INTRODUCTION:

Impaction is the failure of tooth eruption into its anatomical position due to hindrance in the eruption path, improper positioning of a tooth, absence of space, or other impediments. Impacted teeth are those which are unable to erupt in dental arch within the expected time.¹ The impacted third molars are found to have a higher incidence in the mandible than the maxilla.² Mandibular third molars tend to erupt into the oral cavity by the age of 21 years, and the frequency of occurrence of impacted teeth is higher in females than males.³

Mandibular third molars are known to be associated with different pathologies and acquire varied positions and angulations. Clinical and radiographic examinations help in classifying these teeth and diagnose varied pathologies. Impacted teeth may also cause adverse effects on the adjacent tooth which cannot be reversed.⁴

The angle of impacted teeth is measured using the Winter's classification system, by measuring the angle formed between the two longitudinal axes of the second and third molars.⁵ The Pell and Gregory classification system is one of the common methods used to classify the type of third molar impaction. In this system the impacted third molars are classified according to the relation with the adjacent second molars, its position and depth in the bone.⁵

The aim of this radiographic study was to investigate the different angles of third molar impaction, level of eruption, and its association with caries incidence in the second molars among dental patients treated in the Department of Oral and Maxillofacial Surgery in our institution.

METHODS:

This research was carried out on the case records of patients who underwent extraction of impacted mandibular third molars. A total of 35 patients presenting with lower third molar impactions reporting to the Department of Oral and Maxillofacial Surgery, Saveetha dental college and Hospital, were assessed. The inclusion criteria were age of the patients should be 18 years and above. Patients with absence of the adjacent mandibular second molars and who were below 18 years of age were excluded from the study. Clinical symptoms and pathology associated with the impacted lower third molars were recorded. Preoperative CBCT were used and the angulation of impacted mandibular third molars were determined and compared to determine the relationship with incidence of caries on the distal surface of the second molar. In this study, the angulation of the impacted teeth was defined according to stated standard definitions. The angulations were measured using tools available in the SIRONA software. Data collected, statistically analyzed and results obtained.

RESULTS:

The distribution of impacted lower third molars in our study based on the type of angulation is given in table 1. In this study, the incidence of distal caries in second molars was 45.7% , which was present in16 out of 35 patients. Among them, the percentage of distal caries in second molar in relation to the type of impacted lower third molars is depicted in Table 2.

Table 1. Distribution of angulation of impacted third molar

S. NO	Type	Percentage
1	Mesioangular	56%
2	Horizontal	29%
3	Vertical	12%
4	Distoangular	3%

Table 2.Incidence of distal caries in second molar in relation to type of impaction

S. No	Type of Impaction	Caries Incidence
1	Mesioangular	62%
2	Horizontal	27%
3	Vertical	11%
4	Distoangular	0%

DISCUSSION:

Removal of impacted mandibular third molars is one of the most common oral surgical procedures performed. Many investigators have questioned the necessity of removal in patients who are free of symptoms or associated pathologies.

Mesioangular position was the most common type of impaction in our study, with a distribution of 56% among all the impactions. This is supported by many other studies, which also exhibit a similar incidence ranging from 33.4% to 62%.^6-9 Horizontal impactions were present in 29% of patients in our study. Haidar and Shalhoub¹⁰ and Reddy and Prasad ¹¹ found that vertical impaction was the most common type of third molar impaction which is contrary to our finding. In the current study, vertical impaction was observed only in 12% of the patients. Byahatti et al. (38%)⁹ and Sandhu and Kaur (42%)¹² recorded a difference in Libyan and Asian-Indian populations, respectively, and this can be due to different classification systems used. The present study showed that incidence of the bilateral presence of impaction was relatively lesser than unilateral impaction. This is lower than that reported by Quek et al. (63%).⁶

McArdle and Renton also had found an angulation of mandibular third molars between 40° and 80° to the second molars was associated with distal cervical caries in the adjacent second molars on the evaluation of 100 patients who had 122 mandibular third molars.¹³ Another factor that is associated with the increased chances of developing distal cervical caries is the point of contact that the third molar makes with the second molar. It has been seen that partially erupted mesioangular impacted mandibular third molars which are in proximity and contact with the cementoenamel junction of the second molar have a higher risk of developing caries in this region.¹⁴ The risk of secondary caries decreases if the third molar contacts the second molar above the cementoenamel junction.

When evaluating the prevalence of caries on the mandibular second molars, mesioangular impactions had significantly higher scores than others. According to our study, the incidence of distal caries in second molars was higher (62%) associated with the mesioangular type of impactions. It was 27% with horizontally angulated molars followed by 11% for vertical impactions. The results suggest that the second molar distal caries justifies prophylactic mandibular third molar removal that has an angulation of 30-70° with a contact point on the cementoenamel. Extraction of a mesioangular third molar before the development of distal cervical caries in the second molar could thus benefit the dental health of a patient.¹⁵

Allen et al⁴ pointed out that disease or potential disease in the adjacent second molar teeth passed unnoticed in the NICE guidelines for surgical extraction of third molars. Mesioangular and horizontal mandibular third molars have been found to have a high risk of caries development and periodontal tissue damage at the second molar. Prophylactic removal of mesioangular and horizontal mandibular third molars has been suggested, especially for molars with an impaction depth of Level A. Risk factors for the development of caries in the second molar appeared to be erupted lower third molars and mesioangular impaction present for 4 to 5 years.¹⁶ Deeply impacted and unerupted mandibular third molars do not pose a great risk for caries development or pericoronitis.

Thus, mesioangularly impacted third molars showed pathologic lesions most frequently. Caries of the second molar adjacent to the third molar was more frequent in erupted maxillary third molars and mesioangular mandibular third molars.¹⁷ Periodontal bone loss was more frequent than caries in the second molars adjacent to mesioangular third molars, and the prevalence of alveolar bone loss was relatively high in second molars adjacent to horizontal or inverted mandibular third molars.¹⁸ With careful monitoring, the development of lesions in adjacent second molars may be detected early, and a mesioangular or horizontal third molar associated with caries of the second molar should be removed and a restoration should be placed on the adjacent second molar.⁴

Oral hygiene instruction and preventive advice should be emphasized to patients with mesioangularly or horizontally impacted third molars. The development of caries in the distal aspect of the mandibular second molar not only indicates the need for lower third molar extraction, but also requires restorative and possible endodontic treatments of the adjacent second molar. Furthermore, lower second molar extraction might be necessary in cases where the carious lesion is subgingival.¹⁶

Several studies have described in detail regarding impacted third molar teeth, complications during surgical removal of impacted teeth and the various drugs used for this procedure in dentistry.^19-23 It is also emphasized that maintenance of oral hygiene is essential in patients with partially erupted impacted teeth, which prevents the occurrence of dental caries and periodontal problems in that region.^24-28

CONCLUSION:

The prophylactic extraction of impacted mandibular third molars is justified by the incidence of distal caries in the second molars. Results of the present study showed that prophylactic extraction of mandibular third molars can be related to mesioangular positioning of the impacted third molar, particularly when it is above 30°. Therefore, to maintain the long-term health of adjacent mandibular second molar, it is stated that impacted third molar with mesial angulation between 30° and 70°, in particular, lying at Level A and Class I dictates for prophylactic removal of the impacted mandibular third molar.

CONFLICT OF INTEREST:

The authors declare no conflict of interest.

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Received on 11.02.2018 Modified on 10.03.2018

Research J. Pharm. and Tech 2018; 11(6): 2309-2312.

DOI: 10.5958/0974-360X.2018.00428.6