A practice-based research network on the survival of ceramic inlay/onlay restorations

Abstract

Objective

To evaluate prospectively the longevity of ceramic inlay/onlay restorations placed in a web-based practice-based research network and to investigate risk factors associated with restoration failures.

Materials and methods

Data were collected by a practice-based research network called Ceramic Success Analysis (CSA). 5791 inlay/onlay ceramic restorations were placed in 5523 patients by 167 dentists between 1994 and 2014 in their dental practices. For each restoration specific information related to the tooth, procedures and materials used were recorded. Annual failure rates (AFRs) were calculated and variables associated with failure were assessed by a multivariate Cox-regression analysis with shared frailty.

Results

The mean observation time was 3 years (maximum 15 years) of clinical service, and AFRs at 3 and 10 years follow up were calculated as 1.0% and 1.6%. Restorations with cervical outline in dentin showed a 78% higher risk for failure compared to restorations with margins in enamel. The presence of a liner or base of glass-ionomer cement resulted in a risk for failure twice as large as that of restorations without liner or base material. Restorations performed with simplified adhesive systems (2-step etch-and-rinse and 1-step self-etch) presented a risk of failure 142% higher than restorations performed with adhesives with bonding resin as a separate step (3-step etch-and-rinse and 2-step self-etch). 220 failures were recorded and the most predominant reason for failure was fracture of the restoration or tooth (44.5%).

Conclusions

Ceramic inlay/onlay restorations made from several glass ceramic materials and applied by a large number of dentists showed a good survival. Deep cervical cavity outline, presence of a glass ionomer lining cement, and use of simplified adhesive systems were risk factors for survival.

Introduction

Restorative work is the core business of dentistry. It is estimated that every year 500 million dental direct restorations are placed worldwide , of which most are composite resin restorations . Restorations are placed due to caries, fractures, or tooth wear, and a high number of restorative procedures is indicated to replace restorations that have failed . As an alternative for direct restorations, indirect restorations may be placed using metal, composite, and/or ceramic restorative materials. Indirect inlay/onlay restorations provide more control over shape and function, particularly in larger defects in posterior teeth. Due to increased esthetic demands by patients, it is likely that most indirect restorations are currently made from ceramic materials.

Indirect ceramic restorations can be made either by a dental technician in the laboratory or by using CAD/CAM systems to make chairside restorations in a single session. Longevity reports vary between 0 and 7.5% annual failure rate (AFR) for ceramic inlays/onlays , while for chairside fabricated restorations (in this case the CEREC ® system) this is between 0.8% and 4.8% AFR . Indirect ceramic restorations have shown comparable or slightly better clinical performance than direct composite restorations, especially when taking into account the fact that indirect restorations are generally larger .

The procedure of placing indirect inlay/onlay restorations includes many steps and a wide variation of ceramic materials and luting cements can be used. Some factors related to the materials, such as ceramic properties or characteristics of the adhesive luting technique, have been investigated extensively in vitro . Clinical studies with limited sample size also have shown the influence of factors related to patients and operators on the clinical outcome of ceramic inlays/onlays . However, there is a lack of clinical studies analysing the combined role of different risk factors on restoration longevity and performance, where each factor might be compensating for another. For such study design, a large sample size is mandatory, which is usually hard to achieve in randomized controlled trials (RCTs).

While RCTs allow us to investigate differences between therapies or materials under ideal circumstances, the general dental practitioner is also interested in the outcome of a therapy under ‘real world’ conditions, i.e. where restoration, patient and practice level factors together influence the results. The sheer number of variables involved in a general practice setting requires a very large number of restorations in a dataset, in order to support a multivariate statistical approach . The possibilities of digital data collection offer new opportunities in this respect. In Germany, the initiative was taken in 1994 to start with a longevity survey on indirect ceramic inlay/onlay restorations, mainly using the CEREC system. Since 2008 available as an online platform, dentists can join this group with a certain amount of restorations for which data are uploaded on a website. This resulted in a large data set with information on inlay/onlay restorations placed routinely by dental practitioners and followed up for several years.

The aim of this study was to evaluate prospectively the longevity of ceramic inlay/onlay restorations placed in a web-based practice-based research network and to investigate risk factors associated with restoration failures.

Materials and methods

Practice-based research network

Data for this study were collected by a practice-based research network called Ceramic Success Analysis (CSA). Starting in 1994, the Society for Dental Ceramics (SDC) in Germany invited dentists to make specific recordings on all single ceramic restorations (inlays, onlays, and crowns) that were placed in their dental practices, including CAD-CAM chairside fabricated restorations and restorations manufactured by dental laboratories. In general, dentists who were enrolled in specific continuing education or training courses, especially on CAD-CAM restorations, were invited to join the network and introduce data from their restorations into the database. For becoming a member of the CSA project, each dentist was required to accept security and data protection conditions and had to follow protocols to include cases into the system. Between 1994 and 2007, the dentists used a Microsoft Access programmed databank and sent the data regularly via disc to the SDC. From 2008 onward, data collection was carried out via an internet platform ( www.csa-online.net ) in several languages, allowing dentists from other countries also to join the network. In total, 167 dentists from six countries (161 from Germany, 2 from Chile, 1 from China, 1 from Spain, 1 from France, and 1 from USA), uploaded data until 2014 on almost 6000 inlay/onlay restorations. Information on operator experience was not collected on this study.

Data recording

Originally, each professional could initially take part of the study with 50 cases, with a limit of one restoration per patient. Recently, including more than one restoration per patient into the dataset has been made possible. For all restorations recorded data included information such as date of treatment, type of restoration, surfaces included in the preparation, and materials used. Follow up was documented during regular check-up visits in the practice or when a problem occurred. Therefore, this study was a non-interventional trial, which according to guidelines for good clinical practice (Clinical trials – Directive 2001/20/EC), was not subject to Medical Ethical Committee approval. Patient and operator characteristics were analyzed anonymously according to privacy legislation. Dentists placed the restorations using the protocol they considered appropriate for each case with informed consent of the patient. The choice for specific materials, brands, and techniques was at the discretion of the operators.

Data analysis

The variables that were recorded by the dentists are listed in Table 1 (variables related to teeth and restorative procedures) and Table 2 (variables related to materials used). Both tables show description of the variable, categorization (when applied), and distribution of inlays/onlays in different variable groups. For adhesives, resin-based luting agents, and ceramics used in the restorative procedure, the dentist recorded the name and brand of products. For the analysis, each material was categorized ( Table 2 ) according to ceramic type, ceramic processing technique, adhesive system, and polymerization characteristic of resin-based luting agents. All restorations with missing data for variables (except for patient age) were excluded from the analysis.

Table 1
Distribution of ceramic inlay/onlay restorations according to tooth/restoration variables ( N = 5791).
Variable Description Outcome N %
Tooth Type of restored tooth Molar 3793 65.5
Premolar 1998 34.5
Number of restored surfaces Number of tooth surfaces included in the restoration 1 205 3.5
2 1359 23.5
3 2256 39.0
>4 1971 34.0
Endodontic treatment Presence of endodontic treatment Yes 391 6.8
Cavity outline Cervical margins of restoration Enamel 3162 54.6
Dentin 2629 45.4
Use of liner or base Liner or base material None 4856 83.9
Glass-ionomer 410 7.1
Composite 344 5.9
Others 181 3.1
Rubber dam Use of rubber dam during cementation Yes 3732 64.4
Matrix Matrix used during cementation Yes 3147 54.3
Silane Silane applied to ceramic Yes 5542 95.7
Ultrasonic cementation Use of ultrasonic device for cementation Yes 3420 59.1
Dental flossing Use of dental floss to remove excess luting agent Yes 3603 62.2
Oxygen-blocking Use of oxygen-blocking gel before cement photoactivation Yes 2412 41.7
Eva instrument Use of Eva oscillating instrument for finishing interproximal or cervical restoration areas Yes 575 9.9

Table 2
Distribution of ceramic inlay/onlay restorations according to materials variables ( N = 5791).
Variable Materials used Outcome N %
Ceramic FP : CEREC Block C In (Sirona); VITABLOCS ® TriLuxe forte, VITABLOCS ® RealLife, VITABLOCS ® TriLuxe, VITABLOCS ® Mark II (VITA)
LEU : HeraCeram, HeraCeramSun (Heraeus); IPS Empress CAD, IPS Empress Esthetic, ProCAD (Ivoclar); OPC press (Jeneric Pentron); Imagine PressX (Wieland)
LD : IPS e.max CAD, IPS Empress, IPS e.max Press (Ivoclar)
Ceramic type
Feldspathic porcelain (FP) 4475 77.3
Leucite glass-ceramic (LEU) 1076 18.6
Lithium dissilicate glass-ceramic (LD) 240 4.1
Processing technique
Monolithic restoration 5689 98.2
Veneered restoration 102 1.8
Adhesive Separate : Xeno III (Dentsply); AdheSE DC, Syntac Classic; Multilink Automix system (Ivoclar); Clearfil SE Bond; Panavia F2.0 system (Kuraray); Contax Bond, LuxaBond (DMG); OptiBond FL (Kerr); Adper™ Scotchbond™ MP (3M ESPE)
Simplified : One-Step Plus (Bisco); A.R.T. Bond (Coltene); Adhesive (Cumdente); Adper Scotchbond 1 XT, Pertac Universal Bond, Adper™ Prompt™, Scotchbond™ Universal Adhesive (3M ESPE); CharmBond (DentKist); Prime & Bond 2.1, Prime&Bond NT, XP Bond (Dentsply), ExciTE F (Ivoclar); Futurabond DC (Voco); G-BOND (GC); GLUMA® 2 Bond, I-BOND Total Etch (Heraeus); OptiBond Solo Plus (Kerr); Permaflow DC (Ultradent); VITA A.R.T. Bond (Vita)
Use of separate bonding resin
Separate bonding resin (3-step total-etch or 2-step self-etch adhesives) 4711 81.4
Simplified adhesive (2-step total-etch or 1-step self-etch adhesives) 845 14.6
Other a 235 4.1
Resin-based luting agent Photoactivated : Adaptic LC (Johnson & Johnson); ApaFill, ApaFlow (Cumdente); Brilliant NG, Synergy Nano Formula (Coltene); Ceram X, SpectrumTPH, X-flow (Dentsply); Charisma, Charisma flow, Durafill VS, Venus Composite (Heraeus Kulzer); Enamel plus HFO (Mycerium); Palfique Estelite LV (Tokuyama); Filtek Supreme, Filtek Supreme XT, Filtek Z100 MP, Filtek Z250 MP, Filtek Z500 (3M ESPE); Pertac (ESPE); Gradia Direct X, Gradia ® Direct LoFlo (GC); Herculite XRV, Prodigy, Point 4 (Kerr); Grandio (Voco); Tetric Ceram HB, Tetric EvoCeram, Tetric Evoflow, Heliomolar (Ivoclar)
Dual-cured : Bifix QM, Bifix SE (Voco); BisCem, Duo-link Universal (Bisco); Calibra, SmartCem2 (Dentsply); PermaCem Dual Smartmix, Vitique (DMG); Clearfil SA, Clearfil Esthetic Cement EX, Panavia F2.0 (Kuraray); Dual Cement, Multilink Automix, Multilink Sprint, SpeedCEM, Variolink II, Variolink Ultra, Variolink Veneer (Ivoclar); Duo Cement Plus, Duo Cement Plus (Coltene); Fantestic Core DC (R-dental); G-CEM (GC); iCEM Self Adhesive, Twinlook, (Heraeus Kulzer); Maxcem Elite, Nexus 2, NX3 Nexus, Porcelite Dual Cure, (Kerr); RelyX Unicem, RelyX Ultimate, RelyX ARC, 3M Opal (3M ESPE); PermaFlo DC (Ultradent); Sonocem (ESPE); Duo Cement (Vita)
Polymerization mode
Photoactivated luting agent 3430 59.2
Dual-cured luting agent 2361 40.8
a Combination of 195 restorations with no specified materials and 40 restorations luted with self-adhesive resin-based luting agents.

During the observation period, patients attended the same dental practice and maintained routine visits according to their dental treatment needs, without visiting other dentists during the period. In the check-up visits, or when a problem occurred, the restorations were inspected by the dentist in the practice, usually the same person that placed the restoration. When a dentist considered the restoration as clinically unacceptable, i.e. needing intervention, it was considered a failure and date and reason for failure were recorded. As only some dentists also recorded the type of intervention for failed restorations, this information was not included in the study. The date of the last check-up visit was recorded as the censoring date for restorations still in place without failure.

Statistical analyses were performed using STATA 12 software package (StataCorp LP; College Station, TX, USA). Descriptive statistics was used to report the frequency distribution of restorations by independent variables and reasons for failure. Annual failure rates (AFRs) were calculated from life tables according to the formula: (1 − y ) z = (1 − x ), in which “ y ” expresses the mean AFR and “ x ” the total failure rate at “ z ” years. The proportional-hazards test was assessed for each variable. Variables associated with failure were assessed by a multivariate Cox-regression analysis with shared frailty, taking into account that observations within the same group (dentist) are correlated, sharing the same frailty. Hazard ratios (HRs) with respective 95% confidence intervals (CIs) were determined. A significance level of 5% was considered for all analyses.

Materials and methods

Practice-based research network

Data for this study were collected by a practice-based research network called Ceramic Success Analysis (CSA). Starting in 1994, the Society for Dental Ceramics (SDC) in Germany invited dentists to make specific recordings on all single ceramic restorations (inlays, onlays, and crowns) that were placed in their dental practices, including CAD-CAM chairside fabricated restorations and restorations manufactured by dental laboratories. In general, dentists who were enrolled in specific continuing education or training courses, especially on CAD-CAM restorations, were invited to join the network and introduce data from their restorations into the database. For becoming a member of the CSA project, each dentist was required to accept security and data protection conditions and had to follow protocols to include cases into the system. Between 1994 and 2007, the dentists used a Microsoft Access programmed databank and sent the data regularly via disc to the SDC. From 2008 onward, data collection was carried out via an internet platform ( www.csa-online.net ) in several languages, allowing dentists from other countries also to join the network. In total, 167 dentists from six countries (161 from Germany, 2 from Chile, 1 from China, 1 from Spain, 1 from France, and 1 from USA), uploaded data until 2014 on almost 6000 inlay/onlay restorations. Information on operator experience was not collected on this study.

Data recording

Originally, each professional could initially take part of the study with 50 cases, with a limit of one restoration per patient. Recently, including more than one restoration per patient into the dataset has been made possible. For all restorations recorded data included information such as date of treatment, type of restoration, surfaces included in the preparation, and materials used. Follow up was documented during regular check-up visits in the practice or when a problem occurred. Therefore, this study was a non-interventional trial, which according to guidelines for good clinical practice (Clinical trials – Directive 2001/20/EC), was not subject to Medical Ethical Committee approval. Patient and operator characteristics were analyzed anonymously according to privacy legislation. Dentists placed the restorations using the protocol they considered appropriate for each case with informed consent of the patient. The choice for specific materials, brands, and techniques was at the discretion of the operators.

Data analysis

The variables that were recorded by the dentists are listed in Table 1 (variables related to teeth and restorative procedures) and Table 2 (variables related to materials used). Both tables show description of the variable, categorization (when applied), and distribution of inlays/onlays in different variable groups. For adhesives, resin-based luting agents, and ceramics used in the restorative procedure, the dentist recorded the name and brand of products. For the analysis, each material was categorized ( Table 2 ) according to ceramic type, ceramic processing technique, adhesive system, and polymerization characteristic of resin-based luting agents. All restorations with missing data for variables (except for patient age) were excluded from the analysis.

Table 1
Distribution of ceramic inlay/onlay restorations according to tooth/restoration variables ( N = 5791).
Variable Description Outcome N %
Tooth Type of restored tooth Molar 3793 65.5
Premolar 1998 34.5
Number of restored surfaces Number of tooth surfaces included in the restoration 1 205 3.5
2 1359 23.5
3 2256 39.0
>4 1971 34.0
Endodontic treatment Presence of endodontic treatment Yes 391 6.8
Cavity outline Cervical margins of restoration Enamel 3162 54.6
Dentin 2629 45.4
Use of liner or base Liner or base material None 4856 83.9
Glass-ionomer 410 7.1
Composite 344 5.9
Others 181 3.1
Rubber dam Use of rubber dam during cementation Yes 3732 64.4
Matrix Matrix used during cementation Yes 3147 54.3
Silane Silane applied to ceramic Yes 5542 95.7
Ultrasonic cementation Use of ultrasonic device for cementation Yes 3420 59.1
Dental flossing Use of dental floss to remove excess luting agent Yes 3603 62.2
Oxygen-blocking Use of oxygen-blocking gel before cement photoactivation Yes 2412 41.7
Eva instrument Use of Eva oscillating instrument for finishing interproximal or cervical restoration areas Yes 575 9.9
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Nov 23, 2017 | Posted by in Dental Materials | Comments Off on A practice-based research network on the survival of ceramic inlay/onlay restorations
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