Contrary to intuitive preconceptions, patients with Parkinson’s disease (PD) have been reported to have less carious teeth. The present study was undertaken to seek responsible factors for this unexpected finding. The PD patients consisted of 31 consecutive university hospital outpatients who were 60 years old or over, and the controls of 104 comparable outpatients at a dental clinic. They were inspected for their dental status, and interviewed on their toothbrushing habits and dietary preferences. Their unstimulated saliva samples were collected and their flow volume and pH were measured. The total numbers of carious teeth (DMFT: Decayed, Missing, and Filled Teeth) and other related variables were compared between the two groups by stratification. In total, the DMFT for the PD patients was significantly fewer than for the control. The salivary flow and pH were correlated to the DMFT, but the difference between the two groups was not significant. Frequency of toothbrushing was higher among the PD patients. The lower DMFT among the patients became insignificant when salivary pH was 6 or less, toothbrushing was 2 times a day or less, or the response was positive to the question on the habit of eating snacks between regular meals. In summary, the oral health of PD outpatients with mild symptoms was better than the controls. However, in cases with poor oral hygiene status, the PD patient’s oral health was not different from the control. This suggests that they are not invariably protected from caries-associated factors. The generic property of PD may not fully explain the apparent difference in DMFT.