A 7-Year Retrospective Analysis on Surgical Removal of Impacted Mandibular Third Molar at a Tertiary Care Center in Kuantan, Malaysia

Malaysian Dental Journal

Vol 1/2020

MALAYSIAN DENTAL JOURNAL

Soh Chen Loong1, Tan Peh Ge2, Kamini a/p G Raman2 1Oral and Maxillofacial Surgeon, Oral and Maxillofacial Surgery Department, Hospital Tengku Ampuan Afzan, Kementerian Kesihatan Malaysia.

2Dental Officer, Oral and Maxillofacial Surgery Department, Hospital Tengku Ampuan Afzan, Kementerian Kesihatan Malaysia.

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ABSTRACT

Aim: To assess the frequency of complications in relation to impacted third molar surgery and complications in relation to operator experience and difficulty score of impacted third molar.

Materials and Methods: This is a retrospective study involving 1577 cases of surgical removal of impacted mandibular third molar in Hospital Tengku Ampuan Afzan, Kuantan from January 2012 to December 2018. Radiographs, either intraoral periapical radiographs or orthopantomogram, in patient’s records were analysed and the tooth are classified according to Pell and Gregory classification of impacted mandibular third molar and difficulty scored according to Pederson Index.

Results: The complications reported in our study are paraesthesia, dry socket and post-operative infection. Paraesthesia is the most prevalent complication, accounting for 1.4% (n=22) of all cases. Dry socket is the second most common complication at 1.3% (n=21), followed by post-operative infection at 0.8% (n=13). The overall complication rate is 3.5%.

Conclusion: Risk and complications from surgical removal of impacted mandibular third molar is relatively low. Operator experience is significantly related to paraesthesia (p < 0.05) whereas post-operative complications are not related to difficulty of surgery. Suggestions for future research include development of a new

Malaysian Dental Journal

Vol 1/2020 index or scale which incorporates all factors that are shown to be associated with higher difficulty and reflects the true difficulty of the surgery.

Keywords: Impacted third molar, minor oral surgery, complications

INTRODUCTION

Tooth impaction is a pathological condition where a tooth fails to achieve its normal functional position. In humans, mandibular third molar is the most common impacted teeth. Bony obstruction in the path of eruption or obstruction by adjacent tooth causes failure of incomplete eruption in mandibular third molar.1 Other less common causes of impacted third molar are abnormal positioning of the tooth bud, supernumerary tooth and retained, ankylosed deciduous tooth.1

Impacted mandibular third molar may remain asymptomatic or may be associated with several pathologies such as caries, periodontitis, pericoronitis, cysts, tumours and also root resorption of the adjacent tooth. Symptomatic impacted third molars are clinically indicated to be removed via minor oral surgery. In the field of oral and maxillofacial surgery, surgical removal of impacted lower third molars are one of the most common dentoalveolar surgery performed.2

Proper pre-operative planning and adherence to surgical principles decreases the incidence of complications. However, as in all surgical procedures, there is a still risk of post-operative complications. The common complications of third molar removal are alveolar osteitis, infection, bleeding and paraesthesia of the inferior alveolar nerve and lingual nerve. Mandible fracture and iatrogenic displacement of third molar are rare but severe complications which should be informed to patient prior to surgery.3

This article addresses the frequency of specific complications and factors that contribute to increased rates of complication in impacted third molar surgery. Complications that were looked into in this study were alveolar osteitis, infection and paraesthesia in relation to operator experience and difficulty of removal of impacted third molar.

Malaysian Dental Journal

Vol 1/2020 MATERIALS AND METHODS

Medical records of patients referred to Oral and Maxillofacial Surgery Department at Hospital Tengku Ampuan Afzan for surgical removal of impacted mandibular third molar from January 2012 to December 2018 were retrospectively collected. Ethical approval was obtained from Malaysia Research and Ethics Committee prior to data collection (NMRR-18-4000-41593 IIR).

Patients’ demographic details, location of impacted tooth, type of anaesthesia, presence of complications, position, level and angulation of tooth and operator level of experience were recorded.

Radiographs, either intraoral periapical radiographs or orthopantomogram, in patient’s records were analysed. Based on the radiographs, the depth of impacted third molar in relation to occlusal plane (Class A, B, C) was recorded along with the distance or width between the vertical ascending mandibular ramus and the distal surface of the second molar (Class I, II, III) according to the classification of Pell and Gregory.4 The angulation of impacted third molar was documented based on Winter’s classification with reference to the angle formed between the intersected longitudinal axis of the second and third molars. Pederson scale is used to determine operative difficulty based on the angulation and Pell and Gregory classification.5 Difficulty score was assigned in accordance to Table 1.

Classification Value

Spatial Relationship

Mesioangular 1

Horizontal/transverse 2

Vertical 3

Distoangular 4

Depth

Level A: High occlusal level 1

Malaysian Dental Journal

Vol 1/2020 Level B: Medium occlusal level 2

Level C: Deep occlusal level 3

Ramus

Class 1: Sufficient space 1

Class 2: Reduced space 2

Class 3: No space 3

Difficulty index

Very difficult 7-10

Moderate difficult 5-6

Slightly difficult 3-4

Table 1: Difficulty index for the removal of impacted mandibular 3rd molars

The complications looked into were paraesthesia, alveolar osteitis and infection. Pain, bleeding, swelling and trismus were regarded as expected sequelae and thus not included as complications in this study. Mandibular fractures and iatrogenic displacement of tooth were not observed within our study population.

STATISTICAL ANALYSIS

Data is analysed using IBM SPSS Statistics for Windows, Version 20.0 (Armonk, NY: IBM Corp). Comparative statistics were done using Chi-square and Fisher’s exact tests as appropriate. A P<0.05 was considered significant.

RESULTS

A total of 1577 of surgical removal of impacted mandibular third molars were done within a 7-year period from 2012 to 2018. Of this 1577 cases, 54% (n=852) are females and 46% (n=725) are males. The mean age of patients is 28 years old.

The number of 38 and 48 surgically removed was almost similar, with a slight predominance of 38 at 51.9% (n=818) and 48 following closely at 48.1% (n=759)

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Vol 1/2020 Mesioangular impaction accounted for the highest percentage of all types of angulation at 41.2% (n=649), followed by horizontal impaction at 36.8% (n=580). Vertical impaction was the third most common impaction at 13.4% (n=212). Distoangular impaction accounted for 8% (n=126) of all reported third molar surgery done at our study site. Other types of impaction, such as buccal and lingual impaction only accounted for 0.6% (n=10). Table 2 shows the mean of patients’ age, site of operation, distribution of gender and each type of impaction, depth of tooth in relation to adjacent tooth and position of tooth in relation to anterior border of ramus of mandible.

Sample characteristics n=1577

Age, Mean ± SD 27.86 ± 6.1 27.86 ± 6.1

Gender Male 725 (46)

n (%) Female 852 (54)

Impacted mandibular 38 818 (51.9) third molar

n (%) 48 759 (48.1)

Mesioangular 649 (41.2)

Horizontal 580 (36.8) Angulation of impacted third molar Vertical 212 (13.4)

n (%) Distoangular 126 (8)

Others 10 (0.6)

Table 2: Distribution of patients with regards to age, gender, site of operation and angulation of impacted third molar.

With regards to Pell and Gregory classification, the most commonly observed type of classification was A1 at 45.3% (n=715), followed by A2 at 32.0 (n=520). Figure 1 shows the percentage and frequency of each type of classification.

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Vol 1/2020

Figure 1: Frequency of impacted mandibular third molar in relation to Pell and Gregory classification

Difficulty score is calculated based on Table 1. Buccal and lingual impaction are not covered under Pederson Difficulty Index, thus they are not included in data analysis and will be discussed separately. As seen in Figure 2, the most common group in this study is ‘slightly difficult’ at 48.6% (n=762), followed by moderately difficult’ at 40.2% (629). Only 11.2% (n=176) of impacted mandibular third molar belong in ‘very difficult’ group.

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Vol 1/2020

Figure 2: Frequency of impacted mandibular third molar in relation to Pederson Difficulty Index

The overall percentage of complication is 3.5%.

The most common complication in our study population is paraesthesia. A total of 22 cases of paraesthesia was seen, which accounts for 1.4% of all cases. Paraesthesia was more commonly seen in surgical removal of tooth 38 (54.5%, n=12), followed by tooth 48 (45.5%, n=10). Involvement of the inferior alveolar nerve only was the most common (81.8%, n=18). Lingual nerve involvement only and both inferior alveolar nerve and lingual involvement had 2 cases each. Most of the paraesthesia resolved with time, with 77.3% (n=17) being transient paraesthesia. Only 22.7% (n=5) were permanent paraesthesia. The location of the impacted third molar, either on the right or left, is not significantly associated with paraesthesia (p value = 0.797). Injury to inferior alveolar nerve is reported to happen more frequently in association with 38. Table 3 shows the details regarding paraesthesia in relation to tooth.

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Vol 1/2020

Percentage (n) Nerve Percentage of total Permanent/Transient involved paraesthesia (n) Paraesthesia

38 54.5 (12) IAN 50 (11) 2/9

LN 0 (0) 0/0

IAN+LN 4.5 (1) 0/1

48 45.5 (10) IAN 31.8 (7) 2/5

LN 9.1 (2) 1/1

IAN+LN 4.5 (1) 0/1

Total 100 (22) 100 (22) 5/17

Table 3: Distribution of paraesthesia as a complication

(IAN: Inferior alveolar nerve; LN: Lingual nerve; IAN+LN: Involvement of both inferior alveolar nerve and lingual nerve)

Dry socket was the second most common complication at 1.3% (n=21).

Lastly, at 0.8%, with only 13 reported cases, post-operative infection was the least common complication. Post-operative infection in our centre is diagnosed as such when there is persistent swelling, pus discharge from the operative site, non- resolving trismus and worsening pain. No other complications were reported in our study.

In this centre, surgical removal of impacted third molar are removed by either dental officer or oral and maxillofacial surgeons. 78.6% (n=1240) of cases were performed by dental officers and the remaining 21.4% (n=337) were done by specialists.

Surgical removal of impacted mandibular third molars were removed either under general anaesthesia or local anaesthesia. 1309 of cases were carried out under local anaesthesia and 268 cases were done under general anaesthesia in the operation theatre either under day care or conventional operation. Out of all 1577 cases,

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Vol 1/2020 specialists performed 263 cases under general anaesthesia and 74 cases under local anaesthesia.

When complication rates are compared between the two groups of the operator, paraesthesia is noted to be significantly higher among specialists (p value= 0.014). There is no statistically significant difference between operator for dry socket (p- value= 0.101) and post-operative infection (p-value= 1.000)

More difficult cases are performed under general anaesthesia, with a mean difficulty score of 5.06 for cases done under general anaesthesia and 4.6 for cases done under local anaesthesia. When comparing operator and the difficulty score, it is noted specialists operated on more difficult cases with a mean of 5.15, which is moderately difficult.

There is no statistically significant difference between types of anaesthesia and all 3 complications recorded in this research. In addition, there is no correlation between difficulty score and all 3 complications. The p-values for each complication in relation to types of anaesthesia and difficulty score can be seen in Table 4.

p-value

Complications n (%) Difficulty Type of Anaesthesia score

Paraesthesia 22 (1.4) 0.402 0.332

Dry socket 21 (1.3) 0.235 0.817

Infection 13 (0.8) 1.000 0.315

Total 56 (3.5)

Table 4: Complications of surgical removal of impacted mandibular third molar (paraesthesia, dry socket and infection) in relation to types of anaesthesia (local anaesthesia versus general anaesthesia) and difficulty score.

Malaysian Dental Journal

Vol 1/2020 DISCUSSION

Surgical removal of impacted third molar is a routine procedure especially in the oral and maxillofacial surgery setting. Complications can range from the common complications as reported in this study to rarer complications such as mandible fracture, subcutaneous emphysema and dislodgement of instruments into submandibular space.3 Even though the less common complications were not observed in our study, it should still be informed to patient. Post-operative complications can be distressing to patients, with worsening quality of life post- operatively which usually returns to normal in as early as 7 days. Therefore, patients must be informed of the surgical risks prior to operation.6

Paraesthesia is a known risk in impacted third molar surgery. Due to the close proximity of the lingual nerve and inferior alveolar nerve to an impacted third molar, there is a tendency to damage the above-mentioned nerves during removal of an impacted third molar.

With regards to the inferior alveolar nerve injury, risk factors include patient age from 26-30 years, horizontally impacted teeth, close radiographic proximity to the inferior alveolar canal and treatment by trainee surgeons.7 For lingual nerve paraesthesia, risk factors are male patients, distoangular impactions, close radiographic proximity to the IAC, and treatment by trainee surgeons.7

Paraesthesia rates within our studies are similar to other studies. The overall percentage of paraesthesia is 1.4%, which is within the reported range from 0.5% to 22%. 8 Percentage of isolated lingual nerve paraesthesia is 0.001%, on the lower end of the reported range of 0-23.0% whereas percentage of isolated inferior alveolar nerve paraesthesia is 0.011%, lower than the reported range of 0.4-8.4%7

Interestingly in our research, there is a higher paraesthesia complication rate among specialist, which is statistically significant. Similar findings were also reported by Leung et al. 9 This can be due to higher difficulty of cases being assigned to the specialists or due to the smaller sample size for the specialist group, magnifying the complication rates among the group.

Dry socket, also known as alveolar osteitis is a diagnosis characterised by severe, throbbing pain that often happens 3 days after extraction or surgical removal of a tooth.10 It is often accompanied by halitosis and on examination, the socket is devoid

Malaysian Dental Journal

Vol 1/2020 of a blood clot with exposed bone or a socket filled with food debris.10 Risk factors for dry socket include higher difficulty of surgery, female patients, use of oral contraceptives, smoking and poor oral hygiene.10 Risk of dry socket can be reduced by use of chlorhexidine mouthwash 0.12-0.2% and chlorhexidine gel.10

The frequency of dry socket ranges from 0.3%-26% and 1%-37.5%.3, 11 We report a 1.3% frequency of dry socket within our study population. Dry socket can significantly affect patient’s quality of life and treatment need to be carried out to relieve patient’s symptoms. Treatments for dry socket include curettage and irrigation with chlorhexidine rinse, placement of intrasocket medicaments such as Alvogyl which consists of butamben, eugenol and iodoform, and low-level laser treatment.10 In our study, operator experience is not significantly related to dry socket. A similar finding is reported by Abu Younis and Abu Hantash.12

Patients with postoperative infection can present with localised infection, with pain, swelling and minimal discharge and systemic symptoms such as fever to severe orofacial infection involving the deep fascial spaces.13 Submandibular space infection is the most common infected fascial space and it should be treated as an emergency due to its potential of causing life threatening complications.14

Post-operative infection rate in our study is reported at 0.8%, which is within the rates reported by other studies which is from 0.8% to 4.2%. Risk factors for this complication includes age, degree of impaction, need for bone removal or tooth sectioning, exposure of the inferior alveolar neurovascular bundle, presence of gingivitis or pericoronitis, surgeon experience, use of antibiotics and location of surgery.3 In our study, the surgeon’s experience is not related to post-operative infection and this is supported by Brunello et al.15

Surgical removal of impacted third molar can be done either under local or general anaesthesia. The majority of cases are performed under local anaesthesia as seen in our study and other studies as well.16, 17 General anaesthesia have a higher risk of complication compared to local anaesthesia, with complications such as nausea and vomiting and even death.18, 19

In view of these complications, only selected case is done under general anaesthesia. The indications for general anaesthesia in dentistry includes patient with severe gag reflex, difficulty in maintaining mouth opening for procedure and when procedure is likely to be extensive and difficult.20 This correlates with our data where more difficult

Malaysian Dental Journal

Vol 1/2020 third molar surgery are done under general anaesthesia. There is no correlation between types of anaesthesia and complications in our study.

In Malaysia, there is no specific classification or difficulty scoring during the referral of cases to a specialist clinic. However, Pell and Gregory classification is the most commonly utilised classification in our setting and Pederson Index is used to calculate the difficulty score.

In our study, difficulty score is not correlated with rates of complications. Difficulty score is only associated with difficulty in taking out the tooth and is not correlated with any complications in our study. Higher difficulty of surgery is associated with dry socket and infection; However, the complications are due to longer surgical procedure and more extensive tissue manipulation rather than a higher degree of difficulty.

Pell and Gregory classification and its associated difficulty scale, Pederson scale are not reliable predictors in surgical difficulty. It is the most utilised classification as it only requires radiographic assessment, does not require clinical assessment and thus quick to be carried out.

However, Pederson index has shown low sensitivitiy and specificity in predicting the difficulty of surgery for impacted mandibular third molar. Clinicians must be made aware of its drawbacks as it is not the most suitable tool for prediction of difficulty.21

Gonzales et al 22 determined patient’s body weight, distal space available for eruption, bulbous root and need for tooth sectioning are factors which are associated with higher difficulty. Out of these criteria, only distal space available for eruption is included in Pederson Index for difficulty. Currently, there are no classification that take into account all these factors. 22

CONCLUSION

Risk and complications from surgical removal of impacted mandibular third molar is relatively low. However, complications experienced will affect patient’s quality of life. Operator experience is significantly related to paraesthesia but it is likely due to the difficult cases being assigned to specialists. Post-operative complications are not related to difficulty of surgery.

Malaysian Dental Journal

Vol 1/2020 Preoperative assessment is important to assess the difficulty in removal of impacted third molar. Suggestions for future research include a modification to Pederson Index or development of a new index or scale which incorporates all factors that are shown to be associated with higher difficulty.

ETHICAL APPROVAL Ethical approval obtained from Malaysia Research and Ethics Committee (NMRR- 18-4000-41593 (IIR))

FUNDING No funding

CONFLICT OF INTEREST None declared

ACKNOWLEDGEMENT We would like to thank the Director General of Health Malaysia for his permission to publish this article.

Malaysian Dental Journal

Vol 1/2020 REFERENCES

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Vol 1/2020 21. Bali A, Bali D, Sharma A, Verma G. Is Pederson Index a True Predictive Diffificulty Index for Impacted Mandibular Third Molar Surgery? A Meta-analysis. J Maxillofac Oral Surg. 2013;12(3):359-364.

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