The objective of this study is to investigate whether the 3D scanner and accompanying software, as well as the transillumination method, can identify changes in primary caries lesions in caries-active patients, where selected lesions achieve a higher degree of plaque control than others over an 8-month period.

The working hypothesis of this study is that the two methods, scanning and transillumination, are as good as the traditional method (clinical examination complemented by radiographs) to assess whether caries lesions are progressing, stable or regressing. Progression, stability or regression of selected caries lesions are thus the endpoint, and the rationale is to investigate whether more objective measures can replace/supplement a subjective method to assess progression, stability or regression of caries lesions.

Caries is a non-infectious disease of the hard tissues of the teeth that occurs with very high prevalence around the world. The aetiology and pathogenesis of the disease are well understood. Bacterial accumulation on the teeth (dental plaque) concomitant with the ingestion of fermentable carbohydrates promotes acid production deep within the plaque, which progressively demineralizes the underlying hard dental tissue. Caries thus involves mineral loss from the first crystal disintegrating (not clinically identifiable) through gradually increased demineralization, with the mineral loss being identified early by the tooth tissue changing colour, through the physical appearance of a fracture (cavity) in the tooth, to the complete damage of the tooth. Demineralization can be halted or controlled by daily brushing with fluoride toothpaste, provided that brushing, possibly supplemented with flossing, is carried out as demonstrated by dentists or dental hygienists. Adding professional cleaning, i.e. plaque removal with rotary brushes and flossing and performed by dentists/ dental hygienists or clinic assistants, e.g. once a month, can ensure that the lesion is stopped if daily home dental care is not optimal. If caries has occurred, it can be treated non-operatively or surgically, complemented by risk-related initiatives.

Caries can develop in relation to previously placed fillings. This is referred to as secondary caries. In contrast, the term primary caries is used for caries located on unfilled/restored areas of the tooth or its root surfaces. Whether primary or secondary, caries lesions' severity is classified as superficial, moderate or extensive. The last two diagnoses usually require operative treatment, i.e. a filling, or root canal treatment or extraction.

Caries is detected and diagnosed using a number of methods, the most common being a clinical visual/tactile examination of the teeth, complemented by radiographs. However, this method is highly subjective, and thus with large variation among dentists and dental hygienists, resulting in different treatment strategie. In addition, radiographs lack sensitivity in terms of detection of the initial caries lesions.

Researchers have therefore developed various devices and methods for a more objective modulation of mineral loss, including monitoring of individual caries lesions. Perhaps best known is the QLF (Quantitative Light Fluorescence) system, which uses fluorescence measurements of the tooth's response to demineralization. The latest technology using fluorescence for caries detection and classification is the intraoral 3D scanner with the integrated automated caries registration system, which has been developed and now for a few years has been tested in both in vitro and in vivo studies at the Department of Odontology of the University of Copenhagen (OI).

The technique is based on the fact that healthy and demineralized tooth tissue absorbs the blue-violet light (wavelength ~415 nm) and emits back fluorescent light with different light intensities, from bright green to brownish to red. In terms of detection and classification of caries lesions on occlusal surfaces, the scanner has overall a better reproducibility and a comparable accuracy expressed through sensitivity and specificity compared to a combination of the clinical and radiological examination.

Another method that has been widely investigated for the detection of initial proximal (between teeth) and occlusal caries lesions, without the use of ionizing radiation, is transillumination with near-infrared light (wavelength ~780 nm). In the transillumination method, the light is transmitted through the dental tissue. The caries lesions appear dark, like shadows, due to the scattering and absorption of the light in the porous demineralized tissue. In contrast, the healthy, transparent enamel tissue appears brighter as light penetrates this tissue with very low light scatter and almost no light absorption. This method is used by the intraoral camera "DIAGNOcam" (KaVo, Biberach, Germany) and has also been investigated by researchers from the Department of Odontology at the University of Copenhagen and 3Shape (3Shape TRIOS A/S, Copenhagen, Denmark) for implementation in the 3D intraoral scanner system. This has shown improved sensitivity in detecting initial approximal caries lesions that can be treated with preventive, non-operative methods.

One of the areas that remain to be investigated regarding the usefulness of the 3D scanner and transillumination camera as a caries diagnostic method is the monitoring of caries lesions between two or more examinations in the clinic, including how the systems respond to lesions that have received intensive treatment to stop their progression.

Method:

18-30-year-old young adults in Denmark with high caries activity. Potential participants are found by advertising for caries-active patients in the daily press, on the OI website or an announcement board at the OI.

When contacting a potential participant, information is provided about the study, in addition to what is stated in the advertisement, on the website or on announcement boards. After that the a clinical screening is conducted.

Participants (n ~33) are offered common caries prevention initiatives: improved self-care, toothbrush instruction using 1450 ppm fluoride toothpaste, dietary advice and topical fluoride treatment. In addition, selected superficial caries lesions on individual participants will be professionally cleaned once a month.

Study participants will receive dental check-ups at shorter intervals (approximately every 1.5 months) compared to standard treatment.

Participants with lesions requiring restorative treatment (media/profound lesions) or with teeth that must be extracted due to caries will be treated at the OI according to the usual rules.

A traditional clinical and radiological examination also includes the diagnosis of other pathological conditions of the oral cavity, which, if identified, will be treated at the OI, according to the usual rules, or the participant will be referred to a private dentist. Other diseases of the teeth and supporting tissues likely to be diagnosed in 18- to 30-year-olds are gingivitis, erosions and wisdom teeth which only partially emerge into the oral cavity (dentis retentus).

The examination shall be carried out at the Department of Odontology, University of Copenhagen (OI) First visit (Baseline) i) Relevant medical history. ii) Records: tooth and filling status (chart), as well as clinical plaque and gingival index ad modem Løe & Silness (1963) on selected teeth: 6+, 3+, 1+, +2, +4, +7, 7-,5-, 2-, -1, -3, -6.

iii) X-rays: 2 BW (X-ray device SOREDEX, MINRAY®; Image plates VistaScan; Image plate scanner VistaScan Mini View, Dürr Dental) with special holders for reproducible images.

iv) Dental cleaning and professional plaque removal, including flossing. v) 3D scanning vi) Transillumination method vii) ICDAS (International Caries Detection and Assessment System) registration viii) Treatment plan. ix) Treatment. Second visit (1.5 months) 3D intraoral scanning and ICDAS registration. Third visit (3 months) As at baseline, but no radiographs (BW). Fourth visit (~6 months) 3D intraoral scan and ICDAS registration. Fifth visit (8 months) As at 1st visit

In addition, participants will need to come a number of times to have their caries lesions that require restorative treatment treated.

At each visit, also when lesions are treated with fillings, polishing of selected lesions will be performed.

Monitoring plan The monitoring plan will be carried out in accordance with the standard procedures for clinical research at the Department of Odontology, University of Copenhagen.

Dental student Maria K. Riis will be responsible for daily data handling, secure data archiving, and recruitment of study participants.

Staff will be responsible for the overall monitoring of the study. This person (monitor) will soon be appointed by the Department of Odontology and will be responsible for a monthly check of the progress of the study, including the following parameters:

1. Verification of the presence of the consent form.
2. Verification that participants meet inclusion and exclusion criteria.
3. Verification of data collected versus source data.
4. Compliance with the protocol and documentation of any deviations

The reason for selecting participants aged 18 to 30 years is that they are more likely to have primary caries lesions (which is the focus area) than secondary caries lesions. In addition, other dental and oral diseases requiring treatment, such as extensive tooth wear, are less likely to be found during the traditional clinical and radiological examination conducted for the study in 18- to 30-year-olds compared to older individuals.

In addition, patients with chronic medical diseases or impaired salivary secretion are excluded as they are expected to have more extensive dental problems, which are not the focus of this study.

Publication of results The study protocol will be registered at www.ClinicalTrials.gov. The study results will be published in international scientific journals under the terms of the research agreement (09.01 Research collaboration agreement CPH (Copenhagen) University), to which this document is Appendix 2. This applies to negative, positive or inconclusive results. If contrary to expectations, publication in national/international journals is unsuccessful, the investigators will ensure, under the terms of the research agreement (09.01 Research collaboration agreement CPH University), that the data are published on the department's website. The research agreement (09.01 Research collaboration agreement CPH University) states that 3Shape can request that manuscript submission be postponed by up to three (3) months from the date of receipt, provided 3Shape proves that the postponement is important for 3Shape's prospects of acquiring intellectual property rights protection of the knowledge that the University has. The disclosure of knowledge shall always be made in compliance with the obligation of professional secrecy. The research agreement (09.01 Research collaboration agreement CPH University) states that 3Shape will use the anonymized clinical data for product development, regulatory and commercial activities related to 3Shape's products.

Inclusion Criteria:

• Medically healthy young adult patients (18-30 years old) where individuals must have ≥ 20 teeth.
• Two or more active caries lesions

Exclusion Criteria:

• Patients with impaired salivary secretion
• Patients with chronic medical diseases.