Modified Ridge Splitting Technique Using Autogenous Bone Blocks (MRS)

Patients were required to rinse with a 0.2% chlorhexidine solution for 1 min before surgery. Under local anesthesia, a full-thickness flap was raised from a crestal incision with a mesial releasing incision to access the alveolar ridge and the retromolar area. A midcrestal osteotomy was preformed, leaving a safety zone of at least 2 mm from the adjacent tooth. Two vertical releasing osteotomies were performed at the mesial and distal ends of the mid-crestal osteotomy. Apically, the vertical osteotomies were connected horizontally with a superficial corticotomy. Osteotomies and corticotomies were carried out using a piezoelectronic device (NSK Variosurg3 Ultrasonic Bone Surgery System, NSK Europe GmbH, Eschborn, Germany.) Chisels were inserted in the midcrestal osteotomy to create a green-stick fracture to allow extensive mobilization of the buccal cortical.

After mobilization of the buccal cortical, an autologous bone block with dimensions corresponding to that of the bone defect created in the recipient site was harvested from the retromolar area and was placed as a spacer between the buccal and lingual cortical plates. The block was stabilized using osteosynthesis screws (Meisinger Screw System, Hager and Meisinger GmbH, Neuss, Germany). Both lingual and buccal flaps were mobilized to allow tension-free primary closure. The flap was closed with horizontal mattress sutures, and then single interrupted sutures closed the edges of the flaps. Suture removal took place after 14 days. All patients received amoxicillin and clavulanate (Aktil Duo 875 mg/125 mg, Sandoz Hungária Kft., Budapest, Hungary) 1 g twice per day, starting at the day of the surgery and continuing for 7 days. In case of amoxicillin allergy, clindamycin (Dalacin 300 mg, Pfizer Inc., New York, NY, USA) was prescribed four times a day for 7 days. Furthermore, a non-steroid anti-inflammatory drug, diclofenac (Cataflam 50 mg, Novartis Hungária Kft., Budapest, Hungary), 3 times a day for 3 days, and 0.2% chlorhexidine mouth rinse (Corsodyl, GlaxoSmithKline Consumer Healthcare GmbH \& Co. KG, München, Germany), twice a day for 2 weeks, were prescribed to the patients. During the healing period, patients did not wear temporary prostheses.

Surgical re-entry took place after 3 months of healing. Implant bed preparation was carried out with rotatory instruments powered by a surgical micromotor (MasterSurg Surgical Systems, KaVo Dental Systems Japan, Co., Ltd., Tokyo, Japan). A trephine drill with an external diameter of 3.0 mm and an internal diameter of 2.0 mm (330 205 486 001 020 Hager and Meisinger GmbH, Neuss, Germany) with external cooling at a drill rotation speed of 800 rpm to the depth of 8 mm was used to remove bone core biopsy samples for histologic analysis. Implant beds were finalized according to the instructions of the implant manufacturer at a rotation speed of 800 rpm. Implants (Nobel Replace Conical Connection, Nobel Biocare AG, Kloten, Switzerland) were placed submerged in the augmented bone. Implant uncovery procedure took place 3 months after implant placement.

Clinical measurements:

Measurements were carried out using Williams probe (Karl Hammacher GmbH, Solingen, Germany) prior to ridge splitting surgery after the full thickness flap elevation, to evaluate the width of the alveolar ridge (preoperative measurement) and after a 3-month healing period, before implant placement (postoperative measurement). The width of the alveolar ridges was measured at 3, 10, and 15 mm from the reference point.

Histomorphometry:

Bone core biopsy material was fixed in 10% buffered formaldehyde solution. Following decalcination and dehydration, the biopsy material was embedded in paraffin and 20 µm sections were prepared. The sections were stained with routine haematoxylin eosin stain. Sections were evaluated under a light microscope in magnification 40×-400× .

Micro-CT analysis:

The bone core biopsy samples were scanned using a microcomputed tomography (μCT) scanner (Skyscan 1172 X-ray microtomograph, Bruker µCT, Kontich, Belgium).