Clinical outcomes of lithium disilicate single crowns and partial fixed dental prostheses: A systematic review Sascha Pieger, DMD, Dr med dent,a Arif Salman, BDS, MDS,b and Avinash S. Bidra, BDS, MSc University Medical Center Hamburg-Eppendorf, Center for Dental and Oral Medicine, Hamburg, Germany; Bharath University Sree Balaji Dental College, Chennai, India; University of Connecticut Health Center, Department of Reconstructive Sciences, Farmington, Conn Statement of problem. Lithium disilicate is a relatively new and popular restorative material for esthetic and functional rehabilitations, but the evidence for clinical outcomes is not clear. Purpose. The purpose of this systematic review was to analyze the short-term (1- to 5-year) and medium-term (5- to 10-year) survival rates of lithium disilicate single crowns and partial fixed dental prostheses. Material and methods. An electronic search for articles in the English-language literature published between January 1998 and June 2013 was performed with the PubMed search engine. The specific search terms used were lithium disilicate, lithium silicate, IPS e max, IPS Empress, CAD CAM, pressed ceramic, monolithic, and bilayer. After applying predetermined inclusion and exclusion criteria, the definitive list of selected articles was suitable only for calculating the interval survival rate and cumulative survival rate. Results. The electronic search resulted in 2033 titles. The systematic application of inclusion and exclusion criteria resulted in 12 clinical studies that addressed the clinical outcomes of lithium disilicate restorations. Of these, 2 were randomized controlled trials, 5 were prospective studies, 1 was a retrospective study, and 4 studies were descriptive in nature. All 12 studies reported on tooth-retained lithium disilicate restorations. The 2-year cumulative survival rate for single crowns was 100%, and the 5-year cumulative survival rate was 97.8%. The 2-year cumulative survival rate for fixed dental prostheses was 83.3%, and the 5-year cumulative survival rate was 78.1%. The cumulative survival rate over a 10-year period, primarily owing to data from 1 study, was 96.7% for single crowns and 70.9% for fixed dental prostheses. Conclusions. For lithium disilicate single crowns, the existing evidence indicates excellent short-term survival rates, but the evidence for medium-term survival is limited. For lithium disilicate fixed dental prostheses, the evidence for short-term survival is fair, although limited, but the evidence for medium-term survival is not promising. The majority of failures in both types of restorations were reported in the posterior region. (J Prosthet Dent 2014;-:---)

Clinical Implications When choosing lithium disilicate as the restorative material for single crowns, clinicians should be aware that the short-term survival for this type of restoration is excellent, but presently, clinical evidence for medium-term survival is limited. For fixed dental prostheses, caution is advised for the use of lithium disilicate until further clinical evidence shows favorable long-term results.

a

Assistant Professor, Department of Dental Prosthetics, University Medical Center Hamburg-Eppendorf, Center for Dental and Oral Medicine; Former ITI Scholar, University of Connecticut Health Center. b Assistant Professor, Department of Periodontology, Bharath University Sree Balaji Dental College; Former ITI Scholar, University of Connecticut Health Center. c Assistant Professor and Assistant Program Director, Post-Graduate Prosthodontics, Department of Reconstructive Sciences, University of Connecticut Health Center.

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Volume Ceramic restorations are widely used in the anterior and posterior region of the oral cavity and are expected to fulfill esthetic and functional demands.1-12 For this reason, numerous kinds of ceramic systems have been developed for clinical use.13 Currently, 2 of the most popular ceramic restorative materials are lithium disilicate and zirconia, with lithium disilicate having higher translucency and lower mechanical strength than zirconia.14-17 Both materials can be used for either a monolithic restoration or as a core material with veneered porcelain.14-17 Common complications that have been reported for both materials include cracking, chipping, and the fracture of the veneering porcelain material.18,19 These complications have been reported to be higher in the posterior region.20 Moreover, ceramic fixed dental prostheses (FDPs) exhibit higher rates of fracture of the core framework than single crown restorations.21 The evolution of lithium disilicate as a restorative material dates back to 1998, when it was introduced to dentistry as IPS Empress 2 (Ivoclar Vivadent).22 It was the second generation of heat-pressed ceramic and contained lithium disilicate material as the main crystalline phase.23 The manufacturer’s indications for this material ranged from veneers, inlays, onlays, and crowns to 3-unit FDPs in the anterior region.24-27 The clinical data for Empress 2 indicated higher survival rates for single crowns and significantly lower survival rates for 3-unit FDPs.28 This material was eventually discontinued by the manufacturer, and a reformulated and optimized composition of lithium disilicate ceramic was introduced under the trade name IPS e.max (Ivoclar Vivadent). This is a patented material exclusively manufactured by Ivoclar Vivadent and is available in a pressable version (IPS e.max Press) or as a partially crystallized ceramic block for CAD/CAM machining (IPS e.max CAD).23 Unlike its predecessor Empress 2, which could only be used as framework material, the pressable and

machinable version of IPS e.max can be used in a monolithic form. The availability of this relatively translucent highstrength monolithic ceramic material combined with the emerging demand for metal-free restorations is probably why the use of lithium disilicate restorations is so widespread.14 Given its popularity, there is a need to review and synthesize existing clinical data on the survival of lithium disilicate restorations. The purpose of this systematic review was to analyze the short-term (1- to 5-year) and medium-term (5- to 10-year) survival rates of natural tooth-borne lithium disilicate single crowns and FDPs.

MATERIAL AND METHODS An independent electronic search of the English-language literature was performed with the PubMed search engine and Cochrane Library database by multiple investigators. The specific terms that were used for the electronic search were lithium disilicate, lithium silicate, IPS e max, IPS Empress, CAD CAM, pressed ceramic, monolithic, and bilayer. The period searched was from January 1998 to June 2013. The limits applied to the search were humans, English, and dental journals. The inclusion criteria were any English-language article or bilingual article with English as one of the languages in a peerreviewed journal and any clinical study on humans involving any of the search terms listed previously. The exclusion criteria were as follows: articles that did not pertain to the search terms described in the inclusion criteria; review or technique articles without an associated clinical trial and data; case reports, case series, or descriptive studies with fewer than 10 naturaltooth-supported lithium disilicate restorations; patients or data duplicated in other included articles; and articles that did not provide the required data or did not allow extraction of the required data on lithium disilicate single crowns and FDPs. The electronic search process was systematically conducted in 3 stages. In

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stage 1, the investigators independently screened all relevant titles of the electronic search, and any disagreement was resolved by discussion. In situations where the application of exclusion criteria was not clear, the controversial article was included for consideration in the abstract stage. In stage 2, the investigators independently analyzed abstracts of all selected titles, and disagreements were resolved by discussion. In situations of uncertainty, the abstract was included for the subsequent full-text stage. After the application of exclusion criteria, the definitive list of articles was screened at stage 3 by the investigators to extract qualitative and quantitative data. A supplemental search was conducted based on the references from the definitive list of fulltext articles from stage 3 and on additional articles published beyond the terminal search date (June 2013 to November 2013). The definitive list of articles was analyzed for short-term and medium-term survival rates of lithium disilicate single crowns and FDPs by using an actuarial method for life table analysis. Additionally, qualitative data were analyzed across all the definitive studies that were included. In this systematic review, the authors defined failure as the fracture of any part of a restoration that required the removal or remake of the restoration. Short-term survival was defined as the presence of the restoration in function 1 to 5 years after cementation, and medium-term survival was defined as the presence of the restoration in function 5 to 10 years after cementation. By using the actuarial method for life table analysis, the extracted quantitative data at stage 3 were used to calculate the interval survival rate (ISR) and the cumulative survival rate (CSR). Both elements were used to compute the ratio of surviving restorations in a group during a specific interval (ISR) or the ratio of surviving items over the entire observation period (CSR).29 The calculation of the interreviewer agreement at the title and abstract stage was performed by using the Cohen kappa method.

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RESULTS The initial electronic search using the specific search terms yielded 2033 titles at stage 1. Of these, 136 articles were carried forward to the abstract stage, and, subsequently, 38 articles were carried forward to the full-text analysis stage. After further scrutiny, 26 articles15,24-28,30-49 were excluded (Table I). Finally, qualitative and quantitative data were extracted from 12 full-text articles (Tables II, III). Of these articles, 2 were designed as randomized controlled trials,2,5 5 studies were prospective,1,3,6,7,12 1 was retrospective,8 and 4 studies did not specify the study design and were considered by the authors to be descriptive in nature.4,9-11 All 12 studies reported on tooth-retained lithium disilicate restorations. With regard to the method of fabrication, 3 studies used IPS e.max Press,3,7,10 2 studies used IPS e.max CAD,1,6 and 1 study used both systems.4 Three studies reported on the

Table I.

use of IPS Empress 2,8,11,12 and 1 randomized controlled trial (RCT) compared IPS e.max Press with Empress 2.2 Two studies did not specify the manner in which the lithium disilicate material was used.5,9 All 12 studies cemented the restorations with self-adhesive resin cement or resin-modified glass ionomer cement. Of the 12 studies, 5 studies reported support from the manufacturer of lithium disilicate (Ivoclar Vivadent),1,3,5,6 and 5 studies4,7,8,11,12 did not report any study support. One study was funded by the Thailand Research Fund Grant,9 and one study acknowledged the support of the manufacturer and the National Institutes of Health (NIH).2 A total of 519 participants from all of the 12 studies received 841 lithium disilicate restorations. Of these, 696 were single crowns, and 145 were FDPs. The sample size ranged from 15 participants to 146 participants per study. Seven studies reported on the use of lithium disilicate for single

Exclusion of 26 full-text articles based on predetermined exclusion

criteria

Exclusion Criteria Applied

Article Excluded

Articles that did not pertain to search terms described in inclusion criteria

Schenke et al31 (2012) Vanoorbeek et al34 (2010) Schulte et al43 (2005) Sjögren et al45 (2004) Posselt and Kerschbaum48 (2003) Reiss and Walther49 (2000)

Articles without associated trial and clinical data

Chu15 (2012) Fradeani et al32 (2012) Edelhoff and Brix33 (2011)

Case report/series with fewer than 10 restorations

Roman-Rodriguez et al35 (2010) Kurbad and Reichel44 (2005)

Patients or data repeated in other included articles

Reich et al36 (2010) Wolfart et al38 (2009) Wolfart et al42 (2005) Esquivel-Upshaw et al46 (2004)

Articles that did not provide required data or did not allow extraction of required data on lithium disilicate restorations

Sun et al30 (2013) Guess et al25 (2013) Sola-Ruiz et al24 (2013) Silva et al26 (2011) Harder et al37 (2010) Etman et al40 (2008) Mansour et al39 (2008) Toksavul and Toman27 (2007) Esquivel-Upshaw et al41 (2006) Marquardt and Strub28 (2006) Wolfart et al47 (2003)

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crowns,1,2,4,6-9 and 4 studies reported on FDPs.3,5,10,12 One study investigated the clinical performance of both single crowns and FDPs.11 The data from 9 of the 12 studies could be extracted to classify anterior (canine to canine) or posterior (premolars and molars) restorations.1,2,4-9,11 Data from the remaining 3 studies could not be extracted to classify the location of the restoration.3,10,12 Altogether, the 9 studies that reported on location evaluated 257 anterior restorations and 463 posterior restorations. The most common technical complication reported was fracture of the core framework,1,3-5,7,8,10-12 followed by chipping of the veneering porcelain2,3,5,8,11 and debonding of the restoration from the tooth.2-4,6 The most commonly reported biologic complications included the need for endodontic treatment1,3,8 and the presence of secondary caries.1,4,10 A wide range of follow-up (0.5-11 years) was reported across the various studies. Two studies had a follow-up period of less than 1 year.4,12 One study had a follow-up period greater than 5 years,5 and 2 studies had a follow-up period greater than 10 years.3,8 A life table survival analysis was presented in 5 studies.1,3,5,8,11 From the remaining 7 studies,2,4,6,7,9,10,12 data had to be extracted by the authors of this systematic review to be included in a pooled life table survival analysis (Table IV, Fig. 1). The pooled data from all included studies showed a total of 34 failures out of 841 restorations (4%), with 38% of all failures (13 of 34) occurring during the first year. The analysis of failure by restoration type indicated a significant difference between single crowns and FDPs (Tables V, VI). Single crowns did not experience any failure up to the third year and experienced a total of 9 failures in this analysis. Of these 9 failures, 7 failures (77.7%) were identified in the posterior region. Furthermore, the total number of failures for single crowns consisted of 5 core fractures and 4 fractures of the veneering ceramic. In contrast, FDPs

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Table II.

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Qualitative data from definitive 12 studies on lithium disilicate ceramic material

Author

Material/ Number Number of Number of Number of Layering Restorations, Restorations, Restorations, Type of of Type Posterior Restoration Technique Setting Anterior Total of Study Patients

Reich and Schierz1 (2013)

Prospective

34

41

0

41

SC

E.max CAD LT/ University/ monolithic Private practice

Esquivel-Upshaw et al2 (2013)

RCT

32

24

0

24

SC

E.max Press & Empress 2/ mono- and bilayer

University

Kern et al3 (2012)

Prospective

28

36

NR

NR

FDP

E.max Press/ monolithic

University

Cortellini and Canale4 (2012)

NR

76

235

136

99

SC

E.max Press & E.max CAD/ monolithic

Private practice

Makarouna et al5 (2011)

RCT

37

18

8

10

FDP

not specified/ bilayer

University

Fasbinder et al6 (2010)

Prospective

43

62

0

62

SC

E.max CAD LT/ monolithic

University

Etman and Woolford7 (2010)

Prospective

NR

30

0

30

SC

E.max Press/ bilayer

University

Valenti and Valenti8 (2009)

Retrospective

146

263

101

160

SC

Empress 2/ bilayer

Private practice

Suputtamongkol et al9 (2008)

NR

30

29

0

29

SC

not specified/ bilayer

University

Esquivel-Upshaw et al10 (2008)

NR

21

30

NR

NR

FDP

E.max Press/ bilayer

University

Taskonak and Sertgöz11 (2006)

NR

15

40

12 (for SC only)

8 (for SC only)

SC/FDP

Empress 2/ bilayer

University

Sorensen et al12 (1999)

Prospective

57

41

NR

NR

FDP

Empress 2/ bilayer

University

FDP, fixed dental prosthesis; NR, not reported; RCT, randomized controlled trial; SC, single crown.

experienced 13 failures during the first year and a total of 25 failures in this analysis. Of 25 failures, 17 (68%) were identified in the posterior region. The cumulative survival rates (CSRs) computed for a 5-year interval were 97.8% for single crowns and 78.1% for FDPs. The CSR over a 10-year interval, owing mainly to the report from 2 studies,3,8 was 92.6% for all types of restorations, 96.7% for single crowns, and 70.9% for FDPs. Because of the heterogeneity and paucity of the analyzed data, it was not possible to compare qualitative and quantitative data or draw conclusions for clinical outcomes in relation to the region of the restoration (maxillary versus mandibular and anterior versus posterior regions) or regarding the material (IPS e.max Press versus IPS e.max CAD versus IPS Empress 2) or for other

secondary outcomes such as esthetics or marginal fit.

DISCUSSION The purpose of this systematic review was to analyze the short-term and medium-term results of studies dealing with the clinical outcomes of lithium disilicate single crowns and FDPs. Lithium disilicate was first introduced in dentistry in 1998 but has become popular only in the past decade. Anticipating that long-term survival data would be unavailable, the authors designed this review to assess only the short-term and medium-term survival rates of lithium disilicate single crowns and FDPs in an effort to understand the material’s long-term clinical potential. The predetermined inclusion criteria for this systematic review were broad to

The Journal of Prosthetic Dentistry

permit inclusion of as many articles as possible. In this systematic review, the articles were scrutinized by multiple investigators to minimize error during the review process and the selection bias of the articles included. Disagreement was resolved by discussion, and doubtful articles were carried forward to the subsequent stage. Articles that did not meet the various predetermined criteria for inclusion were analyzed in depth before being finally excluded. In this systematic review, only 2 RCTs were identified that compared lithium disilicate with the gold standard of metal ceramic restorations.2,5 Esquivel-Upshaw et al2 compared the performance of metal ceramic crowns with single-layered IPS e.max Press and bilayered IPS Empress 2 crowns and found a 100% survival rate for all crowns after 3 years. Nevertheless,

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Table III.

5 Quantitative data of definitive 12 studies on lithium disilicate ceramic material

Author

Number of Number of Number of Number of Failures During Failures After Range of Nature of Type of First Year Follow-up (y) Failure First Year Restoration Patients Restorations

Reich and Schierz1 (2013)

SC

34

33

0

1

NR

Fracture of the core ceramic

Esquivel-Upshaw et al2 (2013)

SC

32

24

0

0

1.1-3 years

N/A

Kern et al3 (2012)

FDP

28

36

0

3

6.6-11.1 years

Fracture of the core ceramic

Cortellini and Canale4 (2012)

SC

76

235

0

1

0.5-4 years

NR

Makarouna et al5 (2011)

FDP

37

18

6

NR

NR

Fracture of the core or veneering ceramic (or both)

Fasbinder et al6 (2010)

SC

43

62

0

0

NR

NR

Etman and Woolford7 (2010)

SC

NR

30

0

1

NR

NR

Valenti and Valenti8 (2009)

SC

146

263

0

6

NR

Fracture of the core or veneering ceramic (or both)

Suputtamongkol et al9 (2008)

SC

30

29

0

0

NR

NR

Esquivel-Upshaw et al10 (2008)

FDP

21

30

0

4

NR

NR

Taskonak and Sertgöz11 (2006)

SC/FDP

15

40

3

5

NR

Fracture of the core ceramic

Sorensen et al12 (1999)

FDP

57

41

4

NR

0.5-1.5 years

NR

FDP, fixed dental prosthesis; NR, not reported; SC, single crown; N/A, not applicable.

lithium disilicate crowns showed more crown wear and surface roughness than metal ceramic crowns, with statistically significant differences in surface texture and crown wear found at the third year. The second RCT, conducted by Makarouna et al,5 compared the clinical outcome of metal ceramic FDPs with lithium disilicate FDPs. Based on a 6-year survival rate of 62.7% for ceramic FDPs, the authors concluded that clinicians should be cautious as to the use of lithium disilicate for FDPs. Recently published results by Sola-Ruiz et al24 indicate that the long-term survival of

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lithium disilicate FDPs is discouraging, with a 10-year survival of IPS Empress 2 FDPs at 71.4%. The results from the present systematic review confirm these previous results. One of the most significant challenges of data extraction in this systematic review was the lack of information about the time the failure occurred and the number of restorations over the followed-up period. Two studies reported a follow-up period of 10 years, one assessing single crowns8 and another assessing FDPs.3 All other clinical trials were

conducted with a wide range of follow-up periods (0.5 to 11 years), with the most common follow-up period being in the 1- to 2-year range. The application of the first 3 predetermined exclusion criteria in this systematic review was straightforward. Articles that did not pertain to the search terms, articles without associated clinical trial and data, and case reports and case series with fewer than 10 restorations were excluded without any issues. The authors decided on 10 restorations as the minimum sample size in a study to ensure a credible

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Life table analysis for all lithium disilicate restorations (single crowns and fixed dental prostheses combined) showing cumulative survival rate among definitive 12 included studies

Table IV.

Interval Survival Rate (%)

Cumulative Survival Rate (%)

841

98.45

98.45

6

451

98.66

97.14

4

381.5

98.95

96.12

399

2

374.5

99.46

95.61

3

314

3

271.5

98.89

94.55

5-6

3

293

2

282.5

99.29

93.88

6-7

2

293

3

293

98.97

92.92

7-8

2

292

0

291.5

100

92.92

Time Interval (y)

Number of Studies Reporting Interval

Number of Restorations in Interval

Number of Failures in Interval

0-1

12

841

13

1-2

10

581

2-3

8

448

3-4

7

4-5

Number of Restorations At Risk

8-9

2

289

0

287.5

9-10

2

289

1

289

10-11

2

288

0

287.5

100

92.92

99.65

92.60

100

92.60

300 250 200 150 100 50 0

0-1 Y

1-2 Y

2-3 Y

3-4 Y

4-5 Y

5-6 Y

6-7 Y

7-8 Y

8-9 Y

9-10 Y 10-11 Y

Reich and Schierz (2013)

Makarouna et al (2011)

Suputtamongkol et al (2008)

Esquivel-Upshaw et al (2013)

Fasbinder et al (2010)

Esquivel-Upshaw et al (2008)

Kern et al (2012)

Etman and Woolford (2010)

Taskonak and Sertgöz (2006)

Cortellini and Canale (2012)

Valenti and Valenti (2009)

Sorensen et al (1999)

1 Bar graph showing number of lithium disilicate restorations (both single crowns and fixed dental prostheses) in each included study at different time intervals (in years [Y]). Note attrition of number of restorations reported during each follow-up period. Also note that only 2 out of 12 studies reported follow-up data beyond the fifth year interval.

sample size and maximize the amount of extracted data. The articles that needed to be excluded because of redundant data published by similar authors from previous studies and articles that did not allow data extraction were independently reanalyzed by the investigators before making a definitive decision on their exclusion. Silva et al26 observed no fractures among 440 pressed lithium disilicate restorations, including inlays,

onlays, crowns, and FDPs, but did not report the distribution of the type of restoration and the number of followed-up restorations over the observation period. Harder et al37 investigated the 8-year outcome of inlayretained lithium disilicate FDPs and stated that 40% of the FDPs were lost owing to fracture of the inlay retainer but did not report on the time when the fracture occurred. Mansour et al39 evaluated the clinical performance of

The Journal of Prosthetic Dentistry

82 IPS Empress 2 crowns and reported on 3 fractures, but the extraction of data related to the time of the failure was not feasible. Toksavul and Toman27 rated the clinical outcome of 79 IPS Empress 2 crowns and observed 1 fractured crown but did not report when the failure occurred; this article was also excluded. The calculation of the true survival rate of lithium disilicate restorations was not feasible because of the various

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Life table analysis for lithium disilicate single crowns showing cumulative survival rate among 8 studies that reported data on single crowns

Table V.

Number of Restorations At Risk

Time Interval (y)

Number of Studies Reporting the Interval

Number of Restorations in Interval

Number of Failures in Interval

0-1

8

696

0

696

1-2

7

505

0

2-3

5

386

2

3-4

4

341

4-5

1

5-6 6-7

Interval Survival Rate (%)

Cumulative Survival Rate (%)

100

100

409.5

100

100

326.5

99.38

99.38

2

318.5

99.37

98.76

261

2

221

99.09

97.86

1

260

2

259.5

99.22

97.11

1

260

1

260

99.61

96.74

7-8

1

259

0

258.5

100

96.74

8-9

1

259

0

259

100

96.74

9-10

1

259

0

259

100

96.74

10-11

1

259

0

259

100

96.74

factors listed previously. The existing data only permitted the calculation of the ISR and CSR. As not all patients in the included studies were followed up for a minimum of 1 year, the first-year ISR of 98.45% for all lithium disilicate restorations does not represent a true 1-year survival rate. However, the 100% 2-year CSR for single crowns is remarkable. In a prospective clinical trial by Marquardt and Strub,28 27 single crowns and 31 FDPs made of IPS

Empress 2 were followed up for up to 5 years. None of the single crowns fractured, but the framework of 3 FDPs did. The examination of the fractured fragments under a scanning electron microscope disclosed underextended dimensions of the connector area as the main reason for fractures. This finding has been validated by other clinical studies.38,46 The authors also stated that catastrophic failures such as fracture of the framework occurred predominantly in FDPs replacing missing

posterior teeth.3 This finding was confirmed by the data of the present systematic review, where 68% of all FDP fractures were identified in the posterior region. Similarly, most fractures reported for single crowns occurred in the posterior region. No studies in this systematic review compared the overall clinical performance of lithium disilicate with other ceramic systems. However, single clinical parameters such as the wear or surface texture of different restorative

Table VI. Life table analysis for lithium disilicate fixed dental prostheses showing cumulative survival rate among 5 studies that reported data on fixed dental prostheses Interval Survival Rate (%)

Cumulative Survival Rate (%)

91.03

91.03

71.5

91.60

83.39

2

45

95.55

79.68

58

0

56

53

1

50.5

2

33

0

6-7

1

33

7-8

1

8-9

1

9-10 10-11

Time Interval (y)

Number of Studies Reporting the Interval

Number of Restorations in Interval

Number of Failures in Interval

0-1

5

145

13

1-2

4

96

6

2-3

3

62

3-4

3

4-5

2

5-6

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Number of Restorations At Risk 145

100

79.68

98.01

78.11

23

100

78.11

2

33

93.93

73.37

33

0

33

100

73.37

30

0

28.5

100

73.37

1

30

1

30

96.66

70.93

1

29

0

28.5

100

70.93

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Volume materials such as metal ceramic, zirconia, or lithium disilicate have been compared. Esquivel-Upshaw et al41 conducted an in vivo study and showed significantly higher occlusal wear rates for lithium disilicate core ceramic opposing enamel than for the wear rate of enamel to enamel. In a direct comparison of the wear rate of crowns made with 3 different ceramic systems, Procera AllCeram crowns (Nobel Biocare) showed the highest wear rate to enamel, followed by lithium disilicate crowns and metal ceramic crowns. Metal ceramic crowns exhibited the lowest wear to enamel over the 2-year observation period.40 A recent RCT has also reported more wear and surface roughness of veneered lithium disilicate crowns than of metal ceramic crowns.2 This roughness may lead to higher plaque accumulation, greater wear of the opposing dentition, and periodontal disease.50,51 Future clinical studies should address these issues to better understand the longterm clinical potential and prognostic nature of this promising material.

CONCLUSIONS Within the limitations of this systematic review, the following conclusions were drawn. For lithium disilicate single crowns, the short-term evidence (1 to 5 years) indicates an excellent survival rate with a 2-year CSR of 100% and a 5-year CSR of 97.8%. The evidence for medium-term survival (5 to 10 years) is limited, with data from 1 study contributing to a 10-year CSR of 96.7%. Most single crowns failed in the posterior region. For lithium disilicate FDPs, the short-term evidence (1 to 5 years) indicated a 5-year CSR of 78.1%, which is not promising. The evidence for medium-term survival (5 to 10 years) is limited, with data from 1 study contributing to a discouraging 10-year CSR of 70.9%. Most FDPs also failed in the posterior region. The cumulative survival rates estimated in this systematic review are based on only the reported data. The true survival rate for both single crowns and FDPs is

unknown because of insufficient data, the loss of patients to follow-up, and the inconsistent manner of reporting.

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Corresponding author: Dr Avinash S. Bidra University of Connecticut Health Center 263 Farmington Ave, L6078 Farmington, CT 06030 E-mail: [email protected] Copyright ª 2014 by the Editorial Council for The Journal of Prosthetic Dentistry.

Clinical outcomes of lithium disilicate single crowns and partial fixed dental prostheses: a systematic review.

Lithium disilicate is a relatively new and popular restorative material for esthetic and functional rehabilitations, but the evidence for clinical out...
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