Edited by: Thomas Dandekar, University of Würzburg, Germany
Reviewed by: Alpdogan Kantarci, Forsyth Institute, USA; Nick Stephen Jakubovics, Newcastle University, UK; Giovanni Di Bonaventura, “G. D'Annunzio” University of Chieti-Pescara, Italy
*Correspondence: Inmaculada Tomás
This article was submitted to Infectious Diseases, a section of the journal Frontiers in Microbiology
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The oral cavity contains hard as well as soft tissue surfaces, all of which are potentially available as susceptible areas for the development of oral biofilms (Newman and Wilson,
Biofilms are important, because some resident species contribute to the maintenance of oral health and other species have the potential to cause local or systemic disease (Newman and Wilson,
The creation of
In several
The literature defines several specific devices which were designed to form a PL-Biofilm
A systematic review protocol was made in the planning stages according to the PRISMA checklist and approved by all authors. This review is reported according the PRISMA statement (Liberati et al.,
This was the Patient/Population Intervention Comparison Outcome (PICO) question: In adult population, what are the advantages and disadvantages of the different types of devices that have been used for the growing of
The components of the PICO were:
Population: all adult volunteers (over 18 years old) wearing intraoral devices.
Intervention: type of device used for the growing of
Comparisons: between different types of devices.
Outcomes: advantages and disadvantages of each of the different devices.
All types of
The literature search for relevant articles was conducted using the electronic database OVID MEDLINE and OVID EMBASE, the date of the last update was 16th of June 2015. The search strategy included the following search words:
MeSH terms in all trees/subheadings: “dental plaque,” “biofilms,” and “splints.”
Keywords for dental plaque and biofilm: “dental plaque,” “dental deposit*,” “biofilm*,” “biofouling,” and “oral ADJ bacteria.”
Keywords for splints: “appliance*,” “stent*,” “splint*,” “ferule*,” “device*,” “apparatus,” “mechanism*,” and “gadget*.”
The same search strategy was used in the OVID EMBASE database, adapting the MeSH terms. Manual search was done by the reviewers after checking the reference lists of the relevant studies.
Study selection was conducted independently by two reviewers (IP-L and VQ) in the following stages: (1) initial screening of potentially suitable titles and abstracts meeting the inclusion criteria and (2) screening of the full texts identified as possibly relevant in the initial screen. The assistance of translators was sought for studies that were not in English.
Data were extracted using predefined data extraction forms including type of device, localization, substrate, number of participants, biofilm age, microbiological technique to analyze the biofilm, volunteer experience and removal and retention of the substrate.
Disagreements between reviewers were solved through discussion and consensus Kappa index at the first stage was 0.93 and 0.90 at the second stage. A difficulty in the systematic review was the poor description of a device or the absence of correlation between the description and the photographs presented. When doubts appeared, author contact was required. In studies where author contact was not successful and it was not possible to achieve an agreement in the type of device used, the decision was the exclusion.
After reading the full text, descriptive summary analyses were reported, following systematic review guidelines (Mulrow et al.,
Fourteen important qualities and characteristics of the ideal device were standardized by the authors for the analysis of each apparatus. The first eight questions were focused on the technical characteristics, the next three questions investigated the influence of the device on the volunteer's comfort and the final three questions were about manufacturing, placement and economic cost (Table
1 | Teeth pre-treatment is not necessary |
2 | Specific teeth are not necessary |
3 | No accidental unsticking |
4 | Allows eating |
5 | Easy withdrawal by the volunteer |
6 | Easy withdrawal of the sample |
7 | No contact with cheek /tongue |
8 | Allows salivary flow through the splint |
9 | Allows good oral hygiene |
10 | Good aesthetic |
11 | Little bulky |
12 | Adaptable on the 1st appointment |
13 | Easy placement at 1st time |
14 | Inexpensive material |
The degree of agreement between reviewers was more than 97% at the first and second stages. After the initial search and removing duplications, 787 papers were found. When the titles and abstracts were read, the reviewers selected 127 papers. Following text screening, 16 papers were excluded due to the use of the patient's prosthesis or orthodontic devices, lack of information about the device or other factors, such as not analyzing the biofilm microbiologically or including population of less than 18 years of age. Finally, 111 papers were selected for assessment of the full text (Figure
All of these were written in English, with the exception of one which was in Chinese.
All characteristics of the selected studies are in the Data Sheet
The most commonly used substrates for the development of
This went from 4 h (Nyvad and Fejerskov,
The most commonly used techniques in these studies are those based on visualizing the oral biofilm with fluorescence microscopes [both epifluorescence and Confocal Laser Scanning Microscope (CLSM)] (Benelli et al.,
Another common technique has been the Colony Forming Units (CFU) counting (Creanor et al.,
Palatal devices (Figures
On the other hand, buccal devices have been used extensively, allowing the definition of six different groups: AcD (Figures
In summary, Tables
Benelli et al., |
Gameiro et al., |
Creanor et al., |
Cury et al., |
Lima et al., |
Macpherson et al., |
Hara et al., |
Schwarz et al., |
Macpherson et al., |
Tenuta et al., |
Sousa et al., |
Jenkins et al., |
Auschill et al., |
Beyth et al., |
Rasperini et al., |
Paes Leme et al., |
de Mazer Papa et al., |
Sreenivasan et al., |
Pecharki et al., |
Brighenti et al., |
Re et al., |
Ribeiro et al., |
Cochrane et al., |
|
Korytnicki et al., |
Teixeira et al., |
|
Schwarz et al., |
Melo et al., |
|
Arthur et al., |
Pierro et al., |
|
Schwarz et al., |
Bittar et al., |
|
Scotti et al., |
Padovani et al., |
|
Paes Leme et al., |
Author, year [references] | Nyvad and Fejerskov, |
Groessner-Schreiber et al., |
Strassler et al., |
Rimondini et al., |
Leonhardt et al., |
Sennhenn-Kirchner et al., |
García-Caballero et al., |
The evaluations of each buccal device group according to the ideal characteristics they should meet are presented in Table
Pre-Treatment of Specific Teeth
The pre-treatment of teeth is only necessary in the LiD group; it needs from etching, bonding and a composite to be glued onto specific teeth (first and second molars).
Accidental Unsticking
Accidental loss of samples has been found in the LiD, AcD, AcMD and MD groups. Conversely in TPD and IDODS groups no loss of specimens has been reported.
Eating and Chewing with the Device
The LiD allows the user to eat whilst wearing it, without the need for its withdrawal, as happens with AcMD and MD. The AcD, TPD and IDODS do not permit chewing, because they cover the occlusal zone of the molars.
Withdrawal by the Volunteer
All of the apparatus, with the exception of the LiD, can easily be withdrawn by the volunteer in order to perform their oral hygiene measures normally (according to the protocol of the study).
Withdrawal of the Sample by the Investigator
The withdrawal of the sample from the LiD, AcD and AcMD by the investigator is done with a forceps or a bracket-removing plier. On the other hand, in the TPD, the investigator must take the sample by its backside with tweezers (Burgers et al.,
Contact with Cheek and Tongue
The TPD, MD and IDODS have a special framework (with composite in MD) which protects the substrate from making contact with anything other than from the saliva or any other liquids inside the mouth (antiseptic agent). In the AcMD, the disk is located in a sheltered space between the tooth and the device, which protects the biofilm from contact with the cheek and tongue.
Salivary Flow through the Splint
Only the IDODS allows salivary flow through it, leaving both sides of the disk exposed.
Volunteer's Comfort
AcD are very voluminous, dramatically affecting the phonetics and the esthetics of the volunteers; the same is true for the metal used in the AcMD. Conversely, the LiD (situated in the posterior molar), the TPD and the IDODS (both made of transparent material) are less voluminous. For these reasons, they slightly affect the phonetics and the esthetics.
Adaptability, Placement and Manufacturing Cost
Manufacturing processes for these devices are very diverse. All devices except the LiD need a plaster model of the volunteer to be made in order for the device to fit properly. The LiD, being a standard apparatus, does not need any type of individualisation prior to placement. Other devices such as AcD and TPD or the IDODS need a laboratory process, but their fabrication is simple and not too expensive. However, the AcMD and overall the MD (made of Cobalt and Chrome) requires a more complex laboratory process which increases the cost of the device.
In regard to the placement in mouth, there are also differences between the LiD and other devices, due to the fact that it must be placed in the clinic with the proper isolation and specific protocols, similar to those used in bracket bonding. However, all of the other devices are given to volunteers with the instructions for correct use, in the same way as if they were removable orthodontic retainers.
Teeth pre-treatment is not necessary | ✓ | ✓ | ✓ | ✓ | ✓ | 5/1 | |
Specific teeth are not necessary | ✓ | ✓ | ✓ | ✓ | ✓ | 5/1 | |
No accidental unsticking | ✓ | ✓ | 2/4 | ||||
Allows eating | ✓ | ✓ | ✓ | 3/3 | |||
Easy withdrawal by the volunteer | ✓ | ✓ | ✓ | ✓ | ✓ | 5/1 | |
Easy withdrawal of the sample | ✓ | ✓ | 2/4 | ||||
No contact with cheek /tongue | ✓ | ✓ | ✓ | ✓ | 4/2 | ||
Allows salivary flow through the splint | ✓ | 1/5 | |||||
Allows good oral hygiene | ✓ | ✓ | ✓ | ✓ | ✓ | 5/1 | |
Good esthetic | ✓ | ✓ | ✓ | 3/3 | |||
Little bulky | ✓ | ✓ | ✓ | ✓ | ✓ | 5/1 | |
Adaptable on the 1st appointment | ✓ | 1/5 | |||||
Easy placement at 1st time | ✓ | ✓ | ✓ | ✓ | ✓ | 5/1 | |
Price of the material | + | ++ | ++++ | +++++ | +++ | ++++ | |
5/8 | 4/9 | 8/5 | 8/5 | 10/3 | 11/2 |
No previous reference was found to give the authors a base to work with the characteristics of the different devices. Given this circumstance, a list of fourteen important qualities and characteristics was standardized. The fact that the authors have also designed one of the apparatus reviewed could be a potential source of bias. When the list of items was devised the authors tried to abstract from their own design trying to be as “objective” as possible. The items were chosen, based on the authors' experience, for being of capital importance in an “ideal” device. Later, this checklist was modified after completely reading the selected articles in the present review.
The classification of the apparatus was designed prior to the start of the study and subsequently modified in order to clarify its presentation. As the group has previous experience in the field, a first classification based on the material of the device was established. After the data extraction, this classification was extended introducing the position of the substrates.
The review was focused mainly on buccal devices due to fact that both palatal and lingual devices have been less used in the existing literature. In the latter types of devices, the PL-Biofilm was always exposed to contact with the tongue; for this reason, the biofilm would be very disturbed. To prevent this from happening, authors devised protections such as a plastic mesh (in palatal devices) or an artificial gap between the device and the lingual gingiva (in lingual devices). These protections would surely modify the growing environment of the PL-Biofilm, causing possibly, a lack of representativeness of the dental biofilm attached to the enamel surface. On the contrary, these devices permit the development of PL-Biofilm in absence of contact with the oral environment and poor renovation of saliva on its interior, allowing for the growing of biofilm covered with stagnated saliva. This particularity makes them to be useful for the replication of dental caries models. In any case, their use in PL-Biofilm studies is scarce (10 times less than buccal devices). A possible reason for this might be the big influence in phonetics that these devices have.
As previously stated, the intraoral devices for the development of PL-Biofilm have been faced to obtain very different results. These range from studying the covering grade of the biofilm, its thickness, bacterial viability or composition before and after applying several antimicrobial agents to the analysis of the effects that the PL-Biofilm itself may have onto a specific substrate. As stated in the material and methods section, the present review was only focused on the use of these devices in order to obtain a PL-Biofilm for a posterior microbiological evaluation. This evaluation has been done by CFUs, electronic microscopes (SEM or TEM), CLSM (after previous staining with dual live/dead fluorochromes or FISH and DAPI for bacterial identification and differentiation). All devices presented good properties in order to use one or another technique. In some cases the necessity of using one or another technique is going to be more related to the type of substrate that it is being used. For CFUs analysis, no troubles were found in any study in terms of collection of the sample, since the sample is harvested normally by vortexing the PL-Biofilm with the substrate (Leonhardt et al.,
Probably, in an effort to search the most similar substrate to the natural tooth surface, the most commonly used substrate has been the human enamel. Nowadays, other substrates such as titanium (Gosau et al.,
The quantity of the substrates used depends on the design of the apparatus and the specific requirements for the aim of each of the studies. Depending on the latter, some devices are not eligible due to the impossibility of inclusion of enough samples (i.e., a study needing from more than four different samples from the same volunteer cannot be conducted using a LiD).
Scanning and Transmission Electronic Microscopy techniques, traditionally considered as the Gold standard for the visualization of the biofilm (Al-Ahmad et al.,
A wide range of biofilm maturation has been found in this review. Of course, this is a characteristic which is directly related to the aim of the studies. As the devices may be used for long periods of time, the apparatus should be properly designed, not affecting the volunteer's comfort. In the present review, the authors have taken into account that dental biofilm in terms of maturation may be generally considered after 4 h. Before this time, there may possibly exist bacteria adhered to the acquired pellicle. In fact, Hannig et al. (
The pre-treatment of the teeth with etching, bonding/de-bonding procedures and the posterior composite removal could damage enamel. This could result in the production of white-lesions or demineralizations similar to those caused by fixed orthodontia (Artun and Thylstrup,
Accidental loss of samples is a problem that has been found in those apparatus (LiD) where disks are attached to the tooth surface. The same situation has been reported in the AcD, AcMD, and MD groups, where specimens are glued or fixed to the device with wax. TPD and IDODS have specific zones where the disks are perfectly retained. Accidentally dropping samples is an important issue, not only for the study, which will lose a specimen, but for medical reasons, due to the potential bronchial aspiration of the disk, which would cause an emergency situation.
A common limitation that applies to most devices is the inability to eat with the apparatus while wearing it. This characteristic would allow the analysis of the biofilm growing in the presence of nutrients coming directly from food. Although, the withdrawal period during meals is brief (15–30 min) and the devices are generally kept in a humid environment, this action implies that the biofilm is not exposed to nutrients or the self-cleansing action of chewing.
The impossibility to remove the LiD by the volunteer hinders the oral hygiene level in the vicinity of the device. Other devices can be removed by the volunteer in order to perform their oral hygiene measures normally (according to the protocol of the study). The ability to brush the teeth makes the use of these devices suitable for volunteers with specific oral diseases, who need to maintain good oral hygiene, such as patients with periodontitis. The study of this biofilm
The withdrawal of the sample from the LiD by the investigator with a forceps or bracket-removing pliers might disturb the
Another important factor which could disturb the biofilm is contact with the cheeks and tongue during the period when the device is inside the oral cavity. In most apparatus, this issue has been solved with the design of a specific framework that protects the substrate. In the case of the AcMD, the disk is located facing the teeth, avoiding contact with the cheeks. In this specific situation, the growing conditions of the PL-Biofilm are completely different from the real situation given in the buccal teeth surface.
During the oral biofilm formation, the flow of saliva supplies the disk with nutrients (Bowden and Li,
Another important criterion that should be taken into account when designing a biofilm device is its effect on the volunteer's comfort. The normal life of subjects is altered by all devices, especially by the bulk of the device and the type of material used, both esthetically and phonetically. If the volunteer's comfort is not affected or is affected as little as possible by the wearing of the device, the volunteer will better fulfill the protocol. If the device is uncomfortable or not esthetic, the volunteers might change their diet or reduce the duration for which the device is placed inside the oral cavity. Every change in their normal life will produce a bias in the growing biofilm. Despite the importance of these parameters, only one study which discussed the volunteer's experience with the device was found after this review (Prada-López et al.,
Finally, it is important to highlight that some authors made small variations from the prototype. For instance, in 2012, Gu et al. (
After this deep review of the existent literature, the authors would like to show their own perspective of the “ideal”
The majority of the published papers have not described the device or the manufacturing methodology properly. In these cases, reproduction of any device would be more difficult, and standardization would be impossible. Consequently, the potential to compare results between studies or to apply the same methodology would be a utopian situation. For this reason, a specific description would be very useful when any groups subsequently design new devices, as previously included by some authors (Robinson et al.,
In addition, no papers could be identified which have compared the characteristics of the device-formed-biofilm positioned at buccal (PL-Biofilm) with the tooth-formed-biofilm (dental plaque). From the authors' point of view, the quality or the relevance of the PL-Biofilm should be the primary issue of every study on oral biofilm. When using a device in order to assess
In the present review, only one study which used self-perception questionnaires was identified. Prada-López et al. (
Buccal devices were the most commonly used for the study of
Papers should include more information about manufacturing their devices. Therefore, any new device must consider the limitations of the previous ones, paying particular attention to the needs of the volunteer and the biofilm formation. In addition, all of the devices must test the volunteer's experience and the microbiological differences between device-formed biofilm and tooth-formed biofilm and studies should include a feedback exercise.
IP, VQ Conception and design of the review, revising of the literature, acquisition, and analysis of data and drafting the article. CV Making different devices for obtaining figures and revising of the literature. DS, IT Conception and design of the review, revising of the literature and manuscript and final approval.
This work was supported by project EM2014/025 from Regional Ministry of Culture, Education and University (regional government of Galicia, Spain), which is integrated in Regional Plan of Research, Innovation and Development 2011–2015. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
The Supplementary Material for this article can be found online at:
Acrylic Device
Acrylic and Metal Device
Colony Forming Units
Confocal Laser Scanning Microscope
Diamidino-2-Phenylindole
Fluorescence
Intraoral Device of Overlaid Disk-holding Splints
Leeds
Metal Device
Patient/Population Intervention Comparsion Outcome
Plaque-Like Biofilm
Thermoplastic Device.