Study of the risk factors associated with the development of malocclusion

Background/Aim. Research of the most common causes of irregularities of jaws and teeth is designed in order to find the most efficient mode of their prevention. Frequency of orthodontic malformations (malocclusions) is as high as 60% to 80% in this region with an increasing tendency. Researching the risk factors for orofacial irregularities is designed with the purpose of creating a standardized methodology for risk evaluation, frequency and degree of orthodontic irregularities of face, jaws and teeth. The aim of the study was to identify and analyze the causal factors that lead to forming malocclusions in patients from the Province of Vojvodina and create a uniform methodology for epidemiological research. Methods. The research included 127 patients from the current casuistics of the Vojvodina Stomatology Clinic – Department for Jaw Orthopedics. Data for Questionnaire for Epidemiological Surveillance were obtained from medical records of patients, heteroanamnesis, objective findings, functional analysis of stomatognathic system, and additional diagnostic methods. Results. The average number of the risk factors was 2.59 per patient, of which 56% were morphological factors, and 44% functional. Acquired risk factors made up 61% of the total number, while congenital risk factors made up 39%, of which 15% were hereditary and 24% were nonhereditary. Conclusion. Implementing the Questionnaire for Epidemiological Surveillance, general distribution of anomalies could be presented by the Anomaly index (AI), which dictates the introduction of a standardized questionnaire for epidemiological screening, which would preclude ambiguousness and the differences between the epidemiological research data would be cut to the minimum.


Introduction
Orofacial irregularities, in addition to dental caries and periodontal desease, are becoming more present both in children and adults, and present a significant percentage of dis-eases of the orofacial region, and thus a special medical and socioeconomic problem.
Precise data on the prevalence of these irregularities do not exist, and in our region the percentage of these irregularities range between 60% and 80% and have a tendency of Petrovi Dj, et al.Vojnosanit Pregl 2013; 70 (9): 817-823.further growth.In modern societies the prevalence of malocclusions ranges between 40% and 80%, and in the Nordic countries 43% to 79%, with the need for treatment between 30% and 75% [1][2][3][4] .
As it is impossible to include all the affected by treatment, the solution is in the prevention of developmental disorders of the orofacial structures through daily practice.Orthodontists, in addition to treatment, are dealing with epidemiology and prevention of orthodontic anomalies, but not enough, and there is poor cooperation with other preventive care providers.
According to the American epidemiological study in 1991 class II malocclusion is the most widespread orthodontic anomaly among the North American population.The results of this study showed that class II malocclusion prevalence declines with age.This irregularity is present 25%-30% in the mixed dentition, 20%-25% in early permanent dentition, while in adults its presence is reduced to 15%-20% 5 .Epidemiological surveys carried out in Western and Northern Europe demonstrate a similar prevalence of distal bite in European populations [6][7][8] .Caucausians in South Africa show a similar representation of class II as does the European population 9 .The prevalence of class II malocclusion was significantly lower in Arab (10%-15%) and Hispanic population (10%-15%), while it was least present in subjects of African-American origin (0%-2%) [10][11][12][13][14][15] .
Upon formation of the National program of preventive dental care, based on the methodology of the World Health Organization (WHO), the study results showed that in our country at the age of 6 between 12% and 32% of children have an orthodontic anomaly, at the age of 12 between 36% and 64 %, and at the age of 15 38% to 60%.Since the WHO form is general, and does not include all the specific disorders of growth and development, in line with our previous findings, we can conclude that the occurrence of orthodontic anomalies in our country is even greater than this type of questionnaire can determine [16][17][18] .
Etiological factors that may lead to irregularities in the face, jaws and teeth can be differently divided and classified, and depending on the author, there are different classifications.It is particularly important to note that there are a number of different etiological factors that may cause disruption of normal growth and development of the orofacial region.They may be biological, chemical, physical, mechanical, nutritional, genetic or psychosomatic.
In the first half of the 20th century, local or external causal factors, among which are functional, were considered the most important, because of the prevalent attitude that malocclusions are a modern civilization disease caused by inadequate function of the jaws in modern life conditions.In the second half of the last century heritage took over the role of the causal factor [19][20][21][22] .
Today we can surely say the etiology of malocclusion is not simple, and that it is multifactorial and interdependent, which makes classification and systematization of malocclusion even more complex and difficult 23 .
Class III malocclusion is widely associated with heredity, which is confirmed in some classic family studies 24 .
However, a wide range of non-hereditary factors may contribute to the development of Class III malocclusion -enlarged tonsils, inability to breath through the nose, hormonal disorders, habit of mandibular protrusion, trauma and disease, early loss of first permanent molars and incorrect growth direction of permanent incisors or premature loss of deciduous incisors [25][26][27] .
Open bite has a multifactorial etiology also.It appears that no single factor could be the most frequent and the biggest culprit for the occurrence of open bite.Factor classification is divided into two groups -general and local 28 .
Profitt et al. 26 have divided all etiological factors important for the development of diseases and irregularities in the stomatognathic system, into developmental, functional, and traumatic.The most important cause for the malocclusion development is disproportion between the size of the jaws and teeth, and jaws themselves.The reasons for this can be found in a large population migration and mixing of different ethnic groups and nations that is characterized by genetic diversity 29 .These changes influence inherited variations in morphology and function.Inheritance cannot be viewed as a separate causal factor of malocclusions, but only in interaction with other etiological factors.Malocclusions should be observed primarily as a developmental problem, and each developmental phase has its own prevention and activities.Prevention in the infant period referres to introduction of regular diet, prevention of the formation of bad habits and functions as well as their importance for future relationship of the jaws and teeth health [28][29][30] .
The aim of this study was to identify and analize causal factors that lead to forming malocclusions in patients from the Province of Vojvodina and create a uniform methodology for epidemiological research.

Methods
The study included 127 patients of the Department of Orthodontics, Dental Clinic of Vojvodina, examined in the period of one calendar year (January-December).A sample comprised of ethnicaly mixed population from the area of the Province of Vojvodina.Data were abstracted from medical records of patients.Exclusion criteria from the study included: congenital cleft lip, jaw and/or palate, which because of the complexity of the anomalies and the factors that contribute to its development, represent a speciffic set of problems, and thus may blurr the results.
The average age of the patients was 10.70 years, with minimum of 6.68 and maximum of 25.84 years.
In diagnostic examination of the patients in order to better understand the causes of anomalies and causal treatment, we unflaggingly took data through heteroanamnesis, objective findings, functional analysis of stomatognathic system, and additional diagnostic methods specific for orthodontics as a branch of dentistry (dentoalveolar occlusal findings, gnatometric and radiological analysis).Data obtained by systematic examination were entered in table and processed statistically to obtain mean values, standard deviations and percentages.The data provided good insight into the present population problems, revealing the extent eventual treatment.In order to have clearer insight into the necessary measures, we used statistical list of attending second and fifth grade of elementary school (Table 1).
According to the existing rules and forms, medical check-ups in the second and fifth grade of elementary school are used to implement interceptive and therapeutic measures of already developed anomalies.
Groups of factors are conditionally divided into "morphological" and "functional", in order to diviside the factors that are predominantly of orthodontic anomalies in the narrow sense, and those who represent dysfunction of adjacent soft tissue, which leads to the creation of conditions for the occurrence of anomalies or support the development of already developed anomalies.Of the morphological irregularities the most frequent were: crowding (primary, secondary and combined); spacing (primary and secondary); the loss of permanent teeth in mixed dentition period; congenital disorders of number of teeth (hypodontia and hyperdontia); impaction and retention of teeth; fibrous and proccident frenulum; trauma of facial bones, jaws and teeth and recurrence of similar anomalies in the family -heritability.
Among the oral functions, the standard methods were used to investigate: the position and tone of the tongue; chronic enlargement of the tonsils and adenoid vegetation; chronic and frequent ear, nose and/or throat inflammations; habitual mouth breathing; deviation of the mandible; harmful habits and parafunctions as a separate subgroup (pacifier used over 3 years of age, nail biting, lip biting, finger and tongue sucking, etc.).
In particular, we observed skeletal interjaw relations in sagittal (class), vertical and transversal dimension as an indicator of mutual developmental dis/harmony and position of the upper and lower jaw.
The risk factors registered this way, were statistically analyzed to have better insight into their distribution and relationships.
Test evaluation was performed regarding: addition of points that shows a total degree of risk: low-risk -less than 1/3 of the total possible number of points; medium risk -up to 2/3 of the total possible number of points; high risk -over 2/3 of the total possible number of points.

Results
Analyzing the total number of potentially harmful factors per patient, we found the following (Figure 1): the number of factors identified ranged between 0 and 6; the most common factor was 3 per patient (29.92%); the rarest registered were the factors 0 (1.57%) and 6 (0.7%); one identified factor had 19.68% of the patients; two factors were registered in 26.77% of the patients; four factors were registered in 14.17% of the patients; five factors were found in 7.1% of the patients.An average number of factors per patient was 2.59 with the standard deviation of 1.24.This means that factors distribution follows the Gaussian curve, and includes about two thirds of the sample, which in our case amounts to about 70%.

Table 5 The ratio of irregular functions and bad habits
Irregularities n (%) Irregular functions 105 (72) Bad habits 40 (28) Total 145 (100) Irregular functions were present in the following relationship: deviation of the mandible in 45% of the cases; malposition of the tongue and tongue hypotonia in 24% of the cases; enlarged tonsils and adenoid vegetation caused disorder in 20% of the cases; habitual mouth breathing in 6% of the subjects; chronic inflammation of the ear, nose and throat with obstruction of the upper respiratory tract as a harmful factor in 5% of the cases (Table 6).Harmful habits and parafunctions were further divided into the following most commonly recorded factors: the use of pacifiers (dummies) over the age of 3 in 13% of this group of factors; biting nails in 60% of the cases; biting lips in 15% of the cases; finger sucking in 12% of cases (Table 7).If the factors were to be viewed as acquired or congenital, the relationship was as followed: acquired factors made 61% of a total member of the factors and congenital factors 39% of the cases.
A more detailed insight into the hereditary factors revealed: discrepancy between a required and the available space for teeth in 20% of the cases (17% primary crowding, and 3% primary spacing); irregularities of the number of the teeth were present in 4% of the cases (3% hypodontia, 1% hyperdontia); recurrence of similar anomalies in the family in 15% (Table 8).tion of epidemiological studies to determine the presence and types of anomalies in a particular population is important, but also for monitoring the trends of their reduction conducted after the preventive, interceptive and therapeutic measures.Therefore, we suggest the Questionnaire for Epidemiological Surveillance (Table 9).

The general distribution of anomalies can be displayed by the index of anomaly (AI).
This would help avoid the generality and reduce the measures of differences in data obtained by epidemiological studies.
Researches of experts from multiple disciplines would create the conditions to penetrate deeper into the etiology of orthodontic problems, and to analyze their impact on the general and local development.Based on study of genetic and epigenetic factors, finding of the dominant risk factors and by analyzing the obtained results, it would be possible to make the most appropriate model of primary and secondary preventive care, which would be based on the latest scientific achievements in the field of causes of tooth and jaw irregularities.

Discussion
Not many research papers have been published on this topic, so we suggested a uniform methodology, in order to obtain the results that are comparable within our region.
For each patient data were collected widely in an otherwise difficult separation of numerous factors that sometimes independently, often in combination, lead to disruption in the growth and development of the stomatognathic system.The combination and multifactoriality as well as overlapping effects of individual factors, are the cause of severe orientation and selection of the right causal treatment of malocclusions.This is more helpful for understanding possible causes of malocclusions, as well as developmental disorders, and step towards preventing these disorders wherever possible.
If we observe the results of analysis of saggital interjaw skeletal relations considering numerous factors that may contribute to the development of irregularities of teeth and jaws, a striking approximation of the average and standard deviation of the factors in all three classes is noticeable, so that we can state that there is no difference between the classes, depending on the number and types of factors that might be contributable.
The opinion that orthodontic anomalies depend on multifactorial etiology is supported by finding that most patients had registered 2, 3 and 4 etiological factors, which was also a finding in an El-Mangoury and Mostafa's research 9 .The fact that there was a minimum number of patients with no registered potentially contributing risk factors can be explained by the eventual presence of some other, less frequent or more hidden factors than those tested routinely, such as inaccurate data obtained from a patient or guardian while taking history, or of the diagnosis failure therapist.
The phenomenon that a certain number of cases had 5 or 6 etiological factors can be partly attributed to the presence of overlapping between the present acting factors in some areas.Such conclusion is in accordance with other authors 27 .Since it is artificial, no matter how detailed it is, replications are possible.
Observing the basic representation of a group of risk factors we found that the "morphological" factors represent 56% of identified risk factors, and "functional" 44%.Similar findings have been presented in other research studies [31][32][33] .This shows that almost half of the disorders could be influenced on at early age, either by allowing proper function of any preventive eradication of bad habits or reeducated functions of the soft tissue of stomatognathic system.The importance of this fact is even greater if we deeper analyze the functional factors -72% of these factors in the sample were bad habits (use of a pacifier, nail biting, lip biting, finger and tongue sucking), that can be eradicated by certain measures, after which a significant reduction of expression could be expected, or abnormalities would not develop at all.Sousa et al. 34 confirmed a similar percentage in their study -65% of functional factors were bad habits.Incorrect functions (deviation of the mandible, abnormal position and hypotonia of the tongue, habitual mouth breathing, etc.), representing 28% of functional depending factors, could be removed by timely interception, functions reeducation, as well as collaboration with specialists in other fields of medicine, that would lead to irregularities of significantly lesser extent.It is therefore important to raise the level of consciousness of wider population and health care providers in other branches of medicine, to achieve a better acquaintance, primarily with health and socioeconomic consequences, of relatively easy to recognize factors and measures of preventive action.
Among the "morphological" factors we can differentiate hereditary congenital and non-hereditary disorders which themselves are an orthodontic anomaly (primary crowding, anomalies of tooth shape and number, undesirable frenulum fixation, diasthema, etc.), and acquired postnatal disorders, which affect the formation or disorders or complicate the existing ones, and they could be promptly removed (secondary crowding, loss of permanent teeth in a period of growth and development, trauma, etc.).The same divison of morphological factors has been revealed by Mossey 19 .Acquired disorders could be the onset prevented or mitigated by improving the knowledge of population about the means of early detection, and easy removal of identifiable risk factors 35,36 .That would greatly influence spread reduction, or in some cases, where disorders are only a part of the mosaic of factors, the reduction in expression and severity of anomalies.In individuals with an emphasized anomaly it could significantly alleviate the quality of life.
The fact that additionally supports previous statements is that if we examine the relationship between the incidence of hereditary and acquired factors in the sample, the possibility of good prevention is even more obvious: acquired factors represented 61% of the total factors, while genetic factors were present in 39% of the cases.
For risk assesment, it is better to use a standard, known method, and for the epidemiological research, we suggest our Epidemiological Questionnaire (in the results section).

Conclusion
We suggest the use of Questionnaire for Epidemiological Surveillance.As the anomalies are often combined, it is difficult to classify and display a unique index.Evaluation of morphological and functional findings should be registered for each symptom of irregularities in a premade survey list and should always be done in the same sequence in sagittal, vertical and transversal, and other irregularities.In that way errors would be reduced to a minimum extent.Epidemiological surveillance should be performed: for deciduous dentition, at the age of 5 to 6; mixed dentition at the end of the mixed dentition period in the 12th year of life; permanent teeth in high school children at the age of 18, at the end of the period of active growth and development.

Fig. 1 -
Fig. 1 -The number of patients with risk factors.