Maxillary molar mesialization with the use of palatal mini-implants for direct anchorage in an adolescent patient

Micro finite element analysis of continuously loaded mini-implants - A micro-CT study in the rat tail model

Implant migration has been described as a minor displacement of orthodontic mini-implants (OMIs) when subjected to constant forces. Aim of this study was to evaluate the impact of local stresses on implant migration and bone remodelling around constantly loaded OMIs. Two mini-implants were placed in one caudal vertebra of 61 rats, connected by a nickel‑titanium contraction spring, and loaded with different forces (0.0, 0.5, 1.0, 1.5 N). In vivo micro-CT scans were taken immediately and 1, 2 (n = 61), 4, 6 and 8 (n = 31) weeks post-op. Nine volumes of interest (VOIs) around each implant were defined. To analyse stress values, micro-finite element models were created. Bone remodelling was analysed by calculating the bone volume change between scans performed at consecutive time points. Statistical analysis was performed using a linear mixed model and likelihood-ratio-tests, followed by Tuckey post hoc tests when indicated. The highest stresses were observed in the proximal top VOI. In all VOIs, stress values tended to reach their maximum after two weeks and decreased thereafter. Bone remodelling analysis revealed initial bone loss within the first two weeks and bone gain up to week eight, which was noted especially in the highest loading group. The magnitude of local stresses influenced bone remodelling and it can be speculated that the stress related bone resorption favoured implant migration. After a first healing phase with a high degree of bone resorption, net bone gain representing consolidation was observed.

Accuracy of Palatal Orthodontic Mini-Implants Placed Using Fully Digital Planned Insertion Guides: A Cadaver Study

Digital workflows have become integral in orthodontic diagnosis and therapy, reducing risk factors and chair time with one-visit protocols. This study assessed the transfer accuracy of fully digital planned insertion guides for orthodontic mini-implants (OMIs) compared with freehanded insertion. Cone-beam computed tomography (CBCT) datasets and intraoral surface scans of 32 cadaver maxillae were used to place 64 miniscrews in the anterior palate. Three groups were formed, two using printed insertion guides (A and B) and one with freehand insertion (C). Group A used commercially available customized surgical templates and Group B in-house planned and fabricated insertion guides. Postoperative CBCT datasets were superimposed with the planning model, and accuracy measurements were performed using orthodontic software. Statistical differences were found for transverse angular deviations (4.81° in A vs. 12.66° in B and 5.02° in C, p = 0.003) and sagittal angular deviations (2.26° in A vs. 2.20° in B and 5.34° in C, p = 0.007). However, accurate insertion depth was not achieved in either guide group; Group A insertion was too shallow (-0.17 mm), whereas Group B insertion was deeper (+0.65 mm) than planned. Outsourcing the planning and fabrication of computer-aided design and computer-aided manufacturing insertion guides may be beneficial for certain indications; particularly, in this study, commercial templates demonstrated superior accuracy than our in-house-fabricated insertion guides.

Accuracy of the digital workflow for guided insertion of orthodontic palatal TADs: a step-by-step 3D analysis

Background

The introduction in the orthodontic field of the digital workflow for guided insertion of palatal TADs and the development of the 1-visit protocol led to the reduction of chair time and the possibility of complete customization of designs and materials. Conversely, the reduction of operative steps implicates a lower tolerance of deviations between the planned and the actual position of the miniscrews, particularly when the orthodontic device is fixed on 4 palatal TADs or has a rigid structure. This study aims to analyze the influence of each step of the digital workflow on the deviation of the miniscrews’ axis of insertion in a bicortical sample. The null hypothesis is that there are no significant differences in the deviations among the operative steps.

Methods

33 subjects were selected for insertion of bicortical palatal miniscrews with a 1-visit protocol. Digital files were collected at the three stages of the workflow (i.e., digital planning, laboratory prototype, post-insertion impression). A 3D software analysis was performed on a total of 64 miniscrews. After automatic shape recognition of the guiding holes of the digital plan and the scanbodies of the laboratory prototype and post-insertion impression as geometric cylinders, their three-dimensional longitudinal axis was traced and the deviation among them was calculated. Friedman test with Bonferroni correction was performed to assess the significance of the deviations among the three steps, with significance set at p < 0.05.

Results

The laboratory step has a significantly lower degree of deviations (2.12° ± 1.62) than both the clinical step (6.23° ± 3.75) and the total deviations (5.70° ± 3.42). No significant differences were found between miniscrews inserted on the left or the right side.

Conclusions

This study suggests that laboratory procedures such as surgical guide production or rapid prototyping don’t play a significant role in the degree of deviations between the planned and the positioned palatal TADs. Conversely, the clinical steps have a bigger influence and need to be carefully evaluated. Despite this difference, there is a cumulative effect of deviations that can lead to the failure of the 1-visit protocol.

Maxillary space closure using a digital manufactured Mesialslider in a single appointment workflow

New digital technologies, many involving three-dimensional printing, bring benefits for clinical applications. This article reports on the clinical procedure and fabrication of a skeletally anchored mesialization appliance (Mesialslider) using computer-aided design/computer-aided manufacturing (CAD/CAM) for space closure of a congenitally missing lateral incisor in a 12-year-old female patient. The insertion of the mini-implants and appliance was performed in a single appointment. Bodily movement of the molars was achieved using the Mesialslider. Anchorage loss, such as deviation of the anterior midline or palatal tilting of the anterior teeth, was completely avoided. CAD/CAM facilitates safe and precise insertion of mini-implants. Further, mini-implants can improve patient comfort by reducing the number of office visits and eliminating the need for orthodontic bands and physical impressions.

Clinical guidelines to integrate temporary anchorage devices for bone-borne orthodontic appliances in the digital workflow

In this article, we demonstrate different approaches to enhance the integration of temporary anchorage devices in the digital workflow of the daily orthodontic practice. We describe methods of varying complexity which could be used depending on the equipment available in the orthodontic clinic.