This study was approved by the Medical Ethics Committee of College of Stomatology, Xi’an Jiaotong University, (Approval No: 2023-XJKQIEC-033-002), and informed consent was obtained from all patients.
1.1. Main Equipment and Software
Cone Beam Computed Tomography (CBCT, HiRes3D, LARGEV, China); Dental high-speed handpiece (NSK, Japan); Navigational instruments (DHC-DI2,Dekaier, China); Mandibular positioner (Right mandibular third molar:13M+C24 ,Left mandibular third molar:24M+C13,Dekaier, China); MIMICS 21.0 (21.0, Belgium).
RDN system - combination of both software and hardware. The hardware includes three parts: a,c) a computer with a display; b) tracing instruments, such as positioners and specialized handpieces; d). a tracking system, which typically includes a set of cameras that detect objects. (as Fig.1 showed). RDN software provides preoperative planning support and real-time intraoperative guidance.
1.2. Clinical Data
This study contained the records of 160 patients who participated in the Department of Oral and Maxillofacial Surgery at Xi'an Jiaotong University between January and December 2023. The study focused on 160 mandibular impacted third molars in a deep-positioned horizontal impaction. The inclusion criteria for this study are as follows: ①Deep horizontal third molars that are overlapped the inferior alveolar nerve, as confirmed by imaging; ②no adjacent second molar is missing, ③and there is no severe caries. Exclusion criteria for this study include: ①The presence of severe chronic inflammation or granulation tissue; ②the existence of cysts, tumors, or fractures in the lower third molar area; ③and severe decay or apical inflammation in the adjacent second molar; ④patients who are unable to comply with medical advice for timely follow-up or have incomplete records, which may affect the evaluation of treatment effectiveness; ⑤and preoperative allergies to amoxicillin and loxoprofen.
Prior to surgery, CBCT scans were performed on all patients to assess the relationship between the impacted lower horizontal third molars and adjacent teeth, the number of tooth roots, and their association with the mandibular nerve canal. The administration of antibiotics (amoxicillin) and painkillers (loxoprofen) as a preventive measure was carried out before surgery. The study included 74 males and 86 females, with ages ranging from 18 to 37 years and a mean age of 24.12 years. The patients were randomly assigned to the experimental and control groups, each containing 80 cases of mandibular impacted third molars in a deep-positioned horizontal impaction. (See Table 1)
Table 1
Category
|
Experimental
Group (n=80)
|
Control Group (n=80)
|
Total (n=160)
|
Number of patients
|
80
|
80
|
160
|
Gender
|
- Male: 35
|
- Male: 39
|
- Male: 74
|
- Female: 45
|
- Female: 41
|
- Female: 86
|
Age, years
|
- Range: 18-35
|
- Range: 20-37
|
- Range: 18-37
|
- Mean: 23.7
|
- Mean: 24.54
|
- Mean:
24.12
|
Previous Dental Procedures
|
None
|
None
|
None
|
Presence of Pericoronitis
|
None
|
None
|
None
|
Systemic Health Conditions
|
Healthy
|
Healthy
|
Healthy
|
1.3 Navigation Planning, Design, and Application Methods
1.3.1 Data Collection
Select a mandibular positioner: Place the U-shaped tube filled with silicone rubber as a reference coordinate system in the area where the impacted tooth is located and have the patient wear it to capture CBCT images.
1.3.2 Extraction Plan Design
Import the collected CBCT data into Mimics 21.0 software and segment and reconstruct the impacted tooth, adjacent teeth, surrounding bone tissues, and important anatomical structures, such as nerves. Conduct three-dimensional measurement analysis, with the measurement data used to determine the safe distance between the impacted tooth and important anatomical structures for subsequent navigation identification. (Fig. 2)
1.3.3 Intraoperative Application of Dynamic Navigation
(1) Installation of the navigation system: ① Assembly: Assemble the dental high-speed handpiece instrument with the navigation emitter and prepare the silicone rubber model (Fig. 3a). ② Calibration: Establish the reference coordinate system of the dental high-speed handpiece instrument (Fig. 3b). ③ Matching: Use dental resin to fix the reference template in the contralateral area of the mandible for matching (alignment between the dental high-speed handpiece instrument and CBCT) (Fig. 3c). ④ Validation of navigation matching accuracy: Place the fissure drill of the dental high-speed handpiece instrument on the anatomical cusp of the mandibular tooth for navigation accuracy validation. (Fig.3d)
(2) Extraction: ① Precise positioning of the impacted tooth under RDN guidance(Fig. 4b); ②Remove the bone covering the crown surface by matching the dental high-speed handpiece instrument attached to the navigation system closely to the tooth crown surface (Fig. 4c); ③Cut along the direction previously planned for tooth cutting. During the cutting process, pay attention to real-time monitoring of the relationship between the dental high-speed handpiece instrument and the mandibular nerve to segment and remove the tooth(Fig. 4d, e). After flushing the socket with physiological saline, and intermittently suture the wound(Fig. 4f). The control group used the traditional minimally invasive tooth extraction method for extracting the impacted tooth.
1.3.4 Recorded Indicators
Time indicators: ①Preoperative design time: time taken to design the tooth extraction plan before surgery. ② Navigation installation time: time taken from navigation calibration to completion of matching. ③ Surgical time: time taken from flap incision to suture completion.
Complications: ① Adjacent tooth damage: neighboring teeth are not loose, experiencing discomfort or mild biting pain. ② Inferior alveolar and lingual nerve damage: sensation abnormalities in the tip of the tongue and lower lip after the effects of anesthesia wear off.
1.4 Statistical Analysis
Data processing was conducted using SPSS 23.0 software. The t-test was used for statistical analysis. Results are presented as "mean ± standard deviation." A p-value of less than 0.05 indicates statistical significance.