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Table of Contents
ORIGINAL ARTICLE
Year : 2021  |  Volume : 9  |  Issue : 4  |  Page : 103-106

Assessment of the effect of the length of orthodontic mini-screw implants on their long-term stability


1 Department of Orthodontics and Dentofacial Orthopaedics, Aditya Dental College and Hospital, Beed, Maharashtra, India
2 Department of Orthodontics and Dentofacial Orthopaedics, Yogita Dental College and Hospital, Khed, Ratnagiri, Maharashtra, India

Date of Submission18-Oct-2021
Date of Acceptance07-Nov-2021
Date of Web Publication27-Dec-2021

Correspondence Address:
Dr. Ranjit Omprakash Pawar
Department of Orthodontics and Dentofacial Orthopaedics, Aditya Dental College and Hospital, Sarda Estate, Pimpalner Road, near Nalwandi Naka, Beed. 431122, Maharashtra.
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/INJO.INJO_33_21

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  Abstract 

Background: In recent years, micro-screws have been widely used to reinforce anchorage during orthodontic therapy. Although micro-screws are now widely used clinically, biomechanical and histological research about the influence of loading protocols on the long-term stability of micro-screws is still confusing and limited. Aims and Objectives: The aim of this study is to assess the effect of the length of orthodontic mini-screw implant on their long-term stability. Materials and Methods: A total of 100 patients were included in the present study. Calculation of optical bone density was done in all the cases. Each patient received both the 6- and 8-mm long temporary intraoral skeletal anchorage devices (TISAD/TAD), in randomly selected mandibular quadrants (left or right). Loading of the TISAD/TAD was done with forces parallel to the occlusal plane by using NiTi springs. Results: It was observed that in Group 1 patients with 8 mm TISAD length, stability was seen in 80% of the cases, while failure occurred in 20% of the cases. In the Group 2 patients with 6 mm TISAD length, stability was seen in 70% of the cases, while failure occurred in 30% of the cases. Conclusion: In comparison to the 6 mm mini-screws, the stability of 8 mm orthodontic mini-screw implants is higher.

Keywords: Long-term stability, mini-screw implants, orthodontics, TISAD/TAD/anchorage


How to cite this article:
Pawar RO, Patil CD, Narote P, Khan R, Jadhav S, Chavan A. Assessment of the effect of the length of orthodontic mini-screw implants on their long-term stability. Int J Oral Care Res 2021;9:103-6

How to cite this URL:
Pawar RO, Patil CD, Narote P, Khan R, Jadhav S, Chavan A. Assessment of the effect of the length of orthodontic mini-screw implants on their long-term stability. Int J Oral Care Res [serial online] 2021 [cited 2022 Jun 27];9:103-6. Available from: https://www.ijocr.org/text.asp?2021/9/4/103/333814




  Introduction Top


In recent years, micro-screws have been widely used to reinforce anchorage during orthodontic therapy. Compared with traditional anchorage, such as extraoral headgear, transpalatal arch, or oral implant, micro-screws possess the advantages of small size, simple surgical insertion procedure, straightforward removal, lower cost, and independence from patient compliance.[1],[2] However, orthodontic micro-screws tend to suffer a failure rate of about 10%–30%, which is much higher than conventional implants.[1],[2],[3]The surrounding bone of micro-screws after insertion needs time to heal in order to provide stable support.[4] However, immediate or early activation of micro-screws is proposed to diminish the rehabilitation time and the period of orthodontic treatment.[5],[6] Therefore, scholars have evaluated the impact of healing time, loading magnitude, and loading direction on the stability of micro-screws in animal experiments. The stability of micro-screws includes primary stability and long-term stability. Primary stability represents the mechanical interlock of micro-screws, which depends on the amount and thickness of cortical bone surrounding the micro-screw’s threads. Long-term stability means biological ability to resist drop, and this stability is related to osseo-integration. Immediate or early loading may inhibit the osseo-integration process between the bone and micro-screw and may cause micro-movements of micro-screws.[7] In clinical practice, the orthodontists’ concern is which loading protocol would be more suitable. Temporary intraoral skeletal anchorage devices (TISAD/TAD) have many advantages, such as low price, ease of insertion and removal, and rare complications related to their application, but most of all they ensure excellent biomechanics of tooth movement and anchorage control, even in uncooperative patients.[7],[8],[9],[10],[11]Therefore, the aim of this prospective study was to analyse the influence of one factor only, the length of TISAD/TAD on the long-term stability of TISAD/TAD in the mandible and in a homogenous group of patients to minimize the fortuity of the results.


  Materials and Methods Top


A total of 100 patients scheduled to undergo orthodontic mini-screw dental implants were included in the present study. All procedures performed in the study were conducted in accordance with the ethical standards given in 1964 Declaration of Helsinki, as revised in 2013. The study proposal was submitted for approval and clearance was obtained from the ethical committee of our institution. A written informed consent was obtained from each participant. Healthy subjects more than 20 years of age were included in the present study. The range was from 20 to 25 years. We also recorded optical bone density between right and left sides of all the patients. Either 8 mm (Group 1) or 6 mm (Group 2) orthodontic implant mini-screw was used on one side of the arch. Hence, all the individual subjects received both 8- and 6-mm long intraoral skeletal anchorage devices (TISAD/TAD), in randomly selected quadrants. Skilled and experienced orthodontists carried out all the orthodontic procedures. Adequate instructions were given to all the subjects in relation to maintenance of strict oral hygiene. Using NiTi springs, loading of the TISAD/TAD were commenced with forces parallel to the occlusal plane by using NiTi springs. For a time period of 1 year, all the patients were observed. All the results were analyzed by SPSS software.


  Results Top


In the present study, a total of 100 patients with mean age of 22.5 years were included in which 40% of the patients were males while remaining 60% were females [Figure 1]. In all the patients, two types of orthodontic mini-screws were inserted with one type of mini-screw in each arch. It was observed that in Group 1 patients with 8 mm TISAD length, stability was seen in 80% of the cases, while failure occurred in 20% of the cases. In the Group 2 patients with 6 mm TISAD length, stability was seen in 70% of the cases, while failure occurred in 30% of the cases [Table 1].
Figure 1: Demographics in the study

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Table 1: Stability of TISAD

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  Discussion Top


It is quite likely that orthodontic mini-screw implants may not obtain long-term stability because of many factors. These factors may be assigned to different groups: patient related (systemic diseases, smoking, habits, hygiene, the level of immunity, etc.), orthodontist related (treatment methodology, experience), and TISAD/TAD related (size, surface coating, and shape).[8],[9],[10],[11] The clinical trials, which have been designed to improve the rate of TISAD/TAD stability until the therapeutic goal is obtained (also known as the success rate), require distinguishing factors that have the greatest and most decisive influence on maintaining mini-screw implants in the oral cavity. According to the available data, a statistically significant relationship was not shown by some studies.[7],[8],[9],[10],[11] The authors concluded that the minimum length of the TISAD/TAD should be at least 6 mm. If an assumption is made that 6 mm is the minimal length and the longer mini-screw implants give better results, the conclusions drawn by Chen et al.[7] will be consistent with the results of the present study, in which using 6-mm long TISAD/TAD was less successful than the application of 8-mm long TISAD/TAD. However, Chen et al. conclude that further research may show that shorter and smaller TISAD/TAD can be more successful in the toothed area, because “slimming” the size poses a lower risk of contact between the mini-screw implants and the dental roots. This view has been confirmed by Kuroda et al.,[4] who demonstrated in the in-vivo studies that the proximity of the dental roots may be one of the main factors responsible for the failure of TISAD/TAD. On the contrary, the meta-analysis of the factors determining the success rate of TISAD/TAD conducted by Papageorgiou et al.[8]revealed that the length of the mini-screw implant was unimportant. However, according to these authors, both the proximity to the root and too high torque during the TISAD/TAD insertion may increase the risk of their loss. In our study, the risk of the contact between TISAD/TAD and the roots of the adjacent teeth was reduced, but at the stage of the research methodology by using the original method of insertion, whose effectiveness is 93.46%. Moreover, the radiologic verification carried out after each TISAD/TAD insertion excluded the patients who were predisposed to the loss at the very beginning. As to mechanical consideration, Wilmes et al.[9] reported that the longer TISAD/TAD may cause higher torque during screwing in, which can lead to the micro-damage of the bone and the consequent loss of the mini-screw implant. Nevertheless, our results prove that, even if such a factor existed, it is irrelevant from a clinical point of view. Perhaps it resulted from the mandatory predrilling during every insertion of the mini-screw implant. Study conducted by Kau et al.[10] proved that, on average, 71.2% of the TISAD/TAD thread area contacts with the alveolar bone. It can therefore be assumed that the absolute contact surface in longer TISAD implants will provide better initial stability. This is consistent with our results; nonetheless, it should be noted that the good initial stability was a sine qua non inclusive criterion for both 6- and 8-mm long mini-screw implants. Here, we can pose the question as to whether better resistance to the mechanical pressure, which is exerted on TISAD/TAD during the orthodontic treatment, is the major factor responsible for the higher success rate of 8-mm long mini-screw implants. The positive answer can be supported by the results of the in vitro studies presented by Petrey et al.[11]They reported that the deeper placement of the mini-screw implants in the bone structure, which requires a greater length of TISAD/TAD, provides better resistance to the orthodontic forces. However, the same authors found that from a purely mechanical point of view, even short, 6-mm long mini-screw implants remain stable, provided that the proper value of orthodontic forces are preserved. In our study, all TISAD/TAD were loaded in the same manner, without exceeding the value defined as the maximum force the orthodontic mini-screw implants may withstand, which allows us to relate the premature TISAD/TAD loss to their length rather than to their loading protocol. We propose that strictly obeying the rules of the Wroclaw method helped to eliminate a significant number of the recognized factors that are under the control of an operator that might predispose to loss of the mini-screw implants. Moreover, the far-reaching unification of the study group in terms of the host-dependent, well-known factors as well as the random placement of TISAD/TAD of different lengths allow the extensive isolation of a single tested variable affecting the loss or maintenance of TISAD/TAD.


  Conclusion Top


It can be concluded that stability of 8 mm orthodontic mini-screws is higher than that of 6 mm mini-screws. Therefore, we recommend further studies in future for better exploration of results.


  Acknowledgement Top


Nil.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Geron S, Shpack N, Kandos S, Davidovitch M, Vardimon AD. Anchorage loss–a multifactorial response. Angle Orthod 2003;73:730-7.  Back to cited text no. 1
    
2.
Shpack N, Davidovitch M, Sarne O, Panayi N, Vardimon AD. Duration and anchorage management of canine retraction with bodily versus tipping mechanics. Angle Orthod 2008;78:95-100.  Back to cited text no. 2
    
3.
Isaacson RJ, Lindauer SJ, Davidovitch M. The ground rules for arch wire design. Semin Orthod 1995;1:3-11.  Back to cited text no. 3
    
4.
Kuroda S, Sugawara Y, Deguchi T, Kyung HM, Takano-Yamamoto T. Clinical use of miniscrew implants as orthodontic anchorage: Success rates and postoperative discomfort. Am J Orthod Dentofacial Orthop 2007;131:9-15.  Back to cited text no. 4
    
5.
Prabhu J, Cousley RR. Current products and practice: Bone anchorage devices in orthodontics. J Orthod 2006;33:288-307.  Back to cited text no. 5
    
6.
Miyawaki S, Koyama I, Inoue M, Mishima K, Sugahara T, Takano-Yamamoto T. Factors associated with the stability of titanium screws placed in the posterior region for orthodontic anchorage. Am J Orthod Dentofacial Orthop 2003;124:373-8.  Back to cited text no. 6
    
7.
Chen Y, Kyung HM, Zhao WT, Yu WJ. Critical factors for the success of orthodontic mini-implants: A systematic review. Am J Orthod Dentofacial Orthop 2009;135:284-91.  Back to cited text no. 7
    
8.
Papageorgiou SN, Zogakis IP, Papadopoulos MA. Failure rates and associated risk factors of orthodontic miniscrew implants: A meta-analysis. Am J Orthod Dentofacial Orthop 2012;142:577-595.e7.  Back to cited text no. 8
    
9.
Wilmes B, Ottenstreuer S, Su YY, Drescher D. Impact of implant design on primary stability of orthodontic mini-implants. J Orofac Orthop 2008;69:42-50.  Back to cited text no. 9
    
10.
Kau CH, English JD, Muller-Delgardo MG, Hamid H, Ellis RK, Winklemann S. Retrospective cone-beam computed tomography evaluation of temporary anchorage devices. Am J Orthod Dentofacial Orthop 2010;137:166.e1-166.e5  Back to cited text no. 10
    
11.
Petrey JS, Saunders MM, Kluemper GT, Cunningham LL, Beeman CS. Temporary anchorage device insertion variables: Effects on retention. Angle Orthod 2010;80:446-53.  Back to cited text no. 11
    


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