Susanne Stampf

High-dose tranexamic acid is related to increased risk of generalized seizures after aortic valve replacement

OBJECTIVE To investigate the incidence of postoperative generalized seizures in patients undergoing aortic valve replacement (AVR) under extracorporeal circulation, who received either high-dose tranexamic acid (TXA) or epsilon aminocaproic acid (EACA) as an antifibrinolytic agent. METHODS This retrospective analysis comprised 682 consecutive patients undergoing AVR with or without simultaneous coronary artery bypass surgery. Patients operated on before March 2008 were treated intra-operatively with TXA (100 mg kg⁻¹; n = 341), patients operated on after March 2008 received EACA (50 mg kg⁻¹ loading dose, followed by 25 mg kg⁻¹ h⁻¹, and an additional 5 g in the extracorporeal circuit; n = 341). RESULTS Clinically diagnosed generalized seizures were observed within the first 24h postoperatively, more frequently in patients receiving TXA compared with EACA (6.4% vs 0.6%, p < 0.001, difference = 5.8%, 95% confidence interval 3.1-8.5%). Besides the antifibrinolytic agent, three other variables differed significantly between patients with and without postoperative seizures: age (mean (SD), 77.0 (5.9) years vs 73.2 (9.0) years, p = 0.039), preoperative creatinine clearance (55.4 (16.5)ml min⁻¹ vs 72.6 (28.5)ml min⁻¹, p = 0.002), and administration of recombinant activated factor VIIa (3 out of 24 patients (12.5%) vs 8 out of 658 patients (1.2%), p = 0.005). Logistic regression analysis demonstrated a significant impact of the antifibrinolytic drug, creatinine clearance, and the application of recombinant activated factor VIIa on the occurrence of generalized seizures. CONCLUSIONS Our results indicate that high-dose TXA is associated with an increased incidence of postoperative generalized seizures in patients undergoing AVR compared with EACA, especially when suffering from renal impairment. A possible association between recombinant activated factor VIIa and the occurrence of postoperative seizures needs further investigation.

Accuracy of computer-aided design/computer-aided manufacturing–generated dental casts based on intraoral scanner data

BACKGROUND Little is known about the accuracy of physical dental casts that are based on three-dimensional (3D) data from an intraoral scanner (IOS). Thus, the authors conducted a study to evaluate the accuracy of full-arch stereolithographic (SLA) and milled casts obtained from scans of three IOSs. METHODS The authors digitized a polyurethane model using a laboratory reference scanner and three IOSs. They sent the scans (n = five scans per IOS) to the manufacturers to produce five physical dental casts and scanned the casts with the reference scanner. Using 3D evaluation software, the authors superimposed the data sets and compared them. RESULTS The mean trueness values of Lava Chairside Oral Scanner C.O.S. (3M ESPE, St. Paul, Minn.), CEREC AC with Bluecam (Sirona, Bensheim, Germany) and iTero (Align Technology, San Jose, Calif.) casts were 67.50 micrometers (95 percent confidence interval [CI], 63.43-71.56), 75.80 μm (95 percent CI, 71.74-79.87) and 98.23 μm (95 percent CI, 94.17-102.30), respectively, with a statistically significant difference among all of the scanners (P < .05). The mean precision values were 13.77 μm (95 percent CI, 2.76-24.79), 21.62 μm (95 percent CI, 10.60-32.63) and 48.83 μm (95 percent CI, 37.82-59.85), respectively, with statistically significant differences between CEREC AC with Bluecam and iTero casts, as well as between Lava Chairside Oral Scanner C.O.S. and iTero casts (P < .05). CONCLUSION All of the casts showed an acceptable level of accuracy; however, the SLA-based casts (CEREC AC with Bluecam and Lava Chairside Oral Scanner C.O.S.) seemed to be more accurate than milled casts (iTero). PRACTICAL IMPLICATIONS On the basis of the results of this investigation, the authors suggested that SLA technology was superior for the fabrication of dental casts. Nevertheless, all of the investigated casts showed clinically acceptable accuracy. Clinicians should keep in mind that the highest deviations might occur in the distal areas of the casts.

Estimators and confidence intervals for the marginal odds ratio using logistic regression and propensity score stratification.

Propensity score methods are widely used to estimate treatment or exposure effects in observational studies. In studies with binary response the effect can be described as an odds ratio, and the Mantel-Haenszel estimator is traditionally used for stratified data. Although propensity score methods are designed for marginal treatment effects, it has been shown that the Mantel-Haenszel estimator stratified for propensity score is a questionable estimator for the marginal odds ratio, which describes the change in odds of response if everybody versus nobody were treated.We studied recently proposed alternative estimators for the marginal odds ratio, one stratified for propensity score, the other derived from logistic regression. Additionally, we adapted the methodology of the logistic regression based estimator for the derivation of a marginal odds ratio estimator to covariate adjustment by the propensity score. We also derived corresponding variance estimators using the Delta-method.The estimators were illustrated and compared to the inverse probability weighted estimator and the stratified Mantel-Haenszel estimator in a study dealing with respiratory tract infections in children in Germany. Furthermore, simulation studies that were carried out to investigate relative bias, variance and coverage probability showed reasonable performance of marginal odds ratio estimators if response rates or regression based approaches were used. Their variances were accurately estimated. In contrast, the stratified Mantel-Haenszel estimator was substantially biased in some situations due to problems of non-collapsibility and thus it is generally inappropriate for a reliable estimation of the marginal odds ratio.

Evaluation of Zirconia‐Based All‐Ceramic Single Crowns and Fixed Dental Prosthesis on Zirconia Implants: 5‐Year Results of a Prospective Cohort Study

Objective The objective of this 5-year cohort investigation was to determine the survival and success rate of all-ceramic reconstructions on zirconia oral implants. Material and Methods Ninety-three patients received 122 one-piece zirconia implants. One hundred seventeen implants were restored with 63 single crowns (SCs) and 27 three-unit bridges (fixed dental prostheses, FDPs) fabricated using zirconia frameworks (Procera® Zirconia, Nobel Biocare®, Goteborg, Sweden) hand-layered with a silicate ceramic (NobelRondo™ Zirconia, Nobel Biocare®). With any occurrence of chipping regarded as an event, Kaplan-Meier success curves were plotted. Covariates (gender, location, manufacturing date) were estimated by the use of log-rank tests. Results Eighty-nine patients received prosthetic reconstructions. Sixty-three of them were seen at the 5-year follow-up, with a mean observation time of 58.2 months (47 patients with SCs, 16 patients with FDPs). Reasons for the decreasing number of patients at the follow-up sessions included dropouts due to implant loss (n = 21), moving (n = 3), missed appointments (n = 1), and severe illness (n = 1). Over half of the SCs (57.2%) and 38% of the FDPs were successful after an observation time of 5 years (overall success rate of 51.7%). The performed log-rank tests revealed no statistically significant differences for the success curves regarding the above-mentioned covariates. Among the 63 restorations that completed the study, 11 of 47 SCs and one of 16 FDPs had to be replaced due to the severity of the observed chipping. This results in survival rates of 76.6% for the SCs and 93.8% for the FDPs. No framework fractures or decementations were observed in any group. Conclusion Hand-layering of zirconia-based SCs and FDPs with NobelRondo™ Zirconia restoring one-piece zirconia implants did not show acceptable survival and success rates. Meanwhile, the material has been recalled from the market. It is advised that new materials should undergo adequate preclinical evaluation before coming to the market.OBJECTIVE The objective of this 5-year cohort investigation was to determine the survival and success rate of all-ceramic reconstructions on zirconia oral implants. MATERIAL AND METHODS Ninety-three patients received 122 one-piece zirconia implants. One hundred seventeen implants were restored with 63 single crowns (SCs) and 27 three-unit bridges (fixed dental prostheses, FDPs) fabricated using zirconia frameworks (Procera(®) Zirconia, Nobel Biocare(®), Göteborg, Sweden) hand-layered with a silicate ceramic (NobelRondo(™) Zirconia, Nobel Biocare(®)). With any occurrence of chipping regarded as an event, Kaplan-Meier success curves were plotted. Covariates (gender, location, manufacturing date) were estimated by the use of log-rank tests. RESULTS Eighty-nine patients received prosthetic reconstructions. Sixty-three of them were seen at the 5-year follow-up, with a mean observation time of 58.2 months (47 patients with SCs, 16 patients with FDPs). Reasons for the decreasing number of patients at the follow-up sessions included dropouts due to implant loss (n = 21), moving (n = 3), missed appointments (n = 1), and severe illness (n = 1). Over half of the SCs (57.2%) and 38% of the FDPs were successful after an observation time of 5 years (overall success rate of 51.7%). The performed log-rank tests revealed no statistically significant differences for the success curves regarding the above-mentioned covariates. Among the 63 restorations that completed the study, 11 of 47 SCs and one of 16 FDPs had to be replaced due to the severity of the observed chipping. This results in survival rates of 76.6% for the SCs and 93.8% for the FDPs. No framework fractures or decementations were observed in any group. CONCLUSION Hand-layering of zirconia-based SCs and FDPs with NobelRondo(™) Zirconia restoring one-piece zirconia implants did not show acceptable survival and success rates. Meanwhile, the material has been recalled from the market. It is advised that new materials should undergo adequate preclinical evaluation before coming to the market.

Alumina reinforced zirconia implants: 1-year results from a prospective cohort investigation

OBJECTIVE The objective of this investigation was to determine the clinical and radiographic outcome of a one-piece alumina-toughened zirconia (ATZ) oral implant for single tooth replacement after 1 year. MATERIALS AND METHODS A total of 27 patients received one ATZ implant each in a one-stage implant surgery with immediate temporization. Standardized radiographs were taken at implant insertion and after 1 year to monitor peri-implant bone loss. Several soft tissue parameters were evaluated at prosthesis insertion and at the 1-year follow-up. RESULTS Three patients did not receive a prosthetic reconstruction due to implant loss during the healing period. As a result, 24 patients were seen at the 1-year follow-up, giving a cumulative survival rate of 88.9%. The average marginal bone loss after 1 year was 0.77 mm. Only two implants (8.3%) lost at least 2 mm bone, whereas none of the implants lost more than 3 mm. Probing depth and clinical attachment level increased over 1 year at the implant sites, whereas gingival recession remained stable. Mombellis bleeding and plaque indices showed no statistically significant change within the first year. CONCLUSION Owing to a total of 27 inserted implants, three failures within the first 4 months after implant placement carry weight. Therefore, the cumulative survival rate of the presented ceramic implant was slightly below reported survival rates of titanium implants when immediately restored. The recorded radiographic bone loss and peri-implant soft tissue parameters showed promising short-term results. The presented ATZ implant seems to be a candidate for clinical usage.

Evaluation of an improved endodontic teaching model: do preclinical exercises have an influence on the technical quality of root canal treatments?

AIM To investigate whether the preclinical application of an electronic root canal length measurement device (ERCLMD) leads to more accurate working length (WL) determinations in a preclinical endodontic course and if this exercise effects the technical quality of root canal procedures when treatments are performed on patients for the first time. METHODOLOGY Root canal treatments performed by two consecutive groups of third year students (group 1: n = 39, group 2: n = 44) were compared in the preclinical course and when root canal treatments were performed on patients in the following term. Two different teaching models were applied in the preclinical endodontic course. WL in group 1 was determined with radiographs only. The teaching model applied in group 2 allowed the application of an ERCLMD. When treatments were performed on patients, both groups used the same technique to determine WL. It was first determined using an ERCLMD and verified radiographically. Master cone and root filling lengths were evaluated using radiographs, and comparisons between both groups were made using Fischers exact test. RESULTS Root fillings performed by students of group 2 were more often classified as acceptable. This observation was made in the preclinical endodontic course and when treatments were performed on patients. CONCLUSIONS The application of an ERCLMD in combination with radiographs is more accurate to determine WL than radiographs alone. Students practiced the use of ERCLMDs with the new model and benefited from this experience when performing their first root canal treatments on patients.

Correction of confounding bias in non-randomized studies by appropriate weighting.

In non-randomized studies, the assessment of a causal effect of treatment or exposure on outcome is hampered by possible confounding. Applying multiple regression models including the effects of treatment and covariates on outcome is the well-known classical approach to adjust for confounding. In recent years other approaches have been promoted. One of them is based on the propensity score and considers the effect of possible confounders on treatment as a relevant criterion for adjustment. Another proposal is based on using an instrumental variable. Here inference relies on a factor, the instrument, which affects treatment but is thought to be otherwise unrelated to outcome, so that it mimics randomization. Each of these approaches can basically be interpreted as a simple reweighting scheme, designed to address confounding. The procedures will be compared with respect to their fundamental properties, namely, which bias they aim to eliminate, which effect they aim to estimate, and which parameter is modelled. We will expand our overview of methods for analysis of non-randomized studies to methods for analysis of randomized controlled trials and show that analyses of both study types may target different effects and different parameters. The considerations will be illustrated using a breast cancer study with a so-called Comprehensive Cohort Study design, including a randomized controlled trial and a non-randomized study in the same patient population as sub-cohorts. This design offers ideal opportunities to discuss and illustrate the properties of the different approaches.

Long-term outcome of one-piece implants. Part I: implant characteristics and loading protocols. A systematic literature review with meta-analysis.

PURPOSE The aim of this systematic review was to evaluate the long-term clinical performance of one-piece implants. MATERIALS AND METHODS An electronic MEDLINE search complemented by a manual search was conducted to identify randomized and prospective cohort studies on one-piece implants. Additional inclusion criteria were: a mean follow-up period of at least 5 years and an inception cohort where more than 80% of the enrolled patients remained in the study at the 5- or 10-year observation point. RESULTS Sixty-six studies from an initial yield of 597 titles were selected, and the data were extracted. Of the full-text articles examined, 46 were excluded from the final analysis. A total of 20 articles were finally selected. All studies were published between 1995 and 2011. Two different study designs were included: 4 randomized controlled trials and 16 prospective cohort studies. The studies were analyzed and classified according to the follow-up period, the type of implant surface, the type of edentulism, the type of loading protocol, and the type of setting. The meta-analysis of the included studies showed an implant survival rate for one-piece, one-part implants of 96.79% (95% CI: 94.04% to 98.71%) after 5 years. In one-piece, two-part implants, the survival rate was slightly higher: 98.16% (95% CI: 96.48% to 99.31%) after 5 years and 96.83% (95% CI: 93.12% to 99.24%) after 10 years. CONCLUSION Within the limits of this systematic review, it can be concluded that high long-term survival rates can be observed with one-piece implants. Further randomized clinical trials are needed to provide more information about the outcome of different variables associated with one-piece implants.

Effect of two different healing times on the mineralization of newly formed bone using a bovine bone substitute in sinus floor augmentation: a randomized, controlled, clinical and histological investigation

PURPOSE To investigate the amount of the mineralization of a bovine bone substitute material in sinus floor augmentation after healing times of 3 and 6 months. MATERIALS AND METHODS Fifty-one patients were randomized into two healing time groups and received sinus floor augmentations with a bovine bone material. After 3 or 6 months of healing, trephine bone biopsies were retrieved. The biopsies were processed for histological and histomorphometric evaluations to primarily investigate the amount of mineralized bone in the augmented area and secondarily compare the amount of mineralized bone in the augmented area and in the pristine bone. Statistical tests were performed to analyse the fraction of the mineralized bone (p < 0.05). RESULTS The biopsies of both groups showed remnants of the well-integrated bone substitute material. The histology revealed osteoblasts, osteocytes with osteoid, and osteoclasts. The mean percentage of mineralized bone in the augmented area was 23.8% (3 months group) and 23.6% (6 months group; p = 0.9246); the amount of remaining bone substitute material was 35% (3 months group) and 33.9% (6 months group; p = 0.6325). CONCLUSION It can be concluded that the bone maturation in the augmented sinus using the bovine bone material is similar after 3 and 6 months. Thus, implant installation after 3 months following a lateral window sinus floor augmentation approach using a bovine bone material seems to be clinically acceptable.

Long-term outcome of one-piece implants. Part II: Prosthetic outcomes. A systematic literature review with meta-analysis.

PURPOSE To evaluate the long-term clinical performance of prosthetic reconstructions on one-piece implants, with a focus on technical and biological complications. MATERIALS AND METHODS An electronic MEDLINE search complemented by a manual search was conducted to identify randomized and prospective controlled clinical trials on one-piece implants. Additional inclusion criteria were a mean follow-up period of at least 5 years and an inception cohort where more than 80% of the enrolled patients remained in the study at the 5- or 10-year observation point. RESULTS Sixty-six studies from an initial yield of 597 titles were selected, and the data were extracted. Of the full-text articles examined, 46 were excluded and a total of 20 articles were finally selected. All studies were published between 1995 and 2011. Two different study designs were identified: 4 randomized controlled trials and 16 prospective cohort studies. The studies were analyzed and classified according to study type, patient characteristics, prosthetic characteristics, and biologic and technical complications after 5 and 10 years. The meta-analysis of the included studies showed a prosthetic survival rate for one-piece, one-part implants of 82.81% after 5 years and 97.85% and 98.24% in two-part implants after 5 and 10 years, respectively. Although the prosthetic survival rates were high, complications were frequent: complications of the suprastructure (18.44% to 18.75%), screw loosening/fracture (7.64%), soft-tissue complications (4.69% to 8.25%), sensory disturbances (0.36% to 6.25%), implant loss before loading (0% to 0.23%) and during function (1.10% to 3.21%), and implant fracture (0.0004%). CONCLUSION Within the limits of this systematic review, it can be concluded that despite high long-term prosthetic survival rates, technical and biologic complications are frequent in one-piece implants, both in one-part and two-part designs. Further randomized clinical trials are needed to provide more information about the outcome of different variables associated with this type of implant design.