Objective The aim of this study was to develop an objective method to assess the degree of bristle splaying of used manual toothbrushes and to investigate their plaque removal efficacy. Methods A randomized controlled trial targeting Hiroshima University students was performed to assess the plaque removal efficacy of polybutylene terephthalate (PBT) manual toothbrushes. Participants were randomly assigned to the soft toothbrush group (n = 40) or the medium toothbrush group (n = 40). A small number of participants discontinued the intervention for personal reasons in both the medium (n = 6) and soft (n = 2) toothbrush groups. Toothbrushes were collected immediately after first use (T0: baseline), after 1 month of use (T1: month 1), after 2 months of use (T2: month 3) and after 3 months of use (T3: month 6), following the allocation of a new toothbrush. The bristle surface area was measured using digital software. Results The surface area of the bristles was significantly greater at T1, T2 and T3 than at T0 in the medium toothbrush group (n = 34) and soft toothbrush group (n = 38) (P < .001). Importantly, plaque removal efficacy, calculated from a modified plaque control record score and modified patient hygiene performance score, was significantly lower at T2 than at T0 in both groups. Conclusions Our method for evaluation of bristle splaying is considered to be reliable and reproducible. PBT toothbrushes may become less effective after two months of use.

Background: The associations between oral human herpesvirus-6 (HHV-6) and HHV-7, periodontal conditions, and lifestyle-related diseases, such as hypertension, diabetes, and dyslipidemia, have not been fully investigated in older adults. Methods: Seventy-four older patients who visited Hiroshima University Hospital were enrolled. Tongue swab samples were employed, and a real-time polymerase chain reaction was performed to detect HHV-6 and HHV-7 DNA. Dental plaque accumulation, probing pocket depth, and bleeding on probing (BOP) (i.e., a sign of periodontal inflammation) were examined. The periodontal inflamed surface area (PISA) value (i.e., an indicator of the severity of periodontitis) was also examined. Results: Of the 74 participants, one participant (1.4%) was HHV-6 DNA-positive and 36 participants (48.6%) were HHV-7 DNA-positive. A significant association between HHV-7 DNA and probing depth was found (p = 0.04). The HHV-7 DNA-positive participants had a higher positive rate of a ≥ 6-mm periodontal pocket with BOP (25.0%) than the HHV-7 DNA-negative participants (7.9%). Additionally, the HHV-7 DNA-positive participants had a higher PISA value than the HHV-7 DNA-negative participants. However, there was no significant association between HHV-7 and the PISA value (p = 0.82). No significant association was found between HHV-7 and lifestyle-related diseases (p > 0.05). Conclusions: Oral HHV-7 infection is associated with a deep periodontal pocket.