Abstract-Maxillary sinus perforation is one of complication from tooth extraction that could create a connection between antrum and oral cavity (oroantral communication). The aim of this research is to determine the level of dentists' knowledge about the initial treatment to handle the sinus maxillary perforation in District Helvetia, Medan in year 2017. This research is a descriptive survey; the population is every dentist in District Helvetia, Medan. The population is made as the sample (total sampling), so the amount of the sample in this research is 56 people. The results showed us that there is 69.64% of the dentist are categorizes as knowledgeable, 30.36% of dentists are knowledgeable enough and 0% of the dentist are categorized as not knowledgeable. The level of dentist knowledge about the initial treatment to handle the sinus maxillary perforation in District Helvetia, Medan in year 2017, 69.64% knowledgeable, 30.36% knowledgeable enough and no one is not knowledgeable.