Dental Research Journal最新文献

Background: This study aimed to assess the effect of local injection of injectable platelet-rich fibrin (i-PRF) on bone remodeling during orthodontic tooth movement in dogs.

Materials and methods: In this animal study, the maxillary first premolars of four adult male mixed-breed dogs were bilaterally extracted, and a nickel-titanium closed coil spring with 150 g force was placed between the canine and second premolar teeth. One quadrant of the maxilla was randomly selected as the test quadrant, and 0.5 cc i-PRF was injected into the periodontal ligament (PDL) around the second premolar at 1, 21, and 42 days. The other quadrant served as the control group and received saline injections. The dogs were sacrificed after 63 days, histological sections were prepared, and changes in bone remodeling were assessed by comparing the percentage of osteogenesis and number of osteoblasts and osteoclasts between the two groups by the Wilcoxon and Mann-Whitney U-tests (α = 0.05).

Results: The percentage of osteogenesis (16.0% ± 4.96% in i-PRF and 13.5% ± 4.43% in the control), the percentage of newly formed lamellar bone (10.25% ± 2.87% in i-PRF and 8.75% ± 2.36% in the control), the percentage of woven bone (5.75% ± 2.21% in i-PRF and 4.75% ± 2.36% in the control), the number of osteoblasts (15.0 ± 3.46 in i-PRF and 11.75 ± 2.36 in the control), and the number of osteoclasts (11.25 ± 4.34 in i-PRF and 6.25 ± 2.62 in the control) were not significantly different between the two groups (P > 0.05).

Conclusion: PDL injection of i-PRF around the second premolars of dogs under orthodontic force had no significant effect on bone remodeling.

Background: Few studies assessed the effect of coping material (particularly milled metal copings) on the retentive strength of cements and reported contradictory results. Thus, this study aims to assess the marginal leakage and retentive strength of implant-supported milled zirconia and cobalt-chromium (Co-Cr) copings cemented with different temporary cements.

Materials and methods: In this in vitro study, Zirconia and Co-Cr copings were fabricated on 100 straight titanium abutments. Each group of copings was divided into five subgroups (n = 10) for the use of different cements: permanent zinc-phosphate (ZP) cement, temporary zinc oxide eugenol cement (temp bond [TB]), calcium hydroxide-based temporary cement (Dycal [DC]), polymer-based eugenol-free acrylic-urethane temporary cement (Dentotemp [DT]), and methacrylate-based temporary cement (Implantlink [IL]). The retentive strength and marginal leakage of restorations were assessed. Data were analyzed by one-way ANOVA, Tukey, and Fisher's exact tests (α = 0.05).

Results: In the Co-Cr group, the retentive strength values (in Newtons) were as follows: ZP (411.40 ± 5.19) >DC (248.80 ± 5.01) >IL (200.10 ± 5.06) >DT (157.90 ± 5.19) >TB (98.50 ± 6.88). This order was as follows in the zirconia group: ZP (388.70 ± 5.35) >DC (226.60 ± 5.08) >IL (179.00 ± 3.71) >DT (136.00 ± 4.88) >TB (78.60 ± 3.50). All pairwise comparisons were statistically significant (P < 0.001). The difference in marginal leakage was not significant among the groups (P = 0.480).

Conclusion: The type of coping material and cement type significantly affected retentive strength, but not marginal leakage, of implant restorations. Milled Co-Cr copings showed higher retentive strength than zirconia copings, and ZP cement followed by DC yielded the highest retention.

Background: This study aimed to assess the effect of hydroalcoholic extract of the whole pomegranate fruit on Streptococcus mutans (S. mutans) and Lactobacillus acidophilus (L. acidophilus) and its clinical effect on dental plaque formation in 8-10-year-old children.

Materials and methods: This study was conducted in two phases of in vitro and clinical trial. In the in vitro phase, the antibacterial effect of 50%-50% hydroalcoholic extract of whole pomegranate fruit on S. mutans and L. acidophilus was assessed by the disc diffusion test. In the double-blind cross-over clinical trial phase, 14 children between 8 and 10 years were randomly assigned to two groups of 38% pomegranate mouthwash and 0.12% chlorhexidine (CHX) after assessing their baseline dental plaque by oral hygiene index-simplified (OHI-S). The children were asked not to use any other plaque control measure during the study. Their OHI-S score was measured again after 5 and 14 days using disclosing tablets. Data were analyzed by t-test and paired t-test at 0.05 level of significance.

Results: The hydroalcoholic extract of pomegranate showed a positive antibacterial effect on S. mutans and L. acidophilus. However, its inhibitory effect was significantly lower than that of 0.12% CHX (P < 0.05). None of the tested mouthwashes inhibited plaque formation, but pomegranate mouthwash and CHX decreased the OHI-S score by 34% and 36%, respectively (P < 0.05), with no significant difference between them (P > 0.05).

Conclusion: The whole pomegranate fruit hydroalcoholic extract showed significant inhibitory effects on S. mutans and L. acidophilus. Furthermore, 38% pomegranate mouthwash had a comparable efficacy to CHX in the reduction of dental plaque.

Background: This study aimed to assess the effect of local administration of injectable platelet-rich fibrin (i-PRF) on root resorption during orthodontic tooth movement in dogs.

Materials and methods: This animal study was conducted on 4 adult male mongrel dogs. The right and left maxillary first premolars of the dogs were extracted, and a Nickel-Titanium closed coil spring was used to connect the canine to the second premolar with 150 g load. Next, 0.5 cc of i-PRF was injected in one quadrant of the maxilla around the second premolar into the periodontal ligament. The other quadrant of the maxilla served as the control group and received saline injection. Injections were performed at 1, 21, and 42 days, and the dogs were sacrificed after 63 days. Histological sections were prepared and cementum resorption, secondary cementum formation, and number of cementoblasts and cementoclasts were compared between the two groups by the Friedman test, Wilcoxon test, and Mann-Whitney test (α = 0.05).

Results: The mean percentage of cementum resorption (17.75% ± 5.56%) and secondary cementum formation (14.50% ± 6.65%), and the mean number of cementoblasts (10.25 ± 2.36) and cementoclasts (9.75 ± 4.71) were insignificantly higher in the i-PRF group than the corresponding values (13.75% ± 4.34%, 8.50% ± 2.88%, 7.75 ± 1.25, and 6.50 ± 3.10, respectively) in the control group (P > 0.05).

Conclusion: Administration of i-PRF insignificantly increased the percentage of cementum resorption, secondary cementum formation, number of cementoblasts, and number of cementoclasts.

Background: Dentists begin the diagnosis by identifying and enumerating teeth. Panoramic radiographs are widely used for tooth identification due to their large field of view and low exposure dose. The automatic numbering of teeth in panoramic radiographs can assist clinicians in avoiding errors. Deep learning has emerged as a promising tool for automating tasks. Our goal is to evaluate the accuracy of a two-step deep learning method for tooth identification and enumeration in panoramic radiographs.

Materials and methods: In this retrospective observational study, 1007 panoramic radiographs were labeled by three experienced dentists. It involved drawing bounding boxes in two distinct ways: one for teeth and one for quadrants. All images were preprocessed using the contrast-limited adaptive histogram equalization method. First, panoramic images were allocated to a quadrant detection model, and the outputs of this model were provided to the tooth numbering models. A faster region-based convolutional neural network model was used in each step.

Results: Average precision (AP) was calculated in different intersection-over-union thresholds. The AP50 of quadrant detection and tooth enumeration was 100% and 95%, respectively.

Conclusion: We have obtained promising results with a high level of AP using our two-step deep learning framework for automatic tooth enumeration on panoramic radiographs. Further research should be conducted on diverse datasets and real-life situations.

Background: Dental caries is a preventable multifactorial disease, with Streptococcus mutans being suggested to be its primary pathogen. Our study aim was to compare the effects of three different low-cost and easy-to-use regimens with that of the gold standard (chlorhexidine [CHX] mouthwash) on the count of salivary S. mutans in dental students over 30 days.

Materials and methods: In this single-blinded parallel randomized controlled clinical trial, a total of 120 dental students were included and randomly allocated into four intervention groups: (1) CHX mouthwash (control(, (2) probiotic yogurt, (3) casein phosphopeptide-amorphous calcium phosphate chewing gum, and (4) xylitol chewing gum. Salivary S. mutans counts were evaluated at baseline, 15 days, and 30 days after initiation of the study and compared at different times and among different groups using the repeated measures analysis of variance design analysis and least significant difference test with SPSS software version 20. The level of significance was determined to be 0.05.

Results: The microorganism count variable at baseline, first, and second follow-ups was significantly different for all groups except the probiotic yogurt group (P = 0.340). S. mutans count was significantly different when comparing the first follow-up and baseline values in the CHX and xylitol gum groups (P = 0.027, P = 0.037). When comparing the second follow-up with baseline values, a significant difference was observed in the xylitol gum group (P = 0.003).

Conclusion: Xylitol chewing gum seems to be a viable alternative to the gold standard (CHX mouthwash) in reducing the salivary count of S. mutans.

Background: Oral squamous cell carcinoma (OSCC) is the most common malignant tumor among oral cancers. Cyclin D1 and Ki-67 have associated with cell division. The aim of this study was to compare the expression of these markers in OSCC with and without cervical lymph node (LN) metastasis.

Materials and methods: This cross-sectional study was performed on 40 OSCCs with and without cervical LN metastasis (20 in each group) that was recorded in the pathology archive of Ayatollah Kashani Hospital in Isfahan. Clinical information including age, gender, and location was collected. Some histopathological parameters including depth of invasion, lymphovascular invasion (LVI), perineural invasion (PNI), number of LN metastases, histopathological grade, and stage of disease were evaluated. Immunohistochemical staining was performed for cyclin D1 and Ki-67. All data were entered into SPSS24 software and were analyzed by Mann-Whitney, Kruskal-Wallis, Chi-square, Fisher's exact, and t-tests. P < 0.05 was considered statistically significant.

Results: Based on LVI and stage of disease, a significant correlation was found between the two groups (P < 0.001). There was a significant difference between the two groups based on cyclin D1 expression (P = 0.05). The expression of the Ki-67 showed a significant difference based on tumor location (P = 0.026) and PNI (P = 0.033).

Conclusion: The use of markers should be considered in determining the prognosis of OSCC, and the cyclin D1 marker is one of the useful markers for predictors of cervical LN metastasis.