Effects of acid etching and calcium chloride immersion on removal torque and bone-cutting ability of orthodontic mini-implants

Comparison between microporous and nanoporous orthodontic miniscrews : An experimental study in rabbits

PURPOSE

Surface characteristics of orthodontic miniscrews might affect survival rates and removal torque values (RTVs). This experimental study aimed to clarify whether and why a microporous or nanoporous surface promotes higher survival rates and RTVs for orthodontic miniscrews.

METHODS

Using a split-leg design, one set each of nonporous (sham control, n = 24) and microporous (control, n = 6), and three sets of nanoporous (experimental, n = 6 per set) miniscrews were implanted in the tibias of 12 New Zealand rabbits and immediately loaded with 1.5 N nickel-titanium coil springs for 12 weeks. The surface morphology, micropores, and nanotube diameters of the miniscrews were examined using scanning electron microscopy and field-emission scanning electron microscopy. The surface composition and thickness were determined using Auger electron spectroscopy. The survival rates and RTVs of each set were assessed.

RESULTS

The nanoporous miniscrews had higher survival rates, RTVs (p < 0.001), and thicker nanotube oxide thicknesses (p < 0.001) than the nonporous and microporous miniscrews. The nonporous and microporous miniscrews had no nanotube structures. The surface oxide composition was titanium dioxide (TiO2). The threshold RTV, TiO2 thickness, and nanotube diameter of nanoporous miniscrews needed to promote the experimental survival rate to 100% was determined to be 6.6 ± 0.8 N-cm (p < 0.05), 22.5 ± 4.8 nm (p < 0.05), and 17.6 ± 2.3 nm or above, respectively.

CONCLUSION

Nanoporous surfaces promoted higher survival rates and RTVs than microporous miniscrews. This could be due to TiO2 nanotube structures with thicker oxide layers in nanoporous miniscrews.

Comparison of Biomechanical Properties of Surface-Treated and Untreated Machined Orthodontic Mini-Implants: An In Vitro Study

Background and Objectives:

The use of mini-implants has become more popular, and there has been a heightened focus on factors that contribute to their success. The purpose of the study is to compare the effects of various surface treatment methods of mini-implants on their bone cutting capacity, insertion torque required, and fracture resistance when compared with the untreated machined mini-implants.

Materials and Methods:

The study included 4 groups. Each group consisted of 10 orthodontic mini-implants (OMIs). The first experimental group contains titanium oxide coated mini-implants, the second group contains grit-blasted implants with aluminum oxide, the third group consists of mini-implants coated with hydroxyapatite crystals, and the control group is formed by untreated machined mini-implants. Each group is evaluated for cutting efficiency, maximum insertion torque, and fracture resistance using a customized torque testing gauge.

Results:

The results showed that surface treating OMIs with hydroxyapatite particles increases the surface roughness, thereby enhancing their stability without decreasing the bone cutting ability compared with OMIs without surface treatment.

Conclusion:

Roughened surface of OMIs with hydroxyapatite particles exhibited maximum fracture resistance without decreased corresponding bone cutting efficiency.

[Efficacy of vertical control by using mini-implant anchorage in maxillary posterior buccal area for Angle class Ⅱ extraction patients]

OBJECTIVE

To investigate the efficacy of vertical control by using conventional mini-implant anchorage in maxillary posterior buccal area for Angle class Ⅱ extraction patients.

METHODS

Twenty-eight Angle class Ⅱ patients [9 males, 19 females, and age (22.6±2.8) years] were selected in this study. All of these patients were treated by using straight wire appliance with 4 premolars extraction and 2 mini-implant anchorage in maxillary posterior buccal area. In this study, the self-control method was used to measure and analyze the lateral radiographs taken before and after orthodontic treatment in each case, the main cephalometric analysis items were related to vertical changes. The digitized lateral radiographs were imported into Dolphin Imaging Software (version 11.5: Dolphin Imaging and Management Solutions, Chatsworth, California, USA), and marked points were traced. Each marked point was confirmed by two orthodontists. The same orthodontist performed measurement on the lateral radiographs over a period of time. All measurement items were required to be measured 3 times, and the average value was taken as the final measurement result.

RESULTS

Analysis of the cephalometric radiographs showed that, for vertical measurements after treatment, the differences of the following measurements were highly statistically significant (P < 0.001): SN-MP decreased by (1.40±1.45) degrees on average, FMA decreased by (1.58±1.32) degrees on average, the back-to-front height ratio (S-Go/N-Me) decreased by 1.42%±1.43% on average, Y-axis angle decreased by (1.03±0.99) degrees on average, face angle increases by (1.37±1.05) degree on average; The following measurements were statistically significant (P < 0.05): the average depression of the upper molars was (0.68±1.40) mm, and the average depression of the upper anterior teeth was (1.07±1.55) mm. The outcomes indicated that there was a certain degree of upper molar depression after the treatment, which produced a certain degree of counterclockwise rotation of the mandibular plane, resulting in a positive effect on the improvement of the profile.

CONCLUSION

The conventional micro-implant anchorage in maxillary posterior buccal area has a certain vertical control ability, and can give rise to a certain counterclockwise rotation of the mandible, which would improve the profile of Angle Class Ⅱ patients.

Effect of surface treatment on the mechanical stability of orthodontic miniscrews

OBJECTIVES

To provide collective quantitative evidence about the effect of surface treatments on the mechanical stability of orthodontic miniscrews (MSs).

MATERIALS AND METHODS

The study was registered in PROSPERO (No. CRD42020209652). The research question was defined according to the PICO (population, intervention, control, and outcomes) format. Various research databases were searched for animal and human studies on effects of surface treatment on the mechanical stability of MSs. Both prospective and retrospective in vivo clinical studies published in English were included. The risk of bias was assessed using SYRCLE's risk of bias tool for animal studies. The meta-analysis was conducted using RevMan 5.4.

RESULTS

A total of 109 articles were identified; 14 were included in the systematic review, and seven studies with sandblasting, acid etching (SLA) methods of surface treatment were included for meta-analysis. The number of study participants ranged from 6 to 24 (total n = 185), with a mean of 13.2. A total of 949 MSs were used with a mean of 67.8. The overall success rate for surface-treated MSs ranged from 47.9% to 100%. Forest plot of removal torque values showed significantly higher values for SLA surface-treated MSs compared with controls with a standard mean difference of 2.61 (95% confidence interval = 1.49-3.72, I2 = 85%). Forest plot of insertion torque showed a standard mean difference of -6.19 (95% confidence interval = -13.63-1.25, I2 = 98%, P = .10).

CONCLUSIONS

Surface treatment of MSs improved primary and secondary stability with good osseointegration at the bone-implant surface. However, significant heterogeneity across the studies included in the meta-analysis made it difficult to draw conclusions.

Evaluation of the long-term stability of micro-screws under different loading protocols: a systematic review

The aim of this systematic review was to investigate the association between the different factors of loading protocols and the long-term stability of micro-screws from biomechanical and histological viewpoints. Searches were performed on PubMed, Embase, Cochrane Library, Wanfang and CNKI databases for animal experiments comparing loading protocols and the long-term stability of micro-screws. Among 1011 detected papers, 16 studies met the eligibility criteria and were selected for analysis. Most studies showed medium methodological quality for evaluation of micro-screws' long-term stability. Five studies reported that loading would not destroy the long-term stability of micro-screws. Three studies indicated that low-intensity immediate loading or a 3-week minimal healing time was acceptable. Two studies reported that the loading magnitude was a controversial issue with regard to the micro-screws' long-term stability. Two studies suggested that counterclockwise loading could decrease the long-term stability of micro-screws. In conclusion, immediate loading below 100g force, healing time greater than 3 weeks, regular loading below 200g force and a clockwise direction of force supported the long-term stability of micro-screws. Further studies relating to the combination of varying loading conditions will be needed.