The loss of jaw position relationship will seriously affect the face and masticatory function of patients, and accurate restoration of vertical dimension of occlusion (OVD) is the key to occlusal reconstruction in edentulous patients. There are many methods to measure OVD in edentulous patients. In this paper, the working principle, scope of application, advantages and disadvantages, measurement methods and operation points of OVD recording method are reviewed in order to provide some reference for clinical treatment. The results show that the pre- extraction recording method is more objective and accurate, but the diagnosis model before extraction is required to accurately reflect the patients′ original OVD; the rest and stop jaw reference method is easily affected by subjective factors, and the edentulous patients with unstable jaw relationship are forbidden; the swallowing method is more subjective, especially suitable for patients with emotional tension and poor coordination; The facial landmark measurement method is more objective, but it is also affected by some subjective measurement factors. The patients with maxillofacial malformation are forbidden; the subjectivity of speech method is strong, and the accuracy of measurement results is closely related to the clinical experience of doctors, and the patients with aphasia and deafness are forbidden. X-ray cephalometric method and finger measurement method have strong objectivity. They are new measurement methods in recent years and have a bright future. Among them, finger measurement method is especially suitable for patients with maxillofacial deformity or postoperative deformity of tumor.

Er: YAG laser bleaching is a new tooth bleaching method compared with traditional bleaching technology. The Er: YAG laser significantly improves the bleaching efficiency, has the advantages of high safety, short treatment time and excellent bleaching effect and is widely used in clinical operations. This paper summarizes the working principle and bleaching characteristics of Er: YAG laser bleaching technology and its effect on tooth structure. The existing literature suggests that the high absorption of water and hydroxyapatite by the Er: YAG laser makes it work well on waterbearing tissues and dental tissues. When it is absorbed by the bleaching agent on the tooth surface, it accelerates the catalytic oxidation - reduction reaction and selectively acts on the pigment particles deposited on the tooth, thereby achieving the effect of tooth bleaching. Er: YAG laser bleaching can be applied to most discolored teeth. The bleaching process is rapid and effective. During the bleaching process, for the dental pulp tissue, the temperature of the pulp cavity is lower than the critical value of 5.6 ℃, causing no pathological damage to the dental pulp tissue. For the hard tissues of the teeth, laser irradiation will cause changes in the chemical composition of calcium and phosphorus. The enamel presents a unique lava-like shape, and the bonding strength of the tooth increases after bleaching. Compared with other lasers, the Er: YAG laser has a wavelength close to the peak of water, and adding other ingredients to the bleaching agent is not required. Almost all the energy is used for the bleaching agent, with no damage to the surrounding tissues.