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The purpose of this retrospective study was to evaluate risk factors for external root resorption (ERR) on maxillary second molars (MxM2) in association with impacted third molars (MxM3) using cone beam computed tomography (CBCT) scans. The angles between the axes of MxM2/MxM3 (inclination) were measured. Further, ERR on MxM2 was classified as absent, slight, moderate, or severe. Contact location between MxM3 and MxM2, the size of the dental follicle, type of impaction, root formation, and patient demographic characteristics were also assessed. Half of the 84 MxM2 showed ERR (slight 36.9%, moderate 6.0%, severe 7.1%). Patient age was a significant factor for the presence of ERR (P = 0.03). The inclination was also a relevant factor, with transverse MxM3 exhibiting the highest risk of ERR (P = 0.02). The cervical third (28.6%) showed a significantly lower risk percentage of ERR compared to the apical (73.7%) and middle thirds (60.6%) of the root (P = 0.004). Based on these findings, clinicians assessing the need for surgical removal should be able to selectively identify impacted MxM3 at risk of causing ERR on MxM2 early on, especially when the MxM3 is located in close contact with the apical and middle thirds of the MxM2 roots and has a transverse inclination., (Copyright © 2019 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.)

This randomized controlled trial (RCT) (ClinicalTrials.gov ID: NCT03001791) compared excisional biopsies of fibrous hyperplasia performed using a CO 2 laser (140Hz, 400μs, 33mJ), Er:YAG laser (35Hz, 297μs, 200mJ, air-water cooling), or scalpel (15c blade). Clinical parameters recorded were duration of the intervention, intraoperative bleeding, need for electrocauterization and/or suturing, postoperative side effects, complications, pain, and intake of analgesics. Histopathological linear measurements of the thermal damage zone were performed on the laser biopsies. Results showed that the duration of the intervention was significantly shorter for both lasers compared to the scalpel (P<0.001). Intraoperative bleeding occurred less frequently with the CO 2 laser (P<0.001). Additional electrocautery was used in 92% of Er:YAG laser interventions (P<0.001). Postsurgical complications, pain, and the intake of analgesics did not differ between the groups. The measured thermal damage zones differed significantly between the CO 2 laser (median of 72.6μm) and Er:YAG laser (30.9μm) (P<0.001). This RCT showed that CO 2 laser, Er:YAG laser, and scalpel are all adequate for excisional biopsies of small lesions in the oral mucosa. While patient postoperative morbidity is similar, the ideal instrument can be selected according to the surgical advantages preferred for the individual situation., (Copyright © 2019 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.)

External root resorption (ERR) affecting mandibular second molars (M2) may occur when the adjacent third molar (M3) is impacted in close proximity. This retrospective cohort study aimed to assess the presence, severity, and location of ERR on M2 due to M3 using cone beam computed tomography (CBCT) scans and to identify associated factors. The angle between the axis of M2 and M3 was measured. ERR on M2 was classified as absent, slight, moderate, or severe. The location of contact between M3 and M2, the size of the dental follicle, and patient demographic characteristics were recorded. A total of 433 patients with 640 M3 were included. A male predilection was found with regard to ERR (P=0.0004). ERR was identified on 31.9% of M2 and was slight in 30.2%, moderate in 1.4%, and severe in 0.3% of cases. The presence of ERR was associated with direct contact between M2 and M3 (P<0.0001), the angle between M2 and M3 (P<0.0001), the inclination of M3 (P=0.001), and the location of contact (P=0.0005). This study showed ERR to be a frequent finding. ERR is associated with a mesioangular position of M3 in more than one third of cases, and a proximity ≤0.5mm between M2 and M3 favours ERR., (Copyright © 2018. Published by Elsevier Ltd.)