of most frequent dental anomalies in orthodontic patients is similar to that in the general population.