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Why Do Wisdom Teeth (Third Molars) Require An Extraction?

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It’s imperative to understand the basic anatomy of a tooth, to begin with. Usually, children are taught this at an early stage that humans have a set of thirty-two teeth in their oral cavity. Sixteen teeth in the upper arch, this arch is called maxilla and sixteen teeth in the lower arch named mandible. It can further be divided into four quadrants. Upper right and left, lower right and left. Third molars are situated further back in each quadrant. You may be able to find it when you swipe your tongue most posteriorly to the last tooth found, these are the wisdom teeth that you are touching. However, it’s never mentioned that third molars which in layman terminology are also known as “wisdom teeth” do not carry much importance regarding mastication. Mastication is the process of chewing down on food so that swallowing the meal becomes easy.

A tooth, when seen in a sagittal view, can be divided into a clinical crown that is visible in the oral cavity and the roots which are located underneath the crown not visible in the oral cavity. These roots are embedded in the bone named alveolar bone and holding them tightly in a cup-like fashion is an alveolar socket. Third molars are usually smaller in size in comparison to their counter tooth making them the smallest molars hence may not come in contact when a person closes his/her bite. Compared to the rest of the teeth, the crowns of these molars are irregular. They may be sharper than the adjacent teeth or bulky in appearance. These molars have a variation in their development, not only in their crowns but also in their roots. Their roots might be divergent, conical or malformed. In this case, the malformed roots can rarely cause infection either at the tip of the root called apex or irritate the adjacent roots. Thus, in such instance extraction becomes compulsory. 

There are multiple factors that might be disease-related in which wisdom teeth are present but are unable to erupt although in other cases, they have partially erupted. These factors determine if the third molars will require extractions.Advertisement

Several major factors may play an important role in choosing third molar extraction.

Prosthodontic-related third molars extractions

Complete dentures construction:  Sometimes old patients who have lost most of their dentition will require extraction of all the remaining teeth including the third molars. This is a pre-requisite for the construction of a complete denture. Until all the teeth including the third molar are not extracted, it is not called a “complete denture”. On top of that, the last tooth would not allow the extension of the denture to seat on the retromolar pad area.

Partial denture construction: At times patients of different ages might require a maxillary or mandibular partial denture due to missing teeth for several reasons. For instance, one whole upper right quadrant is missing all seven teeth ‘2.1 to 2.7’ except the third molar. In such a case, you will have to extract the third molar for the construction of the upper left partial denture.

Dental crowding 

In a few patients, the arch length might be insufficient to accommodate the eruption of the permanent dentition competently. In such cases, third molar extraction is required to make space for the eruption of permanent teeth. This will eventually require orthodontic brackets placement and wiring to correct the teeth in class one molar relationship. 

Clinical crown angulation and Morphology  

Mucosal Irritation: Wisdom teeth may constantly irritate the buccal mucosa also known as the inner cheek. The inner cheek covers the ramus, ramus is the anterior portion of the mandible. If the third molar is buccally tilted, it might cause irritation to this portion and might interfere upon opening and closing the jaw. 

Cheek biting; can also be a cause due to buccally tilted third molars. When the buccal mucosa lies in between the tilted third molars, the cheek is bitten upon closure of the jaw. This can cause hypertrophy of the buccal mucosa due to repeated trauma to the buccal mucosa upon biting. In such cases, extraction is the best solution otherwise it might lead to very painful swelling and ulceration of the mucosa.

Bulbous and/or sharp third molars;such morphology of the wisdom teeth may also cause ulceration of the buccal mucosa due to constant irritation.

Amorphous third molar’s morphology can be troublesome when constructing a denture. The irregular tooth structure can cause impingement when the base of the denture is seated. 

Impacted third molars

Third molars can be completely impacted or partially impacted. The tooth being vertically impacted has a relation to the occlusal plane. Extracting completely impacted third molars which is deep in relation to the occlusal plane is much more difficult than the ones which are partially impacted or close to the occlusal plane. Another factor that requires an assiduous effort in wisdom tooth extraction is their horizontal angulation. The distoangular impaction of the third molar in the mandible is the most difficult extraction to perform. Although, Mesioangular third molar impactions are the most difficult extractions in the maxilla. When the third molar is horizontally impacted and its crown is absorbing the distal portion of the second molar which lies next to it, extraction becomes a momentous action. If not, then this will increase the chances of distal caries in the second molar which will eventually lead to tooth structure destruction. Sometimes the lower third molars which are closer to the Inferior alveolar nerve might eventually start compressing the never. This nerve also supplies the lower lip that can lead to temporary numbness of that side of the lip. If no action is taken this may cause permanent nerve damage thus numbness of the lower lip. Healthy adjacent teeth might end up requiring an RCT or an extraction which can be avoided by early extraction of the angulated molar. 

Carious tooth

Caries attack is not only limited to the first and second molars. It can include the third molars as well. When this happens, filling the tooth with composite or amalgam is not the most logical decision since the third molars are too far posterior in the arch. Not only that but they are not as significant as other molars such as first and second to maintain the occlusal table’s anatomy. The best option, in this case, is extraction but still, the patient’s treatment affordability is a determinant to consider.

Poor crown to root ratio 

The ideal crown to root ratio is 2:3. Crown to root ratio that is 1:2 is still tolerable but 1:1 is not. Third molars that have had caries occurrence or trauma which leads to loss of more than half of the clinical crown structure will have a poor prognosis to RCTs or fillings. Inevitably extraction is the answer.

Periodontal etiology 

On certain occasions when clinically observed, there can be a periodontal defect in the distal region of the second molar. This is caused when the third molars are mesially angulated and causing food accumulation in the interproximal region of the two molars. Gingivitis leads to periodontitis since flossing and brushing is almost impossible in this area. This leads to deep periodontal pockets with surrounding alveolar bone loss. These defects may further progress into bone loss at the furcation area of the second molar. The prognosis is poor for these teeth and eventually, the second molar will have to be extracted.   

Crown and root fracture

The prognosis of the fractures of the clinical crown depends on the region of fracture. Occlusal crown fractures have a good prognosis and barely require extraction. Composite or amalgam fillings are the treatment of choice. Middle third crown fractures have a poorer prognosis. The worst prognosis involves the fractures where the crown and root intersect. These fractures require extraction. In the case of root fractures, the coronal third and middle third will usually require extraction whereas the apical third fractures usually just require apicoectomy for a good prognosis.

 Vertical root fracture runs from the occlusal portion of the crown to the end of the apex beyond the gum line. The only feasible treatment, in this case, is the extraction of the third molar.

Operculitis & pericoronitis 

Operculitis is the inflammation caused by constant irritation from the contralateral third molar pressing on the operculum that is overlying gum of the molar. Accumulation of the bacteria and debris beneath the gum can lead to pericoronitis. This is extremely painful and may cause severe inflammation which could lead to difficult mouth opening. Since the wisdom teeth are not of any significant importance, their extraction, in this case, is the best treatment of choice.

Cysts & infections

Several cysts related to a tooth warrant an extraction to resolve the etiology. Dentigerous cysts are the cysts that cover the crown of an unerupted permanent tooth, usually found in the third molar region. These cysts have the potential to transform into ameloblastoma which is malignant. Enucleation is required along with the extraction of the involved molar since these teeth are non-vital. Usually periapical radiolucency or also known as radicular cyst which signifies root apex infection will usually require extraction because the tooth is non-vital. Periapical or periodontal abscesses require drainage and ultimately extraction of the involved tooth.

Failed RCT 

Broken tooth after RCT’s should be extracted due to poor prognosis. In a few clinical scenarios, patients who previously had a root canal treatment come with endo-perio lesions which in simpler words mean that infection at the base of the root’s apex has now spread laterally and involved the periodontal ligament space. Bone loss, periodontal space widening, and radiolucency can be observed on the x-ray. The tooth becomes mobile and tender to percussion. Extraction instantly causes relief of the pain and pressure.

All the extractions should be performed under proper clinical setting by a competent dentist. Hemostatic measures should be readily available especially for patients who suffer from blood disorders or are on a blood thinner such as aspirin due to certain heart conditions. Local anesthesia generally used is lidocaine with 1:100000 epinephrine. For a longer duration of surgery, bupivacaine is the choice of anesthesia to use. In the case of several third molars extraction, general anesthesia is considered. Patients should be asked to have had breakfast before their appointment on that day. Patients with certain diseases such as tuberculosis should be dealt with accordingly. 

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Written by dr-talhahr

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