Effect of piezocision procedure in levelling and alignment stage of fixed orthodontic treatment: a randomized clinical trial

Study design

This two-arm parallel-group randomized clinical trial was carried out at the Specialist Orthodontic Clinic, Universiti Sains Malaysia.

Ethical consideration

Ethical approval has been obtained from the review board of the institution of Universiti Sains Malaysia (USM) No: (USM/JEPeM/17110591). All methods were performed in accordance with the relevant guidelines and regulations. Written informed consent was obtained before the patients were randomized into the treatment groups. The trial was registered with Australian New Zealand Clinical Trials Registry (ANZCTR) with the trial number of ACTRN12621001350819.

Sample size calculation

Sample size calculation was performed using the online calculator¹⁷, assuming that a minimum of four (4) weeks (28 days) difference in treatment time between the two treatment arms is beneficial to the patients and clinicians. Using the SD = 14.18 days from a study to correct the levelling and alignment in severe maxillary incisor crowding², power = 0.9 and significance level = 0.05, the calculation showed that six patients per arm were required in this study. Considering a drop-out rate of 30%, the study had recruited eight (8) patients per group (N = 16).

Patients selection

Patients were selected among those who attended the Specialist Orthodontic Clinic at Hospital Universiti Sains Malaysia for assessment of orthodontic treatment. All routine orthodontic diagnostic records such as study models, orthopantomograms, lateral cephalograms, extraoral and intraoral photographs, gingival recession and pocket depth were taken for initial pre-treatment record, diagnostic purposes and treatment plan. Patients who met the inclusion and exclusion criteria were invited to participate in the study. The inclusion criteria were; (1) adults aged between 18 and 30 years, (2) clinically healthy without systemic disease or medical condition, (3) have LII of 7–9 mm in the anterior maxilla and require bilateral extraction of the first premolars, (4) feasible to bond the brackets and engage the initial archwire into the brackets of all the bonded maxillary teeth, and perform the piezocision procedure on the experimental group on same day, (5) vital teeth and periodontal tissues with probing depth < 3 mm across the entire dentition and less than 2 mm clinical attachment loss, and (6) no radiographic evidence of root resorption. The exclusion criteria were: (1) syndromic craniofacial deformities, (2) taking medication such as NSAID’s, bisphosphonates or corticosteroids medications throughout the study period, (3) had a history of previous orthodontic treatment, and (4) had missing or impacted permanent teeth except for the third molar.

From a total of 187 patients screened between April 2018 to December 2019, 156 did not meet the criteria and 15 had declined from participating. Sixteen patients who met the inclusion and exclusion criteria were recruited over the stated period and briefed about the purpose of study, conventional orthodontic treatment, piezocision procedure, and the risks and benefits of participation.

Randomization and treatment allocation

Random allocation and allocation concealment was performed by preparing 16 sealed and unnumbered envelopes containing a piece of paper printed with the word ‘Piezocision’ or ‘Conventional’. Each consented patient was asked to select one envelope and opened it in front of the researcher (S.S.) for the record. This approach prevents selection bias in this unblinded trial and randomly assigns the patients to the treatment groups.

Orthodontic procedures

Both groups were treated with conventional fixed orthodontic appliance following seven to ten days after bilateral first premolar extraction. Pre-adjusted edgewise McLaughlin Bennett Trevisi prescription metal brackets and buccal tube (Natural orthodontic product) of the 0.022-in. slot were bonded from the right first molar to the left first molar. In piezocision group bonding of brackets and activation of initial arch wire was performed on same surgery day. To initiate the levelling and alignment phase of both groups, a 0.012-in. nickel-titanium archwire (3M Unitek) was inserted. Following, the archwire sequences 0.016-in., 0.017 × 0.025-in., and 0.019 × 0.025-in. nickel-titanium were used for ideal alignment. Each number of archwires were replaced only when the possibility for full engagement into the brackets slot with a minimal amount of bending and without expressing excessive force on anterior tooth movement². The patients were evaluated every 4–6 weeks¹¹. The levelling and alignment stage was considered as complete when the LII of the anterior teeth is 0 mm and the final archwire 0.019 × 0.025 ss can be passively inserted into all brackets.

Piezocision procedure

The piezocision procedure followed that described in Dibart et al.³, but the subsequent follow-up visits were modified to 4–6 weeks instead of every 2 weeks originally. Before the surgical procedure started, patients rinsed the mouth with 0.2% chlorhexidine for 1 min. Then, using the panoramic radiograph as a guide, the root proximity and long axis of the teeth were determined and seven corticotomy lines were marked on the mucogingiva using a marker pen. Each line started at 3 mm away from the interdental papilla to preserve the papillary gingival margin and alveolar crest and extended upwards to about 4–5 mm in length. Next, local anaesthetic was administered using 2% Lidocaine with 1:100,000 epinephrine. After anaesthesia was achieved, an incision was made using 15C surgical scalpel blade through the gingiva on each of the marked lines at 45°–60° to the long axis of the teeth. The gingiva was then slightly elevated laterally to check the alveolar cortical bone and root. Piezocision was not performed in cases where there was root proximity³.

Cortical alveolar bone incisions were made using a piezosurgery blade (BS1 insert, Satelec Acteon Group) and it was positioned at the same angulation as the scalpel blade to make a 3 mm depth cut into the medullary bone. The depth of the corticotomy cut was determined using the marking on the BS1 blade and maintained throughout the corticotomy line. The piezotome device was set at low-frequency ultrasonic waves (28–36 kHz) for cutting cortical bone with a continuous 60% saline irrigation (Fig. 1). High-speed suction was used to remove excess fluid from the surgical area. Hemostasis was achieved using cotton gauze and thumb pressure. No sutures were placed after the procedure (Fig. 2). No bone grafting placement was performed. Post-operatively, the patients were advised to take analgesics (paracetamol) only when necessary, carefully brush the teeth and used 0.2% chlorhexidine mouthwash twice a day for one (1) week. All experimental subjects were advised to contact the Orthodontic Clinic of Hospital Universiti Sains Malaysia immediately if there was any complication after the surgery. All clinical procedure was carried out by one co-author (S.S) who is a qualified orthodontist.

Primary and secondary outcome measures

Study outcomes were assessed at four time-points: before treatment (T0), 1-month post-treatment (T1), 2 months post-treatment (T2), and at the end of levelling and alignment stage (T3). Treatment time is defined as the number of days passed from T0. The primary outcome measure was the overall treatment time (T3-T0), defined as the total number of days to complete the alignment and levelling stage.

The secondary outcomes included the changes in LII (mm), alignment rate (mm/month), pocket depths, gingival recession, and pulp vitality, and patient’s perception of pain during the procedure and satisfaction with the piezocision procedure. LII assesses the severity of crowding and measured the total horizontal distance between two adjacent contact points of 6 anterior teeth¹⁸. The measurement was made using an electronic digital calliper to the nearest 0.01 mm on a dental cast taken at each time-point. The alignment rate at T1, T2 and T3 were the ratio of the difference in LII between two consecutive time points divided by the treatment time (per month) ((e.g. ; alignment ; rate ; at ; T2= frac{{LII}_{T2}- {LII}_{T1}}{T2-T1})). Gingival recession and pocket depth were assessed at T0 and T3 using a Williams periodontal probe (Hu Friedy, Chicago, III). Gingival recession was the distance from the cementoenamel junction to the free gingival margin at the labial site only. Pocket depth was recorded at three sites on the buccal side (mesiobuccal, buccal and distobuccal) to nearest 1 mm. The mean changes in gingival recession and pocket depth between T3 and T0 were calculated¹⁹.

Assess of pulp vitality

Tooth vitality was recorded using an electric pulp tester (EPT) at T0 and T3. The teeth were isolated using cotton rolls, dried thoroughly, and applied with toothpaste before testing. The procedure was performed carefully to avoid contact between the tip of the tester and orthodontic wire, brackets, lips or tongue²⁰. The gingival, periodontal and vitality status are also monitored at each visit.

Patient’s perception of piezocision procedure

The experimental group completed a self-administered questionnaire that assessed the perception of pain and satisfaction with the procedure at the end of surgery and collected one (1) week later. The patients were asked whether they felt any pain after the surgery and to rate the response using a unidimensional measure that ranges from 0–10, which is then categorized as no pain (0), mild pain (1–3), moderate pain (4–6), severe pain (7–10). Satisfaction with the surgical procedure was assessed using the similar rating and the score was categorized as extremely unsatisfied (0), unsatisfied (1–2), neutral (3–5), satisfied (6–8), extremely satisfied (9–10)²¹.

Statistical analysis

Descriptive analysis was carried out to summarize the sample and examine the data distribution. The t-tests and Chi-square test was used to compare the parameters between the control and experimental groups. Comparison between groups analyses followed the per-protocol principle. Comparison of the overall treatment time and changes in LII between the two groups were compared using independent t-test. The alignment rate was analysed using one-way repeated-measures analysis of variance. Significance level was set at 5%. Data were analyzed using SPSS version 26 (Chicago, USA).

Reliability study

Reliability study was carried out by randomly selecting six dental casts and re-measure the LII one (1) month after the first assessment. The result showed strong intra-examiner reliability (intra-class coefficient, ICC = 0.99).