The Endocrown; a Prospective Randomised Clinical Trial of Three Different Ceramics
Phase: NA
Conditions: Pulp Disease, Dental, Dental Caries, Dental Leakage
Sponsor: University of Jordan

Research Protocol 
 
 
Date: Jan 10th, 2018 
Title: Survival of Endocrowns Made from Different Ceramics 
NCT number: NCT03542019 
 
 
 

Background: Endodontically treated teeth often lose a significant amount of tooth structure due to 
caries or trauma, which renders them at risk of catastrophic fractures1. Their restoration requires a 
means to protect the cusps from the wedging forces of occlusion. Cuspal coverage using full metal or 
porcelain crowns has been traditionally used and has been demonstrated to improve their survival 
rate2, 3.  
Recently, the demand for more aesthetic and conservative restorations has grown, and the 
introduction of CADCAM technology has allowed the preparation and cementation of indirect 
restorations at the same day. Adhesive indirect restorations have become popular and their 
application in dentistry has involved the restoration of endodontically treated teeth. Full and partial 
onlays and full coverage crowns have been used successfully to provide cuspal protection4. The 
endocrown is another form of adhesive indirect restorations that incorporates the core and cuspal 
coverage in one unit which is then bonded to the remaining tooth structure 5. Endocrowns can be 
made from different types of ceramics. Lithium disilicate ceramic has been used extensively for this 
purpose due to its favourable physical properties, good aesthetics and its predictable bonding to tooth 
structure 6. However, when milled from ingots, it requires an additional step of crystallization which 
will increase marginal gaps 7, 8. This step is also time consuming and in a busy practice may be 
considered a draw back to the material.  
Zirconia has become a popular option in dentistry due to its superior toughness and fracture resistance 
compared with other types of ceramics. When the CAD/CAM technology is used, zirconia restorations 
are usually milled from pre-sintered blocks which must be sintered after milling in order to achieve 
their maximum strength. This step is time consuming.  
Hybrid ceramics are a new category of ceramics with a dual ceramic-polymer network that 
incorporates the benefits of ceramic and composite materials offering strength, flexibility, crack 
prevention properties and a superior abrasion behaviour 9. Furthermore, hybrid ceramics require no 
additional steps following their milling from CAD/CAM blocks.  They can be bonded to the tooth 
straight after its milling which is a favourable property in a busy dental practice.  
Clinical data on the longevity of this type of restorations is scarce 10. The aim of this study is to assess 
the short and long-term outcomes of endocrowns made from three different materials; Lithium 
disilicate ceramic (IPS e.max ®), monolithic translucent zirconia and a hybrid ceramic (Vita Enamic®).   
 
Material and methods:  
Sample size calculation: 

Sample size per each group was set at 20 restorations based on similar studies investigating the outcome of 
different restorations on root canal treated teeth. 
Inclusion criteria: 
Root canal treated molars with significant loss of tooth structure and supra-gingival margins that 
are scheduled for cuspal-covering indirect restorations are included in this study. 
Exclusion criteria: 
Teeth with extensive cracks or fractures  
Teeth with deep subgingival margins  
Non-functional teeth (no opposing dentition) 
Teeth with advanced periodontitis 
 
Following root canal treatment, teeth will be randomly allocated into one of three groups according to 
the material of the endocrown they will receive; group A (n= 20): IPS e.max lithium disilicate ceramic, 
group B (n= 20): monolithic translucent zirconia, and group C (n= 20): Vita Enamic hybrid ceramic. 
Preparation of all teeth will be performed by the same operator. Impressions will be made using a 
conventional 2-stage putty and wash silicone impression material (We’ll choose one) and the same 
dental technician will provide all the endocrowns by milling them from CAD/CAM blocks. Cementation 
will be done under rubber dam isolation using the recommended protocol for each material.  
Clinical follow-up assessment will be made at 6 months, 1 year, 2 years and 5 years post-operatively. 
This will include assessment of the restoration integrity, marginal integrity and marginal discoloration, 
pink and white aesthetic scores and pocket probing depths. 
Radiographic assessment will be made at 1 year, 2 years and 5 years post-operatively to detect the 
presence of restoration defects and recurrent caries. 
Patient satisfaction will be assessed on a visual analogue scale (0-10) 
All assessments will be done by an experienced independent clinician unaware of the material used.  
 
Statistical analysis  
Non-parametric tests will be used to discern any statistically significant difference between groups. 
Wilcoxon signed-rank and Mann-Whitney tests will be used for tooth integrity, marginal integrity 
and discoloration, PES&WES and patient’s satisfaction. Non-parametric T-test will be used for 
radiographic parameters.  
Weibull distribution will be used o predict long-term survival rates per each group. 
Funding: 
This research needs funding to cover the cost of a) the lab fees of fabricating 60 endocrowns and 
b) the resin cement systems. Please see attached sheet. 
 
 

Data collection form (appendix 1): 
 
Patient: ____________________________________ 
DOB: ______________________________________ 
Tooth: _____________________________________ 
Material (coded): ____________________________ 
Date: ______________________________________ 
 
a- Clinical examination:  
Endocrown failure: Yes / No (Specify type of failure) _____________________________________ 
Weeks from cementation to failure: __________________________________________________ 
Modified USPHS criteria (use Alpha, Bravo, Charlie and Delta as in the key) 
Margins: ____________________________________________________________________   
Anatomic form: ______________________________________________________________ 
Texture: ____________________________________________________________________ 
Colour match: _______________________________________________________________ 
BoP/ pockets: ___________________________________________________________________ 
b- radiographic examination:  
Secondary caries (0: absent, 1: present) _____________________________________________ 
Proximal caries in adjacent teeth (0: absent, 1: enamel, 2: dentine) _______________________ 
Excess cement (0: absent, 1: detectable, 2: gross): _____________________________________ 
Periapical infection: (0: absent, 1: present/ improving, 2: present/ not improving or getting worse) _________ 
 
c- Patient-reported satisfaction (use the VAS below):  
Shade: _______________________________________ 
Shape: _______________________________________ 
Quality of proximal contacts  
(Food impaction/ ability to floss) _______________________ 
Chewing ability ________________________________ 
Overall satisfaction _____________________________ 
 
ID: ______________________________ 
Phone no.: _______________________ 
e-mail: __________________________ 
________________________________ 

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