1

Introduction

In 1971, Cvar and Ryge proposed five criteria (color match, cavosurface marginal discoloration, anatomic form, marginal adaptation and caries) for the clinical assessment of dental restorations . Those criteria were revised in 1980 and were called “modified Ryge criteria” or “modified United States Public Health Service (USPHS) criteria” . In addition to the initial five criteria, new categories such as occlusion, postoperative sensitivity, fracture, retention and others were taken into account. For each category, different items allow to score the restoration as follows: A (Alpha)- restoration which is clinically ideal, B (Bravo)- restoration showing minor deviations from the ideal but nevertheless acceptable (except for retention and secondary caries), C (Charlie)- restoration which should be replaced for preventive reasons to avoid the likelihood of future damage and D (Delta)- restoration requiring immediate replacement. However, authors did not always use the same definitions to assign the scores. Moreover, the modified USPHS criteria were developed when amalgam restorations were commonly used and when adhesive materials had a limited longevity. In order to make these criteria more selective, researchers had to modify and adapt them, which led to “modified Ryge criteria”. Nevertheless, many restorations continued to receive an alpha score after 12 or 18 months .

To detect early deterioration and sign of failures, a more sensitive and discriminative scale than the “modified Ryge criteria” was required and in 2007, Hickel et al. proposed a new system based on three criteria categories: aesthetic, functional and biological ( Table 1 ) . Each category was divided into subcategories to allow for more detailed description and analysis. Each subcategory was scored according to a five-step grading of the restoration: score 1- the restoration is excellent/fulfills all quality criteria; score 2- the restoration is still highly acceptable, though one or more criteria deviate from the ideal (no risk of damage); score 3- the restoration is sufficiently acceptable but with minor shortcomings; score 4- the restoration is unacceptable but repairable; score 5- the restoration has to be replaced. The final score in each category was the most severe score obtained among all subcategories. The criteria defined by Hickel et al. were approved by the Science Committee of the FDI World Dental Federation in 2007 and considered in 2008 as “Standard Criteria” . Their use was thus recommended in clinical trials assessing dental restorations in terms of materials, operative technique/intervention, as well as in clinical practice to determine whether a restoration should be maintained, repaired or replaced . However, the authors outlined that investigators should not necessary use the full set of the 16 criteria but select the most suitable, according to the objectives of their study. Moreover, they added that the five-step grading may also be reduced to four-steps (two acceptable and two unacceptable) or to two-steps by combining scores 1–3 and scores 4 and 5 into “acceptable restoration” and “unacceptable restoration” respectively. Then, the first uses and feedbacks led to modifications of some criteria and scores in 2010 . Since then, no update or further feedbacks have been published regarding their application in clinical studies.

A scoping review was conducted to explore the extent of the use of FDI criteria, 10 year after their introduction. The primary aim of this manuscript was to compare the amount of studies using the FDI and/or the modified USPHS criteria. The secondary aim was to analyse the use of the FDI criteria in clinical trials evaluating direct dental restorations.

2

Materials and methods

A scoping review was conducted to explore a wide range of literature on the use of the FDI criteria, irrespective of the quality of the studies . Table 2 presents the whole search strategy.

A first systematic electronic search was performed using the keyword “FDI criteria” on Medline/PubMed database. Inclusion criteria were: all the clinical trials (randomized or non-randomized, controlled, prospective and retrospective studies) published between January 2007 to April 2017 that used FDI criteria to evaluate direct restorations on primary or permanent teeth. Exclusion criteria were: in vitro studies, case reports and review articles, as well as publications not written in English language. This systematic search followed the PRISMA statement for reporting . The selection of studies was conducted by two independent reviewers (TM and ED). A screening of titles was performed. Irrelevant publications were excluded. Then, the screening of abstracts led to a selection of studies in compliance with the inclusion criteria. Full texts were finally reviewed. In case of disagreement, a consensus was obtained with supervisors (BG and SD). For each paper, the following data − study design, dentition, FDI criteria used in the study, other criteria used if applicable, training and calibration of examiners ( Table 3 ) – were extracted independently and in duplicate by the two reviewers. These data were collected in an Excel spread sheet. In case of disagreement regarding the extraction of data, a consensus was obtained with supervisors (BG and SD). A manual screening was also carried out among the references of selected articles in order to gather further relevant papers.

Corresponding authors of the included articles were contacted by e-mail, to clarify their choice of FDI criteria. They were sent a two-column personalized table. The first column was pre-filled with the criteria they did not use in their study. They were asked to explain the reasons in the second column.

A second systematic electronic search regarding the use of the modified USPHS criteria was performed with a combination of both keywords “USPHS criteria” AND “Ryge criteria” on Medline/Pubmed database to identify studies published between January 2007 and April 2017. Only the number of studies per year was reported to explore in which extend FDI criteria have been used in clinical studies since their introduction, compared to USPHS criteria. As this study focuses on FDI criteria, the abstracts and full texts of studies using USPHS were not considered.

Finally, the ClinicalTrials.gov database was also queried for on-going studies using either the FDI criteria or the modified USPHS criteria, with the keywords “FDI criteria”, “USPHS criteria” and “Ryge criteria”, respectively. The website distinguishes studies with an open recruitment status − such as “recruiting”, “not yet recruiting” or “available for expanded access” − and those with a closed recruitment status, including “completed” or “active, not recruiting” studies. The number of on-going studies (in open and closed recruitment) was then reported. Clinical trials exceeding their completion date and those with no verification of the recruitment within the past two years on the website ClinicalTrials.gov are noted as “unknown”. In both cases, they were excluded.

2

Materials and methods

A scoping review was conducted to explore a wide range of literature on the use of the FDI criteria, irrespective of the quality of the studies . Table 2 presents the whole search strategy.

A first systematic electronic search was performed using the keyword “FDI criteria” on Medline/PubMed database. Inclusion criteria were: all the clinical trials (randomized or non-randomized, controlled, prospective and retrospective studies) published between January 2007 to April 2017 that used FDI criteria to evaluate direct restorations on primary or permanent teeth. Exclusion criteria were: in vitro studies, case reports and review articles, as well as publications not written in English language. This systematic search followed the PRISMA statement for reporting . The selection of studies was conducted by two independent reviewers (TM and ED). A screening of titles was performed. Irrelevant publications were excluded. Then, the screening of abstracts led to a selection of studies in compliance with the inclusion criteria. Full texts were finally reviewed. In case of disagreement, a consensus was obtained with supervisors (BG and SD). For each paper, the following data − study design, dentition, FDI criteria used in the study, other criteria used if applicable, training and calibration of examiners ( Table 3 ) – were extracted independently and in duplicate by the two reviewers. These data were collected in an Excel spread sheet. In case of disagreement regarding the extraction of data, a consensus was obtained with supervisors (BG and SD). A manual screening was also carried out among the references of selected articles in order to gather further relevant papers.

Corresponding authors of the included articles were contacted by e-mail, to clarify their choice of FDI criteria. They were sent a two-column personalized table. The first column was pre-filled with the criteria they did not use in their study. They were asked to explain the reasons in the second column.

A second systematic electronic search regarding the use of the modified USPHS criteria was performed with a combination of both keywords “USPHS criteria” AND “Ryge criteria” on Medline/Pubmed database to identify studies published between January 2007 and April 2017. Only the number of studies per year was reported to explore in which extend FDI criteria have been used in clinical studies since their introduction, compared to USPHS criteria. As this study focuses on FDI criteria, the abstracts and full texts of studies using USPHS were not considered.

Finally, the ClinicalTrials.gov database was also queried for on-going studies using either the FDI criteria or the modified USPHS criteria, with the keywords “FDI criteria”, “USPHS criteria” and “Ryge criteria”, respectively. The website distinguishes studies with an open recruitment status − such as “recruiting”, “not yet recruiting” or “available for expanded access” − and those with a closed recruitment status, including “completed” or “active, not recruiting” studies. The number of on-going studies (in open and closed recruitment) was then reported. Clinical trials exceeding their completion date and those with no verification of the recruitment within the past two years on the website ClinicalTrials.gov are noted as “unknown”. In both cases, they were excluded.