19 May 2023

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Effect of piezocision-assisted lower second molar protraction on periodontal tissues, alveolar bone height, and lower second molar root resorption

Davide Elsido

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Orthodontic treatment duration varies depending on the type of malocclusion, extraction or nonextraction treatment plan and patient compliance. Generally, treatment involving closing extraction spaces may prolong treatment duration. Conventional treatments using fixed appliances require 18 to 24 months, where it takes one-third to one-half of this duration to close the extraction space.

Many techniques have been developed to accelerate orthodontic tooth movement and, hence, shorten treatment time. These include surgical and nonsurgical approaches. 

Surgical techniques rely on the concept of the regional acceleratory phenomenon (RAP). When a surgical wound is created, it induces the healing process and increases the number of inflammatory mediators around injured tissue. Consequently, bone cells — osteoclasts and osteoblasts — are stimulated to start bone turnover. Additionally, surgical cuts around teeth to be moved orthodontically will lead to a decrease in bone density, which will enhance tooth movement. 

In 2009, Dibart et al. introduced piezocision as a minimally invasive technique to accelerate tooth movement. Piezocision is a flapless surgical technique that involves microsurgical cuts through gingiva to allow the piezoelectric knife to reach the cortical bone in the interproximal area.

Although the impact of piezocision on periodontal tissues and root resorption has been studied during many dental movements, no study has reported the impact of piezocision on periodontal tissues and root resorption of the lower second molar after protraction to close old first molar extraction space. 

It has been shown that cortical bone density is greater in the mandible than in the maxilla and in the molar area compared to the canine region. The increased bone turnover and decreased regional bone densities that accompany piezocision may affect alveolar bone height and second molar root resorption. A study published in The Angle Orthodontist in February 2023 assessed the effect of piezocision on periodontal tissues and alveolar bone height and detected lower second molar mesial root resorption in piezocision-assisted lower second molar protraction compared to no-piezocision molar protraction.

Twenty-one subjects who presented with bilateral extraction of lower first molars were included in the study. The patients were divided into two groups

• Group 1: Piezocision-assisted molar protraction (right or left side of subjects) in which piezocision was performed immediately before lower second molar protraction and,
• Group 2: No-piezocision molar protraction in which lower second molar protraction was not surgically assisted. 

Plaque index (PI), gingival index (GI), periodontal pocket depth (PPD), width of keratinized gingiva (WKG), gingival recession (GR), lower second molar mesial root resorption, alveolar bone height, and mandibular bone height were recorded at T1, immediately before molar protraction, and at T2 after second molar space closure.

More second molar mesial root resorption was found in the non-piezocision assisted molar protraction group compared to the piezocision group. This can be explained by the fact that less bone resistance and more osteoclastic activity associated with piezocision can reduce the likelihood of hyalinization necrosis and, hence, root resorption.

Limitations of this study included: greater female-to-male ratio, two-dimensional records were used to record root resorption, and root resorption was measured only on the mesial root of the second molar. The mesial root of the second molar was assessed because of its proximity to the piezocision cut and, also, it was protracted against the more dense, old, first molar extraction space.

In the piezocision-assisted molar protraction group, significant changes were detected in the WKG (P < .001), GR (P < .05), and the mandibular bone height (P < .001). Compared to the no-piezocision group, piezocision-assisted molar protraction resulted in an increased WKG (P < .001) and less second molar mesial root resorption (P < .01).

In conclusion, piezocision does not have any detrimental effect on the periodontium and produces less root resorption.

Elham S. Abu Alhaija; Marwan M. Al-Areqi; Raed AlShami; Emad F. Al Maaitah; Ahed Al Wahadni. "Effect of piezocision-assisted lower second molar protraction on periodontal tissues, alveolar bone height, and lower second molar root resorption." Angle Orthod (2023) 93 (3): 306–312.