Effect of Immediate versus delayed loading of orthodontic miniscrews on miniscrews stability, patients pain perception and quality of life: A randomized clinical trial

Mini-implants (MI) or Mini-screws (MS) also commonly known as Temporary Anchorage Devices (TADs) have become a mainstay in the field of orthodontics. These devices not only limit anchorage demands but have also expanded the envelope of discrepancy to treat malocclusions non- surgically which earlier could not have been possible. The popularity of TADs can be attributed to their ease of placement, varied applications, and affordable cost. TADs reported to have an average survival rate of 84% (range 57–95.3%) which is largely dependent on factors governing primary and secondary stability.[i] The primary stability pertains to the mechanical holding of MS in the bone, while the secondary stability relates to biological retention. Broadly, the factors affecting the stability can be grouped into a host, miniscrew and technique-related factors. Though host and MS related factors are beyond the control of a clinician. The technique related factors can be effectively altered by the clinician to maximise the survival rate of TADs. One such factor of concern is the loading protocol or force application through MS.  Two loading protocols have been proposed for TADs, namely, immediate and delayed. Though significant research has been done and norms have been established on the structural components and design of the TADs and predominant host factors responsible for MI stability, there still remains a lacuna on the loading protocol. Though recent systematic reviews and umbrella reviews[ii] have pointed out that loading protocols don’t usually alter the MI stability, these conclusions have been drawn from case series and case reports with no quality RCTs as basis. A major factor that effects MI stability is peri-implant inflammation with conclusive evidence pointing towards the fact that increased inflammation results in decreased implant stability.2 Recently research done by kaur et al [iii] [iv] have provided an insight on biological markers associated with peri-implant crevicular fluid (PIMCF). They reported an increase in PIMCF inflammatory markers (ILs and TNF- alpha) from the day of MS placement till 21 days later followed by gradual decrease. This pointed the authors to suggest a delayed loading of miniscrews by 21 days. However, whether early loading protocol and a consequent increase in inflammation results in decreased miniscrew stability have not been tested in a well structured Randomized Clinical Trial. Also, if delayed force application through MI result in any benefit for the patient or clinician in terms of stability, pain perception and quality of life has not been studied in the controlled environment.

Therefore, the present trial will evaluate and compare the early versus delayed loading (after 21 days of insertion) of miniscrews. The study will also evaluate the pain perceived and the effect of loading protocol on the quality of life.

Research question and hypothesis: Will there be a difference in MI stability, patients’ pain perception and quality of life amongst two groups with Immediate and delayed loading (after 21 days of screw insertion) of orthodontic MI in orthodontic patients undergoing extraction treatment?

Aim: To evaluate the effect of immediate and delayed (21 days) loading of orthodontic miniscrews on screws stability, patients’ pain perception and quality of life

Objectives

1.     To evaluate and compare the stability of orthodontic MS between Group 1 and Group 2 of patients undergoing extraction treatment with fixed mechanotherapy and space closure using anchorage from MS.

2.     To evaluate and compare the patients’ pain perception between Group 1 and Group 2.

3.     To evaluate and compare the patients’ quality of life between Group 1 and Group 2.

 The null hypothesis to be tested is that no statistically significant difference exists between immediate and delayed loading of orthodontic MS on screw stability, patients’ pain perception and quality of life.

Methodology: include the following sub-heads:

 Â·       Study design and settings: Randomized clinical trial; Department of Orthodontics, PGIDS, Rohtak

·       *Study**population:*Adult orthodontic patients having Angle’s Class I bimaxillary protrusion requiring all first premolars extraction treatment plan and to be treated with fixed mechanotherapy and space closure with MS in all the four quadrants.

·       Study conduct: The present study will be conducted on a sample size of 32 patients having Angle’s Class I bimaxillary protrusion requiring all first premolars extraction with the insertion of MS in all the four quadrants between the inter-radicular space of second premolar and first molars. The titatnium miniscrews of 1.6 mm X 8 mm in dimensions will be inserted by single experienced operator after local infiltration with 2% lignocaine + 1:100000 adrenaline local anaesthetic agent.

The sample will be divided into two groups of 16 each requiring insertion at the total of 128 sites in all the patients. The patients will be allocated to the two groups (Group 1 with immediate loading/ force application from the MS and Group 2 with delayed loading/ force application after 21 days of insertion from the MS) using block randomization.

1.     Miniscrews stability will be assessed till the closure of spaces created by the extraction of first premolars/ retraction of the anterior teeth which normally requires 6 months and the miniscrew stability will be assessed according to the criteria suggested by Luzi et al. (2007)

2.     Pain assessment will be assessed with Visual Analogue Scale (VAS) consists of an unmarked 100 mm long horizontal line that is weighted at both ends with the 2 extremes of pain (i.e. “no pain” and “worst pain imagined”). A vertical line drawn on the scale location which would best represent their pain perception at the given time interval without anybody’s assistance will be calculated. The VAS score proforma will be given to the patients’ and filled by them at home at the given time intervals written on the top of the proforma.

3.     Patients’ will fill the Oral Health Impact Profile (OHIP-14) questionnaire for the assessment of quality of life. The OHIP-14 questionnaire will be given to the patients’ and will be filled by them at home at the given time intervals written on the top of the proforma.

Pain perception and quality of life will be assessed at following time points:

0 day (4 hours), 1 day, 7 days, 21 days, 3 months, 6 months after insertion of MS

A methodology flow chart indicating the study plan is attached as Annexure 4.

·       Intervention: Loading of miniscrew for space closure started immediately after their placement (Group 1) and Loading of miniscrew for space closure started 21 days (delayed) after their placement (Group 2)

·       Sample size calculation: The sample size was estimated using a previous study’s standard deviation of 23 mm and a clinically significant difference of 20 mm on a 100-mm VAS at a power of 0.80 and an alpha of 0.05, resulting in 15 subjects needed per group.