The purpose of this randomized clinical trial is to compare the clinical/radiographic success of Hall technique and modified Hall technique in the treatment of primary molars with deep dentine carious lesions in children (3-12-year-old). The secondary aim is to examine the effect of marginal ridge breakdown level on treatment success.

Untreated caries in deciduous teeth affect 532 million children worldwide. According to the Turkey Oral and Dental Health Profile study conducted in 2018, the prevalence of untreated caries in 5-year-old children is 64.4%. The traditional treatment of dentine caries is to restore the teeth after removal of the carious tissue. There is increasing evidence for minimally invasive interventions as an alternative to this traditional operative/restorative treatment.

One of the minimally invasive treatment approaches applied in children is the Hall Technique. Local anesthesia and tooth preparation are not required in this technique, and decayed primary molars are covered with stainless steel crowns without removing any carious tissue. The Hall technique has advantages such as preventing aerosol formation, shortening the treatment time, increasing patient cooperation, and reducing the need for general anesthesia and sedation in noncompliant patients. Its popularity has also increased during the Covid-19 process.

The success of the Hall technique in primary teeth with deep caries has been investigated in a limited number of clinical studies, and it has been observed that the technique has lower success rates in teeth with deep caries than in teeth with shallow/medium depth caries. To answer the question of whether modifying the Hall technique (removing the necrotic carious dentin layer manually with excavators before placing a stainless-steel crown) in deeply carious primary molars will increase the success of the original Hall technique (placing stainless steel crown without any intervention to the carious lesion), a randomized study was designed.

268 healthy children between the ages of 3-12 will be recruited from Ankara Yıldırım Beyazıt University Faculty of Dentistry, Department of Pediatric Dentistry outpatient clinic. Participants who met the inclusion criteria and agreed to participate will be randomly allocated to Group 1 (Modified Hall Technique) or Group 2 (Hall Technique).

The allocation of patients in each group will be carried out by a random list. The sequence will be generated by a computerized random number generator. Enclosed assignments in sequentially numbered, opaque, sealed envelopes will be used as allocation concealment mechanism. Group allocation will be performed by an independent researcher, not involved in the study.

Clinical and radiographic success of treatments will be determined at follow-up appointments at 3rd, 6th and 12th months by one blinded examiner. In follow-up appointments; treatments will be recorded as "successful" (restoration appears satisfactory, no intervention required/ no clinical signs or symptoms of pulpal pathology/ no pathology visible on radiographs/ tooth exfoliated), "minor failure" (crown perforation/ new caries (around margins)/ restoration loss; tooth restorable/ reversible pulpitis treated without requiring pulpotomy or extraction) or "major failure" (irreversible pulpitis or dental abscess requiring pulpotomy or extraction/ inter-radicular radiolucency/ restoration loss; tooth unrestorable/ internal root resorption).

Inclusion Criteria:

• Medically healthy children
• Participants attending follow-up appointments
• Children having at least one primary molar tooth with deep dentin caries involving occluso proximal surfaces.

Tooth inclusion criteria:

• Vital pulp with symptom-free or reversible pulpitis
• Presence of marginal ridge breakdown and accessible cavity with hand instruments,
• Presence of active cavitated carious lesion (Code 3 with Nyvad criteria for caries lesion activity and severity assessment- Nyvad et al., 1999)
• Absence of spontaneous or prolonged pain related with irreversible pulpitis
• Absence of fistula or abscess near the tooth
• Absence of pathological mobility
• Absence of pain on percussion
• Absence of pulp exposure
• Caries lesion located in ½ inner part of dentin radiographically
• Presence of sound dentin layer between the deepest part of the carious lesion and the pulp radiographically
• Absence of periapical or furcation pathologies on radiographs
• Absence of internal and external root resorption on radiographs
• More than ½ of root remaining

Exclusion Criteria:

• Any systemic disease, physical or mental disorder
• Children or parents who doesn't accept to participate and sign the informed consent
• Clinical or radiographic signs of pulpal or peri-radicular pathology
• Caries cavity which cannot be accessible to hand instruments
• Physiological root resorption more than 1/2 of the root in primary molars

Participant, investigator evaluating treatment success at follow-up appointments and biostatistician will be blinded