ABSTRACT
The goal of this study was to identify MSX1 gene variants in multiple Chinese families with nonsyndromic oligodontia and analyse the functional influence of these variants. Whole-exome sequencing (WES) and Sanger sequencing were performed to identify the causal gene variants in five families with nonsyndromic oligodontia, and a series of bioinformatics databases were used for variant confirmation and functional prediction. Phenotypic characterization of the members of these families was described, and an in vitro analysis was performed for functional evaluation. Five novel MSX1 heterozygous variants were identified: three missense variants [c.662A>C (p.Q221P), c.670C>T (p.R224C), and c.809C>T (p.S270L)], one nonsense variant [c.364G>T (p.G122*)], and one frameshift variant [c.277delG (p.A93Rfs*67)]. Preliminary in vitro studies demonstrated that the subcellular localization of MSX1 was abnormal with the p.Q221P, p.R224C, p.G122*, and p.A93Rfs*67 variants compared to the wild type. Three variants (p.Q221P, p.G122*, and p.A93Rfs*67) were classified as pathogenic or likely pathogenic, while p.S270L and p.R224C were of uncertain significance in the current data. Moreover, we summarized and analysed the MSX1-related tooth agenesis positions and found that the type and variant locus were not related to the severity of tooth loss. Our results expand the variant spectrum of nonsyndromic oligodontia and provide valuable information for genetic counselling.
Subject(s)
Humans , Anodontia/genetics , MSX1 Transcription Factor/genetics , Pedigree , Exome SequencingABSTRACT
With the rapid development of the chair-side computer aided design and computer aided manufacture (CAD/CAM) technology, its accuracy and operability of have been greatly improved in recent years. Chair-side CAD/CAM system may produce all kinds of indirect restorations, and has the advantages of rapid, accurate and stable production. It has become the future development direction of Stomatology. This paper describes the clinical application of the chair-side CAD/CAM technology for anterior aesthetic restorations from the aspects of shade and shape.
ABSTRACT
Objective:To classify the interforaminal arch form of edentulous mandibles by measuring the anterior-posterior distance (A-P distance) of implants planned to be inserted in All-on-4 protocol using conebeam computed tomography (CBCT) data, and to investigate the influence of the arch form on the All-on-4 distally tilted implants.Methods: Seventy-four CBCT images of edentulous mandibles were collected, including 35 males and 39 females respectively.All-on-4implant supported fixed prostheses were designed for these patients based on the CBCT data.The A-P distance was measured in the plane which crossed bilateral mental foramens and was parallel to the occlusal plane.The interforaminal arch form of edentulous mandibles were classified according to the A-P distance.The radian of the jaw arch 7.5 mm mesially to the mental foramen was measured bilaterally, and its correlation with the A-P distance was studied.Results: The average A-P distance of implant supported fixed prostheses planned in the interforaminal region was (8.5±1.5) mm (minimum 4.5 mm, maximum 11.8 mm).In the study, 12.2% of the subjects'' mandibles were classified as square arch form with A-P distances ≤7 mm, 54.0% were classified as ovoid with A-P distances >7 mm and ≤9 mm, 33.8% were classified as tapered with A-P distances >9 mm.Bilaterally, 148 results of the radian of the jaw arch 7.5 mm mesially to the mental foramen were obtained, and the average radian was 15.9°±5.5° (minimum 5.6°, maximum 35.2°).The radian and the A-P distance showed a negative correlation with statistical significance.Conclusion: In this research, the ovoid arch form was the most common type in edentulous mandibles, followed by tapered arch form.The square arch form showed the lowest percentage.As the arch form went squarer, the A-P distance became shorter, the radian of the jaw arch mesially to the mental foramen went greater, and the bone width that distally tilted implants need became bigger.The interforaminal arch form of the edentulous mandible should be analyzed before an implant supported fixed restoration is designed in the interforaminal region.The angle of inclination of distal implants should be reasonable.The bone width of the distal implant site must be adequate.The square arch form contributes negatively to the structure of implant supported fixed prostheses with distal cantilever design.
ABSTRACT
Objective:To screen the ectodysplasin A (EDA)gene mutation in the patients with non-syndromic tooth agenesis and ectodermal dysplasia,and to analyze the phenotype of missing teeth pattern in these two groups of patients.Methods:In the study,174 patients with tooth agenesis (143:non-syn-dromic,31:ectodermal dysplasia)and 451 health control volunteers were enrolled from the clinic,and the genome DNA was extracted from either peripheral blood or oral mucosal swab.The coding region of EDA gene was then amplified by PCR,sequenced and blasted to online NCBI database.The missing teeth were recorded for all patients,and the missing teeth from patients with EDA mutation were com-pared among the different dentition sites.Results:33 patients were identified with EDA mutation.In the non-syndromic patients,13 /143(9.09%)were identified with EDA mutation,while in patients with ec-todermal dysplasia,20 /31 (64.52%)were found with EDA mutation.Ten novel EDA mutations were identified (c.769G >C[p.G257R],c.936C >G[p.I312M],c.223G >A[p.E75K],c.1166C >T[p. P389L],c.133G >C[p.G45R],c.1109G >A[p.E370K],c.914G >T[p.S305I],c.916C >T[p. Q306X],c.602G >T[p.G201V],c.88 -89insG[p.A30GfsX69]).For each dentition site there was no statistic difference in the number of missing teeth between the left and right sides,so the number from both sides were combined later in the analysis.In the patients with EDA mutation,the non-syndromic pa-tients had fewer missing teeth (15.9 ±6.4 missing teeth for each,207 /364 in total)than the patients with ectodermal dysplasia (23.9 ±4.3,478 /560).In the non-syndromic patients with EDA mutation, the maxillay central incisors and first molars were less affected,with the same missing rate as 19.2% (5 /26).While the mandibular central incisors (with a missing rate of 76.9%,20 /26),the maxillary late-ral incisors (the missing rate:88.5%,23 /26 ),the mandibular lateral incisors (the missing rate:80.8%,21 /26),and the maxillary first premolars (the missing rate:80.8%,21 /26)were more likely to be missing.In the ectodermal dysplasia patients with EDA mutation,only maxillary central incisors (the missing rate:60%,24 /40),maxillary canines (the missing rate:70%,28 /40),mandibular ca-nines (the missing rate:67.5%,27 /40),maxillary first molars (the missing rate:65%,26 /40)and mandibular first molars (the missing rate:72.5%,29 /40)had higher possibility of persistence.Teeth at other dentition sites were more likely to be affected (the minimum missing rate:87.5%,35 /40). Conclusion:The findings would help to reveal the EDA gene and its function in ectodermal organogene-sis.
ABSTRACT
Objective:To investigate the distribution and content of transforming growth factor-β1 (TGF-β1)and vascular endothelial growth factor (VEGF)in concentrated growth factors (CGF)gel, and to clarify the difference among different layers of CGF.Methods:Venous blood samples were col-lected from 6 healthy volunteers to prepare CGF.The distribution,integrated optical density (IOD)and average optical density (AOD)of TGF-β1 and VEGF in CGF gel and red blood cell (RBC)layer were measured using immunohistochemistry.The concentrations of TGF-β1 and VEGF in the supernatant se-rum at baseline and the CGF releasate after 1 day were evaluated with enzyme-linked immunosorbent as-says.Results:Abundant TGF-β1 and VEGF were concentrated in CGF gel.However,only a little could be found in polykaryocytes and sporadic platelets in RBC layer.Platelets and leukocytes were concentra-ted in between the two layers with high expression of TGF-β1.The concentrations of TGF-β1 and VEGF in the CGF releasate(55 236.78 ±3 686.34),(610.99 ±148.81)ng/L were significantly higher than those in the supernatant serum (20 710.20 ±4 523.14),(335.20 ±51.69 )ng/L (P <0.001 ). Conclusion:CGF contains high quantities of TGF-β1 that can promote new bone formation and tissue healing.We suggest that CGF gel should be used right after being prepared.Supernatant serum and the area between CGF gel and RBC layer could also be mixed with bone substitute materials.
ABSTRACT
Objective:To evaluate the precision of digital impressions taken under simulated clinical impression taking conditions with TRIOS and to compare with the precision of extraoral digitalizations . Methods:Six #14 -#17 epoxy resin dentitions with extracted #16 tooth preparations embedded were made.For each artificial dentition , ( 1 ) a silicone rubber impression was taken with individual tray , poured with type IV plaster ,and digitalized with 3Shape D700 model scanner for 10 times;(2) fastened to a dental simulator , 10 digital impressions for each were taken with 3Shape TRIOS intraoral scanner .To assess the precision , best-fit algorithm and 3 D comparison were conducted between repeated scan models pairwise by Geomagic Qualify 12.0, exported as averaged errors (AE) and color-coded diagrams.Non-parametric analysis was performed to compare the precisions of digital impressions and model images .The color-coded diagrams were used to show the deviations distributions .Results:The mean of AE for digital impressions was 7.058 281 μm, which was greater than that of 4.092 363 μm for the model images (P<0.05).However, the means and medians of AE for digital impressions were no more than 10 μm, which meant that the consistency between the digital impressions was good .The deviations distribution was uniform in the model images ,while nonuniform in the digital impressions with greater deviations lay mainly around the shoulders and interproximal surfaces .Conclusion:Digital impressions with TRIOS are of good precision and up to the clinical standard .Shoulders and interproximal surfaces scanning are more difficult.
ABSTRACT
This paper is aimed to develop a computerized three dimensional system for displaying and analyzing mandibular helical axis pathways. Mandibular movements were recorded using a six-degrees-of-freedom ultrasonic jaw movement recording device. The three-dimensional digital models of the midface and the mandible were reconstructed and segmented from CT skull images. The digital models were then transformed to the coordinate system of mandibular motion data by using an optical measuring system. The system was programmed on the base of the Visualization ToolKit and Open Scene Graphics Library. According to the motion data, transformation matrices were calculated to simulate mandibular movements. Meanwhile, mandibular helical axis pathways were calculated and displayed three dimensionally by means of an eigenvalues method. The following parameters of mandibular helical axis were calculated: the rotation around instantaneous helical axis, the translation along it, its spatial orientation, its position and distance relative to any special reference point. These parameters could be exported to describe comprehensively the whole mandiblular movements. It could be concluded that our system would contribute to the study of mandiblular helical axis pathways.
Subject(s)
Humans , Imaging, Three-Dimensional , Mandible , Models, Anatomic , Movement , RotationABSTRACT
BACKGROUND: The strength and elasticity of general starch can be enhanced dramatically after plastic blends. The major characters of this material are magnitude molecular weight, many enwinded points, extreme containment of small molecules,and great gelation ability. It can be used as a biodegradable replacement of alginate. Furthermore, by adding osteoinductive factors, thermoplastics starch (TP) can be used as an organic engineering material, which can provide dual functions:anti-bleeding and bone formation. TP can also be used as intraoral tissue formation membrane and burn dressings.OBJECTIVE: To evaluate the bio-safety of TP through a cytotoxicity test.DESIGN: A controlled observation.SETTING: Beijing Research Institute of Traumatology and Orthopaedics; Beijing Jishuitan Hospital; Beijing University of Chemical Technology; Peking Univesity School of Stomatology.MATERIALS: The experiment was conducted at the laboratory of Beijing Research Institute of Traumatology and Orthopaedics from April to October in 2006. TP sample was obtained by plasticization of corn starch (12 wt % water content) with glycerol in a Haake Rhenmix at 110℃ and with 80 rounds per minute for 25 minutes, elongation at break from 115.3% to 245.3%. It was prepared by Beijing Key Laboratory for Preparation and Processing of Novel Polymeric Materials, Beijing University of Chemical Technology. Mouse fibroblast L-929 cell strain was provided by the cell bank of Peking University Health Science Center.METHODS: 1 × 107 L-1 cell aqueous suspension was cultured into leaching liquor ( 50% ), serving for TP group, and routine culture medium served for negative control group. Effect of TP on relative growth rate of L-929 cell strain was quantitatively measured by MTI" assay. The cytotoxicity of TP was evaluated according to GB/T16175-1996. Morphological changes and proliferation of cells were observed after2, 4, and 7 days of culture in the medium through an inverted phase contrast microscope.MAIN OUTCOME MEASURES: Cytotoxicity, morphological changes and proliferation of cells, and cell relative growth rate.RESULTS: Cytotoxicity: After 2 and 4 days of incubation, the absorbance (A) value was lower in the TP group than in the negative control group. After 7 days of incubation, the A value was significantly higher compared to negative control group (P＜0.01). It indicated that after 2 and 4 days of incubation, the cytotoxicity in the TP group was larger than in the negative control group, while after 7 days of incubation, it was on the opposite. All the test time, TP's cytotoxicity grade ranged from 0 to 1. Morphological change and proliferation of cells: After 2 days of incubation, both groups of cells were not extended to the outside of the scope, with a majority shape of being round, triangle, and quadrangle in the TP group or fusiform cells in the negative control respectively. Four days later, there were gaps among cells in the TP group, while in the negative control group, there were hardly any distance between cells and some cells piled up. Seven days later, cells in starch medium suddenly grew up to such a degree that all the cells lapped over and presented with more bloom than the negative control. Cell relative growth rate: After 2, 4, and 7 days of incubation, relative growth rate increased with time, being 85.63%,82.22%, and 113.05%, respectively.CONCLUSION: TP has no evidence of cytotoxicity and has good bio-safety.
ABSTRACT
Oligopeptide T2, a kind of PA (Peptide Amphiphile) molecule, which could build up nano-fiber by self-assembly was designed and synthesized in this study. And the double-diffusion gel system was applied on this molecule to investigate its biomineralization features in vitro. The results showed that T2 could obviously reduce the hydroxyapatite (HA) formation period. And HA was found to possess the characteristics of non-crystalline by analysis of X-ray diffraction (XRD) and scanning electronic microscopy (SEM). These findings point to the conclusion that the negatively charged zone in T2 might make this molecule have the function of promoting HA biomineralization in vitro. And the mechanism responsible for the procession of HA biomineralization needs further research.
Subject(s)
Biocompatible Materials , Chemistry , Bone Substitutes , Chemistry , Calcification, Physiologic , Durapatite , Chemistry , Oligopeptides , ChemistryABSTRACT
Objective: To search for a simple and rapid cell culture method for human gingival epithelial cells with a high success rate. Methods:Culture medium containing serum has been proved to have the ability of accelerating the early adhesion of human gingival tissue blocks, and the migration of gingival epithelial cells from the rim of the blocks. By means of this, we introduced the serum containing DMEM to the cell culture medium within the first 7-10 days, and changed with serum free cell culture medium to accelerate the mitosis, proliferation, and migration of the gingival epithelial cells, which had moved out from the tissue blocks. Using the combined method, cells were identified by the method of morphology, immunohistochemistry and analysis of the cell growth curve, as well as SEM. Compared study of the effects on the cell growth between combined method and serum containing DMEM or serum free EpiLife culture method was conducted. Results: Cells were harvested within 17-22 days. Primary culture success rate was 90.6%. Cultured cells were slabstone shaped. Immunohistochemistry analysis of keratin antibody showed a positive result. The cells had stronger ability of migration and proliferation in the serum free cell culture medium compared with that in the serum medium. Conclusion: This method can culture the gingival epithelium cells conveniently with accelerated speed.
ABSTRACT
Objective:To investigate the fatigue damage mechanism of porcelain,and its relation with the microscopic defects in clinically failed all-ceramic crowns.Methods: Collecting the bilayered all-ceramic crowns failed in vivo.The fractured surfaces and occlusial surfaces of failed crowns were examined by an optical microscope followed by detailed fractography investigations using a field emission scanning electron microscope.When chemical impurities were of concern,energy-dispersive X-ray spectroscopy analysis was performed to examine chemical composition.A standard practice for fractography failure analysis of advanced ceramics is applied to disclose the fracture mode,and damage character.Results: Three types of fracture features are defined as breakdown of the entire crown,and porcelain chipping-off/delamination.Alumina crowns were usually characterized by breakdown of the entire crown,while zirconia crowns by porcelain chipping-off and delamination.The fatigue damage of porcelain was classified into surface wear,cone crack,and porcelain delamination.The observed microscopic defects in this study included air bubbles and impurity particles.Conclusion: The multi-point occlusial contacts were recommended in all-ceramic restorations clinically.The thickness of porcelain is important for the anti-fatigue ability of porcelain.Cautions have to be taken to avoid contaminations during the veneering processes.
ABSTRACT
Objective:To evaluate clinical application of American College of Prosthodontics classification system for complete edentulism;and to analyze the relationship between clinician's rating of general degree of difficulty of each case and patients' rating of denture satisfaction.Methods:One hundred and seven edentulous patients were examined clinically using American College of Prosthodontics(ACP) classification for complete edentulism.The least heights of patients' mandible were measured on panoramic radiographs.Clinician rated general degree of difficulty of each case on visual analogue scale.Six month following denture delivery,patients rated their denture using Mcgill satisfaction Visual Analog Scale(VAS).Multivariate linear regression analysis were conducted to analyze the relationship between clinican's rating of general degree of difficulty and mandibular bone height adjusting for confounding factors such as mandibular ridge form,soft tissue quality etc.Pearson correlation analysis was conducted to analyze the correlation between clinician's rating of case difficulty and patients' rating of denture satisfaction.Results: Advanced residual ridge resorption were found in around 80%(83/105) of all the cases.When the least mandibular bone height were measured on panoramic radiographs,intra-examiner reliability was 0.96,inter-examiner reliability was 0.90.Cases were rated as more difficult when patients showed lower mandibular bone height,unfavoriate ridge form(knife ridge and irregular ridge),mobile soft tissue and longer period of wearing time of their previous dentures.No significant correlation(r
ABSTRACT
Objective:To analyze occlusal contact areas on the working and nonworking sides during unilateral mastication.Methods: Eighteen subjects without any temporomandibular disorder(TMD) symptoms participated in the present study.The subjects were presented with 3 g gum for right masticating.Chewing movement was simulated using virtual craniofacial movement simulation system.Then occlusal contact areas were calculated at four selected moments during the closing phase in the third chewing cycle: the occurrence of occlusal contact,one third time,two thirds time,the intercuspal occlusion.Results: During the closing phase in the third chewing cycle,the total occlusal contact areas on working side increased from(9.3?0.4) mm2 to(39.2?1.2) mm2,and that on nonworking side increased from(2.3?0.5) mm2 to(40.3?1.2) mm2.At the occurrence of occlusal contacts,occlusal contact areas of the first and second mandibular molars were on average(3.7?0.2) mm2 and(3.5?0.2) mm2 on working side,and(0.5?0.2) mm2 and(1.2?0.3) mm2 on nonworking side,respectively.However,when the mandible moved to the intercuspal position,their areas were sharply increased to(14.8?0.7) mm2 and(13.9?0.4) mm2 on working side,and(13.6?0.5) mm2 and(12.1?0.5) mm2 on nonworking side,respectively.In addition,nonworking-side contacts were observed for 12 subjects at the occurrence of occlusal contacts,and for all subjects at two thirds time.Conclusion: This paper provides a new method useful for analyzing occlusal contacts during functional movements.This study revealed the pattern of occlusal contacts during the closing phase in the chewing cycle.Moreover,it was confirmed that nonworking-side contacts occurred during unilateral mastication.
ABSTRACT
Objective:To investigate the short-term and long-term effects of occlusal rehabilitation on the co-contractration patterns of masticatory muscles of patients with extensive tooth wear.Methods: Twenty-nine patients with severe tooth wear were selected and conducted with occlusal rehabilitation.The surface electromyography(EMG) of masseter(MM),anterior temporalis(TA) and posterior temporalis(TP) at rest position,during clenching and chewing were separately recorded in the stage of pre-treatment,1 month after temporary restoration,1 month after permanent restoration and long-term observation(mean 3.5 years).The Asymmetry Indexes(AI) of bilateral muscles,Activity Indexes of MM/TA,MM/TP and TA/TP were compared in each stage.Results:(1) After occlusal rehabilitation,all the AIs of bilateral MM,TA and TP at rest position,during clenching and chewing showed obvious decrements.(2) In every stage of occlusal rehabilitation,all of the Activity Indexes of MM/TA at rest position,during clenching and chewing had no obvious changes.(3) The Activity Indexes of MM/TP and TA/TP during clenching and chewing significantly increased after occlusal rehabilitation.Conclusion: The treatment of occlusal rehabilitation can significantly improve the bilateral symmetry of masticatory muscles in patients with extensive tooth wear,and also change the coordinated EMG activity of different masticatory muscles.
ABSTRACT
Objective: To evaluate the influence of retention-form design of resin bonded fixed partial dentures(RBFPDs). Methods: Forty-five metal replicas of posterior metal RBFPDs were divided into 3 groups(n=15):C shape(control group), C shape + axial groove, C shape + pin hole. All the replicas were luted with Panavia F cement and subgroup of 5 specimens were subject to 70 N compressive load cycling for 0 cycles, 240 000 cycles , and 1 200 000 cycles respectively .Half of the cycles was on the central fossa of the pontics and half on the buccal inclined surface of the lingual cusp. Forces for dislodgment of the specimens were applied along the long axis of the abutment at a crosshead speed of 1.0 mm /min. The separation forces were recorded as maxium retention force at the time of dislodgement. Results: Se-paration forces of the C shape group (566.82?71.59 N)0.05). After 1 200 000 cycles, the retention force of the RBFPDs decreased significantly (P
ABSTRACT
Objective: To evaluate the possibility of self-assembly oligopeptide(T2) for dental enamel biomimetics, especially for the prism’s crystal texture since it could prompt calcium phosphate precipitated in gel carrier. Methods:SEM (Scaning electron microscope) and TEM (Transmission electron microscope) were used to observe the morphologic presentation and ED(Electron diffraction) to crystal texture comparing with the human molar enamel powder. Results: (a) Flake-like and needle-like octacalcium phosphate precipitated in the gel carrier with self-assemble oligopeptide(T2). They transformed into rod-like hydroxyapatite crystals gradually in the following 2-4 weeks. (b) The rod-like hydroxyapatite may arrange or grow into bundles which are similar to the human enamel prisms in both appearance and size. (c) The rod-like hydroxyapatite showed polycrystal while the enamel prisms showed monocrystal under examination of ED. Conclusion:The self-assemble oligopeptide(T2) could regulate the speed of nucleation and crystallization of hydroxyapatite in morphology and crystalline size. Thus, the self-assembly oligopeptide and the gel carrier mineralization system could be primarily applied in biomimetic use for the crystallization of hydroxyaptite in dental prism in vitro.
ABSTRACT
Objective: To evaluate the effect of core∶dentin thickness ratio on the flexure strength, fracture mode and origin of bilayered IPS Empress Ⅱceramic composite specimens. Methods: IPS EmpressⅡ core ceramic, dentin porcelain and bilayered composite specimens with core∶dentin thickness ratio of 2∶1 and 1∶1 were tested in three-point flexure strength. Mean strengths and standard deviations were determined. The optical microscopy was employed for identification of the fracture mode and origin. Results: The flexure strength of dentin porcelain was the smallest (62.7 MPa), and the strength of bilayered composite specimens was smaller than single-layered core ceramic(190.2 MPa). The core∶dentin ratio did not influence the strength of bilayered composite specimens. The frequency of occurrence of bilayered specimen delaminations was higher in the group of core∶dentin thickness ratio of 1∶1 than in the group of 2∶1. Conclusion: IPS Empress Ⅱcore ceramic was significantly stronger than veneering dentin porcelain. Core∶dentin thickness ratio could significantly influence the fracture mode and origin, and bilayered IPS Empress Ⅱceramic composite specimens showed little influence in the fracture strength.
ABSTRACT
Objective: To evaluate the biocompatibility of polymethylmethacrylate(PMMA) denture base resin containing silver-supported antimicrobial agent STR-1 of nanometer level in vitro. Methods: According to the national standards for biological evaluation of dental materials, the cytotoxicity of denture base resin containing STR-1 at concentrations of 5 g/L and 10 g/L was examined by molecular filtrating method, and the hemolysis of STR-1, denture base resin containing STR-1 at concentrations of 5 g/L and 10 g/L was also surveyed. Results: The control denture base resin without containing STR-1 and the denture base resins containing STR-1 at concentrations of 5 g/L and 10 g/L were not cytotoxic to L929 cells. Two hours and 24 hours after cell culturing, the filter membranes of the control and experimental groups were stained evenly with blue color. The staining intensity was not decreased and the fading areas were 0 mm~2 during the culturing. The cytotoxicity grades were 0. The hemolysis rates of the antimicrobial agent STR-1 and the denture base resins containing STR-1 at concentrations of 5 g/L and 10 g/L were 1.7%, 3.5% and 3.7% respectively. They were less than the national guild standard 5% which represent no hemolysis. Conclusion: The PMMA denture base resins containing silver-supported antimicrobial agents STR-1 of nanometer level at concentrations of 5 g/L and 10 g/L exhibit good biocompatibility.
ABSTRACT
<p><b>OBJECTIVE</b>To investigate the variation in movement traces of different condylar reference points.</p><p><b>METHODS</b>In 30 healthy subjects, mandibular movements were recorded during protrusion and open-closing of the jaw. The kinematic center and terminal hinge axis point of the condyle were used as reference points.</p><p><b>RESULTS</b>The kinematic center was located anteriorly and superiorly with respect to the terminal hinge axis point. The trace distance of the kinematic center was longer than that of the terminal hinge axis point of the condyle during opening. In contrast to differences in trace distances of the left and right condylar terminal hinge axis points, no such left-right differences were found for the kinematic centers. The ratio between the distance of opening trace and the distance of protrusion trace of the kinematic center was above 1.5.</p><p><b>CONCLUSIONS</b>In comparison to the terminal hinge axis, the kinematic center shows fewer variations in the movement traces.</p>
Subject(s)
Adult , Humans , Biomechanical Phenomena , Jaw , Physiology , Mandibular Condyle , Physiology , MovementABSTRACT
<p><b>OBJECTIVE</b>To investigate the activities of head, neck and upper trunk muscles with mandibular movement in normal adults.</p><p><b>METHODS</b>The integral data of surface electromyography (EMG) had been recorded to analyze the activities of anterior temporal (Ta), posterior temporal (Tp), sternocleidomastoid (SCM) and trapezius (TRAP) muscles with mandibular movement in ten normal adults.</p><p><b>RESULTS</b>The former mentioned muscles acted constantly when the mandible was in the rest position. The activities of Ta, Tp and SCM muscles increased with protrusion of mandible, mouth opening, tapping, maximum clenching, and chewing movements. The amplitudes of the increased activity of these muscles were correlated significantly with each other. When the activities of Ta and Tp muscles increased to 56 times and 25 times respectively, the activity of SCM muscle increased to 5 - 6 times. The activity of trapezius muscle increased with protrusion of mandible and opening movement, but tended to stop with the maximum clenching and chewing movement. The correlations of left and right sides of the same muscles had been found.</p><p><b>CONCLUSIONS</b>The muscles of head, neck and upper trunk can act as contributors to keep the mandibular positions and take part in the mandibular movements.</p>