Viecilli et al. investigated the effects of initial periodontal ligament stresses on orthodontic external root resorption and identified that compressive stresses between −9.92 and −7.75 kPa were associated with bone resorption without significant root resorption.¹ Attention to the periodontal ligament is critical for effective biomechanics in tooth movement because the periodontal ligament enables but also limits such movement. Both excessive and insufficient force applied to the root of a tooth can compromise the biomechanics involved.

In conventional fixed orthodontic appliances, the anchorage point is located on adjacent teeth using brackets. The applied forces can affect neighbouring teeth, leading to unintended side effects, such as undesired tooth movement. Anchoring an appliance on a broader group of teeth with significant bone retention can minimise unwanted outcomes when moving one or a few teeth. However, when movement involves teeth with substantial bony support, standard appliances may prove inefficient.

From a biomechanical perspective, forces must be anchored in structures resistant to movement to avoid unwanted reactions. These include the maxillary or mandibular bone. When used as anchorage points, they allow for precise application of force to specific teeth without affecting others. Temporary anchorage devices such as orthodontic mini-implants serve this purpose. They are anchored directly to the bone and can be safely and easily removed once treatment is complete. The manner in which temporary anchorage devices are connected to the appliance depends on the chosen system and design. Typically, the procedure follows a two-stage protocol.

Two-stage procedure

This traditional approach separates implant placement and appliance installation into distinct clinical stages, typically spread across multiple appointments. Implant placement is performed either free-hand or via a guided technique. Guidance based on digital planning is demonstrably safer and more clinically effective, making optimal use of patient-specific anatomical conditions. Registration of implant positions is then done using scan body systems (this was previously done with impressions). This step supports planning of the appliance structure.

In the first stage, the design of the appliance is typically not yet considered; only its purpose is outlined. The final appliance design must be adapted to the patient’s unique intra-oral conditions. The design and installation of the appliance takes place in the second stage. Based on digitally or physically recreated implant positions, the appliance is fabricated and fitted during a subsequent visit.

Although still widely used, this two-stage approach is increasingly regarded as suboptimal given today’s digital design capabilities. The digital workflow may include planning of implant placement, creation of surgical guides (using CBCT scans) and digital reconstruction of implant locations using a scan body system. In practice, the single-stage procedure has gained popularity owing to its advantages in precision, efficiency and patient comfort. This method requires an intra-oral scan and CBCT scan.

Single-stage procedure using DDS-Pro software

This digitally driven method enables the entire process—from planning to appliance placement—to be completed in a single clinical session. It involves the following steps:

1. capture and analysis of the CBCT scan and intra-oral scan to determine optimal mini-implant placement in line with anchorage needs and appliance design;
2. creation of surgical guides for precise implantation;
3. fabrication of the appliance for installation immediately after implantation; and
4. implantation and appliance installation using a 3D-printed guide.

DDS-Pro software (Polorto) supports both the two-stage and single-stage approaches. However, the single-stage method eliminates implant position discrepancies commonly encountered in the two-stage workflow. It also significantly enhances installation accuracy, improving reproducibility and eliminating the need for additional appointments or chairside adjustments.

Once 3D planning has been completed, mini-implants can be placed with high precision, independent of the operator’s manual skill. The appliance, anchored to these implants, functions exactly as designed.

Clinical application

In my practice, I frequently apply the single-stage approach for orthodontic cases requiring precise tooth alignment or for which conventional anchorage is inadequate. This method ensures that treatment progresses as planned, improving both outcomes and the patient’s experience.

One recent case involved a 29-year-old woman who presented with a severe crossbite unresponsive to standard therapy. I opted to use orthodontic micro-implants to enable controlled molar movement, thereby avoiding surgical intervention. The implants provided full control over tooth positioning, reducing treatment duration. After successful completion, the implants were removed without incident or complication.

This technique is also advantageous in borderline cases that would previously have required surgery, such as crossbite correction using miniscrew-assisted rapid palatal expander procedures or posterior tooth intrusion in open bite cases. Orthodontic micro-implants are minimally invasive and offer an effective alternative for managing complex malocclusions. In my experience, the single-stage approach using orthodontic mini-implants and DDS-Pro software is among the most powerful tools for delivering fast, accurate and patient-friendly orthodontic care.