PREVALENCE OF HYPODONTIA IN ORTHODONTIC PATIENTS AT NOBEL MEDICAL COLLEGE, BIRATNAGAR

Prevalence of Hypodon a in Orthodonic pa ents at Nobel Medical College, Biratnagar. Anand Acharya, Nidhi Giri, Raj Kumar Jha, Jitendra Singh BJHS 2021;6(3)16. 1626 1630. Introduc on Hypodon a or tooth agenesis is the most common developmental anomaly in craniofacial region. The mul tude of problems in pa ents with hypodon a includes aesthe c, periodontal damage, malocclusion, inar culate speech and alveolar bone deficiency. This commonly encountered condi on in orthodon c department has variable site of occurrence, some mes associated with syndromes.


INTRODUCTION
Hypodon a is the absence of one to six teeth excluding third 1,2 molars. Hypodon a or tooth agenesis is the most common 3 developmental anomaly in craniofacial region. Absence of more than six teeth excluding third molars is known as 4,5 oligodon a. The complete failure of den on to develop is 6 called anodon a. Any tooth can be missing congenitally but there is a tendency for certain teeth to be missing more frequently than others. Graber has reported that overall frequency of missing teeth except third molars to be ranging from 1.6% to 9.6% in various series of studies in different 7 countries. Hypodon a may be associated with a recognized gene c syndrome or can occur as a nonsyndromic isolated [8][9][10][11] trait. In some instances familial tendency of congenitally missing single tooth has also been reported, although 7 e ology has been unknown. Hypodon a not only induces psychosocial problem but also imparts economical burden to the pa ents. The treatment of hypodon a needs mul disciplinary approach. The mul tude of problems in pa ents with hypodon a includes aesthe c, periodontal damage, malocclusion, inar culate speech and alveolar bone deficiency. Individuals with hypodon a has deep overbites and spacing, reducing the size of occlusal table leading to over erup on of opposing tooth, non working interferences and poor gingival contours. Early detec on of dental anomalies is vital to provide comprehensive treatment and prevent malocclusions. Study by Laing E et al shows chewing problems in pa ents with hypodon a who had deciduous 12 teeth associated with missing permanent teeth exfoliated. Some studies also concluded anterior hypodon a has a 13 significant effect on skeletal rela onships. Hypodon a in anterior region can accompany retrognathic maxillae, prognathic mandibles and smaller lengths of posterior 14 cranial base. It is not conclusive whether it tends to occur more in the maxilla or mandible and also in the anterior 1 5 versus posterior segments. Higher prevalence of advanced hypodon a (congenital missing more than 4 teeth except third molars) and mandibular lateral incisor agenesis 16 were found in Japanese popula on. One of the research conducted in Kathmandu, Nepal showed that hypodon a was present in 7.48 percent of orthodon c pa ents where as maxillary lateral incisor was found to be the most common congenital missing and 17,18 microdon c tooth.
No such researches have been conducted so far in this region. The aim of our study was to know the pa erns and types of hypodon a in orthodon c pa ents a ending orthodon c department at Nobel Medical College, Biratnagar.

METHODOLOGY
Cross sec onal study of 260 orthodon c pa ents' pretreatment records i.e., casts, orthopantomogram, lateral cephalometric radiographs and photographs were taken as study materials as per convenient sampling method. This proposed study was approved by the ethical commi ee of Nobel Medical College and the study dura on was from March 2021 to August 2021 at department of Orthodon cs, Nobel Medical College. ANB angle was used to segregate malocclusion types. ANB angle between 2 and 4 degrees were categorized as class I occlusion/ malocclusion. Accordingly, higher and lower ANB angles were categorized as class II and class III malocclusions, respec vely. Wits appraisal measurement was used in doub ul ANB angle cases. Wit's appraisal of 0 to -1 were classified as class I, those with posi ve Wit's measurements were classified as class II and nega ve Wit's measurements more than -1 as class III.

Sta s cal Analysis:
The data was analyzed by using the Sta s cal package for Social Sciences version 23.0 so ware (SPSS IncChicago,IL,USA). Descrip ve sta s cs was used to summarize the data and chi square test was used to find the level of significance among genders. Exclusion criteria were pa ents with previous history of orthodon c treatment, craniofacial syndromes such as cle s, history of teeth trauma, previous extrac ons due to caries or periodontal disease, incomplete pa ent records. Third molar was not considered throughout the study. All the permanent teeth except third molars calcifica on had been completed by 9 years and cases with missing teeth due to extrac on were not included in the study on account of confounding the result. Early detec on before that age may 1 be unreliable and confound the result. Calcifica on of 4 premolars may be delayed due to various factors.

RESULTS
The distribu on of tooth agenesis according to gender in different malocclusion groups is shown in Table 1.From the total cases examined, 77(29.6%) were males and 183 (70.4%) were females. Class I malocclusion was found in 171 pa ents (65.8%) which is the most common malocclusion among the study pa ents. [ Table 1]. Congenital absence of one or more teeth was observed in 28 out of 260 pa ents, with a frequency of 10.8%. Also, among the 28 pa ents with hypodon a, 20 (11.7%) pa ents belonged to class I, 7(8.6%) belonged to class II, and 1(12.5%) belonged to class III malocclusion [ Figure 1].  Also, from all of the pa ents with missing teeth, 11 (4.23%) were males and 17 (6.54%) were females [ Table 2]. Chi square test was done to know distribu on of hypodon a among genders and different classes of malocclusion and it showed that most of the hypodon a was found in class I malocclusion (71.4%) and females were affected more though not significant(P=0.235). On the other hand lowest number of class III malocclusion pa ents (3.6%) had hypodon a [ Table 3].
Out of 28 hypodon a pa ents, 15(53.6%) had missing teeth in the upper arch in all types of malocclusion where as 21(75%) had bilateral missing teeth. This higher frequency of hypodon a in the upper arch was observed in all types of malocclusions [ Table 4]. Table 3: Distribu on of gender across different classes of malocclusion among par cipants with hypodon a. There were a total of 69 missing teeth in our examined pa ents. Of all 69 missing teeth, the most (68%) was observed in class I group, and the least amount belonged to class III group (10%). However, there was no sta s cal significant difference between different malocclusions in the number of missing teeth. (Chi-square test, P > 0.05).The most and the least affected teeth were upper lateral incisor (30.43%) and lower first premolar (1.45%), respec vely. Thus, the most prevalent missing tooth types were found more in class I pa ents and females had more number of absent teeth (54%).[ Table 5]

DISCUSSION
Out of 260 pa ents, 10.8% had hypodon a. Age range of our pa ents were 9 to 32 years. Female orthodon c pa ents show higher preponderance as compared to males in our study owing to more esthe c concern of females consistent with many other researches. Hypodon a was found in 10.8% of our study pa ents which was higher than study by Gupta et al (7.48%) in the orthodon c pa ents in 17 Kathmandu. Different ethnicity or geographic difference in the study could also affect the result. H K Sony et al in a study conducted in Varodara, Gujrat India reported hypodon a present in 11.01% of cases which is comparable to our 19 study. The highest prevalence was found to be in German 20,21 popula on (12.6%)and least in the Malaysian (2.8%). Overall hypodon a was found to be more common in females(6.54%) as compared to males(4.23%) but not sta s cally significant. Similarly, out of 28 pa ents with missing teeth 17(61%) were females and 11(39%) were 17,22-,26 males, comparable to previous study. The missing teeth were more o en absent in the maxillary 22,[27][28][29] arch consistent with the previous research.
Upper lateral incisors was the most commonly missing where as lower first premolar was least commonly missing. H K Sony et al, Chung et al and Hassan et al reported missing teeth 19,30,31 was more frequently found in mandibular arch.
The prevalence of congenitally missing teeth was almost equal 32 in both the jaws as reported by Polder et al. Bilateral missing lateral incisor was more frequently noted. Polastri in the study on Italian popula on had similar findings whereas Graccoet al., Laganàet al., and Sato et al. found that the most affected tooth was the mandibular second premolars [33][34][35][36] followed by maxillary lateral incisor. The reason behind this difference could be a ributed to difference in sample size, type of popula on, gene c factors and method of data collec on in the different study groups. Most of our hypodon a pa ents belonged to class I malocclusion group (68%) which is similar to the findings of 37 Celikoglu et al. The least number of pa ents belonged to class III group, sta s cal significance was not observed though. About 65.8% of our pa ents had class I malocclusion followed by 31.2% class II and least 3.1% class III which was  38 Biratnagar.

CONCLUSION
The higher prevalence of hypodon a in Orthodon c pa ents in this region warrants careful inspec on and inves ga on before embarking on the diagnosis and treatment planning. It seems hypodon a appears more in the maxilla than in the mandible and it can accompany various complica ons.

RECOMMENDATION
From our study we have found that hypodon a is common in orthodon c pa ents. Proper inves ga ons like case history, orthopantamogram and study models are mandatory. Further research is recommended increasing the sample size and segrega ng the ethnicity to find ethnic preponderance of hypodon a in this region.

LIMITATIONS OF STUDY
Our study had samples collected from a single center only which could limit actual reflec on of hypodon a in the orthodon c pa ents in this region. Furthermore sample size was small for the prevalence study.

ACKNOWLEDGEMENT
I would like to thank Dr Tarakant Bhagat, Department of Community Den stry, BPKIHS for sta s cal analysis and interpreta on of data and IRC Nobel Medical College for ethical clearance .