Oral implant surgery has been commonly performed in the clinic, but implant complications due to anatomical factors of the jaw bone occur clinically. The occurrence of these complications, in addition to the factors of anatomical variation, has a lot to do with the unfamiliarity of the surgeon with the anatomy related to the jaw bone. In the light of our own clinical experience and our own sessions in recent years, we would like to review the relevant anatomy of the jaw bone and its imaging manifestations in order to help the beginners to be well informed during surgery and to reduce the occurrence of complications. I. Mandibular canal and inferior alveolar vascular nerve bundle The inferior alveolar vascular nerve bundle enters the mandibular canal through the mandibular foramen medial to the mandibular ascending branch. The mandibular canal, also known as the mandibular nerve canal, is a thin canal that travels between the osteophytes of the mandible and is shown as a transmissive band approximately 3 mm wide on a curved tomographic radiograph. The wall of the mandibular canal is composed of bone dense material, which is thicker near the end of the mandibular foramen and thinner as it extends proximally and medially. The wall of the mandibular canal is not always clearly visible on curved tomographic radiographs, and sometimes the canal wall is incomplete or even blurred from the first molar onwards. Generally, there is a sense of increased resistance when the mandibular canal is encountered during implant preparation, but the surgeon cannot judge whether the mandibular canal has been reached by feel alone, because the twist drill may drill into the canal without warning due to the incompleteness of the bone dense of the canal wall. Conversely, when increased resistance is encountered in the posterior region of the implant preparation hole, it may also just encounter areas of increased bone mineralization, such as the internal and external bone plates of the mandible. We have measured 200 curved tomographic x-rays and found that the morphology of the mandibular canal course in curved tomographic x-rays can be divided into four categories: linear, 12.75%, scooped, 29.25%, elliptical-arc, 48.5%, and folded, 9.5% About 1% of the mandibular canals bifurcate up and down at the proximal-middle end. The bifurcated canal may show more than one chin hole, but the bifurcation may not be visible on the panoramic or apical slice. Thus, a hidden mandibular canal bifurcation can cause the surgeon to incorrectly estimate the amount of bone above the mandibular canal. In the mandibular canal, the inferior alveolar artery may be higher than the nerve, and when drilling too deep for implant surgery at this time, it may only cause bleeding but not nerve injury. II. Chin hole and chin canal The mandibular canal is divided into the chin canal and the incisal canal in the premolar area (see Figure 4). The chin canal turns posteriorly, superiorly and externally to open at the chin foramen. The concepts of chin canal and chin nerve loop are currently understood differently in various literature and can be easily confused. The chin canal refers to the turning part of the mandibular canal in front of the chin hole, which is an extension of the mandibular canal, and the mandibular neurovascular bundle within the chin canal is called the chin nerve ring. The length of the chin canal varies, and in most cases it turns posteriorly, superiorly, or externally, which is also referred to in some literature as forming a nerve collar. When implants are placed anterior to the chin hole, it is advisable to first perform a CT examination to determine the presence of this collaterals. If this cannot be determined preoperatively, it is generally accepted that placing the implant 6 mm anterior to the chin hole will avoid damage to the collaterals. The inferior alveolar nerve passes through the chin foramen and is called the chin nerve. The chin foramen is funnel-shaped. The chin holes are usually one on each side. However, the presence of a second chin foramen on the buccal side is rare, often due to a bifurcation of the mandibular canal, and the smaller second chin foramen is called the paracentral chin foramen (see Figure 3). The average diameter of the chin foramen was 2.50±0.65 mm, which was larger in males than in females, as measured on 200 surface tomography x-rays. There are three locations of the chin foramen: (1). Located between the first and second premolar, 48.5%, (2). The chin hole is located between the second premolar and the first molar in 8.75%. 25% of Chinese people have a chin hole located on the coronal side of the premolar root tip.1 The mandibular incisor canal is another continuation of the mandibular canal, starting from the proximal middle of the chin canal, continuing in the midline direction and gradually becoming thinner, and ending below the mandibular lateral or central incisor. The incisive canal contains the incisive neurovascular vessels originating from the mandibular neurovascular bundle, which innervates the first premolar, cuspids, central incisors and lateral incisors. The incisive canal is generally much thinner than the mandibular canal and is located in the middle third of the mandible. The incisive canal can be seen on curved tomographic radiographs in only 15% of cases, and is largely detected on CT scans. Sometimes there are unusually large incisive canals. It has been reported that if the thicker incisive nerve is compressed, postoperative facial pain may result and the implant may eventually have to be removed.2 Therefore, the incisive canal and the incisive nerve need to be considered when deeper implants are placed in the bilateral interchin foramen area or when bone is removed from the chin. The lingual foramen and lingual chin foramen The small hole in the lingual bone plate of the mandible is called the lingual foramen, which is the opening of the lingual canal (see Figure 6) and has an average diameter of 0.7 mm. The lingual chin foramen is often present in the lingual bone plate of the mandibular premolar region and has a smaller diameter of 0.6 mm. 3 could be shown on the apical slice. The lingual foramen and lingual canal on the medial lingual bone plate of the mandible and the thicker nasopalatine canal were visible in the maxilla. The authors had a scoring study of mandibular lingual foramina and lingual canal on CBCT and OPG in 33 patients and showed that the presence of lingual foramina was 100% and multiple lingual foramina were present in about 44.4 to 60.0% of individuals. The presence of lingual chin foramina ranged from 70.0% to 78.0%, with a predominance of one lingual chin foramen in each mandible.4 Both lingual and lingual chin foramina have vessels passing through them that anastomose with the sublingual artery or are branches of the sublingual artery. If the vessels in the lingual and lingual chin holes are drilled during implant preparation, bleeding can occur. It is generally accepted. Diameter V. Maxillary sinus The maxillary sinus is the largest sinus, and the sinus cavity resembles a transverse cone. The maxillary sinus is lined with a mucoperiosteal membrane that is approximately 0.3 to 0.8 mm thick and can become hyperplastic when there is chronic inflammation of the maxillary sinus. For maxillary sinus lift, with a thickened maxillary sinus membrane but without maxillary sinus effusion, it is usually possible to operate, but it is best to consult with a pentothoracic surgeon before surgery. We have studied the CT reconstructed images of the maxillary sinus floor in 57 adults.6 We found that: 1. The morphology of the maxillary sinus floor wall is divided into flat, triangular, and split crest types, with the flat type being the most common and possibly asymmetrical bilaterally (see Figure 8). 2. The lowest point of the maxillary sinus floor wall is often located between the maxillary second premolar and first molar; 3. The maxillary sinus floor is predominantly buccal; 4. The average volume of the maxillary sinus is The average distance between the maxillary sinus opening and the sinus floor is 28.5±5.7 mm, with the longest being 41.4 mm and the shortest being 14.0 mm. When performing maxillary sinus lift, the implant material placed in the sinus should not exceed the height of the sinus opening to avoid blocking the exit and causing inflammation of the maxillary sinus. Six, the nasopalatine canal and incisal foramen The nasopalatine canal, also known as the incisal canal, has an average length of 8.1mm and contains the nasopalatine nerve and blood vessels. The nasopalatine canal opens into the incisor foramen (see Figure 6). Sometimes an abnormally large nasopalatine canal can occur, which may then interfere with implantation in the maxillary mesial incisor region. Injury to the nasopalatine nerve and vessels is not necessarily too harmful, but only occasionally causes numbness in the anterior palate. Therefore, some scholars have placed implants directly in the nasopalatal canal for retention in edentulous patients with extreme resorption of the maxilla. Bone island refers to a focal X-ray blocking plaque in the jaw bone, also known as endogenous bone warts (Enostosis) or bone spots (Bovespot), which are abnormal bone development. Enostosis is an abnormality of bone development. It is usually found on radiographs without clinical symptoms. It is not the same as dense osteitis, which is a focal plaque of dense bone caused by chronic inflammation. The incidence of intra-maxillary bone islands is about 3-6%, mainly in the first molar and premolar regions of the mandible, and there is no difference in the incidence between men and women.7 It has two types, an endogenous enlargement in the lingual-buccal cortex of the jaws and a dense bone mass in the bone marrow of the jaws, which can be clearly diagnosed by CT examination. There is a feeling of increased resistance when the prepared cavity encounters the bone island.