Introduction
============

"Dental caries is a biofilm-mediated, sugar-driven, multifactorial, dynamic disease that results in the phasic demineralization and remineralization of dental hard tissues." [@JR_1] A multifactorial origin has been identified in which the presence of acidogenic bacteria, salivary disturbances, and sugar consumption/frequency are known to play a vital role in disease progression. [@JR_2] Caries is a common chronic disease which has a high prevalence rate among adults and children. [@OR_3] Approximately 2.4 billion people with untreated lesions have been estimated worldwide. [@JR_4] Untreated carious lesions commonly lead to functional, aesthetic, and psychological problems, as well as a poor quality of life. [@JR_5] Delay in the treatment of a carious tooth eventually leads to pulpal involvement and painful mastication potentially resulting in indigestion, [@JR_6] malnutrition, [@JR_7] and systemic infections, which in turn increase the treatment need and consequently increase the cost of dental and medical care provided to the patient.

The citation count of an article is an indicator of its impact in its respective field. A classic article is defined as an article having secured a citation count of 100 or above. [@JR_8] The growth of a particular field or specialty can be studied by performing a bibliometric analysis. It also provides vital information regarding the prominent areas of individual medical and dental specialties. [@JR_9] Various bibliometric analyses have documented the citation classics in the field of dentistry, [@JR_10] [@JR_11] [@JR_12] [@JR_13] [@JR_14] [@JR_15] [@JR_16] [@JR_17] [@JR_18] [@JR_19] [@JR_20] but no study has been performed to study the characteristic features of the publications on caries research which have been cited most often.

The current study is focused on identification and analysis of the top 100 publications which have been cited most often regarding dental caries and to highlight the change in current trends, centers of excellence in caries research, dominant types of methodology, and technological developments made during the elapsed time.

Materials and Methods
=====================

Protocol
--------

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses ( PRISMA) guidelines were followed for the preparation of this report. [@JR_21]

Search Strategy
---------------

The Web of Science (WoS) group of Clarivate Analytics was used to perform a literature search on April 1, 2019 enabling the search through "All Databases." The title section was searched using the search terms described below in inclusion criteria. The database was searched without any restriction on the language of the article, study design, or publication year. Based on the WoS results, 31,584 articles were retrieved which were then arranged according to number of citations. One hundred articles with the largest number of citations were tabulated. A manual cross-matching of citation count was performed on the Elsevier's database (Scopus) and the Google Scholar (GS). The top 100 "classic" publications were selected by two reviewers independently and the final list was unanimously agreed upon. The [Supplementary Fig. S1](#SM0333-001){ref-type="supplementary-material"} (online only) shows the process of selection of articles according to PRISMA guidelines.

Inclusion Criteria
------------------

Inclusion criteria were the presence of "caries" OR "carious" OR "cariogenic" OR "cariology" OR "tooth decay" OR "teeth decay" OR "tooth cavity" OR "teeth cavity" OR "tooth cavities" OR "teeth cavities" OR "dental cavity" OR "dental cavities" OR "dental decay" in the title of the article and publication in a peer-reviewed journal.

Exclusion criteria
------------------

Articles having less than 100 citations according the WoS "All Databases" and publications in journals with low (≤0.500) or no impact factor were excluded.

Data Extraction
---------------

Article authorship, title of article, counts of citation (WoS, Scopus, and GS), publication year, citation density, current citation index (CCI) (2019), institution and country of publication, journal of article, evidence level based on methodology, and keywords description were noted for each selected publication.

Graphical Analysis
------------------

VOSviewer is a free software platform which is used for bibliometric mapping based on visualization of similarities. [@JR_16] We used this software to visualize the clusters of author keywords which have been used in the top-cited articles. This method of mapping has been used previously and provides a simplistic representation of data. [@JR_18]

Statistical Analysis
--------------------

IBM SPSS Statistics processes version 24 for Windows was used to perform descriptive and bivariate analyses. The Shapiro--Wilk test was performed to check data normality. Based on distribution and normality of the data, mean (standard deviation) or median (interquartile range) were calculated. The Kruskal--Wallis test was performed to analyze the median differences between the independent groups and differences within each group was checked by post hoc testing. The Mann--Kendall trend test was performed to analyze an increase or decrease in the time-dependent trends. To evaluate the correlation between the age of the journal and the publication count in the journal the Spearman-rank test was performed. A value of *p* \< 0.05 was considered statistically significant.

Results
=======

Authorship
----------

Three hundred and one authors made contributions to the list of top 100 "classics." J.D. Featherstone ( *n* = 6) had the highest publication count followed by P. Axelsson ( *n* = 5), J. Lindhe ( *n* = 5), B. Nyvad ( *n* = 4), N.B. Pitts ( *n* = 4), B. Krasse ( *n* = 3), and J. van Houte ( *n* = 3). Twenty-two authors contributed to two "classics" each, among the list of top 100 "classics." The [Supplementary Table S1](#SM0333-002){ref-type="supplementary-material"} (online only) shows the number of instances at which an author appeared as the first author, as the corresponding author, as the first and the corresponding author, and as the coauthor.

Citation Count, Citation Density, and Current Citation Index
------------------------------------------------------------

A total of 297,496 (WoS), 27,713 (Scopus), and 53,648 (GS) citations were calculated for the list of top 100 "classics." The range of citations varied from 175 to 2,003 (WoS), 89 to 1,981 (Scopus), and 126 to 3,492 (GS). The average number of annual citations is termed as citation density which was calculated as 297.49 (WoS), 277.13 (Scopus), and 536.48 (GS) collectively. "Role of *Streptococcus mutans* in human dental decay" (citation density = 62.59) was the most cited "classic" article with 2,003 (WoS), 1,981 (Scopus), and 3,492 (GS) citations. [@JR_22] "Genome sequence of *Streptococcus mutans* UA159, a cariogenic dental pathogen" (citation density = 69.68) was ranked as the second "classic" article with 1,115 (WoS), 652 (Scopus), and 955 (GS) citations. [@JR_23] "Dental caries" (citation density = 82.27) was ranked as the third "classic" article with 905 (WoS), 952 (Scopus), and 1,954 (GS) citations. [@JR_24] "Global burden of untreated caries: A systematic review and meta-regression" had the highest citation density of 89.0. [@JR_25] The list of top 100 "classics" on dental caries are presented in [Table 1](#TB_1){ref-type="table"} along with their citation counts in WoS, Scopus, and GS and their citation density.

###### Ranking list of the top 100 most cited articles on caries research

  Rank   Title of the article                                                                                                                                                                                                                                                                                     No. of citation (Web of Science)   No. of citation (Scopus)   No. of citation (Google Scholar)   Citation density   CCI 2019
  ------ -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ---------------------------------- -------------------------- ---------------------------------- ------------------ ----------
  1      Loesche WJ: Role of Streptococcus mutans in human dental decay. Microbiol Rev 1986;50:353--380                                                                                                                                                                                                           2,003                              1,981                      3,492                              62.59              64
  2      Ajdić D, McShan WM, McLaughlin RE, Savić G, Chang J, Carson MB, Primeaux C, Tian R, Kenton S, Jia H: Genome sequence of Streptococcus mutans ua159, a cariogenic dental pathogen. Proc Natl Acad Sci USA 2002;99:14434--14439                                                                            1,115                              652                        955                                69.68              29
  3      Selwitz RH, Ismail AI, Pitts NB: Dental caries. Lancet 2007;369:51--59                                                                                                                                                                                                                                   905                                952                        1,954                              82.27              98
  4      Gustafsson BE, Quensel C, Lanke LS, Lundqvist C, Grahnen H, Bonow B, Krasse B: The vipeholm dental caries study. The effect of different levels of carbohydrate intake on caries activity in 436 individuals observed for five years. Acta Odontol Scand 1954;11:232--364                                567                                323                        976                                8.86               4
  5      Ismail A, Sohn W, Tellez M, Amaya A, Sen A, Hasson H, Pitts NB: The international caries detection and assessment system (ICDAS): An integrated system for measuring dental caries. Community Dent Oral Epidemiol 2007;35:170--178                                                                       486                                497                        930                                44.19              58
  6      Keyes PH: Dental caries in the molar teeth of rats: II. A method for diagnosing and scoring several types of lesions simultaneously. J Dent Res 1958;37:1088--1099                                                                                                                                       442                                289                        518                                7.37               9
  7      Featherstone JD: The science and practice of caries prevention. J Am Dent Assoc 2000;131:887--899                                                                                                                                                                                                        437                                496                        1,132                              24.28              24
  8      Featherstone JD: Prevention and reversal of dental caries: Role of low level fluoride. Community Dent Oral Epidemiol 1999;27:31--40                                                                                                                                                                      428                                480                        988                                22.53              36
  9      Fitzgerald RJ, Keyes PH: Demonstration of the etiologic role of streptococci in experimental caries in the hamster. J Am Dent Assoc 1960;61:9--19                                                                                                                                                        427                                230                        724                                7.36               2
  10     Axelsson P, Lindhe J: Effect of controlled oral hygiene procedures on caries and periodontal disease in adults. J Clin Periodontol 1978;5:133--151                                                                                                                                                       413                                342                        737                                10.32              4
  11     Terleckyj B, Willett N, Shockman G: Growth of several cariogenic strains of oral streptococci in a chemically defined medium. Infect Immun 1975;11:649--655                                                                                                                                              403                                230                        431                                9.37               6
  12     Axelsson P, Nyström B, Lindhe J: The long‐term effect of a plaque control program on tooth mortality, caries and periodontal disease in adults: Results after 30 years of maintenance. J Clin Periodontol 2004;31:749--757                                                                               400                                421                        816                                28.57              36
  13     Becker MR, Paster BJ, Leys EJ, Moeschberger ML, Kenyon SG, Galvin JL, Boches SK, Dewhirst FE, Griffen AL: Molecular analysis of bacterial species associated with childhood caries. J Clin Microbiol 2002;40:1001--1009                                                                                  400                                403                        713                                25.00              25
  14     Marthaler T: Changes in dental caries 1953--2003. Caries Res 2004;38:173--181                                                                                                                                                                                                                            397                                408                        866                                28.35              13
  15     Takahashi N, Nyvad B: The role of bacteria in the caries process: Ecological perspectives. J Dent Res 2011;90:294--303                                                                                                                                                                                   384                                397                        639                                54.85              55
  16     Wiegand A, Buchalla W, Attin T: Review on fluoride-releasing restorative materials---fluoride release and uptake characteristics, antibacterial activity and influence on caries formation. Dent Mater 2007;23:343--362                                                                                  366                                378                        655                                33.27              34
  17     Beltrán-Aguilar ED, Barker LK, Canto MT, Dye BA, Gooch BF, Griffin SO, Hyman J, Jaramillo F, Kingman A, Nowjack-Raymer R: Surveillance for dental caries, dental sealants, tooth retention, edentulism, and enamel fluorosis; united states, 1988-1994 and 1999-2002. MMWR Surveill Summ 2005;54:1--43   366                                455                        728                                28.15              12
  18     Van Houte J: Role of micro-organisms in caries etiology. J Dent Res 1994;73:672--681                                                                                                                                                                                                                     362                                395                        803                                15.08              15
  19     Tjäderhane L, Larjava H, Sorsa T, Uitto V-J, Larmas M, Salo T: The activation and function of host matrix metalloproteinases in dentin matrix breakdown in caries lesions. J Dent Res 1998;77:1622--1629                                                                                                 356                                360                        561                                17.80              18
  20     Aas JA, Griffen AL, Dardis SR, Lee AM, Olsen I, Dewhirst FE, Leys EJ, Paster BJ: Bacteria of dental caries in primary and permanent teeth in children and young adults. J Clin Microbiol 2008;46:1407--1417                                                                                              351                                337                        641                                35.10              39
  21     Featherstone J, Ten Cate J, Shariati M, Arends J: Comparison of artificial caries-like lesions by quantitative microradiography and microhardness profiles. Caries Res 1983;17:385--391                                                                                                                  346                                342                        563                                9.88               11
  22     Bowen W, Koo H: Biology of Streptococcus mutans-derived glucosyltransferases: Role in extracellular matrix formation of cariogenic biofilms. Caries Res 2011;45:69--86                                                                                                                                   340                                344                        525                                48.57              49
  23     Harris R, Nicoll AD, Adair PM, Pine CM: Risk factors for dental caries in young children: A systematic review of the literature. Community Dent Health 2004;21:71--85                                                                                                                                    333                                360                        781                                23.78              22
  24     Bagramian RA, Garcia-Godoy F, Volpe AR: The global increase in dental caries. A pending public health crisis. Am J dent 2009;22:3--8                                                                                                                                                                     330                                357                        694                                36.66              31
  25     Bratthall D, Hänsel‐Petersson G, Sundberg H: Reasons for the caries decline: What do the experts believe? Eur J Oral Sci 1996;104:416--422                                                                                                                                                               328                                377                        744                                14.90              10
  26     Axelsson P, Lindhe J: Effect of controlled oral hygiene procedures on caries and periodontal disease in adults: Results after 6 years. J Clin Periodontol 1981;8:239--248                                                                                                                                304                                284                        614                                8.21               8
  27     Yamashita Y, Bowen W, Burne R, Kuramitsu H: Role of the Streptococcus mutans GTF genes in caries induction in the specific-pathogen-free rat model. Infect Immun 1993;61:3811--3817                                                                                                                      303                                297                        388                                12.12              7
  28     Näse L, Hatakka K, Savilahti E, Saxelin M, Pönkä A, Poussa T, Korpela R, Meurman JH: Effect of long--term consumption of a probiotic bacterium, Lactobacillus rhamnosus GG, in milk on dental caries and caries risk in children. Caries Res 2001;35:412--420                                            299                                314                        592                                17.58              14
  29     Gibbons R, Berman K, Knoettner P, Kapsimalis B: Dental caries and alveolar bone loss in gnotobiotic rats infected with capsule forming streptococci of human origin. Arch Oral Biol 1966;11:549--560                                                                                                     297                                159                        401                                5.71               1
  30     Krasse B: Human streptococci and experimental caries in hamsters. Arch Oral Biol 1966;11:429--414.                                                                                                                                                                                                       286                                184                        361                                5.50               \-
  31     Marthaler TM, Brunelle J, Downer M, König K, Truin G, Künzel W, O'Mullane D, Møller I, von der Fehr F, Vrbic V: The prevalence of dental caries in Europe 1990-1995. Caries Res 1996;30:237--255.                                                                                                        281                                331                        679                                12.77              6
  32     Fejerskov O: Changing paradigms in concepts on dental caries: consequences for oral health care. Caries Res 2004;38:182--191                                                                                                                                                                             279                                306                        817                                19.92              23
  33     Kaste LM, Selwitz RH, Oldakowski RJ, Brunelle J, Winn DM, Brown LJ: Coronal caries in the primary and permanent dentition of children and adolescents 1--17 years of age: United states, 1988--1991. J Dent Res 1996;75:631--641                                                                         278                                323                        609                                12.63              4
  34     Vargas CM, Crall JJ, Schneider DA: Sociodemographic distribution of pediatric dental caries: Nhanes iii, 1988--1994. J Am Dent Assoc 1998;129:1229--1238                                                                                                                                                 277                                328                        603                                13.85              4
  35     Lussi A, Imwinkelried S, Pitts N, Longbottom C, Reich E: Performance and reproducibility of a laser fluorescence system for detection of occlusal caries in vitro. Caries Res 1999;33:261--266                                                                                                           276                                307                        533                                14.52              6
  36     Gibbons R, Houte J: Dental caries. Annu Rev Med 1975;26:121--136                                                                                                                                                                                                                                         269                                158                        356                                6.25               1
  37     Kassebaum N, Bernabé E, Dahiya M, Bhandari B, Murray C, Marcenes W: Global burden of untreated caries: a systematic review and metaregression. J Dent Res 2015;94:650--658                                                                                                                               267                                290                        480                                89.00              86
  38     Nyvad B, Machiulskiene V, Bælum V: Reliability of a new caries diagnostic system differentiating between active and inactive caries lesions. Caries Res 1999;33:252--260                                                                                                                                 262                                282                        544                                13.78              19
  39     Gibbons R, Banghart S: Synthesis of extracellular dextran by cariogenic bacteria and its presence in human dental plaque. Arch Oral Biol 1967;12:11--24                                                                                                                                                  260                                125                        315                                5.09               2
  40     Axelsson P, Lindhe J, Nyström B: On the prevention of caries and periodontal disease: Results of a 15‐year longitudinal study in adults. J Clin Periodontol 1991;18:182--189                                                                                                                             260                                264                        557                                9.62               8
  41     Petersen PE, Lennon MA: Effective use of fluorides for the prevention of dental caries in the 21st century: The WHO approach. Community Dent Oral Epidemiol 2004;32:319--321                                                                                                                             258                                212                        511                                18.42              19
  42     Fried D, Xie J, Shafi S, Featherstone JD, Breunig T, Le CQ: Imaging caries lesions and lesion progression with polarization sensitive optical coherence tomography. J Biomed Opt 2002;7:618--628                                                                                                         258                                276                        487                                16.12              7
  43     Axelsson P, Lindhe J: The effect of a preventive programme on dental plaque, gingivitis and caries in schoolchildren. Results after one and two years. J Clin Periodontol 1974;1:126--138                                                                                                                257                                222                        430                                5.84               2
  44     Tanzer JM, Livingston J, Thompson AM: The microbiology of primary dental caries in humans. J Dent Educ 2001;65:1028--1037                                                                                                                                                                                256                                268                        541                                15.05              13
  45     Sakanaka S, Kim M, Taniguchi M, Yamamoto T: Antibacterial substances in Japanese green tea extract against Streptococcus mutans, a cariogenic bacterium. Agric Biol Chem 1989;53:2307--2311                                                                                                              252                                273                        497                                8.68               \-
  46     Nakajima M, Sano H, Burrow M, Tagami J, Yoshiyama M, Ebisu S, Ciucchi B, Russell C, Pashley DH: Tensile bond strength and SEM evaluation of caries-affected dentin using dentin adhesives. J Dent Res 1995;74:1679--1688                                                                                 251                                258                        436                                10.91              2
  47     Keyes PH: The infectious and transmissible nature of experimental dental caries: Findings and implications. Arch Oral Biol 1960;1:304--320                                                                                                                                                               250                                161                        580                                4.31               3
  48     Moreno EC, Kresak M, Zahradnik RT: Fluoridated hydroxyapatite solubility and caries formation. Nature 1974;247:64--65                                                                                                                                                                                    244                                237                        314                                5.54               10
  49     Lussi A, Megert B, Longbottom C, Reich E, Francescut P: Clinical performance of a laser fluorescence device for detection of occlusal caries lesions. Eur J Oral Sci 2001;109:14--19                                                                                                                     240                                261                        487                                14.11              7
  50     Loesche W, Rowan J, Straffon L, Loos P: Association of Streptococcus mutans with human dental decay. Infec Immun 1975;11:1252--1260                                                                                                                                                                      240                                187                        394                                5.58               1
  51     Leme AP, Koo H, Bellato C, Bedi G, Cury J: The role of sucrose in cariogenic dental biofilm formation---new insight. J Dent Res 2006;85:878--887                                                                                                                                                         239                                249                        431                                19.91              20
  52     Mjör IA, Toffentti F: Secondary caries: A literature review with case reports. Quintessence Int 2000;31:165--179                                                                                                                                                                                         238                                246                        435                                13.22              7
  53     Chaussain-Miller C, Fioretti F, Goldberg M, Menashi S: The role of matrix metalloproteinases (MMPs) in human caries. J Dent Res 2006;85:22--32                                                                                                                                                           237                                240                        406                                19.75              17
  54     Nyvad B, Kilian M: Comparison of the initial streptococcal microflora on dental enamel in caries-active and in caries-inactive individuals. Caries Res 1990;24:267--272                                                                                                                                  235                                216                        356                                8.39               6
  55     Moreno E, Kresak M, Zahradnik R: Physicochemical aspects of fluoride-apatite systems relevant to the study of dental caries. Caries Res 1977;11:142--171                                                                                                                                                 230                                215                        283                                5.60               2
  56     Aoki A, Ishikawa I, Yamada T, Otsuki M, Watanabe H, Tagami J, Ando Y, Yamamoto H: Comparison between er: Yag laser and conventional technique for root caries treatment in vitro. J Dent Res 1998;77:1404--1414                                                                                          227                                246                        399                                11.36              5
  57     Guggenheim B, Schroeder H: Biochemical and morphological aspects of extracellular polysaccharides produced by cariogenic streptococci. Helv Odontol Acta 1967;11:131--152                                                                                                                                224                                111                        287                                4.39               \-
  58     Moynihan P, Kelly S: Effect on caries of restricting sugars intake: Systematic review to inform who guidelines. J Dent Res 2014;93:8--18                                                                                                                                                                 222                                249                        466                                55.50              57
  59     Munson M, Banerjee A, Watson T, Wade W: Molecular analysis of the microflora associated with dental caries. J Clin Microbiol 2004;42:3023--3029                                                                                                                                                          221                                220                        370                                15.78              14
  60     Bratthall D: Introducing the significant caries index together with a proposal for a new global oral health goal for 12‐year‐olds. Int Dent J 2000;50:378--384                                                                                                                                           216                                219                        576                                12.00              10
  61     Sheiham A: Dental caries affects body weight, growth and quality of life in pre-school children. Br Dent J 2006;201:625--626                                                                                                                                                                             215                                224                        479                                17.91              21
  62     Byun R, Nadkarni MA, Chhour K-L, Martin FE, Jacques NA, Hunter N: Quantitative analysis of diverse lactobacillus species present in advanced dental caries. J Clin Microbiol 2004;42:3128--3136                                                                                                          214                                207                        370                                15.28              10
  63     Fejerskov O, Thylstrup A, Larsen MJ: Rational use of fluorides in caries prevention: A concept based on possible cariostatic mechanisms. Acta Odontol Scand 1981;39:241--249                                                                                                                             214                                202                        378                                5.78               6
  64     Shi X-Q, Welander U, Angmar-Månsson B: Occlusal caries detection with KaVo DIAGNOdent and radiography: An in vitro comparison. Caries Res 2000;34:151--158                                                                                                                                               207                                233                        376                                11.50              6
  65     Filstrup SL, Briskie D, Da Fonseca M, Lawrence L, Wandera A, Inglehart MR: Early childhood caries and quality of life: Child and parent perspectives. Pediatr Dent 2003;25:431--440                                                                                                                      206                                219                        449                                13.73              15
  66     Dreizen S, Brown LR, Daly TE, Drane JB: Prevention of xerostomia-related dental caries in irradiated cancer patients. J Dent Res 1977;56:99--104                                                                                                                                                         206                                208                        319                                5.02               4
  67     Takahashi N, Nyvad B: Caries ecology revisited: Microbial dynamics and the caries process. Caries Res 2008;42:409--418                                                                                                                                                                                   204                                220                        450                                20.40              17
  68     Levitch L, Bader J, Shugars D, Heymann H: Non-carious cervical lesions. J of Dent 1994;22:195--207                                                                                                                                                                                                       201                                202                        447                                8.37               4
  69     Alaluusua S, Renkonen OV: Streptococcus mutans establishment and dental caries experience in children from 2 to 4 years old. Eur J Oral Sci 1983;91:453--457                                                                                                                                             200                                111                        405                                5.71               1
  70     Van Nieuw Amerongen A, Bolscher JG, Veerman EC: Salivary proteins: Protective and diagnostic value in cariology? Caries Res 2004;38:247--253                                                                                                                                                             199                                246                        458                                14.21              11
  71     Lukacs JR, Largaespada LL: Explaining sex differences in dental caries prevalence: Saliva, hormones, and "life‐history" etiologies. Am J Hum Biol 2006;18:540--555                                                                                                                                       198                                203                        423                                16.5               15
  72     Pitts N: ICDAS-an international system for caries detection and assessment being developed to facilitate caries epidemiology, research and appropriate clinical management. Community Dent Health 2004;21:193--198                                                                                       198                                225                        405                                14.14              18
  73     Fusayama T: Two layers of carious dentin; diagnosis and treatment. Oper Dent 1979;4:63--70                                                                                                                                                                                                               198                                185                        377                                5.07               8
  74     Edwardsson S: Characteristics of caries-inducing human streptococci resembling Streptococcus mutans. Arch Oral Biol 1968;13:637--646                                                                                                                                                                     197                                111                        261                                3.94               1
  75     Ahola A, Yli-Knuuttila H, Suomalainen T, Poussa T, Ahlström A, Meurman JH, Korpela R: Short-term consumption of probiotic-containing cheese and its effect on dental caries risk factors. Arch Oral Biol 2002;47:799--804                                                                                196                                203                        393                                12.25              7
  76     De Stoppelaar J, Van Houte J, Dirks OB: The relationship between extracellular polysaccharide-producing streptococci and smooth surface caries in 13-year-old children. Caries Res 1969;3:190--199                                                                                                       195                                179                        331                                3.97               \-
  77     Petersen PE: Sociobehavioural risk factors in dental caries--international perspectives. Community Dent Oral Epidemiol 2005;33:274--279                                                                                                                                                                  193                                196                        479                                14.84              6
  78     Kleinberg I: A mixed-bacteria ecological approach to understanding the role of the oral bacteria in dental caries causation: An alternative to Streptococcus mutans and the specific-plaque hypothesis. Crit Rev Oral Biol Med 2002;13:108--125                                                          192                                205                        409                                12.00              11
  79     Casamassimo PS, Thikkurissy S, Edelstein BL, Maiorini E: Beyond the DMFT: The human and economic cost of early childhood caries. J Am Dent Assoc 2009;140:650--657                                                                                                                                       191                                207                        377                                21.22              17
  80     Köhler B, Andréen I, Jonsson B: The earlier the colonization by mutans streptococci, the higher the caries prevalence at 4 years of age. Oral Microbiol Immunol 1988;3:14--17                                                                                                                            190                                207                        379                                6.33               1
  81     Loesche W, Syed S: Predominant cultivable flora of carious plaque and carious dentine. Caries Res 1973;7:201--216                                                                                                                                                                                        189                                159                        242                                4.20               \-
  82     Beighton D: The complex oral microflora of high‐risk individuals and groups and its role in the caries process. Community Dent Oral Epidemiol 2005;33:248--255                                                                                                                                           187                                187                        375                                14.38              12
  83     Burne RA, Marquis RE: Alkali production by oral bacteria and protection against dental caries. FEMS Microbiol Lett 2000;193:1--6                                                                                                                                                                         186                                183                        295                                10.33              16
  84     Makinen K, Bennett C, Hujoel P, Isokangas P, Isotupa K, Pape Jr H, Makinen P: Xylitol chewing gums and caries rates: A 40-month cohort study. J Dent Res 1995;74:1904--1913                                                                                                                              185                                199                        368                                8.04               2
  85     Zinner DD, Jablon JM, Aran AP, Saslaw MS: Experimental caries induced in animals by streptococci of human origin. Exp Biol Med 1965;118:766--770                                                                                                                                                         185                                93                         256                                3.49               1
  86     Yoshiyama M, Tay F, Doi J, Nishitani Y, Yamada T, Itou K, Carvalho R, Nakajima M, Pashley D: Bonding of self-etch and total-etch adhesives to carious dentin. J Dent Res 2002;81:556--560                                                                                                                184                                181                        325                                11.50              8
  87     Marshall TA, Levy SM, Broffitt B, Warren JJ, Eichenberger-Gilmore JM, Burns TL, Stumbo PJ: Dental caries and beverage consumption in young children. Pediatrics 2003;112:e184--e191                                                                                                                      183                                215                        417                                12.20              7
  88     Hillson S: Recording dental caries in archaeological human remains. Int J Osteoarchaeol 2001;11:249--289                                                                                                                                                                                                 183                                191                        374                                10.76              \-
  89     Brunelle J, Carlos J: Recent trends in dental caries in us children and the effect of water fluoridation. J Dent Res 1990;69:723--727                                                                                                                                                                    181                                180                        410                                6.46               \-
  90     Brännström M: The hydrodynamic theory of dentinal pain: Sensation in preparations, caries, and the dentinal crack syndrome. J Endod 1986;12:453--457                                                                                                                                                     180                                186                        402                                5.65               6
  91     Narvai PC, Frazao P, Roncalli AG, Antunes J: Dental caries in Brazil: Decline, polarization, inequality and social exclusion. Rev Panam Salud Publica 2006;19:385--393                                                                                                                                   179                                156                        126                                14.91              2
  92     Kidd EAM, Fejerskov O: What constitutes dental caries? Histopathology of carious enamel and dentin related to the action of cariogenic biofilms. J Dent Res 2004;83:35--38                                                                                                                               178                                228                        580                                12.71              15
  93     Årtun J, Brobakken BO: Prevalence of carious white spots after orthodontic treatment with multibonded appliances. Eur J Orthod 1986;8:229--234                                                                                                                                                           178                                170                        372                                5.56               7
  94     Larsen M: The nature of early caries lesions in enamel. J Dent Res 1986;65:1030--1031                                                                                                                                                                                                                    176                                164                        346                                5.50               4
  95     Michalek SM, Mestecky J, Arnold R, Bozzo L: Ingestion of Streptococcus mutans induces secretory immunoglobulin A and caries immunity. Science 1976;192:1238--1240                                                                                                                                        176                                94                         235                                4.19               1
  96     Von der Fehr FR, Loe H, Theilade E: Experimental caries in man. Caries Res 1970;4:131--148                                                                                                                                                                                                               176                                172                        297                                3.66               2
  97     Fitzgerald R, Jordan H, Stanley H, Poole W, Bowler A: Experimental caries and gingival pathologic changes in the gnotobiotic rat. J Dent Res 1960;39:923--935                                                                                                                                            176                                89                         256                                3.03               \-
  98     Burt BA, Pai S: Sugar consumption and caries risk: A systematic review. J Dent Educ 2001;65:1017--1023                                                                                                                                                                                                   175                                188                        407                                10.29              5
  99     Mitchell TJ: The pathogenesis of streptococcal infections: From tooth decay to meningitis. Nat Rev Microbiol 2003;1:219--230                                                                                                                                                                             175                                169                        287                                11.66              12
  100    De Jong EdJ, Sundström F, Westerling H, Tranaeus S, Ten Bosch J, Angmar-Månsson B: A new method for in vivo quantification of changes in initial enamel caries with laser fluorescence. Caries Res 1995;29:2--7                                                                                          174                                192                        212                                7.56               4

The Shapiro--Wilk test revealed that the data distribution of citation count, age of publication, and citation density were not normal ( *p* \< 0.01). The trend towards a greater number of citation counts with publication age was not significant ( *r* = 0.006, *p* = 0.952) as shown in [Fig. 1](#FI00333-1){ref-type="fig"} . However, a negative trend towards an increased citation density with increasing time since publication was found to be significant ( *r* =--0.545, *p* \< 0.01) as shown in [Fig. 2](#FI00333-2){ref-type="fig"} .

![Association of citation count with age of publication.](10-1055-s-0040-1703419_00333_01){#FI00333-1}

![Change of citation density with age of publication.](10-1055-s-0040-1703419_00333_02){#FI00333-2}

According to the CCI based on the year 2019, two out of the top six articles were systematic reviews, three were field expert reviews, and one was caries management system/tool. These findings highlight the sustainability and current relevance of information provided in systematic reviews and expert opinions.

Publication Year
----------------

The "classic" publications on the topic of caries were published between 1954 [@JR_26] and 2015 [@JR_25] as displayed in [Fig. 3](#FI00333-3){ref-type="fig"} . Ten articles were published in 2004 which was the highest number of publications in any one year. Chronologically, 2 publications in 1950s, 10 in 1960s, 12 in 1970s, 10 in 1980s, 18 in 1990s, 44 in 2000s, and 4 since 2010 were classified as "classics." From 2000 to 2005, peaks were noticed in the number of "classic" articles, that is, 32. Four out of 100 "classics" were published after the year 1999.

![The time trends in the top 100 most cited caries research articles according to their categories.](10-1055-s-0040-1703419_00333_03){#FI00333-3}

Institution and Country of Publication
--------------------------------------

The corresponding author of each article and their affiliations revealed that authors from 13 countries made contributions toward caries research. The highest number of publications originated from the United States ( *n* = 45) followed by Sweden ( *n* = 14), United Kingdom ( *n* = 11), Switzerland ( *n* = 7), Denmark ( *n* = 5), Japan ( *n* = 4), Finland ( *n* = 4), Netherlands ( *n* = 3), Norway ( *n* = 2), Brazil ( *n* = 2), Germany ( *n* = 2), France ( *n* = 1), and Australia ( *n* = 1).

The highest number of publications originated from the "University of Gothenburg, Gothenburg, Sweden" ( *n* = 7) among 50 other institutions, "School of Dentistry, University of Michigan, Ann Arbor, Michigan, United States" ( *n* = 6), "National Institutes of Health, Bethesda, Maryland, United States" ( *n* = 5), "School of Dentistry, University of California at San Francisco, San Francisco, California, United States" ( *n* = 5), "Forsyth Dental Center, The Forsyth Institute, Massachusetts, United States" ( *n* = 4), "Royal Dental College, Aarhus University, Aarhus, Denmark" ( *n* = 4), "School of Dentistry, University of Lund, Lund, Sweden" ( *n* = 3), "Dental Institute, King's College London, London, United Kingdom" ( *n* = 3), "School of Dentistry, Karolinska Institutet, Solna, Sweden" ( *n* = 3), and "Institute of Dentistry, University of Helsinki, Helsinki, Finland" ( *n* = 3).

Journal of Publication
----------------------

The 100 "classic" publications on the topic of caries were published across 40 peer-reviewed journals. The journals associated with the most number of publications were " *Journal of Dental Research* " ( *n* = 19), " *Caries Research* " ( *n* = 17), and " *Archives of Oral Biology* " ( *n* = 6). The impact factors of journals ranged from 0.784 ( *Pan American Journal of Public Health* ) to 53.254 ( *The Lancet* ). [Table 2](#TB_2){ref-type="table"} summarizes the complete list of all journals.

###### List of journals which published the top 100 "classic" articles on caries research

  Journal name                                                     No. of publication   Impact factor   Journal name                                                                      No. of publication   Impact factor
  ---------------------------------------------------------------- -------------------- --------------- --------------------------------------------------------------------------------- -------------------- ---------------
  Journal of Dental Research                                       19                   5.383           Caries Research                                                                   17                   2.188
  Archives of Oral Biology                                         6                    2.050           Community Dentistry and Oral Epidemiology                                         5                    1.992
  Journal of the American Dental Association                       4                    2.486           Journal of Clinical Periodontology                                                5                    4.046
  Journal of Clinical Microbiology                                 4                    4.054           European Journal of Oral Sciences                                                 3                    1.655
  Infection and Immunity                                           3                    3.256           Community Dental Health                                                           2                    0.956
  Acta Odontologica Scandinavica                                   2                    1.522           Journal of Dental Education                                                       2                    1.102
  The Lancet                                                       1                    53.254          Nature                                                                            1                    41.577
  Science                                                          1                    41.058          Nature Reviews Microbiology                                                       1                    31.851
  Annual Review of Medicine                                        1                    14.970          Microbiology and Molecular Biology Reviews                                        1                    13.439
  MMWR: Morbidity and Mortality Weekly Report                      1                    12.888          Proceedings of the National Academy of Sciences of the United States of America   1                    9.504
  Pediatrics                                                       1                    5.515           Dental Materials                                                                  1                    4.039
  Journal of dentistry                                             1                    3.770           Journal of Endodontics                                                            1                    2.886
  Oral Microbiology and Immunology (Molecular Oral Microbiology)   1                    2.853           Experimental Biology and Medicine                                                 1                    2.413
  Journal of Biomedical Optics                                     1                    2.367           Operative Dentistry                                                               1                    2.130
  European Journal of Orthodontics                                 1                    2.033           Pediatric Dental Journal                                                          1                    1.947
  FEMS Microbiology Letters                                        1                    1.735           American Journal of Human Biology                                                 1                    1.575
  International Journal of Osteoarchaeology                        1                    1.432           International Dental Journal                                                      1                    1.389
  British Dental Journal                                           1                    1.274           Agricultural and Biological Chemistry                                             1                    1.255
  Helvetica Odontologica Acta                                      1                    1.209           Quintessence International                                                        1                    1.088
  Pan American Journal of Public Health                            1                    0.784           American Journal of Dentistry                                                     1                    0.760

A significant trend ( *p* \< 0.05) occurred between a specific journal age and the quantity of "classics" published in that journal ( *r* = 0.321). However, a statistically nonsignificant trend ( *p* = 0.196) occurred between the quantity of "classics" published in a specific journal and the impact factor of that journal.

Methodological Design
---------------------

The most common study design among "classics" was review-type ( *n* = 40), clinical studies ( *n* = 23), laboratory studies ( *n* = 16), animal studies ( *n* = 15), new classification/tool/technique ( *n* = 5), and cohort studies ( *n* = 1). Statistical significance was not detected ( *p* = 0.808) when exploring the median difference in the citation count per "classic," between review-type articles 238 (range: 175--2,003), clinical studies 258 (range: 176--567), laboratory studies 224 (range: 184--403), animal studies 250 (range: 176--442), and new classification/tool/technique 207 (range: 174--486).

Evidence Level
--------------

The top 100 most-cited "classic" articles could be categorized into all evidence levels. The greatest number of articles were within evidence level V ( *N* = 41) followed by evidence level IV ( *n* = 26), evidence level III ( *n* = 16), evidence level II ( *n* = 13), and evidence level I ( *n* = 4). Among these evidence levels, the citation density ( *r* = 0.088, *p* = 0.383) and the total citation counts ( *r* =--0.178, *p* = 0.077) did not vary significantly.

Keywords
========

A total of 190 unique keywords were found among these "classic" articles. The frequency of occurrence of these keywords were counted as dental caries ( *n* = 24) followed by caries ( *n* = 16), *Streptococcus mutans* ( *n* = 14), fluoride ( *n* = 6), dentin ( *n* = 5), lactobacillus ( *n* = 5), saliva ( *n* = 5), *Actinomyces* ( *n* = 4), dental plaque ( *n* = 4), and gingivitis ( *n* = 4). [Fig. 4](#FI00333-4){ref-type="fig"} shows the network analysis of the keywords. Where the keywords are presented as cluster of nodes and the node size represents the frequency of usage of a certain keyword. The size of the node is directly proportional to the usage frequency of a keyword. The thickness of the edges between two keyword nodes represents the closeness of interactions. The node color of the keywords represents their cluster.

![Keyword network analysis.](10-1055-s-0040-1703419_00333_04){#FI00333-4}

Discussion
==========

The current study focused on the identification and analysis of the top 100 "classics" on dental caries and to highlight the change in current trends, centers of excellence in caries research, dominant types of methodology, and technological developments made over time. In the research field, a publication cited 100 or more times is considered as a "classic" article. [@JR_27] Therefore, all articles included in this study can be termed as "classic" in the field of dental caries. WoS was used as a benchmark database as it is capable of measuring the number of citations since 1945 until date. [@JR_17] Upon cross-matching the citation counts of "classic" publications with Scopus and GS, a considerable fluctuation was evident which varied between 89 to 952 (Scopus), and it ranged between 126 to 1,954 (GS). The evident fluctuation in the citation counts among different databases emphasizes the role of database selection in scientometry. The chance of duplicate article was not expected as only one database was utilized. Nevertheless, it is noteworthy that only citations from 1996 onwards are measured by Scopus. GS includes in its list different forms of cited materials including Web pages, thesis/dissertations/notes, etc., which can provide misleading results while performing an assessment of the most often cited scientific articles in peer-reviewed journals. [@JR_28]

Publication age tends to increase the number of citations for any field regardless of their journal impact. [@JR_29] Nevertheless, this assumption is not supported by the current study as 48% publications were from 2000 to 2015 and 52% were from 1954 and 1999. Although recently published articles (past 15 years) have a lower probability of making it to the "classic" list, [@JR_15] 29 publications were included from 2004 to 2018. This finding emphasizes the relevance, quality, and impact of the topic of a publication on the clinical practice and research. Recently published articles (after 2015) have also been highly cited; however, it is still too early to foresee how the publication age influences the citation count of these publications.

In addition to current study, other bibliometric studies have documented that authors from Africa, South America, Asia, and the Middle East whether being the corresponding or first authors did not make a major contribution which could be counted toward the "classic" articles. [@JR_30] [@JR_31] [@JR_32] [@JR_33] Possible explanations might include language barriers, gaps in professional networking, conducting research, and limited information access. The findings of current study identify a need to turn the focus of caries research toward developing countries where it is more widespread. [@JR_34] The United Nations Organization and the World Health Organization could play a key role in promoting these health care developments.

A total of 301 authors contributed to these "classic" articles. Most of the authors contributed as the first author and the corresponding author simultaneously. J.D.B. Featherstone contributed the most as the corresponding author in three articles. A single author wrote 21 articles and only 2 authors contributed in another 32 articles. Interestingly, N.B. Pitts contributed as the last author of two of the top five "classic" articles which were written by the same author.

The United States have ample financial resources, a larger scientific population, and active researchers which explains its significant contribution to the field of dental caries and explains its greater contribution to the list of top 100 "classics". [@JR_13] [@JR_31] [@JR_33] [@JR_35] [@JR_36] [@JR_37] [@JR_38] In addition to the unparalleled research activity of the United States, authors have shown a tendency to favor citation of publication originating from within the United States. [@JR_39] It is interesting to note that 35 out of 45 articles originating from the United States were published in the journals of origin other than the United States. The Scandinavian countries despite their smaller population size made considerable contributions ( *n* = 21).

In research, the highest quality of evidence is extracted from randomized controlled trials (RCTs) and presented in systematic reviews which are then subjected to meta-analyses to form an evidence base. [@JR_40] The current study identified 13 RCTs and 4 systematic reviews which were included as "classic" articles. It is noteworthy to mention that the Cochrane reviews could not secure a position in the current study although they are internationally recognized as the highest level of evidence base. [@JR_34] A possible explanation of this exclusion is the lower number of citations received by Cochrane reviews is that WoS covers the updated version of Cochrane reviews which started in 2005 and have not yet gained significant age of publications. [@JR_34] Although narrative reviews are classified as a lower level of evidence, 29 review-type publications made to the list of "classic" articles. The presence of so many reviews (36%) signifies the preference of several authors in compiling existing knowledge and information on the topics within the field of caries for the advantage of coresearchers and readers. With the changing trends, evidence-based dentistry has gained significant importance, whereas the current study indicates that the most often cited articles had lower levels of evidence and not necessarily the greatest scientific importance [@JR_41] ; this finding has been previously documented. [@JR_13] [@JR_15]

High impact factor journals such as the *The Lancet* , *Nature* , *Science* , *Annual Review of Medicine* , *Journal of Dental Research* , and *Caries Research* have published most of the "classic" publications. An inclination toward publishing in influential journals was noted which follows Bradford's law, that "most researchers secure their citations from a few specific core journals." [@JR_42] Publication by these authors in other journals may result in reduction of impact of their publication. *Journal of Dental Research* , *Journal of Clinical Periodontology* , and *Caries Research* are identified as the specific nucleus journals of research related to the caries research.

Keywords are the most important component of a research paper in terms of accessibility. Keywords act as "sources codes" which are used to retrieve the relevant published literature from an infinite database of knowledge. [@JR_43] [@JR_44] We identified the most commonly used keywords relevant to the dental caries to enable and facilitate study of dental caries through different search engines. "Fluoride" was identified as the fourth most commonly used keyword by authors after " *Streptococcus mutans* ." The presence of increased levels of *Streptococcus mutans* in saliva has been correlated with an increased prevalence of caries in numerous studies. [@JR_45] [@JR_46] Therapeutic effect of fluoride on reducing the prevalence of dental caries has been widely reported. [@JR_47] [@JR_48] Nevertheless, limitation of dosage according to the recommendations plays a key role to avoid further complications. [@JR_49]

Although it is questionable to judge the validity of a publication based on citation counts, a strong association between impact on a field and high citation counts has been reported. [@JR_50] Factors which influence the counts of citation of a publication include recitation of highly cited article, author reputation in a specific field, and preference of a specific (reputable) journal. The factors described above and others make the number of citations an impartial reflector of the impact and quality of a publication. Modern day platforms such as hashtags, likes, tweets, shares, downloads, and trends depict the influence of electronic media and the impact of a publication on a day-to-day basis which might project a publication as the most cited within the first 3 days of its publication. [@JR_51]

The strengths of this study are: an accepted and commonly used technical methodology, high interrater reliability due to simple inclusion and exclusion criteria, and quality control through two independent investigators and discussion to resolve inconsistencies. The limitations of this study include the fact that the WoS "All Databases" did not measure citations for articles published before 1945. Hence, there might be a possibility of omission of important publications before this date. Second, a publication can have many coauthors from different regions of the world, but the address and affiliation of the corresponding author could only be recognized and has been documented which could have resulted in the possible contributions from other countries and institutions of the world being missed. Third, only the articles published in indexed journals were included: however, it appears unlikely that such a publication would have a high citation count.

Conclusion
==========

This is the first study reporting the list of top 100 "classics" on dental caries. Citation density and citation count did not have a significant association with the publication year. This study despite its inherent limitations attempts to provide a quantitative measure of the impact that a publication imparts on its relevant specialty/field.

**Conflict of Interest** None declared.

Supplementary Fig. S1
=====================

###### 

Supplementary Material

###### 

Supplementary Material

Supplementary Table S1
======================

###### 

Supplementary Material

###### 

Supplementary Material
