This Feasibility Study Will Evaluate the Study Protocols for Treatment and Follow-up Controls of Primary Molars With Caries in Children Treated With Stainless Steel Crowns or Conventional Fillings. Treatment Success and Potential Failures Will be Followed at 3, 6 and 12 Months Post Treatment.

The overall aim of this project is to evaluate the feasibility of recruiting patients to an adequately powered RCT where treatment with stainless steel crowns cemented with Hall-technique is compared to conventional fillings in cavitated primary molars in terms of tooth survival and cost effectiveness. The scope of the feasibility study also includes treatment group comparisons of predefined outcomes.

The results from this feasibility study will inform the design of a future randomised controlled trial (RCT), which will generate new knowledge on how to treat dental caries in young children using methods that are child friendly, easy to perform and cost effective.

Study design and setting This study will use a two-site, parallel group 1:1 RCT design with two different treatment arms: Hall-technique and conventional fillings.

Patients will be recruited at the public dental clinics in Avesta and Borlänge, patients will be offered to take part of the study if they meet the inclusion criteria at the time of their regular dental exam.

Sample size In this feasibility study 100 teeth will be included, 50 teeth will be treated with Hall-technique, and 50 teeth will be treated with conventional fillings. Each child can have one tooth included in the feasibility study.

No formal sample size calculation based on treatment effectiveness was conducted for the feasibility study, as the primary outcomes concern feasibility rather than hypothesis testing. The sample size was therefore determined pragmatically to allow sufficiently precise estimation of key feasibility parameters, including recruitment rate, retention, protocol adherence and acceptability, while remaining feasible within the available study sites and recruitment period. A total of 100 participants (50 per treatment arm) will be included. This corresponds to approximately 20% of the estimated sample size of 500 participants required for the future definitive RCT.

Randomisation Participants at each site will be randomised to either the intervention or the comparator arm according to the allocation sequence generated using the US National Cancer Institute's Clinical Trial Randomization Tool. The allocation sequence generation applied the maximum tolerated imbalance (MTI) method with two study sites; set MTI = 5; and employed the asymptotic maximal procedure.

Description of intervention Children who meet the inclusion criteria, and whose parent or legal guardian provides written consent, are offered to take part in the feasibility study when visiting their regular dental clinics for routine check-ups. Preventive caries treatment, such as dietary advice, toothbrush instructions and application of fluoride varnish is provided equally in both treatment arms. Preventive treatment will be performed by a dental hygienist or a dental nurse at intervals of 3-6 months according to caries risk and progression.

The two different treatment arms are:

1. Prefabricated stainless steel crowns cemented with Hall-technique where no carious tissue is removed before cementation of the crown (Intervention). 2-3 days prior to cementation of the stainless steel crown separators are applied with dental floss approximal of the tooth indented to treat. Before treatment the teeth are brushed clean of plauque with a tooth brush and separators are removed. Crown size are tried out before the crown are cemented with glas ionomer cement.
2. Conventional filling with total excavation of carious tissue or, selective caries removal where carious tissue is left closest to the tooth pulp, and filling with glass ionomer (Comparator). Topical anaesthesia, Lidocain 5% is applied for four minutes before local anaethesia (Xylocain Dental Adrenalin 20 mg/ml + 12,5 mikrogram/ml) are applied to the tooth using The Wand. There after carious tissue is removed using the method of full or selective excavation. A conventional filling using glas ionomer is applied to the cavity. The dentist will independently choose the method of excavation depending on the depth of the carious lesion and the child's ability to cooperate during treatment.

All dental treatment and follow-up controls will be performed in public dental clinics in Avesta or Borlänge in the region of Dalarna by dentists with experience in treating children aged 3-7 years with caries disease.

Data collection and analysis In this feasibility study, data will be collected at baseline (first visit for treatment) and follow-up visits, using clinical and, when indicated, radiographical examinations for secondary outcome measures. Children will be followed up after initial treatment at 3, 6 and 12 months post-treatment for a total of 3 follow-up visits. At follow-up visits, clinical examinations will be performed, and radiographical examinations only when indicated. Indications for dental radiographical examinations in children could be dental caries, pain or clinical signs of infection.

Qualitative data will be collected to assess the primary outcome study protocol acceptance and adherence by dentists and parents, through semi-structured interviews, where all dentists participating in the feasibility study and five parents from each treatment arm will be invited to participate. Qualitive data from the interviews of the dentists will be used in a later planned study Data regarding pain experience during treatment is reported by use of Wong-Baker Faces pain rating scale. Data on chosen method of excavation in treatment arm 2, time spent, use of local anaesthesia, material expenses, performed treatment, radiological examination, use of nitrous oxide or Midazolam, and travelling time and distance for parents will be collected at baseline through forms filled in by dental staff.

At every follow-up visit data regarding tooth survival defined as time from randomisation to extraction or physiological exfoliation, with physiological exfoliation treated separately from treatment-related failure will be collected. Data on episodes of pain or infection, need for antibiotics or pain medication, lost or fractured filling or crown, new caries lesions, missed or cancelled appointments and received preventive treatment will also be collected through forms filled in by dental staff and questionnaires filled in by parents. Data collection from patient records will be collected after approval from the Region of Dalarna. Data from patient records will be collected by a person working at the Pediatric Dentistry department in Falun, who is not associated with the research project and appointed by head of operations at the Pediatric Dentistry department, Centrum Oral Rehabilitering Falun.

All data collected will not be analysed in this feasibility study but are planned to be analysed in the future RCT study. Data is therefore collected in the feasibility study to enable evaluation of the study protocol for the future RCT.

Statistical analysis Descriptive statistics will be calculated and presented as median and percentiles for time to recruit, as mean and standard deviation for individual-level continuous variables, and as frequencies and percentages for categorical variables. Time to recruit will be compared between trial sites. Treatment group comparisons of predefined outcomes except for time to recruit will be conducted using t-tests, Chi-square and Fisher's exact test as appropriate by variable distribution. Significance level 0.05 will be applied.

• Stainless steel crowns (Procedure): A prefabricated stainless steel crown will be cemented with Hall-technique with a glas ionomer cement without prior caries excavation.
• Conventional fillings (Procedure): A primary molar with a carious lesion will be treated with a conventional filling with glas ionomer after complete or partial carious excavation.

Primary outcomes

• Parents and dentists' acceptance of study protocols assessed qualitatively in semi-structured interviews. [Interviews will start after the 12 month follow-up controls and will take approximately 3 months to complete and analyze.]: All participating dentists and 5 parents from each treatment arm will be invited to take part in semi-structured interviews where acceptance of study protocols will be investigated qualitatively through semi-structured interviews.
• Time for recruitment of participants to the study [Time for recruitment will be assessed as soon as 100 participants are enrolled in the study, estimated 1 year after the recruitment of participants starts.]: The time it takes to recruit 100 participants from recruitment of participant nr 1 to participant nr 100.
• Drop-out rate [From enrollment to the 12 months post treatment follow-up control]: Number of participants who drop out of the study before the 12 months follow-up control.

Secondary outcomes

• Tooth survival after 12 months [from start of treatment to end of last follow-up control 12 months post treatment]: Incidence of tooth loss/extraction due to pain (pulpitis) or infection (apical periodontitis) at the 12 month follow-up control.
• Incidence of treated teeth in the study diagnosed with pain (pulpitis) or infection (apical periodontitis). [from start of treatment to end of last follow-up control 12 months post treatment]: Incidence of treated teeth in the study diagnosed with pain (pulpitis) or infection (apical periodontitis) in treated tooth at folllow-up control visits or emergency visitis. Pain can be diagnosed clinically and infection can be diagnosed clinically or on radiographs.
• Incidence of loss of stainless steel crown or filling [From start of treatment to end of last follow-up control 12 months post treatment]: Number of participants with loss of stainless steel crown or filling diagnosed clinically at follow-up visits or at emergency visits.

Sex: All, ages: 3 Years to 7 Years

Inclusion Criteria:

Children aged 3-7 years with:

* Asymtomatic primary molar with dentin caries diagnosed clinically or on a bite-wing radiograph
* Ability to cooperate to operative treatment with or without sedation of nitrous oxide or Midazolam

Exclusion Criteria:

* Unability to cooperate to operative treatment with or without sedation
* Clinical or radiographical signs of pulpitis or apical infection of the tooth/teeth intended to treat in the study

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• Georgios Tsilingaridis, Vice Dean, Associate professor, Study chair, Karolinska Institutet, Department of Dental Medicine, Division of Orthodontics and Pediatric Dentistry