Prevalence and associated factors for mandibular Premolar impaction in various malocclusions

Hemashree J1, Ravindra Kumar Jain*2, Manjari Chaudhary3 1Saveetha Dental College & Hospitals, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai, Tamil Nadu, India 2Department of Orthodontics and dentofacial orthopedics, Saveetha Dental College & Hospitals, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai, Tamil Nadu, India 3Department of Oral Medicine and Radiology, Saveetha Dental College & Hospitals, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai, Tamil Nadu, India


INTRODUCTION
Teeth which fail to erupt to the level of the occlusal plane even after 2 /3 rd root formation is completed are termed as impacted teeth (Archer, 1961). An eruption of a tooth might be obstructed usually by adjacent teeth or dense bone or soft tissue and also may cause impaction. It is theoretically impossible for all the teeth to follow the correct eruptive path and can sometimes be impacted within the dentoalveolar process or other unusual anatomic sites such as nasal/sinus cavities (Alling and Catone, 1993). Also, the unerupted cyst might be associated with any offending pathology. This is why it is essential to perform a thorough clinical and radiographic examination when there is any deviation from the usual eruption schedule (Rubika et al., 2015;Samantha et al., 2017).
The order of frequency of impacted teeth includes permanent third molars, permanent maxillary canines followed by mandibular premolars (Ro and Tin-Oo, 2009;Yamaoka et al., 1996). The etiology of tooth impaction is multifactorial. The etiology of impaction of teeth other than the third molars are poorly de ined (Tang and Sayaniwas, 2006). Impaction of teeth might be due to a mesial drift of teeth which is the result of premature loss of primary teeth. It can also be due to any ectopic positioning of developing tooth buds or any pathology such as in lammatory or dentigerous cyst (Kalia and Aneja, 2009). They can also be associated with syndromes like cleidocranial dysostosis (Suri et al., 2004). Since the mandibular canines and mandibular irst molars erupt before the mandibular premolars, an arch length tooth discrepancy in the premolar region can lead to impaction of the second premolars. The prevalence of premolar impaction varies greatly and may according to age and gender. According to the previous literature and studies of mandibular premolar impaction, a classi ication for mandibular premolar impaction is suggested by Mehta et al. (2017). Treatment methods suggested for impacted teeth include interceptive orthodontics, surgical exposure and extraction depending on the position of impacted teeth, and also their relationship with adjacent teeth (Frank, 2000). Most of the cases of premolar impaction are reported accidentally on routine screening of patients or when the patients report to the clinic for some other dental problem. Impacted premolar are sometimes advised for removal by orthodontists before the start of treatment (Jain et al., 2014;Kamisetty et al., 2015). Disimpaction of impacted teeth and bringing them to occlusion is one of the most common challenging problems faced by an orthodontist clinical practice (Sivamurthy and Sundari, 2016). Detailed knowledge of the development, eruption paths and patterns of the teeth is needed for successful management of impacted teeth (Krishnan et al., 2018;Kumar et al., 2011).
Previously our team had conducted numerous clinical studies (Felicita, 2017a(Felicita, ,b, 2018 and case reports (Felicita et al., 2012;Dinesh et al., 2013;Krishnan et al., 2015) over the past 5 years. Now we are focussing on retrospective studies. The idea for this study stemmed from the current interest in our community. So this study aims at evaluating the premolar impaction among subjects visiting Saveetha Dental College.

Study setting
This cross-sectional retrospective study was conducted among a total of 886 subjects who reported to the Orthodontic department at Saveetha Dental College during June 2019 -March 2020. Digital records were used to retrieve the data. Ethical approval was obtained from the Institutional Ethical Committee. SDC/SIHEC/2020/DIASDATA/0619-0320

Data Collection
OPG and intraoral photographs of 886 subjects were checked and noted for impacted mandibular premolars. Demographic data such as age, gender and Skeletal Malocclusion of the patient was recorded. Relevant Data was entered in Microsoft Excel Sheet. Repeated and incomplete data were excluded. Data veri ication was done by an external reviewer.

Statistical Analysis
Data entered in excel sheet and later transferred to the SPSS Software (version 20.0) for statistical analysis. Variable de inition process was done. Both descriptive and inferential statistics were employed. Level of signi icance was set at p < 0.05.

RESULTS AND DISCUSSION
The following results can be inferred from this study, 1. Out of 886 subjects, there were only four subjects who had mandibular premolar impaction,  and all the four impacted premolars were mandibular second premolars Prevalence of mandibular premolar impaction was 0.5% in this study.

Prevalent age of mandibular premolar
impaction was 18 -25 years, according to this study.
3. Both Angles Class I and class II malocclusions were associated with mandibular premolar impaction. Among these, Class I skeletal malocclusion had a higher prevalence [Figure 2]. It was noted that 75% of the subjects had Skeletal Class I malocclusion, whereas only 25% of the patients had Skeletal Class II malocclusion.
According to this study, it was noted that 0.34 % of the females had premolar impaction, whereas it was only about 0.11% among the males. Prevalent age of premolar impaction was 18 -25 years, according to this study.
Premolar impaction, according to this study, was found to be 0.5% prevalent among 886 subjects. According to a study done by Collett (2000) reported the mandibular 2nd premolar impaction accounted for about 24% approximately of all the dental impactions. The overall prevalence of mandibular premolar impaction in adults has been reported to be 0.5% (Laskin and Petersen, 1997;Manjunatha et al., 2014) (0.1% to 0.3% for maxillary premolars and 0.2% -0.3% for mandibular premolars). Mcnamara and Mcnamara (2005) and Simsek-Kaya et al. (2011) have also reported that mandibular premolar impaction has less signi icance in comparison with other impacted teeth. The most common reason reported for mandibular premolar impaction is lack of availability of space, or it can be due to environmental and genetic in luences. The inding of this current study was in agreement with the other studies.
Premolar impaction is most prevalent in the younger age group. According to this study, it was from 18 -25 years of age. Mustafa (2015) in his study quoted that the 20 -25years age group had a higher rate of prevalence of impacted premolars. Prevalansı (2013) in his study reported that the mean age was 23.2 ± 2.4 in the Anatolian population. This prevalence in the lower age group is because patients visit the dentist more frequently for orthodontic correction. This inding is in agreement with the indings of the previous studies.
Female predilection was reported for mandibular premolar impaction in this study. Mishra and Pandey (2017) and Oikarinen and Julku (1974), in their study also reported similar indings. Even though there is no statistical signi icance, there is not much literature evidence in support of this. Jain and Kallury (2011) have reported that there is no statistical signi icance between skeletal malocclusion and premolar impaction. In this study, skeletal Class I malocclusion was reported with mandibular premolar impaction. Though most of the cases of mandibular premolar impaction are asymptomatic, its management is important esthetically and functionally to the patient. In case the patient is indicated for the treatment of an impacted tooth, a thorough assessment and diagnosis of all indings is fundamental to decide a suitable treatment plan.
Early diagnosis and early treatment are the most important keys for correction of mandibular second premolar impaction. The following observations should be made 1)presence of any congenitally missing teeth 2)whether the condition is generalized or localized 3)whether the succedaneous tooth has a proper size and shape potential factors for eruption and whether there is any delay in eruption is due to over-retained primary teeth (such as ankylosis or incomplete root resorption). The presence of overlying soft tissue or bone might be an impeding factor for an eruption of any tooth. Space management of deciduous molars will frequently facilitate the uneventful eruption of premolars. Orthodontic guidance for an eruption of teeth is usually never indicated if problems are often detected at an early period and managed properly. Treatment of impacted teeth can be dif icult and unpredictable if proper diagnosis and planning to assess whether it is favourable or not (Vikram et al., 2017;Viswanath et al., 2015). Various diagnostic aids can be used for assessment like IOPA, CBCT. Treatment of impacted teeth involves an interdisciplinary approach involving both the Orthodontist and the oral surgeon. Although there are many theories to support the evidence for impacted teeth, nothing has been proved. Most commonly accepted theory will be the discrepancies between jaw size and tooth size.
Further studies with much larger sample size, including the treatment options for impacted premolar teeth will be included in the study. Current limitations of the study will be eliminated.

CONCLUSION
Within the limits of the study, it was observed that mandibular premolar impaction was common among the younger age group with a female predilection. It was associated with Skeletal Class I malocclusion, but none of these indings was signi icant.

ACKNOWLEDGEMENT
Thanks to Saveetha Dental college for allowing me to review the case sheets.