Two-Year Follow-up Comparison of Three Surgical Techniques for Implant Placement in Posterior Maxilla with Limited Alveolar Bone Height.

PURPOSE: The aim of this pilot study was to compare three surgical techniques (bicortical fixation, unicortical fixation, and indirect sinus elevation) for implant placement in the posterior maxilla with limited alveolar bone height. This 2-year follow-up assessment on the implants of a previously published prospective clinical trial compared (1) restoration/implant stability among the three surgical groups, (2) intrasinus bone formation between the bicortical fixation and indirect sinus elevation groups, and (3) implant and prosthetic complications reported among the three groups. MATERIALS AND METHODS: For the original prospective study, 38 patients were recruited, exhibiting 7 to 11 mm of alveolar bone coronal to the sinus floor as confirmed by preoperative CBCT, and 45 implants were placed using three randomly assigned surgical techniques. No patient received more than two implants, which were placed in opposite sides of the maxilla and using different surgical techniques. At the 2-year follow-up assessment, 32 patients with 37 implants were evaluated. The 2-year follow-up restoration/implant stability was measured with the Periotest stability measuring device. Intrasinus bone formation was measured from the 2-year follow-up CBCT in comparison to the preoperative CBCT. Clinical examination was also performed to identify loose implants and/or implant crowns and signs of peri-implantitis. Patients were interviewed regarding complications experienced with the study implants/restorations, and electronic charts were thoroughly reviewed to identify records of complications. RESULTS: No significant difference in restoration/implant stability (Periotest value [PTV]) was seen between the bicortical fixation, unicortical fixation, and indirect sinus elevation groups (-1.69 [0.80], -1.76 [0.80], -2.22 [0.60], respectively, P = .76) at the 2-year follow-up. The indirect sinus elevation group showed more intrasinus horizontal (1.99 [0.17] vs 1.47 [0.16] mm, P = .03) and vertical (3.15 [0.43] vs 2.35 [0.38] mm, P = .13) bone gain compared with the bicortical fixation group. CONCLUSION: Within the limitations of this study, placing implants using a bicortical fixation surgical technique in moderately limited alveolar bone height (7 to 11 mm) was not significantly different from the other two techniques and may be a feasible option with limited risks while allowing longer implant placement and negating the need for indirect sinus augmentation, which is accompanied by additional expense and surgical morbidity to the patient.

The effects of image acquisition control of digital X-ray system on radiodensity quantification.

OBJECTIVES: Aluminum step wedge (ASW) equivalent radiodensity (eRD) has been used to quantify restorative material's radiodensity. The aim of this study was to evaluate the effects of image acquisition control (IAC) of a digital X-ray system on the radiodensity quantification under different exposure time settings. MATERIALS AND METHODS: Three 1-mm thick restorative material samples with various opacities were prepared. Samples were radiographed alongside an ASW using one of three digital radiographic modes (linear mapping (L), nonlinear mapping (N), and nonlinear mapping and automatic exposure control activated (E)) under 3 exposure time settings (underexposure, normal-exposure, and overexposure). The ASW eRD of restorative materials, attenuation coefficients and contrasts of ASW, and the correlation coefficient of linear relationship between logarithms of gray-scale value and thicknesses of ASW were compared under 9 conditions. RESULTS: The ASW eRD measurements of restorative materials by three digital radiographic modes were statistically different (p = 0.049) but clinically similar. The relationship between logarithms of background corrected grey scale value and thickness of ASW was highly linear but attenuation coefficients and contrasts varied significantly among 3 radiographic modes. Varying exposure times did not affect ASW eRD significantly. CONCLUSIONS: Even though different digital radiographic modes induced large variation on attenuation of coefficient and contrast of ASW, E mode improved diagnostic quality of the image significantly under the under-exposure condition by improving contrasts, while maintaining ASW eRDs of restorative materials similar. Under the condition of this study, underexposure time may be acceptable clinically with digital X-ray system using automatic gain control that reduces radiation exposure for patient.