Dentinal microcracks induced by endodontic procedures: A scientometric and bibliometric analysis.

Background: Due to the large number of publications relating the occurrence of dental microcracks to endodontic procedures, this bibliometric study evaluated the scientific pattern and trends in literature and provided an overview of scientific production in this context. Aim: To analyze, quantify, and characterize the scientific production and trends of published articles evaluating dentinal microcracks formation after endodontic treatment procedures between 2010 and 2020 using bibliometric indicators. Materials and
Methods: Published articles were found by the search in the Medline (PubMed) and Scopus database using the combination of the following keywords: Dentinal crack OR Dentinal Microcrack OR Crack formation OR Dentin Defect AND Endodontic treatment OR Root canal preparation OR Canal Preparation OR Root canal treatment OR endodontic procedures. The search was also conducted in the Journal of Endodontics and International Endodontic Journal. After inclusion and exclusion criteria application, data from all studies included were collected.
Results: Among the 556 results after the search, 45 studies were included and analyzed in this bibliometry. No trend was observed in terms of the increasing number of articles over time. Most of them used an in vitro design, compared the effect of different endodontic techniques/systems for root canal instrumentation on dentinal microcracks formation, and were conducted in Turkey, Brazil, and India. Journal of Endodontics and International Endodontic Journal were the main journals with a higher number of articles published. Interestingly, studies conducted with some funding did not lead to higher citation numbers. Moreover, a relevant proportion of studies did not consider the inclusion of control groups, baseline evaluation, or statistical analysis. Micro-CT was the main technique used to evaluate microcrack presence.
Conclusion: Microcrack formation after the use of different endodontic techniques/systems has been constantly evaluated in the literature. There is a pattern of methodologies used, which may explain the concentration of these studies in specific journals and countries. Copyright:

INTRODUCTION

Endodontic procedures directly affect root canal structure. The different techniques can generate some root defects, although endodontic treatment systems have been constantly enhanced over time.[123] The different endodontic systems used optimize root canal instrumentation and shaping, filling procedures, and clinical time.[45] However, these systems may lead to tooth structure removal and higher mechanical load on the root canal, thereby affecting tooth integrity.[567]

Dentinal microcracks have been associated as a common sequel of root canal treatment procedures.[891011] which presence can reduce root resistance.[212] In fact, the literature has suggested that some dentinal defects can act as the first step to vertical tooth fracture and, consequently, result in tooth extraction.[12] Recently, a systematic review suggested that when a proper technique is applied to treat root canals, the risk for dentinal microcrack can be reduced.[5]

Dentinal microcrack has been evaluated and compared with different treatment modalities since that different root canal instrumentation systems have been developed.[131415] Previous in vitro, in situ, and in vivo studies have evaluated the effect of different instrumentation systems, disinfection protocol, endodontic retreatment, and filling procedures on dentinal microcrack development.[161718192021] These different approaches to evaluate dentinal microcracks presence and the different reasons to generate these defects suggest no clear pattern or evidence in this topic. In this context, dentinal microcrack evaluation after endodontic treatment is an emerging and important topic to be considered by scientific evidence to guide clinical approach and reduce this undesirable situation. Therefore, the bibliometric evaluation of studies in this topic may contribute significantly to evaluating the pattern of scientific evidence generated, its impact, gaps to be considered by the literature, and to guide future studies.

Bibliometric analyses are important tools to identify trends and patterns of scientific evidence produced on a specific topic, or in a specific area or journal.[2122] This kind of approach evaluates different aspects of articles produced in a specific field both quantitatively and qualitatively and provides information gathered from a specific level (authors) to a broader level (countries/world).[2123] Therefore, bibliometry can be considered a relevant metric of science, and an extremely important tool that can be used to provide an overview of both oppositional and relevant new topics, such as microcrack formation after endodontic treatment. Moreover, identification of such patterns is very useful in identifying the problems and gaps to be overcome by future studies, mainly in terms of methodology, scientific progress, and ultimate improvement in therapeutic approaches, clinical longevity, and success rates.[2425] However, no previous study has conducted a bibliometric analysis of the literature to improve the existing knowledge by evaluating the effect of endodontic treatment procedures on dentinal microcrack development.

This study aimed to analyze, quantify, and characterize scientific production and trends of published articles evaluating dentinal microcrack formation after endodontic treatment procedures between 2010 and 2020, using bibliometric indicators.

MATERIALS AND METHODS

Search strategy

A scientific search was conducted to answer the following question: “What is the scientific production, regarding dentinal microcrack formation after endodontic treatment procedures, made in the last 10 years?” This bibliometric analysis took into account the scientific production between 2010 and 2020 and was made on October 17, 2020, in the MEDLINE (PubMed) and Scopus databases. The combination of the following keywords was used to query the database: Dentinal crack OR Dentinal microcrack OR Crack formation OR Dentin defect AND Endodontic treatment OR Root canal preparation OR Canal preparation OR Root canal treatment OR Endodontic procedures. The search was conducted in the field of interest and considered the title, keywords, and abstract of the studies. Moreover, the combination of some keywords (dentinal microcrack and endodontic treatment) was used to identify studies published in the Journal of Endodontics and International Endodontic Journal, the two endodontic journals with the highest impact factor according to the Web of Science Journal Citation Reports. The list of references of the included studies was also checked for any additional studies that may not have been included in the previous search. The inclusion criteria involved only studies reporting on dentinal microcracks after endodontic treatment procedures, qualitative and/or quantitative evaluation of microcracks, and studies published in English; in vivo, ex vivo, in vitro, and in situ studies; studies using human teeth. The exclusion criteria consisted of reviews and case reports; letters to the editor and comments; any study that did not meet the specifications of the inclusion criteria. The first step was to exclude all the duplicates of the two databases; then, all the studies were screened according to the topic and field by reading their title and abstract. All the studies in the field, which met the inclusion criteria, were selected for full-text eligibility. Thus, only studies were included in this bibliometric analysis.

Data collection

The following data were collected from the studies: First, the author, journal, year of publication according to the database or the information provided in the paper, country of the corresponding author, university/school/institute of the corresponding author, number of institutions in the article, impact factor of the journal, number of citations in the Scopus database, average citations per year, funding, design, main purpose, endodontic system (hand/manual, reciprocating and/or rotary), the technique used to evaluate the existence of microcracks, the period between treatment and microcrack evaluation, teeth used, existence of a control group, baseline evaluation, statistical analysis, and possible conflicts of interest.

Data analysis

A descriptive analysis of the variables collected was performed using Microsoft Excel software. Graphs were made using PRISM 8 Software (Microsoft Corporation, Redmond, Washington, USA, GraphPad Software, Inc., San Diego, California, USA).

RESULTS

A total of 556 publications related to the topic were identified in the databases and journals selected. Among them, 45 studies were included and analyzed in this bibliometry after applying the search strategy and inclusion criteria. There is no clear trend in terms of an increase in the number of articles published per year from 2010 to 2020 [Figure 1a]. In 2018–2020, an average of 5.3 studies was published per year evaluating dentinal microcrack formation after endodontic treatment. The year 2017 had the highest number of articles published (14 articles). However, the analysis conducted suggests a slight increase in the number of funded studies over time and a clear decrease in nonfunded/uninformed studies between 2017 and 2020 [Figure 1a].

Figure 1

(a) Total number of studies published per year between 2010 and 2020, and according to funding. (b) Distribution of studies according to the three countries with the highest number of papers published: Number of papers per country, and percentage of studies with funding in each country. (c) Average number of institutions in the studies conducted in each country. (d) Venn diagram of the three countries with the highest number of papers published, according to the journal of publication

All the articles were published between 2012 and 2020, and 88% used an in vitro experimental design [Table 1]. Interestingly, most of the studies evaluated the effect of different techniques or systems (comparisons) on dentinal microcrack formation [Table 1]. Considering the techniques applied in each study, most of the studies compared the differences among rotary, reciprocating, and self-adjusting file systems. These studies were developed in countries from the Americas, Europe, and Asia. The results highlight that the topic of development and application of new instrumentation systems has been evaluated constantly regarding the effect on dentinal microcrack formation.

Table 1

Description of the studies included, according to year, country of the corresponding author, experimental design, main purpose of the study and root instrumentation technique

Study	Year	Country of the corresponding author	Design	Method	Main purpose	Dental group	Technique
Yoldas et al.[8]	2012	Turkey	In vitro	Stereomicroscope	Technique/system comparison (instrumentation)	Mandibular first molars	H, RO, SAF
Liu et al.[26]	2013	Netherlands	In vitro	Microscope	Technique/system comparison (instrumentation)	Mandibular incisors	RO, SAF, REC
De-Deus et al.[27]	2014	Brazil	In vitro	µCT	Technique/system comparison (instrumentation)	Mandibular molars	REC
Arias et al.[28]	2014	USA	In situ	Microscope	Technique/system comparison (instrumentation)	Mandibular incisors	H, RO
Ashwinkumar et al.[29]	2014	India	In vitro	Microscope	Technique/system comparison (instrumentation)	Mandibular first molars	H, RO, REC
Aydin et al.[30]	2015	Turkey	In vitro	µCT	Technique/system comparison (instrumentation)	Mandibular premolars	REC
Çiçek et al.[31]	2015	Turkey	In vitro	SEM	Technique/system comparison (instrumentation)	Mandibular molars	H, RO, REC
Kansal et al.[32]	2014	India	In vitro	Stereomicroscope	Technique/system comparison (instrumentation)	Mandibular premolars	RO, REC
Priya et al.[33]	2014	India	In vitro	Stereomicroscope	Technique/system comparison (instrumentation)	Mandibular central incisors	H, RO, REC
Li et al.[34]	2015	China	In vitro	Stereomicroscope	Technique/system comparison (instrumentation)	Molars	RO, REC
Ceyhanli et al.[35]	2016	Turkey	In vitro	µCT	Technique/system comparison (instrumentation)	Mandibular molars	RO, REC
Ustun et al.[36]	2015	Turkey	In vitro	µCT	Test instruments	Mandibular incisors	H, RO, REC
Pop et al.[37]	2015	England	In vitro	SRCT	Technique/system comparison (instrumentation)	Molars	RO, REC
Caballero et al.[38]	2015	Peru	In vitro	SEM	Instrumentation material evaluation	Mandibular molars	RO, REC
Gergi et al.[39]	2015	Lebanon	In vitro	Microscope	Technique/system comparison (instrumentation)	Molars	RO, REC
Miguéns-Vila et al.[40]	2017	Spain	In vitro	LED transillumination	Technique/system comparison (curved root)	Mandibular premolars	RO
Bahrami et al.[41]	2017	USA	In situ	LED transillumination	Technique/system comparison (instrumentation)	Mandibular incisors, canines and premolars	H
Bayram et al.[42]	2017	Turkey	In vitro	µCT	Test new technique/system (instrumentation)	Mandibular premolars	RO, SAF
De-Deus et al.[43]	2017	Brazil	In situ	µCT	Technique/system comparison (instrumentation)	Mandibular molars	RO
Bayram et al.[44]	2017	Turkey	In vitro	µCT	Technique/system comparison (instrumentation)	Mandibular incisors	RO
de Oliveira et al.[14]	2017	Brazil	In vitro	µCT	Technique/system comparison (instrumentation)	Mandibular incisors	H, RO, REC
De-Deus et al.[16]	2017	Brazil	In vitro	µCT	Technique/system comparison (filing)	Maxillary premolars	REC
Saha et al.[45]	2017	India	In vitro	SEM	Technique/system comparison (instrumentation)	Mandibular premolar	RO
Zuolo et al.[46]	2017	Brazil	In vitro	µCT	Technique/system comparison (instrumentation)	Mandibular incisors	RO, REC
Koçak et al.[47]	2017	Turkey	In vitro	µCT	Retreatment effect	Mandibular premolar	RO
Kfir et al.[48]	2017	Israel	Ex vivo	Section and Magnification	Technique/system comparison (instrumentation)	Maxillary first premolars	RO
Bucchi et al.[49]	2017	Spain	In vitro	Clinical exam and SEM	Technique/system comparison (root-end)	Nonspecified	H
Kesim et al.[13]	2017	Turkey	In vitro	Stereomicroscope	Technique/system comparison (instrumentation)	Mandibular premolars	H, RO, REC
Pedullà et al.[9]	2017	Italy	In vitro	Stereomicroscope	Technique/system comparison (instrumentation)	Mandibular central incisors	RO, REC
Jain et al.[50]	2018	India	In vitro	µCT	Technique/system comparison (retreatment)	Mandibular premolars	H, REC
Braun et al.[18]	2018	Germany	In vitro	Photographic	Disinfection protocol	Nonspecified	REC
Li et al.[51]	2018	China	In vitro	µCT	Technique/system comparison (instrumentation)	Mandibular first molars	RO, REC
Langaliya et al.[52]	2018	India	In vitro	Stereomicroscope	Technique/system comparison (instrumentation)	Nonspecified	H, RO
John et al.[53]	2018	India	In vitro	Stereomicroscope	Technique/system comparison (instrumentation)	Maxillary central incisors	REC
PradeepKumar et al.[19]	2019	Canada	In vivo	µCT	Technique/system comparison (instrumentation)	Maxillary and mandibular premolars	RO, H
Çapar et al.[54]	2019	Turkey	In vitro	Stereomicroscope	Test techniques used to evaluate microcracks	Mandibular incisors	RO
Rödig et al.[55]	2019	Germany	In vitro	µCT	Technique/system comparison (instrumentation)	Mandibular premolars and maxillary molars	RO, REC
Aksoy et al.[15]	2019	Turkey	In vitro	µCT	Technique/system comparison (instrumentation)	Mandibular molars	RO, REC
Uğur Aydın et al.[56]	2019	Turkey	In vitro	µCT	Technique/system comparison (instrumentation)	Mandibular first molars	RO, REC
Sachdeva et al.[57]	2019	India	In vitro	µCT	Root-end cavity preparation	Mandibular premolars	RO
Katanec et al.[58]	2020	Croatia	In vitro	µCT	Technique/system comparison (instrumentation)	Maxillary premolars	RO
Almeida et al.[59]	2020	Brazil	In vitro	µCT	Technique/system comparison (retreatment)	Mandibular molars	REC
Jamleh et al.[11]	2020	Saudi Arabia	In vitro	µCT	Effect of temporary filling placement	Maxillary premolars	H
Alkahtany[60]	2020	Saudi Arabia	In vitro	Microscope	Technique/system comparison (instrumentation)	Mandibular molars	RO
Vieira et al.[21]	2020	Brazil	In vitro	µCT, SEM	Techniques used to evaluate microcracks and type of canal	Mandibular incisors and molars	REC

µCT: Microcomputed tomography, H: Hand/manual instruments, RO: Rotary, REC: Reciprocating, SAF: Self-adjusting file, SEM: Scanning electron microscopy, SRCT: Synchrotron radiation-based µCT, LED: Light-emitting diode

Turkey, India, and Brazil were the three countries with the highest number of articles published, respectively [Figure 1b]. Of these, Brazil was the country with the highest number of institutions per article: An average of 4.2 institutions per study [Figure 1c]. Although Turkey, India, and Brazil were the three countries with the highest number of articles published in the area of dentinal microcrack [Figure 1d], they published articles in only two journals, the Journal of Endodontics and the International Endodontic Journal [Figure 2a].

Figure 2

Characterization of journals and studies included. (a) Number of studies published in the five journals with the highest number of papers published, average citations in papers published in each journal, and average citations per year in each journal. (b) Average number of citations according to the impact factor of the journal. (c) Average number of citations according to funding. (d) Presence of dentin microcracks in the test group. (e) Teeth used in each study. (f) Presence of a control group in the studies. (g) Baseline evaluation in the study, before endodontic treatment. (h) Statistical analysis of data. (i) Techniques used to evaluate presence of dentin microcracks

The Journal of Endodontics had the highest number of studies published, followed by the International Endodontic Journal, Clinical Oral Investigations, European Journal of Dentistry and Journal of Conservative Dentistry [Figure 2a]. Moreover, the studies published in the Journal of Endodontics also showed the highest average of citations in the Scopus database [Figure 2a]. As expected, the articles published in the journals with the highest impact factor also showed the highest average of citations [Figure 2b]. Interestingly, studies conducted with funding did not show a higher average of citations compared to those without any funding [Figure 2c].

Two journals had the highest number of articles published in this field, Journal of Endodontics and International Endodontic Journal. The main countries publishing in these journals were Turkey and Brazil [Table 2], in that Turkey was the country with the highest number of papers.

Table 2

Three countries with the highest number of papers in the two journals with the highest number of papers

Country	n
Journal of endodontics
1st Turkey	4
2nd Brazil	4
1st USA	2
International endodontic journal
1st Turkey	1
2nd India	1
1st Brazil	1

In terms of study design and results, most of the studies found dentinal microcrack formation in the test group after endodontic procedures [Figure 2d]. Human molars and premolars were the teeth most widely used in the studies to evaluate this outcome [Figure 2e]. Although most of the studies evaluated and compared different endodontic techniques and systems, 42% of the studies did not include or report any control group [Figure 2f]. However, 24% of the studies conducted no baseline analysis to check the existence of previous microcracks before the endodontic procedures were initiated [Figure 2g]. Moreover, although group comparison is an important parameter to be evaluated, few studies conducted any statistical analysis [Figure 2h].

Flow diagram of selected studies

Another important parameter is the technique used to evaluate dentinal microcrack formation. Most of the articles used micro-computed tomography (CT) as the standard and best technique to identify dentinal microcracks [Figure 2i]. However, other techniques have been applied, such as stereomicroscopes and scanning electron microscopy. It is important to highlight those techniques should be standardized to allow comparison between different studies.

DISCUSSION

This study evaluated for the first time the scientific trend of published articles between 2010 and 2020 evaluating microcrack formation after endodontic procedures. This bibliometric overview provided relevant information to identify important countries and journals publishing on this topic. Although different endodontic techniques and systems have been developed over time, interestingly, there is no increased number of published articles studying dentinal defects,[51315] such as microcracks.[5] Since these systems, mainly mechanized techniques may lead to higher mechanical load on the root canal,[67] it is extremely important that new systems be evaluated in terms of dentinal microcracks formation.

In addition, an evident decrease was found to no funding studies in the recent year (2017–2020), and a slight increase for funded studies, which suggests that the endodontic industry is may provide some support for researchers to evaluate new systems. In fact, funding in Dentistry research represents an important part of financial support in the biomedical area, and the previous study showed no gender difference in the award rate.[61]

Turkey was the country with the highest number of published articles, followed by India and Brazil. This is an interesting finding that supports another finding, namely that high and middle-income countries are publishing in this field. However, most likely, the studies by middle-income countries are supported by funding agencies intent on promoting scientific production in the country. This is the case of Brazil, which has conducted a higher number of funded studies than Turkey. Moreover, the studies published in Brazil reveal a higher number of institutions per study, that is, 4.2 institutions. This pattern is quite common in dental research and has also been observed in other topics of research, such as implantology,[62] and even other areas, such as virology.[63] What may be driving the high-quality profile of articles being published is the collaboration among different scientific research institutions. Actually, the present study confirmed that increased scientific production is connected to greater collaboration. This research networking system offers several advantages to scientific development, including new knowledge, new researchers, and improved studies and curriculum.[62] Our findings on Indian studies also corroborate a recent survey that revealed a growing trend of publications from India in the area of Regenerative Endodontics.[64]

As expected, most of the studies presented a in vitro design. The only study designed as an in vivo assay performed in vivo endodontic treatment and microcrack evaluation after tooth extraction.[19] This kind of approach mimics what occurs in endodontic clinical treatment, except that tooth extraction procedures may lead to dentinal microcracks,[17] and baseline evaluation is an important parameter to differentiate the defects caused solely by endodontic procedures. Since most of the studies were conducted with extracted human teeth, and the extraction procedure may lead to some dentinal cracks, it should be underscored that this procedure requires the appropriate selection of teeth.[65] Furthermore, there may be previous microcracks in the dentin of human teeth, caused by functional and parafunctional habits. Therefore, in vitro design is the first option for carrying out this evaluation. Another possibility for studies on this topic are studies on cadaver mandibles/maxillas, in order to satisfactorily reproduce most of the clinical conditions and reduce the risk of bias.[162841] Although most studies have evaluated the effect of different techniques and systems used for root canal instrumentation on dentinal microcrack formation, they have not evaluated this effect across each step of endodontic treatment. Identification of each specific step and instrument involved in microcrack formation could provide important information that would optimize the endodontic systems and possibly prevent this kind of defect. In this respect, another important parameter constituting an essential part of the scientific method is the use of control groups.[66] to compare the real effect of the tested systems on dentinal microcrack formation. In summary, future studies should consider the baseline evaluation to estimate possible microcracks resulting from endodontic treatment, and the use of control groups to identify the real effect of the procedure. Moreover, the identification of dental microcrack formation after each step of the endodontic treatment should also identify the several different endodontic systems used, to guide clinical practices and enable prevention of this defect.

The Journal of Endodontics had the highest number of articles published in this field, ultimately leading to the highest average of total and yearly citations. Although the journal is American, Turkey was the country with the highest number of papers published in the Journal of Endodontics, highlighting the international nature of the journal, and its role as one of the leading journals in endodontic research and clinical practice. Moreover, this journal has also been the main choice for the publication of articles focusing on other topics, such as regenerative endodontics.[67] Considering that the impact factor is a measure of the article's citations, the studies published in journals with a higher impact factor showed a higher average number of citations. The same citation average was found for studies that showed no effect involving the parameter of citations that could be derived from funding.

In terms of methodology, micro-CT was the main technique used to evaluate dentinal microcracks in the root canal. Overall, different microscopic techniques have been used to perform these evaluations, but some studies do not specify the microscopic technique used, thereby hindering production by others authors. Micro-CT analysis has been widely used in endodontics and provides a quantitative and qualitative assessment for endodontic procedures, including information regarding the location and size of the microcrack after endodontic procedures.[6869] Previous studies have evaluated different methods of identifying dentinal microcracks after endodontic treatment, and have found no difference between micro-CT and stereomicroscope.[54] Although scanning electron microscopy identified a higher percentage of microcracks than micro-CT or stereomicroscopy,[7071] the sample preparation for this analysis can result in new microcrack formation, thus overestimating the incidence of microcracks.[54] Furthermore, stereomicroscope requires sectioning of the root, thereby not allowing adequate evaluation before endodontic treatment is initiated. For this reason, micro-CT has been considered the best method to identify dentinal microcrack formation and should be considered as such by future studies.

The basic limitation of this study is based on the fact that all the studies included come from two scientific databases and the two main journals in the field of endodontics. Therefore, the studies not included in these databases were not considered for analysis. Moreover, other limitations regard study terminology and concepts, considering that some studies may have been excluded from analysis because they use different terms to characterize dentinal microcracks or evaluate cracks, mainly in terms of fracture. In addition, this study showed the scientific trend only between 2010 and 2020.

CONCLUSION

This bibliometric study revealed that although new endodontic techniques and systems have been developed, they have not led to a greater number of studies focusing on dentinal microcrack formation between 2010 and 2020. Most of the studies were conducted in Turkey, India, and Brazil, and were published in the Journal of Endodontics. Publication in journals with a higher impact factor led to a higher number of citations, but the citation numbers were not affected by funding. In terms of experimental design, a relevant number of published articles did not consider the inclusion of control groups or baseline evaluation to identify the microcracks existing before initiating endodontic procedures, a factor that should be considered in future studies. Moreover, although micro-CT has been considered the best method to evaluate microcracks, some studies used other microscopic techniques. This overview provides important information on the pattern and trend of publications evaluating dentinal microcracks after endodontic procedures and highlights the important parameters that should be considered by future studies to elucidate this topic and guide clinical practice safely. The authors suggest that further studies be conducted to elucidate the relationship between endodontic procedures and microcrack formation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.