Abstract
The aim of this study was to evaluate the occurrence of interradicular temporary anchorage devices (TAD) loss installed to anchor canine retraction performed in association to alveolar corticotomy (AC) versus piezocision (PZ) surgeries. One hundred maxillary self-drilling TAD were installed in 50 patients who needed first maxillary premolars extractions. One week later, AC or PZ surgeries were performed surrounding the canine and the extraction sites. A group without any adjunct surgery to accelerate tooth movement was used as control. TAD stability was evaluated throughout the 6 months of canine retraction. A total of 7, 8 and 9 TAD were lost in the AC, PZ and control groups, respectively. No significant difference in TAD stability among the groups was observed ( p > 0.05). Despite the increased inflammatory response due to AC or PZ, TAD stability was not compromised.
Introduction
Temporary anchorage devices (TAD) are established as a powerful instrument to improve anchorage during orthodontic treatment. Some of the most relevant advantages include minimal surgical intervention, absolute anchorage, immediate loading and low costs. However, TAD occasionally need to be removed during treatment due to mobility. In this regard, previous studies have investigated the risk factors associated with TAD failure in order to facilitate usage. Factors such as bone quality and quantity, screw diameter, length, and design have been related to TAD stability.
Orthodontic treatment efficiency may be influenced by biomechanical and biological factors. Thus, distinct procedures such as surgeries, laser irradiation and vibration forces have been used adjunctively to TAD to accelerate tooth movement and reduce the overall treatment duration. In this regard, alveolar corticotomy (AC) is a surgical technique that promotes the regional accelerated tooth movement phenomenon (RAP). RAP involves reducing resistance to tooth movement through alveolar bone decortication. Wound healing in decorticated areas progresses through recruitment of immune regulatory and inflammatory cells. This targeted healing allows for guided bone remodeling. Decreased resistance through bone facilitates orthodontic tooth movement and results in treatment time reduction. More recently, piezocision (PZ), a more controlled, less invasive decortication method, was introduced as an alternative to AC. This flapless technique involves a soft tissue incision with a scalpel and alveolar bone decortication with an piezo-scalpel tool. Like AC, PZ injuries are claimed to be capable to induce RAP and therefore accelerate the orthodontic treatment, but with less surgical trauma.
Since decortication surgeries are used to accelerate tooth movement they are increasingly been performed as an adjunct with TAD, and since decortication can interfere with TAD survival due to alteration in bone characteristics, bone metabolism, and healing, the question arises: is there any impact on TAD stability when TAD are placed in conjunction with AC versus PZ? Therefore, this study was conducted to evaluate TAD loss in sites adjacent to AC versus PZ decortication and no decortication (control).
Material and methods
Ethical approval
This study was approved by the Institutional Review Board of the Pontifical Catholic University of Minas Gerais (Protocol # 1.017.013) and was conducted in accordance with the principles for medical research involving humans established in the Helsinki Declaration. An informed consent was obtained from all individuals prior to their participation and subjects’ rights were protected at all times.
TAD placement
A total of 100 interradicular maxillary TAD were installed by a trained surgeon in 50 patients (21 males and 29 females; age 15–38 years) at the Graduate Program in Orthodontics of the Pontifical Catholic University of Minas Gerais, Brazil. Orthodontic treatment with fixed appliances was initiated and all treatment plans involved first upper premolar extractions. The exclusion criteria included pregnant women, individuals with active periodontal disease, or signs of gingival inflammation and those with systemic diseases and/or use of any medication that might influence on bone metabolism.
Bite-wing radiographs (with the film apically displaced to capture maximum root surfaces) were obtained prior to TAD placement in order to evaluate adequate space between the roots and plan insertion site. All self-drilling TAD (1.5 × 6 mm, Morelli®, Sorocaba, SP, Brazil) were placed under local anesthesia, parallel to the occlusal plane between the roots of maxillary second premolars and first molars on the muco-gingival margin ( Fig. 1 ). TAD were placed without flap elevation. No load was applied on the insertion day and oral hygiene instructions were given to the patients in order to maintain plaque control. TAD were observed for 180 days.
Surgical decortication and piezocision
A randomization using the QuickCalcs program (GraphPad Software, Inc., La Jolla, CA, USA) determined the maxillary side in which would be performed AC, PZ or no surgical procedure (control). One week after TAD placement, all decortication surgeries were done by the surgeon under local anesthesia.
AC decortication involved a full-thickness mucoperiosteal flap surgery with vertical and horizontal corticotomies using conventional handpiece and round bur. Corticotomies surrounding the canine root and on the extraction site ( Fig. 2 ) were performed through cortical plate. Spherical perforations limited to the depth of the cortical bone were also performed, the flap was then repositioned and sutured.
PZ decortication involved three vertical linear soft tissue incisions with a number 15 scalpel blade. Vertical bone decortication was performed with 3 mm depth and 5 mm height using piezoelectric tips (SF3 insert Piezo DentSurg, CVDentus®, São José dos Campos, SP, Brazil). Decortication occurred mesially and distally to the canine root, as well as mesially to the second premolar ( Fig. 3 ). The incisions were not sutured, as suggested by the authors who initially described the PZ procedure.
Orthodontic activation
Immediately following surgical decortication procedures, a closed NiTi coil spring (Dentsply GAC ® , Islandia, NY, USA) was attached from the TAD to a hook soldered on the canine bracket and a distalization force of 120 g was applied from this day until the end of the observation period of 6 months ( Fig. 4 ). Every 14 days, the force was measured and the coil spring was reactivated if the load had decreased. TAD stability was verified at every appointment. TAD was considered lost when patient was without it at appointment time or if TAD presented mobility (which would interfere in its use as an anchorage for the remaining orthodontic canine retraction).
Statistical analysis
A survival analysis was conducted to evaluate differences in the TAD loss (TAD stability) among groups. The results obtained in each group were plotted in Kaplan-Meier survival curves, indicating the time (in days) of the occurrence of the following event: TAD loss. Differences between groups were analyzed using the Log-Rank test (Mantel-Cox). Censured data were generated. The significance level was set at 5%. Statistical analysis and plotting were performed using GraphPad Prism 5.0 software (GraphPad Software, San Diego, California, USA).
Material and methods
Ethical approval
This study was approved by the Institutional Review Board of the Pontifical Catholic University of Minas Gerais (Protocol # 1.017.013) and was conducted in accordance with the principles for medical research involving humans established in the Helsinki Declaration. An informed consent was obtained from all individuals prior to their participation and subjects’ rights were protected at all times.
TAD placement
A total of 100 interradicular maxillary TAD were installed by a trained surgeon in 50 patients (21 males and 29 females; age 15–38 years) at the Graduate Program in Orthodontics of the Pontifical Catholic University of Minas Gerais, Brazil. Orthodontic treatment with fixed appliances was initiated and all treatment plans involved first upper premolar extractions. The exclusion criteria included pregnant women, individuals with active periodontal disease, or signs of gingival inflammation and those with systemic diseases and/or use of any medication that might influence on bone metabolism.
Bite-wing radiographs (with the film apically displaced to capture maximum root surfaces) were obtained prior to TAD placement in order to evaluate adequate space between the roots and plan insertion site. All self-drilling TAD (1.5 × 6 mm, Morelli®, Sorocaba, SP, Brazil) were placed under local anesthesia, parallel to the occlusal plane between the roots of maxillary second premolars and first molars on the muco-gingival margin ( Fig. 1 ). TAD were placed without flap elevation. No load was applied on the insertion day and oral hygiene instructions were given to the patients in order to maintain plaque control. TAD were observed for 180 days.
