Single implant retained overdentures: Evaluation of effect of implant length and diameter on stress distribution by finite element analysis.

PURPOSE: Single implant retained mandibular overdenture treatment has been shown to be a minimally invasive, satisfactory, and cost-effective option for edentulous individuals. However, the impact of implant diameter and length on stress distribution at the implant, bone, and other components in this treatment approach remains unclear. The purpose of this 3D finite element analysis was to evaluate the effect of implant length and diameter on equivalent von Mises stress and strain distribution in single implant retained overdentures at bone, implant, and prosthetic components. MATERIALS AND METHODS: Nine models were constructed according to implant lengths (L) (8, 10, 12 mm) and diameters (D) (3.3, 4.1, 4.8 mm). The implants were positioned axially, in the midline of the mandible. A 3D model of the edentulous mandible was created from a computed tomography image. A single implant, abutment with insert PEEK and a housing, acrylic denture, and Co-Cr framework were modeled separately. In the ANSYS software program, occlusal loads were applied as 150 N, bilaterally vertical direction, or unilaterally oblique direction to the first molar. Minimum principal stress values were evaluated for bone and equivalent von Mises stress and strain values were evaluated for implant and prosthetic components. RESULTS: Von Mises stress values for vertical load increased at implant, housing, and insert PEEK for all groups when the length of the implant increased. When oblique load was applied, 3.3 mm diameter implant groups showed maximum von Mises stress values for implants, cortical bone, cancellous bone, and housing among all groups. A minimum stress level for implant was found in D4.1/L8 group. Regarding the insert PEEK, strain values were found to be higher as the diameter of the implant increased both for vertical and oblique loads. Cortical bone showed higher minimum principal stress values as compared to cancellous bone under both loading conditions. CONCLUSIONS: The 3.3 mm diameter implant groups exhibited the highest von Mises stress and strain values for both loading conditions at the implant. The diameter of the implant had a greater impact on stress and strain levels at the implant site compared to length. For vertical loading, stress value increased at implant, housing, and PEEK when the length of the implant increased.

Evaluation of YouTube as an information source for denture care.

STATEMENT OF PROBLEM: Denture cleaning is indispensable to the maintenance of good oral and systemic health for denture users. Nowadays people often consult YouTube about health-related topics, including denture care. However, the quality of the information about denture care presented on YouTube is unknown. PURPOSE: The purpose of this study was to evaluate the usefulness and quality of popular videos about denture care shared by different uploaders on YouTube and to evaluate the demographic characteristics of the videos. MATERIAL AND METHODS: Google Trends showed that "denture cleaning" was the most searched keyword on the topic. This keyword was used to search YouTube videos. Of the 200 most-watched videos, 109 videos were selected for analysis. Included videos were analyzed for their demographic data, including number of views; number of likes, dislikes, and comments; days since upload; duration and number of subscribers; an 8-point usefulness score system, a global quality scale (GQS); video sources; target groups; and primary purposes of the videos. Statistical analyses were conducted by using the Kruskal-Wallis test, post hoc Mann-Whitney U test, Pearson chi-squared test, and Spearman correlation analysis, which was used to investigate the relationship among total content score, GQS score, and video demographics. Cohen kappa statistics was used to measure the reliability of the investigator's evaluations of the videos (α=.05). RESULTS: Based on the usefulness score, 59.6% of the videos were classified as poor, 32.1% as moderate, and 8.2% as good. No statistically significant differences were found among usefulness scores according to the video demographics, except lower GQS score of poor content videos (P<.001). The overall mean ±standard deviation GQS score was 1.92 ±1.0 out of 5. Videos were primarily uploaded (38.5%) from commercial companies. No statistically significant difference was found between video sources and usefulness scores (P>.05). The number of videos with poor content was significantly higher than the number with moderate and good content among the videos primarily intended for the education of health professionals (P<.001). CONCLUSIONS: The majority (59.6%) of YouTube videos on denture care received poor content quality ratings, independent of video demographics. Therefore, YouTube is not suitable as the only source of information on denture care. Dentists and prosthodontists should take more responsibility for enriching the content of video-sharing platforms because this content can affect the behavior of patients and their attitudes about denture care.

Discoloration Behavior of Resin Cements Containing Different Photoinitiators.

The purpose of this study was to evaluate the sorption, solubility, and color stability of amine-free conventional light-cure and dual-cure resin cements and an amine-containing self-adhesive dual-cure resin cement. Sixty specimens were prepared using a light-cure resin cement (Variolink Esthetic LC, Ivoclar Vivadent; VE-LC), a dual-cure resin cement (Variolink Esthetic DC, Ivoclar Vivadent; VE-DC), and a self-adhesive dual-cure resin cement (RelyX U200, 3M ESPE; RXU200). The water sorption and solubility were tested by immersing the specimens in distilled water for 7 days. Kruskal-Wallis test was applied to the data. ΔE values of 1-day and 7-day immersion in black tea were analyzed using one-way analysis of variance followed by Tukey honest significant difference test (n = 10). There was no statistically significant difference among the groups in terms of sorption and solubility. The mean ΔE of RXU200 for the 0/1 and 0/7 days were found to be significantly lower than that of VE-LC and VE-DC (P < .05). ΔE values of the VE-LC and VE-DC groups did not reveal statistical difference. It should be taken into account that discoloration of resin cements remains a problem even with amine-free products.

Effect of Different Light-Curing Modes on Bond Strength of Ceramic Laminate Veneers.

PURPOSE: To investigate whether high-level irradiance and short light exposure times with light-emitting diode (LED) curing units could provide bond strength comparable to halogen lights for ceramic laminate veneers (CLVs). MATERIALS AND METHODS: A total of 160 extracted human maxillary central incisors were prepared to receive CLVs (lithium disilicate) in shades A1 and A3.5. CLVs were luted with light-curing (LC) and dual-curing (DC) resin cements using four protocols: 3 seconds in extra power mode, 8 seconds in high power mode, or 10 seconds in standard mode with an LED unit, or 40 seconds with a conventional halogen light from all aspects (n = 10). Following thermal cycles, shear bond strength test was performed with a universal testing machine. Data were analyzed using one-way analysis of variance and post hoc Tukey test. Failure modes were classified under a stereomicroscope, and data were analyzed using Pearson chi-square test (P = .050). RESULTS: According to the intragroup comparison of different irradiation protocols, the mean shear bond strength of the A1-LC-10 group was found to be significantly higher than that of the A1-LChalogen group (P = .026). Shear bond strength values of the A1-LC-10 group and A3.5-LC-10 group were significantly higher than that of the A3.5-DC-10 group (P = .003). The A3.5-DC-3, A3.5-LC-3, and A1-DC-8 groups revealed the significantly most adhesive failures, and the A1-LC-8 group revealed the most mixed failures (P < .001). CONCLUSION: Both light and dark ceramic shades with LC cement combination responded the best to the standard mode of 10-second exposure time with LED application. However, with conventional halogen light application, the highest bond strength values were obtained with DC cement and light ceramic shade combination.

Effect of Sterilization on Bond Strength and Mechanical Properties of Fiber Posts.

PURPOSE: To determine the effects of two different sterilization methods on the pull-out bond strength, flexural strength, and elastic modulus of glass-fiber posts. MATERIALS AND METHODS: A total of 69 glass-fiber posts were used. The posts were divided into three groups according to applied sterilization method: 1) control, 2) ethylene oxide gas (EOG), and 3) autoclave. The microstructure of three posts from each group was evaluated by SEM and energy-dispersive X-ray spectroscopy (EDS). Thirty glass-fiber posts were used to evaluate pull-out bond strength. The three-point bending test was performed to analyze the flexural strength on another 30 glass-fiber posts. Failure modes were categorized microscopically after the pull-out test. After the three-point bending test, micromorphology at the bending area was examined using SEM. RESULTS: One-way ANOVA indicated no statistically significant differences among the group means in terms of bond strength (p > 0.05), flexural strength (p > 0.05), or elastic modulus (p > 0.05). EDS revealed that the weight percentage of surface oxygen atoms in the EOG- and autoclave-sterilization groups were significantly higher. SEM images were similar. CONCLUSION: The results of this study show that glass-fiber posts can be sterilized either by autoclave or EOG when necessary, without any negative effect on bond strength, flexural strength, or elastic modulus.

Multidisciplinary Treatment of Severe Upper Incisor Root Resorption Secondary to Transposed Canine.

OBJECTIVE: Tooth transposition is a rare dental anomaly that could lead to undesirable side effects on other teeth. This case report aims to describe the multidisciplinary treatment of a patient with a severely resorbed permanent maxillary central incisor due to transposition with the permanent canine. CLINICAL CONSIDERATIONS: A girl aged 13 years and 7 months with a chief complaint of a pink spot on her maxillary left incisor with a slightly erupted tooth above it was referred to our clinic. Her left maxillary canine was transposed to her left central incisor site. The left canine was impacted and had caused severe resorption of the left central incisor root. Her maxillary left canine was substituted for the central incisor after the compulsory extraction of her left central incisor. The canine was prosthetically restored after orthodontic treatment. The results were stable 1 year after treatment had been completed. CONCLUSIONS: Orthodontic treatment in coordination with other dental specialties like prosthodontics, periodontology and oral and maxillofacial surgery can provide functional and esthetic outcome in cases of severely transposed canines. CLINICAL SIGNIFICANCE: This is a rare case of transposition that shows the significant root resorption on the maxillary central incisor due to the ectopic eruption of the canine. Canine substitution for the central incisor was chosen as a treatment plan instead of placing an implant. An esthetic smile and a functional occlusion were established at the end of the treatment. (J Esthet Restor Dent 29:5-12, 2017).

Effect of 3 cements on white spot lesion formation after full-coverage rapid maxillary expander: A comparative in-vivo study.

INTRODUCTION: The aim of this study was to assess the effects of 3 luting agents (glass ionomer cement, compomer, and polycarboxylate cement) on white spot lesion formation in patients with full-coverage bonded acrylic splint expanders. White spot lesion formation was assessed with quantitative light-induced fluorescence. METHODS: Full-coverage rapid maxillary expanders were cemented with glass ionomer cement, compomer, and polycarboxylate cement in groups 1, 2, and 3, respectively. A control group comprised patients who never had orthodontic treatment. Quantitative light-induced fluorescence images taken before and after rapid maxillary expansion treatment were analyzed for these parameters: the percentages of fluorescence loss with respect to the fluorescence of sound tooth tissue (ΔF) and maximum loss of fluorescence intensity in the whole lesion; lesion area with ΔF equal to less than a -5% threshold; and the percentage of fluorescence loss with respect to the fluorescence of sound tissue times the area that indicated lesion volume. RESULTS: All 3 groups showed statistically significantly greater demineralization than the control group. The 3 experimental groups differed from each other in half of the parameters calculated. Teeth in the polycarboxylate group developed the most white spot lesions. CONCLUSIONS: With the highest rate of white spot lesion formation, polycarboxylate cements should not be used for full-coverage bonded acrylic splint expanders. Compomers may be preferred over glass ionomer cements, based on the findings of this study.

White spot lesion formation after treatment with full-coverage rapid maxillary expanders.

INTRODUCTION: The aim of this study was to evaluate whether treatment with full-coverage bonded acrylic splint expanders causes formation of white spot lesions using quantitative light-induced fluorescence. METHODS: The experimental group underwent rapid maxillary expansion (RME) (n = 16; 6 boys, 10 girls; mean age, 14.1 ± 2.2 years), and the control group received no orthodontic treatment (n = 17; 9 men, 8 women; mean age, 20.7 ± 1.1 years). Quantitative light-induced fluorescence images of the RME patients were taken before cementation and after decementation of the appliances. The images of the control group comprised quantitative light-induced fluorescence images taken 3 months apart. Four parameters were calculated for 10 anterior teeth. RESULTS: Between cementation and decementation, statistically significant differences were found in all 4 parameters in the RME group, whereas no significant changes were found in any parameters in the control group. A comparison of the measured parameters between the RME and control groups showed statistically significant differences. CONCLUSIONS: Patients treated with a full-coverage bonded appliance tended to develop more white spot lesions than did the control subjects.

Cytotoxic and genotoxic effects on gingival fibroblasts from static magnetic fields produced by dental magnetic attachments.

OBJECTIVE: To investigate cytotoxic and genotoxic effects of static magnetic field (SMF) produced by dental magnetic attachments on human gingival fibroblasts in vitro. BACKGROUND: Magnetic attachments have numerous roles in dental prosthesis fixation, but few reports evaluate possible biological effects of static magnetic field (SMF) on human gingival tissues, particular genotoxic effects. MATERIALS AND METHODS: The Dyna (500-gr breakaway force) and Steco (173-gr breakaway force) dental magnetic attachments were embedded into autopolymerising acrylic resin in four different configurations each, including single and double magnets. Gingival biopsy was performed on 28 individuals during third molar extraction, and each sample was divided into two pieces for culture under SMF exposure or as a control. In total, seven test and seven control gingival fibroblast cultures were performed for each group resulting in 56 gingival fibroblast cultures. The test culture flasks were placed atop the magnet-embedded resin blocks. After cultures were terminated, mitotic index (MI) and micronucleus (MN) rates were analysed at a p = 0.05 significance level by Wilcoxon's test; intergroup differences were analysed with a Kruskal-Wallis test. RESULTS: There was no significant difference in intragroup or intergroup MI rates. The double Dyna (p = 0.023) and double Steco (p = 0.016) groups had statistically significant intragroup differences in the MN rates. There were no statistically significant differences in MN rates in intergroup analyses. CONCLUSION: In particular, higher magnetic fields from dental magnetic attachments might be toxic genetically to human gingival fibroblasts. However, there is need for further investigations from different aspects to detect any genotoxicity.