Many people suffer from oral diseases in their daily lives, and avoiding pain is a natural trait of everyone. The uncomfortable experience during oral treatment will inevitably lead to anxiety and fear in patients, thus negating oral treatment. Local anesthesia can inhibit the transmission of pain sensation, preventing it from reaching the central nervous system. Most ordinary oral treatments can be performed under local anesthesia. With the increasing emphasis on dental health and the popularity of dental clinics, the number of dental treatment patients is growing day by day; As an essential medical consumable for local anesthesia in dentistry, dental injection needles play an important role in clinical dental treatment. Clinical doctors select appropriate injection equipment based on the patient's clinical conditions and experience to achieve safe and effective local anesthesia injection. 

1.Introduction to Dental Local Anesthesia 

There are studies showing that methods for relieving toothache have already emerged in primitive societies, and local anesthesia injections have been used in oral treatment since 1884 to alleviate pain. Local anesthesia can be defined as the loss of sensation in a specific area, where the affected area is only a small part of the body. Reaching a certain depth of local anesthesia using safe methods is defined as successful and effective analgesia. At present, there are five types of injectable local anesthetics available in the dental department, namely articaine, bupivacaine, lidocaine, meprazole, and prilocaine, which have been packaged and applied in oral treatment. The drugs used for local anesthesia in the oral cavity are relatively safe and can basically meet clinical needs. The most important difference between local anesthesia and general anesthesia is that when the local anesthetic is effective, the patient can still remain awake. In current oral treatment, sedation or general anesthesia is usually not given to achieve the goal of absolute pain relief. It can be completed under local anesthesia, thus avoiding the risks of general anesthesia. 

（1） Routine administration route of oral local anesthesia 

There are two main routes of administration for oral local anesthesia: surface anesthesia and submucosal injection. Generally speaking, surface anesthesia requires the use of higher dosage concentrations of local anesthetics, which have more potential toxicity, and surface anesthesia is more suitable for mucous membranes compared to skin anesthesia. Subcutaneous injection and submucosal injection can allow local anesthetics to reach nerve endings more quickly, resulting in faster of anesthesia on the surface of the adhesive.

 In clinical treatment, a combination of surface anesthesia and local injection of fresh hemp can also achieve better anesthesia effects. There are other alternative methods in clinical practice to achieve the effect of local anesthesia, such as pressure, hypothermia, electrical stimulation, and trauma, but they are not widely used. 

（2）There are three basic oral anesthesia injection methods in oral clinical treatment: local infiltration, regional block, and nerve block. The injection site of local infiltration anesthesia is only a few millimeters away the needle insertion site, such as jaw injection, usually between 3.6mm; The injection site for regional block anesthesia is usually located far away  the needle insertion site, such as in the case of Kai nerve block anesthesia; Neuroblock anesthesia is usually administered to nerve trunks further away f the treatment area, such as mandibular nerve block anesthesia.Clinical doctors need to choose the appropriate injection method for local anesthesia injection in the oral cavity, mainly including the selection of injection puncture site, injection path, and injection site. In surgery, it is necessary to prepare appropriate medical consumables, choose the optimal needle insertion path, and ensure the safety of injection and patient comfort to the greatest extent possible. The depth at which the injection needle enters depends on the position of the injection site and the injection site. The farther the injection site is  the injection site, the greater the possibility of needle tip deviation, which may cause incomplete anesthesia. For example, during nerve block anesthesia, the distance between the needle insertion site and the injection site can usually reach 16-27mm, or even further. 

2.Overview of Dental Injection Needle Products: 

The injection of oral local anesthetics is generally carried out through disposable sterile dental injection needles, which are installed on dental cartridge syringes that comply with the 1509997 standard, to inject local anesthetics into submucosal and subcutaneous instruments. The injection needle consists of a needle holder and a protective cover. One end of the needle tube is the puncture end and the other end is the docking end. Various models and specifications are specified according to different lengths and diameters, and it is disposable and sterile. Since 1959, stainless steel injection needles have been used in clinical practice, avoiding repeated disinfection of the needle tube and reducing the risk of disease transmission. 

（1） Model and specification setting basis 

The choice of dental injection needle depends on the injection site, injection depth, and clinical injection technique required for oral local anesthesia. Oral local anesthesia injection needles are often divided into three types based on the effective length of the puncture end ( the needle tip to the needle seat): long, short, and ultra short. The length of injection needles produced by different manufacturers of listed products also varies slightly, with typical lengths generally being 35mm for long needles, 25mm for short needles, and 12mm for ultra short needles. Long needles are commonly used for nerve block anesthesia where the distance between the needle insertion site and the injection site is relatively long, while short needles are commonly used for injections where the puncture site is not deep, such as infiltration anesthesia and maxillary block anesthesia; Ultra short needles are commonly used for superficial injections, such as injection into the genital area. Regardless of the specific injection technique, it is important to avoid completely inserting the injection needle into the tissue. 

The commonly used inner diameter specifications for dental injection needles are 27G, 30G, and 31G. The choice of specifications depends on the depth of anesthesia puncture, the risk of positive pullback, and the clinical experience of the doctor. For example, if the structure of the inferior alveolar nerve tissue is dense, the displacement of the injection needle needs to be considered. Injection needles with larger inner diameters have smaller displacement during puncture, while injection needles with smaller inner diameters are prone to bending and significant displacement; When there is a high risk of axial positivity at the injection site, some clinical doctors tend to choose injection needles with larger inner diameters to increase the convenience and accuracy of retraction, such as the inferior alveolar nerve, posterior alveolar nerve, chin nerve, and nasopalatine nerve under anesthesia. Clinical trials have shown that using commonly used injection needles does not result in statistically significant differences in patient comfort, but many doctors still believe that the discomfort caused by small-sized injection needles is relatively small. Clinical doctors choose the most suitable injection needle based on the different parameters and surgical habits mentioned above. Each injection needle has its own advantages in different injection techniques and application sites. 

（2） Performance research 

The industry standard W/T0587 "Disposable Sterile Dental Injection Needles" provides physical performance requirements for disposable sterile dental injection needle materials, product appearance, size, pinhole patency, needle tip, needle seat, chemical performance requirements such as acidity and alkalinity, and extractable metal content. It also includes biological performance requirements such as sterility and bacterial endotoxins. It is recommended that relevant products comply with the requirements of the standard. For recommended requirements that are not applicable, the scientific and reasonable reasons for their inapplicability should be explained. The rigidity, toughness, and corrosion resistance of dental injection needles and tubes should meet the requirements of GB/T18457, and their rigidity and puncture force directly affect the patient's injection comfort. In the field of dentistry, rigidity refers to the reaction force exerted by the push rod on each unit area during the displacement process, which is directly related to the displacement. The good puncture performance of injection needles will enable them to penetrate tissues more smoothly, penetrate tight tissues such as ligaments more deeply, reduce the possibility of tissue damage, and facilitate the achievement of their expected functions. 

3.Clinical use risks of dental injection needles: 

Clinical doctors should choose the appropriate diameter and length of the injection needle based on the depth of injection and the type of tissue it penetrates. Choosing an appropriate length of injection needle can reduce the risk of needle breakage. During clinical use, do not bend, avoid applying other stresses to the injection needle, and avoid excessive needle movement, as this may cause serious harm to patients and doctors. During the injection process, it is advisable to avoid inserting the injection needle into the entire needle body and the needle socket connection. When the injection needle completely penetrates the tissue, sudden movement of the patient can easily cause the injection needle to break, and a lever force can be formed between the injection needle and the handcart, leading to the breakage of the injection needle. (4) It is not recommended to change the direction of the injection needle arbitrarily during deep injection. When the direction of the injection needle must be adjusted, it is recommended to retreat to at least half of the needle insertion depth before re inserting. When anesthetizing deep tissue, it is recommended to choose a longer and larger diameter injection needle. If the patient's mandible is too wide or large, the injection needle should touch the bone surface. When inserting the injection needle into tissue to the maximum extent possible, the visible needle body should be retained. This can reduce the risk of needle breakage and facilitate easy retrieval in case of needle breakage. During the injection process, it is important to avoid both rapid injection rates and excessive pressure to prevent pain and discomfort for the patient 

4. Conclusion 

Dental injection needle products have been used for a long time in oral local anesthesia injection. Each dental injection needle can be applied to different injection sites, with its own advantages in different injection techniques and application sites. However, clinical doctors still need to choose the most suitable injection needle size according to the patient's situation and product instructions in their field of responsibility. With the development of the times, the design of injection needles should be further optimized in order to reduce tissue damage, alleviate patient pain, and improve patient comfort.