Anatomic limitations often associated with the posterior maxilla are flat palatal vault, deficient alveolar height, inadequate posterior alveolus, increased pneumatization of the maxillary sinus, and close approximation of the sinus to the crestal bone. Maxillary bone, primarily medullary and trabecular, has less quantity and bone density than the premaxilla or mandible. Adjacent cortices of compact bone are generally very thin, providing minimal strength (1).
In a great number of cases, implant prosthetic rehabilitation in the upper jaw is difficult, since extensive resorption of bone occurs as a consequence of pneumatization of the maxillary sinus following the loss of teeth. The surgical technique of lifting the sinus floor consists of the elevation of the sinus floor cranially and reinforcement of the bone defect in order to create sufficient height and width of the alveolar ridge for implant insertion (2). Various grafting materials have been proposed for the grafting procedure: autogenous bone from the iliac crest or maxillary tuberosity, demineralized freeze-dried bone, hydroxyapatite (HA), beta-tricalcium phosphate (ß-TCP), inorganic deproteinized bovine bone and combination of these and others (3, 4). Regarding remodeling in augmented sinus areas, the behavior of the autologous bone from the iliac crest and the xenogenic material was ultimately very similar at the implant apex, although for bovine bone material the resorption was much slower than that of this autogenous graft (5). The behavior of autologous bone from the chin seemed similar to that of xenogenic material, probably because of the dense cortical composition of such grafts (5). An ideal maxillary sinus bone-grafting material should provide biological stability, ensure volume maintenance, and allow the occurrence of new bone infiltration and bone remodeling. Over time, bone-grafting materials and implants should achieve osseointegration. After the restoration of the upper part of the implant has been completed, there should be no bone loss and the materials should be stable; there should be a predictable success rate (6).
Measuring implant stability at placement and its subsequent change during healing provides useful information for monitoring the process of osseointegration, planning a loading protocol, and evaluating various conditions of osseointegration on implant and host sides (7-11). Implant stability and successful osseointegration are prerequisites for implant survival (12). Meredith et al. and Sennerby et al. were first to propose Resonance Frequency Analysis (RFA) as a highly effective qualitative method to assess implant stability (13, 14).
Ostell ® ISQ (Gamlestadsvägen 3B, Göteborg, Sweden) is a handheld instrument that involves the use of a noninvasive technique for measuring dental implant stability. Nedir et al. (15) evaluated the Osstell as a diagnostic tool at implant placement and concluded that implant stability could be reliably determined for implants with an ISQ≥47. The ISQ unit is based on the underlying resonance frequency ranging from 1 (lowest stability) to 100 (highest stability) (16).
The aim of this study was to evaluate the implant stability of Bredent Sky Blue implants of different diameters following sinus lift (9 months after the surgery).
Material and Methods
This study included 9 male patients with an existing indication for unilateral or bilateral sinus lift procedure. The mean age of patients was 49.89, ranging between 45 and 66 years. All patients included in this study were healthy, without any systemic diseases. Patients with systemically compromised conditions e.g. diabetes, osteoporosis, and those with mental disorders, poor oral hygiene, a history of radiotherapy were excluded.
Before the surgical procedure all patients had signed a questionnaire recommended by the World Dental Federation (FDI).
The total number of implants was 30. The length was 10 mm, 12 mm or 14 mm which was determined according to the available space. The implant diameter included 3.5 mm, 4.0 mm, 4.5 mm or 5.5 mm according to the available ridge width.
One hour prior to the surgery patients took ibuprofen 600mg. The surgical procedures (lateral window approach, single stage) were performed under local anesthesia. In all cases, the sinus cavity was grafted with a combination of allograft material MinerOss® cortical&cancellous (BioHorisons) 2.5 mlł and Ossceram nano (Bredent, 40% β-tricalciumphosphate and 60% hydroxylapatite, granule size 0.8-1.5 mm) at a ratio 1:1. Buccal window was covered with collagen membrane (Mem-Lok, Biohorizons). The implants were then placed immediately in the prepared site. Control cone beam computed tomography (CBCT) scan was recorded to exclude dislocation of the bone grafting material. After the surgery, patients took dexamethason 4ml. Day after surgery, patients took methylprednisolone 80 mg. Following days after the surgery, patients took 2 x1000 mg amoxicillin/potassium clavulanate and ibuprofen if necessary. Sutures (interrupted) were removed 7-10 days after the surgery.
Patients were advised to follow standard postoperative instructions, which included ice-pack, soft high nutrient diet, thorough rinsing with antiseptic mouthwash (chlorhexidine gluconate 0.2%). The patients were instructed to avoid sneezing, nose blowing, or other actions that might create high intranasal pressure or vacuum. No implant loss was observed during the study period.
After the time of 9 months, ISQ levels were measured by Osstell ISQ device Type FW 7660M/05 with SmartPeg abutment. ISQ accuracy is within +/- 0.5 units for a single SmartPeg. For each implant, a mean ISQ value was calculated on the basis 3 ISQ measurements recorded from different directions: mesiodistally and vestibulo-orally.
There were 8 implants with 3.5 mm in diameter, 6 implants with 4.0 mm in diameter, 10 implants with 4.5 mm in diameter and 6 implants with 5.5 mm in diameter. There were 14 implants 10 mm long, 14 implants were 12 mm long and 2 implants were 14 mm long. The ISQ values were from 68 to 84.
The mean /± standard deviation of the stability values (ISQ) measured using Resonance Frequency Analysis for implants of different diameter following sinus lift are presented in Table 1.
In the present study, implant stability was assessed at 9 months after sinus lift surgery. We performed lateral window approach single-stage sinus floor elevations. Since their introduction into clinical practice, different sinus augmentation procedures have demonstrated their effectiveness regarding the enhancement of native bone in maxillary areas with atrophic ridges and pneumatized sinuses (17). Boyne and James in 1980 proposed a lateral approach to sinus lifts (18). Summers introduced clinical practice techniques using a transcrestal approach, based on the use of osteotomes (19, 20). Pal et al. found no significant difference in pain, swelling, stability, and gingival status between both a transcrestal and lateral approach with an organic bovine bone graft (Bio-Oss, Geistlich biomaterials, Switzerland). Increase in bone height was significantly greater in the lateral approach than in the transcrestal approach (21).
Bone graft materials may affect implant survival rate. Yoon et al. evaluated the height of alveolar bone, sinus approach technique, bone material and the clinical survival rate of Astra Tech implants in the maxillary molar region performed with sinus lift and bone graft. Ninety-nine Astra Tech implants (Osseospeed, Astra Tech AB, Mölndal, Sweden) placed in the maxillary molar region using sinus lift from September 2009 to February 2012 were selected with a minimum follow-up period of 1 year. The bone graft materials used were autogenous bone and allogenic bone, xenogenic bone (Bio-Oss; Geistlich Pharma AG, Wolhusen, Switzerland), alloplastic bone (Osteon; Genoss, Suwon, Korea), and autogenous bone graft materials. They found no correlation between the approach methods to the maxillary sinus or bone graft materials used and implant failure (22). In the present study, we used two different grafting materials (mineralized allograft and β-tricalciumphosphate/ hydroxylapatite). No implant loss was observed during the study period and the ISQ values were from 68 to 84 after, which may be regarded as successful. It appears that sinus bone-grafting materials, which were used in our study, provided biological stability.
Ghanbari et al. investigated radiographic and clinical comparison of Algipore (marine-derived carbonated red alga that is chemically converted into hydroxyapatite) with decalcified freeze-dried bone allograft (DFDBA) in the open maxillary sinus lift technique using piezoelectric instruments. After nine months there were no considerable clinical or radiological differences in outcome between Algipore and DFDBA and both of them were recognized as acceptable materials for sinus lift procedures (23). Jelušić et al. evaluated implant stability following sinus lift with two grafting materials (pure-phase ß-TCP or HA/ß-TCP material), and compared it with the implants placed in a pristine posterior maxilla. Their results clearly demonstrated that the examined implant stability is comparable among implants placed in the posterior maxilla regardless of sinus lift or grafting procedure. ISQ values were shown not to be influenced by a particular grafting material, because no significance was observed in comparison to ISQ values of corresponding implants in non-augmented sites. The mean values of stability of implants that were inserted in the posterior maxilla with or without augmentation procedure were 78.9±6.3 and 78.7±6.1, respectively. The mean value of stability of implants that were inserted in the posterior maxilla with β-tricalciumphosphate/hydroxylapatite was 79.8±6.8 (12). These values were similar to ours: 77.73 ± 2.93 mesiodistally and 77.98 ± 2.72 vestibulo-orally. Degidi et al. found positive correlation between ISQ values and implant diameter and length (24). For that reason, we calculated mean ISQ values for implants of different diameter. The highest mean ISQ values were 82 (1.414) mesiodistally and 82 (2.828) vestibulo-orally for implant of diameter 4x12 mm. The lowest ISQ value was 74 (5.71) vestibulo-orally for implant of diameter 4x10 mm. It was observed in our study that it is reliable to insert dental implants during the same surgery during which the reconstructive technique is performed.
The mean values of stability of Bredent Sky Blue implants of different diameters following lateral window approach sinus lift procedure were 77.73 ± 2.93 and 77.98 ± 2.72, respectively.
Our clinical results demonstrated that a combination of allograft material MinerOss® Cortical and Cancellous and Ossceram nano (40% β-tricalciumphosphate and 60% hydroxylapatite) provided biological stability and a high rate of osseointegration.