Optimization of Tilted Implant Geometry for Stress Reduction in All-on-4 Treatment Concept: Finite Element Analysis Study.

PURPOSE: The aim of this work was a finite element analysis of the effect of a sloped platform in tilted implants in the All-on-4 treatment concept on the level of maximum stresses in compact bone. MATERIALS AND METHODS: Finite element modeling of the stresses at tilted microthread implants with standard and sloped abutment platform under four loading conditions and two levels of osseointegration was performed. RESULTS: The sloped abutment platform in tilted implants positioned at rim bone level resulted in a two to four times reduction of the maximum von Mises stresses in the adjacent cortical bone compared with the standard platform. These stresses were well below the yield stress of the cortical bone. The main importance of the proposed sloped platform in tilted implants is substantial stress reduction in the case of immediate loading. The stress reduction also results in the reduction of the deformation of the framework of the All-on-4 concept. CONCLUSION: The suggested modification of the slope of the abutment platform on tilted implants is recommended as a technically simple and highly effective solution for significant reduction of maximum stresses in the cortical bone around the implant.

Clinical Management of Two Root Resorption Cases in Endodontic Practice.

Root resorption is a pathological process involving loss of hard dental tissues. It may occur as a consequence of dental trauma, orthodontic treatment, and bleaching, and occasionally it accompanies periodontal disease. Although the mechanism of resorption process is examined in detail, its etiology is not fully understood. Wide open apical foramen is more difficult to manage and the root canal may often overfill. In this report we present two cases of root resorption and describe means for its clinical management. We conclude that useful measure of a success or failure in managing root resorption is the persistence of the resorption process. It is a clear sign of an active ongoing inflammatory process and shows the clinical need for retreatment.

Fracture Resistance of Endodontically Treated Maxillary Premolars Restored by Various Direct Filling Materials: An In Vitro Study.

The aim of this study is to compare the effect of various restorative materials on fracture resistance in maxillary premolars. Premolars (n = 64) with no restorations or cracks were selected. MOD cavities were prepared considering the buccolingual width to be equal to half of the intercuspal distance. The specimens were randomly divided into 8 groups, 8 specimens each: group A intact teeth, group B unfilled cavity, group C composite made by oblique layering technique, group D composite with 2 mm cusp coverage, group E bulk-filled posterior composite, group F glass-ionomer, group G amalgam, and group H composite with proximal boxes. The specimens were subjected to an axial compression load with the mean values of fracture resistance in group A: 1289 N, group B: 181.75 N, group C: 445.38 N, group D: 645.88 N, group E: 355.13 N, group F: 352.00 N, group G: 191.38 N, and group H: 572.00 N. There was no significant difference between groups B and G, between C and D, E, and F, and between group D and H. All other measurements were statistically significant. We conclude that composite restoration with cusp coverage is the most ideal nonprosthetic solution for endodontically treated teeth. Cusp coverage increases the fracture resistance compared to the conventional cavity design.

Monozygotic twins with idiopathic internal root resorption: A case report.

This study presents the first case of internal root resorption in monozygotic twins. Genetic factors have been implicated in the development of root resorption lesions. The link between interleukin (IL)-1 gene polymorphism and root resorption had been reported. However, these studies have involved external root resorption. Twin healthy 17 year old Caucasian sisters were diagnosed with internal root resorption in their upper left central incisor. Neither had a history of orofacial trauma and neither had received orthodontic treatment. The presence of IL-1beta+C3953 allele is the sign of predisposed susceptibility to an exaggerated inflammatory response, including a limited feedback mechanism as a consequence of IL-1RN mutation. Most investigators agree that the listed polymorphism presents a significantly higher risk for development of pathological resorption. These were thought to be cases of true idiopathic resorption as none of the other factors related to root resorption was found.