Early implant failure: a retrospective analysis of contributing factors

PURPOSE: The aim of this retrospective study was to determine the prevalence of early implant failure using a single implant system and to identify the factors contributing to early implant failure. METHODS: Patients who received implant treatment with a single implant system (Luna®, Shinhung, Seoul, Korea) at Dankook University Dental Hospital from 2015 to 2017 were enrolled. The following data were collected for analysis: sex and age of the patient, seniority of the surgeon, diameter and length of the implant, position in the dental arch, access approach for sinus-floor elevation, and type of guided bone regeneration (GBR) procedure. The effect of each predictor was evaluated using the crude hazard ratio and the adjusted hazard ratio (aHR) in univariate and multivariate Cox regression analyses, respectively. RESULTS: This study analyzed 1,031 implants in 409 patients, who comprised 169 females and 240 males with a median age of 54 years (interquartile range [IQR], 47–61 years) and were followed up for a median of 7.2 months (IQR, 5.6–9.9 months) after implant placement. Thirty-five implants were removed prior to final prosthesis delivery, and the cumulative survival rate in the early phase at the implant level was 95.6%. Multivariate regression analysis revealed that seniority of the surgeon (residents: aHR=2.86; 95% confidence interval [CI], 1.37–5.94) and the jaw in which the implant was placed (mandible: aHR=2.31; 95% CI, 1.12–4.76) exerted statistically significant effects on early implant failure after adjusting for sex, age, dimensions of the implant, and type of GBR procedure (preoperative and/or simultaneous) (P<0.05). CONCLUSIONS: Prospective studies are warranted to further elucidate the factors contributing to early implant failure. In the meantime, surgeons should receive appropriate training and carefully select the bone bed in order to minimize the risk of early implant failure.

A one-dimensional fluid simulation method of branching narrow vessel for real-time angiography simulation.

This paper proposes a one-dimensional fluid simulation method for real-time simulation of the contrast medium in a narrow blood vessel. A narrow vessel is modeled with the branches organized in a hierarchy. The density of the contrast medium on each branch is computed using the one-dimensional fluid model. The density at the last point of branch is conveyed to the first point of the following branches. The position of the density computation is determined to continuously convey the simulation results from a large vessel to a narrow vessel. The average computation time with the proposed method is 16.18 ms that is less than 21.25 ms of the particle-based method.

Markerless registration for image-guided endoscopic retrograde cholangiopancreatography (ERCP).

This paper proposes methods for markerless registration, which enable tracking pose of the endoscope camera in real time for implementation of the image-guided ERCP. Edge-based initialization is developed to determine the initial pose of the endoscope camera. Images of virtual endoscope are rendered from the virtual 3D organ model constructed from the patient's CT images. The similarity between edges on the image of the virtual and real endoscope is exploited for registration. An optical-flow-based tracking method is developed to track the changes starting from the initial pose of the endoscope camera in real time. The redefinition method is proposed to prevent the accumulation of the tracking error. Accuracy of the proposed methods is compared with the previous methods. The initialization method reduces 5.2 mm, 33.1 degrees, and 10.9 degrees of the position, direction, and roll angle error, on average, respectively. The tracking method reduces 3.5 degrees and 1.7 degrees of the hysteresis error in the direction angle and roll angle, respectively, with 15% faster update rate.

The role of contrast enhanced computed tomography in the diagnosis of low density pulmonary nodules

Contrast enhanced CT manifestations of 141 pulmonary nodules having internal density less than 40 HU were evaluated to study the prevalence of causative disease and their differential points. Tuberculosis (n = 79) was most common, active in 96%. There were 22 cancers, 10 abscesses, 9 paragonimiases, 8 cysts, 7 metastases, 4 aspergillomas without air meniscus sign, and so on. 35% of the benign lesions were greater than 3 cm in diameter and 67% of benign lesions did not show a smooth outer margin. Lung cysts and aspergillomas showed relatively thin peripheral enhanced rim (PER), sharp transitional zone (TZ), a smooth inner border (IB), and homogeneous low densities (LD). Tuberculous nodules tended to be smaller in size with thin PER and most had smooth IB and homogeneous LD. Paragonimiasis, abscess, and cancer tended to present with thick PER and lobulated IB. Lung abscess and paragonimiasis both showed homogeneous LD and narrow TZ. However, in paragonimiasis, multiple locules were seen. Lung cancer showed wider TZ and heterogeneous LD. The size and outer margin of pulmonary nodules as a diagnostic criteria is less useful in LD pulmonary nodule. Therefore, CT can be more useful in differentiating the benign from the malignant lesions by observing a more specific and characteristic pattern of peripheral enhanced rim, transitional zone, inner border, and homogeneity of low density area.