Lower third molar extraction is one of the most frequently performed surgical procedures in dentistry. Common sequelae, including pain, swelling and trismus, can severely affect patients' quality of life during the immediate postoperative period.

The aim of this randomized-controlled trial is to clinically evaluate the reduction of lower third molar extraction-related complications, such as swelling and pain, and wound healing, following submucosal infiltration of injectable platelet rich fibrin.

Forty young patients with a partially or totally impacted lower third molar, with an equivalent degree of difficulty, will be selected. All patients will be randomly treated by using 2 different therapeutic approaches, thereby yielding 2 different study groups, each of which is composed of 20 cases: in the first group, the extraction socket will be left healing spontaneously, while in the other side the socket will be filled with i-PRF.

This study was designed as a double-blind research since the investigator will be unaware of their treatment allocation before surgery, and one clinician, not involved in patient treatment and not aware of what therapeutic approach used for the different sites of treatment, will perform clinical measurement of the outcomes on the surgery day, 3th and 7th days after surgery.

A software will be used to produce a random sequence of 20 integer numbers without duplicates generated from atmospheric noise and concealed in closed envelopes by one of the investigators. At the time of the patient's first surgery, the envelope will be opened and patient allocated to group 1 or group 2.

Prior to surgery, photographic documentation consisting of frontal extraoral photograph, extraoral latero-lateral photograph of the surgery site, extraoral latero-lateral photograph of the opposite site will be performed.

The swelling will be measured summing two linear measurements of distance between Tragus and Pogonion and then Gonion and Commissura labialis points.

Immediately after surgery, the surgeon opens the envelope containing the information about the patient's group membership. In case of i-PRF group, 20 mL will be prepared.

Everyday after surgery, each patients will compile the visual analogic scale to evaluate the pain score.

On 3th and 7th day after surgery, linear measurements of swelling will be taken. Then, on 3th, 7th, 14th, 28th days the wound healing index by Landry will be evaluate.

The Student t test will be used to compare the differences between the two analysed groups. Potential differences between pain, swelling and wound healing based on gender, age and time of surgery will be assessed by using Student's t-test and one-way analysis of variance (ANOVA).

Inclusion Criteria:

• Need for extraction of totally or partially impacted lower third molar
• Equivalent degree of difficulty of lower third molar extraction
• Patients able to understand and sign informed consent

Exclusion Criteria:

• General contra-indications for surgery (systemic disease, compromised immune system etc);
• Tobacco smoking
• Alcohol and drug abuse
• Pregnancy and breastfeeding
• Patients taking any medications which might interfere with healing
• Dysplastic processes in the affected tooth elements
• Non-cooperative patients

EXCLUSION CRITERIA DURING FOLLOW-UP - Patients who do not adhere throughout the duration of follow-up to the specialist visits

POSTOPERATIVE EXCLUSION CRITERIA

- Taking more than two doses of prescribed anti-inflammatory/analgesic medication

The investigator will be unaware of their treatment allocation before surgery. One clinician, not involved in patient treatment and not aware of what therapeutic approach, performed clinical measurement of face swelling on the surgery, 3th and 7th days.