1. A system for capturing and displaying an image of an entire oral cavity, the system comprising: (i) a handheld intraoral camera comprising a reflecting mirror arranged at a predetermined angle at a front end of the intraoral camera, a camera for continuously capturing rows of teeth in an oral cavity, and illumination devices arranged around the camera, an output of the illumination devices being reflected by the reflecting mirror and used to illuminate an observed portion of the oral cavity; (ii) a storing medium having installed therein a graphic software configured to combine a left panoramic tooth row image and a right panoramic tooth row image to form a full panoramic tooth row image; (iii) a computer processor programmed to operate the graphic software of the storing medium to combine the left panoramic tooth row image and the right panoramic tooth row image to form the full panoramic tooth row image; and (iv) a monitor configured to display the full panoramic tooth row image combined at the computer processor; wherein the intraoral camera is introduced into the oral cavity between and is manually moved and operated, the intraoral camera being configured to capture digital still images from a back tooth position to a front tooth position of an exterior surface of a tooth row by using a continuous capture technique, wherein a left set of continuously captured digital still images is obtained in an area ranging from a left back tooth to a center of front teeth of a tooth row, and a right set of continuously captured digital still images is obtained in an area ranging from a right back tooth to a center of the front teeth of the tooth row, and the computer processor is programmed to: (a) generate the left panoramic tooth row image by combining digital still images from the left set of continuously captured digital still images, wherein a first left digital still image including the center of the front teeth is combined with a second left digital still image taken adjacent to the first left digital still image and having an overlapping portion with the first left digital still image, to form a first left combined image, the first left combined image is combined with a third left digital still image taken adjacent to the second left digital still image and having an overlapping portion with the second left digital still image, to form a second left combined image, and a previous left combined image is repeatedly combined with an adjacent left digital still image until a last left combined image is combined with a last left digital still image positioned at the left back tooth adjacent to the last left combined image and having an overlapping portion with the last left combined image, thereby forming the left panoramic tooth row image, (b) generate the right panoramic tooth row image by combining digital still images from the right set of continuously captured digital still images, wherein a first right digital still image including the center of the front teeth is combined with a second right digital still image taken adjacent to the first right digital still image and having an overlapping portion with the first right digital still image, to form a first right combined image, the first right combined image is combined with a third right digital still image taken adjacent to the second right digital still image and having an overlapping portion with the second right digital still image, to form a second right combined image, and a previous right combined image is repeatedly combined with an adjacent right digital still image until a last right combined image is combined with a last right digital still image positioned at the right back tooth adjacent to the last right combined image and having an overlapping portion with the last right combined image, thereby forming the right panoramic tooth row image, and (c) generate the full panoramic tooth row image by detecting a digital still image of the center of the front teeth in each of the left panoramic tooth row image and the right panoramic tooth row image, superposing the two digital still images of the center of the front teeth to combine the left panoramic tooth row image and the right panoramic tooth row image, thereby forming the full panoramic tooth row image.