Juan Carlos Prados-Frutos

Platelet-rich plasma may prevent titanium-mesh exposure in alveolar ridge augmentation with anorganic bovine bone

OBJECTIVE Bone augmentation with the titanium-mesh (Ti-mesh) technique is susceptible to a large rate of complications such as morbidity of bone graft donor site, and mesh exposure to the oral cavity. The purpose of this study was to evaluate the effectiveness of anorganic bovine bone (ABB) in alveolar bone augmentation with the Ti-mesh technique. In addition, we investigated the effect of platelet-rich plasma (PRP) in preventing mesh exposure by using it to cover the Ti-mesh. PATIENTS AND METHODS Patients included in the clinical trial were randomly allocated by a blinded assistant into two groups. The 30 patients recruited for this study underwent 43 alveolar bone augmentation with the Ti-mesh technique using ABB as graft material in all of them. In 15 patients, the Ti-meshes were covered with PRP (PRP group) whereas in the other 15 the Ti-meshes were not (control group). After 6 months, patients were called for clinical, radiographic, and histological evaluation, and implant placement surgery. A total of 97 implants were placed in the augmented bone and their evolution was followed up for a period of 24 months. RESULTS Significant differences were found between the two study groups in terms of complications and bone formation. In the control group, 28.5% of the cases suffered from mesh exposure, while in the PRP group, no exposures were registered. Radiographic analysis revealed that bone augmentation was higher in the PRP group than in the control group. Overall, 97.3% of implants placed in the control group and 100% of those placed in the PRP group were successful during the monitoring period. We suggest that the positive effect of PRP on the Ti-mesh technique is due to its capacity to improve soft tissue healing, thereby protecting the mesh and graft material secured beneath the gingival tissues. CONCLUSIONS Alveolar bone augmentation using ABB alone in the Ti-mesh technique is sufficient for implant rehabilitation. Besides, covering the Ti-meshes with PRP was a determining factor in avoiding mesh exposure. Ti-mesh exposure provoked significant bone loss, but in most cases it did not affect the subsequent placement of implants.

Finite-element simulation of flexor digitorum longus or flexor digitorum brevis tendon transfer for the treatment of claw toe deformity.

Claw toe deformity sometimes leads to dorsiflexion of the metatarsophalangeal joint (MPJ) and plantar flexion of the proximal (PIPJ) and distal interphalangeal (DIPJ) joints. Flexor digitorum longus tendon transfer (FDL) is currently the gold standard for the correction of this problem. Transfer of the flexor digitorum brevis (FDB) has been recently proposed as an alternative method to treat such deformity. The aim of this work is to compare the biomechanical outcome of these two methods by means of finite-element simulation. The results show that the reduction in the dorsal displacement of the proximal phalanx (PP) for the second and third toes were very similar (about 4.3 mm for each intervention), both achieving a significant reduction in MPJ dorsiflexion when compared to no intervention (displacements are reduced by approximately 51%). In the fourth and fifth toes, only a small correction in the deformity was achieved with both the techniques (10% and 7%, respectively). FDB and FDL tendon transfer reduced the stress level when compared with the non-operated pathologic foot (the reduction of stresses for the second and third PP ranged between 20% and 40%). FDB transfer resulted in a more uniform distribution of stress along the entire toe, although differences were small in all cases. These results confirm that both the tendon-transfer techniques are effective in the treatment of claw toe deformity. Therefore, the choice of technique is at the discretion of the surgeon.

Prenatal pathogenesis of the transposition of great arteries

Transposition of the great arteries (TGA) is one of the most spectacular cardiovascular anomalies as far as the clinical picture, as well as its treatments are concerned.

Stress transfer properties of different commercial dental implants: a finite element study

Dental implantology has high success rates, and a suitable estimation of how stresses are transferred to the surrounding bone sheds insight into the correct design of implant features. In this study, we estimate stress transfer properties of four commercial implants (GMI, Lifecore, Intri and Avinent) that differ significantly in macroscopic geometry. Detailed three-dimensional finite element models were adopted to analyse the behaviour of the bone-implant system depending on the geometry of the implant (two different diameters) and the bone–implant interface condition. Occlusal static forces were applied and their effects on the bone, implant and bone–implant interface were evaluated. Large diameters avoided overload-induced bone resorption. Higher stresses were obtained with a debonded bone–implant interface. Relative micromotions at the bone–implant interface were within the limits required to achieve a good osseointegration. We anticipate that the methodology proposed may be a useful tool for a quantitative and qualitative comparison between different commercial dental implants.

Silicon calcium phosphate ceramic as novel biomaterial to simulate the bone regenerative properties of autologous bone

This study was conducted to develop novel ceramic bone substitute that resembles the autologous bone behavior when used as graft material. Solid-state reaction at 1100°C was performed to synthesize β-tricalcium phosphate (β-TCP) and biphasic calcium phosphate (BCP). The ceramics were further analyzed to characterize phase composition, microstructural properties, cytocompatability and then challenged to regenerate critical bone defects in the parietal bone of rabbits. X-ray diffraction analysis confirmed the production of β-TCP and indicated the synthesis of novel BCP composed of β-TCP and silicocarnotite (calcium phosphate silicate mineral). The cytocompatibility test with human osteoblast cell line revealed enhanced cell proliferation on the BCP ceramic. The novel BCP induced the filling of about 73% of the bone defect with a newly formed bone tissue and an almost complete degradation after 12 weeks of healing. This novel ceramic resembles the autologous bone properties of complete degradation and efficient enhancement of bone formation, making it promising as bone graft material.

Advantages and Drawbacks of Proximal Interphalangeal Joint Fusion Versus Flexor Tendon Transfer in the Correction of Hammer and Claw Toe Deformity. A Finite-Element Study

Correction of claw or hammer toe deformity can be achieved using various techniques, including proximal interphalangeal joint arthrodesis (PIPJA), flexor digitorum longus tendon transfer (FDLT), and flexor digitorum brevis transfer. PIPJA is the oldest technique, but is associated with significant complications (infection, fracture, delayed union, and nonunion). FDLT eliminates the deformity, but leads to loss of stability during gait. Flexor digitorum brevis tendon transfer (FDBT) seems to be the best surgical alternative, but it is a recent technique with still limited results. In this work, these three techniques have been analyzed by means of the finite-element method and a comparative analysis was done with the aim of extracting advantages and drawbacks. The results show that the best technique for reducing dorsal displacement of the proximal phalanx is PIPJA (2.28 mm versus 2.73 mm for FDLT, and 3.31 mm for FDBT). However, the best technique for reducing stresses on phalanges is FDLT or FDBT (a reduction of approximately 35% regarding the pathologic case versus the increase of 7% for the PIPJA in tensile stresses, and a reduction of approximately 40% versus 25% for the PIPJA in compression stresses). Moreover, the distribution of stresses in the entire phalanx is different for the PIPJA case. These facts could cause problems for patients, in particular, those with pain in the surgical toe.

Short faces, big tongues: developmental origin of the human chin.

During the course of human evolution, the retraction of the face underneath the braincase, and closer to the cervical column, has reduced the horizontal dimension of the vocal tract. By contrast, the relative size of the tongue has not been reduced, implying a rearrangement of the space at the back of the vocal tract to allow breathing and swallowing. This may have left a morphological signature such as a chin (mental prominence) that can potentially be interpreted in Homo. Long considered an autopomorphic trait of Homo sapiens, various extinct hominins show different forms of mental prominence. These features may be the evolutionary by-product of equivalent developmental constraints correlated with an enlarged tongue. In order to investigate developmental mechanisms related to this hypothesis, we compare modern 34 human infants against 8 chimpanzee fetuses, whom development of the mandibular symphysis passes through similar stages. The study sets out to test that the shared ontogenetic shape changes of the symphysis observed in both species are driven by the same factor – the space restriction at the back of the vocal tract and the associated arrangement of the tongue and hyoid bone. We apply geometric morphometric methods to extensive three-dimensional anatomical landmarks and semilandmarks configuration, capturing the geometry of the cervico-craniofacial complex including the hyoid bone, tongue muscle and the mandible. We demonstrate that in both species, the forward displacement of the mental region derives from the arrangement of the tongue and hyoid bone, in order to cope with the relative horizontal narrowing of the oral cavity. Because humans and chimpanzees share this pattern of developmental integration, the different forms of mental prominence seen in some extinct hominids likely originate from equivalent ontogenetic constraints. Variations in this process could account for similar morphologies.

A new iron calcium phosphate material to improve the osteoconductive properties of a biodegradable ceramic: a study in rabbit calvaria

β-tricalcium phosphate (β-TCP) is an osteoconductive and biodegradable material used in bone regeneration procedures, while iron has been suggested as a tool to improve the biological performance of calcium phosphate-based materials. However, the mechanisms of interaction between these materials and human cells are not fully understood. In order to clarify this relationship, we have studied the iron role in β-TCP ceramics. Iron-containing β-TCPs were prepared by replacing CaCO3 with C6H5FeO7 at different molar ratios. X-ray diffraction analysis indicated the occurrence of β-TCP as the sole phase in the pure β-TCP and iron-containing ceramics. The incorporation of iron ions in the β-TCP lattice decreased the specific surface area as the pore size was shifted toward meso- and/or macropores. Furthermore, the human osteoblastlike cell line MG-63 was cultured onto the ceramics to determine cell proliferation and viability, and it was observed that the iron-β-TCP ceramics have better cytocompatibility than pure β-TCP. Finally, in vivo assays were performed using rabbit calvaria as a bone model. The scaffolds were implanted for 8 and 12 weeks in the defects created in the skullcap with pure β-TCP as the control. The in vivo behavior, in terms of new bone formed, degradation, and residual graft material were investigated using sequential histological evaluations and histomorphometric analysis. The in vivo implantation of the ceramics showed enhanced bone tissue formation and scaffold degradation for iron-β-TCPs. Thus, iron appears to be a useful tool to enhance the osteoconductive properties of calcium phosphate ceramics.

A random fatigue of mechanize titanium abutment studied with Markoff chain and stochastic finite element formulation

Abstract To measure fatigue in dental implants and in its components, it is necessary to use a probabilistic analysis since the randomness in the output depends on a number of parameters (such as fatigue properties of titanium and applied loads, unknown beforehand as they depend on mastication habits). The purpose is to apply a probabilistic approximation in order to predict fatigue life, taking into account the randomness of variables. More accuracy on the results has been obtained by taking into account different load blocks with different amplitudes, as happens with bite forces during the day and allowing us to know how effects have different type of bruxism on the piece analysed.

State anxiety and depression as factors modulating and influencing postoperative pain in dental implant surgery. A prospective clinical survey

Objetives: To determine whether preoperative state anxiety and depression modulate or influence objective and subjective postoperative pain following dental implant insertion. Study Design: Prospective, clinical study with 7-day follow-up of a sample of 105 subjects who preoperatively completed the state anxiety questionnaire (STAI-E) and Beck Depression Inventory (BDI) and postoperatively, at 2 and 7 days, recorded objective pain with the Semmes-Weinstein mechanical esthesiometer (SW test) and subjective pain with the Visual Analog Scale (VAS). Results: 85.6% and 81.5% of patients, respectively, recorded no signs of state anxiety or depression. The correlation between anxiety and depression for both maxillary bones was the lower (P=0.02). The correlation between subjective and objective pain at 2 and 7 days, and the anatomic regions intervened, was statistically significant in the mandible at day 7 (P<0.01), and highly significant (P<0.001) for the other variables. The correlation between state anxiety and objective pain at day 7 was nearly statistically significant (P=0.07). Conclusions: The correlation between state anxiety and depression, and objective and subjective pain at day 7 was not statistically significant. A strong correlation was found between objective and subjective pain in the immediate postoperative period. Key words:Anxiety, depression, postoperative pain, dental implants.