104,810 research outputs found
Implant site preparation using a single bur versus multiple drilling steps: 4-month post-loading results of a multicenter randomised controlled trial
No full textPurpose: To compare the clinical outcome of implants inserted in sites prepared with a simplified protocol consisting of one single drill versus multiple conventional drilling steps. Materials and methods: In two private clinics, 40 patients, requiring one single implant and having a residual bone height of at least 10 mm and a thickness of at least 5 mm measured on computerised tomography (CT) scans, were randomised after flap elevation to have the implant site prepared using a single drilling step with a newly designed tapered-cylinder drill (1-drill group) or a conventional procedure with multiple drills (multiple-drill group). Implants were left to heal non-submerged for 3 months and then they were loaded with a final metal-ceramic crown. Outcome measures were: implant failure; any complications; peri-implant marginal bone level changes assessed by a blinded outcome assessor operation time; operator preference and post-surgical pain, swelling and analgesic consumption. All patients were followed up to 4 months after implant loading. Results: Twenty patients were randomised to the 1-drill group and 20 patients to the multiple-drill group. No implant failed and no complications occurred. Four months after loading, implants in the 1-drill group lost 0.54 mm of peri-implant bone versus 0.41 mm for the implants in the multiple-drill group. There were no statistically significant differences for marginal bone level changes between the two groups (difference 0.13 mm, 95% CI -0.21; 0.47, P = 0.108). Less time which was statistically significant (3.66 mins, 95% CI 2.69; 4.63, P < 0.0001) was required to place the implant with the single bur. Both operators always preferred the single bur technique. Postoperatively, patients in the 1-drill group vs patients in the multiple-drill group reported statistically significant differences for pain level (difference 27.5, 95% CI 3.3; 51.7, P < 0.0001), number of days in which the swelling persisted (difference 3.4, 95% CI 2.4; 4.4, P < 0.0001) and the number of analgesic drugs taken (difference 2.8, 95% CI 1.4; 4.2, P < 0.0001) Conclusions: Within the limits of this trial, both drilling techniques produced successful results over a 4-month post-loading follow-up period, but the single bur procedure required less surgical time and lead to less postoperative morbidity. Conflict-of-interest statement: Dr Paolo Guazzi and Dr Tommaso Grandi served as consultants for JDentalCare. This study was completely self-financed and no funding was sought or obtained, not even in the form of free materials
Finite plasticity in P^T P. Part I: constitutive model
No full textWe address a finite-plasticity model based on the symmetric tensor P^T P instead of the classical plastic strain P. Such a structure arises by assuming that the material behavior is invariant with respect to frametransformationsoftheintermediateconfiguration.The resulting variational model is lower dimensional, symmetric and based solely on the reference configuration. We discuss the existence of energetic solutions at the material-point level as well as the convergence of time discretizations. The linearization of the model for small deformations is ascertained via a rigorous evolution-Gamma-convergence argument. The constitutive model is combined with the equilibrium system in Part II where we prove the existence of quasistatic evolutions and ascertain the linearization limit (Grandi and Stefanelli in 2016)
Immediate loading of four (all-on-4) post-extractive implants supporting mandibular cross-arch fixed prostheses: 18-month follow-up from a multicentre prospective cohort study
No full textAim: To evaluate the outcome of immediately loaded mandibular cross-arch prostheses according to the 'all-on-4' concept supported by implants placed in fresh extraction sockets up to 18 months after loading. Materials and methods: In total, 47 patients with a mean age of 62.3 years (range 52 to 78) were rehabilitated with an immediately loaded fixed cross-arch prosthesis supported by four post-extractive implants. A total of 188 implants were inserted. Patients received a provisional fixed dental prosthesis with a metal framework within 48 hours after surgery and a permanent one 6 months later. The patients were evaluated clinically and radiographically at implant placement and at 6-, 12- and 18-month follow-up examinations. Results: At the 18-month follow-up, no implant failed and all restorations were stable. Peri-implant bone levels amounted to 0.31 ± 0.12 mm after 6 months, 0.58 ± 0.112 mm after 12 months and 0.7 ± 0.107 mm after 18 months. No significant differences in bone loss were found between axially placed and tilted implants at the 6-month (0.06 mm; P = 0.115), the 12-month (0.12 mm; P = 0.062) and the 18-month follow-up (0.08 mm; P = 0.146). Three patients had a fracture of the provisional restoration, but all of the definitive prostheses remained stable throughout the study period without any complications. Conclusions: Within the limits of this study, it can be suggested that immediately loaded mandibular cross-arch fixed dental prostheses can be supported by four post-extractive implants, however larger and longer follow-ups are needed. Conflict-of-interest statement: Dr Tommaso Grandi and Dr Paolo Guazzi serve as consultants for JDentalCare. This study was completely self-financed and no funding was sought or obtained, not even in the form of free materials
One abutment-one time versus a provisional abutment in immediately loaded post-extractive single implants: A 1-year follow-up of a multicentre randomised controlled trial
No full textPurpose: To compare immediately loaded post-extractive single implants using a definitive abutment versus provisional abutment later replaced by custom-made abutment. Materials and methods: In two private clinics, 28 patients in need of one single post-extractive implant in the maxilla or mandible from the left second premolar to the right second premolar area were randomised shortly before tooth extraction to provisional abutment (PA) and definitive abutment (DA) groups. Three patients had to be excluded for buccal wall fracture after tooth extraction. In the PA group, implants were immediately restored using a platform-switched provisional titanium abutment and definitive platform-switched titanium abutments were used in the DA group. In both groups, a non-occluding provisional single crown was provided. Implants were definitively restored after 4 months. In the PA group, the abutment was removed and the impression was made directly on the implant platform. In the DA group an impression of the abutment was made using a retraction cord. Outcome measures were: implant failures; complications; and marginal peri-implant bone level changes. Patients were followed up to 1 year after loading. Results: Twelve patients were randomised to the DA group and 13 patients to the PA group. At the 12-month follow-up, no implant failed. One biological complication occurred in the DA group and one mechanical complication occurred in the PA group. All complications were successfully treated. One year after loading, implants in the DA group lost an average of 0.11 mm (SD: 0.06) of periimplant bone and implants in PA group about 0.58 mm (SD: 0.11). At the 12-month follow-up, there was a statistically significant difference in bone level change between groups (mean difference: 0.48 mm, CI 95% 0.40; 0.55, P < 0.0001). Conclusions: Within the limits of this study, the non-removal of abutments placed at the time of surgery resulted in the maintenance of 0.5 mm more bone levels around immediately restored postextractive single implants than repeated abutment removal, although this amount of bone maintenance may not have a clinical impact Con?icts of interest noti?cation: Dr Tommaso Grandi and Dr Paolo Guazzi serve as consultants for JDentalCare. This study was completely self-?nanced and no funding was sought or obtained, not even in the form of free materials
Immediate, early (3 weeks) and conventional loading (4 months) of single implants: Preliminary data at 1 year after loading from a pragmatic multicenter randomised controlled trial
No full textPurpose: To compare the clinical outcome of single implants which underwent immediate nonocclusal loading with implants subjected to early non-occlusal loading at 3 weeks, and implants conventionally loaded at 4 months. Materials and methods: One hundred and five patients in five private practices requiring a single implant-supported crown were randomised to immediate loading (35 patients), early loading (35 patients) and conventional loading (35 patients) groups. To be immediately or early loaded, implants had to be inserted with a torque superior to 45 Ncm. Immediately and early loaded implants received non-occluding temporary crows, whereas conventionally loaded implants were directly restored with definitive crowns. Temporary crowns were replaced by definitive ones after 4 months. Outcome measures were crown and implant failures, complications and peri-implant marginal bone level changes recorded by a blinded assessor. Results: Two patients dropped out from the immediate loading group up to 1-year post-loading. Two implants failed, one in the immediately loaded and one in the early loaded group (P = 0.601). One immediately loaded implant and two early loaded implants were affected by one complication each (P = 0.162). Mean peri-implant marginal bone loss after 1 year was -0.120 ± 0.230 mm (95% CI -0.35, 0.10) for immediate, -0.390 ± 0.840 mm (95% CI -1.23, 0.45) for early and -0.201 ± 0.306 mm (95% CI -0.51; 0.11) for conventionally loaded implants. There were no statistically significant differences for any of the outcome measures between the three loading strategies up to 1-year post-loading. Conclusions: No major clinical differences were observed with regard to implant survival, complications and marginal bone level changes when loading single implants immediately, early or conventionally. Conflict-of-interest statement: This trial was partially funded by JDentalCare, the manufacturer of the implants evaluated in this investigation, however data belonged to the authors and by no means did the manufacturer interfere with the conduct of the trial or the publication of the results. Dr Tommaso Grandi, Paolo Guazzi, Rawad Samarani and Marco Esposito are consultants for JDentalCare
Principal component analysis of the t-wave for mortality Prediction in hemodialysis patients.
No full textPRINCIPAL COMPONENT ANALYSIS OF THE T-WAVE FOR MORTALITY
PREDICTION IN HEMODIALYSIS PATIENTS
Patients undergoing hemodialysis (HD) therapy often experience alterations in cardiac excitability and
have accounting for an estimated 3-year cumulative probability of cardiovascular death of 39.5% of
total deaths [1]. Abnormalities in ventricular repolarization and its dispersion could be a cause of HD-induced
arrhythmogenic effect.
Nowadays, no ECG-derived parameter has been proven to predict the risk of cardiovascular death.
QT dispersion (QTd) has been proposed, however, some concerns have been raised about uncertainty
of the QT dispersion measurement and technical difficulties in measuring the QT interval.
Principal component analysis (PCA) of the T-wave vector applied to 12-lead recordings has been
proposed to obtain an ECG marker of vulnerability to ventricular arrhythmias and of cardiovascular
mortality [2]. Several studies showed that the ratio of the second to first eigenvalues (PCA ratio) more
accurately represents repolarization abnormalities than QTd in a large general population sample [3,4].
The aim of this study was to explore the predictive value of the PCA ratio parameter for all-cause and
cardiac mortality in a retrospective study on HD patients.
METHODS
The selected subjects were 122 patients (46 women and 76 men, mean age 77±10) in whom digital
ECG recordings were available for the analysis from previous clinical studies. Standard holter 12-lead
recordings (H-12 Holter, Mortara Instrument Inc., Milwaukee, Wisconsin, USA) were collected
starting with the dialysis session. ECGs were sampled at 180 Hz or 1kHz and stored to a PC hard disk
for subsequent analysis.
PCA is an established method for representing data and, when applied to T-wave, it describes features
of repolarization in a manner that is less dependent on precise determination of T-wave offset.
Singular value decomposition was applied to the covariance matrix of the raw ECG data
corresponding to T-wave from the eight independent ECG leads. Then, the main eigenvectors of the
spatial T-wave were computed. The first eigenvector accounts for most of the energy in repolarization
when applied to the normal T-wave vector, whereas inhomogeneous repolarization, if present, is
indicated by a relevant contribution of the second and third components. Thus, the ratio of the second
to first eigenvalues of the spatial T-wave vector (PCA ratio) generated from the 12-lead digital ECG
serves as a measure of T-wave complexity or
heterogeneity of repolarization, with
increasing values referring to higher amount
of complexity. As shown in fig. 1 the PCA
ratio provides information that can be
visualized by analogy as the long and short
axes of the three-dimensional T-wave loop
and provides an estimate of the relative
fatness of the T-wave loop relative to its peak
amplitude, in which a fatter loop with a
higher PCA ratio reflects more complex Twave
morphology.
A median value of PCA was computed for
each patient throughout the whole ECG
recording. Following the Strong Heart Study
[3] a threshold for PCA ratio in men and
women, independently of gender, was
defined as 28%. Deaths were identified in an ongoing surveillance in each dialysis center and were
verified through review of medical records. Deaths were classified as cardiac if caused by myocardial
infarction, sudden death from CHD, or congestive heart failure by an independent review panel of
physicians unaware of PCA ratio findings. After a maximum follow-up of 5 years, patients were
censored as dead or alive considering the days from the date of the first ECG recording. Patients were
then divided in two groups depending on the median PCA ratio value. Endpoints were all-cause
mortality and cardiac mortality.
Mortality rates were calculated and plotted according to the Kaplan-Meier analysis. P<0.05 was
considered significant.
RESULTS AND DISCUSSION
During the fo..
A comparison of two implants with conical vs internal hex connections: 1-year post-loading results from a multicentre, randomised controlled trial
No full textPurpose: To compare the clinical and radiological outcomes of identical implants with conical or internal hex connections. Methods: A total of 90 patients with partial edentulism requiring one implant-supported prosthesis were randomly allocated in two equal groups (n = 45) to receive either implants with a conical connection or implants of the same type, but with an internal hex connection at three centres. Patients were followed for 1 year after loading. Outcome measures were implant failures, any complication and marginal bone level changes. Results: One patient (2.2%) belonging to the internal hex group dropped out. One implant (2.2%) failed in the conical group. There were no statistically significant differences in implant failures between the two groups (2.2% vs. 0%, difference 2.2; 95% CI: -1.3; 5.7; P = 0.315). Two complications occurred in the conical group and two in the internal hex group (P = 1.000, difference 0.00, 95% CI: -3.1; 3.1). The 12-month peri-implant bone resorption was similar in both groups: 0.56 ± 0.53 mm (95% CI 0.03; 1.09) in the conical group and 0.60 ± 0.62 mm (95% CI 0.02; 1.22) in the internal hex group (difference = 0.04 ± 0.55, 95% CI: -0.51; 0.59, P = 0.745). Conclusions: Within the limitation of this study, preliminary short-term data (1 year post-loading) did not show any statistical differences between the two internal connection types, therefore clinicians could choose whichever connection they prefer
Immediate loading of two unsplinted implants retaining the existing complete mandibular denture in elderly edentulous patients: 1-year results from a multicentre prospective cohort study
No full textPurpose: To evaluate the outcome of two freestanding implants immediately loaded retaining an existing mandibular complete denture in elderly edentulous patients up to 1 year after loading. Materials and methods: 42 patients with a mean age of 76.5 years (range 71 to 89) were selected for stabilising their mandibular complete denture with two implants placed mesial to the mandibular canine position bilaterally. Individual ball abutments were connected and torqued at 30 Ncm and the existing complete denture was immediately attached. No postoperative limitations to chewing function were given. The patients were evaluated clinically and radiographically at implant placement and at 6-and 12-month follow-up examinations. Results: At the 12-month follow-up no implant failed. Peri-implant bone resorption was 0.203 mm (CI 95% 0.322; 0.086) after 6 months and 0.298 mm (CI 95% 0.425; 0.173) after 12 months. Of the 42 cases, 3 had major prosthetic complications and 5 patients required minor extra maintenance appointments. Conclusions: Within the limits of this study, it can be suggested that the immediate loading of two unsplinted implants retaining the existing complete mandibular denture in elderly patients can result in favourable implant survival and peri-implant bone healing, however larger and longer follow-ups of 5 years or more are needed
Combinatorial aggregation
No full textMy PhD thesis aims at carrying out a complete analysis of problems of combinatorial aggregation, with particular attention to the binary case, in which a set of individuals each make a choice over a finite number of issues, and such choices have to be aggregated into a collective one
A 3-year report from a multicentre randomised controlled trial: Immediately versus early loaded implants in partially edentulous patients
No full textPurpose: To compare implant failure, prosthesis failure and radiographic bone level changes of immediate non-occlusal loading versus early loading in partially edentulous patients 3 years after implant placement. Materials and methods: A total of 80 patients with partial edentulism were selected for a two implant-supported immediate restoration and randomised to immediate loading (test group) or early loading (control group) after 2 months, 40 patients for each group. To be included in the study, implants had to be inserted with a torque =30 Ncm. In the test group, implants were provided with non-occluding temporary restorations. In the control group, healing abutments were attached and implants were left to heal nonsubmerged. Definitive prostheses were delivered 2 months after surgery with full occlusal contacts. The outcome variables were implant failure, prosthesis failure, complications and radiographic bone level changes at implants 3 years after loading. The assessor was blinded to group assignment. Results: Eighty-one implants were immediately loaded and 80 were early loaded. Two immediately loaded patients and 1 early loaded patient dropped out at 3 years. No implant failed. Two complications occurred in the immediate loading group and 1 in the early loading group. There were no significant differences in bone levels changes at 36 months between the two groups (P = 0.67; difference 0.2 mm; 95% CI -0.23, 0.63). Immediately loaded implants lost 0.90 mm (95% CI 0.63, 1.17) and early loaded implants 1.10 mm (95% CI 0.81, 1.39). Conclusion: If adequate primary stability was achieved, no statistically significant difference in failure rates, complications or bone level changes between implants loaded immediately or early were observed 3 years after placement in partially edentulous patients
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