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.
- PROCERA ALUMINA / ZIRCANIA
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.
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.
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.
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.
The high cumulative implant survival rate
indicates that the immediate function concept for completely
edentulous maxillae may be a viable concept.
PROCERA ALUMINA / ZIRCANIA
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.
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
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).
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
Y-TZP ceramic processing from coprecipitated powders: A comparative
study with three commercial dental ceramics.
Materials Science and Technology Center, Nuclear and Energy Research
Institute, IPEN-CNEN/SP, São Paulo, Brazil.
(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).
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).
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.