The Effects of Corticotomy and Piezocision in Orthodontic Canine Retraction: A Randomized Controlled Clinical Trial.

Background: There have been many studies and experiments to evaluate the effectiveness of different types of dental treatment. Maxillary canine extraction is such a dental treatment which can be performed through either alveolar corticotomy (AC) or piezocision (PZ). The current study aims to compare the effectiveness of these two types of dental procedures. It is based on a randomized clinical trial (RCT) through the split-mouth technique supported by a parallel group design. The participants in the trial were selected on the basis of a medical criterion. The clinical trial involved extraction of both the first maxillary premolar teeth through use of orthodontic instruments. This study aims to evaluate the comparative effectiveness of alveolar corticotomy and piezocision corticotomy in acceleration of maxillary canine retraction and how it can be used for expression of multiple bone remodeling gingival crevicular fluid (GCF). As part of this study, a RCT was performed on the basis of split-mouth technique at the Department of Orthodontics of Pontifical Catholic University at Minas Gerais in Brazil. The sample size for the clinical trial consisted of people who required extraction of maxillary premolar teeth after canine extraction. After digital intraoral scans, the cumulative distal movement of canines was measured on the basis of superimposition of digital model and the results were considered as the primary outcome of the study. The GCF bone remodeling samples were considered as the secondary outcomes.
Results: 50 patients, involving 22 males and 28 females were analyzed in this particular clinical trial. The age range that was considered for this clinical trial was 19-33 years. In case of understanding the distal movement between control and AC, no statistical significance was observed in Group1 (G1). Lower cumulative cervical and incisal measurements in case of PZ was lower than the measurement in the control state. In all the groups, the expression of the biomarkers had occurred in specific timepoints (P < 0.05) but no distinct pattern was observed. Conclusions: In order to accelerate the maxillary canine retraction, PZ and AC were ineffective. No distinct induction pattern of biomarker expression was noted as well. Copyright:

BACKGROUND

In the last few decades many new developments in dental treatment have developed as alternatives in orthodontic treatment. This is mainly because many patients have been complaining of the sufferings associated with orthodontic dental treatment which prolongs for a long duration of time. As per existing research, the new alternatives are based on developments in the area of orthodontic teeth movement which is also known as OTM.[1] Most of the studies in existing literature on dental treatment are based on alveolar corticectomy (AC). AC is a procedure which deliberately causes alveolar injuries to the cortical bone within medical constraints.[2] The objective of the procedure is to increase bone metabolism and decrease bone density. This surgical procedure provides acceleration to the area around the cortical bone which results in faster orthodontic movements. However clinical evidence of an outcome is not found easily in existing research in dentistry.[3]

In the opinion of some researchers and medical professionals in this field, piezocision (PZ) is a better alternative to alveolar corticectomy. This surgical procedure is also more popular and applied more frequently in comparison with AC. In PZ, short incisions are made to the cortical bone which is aimed at accelerating the orthodontic teeth movement. However, there is also a difference of opinion among medical professionals on the relative effectiveness of PZ which is documented in the existing literature on dentistry.[4] It is only because of these reasons that there is a considerable gap in the existing literature on the comparative effectiveness of AC and PZ. The current clinical trial performed at a randomization center aims to bridge this perceived gap in the existing literature on dentistry. This type of clinical trial is known as randomized clinical trial or RCT. In this clinical trial, the effects of surgical procedures on alveolar bone are assessed on the basis of a longer follow-up period, superimposition of a digital model and molecule-based test of gingival crevicular fluid. In this way, a RCT helps to evaluate the effects of these surgical procedures on the underlying alveolar bone in terms of the acceleration of maxillary canine retraction.[5]

There are two aspects of OTM: resorption and apposition. When force is applied to the area around the cervical bone then the bone experiences resorption on the side where pressure is applied while the side experiencing tension undergoes bone apposition.[6] As per existing literature, conventional movements in the teeth are caused by the biomechanical forces of resorption and apposition when applied to a bone in the dental area.[7] Various types of dental problems can be addressed with treatment based on the acceleration of OTM.

MATERIALS AND METHODS

Trial design

The trial for this research was based on the split-mouth technique and it was a randomized and controlled clinical trial. This trial was also supported by a parallel group design. An inclusion criterion was devised which formed the basis of selection of participants. One important aspect of the clinical trial was that it was registered with the government and no changes were made to the methodology and the various processes included in the trial after the selection of participants. The split-mouth technique is one of the most effective and frequently used techniques in dentistry. It offers a better view of all the teeth in the mouth, which makes it easier for a researcher to conduct the trial and make his observations for the study. The split-mouth technique is also safer for the participant on whom the clinical trial is being conducted. The split-mouth technique used in this clinical trial was also more effective and safer, as it was conducted under controlled conditions. As the trial was also randomized, there was minimum chance of any bias creeping into the trial.

Participants

As it has been already mentioned in the section on trial design, a selection criterion was applied for the participants which included the following specifications:

Orthodontic need for extraction of first maxillary premolar teeth. This selection criteria for the patients ensured that there was no physiological harm or damage done to the participants when the trial was conducted on them.

There was also an age criterion for the participants as people in the age group of 19–33 years were only selected for the study.

Furthermore, only people with good oral health were selected for the clinical trial to minimize the risk of damage to the teeth from the trial.

Other criteria for the trial were that a participant for the trial should have all the upper teeth except the third molar teeth.

It was also ensured that a participant in the trial was available for medical consultation for a period of at least two weeks.

Patients suffering from periodontitis, systemic diseases, craniofacial syndromes and altered bone metabolism were disqualified from participation in the randomized clinical trial. Even people with pregnancy, smoking habit, or those who regularly took anti-inflammatory drugs were also selected for the trial.

A total of 675 people were selected as the target population

Interventions

As part of the clinical trial, orthodontic appliances were used to extract both the maxillary first premolar teeth. After the extraction, preliminary levelling and alignment were applied to the participants. After a passage of four years, a stainless-steel wire was inserted and mini screws were fixed between the roots of the 2nd premolar and 1st premolar teeth to ensure that the teeth were completely anchored.[8] Following these procedures, the participants in the trial were randomly divided into three groups. For the participants in the first group, AC was inserted in that side of the jaw which was used for experiment while the contralateral side of the jaw was used for control. In the second group, PZ was applied to the experimental side while using the contralateral side for control. The last group included participants who had experienced both AC and PZ.

The surgical procedures were restricted to the buccal area and were performed only once in the experimental side. Just after the control or surgical procedures, extraction of the canine was initiated. After every two weeks, the patients were tested for verification of retraction force. Digital intraoral scans were performed three times on the participants after the beginning of canine retraction. After that, intraoral digital scans were performed after every two weeks till a maximum period of six months. Gingival cervical fluid (GCF) was collected from the participants after the clinical procedure.

Sampling

The size of the sample was decided on the basis of the outcomes of a previous study which was also based on the evaluation of OTM rate. Based on a power of 80% and a significance level of 5%, the total sample size was fixed at with participants in each group. The age range of 19–38 years for each of the participants was considered for determination of the sample size. There was a possibility of some changes due to the age range of the participants. However, it was made up by application of the split-mouth model for this randomized clinical trial. Before the start of the study, randomization was performed by block to determine the nature of the group and decision regarding the experimental and control sides.[9] Steps were taken to ensure that the scars were not visible as the digital models were coded prior to the clinical trial and consequently cut above the teeth cervical margin in the buccal side. The details of allocation of the groups and decisions regarding the control and experimental sides were concealed as the procedure was performed at a randomization center.[10] Only the dental surgeon was informed about the details of allocation regarding the group as well as the control and experimental sides.

Statistical analysis

R software was used to conduct data analysis. The test variables concerned 50 randomized digital models which were remeasured after an interval of one month. The intraclass correlation coefficient ranging 0.94 and 0.99 represents intrarater reliability. Standard deviation and mean for all the variables were calculated. Marginal log-linear regression was done to compare the retraction of the sides over time and also for comparing the biomarker levels. The significance level considered here was 5% for interpreting all the statistical tests.

RESULTS

Random inclusion of the participants was done based on the inclusion criteria and after randomization, the sample number was 53. Three groups that were divided for the clinical trial include Corticotomy * Control (CC) (17), Piezocision * Control (PC) (18), and Corticotomy * Piezocision (CP) (17). Before receiving any kind of orthodontic treatment, one patient within the CC group had left the process. One patient from the PC group had left the city in between the process. The flow of the participants during the clinical trial process is described in the CONSORT flow chart [Figure 1]. Therefore, the final sample size for the present study was 50. The mean age for group 1 (CC) was 20.9 years, age for group 2 (PC) was 20.1 years, and for group 3 (CP) was 21.1 years. All the patients involved in the process were within the age range of 19–33 years. Total number of female patients in this process was 28. Continuous follow-up was necessary for this clinical trial. The follow-up occurred until April 2019. The different types of malocclusions for each group and related data are presented in Table 1.

Figure 1

Study flowchart

Table 1

Patient’s baseline characteristics

	Group 1	Group 2	Group 3
Participants	16	17	17
Age (Mean and SD)	20.9 (7.02)	20.1 (6.91)	21.1 (6.87)
Gender
Male	7	8	7
Female	9	10	9
Malocclusion
Class I	7	6	9
Class II division 1	8	8	4
Class II division 2	1	2	2
Anterior crowding	6	6	5
Deep bite	3	2	3
Open bite	3	4	3
Posterior crossbite	1	1	0
Biprotrusion	3	2	6

In group 1, no significant differences were observed at any point of the evaluated time for the cervical and incisal measurements between the control sides and AC (P > 0.05) [Table 2].

Table 2

Comparison of incisal and cervical accumulative moved distances (mm) between sides over time - group 1

Source	Incisal					Cervical
	Mean	S.D.	Exp (β)	C. I.	P	Mean	S.D.	Exp (β)	C. I.	P
1 week
Control	0.35	0.13	1	-	-	0.15	0.11	1	-	-
Corticotomy	0.29	0.12	1.02	[0.87; 1.23]	0.728	0.19	0.14	0.97	[0.77; 1.12]	0.572
2 weeks
Control	0.51	0.26	1	-	-	0.25	0.2	1	-	-
Corticotomy	0.46	0.33	1.02	[0.87; 1.22]	0.716	0.19	0.13	0.96	[0.77; 1.12]	0.578
4 weeks
Control	0.77	0.4	1	-	-	0.36	0.19	1	-	-
Corticotomy	0.91	0.29	1.04	[0.88; 1.22]	0.693	0.4	0.22	0.94	[0.79; 1.11]	0.6
6 weeks
Control	1.24	0.39	1	-	-	0.48	0.18	1	-	-
Corticotomy	1.26	0.44	1.05	[0.88; 1.22]	0.672	0.47	0.27	0.95	[0.79; 1.11]	0.61
8 weeks
Control	1.7	0.34	1	-	-	0.87	0.27	1	-	-
Corticotomy	1.85	0.84	1.03	[0.88; 1.22]	0.654	0.82	0.47	0.96	[0.79; 1.11]	0.626
10 weeks
Control	2.07	0.66	1	-	-	1.14	0.35	1	-	-
Corticotomy	2.24	0.9	1.05	[0.88; 1.22]	0.64	1.05	0.46	0.96	[0.80; 1.17]	0.663
12 weeks
Control	2.44	0.87	1	-	-	1.3	0.4	1	-	-
Corticotomy	2.61	1.03	1.05	[0.88; 1.23]	0.63	1.27	0.65	0.96	[0.80; 1.17]	0.72
14 weeks
Control	2.8	1.01	1	-	-	1.47	0.52	1	-	-
Corticotomy	3.01	1.06	1.03	[0.88; 1.24]	0.625	1.45	0.64	0.97	[0.80; 1.17]	0.742
16 weeks
Control	3.19	0.85	1	-	-	1.74	0.57	1	-	-
Corticotomy	3.35	1.26	1.04	[0.88; 1.24]	0.622	1.62	0.73	0.95	[0.80; 1.19]	0.772
18 weeks
Control	3.68	0.91	1	-	-	1.95	0.56	1	-	-
Corticotomy	3.6	1.13	1.04	[0.87; 1.26]	0.623	1.92	0.66	0.97	[0.79; 1.21]	0.811
20 weeks
Control	3.7	1.15	1	-	-	2.1	0.71	1	-	-
Corticotomy	3.77	1.11	1.04	[0.87; 1.27]	0.626	2.01	0.76	0.97	[0.78; 1.23]	0.837
22 weeks
Control	3.95	1.3	1	-	-	2.19	0.92	1	-	-
Corticotomy	3.7	1.04	1.04	[0.86; 1.28]	0.631	2.19	0.85	0.97	[0.77; 1.25]	0.882
24 weeks
Control	3.91	1.46	1	-	-	2.26	0.93	1	-	-
Corticotomy	3.88	1.03	1.06	[0.85; 1.30]	0.636	2.14	0.58	0.98	[0.76; 1.28]	0.917

In case of group 2, in cervical and incisal measurements, significant differences were observed between PZ and control sides. The entitled measurements mentioned here were observed during the period of T2 to T13 (P < 0.05). In the PZ side canines, a constant tendency of lower cumulative distance was observed during the measurement process [Table 3].

Table 3

Comparison of incisal and cervical accumulative moved distances (mm) between sides over time - group 2

Source	Incisal					Cervical
	Mean	S.D.	Exp (β)	C. I.	P	Mean	S.D.	Exp (β)	C. I.	P
1 week
Control	0.4	0.23	1	-	-	0.2	0.16	1	-	-
Piezo	0.33	0.18	0.72	[0.63; 0.84]	0.000*	0.18	0.14	0.82	[0.69; 0.97]	0.055
2 weeks
Control	0.61	0.33	1	-	-	0.22	0.13	1	-	-
Piezo	0.48	0.3	0.76	[0.65; 0.86]	0.000*	0.23	0.14	0.83	[0.69; 0.96]	0.030*
4 weeks
Control	1.1	0.69	1	-	-	0.42	0.27	1	-	-
Piezo	0.78	0.32	0.76	[0.65; 0.86]	0.000*	0.32	0.18	0.81	[0.68; 0.97]	0.006*
6 weeks
Control	1.48	0.75	1	-	-	0.56	0.32	1	-	-
Piezo	1.14	0.58	0.76	[0.65; 0.86]	0.000*	0.4	0.27	0.79	[0.68; 0.93]	0.001*
8 weeks
Control	1.86	0.95	1	-	-	0.69	0.45	1	-	-
Piezo	1.36	0.66	0.76	[0.65; 0.86]	0.000*	0.46	0.25	0.77	[0.66; 0.88]	0.000*
10 weeks
Control	2.44	1.06	1	-	-	0.99	0.55	1	-	-
Piezo	1.84	0.87	0.76	[0.65; 0.86]	0.000*	0.75	0.35	0.77	[0.67; 0.85]	0.000*
12 weeks
Control	2.54	1.16	1	-	-	1.15	0.59	1	-	-
Piezo	2.12	0.96	0.76	[0.65; 0.86]	0.000*	0.86	0.4	0.78	[0.65; 0.85]	0.000*
14 weeks
Control	3.15	1.29	1	-	-	1.48	0.67	1	-	-
Piezo	2.49	1.17	0.77	[0.65; 0.86]	0.000*	1.04	0.56	0.71	[0.62; 0.83]	0.000*
16 weeks
Control	3.46	1.26	1	-	-	1.62	0.6	1	-	-
Piezo	2.72	1.16	0.77	[0.65; 0.86]	0.000*	1.19	0.59	0.66	[0.59; 0.84]	0.000*
18 weeks
Control	3.65	1.24	1	-	-	1.77	0.86	1	-	-
Piezo	2.84	1.35	0.76	[0.65; 0.87]	0.000*	1.25	0.55	0.69	[0.58; 0.83]	0.000*
20 weeks
Control	3.77	1.37	1	-	-	1.7	0.66	1	-	-
Piezo	2.78	1.48	0.79	[0.65; 0.88]	0.000*	1.39	1.33	0.68	[0.56; 0.77]	0.000*
22 weeks
Control	4.1	0.99	1	-	-	2.19	0.78	1	-	-
Piezo	2.97	1.19	0.78	[0.65; 0.88]	0.000*	1.32	0.65	0.67	[0.54; 0.81]	0.000*
24 weeks
Control	4.18	0.99	1	-	-	2.18	0.6	1	-	-
Piezo	2.95	1.13	0.77	[0.66; 0.89]	0.000*	1.45	0.6	0.65	[0.47; 0.8]	0.000*

In group 3, significant differences were observed between PZ and AC. This was done from T9 (incisal) and from T8 to measure the cervical sides (P < 0.05). In the PZ side, a lower cumulative distance of progressive manner was observed from the measurements [Table 4].

Table 4

Comparison of incisal and cervical accumulative moved distances (mm) between sides over time - group 3

Source	Incisal					Cervical
	Mean	S.D.	Exp (β)	C. I.	P	Mean	S.D.	Exp (β)	C. I.	P
1 week
Corticotomy	0.45	0.19	1	-	-	0.16	0.12	1	-	-
Piezocision	0.54	0.33	1.14	[0.87; 1.32]	0.346	0.18	0.12	1.1	[0.83; 1.54]	0.431
2 weeks
Corticotomy	0.57	0.25	1	-	-	0.19	0.16	1	-	-
Piezocision	0.63	0.29	1.11	[0.85; 1.31]	0.446	0.23	0.17	1.16	[0.83; 1.42]	0.513
4 weeks
Corticotomy	0.87	0.38	1	-	-	0.32	0.18	1	-	-
Piezocision	0.99	0.48	1.08	[0.85; 1.31]	0.673	0.37	0.21	1.12	[0.82; 1.39]	0.75
6 weeks
Corticotomy	1.34	0.49	1	-	-	0.45	0.21	1	-	-
Piezocision	1.38	0.69	1	[0.83; 1.26]	0.987	0.45	0.29	0.97	[0.72; 1.21]	0.92
8 weeks
Corticotomy	1.8	0.7	1	-	-	0.68	0.29	1	-	-
Piezocision	1.59	0.69	0.99	[0.80; 1.12]	0.66	0.54	0.38	0.98	[0.7; 1.11]	0.58
10 weeks
Corticotomy	2.15	0.89	1	-	-	0.89	0.37	1	-	-
Piezocision	1.95	0.89	0.96	[0.77; 1.08]	0.39	0.76	0.34	0.83	[0.77; 1.05]	0.29
12 weeks
Corticotomy	2.87	0.96	1	-	-	1.18	0.59	1	-	-
Piezocision	2.39	0.93	0.91	[0.75; 1.11]	0.184	0.98	0.58	0.88	[0.64; 1.09]	0.136
14 weeks
Corticotomy	3.38	0.92	1	-	-	1.47	0.48	1	-	-
Piezocision	2.75	0.96	0.89	[0.72; 1.08]	0.07	1.11	0.41	0.84	[0.69; 1.08]	0.041*
16 weeks
Corticotomy	3.7	0.98	1	-	-	1.58	0.48	1	-	-
Piezocision	3.1	1.1	0.86	[0.72; 0.99]	0.049*	1.2	0.5	0.79	[0.67; 0.91]	0.029*
18 weeks
Corticotomy	3.92	0.71	1	-	-	1.98	0.51	1	-	-
Piezocision	3.19	1.24	0.84	[0.69; 0.97]	0.020*	1.35	0.75	0.7	[0.52; 0.97]	0.013*
20 weeks
Corticotomy	4.28	0.97	1	-	-	2.11	0.66	1	-	-
Piezocision	3.48	1.26	0.79	[0.67; 0.97]	0.023*	1.58	0.88	0.79	[0.59; 0.83]	0.014*
22 weeks
Corticotomy	4.47	0.97	1	-	-	2.38	0.78	1	-	-
Piezocision	3.58	1.18	0.79	[0.65; 0.85]	0.01*	1.77	1	0.69	[0.43; 0.81]	0.013*
24 weeks
Corticotomy	4.48	0.95	1	-	-	2.65	0.69	1	-	-
Piezocision	3.97	0.87	0.74	[0.55; 0.87]	0.001*	2.14	0.77	0.69	[0.41; 0.87]	0.012*

Irrespective of any group, significant differences which were isolated and time-dependent were only observed in the biomarker levels of the bones between the sides. In case of Group1 (G1) (T7), interleukin-1β (IL-1β) levels were higher and it was on the intervention side. This was applicable for G2 (T2, T7) as well. These comparisons were done opposite to the control side (P = 0.000; P = 0.000; P = 0.0012). In case of the comparison of the techniques (G3 group), on the AC side (T5) IL-1β levels were recorded higher (P = 0.033). The IL-1β level was lower in case of PZ side.

No significant difference between sides could have been expressed by the tumor necrosis factor–α (TNF-α) expression. No difference was observed irrespective of exposure or non-exposure to surgical procedures. In the PZ side (T5), the RANKL levels were higher. The comparison was done against the AC side (P = 0.014, G3). However, osteoprotegerin (OPG) levels had been reported as low in the AC side (T5, T7). In the case of Dickkopf (DKK), the levels were low for the PZ side (T3) in comparison with the control side, as measured in G2. In contrast with this, for G3 the DKK-1 concentration was higher in the PZ side. Confidence interval (CI) for all the cases was 95%.

DISCUSSION

Following a longer follow-up period, the present data was collected. Biomarker analysis of GCF bone was done which indicated that canine retraction acceleration was not effectively done by AC. The present result highly differed from the surgical procedure involving AC that was previously done on the palatal and vestibular cortical bones.[11] Regional Acceleratory Phenomenon (RAP) is directly proportional to the injury amounts of bones.[12] In order to accelerate OTM, additional injury or palatal injury is required. Canine bracket is the power center of the teeth. For applying the force which is closer to the center of resistance of the tooth, canine teeth play an important role.[13] In order to achieve great inclination, the force is directly applied on the canine brackets. This force application is also helpful in increasing the tooth movement rate and less movement of the associated body as well.[13]

In the current study, canine retraction rate was low due to the process of canine extractions. Extractions accelerate OTM and induce RAP. Therefore, conducting extractions just before the retraction can cause movement acceleration to a greater level.[14] In order to reduce the surgical trauma of the patient, leveling and extraction before alignment were performed in the present clinical trial process. The trial results showed that canine movement acceleration was not effectively done by PZ. If the evaluation of OTM of other trials are observed then the difference can be noted here. In some of the previous studies, it was noted that PZ could significantly cause canine retraction.[15]

A standardized vertical extension of PZ was taken at the initiation of the clinical trial followed by proper depth and breath. In order to execute proper retraction, an elastomeric chain was used. Nickel-titanium coil springs were not used in the described clinical trial. In contrast, the result of this clinical trial revealed that PZ had slowed down the retraction process which is quite uncommon if results of other studies are considered. Though from the data analysis, it was not possible to tell the causes behind PZ dealing with the retraction process.

In case of orthodontic movement, the GCF cytokine levels change over time significantly. The comprehensive effects of PZ and AC on the molecular levels were not deciphered from this research process as well. The biomarker data in this case reinforced the clinical data concerned with the inability of PZ and AC in stimulating different expressions of the remodeling molecules of the bones. Inflammatory mediators which are related with GCF are not differentiated by movement types. In the gingival sulcus, the fluid presents free circulation.

CONCLUSION

Corticotomy and piezocision appeared to be impactful in accelerating canine retraction but did not induce distinct patterns of biomarker expression in GCF in this randomised clinical trial. However, because only the canine distalization movement was studied in this study, these findings cannot be generalised to other types of orthodontic movements. These particular aspects were suggested by previously conducted relevant animal studies. However, during the treatment and research, any kind of harm was not noticed. This study did aim to evaluate the root resorption. From this context, it was found that bone density decrement can further reduce excessive pressure's possible accumulation in periodontal ligament. It can also decrease root resorption's subsequent occurrence. It also indicates no consensus between the studies and further investigations is essential.

On the basis of the results and findings of the randomized clinical trial in the present research, it can be concluded that piezocision and corticotomy are not effective for accelerating canine reaction. It has also been found that these two factors have not induced distinct patterns on the expressions of the biomarkers in the GCF. Considering all of these aspects, it can be stated that these key findings of the present study cannot be generalized to any other kinds of orthodontic movements. As for this particular reason, only the movement of canine distalization has been investigated in this current research. Moreover, on the basis of the ineffectiveness found in this present research and costs of the PZ and AC, the suggestions for such surgeries for accelerating canine retraction are under question.

Financial support and sponsorship

Department of orthodontics and Dentofacial Orthopedics, Y.M.T. Dental college, Navi Mumbai.

Conflicts of interest

There are no conflicts of interest.