Effects of scaffold microstructure and mechanical properties on regeneration of tubular dentin / 华西口腔医学杂志

Tubular dentin is of great significance in the process of tooth tissue and tooth regeneration, because it is not only the structural feature of primary dentin, but also can affect the tooth sensory function, affect the differentiation of dental pulp cells and provide strong mechanical support for teeth. Scaffold is one of the three elements of tissue engineering dentin regeneration. Most experiments on dentin regeneration involve the study of the microstructure and mechanical properties of the scaffold. The microstructure and mechanical characteristics of scaffold materials have important effects on the differentiation and adhesion of odontoblast, it can directly affect the tissue structure of regenerated dentin.

Development of tilted implant for free end of maxillary posterior teeth / 华西口腔医学杂志

Vertical bone insufficiency in the maxillary posterior teeth is a common clinical situation. At present, the bone insufficiency in the maxillary posterior teeth is mainly overcome by bone grafting through maxillary sinus floor elevation. Compared with traditional axial implantation, tilted implantation can better avoid bone grafting, reduce complications, shorten the treatment cycle, reduce the treatment cost for patients, and gradually be promoted in clinical settings. This article reviews the concept, biomechanics, clinical evaluation, and digital trend of tilted implants of maxillary posterior teeth.

Research progress on chitosan composite scaffolds in bone tissue engineering / 华西口腔医学杂志

Bone tissue engineering is a scientific field devoted to the development of materials that can repair or replace human bone tissue with biological and engineering methods. The stent, which provides structural support and adhesion sites for cell and tissue growth, is one of the key elements in tissue engineering. The scaffold may comprise metal, polymer, and ceramic biomaterial. The polymer scaffold is widely used due to its biocompatibility, biodegradability, and mechanical stability. Chitosan, as a natural polymer, is derived from chitin and has played a particularly important role in bone tissue engineering over the past two decades. In recent years, chitosan composites and their application in bone tissue engineering have received considerable attention due to their small foreign body reaction, excellent antibacterial properties, plasticity, suitability for inward cell growth, and bone conduction. This review will discuss the biocompatibility and osteogenesis research in vivo and in vitro of several common chitosan composites in bone tissue engineering.

Effect of alendronate sodium on torque-out testing on implant-bone interfaces in estrogen-deficient rabbits with alendronate systemic administration / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the influence of systemic application of Alendronate sodium, a bone resorption inhibitor, on the osseointegration of implant-bone interface in estrogen-deficient rabbits through mechanical assessment.</p><p><b>METHODS</b>27 five-month-old Japanese white female rabbits were randomly divided into three groups (9 rabbits each group). An ovariectomy group (OVX), an ovariectomy and Alendronate sodium group (ALN) and a shamed-operated group (S). 12 weeks after operation, implants were installed into bilateral distal femurs and proximal tibias in each group. Alendronate sodium was administrated by intraperitoneal injection in ALN group; meanwhile equivalent of normal saline was administrated by intraperitoneal injection in OVX group and S group. Bone mineral density was measured right after the implant operation and also in 4, 8, 12 weeks. Torque-out values were measured in 4, 8, 12 weeks after animal sacrifice.</p><p><b>RESULTS</b>Bone mineral density of tibias in ALN group was closed to S group and was significantly different from OVX group (P < 0.05) after 8 weeks. While after 12 weeks, the bone mineral density of tibias and femurs in ALN group was both closed to S group and was significantly different from OVX group (P < 0.05). The torque-out values of tibias in ALN group were closed to S group and were significantly different from OVX group (P < 0.05) after 8 weeks. After 12 weeks, the torque-out values of tibias and femurs in ALN group were both closed to S group and were significantly different from OVX group (P < 0.05).</p><p><b>CONCLUSION</b>Systemic application of Alendronate sodium in osteoporosis rabbits can improve the bone-implant osseointegration significantly.</p>

Research on the influence of different implant site on the implant-bone-interface stress distribution in zygomatic implant denture / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To probe the implant-bone-interface stress distribution of zygomatic implant denture concerning different implant sites.</p><p><b>METHODS</b>Three-dimensional finite element model for severe atrophy maxillary posterior-tooth area was established biomechanically in this study by computer technique and zygomatic implant was simulated into the model in the first-maxillary-premolar region, the second-maxillary-premolar region, the first-maxillary-molar region and the second-maxillary-molar region respectively. Vertical loading, buccal (30 degrees) loading and lingual (30 degrees) loading were preformed, 100 N. Then these load cases were calculated and analyzed.</p><p><b>RESULTS</b>1) When the implant site was placed in the first-maxillary-premolar region, the buccal side of zygomatic implant exposed out of the bone and didn't meet the clinical request. 2) As far as the tensile stress peak value in the maxillary posterior-tooth area was concerned, the highest value was recorded when the implant was placed in the second-maxillary-molar region, and then the medium value was recorded when the implant was placed in the second-maxillary-premolar region, and the smallest was recorded when the implant in the first-maxillary-molar region. As far as the compressive stress peak value in the maxillary posterior-tooth area was concerned, the highest value was recorded when the implant was placed in the second-maxillary-molar region, and then the medium was recorded when the implant was in the first-maxillary-molar region, and the smallest value was presented when the implant was in the second-maxillary-premolar region. As far as the tensile and compressive stress peak values in the zygomatic area were concerned, the highest value was recorded when the implant was in the second-maxillary-premolar region, and then the medium value when the implant was in the first-maxillary-molar region, and the smallest when the implant was in the second-maxillary-molar region.</p><p><b>CONCLUSION</b>The first-maxillary-molar region is the best implant site of zygomatic implant denture.</p>

A retrospective study of infection after onlay graft / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the treatment and prevention of infection after alveolar crest onlay bone graft.</p><p><b>METHODS</b>From January 2006 to May 2010, 11 infection cases after onlay graft on alveolar crest were reviewed to evaluate the infection time, clinical situation, treatment measure, and therapeutic effect.</p><p><b>RESULTS</b>The infection of all 11 cases occurred about 15 days after bone graft, which showed either soft tissue fistulae or bone graft exposure in the oral cavity. Three cases failed because of persistent infection. The infection of the other 8 cases was controlled after a series of comprehensive therapy, and most of the bone graft was reserved and implant restoration finally completed.</p><p><b>CONCLUSIONS</b>After the effective and comprehensive therapy, infected bone graft can be reserved. But to ensure the survival rate of bone graft, the most important thing is to prevent infection in perioperative period.</p>

Finite element analysis of the effects of implant thread locations on stress distribution / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effects of different implant thread locations on stress distribution in implant and bone under concentrated load, and discuss the best design of location of implant thread.</p><p><b>METHODS</b>The stress in implant-bone interface of implants with different thread locations (model A, B, C, D), which were loaded in axial and oblique 450 to axle, were analyzed by Solidworks 2005 plus and Cosmos/works 7.0 software.</p><p><b>RESULTS</b>The stresses in cervical cortical bone of implant with model C were lower than others. But under oblique load, the stresses of implant and cancellous bone in model C were higher than model A. The stresses distribution of model B was obviously concentrated, and under axial load, all kinds of stresses in this model were higher than others. The stress distribution in model A and D were more even, the stress concentrated more on implant neck, upper part of cortical bone and the lowest thread on implant. The stresses in interface under oblique load were much higher than those under axial load.</p><p><b>CONCLUSION</b>The location of thread has effect on stress distribution in implant-bone interface. More attention should be paid to it when we design implants, and we should try to avoid oblique load in implant prosthodontics.</p>

Effects of alveolar bone resorption on stress of tooth/implant-supported restoration connected by precision attachment / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effects of alveolar bone resorption on stress of tooth/implant-supported restoration connected by precision attachment using three-dimensional finite element(FEM) approach.</p><p><b>METHODS</b>The FEM was applied to analyze the stress distribution of tooth/implant-supported restoration connected by precision attachment under various loading conditions when the alveolar bone was absorbed to different level.</p><p><b>RESULTS</b>The stress values of the tooth, implant and their surrounding bone increased when their surrounding bone decreased by bone absorption.</p><p><b>CONCLUSION</b>The stress values of the tooth, implant and their surrounding bone were closely related with the bone resorption.</p>

Stress analysis of the staggered and straight placement of implants in the mandibular posterior region under the localized load / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To compare the stress distribution of the staggered and straight placement of implants in the mandibular posterior region.</p><p><b>METHODS</b>Using three-dimensional finite element approach to analyze the stress distribution and variance regularity under the localized load.</p><p><b>RESULTS</b>Under vertical load, the stress peak value reduced when wide implant was placed straight (min: 3.70 MPa), but slightly increased when normal implant was placed staggered (max: 8.32 MPa); under the inclined load from buccal to lingual direction, the stress peak value reduced when the wide implant was placed in straight line (min: 12.29 MPa) or normal implant was placed staggered with buccal offset configuration (min: 15.48 MPa), but increased with lingual offset configuration (max: 23.60 MPa).</p><p><b>CONCLUSIONS</b>Wide implant (> or = 4 mm) with straight placement should be adopted to reduce the stress peak value and improve stress distribution, when the buccolingual diameter of the alveolar ridge in the mandibular posterior region was wide.</p>

Three dimensional finite element stress analysis on superstructure of the fixed bridge supported by tooth-implant / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To reveal the stress distribution in the superstructure of fixed bridge supported by tooth-implant in the process of mastication for improvement of denture design.</p><p><b>METHODS</b>The stress distribution and displacement of the superstructure were studied and analyzed by means of CT Scan, CAD and three-dimensional finite element when various loads were applied.</p><p><b>RESULTS</b>(1) The stress distribution in abutments under oblique loads at forty-five degrees was uneven and the peak value was 4 - 6 times higher than that under vertical loads. Stress concentration occurred with significant compressive stress. (2) Compressive stress widely distributed in the middle area of occlusal surface of pontic, whose peak value under concentrated loads was significantly higher than that under disperse loads. The loading direction had no effect on the stress concentration. (3) The maximum displacement of implant abutment in medial-distal direction was greater than that of the neck of nature tooth.</p><p><b>CONCLUSIONS</b>The mechanic complications of superstructure could be prevented by reducing oblique loads and concentrated ones. It is certain that the further improvements of curve-resistance of pontics and press-resistance of abutments are available.</p>