# Automatic Tooth Detection and Numbering Using a Combination of a CNN and Heuristic Algorithm
## 1 Introduction  
Dental panoramic radiography (DPR) is an examination that uses an extremely small dose of ionizing radiation to capture a single image of the entire mouth. This technique is commonly applied by dentists and oral surgeons in their everyday practice and has significant potential in the planning of treatment involving dentures, braces, extractions, and implants.  
DPR is a commonly used imaging method applied to an overall evaluation of the jaw bones and teeth. Compared to intraoral radiographs, it has the advantages of a shorter imaging time, lower exposure dose, and the ability to approximate the real size and location of the major anatomical structures in the oral and maxillofacial region more accurately. Therefore, DPR not only complements an oral examination consisting of questionnaires and visual examinations, but also serves as an indicator of permanent and objective records of teeth and hard tissues [1].  
Although DPR is part of a basic examination, only professionally trained doctors can read a DPR image. As a result, several attempts to aid in the diagnosis by an automatic reading of panoramic images have remained at the early stage of development owing to problems such as diagnostic accuracy [2].  
The recent development of big data and cloud technology has vastly augmented the availability of learnable medical information and algorithms. Algorithms for panoramic images using artificialintelligence (AI) have been recently applied in various fields, including maxillary bone, tooth age, and osteoporosis determination [3].  
Tooth and implant detection and tooth numbering are fundamental concepts that have been used in various studies applying AI to the analysis of DPR images. Tooth detection involves determining whether a tooth is a prosthesis. Tooth numbering refers to numbering the prostheses and teeth by locating a divided prosthesis and obtaining its relationship with the surrounding teeth.  
The tooth detection and numbering from a DPR image can be utilized as primary statistical data and identification information because teeth are the hardest tissues in the human body and are composed of enamel, dentin, and chalk [4].  
Tooth numbering information can also be applied to the development of various other algorithms. The location information of the panorama can be linked to the existing readings, upon which new algorithms can be developed.  
Although algorithms for automatically detecting and diagnosing the condition or number of a tooth using panoramic information have been occasionally used, the methods applied in existing studies do not support an automatic tooth detection within a specific location and have a drawback of requiring the user to manually set the tooth position first [5; 6; 7; 8; 9; 10]. Although the accuracy of tooth detection and numbering has increased in recent studies [11; 12], a high detection rate for images containing implant fixtures and crowns has not yet been achieved [13]. Thus, in this study, an algorithm is proposed for modeling, detecting, and numbering implant fixtures, crowns, and normal teeth using complex panoramic images that include information on various dental treatments.