Investigating the effect of abutment-implant connection type on abutment screw loosening in a dental implant system using finite element methods.

Background. The most common problem associated with dental implants is the abutment screw loosening. This research aimed to investigate the effect of the type of connection on screw loosening, using a finite element method (FEM). Methods. Periosave system and different types of the implant-abutment connection were used for modeling. After being measured, CAD files were modeled using CATIA software and imported to the ANSYS analysis software, and the model was loaded. Results. A force of 100 N was applied at 0.1 second, and no force was applied at 0.42 second. The screw head deformation at 0.1 and 0.42 seconds was 8 and 3.8 µm, and 7.6 and 2.8 µm at morse taper and octagon dental implant connections, respectively. The displacement rate of the internal surface of the abutment at 0.1 and 0.42 seconds was 10.7 and 8.4 µm, and 5.7 and 5.6 µm in the octagon and morse taper dental implant connections, respectively. The displacement of the implant suprastructure-abutment interface from the screw head at 0.1 and 0.42 seconds was 9 and 7 µm, and 7 and 6 µm in the morse taper and octagon dental implant connections, respectively. At intervals of 0 to 0.1 seconds and 0.6 to 0.8 seconds, the octagon connection was separated at the maximum screw head displacement and the internal part of the abutment, but the morse taper connection did not exhibit any separation. In the above time intervals, the results were similar to the maximum state in case of the minimum displacement of the screw head and the internal part of the abutment. Conclusion. Screw loosening is less likely to occur in the morse hex connection compared to the octagon connection due to the lack of separation of the screw from the internal surface of the abutment.

Activation Toll-Like Receptor7 (TLR7) Responsiveness Associated with Mitogen- Activated Protein Kinase (MAPK) Activation in HIOEC Cell Line of Oral Squamous Cell Carcinoma.

STATEMENT OF THE PROBLEM: Oral squamous cell carcinoma is the most common oral malignancy. Toll-like receptor (TLR) activation led to alterations in the levels of mRNA encoding the TLR accountable for recognizing the inducing agonist and cross-regulation of other TLR. PURPOSE: The purpose of this study is determination of mitogen-associated protein kinase (MAPK) activation in human immortalized oral epithelial cell (HIOEC) line via up regulating of TLR7. MATERIALS AND METHOD: expression of TLR7 was measured in HIOEC and normal cells by quantitative real-time polymerase chain reaction (qRT-PCR) and samples were calibrated by ß-actin. RESULTS: Western blot analysis discovered high expression of TLR7 and MAPK in HIOEC cell lines. TLR7 was over-expressed in HIOEC cell line. Imiquimod-induced expression of interleukin (IL)-6, IL-8, and vascular endothelial growth factor (VEGF) was inhibited by TLR7 siRNA in HIOEC cells as determined by reverse transcription polymerase chain reaction (RT-PCR). Mean fluorescence intensity of nuclear p38 expression was determined in HIOEC cell lines (p< 0.05). RT-PCR analysis of IL-6, IL-8, and VEGF mRNA expression in HIOEC cells stimulated with imiquimod (1 µg/ml) for indicated time points. CONCLUSION: TLR7 is functionally over-expressed in HIOEC cell line of oral squamous cell carcinoma and development of resistance to cisplatin in human oral squamous cell carcinoma might occur through the mechanism involving activation of TLR7 and its dependent signaling pathway.

Quercetin Decreases Th17 Production by Down-Regulation of MAPK- TLR4 Signaling Pathway on T Cells in Dental Pulpitis.

STATEMENT OF THE PROBLEM: Quercetin is a pharmacological flavonoid that can inhibit high mobility group box1 (HMGB1) protein, a non-histone nuclear protein that is implicated in inflammation. Th17 cells are important cells in the pathogenesis of inflammation. Pulpitis is the inflammation of dental pulp, which usually is accompanied by pain. Quercetin may alleviate this inflammation. PURPOSE: The current study aimed to compare blocking of HMGB1 function and stimulation of HMGB1 function with quercetin and investigate the effects of the blockage on T helper 17 (Th17) cells and mitogen-activated protein kinase Toll-like receptor 4 (MAPK-TLR4) signaling pathway. MATERIALS AND METHOD: T cells isolated from the pulp involved with pulpitis and the normal pulp were cultured. The cells suspensions were plated in 6-wells culture plates and stimulated with 0.5 µg/ml of HMGB1 for 2, 4, 8, and 12 hours. For blocking TLR4, 10 µg/ml rabbit anti-human TLR4 antibody was added 1 hour before treatment with HMGB1. RESULTS: The level of these cytokines decreased; moreover, western blot data showed that quercetin could decrease MAPK signaling pathway by means of inhibition of HMGB1 on T cells. The results showed the reduction of TLR4 pathway and Th17 cell polarization. CONCLUSION: Our results indicated that the levels of IL-17, IL-33, and IL-6 in supernatants from patients' cultured T cells were increased after stimulation with HMGB-1 following employing quercetin. It also could inhibit MAPK signaling pathway, which subsequently could decrease Th17 production and IL-17. Quercetin could decrease pro-inflammatory cytokines and IL-17 production.

A time-saving method for transferring occlusal vertical dimension and centric relation of complete denture to a full arch implant prosthesis.

AIM: This clinical report describes a time-saving recording procedure for implant prosthesis. BACKGROUND: In implant prosthodontics, a few procedures have been suggested to record jaw relationships. Record bases with occlusion rims supported by healing abutments, or screw retained bases are the conventional methods used for mounting definitive implant casts in the articulator. CONCLUSION: The method described in this article reduces the chair time and is comfortable for both the patient and clinician. CLINICAL SIGNIFICANCE: In this article, a chair side technique is presented for articulating the definitive implant casts that maintains the established OVD and CR of the patient's existing complete dentures.

Rehabilitation of a partial nasal defect with facial prosthesis: a case report.

>Malignancies of the midface result in cosmetic deformities that make maxillofacial prosthesis as an integral part of the treatment plan. Facial defects can be devastating in their impact on physical structure and function of the affected individual, leading to potentional compromises in quality of life. Reconstruction of nasal defects is a challenge for the prosthodontist because of esthetic and retention problems associated with the facial prosthesis. This paper reports the rehabilitation of a partial nasal defect caused by basal cell carcinoma treatment using a nasal prosthesis made with silicone elastomers and mechanical and anatomical retentive aids. The patient had no problem with the prosthesis, except for a partial loss of extrinsic coloration in the two-year follow-up.