The aim of this study is to evaluate the clinical and histological pulp responses when MTA and a combined of MTA/PRF is used as pulp-capping agents after partial pulpotomy.

Partial pulpotomy is generally considered as the treatment of choice for immature permanent teeth with reversible injury. Mineral trioxide aggregate (MTA) is a gold standard material as pulp capping agent in term of vital pulp therapy. Despite many advantages, MTA has a long setting time, little biological inductivity, difficult handling characteristics and high cost.

An essential aspect of tooth tissue engineering is the identification of a suitable scaffold to support cell growth and tissue regeneration. Platelet-Rich Fibrin (PRF) is a second generation platelet concentrate. It is strictly autologous and helps to release the growth factors necessary for the regeneration of dentin pulp complex. Therefore, PRF seems to be a suitable scaffold in vital pulp therapy.

Study sample, 24 intact maxillary or mandibular premolars which will be extracted for orthodontic reasons in 12 healthy volunteers. The sample will be chosen from the patients who are coming to the Orthodontic department in the Faculty of dentistry - Damascus university.

This study will be performed as split mouth study. For each selected patient, one premolar will be randomly allocated to MTA only and the other to combined MTA/PRF by a toss of coin. The main operator will give each patient a numerical code (from 1 to 12) whilst the teeth will have an alphabetical coding (e.g. For the patient coded as 1, premolar with MTA will be coded as 1-a, the other premolar with MTA/PRF will be coded as 1-b). In all patient documents, the teeth will be labeled in the same way so that the clinical examiner and a pathologist will be blinded to the capping technique used for each tooth whilst the main operator who perform a pulpotomy will know which technique is used for each premolar.

Postoperative pain and sensitivity to thermal stimuli will be analyzed after the treatment between two sides.

After 8 weeks, the teeth will be extracted and histologically evaluated in terms of inflammation, dentin bridge formation and its appearance.

Inclusion Criteria:

1. No systemic disease and no medication consumption.
2. Participants, with healthy first premolars in either of the jaws, assigned for orthodontic extraction (scheduled extraction of the maxillary/mandibular premolars).
3. The premolar teeth needed to be fully erupted.
4. The premolar teeth needed to respond within the normal range to cold testing and heat testing.
5. The patients' parents had read, signed and thoroughly understood the informed consent.

Exclusion Criteria:

1. Presence of systematic disease and medication consumption of any type.
2. Anti-inflammatory medicine taken before and during the time of study.
3. Premolars with caries, restoration or any abnormality on periapical radiographs.
4. If the premolar teeth were not fully erupted.
5. If the premolar teeth revealed a lingering pain (a pain sensation that had the tendency to linger as a dull ache after the stimulus had been removed upon cold testing and heat testing).