Amount of Local Anesthetic Solution Used in Mandibular Third Molar Surgery- A Retrospective Analysis

Mandibular third molar is the most commonly impacted teeth and surgical removal of them is the most common minor oral surgical procedure done under local anesthesia in the outpatient department. For a comfortable patient experience and best surgical results, emphasis should be made on a pain-free procedure. In this study, we aim to analyse retrospectively the amount of local anesthetic solution used during surgical removal of impacted mandibular third molar and to find if any association between the amount of local anesthesia used and Pederson's difficulty Index (PDI) of the impacted teeth. Retrospective observational study conducted among patients reporting to the Department of Oral and Maxillofacial Surgery, Chennai for the surgical removal of impacted mandibular third molar between the study period June 2019 to March 2020. 658 patients who fulfilled the inclusion and exclusion criteria were included in the study. Data regarding patients demography, site of impaction, Pederson Difficulty Index of impacted teeth, amount of local anesthesia used were rewarded. The data were statistically analysed using descriptive statistics in IBM SPSS version 20 software. Study population included 58.4% males and 41.6% females, majority of them in the 3rd decade of life. (53.6%) with mean age 29.1 years. Of 658 impacted teeth analysed 54.4% were moderately difficult followed by minimally difficult 38.4% and very difficult 7.1% according to PDI. A significant association was found between the amount of local anesthesia used and PDI score of impacted teeth. In 64.7% cases 2ml of local anesthesia was sufficient to achieve anesthesia during the procedure. 2ml of local anesthesia is sufficient to achieve adequate anesthetic effect in surgical removal of impacted molar. As PDI increased, the amount of local anesthesia used also increased.

Local Anesthesia, Third Molar Surgery, Impacted Third Molar, Dif iculty Index ABSTRACT Mandibular third molar is the most commonly impacted teeth and surgical removal of them is the most common minor oral surgical procedure done under local anesthesia in the outpatient department. For a comfortable patient experience and best surgical results, emphasis should be made on a pain-free procedure. In this study, we aim to analyse retrospectively the amount of local anesthetic solution used during surgical removal of impacted mandibular third molar and to ind if any association between the amount of local anesthesia used and Pederson's dif iculty Index (PDI) of the impacted teeth. Retrospective observational study conducted among patients reporting to the Department of Oral and Maxillofacial Surgery, Chennai for the surgical removal of impacted mandibular third molar between the study period June 2019 to March 2020. 658 patients who ful illed the inclusion and exclusion criteria were included in the study. Data regarding patients demography, site of impaction, Pederson Dif iculty Index of impacted teeth, amount of local anesthesia used were rewarded. The data were statistically analysed using descriptive statistics in IBM SPSS version 20 software. Study population included 58.4% males and 41.6% females, majority of them in the 3rd decade of life. (53.6%) with mean age 29.1 years. Of 658 impacted teeth analysed 54.4% were moderately dif icult followed by minimally dif icult 38.4% and very dif icult 7.1% according to PDI. A signi icant association was found between the amount of local anesthesia used and PDI score of impacted teeth. In 64.7% cases 2ml of local anesthesia was suf icient to achieve anesthesia during the procedure. 2ml of local anesthesia is suf icient to achieve adequate anesthetic effect in surgical removal of impacted molar. As PDI increased, the amount of local anesthesia used also increased.

INTRODUCTION
Archer in 1975 de ined an impacted tooth as a tooth that is completely or partially unerupted and is positioned against another tooth, bone or soft tissue so that its further eruption is unlikely (Santosh, 2015). Literature from around the world states mandibular third molars to be the most commonly impacted tooth (Kruger et al., 2001;Gisakis et al., 2011;Alsadat-Hashemipour et al., 2013). This can be due to discrepancy in jaw and tooth size which can be attributed in part to evolution, aberrant position of third molar in the arch due to dense external oblique ridge or due to retarded maturation of third molar because of lag in dental development when compared to skeletal development (Carter and Worthington, 2016;Padhye et al., 2013;Kumar et al., 2017;Msagati et al., 2013).
These impacted teeth also give rise to various pathologies of odontogenic origin making (Celikoglu et al., 2010;Jesudasan et al., 2015;Nagappan et al., 2016; the prophylactic removal of third molars more common in recent times (Ravikumar and Narayanan, 2018;Shoshani-Dror et al., 1985;Muralidharan et al., 2019). Surgical removal of mandibular third molar is a routine and the most common minor oral surgical procedure done in the outpatient department under local anesthesia (Rashid et al., 2018). The prime factor that provides for the best surgical outcome and patient satisfaction/experience is a pain-free procedure (Sekhar et al., 2001;Jerjes et al., 2009;Danda et al., 2010). No amount of emphasis made can fully substantiate the importance of a pain-free procedure that is done on a conscious patient (Pacey, 2014;Shanmugaavel et al., 2016). Hence, achieving adequate anesthesia of the surgical site is the irst and the most important step in the surgical removal of third molars (James and Maheshwari, 2017;Kumar, 2017;James and Nazar, 2018). Various nerve block techniques have been proposed over the years for the same, popularly, the conventional inferior alveolar nerve block technique, Vazirani Akinosi technique, Gow-Gates mandibular nerve block technique (Malamed, 2020).
Though the nerve block technique used to anesthetize the surgical site is an independent decision of the surgeon, the most commonly used technique is the Conventional Inferior Alveolar Nerve Block (IANB) technique. This can be due to the fact that this is where the surgical training of an oral and maxillofacial surgeon begins and is a foundation upon which the surgeon builds his skills (Okamoto et al., 2000;Thangavelu et al., 2012;Christopher et al., 2018).
As much as the anesthesia technique, the amount of anesthetic solution and the type of anesthetic solution used are also of clinical importance. The composition of anesthetic solutions has evolved drastically since the introduction of novocaine (Kumar, 2015;Bahl, 2004;Deepa and Thirrunavukkarasu, 2010;Ogle and Mahjoubi, 2012). Nowadays, longer acting and more potent local anesthetic solutions with potentially lesser complications have been introduced (Srisakthi, 2014;Hariharan et al., 2014;Jain and Nazar, 2018;Ramadurai et al., 2019). Nonetheless, the gold standard still continues to 2% lignocaine. Adrenaline in concentrations 1:80,000, 1:1,00,000 or 1:2,00,000 is used along with lignocaine for its vasoconstrictor property. This provides more visibility, increases the concentration of the drug and reduces systemic absorption of lignocaine (Malamed, 2020;Okamoto et al., 2000). With respect to the amount of local anesthetic solution used, the maximum recommended dose (MRD) of 2% lignocaine with adrenaline is 7mg/kg up to 500mg. The MRD of plain 2% lignocaine is 4.4mg/kg up to 300mg. Hence, the amount of local anesthesia used in mandibular third molar surgery is crucial and while aiming to provide a pain-free comfortable experience, the overzealous use should be cautioned against (Defosse, 1999;Becker and Reed, 2012;Ogle and Mahjoubi, 2011).
In this study, we aim to retrospectively assess the amount of local anesthesia being used in surgical removal of impacted mandibular third molar.

METHODOLOGY
The retrospective observational study was conducted among the patients reporting to the Department of Oral and Maxillofacial surgery at Saveetha Dental College and hospital, Chennai during the time period June 2019 to March 2020.
The approval for the study was given by the "Institutional Ethical committee, SIMATS Review Board".
The inclusion criteria for the study were patients of any age and gender undergoing surgical extraction of impacted mandibular third molar under local anesthesia.
The exclusion criteria for the study were patients undergoing closed extraction of mandibular third molar either in local or general anesthesia and open extraction of mandibular third associated with any pathologies, patients with a history of debilitating systemic diseases and mentally or physically challenged patients.

Diagnostic Criteria
The diagnosis of impacted mandibular third molar was made with clinical indings and radiographic interpretations using intra-oral periapical radiograph (IOPA) and orthopantomogram (OPG). Based on their interpretations, the dif iculty of extraction was predicted using Pederson's Dif iculty Index (PDI) as minimally dif icult, moderately dif icult and very dif icult.

Data Collection
The patient demographic details and data pertaining to study parameters were retrieved from "DIAS-Dental Information Archive System" provided by the institution.
A total of 782 patients had reported to the department of oral and maxillofacial surgery at Saveetha Dental College, Chennai for surgical extraction of mandibular third molar under local anesthesia between the study duration (June 2019 to March 2020). Of the 782 patients, only 658 ful illed the inclusion criteria and exclusion criteria and were included in the study. The sample size of the population studied is 658.

Study Parameters
From DIAS, the following data were extracted for the purpose of the study: 4. Amount of local anesthetic used during the procedure in millilitre (ml)

Surgical Procedure
All the surgical removal of impacted teeth were carried out by residents (postgraduate students) of oral and maxillofacial surgery in their inal year of training. For standardization, only cases which used 2% lignocaine with 1:2,00,000 adrenaline and employed conventional inferior alveolar nerve blocking (IANB) technique were included in the study. And in all the cases either wards or modi ied wards incision was used to gain access to the surgical site. Closure was done using 3-0 silk suture.

Statistical Analysis
The data obtained was subsequently tabulated in an excel spreadsheet and was exported to IBM SPSS version 20.0 for statistical analysis. The data was analysed descriptively measuring mean, standard deviation, percentage and frequency. The association between different study parameters were analysed using Pearson Chi-square test at 95% con idence interval. The output was generated as tabular or graphical representation.

RESULTS AND DISCUSSION
Analysis of the demographic data of the study population revealed that a majority of them were in their 3 rd decade of life (53.6%) with mean age 29.1 years when they underwent surgical removal of lower third molar (Figure 1). Gender distribution did not show much signi icance with 58.4% being males and 41.6% being females (Figure 2). The study population underwent surgical removal of 38 (54.1%) more than 48 (45.9%), though not statistically signi icant (Figure 3). Of the 658 impacted teeth included in the study, 54.4% were moderately dif icult, 38.4% were minimally dif icult and 7.1% were very dif icult as per Pederson's Dif iculty Index (PDI) (Figure 4). Distribution of the amount of local anesthesia used during the procedure revealed that 2ml was suf icient to achieve adequate anesthetic  effect in 64.7% cases. This was followed by 4ml (17.2%), 3ml (14.6%), 5ml (1.8%), 6ml (1.4%), 8ml and 10ml (0.2%) ( Figure 5). Association between PDI of impacted mandibular molar and amount of local anesthesia used was statistically signi icant with p < 0.01 at con idence interval 95% ( Figure 6) ( Table 1).

Figure 6: Grouped bar graph showing association between Pederson's Dif iculty Index (PDI) of impacted mandibular third molar and amount of LA used during its surgical removal at CI 95%
Al-Dajani et al. in 2017 studied the patterns of mandibular third molar impaction in Saudi population and concluded that it was more prevalent in the second and third decade of life with a mean age of 33.5 years (Al-Dajani et al., 2017). A similar study conducted by Mitra et al. in 2016 in Indian population of Ranchi revealed mandibular third molar impaction to be more common in males of age group 21-25 years (Mitra, 2016).
The demographic data of our study population revealed similar results where the majority of patients who underwent mandibular third molar impaction surgery were in their 3 rd decade of life (53.6%) with a mean age of 29.1 years. The distribution of gender did not reveal any signi icant difference ( male -58.4%, female -41.6%) though it refuted the recent results from ; Enabulele and Obuekwe (2017); Al-Dajani et al. (2017); Dubey et al. (2019). This can be due to our stringent inclusion and exclusion criteria (Al-Dajani et al., 2017;Enabulele and Obuekwe, 2017;Dubey et al., 2019). Mahdey et al. in 2015 retrospectively analysed the Pederson's Dif iculty Index (PDI) of impacted mandibular third molar in Malaysian population using 1249 orthopantomograms (OPGs). They concluded that the majority of impacted mandibular third molars were "very dif icult" as per PDI (Mahdey, 2015). In our study however, we found that "moderately dif icult" mandibular third molars were more subject to surgical removal (54.4%).
An innovative evaluation in our study was that of the amount of local anesthetic solution used during the duration of surgical removal of mandibular third molar. We observed that in 64.7% cases only 2ml local anesthetic solution was used. The largest amount of local anesthetic solution used in this study was 10ml in 0.2% of cases corresponding to the "very dif icult" category of PDI. Malamed in his "Handbook of local anesthesia" recommends the amount of local anesthesia solution (with adrenaline) required to anesthetize each nerve. For inferior alveolar nerve blocks following the conventional technique he recommends the following: Inferior alveolar nerve-1.5ml, lingual nerve-0.2ml, long buccal nerve-0.3ml. Hence, 2 ml of local anesthetic solution containing adrenaline is suf icient to provide adequate anesthesia in conventional IANB technique (Malamed, 2020). Our inding is consistent with Malamed's statement. Association between PDI of impacted mandibular third molar and amount of local anesthesia used was statistically signi icant with p < 0.01 at con idence interval 95%.
In Figure 1, X-axis represents age in decade and Y-axis represents the percentage; patients with impacted mandibular third molars underwent open extraction of the impacted tooth more commonly in the third decade of life (55.78%). In Figure 4, the most commonly impacted mandibular third molars were moderately dif icult (54.41%) as per the PDI. In Figure 5, X-axis represents the amount of LA used during the procedure (in ml) and Y-axis represents the percentage; 2ml (64.74%) of LA solution was used the maximum while 8ml (0.15%) and 10ml (0.15%) were used the minimum. In Figure 6, X-axis represents the PDI of impacted mandibular third molar and Y-axis represents the amount of LA used in percentage and count; Chi-square test: p< 0.01 shows signi icant association i.e. as the PDI score increased, the amount of LA used also increased.

Limitations
In this retrospective observational study, the popularly used classi ication of mandibular third molar impaction viz. Winters, Pell and Gregory classi ication were not considered individually even though Pederson's Dif iculty Index is based on these classi ications. Also, this retrospective analysis is restricted to a single study niche reporting to a dental college within a narrow study duration.

CONCLUSION
Within the limits of our study, we found that 2ml of 2% lignocaine with adrenaline (1:1,00,000 or 1:2,00,000) is suf icient in achieving adequate anesthesia during surgical removal of the third molar in most cases and the amount of local anesthetic solution used may increase with increased PDI score.