Unlocking Endocrown Restoration Expertise Among Dentists: Insights from a Multi-Center Cross-Sectional Study

Background

The management of endodontically treated teeth (ETT) from the perspective of restorative care is a contentious topic as retention in such teeth is typically weakened. In order to treat these endodontically treated molars, post-and-core followed by metal or ceramic crowns have historically been the preferred gold standard restorative materials [1]. Post-and-core crown is a dental prosthesis for such ETT teeth, and it is usually completed by implanting a metal [2] or a fiber-reinforced composite [3] post-and-core into the root canal. However, with technological advancement, a macro-retentive design like a post is no longer necessary for the restoration of severely damaged teeth and this paradigm changes towards post-less restorations by using the pulp chamber as an extension has been made possible by adhesive techniques, which integrate the crown and core into a single monobloc [4]. This Monoblock approach, which served as the predecessor of endocrown (EC) was introduced by Pissis in 1995 and was used for the first time by Bindl and Mormann in 1999 [1]. In 2018, Tzimas et al described ECs as indirect monoblock restorations that rely on the pulp chamber of endodontically treated teeth (ETT) for retention and is made up of a pulp chamber, a circular butt-joint edge, and a central retention cavity [5]. The EC approach is indicated mainly when there is an extreme dental coronal loss and restricted interproximal distance. Additionally, ECs have shown advantages over conventional crowns in terms of application, less preparation and working time, and cost [6]. In teeth with short, destroyed, dilacerated, or narrow and calcified roots, ECs have become a viable restorative option [7,8] by providing a more favorable distribution of masticatory stresses and are more practical, conservative, and aesthetically pleasing [9]. This results in macromechanical retention (given by the pulpal walls) and microretention (by utilizing adhesive cementation) thereby preserves and protects the remaining tooth structure by reducing fracture resistance [10].

Also, there is a growing consensus that single, all-ceramic ECs with excellent mechanical qualities and high biocompatibility should be produced thanks to advancements in ceramic technology, particularly dental CAD/CAM systems [11,12]. These advancements in CAD/CAM technology, which offers accuracy, esthetics, and less time-consuming restorative procedures, has opened up new possibilities in material processing and tooth restoration [4] as the anatomic contour and surface textures of the ECs created using the CAD/CAM approach are superior. Thus, ECs fabricated using CAD/CAM and pressable ceramic technology can be considered as a reliable option for the restoration of moderately mutilated endodontically treated posterior teeth [13].

Despite the rising popularity of EC restorations among dental practitioners, the question that remains is whether dental professionals should consider utilizing EC instead of conventional procedures with intra-radicular posts. Most studies on endodontic crowns for teeth showed outcomes that were similar to or slightly superior to other conventional procedures (ETT). Several in vitro studies also examined how well the EC performs in comparison to conventional post retention crowns [9,14,15]. A study by Rasidi et al was also carried out in India in 2021 to evaluate dental professionals’ awareness, knowledge, and opinions regarding the use of EC as a postendodontic care strategy demonstrating an appropriate level of understanding and awareness of the use of EC as a post-endodontic care tool [16]. Another retrospective study was also carried out by Alotaiby et al in 2021 by dental students and residents in Riyadh, Saudi Arabia, and they concluded that EC is a conservative restoration method for endodontically treated teeth, particularly molars, with a very acceptable long-term survival rate and good biomechanical and functional efficiency [10]. Another study, by Soliman et al in 2021, was conducted amongst dentists in SA to evaluate post-core-crown restoration [17].

However, to the best of our knowledge, no international studies have been conducted to evaluate the knowledge and practice of ECs. To satisfy the patient’s demands and expectations with long-term restorative success, dentists should be knowledgeable about every possible dental treatment option. Thus, this web-based cross-sectional survey was conducted to evaluate the level of awareness, state of knowledge, and opinions towards EC as post-endodontic restoration among Saudi Arabia (SA) dentists and to compare their knowledge with some dentists who graduated from other countries.

Material and Methods

STUDY SETTING:

A cross-sectional, web-based questionnaire study was conducted amongst interns or graduated dentists practicing in government set-ups, private dental centers, and dental colleges from (SA) and different nationalities (dentists graduated from other countries) through an e-survey using Google Forms between December 2022 and January 2023.

STUDY POPULATION AND SAMPLING TECHNIQUE:

Snowball sampling technique was used to select the peers from SA and other countries among different groups. Sample size was calculated using G Power 3.1.9.4 at 95% confidence interval where α=0.05, (1−β)=80% and effect size=0.2. A total of 580 sample size was calculated.

STUDY TOOLS AND DATA COLLECTION:

The 18-item closed questionnaire was framed in accordance with the 2021 study by Soliman et al, with some modifications [17]. Lawshe’s methods [19] were used for content validity using judgments from a panel of 10 subjects matter experts (SME’s). The reliability was also established by test-retest among 20 volunteers of similar populations. The kappa value was 0.9, which indicated high reliability. This was followed by pilot testing among 10 volunteers who were asked to answer the questionnaire and provide feedback on content, clarity, and brevity of the questionnaire.

Check boxes were provided, and participants had to click on any one option for each question. Care was taken that one person could answer the questionnaire only once and all questions were mandatory. The responses were directly recorded through Google Forms. Since this was an e-survey, the informed consent was included in the Google form, and they were sent through WhatsApp.

QUESTIONNAIRE PARTS:

An English version of a web-based self-administrated questionnaire divided into 3 parts was distributed. The questionnaire consisted of a brief explanation of the purpose of the study, method of data collection, and close-ended questions. The first part of the questionnaire included questions regarding socio-demographic characteristics of the participants. The second part of the questionnaire consisted of 11 questions in relation to general knowledge of EC. The third part of the questionnaire consisted of 7 questions in relation to general practicing of EC and dental practicians. The responses were completely anonymous to ensure confidentiality.

DATA ANALYSIS:

Data were analyzed using statistical software R, version 4.2.2 (R Foundation for Statistical Computing) and Microsoft Excel. Categorical variables were represented by frequency and percentages. Chi-square test was used check the association between categorical variables. P-value less than or equal to 0.05 indicates statistical significance.

Results

A total of 583 participants were included in the survey. Among them, 51.11% were females and 48.89% were males; 56.43% of the participants were interns, 23.33% of the participants being graduated with less than 5 years of experience; 20.24% of the participants graduated with more than 5 years of experience; 50% of participants graduated from Saudi Arabia (SA); and 39.45% were working in the private sector and 21.61% were from the government sector (Figure 1).

On asking the participants about the information on EC, 45.97% stated that they were informed about EC through friends, and 61.23% of the participants stated that EC restorations are indicated for molar teeth. The goal of EC usage is to achieve minimally invasive preparations and to conserve the existing tooth structure as suggested by 69.64% of the participants; 40.14% of the participants also stated that the finish line of EC preparation is butt joint; and 63.46% of the participants answered that the material of choice for EC is all ceramic. Almost 52.32% stated that ECs are fabricated using CAD/CAM technology and 36.88% indicated it was true that EC design showed higher fracture resistance than conventional crowns. The recommended amount of the remaining pulp chamber height to be left for retention of EC is 3 mm, which was stated by 37.74% of the participants. Additionally, 40.48% participants also stated that if the floor of the pulp chamber is not completely flattened, the incidence of failure of ECs will increase; 50.09% mentioned that EC sometimes increases the rate of tooth fracture and 66.72% of participants answered that EC was an alternative to conventional post-and-core (Figure 2).

On questioning about EC practices in their clinics, only 41.17% of participants had performed cementation of EC in their clinic in the past years. Also, 37.39% of participants sometimes use rubber dams during EC cementation, and 42.88% of participants used X-rays to check the remaining height of the pulp chamber. When asked about the cause of restoration failures, 68.27% of the participants answered ECs debonding as one of the main cause of restoration failures and 66.72% of the participants stated that preparing ECs is more difficult than conventional post-and-core and crown preparations, and 69.98% of the participants stated that EC preparations and making impressions are more time-consuming than conventional post-and-core and crown preparations (Figure 3).

Using chi-square test alone and chi-square test with Monte Carlo simulation, there was a significant association (p<0.05) of knowledge and practice with the parameters such as gender, level of education, country of graduation, and working place of the participants (Tables 1, 2).

Discussion

The adoption of EC in clinical practice recently provided several benefits over post-core, which has been considered as a gold standard procedure in restoring ETT [20]. EC aims to preserve the remaining tooth structure available for bonding while maintaining the biomechanical integrity of ETT-compromised structures. ECs offer greater mechanical characteristics, minimum tooth structure loss, fewer clinical processes, reduced costs, and better esthetics [1,21–23]. Thus, we conducted this web-based cross-sectional survey to comprehensively and objectively evaluate the level of awareness, state of knowledge, and opinions towards EC as post-endodontic restoration among SA dentists and to compare their knowledge with some dentists who graduated from other countries. We used a Google questionnaire instead of a face-to-face questionnaire as we wanted to collect data from different nationalities and an e-survey was most suitable.

The samples included participants from SA and other countries who had different levels of knowledge and experience. Duration and language of teaching in SA for under graduation is 6 years study with an additional 1 year of compulsory internship, whereas in other countries it is only 5 years of study and a 1-year internship. Additionally, the language of teaching in SA is primarily English because of high number of Western staff members, while in other countries staff members teach in the local language only. Thus, economic status plays a significant role for offering payment for this type of costly treatment and this could be the reason for less knowledge and practice regarding EC usage among dental practitioners in SA. Based on the current study findings, they still employ traditional techniques, but the interns were the most enthusiastic about using it in clinical settings compared to dentists with experience of less and more than 5 years.

A successful and primarily minimally invasive EC prostheses can reduce the frequency of post-placement failures [11]. EC restorations have fewer interfaces in the restorative system [24], needless ETT preparation, and increased durability of the tooth structure [25–27]. In the present study assessing dental practitioners’ knowledge, most (69.64%) stated that the goal of EC usage is to achieve minimally invasive preparations and to conserve the existing tooth structure. The interns found this to be true the most and it could be attributed to their recent gain of knowledge from college.

The materials used for EC are ceramics that have been strengthened with lithium disilicate, or monolithic zirconia. Lithium disilicate is the most preferred material for EC due to its high aesthetic value and adequate mechanical strength [25,27]. Resin composite materials have problems with microleakage [24], it is less durable and more prone to fracture than LDGC [28]. However, while using this approach, the preparatory design and material selection should be considered [23,29,30]. Similar findings were recording by Wahab et al, who investigated the preferences of Jordanian dentists for EC materials [22]. The present study demonstrated the related finding that most participants (63.46%) preferred LDGC as the material of choice for EC. the interns from SA had more recent knowledge of about these materials than other dentists.

In relation to bonding surface, a butt-joint margin or a flat EC displays more remaining tooth tissue and less bonding area than a 90-degree shoulder EC produces [11,31]. However, there is not much scientific data to support this suggestion. Additionally, increased consistent stress distributed over the cervical butt-joint and axial walls was seen in the butt-joint margin and 20° bevel margin [13,32] in comparisons with the shoulder margin. This might significantly increase the risks of restoration debonding [33]. In a survey conducted by Rasidi et al, the majority of dentists (80.83%) responded that butt-joint finish line was used during EC preparation [16]. This is because forces applied to this type will reduce the amount of pressure on the pulpal floor [1,8,9,34]. Thus, EC preparation consists of an equigingival butt-joint margin and a central retention cavity into the pulp chamber. This is comparable to the present results, as a majority (40.14%) stated butt-joint as the finish line of EC preparation, which was mostly correctly answered by interns.

In support of these results, Sedrez-Porto et al demonstrated that EC restorations outperformed conventional restorations and have high fracture strength and are preferred over other conventional restorations [9]. This is in line with other research that has established the validity of bonded ECs over conventional ones [11,16]. Abu-Nawareg et al revealed that ECs had greater fracture strength values than conventional crowns [35]. In our study, 36.88% of participants stated that EC design showed higher fracture resistance than conventional crowns. The rest mostly replied with “I don’t know”. This may be because there is less use of ECs in private clinics in SA and other countries compared to traditional crowns. Thus, EC designs demonstrated superior fracture resistance to conventional post-core-crown design [4,35].

According to a qualitative survey by Rasidi et al, most participants (82.5% dentists) believed that pressable ceramic technology can be used to construct an EC [16], but the present study results disagree with those findings. On questioning about ECs fabrication, interns from SA were more likely to answer that ECs are fabricated using CAD/CAM technology. Also, in the study by Rasidi et al, when asked to list the advantages of EC has over a traditional crown, the majority (56.67%) said it will take the least amount of time and 25.0% said it requires the least amount of preparation [16]. This was contrary to our study findings, as 66.72% of interns stated that preparing ECs is difficult in comparison to conventional post-core-crown preparations. Rasidi et al [16] found that only 27.5% of dental practitioners said that they have really used EC, whereas most (72.5%) said they had never used it before based on their training experience. This also supported our findings, as the majority of participants (42.02%) had never cemented ECs in their clinics. This is due to the fact that the most popular procedure is prefabricated post-core, followed by EC and cast post-core [17].

Moreover, in the present survey, the majority of interns (50.09%) claimed that EC can occasionally increase the rate of tooth fracture, and 66.72% mentioned EC as a substitute for traditional post-core. In addition, Ghoul et al showed that 90% of EC failures involved tooth fractures and displacement of the restoration on the side opposite the incidence of stress [36]. To ensure proper isolation, a rubber dam was used. The tooth surface was treated with etchant (37% phosphoric acid) for 15 seconds, after which it was thoroughly washed and allowed to dry naturally. Next, a bonding agent was applied to the tooth, and it was polymerized for 20 seconds under a curing light [37,38]. In this study also, very few participants (37.39%) sometimes used rubber dams during EC cementation.

Further, the difference in elasticity between tougher ceramics and softer dentine causes danger of debonding and root fracture with ceramics as they have different moduli of elasticity. Hence, choosing the right case is essential to the clinical success of ECs [16]. Debonding was cited as the main drawback of EC by the majority of dental professionals (80.0%) [14]. These findings were comparable to the present study findings (68.27%), as debonding of ECs is one of the main causes of restoration failure [39]. This has been proved to be an excellent strategy since the procedure is uncomplicated and facilitates the steps of impression taking and protects the periodontium. Moreover, ceramic has similar wear characteristics to actual teeth and has the benefits of biocompatibility. However, in our study the majority were interns (69.98%) who also stated that EC preparations and impression-making are more time-consuming in comparison to others. Deepak et al also conducted a cross-sectional survey to examine the dentists in Chennai’s level, concluding that ECs can be a viable alternative to severely damaged crowns [11]. The different answers found in this study indicated the need for clear protocol for diagnosis, indication, application, and cementation of EC. This was specifically true for the graduates with and without experience, as it depends on the constant use of the material and procedures in practice to be abreast of the knowledge associated with them. Additionally, future research is needed also about partially explored variables such as flexural [40] and compressive strengths [41] of EC. Further research is needed to test mechanical properties of these frameworks. Another reason for the above findings could be the economic status playing a role in offering payment for this type of costly treatment.

The limitation of this study firstly includes the sample size from a single population and a brief study period, which does not accurately reflect the size of the population, and the results of this retrospective study should be evaluated cautiously. Secondly, the FIFA world cup was conducted in Qatar during our study, contributing to a low response rate. Also, the duration of BDS programs in the included countries is different, which could be responsible for rigorous training. The language of teaching is mainly English in SA because of the high number of international staff as compared to the remaining countries, which have local staff members. This may also be responsible for disparities in understanding among the participants.

Conclusions

ECs can be used as an alternative to the traditional post-core for restoring root canal-treated teeth with severely damaged dental tissue. Overall knowledge and practice of ECs were low among all participants regardless of their experience and country of graduation. The above results with respect to dentists from SA highlight the fact that ECs must be included in the curricula for theory and clinicals. It should be considered as a topic for continuing education programs after graduation so that dentists can perform different treatment modalities to best suit the needs of patients.