The most popular classification was that introduced by Kwak et al. The simplest of all these systems consists of three classes, class 1: root tip is outside the sinus, class 2: root tip is against the sinus wall, and class 3: root tip is in the sinus. Many studies used different scoring systems to categorize the sinus-root relation in different populations. This is related to its three-dimensional nature that can provide information that was lost or restricted due to superimposition, magnification, and blurring of the 2D imaging. However, cone beam computed tomography (CBCT) was the imaging modality used by most of the researchers to study the sinus-root relation. The two-dimensional (2D) imaging, represented in the periapical and the panoramic radiography, is considered the most widely available modality that provides acceptable data with minimal dose and cost. These include rotating or advancing soft tissues such as palatal flap, submucosal tissue, buccal flap, submucosal tissue, buccal fat pad, and tongue flap. A general practitioner may prefer to refer this case to a maxillofacial surgeon who should bear in mind that it is a complicated procedure that may require the closure of the fistula by one of the following methods: local flaps, distant flaps, and grafting. Having a previous idea about the high probability of the occurrence of an oroantral communication may strongly affect the treatment plan. This accident, which has always been a concern for dental practitioners, consists in the violation of the maxillary sinus floor (MSF) and may or may not involve tearing of the Schneiderian membrane. This leads to the occurrence of the popular accident known as oroantral fistula or oroantral communication. The sinus becomes at a risk of exposure to the oral cavity either due to a surgical procedure carried out in the area of the maxillary posterior teeth or due to a pathologic invasion from a lesion arising from this area. This is due to the close proximity of its floor to the apices of the premolar and molar roots that are separated from the sinus floor either by a thin layer of bone or by its mucous membrane which is called Schneiderian membrane. It is considered the most important paranasal sinus that impacts most of the work of the dentists and the maxillofacial surgeons. The maxillary sinuses (MS) are one of the four paired sets of the paranasal sinuses and the first to develop in fetal life. Left second molars are at a higher risk of oroantral communications on surgical or endodontic procedures compared to other molars due to its highest probability of intrusion into the sinus. The side and type of tooth are of higher impact on the probability of its intrusion into the sinus compared to the type of root.
In a sample of the Egyptian population, males exhibit higher probability of root protrusion into the sinus than females. As for the individual root with the highest probability of intrusion, the mesio-buccal root of the right third molar is the most frequent root to intrude the sinus (71.4%) and the mesio-buccal root of the right first molar is the least frequent (22.7%). However, the difference in both type of tooth and type of root was statistically non-significant ( p = 0.051 and 0.869 respectively). According to the type of root, the mesiobuccal root showed the highest probability of intrusion into the sinus (50.9%) followed by the palatal root (49.1%) then the distobuccal root (47.4%).
As for the type of tooth, the second molar showed the highest probability of root intrusion into the sinus (55.3%) followed by the third molars (52.6%) then the first molars (40.9). The probability of root intrusion in the left molars (54.2%) was non-significantly ( p = 0.067) higher than that of the right side (44.3%). The percentage of root intrusion into the sinus in males (56.9%) was significantly ( p = 0.01) higher than females (42.9%). The total number of roots located outside the sinus was 121 (35.3%), while those contacting the sinus floor were 80 (23.3%) and those intruded the sinus were 141 (41.2%). Predicting the probability of protrusion of each root into the sinus will consequently predict the probability of occurrence of the oroantral fistula in a sample of the Egyptian population.
The aim of this study is to evaluate the relationship between each maxillary molar root and maxillary sinus floor using cone beam computed tomography. The proximity of the maxillary sinus floor to the maxillary molar roots increases the probability of oroantral communication on conducting any surgical or endodontic procedure in the involved area.