Objectives The present study aims to evaluate patients' knowledge about toothbrush disinfection (TBD), plaque control, knowledge, and awareness of periodontal diseases (P-knowledge and P-awareness). Methods The study enrolled 121 participants (70 women and 51 men). Participants were asked to fill out a survey containing questions about demographic characteristics, toothbrushing habits, toothbrush storage conditions, toothpaste use, TBD, P-knowledge, and P-awareness. The periodontal clinical parameters (GI, PI, PPD, CAL, BOP, and GR) and DMFT index were recorded. The patients were informed about TBD, and 1 month later, the participants were contacted again and asked whether they disinfected their toothbrushes. Results The participants (51.2%) do not have any knowledge about TBD. Most of those who reported disinfecting their toothbrushes think that washing toothbrushes with tap water is disinfection (23.1%). One month after the TBD training, only 36.3% of the participants reported that they disinfected, albeit not regularly, their toothbrushes with white vinegar. While there was no statistically significant relationship between genders in terms of visiting dentists, a significant relationship was found between genders in terms of toothbrushing frequency (p < 0.05). P-awareness was found to be "medium" while P-knowledge was at a "low" level. While there was no statistically significant difference between income levels in terms of P-knowledge levels, a significant difference was found between genders and educational backgrounds in terms of P-knowledge levels (p < 0.05). Conclusions The results of the study suggest that the participants do not have enough knowledge about toothbrush storage conditions, toothpaste sharing, and TBD. Collaborating with dental hygienists to raise awareness about oral health and TBD may have a positive impact.