Stability of miniscrews with different continuous orthodontic forces as measured by cone-beam computed tomography

PurposeMiniscrew stability is a key for successful orthodontic anchorage reinforcement. Light force as 50 g has been proposed to efficiently retract canine; however, for miniscrew stability, its efficiency is still questionable. This study aimed to evaluate and compare miniscrew displacements loaded with 50 and 150 g to retract upper canines.Subjects and methodsTwenty four miniscrews (1.4 mm diameter and 7 mm length) were placed in twelve orthodontic patients (female, 22.55 ± 4.8 years old) who required miniscrews for maximum anchorage. Cone-beam computed tomography (CBCT) was taken to assess the miniscrew displacement in three dimensions. The X, Y, Z coordination points at the miniscrew head and tail with anterior nasal spine as a reference point were recorded and analyzed the displacements during 3 months using one-sample t-test and pair t-test.ResultsMiniscrews were significantly displaced after loading 50 and 150 g at 2 and 3 months compared to baseline (P < 0.001). At 2 months, the displacement of the miniscrews at head and tail had no statistical significance between 50 and 150 g (P > 0.05). However, at 3 months, there were statistically significant displacements between 50 and 150 g. This displacement was found to be greater in 150 g and at head more than at tail (P < 0.05).ConclusionThis study concluded that miniscrews could be significantly displaced with 50 and 150 g during 3 months wherein the heavier loading force essentially caused more miniscrew mobility. Clinically, it is suggested to use proper magnitude of force to miniscrews with care in order to overcome orthodontic anchorage failure.     

Primary failure rate for 1680 extra-alveolar mandibular buccal shelf mini-screws placed in movable mucosa or attached gingiva

Objective:To compare the initial failure rate (≤4 months) for extra-alveolar mandibular buccal shelf (MBS) miniscrews placed in movable mucosa (MM) or attached gingiva (AG).Materials and Methods:A total of 1680 consecutive stainless steel (SS) 2 × 12-mm MBS miniscrews were placed in 840 patients (405 males and 435 females; mean age, 16 ± 5 years). All screws were placed lateral to the alveolar process and buccal to the lower first and second molar roots. The screw heads were at least 5 mm superior to the soft tissue. Loads from 8 oz–14 oz (227 g–397 g, 231–405 cN) were used to retract the mandibular buccal segments for at least 4 months.Results:Overall, 121 miniscrews out of 1680 (7.2%) failed: 7.31% were in MM and 6.85% were in AG (statistically insignificant difference). Failures were unilateral in 89 patients and bilateral in 16. Left side (9.29%) failures was significantly greater (P < .001) compared with those on the right (5.12%). Average age for failure patients was 14 ± 3 years.Conclusion:MBS miniscrews were highly successful (approximately 93%), but there was no significant difference between placement in MM or AG. Failures were more common on the patient''s left side and in younger adolescent patients. Having 16 patients with bilateral failures suggests that a small fraction of patients (1.9%) are predisposed to failure with this method.     

Technological advances in nontraditional orthodontics

New technological advances have helped the orthodontic profession progress in traditional and surgical methods of treatment. The profession has seen transitions from traditional braces to self-ligating brackets, lingual braces, removable aligners, and more advanced technology, which have helped to address concerns that include but are not limited to better diagnostics, anchorage control, length of treatment, and esthetics. An increase in the number of adult patients seeking orthodontic treatment and the need for a timely efficient care will continue to drive technology and the use of cone beam computed tomography, miniscrews, piezocision, distraction osteogenesis, and bioengineering.     

Class II treatment by palatal miniscrew-system appliance: A case report

This case shows that using a rapid palatal expander (RPE) and then a pendulum appliance anchored to palatal miniscrews is an option for improving treatment management in a noncompliant patient requiring maxillary expansion and molar distalization in the late mixed dentition. First, an RPE was used to expand the maxillary arch. Then, a modified pendulum appliance was used to distalize the maxillary first permanent molars. Optimal positioning of two palatal miniscrews enabled both appliances to be supported by skeletal anchorage. Treatment was finished using multibracket fixed appliances, and after 2 years, skeletal Class I as well as dental Class I canine and molar relationships were achieved.     

Do orthopedic corrections of growing retrognathic hyperdivergent patients produce stable results?

Objectives:To determine if posterior dental intrusion produces stable orthodontic and orthopedic corrections in growing retrognathic hyperdivergent patients.Materials and Methods:The sample included 14 subjects (five males and nine females), who were 13.4 ± 0.7 years pretreatment, treated for 3.5 years, and followed for 3.6 years posttreatment. During the initial orthopedic phase, 150 g NiTi coil springs were attached to two palatal miniscrew implants (MSIs) for maxillary intrusion; two buccal mandibular MSIs were used for posterior vertical control. Full orthodontic therapy was initiated to correct the malocclusions during the orthodontic phase. Patients were recalled a minimum of 1 year posttreatment (mean 3.6 ±1.6 years). Patients were compared to matched untreated controls.Results:Relative to the untreated controls, during treatment and retention, maxillary and mandibular molars underwent 2.8 mm and 3.7 mm of relative posterior intrusion, respectively. Maxillary incisors were extruded 1.3 mm and the mandibular incisors underwent 2.9 mm of relative intrusion. Overall orthopedic changes included a reduction in the mandibular plane angle (MPA; 3.3°), an increase in SN-Pg (2.4°), an increase in S-N-B (2.1°), and a 4.3 mm relative reduction in anterior facial height. The maxillary incisors, which showed 0.6 mm of intrusion (relative to controls), was the only dental or skeletal measure to show a statistically significant between-group posttreatment difference.Conclusions:Except for maxillary incisor position, the substantial dental intrusion and associated orthopedic corrections that were produced during treatment remained stable post-treatment.     

Biomechanical comparison of three 2.7-mm screws and two 3.5-mm screws for fixation of simple oblique fractures in human distal fibulae

Background

Fixation of simple oblique fractures of short tubular bones with only inter-fragmentary screws is simple and clinically useful. This study compared the biomechanical properties of fixation using three 2.7-mm mini-screw and two conventional 3.5-mm lag screw constructs for simple oblique fractures of the distal fibula in human osteoporotic bone.

Methods

Simple oblique fractures of the distal fibula at the level of the syndesmosis were simulated in 15 paired fresh frozen ankles, and the calcaneal bone mineral density was measured in each. Fixation with either three 2.7-mm mini-screws (new system) or two 3.5-mm cortical screws (conventional system) was performed in each pair of ankles. The sample size for each type of stress (cantilever bending stress, five pairs; external rotational load to failure, 10 pairs) was calculated before the test. The biomechanical variables (maximal failure load and construct stiffness) of the two fixation groups were compared using a non-inferiority test method with a pre-specified non-inferiority margin.

Findings

The bone mineral density of the calcaneus was assessed as osteoporotic based on reference values for 20- to 29-year-old healthy Koreans. The new system was not inferior to the conventional system in terms of the tested biomechanical properties. The construct failure was initiated from the distal-most screw hole in the anterior cortex.

Interpretation

Fixation with only three 2.7-mm mini-screws provided biomechanical stability comparable to two 3.5-mm cortical screws for simple oblique osteoporotic fractures in the distal fibula under one-shot stress. Mini-screw application for this common fracture might extend the scope of surgical indications for the screws-only fixation method.     

Anchorage control using miniscrews in comparison to Essix appliance in treatment of postpubertal patients with Class II malocclusion using Carrière Motion Appliance:: A randomized clinical trial

ObjectivesTo evaluate anchorage control using miniscrews vs an Essix appliance in treatment of Class II malocclusion by distalization using the Carrière Motion Appliance (CMA).Materials and MethodsTwenty-four postpubertal female patients with Class II, division 1 malocclusion were randomly distributed into two equal groups. CMA was bonded in both groups, and one group was treated with miniscrews as anchorage (12 patients, mean age = 18.0 years) while the other group was treated with an Essix appliance as anchorage (12 patients, mean age = 17.8 years). For each patient, two cone-beam computed tomographic scans were obtained: one preoperatively and another after completion of distalization.ResultsIn the Essix appliance group, there was a statistically significant anterior movement (2.2 ± 1.43 mm) as well as proclination of the lower incisor (5.3° ± 4.0°), compared to a nonsignificant anterior movement (0.06 ± 1.45 mm) and proclination (0.86° ± 2.22°) in the miniscrew group. The amount of maxillary molar distalization was higher in the miniscrew group (2.57 ± 1.52 mm) than in the Essix appliance group (1.53 ± 1.11 mm); however, the difference was not statistically significant.ConclusionsMiniscrews led to a decrease in the amount of anchorage loss in the mandibular incisors, both in terms of anterior movement and proclination.     

Comparative Evaluation of Drill-Free and Self-Tapping Titanium Miniscrews for Semi-Rigid Internal Fixation in Maxillofacial Trauma

IntroductionConventional semi-rigid fixation systems in maxillofacial trauma use self-tapping titanium miniscrews (STS) that require preliminary drilling of a pilot hole. Although drill-free miniscrews (DFS) accompany these systems, they have not dominated practice despite their allure of improved screw-bone contact and holding power. The COVID-19 pandemic has brought these DFS to light as they avoid aerosol production. The present study has compared DFS to STS in patients being treated with miniplate fixation for maxillofacial trauma to understand their feasibility for maxillofacial fracture fixation. MethodologyThis prospective case–control study sampled 16 patients each with zygomaticomaxillary buttress fracture and parasymphysis fracture of the mandible and grouped alternating patients as case (DFS) and control (STS). Intraoperatively duration of fixation, incidence of screw failures and fragment stability; postoperatively occlusion, neurosensory deficits, teeth vitality and infection and removal rates were evaluated at postoperative week 1, 3, 6, 12 and 24 using Cramer''s V test. A P value < 0.05 was considered significant.ResultsIn the 32 patients evaluated, DFS reduced internal fixation time at zygomaticomaxillary buttress (P = 0.001) but not at parasymphysis (P = 0.206). No significant difference in screw failures or fragment stability was observed. Stable occlusion was maintained in all groups with vital teeth and intact neurosensory function, but the summative incidence of infection was significant at week 24 when STS was used at parasymphysis (P = 0.019).DiscussionWhile DFS may facilitate ease of insertion with a single instrument pick-and-screw-in approach, avoiding thermal osteonecrosis and aerosol production, they fail to confer any other clinical advantage.