In vitro assessment of internal implant-abutment connections with different cone angles under static loading using synchrotron-based radiation.

BACKGROUND: The stability of implant-abutment connection is crucial to minimize mechanical and biological complications. Therefore, an assessment of the microgap behavior and abutment displacement in different implant-abutment designs was performed. METHODS: Four implant systems were tested, three with a conical implant-abutment connection based on friction fit and a cone angle < 12 ° (Medentika, Medentis, NobelActive) and a system with an angulated connection (< 40°) (Semados). In different static loading conditions (30 N - 90º, 100 N - 90º, 200 N - 30º) the microgap and abutment displacement was evaluated using synchrotron-based microtomography and phase-contrast radioscopy with numerical forward simulation of the optical Fresnel propagation yielding an accuracy down to 0.1 µm. RESULTS: Microgaps were present in all implant systems prior to loading (0.15-9 µm). Values increased with mounting force and angle up to 40.5 µm at an off axis loading of 100 N in a 90° angle. CONCLUSIONS: In contrast to the implant-abutment connection with a large cone angle (45°), the conical connections based on a friction fit (small cone angles with < 12°) demonstrated an abutment displacement which resulted in a deformation of the outer implant wall. The design of the implant-abutment connection seems to be crucial for the force distribution on the implant wall which might influence peri-implant bone stability.

Essay III: Adhesive restorative options for restorative space management in the anterior zone with or without orthodontic pretreatment: some clinical considerations and case presentations.

An unfavorable relationship between the form and dimension of the dental arch and the number, dimension, and shape of the existing teeth can pose several esthetic, biologic, and functional problems. In this article, the various restorative options are discussed based on clinical and scientific evidence: Gap closure and substitution of missing teeth: restorative transformation of substituted teeth into homologous teeth with odontoplasty, direct composite, etched pieces or porcelain veneers. Gap opening and tooth replacement with all-ceramic adhesive bridges, including pontic site development. Gap distribution and restorative compensation with direct composite restorations, etched pieces or porcelain veneers. Gap shifting and restorative compensation with all-ceramic adhesive bridges, composite, etched pieces or veneers. Gap compensation by reconstructive compensation without orthodontics. The reconstructive tools including composite restorations, ceramic veneers, and adhesive bridges are discussed, and numerous cases are presented to illustrate the concepts.

The ideal restoration of endodontically treated teeth - structural and esthetic considerations: a review of the literature and clinical guidelines for the restorative clinician.

In restorative dentistry, the non-vital tooth and its restoration have been extensively studied from both its structural and esthetic aspects. The restoration of endodontically treated teeth has much in common with modern implantology: both must include multifaceted biological, biomechanical and esthetic considerations with a profound understanding of materials and techniques; both are technique sensitive and both require a multidisciplinary approach. And for both, two fundamental principles from team sports apply well: firstly, the weakest link determines the limits, and secondly, it is a very long way to the top, but a very short way to failure. Nevertheless, there is one major difference: if the tooth fails, there is the option of the implant, but if the implant fails, there is only another implant or nothing. The aim of this essay is to try to answer some clinically relevant conceptual questions and to give some clinical guidelines regarding the reconstructive aspects, based on scientific evidence and clinical expertise.

Nonvital teeth and porcelain lanminate veneers--a contradiction?

Porcelain laminate veneers are widely accepted as the treatment of choice to noninvasively restore the esthetics and function of anterior teeth, provided there is a sufficient amount of tooth structure to support the reconstruction. However, there are certain esthetic limitations if the underlying tooth structure is discolored, which may occur in cases of nonvital roots. This article describes how to manage this esthetic challenge. Internal bleaching, tooth-colored internal buildups, and preparation guidelines are discussed via clinical case presentations.