Puck van der Wouden*, Geert van der Heijden**, Hagay Shemesh***, Peter van den Besselaar****

*p.vd.wouden@acta.nl

ORCID: 0000-0003-2721-9670

Section of Integrative Oral Healthcare, Academic Center for Dentistry Amsterdam ACTA, the Netherlands

**geert.vander.heijden@acta.nl

0000-0003-4979-2099

Section of Integrative Oral Healthcare, ACTA, the Netherlands

***h.shemesh@acta.nl

0000-0002-4840-048X

Division of Endodontology, ACTA, the Netherlands

p.a.a.vanden.besselaar@vu.nl

0000-0002-8304-8565

Department of Organization Sciences, Vrije Universiteit Amsterdam, the Netherlands

Abstract

In this paper we address the question whether (i) the Dutch dental research portfolio reflects the dental care demand, and whether (ii) the results of this research does reach the dental care professionals. In order to answer these questions, we analyzed the content of the Dutch Journal of Dentistry (NTvT), a Dutch language professional journal which explicitly aims at disseminating useful knowledge to dental professionals.

The research topics addressed in the journal were compared with (i) dental publications written by authors with a Dutch affiliation in international journals and with (ii) expenditures in the various types of oral healthcare.

The analysis shows topical change over time, with more emphasis in NTvT on topics as social dentistry, and less attention for basic science topics. At the same time, the Dutch dental research portfolio (reflected by publications in international journals) does not reflect that trend. In addition, it appears that the largest domains of care with the highest share of oral healthcare expenditures (e.g. cariology and prevention) have the lowest attention in research. This applies to both international publications, as to the research disseminated through the professional journal NTvT.

1. Introduction

The Netherlands is among the ten best performing countries in oral health research, both measured in numbers of publications and in terms of scientific impact (van der Wouden, et al. 2022)¹ However, insight into knowledge from these publications is limited for Dutch oral health care practitioners (OHPs) for several reasons. First, many journals charge a high fee for individuals not related to an academic institution. Second, scientific publications are not always easy to read or interpret for the clinician. Third, reading a few publications is not enough to get acquainted with research, while healthcare professionals lack time to digest large volumes of publications. (Glasziou & Haynes, 2005)

Journals like the Dutch Journal of Dentistry (Nederlands Tijdschrift voor Tandheelkunde - NTvT) can be regarded as media that disseminate knowledge from oral health research to OHPs. NTvT is one of the few journals focused on the Dutch and Belgian oral healthcare field. With a circulation of almost 5,000 copies in the year 2019, it informs a substantial part of OHPs about scientific knowledge in the field of oral healthcare.

The readers of publications in NTvT are mostly Dutch and Belgian OHPs. The role of local journals, like NTvT, is not only to disseminate scientific knowledge from international research to the local field, but also to disseminate application-oriented knowledge. (Sambunjak et al., 2009; Sanz et al., 1995) This type of professional journals therefore may create productive interactions between users and producers of knowledge (De Jong et al 2012, 2014).

We systematically mapped topics that were addressed in NTvT over the past 18 years, and the changes over time in the distribution of research topics over subfields of oral health research.

We discuss the content of NTvT from two perspectives. Firstly, we determined to what extent publications in NTvT represent the international publications with a Dutch affiliation. Secondly, we relate the content of NTvT to the demand for oral health care, expressed in terms of expenditures of oral health care. By this, we determine whether areas of oral health care represented in publications in NTvT reflect the pattern in oral healthcare expenditures.

De Kruif et al. (2017) related the shares of Dutch publications in different biomedical research fields to the shares of expenditures for various fields of health care, and showed that intellectual disability, dementia and oral diseases account for large proportion of the healthcare expenditures, but relatively little research is conducted in these fields (Figure 1). In this study we perform a detailed analysis for the subfields of oral health research.

Figure 1. Share in scientific output by expenditures – medical domain, the Netherlands

Source: T.M. de Kruif et al 2017

2. Material & Methods

2.1 Mapping the publications of NTvT

For this study we used the 1439 publications published in NTvT between 2000 and 2017. The publications were divided into six overlapping four-year periods: 2000-2003; 2003-2006; 2006-2009; 2009-2012; 2012-2015; 2015-2018. All PDF files were converted into text (TXT) files, and all words were extracted. All terms that are relevant for dentistry and oral healthcare - research and practice - were selected independently by two of the authors (PW and PB). The results were compared, discrepancies were discussed and resolved, and the final list was achieved. All publications were indexed based on the terms on this list.

For each of the six periods, the terms were clustered using co-word analysis, resulting in clusters of publications representing dental research topics. Term extraction and co-word analysis were done with the program CorTexT. For each of the six periods a map was made (Figure 2 as an example), indicating the clusters as colored circles. The size of the cluster in each map indicates how many publications were included in the cluster. Each triangle within a cluster represents a term, and the larger the triangle is, the more often the term appears in the set of publications.

Finally, the clustering was examined by three oral health care experts. They determined the topic of each cluster by its set of terms. Based on their topics, the clusters were then categorized into dental subfields. For example, in one of the maps a cluster consisted of the following terms: bisphosphonates, osteonecrosis, necrosis, face, swelling. This cluster has been identified as the topic 'bisphosphonates and osteonecrosis' and has been categorized in the subfield 'Oral Medicine'. Clusters with only one or two terms were ignored.

2.2 Comparing publications in NTvT and international journals

For the international publications, we limited the analysis to publications (referred to as 'article', 'review' or 'proceedings paper') included in the Web of Science (WoS) category Dentistry, Oral Surgery & Medicine. We categorized the journals in WoS, based on journal titles into dental subfields. All international publica-tions were distributed over the dental subfields, except publications that were published in general dental journals, as these cover multiple dental subfields. For each dental subfield we calculated the share of publications in that subfield as a percentage of all publications in WoS category Dentistry, Oral Surgery & Medicine.

Next, we calculated for each dental subfield the share of publications in that subfield as a percentage of all publications in NTvT. We compared the distribution of publications in NTvT with the distribution in international journals written by authors with a Dutch affiliation over dental subfields.

2.3 The costs of oral health care and NTvT publications

We compared research topics covered in publications in NTvT with expenditures in oral health care. We used oral health care claims data in the Netherlands from the year 2014 from VEKTIS. VEKTIS is the organization that administers data from healthcare insurers. Claims data are classified in UPT categories. The UPT categories are clusters of treatment codes, and each code represents a treatment fee. These codes and UPT categories are established by the Dutch Healthcare Authority (NZA), and each UPT category represents a dental subfield. We matched the UPT categories to dental subfields by which NTvT publications were classified. Only disease specific subfields or dental subfields that focus on specific treatment for which an UPT category exists were included. This excluded analysis of, for example, topics covering social dentistry, or research subfields that focus on a certain patient group (e.g. children). Also, UPT categories C (consultation) and A (anesthesia) were not included in this analysis, since these categories were so generic it was not possible to match these with a specific research subfield. In addition to the claims data from VEKTIS, the costs of oral health care filed under the Exceptional Medical Expenses Act (AWBZ) were included in the analysis. In table 2 these data are presented.

3. Findings

Figures 2 maps the period 20122015, and in that period almost one third of clusters cover a medical topic, and the domain of Oral, Maxillofacial and Facial Surgery (OMFS) and Oral Medicine have a similar share (Table 1).

Figure 2: Map of NTVT publications 2012-2015

The number of topics (clusters) per dental subfield varied during the periods. Some were present in all periods, and some occurred only once (Table 1).

Table 1: Number of clusters per dental subfield for 6 subsequent 4-year periods

	2000-2003	2003-2006	2006-2009	2009-2012	2012-2015	2015-2017	Total
Oral, Maxillofacial and Facial Surgery (OMFS)	4	6	3	4	4	4	25
Social dentistry/Public & individual oral health	2	2	3	3	3	4	17
Special needs dentistry	2	2	2	2	3	3	14
Oral Medicine	1	1	1	2	4	1	10
Prosthetic dentistry	2	1	2	2	1	1	9
Orofacial Pain and Dysfunction	1	1	2	1	1	2	7
Multidisciplinary	1	1	1	1	1	2	7
Periodontology	1	2	1	1	1	1	7
Orthodontics	1	1	1	1	1	1	6
Prevention	1	1	1	1	1	1	6
Endodontology	0	1	1	1	1	1	5
Materials sciences	1	0	1	1	1	1	5
Cariology	1	1	0	0	0	1	3
Implantology	0	0	1	0	1	1	3
Pediatric dentistry	0	0	0	0	1	1	2
Basic sciences	0	1	1	0	0	0	2
Imaging	0	1	0	0	0	1	2
Miscellaneous	0	0	1	0	0	1	2
General medicine	0	0	0	0	1	0	1
Total number of clusters per map	18	22	22	20	25	27

During the studied period most clusters concern OMFS topics: a substantial amount of attention in NTvT is devoted to topics concerning oral surgery. Next are clusters concerning social dentistry, followed by special needs dentistry and oral medicine. The number of clusters changed over time for some subfields, and the subfields implantology and pediatric dentistry emerged. The subfields basic science and cariology were hardly covered in publications in NTvT. For both these topics no clusters were seen in several periods, and the clusters seen appeared small with little thematic variation.

Figure 4 the presents the shares of publications distributed over the research subfields both in NTvT and in international journals. The shares of publications are correlated to the expenditures in oral health care for the UPT categories as displayed in the Annex. In some subfields the share of international publications exceeds the share in NTvT (if the red square is higher than the blue dot – e.g. for the subfield periodontology), while in other fields the opposite is observed (e.g. for the subfield prosthetic dentistry). The subfield OMFS is a clear outlier. The share of publications of this subfield in especially international journals by authors with a Dutch affiliation was large compared to that from other research fields. Also, when related to expenditures for oral healthcare the share of publications is large. The authors with a Dutch affiliation in the dental subfields implantology, dental materials and periodontology show a strong international orientation, while for the dental subfield prosthetic dentistry and special needs dentistry applies that these are relatively often published in NTvT. For other dental subfields, the share of publications in NTvT and the share of international publications is similar.

An important finding is that the subfields cariology and prevention account for the largest share of oral healthcare costs – approximately one third of yearly expenditures are attributed to these subfield -, but that publications on these topics account for only about 5% in NTvT and in international journals.

Figure 4: Shares of expenditures by shares of publications

4. Conclusion and Discussion

In this study, we analyzed which topics in oral health research have been covered in publications in NTvT over the past 18 years. We compared the topics of publications in NTvT with publications from authors with Dutch affiliation in international journals. Per dental subfield we compared the share of NTvT publications to publications from authors with Dutch affiliation and with the share in costs of oral healthcare. Our study provides insight for the dental profession into which topics have been discussed, emerged or disappeared during this period and thereby may provide information for policy and planning for research and editors.

Research from the OMFS subfield comprises the largest share of Dutch oral health research. This conclusion applies to both publications in NTvT and to international publications affiliated to Dutch authors. This can be explained by the fact that OMFS professionals work in a research environment of academic medical centers, in which there are established networks that stimulate collaboration and participation in research. In addition, research is quite common as part of the OMFS postgraduate professional training program, either before enrolment or as PhD after enrolment in the program. For the dentistry training program this incentive does not apply. Another explanation can be found in the relatively high number of OMFS-specific international journals (17) among the 117 dental journals in WoS. These specialized journals provide a substantial platform for publishing, and therefore Dutch researchers in the OMFS subfield may be less likely to publish outside their subfield in for example journals with an interdisciplinary character or non-dental journals.

For the subfield special needs dentistry, the opposite applies. The share of international publications from this subfield was the smallest of all subfields. Only two specialized journals were available during the studied period. These two journals allow only a limited number of publications. In order to publish publications on special needs dentistry, researchers are therefore compelled to publish in interdisciplinary dental journals or non-dental journals (e.g. journals on anesthesiology or on care for the disabled). Publications on special needs dentistry in these journals are missed in our analysis.

We compared the share in expenditures of oral healthcare per subfield to the share of NTvT publications for each research subfield and found OMFS to be a clear outlier. While there were some limitations in using UPT categories of claims data (e.g. some dental research subfields could not be linked with a UTP category) our approach provides a general picture of the relation between the pattern of oral health research with the pattern of expenditures in oral health care: There is only little research related to the largest care domains.

A limitation of our study is the exclusion of international publications with a Dutch affiliation published in non-dental journals. We calculated the ratio between publications in dental journals and non-dental journals for one dental research institute to estimate the impact for this decision. For the period 2000 up to 2018, 4277 publications had a Dutch affiliation in WoS. Of these, 1564 (37%) publications were affiliated with the Academic Center for Dentistry Amsterdam (ACTA). According to ACTA's 2016 Annual Research Report 149 of the 253 (59%) publications affiliated with ACTA were published in non-dental journals. (ACTA Research institute, 2016) It however is unclear whether these concern publications on dental topics in non-dental journals, which eventually may have been missed in our analysis, or publications on non-dental topics which were rightly excluded from our analysis. However, as we showed elsewhere, the (citation) relations between the publications of dental researchers in basic science journals and publications in dental research journals are rather weak (Van der Wouden et al. 2022).

Relatively few publications in NTvT cover topics of basic science. NTvT mainly focuses on the OHPs and the work field, for whom findings from basic science might be of limited relevance and applicability. The Health Council of the Netherlands reported in Perspectives on oral health care (De Mondzorg van Morgen) that almost 50% of the Dutch publications covered basic science, while the proportion of applied research was relatively low (Health Council of the Netherlands, 2012). For researchers affiliated to the dental research institutes that perform research in basic science, publishing in NTvT might be unattractive. It is, however, unclear whether basic science researchers are either not willing or not able to address the priorities of the Dutch OHPs. (Brand, 2018)

A recent research project called Research Agenda for Oral Health (Kennisagenda Mondgezondheid) has identified and prioritized the information needs of the OHPs and patients. (Health Council of the Netherlands, 2012; Mondzorg2020, 2018; van der Wouden, Hilverda, et al., 2022; Wouden et al., 2021) For the Research Agenda for Oral Health, topics on behavior change and healthcare system research topics were prioritized. When programming future research, the priorities of the research agenda should be taken into account. Consequently, a targeted research portfolio can be established which may contribute an increase in the societal value of oral health research.

5. References

ACTA Research institute, G. (2016). Annual Research Report 2016. 109.

Brand, H. (2018, mei 4). Taalstrijd. NTVT. http://www.ntvt.nl/tijdschrift/editie/artikel/t/taalstrijd

Stefan de Jong, Pleun van Arensbergen, Floortje Daemen, Barend van der Meulen & Peter van den Besselaar: Evaluating research in its context: an approach and two cases. Research Evaluation 20 (2011) March

Stefan de Jong, Katherine Barker, Deborah Cox, Torsten Sveinsdottir, Peter Van den Besselaar, Understanding societal impact through studying productive interactions. Research Evaluation 23 (2014) 2, 89-102

de Kruif, T. M. (2017). Maat en getal bij de biomedische onderzoeksagenda van Nederland. Ned Tijschrift Geneeskd., 5.

Glasziou, P., & Haynes, B. (2005). The paths from research to improved health outcomes. Evidence-Based Nursing, 8(2), 36–38. https://doi.org/10.1136/ebn.8.2.36

Health Council of the Netherlands. (2012). Perspectives on oral health care. Health Council of the Netherlands.

Mondzorg2020. (2018). Kennisagenda Mondgezondheid—Mondzorgprofessionals aan het woord. ACTA.

Sambunjak, D., Huić, M., Hren, D., Katić, M., Marušić, A., & Marušić, M. (2009). National vs. international journals: Views of medical professionals in Croatia. Learned Publishing, 22(1), 57–70. https://doi.org/10.1087/095315108X378785

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van der Wouden, P., Hilverda, F., van der Heijden, G., Shemesh, H., & Pittens, C. (2022). Establishing the research agenda for oral healthcare using the Dialogue Model—Patient involvement in a joint research agenda with practitioners. European Journal of Oral Sciences, 130(1), e12842. https://doi.org/10.1111/eos.12842

van der Wouden, P., van der Heijden, G., Shemesh, H., & van den Besselaar, P. (2022). Evidence and consequences of academic drift in the field of dental research: A bibliometric analysis 2000–2015. BDJ Open, 8(1), Art. 1. https://doi.org/10.1038/s41405-022-00093-w

van der Wouden, P., Shemesh, H., & Heijden, G. J. M. G. van der. (2021). Research priorities for oral healthcare: Agenda setting from the practitioners’ perspective. Acta Odontologica Scandinavica, 0(0), 1–7. https://doi.org/10.1080/00016357.2021.1887929

Van der Wouden, P., van der Heijden, G., Shemesh, H., & van den Besselaar, P. (2019) De inhoud van publicaties in het Nederland Tijdschrift voor Tandheelkunde. Een patroonanalyse over de tijd. Ned Tijdschr Tandheelkd 126: 91-100.

Annex: Categories of oral healthcare expenditures UPT and the matching research subfields

Oral health care expenditures (UPT categories)	Research subfields
V (fillings)	Cariology
M (prevention)	Prevention
C (consultation)	Not included in the analysis
Orthodontics	Orthodontics
P (removable prosthetics)	Prosthetic dentistry
R (fixed prosthetics)	Dental Materials
J (implantology)	Implantology
Oral surgery	Oral and maxillofacial surgery
X (X-ray)	Radiology
T (periodontology)	Periodontology
E (endodontology)	Endodontology
H (surgery)	Oral and maxillofacial surgery
A (anaesthesia)	Not included in the analysis
G (gnathology)	TMD
AWBZ	Special needs dentistry
X special needs groups	Special needs dentistry
U (hourly rate)	Special needs dentistry
B (sedation)	Special needs dentistry

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1. Using bibliometric indicators linked to these publications (Cartes-Velásquez & Manterola Delgado, 2014; Gingras, 2016).↩︎