3D finite element analysis of the influence of upper lip pressure on the maxilla for patients with unilateral alveolar cleft / 口腔疾病防治

Objective @#To investigate the biomechanical effects of upper lip pressure on the maxilla in patients with a unilateral alveolar cleft and provide evidence for clinical diagnosis and treatment. @*Methods @#A 3D finite element maxillary model was generated based on cone beam CT (CBCT) data from an 11-year-old female patient with a unilateral alveolar cleft. Two different kinds of upper lip pressure, postsurgery pressure and normal pressure, were applied to the model. The displacement and stress of each reference node were compared and analyzed. @*Results @# By loading upper lip pressure, the maxillary alveolar crest rotated toward the defect and was displaced downward and backward. The displacement of the noncleft side was greater than that of the cleft side and it decreased gradually from the anterior to the posterior. The stress was concentrated on the anterior portion of the alveolar crest. The stress on the noncleft side was greater than that on the cleft side and it decreased gradually from the anterior to the posterior. The maximum stress was concentrated on the palate around the defect. The displacement and stress in the postsurgery group were greater than those of the normal group (P<0.05). @*Conclusion @#By loading upper lip pressure, the maxilla demonstrated asymmetry three-dimensionally. The adverse effects on the maxilla could be mitigated by reducing the upper lip pressure.

Risco de perda óssea de implantes cone-morse, hexágono externo e interno em próteses totais fixas na maxila ­ análise por elementos finitos 3D / Risk of bone loss for morse taper, external, and internal hexagon dental implants in complete fixed implant-supported prostheses ­ a 3D finite element analysis

Objetivo: analisar comparativamente o risco de perda óssea peri-implantar em próteses totais fixas na maxila, suportadas por seis implantes paralelos, utilizando conexões do tipo hexágono externo (HE), hexágono interno (HI) e cone-morse (CM) através do método dos elementos finitos 3D. Material e métodos: modelos geométricos de uma maxila e prótese foram construídos e unidos aos modelos de implantes de geometria externa semelhante para representar próteses totais maxilares parafusadas, suportadas por seis implantes paralelos cada uma. Os modelos foram submetidos a cargas mastigatórias axiais e oblíquas. Resultados: o risco de perda óssea na carga oblíqua é muito superior à carga axial; nessa condição, a conexão CM apresentou o menor risco de perda óssea e as conexões HE e HI apresentaram risco semelhante, com risco ligeiramente maior do HI. Conclusão: implantes com conexão CM apresentam menor risco de perda óssea peri-implantar, e implantes com conexão HE e HI apresentam risco similar em próteses totais fixas com implantes paralelos.

Objective: to analyze the risk of peri-implant bone loss in complete fixed, implant-supported prosthesis over six parallel implants using the external hex (EH), internal hex (IH), and morse cone (CM) connections through a 3D finite element method. Material and methods: geometric models of a maxilla and prosthesis were constructed and attached to implant models with similar external geometry to represent maxillary screw-retained dentures supported by six parallel implants each. The models were submitted to axial and oblique masticatory loads. Results: the risk of bone loss under oblique loading is higher than for axial loading; in this condition, the CM connections demonstrated the lowest risk of bone loss, with EH and IH connections showing similar risks, although slightly higher for IH. Conclusion: CM implants present less risk for peri-implant bone loss, and the EH and IH had similar values for complete fixed implant-supported restorations over parallel dental implants.

Three-dimensional finite element analysis of the stress distribution and displacement in different fixation methods of bilateral sagittal split ramus osteotomy

OBJECTIVES: This study evaluated a range of fixation methods to determine which is best for the postoperative stabilization of a mandibular osteotomy using three-dimensional finite element analysis of the stress distribution on the plate, screw and surrounding bone and displacement of the lower incisors. MATERIALS AND METHODS: The model was generated using the synthetic skull scan data, and the surface model was changed to a solid model using software. Bilateral sagittal split ramus osteotomy was performed using the program, and 8 different types of fixation methods were evaluated. A vertical load of 10 N was applied to the occlusal surface of the first molar. RESULTS: In the case of bicortical screws, von-Mises stress on the screws and screw hole and deflection of the lower central incisor were minimal in type 2 (inverted L pattern with 3 bicortical repositioning screws). In the case of plates, von-Mises stress was minimal in type 8 (fixation 5 mm above the inferior border of the mandible with 1 metal plate and 4 monocortical screws), and deflection of the lower central incisor was minimal in types 6 (fixation 5 mm below the superior border of the mandible with 1 metal plate and 4 monocortical screws) and 7 (fixation 12 mm below the superior border of the mandible with 1 metal plate and 4 monocortical screws). CONCLUSION: Types 2 and 6 fixation methods provide better stability than the others.

A comparison of fixation methods using three-dimensional finite element analysis following anterior segmental osteotomy

OBJECTIVES: This study sought to evaluate fixation methods and determine the best method for the postoperative stabilization of maxillary osteotomy. For our analysis we performed a three-dimensional finite element analysis of stress distribution on the plate, screw, and surrounding bone, as well as displacement onto the plate. MATERIALS AND METHODS: We generated a model using synthetic skull scan data; an initital surface model was changed to a solid model using software. Modified anterior segmental osteotomy (using Park's method) was made using the program, and four different types of fixation methods were used. An anterior load of 100 N was applied on the palatal surface of two central incisors. RESULTS: The Type 1 (L-shaped) fixation method gave stresses of 187.8 MPa at the plate, 45.8 MPa at the screw, and 15.4 MPa at the bone around the plate. The Type 2 (I-shaped) fixation method gave stresses of 186.6 MPa at the plate, 75.7 MPa at the screw, and 13.8 MPa at the bone around the plate. The Type 3 (inverted L-shaped) fixation method gave stresses of 28.6 MPa at the plate, 29.9 MPa at the screw, and 15.3 MPa at the bone around the plate. The Type 4 (I-shaped) fixation method gave stresses of 34.8 MPa at the plate, 36.9 MPa at the screw, and 14.9 MPa at the bone around the plate. The deflection of the plates for the four fixation methods was 0.014 mm, 0.022 mm, 0.017 mm, and 0.018 mm, respectively. CONCLUSION: The Type 3 (inverted L-shaped) fixation method offers more stability than the other fixation methods. We therefore recommend this method for the postoperative stabilization of maxillary osteotomy.

A 3-D finite element analysis on the mandibular movement pattern and stress distribution during symphyseal widening / 대한치과교정학회지

OBJECTIVE: The objective of this study was to evaluate the displacement pattern and the stress distribution of the finite element model 3-D visualization during symphyseal widening according to the osteotomy position, osteotomy type, and distraction device. METHODS: The kinds of distraction devices used were tooth-borne type, hybrid type, bone-borne type and tooth-borne type 30degrees angulated, and the kinds of osteotomy design were vertical osteotomy line between the central incisors and step osteotomy line through the symphysis. RESULTS: All reference points of the mandible including the condyles were displaced laterally irrespective of the osteotomy position, osteotomy method and distraction device. The anteroposterior or vertical displacements showed small differences between the groups. The widening pattern of the osteotomy line in the tooth-borne type of device was v shaped, and that of bone-borne type was a reverse v shape. However, the pattern in the hybrid type was parallel. The lateral displacement of the mandibular angle by the bone-borne device was more remarkable than the other types of devices. The displacement by the 30degrees angulated tooth-borne type was different between the left and right sides in both the transverse and anteroposterior aspects. CONCLUSION: The design of the distraction devices and osteotomy line can influence the displacement pattern and the stress distribution during mandibular symphyseal distraction osteogenesis procedures.

The pattern of movement and stress distribution during retraction of maxillary incisors using a 3-D finite element method / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to evaluate the displacement pattern and the stress distribution shown on a finite element model 3-D visualization of a dry human skull using CT during the retraction of upper anterior teeth. METHODS: Experimental groups were differentiated into 8 groups according to corticotomy, anchorage (buccal: mini implant between the maxillary second premolar and first molar and second premolar reinforced with a mini implant, palatal: mini implant between the maxillary first molar and second molar and mini implant on the midpalatal suture) and force application point (use of a power arm or not). RESULTS: In cases where anterior teeth were retracted by a conventional T-loop arch wire, the anterior teeth tipped more postero-inferiorly and the posterior teeth moved slightly in a mesial direction. In cases where anterior teeth were retracted with corticotomy, the stress at the anterior bone segment was distributed widely and showed a smaller degree of tipping movement of the anterior teeth, but with a greater amount of displacement. In cases where anterior teeth were retracted from the buccal side with force applied to the mini implant placed between the maxillary second premolar and the first molar to the canine power arm, it showed that a smaller degree of tipping movement was generated than when force was applied to the second premolar reinforced with a mini implant from the canine bracket. In cases where anterior teeth were retracted from the palatal side with force applied to the mini implant on the midpalatal suture, it resulted in a greater degree of tipping movement than when force was applied to the mini implant between the maxillary first and second molars. CONCLUSION: The results of this study verifies the effects of corticotomies and the effects of controlling orthodontic force vectors during tooth movement.

Biomechanical Analysis of Wrist under Axial Static Compressive Force on Metacarpals / 航天医学与医学工程

Objective To study the force and pressure transmission through normal wrist,and the effect of transverse carpal ligament release on the biomechanics of carpal tunnel.Methods A 3-D finite element model of the wrist based on CT scan images was established.The load transmission of carpus and the distribution of contact stress on radiocarpal joint under axial compressive force on metacarpals as well as the effect of transverse carpal ligament(TCL)release on the displacement of carpal bones were computed and analyzed.Results The computational results of force and pressure transmission through normal carpus matched well with previous studies.The release of TCL resulted in radial and palmar displacement of the scaphoid,flexion and radial rotation of radiocarpal joint as well as a further radial deviation of the whole carpal tunnel.Conclusion A 3-D finite element model of the wrist that includes the carpal tunnel,distal radius and ulna and proximal metacarpals is developed.This model may simulate the load transmission better and contact stress distribution of carpal tunnel and radiocarpal joint,as well as provide an operational plateform for further deeply studing on biomechanical behavior of carpal structure.The computed and analyzed results of the effect of TCL release on the displacements of carpal bones can be served as related theoratic base on carpal tunnel syndrome,carpal tunnel release surgery and recovery after operation.

Analysis of stress in spondylolysis of lumbar spine / 中国矫形外科杂志

[Objective]To investigate the biomechanical pathogenesis of lumbar spondylolysis,and to provide theoretical basis and scientific foundation for the treatment prevention of lumbar spondylolysis.[Method]The three dimension analytical method of finite element was used to set up a 3-D finite element model of whole lumbar vertebral column and to investigate the stress distribution of seven different posture in isthmus of lumbar spine.[Result]The stress of vertebral isthmus increased from L_(1~5) gradually.The concentration phenomenon of the stress prominently appeared in anteflexion and postextension,with the largest postextension position.[Conclusion]Spondylolysis may be caused by the long-term hazard stress on the lumbar isthmus,in high relation with postextension of lumbar spine.