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WETENSCHAP:

De keuzes die we maken om bepaalde materialen te gebruiken, berusten uiteraard op ervaringen uit de praktijk maar ook op de resultaten uit gedegen onderzoek. Wij houden u graag op de hoogte van recente literatuur/onderzoeksmateriaal met betrekking tot onze materialen en methoden.

  Aanbevolen literatuur:

• Esthetic Rehabilitation in fixed prosthodontics
  door: Mauro Fradeani
  volume 1: esthetic analysis
  volume 2: prosthetic treatment

• Interdisciplinary treatment planning
  editor: Michael Cohen

  Onderwerpen:

        - ALL-ON-4
        - PROCERA ALUMINA / ZIRCANIA
        - PY-TZP

  ALL-ON-4

All-on-4 immediate-function concept with Brånemark System implants for completely edentulous maxillae: a 1-year retrospective clinical study.
Department of Surgery and Prosthodontics, Clinica Maló, Lisbon, Portugal. clin.res.dep@clinicamalo.pt

BACKGROUND:
Immediate implant function has become an accepted treatment modality for fixed restorations in totally edentulous mandibles, whereas experience from immediate function in the edentulous maxilla is limited.

PURPOSE:
The purpose of this study was to evaluate a protocol for immediate function (within 3 hours) of four implants (All-on-4, Nobel Biocare AB, Göteborg, Sweden) supporting a fixed prosthesis in the completely edentulous maxilla.

MATERIALS AND METHODS:
This retrospective clinical study included 32 patients with 128 immediately loaded implants (Brånemark System TiUnite, Nobel Biocare AB) supporting fixed complete-arch maxillary all-acrylic prostheses. A specially designed surgical guide was used to facilitate implant positioning and tilting of the posterior implants to achieve good bone anchorage and large interimplant distance for good prosthetic support. Follow-up examinations were performed at 6 and 12 months. Radiographic assessment of the marginal bone level was performed after 1 year in function.

RESULTS:
Three immediately loaded implants were lost in three patients, giving a 1-year cumulative survival rate of 97.6%. The marginal bone level was, on average, 0.9 mm (SD 1.0 mm) from the implant/abutment junction after 1 year.
 
CONCLUSION:
The high cumulative implant survival rate indicates that the immediate function concept for completely edentulous maxillae may be a viable concept.

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  PROCERA ALUMINA / ZIRCANIA

Influence of cementation technique on fracture strength and leakage of alumina all-ceramic crowns after cyclic loading.
Department of Preventive and Restorative Schiences, University of Pennsylvania School of Dental Medicine, Philadelphia, PA 19104, USA. mblatz@dental.upenn.edu

OBJECTIVE:
To compare in vitro the influence of 3 cementation techniques on leakage and fracture strength of alumina all-ceramic crowns after cyclic loading in an artificial chewing simulator.

METHOD AND MATERIALS:
Forty-eight extracted molars were mounted in a way that simulates natural tooth mobility. Crowns (Procera Alumina, Nobel Biocare) were fabricated and inserted with either conventional cementation with zinc phosphate cement without pretreatment (group ZOP); cementation with a universal adhesive resin cement without pretreatment (group HYB); or adhesive bonding with composite resin after pretreatment of the tooth (dentin bonding agent) and the crown (airborne-particle abrasion and a special ceramic priming agent containing adhesive monomers that bond to metal-oxide ceramics) (group ADH). All specimens were stored in artificial saliva and subjected to 1.2 million load cycles in a dual-axis chewing simulator (Willytec). Eight specimens per group were subjected to compressive load until failure, while the remaining 8 specimens were stained and sectioned for measuring of dye penetration. One-way ANOVA and Tukey HSD were used for statistical analyses (alpha = .05).

RESULTS:
Cementation techniques were significantly different (P = .009) in regard to mean load at failure. Fracture strength was significantly greater for ADH (mean load at fracture, 2,782 +/- 419 N) as compared to HYB (1,980 +/- 270 N) or ZOP (1,788 +/- 242 N). All groups differed significantly for leakage values (P < .001), with ADH showing the lowest mean leakage (0.04 +/- 0.07 mm), followed by HYB (0.96 +/- 0.16 mm) and ZOP (2.44 +/- 0.19 mm). CONCLUSION: Cementation technique affects fracture strength and leakage of all-ceramic molar crowns. Fracture strengths were well above natural chewing forces for all cementation methods. However, adhesive bonding significantly increased fracture strength and improved marginal seal of alumina crowns.

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  PY-TZP

OBJECTIVES:
(1) To synthesize 3mol% yttria-stabilized zirconia (3Y-TZP) powders via coprecipitation route, (2) to obtain zirconia ceramic specimens, analyze surface characteristics, and mechanical properties, and (3) to compare the processed material with three reinforced dental ceramics. METHODS: A coprecipitation route was used to synthesize a 3mol% yttria-stabilized zirconia ceramic processed by uniaxial compaction and pressureless sintering. Commercially available alumina or alumina/zirconia ceramics, namely Procera AllCeram (PA), In-Ceram Zirconia Block (CAZ) and In-Ceram Zirconia (IZ) were chosen for comparison. All specimens (6mmx5mmx5mm) were polished and ultrasonically cleaned. Qualitative phase analysis was performed by XRD and apparent densities were measured on the basis of Archimedes principle. Ceramics were also characterized using SEM, TEM and EDS. The hardness measurements were made employing Vickers hardness test. Fracture toughness (K(IC)) was calculated. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey's test (alpha=0.05).

RESULTS:
ANOVA revealed that the Vickers hardness (p<0.0001) and fracture toughness (p<0.0001) were affected by the ceramic materials composition. It was confirmed that the PA ceramic was constituted of a rhombohedral alumina matrix, so-called alpha-alumina. Both CAZ and IZ ceramics presented tetragonal zirconia and alpha-alumina mixture of phases. The SEM/EDS analysis confirmed the presence of aluminum in PA ceramic. In the IZ and CAZ ceramics aluminum, zirconium and cerium in grains involved by a second phase containing aluminum, silicon and lanthanum were identified. PA showed significantly higher mean Vickers hardness values (H(V)) (18.4+/-0.5GPa) compared to vitreous CAZ (10.3+/-0.2GPa) and IZ (10.6+/-0.4GPa) ceramics. Experimental Y-TZP showed significantly lower results than that of the other monophased ceramic (PA) (p<0.05) but it showed significantly higher fracture toughness (6.0+/-0.2MPam(1/2)) values when compared to the other tested ceramics (p<0.05).

SIGNIFICANCE:
The coprecipitation method used to synthesize zirconia powders and the adopted ceramic processing conditions led to ceramics with mechanical properties comparable to commercially available reinforced ceramic materials.