Clinical outcomes of different types of tooth-supported bilayer lithium disilicate all-ceramic restorations after functioning up to 5 years: A retrospective study

Abstract

Objectives

The aim of this retrospective study with large sample was to assess the 5-year clinical outcomes of four different types of restorations made from IPS e.max Press.

Methods

A total of 6855 restorations containing veneers (Vs), single crowns (SCs), 2-unit or multiple-unit combined crowns (CCs) and 3-unit or multiple-unit fixed dental prostheses (FDPs) from 4634 patients were included. Data collection were performed through scrutiny and registration of the records of all patients. The cumulative survival rates (CSRs) and their differences were calculated according to the Kaplan–Meier analysis and Log-Rank test. The differences among the failure rates of different restorations were evaluated according to the Chi-squared test.

Results

The 5-year CSR of all restorations was 96.6%. The 5-year CSRs of CCs (94.4%) and FDPs (90.6%) were both significantly lower than those of SCs (96.5%) and Vs (97.2%). A total failure rate was 3.2%. The failure rate of FDPs was 9.0%, which was significantly higher than those of Vs (2.5%) and SCs (3.3%), and was similar to that of CCs (5.2%). The failure rate of molar SCs (8.2%) was significantly higher than those of anterior (3.2%) and premolar SCs (2.5%). 83.0% of failed restorations happened in the 1st year after cementation and 50.6% happened in the first 3 months. Moreover, ceramic chipping (41.5%) and fracture (37.3%) were the top two reasons. In anterior tooth region, the ceramic damage rate of Vs (1.7%) was significantly lower than those of FDPs (8.1%) and CCs (4.8%), and that of SCs (2.6%) was significantly lower than that of FDPs (8.1%).

Conclusion

IPS e.max Press has an ideal medium-term outcome. The failures mainly occurred in the first 3 months after cementation and the main reasons were ceramic chipping and fracture. Due to higher failure risk, we suggest dentists should be cautious to apply FDPs, CCs and molar SCs.

Introductions

All-ceramic restorations are widely used in the anterior and posterior region as replacements for traditional porcelain-fused-to-metal restorations because of their good esthetic performance, biocompatibility and improved mechanical property . Currently, the most popular ceramic restorative materials are lithium disilicate and zirconia, but lithium disilicate has higher translucency and lower mechanical strength than zirconia . However, improvements on mechanical properties for lithium disilicate ceramic have been made and a reformulated and optimized product was introduced named as IPS e.max Press (Ivoclar Vivadent) . IPS e.max Press provides a flexural strength of approximately 400 MPa and a fracture toughness of approximately 3.0 MPa m 1/2 and both values are approximately 10% higher than those of IPS Empress 2 . With the increasing demand for esthetic restorations, the use of IPS e.max Press, relatively translucent high-strength monolithic ceramic material, is so widespread .

Currently, there have been a few studies reporting short-term clinical data (2–4 years) on IPS e.max Press restorations . And few studies reported medium-term clinical data (5–10 years) . However, all of the above studies involved only one type of tooth-supported restorations, either single crowns (SC) or fixed dental prostheses (FDP) . That is to say, there are few studies reporting clinical outcomes simultaneously involving different types of restorations. In terms of sample size, the amounts of restorations of previous studies ranged from 36 to 235 . Studies with a larger sample size have not been reported. Therefore, it is necessary to gather relatively long-term data of larger sample size for IPS e.max Press restorations with different types.

Therefore, the aim of this retrospective study with large sample was to assess the 5-year clinical outcomes of four different types of restorations made from IPS e.max Press.

Material and methods

Study design

This is a retrospective study on the clinical outcomes of IPS e.max Press restorations containing veneers (Vs), single crowns (SCs), combined crowns (CCs, including 203 2-unit CCs and 66 multiple-unit CCs) and fixed dental prostheses (FDPs, including 66 3-unit FDPs and 45 multiple-unit FDPs). The study included 6855 tooth-supported restorations from 4634 patients (17–63 years old at restorations delivery and mean age = 38.4 years old), who agreed to participate in this study and had received all-ceramic restoration treatment in the Department of Prosthodontics and the Dental Laboratory Center, Affiliated Stomatology Hospital, Fourth Military Medical University in China during the period from July 2008 to April 2013. Informed consent was obtained from all patients on a written form approved by the Ethical Committee of the School of Stomatology, Fourth Military Medical University. 263 out of them (5.68%) lost to follow-up in the halfway and the data of their last follow-up results were also included and analyzed.

Patient selection and indication

Patients who suffered from dental defects, short dentition defects or tooth discoloration were included for all-ceramic restoration and those with bruxism, poor oral hygiene, high caries activity or uncontrolled periodontal diseases were excluded. The abutment teeth of the patients had to meet the following criteria: The tooth mobility ≤grade 1 (maximum horizontal mobility ≤1 mm), vital pulp or qualifiedly endodontical treatment without periapical diseases, alveolar without absorption or absorption <1/3 of the root length and normal occlusion relationship . No cantilever FDPs was permitted. CCs and FDPs were only permitted in the anterior teeth region and V was permitted in the anterior and premolar teeth region. SCs had no region limitation.

Prosthodontic procedures

Rubber dam was used to isolate the moisture and the abutment teeth were conventionally prepared according to the clinically standardized method. The minimum thicknesses of crowns in various areas are 2 mm on the occlusal or incisal surfaces, 1.5 mm on the labial or buccal surfaces, 1 mm on the proximal and lingual surfaces and 1 mm at the shoulder platform, respectively. The minimum thicknesses of the veneers in various areas are 0.3 mm at the cervical 1/3, 0.5 mm at the middle 1/3, 0.8 mm at the incisal 1/3 of the labial surfaces and 0.3 mm at the shoulder platform, respectively. Silicone impression material (DMG, Germany) was used to take impressions of the patient’s dentition and the impressions were cast with Die-Stone gypsum (Heraeus Kulzer Dental Ltd., Germany). IPS e.max Press (Ivoclar Vivadent, Switzerland) were used to fabricate the restorations in the Dental Laboratory Center. In order to meet the demands for optimized esthetics, IPS e.max Ceram veneering material (Ivoclar Vivadent, Switzerland) was applied onto the labial or buccal surfaces of all restorations with the thickness of 0.3 mm. For the veneers, the veneering porcelain were only used on the incisal 1/3 of the labial surfaces.

After the restorations were fabricated, the tissue surfaces of them were etched by 5% hydrofluoric acid gel (IPS Ceramic Etching Gel, Ivoclar Vivadent, Switzerland) for 20 s in the Dental Laboratory Center before they were sent to clinic doctors. This strategy can avoid polluting the air in the consulting room due to the evaporation of hydrofluoric acid and contribute to the treatment of acidic wastewater together in the Dental Laboratory Center.

For full crown restorations cementation, such as single crowns, combined crowns and fixed dental prostheses, the restorations and the abutment teeth were firstly cleaned by alcohol wipes and then blow-dried. RelyX Unicem self-adhesive resin cement (3 M ESPE AG, Germany) was used to cement them according to the instructions. After complete seating, the crown margins were light cured for 3 s to remove excess cement and finally light cured for 20 s.

For the veneers cementation, Panavia F bonding system (Kuraray Noritake Dental Inc., Japan) was used according to the instructions. Firstly, K-Etchant gel (40% phosphoric acid gel, Kuraray Noritake Dental Inc., Japan) was used to clean the ceramic tissue surfaces for 30 s to remove the pollutant, rinsed and then dried. Then Clearfil Porcelain Bond Activator and Clearfil SE Bond Primer were mixed equally to serve as a silane coupling agent, which was coated on the ceramic tissue surfaces for 60 s and then gently air-dried. The abutment teeth were also etched by K-Etchant gel for 10 s, rinsed and then dried. Then ED primer liquid A and B were mixed equally and the mixture was coated on the teeth surfaces for 60 s and then gently air-dried. Finally, the Panavia F paste A and B were mixed equally to cement the veneers. After complete seating, excess cement around the veneer margins was removed by dental disposable micro applicator before light curing. Then the veneer margins were light cured for 3 s to further remove the rest excess cement and finally light cured for 20 s. Oxyguard II was coated at the margin of the veneers before final light-cure to promote curing and then rinsed off 3 min later.

Clinical evaluation

The patients were scheduled for check-ups 6 and 12 months after cementation and then annually. The patients were asked to contact their doctor whenever they had problems with their restorations or abutment teeth. The restoration clinical outcomes of patients during check-ups were evaluated and recorded according to the modified criteria established by the United States Public Health Service (USPHS) . Absolute failure was defined by clinical unacceptable fracture, crack, veneering porcelain chipping, color mismatch, anatomic form mismatch, need of endodontic treatment and restoration losing retention, which required a replacement of the entire restoration. In the present study, restoration losing retention was defined by those restorations that could not be recemented or were lost. The failure restorations due to ceramic damage included those with ceramic chipping, fracture or cracks. The failure rate = the number of failure restorations/the number of total restorations. Data collection were performed through scrutiny and registration of the records of all patients in September 2013 by the authors.

Statistical evaluation

SPSS 18.0 (SPSS Inc., Chicago, USA) was used to analyze the data. The cumulative survival rates (CSRs) and their differences among those of different restorations were calculated according to the Kaplan–Meier analysis and Log-Rank test. The differences among the failure rates of different restorations were evaluated according to the Chi-squared test and their multiple comparison need adjust α level. Statistical analyses were conducted at a significance level of 0.05.

Material and methods

Study design

This is a retrospective study on the clinical outcomes of IPS e.max Press restorations containing veneers (Vs), single crowns (SCs), combined crowns (CCs, including 203 2-unit CCs and 66 multiple-unit CCs) and fixed dental prostheses (FDPs, including 66 3-unit FDPs and 45 multiple-unit FDPs). The study included 6855 tooth-supported restorations from 4634 patients (17–63 years old at restorations delivery and mean age = 38.4 years old), who agreed to participate in this study and had received all-ceramic restoration treatment in the Department of Prosthodontics and the Dental Laboratory Center, Affiliated Stomatology Hospital, Fourth Military Medical University in China during the period from July 2008 to April 2013. Informed consent was obtained from all patients on a written form approved by the Ethical Committee of the School of Stomatology, Fourth Military Medical University. 263 out of them (5.68%) lost to follow-up in the halfway and the data of their last follow-up results were also included and analyzed.

Patient selection and indication

Patients who suffered from dental defects, short dentition defects or tooth discoloration were included for all-ceramic restoration and those with bruxism, poor oral hygiene, high caries activity or uncontrolled periodontal diseases were excluded. The abutment teeth of the patients had to meet the following criteria: The tooth mobility ≤grade 1 (maximum horizontal mobility ≤1 mm), vital pulp or qualifiedly endodontical treatment without periapical diseases, alveolar without absorption or absorption <1/3 of the root length and normal occlusion relationship . No cantilever FDPs was permitted. CCs and FDPs were only permitted in the anterior teeth region and V was permitted in the anterior and premolar teeth region. SCs had no region limitation.

Prosthodontic procedures

Rubber dam was used to isolate the moisture and the abutment teeth were conventionally prepared according to the clinically standardized method. The minimum thicknesses of crowns in various areas are 2 mm on the occlusal or incisal surfaces, 1.5 mm on the labial or buccal surfaces, 1 mm on the proximal and lingual surfaces and 1 mm at the shoulder platform, respectively. The minimum thicknesses of the veneers in various areas are 0.3 mm at the cervical 1/3, 0.5 mm at the middle 1/3, 0.8 mm at the incisal 1/3 of the labial surfaces and 0.3 mm at the shoulder platform, respectively. Silicone impression material (DMG, Germany) was used to take impressions of the patient’s dentition and the impressions were cast with Die-Stone gypsum (Heraeus Kulzer Dental Ltd., Germany). IPS e.max Press (Ivoclar Vivadent, Switzerland) were used to fabricate the restorations in the Dental Laboratory Center. In order to meet the demands for optimized esthetics, IPS e.max Ceram veneering material (Ivoclar Vivadent, Switzerland) was applied onto the labial or buccal surfaces of all restorations with the thickness of 0.3 mm. For the veneers, the veneering porcelain were only used on the incisal 1/3 of the labial surfaces.

After the restorations were fabricated, the tissue surfaces of them were etched by 5% hydrofluoric acid gel (IPS Ceramic Etching Gel, Ivoclar Vivadent, Switzerland) for 20 s in the Dental Laboratory Center before they were sent to clinic doctors. This strategy can avoid polluting the air in the consulting room due to the evaporation of hydrofluoric acid and contribute to the treatment of acidic wastewater together in the Dental Laboratory Center.

For full crown restorations cementation, such as single crowns, combined crowns and fixed dental prostheses, the restorations and the abutment teeth were firstly cleaned by alcohol wipes and then blow-dried. RelyX Unicem self-adhesive resin cement (3 M ESPE AG, Germany) was used to cement them according to the instructions. After complete seating, the crown margins were light cured for 3 s to remove excess cement and finally light cured for 20 s.

For the veneers cementation, Panavia F bonding system (Kuraray Noritake Dental Inc., Japan) was used according to the instructions. Firstly, K-Etchant gel (40% phosphoric acid gel, Kuraray Noritake Dental Inc., Japan) was used to clean the ceramic tissue surfaces for 30 s to remove the pollutant, rinsed and then dried. Then Clearfil Porcelain Bond Activator and Clearfil SE Bond Primer were mixed equally to serve as a silane coupling agent, which was coated on the ceramic tissue surfaces for 60 s and then gently air-dried. The abutment teeth were also etched by K-Etchant gel for 10 s, rinsed and then dried. Then ED primer liquid A and B were mixed equally and the mixture was coated on the teeth surfaces for 60 s and then gently air-dried. Finally, the Panavia F paste A and B were mixed equally to cement the veneers. After complete seating, excess cement around the veneer margins was removed by dental disposable micro applicator before light curing. Then the veneer margins were light cured for 3 s to further remove the rest excess cement and finally light cured for 20 s. Oxyguard II was coated at the margin of the veneers before final light-cure to promote curing and then rinsed off 3 min later.

Clinical evaluation

The patients were scheduled for check-ups 6 and 12 months after cementation and then annually. The patients were asked to contact their doctor whenever they had problems with their restorations or abutment teeth. The restoration clinical outcomes of patients during check-ups were evaluated and recorded according to the modified criteria established by the United States Public Health Service (USPHS) . Absolute failure was defined by clinical unacceptable fracture, crack, veneering porcelain chipping, color mismatch, anatomic form mismatch, need of endodontic treatment and restoration losing retention, which required a replacement of the entire restoration. In the present study, restoration losing retention was defined by those restorations that could not be recemented or were lost. The failure restorations due to ceramic damage included those with ceramic chipping, fracture or cracks. The failure rate = the number of failure restorations/the number of total restorations. Data collection were performed through scrutiny and registration of the records of all patients in September 2013 by the authors.

Statistical evaluation

SPSS 18.0 (SPSS Inc., Chicago, USA) was used to analyze the data. The cumulative survival rates (CSRs) and their differences among those of different restorations were calculated according to the Kaplan–Meier analysis and Log-Rank test. The differences among the failure rates of different restorations were evaluated according to the Chi-squared test and their multiple comparison need adjust α level. Statistical analyses were conducted at a significance level of 0.05.

Results

The cumulative survival rates (CSRs) and their differences of different types of restorations

The CSRs of different kinds of all-ceramic restorations after functioning from 1 to 5 years are shown in Table 1 and Fig. 1 . The results showed the CSR of total restorations after functioning for 5 years was 96.6%. The CSRs of different kinds of restorations had the same trend during the period from 1 to 5 years and the CSRs for 5 years were as follows: Vs (97.2%) > SCs (96.5%) > CCs (94.4%) > DFPs (90.6%). Table 2 shows the statistical results for the CSR differences among different types of restorations through Log-Rank test. There was no significantly statistical difference on the CSRs between SCs and Vs or between CCs and FDPs. On the contrary, the CSRs of CCs and FDPs were both significantly lower than those of SCs and Vs.

Jun 19, 2018 | Posted by in General Dentistry | Comments Off on Clinical outcomes of different types of tooth-supported bilayer lithium disilicate all-ceramic restorations after functioning up to 5 years: A retrospective study
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