Anchorage is an important consideration when planning orthodontic treatment. Anchorage loss, i.e., unwanted tooth movement can have a detrimental effect on the orthodontic treatment outcome. In the past, extraoral headgear, elastics, and a variety of appliances have been designed to overcome this limitation, but these have their own drawbacks, as they all rely on patient compliance to be successful. For this reason, other alternatives for anchorage have been developed, currently micro-implants are becoming increasingly popular in orthodontics1,2 because they provide absolute and skeletal anchorage for orthodontic tooth movements.3,4 Micro-implants are used as temporary fixtures in bone and their greatest advantage lies in their small size, which permits rapid and atraumatic placement in almost all sites within the mouth. In the past decade, there have been rapid advances in the development of micro-implants and they are increasingly used in orthodontics. Micro-implants have become established as practical, inexpensive, highly versatile sources of orthodontic anchorage.
Achievement and maintenance of implant stability are prerequisites for successful clinical outcome of orthodontic treatment. Therefore, measuring the implant stability is an important method for evaluating the success of an implant. Implant stability is achieved at two different stages: primary and secondary. Primary stability of micro-implants comes from mechanical interlocking with the cortical bone, so quantity and quality of bone that the implant is inserted into, surgical procedure, length, diameter, and form of the implant are the crititical factors.5 Secondary stability is developed from regeneration and remodelling of the bone and tissue around the implant after insertion but is affected by the primary stability, bone formation and remodeling.6 The stability of dental implants has been studied thoroughly in animals, mainly relying on histological analysis of osseointegration rates. In humans, resonance frequency analysis (RFA) has proven to be an adequate method because of its non-invasiveness and contactless measurement method.7 Resonance frequency analysis (RFA) uses the principle of a tuning fork and its unit of measurement for determining implant stability is Implant stability quotient (ISQ), which ranges from 0 to 100. The higher the ISQ value, the more stable the implant.
Resonance frequency analysis is regarded as the gold standard for clinical stability measurement of dental implants.8 It was demonstrated that it can be used to assess implant stability any time after insertion.9 Micro-implants differ from current dental implants with respect to size, design, surface characteristics, insertion protocol, and insertion sites. As a consequence, results of RFA measurements are significantly affected by factors such as implant size and design.10 To assess micro-implant stability, specially modified SmartPegs are used. It was shown that this way, RFA delivers reasonable results also for micro-implants.11 Similar to dental implants, for their response to immediate loading, orthodontic micro-implants rely on primary stability,12 hence the time of functional loading is dependent upon the stability of micro-implant. It is, therefore, of an utmost importance to be able to quantify implant stability at various time points and to project a long term prognosis based on the measured implant stability.
Determining primary stability after insertion can help predict success. In this regard, the measurement of insertion torque has been used.13 But studies regarding evaluation of implant stability during various phases of orthodontic treatment following insertion of micro-implants in patients have been very limited.
Hence, the purpose of this study is to evaluate the micro-implant stability during the various phases of orthodontic treatment following micro-implant insertion using the resonance frequency analysis method, and also to derive a clinical implication regarding which phase following insertion of micro-implant is appropriate for loading. This study will also compare the differences among the implant stability values measured among male and female subjects.
Micro-implant stability remains constant during various phases of orthodontic treatment following micro-implant insertion.
To evaluate the micro-implant stability during the various phases of orthodontic treatment following micro-implant insertion.
REVIEW OF LITERATURE
A clinical trial study was done on 17 patients following insertion of 34 non submerged titanium dental implants to determine whether the implant stability quotient values obtained correlated with those made with the electronic device. This study concluded stating that the electronic resonance frequency analyzer and the newer magnetic resonance frequency analyser seem to be capable of measuring similar changes in implant stability over time, however the magnetic device resulted in higher ISQ values measuring the stability of non-submerged dental implants, therefore so concluding that measurements made with the two devices cannot be compared directly.14 A study was done to evaluate the soft bone primary stability of 3 different orthodontic mini-screws by using the resonance frequency analysis. The methodology included Aarhus mini-implant (A), Mini Spider Screws(S) and Micerium Anchorage System (MAS) which were to be investigated. To be compatible with the device used for resonance frequency analysis, the screws were modified (an abutment was soldered on top). Four screws per system were tested. Each screw was placed in 5 excised rabbit femoral condyles, providing experimental models of soft bone. Placement was drill-free for the A screw, whereas the MAS and S screws required a pilot hole through the cortical layer. After each placement procedure, resonance frequency was assessed as a parameter of primary stability. Differences among the systems were analyzed by using analysis of variance for repeated measures, with the level of significance at P< 0.05. The recorded resonance frequencies (in Hz) were (mean ± SD): MAS, 6236.1 ± 192.1; S, 6270.1 ± 99.7; and A, 6193.1 ± 142.4. Differences among the groups were not statistically significant (P > 0.05). This study concluded that the resonance frequency analysis is applicable to comparatively assess the primary stability of orthodontic miniscrews. The 3 systems had similar outcomes in an experimental model of soft bone.15 A study was done to determine whether micromotion at the bone- implant interface is related to the ISQ values. A total of 30 implants were used. Implants were placed in fresh bovine bone samples representing three density categories: hard, normal and soft (H·N·S). Customized electronic equipment connected to a PC was used to register the peak and insertion torque data. A loading device, consisting of a digital force gauge and a digital micrometer was used to measure the micromovements of the implant during the application of 25 N lateral forces. Resonance Frequency Analysis was calculated using the Osstell ISQ and the values were recorded in ISQ units. The data were analyzed for statistical significance by Spearman's rank correlation coefficient tests. The statistical analysis showed significant correlation between ISQ and torque-in and between torque-in values and micromotion. The study concluded stating a high dependence between the observed micromotion and the ISQ values, indicating that micromotion decreased with increasing ISQ values. Contrarily, increasing the peek insertion torque increased the ISQ values.16 A retrospective study was done to elucidate potential confounding factors affecting initial stability of miniscrews inserted to enhance orthodontic anchorage. Four hundred and seven miniscrews inserted in 168 patients treated by 17 orthodontic residents were analysed in a consecutive chart review. The outcome variable was the stability of the miniscrew, measured as a dichotomous variable, 0 if the miniscrew loosened during a 1 week period after insertion to the time of orthodontic force application and a value of 1 otherwise. Potential confounding variables examined were gender, age, jaw, insertion site, tissue type, length and diameter of the miniscrew, and number of previous insertions. Generalized estimating equations (GEE) methods were used to estimate the influence of each factor on stability for the correlated binary outcomes of each patient. A weighted analysis for the GEE approach was also performed for the convergence calculation of the estimation procedure due to a value of 0 in one of the cells. Crude odds ratio (cOR) and adjusted odds ratio (aOR) and their 95 per cent confidence intervals (CI) were calculated for this purpose. The overall success rate after 1 week was 93.1 per cent (379/407). The screws inserted by more experienced clinicians (more than 20 miniscrews) were found to have approximately a 3.6-fold higher success rate of initial stability compared with those inserted by less experienced clinicians after adjusting for the insertion site (aOR = 3.63, P = 0.015). The results of the present study suggest that the initial stability depends on insertion site and clinician experience.17 A study was conducted to investigate whether resonance frequency analysis (RFA) is suitable to measure orthodontic mini-implant stability and to prove whether the resonance frequency of mini-implants in bone fits the range of frequency emitted by the Osstell ISQ device. In this study the SmartPegs in the Osstell ISQ device were modified to fit with the inner screw thread of orthodontic mini-implants, and 110 mini-implants were inserted into porcine pelvic bone. RFA was performed parallel and perpendicular to the run of superficial bone fibers. A suitability test, Periotest, was also performed in the same directions. Compacta thickness was measured using cone-beam computed tomography. Correlation tests and linear regression analysis were carried out between the three methods. Here the RFA results showed a mean Implant Stability Quotient value of 36.36 ± 2.67, and the Periotest mean value was -2.10 ± 1.17. The differences between the two directions of measurement were statistically significant (P > .001) for RFA and the Periotest. There was a high correlation between RFA and the Periotest (r = -0.90) and between RFA and compacta thickness (r = 0.71). The comparison between the Periotest and compacta thickness showed a correlation coefficient of r = -0.64. The study concluded with results which suggested that RFA is feasible as a measurement method for orthodontic mini-implant stability. As a consequence, it could be used for clinical evaluation of current stability and allow stability-related loading of mini -implants to reduce the failure rate.12 A review of studies was conducted on various techniques to measure miniscrew implant stability. This study concluded that with increased popularity, miniscrew implants will soon be implemented extensively in everyday clinical practice and their possible failure will heavily influence the outcome and efficiency of the treatment. As such, an in vivo method to evaluate miniscrew implant stability would hold great clinical implications. By quantifying stability, it would be possible to follow the changes that occur during the transition from primary to secondary stability. Resonance Frequency method which has been used to quantify implant stability in dental implants for the last 10 years holds great potential for quantifying the stability of miniscrew implants. But also stated that mind that most of the literature regarding stability of implants is provided for dental implants, therefore it should be carefully evaluated when orthodontic miniscrew implants are under consideration.18 A clinical pilot study was conducted to evaluate the changes of mini-implant stability over the initial healing period in humans. Here samples of 19 consecutively treated patients were examined. In each patient, a mini-implant of a size of 2 x 9 mm was inserted into the anterior palate. Implant stability was assessed using resonance frequency analysis (RFA) immediately after insertion (T0), 2 weeks later (T1), 4 weeks later (T2), and 6 weeks later (T3). Insertion depth (ID) and the maximum insertion torque (IT) were measured. Data were tested for correlations between RFA, ID, and IT. The results showed mean ID was 7.5 ± 0.6 mm, and the mean IT was 16.8 ± 0.6 Ncm. A correlation was found between RFA and ID (r = .726, P < .0001), whereas no correlations between RFA and IT or between IT and ID were observed. From T0 to T1, the stability (36.1 ± 6.1 implant stability quotient [ISQ]) decreased nonsignificantly by 4.9 ± 6.1 ISQ values (P > .05). Between T1 and T2, the stability decreased highly significantly (P < .001) by 7.9 ± 5.9 ISQ values. From T2 on, RFA remained nearly unchanged (-1.7 ± 3.5 ISQ; P > .05). This study concluded saying that mini-implant stability is subject to changes during the healing process, and during weeks 3 and 4, a significant decrease of the stability was observed. After 4 weeks, the stability did not change significantly.19
OBJECTIVES OF STUDY
The objective of the study is to:
To evaluate micro-implant stability during the various phases of orthodontic treatment following micro-implant insertion.
Derive a clinical implication regarding which phase following the insertion of micro-implant is more appropriate for loading.
MATERIALS AND METHODS SOURCE OF DATA
Study will be conducted in the Department of Orthodontics and Dentofacial Orthopaedics, SDM College of Dental Sciences and Hospital, Dharwad. Twenty micro-implants are required in total which will be inserted in the subjects whose treatment plan comprises of a micro-implant placement in the maxillary posterior region between the roots of first molar and premolar. Subjects will be included in this prospective study after getting an approval from the institutional review board and ethical committee, and subjects consent.
Consent form will be obtained from all the subjects included in the study.
Subjects whose treatment plan comprised of a micro-implant placement.
Subjects with healthy periodontium.
Subjects with good oral hygiene.
Age group above 18 years.
Subjects having systemic disease affecting bone metabolism/ wound healing.
Subjects under any medications, steroids.
After insertion, data of subjects who missed examination appointments.
METHOD OF COLLECTION OF DATA
Micro-implant stability will be evaluated at the following time intervals:
T0: immediately after micro-implant insertion
T1: during loading
T2: 2 weeks later
T3: 4 weeks later
T4: 6 weeks later
T5: Just before removal of micro-implant.
Micro-implant stability will be evaluated using RFA method and Implant stability quotient(ISQ) values will be recorded after insertion (T0), during loading (T1), 2 weeks later (T2), 4 weeks later (T3), 6 weeks later (T4) and just before removal of micro-implant (T5) in two directions perpendicular to each other. Implant stability quotient (ISQ) value measurement will be repeated three times in each direction for each micro-implant. Mean values will be calculated for each direction and overall ISQ values for each mini-implant at each time.
ISQ values recorded in first direction
T5 ISQ values recorded in second direction
T5 Significant differences between the ISQ values at T0, T1, T2, T3, T4 and T5 will be tested with analysis of variance/Duncan post hoc test. A comparison between ISQ values measured in two perpendicular directions to each other will be performed using the paired t test/ Wilcoxon test. A comparison between ISQ values measured among male and female subjects will be performed using the paired t test/ Wilcoxon test. Statistical significance will be tested at P < 0.05.
DOES THE STUDY NEED ANY INVESTIGATION OR INTERACTION TO BE CONDUCTED ON THE PATIENTS OR ANIMALS?
HAS THE ETHICAL CLEARANCE BEEN OBTAINED BY THE INSTITUTION?
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