Formation of a deep periodontal pocket distal to the second molar subsequent to removal of an impacted third molar is a concern. Occurrence of this postoperative complication may be inevitable when a pocket already exists prior to surgery in the region of the impaction. The majority of third molar teeth are not completely bone-impacted; therefore, distoproximal bone loss in the distocervical area of the second molar is not an uncommon preoperative finding (Figure 1). In such cases, third molar removal leaves a defect extending down to the level of the remaining distoproximal bone. This defect may not repair, especially in older patients. This in turn can lead to pocket formation (Figure 2). Preventing this outcome is a challenge. However, in other situations such as a horizontally impacted third molar whose crown is in contact with the distal root of the second molar, a periodontal pocket in this area is not seen preoperatively (Figure 3). This is because the alveolar crestal bone overlying the impaction is intact. Overly aggressive bone removal distal to the second molar may cause a pocket to develop postoperatively. When the overlying crestal bone is removed with the impaction, an osseous defect distal to the second molar, extending down to the base of the bony extraction socket, will result (Figure 4). Once this periodontal lesion (pocket) is established, treatment may require further surgical intervention to eliminate the periodontal pocket, or regenerate the lost periodontal support. Ultimately, extraction of the second molar may be required if the periodontal defect extends to the apex of the second molar tooth. Thus, prevention is essential.
Rationale
The standard procedure to remove impacted third molars includes (1) reflecting a full-thickness mucoperiosteal flap, (2) removing the bone overlying the impaction, (3) removal of the buccal cortical bone, (4) sectioning of the tooth, and (5) removal of the tooth segments and the dental follicle.1 Peterson recommends that during removal of a horizontally impacted third molar, a bur should be used to remove the overlying bone.1 But as previously stated, when the crown of an impacted wisdom tooth is in direct contact with the distal root of the second molar and is not separated by a bony septum (Figure 3), removal of the bone overlying the impaction may result in the formation of a deep periodontal defect on the distal aspect of the second molar. The depth of the resultant defect will be related to the mesio-distal length of the crown plus the angulation and depth of the impaction (Figure 4). The result is a 3-walled (or 2-walled if the buccal plate is removed) bone defect in which bone formation is unpredictable. Epithelium may migrate down the distal surface of the second molar, preventing bone formation (Figure 5). Therefore, during the course of the surgery, it is important to attempt to preserve the bone overlying the impaction (Figure 6).
Surgical Technique
After reflection of a full-thickness mucoperiosteal envelope flap, bone removal is started in the buccal cortex 2 to 3 mm below the bony crest using an electrically driven surgical handpiece and a round surgical bur. Next, an oval window of buccal bone is removed overlying the lateral part of the crown and posterior to the root of the second molar. Care is taken to create the anterior part of the buccal window more than 2 mm from the distal root of the second molar (Figure 7). After the crown and the upper third of the roots are exposed, the impacted tooth is sectioned at the cemento-enamel junction using a round or fissure bur. This will create space into which the sectioned crown can be moved (Figure 8). In order to prevent damage to the lingual cortex or the inferior alveolar nerve, it is safer not to section the tooth completely. A straight elevator is placed in the created vertical groove and rotated so that the crown is separated from its roots. The crown is then sectioned horizontally and delivered buccally in 2 or more pieces. Next, the roots are sectioned at the bifurcation, and the distal and mesial roots are removed separately. Alternatively, the roots may be removed in one piece when they are fused, or they may be removed before removal of the crown when space permits. After removal of the dental follicle, the flap is sutured with the edges of the flap resting on bone.
In the above situation the tooth is fully impacted, and therefore no calculus exists on the distal surface of the second molar. Furthermore, since only a lateral cortical defect is made into the bone in the lateral cortex, there is no need to graft into the defect, and in the majority of cases it will fill with bone. However, if in doubt, especially in older patients, autografts or allografts may be employed with this technique. Further, if plaque and calculus are present on the distal surface of the second molar, careful removal is indicated.
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