Radiographic imaging evaluation of mandibular third molars among patients presenting to private dental college in South India

The most common reason for mandibular third molar impaction is due to reduced space between the distal part of the second mandibular molar and the anterior border of the ascending ramus of the lower jaw. The tooth that is impacted is commonly asymptomatic, or sometimes present with various pathological conditions causing pain and swelling as well as pus discharge. In our current study, we have assessed the patterns of Mandibular third molar impactions using the Orthopantomogram (OPG’s). OPG’s of 150 patients (91 female and 59 male) who were between 18-25 years of age and had impacted mandibular third molars was assessed for gender, the region having the high-est frequency of impaction and the fashion of impaction of the mandibular third molars. The study shows Bilateral impaction was more commonly seen in 26.66% of the study population and case of unilateral impactions the most frequent site is particularly in left side 23.33% and in right 19.33% unilateral impactions. The mesioangular pattern of impaction was more common in both male and female and was followed by distoangular, vertical and horizontal patterns.The study showed that there was no gender bias in the pres-ence of impacted mandibular third molars and the mesioangular pattern of

Agenesis, Impacted tooth, Panoramic radiography, Third molars ABSTRACT The most common reason for mandibular third molar impaction is due to reduced space between the distal part of the second mandibular molar and the anterior border of the ascending ramus of the lower jaw. The tooth that is impacted is commonly asymptomatic, or sometimes present with various pathological conditions causing pain and swelling as well as pus discharge. In our current study, we have assessed the patterns of Mandibular third molar impactions using the Orthopantomogram (OPG's). OPG's of 150 patients (91 female and 59 male) who were between 18-25 years of age and had impacted mandibular third molars was assessed for gender, the region having the highest frequency of impaction and the fashion of impaction of the mandibular third molars. The study shows Bilateral impaction was more commonly seen in 26.66% of the study population and case of unilateral impactions the most frequent site is particularly in left side 23.33% and in right 19.33% unilateral impactions. The mesioangular pattern of impaction was more common in both male and female and was followed by distoangular, vertical and horizontal patterns.The study showed that there was no gender bias in the presence of impacted mandibular third molars and that the mesioangular pattern of impaction was more common.

INTRODUCTION
Surgical removal of an impacted tooth is the usual procedure performed by maxillofacial surgeons everywhere (Ferrús-Torres et al., 2009). The commonly impacted tooth is the third molar tooth (Ryalat et al., 2018). The most frequent cause for impaction of a mandibular third molar is due to reduced space between the distal surface of the second mandibular molar and the anterior border of the ascending ramus of the mandible. These impacted teeth present commonly as asymptomatic few times it may be associated with few pathological conditions causing pain, swelling, infection, trismus (Güven et al., 2000). It sometimes causes mobility of the adjacent tooth by resorption of the neighbouring tooth root (Bataineh et al., 2002). Various researches have suggested that female populations have a greater incidence of impacted mandibular third molar than the male populations. Multiple reasons are established as reasons for impaction of the third molar (Almendros-Marqués et al., 2008). The evolution with a gradual decrease in the size of the mandible and maxilla is said to be one common reason for impaction of the tooth because of the reduced space in the arch. The patients who underwent surgical extraction of an impacted third molar are shown to suffer from pain, swelling, tris-mus and general oral discomfort during the irst few postoperative days. Few other less commonly seen complications are dry socket, wound breakdown, bleeding and neurological injury (Singh, 2019;Babu et al., 2012). In our present study, we aim to retrospectively assess the patterns of Mandibular third molar impactions reporting to our institution using Orthopantomogram.
Few classi ication systems have been used to classify the type of the impacted teeth namely, 1. WINTER'S classi ication 2. PELL AND GREGORY classi ication 3. KELLEY AND KAY classi ication 4. ARCHER'S classi ication of impacted maxillary teeth.
In winter's we see the position/inclination of the impacted tooth to the long axis of the second molar, and the impacted third molar is classi ied as distoangular impaction, mesioangular impaction, horizontal impaction, vertical impaction and transverse impaction. The classi ication we have used in our study is simple and easy to explain to the patient to make them understand (Çolak, 2019). The present aim of our research is to assess the various patterns of impaction of the mandibular third molars using Orthopantomogram to identify, the position of impacted mandibular third molars and also to evaluate the most common gender affected by mandibular third molar. Impacted third molars can also be classi ied according to their angular relationship to the adjacent second molar. Angulation of the impacted third molar can be assessed by looking at the angle formed between the intersected longitudinal axes of the impacted third molar and the adjacent second molar, as described by winter, either visually or by using an orthodontic protractor.

MATERIALS AND METHODS
The study is an observational study carried out retrospectively in Saveetha Dental College and Hospitals, Chennai, India. We included 150 high-quality Orthopantomograms of the patients who reported to our study.
The pattern of impaction of the mandibular molar was studied using Orthopantomogram (OPG).

Inclusion criteria
1. Age of the study groups 18 -25 years.
2. The patient reported for an impacted tooth removal.

Exclusion criteria
Graph 1: Gender distribution Graph 2: Distribution of mandibular impaction in the sample 1. OPG of patients with congenital deformity due to any syndromes were excluded.
2. OPG of patients with any history of trauma, pathology in mandible and patient who has undergone surgery involving mandible were excluded.
3. Poor quality OPG images were excluded.

Ethical Consideration
Approval was obtained from the Institutional Review Board of Saveetha Institute of Medical and Technical Science, India.

Assessment of patterns
The pattern of impaction is derived by checking the angles recorded between the lines intersecting the long axis of the second and third molar.
The angle checked is used to determine the mesial, distal, horizontal and vertical inclination in relation to the second molar.
The radiographs were interpreted for the following: 1. Unilateral or bilateral impacted mandibular third molar.
2. The pattern of an impacted mandibular third molar.      3. Gender difference.

Statistics
The collected data were assessed with IBM SPSS statistics software Version 23.0. To explain the descriptive data statistics frequency analysis, percentage analysis was used for categorical variables, and the mean & S.D were used for continuous variables.

RESULTS AND DISCUSSION
Evaluating the 150 Orthopantogram among the study population, 59 were of male patients (39%) and 91 were of female patients (61%), as shown in Graph 1 and Table 1. Majority of the study population reported were female patients similar to other studies showing females have a higher incidence of impactions when compared to male population (Almendros-Marqués et al., 2008). A signi icant difference was seen in the unilateral and bilateral distribution of third molar impaction. Unilateral impaction was found in 64 radiographs which accounted for 43% of the total and bilateral impaction was seen in 40 people which accounted for 26.6% of the sample as shown graphically in Graph 2 and mentioned in Table 2.
The mesioangular pattern of impaction was more common and was followed by distoangular, vertical and horizontal patterns. Third molar impactions were more common in the right quadrant (34% per cent for the males and about 39% for the females) than in the left quadrant (23.3% in females and 33% in males). There's no sexual predominance seen in impaction pattern or agenesis (Table 3, Table 4, Table 5 and Table 6). These indings are similar to studies done in various other populations (Harsha, 2014;Singh, 2019).
The main reason for a mandibular third molar to be impacted is due to devoid of space for the eruption. The early man ate coarse uncooked food that resulted in attrition of teeth on the occlusal and proximal surfaces of the teeth. This attrition and tendency of mesial drifting of the teeth provided the gap for an eruption of the impacted tooth. Whereas, in modern man, the attrition of teeth does not take place due to eating cooked and soft textured food. Hence, as a result, the space required for third molars eruption by attrition and mesial drifting of teeth is lost (Björk et al., 1956;Akadiri et al., 2010).
Other factors that bring about impactions include the growth of the face, size of the jaw, tooth size, food habits, overlying bone or soft tissue, with the host having systemic diseases etc. A properly positioned third molar erupts between the ages 18 and 24. The other complications associated with a delayed eruption of the mandibular third molar are poor tooth alignment particularly in the lower anterior, mobility of the adjacent tooth due to pathological root resorption, in lammatory conditions and even TMJ dysfunction. The dispensation of the depth of impaction and angulation in the lower third molars seen in our present study is similar to the study by Kramer and Williams. In their study, they have reported 75% of impacted lower third molars were in mesioangular and horizontal angulation. The position of an impacted tooth plays an important role in the clinical implication on the adjacent mandibular second molar, as outlined by various authors (Danda et al., 2010;Stella, 2017).

CONCLUSION
Our study concludes that Orthopantomogram can be used as an excellent assessing tool to see the pattern of impaction, which helps the surgeon to carry out the surgical removal of the impacted tooth. Bilateral and mesioangular impaction is commonly seen in our study population. Agenesis of the lower third molar was widely seen in the female population.

ACKNOWLEDGEMENT
The authors are grateful to the Department of Oral Medicine and Radiology, Saveetha Dental College and Hospitals for providing us with the Orthopantomogram for this research work.

Financial Support
Nil.

Con lict of Interest
There are no con licts of interest.