QSPR study of viscoplastic properties of peptide-based hydrogels.

In this study, the power of machine learning was harnessed to probe the link between molecular structures of peptide-based hydrogels and their viscoplastic properties. The selection of compounds was attempted in accordance with the prescribed full list of peptide-based materials exhibiting hydrogel functionality in the literature. In this pursuit, a complete set of molecular descriptors and fingerprints was considered - accounting for an entry of size 17,968 for each peptide-based structure analyzed. The elastic and viscous moduli response of materials were mapped over a wide frequency spectrum in the range [0.1-100] (rad/s). In general, the results indicate that the frequency-dependent mechanical response of peptide-based hydrogels is statistically correlated with its (inter)molecular attributes, such as charge, first ionization potential (or equivalently electronegativity), surface area, number of chemical substrates, bond type, and intermolecular interactions. The performance of several (supervised) soft computing techniques was measured, for our quantitative structure property relationships model. In addition, the hypothesis of mapping our databank to a new system of principal components was tested, by using an unsupervised methodology, which resulted in enhancement of the prediction accuracy. In terms of significance, the present article provides the first report of frequency-dependent elastic and viscous moduli, for a set of 70 peptide-based formulations with hydrogel functionality.Communicated by Ramaswamy H. Sarma.

Use of bioactive glass doped with magnesium or strontium for bone regeneration: A rabbit critical-size calvarial defects study.

Background: This study aimed to evaluate the amount of bone regeneration in critical defects of rabbit calvaria filled with magnesium- and strontium-doped bioactive glasses. Materials and Methods: In this rabbit critical-size calvarial defects study, 12 male New Zealand white rabbits were randomly divided into two groups. On the calvaria of each rabbit, four lesions (two lesions in the frontal bone and two lesions in the peritoneal bone) were created with a diameter of 8 mm spaced apart. Each lesion was filled in with (1) strontium-doped bioactive glass, (2) magnesium-doped bioactive glass, (3) 45S5 bioactive glass, and (4) empty lesion (control). Six rabbits were sacrificed at the end of 4 weeks, and six rabbits were randomly sacrificed at the end of 8 weeks. Bone sections with a 5-µ thickness of rabbit calvary bone were prepared, and the percentage of new bone, connective tissue, and residual material were calculated in microscopic images. Statistical analysis was performed by two-way ANOVA and Bonferroni additional tests, and the level of significance was set at P < 0.05 in all categories. Results: At 4 weeks, magnesium-doped bioactive glass showed the highest new bone formation with a mean of 11.66 ± 2.64, followed by the strontium-doped bioactive glass with the mean of 11.10 ± 1.69 (P = 0.0001). While at week 8, the highest amount of new bone observed in the strontium-doped group with a mean of 28.22 ± 3.19, and then, the magnesium-doped bioactive glass with a mean of 22.55 ± 3.43 (P = 0.0001). Conclusion: Doping strontium and magnesium in the structure of bioactive glasses increases new bone regeneration in comparison with 45S5 bioactive glass.

Bacterial Colonization on Different Suture Materials Used in Oral Implantology: A Randomized Clinical Trial.

Objectives: This study aimed to compare the colonization of Enterococcus faecalis (E. faecalis), Escherichia coli (E. coli), Streptococcus mutans (S. mutans) and Staphylococcus aureus (S. aureus) isolated from the oral cavity on different suture materials used in oral implantology. Materials and Methods: Patients scheduled for implant surgery were included in this study. After flap approximation, the surgical site was sutured using silk, nylon, polyglactin 910 (Vicryl®) and triclosan-coated polyglactin 910 (Vicryl® Plus) sutures in a randomized order. Seven days after surgery, the sutures were removed and incubated in bile esculin agar (for E. faecalis), MacConkey agar (for E. coli), mitis salivarius agar (for S. mutans), and mannitol salt agar (for S. aureus) at 37°C for 24 h. The colonies were then counted. Data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests. Results: Vicryl® sutures showed the highest accumulation of E. faecalis, followed by Vicryl® Plus, nylon, and silk. There was no significant difference between nylon and silk (P=0.5) or between Vicryl® and Vicryl® Plus (P=0.4). Vicryl® Plus sutures showed the highest accumulation of E. coli followed by Vicryl®, silk and nylon (P<0.01). Vicryl® sutures showed the highest accumulation of S. mutans, followed by Vicryl® Plus, silk, and nylon. Vicryl® Plus sutures showed the highest accumulation of S. aureus, followed by Vicryl®, nylon, and silk. Conclusion: Nylon sutures showed the least microbial accumulation. Vicryl® and triclosan-coated Vicryl® Plus sutures had no advantage over the commonly used silk sutures in decreasing the number of bacteria.

Effect of nonsurgical periodontal therapy on the level of salivary antioxidants in patients with generalized moderate-to-severe chronic periodontitis.

Background: In the course of periodontal diseases, polymorphonuclear leukocytes (PMNs) produce oxidative agents and free radicals, thus triggering oxidant-antioxidant disequilibrium in the saliva. Due to the reduction of antioxidant protective effect, oxidative stress is induced, destroying periodontal tissues. This study aimed to investigate the consequences of the non-surgical phase of periodontal therapy on the level ofsalivary antioxidantsin patients with generalized moderate-to-severe chronic periodontitis. Methods: Un-stimulated salivary samples were collected from 43 patients with generalized moderate-to-severe chronic periodontitis for 5 minutes. Clinical parameters, including clinical attachment loss (CAL), bleeding on probing (BoP) and pocket depth (PD), were recorded in each tooth and subsequently, scaling and root planing (SRP) was carried out. After four weeks, salivary samples were collected once again, and the above-mentioned clinical parameters were recorded. Following centrifugation and freezing at a temperature of -80°C, salivary samples were examined simultaneously in a single day, and the level of their antioxidants was measured with ferric reducing ability of plasma (FRAP) method using a spectrophotometer. Results: The concentration of salivary antioxidants significantly increased four weeks following the non-surgical periodontal therapy (P<0.0001). Moreover, the clinical parameters of CAL, BoP and PD showed a significant decrease in 4 weeks as well (P<0.0001). Conclusion: The level of salivary antioxidants in patients with generalized moderate to severe chronic periodontitis significantly increased after etiotropic periodontal therapy, indicating the possible beneficial influence of periodontal therapy on the level of salivary antioxidants in patients suffering from periodontitis.

Long-term results of immediate implantation in the maxillary molar area with simultaneous sinus floor elevation by the crestal approach and early loading protocol: A retrospective case series follow-up study.

Background: This study aimed to determine the long-term survival rate of implants placed in fresh sockets of extracted maxillary molars with simultaneous sinus floor elevation and early loading protocol. Methods: Nineteen maxillary molar teeth were extracted by tooth sectioning, and the sockets were debrided. Drilling for implant placement (Either Xive, Dentsply or Axiom, Antogyr) was terminated 1 mm short of the sinus floor with a pilot drill. Then, according to Summers' technique, elevation of the Schneiderian membrane and bone grafting were performed. The implants were placed according to non-submerged procedure after sinus grafting and preparation of the desired osteotomy site. Results: The implants had been in function up to 5 years and the mean time of loading was 33.12 months. Analysis of crestal bone loss records indicated a mean of -0.054±0.56 mm of bone resorption (with a range of -0.86 to +0.90 mm). The amount of crestal bone resorption on the mesial and distal surfaces of implants was -0.02±0.559 mm and -0.09±0.59 mm, respectively (P=0.232). Survival rates and success rates were 100% and 95.45%, respectively. Conclusion: Immediate implant placement in the posterior maxilla with simultaneous sinus floor augmentation and early loading was a reliable and predictable approach.