Background: For treating deep caries lesions, selective or stepwise, i. e. one- and two-step incomplete excavation seems advantageous compared with complete caries removal. However, current evidence regarding the success, as defined by not requiring any re-treatments, or survival of teeth after different excavations is insufficient for definitive recommendation, especially when treating deciduous teeth. Moreover, restoration integrity has not been comparatively analyzed longitudinally, and neither patients', dentists' or parents' preferences nor the clinical long-term costs emanating from both initial and re-treatments have been reported yet.

Our primary hypothesis is that success rates differ significantly between selectively and stepwise excavated teeth. Secondary hypotheses are that restoration integrity is assumed to significantly differ between selectively and stepwise excavated teeth.

The treatment of deep caries lesions is associated with significant risks for the pulp, including pulpal exposure and post-operative pulpal complications, which might eventually compromise the retention of the tooth [1]. Moreover, treating deep lesions might be associated with pain and subjective burden both during and after treatment and might generate long-term costs due to re-treatments being required [2, 3].

For deciduous teeth, various treatments for deep lesions have been described: Complete excavation aims at removing all infected and affected carious dentin, with the inherent risk of pulpal exposure. In contrast, stepwise, i. e. two-step excavation leaves carious dentin after the initial excavation step, then seals residual caries under a temporary restoration, and re-enters the cavity in a second step to eventually attempt complete excavation. This approach is thought to facilitate arrest and remineralization of the lesion and to induce development of tertiary dentin, thereby reducing the risk of pulpal exposure and post-operative complications after the second excavation step [4, 5]. Since several studies found sealed residual lesions to be clinically and microbiologically arrested, the need to re-enter was increasingly questioned within the last decade [6]. Selective, i. e. one-step incomplete or partial excavation seals carious dentin under a definitive restoration, omitting any re-entry [7]. Sealing the lesion is thought to deprive residual bacteria from dietary carbohydrates and was found to exert significant antibacterial effects, thus arresting the lesion [8, 9].

However, doubts remain regarding the effects of sealed carious dentin on the long-term quality of the restoration [10]. Moreover, it remains unknown if patients prefer one of both treatments, which might be especially relevant when treating children. Several studies comparing complete with selective or stepwise excavation of deciduous teeth have been published, but only one three-arm study compared selective with stepwise excavation of primary teeth (Tab. 1). In addition, none of these studies assessed patient- or dentists-centered outcomes, i. e. preferences, or analyzed clinically assessed long-term costs emanating from both excavations.

Objectives and Hypotheses The study aims at comparing the success, i. e. the probability of not requiring any re-interventions, and the survival, i. e. the probability of not requiring tooth removal, of selectively versus stepwise excavated vital, non-symptomatic deciduous molars with deep lesions. In addition, we assess the restoration integrity of selectively versus stepwise excavated deciduous molars, evaluate the preference of patients, parents and dentists for one of both strategies, and comparatively assess the costs associated with each strategy.

Our primary hypothesis is that success rates differ significantly between selectively and stepwise excavated teeth. Secondary hypotheses are that restoration integrity is assumed to significantly differ between selectively and stepwise excavated teeth. Moreover, we hypothesize that patients', parents' and dentists' preference is significantly different for selective versus stepwise excavated teeth. Eventually, both initial and long-term costs of excavation methods are supposed to significantly differ.

The planned study is a secondary care-based prospective, multi-center two-arm, parallel-group, randomized controlled trial at three pediatric university dental clinics in Germany. We plan to enroll 300 patients with one or more deeply carious, sensitive and non-symptomatic deciduous molar. One molar per patient will be randomly allocated to receive one of two treatments (selective or stepwise excavation). Total follow-up time will be three years after completion of the initial treatment. Success, survival and restoration integrity will be assessed after one, two and three years. Patients', parents' and dentists' preference will be assessed after each treatment using visual-analogue scale or Likert-rating scales. Costs will be assessed for initial and follow-up treatments and will be based on a micro-costing approach.

Inclusion Criteria:

• Children 3-9 yr
• Good general health
• Minimum one active deep (D3) occlusal/occlusal-proximal, one-/two-surface caries lesion

Exclusion Criteria:

• Participating in other study
• Plan to move or not resident
• Systemic disease or general disability
• Expected limited compliance
• Known allergy to study material expected exfoliation within 18 month