Purpose: This numerical study examined the efficacy and challenges of using resonance frequency analysis to identify the stability of implants placed in mandibles. The study also examined the feasibility of using angular stiffness as an alternative index to quantify dental implant stability in mandibles. Materials and methods: A finite element model consisting of a mandible, an implant, an abutment, and a bonding layer (between the implant and the mandible) was created in commercially available software ANSYS. The level of osseointegration was modeled by varying the stiffness of the bonding layer. Three sets of boundary conditions were imposed on the mandible: fixed, rotationally free, and rotationally restrained. Three implant locations were studied: central, premolar, and molar positions. An alternative abutment mimicking SmartPeg and eight different implant lengths were also included. A modal analysis and a static analysis were conducted to calculate resonance frequencies and angular stiffness, respectively. Results: Two types of vibration modes were found. One was jawbone modes, for which the mandible deformed significantly but not the bonding layer. Resonance frequencies of the jawbone modes were not sensitive to the level of osseointegration. The other was implant modes, for which the bonding layer deformed significantly but not the mandible. Among multiple implant modes obtained, only one was trackable as the level of osseointegration increased. The resonance frequency of the trackable implant mode was very sensitive to the implant location as well as boundary conditions, but not as much to the level of osseointegration. In contrast, angular stiffness was sensitive to the level of osseointegration but not as much to boundary conditions. Conclusion: The efficacy of using resonance frequency analysis to quantify the stability of a dental implant is questionable. Its high sensitivity to implant locations and boundary conditions as well as its low sensitivity to the level of osseointegration cause huge uncertainties in correlating measured resonance frequencies to implant stability. Angular stiffness is a much more reliable indicator because of its high sensitivity to the level of osseointegration and low sensitivity to boundary conditions. Schlagwörter: angular stiffness, dental implant, finite element analysis, resonance frequency analysis, stability

Purpose: This study assessed the ability of resonance frequency measurements to differentiate the stability of implants with different lengths and diameters, and in different densities of bone. Another objective was to identify an alternative parameter capable of quantifying dental implant stability, thus facilitating greater sensitivity for efficacious detection of compromised or failing implants. Materials and Methods: Implants of two different diameters (4 and 5 mm) and six different lengths were individually placed in synthetic bone blocks of three different densities (15, 40/20, and 40 pounds per cubic foot) in combination with two different abutments (short and tall) to evaluate their stability. Resonance frequency measurements were obtained via Osstell ISQ and experimental modal analysis. The resonance frequency measurements were further confirmed via finite element analysis using commercially available software ANSYS. Results: Resonance frequencies measured via Osstell ISQ and experimental modal analysis did not change with respect to the length of the implants. The finite element analysis also confirmed the measured results. Finite element analysis simulations further indicated that angular stiffness at the neck of the implant (ie, the base of the abutment) varied considerably with respect to the implant length and diameter. Moreover, the calculated angular stiffness was independent of the type of abutment used. Conclusion: The results obtained from resonance frequency analyses did not accurately represent dental implant stability. Changes to implant length and diameter did not affect resonance frequencies. In contrast, angular stiffness at the neck of the implant represented a superior index for quantifying dental implant stability. It not only successfully differentiated stability of implants of both varying lengths and diameters, but also produced quantitative data that were independent of the type of abutments used. Schlagwörter: angular stiffness, dental implant, experimental modal analysis, finite element analysis, natural frequency, stability

Anterior restorations represent a great challenge for both the clinician and dental technician. Long-term provisional restorations can be used to test a new restorative design and to improve the predictability of the definitive restoration with regard to shape, shade, occlusion, and soft tissue interface. To improve the clinical outcome and reduce costs, a new treatment strategy was developed. Teeth were restored with long-term provisional crowns fabricated from a polymer material using a computer-aided design/computer-assisted manufacture (CAD/ CAM) system. Definitive all-ceramic restorations fabricated by the same CAD/ CAM system were cemented as duplicates of the individualized provisional crowns after 3 months.

The amount of tooth structure removed for various innovative and conventional preparation designs for fixed prosthodontics was quantified. Four Typodont resin teeth representing maxillary and mandibular premolars and molars were prepared in various abutment designs: adhesive, box (A2); adhesive, wing and groove (A3); mesioocclusal or distoocclusal inlay; mesio-occlusodistal inlay (I3); mesio-occlusodistal onlay; partial crown; half crown (only molars); complete crown, 0.8-mm circumferential tapered chamfer (F1); complete crown, 1.0-mm circumferential rounded shoulder; and complete crown, 1.4- mm axial reduction facial shoulder, 0.7-mm lingual chamfer (F3). After tooth preparation (10 per group), the root was separated from the anatomic crown at the cementoenamel junction. Removal of tooth structure was measured by gravimetric analysis in a high-precision balance. Preparations A3 and F3 were assigned as abutments for metal-supported restorations, whereas all other preparations were used for all-ceramic restorations. When the mean structure removal of all teeth tested was compared, the adhesive and inlay abutments were the least invasive preparation designs, ranging from approximately 5.5% (A2) to 27.2% (I3) tooth structure removal. Complete crowns required the most invasive preparations, ranging from 67.5% (F1) to 75.6% (F3) tooth structure removal. The tooth structure removal required for F3 retainers was almost 14 times greater than for an A2 preparation. Tooth structure removal was also influenced by the morphology of the tooth. The first comprehensive tooth preparation design classification system was introduced. The measurement system used in this study provides an accurate method of quantifying tooth structure removal for fixed prosthodontic preparations. The innovative preparation designs studied conserved significant amounts of tooth structure, yielding a better prognosis for the restored tooth.

Purpose: The aim of the study was to compare results after 1 and 3 years when single crowns supported by CerAdapt (test) ceramic abutments or CeraOne (control) titanium abutments were loaded. Materials and Methods: The material was divided into two groups: in group A, 69 (34 test, 35 control) abutments/crowns from all involved clinics were followed for 1 year; and in group B, 20 (10 test, 10 control) abutments/crowns from one of the clinics were followed for 3 years. Results: No implant failed, giving a cumulative success rate of 100% for the implants. Two CerAdapt abutments in group A fractured, giving a cumulative success rate of 93% for the CerAdapt and 100% for the CeraOne abutments after 1 year. No abutment failed in group B, giving a cumulative success rate of 100% both for the CerAdapt and the CeraOne abutments between 1 and 3 years. The CerAdapt fractures might have been due to the fact that the abutments were impaired through too-extensive preparation and/or had been exposed to a too-high bending moment. Almost no marginal bone loss was recorded, indicating a stable bone situation both at CerAdapt and CeraOne abutments on single-tooth implants. Healthy conditions, with a relatively stable level of the periimplant mucosa in relation to the abutment/crown, were recorded for soft tissues both at CerAdapt and CeraOne abutments. Both clinicians and patients rated the esthetic result as excellent for practically all cases. Conclusion: The results demonstrate the esthetic possibilities and the safety of single-tooth replacement when accepted treatment concepts are followed and documented components are used. The tested abutments worked well, although the fractured CerAdapt abutments indicate that ceramic abutments are more sensitive to handling procedures than the titanium abutments.

1999 wurde IPS Empress 2 (Ivoclar AG, SL) als neues Vollkeramiksystem zur Herstellung von Einzelkronen und dreigliedrigen Brücken im Frontzahnbereich bis zum ersten Prämolaren vorgestellt. Das Empress-2-Keramikmaterial zeichnet sich durch eine völlig neue chemische Zusammensetzung und Kristallstruktur aus, obwohl es mit dem gleichen Verfahren wie das ursprüngliche Material, dem leucitarmierten IPS Empress, im Pressglaskeramik-Verfahren unter Hitze hergestellt wird. Basierend auf den Ergebnissen klinischer Studien werden Konstruktionsrichtlinien von Brückenkonstruktionen sowie Indikationsbereiche von Empress-2-Brücken vorgestellt Schlagwörter: Lithiumdisilikat-Gerüststruktur, Vollkeramiksystem, Brückenkonstruktionen, Zwischengliedverbinder (-konnektor)

The relationship of stress generation upon placement of cement-retained or screw-retained implant restorations has not been thoroughly investigated. Passivity of fit and marginal discrepancies of screw- and cement-retained implant fixed partial denture (FPD) designs were determined using a photoelastic model of a partially edentulous posterior mandibular arch with 3 screw-type implants. Buccal and lingual marginal openings, measured with a traveling microscope before cementation or screw tightening, revealed no statistical difference in adaptation between designs. Screw tightening caused a reduction in marginal opening (changes significant, P .05). The opening with the cemented FPDs was similar before and after cementation. Photoelastic evaluation of the FPDs showed that cement-retained FPDs exhibited a more equitable stress distribution than did their screw-retained counterparts. Schlagwörter: cement-retained, custom abutment, implant biomechanics, implant prosthesis, loading, passive fit, screw-retained, telescopic crown

This Study evaluated the effect of porcelain surface treatment on the shear bond strength of composite resin to various porcelains and porcelain combinations. A variety of feldspathic porcelains with low and medium alumina content were tested. Porcelain/composite resin samples were stored in 37° C water, thermocycled 1,000 times, and tested in shear. A 3-minute etching using hydrofluoric acid significantly increased the bond strength of most of the feldspathic porcelains with low and medium alumina content. Silane application to all types of etched porcelain had no significant effect on bond strength.