Present situation and future of occlusal splint in treatment of oral diseases / 中华口腔医学杂志

Occlusal splint is a removable device for the treatment of oral and maxillary diseases with reversible occlusal treatment property. When patients wear the occlusal splint, the occlusal contact state can be changed and the position of the lower jaw may be adjusted, with the improvement of functions of temporomandibular joints and masticatory muscles. There are various types of occlusal splints, among which stabilization splint, soft occlusal splint and repositioning splint are widely used in the treatment of temporomandibular disorders and night bruxism. For the patients requiring occlusal reconstruction, occlusal splint can be used as an important means to adjust and verify the therapeutic jaw position. As a major trend of research in future, the digital design and production of occlusal splint are still in the initial stage and need to be further improved.

Trigeminal purinergic P2X4 receptor involved in experimental occlusal interference-induced hyperalgesia in rat masseter muscle / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To explore the expression of purinergic p2X4 receptor (P2X4R) in trigeminal ganglion of rats after occlusal interference. Investigation of peripheral receptor mechanism of occlusal interference-induced masticatory muscle pain will aid the development of drug intervention against this condition.</p><p><b>METHODS</b>Experimental occlusal interference was established by application of 0.4 mm metal crown to the upper right first molar of male Sprague-Dawley rats. Real-time PCR assay was used to investigate P2X4R mRNA level in trigeminal ganglion in rats with occlusal interference for 3, 7, 10 and 14 days and in control rats without occlusal interference (n=5 in each). Retrograde labelling combining immunofluorescence was performed to evaluate the percentage of P2X4R-positive cells in masseter afferent neurons (n=5 in each group). Graded concentrations of P2XR antagonist TNP-ATP (0.1, 10, 125, 250, 500 μmol/L) or saline (n=5 in each group) was administrated in right masseter and the mechanical sensitivity of bilateral masseters was measured before occlusal interference application, before the injection, and 30 min as well as 60 min after the injection.</p><p><b>RESULTS</b>Compared with control rats (P2X4R mRNA: right side: 1.00±0.26, left side: 0.94± 0.21; percentage of P2X4R-positive masseter afferents: right side: [64.3±6.3]%, left side: [67.7±5.8]%), the level of P2X4R mRNA in bilateral trigeminal ganglia (right side: 5.98±3.56; left side: 5.06±2.88) of rats with occlusal interference for 7 days up-regulated (P<0.01) and the percentage of P2X4R-positive masseter afferent neurons(right side: [81.7±1.5]%; left side: [82.9±2.3]%) increased (P<0.05). Local administration of 10, 125, 250, 500 μmol/L TNP-ATP increased the mechanical withdrawal threshold in masseter 30 min after injection, compared with those before injection (P<0.05).</p><p><b>CONCLUSIONS</b>Increased expression of trigeminal P2X4R involves in the development of occlusal interference-induced masseter hyperalgesia.</p>

Three-dimensional finite element analysis of influence of occlusal surface height on stress distribution around posterior implant-supported single crown / 北京大学学报(医学版)

Objective:To evaluate the effect of the occlusal surface height of a mandibular posterior implant-supported single crown on stress in bone tissues.Methods:Three-dimensional finite element models of the implant-supported single crown replacing the missing right lower second premolar,mesial and distal natural teeth,periodontal membrane,alveolar bone,loaded rigid body and analog food of almond were established.Using the Federation Dentaire International (FDI)system,the first premolar, the second premolar and the first molar were represented with 44,45,46.Three occlusal surface heights of the crown were studied:(1 )normal height;(2)1 5 μm reduction in height;(3)30 μm reduction in height.The models were loaded by independent loading with maximal occlusal force(44 by 280 N,45 by 360 N,and 46 by 480 N)and average occlusal force(44 by 1 40 N,45 by 1 80 N,and 46 by 240 N)on the single crown;combined loading (maximal occlusal force transformed into uniform load of 3 .7 MPa on top of rigid body,in contact with points on the occlusal surface),and analog almond-like food loading (average occlusal force transformed into uniform load of 1 .67 MPa in simulated food chewing,in contact with points on the occlusal surface).Results:For maximal biting force under independent loading,Von Mises stress peak values in bone tissues around 44,45,and 46 were 82.57 MPa,45.26 MPa and 27.79 MPa;For average biting force,peak values were 41 .28 MPa,22.63 MPa and 1 3.89 MPa.Under com-bined loading,compared with the normal occlusal surface height group,Von Mises stress peak values de-creased 4.6 MPa,by 0.84%;increased 7.52 MPa,by 20.04%,and decreased 1 .8 MPa,by 5.84%, for 45,46,and 44 in the 30 μm infra-occlusion group,respectively.Under food loading,Von Mises stress peak values decreased 0.34 MPa,by 1 .62%;increased 1 .1 1 MPa,by 2.66%;and increased 0.06 MPa,by 0.54%,and for 45,46,and 44 in the 30 μm infra-occlusion group,respectively.Con-clusion:Within the limitation of this study,within 30 μm reduction of the occlusal surface height of im-plant-supported single crown,no significant difference of the peak values was observed.

Influence of the occlusal interference time on masticatory muscle mechanical hyperal-gesia in rats / 北京大学学报(医学版)

Objective:To investigate the relationship between the removal time of 0.2 mm occlusal in-terference and the recovery of masticatory muscle mechanical hyperalgesia in rats.Methods:Forty male Sprague-Dawley rats (200-220 g)were randomly assigned to eight groups,with five rats in each group:(1 )nave group:these rats were anesthetized and their mouths were forced open for about 5 min (the same duration as the other groups),but restorations were not applied;(2 )sham-occlusal interference control group:bands were bonded to the right maxillary first molars which did not interfere with occlu-sion;(3 )occlusal interference group:0.2 mm thick crowns were bonded to the right maxillary first molars;(4)2,3,4,5,and 6 d removal of occlusal interference groups:0.2 mm thick crowns were bonded to the right maxillary first molars and removed on days 2,3,4,5,and 6.The nave group and sham-occlusal interference control group were control groups.The other groups were experimental groups. Bilateral masticatory muscle mechanical withdrawal thresholds were tested on pre-application days 1 ,2, and 3,and on post-application days 1 ,3,5,7,1 0,1 4,21 and 28.The rats were weighed on pre-application day 1 and on post-application days 1 ,2,3,4,5,6,and 7.Results:Between the nave group and the sham-occlusal interference control group,there was no significant difference in the mastica-tory muscle mechanical withdrawal threshold of bilateral temporalis and masseters at each time point.No significant difference was detected between the contralateral side and ipsilateral side in experimental groups (P>0.05 ).In the 2,3,4,and 5 d removal of occlusal interference groups,the masticatory muscle mechanical withdrawal thresholds decreased after occlusal interference and increased after removal of the crowns and recovered to the baseline on days 7,1 0,1 4,and 1 4,respectively [the masticatory muscle mechanical withdrawal thresholds of right masseter muscle were (1 37.46 ±2.08)g,(1 39.02 ± 2.1 1 )g,(1 40.40 ±0.98)g,(1 38.95 ±0.98)g,respectively].In the 6 d removal of occlusal inter-ference group,the masticatory muscle mechanical withdrawal threshold increased after removal of the crowns and became stable since day 1 4.There was a significant difference between the 6 d removal of oc-clusal interference group and the sham-occlusal interference group on day 28(P<0.05),the masticatory muscle mechanical withdrawal thresholds of right masseter muscle were (1 31 .24 ±0.76 ) g and (1 41 .34 ±1 .43)g,respectively.Conclusion:After removal of the 0.2 mm thick crown within 5 days, the mechanical hyperalgesia of the rats could reverse completely.The mechanical hyperalgesia of the rats could only be relieved,but not reverse completely after removal of the 0.2 mm thick crown on day 6.As the time went on,even minor occlusal interference could cause irreversible mechanical hyperalgesia of masticatory muscles.This study suggested that occlusal interference caused by dental treatment should be eliminated as soon as possible,to avoid irreversible orofacial pain.

Data of the quantitative orofacial somatosensory functions of healthy subjects and its influence factors analysis / 北京大学学报(医学版)

Objective:To establish the preliminary somatosensory data stratified by gender, age group, and sites in the trigeminal region through standardized quantitative sensory testing on healthy individuals, and to evaluate the effects of gender, age, and sites on somatosensory functions. Methods: The stan-dardised QST battery developed by the German Research Network on Neuropathic Pain consists totally of 13 different parameters. A total of 70 healthy individuals participated. The subjects were stratified into two groups according to age: younger group ( 16 female, 16 male, age 24 -40 years old ) and elder group (20 female, 18 male, age 41-69 years old) . The test was performed bilaterally over the infraor-bital, mental, and hand regions. Results:The preliminary orofacial somatosensory data stratified by gen-der, age group, and sites were presented. Female were more sensitive than male for most of the parame-ters ( P<0 . 05 ) . Age had a significant effect on most of the parameters ( P<0 . 05 ) , the younger group was more sensitive compared with the elder group (P<0. 01) for heat pain threshold (HPT): younger group (38. 07 ± 2. 94) ℃, elder group (39. 85 ± 3. 52) ℃;warmth detection threshold (WDT):youn-ger group (1.40 ±0.74) ℃, elder group (1.89 ±1.14) ℃; mechanical detection threshold (MDT):younger group (0. 73 ± 1. 66) mN, elder group (1. 41 ± 2. 82) mN; pressure pain threshold ( PPT):younger group ( 171. 71 ± 92. 51 ) kPa, elder group ( 196. 36 ± 73. 73 ) kPa; cold pain threshold (CPT):younger group (25. 90 ± 5. 38) ℃, elder group (21. 64 ± 6. 78) ℃; cold detection threshold (CDT):younger group ( -0. 97 ± 0. 55) ℃, elder group ( -1. 36 ± 0. 90) ℃, and wind-up ratio (WUR):younger group (3. 33 ± 2. 20), elder group (2. 67 ± 1. 68). The inverse results were demon-strated for mechanical pain threshold ( MPT ): younger group ( 111. 50 ± 88. 93 ) mN, elder group (104. 49 ± 94. 94) mN;mechanical pain sensitivity (MPS):younger group (6. 96 ± 5. 61), elder group (8.93 ±6.53), and vibration detection threshold (VDT): younger group (7.44 ±0.52) scale, elder group (7.55 ±0.48) scale (P<0.05). Somatosensory function was site dependent (P<0.001), the two trigeminal sites ( infraorbital and mental) were more sensitive than the hand for CDT, HPT, WDT, thermal sensory limen (TSL), MDT, MPT, MPS, and PPT (P <0. 001), but the inverse result was observed for VDT ( P <0 . 001 ) . Conclusion: The preliminary orofacial somatosensory data of Han Ethnicity stratified by gender, age group, and sites were established. The study evaluated the effects of gender , age and sites on orofacial somatosensory functions by employment standardized quantitative senso-ry testing.

Evaluation and analysis of facial somatosensory changes of chronic masticatory muscle pain patients with quantitative sensory testing / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate and analysis facial somatosensory changes of patients with chronic masticatory muscle pain (MMP) quantitatively.</p><p><b>METHODS</b>The seven parameters of standardized quantitative sensory testing (QST) protocol were used to test the pain sites, contralateral sites of masticatory muscles of 20 chronic MMP patients and the same sites of right masticatory muscles of 20 matched healthy controls. QST thresholds were compared within groups using paired t test and between groups using unpaired t test.</p><p><b>RESULTS</b>Compared to the controls, all seven parameters of bilateral sides of patients had changed. Mainly cold detection thresholds [(-1.2±0.5) and (-1.7±0.9) °C] and cold pain thresholds [(27.6±2.3) and (27.0±2.0) °C] of pain and contralateral sides increased significantly, while warm detection thresholds [(2.0±1.1) and (2.1±1.2) °C], heat pain thresholds [(37.9±3.2) and (39.7±3.9) °C], and mechanical pain thresholds [(49.3±34.1) and (111.8±86.3) mN] of pain and contralateral sides decreased significantly (P<0.05). Mechanical detection thresholds of pain sites [(1.8±1.4) mN] significantly increased (P=0.01).</p><p><b>CONCLUSIONS</b>Chronic MMP patients were detected thermal hyperesthesia, thermal hyperalgesia, and mechanical hyperalgesia. Mechanical hypoesthesia was found at the pain sites of masticatory muscles. Chronic MMP might influence the central modulation of trigeminal nerve system.</p>

Characteristics of experimental occlusal interference-induced masticatory mechanical hyperalgesia of rats / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the relationship between the existence of occlusal interference and masticatory muscle hyperalgesia by exploring the stimulus-response relationship between the duration of occlusal interference and masticatory muscle mechanical withdrawal threshold.</p><p><b>METHODS</b>Occlusal interference with 0.4 mm-thick crowns on rat molars was removed under anaesthesia at 2, 3, 4, 5, and 6 d after wear, and masticatory muscle mechanical withdrawal threshold was tested at 1, 3, 5, 7, 10, 14, 21 and 28 d.</p><p><b>RESULTS</b>Decreased mechanical withdrawal thresholds were detected in temporal muscles and masseter muscles on both sides following occlusal interference (P < 0.05). After removal of crowns at 2, 3, 4 and 5 d, rats exhibited the similar head withdrawal thresholds as the sham-application control in masticatory muscles on both sides at 10, 14, 14 and 21 d (P > 0.05). No significant differences were detected between the contralateral side with the ipsilateral side (P < 0.05). After removal of crowns at 6 d, rats still exhibited significantly decreased head withdrawal thresholds[right temporal muscle: (1.365±0.018) N; right masseter: (1.437 ± 0.024) N] in masticatory muscles on both sides until the last day of the experiment[the sham-application control: right temporal muscle: (1.554±0.040) N, P < 0.001; right masseter: (1.546±0.019) N, P < 0.001].</p><p><b>CONCLUSIONS</b>The mechanical hyperalgesia can disappear after removal of the occlusal interference at 5 d, and the existence of the occlusal interference is positively correlated with the duration of the mechanical hyperalgesia.</p>

Comparative study on three resin cements to restore anterior flared roots / 中国组织工程研究

BACKGROUND: Fiber post is widely used in front teeth aesthetic repair, but some defect teeth cannot form ferrule or thick root canal, which resulted in fiber post prosthetic replacement defluxion and a failure of repair. Presently, new-style resin cement had self sticking component, showing good effects in sticking of fiber post. Whether combination of new-style resin cement can repair affected teeth using fiber post deserves further investigation.OBJECTIVE: Through fatigue test, residual flexural strength and scanning electron microscope (SEM) observation to compare the strength of severely weakened roots restored with three resin cements. METHODS: Eighteen intact maxillary central incisors were collected and formed to severely weakened canals at the same size. Three kinds of resin cements were used to restore. Rely X Unicem, Panavia F and Super-Bond C&B resin cement and identical glass fiber post were used. All the specimens were restored using Ni-Cr ceramic crown, and placed on TCML chewing machine that loaded 1 200 000 cycle forces, and the cycle times when failure occurred were recorded. The samples were intact following loading received residual flexural strength testl SEM was employed to observe breakage surface of the samples. RESULTS AND CONCLUSION: Mean cyclic loading was significantly greater in the Super-Bond C&B Group (1 200 000 times) than in the Relyx Unicem Group (640 000 times) and Panavia F Group (550 000 times) (P< 0.05). No significant difference was detected between the Rely X Unicem and Panavia F Groups. Residual flexural strength was 747.99 N in the Super-Bond C&B Group. SEM demonstrated that Super-Bond C&B formed longer resin processes, which were more than other two groups. Results confirmed that Super-Bond C&B demonstrated better results when restoring flared roots with prefabricated glass fiber posts.

Experimental occlusal interference induces the expression of protein gene products and substance P in masseter muscles of rats / 北京大学学报(医学版)

Objective:To investigate the peripheral mechanism by studying the histological changes of masseter muscles using HE stains and substance P(SP) and protein gene product 9.5(PGP9.5) immunohistochemical stains.Methods: Fifteen male Sprague-Dawley were randomly assigned into occlusal interference group(n=12) and control group(n=3).In occlusal interference group,0.4 mm thick crowns were bonded to the rats'first molar of the maxillary.In the control group,rats were anesthetized and mouths were forced open for about 5 min but restorations were not applied.1,5,10,and 21 d after 0.4 mm occlusal alteration treatment,mechanical pain thresholds of bilateral masseter muscles were quantitatively measured by modified electronic anesthesiometer in control group and occlusal interference group.The rats were euthanized by transcardiac perfusion after deep anesthetization at different time points.The paraffin sections of masseter muscles were made and processed for HE,SP,and PGP9.5 immunohistochemical staining.Results: Decreased head withdrawal threshold to mechanical pressure was detected in masseter muscles on both sides following occlusal interference.Histological stains of masseter muscles presented intact following occlusal interference,and no inflammatory cells were observed in both sides.Intensely stained PGP9.5 was observed at 1 d in occlusal interference groups and maintained until the end of the experiment.SP expression was the most obviously increased at 5 d in both sides and gradually decreased to the level of control.Conclusion: Experimental occlusal interference-induced masticatory muscle pain is associated with peripheral sensitization of nociceptive neurons rather than muscle damage and inflammation.

Animal implantation with a new type of chitosan microspheres/calcium phosphate cement / 北京大学学报(医学版)

Objective:To investigate bioactivity,biodegradation,bone conductive properties,and clinical maneuverability of a novel injectable chitosan microspheres/ calcium phosphate cement(CPC).Methods: The bone defect of ??4 mm?4 mm?6 mm was made at both thighbones of 12 rabbits,and experimental material(chitosan microspheres/CPC) or control material(?-tricalcium phosphate cement,?-TCP) was injected into the defect respectively.The filling situation was evaluated by X-ray 3 days after operation.The rabbits were divided into three groups,four for each group.The samples with chitosan microspheres and the control with ?-TCP were collected at 8,16,24 weeks after operation.Histological examination and scanning electron microscope(SEM) evaluation were performed.Results: The absorption of implants with chitosan microspheres was observed at 8 weeks,and became more apparent at 16 weeks.Different size of cavities were observed in CPC after the degradation of chitosan microspheres.The chitosan microspheres/CPC was dramatically degradated after 24 weeks with a few chitosan microspheres,and new bone replaced the degradated materials.The implants with ?-TCP were absorbed slowly compared with the chitosan microspheres/CPC.The cavities in ?-TCP were small.Conclusion: The chitosan microspheres/calcium phosphate cement has the characters of good biocomptable and osteocombinative ability.Compared with the control material,adding chitosan microspheres into CPC could enhance its degradability and facilitate the new bone formation.

Evaluation of diagnostic sensitivity of electroneurography for facial neurotmesis / 北京大学学报(医学版)

Objective:To evaluate diagnostic sensitivity of electroneurography(ENoG) for facial neurotmesis.Methods:The data of 24 patients suffering from facial neuratmesis on one side,having non-emergency operation,and having preoperative records of ENoG were collected.Among the patients,18 were men and 6 were women,aged from 3 to 55 years(median 28).The duration of injury before ENoG examination was from 1 to 56 days(mean 23.6 days) for them.The electroneurographic examination was carried out for facial nerves on both sides preoperatively.Percentages of evoked potential amplitude reduction on affected sides were calculated according to the value of normal side.The 90% reduction of amplitude was used as a cutting point.The facial neuratmesis was observed during operation.The sensitivity and false negative proportions of ENoG were analyzed.Results:Among the 24 patients with facial neurotmesis,22 had ENoG amplitude reduction over 90%,and 2 having this reduction less than 90%.The sensitivity and false negative proportions of ENoG in patients with facial neurotmesis were 91.7% and 8.3% respectively.Conclusion:The preoperative ENoG examination is high sensitivity for facial neurotmesis.The patients whose ENoG reduction over 90% should be advised to have a facial neurorrhaphy as soon as possible.

Evaluation of inferior alveolar nerve function with trigeminal somatosensory evoked potential during mandibular distraction osteogenesis in monkeys / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To assess sensory function of inferior alveolar nerve in monkeys with mandibular distraction osteogenesis by use of trigeminal somatosensory evoked potential (TSEP).</p><p><b>METHOD</b>Seven young monkeys, 4 approximately 6 kg, were undergone a 13.5 mm bilateral or right-side mandibular lengthening with mandibular angle osteotomy and intraoral bone-born appliance. The inferior alveolar nerve function was assessed with TSEP before surgery, at the completion of distraction, and after four weeks of fixation.</p><p><b>RESULTS</b>No significant differences in latencies and amplitudes of TSEP between the left and right inferior alveolar nerves before surgery. At the completion of distraction, latencies of TSEP showed significant elongation (P < 0.01, P < 0.001) and amplitudes also significantly decreased (P < 0.001). After four weeks of fixation, various degrees of TSEP recovery were identified. The latencies and the amplitude were slightly improved.</p><p><b>CONCLUSIONS</b>Mandibular distraction osteogenesis affects sensory function of inferior alveolar nerves in studied monkeys evaluated with SEP, but recovery is observed four weeks after surgery.</p>

Clinical application of glass fiber-reinforced composite resin-bonded fixed an terior partial denture / 实用口腔医学杂志

0.05).The dental plaque detactable rate of abutment teeth was higher than that of the controls(P

A within-subject comparison of complete denture and implant-supported overdenture: The preliminary study of masticatory function and pattern / 实用口腔医学杂志

Objective:To make a within-subject comparison of masticatory function and pattern between complete denture(CD)and implant-supported overdneture(IOD).Methods: Three edentulous patients volunteered to take part in this test.Each of the patients was rehabilitated with lower CD first and lower IOD later,and with the upper denture of CD.The masticatory efficiency,mandibular movement trace and the surface electromyograph (EMG) of masseters,anterior temporlis and posterior temporlis were measured 3 month after the use of each set of the dentures.Results: With IOD,each patient increased masticatory efficiency,especially when chewing almond.The regulation of chewing cycle,centralization of end traces and occlusal slides of mandibular movement were significantly improved.The electricactivity of masseters,anterior and posterior temporlis all enhanced by means of increasing contract intensity and the rhythm of the mastication was more regular.The muscle activity pattern in two cases transformed from instable to stable,while that of the another patient changed from masseter preponderant pattern to temporlis preponderant pattern.Conclusion: Patients with IOD have a heigher masticatory efficiency,more regular mandibular movement pattern,more effective masticatory muscle contractive pattern and masticatory muscle coordinative pattern than those with CD.

A electroneurographic technique of the facial nerve / 实用口腔医学杂志

砄bjective: To explore an effective method for Electroneurography(ENoG) of facial nerve. Methods: ENoG of 114 normal subjets and 69 patients with traumatic facial nerve injuries were investigated. Latency time(LT), duration time(DT), amplitude(A) and square under the curve(S) were measured in facial muscles when facial nerve was stimulated postauricularly or anteroauricularly. Results: In most facial musles except square muscle of lower lip postauricular stimulation gave longer LT, shorter DT, lower A and smaller S. Conclusion: The postauricular stimulation is effective prior to anteroauricular stimulation for electroneurography of the facial nerve.

Construction of 3-dimensional finite element model of resin-bonded-fixed-partial dentures by dimensional laser scanning and reverse engineering / 实用口腔医学杂志

Objective:To explore a method for setting up three dimensional finite element model of posterior glass fiber reinforced composite resin-bonded-fixed-partial dentures (GFRC-RBFPD) including restoration, periodontal tissue and alveolar bone. Methods:A stone model was fabricated including abutments and pontic of restoration, then it was scanned with laser scanner. Acquired data were integrated in Geomagic 5.0. Basic 3D geometric model was established. Different parts of abutement and prosthesis were designed in I-DEAS 10 NX Series and Geomagic, then periodontal tissue and alveolar bone were set up in Geomagic 5.0. Completed 3D geometric model was input into MSC.Marc Mentat 2003 for mesh generation. Boundary conditions were defined. Model was calculated in Mentat 2003. Results:3D geometric model and finite element model including GFRC-RBFPD, abutments, periodontal membrane and bone (bone lamina dura,cortical bone and cancellous bone) were established.Little contour information was lost, comparability between models was improved.Conclusion:The 3-dimensional laser scanning technique, CAD and mesh generation technique are effective in the establishment of 3-dimensional finite element model of GFRC-RBFPD.

An analysis of electromyographic types of 16 cases with hemimasticatory spasm / 实用口腔医学杂志

Objective:To investigate varied electromyographic types in the patients with hemimasticatory spasm(HMS).Methods:Surface electromyography was recorded to study electromyographic features of 16 cases with HMS.Results:Spasm was found in mandibular rest position in 2 cases and in tooth contact position in 14 cases.During the involuntary spasm of the 14 cases, motor unit potential could be classified into three types:continuous(8 cases), rhythmic(3 cases) and irregular(3 cases).Conclusion:The electromyographic feature of hemimasticatory spasm is characterized by continuous motor unit potential discharge. The spasm is mostly triggered by tooth contact.

Construction of 3-dimensional finite element models of tooth with structure defect restoration by reverse engineering technology / 实用口腔医学杂志

Objective:To construct of 3-dimensional finite element models of mandibular first molar with structure defect restoration.Methods:Reverse engineering technology was used. Geometric models were built by the use of advanced 3-dimensional laser scanning and computer assisted 3-dimensional design technique. The geometric data were introduced into the finite element software for establishing the finite element mesh after being processed.Results:The 3-dimensional finite element models of the minimum distal occlusal structure defect with restoration were created, which included metal crown with exterior anatomic morphology of the mandibular first molar, tooth preparation, filling material and the structure of periodontal membrane.Conclusion: The method may be a useful approach for building models of teeth and relative tissues.