Ridge preservation in prevention of sinus augmentation

Following enrolment, ridge preservation treatments are assigned randomly via computer-generated numbers. Group allocation is concealed in an opaqued envelope which is opened immediately after extraction. Participants are randomly allocated into two ridge preservation groups: 1/ Grafting group - tooth extraction with ridge preservation with large particles (1 to 2mm) of Bio-Oss or Bio-Oss Collagen and Bio-Gide® determined by clinical preference 2/ Control group consists of participants that underwent extraction without a ridge preservation procedure. After a pre-procedural rinse with 0.2% chlorhexidine mouth rinse and administration of local anaesthesia with 4% articaine plus epinephrine (1:100,000), tooth extraction is performed by a single clinician with great care to preserve the buccal bone plate and the surrounding soft and hard tissues. For multi-rooted teeth, roots are sectioned and removed separately to minimise damage to the bony cortex and inter-radicular bone. In all cases, extraction is performed without elevating a mucoperiosteal flap. After tooth extraction, the socket is carefully debrided and irrigated with sterile saline. The integrity of the buccal cortex is inspected visually under magnification with a probe and is recorded as ‘intact’, ‘completely absent’ or ‘presence of dehiscence or fenestrations’. Participants are excluded if more than 50% of the buccal bone height is absent. The participants are then randomly assigned to grafting or control group according to an opaque, concealed, continuously numbered randomisation envelope. Sockets in grafting group are grafted with large Bio-Oss® granules (particle size 1-2mm) or Bio-Oss collagen blocks. To ensure the sockets are filled to the apical region, each root-alveolus of multi-rooted teeth is filled individually. Sufficient material is placed until the graft materials are about 1mm above the alveolar crest. In all test sites, no attempt to obtain primary closure is made. The graft materials are completely covered by a double layer of Bio-Gide® membrane with the marginal soft tissue of the sockets slightly undermined to receive the membrane without mobilisation of the soft tissue to achieve primary closure. Using a 4/0 non-resorbable, monofilament polypropylene suture (Prolene®, Ethicon), a ‘hidden-X’ suture technique is used. In control sites, sockets are left open for spontaneous healing. Intra-operative complications and adverse events during extraction and ridge preservation procedures, such as buccal bone fracture, need for surgical extractions, oro-antral communication and intra-operative bleeding requiring intervention, are recorded. A postoperative regimen of oral tablets amoxicillin 500 mg three times daily for seven days (or 150 mg clindamycin oral tablets four times daily for seven days if the patient is allergic to penicillin) is prescribed, paracetamol 500mg and ibuprofen 150mg is taken as required, for seven days. Participants are instructed to avoid rinsing and spitting for the first 24 hours. After that, participants are advised to use 0.2% chlorhexidine mouthwash for rinsing twice daily and to avoid brushing directly on the surgical site until complete gingival closure occurred. Participants are also advised to avoid chewing on the operated side and to maintain a soft diet for two weeks. Both oral and written postoperative care instructions are given. No removable appliances are used, and the sockets are left to heal undisturbed. All participants are reviewed on a weekly basis during the first month of healing. At the two-week review, participants will be interviewed to assess adherence to the post-operative care and any postoperative complications are recorded including wound dehiscence, loose graft material, wound infection (tenderness on palpation, swelling and suppuration), extra-oral bruising, oedema and other signs of morbidity. In the test groups, sutures are removed after two weeks. All participants are reviewed at four months clinically and a post-operative CT scan is taken to analyse alveolar ridge height at the site of tooth extraction and sinus volume. All clinical measurements are performed by a single examiner blinded to the group assignment. The following clinical parameters are recorded: 1. Patient’s age and gender 2. Number and location of the teeth present in posterior maxilla: first and second premolars, first, second and third molars 3. Number and location of the tooth or teeth extracted in the posterior maxilla: first and second premolars, first, second and third molars 4. Reason for the extraction: periodontal, endodontic, prosthodontic, restorative (caries, cracked tooth), orthodontic etc. 5. Presence of associated pathologies Participants had CT scans before and four months after extraction/ridge preservation. The image acquisition settings are developed in consultation with a specialist Dento-Maxillofacial Radiologist, with the aim of using a low radiation dose protocol to minimise dose exposure while achieving clear imaging quality for measurements. All scanning is performed at a single radiology centre with the same machine by dental radiologists (Somatom Perspectives CT Scanner, Siemens Healthineers Australia, manufactured in China, 130KV, 35mAs dose-modulated exposure, 0.6mm slice thickness, 512x512 image resolution, 150mm FOV). The imaging protocol is standardised to include the occlusal plane of the maxilla teeth and the whole maxillary sinus. The mid-sagittal plane is to be perpendicular to the horizontal plane using vertical and horizontal alignment beams as recommended by the manufacturer. All CT scans are performed with the occlusal plane approximately parallel with the primary X-ray beam during acquisition and with no gantry tilt. The occlusal plane is used as the reference plane for subsequent image reconstruction. All Digital Imaging and Communications in Medicine (DICOM) CT scans data are imported into a 3D dental implant planning software (Simplant Pro 18.0 Dentsply Implants NV, Research Campus 10 3500 Hasslet Belgium). All data sets are allocated a code number so the identity of the participants is masked to the operator. The same operator performed all data set reconstruction and measurements. Patient-related outcome measures for pain, bleeding, swelling, bruising and interference with activities of daily living are evaluated using a Visual Analog Scale (VAS). These are assessed on the day of the extraction, at two weeks and four months reviews. For radiographic assessment, it is not possible to mask the treatment group from the control group on the post-extraction scans due to the presence of the grafting material, however the examiner is blinded to the nature of the treatment group. The protocol for reconstruction of the scans to ensure accurate and reproducible orientation and spatial alignment of the three planes are developed in consultation with an experienced oral and maxillofacial radiologist. A panoramic curve is drawn to bisect the maxillary alveolar ridge, at mid-level between the sinus floor and bony crest on the axial plane. The coronal and sagittal planes are then positioned to place the tooth/extraction site in the middle of the ridge. Specifically, axial slices are assessed to identify the slice which displays the mid-ridge parallel to the long axis of the tooth in the mesio-distal and transverse dimensions. The mid-sagittal and the mid-coronal bisecting lines are then identified on this axial slice. To perform the measurements, each extraction site is considered separately and evaluated in the coronal section corresponding to the centre of the extraction/edentulous site. Bone heights (measured in mm) before and after extraction/ridge preservation are measured at the mid-section of the alveolar ridge where both the coronal and sagittal planes intersect using the linear measurement tool: 1. Pre-extraction mid-ridge height 2. Post-extraction mid-ridge height 3. Pre-extraction buccal-bone height 4. Post-extraction buccal-bone height 5. Pre-extraction palatal-bone height 6. Post-extraction palatal-bone height The difference between the post- and pre-extraction ridge height measurements determined the change in ridge heights over four months. Sinus volume determination is performed via a segmentation technique using the Simplant software. Data sets are excluded if significant sinus opacification or mucosal thickening prevented the ability to perform the masking or segmentation function in Simplant. A mask is initially created to highlight the air-filled cavities, followed by the use of a segmentation tool to manually define the entire volume of the maxillary sinus cavity. This allowed the software to automatically calculate the sinus volume in cubic centimetres. The difference between post- and pre-extraction sinus volume determined the change in sinus volume over four months. The need for sinus augmentation is determined based on the mid-ridge height on the post-extraction CT scan. Lateral sinus augmentation would be required when the residual mid-ridge height is <5mm.