Response to the Letter

To: Editor, The Angle Orthodontist Re: Response to: Efficacy of injectable platelet-rich plasma in reducing alveolar bone resorption following rapid maxillary expansion: A cone-beam computed tomography assessment in a randomized split-mouth controlled trial. Eyad B. Alomari; Kinda Sultan. Angle Orthod. 2019; 89: 705–712.

Thank you for sending these comments to further clarify the methodology of our study.

1. The criteria used to determine whether patients had clinical maxillary transverse deficiency were as follows:

   First, the occlusion was evaluated before assigning the patient in the study. The main criteria were the following:

   • The magnitude of the discrepancy between the maxillary and mandibular posterior teeth was evaluated. If the discrepancy was 4 mm or more, then RME was considered.

   • The number of teeth in crossbite.

   • The initial angulation of the maxillary posterior teeth. If these teeth were normally or buccally inclined in conjunction with normally or lingually inclined mafigndibular posterior teeth in a cross-bite relationship, that was considered a clinically-determined skeletal transverse maxillary discrepancy.

   • A deep palatal vault.

   Second, the previous clinical criteria were confirmed on dental casts by measuring the magnitude of discrepancy in the transverse plane, the relative angulation of the posterior teeth, and the palatal height by the Korkhaus Palatal Index (Palatal height/Palatal width*100=42% in average).

2. For all patients in the study, the expansion screw was activated twice a day until there was an overcorrection of 2-3 mm. Regarding the amount and variation of expansion among patients, the mean expansion was 7.2 ± 0.8mm at the level of the screw.

   The relationship between the amount of expansion and the alveolar defects was not evaluated because the study was focused on PRP and its healing effects compared between the 2 groups.

   1. Regarding the details of the PRP injections, they were as follows:

      • The anesthetic solution was injected at a level above the roots of maxillary first molar and first premolar in order to reduce the effects of mepivacaine on PRP (if present).

      • PRP was prepared and injected subperiosteally in the attached gingiva over the buccal root of the maxillary first premolar and the mesiobuccal root of the maxillary first molar (not intraligamentary). As well, it was injected submucosally at the same root at the level above the mucogingival line. That means there were two injection sites for each root: the first at the middle height of the keratinized gingiva and the other 3 mm above the mucogingival line, 0.5 ml of PRP per site.

      • A 3 ml plastic syringe was used with a 25-gauge needle

      • PRP folds: (3 ± 0.4)

      • PRP was prepared and injected at the same room temperature.