Orthodontic Miniscrew Placement in Interradicular Regions using a Chairside Digital CAD-CAM Surgical Guide

Summary

The goal of this protocol is to present a chairside digital workflow that integrates CBCT and CEREC CAD/CAM technology to design and fabricate in-office, biocompatible surgical guides for orthodontic miniscrew placement, enhancing accuracy while eliminating external software and laboratory-dependent procedures.

Abstract

This study aims to introduce a novel chairside digital technique for creating surgical guides to assist in the placement of orthodontic miniscrews. In this clinical validation study, 12 orthodontic miniscrews were placed in six patients using a chairside economical restoration of esthetic ceramics (CEREC) system combined with cone-beam computed tomography (CBCT). A three-dimensional image was generated by integrating CBCT scans with digital dental models acquired via the chairside digital system. The optimal insertion angle and position for orthodontic miniscrews were planned using this image. A surgical guide was then designed in the computer-aided design (CAD) software and manufactured using the computer-aided manufacturing (CAM) system. Preoperative and postoperative CBCT scans obtained from patients were superimposed to compare the angular deviation, entry-point deviation, and endpoint deviation between the planned and actual miniscrew positions. The mean entry-point and endpoint deviations were 2.4 ± 0.7 mm (range: 1.2–3.4 mm) and 2.4 ± 0.6 mm (range: 1.3–3.4 mm), respectively. The mean angular deviation was 3.8° ± 2.3° (range: 0.4°–7.2°). No miniscrew failures were observed during the 6-month follow-up period. This study successfully developed a chairside CAD/CAM-based miniscrew surgical guide method, and its accuracy and stability were preliminarily validated in patients.

Introduction

Orthodontic miniscrews have gained widespread popularity due to their simplicity, rapid insertion, minimal invasiveness, and cost-effectiveness^1,2,3. Despite these advantages, clinical success is often limited by anatomical constraints, variability in operator skill, and the lack of standardized auxiliary tools. One of the most critical challenges remains the precise positioning of miniscrews, as improper placement may result in root damage or compromise bone integrity³.

Surgical guide systems have been widely recognized as effective tools for improving placement accuracy and minimizing complications^4,5. Most currently available guided systems rely on third-party planning, laboratory fabrication procedures, or collaboration with specialized technicians, which increase treatment cost, prolong turnaround time, and limit immediate chairside implementation⁶. In addition, many workflows involve multiple data-conversion steps and software platforms, increasing the risk of registration errors and reducing procedural efficiency.

To address these limitations, this study introduces a streamlined, chairside digital workflow that integrates cone-beam computed tomography (CBCT) with the Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) system for the design and fabrication of surgical guides. Unlike conventional workflows that require external laboratory support, the proposed method enables fully in-office virtual planning, guide design, and manufacturing within a single integrated platform. This approach reduces dependence on specialized personnel and facilitates same-visit guide fabrication, thereby improving clinical efficiency and accessibility.

Beyond workflow simplification, the present technique offers several additional advantages. First, the direct integration of CBCT data with intraoral digital scans allows precise visualization of tooth roots, alveolar bone morphology, and interradicular spaces, improving the safety of miniscrew placement and reducing the risk of root injury. Second, the use of a tooth-supported guide fabricated from transparent biocompatible resin enhances intraoral stability while permitting direct visual verification of guide seating during surgery. Third, the digitally standardized insertion trajectory may reduce operator-dependent variability and improve reproducibility, particularly in anatomically narrow interradicular regions. Finally, the entirely digital workflow minimizes manual fabrication steps and may improve the consistency and predictability of guide production.

This study aimed to present a chairside digital workflow for guided orthodontic miniscrew placement and to evaluate its placement accuracy, providing preliminary evidence of its clinical feasibility, reproducibility, and potential advantages over conventional guided techniques.

Protocol

This study was approved by the Institutional Review Board of Beijing Tiantan Hospital, Capital Medical University (KY2022-041-01), and was conducted in accordance with the Declaration of Helsinki and institutional human research guidelines. Written informed consent was obtained from all patients prior to participation and initiation of clinical procedures. Six patients treated between April 2022 and June 2023 at the Department of Orthodontics, Beijing Tiantan Hospital, underwent orthodontic miniscrew placement.

1. Obtaining digital data of the targeted area

1. Acquire intraoral digital models.
   1. Perform intraoral scanning using an intraoral scanner to obtain complete maxillary digital dental models. Ensure full-arch coverage and accurate capture of the interradicular regions.
2. Acquire CBCT images.
   1. Acquire CBCT scans of the maxillofacial region using a CBCT unit.
      1. Use a voxel size of 0.16 mm.
      2. Use a field of view of 8 cm × 8 cm, sufficient to include the maxillary dentition and surrounding alveolar bone.
      3. Set imaging parameters according to manufacturer recommendations for orthodontic implant planning.
      4. Ensure clear visualization of alveolar bone and adjacent tooth roots (Figure 1A).

2. Performing virtual planning of miniscrew placement

1. Register CBCT and intraoral scan data.
   1. Import digital dental models and CBCT data into implant-planning software.
      1. Generate a panoramic reconstruction from the CBCT dataset within the software.
      2. Perform initial registration by manually selecting three corresponding teeth on both the digital dental model and the CBCT panoramic view (Figure 1B).
      3. Place the selected teeth adjacent to the planned miniscrew insertion region and include well-defined anatomical dental structures such as molar or premolar cusp tips and ridges.
      4. After selection of the reference teeth, ensure that the software automatically completes the dataset superimposition and surface alignment.
      5. Verify registration accuracy in axial, coronal, and sagittal views before virtual miniscrew planning (Figure 1C).
      6. Repeat the registration process if visible mismatch or alignment discrepancies are identified.
2. Plan miniscrew positions virtually.
   1. Determine miniscrew insertion sites according to the anatomical relationship between alveolar bone morphology and adjacent tooth roots.
      1. Position each miniscrew to maximize cortical bone engagement and avoid root proximity.
      2. Plan miniscrew placement 5–7 mm apical to the alveolar crest.
      3. Set the insertion angle at 30°–40° relative to the long axis of adjacent teeth in accordance with established clinical guidelines (Figure 1D).

3. Fabrication of the surgical guide

1. Design the surgical guide.
   1. Design a tooth-supported surgical guide using CAD software.
      1. Incorporate retention arms and guide sleeves aligned with the planned insertion angulation.
      2. Verify passive seating and adequate support from selected abutment teeth.
      3. Design the guide sleeves to match a 2.0 mm insertion tool diameter.
      4. Define guide dimensions, supporting tooth locations, guide thickness, and inspection windows within the software to ensure intraoral stability and visualization (Figure 1E).
2. Manufacture the surgical guide.
   1. Mill the surgical guide chairside from a transparent biocompatible resin block using an in-office milling unit. Follow the manufacturer’s milling parameters and complete post-processing according to resin instructions, including cleaning and light polymerization if required (Figure 1E).

4. Performing guided miniscrew placement

1. Prepare the surgical site.
   1. Instruct the patient to rinse with 0.2% chlorhexidine solution for 60 s to achieve oral antisepsis before surgery.
2. Administer local anesthesia.
   1. Administer 2% lidocaine with 1:100,000 epinephrine and confirm adequate anesthesia prior to miniscrew insertion.
3. Position the surgical guide.
   1. Seat the surgical guide intraorally and verify complete seating and stability.
      1. Confirm adaptation through the inspection windows.
      2. Ensure that no visible gap greater than approximately 0.5 mm is present between the guide and the supporting tooth surface (Figure 2A).
      3. Apply gentle bilateral finger pressure to verify the absence of rocking or displacement before miniscrew insertion.
      4. If incomplete seating or instability is detected, remove the guide and inspect for scanning inaccuracies, fabrication defects, or occlusal interferences before proceeding.
4. Insert orthodontic miniscrews.
   1. Insert self-drilling miniscrews using an implant motor.
      1. Use miniscrews measuring 1.4 mm in diameter and 8.0 mm in length.
      2. Maintain the preplanned insertion trajectory and angulation during placement.
      3. Perform insertion at a rotational speed of approximately 20–35 rpm under continuous saline irrigation.
      4. Maintain insertion torque according to the manufacturer’s recommendations to minimize excessive stress on cortical bone (Figure 2B,C).

5. Assessing miniscrew position postoperatively

1. Acquire postoperative CBCT images.
   1. Obtain postoperative CBCT scans using the same imaging parameters, voxel size, and field of view as the preoperative scan to ensure standardization and comparability.
2. Superimpose preoperative and postoperative datasets.
   1. Import postoperative CBCT data into analysis software. Superimpose preoperative planning data with postoperative imaging data using identical reference landmarks.
3. Measure placement deviations.
   1. Measure angular deviation, entry-point deviation, and endpoint deviation between the planned and actual miniscrew positions using the software’s built-in analysis tools (Figure 2D).
      1. Define entry-point deviation as the three-dimensional (3D) linear distance between the coronal centers of the planned and placed miniscrews.
      2. Define endpoint deviation as the 3D linear distance between the apical centers of the planned and placed miniscrews.
      3. Define angular deviation as the 3D angle formed between the longitudinal axes of the planned and placed miniscrews.
      4. Record linear deviations in millimeters and angular deviations in degrees.
         NOTE: A schematic flow diagram summarizing the complete digital workflow from intraoral scanning to postoperative accuracy assessment is presented in Figure 3.

Results

A total of 12 orthodontic miniscrews were successfully placed in 6 patients in either the buccal or palatal interradicular regions of the posterior maxilla using the digitally fabricated chairside surgical guide. All surgical guides demonstrated stable intraoral seating during the procedure, and no guide fractures or intraoperative complications were observed. Representative clinical images of guide positioning and guided miniscrew insertion are shown in Figure 2A–C.

Discussion

Orthodontic miniscrew implants have gained widespread clinical acceptance because of their minimal invasiveness, ease of insertion, and effectiveness as temporary anchorage devices. Nevertheless, accurate placement remains technically challenging, particularly in interradicular regions where limited bone availability and close proximity to adjacent roots increase the risk of root damage and miniscrew instability⁷. Previous studies have demonstrated that computer-guided surgical approaches can impr...

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
CEREC Guide Bloc maxi	Dentsply Sirona	REF 6447093	Resin block used to fabricate surgical guide
CEREC Omnicam	Dentsply Sirona	REF 6390327	Intraoral scanner
CEREC SW 4.4	Dentsply Sirona	REF 6731637	Software used to design miniscrew surgical guide
GALILEOS Implant software v 1.9	Dentsply Sirona	REF 6369503	Software used to superimpose digital dental models and CBCT data
GuideMia V5.0	GuideMia Inc.	https://ai.guidemia.com/downloads/	Software used to acess the accuracy of implant placement
Implant motor	W&H SI-923	REF 00900100	Machine used to place miniscrew
Miniscrew	Ormco	REF 601-0021	Orthodontic anchorage device
Orthophos XG 3D	Dentsply Sirona	REF 6303452	CBCT machine