By W. Ivan. Sul Ross State University.
Figure 2 Peak compressive strengths of crosslinked PPF bone graft substitutes following degradation in vitro buy cabgolin 0.5 mg fast delivery. Initial mechanical properties of the synthetic test material were comparable to cancellous bone discount cabgolin 0.5 mg online. The hole was large (4 mm in diameter is a significant defect for the ramus of a rat mandible) and of full thickness buy 0.5mg cabgolin fast delivery, with the periosteum totally disrupted and not replaced buy cheap cabgolin 0.5mg line. In this model, therefore, healing must be attributed to some effect of the implant material. The study allowed comparative histologic and histomorphometric assessments of the degradation and bone cell ingrowth. Results of Histological and Histomorphometric Evaluation Histologic analysis revealed superior healing of the mandibular defects with PPF-based bone repair material when compared to the control defects, which were left empty. New bone forma- tion, reported as the new bone volume index was more pronounced when the graft substitute material was mixed with autograft (Table 1). However, there was no statistically significant difference in the new bone volume index between the two experimental PPF groups mixed with autograft. These results suggest that mixing the PPF-based bone graft substitute with a small amount of autologous bone graft is just as effective as using higher amounts of cancellous autograft for this limited rodent model. Table 1 New Bone Volume Index for Each Implant Type Based on 8 Rats per Group and 4 Weeks Postoperative Follow-Up Test material New bone volume index PPF 51 8 DMB 87 14 Autograft 95 17 PPF/autograft (75/25) 61 10 PPF/autograft (25/75) 67 12 Empty control 33 5 Osseous Grafting Materials for Periodontal Defects 191 Histologic analysis of the bone–implant interface demonstrated biocompatibility of the PPF-based bone graft substitute. Inflammatory cells were only noted in the 1-week groups and were not related to type of material used for mandibular reconstruction. Inflammatory infiltrates were absent in all other groups evaluated at later postoperative follow up times. Results of this study demonstrated both biocompatibility and osteoconductive properties of the porous PPF- based scaffold in a mandibular defect model. These findings have applicability to the further development of bone repair material for reconstructive applications of the mandible. Biomechanical Analysis of Defect Sites Macroindentation testing was conducted to evaluate the stiffness of the test material–bone com- plex at 7 weeks postoperative. The stiffest materials were the positive controls (DMB and autograft) as shown in Table 2. Both PPF and PPF/autograft with a mixing ratio of 25/75 were stiffer than untreated defects. The stiffness of PPF/autograft at a low autograft mixing ratio (25/ 75) was measured and found to be slightly less than untreated defects. Biomechanical results were similar to the histomorphometric findings indicating that the bone–material composite mechanical properties were related to new bone formation. CONCLUSIONS Several materials have been tested for the treatment of osseous periodontal defects. Materials have been evaluated based upon their ability to not only support bony recovery, but also periodon- tal regeneration. The ideal properties of a repair material for periodontal defects are biocompati- bility, osteoconductivity, osteoinductivity, availability, resorbability, ability to stabilize the de- fect site under mechanical stresses, and ease of application. Although several of these properties may be found in certain materials, it is difficult to find a material where all of these criteria are satisfied. A new material based upon the resorbable polymer poly(propylene glycol-co-fumaric acid) has been investigated for the treatment of periodontal defects. The PPF-based bone graft substitute supported new bone formation in a mandibular defect model. The material is osteocon- ductive, but may be mixed with a relatively small percentage of autograft to enhance its bone regenerative properties. Additional studies will be necessary to evaluate the PPF-based graft substitute’s ability to support periodontal regeneration. However, the results indicate that the PPF-based material may provide a new treatment method for oral, maxillofacial, and periodontal defects. Table 2 Stiffness of Test Material/Bone Complex at 7 Weeks Postoperative Test material Stiffness (N/mm) PPF 99 6 DMB 176 40 Autograft 126 39 PPF/autograft (75/25) 54 34 PPF/autograft (25/75) 102 24 Empty control 80 20 192 Hile et al. ACKNOWLEDGMENTS The authors would like to recognize the support provided by NIH/NIAMS Grant No. A clinical and histological evaluation of autogeneous iliac bone grafts in humans.
The tendency of ﬂuids to cavitate depends inversely on their intensity and velocity of movement purchase 0.5 mg cabgolin with mastercard, and directly on the pressures applied buy generic cabgolin 0.5 mg. The micromechanical unidirectional effects cause cabgolin 0.5mg low cost, through direct action discount cabgolin 0.5mg free shipping, displace- ment of intracellular organic molecules with frequent diffusion into the extracellular space, rupture of macromolecular chromosomes, molecule conglomerates originating from the rupture of intermolecular bonds, modiﬁcation in protein spatial structure, formation of free radicals, denaturation of cell membrane components, and electrochemical modiﬁca- tions in cell surface. Ultrasonic waves can be compared to a strong wind striking biological materials with power proportional to ultrasound intensity. This wind causes, depending on its strength, displacements, ruptures, and variations in the shape of biological molecules. The mechanical drive may cause displacement of macromolecules out of their normal cell compartments and, thus, disorders in cell function. Biological functions of macromolecules are conditioned by their presence in the site of reaction. When mechanical waves achieve enough strength, macromolecule ﬂexion and even rupture can occur with its consequent functional loss. Formation of highly reactive oxygen free radicals is another mechanism involved in the damage of surrounding biological structures. The most common process of ultrasound micromechanical activity is protein denaturation. SURGICAL TREATMENT E: ULTRASONIC HYDROLIPOCLASIS & 243 From a stereochemical viewpoint, proteins are made up of primary, secondary, and tertiary structures. Primary structures are possible thanks to peptide bonds—covalent bonds requiring high energy supply to be split. On the other hand, the remaining struc- tures are possible thanks to weak bonds (polar, or hydrogen) requiring a certain spatial closeness of the constituent groups. Because they are weak bonds, weak energy is enough to split them and to separate the constituent chemical groups. Spatial distance hinders, then, the new formation of the same bonds. This causes serious functional damage because it is precisely due to secondary and tertiary structures that proteins form active loci. The thermic effects of ultrasound are attributable to the so-called Joule effect. The mechanical waves of ultrasound cause molecular movements that increase the kinetic energy of molecules: according to Joule’s law, the potential energy of electric charges in movement is partly ceded under the form of heat. This causes the temperature of biologi- cal materials to increase, and when the physiological value of 37 C (98. Cavitation occurs in liquids subjected to ultrasound at frequencies higher than 900 kHz. This determines the formation of vapor and air bubbles inside the liquids; a real explosion of these microbubbles is produced damaging the surrounding structures. For cavitation to occur, tissues require ultrasound intensities 1000 times higher than liquids. However, it must be considered that the human body is made up of 60% water and has anatomical cavities (cerebral ventricles, heart, great vessels, gall bladder, and urinary bladder) with liquid contents. It is known that the application of ultrasound on biological materials soaked in water causes notable damage. This damage does not occur through the cavitation of bio- logical materials, but through the explosion of the microbubbles produced by the cavita- tion of the water present. Water inﬁltration in tissues and the subsequent application of ultrasound cause water cavitation, microbubble formation and explosion, and rupture of surrounding bio- logical materials. It is understood that the more delicate structures (endothelial cells, adipose cells, etc. Ultrasonic hydrolipoclasis (ILCUS) is employed to cause volumetric reduction of tis- sues made up of structures highly sensitive to the mechanical damage resulting from the microbubble explosions caused by cavitation. Indications should be limited to the nonsur- gical treatment of lipomas and to the treatment of localized adiposities as an alternative to liposuction. Because of the inverse relation between ultrasound frequency and penetration, its beam activity is limited to the more superﬁcial strata of the body. In addition, cavitation of the inﬁltrated liquid absorbs quite a large amount of energy so that the ultrasound power that penetrates beneath becomes irrelevant. In any case, treatment of anatomical areas close to or above organs or parenchyma that could be damaged by ultrasound requires special attention.
Consequently cabgolin 0.5 mg line, the incentive for continued investigations aimed at establishing the speciﬁc factors governing the adaptation response of bone is great cabgolin 0.5mg amex. To date buy discount cabgolin 0.5 mg on-line, the majority of work in this area has focused on the femur proven cabgolin 0.5 mg, knee, and more recently the spine. The validity of such ﬁnite element models must be assessed by experimental veriﬁcation. Functionally isolated turkey ulnae were selected, enabling the loading conditions to be characterized completely while the periosteal adaptive responses were monitored and quantiﬁed after four and eight weeks of loading. Subsequently, their three- dimensional FE model of the ulna was validated against a normal strain-gauged turkey ulna under identical loading conditions. Twenty-four mechanical parameters were compared in an attempt to cor- relate the FE results with those obtained experimentally. The pattern of perisoteal bone remodeling was most highly correlated with strain energy density and longitudinal shear stress. Recently, Adams5 extended the preliminary work of Brown et al. A two-dimensional ﬁnite element model of the human femur was subjected to three loading conditions to establish the daily tissue stress level stimulus. Repre- sentative loads consisted of a single-legged stance and extreme cases of abduction and adduction with respective daily load histories of 6000, 2000, and 2000 cycles. Based on the daily load history, the simulation was used to predict the density evolution from an initial homogeneous state. Density distri- butions were established after various iterations (i. As the number of time increments exceeded 30, the differences between the two models became more pronounced. The model incorporating the lazy zone showed little change (elemental density changes < 0. The more realistic density gradients predicted by the lazy zone may warrant attribution to some physiologic counterpart to which it is related. The density changes induced by a metal cap, a metal cap and central peg, and an epiphyseal plate surface prostheses were computed. It was assumed that there was total bone ingrowth in the prosthetic device, rigidly bonding the bone and implant. A generalized, simple model of intramedullary ﬁxation was implemented. Results indicated that the amount of bone resorption is largely dependent upon the rigidity and bonding properties of the implant; these results are compatible with animal experimental data on similar intramedullary conﬁgurations reported in the literature. FE analysis was carried out to investigate the stress patterns in the structure as a whole and to establish the inﬂuences of material and design alternatives on these patterns. A follow-up investigation49 was aimed at evaluating the aforementioned stress patterns at a local rather than global level, enabling a more detailed comparison with bone adaptive behavior. They simulated the distribution of bone density throughout the natural pelvis as well as changes in bone density following total hip arthroplasty. The post-surgical models analyzed simulated fully ﬁxed and loose bone-implant interfaces. The geometrical nature of the ﬁnite element model was based on a two-dimensional slice through the pelvis, passing through the acetabulum, pubic symphysis, and sacroiliac joint. The average daily loading history was approximated with loads from a number of different activities along with the assumed daily frequencies of each. The simulations progressed until a stable bone density or state of little net bone turnover was achieved. The authors simulated the distribution of bone density in the natural pelvis as well as changes in bone density following total hip arthroplasty (THA). When loads representing multiple activities were incorporated, the predicted bone density for the natural pelvis was in agreement with that of the actual bone density distribution (Fig.
Because the section was not FIGURE 29 cut symmetrically generic cabgolin 0.5 mg on-line, the inferior horn of the lateral ventricle BASAL GANGLIA 9 is found only on the right side of this photograph buy discount cabgolin 0.5 mg line, in the temporal lobe buy cabgolin 0.5mg mastercard. The brain is sectioned in the coronal plane through CORONAL SECTION OF HEMISPHERES the diencephalic region 0.5mg cabgolin amex. The gray matter on either side of (PHOTOGRAPHIC VIEW) the third ventricle is the thalamus (see Figure 11). Lateral to this is a band of white matter, which by deﬁnition is This photographic view of the brain is sectioned in the part of the internal capsule, with the lentiform nucleus on coronal plane and shows the internal aspect of the hemi- its lateral side. In order to identify which part this is, the spheres. On the dorsolateral view (small ﬁgure, upper left) learner should refer to the section in the horizontal plane the plane of section goes through both the frontal and the (see Figure 26 and Figure 27); the portion between the temporal lobes and would include the region of the basal thalamus and lentiform nucleus is the posterior limb. From the medial perspective (the ﬁgure on the The parts of the lentifrom nucleus seen in this view upper right), the section includes the body of the lateral include the putamen as well as the two portions of the ventricles with the corpus callosum above, the anterior globus pallidus, the external and internal segments. Since portion of the thalamus, and the third ventricle; the edge the brain has not been sectioned symmetrically, the two of the section also passes through the hypothalamus, the portions are more easily identiﬁed on the right side of the mammillary nucleus, and includes the optic tracts. The claustrum has also been labeled (see section passes in front of the anterior part of the midbrain, below). The structures noted in this section should be the cerebral peduncles, and the front tip of the pons. The deep on the left side of the photograph, is the amygdala (see interhemispheric ﬁssure is seen between the two hemi- Figure OL, Figure 25, and Figure 75A). It is easy to spheres, above the corpus callosum (not labeled, see Fig- understand why this nucleus is considered one of the basal ure 16 and Figure 17). The lateral ﬁssure is also present, ganglia, by deﬁnition. Its function, as well as that of the well seen on the left side of the photograph (also not fornix, will be explained with the limbic system section labeled), with the insula within the depths of this ﬁssure of this atlas (Section D). The white matter is seen internally; it is not possible ADDITIONAL DETAIL to separate out the various ﬁber systems of the white matter (see Figure 19A and Figure 19B). Below the corpus Lateral to the lentiform nucleus is another thin strip of callosum are the two spaces, the cavities of the lateral gray matter, the claustrum. The functional contribution of ventricle, represented at this plane by the body of the this small strip of tissue is not really known. The claustrum ventricles (see Figure 20B, Figure 25, and Figure 76). The is also seen in the horizontal section (see Figure 27). BASAL GANGLIA 10 By deﬁnition, the section has passed through the pos- terior limb of the internal capsule (see Figure 26). Its ﬁbers are seen as continuing to become the cerebral peduncle CORONAL VIEW: MRI (RADIOGRAPH) (see Figure 6 and Figure 7). The plane of section includes the lateral ﬁssure, and the insula (see Figure 17B). The This is a view of the brain similar to the previous brain section, in the coronal plane. The T2 MRI has been temporal lobe includes the hippocampal formation and the adjusted on the viewing screen to invert the displayed inferior horn of the lateral ventricle (see Figure 20A, Fig- ure 20B, and Figure 74). The The lateral ventricle is seen, divided by the septum distinction between the gray matter and the white matter is enhanced with this view; the CSF is dark. Note that the pellucidum into one for each hemisphere (see also Figure 62). Again, the plane of section has passed through the tables of the skull are now white, and the bone marrow is dark. The superior sagittal sinus is seen in the midline, at foramina of Monro, connecting to the third ventricle, which is situated between the thalamus on either side. This view also includes the brainstem — the midbrain The cortex and white matter can be easily differenti- ated. The trigeminal nerve has been identiﬁed The caudate nucleus is diminishing in size, from the head at the midpontine level. The tentorium cerebelli can now (anteriorly) to the body (posteriorly — compare with be clearly seen (see Figure 17 and Figure 41B), with its another coronal section of the brain, see Figure 74).