Effects of metformin on human gingival fibroblasts: an in vitro study.

OBJECTIVE: To investigate the effects of metformin (MF) treatment on the matrix metalloproteinases (MMPs) and proinflammatory cytokines production from lipopolysaccharide (LPS) - stimulated human gingival fibroblasts (HGFs). METHODS: HGFs were obtained from subcultures of biopsies from clinically healthy gingival tissues of patients undergoing oral surgeries. Cell cytotoxicity assay was used to determine the effect of different concentrations of MF on viability of HGFs. HGFs were then incubated and treated with different concentrations of MF and Porphyromonas gingivais (Pg) LPS. MMP-1, MMP-2, MMP-8, MMP-9, IL-1ß, and IL-8 expression analysis was performed using xMAP technology (Luminex 200, Luminex, Austin, TX, USA). Student's t-test for a single sample was used to compare the mean values of the study groups with the control value. A p-value of <0.05 and 95% confidence intervals were used to report the statistical significance and precision of mean values. RESULTS: Concentrations of 0.5, 1- and 2-mM MF had a minimal non-significant cytotoxic effect on the HGFs and caused statistically significant reduction of MMP-1, MMP-2, MMP-8 and IL-8 expressed by the LPS-stimulated HGFs. CONCLUSION: The results of the present study confirm that MF suppresses MMP-1, MMP-2, MMP-8 and IL-8 in LPS-stimulated HGFs suggesting an anti-inflammatory effect of MF and potential adjunct therapeutic role in the treatment of periodontal diseases.

Xylitol content and acid production of chewing gums available in the markets of Saudi Arabia.

To assess the actual xylitol content in sugar-free chewing gums available in a market of Saudi Arabia and investigate its effect on acid production and pH change in vitro. MATERIALS AND METHODS: A total of 29 different brands of xylitol-containing sugar-free chewing gums were collected from five major grocery stores in Saudi Arabia. Xylitol was extracted and its concentration was determined using the D-Sorbitol/Xylitol Enzymatic Kit (Megazyme; Bray, Wicklow, Ireland). The pH of the extracts and the amount of acid production for each product was measured after 15-minute and 30-minute incubation with Streptococcus mutans. Descriptive analysis, concentrations, and one-way analysis of variance (ANOVA) with the least significant difference (LSD) as multiple comparisons were performed. RESULTS: The xylitol content in grams was clearly stated on the labels of 16 products, while it was stated in percentages on the labels of ten products. The mean pH of most of the tested products was 5.857 ± 0.096. Significant differences in pH were recorded among 20 products (p ≤ 0.05). Highly significant differences in pH (p = 0.001) were observed in five of the products. CONCLUSION: The results of this study indicate, using an in vitro model, that xylitol can significantly affect salivary pH. The actual xylitol content in most brands of chewing gums currently available in the markets of Saudi Arabia is less than the concentration recommended for prevention of caries. Accurate information with proper labeling is required to enable dental professionals to take correct and informed decisions about recommending the use of these products.

Role of problem-based learning in undergraduate dental education: a questionnaire-based study.

BACKGROUND: There is a debate regarding the significance of problem-based learning (PBL) model in educational systems. The aim of this study was to assess the awareness of dental students at the Princess Nourah Bint Abdulrahman University (PNU), Saudi Arabia, toward PBL. METHODS: The present cross-sectional study was performed at the College of Dentistry, PNU, Riyadh, Saudi Arabia. An anonymous, standardized and self-administered questionnaire (based on nine items) coded as 1, 2, 3 and 4 was distributed to the first-, second-, third- and fourth-year undergraduate students, respectively, after a seminar that focused on the perceptions of PBL among the students at the end of the academic year 2017. The questionnaire was developed following an exhaustive search of indexed databases. Based on the students' responses (yes/no) to the questions, group mean differences (95% CI) were computed and Pearson's chi-squared test was used for data analysis. Cronbach's alpha coefficient was also determined. The level of significance was set at P<0.05. RESULTS: In total, 238 female undergraduate dental students (61 first-year, 59 second-year, 60 third-year and 58 fourth-year students) were included. The Cronbach's alpha coefficient ranged between 0.82 and 0.93. Group comparisons (95% CI) showed no statistically significant difference in the responses (yes) of students in the first, second, third and fourth year of academic years related to the perceptions listed earlier (P>0.05). CONCLUSION: Perception of female undergraduate dental students at the PNU was inconclusive. Further studies are warranted in this regard.

Evaluation of bone response to titanium-coated polymethyl methacrylate resin (PMMA) implants by X-ray tomography.

High-resolution three-dimensional data about the bone response to oral implants can be obtained by using microfocus computer tomography. However, a disadvantage is that metallic implants cause streaking artifacts due to scattering of X-rays, which prevents an accurate evaluation of the interfacial bone-to-implant contact. It has been suggested that the use of thin titanium coatings deposited on polymeric implants can offer an alternative option for analyzing bone contact using micro-CT imaging. Consequently, the aim of the current study was to investigate bone behavior to titanium-coated polymethylmethacrylate (PMMA) implants by micro-CT and histological evaluation. For the experiment titanium-coated PMMA implants were used. The implants had a machined threaded appearance and were provided with a 400-500 nm thick titanium coating. The implants were inserted in the right or left tibia of 10 goats. After an implantation period of 12 weeks the implants were retrieved and prepared for micro-computer tomography (microCT), light microscopy, and X-ray microanalysis. The micro-CT showed that the screw-threads and typical implant configuration were well maintained through the installation procedure. Overall, histological responses showed that the titanium-coated implants were well tolerated and caused no atypical tissue response. In addition, the bone was seen in direct contact with the titanium-coated layer. The X-ray microanalysis results confirmed the light microscopical data. In conclusion, the obtained results proof the final use of titanium-coated PMMA implants for evaluation of the bone-implant response using microCT. However, this study also confirms that for a proper analysis of the bone-implant interface the additional use of microscopical techniques is still required.

Histological evaluation of oral implants inserted with different surgical techniques into the trabecular bone of goats.

OBJECTIVE: The aim of this study was to investigate the influence of implant surface topography and surgical technique on bone response. MATERIAL AND METHODS: For the experiment, 48 screw-designed implants were used with two different surface finishes, i.e. machined and 'blasted, etched'. The implants were inserted into the left and right medial femoral condyle of eight goats using three different surgical approaches: press-fit (implant diameter=implant bed diamete(r), undersized (implant bed diameter

A mechanical evaluation of implants placed with different surgical techniques into the trabecular bone of goats.

The aim of the study was to assess the effects of surgical technique and implant surface roughness on implant fixation. A total of 48 screw implants with machined or etched surface topographies were placed into the femoral condyles of goats. The implant sites were prepared by a conventional technique, by undersized preparation, or by the osteotome technique. Bone tissue responses were evaluated after 12 weeks of healing by removal torque testing and histologic analysis using scanning electron microscope. The cumulative removal torque value of the etched implants placed with the undersized technique (98 +/- 29 Ncm) was higher (50 +/- 35 Ncm) to a level of statistical significance than machined surface implants placed by the osteotome technique. Scanning electron microscope evaluation indicated that all implants showed interfacial bone contact. The torque test resulted in fracture at the bone-implant interface for all experimental conditions. Installation of etched implants using an undersized preparation of the implant bed resulted in superior bonding strength with the surrounding bone at 12 weeks after surgery. Evidently, the undersized preparation technique improved the early fixation of oral implants in this study.

A meta-analysis of clinical studies to estimate the 4.5-year survival rate of implants placed with the osteotome technique.

PURPOSE: To estimate the survival rate of implants placed with the osteotome technique by means of a systematic review. MATERIALS AND METHODS: The literature was searched using Medline; the search was limited to the years 1953 to 2005. Inclusion criteria were: (1) clinical studies or clinical reports investigating the osteotome technique for dental implantation and (2) control or test group(s) from clinical studies or clinical reports, even if they did not fit with other criteria. By pooling the data of the included studies, overall Kaplan-Meier survival curves were constructed for the periods before and after loading. RESULTS: The initial literature search yielded 164 studies. After selection criteria were applied, 5 studies were considered suitable for inclusion. The combined data of 349 implants revealed survival probabilities of 98% (confidence interval [CI], 97.2% to 100%) until loading and 99% (CI, 94% to 100%) after 56 months of loading. At the end of the observation period 41 implants in 18 patients were still at risk. CONCLUSION: The outcome of dental implantation using the osteotome technique in terms of implant survival seems to be similar to that of implants placed by means of the conventional implantation technique.

The effects of implant surface roughness and surgical technique on implant fixation in an in vitro model.

OBJECTIVES: The aim of the present study was to determine the relationship between implant surface parameters, surgical approach and initial implant fixation. MATERIAL AND METHODS: Sixty tapered, conical, screw-shaped implants with machined or etched surface topography were implanted into the explanted femoral condyle of goats. The implant sites were prepared either by a conventional technique, by undersized preparation, or by the osteotome technique. Peak insertion & removal torque, bone-to-implant contacts (BIC) and morphological bone appearance were assessed by scanning electron microscope (SEM) and micro-computer tomography. (micro-CT). RESULTS: Insertion and removal torque values were significantly higher for etched implants inserted with the undersized technique (115.2 +/- 31.1, 102.9 +/- 36.4 N cm) respectively. Also, the average BIC value was higher for the etched implants placed with the undersized technique (87.5 +/- 5.6), which was statistically significant compared with machined and etched implants inserted by conventional technique. CONCLUSION: In conclusion, this study shows that the surgical technique has a decisive effect on implant fixation (represented in this study by installation torque value/removal torque value and histomorphometric evaluation) in trabecular bone. Nevertheless, additional in vivo studies have to be done to prove the importance of surgical protocol for the final implant-bone response.