Influence of Implant Design on the Biomechanical Environment of Immediately Placed Implants: Computed Tomography-Based Nonlinear Three-Dimensional Finite Element Analysis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Biomechanical Evaluation of Platform Switching in Different Implant Protocols: Computed Tomography-Based Three-Dimensional Finite Element Analysis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influence of Implant Connection Type on the Biomechanical Environment of Immediately Placed Implants - CT-Based Nonlinear, Three-Dimensional Finite Element Analysis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Histomorphometric evaluation of a threaded, sandblasted, acid-etched implant retrieved from a human lower jaw: A case report

The purpose of this study was to histomorphometrically evaluate the bone-to-implant contact and bone area around a titanium implant retrieved from a human lower jaw. A screw-shaped titanium implant (sandblasted and acid-etched surface) was removed from a 68-year-old male after having been in function for 40 months because of a fracture of the abutment screw. Following the implant removal, an undecalcified section was obtained. The histomorphometric analysis showed a rate of 75.40% of bone-to-implant contact and 89.30% of bone area filling within the limits of the implant threads. The surrounding bone healed in a well-organized pattern and could not be differentiated from the anginal alveolus. The histologic evidence showed a high degree of osseointegration in a threaded, sandblasted, and acid-etched implant retrieved from a human lower jaw after functional loading for 40 months. Copyright © 2005 by Lippincott Williams & Wilkins.

Influência do tipo de conexão protética, do platform-switching e do designe do implante no ambiente biomecânico de implantes imediatos com carga imediata

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Nanometer Scale Titanium Surface Texturing Are Detected by Signaling Pathways Involving Transient FAK and Src Activations

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Finite element evaluation of three methods of stable fixation of condyle base fractures

The surgical treatment of mandibular condyle fractures currently offers several possibilities for stable internal fixation. In this study, a finite element model evaluation was performed of three different methods for osteosynthesis of low subcondylar fractures: (1) two four-hole straight plates, (2) one seven-hole lambda plate, and (3) one four-hole trapezoidal plate. The finite element model evaluation considered a load applied to the first molar on the contralateral side to the fracture. Results showed that, although the three methods are capable of withstanding functional loading, the lambda plate displayed a more homogeneous stress distribution for both osteosynthesis material and bone and may be a better method when single-plate fixation is the option.

The effect of different implant neck configurations on soft and hard tissue healing: a randomized-controlled clinical trial

Objective: To compare the soft and hard tissue healing and remodeling around tissue-level implants with different neck configurations after at least 1 year of functional loading. Material and methods: Eighteen patients with multiple missing teeth in the posterior area received two implants inserted in the same sextant. One test (T) implant with a 1.8 mm turned neck and one control (C) implant with a 2.8 mm turned neck were randomly assigned. All implants were placed transmucosally to the same sink depth of approximately 1.8 mm. Peri-apical radiographs were obtained using the paralleling technique and digitized. Two investigators blinded to the implant type-evaluated soft and hard tissue conditions at baseline, 6 months and 1 year after loading. Results: The mean crestal bone levels and soft tissue parameters were not significantly different between T and C implants at all time points. However, T implants displayed significantly less crestal bone loss than C implants after 1 year. Moreover, a frequency analysis revealed a higher percentage (50%) of T implants with crestal bone levels 1–2 mm below the implant shoulder compared with C implants (5.6%) 1 year after loading. Conclusion: Implants with a reduced height turned neck of 1.8 mm may, indeed, lower the crestal bone resorption and hence, may maintain higher crestal bone levels than do implants with a 2.8 mm turned neck, when sunk to the same depth. Moreover, several factors other than the vertical positioning of the moderately rough SLA surface may influence crestal bone levels after 1 year of function.

A Systematic Review of the Clinical Performance of Tooth-Retained and Implant-Retained Double Crown Prostheses with a Follow-Up of ≥3 Years

Purpose: The objective of this review was to systematically screen the literature for data related to the survival and complication rates observed with dental or implant double crown abutments and removable prostheses under functional loading for at least 3 years. Materials and Methods: A systematic review of the dental literature from January 1966 to December 2009 was performed in electronic databases (PubMed and Embase) as well as by an extensive hand search to investigate the clinical outcomes of double crown reconstructions. Results: From the total of 2412 titles retrieved from the search, 65 were selected for full-text review. Subsequently, 17 papers were included for data extraction. An estimation of the cumulative survival and complication rates was not feasible due to the lack of detailed information. Tooth survival rates for telescopic abutment teeth ranged from 82.5% to 96.5% after an observation period of 3.4 to 6 years, and for tooth-supported double crown retained dentures from 66.7% to 98.6% after an observation period of 6 to 10 years. The survival rates of implants were between 97.9% and 100% and for telescopic-retained removable dental prostheses with two mandibular implants, 100% after 3.0 and 10.4 years. The major biological complications affecting the tooth abutments were gingival inflammation, periodontal disease, and caries. The most frequent technical complications were loss of cementation and loss of facings. Conclusions: The main findings of this review are: (I) double crown tooth abutments and dentures demonstrated a wide range of survival rates. (II) Implant-supported mandibular overdentures demonstrated a favorable long-term prognosis. (III) A greater need for prosthetic maintenance is required for both tooth-supported and implant-supported reconstructions. (IV) Future areas of research would involve designing appropriate longitudinal studies for comparisons of survival and complication rates of different reconstruction designs.

Osseointegration of hollow cylinder based spinal implants in normal and osteoporotic vertebrae: a sheep study

INTRODUCTION: Osteoporosis is not only responsible for an increased number of metaphyseal and spinal fractures but it also complicates their treatment. To prevent the initial loosening, we developed a new implant with an enlarged implant/bone interface based on the concept of perforated, hollow cylinders. We evaluated whether osseointegration of a hollow cylinder based implant takes place in normal or osteoporotic bone of sheep under functional loading conditions during anterior stabilization of the lumbar spine. MATERIALS AND METHODS: Osseointegration of the cylinders and status of the fused segments (ventral corpectomy, replacement with iliac strut, and fixation with testing implant) were investigated in six osteoporotic (age 6.9 +/- 0.8 years, mean body weight 61.1 +/- 5.2 kg) and seven control sheep (age 6.1 +/- 0.2 years, mean body weight 64.9 +/- 5.7 kg). Osteoporosis was introduced using a combination protocol of ovariectomy, high-dose prednisone, calcium and phosphor reduced diet and movement restriction. Osseointegration was quantified using fluorescence and conventional histology; fusion status was determined using biomechanical testing of the stabilized segment in a six-degree-of-freedom loading device as well as with radiological and histological staging. RESULTS: Intact bone trabeculae were found in 70% of all perforations without differences between the two groups (P = 0.26). Inside the cylinders, bone volume/total volume was significantly higher than in the control vertebra (50 +/- 16 vs. 28 +/- 13%) of the same animal (P<0.01), but significantly less (P<0.01) than in the near surrounding (60 +/- 21%). After biomechanical testing as described in Sect. "Materials and methods", seven spines (three healthy and four osteoporotic) were classified as completely fused and six (four healthy and two osteoporotic) as not fused after a 4-month observation time. All endplates were bridged with intact trabeculae in the histological slices. CONCLUSIONS: The high number of perforations, filled with intact trabeculae, indicates an adequate fixation; bridging trabeculae between adjacent endplates and tricortical iliac struts in all vertebrae indicates that the anchorage is adequate to promote fusion in this animal model, even in the osteoporotic sheep.

A systematic review of the success of sinus floor elevation and survival of implants inserted in combination with sinus floor elevation. Part II: transalveolar technique

OBJECTIVES: The objectives of this systematic review were to assess the survival rate of implants placed in sites with transalveolar sinus floor elevation. MATERIAL AND METHODS: An electronic search was conducted to identify prospective and retrospective cohort studies on transalveolar sinus floor elevation, with a mean follow-up time of at least 1 year after functional loading. Failure and complication rates were analyzed using random-effects Poisson regression models to obtain summary estimates/ year proportions. RESULTS: The search provided 849 titles. Full-text analysis was performed for 176 articles, resulting in 19 studies that met the inclusion criteria. Meta-analysis of these studies indicated an estimated annual failure rate of 2.48% (95% confidence interval (95% CI): 1.37-4.49%) translating to an estimated survival rate of 92.8% (95% CI): 87.4-96.0%) for implants placed in transalveolarly augmented sinuses, after 3 years in function. Furthermore, subject-based analysis revealed an estimated annual failure of 3.71% (95% CI: 1.21-11.38%), translating to 10.5% (95% CI: 3.6-28.9%) of the subjects experiencing implant loss over 3 years. CONCLUSION: Survival rates of implants placed in transalveolar sinus floor augmentation sites are comparable to those in non-augmented sites. This technique is predictable with a low incidence of complications during and post-operatively.

A systematic review of the success of sinus floor elevation and survival of implants inserted in combination with sinus floor elevation

OBJECTIVES: The objectives of this systematic review were to assess the survival rate of grafts and implants placed with sinus floor elevation. MATERIAL AND METHODS: An electronic search was conducted to identify studies on sinus floor elevation, with a mean follow-up time of at least 1 year after functional loading. RESULTS: The search provided 839 titles. Full-text analysis was performed for 175 articles resulting in 48 studies that met the inclusion criteria, reporting on 12,020 implants. Meta-analysis indicated an estimated annual failure rate of 3.48% [95% confidence interval (CI): 2.48%-4.88%] translating into a 3-year implant survival of 90.1% (95% CI: 86.4%-92.8%). However, when failure rates was analyzed on the subject level, the estimated annual failure was 6.04% (95% CI: 3.87%-9.43%) translating into 16.6% (95% CI: 10.9%-24.6%) of the subjects experiencing implant loss over 3 years. CONCLUSION: The insertion of dental implants in combination with maxillary sinus floor elevation is a predictable treatment method showing high implant survival rates and low incidences of surgical complications. The best results (98.3% implant survival after 3 years) were obtained using rough surface implants with membrane coverage of the lateral window.

Rhythmic synaptic activity induced by mechanical injury of rat CA3 hippocampal area.

Mechanical injury of the CNS frequently results from accidents but also occurs in the course of neurosurgical interventions. A great variety of anatomical and physiological changes have been described to evolve after a brain trauma yet only little is known about processes that occur during a trauma. In the present study, I obtained whole-cell patch clamp recordings from pyramidal cells in hippocampal slice cultures while mechanically lesioning the CA3 area. Electrophysiological analysis revealed that traumatic injury massively increased excitatory and inhibitory synaptic activity in the entire CA3 region. Cutting the CA3 region induced highly rhythmic excitatory postsynaptic currents (EPSCs) that reached frequencies of around 70 Hz. Blocking voltage-dependent sodium channels with tetrodotoxin prevented the increase in synaptic activity and injury-induced neurotransmitter release in CA3 remote from the lesion site. With fast synaptic transmission blocked only neurons in the immediate vicinity of a lesion depolarized and fired action potentials upon mechanical damage. I hence suggest that mechanical injury damages the membrane and induces action potential firing in only a small population of neurons. This activity is then propagated throughout the undamaged CA3 network inducing highly rhythmic discharges. Thus mechanical brain injury initiates immediate functional changes that exceed the lesion site.

Treatment of posttraumatic cubitus varus in children and adolescents. Supracondylar humeral osteotomy using radial external fixation

OBJECTIVE Precise adaptable fixation of a supracondylar humerus osteotomy with a radial/lateral external fixator to correct posttraumatic cubitus varus. INDICATIONS Acquired, posttraumatic cubitus varus as a result of a malhealed and unsatisfactorily treated supracondylar humerus fracture. Idiopathic, congenital cubitus varus (very seldom) if the child (independent of age and after complete healing) is cosmetically impaired; stability of the elbow is reduced due to malalignment (hyperextension); secondary problems and pain (e. g., irritation of the ulnar nerve) are expected or already exist; or there is an explicit wish of the child/parents (relative indication). CONTRAINDICATIONS In principle there are no contraindications provided that the indication criteria are filled. The common argument of age does not represent a contraindication in our opinion, since angular remodeling at the distal end of the humerus is practically nonexistent. SURGICAL TECHNIQUE Basically, the surgical technique of the radial external fixator is used as previously described for stabilization of complex supracondylar humeral fractures. With the patient in supine position, the arm is placed freely on an arm table. Using a 4-5 cm long skin incision along the radial, supracondylar, the extracapsular part of the distal humerus is prepared, whereby great caution regarding the radial nerve is advised. In contrast to the procedure used in radial external fixation for supracondylar humeral fracture treatment, two Schanz screws are always fixed in each fragment at a distance of 1.5-2 cm. The osteotomy must allow the fragment to freely move in all directions. The proximal and distal two Schanz screws are then connected with short 4 mm carbon or stainless steel rods. These two rods are connected with each other over another rod using the tub-to-tub technique. Now the preliminary correction according the clinical situation can be performed and the clamps are tightened. Anatomical axis and function are checked. If these are radiologically and clinically perfect, all clamps are definitively tightened; if the alignment or the function is not perfect, then further adjustments can be made. POSTOPERATIVE MANAGEMENT Due to the excellent stability, further immobilization not necessary. Immediate functional follow-up treatment performed according to pain. RESULTS Adequate healing is usually expected within 6 weeks. At this time the external fixator can be removed in the fracture clinic. Because the whole operation is performed in an extraarticular manner and the mobility of the elbow is not affected, deterioration of function has never been observed. Also regarding the cosmetic/anatomical situation, good results are expected because they were already achieved intraoperatively.

How to achieve maximum charge carrier loading on heteroatom-substituted graphene nanoribbon edges: density functional theory study

The practical number of charge carriers loaded is crucial to the evaluation of the capacity performance of carbon-based electrodes in service, and cannot be easily addressed experimentally. In this paper, we report a density functional theory study of charge carrier adsorption onto zigzag edge-shaped graphene nanoribbons (ZGNRs), both pristine and incorporating edge substitution with boron, nitrogen or oxygen atoms. All edge substitutions are found to be energetically favorable, especially in oxidized environments. The maximal loading of protons onto the substituted ZGNR edges obeys a rule of [8-n-1], where n is the number of valence electrons of the edge-site atom constituting the adsorption site. Hence, a maximum charge loading is achieved with boron substitution. This result correlates in a transparent manner with the electronic structure characteristics of the edge atom. The boron edge atom, characterized by the most empty p band, facilitates more than the other substitutional cases the accommodation of valence electrons transferred from the ribbon, induced by adsorption of protons. This result not only further confirms the possibility of enhancing charge storage performance of carbon-based electrochemical devices through chemical functionalization but also, more importantly, provides the physical rationale for further design strategies.