The present invention relates to an oral scanner for generating a three-dimensional model is inserted into the oral cavity of the patient by a non-contact scanning and a three-dimensional overlay image display method using the same. The oral cavity scanner includes a projector for irradiating a source light source including a visible light source and an IR light source； A camera for acquiring a 3D image of the surface of the oral cavity and an IR image of the gingiva inside to detect the reflected light of the source light source； And an image processing unit for generating a 3D replica model by merging the IR image into a 3D image, wherein the IR image is irradiated with the intraoral overlay by the projector based on the 3D replica model. . According to the oral cavity scanner of the present invention, after generating a three-dimensional replication model consisting of a three-dimensional image of the surface of the oral cavity and the IR image of the gingiva, the IR image in the oral cavity in real time with reference to the three-dimensional replication model The overlay can be investigated and can be usefully used in dental care. In particular, since the implantation position of the fixture can be accurately identified on the basis of the irradiated IR image of the oral cavity during in situ implantation, the gingival incision can be minimized at the pre-abutment assembly stage. The pain of the patient can be reduced and the side effects of the secondary contamination before and after the procedure can be minimized. In addition, such an oral scanner can be combined with the irradiation optical system and the detection optical system required for the acquisition of three-dimensional image and IR image, it is advantageous in miniaturization of the product because it can utilize the irradiation optical system even when overlaying the IR image.본 발명은 본 발명은 환자의 구강 내에 삽입되어 비접촉식으로 스캐닝하여 3차원 모델을 생성하기 위한 구강 스캐너 및 이를 이용한 3차원 오버레이 영상 표시방법에 관한 것이다. 상기 구강 스캐너는 가시광원 및 IR광원을
