Influence of different designs of marginal preparation on stress distribution in the mandibular premolar restored with endocrown / 南方医科大学学报

<p><b>OBJECTIVE</b>To evaluate the effect of different designs of marginal preparation on stress distribution in the mandibular premolar restored with endocrown using three-dimensional finite element method.</p><p><b>METHODS</b>Four models with different designs of marginal preparation, including the flat margin, 90° shoulder, 135° shoulder and chamfer shoulder, were established to imitate mandibular first premolar restored with endocrown. A load of 100 N was applied to the intersection of the long axis and the occlusal surface, either parallel or with an angle of 45° to the long axis of the tooth. The maximum values of Von Mises stress and the stress distribution around the cervical region of the abutment and the endocrown with different designs of marginal preparation were analyzed.</p><p><b>RESULTS</b>The load parallel to the long axis of the tooth caused obvious stress concentration in the lingual portions of both the cervical region of the tooth tissue and the restoration. The stress distribution characteristics on the cervical region of the models with a flat margin and a 90° shoulder were more uniform than those in the models with a 135° shoulder and chamfer shoulder. Loading at 45° to the long axis caused stress concentration mainly on the buccal portion of the cervical region, and the model with a flat margin showed the most favorable stress distribution patterns with a greater maximum Von Mises stress under this circumstance than that with a parallel loading. Irrespective of the loading direction, the stress value was the lowest in the flat margin model, where the stress value in the cervical region of the endocrown was greater than that in the counterpart of the tooth tissue. The stress level on the enamel was higher than that on the dentin nearby in the flat margin model.</p><p><b>CONCLUSIONS</b>From the stress distribution point of view, endocrowns with flat margin followed by a 90° shoulder are recommended.</p>

Tissue engineered tympanic membrane repairment materials with adipose-derived stem cells / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To explore the morphology, proliferative activity and adhesion of adipose-derived stem cells (ASC) seeded in the polylactic-co-glycolic acid (PLGA) scaffold, and to provide experimental data for fabricating tissue engineered tympanic membrane repairment materials.</p><p><b>METHODS</b>Wistar rats were selected, and the ASC were isolated and co-cultured with the PLGA scaffold. The morphology and proliferative activity of ASC in the scaffold were examined by immunofluorescence of Vimentin and Ki67 respectively. All the immunofluorescence signals were analyzed by a confocal laser scan microscopy system FLUOVIEW FV1000. The adhesion of ASC to the PLGA scalfold was determined by scanning electron microscopy.</p><p><b>RESULTS</b>Immunofluorescence of vimentin showed rats ASC displayed normal morphology and grew orderly in the PLGA scalfold. Immunofluorescence of Ki67 showed the normal active proliferation of ASC in the scaffolds. The Ki67 mean positive index (x(-) ± s) of the ASC in the scalfold was (8.21 ± 1.76)%, while in control group (cultured without PLGA scalfold) was (9.06 ± 1.95)%. There was no statistic significance between the two groups (t = 1.03, P = 0.30). Scanning electron microscopy demonstrated ASC adhered well to the PLGA scalfold, the pseudopodia of ASC could also be observed and the proliferative cell conjunction was tight.</p><p><b>CONCLUSION</b>ASC has good biocompatible to the PLGA scaffold and could normally adhere and proliferate in PLGA scaffold.</p>

Effect on cochlea function of guinea pig after controlled release recombinant human bone morphogenetic protein 2 / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The recombinant human bone morphogenetic protein 2 (rhBMP-2) has been used to induce osteogenesis in animals' middle ear and this technique is possible to be used to reconstruct the defects of ossicles. The side effects of the rhBMP-2 in middle ear should be observed before using in clinic. Thus we prepared the controlled release rhBMP-2 and implanted it into the acoustic bulla of guinea pigs. The effect on the cochlea was observed.</p><p><b>METHODS</b>We prepared the acellular cancellous bone, accompanied with rhBMP-2. The material accompanied with rhBMP-2 was implanted into one acoustic bulla of the animal and the opposite side of the acoustic bulla was implanted with acellular cancellous bone without rhBMP-2. Totally 20 guinea pigs were undergone this procedure. After the operation, the auditory brainstem response (ABR) of the animals was tested according to the time sequence. Three months after the operation, the animals were sacrificed. The osteogenesis induced by rhBMP-2, the acoustic bulla and cochlea affected by rhBMP-2 were observed. The structures of hair cells were observed after silver nitrate staining.</p><p><b>RESULTS</b>The animals were recovered soon after surgery. The hearing thresholds of the animals were declined slightly just after the surgery and come back completely after 3 months. Also, the bulla and cochlea were normal in shape. The osteogenesis occurred in the pore of the acellular cancellous bone with rhBMP-2. There was not any abnormal hyperplasia of bone in the bulla and cochlea. The articulation between the stapes and oval window was not merged. The shapes of the hair cells were normal and there was no obvious deletion of the hair cells compared with control group.</p><p><b>CONCLUSIONS</b>The controlled release rhBMP-2 transplanted into the middle ear could induce osteogenesis in the bulla of the animals. It did not affect the shape of the bulla and the hearing threshold of the animal, and did not induce the abnormal hyperplasia of bone in the bulla and might be used to reconstruct the defects of ossicles.</p>

Effect on cochlea function by tissue-engineering ossicle prosthesis containing controlled release bone morphogenetic protein 2 transplanted into acoustic bulla in guinea pig / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To prepare the tissue-engineering ossicle prosthesis which contained controlled release BMP-2 and implant into the acoustic bulla of guinea-pig, and observed the osteogenesis of the prosthesis in the bulla and the effect of the prosthesis on the cochlea.</p><p><b>METHODS</b>The acellular bony microtubule filled with collagen containing BMP-2 as tissue-engineering prosthesis was implanted into the acoustic bulla of the guinea-pig through the retroauricular approach. The prosthesis without BMP-2 was implanted into the contralateral bulla as control. ABR of the animals was checked after surgery at different time to observe the variation of the hearing threshold. After 3 months, the osteogenesis of the prosthesis and its effect on the structure of bulla, cochlea and hair cells was observed by histological technique and silver nitrate staining method.</p><p><b>RESULTS</b>The animals were recovered soon after surgery. The hearing threshold of the animals [(15.5 +/- 2.8) dB SPL] were increased slightly just after the surgery [(28.3 +/- 4.8) dB SPL, P<0.05], and come back completely after 3 month [(16.1 +/- 4.0) dB, P>0.05]. The prosthesis was covered with mucosa finally while the bulla and cochlea were normal in shape. The osteogenesis was occurred at the inner side of the acellular bony tube. There wasn't any abnormal hyperplasia of bone in the bulla and cochlea. The articulation between the stapes and oval window wasn't merged. The shape of the hair cells were normal and there wasn't obvious deletion of the hair cells compared with control group.</p><p><b>CONCLUSIONS</b>The tissue-engineering ossicle prosthesis contained controlled release BMP-2 can induce osteogenesis in the bulla of the animals. This kind of material doesn't affect the shape of the bulla and the hearing threshold of the cochlea, moreover, they doesn't induce the abnormal hyperplasia of bone in the bulla and might be used to reconstruct the defects of ossicles.</p>

Reconstruction of ossicular chain by in situ bone tissue engineering technique / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To make ossicular prosthesis using little columnar acellular cancellous bone combined with bone morphogenetic protein 2 (BMP-2) and implant into rabbits' acoustic vesicle to observe the osteogenesis in situ.</p><p><b>METHODS</b>To prepare the acellular cancellous bone combined with BMP-2 as ossicular prosthesis, the same material without BMP-2 were used in the control group. By retroauricular approach, a hole was made in the posterolateral bone wall of the acoustic vesicle and the prepared materials was implanted. After 3 month, the osteogenesis of the prosthesis with macroscopical anatomy and pathology were observed.</p><p><b>RESULTS</b>The rabbits recovered soon after surgery, the implanted acellular cancellous bones were banded tightly with the bone of the acoustic vesicle bone wall. The surface of all materials was covered with mucosa while osteogenesis was found in the material with BMP-2.</p><p><b>CONCLUSION</b>The acellular cancellous bone with BMP-2 could induce osteogenesis in acoustic vesicle, so this material might be use to reconstruct the defects of ossicular chain.</p>