Clinical and Biochemical Evaluation of Rate of Canine Retraction Following Piezocision through a Recently Extracted Site

INTRODUCTION

An increasing number of adult patients seek orthodontic treatment today, in order to improve esthetics and/or masticatory function. Adult patients have mature bones with higher ratio of cortical bone and low bone turnover. The rate of orthodontic tooth movement is reduced due to these factors. The resulting increase in treatment duration can cause deleterious effects such as white spot lesions, dental caries, root resorption, and decreased patient compliance and satisfaction.

In order to reduce treatment time for such patients, numerous procedures that include systemic and local drug administration, mechanical and physical stimulation, and certain surgical procedures are being used. The surgical procedures utilize the regional acceleratory phenomenon (RAP) observed by Frost in 1983.¹ It is a tissue reaction to noxious stimuli, leading to an increased bone turnover rate by stimulation of osteoblasts and osteoclasts. Diedrich² and Häsler³ conducted studies that showed that tooth movement was faster and caused minimal damage to surrounding tissues.

Piezocision was introduced by Dibart⁴ as a minimally invasive technique to accelerate tooth movement. The procedure involves incisions in the buccal mucosa following local anesthesia. The incisions are made 2–3 mm below the base of the interproximal papilla. Following reflection of the gingiva and periosteum, the piezotome tip is inserted to a depth of 3 mm in order to decorticate the alveolar bone. The procedure can also be used to reflect a flap and place bone grafts, if needed, in a periodontally compromised patient.⁵

Orthodontic tooth movement also brings about changes at a cellular level, which are evident in the form of changes in various enzyme levels in the gingival crevicular fluid (GCF).^6,7 Alkaline phosphatase (ALP) and acid phosphatase (ACP) are the enzymes associated with bone metabolism as indicators of formative and resorptive activity, respectively.^8,9 They are used as reliable indicators of the bone turnover rate at a specific site associated with tooth movement.

A search of literature revealed few studies that compared the rate of tooth movement into a fresh extraction site with and without piezocision.¹⁰ The aim of this study was to compare the rate of canine retraction with and without piezocision. The findings were further supplemented by evaluation of GCF levels for ALP and ACP.

MATERIALS AND METHODS

The present study was carried out following clearance from the institutional scientific and ethical review boards at the AB Shetty Memorial Institute of Dental Sciences, Mangaluru. A total of 15 patients between the ages of 18 years and 26 years, indicated for bilateral extraction of first premolars for their orthodontic treatment, were included at random for this prospective study.

The included individuals had not undergone previous orthodontic treatment, had no systemic diseases (active/controlled) or craniofacial syndromes, maintained good oral hygiene, and had a probing depth of less than 3 mm. A written informed consent was obtained prior to the start of orthodontic treatment from each selected individuals.

A standardized treatment protocol of 0.014″ nickel titanium (NiTi) (GandH wire company, Europa Form I), 0.016″ NiTi, and 0.016″ × 0.022″ NiTi was used for initial leveling and aligning. This was followed by the 0.017″ × 0.025″ stainless steel (SS) wire with which canine retraction was initiated. A random side (right or left, group I) was chosen for piezocision for a given patient while the contralateral side served as control (group II).

Piezocision was done immediately following extraction of the first premolars in the maxillary arch. A unit (Acteon) and handpiece with curved tip was used. The canine and premolar region was anesthetized using 2% lidocaine with adrenaline. An incision was made mesial and distal to the canine. The tip was inserted to a depth of 3 mm (standardized by markings on the tip) and length of 4–5 mm perpendicular to the cortical bone. The same piezocision procedure was carried out by one operator for all patients. Any side, right or left, was chosen at random for the procedure (Fig. 1).

The GCF fluid was collected with the 1–5 μL calibrated volumetric microcapillary pipette. The micropipette was placed in the mesial, central, and distal buccal crevicular region to collect 1 μL of fluid. Samples were collected before starting retraction (T₀), day 1, 3, 7, 14, 21, 42, 60, and 90 (T_1–8) or till end of retraction, whichever occurred first (Fig. 2).

Following the procedure, canines on both sides were ligated to the 0.017″ × 0.025″ SS wire. Retraction was carried out with a power chain placed from the canine bracket to the molar hook. Both maxillary molars were ligated to reinforce anchorage. A force of nearly 150 g as suggested by Reitan¹¹ was applied on both sides. The power chain was changed every 4 weeks on both sides until the end of retraction (Fig. 3).

RESULTS

The measurements (DC, DM) between both groups were statistically insignificant. Measurement at T₀ showed no significant difference. The rate of retraction in the first month i.e., T₁ showed significant change in both groups (p value 0.001). The rate of canine retraction in both groups was highly significant from T₀ to T₆ (Table 1). Overall, group I showed a rate of tooth movement 1.5 times that of group II. No statistically significant anchor loss was seen in either group between T₀ and T₆ (Table 2). There was no significant canine rotation from T₀ to T₆ in either groups or between both groups (Table 3).

The quantitative analysis of enzyme ACP levels showed significant differences between both groups. The values peaked at T₃ for both the groups followed by a decline till T₈ (Table 4 and Fig. 5). Values of group I were highly statistically significant (p %3C; 0.001) compared to group II at all stages except T₀.

The enzyme ALP levels showed no significant difference at the pre-retraction stage among the groups. The ALP levels in both groups increased and peaked at T₅ and gradually declined till T₈ (Table 5 and Fig. 6). The levels in the experimental side were significantly higher (p < 0.001) than the control group at every interval except T₀.

The results indicate that the rate of canine retraction was accelerated by 1.5 times by the use of piezocision along a recent extraction site. The enzyme levels on the intervention side increased significantly more than the control side, suggesting increased bone turnover at the same site.

DISCUSSION

With the increasing average age of the orthodontic patient, bone turnover and cell mobilization and consequently the rate of tooth movement is slower. The rigid bone in adults makes them more prone to periodontal problems when compared to growing children. Treatment time for a patient may range from 12 to 36 months depending on the system used and the biological response elicited. Long-term treatment may lead to periodontal complications, white spot lesions, and reduced patient compliance.

Among the various techniques available for accelerating tooth movement and thus reducing treatment time, piezocision is considered an effective and relatively noninvasive procedure. It is indicated in cases of Class I malocclusion with moderate to severe crowding, for correction of deep bites, selected Class II malocclusions, rapid tooth movement in adults, and simultaneous correction of osseous and mucogingival defects that are present or their prevention.⁴ It is not advised for ankylosed teeth, patients with active periodontal disease, and those with conditions affecting bone turnover.⁵

In the present study, the split-mouth technique was used to assess the rate of canine retraction and associated relevant biochemical changes occurring in the tissues via the GCF. The rate of canine retraction was significantly higher on the piezocision side compared to the control. These results were correlated to the studies by Abbas,¹⁰ Iino,¹² and Moon.¹³ This study recorded a rate of tooth movement nearly 1.5 times compared to the control. This was not as high as that seen by Aksakalli,¹⁴ who found the rate to be two times, probably due to the RAP in the recent extraction sites in our study. Bilateral extractions were done immediately prior to retraction, which affected the RAP on both sides. Despite the advantage, the side with piezocision showed greater rate of tooth movement. This was probably due to more extensive injury to the bone in these areas. As suggested by Frost¹ and Wilcko,¹⁵ more severe the bone injury, more vigorous the healing and faster the tooth movement.

Anchor loss was minimal on either side. Second molars were banded in order to increase the anchorage value. Piezocision has been demonstrated to have no effect on the anchorage.^10,16 It is possible that the presence of the anchor teeth away from the site of extraction and piezocision were responsible for insignificant anchor loss. This highlights the localized or regional aspect of the RAP regardless of the severity of the injury.

No significant rotation of the canine on either side was observed. This was probably due to the use of a 0.017″ × 0.025″ archwire that reduces the amount of tipping that occurs in a 0.022″ slot compared to the 0.016 × 0.022″ wire.

Periodontal health plays an important role in tooth movement. The presence of active periodontal disease is a contraindication for orthodontic tooth movement. The immune response caused by periodontal pathogens leads to increase in inflammation, cytokine production, and bone resorption. Orthodontic tooth movement requires bone remodeling in a balanced environment but in periodontal disease this balance is disrupted.¹⁷ Maintaining periodontal health is especially important in adult patients who may have a history of periodontal disease and could have subideal bone levels. Certain factors such as the history of disease, gingival biotype, width of attached gingiva, and presence of recession increase the risk of developing periodontal problems during orthodontic treatment and require regular monitoring.¹⁸

The GCF contains markers such as proteins, enzymes, and metabolites, which can be used to assess the state of the periodontium. Of these, enzymes associated with bone turnover, i.e., ALP for bone formation and ACP for bone resorption, are of particular interest to an orthodontist.⁷ The levels of ACP and ALP are altered in periodontal disease due to disruption of normal bone turnover.¹⁹ Thus, patients with a gingival score of 1 or below were selected.

Values for ALP were higher on the piezocision side at baseline but insignificant. At T₂ and T₃, the values increased on both sides but were higher on the piezocision side suggesting increased osteoblastic activity. Enzyme levels peaked at T₅ (day 21) suggesting the highest rate of bone formation at this time. The ALP levels declined hereon; however, the levels on the piezocision side were constantly higher than the control. This indicates a higher rate of bone formation, possibly due to a more rapid rate of tooth movement on the experimental side. Perinetti et al.¹⁹ similarly found highest values on the 14th day on the mesial side and 21st day on the distal side. These trends cannot be compared to our study as the samples were collected from all surfaces on the canine.

Acid phosphatase levels were similar and the lowest at baseline (T₀). The values increased on following days and peaked at T₃ (day 7). Similar results were reported by Batra et al.²⁰ who found increased values on the 7th day. They however collected samples from the mesial side. Shetty et al.²¹ reported ACP values highest in the 1st and 2nd weeks. In the present study, the values declined henceforth. Other studies such as that by Farahani et al.²² demonstrated peak levels at T₄ (day 14) but did not measure levels at T₃ (day 7). Similar to this study, the ACP levels declined on both sides from day 14. Highly significant differences of ACP levels between both sides at all times except baseline suggest a higher bone turnover rate on the piezocision side.

The clinical and the biochemical findings in the study strongly reinforce each other. The rate of tooth movement was higher on the piezocision side, which was reflected in the levels of both ALP and ACP. Despite the RAP in play on both sides, the piezocision side showed an increase in both tooth movement and enzyme levels. The enzyme levels detected were greater than those found in similar studies of tooth movement.^21,23 The increased levels of ALP and ACP found in the present study may be attributed to the RAP due to recent tooth extraction.

The rate of canine retraction may vary according to several factors that are not considered in the present study. However, being a split-mouth study, the biological factors may have been neutralized to a great extent. The present study did not consider the effect of different force levels on the rate of canine retraction following the piezocisions. Further studies are required to assess the effect of piezocision on the rate of tooth movement and their long-term stability as well as the gingival status over a period of time. The effect of an increased rate of tooth movement on root resorption also needs to be studied. The enzyme changes and the biochemical effects on the GCF of surrounding teeth may also present an avenue for further research.

CONCLUSION

Taking into account the limitations of the study, piezocision can be an effective procedure for aiding increased rate of tooth movement when used in conjunction with recent extraction sites. The clinical result of increased tooth movement is supported by similar changes in biochemical reaction reflected by the levels of enzymes in the GCF. The procedure would be highly beneficial especially in adult patients seeking orthodontic treatment.

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