Correlation between abutment angulation and off-axial stresses on biomechanical behavior of titanium and zirconium implants in the anterior maxilla: A three-dimensional finite element analysis study.

AIM: The aim of the present study was to evaluate the stress distribution around the titanium and zirconium implant with different abutment angulations in the anterior maxilla to off-axial load. SETTING AND DESIGN: In vitro - Comparative study. MATERIALS AND METHODS: Two models of titanium and zirconium implants (4 mm × 13 mm) and abutment with at 0°, 15°, 25° angulations were modeled to replace missing right central incisor using three-dimensional finite element analysis. A bite force of 178 N was applied on the lingual fossa of crowns at an angle of 120° off-axial to the long axis of implant. STATISTICAL ANALYSIS USED: Nil. RESULTS: Von Misses stresses observed are as follows: (1) at the implant-bone interface Ti 0 (8.31 MPa), Zr 0 (8.57 MPa), Ti 15 (83.59 MPa), Zr 15 (98.07 MPa), Ti 25 (197.8 MPa), and Zr 25 (265.77 MPa); (2) at the implant-abutment interface Ti 0 (5.90 MPa), Zr 0 (6.45 MPa), Ti 15 (19.13 MPa), Zr 15 (19.32 MPa), Ti 25 (38.65 MPa), and Zr 25 (38.26 MPa); and (3) within superstructure Ti 0 (3.11 MPa), Zr 0 (5.02 MPa), Ti 15 (6.17 MPa), Zr 15 (5.02 MPa), Ti 25 (8.15 MPa), and Zr 25 (6.131 Mpa). CONCLUSION: Stress behavior of titanium and zirconium implant with tested abutment angulation at implant-abutment interface and within the superstructure was similar, except at implant-bone interface.

Retraction Note to: Stem Cell Mediated Tooth Regeneration: New Vistas in Dentistry.

[This retracts the article DOI: 10.1007/s13191-011-0110-9.].

Accuracy of two face-bow/semi-adjustable articulator systems in transferring the maxillary occlusal cant.

CONTEXT: The precision of an arbitrary face-bow in accurately transferring the orientation of the maxillary cast to the articulator has been questioned because the maxillary cast is mounted in relation to arbitrary measurements and anatomic landmarks that vary among individuals. AIM: This study was intended to evaluate the sagittal inclination of mounted maxillary casts on two semi-adjustable articulator/face-bow systems in comparison to the occlusal cant on lateral cephalograms. MATERIALS AND METHODS: Maxillary casts were mounted on the Hanau and Girrbach semi-adjustable articulators following face-bow transfer with their respective face-bows. The sagittal inclination of these casts was measured in relation to the fixed horizontal reference plane using physical measurements. Occlusal cant was measured on lateral cephalograms. SPSS software (version 11.0, Chicago, IL, USA) was used for statistical analysis. Repeated measures analysis of variance and Tukey's tests were used to evaluate the results (P < 0.05). RESULTS: Comparison of the occlusal cant on the articulators and cephalogram revealed statistically significant differences. Occlusal plane was steeper on Girrbach Artex articulator in comparison to the Hanau articulator. CONCLUSION: Within the limitations of this study, it was found that the sagittal inclination of the mounted maxillary cast achieved with Hanau articulator was closer to the cephalometric occlusal cant as compared to that of the Girrbach articulator. Among the two articulators and face-bow systems, the steepness of sagittal inclination was greater on Girrbach semi-adjustable articulator. Different face-bow/articulator systems could result in different orientation of the maxillary cast, resulting in variation in stability, cuspal inclines and cuspal heights.

Stem cell mediated tooth regeneration: new vistas in dentistry.

The generation of dental structures and/or entire teeth in the laboratory depends upon the manipulation of stem cells and requires a synergy of all cellular and molecular events that finally lead to the formation of tooth-specific hard tissues, dentin and enamel. This review focuses on the different sources of stem cells that have been used for making teeth in vitro and their relative efficiency. Embryonic, post-natal and adult stem cells were assessed and proved to possess an enormous regenerative potential, but their application in dental practice is still limited due to various parameters that are not yet under control such as the high risk of rejection, cell behaviour, long tooth eruption period, appropriate crown morphology and suitable colour. Nevertheless, the development of biological approaches for dental reconstruction using stem cells is promising and remains one of the greatest challenges in the dental field.