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Journal of Oral Science & Rehabilitation No. 4, 2017

M o u t h w a s h e s a n d b a c t e r i a o n s u t u r e t h r e a d s Each dilution, the first included, was seeded in plates with the same agar-based broth media and incubated for 48 h at 36 ± 1 °C in order to quantify the microbial load. Bacterial colonies were then counted and expressed as colony- forming units per mL (cfu/mL). Concerning the enumeration of bacterial colonies, a bacterial score (BS) was obtained by classifying the enumer ated bacterial colonies according to the following scheme: – Class 0: BS ≤ 103 cfu/mL – Class 1: ≤ 103 cfu/mL BS ≤ 105 cfu/mL – Class 2: ≤ 105 cfu/mL BS ≤1 07 cfu/mL – Class 3: BS > 107 cfu/mL Search for specific anaerobic bacteria: Each sample was seeded on 2 different plates (BBE and brucella blood agar) to determine the eventual presence of anaerobic microbial strains. Seeded plates were placed in the oxygen-free vessels and incubated at 36 ± 1 °C for 7 days. After this period, the plates were analyzed to evaluate the presence of bacterial colonies. In positive cases, individual colonies were reseeded to achieve a pure bacte- rial culture suitable for biochemical recognition. For evaluation of the growth of specific anaerobic bacteria, the classes of “growth” and “no growth” were established, depending on whether bacte- rial growth was observed. S t a t i s t i c a l a n a l y s i s Data were expressed as mean ± standard devi- ation (SD) of BS values, where available. The Mann–Whitney U test for independent samples was used to evaluate the difference between the C-group and H-group. In the case of categorical data, that is growth/no growth classes and absence/presence classes, data were organized in contingency tables and analyzed by the Fisher exact test. A value of P ≤ 0.05 was taken as statis tically significant. Statistical analysis was performed using OpenStat version 26.03.2012 (www.statprograms4u.com). Results The results of the microbiological analysis are summarized in Tables 1–4. Table 1 reports mean ± SD values for BSs calculated from the cfus developed under different conditions. The mean ± SD score of bacteria seeding calculated on TSA was 2.000 ± 1.080 and 1.462 ± 1.198 in the H-group and C-group, respectively. The mean ± SD score of bacteria-seeding calculated on MRS was 1.462 ± 1.050 and 1.077 ± 1.320 in the H-group and C-group, respectively. In all cases, the P values were not statistically signif- icant, meaning that no statistically significant differences were observed between the H-group and the C-group. In more detail, the total bac- terial load developed after seeding BPW solu- tions that had been in contact with suture thread segments on TSA plates and the Lactobacillus spp. developed after seeding BPW solutions that had been in contact with suture thread seg- ments were comparable between groups. Table 2 is the contingency table summarizing data resulting from inoculation on BRU plates. In this case too, no statistically significant dif- ferences between the H-group and C-group were observed (P = 0.411). Tables 3 and 4 are contingency tables summarizing data resulting from scraping suture thread segments on TSA plates and MRS plates, respectively. Again, no statistically significant differences between the H-group and C-group were observed. Inocula- tion in BBE under anaerobic conditions produced negative results (no growth) for all samples and the control. Figure 2 illustrates Petri dishes after the optional development of bacterial colonies. Discussion The present study aimed to evaluate the bacte- rial load on suture threads after their removal in 2 different situations. Patients were assigned either to a chlorhexidine mouthwash or to a zinc one. Among the suture thread samples taken from the 13 patients who used the mouthwash containing chlorhexidine (C-group), 7 showed a high bacterial load (BS = 2 or 3) with the pres- ence of Lactobacillus spp, in 5 cases; 2 of them presented a poor bacterial load (BS = 1); and 4 of them did not present any appreciable micro- bial colonization (BS = 0). The search for specific anaerobic strains, when positive (3 samples), resulted in establishing the presence of Fuso- bacterium varium (1 occurrence), Actinomyces meyeri (1 occurrence) and Streptococcus inter- medius (1 occurrence). Of the 13 suture thread samples taken from patients who used a mouth- wash containing Zn-nHAp/Zn-PCA, 10 showed a high bacterial load (BS = 2 or 3) associated with the presence of Lactobacillus spp., 1 had a mod- erate bacterial load (BS = 1), and 2 did not show any appreciable microbial colonization. The search for specific anaerobic strains, when pos- Journal of Oral Science & Rehabilitation Volume 3 | Issue 4/2017 27

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