Do Mesial Angled Wisdom Teeth Cause Problems to Adjacent Second Molars

An interesting article titled “Mesial Inclination of Impacted Third Molars and Its Propensity to Stimulate External Root Resorption in Second Molars—A Cone-Beam Computed Tomographic Evaluation” written by Anne Caroline Costa Oenning and et al. appears in the 2015 Journal of Oral and Maxillofacial Surgery (vol. 73, pp. 379-386). The authors explore cone-beam computed tomography (CBCT) scans to look at the teeth in the mouth. They look at the  presence of external root resorption (ERR) in second molars adjacent to horizontally and mesioangular impacted mandibular wisdom teeth.

Unlike cavities, ERR is usually asymptomatic and aseptic, unless the pulp cavity has been involved or the lesion has been secondarily infected. Literature attributes the occurrence of this resorption to pressure from an adjacent impacted tooth. This pressure can activate clastic cells responsible for triggering resorption. Studies of periapical and panoramic radiographs have looked at the presence of ERR in second molars adjacent to impacted wisdom teeth. Most of these studies have reported a low prevalence of ERR in second molars ranging from 0.3% to 7%. Even so  cone-beam computed tomographic images have been compared with with panoramic images and the detection of
ERR on second molars was found to 4.3 times greater with the 3D images in a study. The authors therefore set out with their study to further explore these issues.

A total of 217 CBCT scans of patients in Sau Paolo Brazil were used with 120 from one type of scanner and the other 97 from a different type of scanner. Scans were required to have a second molar adjacent to a horizontally or mesioangular impacted mandibular third molar visible. According to what is known as the Winter classification, a wisdom tooth is mesioangular when it is inclined mesially with the long axis at an angle range of 31 to 60 degrees to the occlusal plane and it is horizontal when its axis is at an angle 0 to 30 degrees to a tangent to the occlusal plane of the adjacent teeth.

The overall prevalence of ERR was found to be 49.43%. There were no statistically significant differences found in the detection of ERR by gender or specific wisdom teeth inclination. Of the 70 women included in the study, 58.6% had ERR in at least 1 tooth. Of the men in the study, this proportion was 60.9%, which is not statistically different from the proportion found in women. The results showed the proportion of patients affected by ERR in a younger age group was smaller than in the other age groups.

The authors state

“The high prevalence of ERR lesions in the second molars included in this study reinforces a theory formulated in previous studies performed with conventional radiographs and heterogeneous samples: mesially inclined third molars have greater potential to be associated with pathologic conditions, such as root resorption.”

The authors found that when the wisdom teeth is near the occlusal plane of the second molar and when the wisdom teeth is located at a level between the occlusal plane and the cementoenamel junction of the second molar of patients older than 24 years than they are more associated with the presence of ERR in the adjacent teeth. This study deserves care of understanding for those patients who are considering either retaining or removing asymptomatic wisdom teeth.

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