Yudex Rizcala-Orlando, Vanessa Montoya-Salazar, Daniel Torres-Lagares, José-Luis Gutiérrez-Pérez Master in Oral Surgery. University of Seville. 

INTRODUCTION

The third molars are the teeth that most frequently suffer interrupted eruption and the pathologies associated with it. Thus, according to some studies, 45% of patients have impacted third molars, and of these 75% show symptoms that would benefit from treatment. 

Despite the substantial amount of information published on impacted third molars, there are still aspects that have not been sufficiently studied or researched in the literature, such as the periodontal aspects relating to the impaction of the third molar, and particularly in relation to its close connection with the second molar.⁽¹⁾

Periodontal damage caused by impacted third molars 

Impacted or partially-impacted third molars are very frequently associated with distal attachment loss in the second molar. The kind and magnitude of periodontal damage will depend on the situation and type of impaction. 

a. Third molars impacted in the root surface of the second molar compromise the distal attachment of the second molar and weaken or eliminate the interdental bone partition that separates them. All this leads to the formation of periodontal pockets in which, without adequate plaque control, complications such as pericoronitis and even cellulitis may appear if the infection progresses (Figure 1). 

b. In the case of third molars with close proximity to the second molar, the same circumstance described in the previous case develops, and the diminished interdental bone progressively gives way to periodontopathogenic bacterial aggression. In these cases, where the second molar presents periodontal pockets and attachment loss, extraction of the third molar that is causing this condition is advisable, as otherwise the patient will have difficulty performing proper maintenance and plaque control (Figure 2). 

c. Partially impacted third molars represent an active source of bacterial entry into the distal area of the second molar due to food particle retention and poor hygiene. It has been shown that the second molar, in these circumstances, presents poorer gingival and plaque indexes. These indices improve with extraction of the wisdom tooth. If left to evolve, deep pockets will develop due to loss of attachment, which augments the anaerobic microbiota causing episodes of acute repeated infections which, if continue over time, may lead to chronic distal infection of the second molar^(2,3) (Figure 3). 

TREATMENT 

Once the periodontal damage to the second molar caused by an impacted third molar has been analysed, it is necessary to consider how it will affect clinical performance and, depending on that, a decision on the most appropriate therapy must be made. Three factors were identified: a crestal radiolucent area at the mesial surface of the third molar, an impaction pattern, and the presence of plaque (Figure 4). 

The radiographic presence of a crestal radiolucent area most likely indicates crestal bone loss due to plaque build-up, suggesting an established pre-existing periodontal lesion at the distal surface of the second molar. This will cause a periodontal pocket to develop on the distal side of the second molar which will be susceptible to plaque formation and the development of periodontitis, and which may lead to the loss of the second molar. The formation of pockets and intrabony defects occurs more frequently, and these are more severe the greater the impaction of the third molar crown relative to the second molar, or if it is in apparent contact with it. 

Regarding surgical treatment of asymptomatic third molars, the results of different studies suggest that removal of an asymptomatic third molar can improve the periodontal condition of affected young adults. Comparisons after surgery between subjects with all third molars removed and those retaining their mandibular third molars are based on a limited number of subjects, so data should be interpreted with some caution⁽⁴⁾. 

The aim of clinical performance is to preserve health and prevent periodontal damage to the second molar. First, periodontal risk must be diagnosed and assessed, and accordingly, the most appropriate therapy can be considered. Kugelberg identified a number of factors he called “periodontal risk predictors” whose presence is related to an increased likelihood of periodontal damage to the second molar or periodontal sequelae after removal of the adjacent third molar. These factors are: 

• Plaque visible on the distal surface of the second molar. 

• Probing depth greater than 6 mm on the distal side of the second molar. 

• Bone defect greater than 3 mm on the distal side of the second molar. 

• Sagittal inclination of the third molar of over 50º. 

• Large contact surface area between second and third molars. 

• Resorption of the distal root of the second molar. 

• Wisdom tooth follicle enlarged mesially over 2.5 mm. 

• Smoking. 

With a patient presenting at least three of the predisposing factors of periodontal disease described, extraction should be performed as early as possible in order to minimise the risk of periodontal disease distally to the second molar.  

CONCLUSIONS 

When evaluating the mesial periodontal condition of impacted mandibular third molars, oral health practitioners should watch for signs of periodontal disease showing in the distal areas of the mandibular second molars. It is also important to insist on early extraction of the third molar when some of the predictive factors are present in order to reduce subsequent periodontal problems in the second molar. A review using panoramic radiography is necessary in cases of patients with presence of erupting or erupted wisdom teeth.