Dental implant surgery has become the best solution for missing teeth. The implant-supported prosthesis can be restored for edentulous patients through osseointegration between the dental implant and alveolar bone. Recently, minimally invasive surgery has been popular in dental clinical treatment. The surgical guide template has been widely applied in implant surgery and helps dentists be less invasive in installing the dental implant in the optimal position [1-5]. In addition to the advantages of a minimally invasive, accurate implant position, the dentist can effectively obtain an esthetic prosthesis. With the application of digital dental technology, dental implant surgery has progressed from the traditional significant wound flap surgery to the precise and minimally invasive non-flap method.

When performing non-flap dental implant surgery, the dentist can usually provide preoperative optimal planning assistance; the patient's CBCT medical image will be used to reconstruct the 3D model of the patient's oral cavity, and the quality of the implant area and the surrounding related tissues will be judged from different anatomical perspectives. Then the best plan will be made through computer-aided planning. The dentist will make the implant guide plate with the relevant planning files. Finally, when performing the implant surgery, the dentist only needs to follow the guide hole of the implant guide plate to quickly complete the dental implant surgery. For some patients with poor bone quality (such as the anterior tooth area, where the bone spine is thin), the dentist can also accurately complete the dental implant surgery through the guide plate [6-10]. Compared with traditional flap dental implant surgery, the surgical guide method has the advantages of precision and minimal invasiveness.

Currently, most of the production methods of dental implant guide boards are completed through digital processing at this stage

[11-16]. Usually, doctors only need to complete the operation planning information to generate corresponding surgical guide board files, which can be transmitted to 3D printers for production. Because 3D printing has the advantages of highly complex processing, the guide plate made by 3D printing can be worn by the patient in the oral cavity and has a high sticking effect. At the same time, the processing material is polymer resin, and the overall quality and stability are increased. It has a good effect on the strength of the follow-up doctor in the dental implant process. However, the production method of high-precision 3D printing usually has relatively high machine costs, and not all patients can accept the cost of guide plates. In recent years, the CAD/CAM processing equipment commonly used in dental clinics has been paying more and more attention to other clinical dental applications because of its stable processing precision in addition to traditional dental prosthesis production [16-20]. Therefore, this study aims to discuss the production of implant guide plates by 3D printing and CAD/CAM processing and to evaluate the fitting degree and surgical accuracy of the two methods of guide plates in dentition wear through different aspects. The accuracy evaluation establishes the various assessments of the implant guide template between other processing techniques to provide the best guide plate manufacturing suggestion for future implant surgery.

Implant Model Preparation and Implant Planning

An artificial edentulous dental model of the mandible (TRM636, NISSIN, Kyoto, Japan) was prepared as a reference model for this study (Fig.1). The missing tooth model in this study is used as a reference (partial missing tooth), and CBCT computerized tomography images are taken. The image information of the missing tooth model will be imported into MIRDC Dental software for implant planning, 3D model reconstruction, and implant position planning. When planning dental implants, the PANO perspective is established by drawing the dental arch line, and the regional teeth's anatomical position is inspected through different anatomical perspectives. The clinician can judge the suitable dental implant position based on experience and, at the same time, calculate the soft tissue and cortical bone thickness. After the bone density information, the dentist determines the position of the implant according to the relevant anatomical conditions and then uses the computer simulation to place the appropriate artificial implant to complete the pre-implant planning (Fig.2).

Fig 1. Artificial Edentulous Dental Models of The Mandible.

Fig 2. Implants Planned Using the MIRDC Dental Software.

Digital Implant Guide Plate Model Establishment

After the implant planning, the implant guide template was generated through automatic software modeling. The dentist could clearly understand the direction of future implant implantation and match it with the surgical instrument set through the hole of the implant guide template. At the same time, the data from the implant guide plate can be output to the processing equipment (3D printing and CAD/CAM) for physical production (Fig.3).

Fig 3. Dental Surgical Template by Using 3D Printing.

Accuracy Comparison Analysis Processing

The accuracy comparison analysis processing tool used in this study is the accuracy calculation module in MIRDC dental software, which can read the CBCT image data and STL scanning information before and after dental implant surgery and perform modeling according to the mesh characteristics of the model. Overlapping, this study compares the accuracy of the tooth mold STL files obtained by 3D printing, CAD and CAM respectively, and shows that the model can be optimally positioned through rough positioning and fine positioning procedures (best fit alignment) [21–25], and finally carries out the error calculation and analysis of the overall model (Fig. 4).

Fig 4. The Fitness Evaluation of 3D Printing and CAD/CAM Bonding Surface.

The precision of the 3D printing processing method is relatively high. The accuracy of the surgical guide template using 3D printing and CAD/CAM in this study shows that the overall average error of the 3D printing method is 0.425mm, and the general average error of the CAD/CAM guide plate is 0.493mm. It can be seen from the results that the precision of the CAD/CAM method is slightly lower than that of 3D printing, but the precision value is still in line with clinical use.

Table Captions

Table1. The Accuracy of Surgical Guide Template By 3D Printing And CAD/CAM (N=10).

The use of digital technology to complete guide template production has gradually become a trend [25-28]. The primary factor is that CBCT/CT images can provide the dentist with more detailed and accurate information for pathological assessment and optimal implant planning in a 3D virtual environment. These images help avoid many false judgments ordinary in conventional 2D X-ray images and assist less experienced dentists in performing implant surgery. The main goal of the surgical guide template is the optimal position between planning and placed outcome. This study has completed the guide plate made by 3D printing and CAD/CAM processing. The results show that the 3D printing guide plate method has better accuracy. To explore the reason, the CAD/CAM processing equipment is mechanically processed by tools. For the inner surface of the guide plate, the inner surface of the brace is easily processed due to the number of machining axes of the device, which cannot be processed with high precision, and subsequent wearing occurs. Therefore, the production of dental implant guide plates is still dominated by 3D printing at this stage. Therefore, if it can have smaller tools and multi-axis processing, it will be further used in the production of dental implant guide plates.

This study has preliminarily completed the guide plate made by 3D printing and CAD/CAM processing. The results show that the 3D printing guide plate method has better accuracy.

Disclosure of potential conflicts of Interest

Funding

Zuoying Branch of Kaohsiung Armed Forces General Hospital, KAFGH- ZY_A_110029

Conflict of Interest

The authors declare no conflict of interest.

This article contains no studies with human participants or animals performed by the authors.

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