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IPS e.max for All-Ceramic Restorations: Clinical Survival and Success Rates of Full-Coverage Crowns and Fixed Partial Dentures

Materials

February 2019
12(3):462

DOI:10.3390/ma12030462

License
CC BY 4.0

Authors:

Silvia Brandt

Goethe University Frankfurt

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The IPS e.max system by Ivoclar Vivadent, offering a variety of products and indications, is widely used for all-ceramic restorations. We analyzed the clinical track record of these products in daily clinical practice, associating their restorative survival rate with various parameters to define recommendations for long-term stability. A total of 1058 full-coverage crowns and fixed partial dentures (FPDs) were evaluated retrospectively over up to 66.48 (37.05 ± 18.4) months. All were made of IPS e.max Press, IPS e.max CAD, IPS e.max Ceram or IPS e.max ZirPress and had been delivered by a private dental practice within three years. Uses not recommended by the manufacturer were also deliberately included. The five-year cumulative survival was 94.22% (i.e., 94.69% or 90.58% for glass-ceramic crowns or FDPs and 100% or 90.06% for zirconia-based crowns or FDPs). Significantly superior outcomes emerged for conventional vs. adhesive cementation and for vital vs. non-vital abutment teeth, but not for recommended vs. non-recommended uses. Caution is required in restoring non-vital teeth, but the spectrum of recommended uses should generally be reconsidered and expanded, given our finding of high survival and success rates for IPS e.max ceramics, even for uses not currently recommended by the manufacturer.

. Distribution of restorative materials across the 1058 restorations.

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Kaplan–Meier survival curve for crown restorations.

…

. Patient demographics, restoration types and cementation methods.

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Kaplan–Meier survival curve for FPD restorations.

…

. Five-year Kaplan-Meier survival rates.

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Article

IPS e.max for All-Ceramic Restorations: Clinical

Survival and Success Rates of Full-Coverage Crowns

and Fixed Partial Dentures

Silvia Brandt 1, * , Anna Winter 2, Hans-Christoph Lauer 1, Fritz Kollmar 3,

Soo-Jeong Portscher-Kim 1and Georgios E. Romanos 4,5

1Department of Prosthodontics, Center for Dentistry and Oral Medicine (Carolinum), Johann Wolfgang

Goethe University, Theodor-Stern-Kai 7, 60596 Frankfurt, Germany; h.c.lauer@em.uni-frankfurt.de (H.-C.L.);

s.kim@med.uni-frankfurt.de (S.-J.P.-K.)

2Department of Prosthodontics, Center for Dentistry, Oral Medicine, Julius Maximilian University,

Pleicherwall 2, 97070 Würzburg, Germany; e-winter_a3@ukw.de

3Private Practice Dr. Fritz Kollmar, Friedrich-Ebert-Straße 55, 34117 Kassel, Germany; ﬁtz@dreskollmar.de

4Department of Oral Surgery and Implant Dentistry, Center for Dentistry and Oral Medicine (Carolinum),

Johann Wolfgang Goethe University, Theodor-Stern-Kai 7, 60596 Frankfurt, Germany;

georgios.romanos@stonybrook.edu

5Germany and Department of Periodontology, School of Dental Medicine, Stony Brook University, Stony

Brook, NY 11794, USA

*Correspondence: hajjaj@med.uni-frankfurt.de; Tel.: +49-69-6301-83617; Fax: +49-69-6301-3711

Received: 17 December 2018; Accepted: 29 January 2019; Published: 2 February 2019





Abstract:

The IPS e.max system by Ivoclar Vivadent, offering a variety of products and indications,

is widely used for all-ceramic restorations. We analyzed the clinical track record of these products in

daily clinical practice, associating their restorative survival rate with various parameters to deﬁne

recommendations for long-term stability. A total of 1058 full-coverage crowns and ﬁxed partial

dentures (FPDs) were evaluated retrospectively over up to 66.48 (37.05

18.4) months. All were

made of IPS e.max Press, IPS e.max CAD, IPS e.max Ceram or IPS e.max ZirPress and had been

delivered by a private dental practice within three years. Uses not recommended by the manufacturer

were also deliberately included. The ﬁve-year cumulative survival was 94.22% (i.e., 94.69% or

90.58% for glass-ceramic crowns or FDPs and 100% or 90.06% for zirconia-based crowns or FDPs).

Signiﬁcantly superior outcomes emerged for conventional vs. adhesive cementation and for vital vs.

non-vital abutment teeth, but not for recommended vs. non-recommended uses. Caution is required

in restoring non-vital teeth, but the spectrum of recommended uses should generally be reconsidered

and expanded, given our ﬁnding of high survival and success rates for IPS e.max ceramics, even for

uses not currently recommended by the manufacturer.

Keywords:

IPS e.max system; full-contour crown restorations; ﬁxed partial dentures; survival rate;

success rate

1. Introduction

Patients increasingly know about the availability of dental materials that are both esthetically

pleasing and biocompatible [

]. All-ceramic restorations combine high biocompatibility with good

optical and material properties [

], thus meeting both patient expectations and clinical requirements [

This is why this particular segment of the dental market has been growing for some decades [

All-ceramic restorations may be considered an evidence-based treatment modality, given a large

number of available studies [

–

]. All-ceramic crowns have been shown

in vitro

to be a good alternative

Materials 2019,12, 462; doi:10.3390/ma12030462 www.mdpi.com/journal/materials

Materials 2019,12, 462 2 of 10

to metal-ceramic crowns [

] and clinical results to the same effect were provided by Etman and

Woolford [9].

On closer examination, however, many studies have limitations such as narrow indications or

small case numbers [

–

]. Another problem is strict inclusion and exclusion criteria, resulting in

the overrepresentation of stable periodontal health and good oral hygiene [

–

] while turning a

blind eye to cases involving temporomandibular dysfunction [

–

]. Hence, the qualiﬁcations that

often get attached to the study of restorations have a way of removing the cases studied from daily

clinical practice, where clinicians need to consider a variety of patient-speciﬁc risk factors whenever

they plan and deliver dental restorations. Sometimes they conclude that pushing beyond the spectrum

of indications for a given material is the way to go and, with the patient’s consent, will proceed to

implement this plan.

There is a need for these clinicians to select from a multitude of ceramic materials that are intended

for different indications, require different procedures and come with different recommendations for

retention. IPS e.max (Ivoclar Vivadent, Ellwangen, Germany) is a lithium-disilicate system encompassing

a comprehensive range of products for diverse uses and processing techniques. Being a glass-ceramic

material, lithium silicate combines the advantages of permitting, although not requiring, adhesive

luting for retention [

] in addition to offering maximum esthetics [

] and high fracture resistance [

Thanks to these beneﬁts, it is a material widely used in clinical practice.

Given the increasing use of all-ceramic restorations in clinical practice, it is only reasonable

to investigate them under real-life clinical conditions as well. To ﬁll the aforementioned gaps left

by the limiting inclusion and exclusion criteria of previous studies, we designed a retrospective

investigation into the survival rates of all-ceramic IPS e.max restorations with no exclusion criteria

applied, speciﬁcally including uses of the material not currently recommended by its manufacturer.

Another goal was to analyze how the restorative failures involved were related to speciﬁc clinical

parameters, thus helping to avoid errors and improve survival in daily clinical practice.

2. Materials and Methods

All restorations here evaluated had been delivered in a private practice in Germany between June

2011 and June 2014. The baseline totality of eligible restorations was 1101 full-coverage crowns and

ﬁxed partial dentures (FPDs) made from IPS e.max Press, IPS e.max CAD, IPS e.max Ceram or IPS

e.max ZirPress (Ivoclar Vivadent). All these restorations met our requirement of having been fabricated

in the same dental laboratory in accordance with the manufacturer’s instructions. For evaluation in

this study, we additionally required that the patients complied with follow-up visits.

Given that 43 of these 1101 restorations were not followed up in the years to come, a total

of 1058 restorations eventually met all inclusion criteria for evaluation. Since our intention was to

evaluate the IPS e.max system under real-life conditions, we applied no exclusion criteria, thus specifically

including uses of the material not currently recommended by its manufacturer. Table 1gives an overview

of how the various restorative products were distributed across the 1058 evaluable restorations.

Table 1. Distribution of restorative materials across the 1058 restorations.

Materials n Distribution

Total 1058 100.00%

IPS e.max Press 861 81.38%

Zirconia framework + IPS e.max

ZirPress 87 8.22%

IPS e.max CAD 50 4.73%

Zirconia framework + IPS e.max

Ceram 30 2.84%

IPS e.max Press + IPS e.max

Ceram 27 2.55%

IPS e.max Ceram 3 0.28%

Materials 2019,12, 462 3 of 10

For statistical analysis, general information (age, gender, anonymized patient ID) and additional

treatment-related details were entered in spreadsheet software (Microsoft Excel). The patients were

divided into different groups according to their age at the time of incorporation (

≤

30 years, 31–50 years,

51–70 years,

≥

70 years). The parameters thus recorded included: abutment topography; type

of support by implant and or natural abutment(s); vitality or non-vitality of natural abutments;

nature of the opposing dentition; restorative design; restorative material; use for a recommended

or non-recommended indication; luting technique; technician in charge of fabrication; interval from

delivery to latest follow-up; as well as occurrence and management of complications and failures.

Any complete loss of a restoration was deﬁned as a restorative failure inﬂuencing the survival

curve of the time-to-event analysis. Kaplan–Meier probabilities of survival time could then be

estimated, based on the number of failures documented throughout the observation period, for any

of the crowns and FPDs considered. Aside from these survival rates, success rates were obtained

separately by performing the respective Kaplan–Meier calculations based on all complications rather

than on failures only. The aforementioned parameters were analyzed by log-rank testing for signiﬁcant

associations with restorative survival.

All statistical calculations were performed with BiAS (Biometric Analysis of Samples) software

(rev. 11.05; Epsilon Verlag, Nordhastedt, Germany) and differences were considered signiﬁcant at

p≤0.05

. Approval for the study was obtained from the institutional review board (reference number:

17/2015).

3. Results

3.1. Baseline Data

The 1058 restorations meeting all inclusion criteria were evaluable over an observation period

of up to 66.48 (37.05

18.4) months. They included 922 single or splinted crowns and 136 FPDs in

368 (206 female and 162 male) patients aged 57.84 years at the time of delivery. Maxillary restorations

accounted for 58.57% (540/922) of the crowns and 50.74% (69/136) of the FPDs. Adhesive cementation

were used in 53.31% and conventional cementation in 46.69% of cases. Table 2summarizes pertinent

patient data, the distribution of the 1058 evaluable restorations by type (crowns or FDPs) and jaw

(maxilla or mandible) and the cementation methods used.

Table 2. Patient demographics, restoration types and cementation methods.

Patients Evaluable Restorations

Total (n) 368 Total (n) 1058

Female/male (n) 206/162 Full-coverage crowns (n) 922

Mean age (years) 57.84 Maxilla (n) 540

Cementation Mandible (n) 382

Total (n) 1058

Fixed partial dentures (n)

136

Adhesive (n) 564 Maxilla (n) 69

Conventional (n) 494 Mandible (n) 67

3.2. Non-Recommended Uses and Restoration Subtypes

The manufacturer currently recommends IPS e.max Press and IPS e.max CAD for laminate/occlusal

veneers, inlays/onlays, partial/full-coverage crowns, hybrid abutments/hybrid abutment crowns and

for FPDs not extending beyond second premolars [

]. IPS e.max ZirPress and IPS e.max Ceram are

used for framework veneering. Non-recommended uses accounted for 158 of the 1058 restorations

here investigated, including FPDs supported by teeth (n = 32), implants (n = 9) or combinations of

both (n = 2); splinted crowns supported by teeth (n = 101), implants (n = 9) or both (n = 4); and one

tooth-supported single crown with a cantilever unit (n = 1). Table 3gives a detailed listing of the

restoration subtypes included in our evaluable overall sample of 1058 restorations.

Materials 2019,12, 462 4 of 10

Table 3. Detailed listing of the evaluable crowns and ﬁxed partial dentures (FPDs).

Restorations n Distribution

All restorations 1058 100.00%

Tooth-supported single crowns 615 58.13%

Implant-supported single crowns 156 14.74%

Tooth-supported splinted crowns 126 11.91%

Tooth-supported FPDs 83 7.84%

Implant-supported FPDs 44 4.16%

Other 121 1.98%

Implant-supported splinted

crowns 13 1.23%

1For example, tooth/implant-supported or cantilever FPDs (9)/crowns (12).

3.3. Overall Success and Survival

A total of 35 restorations (3.3%) failed during the observation period, including 27 crowns and

eight FDPs. The cumulative success rates were 97.36% (12 months), 96.32% (24 months), 90.37%

(48 months) and 87.99% (60 months). Based on complete losses, the survival rates illustrated by the

cumulative Kaplan–Meier curve were 98.83% (12 months), 98.41% (24 months), 96.93% (36 months),

95.52% (48 months) and 94.22% (60 months). Based on only the restorations used for non-recommended

indications, ﬁve restorations (three crowns and two FPDs) had failed—all of these being failures

concerning IPS e.max Press as a restorative material. The survival rate of non-recommended uses

scarcely differed (and hence not signiﬁcantly) from recommended uses (p= 0.85). Table 4gives an

overview of the ﬁve-year survival rates broken down by restoration types and the two major restorative

materials involved.

Table 4. Five-year Kaplan–Meier survival rates.

Restorations n Survival

Cumulative (all restorations) 1058 94.22%

All full-coverage crowns 922 94.90%

Recommended uses 807 94.51%

Lithium-disilicate crowns 1768 94.69%

Veneered zirconia-based crowns 39 100.00%

Non-recommended uses 115 94.95%

All ﬁxed partial dentures 136 89.44%

Recommended uses 93 88.47%

Lithium-disilicate FDPs 143 90.58%

Veneered zirconia-based FDPs 50 90.06%

Non-recommended uses 43 95.35%

1Made from IPS e.max products (CAD, IPS, Press with e.Ceram veneers or Ceram).

3.4. Results for the Crown Restorations

Based on the 922 crown restorations, the survival rate was found to vary signiﬁcantly with gender

and age, being higher in male than female patients (log-rank test: p= 0.005) and within the age group

of 31–50 years (log-rank test: p= 0.0043). Signiﬁcant reductions in survival were seen for non-vitality

compared to the vitality of abutment teeth (log-rank test: p= 0.0063) and for adhesive compared to

conventional cementation (log-rank test: p= 0.0003). The 115 crowns used for non-recommended

indications exhibited a survival rate almost identical to the crowns used for recommended indications

(see Table 4). Figure 1illustrates the Kaplan–Meier survival curve for all 922 crown restorations

(ﬁve-year survival: 94.90%). Table 5lists the different causes of all 27 failures.

Materials 2019,12, 462 5 of 10

Table 5. Reasons for biological or technical failure of crown restorations.

Causes of Failure n Distribution

All full-coverage crowns

922

100.00%

Total number of failures 27 2.93%

Fracture of the restoration 5 0.54%

Apical osteitis 5 0.54%

Loss of retention 4 0.43%

Hypersensitivity 4 0.43%

Pre-prosthetic core fracture 3 0.33%

Chipping 2 0.22%

Root fracture 2 0.22%

Loss of implant 1 0.11%

Secondary caries 1 0.11%

Materials 2019, 12 FOR PEER REVIEW 5

Table 5. Reasons for biological or technical failure of crown restorations.

Causes of Failure n Distribution

All full-coverage crowns 922 100.00%

Total number of failures 27 2.93%

Fracture of the restoration 5 0.54%

Apical osteitis 5 0.54%

Loss of retention 4 0.43%

Hypersensitivity 4 0.43%

Pre-prosthetic core fracture 3 0.33%

Chipping 2 0.22%

Root fracture 2 0.22%

Loss of implant 1 0.11%

Secondary caries 1 0.11%

Figure 1. Kaplan–Meier survival curve for crown restorations.

Results for the FPD Restorations

Based on the 136 FPDs, adhesive cementation was again found to reduce the survival rate

compared to non-adhesive cementation (log-rank test: p

0.0318). Unlike with the crown restorations,

however, log-rank testing did not yield any significant differences for any of the other parameters

based on FPDs. Non-recommended uses concerned 43 FPDs. They included the failure of two tooth-

supported FPDs, but the resultant five-year Kaplan–Meier survival rate was actually (though not

significantly) higher for the non-recommended than for the recommended uses (95.35% versus

88.40%; see Table 4). Figure 2 illustrates the Kaplan–Meier survival curve for the 136 FPDs (five-year

survival: 89.44%). Table 6 lists the eight failures involved.

Table 6. Reasons for biological or technical failure of FPD restorations.

Causes of Failure n Distribution

All fixed partial dentures (FPDs) 136 100.00%

Total number of failures 8 5.88%

Endodontic complications 3 2.21%

Ceramic chipping/fracture 2 1.47%

Root fracture 2 1.47%

Preprosthetic core fracture 1 0.74%

Figure 1. Kaplan–Meier survival curve for crown restorations.

3.5. Results for the FPD Restorations

Based on the 136 FPDs, adhesive cementation was again found to reduce the survival rate

compared to non-adhesive cementation (log-rank test: p= 0.0318). Unlike with the crown restorations,

however, log-rank testing did not yield any signiﬁcant differences for any of the other parameters

based on FPDs. Non-recommended uses concerned 43 FPDs. They included the failure of two

tooth-supported FPDs, but the resultant ﬁve-year Kaplan–Meier survival rate was actually (though

not signiﬁcantly) higher for the non-recommended than for the recommended uses (95.35% versus

88.40%; see Table 4). Figure 2illustrates the Kaplan–Meier survival curve for the 136 FPDs (ﬁve-year

survival: 89.44%). Table 6lists the eight failures involved.

Table 6. Reasons for biological or technical failure of FPD restorations.

Causes of Failure n Distribution

All ﬁxed partial dentures (FPDs)

136

100.00%

Total number of failures 8 5.88%

Endodontic complications 3 2.21%

Ceramic chipping/fracture 2 1.47%

Root fracture 2 1.47%

Preprosthetic core fracture 1 0.74%

Materials 2019,12, 462 6 of 10

Materials 2019, 12 FOR PEER REVIEW 6

Figure 2. Kaplan–Meier survival curve for FPD restorations.

4. Discussion

Our results demonstrate the high survival and success rates of IPS e.max materials over up to 60

months. They do diverge somewhat from previous reports. Yang et al. [17], in a similar study design,

reported a cumulative survival rate of 96.6% for 6855 restorations made of IPS e.max Press over five

years. Part of the explanation for our different five-year survival of 94.22% might be that we

investigated not only IPS e.max Press, but the whole IPS e.max range of products. Also, that previous

group conducted their study under defined conditions linked to a military university hospital. The

present study, by contrast, used patient files on record in a private practice. Given that no exclusion

criteria were applied, more of these restorations were bound to be affected by patient-specific risk

factors such as poor oral hygiene or periodontal problems. Also, we deliberately included uses of

materials not currently recommended by the manufacturer.

In 2017, Rauch et al. [12] reported an 87.6% survival rate of lithium-disilicate single crowns after

six years, which is lower than the rate presented here despite fewer risk factors due to defined

exclusion criteria. One should, however, bear in mind the longer observation period in that study

and its low case number of 25 crowns. These crowns were fabricated and inserted in both a private

practice and a prosthetic university department, which incidentally yielded a (though not

significantly) higher complication rate for the university-fabricated restorations. Our 100% survival

rate for zirconia-based single crowns is consistent with another very high survival rate of 98.5%

reported by Miura et al. [22]. Despite the provenance of our data (private practice) and our inclusion

of non-recommended uses, our 90.58% survival rate for glass-ceramic FPDs is virtually identical to

the 90.6% reported by Yang et al. [17], although both of these rates are lower than the 100% five-year

survival for three-unit FPDs reported by Kern et al. [7], which again might be due to the different

local scenarios involved.

Note, however, that all previous studies analyzed restorations conforming to the manufacturer’s

recommendations. For example, Clausen et al. [23] investigated single crowns made of IPS e.max

Press and Obermeier et al. [24] investigated implant-supported crowns made of IPS e.max CAD. The

present study, by contrast, also includes 158 non-recommended uses. While five of these restorations

failed (all of them made of IPS e.max Press), a significant difference between recommended and non-

recommended uses was not observed. Despite this non-significant difference and the limited number

of cases involved, it is nevertheless interesting to note that the non-recommended restorations

actually showed higher survival rates. As a departure from previous studies, it is therefore fair to

suggest that the range of indications listed by the manufacturer should be reconsidered and

expanded where appropriate.

However, one point to consider in comparing our results to those of previous studies is that

consistent definitions of ‘complication’ and ‘failure’ have often been lacking. Different causes of

failure emerged. Technical complications included ceramic defects in the form of full-blown fractures

Figure 2. Kaplan–Meier survival curve for FPD restorations.

4. Discussion

Our results demonstrate the high survival and success rates of IPS e.max materials over up to

60 months. They do diverge somewhat from previous reports. Yang et al. [

], in a similar study

design, reported a cumulative survival rate of 96.6% for 6855 restorations made of IPS e.max Press

over ﬁve years. Part of the explanation for our different ﬁve-year survival of 94.22% might be

that we investigated not only IPS e.max Press, but the whole IPS e.max range of products. Also,

that previous group conducted their study under deﬁned conditions linked to a military university

hospital. The present study, by contrast, used patient ﬁles on record in a private practice. Given that no

exclusion criteria were applied, more of these restorations were bound to be affected by patient-speciﬁc

risk factors such as poor oral hygiene or periodontal problems. Also, we deliberately included uses of

materials not currently recommended by the manufacturer.

In 2017, Rauch et al. [

] reported an 87.6% survival rate of lithium-disilicate single crowns after

six years, which is lower than the rate presented here despite fewer risk factors due to deﬁned exclusion

criteria. One should, however, bear in mind the longer observation period in that study and its low

case number of 25 crowns. These crowns were fabricated and inserted in both a private practice and

a prosthetic university department, which incidentally yielded a (though not signiﬁcantly) higher

complication rate for the university-fabricated restorations. Our 100% survival rate for zirconia-based

single crowns is consistent with another very high survival rate of 98.5% reported by

Miura et al.

[

Despite the provenance of our data (private practice) and our inclusion of non-recommended uses,

our 90.58% survival rate for glass-ceramic FPDs is virtually identical to the 90.6% reported by

Yang et al.

[

], although both of these rates are lower than the 100% ﬁve-year survival for three-unit

FPDs reported by Kern et al. [7], which again might be due to the different local scenarios involved.

Note, however, that all previous studies analyzed restorations conforming to the manufacturer’s

recommendations. For example, Clausen et al. [

] investigated single crowns made of IPS e.max Press and

Obermeier et al. [

] investigated implant-supported crowns made of IPS e.max CAD. The present study,

by contrast, also includes 158 non-recommended uses. While ﬁve of these restorations failed (all of

them made of IPS e.max Press), a signiﬁcant difference between recommended and non-recommended

uses was not observed. Despite this non-signiﬁcant difference and the limited number of cases

involved, it is nevertheless interesting to note that the non-recommended restorations actually showed

higher survival rates. As a departure from previous studies, it is therefore fair to suggest that the range

of indications listed by the manufacturer should be reconsidered and expanded where appropriate.

However, one point to consider in comparing our results to those of previous studies is that

consistent deﬁnitions of ‘complication’ and ‘failure’ have often been lacking. Different causes of failure

emerged. Technical complications included ceramic defects in the form of full-blown fractures or

Materials 2019,12, 462 7 of 10

chipping. Events of this kind have been reported previously to constitute a frequent complication

of all-ceramic single crowns, as evidenced in a 2017 review article by Aldegheishem et al. [

] and

supported by Monaco et al. [

]. Consistent with statements by Reich et al. [

], we also noted failures

resulting from endodontic complications such as hypersensitivity or apical osteitis, as well as from

secondary caries of abutment teeth.

We also demonstrated a statistically signiﬁcant association between survival rate and cementation

type. Both conventional and adhesive cementation can be used with the IPS e.max system.

Adhesive bonding is meant to increase the fracture resistance of restorations [

–

] but is highly

technique-sensitive. Perfect drying/isolation [

] and appropriate etchability of the residual tooth

structure are required. Also, the quality of the bond is amenable to surface conditioning, as has been

demonstrated by applying different methods of cleaning to restorations after etching [

]. Although

Kern et al. [

] and Esquivel-Upshaw et al. [

] observed no difference to this effect, conventional

cementation emerged as superior in the present study. Again, one might implicate our different

study design in this ﬁnding, considering that the restorations we analyzed were inserted in a private

practice, where changing clinicians and practice-related circumstances may have played a role. Yet,

on the ﬂip side of this argument, Rauch et al. [

] reported in their study a higher complication rate

for restorations delivered at a German university hospital than for those delivered by dentists in

private practice.

Another statistically signiﬁcant ﬁnding of the present study was the lower survival rate of crowns

retained on non-vital than on vital teeth. Huettig et al. [

] and Fedorowicz et al. [

] previously

reported a similarly increased rate of complications for non-vital abutment teeth, suspecting that these

were biologically inferior to vital abutments. On another conﬁrmatory note, Toman et al. [

] reported

that the survival rate of crowns was signiﬁcantly reduced on non-vital teeth and suggested that any

restoration of non-vital teeth with lithium-disilicate crowns must be subject to rigorous case selection.

It should be considered that all restorations in our study had been fabricated from products

of the same system (IPS e.max) and manufacturer (Ivoclar Vivadent). A comparable material by

another manufacturer could not be included for comparison because no such material was available

until very recently. This is over and above the fact that such a comparison would not have been

readily feasible, given a clinical background of retrospectively evaluating data from a private practice.

Similar study protocols in which speciﬁc materials were evaluated without comparison have been used

previously [

]. Most importantly, the opportunity to assess one system as used in daily clinical

practice across a wide spectrum of indications clearly outweighed the shortcoming that no different

products were available for comparison.

The present study was designed as a non-experimental, analytical, retrospective cohort study on

the basis of patient ﬁles archived in a private dental practice. Given this design, the correctness and

completeness of the existing documentation had to be taken for granted. While the possibility of any

issues in this regard should not be dismissed, this is a caveat inherent in most retrospective studies [

Given a large data base and a balanced distribution between maxillary and mandibular restorations,

our approach did turn out to be appropriately suited to evaluating the clinical track record of the IPS

e.max system and potential modifying factors.

As a case in point, the documentation available to us indicated for each restoration the dental

laboratory where it had been fabricated. This allowed us to include only restorations known to have

been fabricated by the same laboratory under the supervision of the same master dental technician,

thus ensuring consistent fabrication standards, which can contribute greatly to favorable complication

rates [

]. The detailed patient records also allowed us to consider the fabrication procedures in

evaluating the outcomes. Previous reports on the survival rates of lithium-disilicate restorations

were also based on standardized fabrication processes, but the samples they considered were heavily

qualiﬁed [

–

]. Given our different study objective, which was to verify a real-life track record in

daily clinical practice, we deliberately minimized criteria in compiling our sample. Also, our survival

Materials 2019,12, 462 8 of 10

rates should be considered keeping in mind that any non-recommended uses of the studied material

were speciﬁcally included.

Any complications that occurred were recorded during annual recall appointments, although

the retrospective study design did imply very dissimilar follow-up times and observation periods,

the latter ranging up to 66.48 months (mean 37.05

18.4 months). While this may appear short

compared with a follow-up time of up to 10 years in other studies, it has been shown repeatedly that

most complications with IPS e.max restorations occur in the initial phase after insertion [

Hence, the observation period does seem to be adequately long for a conclusive evaluation of the

material under study.

The present study produced a multitude of results. Thanks to a high case number and a wide

spectrum of products and uses, we were able to address different questions that normally would have

been addressed in separate studies. The fact that we deliberately refrained from exclusion criteria

and used data that had accumulated in daily clinical practice enabled us to review the outcomes

with IPS e.max products in real life. We could only achieve this by accepting risk factors such as

bruxism, poor oral hygiene, periodontal problems, or non-recommended uses with their implications

for long-term success. The high survival rates we obtained despite this background paints a favorable

picture of the clinical track record of IPS e.max in everyday practice. The fact that these rates are highly

consistent with the available literature on the subject underscores the conclusiveness of our ﬁndings.

Also, a research focus on implant-borne IPS e.max restorations would be useful, given the increasing

popularity of all-ceramic restorations for implants and that previous studies on the subject, while

showing favorable material properties and survival rates, have covered limited samples or observation

periods [37,38].

5. Conclusions

Within the limitations of this study, the use of IPS e.max may be recommended in clinical

practice. Caution should be exercised in restoring non-vital teeth and in selecting luting techniques.

High survival rates were obtained even for non-recommended uses of IPS e.max prompted by

patient-speciﬁc considerations. Hence, the spectrum of indications for these products should generally

be reconsidered and expanded where appropriate. Although we reviewed previous reports and ﬁlled

some of the gaps they left, there is a need for further investigations similar in case number and design.

Author Contributions:

Conceptualization, S.B.; methodology, S.B.; software, S.B.; validation, H.-C.L., A.W. and

S.B.; formal analysis, S.B., A.W. and S.-J.P.-K.; investigation, F.K., S.-J.P.-K., H.-C.L. and G.E.R.; resources, S.B. and

F.K.; data curation, F.K. and G.E.R.; writing—original draft preparation, A.W.; writing—review and editing, S.B.,

G.E.R. and H.-C.L.; visualization, S.B.; supervision, G.E.R. and H.-C.L.; project administration and ﬁnal editing of

the manuscript, S.B.

Conﬂicts of Interest: The authors declare no conﬂict of interest.

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Desmistificando O Uso Do Dissilicato De Lítio E De Zircônias Estabilizadas Na Fase Cúbica Em Restaurações Monolíticas: Uma Revisão De Literatura

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Jan 2023

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Jan 2025
BMC Oral Health

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Aug 2024

Purpose Secondary caries around ceramic restorations is the most common reason for the replacement of fixed dental prostheses (FDPs). Therefore, it is important to examine the susceptibility of different ceramic materials to biofilm formation. This study aimed to evaluate biofilm development and associated roughness and color alterations in three lithium disilicate ceramics: Emax CAD (EC), Emax Press (EP), and LiSi Press (LP). Materials and Methods Streptococcus mutans biofilms were grown on the three ceramics ( n = 10 per group) for 7 days. Surface roughness values and color alteration were assessed before and after the biofilm using a non‐contact profilometer and spectrophotometer, respectively. Biofilm growth was evaluated using colony‐forming units (CFUs) and scanning electron microscope (SEM) images. The data were analyzed using one‐way ANOVA and Tukey tests. Results There was a significant ( p ≤ 0.001) growth of S. mutans colonies on EC (6.75 ± 0.56) and EP (6.72 ± 0.54) specimens compared to LP, which showed no biofilm growth. The change in average surface roughness (∆ R a , nm) was significantly lower ( p < 0.001) in the EC specimens (0.029 ± 0.003) compared to the EP (0.055 ± 0.012) and LP (0.041 ± 0.010). When the changes in the R v and R t values were investigated, no significant difference was observed among the groups. Following the biofilm challenge, the change in color (∆ E 00 ) was significantly lower ( p = 0.005) in the LP group (1.68 ± 1.45) compared to the EC group (3.89 ± 1.50) and no significant difference was observed between the EP group (2.74 ± 1.01) and the other two ceramics ( p ≥ 0.05). Conclusion LP ceramics exhibited superior resistance to S. mutans biofilm formation and associated changes in surface roughness and color compared to the Emax CAD and Emax Press ceramics. These findings suggest that the LiSi Press material may be more favorable to mitigate the risk of secondary caries.

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Article

Feb 2025
OPER DENT

Objective This study evaluated the influence of two types of glass ionomer-based luting agent on the clinical performance of metal-free zirconia crowns. Methods and Materials Thirty participants received two full crown restorations in either anterior or posterior teeth, in a split-mouth design. After tooth preparation, impressions with addition-cured silicone were made and casts were obtained. The casts were scanned and 3Y-TZP zirconia copings (Ceramill ZI - Amann Girrbach) were milled using a CAD/CAM system. Glass ceramic (IPS E.max Ceram, Ivoclar Vivadent) was used to create the crown shape. For each participant, one crown was cemented using a conventional glass ionomer (GIC - Meron, Voco), while the other received a resin-modified glass ionomer cement (RMGIC - Meron Plus QM, Voco). The restorations were evaluated by two calibrated examiners after seven days, one year, and two years. The parameters at each evaluated time were analyzed by the Fisher exact test (α=0.05). Results At two years postoperatively, 24 participants attended the recall, and 46 (76.67%) restorations were evaluated. No fractures or secondary caries were diagnosed. Minimal marginal staining was verified in both cements. During the follow-up period, only two anterior crowns cemented with conventional glass ionomer showed loss of retention. No loss of retention was detected in posterior crowns. Conclusion After two years of intraoral service, the crowns cemented with either conventional glass ionomer cement or resin-modified glass ionomer presented acceptable and similar clinical performance for all parameters analyzed in both anterior and posterior teeth.

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Jan 2025

In this case study, an all-ceramic (Emax) crown and a post and core restoration are used to successfully treat external inflammatory root resorption (EIRR) in a mandibular molar. A 21-year-old male patient was diagnosed with EIRR and hypercementosis after presenting with pain and significant damage to his lower right first molar. The patient chose a post and core restoration over extraction and implant placement due to budgetary constraints. Endodontic retreatment, fiber post cementation, core buildup, and Emax crown placement were all part of the treatment. At the one-year follow-up, the patient had a healed periapical region, healthy gingiva, and sound tooth structure. In managing EIRR cases, this case study emphasizes the importance of meticulous treatment planning and execution, focusing on selecting the best course of action for the long-term stability and health of the affected tooth. Both the patient's overall dental health and the expertly crafted restoration contributed to the favorable outcome.

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Article

Dec 2024

Background Zirconia-reinforced lithium disilicate (ZLD) is a promising material for esthetic dental restorations due to its strength, translucency, and color stability. However, its durability under accelerated aging conditions needs further investigation. The present in vitro study evaluated the effect of UV accelerated aging on the translucency and color stability of ZLD at varying thicknesses, using IPS e.max Press (LD) as a reference. Methods Seventy-two samples were divided into two groups: high translucent (HT) Vita Ambria (ZLD) and IPS e.max Press (LD) (n=36, each). Each group was further subdivided into four thicknesses: 0.5, 1.0, 1.5, and 2.0 mm (n=9). The samples were fabricated, polished, and subjected to UV weathering for 384 hours, simulating one year of clinical service. Translucency and color changes were assessed using a spectrophotometer. Data were analyzed using SPSS 20, with independent t-test, paired t-test, and one-way ANOVA at a significance level of P≤0.05. Results Vita Ambria exhibited significantly higher translucency before and after aging compared to IPS e.max press at all thicknesses (P=0.000). In both materials, translucency decreased when the thickness increased (P=0.000), observed before and after UV aging. Vita Ambria also displayed a greater color change (ΔE=2000) compared to IPS e.max press across all thicknesses (P=0.000). Conclusion ZLD exhibited higher translucency than LD before and after accelerated artificial aging, indicating that the accelerated aging process adversely impacted the optical properties of the tested material. However, LD demonstrated superior color stability.

Comparative Invitro Testing of the Tensile Bond Strength Under Artificial Aging Between Different Lithium Disilicate Ceramics to Composite Substrate: A Novel Methodology

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Full-text available

Aug 2024

Objective The purpose of this study is to compare the tensile bond strength values to composite substrate pre- and post-aging between IPS E.max CAD and Initial LiSi. Methods The study utilized four blocks of IPS E.max CAD LT/B1 C14 (Ivoclar Vivadent, Liechtenstein, Germany) (referred to as E) and four blocks of Initial LiSi LT/B1 (GC, Tokyo, Japan) (referred to as L). These blocks were milled to produce 76 ceramic bars measuring 2 mm × 2 mm × 10 mm (E = 38, L = 38/n = 19). After acid etching with hydrofluoric acid (BISCO, Schaumburg, IL, USA) and silane application (BIS-SILANE, BISCO), the specimens were embedded in putty (Express STD, 3M, Decatur, AL, USA) to create a mold for the resin cement (RelyX U200, 3M). Subsequently, one group of each brand underwent mechanical tensile testing (E0 and L0), while the other groups were subject to tensile testing after artificial aging involving 500 thermal cycles between 5 and 55°C (E5 and L5). The mean tensile strength for each group (E0, E5, L0, and L5) was determined using the Brown-Forsythe one-way ANOVA and Tamhane’s post hoc tests. Results Initial LiSi showed a superior pre-aging mean (11.7 MPa). However, both materials had identical post-aging means (7.6 MPa). There were no statistically significant differences, except between the dependent Initial LiSi groups (L0-L5). Most failure modes were mixed (cohesive cement and adhesive). There were no cohesive failures on the cement side except in three specimens of Initial LiSi post-aging. Conclusion The tested conditions have shown that Initial Lisi exhibited the highest pre-aging mean; however, it exhibited inferior bond stability under aging conditions compared to IPS E.max CAD. Analyzing the microstructure before and after aging may provide insights into the greater decrease in bond strength observed in the Initial LiSi specimens.

Mechanical performance of cement- and screw-retained all-ceramic single crowns on dental implants

Article

Full-text available

Mar 2018
CLIN ORAL INVEST

Objectives: This in-vitro study was performed to compare the contact wear, fracture strength and failure mode of implant-supported all-ceramic single crowns manufactured with various fabrication and fixation concepts. Materials and methods: Fifty dental implants (Conelog Ø 4,3mm/L11mm, Camlog Biotechnologies AG) were embedded and treated with all-ceramic molar single-crowns. Three groups received hand-layered zirconia crowns (IPS e.max Ceram/ IPS e.max ZirCAD, Ivoclar Vivadent AG): CZL (cement-retained zirconia-based layered) group crowns were cemented conventionally, SZL (screw-retained zirconia-based layered) group crowns were screw-retained, MZL (modified zirconia-based layered) group crowns showed a different coping design with screw retention. The specimens of SST (screw-retained sintering-technique) and SFL (screw-retained full-contour lithium-disilicate) group were CAD/CAM (Computer-aided design/computer-aided manufacturing) fabricated in the sintering technique (IPS e.max ZirCAD/IPS e.max CAD, Ivoclar Vivadent AG) and full-contour of lithium disilicate (IPS e.max CAD, Ivoclar Vivadent AG) respectively and screw-retained. All specimens underwent artificial aging, load until failure and a scanning electron microscopy (SEM) analysis. The received data were statistically compared (one-way ANOVA; Student-Newman-Keuls test; Mann-Whitney U-test) at a significance level of 5%. Results: Mouth-motion fatigue testing caused two abutment fractures (SST group and SZL group) and two chipping events (CZL group). Specimens of MZL group showed statistically significant less contact wear compared to the other groups (p<0.001). There was no statistical difference between the groups in terms of the maximum fracture load. SEM-analysis showed a more homogenous structure and surface of CAD/CAM fabricated specimens towards manually veneered components. Conclusions: The mode of retention did not influence the fracture resistance but the failure patterns of the specimens. CAD/CAM milled lithium-disilicate crowns seemed to be a preserving factor for dental implants. Clinical relevance: The mode of retention and veneering influences the mechanical performance of implant-supported single crowns.

Clinical evaluation of zirconia-based all-ceramic single crowns: an up to 12-year retrospective cohort study

Article

Full-text available

Mar 2018
CLIN ORAL INVEST

Objectives: This study aims to investigate the incidence of clinical complications with tooth-supported zirconia-based all-ceramic single crowns and identify pertinent risk parameters. Materials and methods: A retrospective cohort study (May 2004 to April 2016) utilizing clinical records of patients receiving yttrium-oxide-partially stabilized zirconia (Y-TZP)-based all-ceramic crowns placed at Tohoku University Hospital was performed. The length of time of treatment success (complication event-free) and restoration survival (including minor complication events and remaining clinically functional) were estimated using Kaplan-Meier analysis. Multilevel survival analysis was used to identify risk factors. Results: One hundred thirty-seven crowns were evaluated (mean follow-up time, 7.0 years). A total of 21 crowns experienced at least one complication with fracture of veneering ceramic being the most common (16 crowns). Estimated success and survival rates at 5 years (96.9 and 98.5%, respectively) decreased at 10 years to 62.1 and 67.2%, respectively. The risk of complications was significantly higher for molar crowns compared to anterior crowns (p < 0.01). A significant association of complications with metal antagonist restorations was shown by univariate analysis (p < 0.01). Conclusions: Given the study limitations, Y-TZP single crowns placed on anterior teeth demonstrated encouraging clinical results over a period of up to 10 years. However, there is a substantial risk of complications with posterior teeth within 10 years of restoration placement. Clinical relevance: Treatment with zirconia-based all-ceramic crowns for molar teeth with metal antagonist occlusion should be undertaken with caution.

Chair-side generated posterior monolithic lithium disilicate crowns: clinical survival after 6 years

Article

Full-text available

Jul 2017
CLIN ORAL INVEST

Objectives The objective of this prospective clinical study was to evaluate the clinical performance of chair-side generated monolithic lithium disilicate crowns after 72 months. Materials and methodsForty-one posterior full contour crowns made of lithium disilicate ceramic were inserted in 34 patients with a chair-side CAD/CAM technique. One crown per patient was randomly selected for evaluation at baseline, 6, 12, 24, 36, 48, 60 and 72 months according to the modified US Public Health Service criteria. ResultsAfter a mean examination time of 73.2 months (SD ± 1.7 months), 25 crowns were available for re-examination. Within the observation period, three failures occurred due to one crown fracture after 2.9 years, an abutment fracture after 6.0 years, and one severe endodontic problem after 6.1 years. One lithium disilicate crown showed a loss of retention after 2 years but could be reinserted. There were two events of caries below the crown margin, one after 24 and another one after 48 months. Both teeth received cervical adhesive composite fillings. Two abutment teeth changed their sensibility perception from positive to negative within the first 13 months. The failure-free rate was 87.6%, and the complication-free rate was 70.1% after 6 years according to the Kaplan-Meier analysis. Conclusions Due to the fact that there was only one severe technical complication and the severe biological complications were in a normal range, the clinical performance of monolithic lithium disilicate crowns in the posterior region was completely satisfying. Clinical relevanceThe chair-side application of monolithic lithium disilicate crowns can be recommended.

Marginal Adaptation, Gap Width, and Fracture Strength of Teeth Restored With Different All-Ceramic Vs Metal Ceramic Crown Systems: An in Vitro Study

Article

Full-text available

Sep 2016

ABSTRACT This study evaluated marginal adaptation before and after thermomechanical (TCML) loading, gap width and fracture strength of all-ceramic single crowns, as compared to porcelain-fused-to-metal (PFM). Thirty extracted premolars were prepared with a round shoulder of 1.0 mm depth. Specimens were restored with zirconia–ceramic (Group 1), lithium disilicate (Group 2) and metal–ceramic single crowns (Group 3). The replica of each sample was observed with a scanning electron microscope (SEM) to evaluate the crown–cement (c–c) and tooth–cement interface (t–c). After TCML, perfect margins decreased to 91.3% (c–c) and 93.9% (t–c) in Group 1, 94.6% (c–c) and 96.0% (t–c) in Group 2 and 73.5% (c–c) and 53.1% (t–c) in Group 3. The mean fracture strengths were 654.8 ± 98.1 N for Group 1, 551.3 ± 127 N for Group 2 and 501.43 ± 110.1 N for Group 3. All-ceramic systems could substitute for metal–ceramic crowns, but chipping of veneering ceramics, especially in zirconia-based crowns, should be investigated.

In vitro performance and fracture resistance of CAD/CAM-fabricated implant supported molar crowns

Article

Full-text available

May 2017
CLIN ORAL INVEST

Objectives The aim of this study is to investigate the performance and fracture resistance of different CAD/CAM ceramic and composite materials as implant- or tooth-supported single crowns with respect to the clinical procedure (screwed/bonded restoration). Materials and methods One hundred twenty crowns were fabricated on implants or human molar teeth simulating (a) chairside procedure ([CHAIR] implant crown bonded to abutment), (b) labside procedure ([LAB] abutment and implant crown bonded in laboratory, screwed chairside), and (c) reference ([TOOTH] crowns luted on human teeth). Four materials were investigated: ZLS (zirconia-reinforced lithium silicate ceramic; Celtra Duo, Degudent: polished (P)/crystallized (C)), RB (resin-based composite; Cerasmart, GC), and RIC (resin-infiltrated ceramic; Enamic, Vita-Zahnfabrik). LiS (lithiumdisilicate; Emax CAD, Ivoclar-Vivadent) served as reference. Combined thermal cycling and mechanical loading (TCML) was performed simulating a 5-year clinical situation. Fracture force was determined. Data were statistically analyzed (Kolmogorov-Smirnov test, one-way ANOVA; post hoc Bonferroni, α = 0.05). Results One crown of ZLS_C[LAB] (1,200,000 cycles) and RB[CHAIR] (890 cycles) failed during TCML. Fracture values varied between 977.7 N(RB) and 3070.4 N(LiS)[CHAIR], 1130.6 N(RB) and 2998.1 N(LiS)[LAB], and 1802.4 N(ZLS) and 2664.3 N(LiS)[TOOTH]. Significantly (p < 0.003) different forces were found between the materials in all three groups. ZLS_C, RIC, and RB showed significantly (p < 0.014) different values for the individual groups. Conclusions Partly ceramic and resin-based materials performed differently on implant or tooth abutments. The insertion of a screw channel reduced the stability for individual crown materials. Insertion of the screw channel should be performed carefully. Clinical relevance All restorations were in a range where clinical application seems not restricted, but insertion of a screw channel might reduce stability of individual materials.

Early complications and performance of 327 heat-pressed lithium disilicate crowns up to five years

Article

Full-text available

Jun 2016

Purpose: The prospective follow-up aimed to assess the performance of lithium disilicate crowns and clinical reasons of adverse events compromising survival and quality. Materials and methods: 58 patients were treated with 375 heat-pressed monolithic crowns (emax press), which were bonded with resin cement (Multilink automix). Annual recalls up to five years included a complete dental examination as well as quality assessment using CDA-criteria. Any need for clinical intervention led to higher complication rate and any failure compromised the survival rate. Kaplan-Meier-method was applied to all crowns and a dataset containing one randomly selected crown from each patient. Results: Due to drop-outs, 45 patients (31 females, 14 males) with the average age of 43 years (range = 17-73) who had 327 crowns (176 anterior, 151 posterior; 203 upper jaw, 124 lower jaw) were observed and evaluated for between 4 and 51 months (median = 28). Observation revealed 4 chippings, 3 losses of retention, 3 fractures, 3 secondary caries, 1 endodontic problem, and 1 tooth fracture. Four crowns had to be removed. Survival and complication rate was estimated 98.2% and 5.4% at 24 months, and 96.8% and 7.1% at 48 months. The complication rate was significantly higher for root canal treated teeth (12%, P<.01) at 24 months. At the last observation, over 90% of all crowns showed excellent ratings (CDA-rating Alfa) for color, marginal fit, and caries. Conclusion: Heat pressed lithium disilicate crowns showed an excellent performance. Besides a careful luting, dentists should be aware of patients' biological prerequisites (grade of caries, oral hygiene) to reach full success with these crowns.

A comparative study of progressive wear of four dental monolithic, veneered glass-ceramics

Article

May 2017
J MECH BEHAV BIOMED

Objectives: This study evaluated the wear performance and wear mechanisms of four dental glass-ceramics, based on the microstructure and mechanical properties in the progressive wear process. Methods: Bar (N = 40, n = 10) and disk (N = 32, n = 8) specimens were prepared from (A) lithium disilicate glass-ceramic (LD), (B) leucite reinforced glass-ceramic (LEU), (C) feldspathic glass-ceramic (FEL), and (D) fluorapatite glass-ceramic (FLU). The bar specimens were tested for three-point flexural strength, hardness, fracture toughness and elastic modulus. The disk specimens paired with steatite antagonists were tested in a pin-on-disk tribometer with 10N up to 1000,000 wear cycles. The wear analysis of glass-ceramics was performed using a 3D profilometer after every 200,000 wear cycles. Wear loss of steatite antagonists was calculated by measuring the weight and density using sensitive balance and Archimedes' method. Wear morphologies and microstructures were analyzed by scanning electron microscopy (SEM). The crystalline phase compositions were determined using X-ray diffraction (XRD). One-way analysis of variance (ANOVA) was used to analyze the data. Multiple pair-wise comparison of means was performed by Tukey's post-hoc test. Results: LD showed the highest fracture toughness, flexural strength, elastic modulus and crystallinity, followed by LEU and FEL, and FLU showed the lowest. However, the hardness of LD was lower than all the other three types of ceramics. For steatite antagonists, LD produced the least wear loss of antagonist, followed by LEU and FEL, and FLU had the most wear loss. For glass-ceramic materials, LD exhibited similar wear loss as LEU, but more than FLU and FEL did. Moreover, fracture occurred on the wear surface of FLU. Conclusions: In the progressive wear process, veneering porcelains showed better wear resistance but fluorapatite veneering porcelains appeared fracture surface. Monolithic lithium disilicate glass-ceramics with higher mechanical properties showed more wear loss, however, they did not fracture and produced less wear loss of antagonists.

Basiswissen Medizinische Statistik

Article

Jan 2010

Christel Weiss

Enhancing the Bioactivity of Yttria-Stabilized Tetragonal Zirconia Ceramics via Grain Boundary Activation

Article

Apr 2017

Yttria-stabilized tetragonal zirconia (Y-TZP) has been proposed as a potential dental implant due to its good biocompatibility, excellent mechanical properties, and distinctive aesthetic effect. However, Y-TZP cannot form chemical bonds with bone tissue because of its biological inertness, which affects the reliability and long-term efficacy of Y-TZP implants. In this study, to improve the bioactivity of Y-TZP ceramics while maintaining their good mechanical performance, Y-TZP was modified by grain boundary activation via the infiltration of a bioactive glass (BG) sol into the surface layer of Y-TZP ceramics under different negative pressures (atmospheric pressure, -0.05 and -0.1 kPa), followed by gelling and sintering. The in vitro bioactivity, mechanical properties and cell behavior of the Y-TZP with improved bioactivity were systematically investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), electron probe microanalysis (EPMA) and Raman spectroscopy. The results of the bioactivity test conducted by immersing Y-TZP in simulated body fluid (SBF) showed that a bone-like apatite layer was produced on the entire surface. The mechanical properties of the modified Y-TZP decreased as the permeation negative pressure in the BG infiltration process increased relative to those of the Y-TZP blank group. However, the samples infiltrated with the BG sol under 0.05 kPa and atmospheric pressure still retained good mechanical performance. The cell culture results revealed that the bioactive surface modification of Y-TZP could promote cell adhesion and differentiation. The present work demonstrates that the bioactivity of Y-TZP can be enhanced by grain boundary activation, and the bioactive Y-TZP is expected to be a potential candidate for use as a dental implant material.

Success and Survival of Various Types of All-Ceramic Single Crowns: A Critical Review and Analysis of Studies with a Mean Follow-Up of 5 Years or Longer

Article

Mar 2017
INT J PROSTHODONT

Purpose: The aim of this critical review was to assess the survival and success rates of all-ceramic single crowns manufactured using different ceramic materials with a mean follow-up time of 5 years or longer. Materials and methods: An electronic search of studies published between 1980 and 2014 complemented by manual searching was conducted in Medline and Scopus. The terms ceramic, crown, survival, success, longevity, and complications were selected as keywords. Predetermined inclusion and exclusion criteria guided the search. Data were extracted and assessed by two independent reviewers. The results were statistically analyzed according to the type of material, and survival/success rate was calculated by assuming a Poisson-distributed number of events. Results: The initial search yielded 972 articles. After subsequent filtering, 14 studies were selected. The inter-reviewer agreement was rated as good (κ = 0.65) and very high agreement (κ = 0.93) during the identification and screening phases, respectively. No studies on densely sintered zirconia or feldspathic crowns satisfied the minimum follow-up time. Only one study of each of the following materials satisfied the inclusion criteria: lithium disilicate, leucite reinforced, pressed Al₂O₃, and sintered Al₂O₃. Meta-analysis of the included studies on other materials resulted in the following estimated survival and success rates: for densely sintered alumina crowns, 93.8% and 92.75%, respectively; for fluoromica reinforced, 87.7% and 87.7%, respectively; and for glass-infiltrated alumina core, 94.4% and 92%, respectively. Crown fracture was considered the most frequent complication. Conclusion: Based on the present critical review, there was no evidence to support the superior application of a single ceramic system or material. Further long-term prospective studies are required.