Hippocampus is involved in 17β-estradiol exacerbating experimental occlusal inter- ference-induced chronic masseter hyperalgesia in ovariectomized rats / 北京大学学报(医学版)

OBJECTIVE@#To investigate the influence of chronic masseter hyperalgesia induced by 17β-estradiol (E2) and experimental occlusal interference (EOI) on underlying mechanism in hippocampus of ovariectomized (OVX) rats.@*METHODS@#In the study, 32 OVX rats were randomly divided into 4 groups (8 rats/group): The control group was OVX group, and 0 μg/d E2 (vehicle) injection was started 7 d after OVX without EOI; in the experimental group (1) OVX + E2 group, 80 μg/d E2 injection was started 7 d after OVX without EOI; in the experimental group (2) OVX + EOI group, vehicle injection was started 7 d after OVX and EOI was applied 17 d after OVX; in the experimental group (3) OVX + E2 + EOI group, 80 μg/d E2 injection was started 7 d after OVX and EOI was applied 17 d after OVX. Bilateral masseter muscle mechanical withdrawal thresholds were measured before OVX, 7 days after OVX (before E2 injection), 17 days after OVX (10 days after E2 injection and before EOI) and 24 days after OVX (7 days after EOI). Immunofluorescence staining was used to reveal phospho-extracellular signal regulated kinase 1/2 (p-ERK1/2)-positive neurons in CA3 of hippocampus. The protein expression of p-ERK1/2 in hippocampus was detected using Western Blot.@*RESULTS@#Compared with the control group [left side: (135.3±8.5) g, right side: (135.4±10.8) g], bilateral masseter muscle mechanical withdrawal thresholds of OVX+E2 group [left side: (113.3±5.6) g, right side: (112.5 ± 5.6) g] and OVX+EOI group [left side: (93.3±5.4) g, right side: 90.8±5.5) g] were decreased (P < 0.01). Bilateral masseter muscle mechanical withdrawal thresholds were significantly lower in OVX+E2+EOI group [left side: (81.2±6.2) g, right side: 79.8±7.7) g] than in the control, OVX+E2 and OVX+EOI groups (P < 0.05). The proportion of p-ERK1/2 positive neurons in the CA3 region of the hippocampus was increased in the control, OVX+E2, OVX+EOI and OVX+E2+EOI groups in turn, and the difference between the groups was statistically significant (P < 0.05). p-ERK1/2 protein expression was increased in the control, OVX+E2 and OVX+EOI groups in turn, but the difference was not statistically significant (P>0.05). p-ERK1/2 expression was significantly higher in OVX+E2+EOI group than in the other three groups (P < 0.05).@*CONCLUSION@#High concentration of E2 could exacerbated EOI-induced chronic masseter hyperalgesia in ovariectomized rats, and its central mechanism may be related to the upregulation of the phosphorylation of ERK1/2 in hippocampus.

Effect of porous zirconia ceramics on proliferation and differentiation of osteoblasts / 北京大学学报(医学版)

OBJECTIVE@#To investigate the effect of porous surface morphology of zirconia on the proliferation and differentiation of osteoblasts.@*METHODS@#According to different manufacturing and pore-forming methods, the zirconia specimens were divided into 4 groups, including milled sintering group (M-Ctrl), milled porous group (M-Porous), 3D printed sintering group (3D-Ctrl) and 3D printed porous group (3D-Porous). The surface micromorphology, surface roughness, contact angle and surface elements of specimens in each group were detected by scanning electron microscope (SEM), 3D laser microscope, contact angle measuring device and energy-dispersion X-ray analysis, respectively. MC3T3-E1 cells were cultured on 4 groups of zirconia discs. The cell morphology of MC3T3-E1 cells on zirconia discs was eva-luated on 1 and 7 days by SEM. The cell proliferation was detected on 1, 3 and 5 days by cell counting kit-8 (CCK-8). After osteogenic induction for 14 days, the relative mRNA expression of alkaline phosphatase (ALP), type Ⅰ collagen (Colla1), Runt-related transcription factor-2 (Runx2) and osteocalcin (OCN) in MC3T3-E1 cells were detected by real-time quantitative polymerase chain reaction.@*RESULTS@#The pore size [(419.72±6.99) μm] and pore depth [(560.38±8.55) μm] of 3D-Porous group were significantly larger than the pore size [(300.55±155.65) μm] and pore depth [(69.97±31.38) μm] of M-Porous group (P < 0.05). The surface of 3D-Porous group appeared with more regular round pores than that of M-Porous group. The contact angles of all the groups were less than 90°. The contact angles of 3D-Ctrl (73.83°±5.34°) and M-Porous group (72.7°±2.72°) were the largest, with no significant difference between them (P>0.05). Cells adhered inside the pores in M-Porous and 3D-Porous groups, and the proliferation activities of them were significantly higher than those of M-Ctrl and 3D-Ctrl groups after 3 and 5 days' culture (P < 0.05). After 14 days' incubation, ALP, Colla1, Runx2 and OCN mRNA expression in 3D-Porous groups were significantly lower than those of M-Ctrl and 3D-Ctrl groups (P < 0.05). Colla1, Runx2 and OCN mRNA expressions in M-Porous group were higher than those of 3D-Porous group (P < 0.05).@*CONCLUSION@#The porous surface morphology of zirconia can promote the proliferation and adhesion but inhibit the differentiation of MC3T3-E1 cells.

Method and accuracy of determining the jaw position of repositioning splint with the aid of digital technique / 北京大学学报(医学版)

OBJECTIVE@#To establish the workflow of determining the jaw position of repositioning splint with the aid of digital technique, and to evaluate the accuracy of this workflow and compare the accuracy of raising different vertical dimensions in vitro.@*METHODS@#A volunteer was recruited. The data of full-arch scans, cone beam computed tomography (CBCT) image and ultrasonic jaw motion tracking of the volunteer were acquired. The full-arch scans were merged with the CBCT image, which were then matched to the jaw motion tracking reference system. The jaw position of repositioning splint was determined when the anterior teeth opening was 3 mm and the condyle was in centric relation of the fossa in the sagittal plane. A digital repositioning splint was designed in the software based on virtual articulator and fabricated with additive manufacturing technique. After the splint was tried in, another CBCT image was taken and a qualitative analysis was conducted to compare the position of condyle between these two CBCT images. In the in vitro study, standard dental plaster casts with resin ball markers attached to the base were mounted onto a fully adjustable articulator in the intercuspal position. The dental casts were scanned by an extraoral scanner to establish digital models. The ultrasonic jaw motion tracking device was used to obtain simulated jaw movements on the articulator, which was repeated for three times. The digital models and data of jaw movements were merged in one coordination with the aid of bite forks. The jaw position of repositioning splint was determined by adjusting data of jaw movements, each of which was used to determine three vertical jaw positions 4 mm, 5 mm, and 6 mm with the horizontal jaw position of protrusion 2 mm. The virtual articulators with differently adjusted jaw movements were applied in designing repositioning splints, and the final repositioning splints and virtual jaw relationships were exported in STL format. Then the repositioning splints were fabricated with additive manufacturing technique and tried in plaster casts on the mechanical articulator, which were scanned and the jaw relationships on the mechanical articulator were exported later. The virtual jaw relationships and scanned jaw relationships were registered according to lower models and displacement of upper models was calculated. Ball markers were fit to acquire the coordinates of centers and absolute difference values of centers along three coordinating axes X, Y, and Z were calculated. One-way analysis of variance was conducted using SPSS 18.0 software to compare deviations of the three different vertical jaw relationships in two-side test and the significance level was 0.05.@*RESULTS@#With the aid of multi-source data fusion and individualized jaw motion, the clinical workflow of determining jaw position of repositioning splint was preliminarily established. The designed jaw position was realized on the right and the condyle was more inferior than the designed position on the left. Both displacement of the upper models and absolute difference values of centers showed no significant differences (P>0.05) in different vertical jaw dimensions. The displacement of the upper models was (0.25±0.04) mm. The absolute difference values of centers along the three coordinating axes X, Y, and Z were respectively (0.08±0.01) mm, (0.30±0.02) mm, and (0.21±0.04) mm.@*CONCLUSION@#A novel method of determining the jaw position of repositioning splint with the aid of digital technique is established. It is proved to be feasible by try-in after multi-data fusion, computer-aided design and computer-aided manufacturing. As is shown in vitro, it is accurate to apply this method in adjusting jaw position. Further clinical trial will be designed to evaluate its clinical effect.

In vitro evaluation of the application of digital individual tooth tray in the impression making of mandibular full-arch crown abutments / 北京大学学报(医学版)

OBJECTIVE@#To establish a method for the production of digital individual tooth tray based on three-dimensional (3D) scan, computer-aided design (CAD) and 3D printing, and to evaluate the effect of impression taking of full-arch crown abutments by digital individual tooth tray technique and conventional method through in vitro study.@*METHODS@#The full crown preparation was performed on all the fourteen resin teeth in a standard model of mandibular dentition. The surface data of prepared abutments was collected by 3D scanning. A new project was created in a dental CAD software including all the fourteen teeth in the mandibular dentition. The design modules of anatomy crown and coping were selected for each tooth. The dentition was divided for three sections: right posterior teeth, anterior teeth, and left posterior teeth areas. The connector design was added between the abutments within the same section. The scanned data of the abutments were imported. The occlusal plane and insertion path were determined. The position of margin line, as well as the shape of anatomy crown and connector as the main body of the individual tooth tray were designed for each abutment. The shape of coping was generated as the space for holding the impression material. The finalized data of the main body was imported into Geomagic software. The retentive attachment was added at the external surface and the tissue stop was formed at the internal surface. The completed individual tooth tray was manufactured by 3D printing with resin material. The data of full-arch crown abutments were modified and printed. The conventional dentition trays A and B, as well as digital individual tooth tray were designed and printed for four copies each. The polyether impressions of the full-arch abutments were made by conventional one-step method using dentition tray A, and by sectional-impression technique using digital individual tooth tray and dentition tray B for four times each. The time spent for each impression taking and the numbers of defects at the shoulder and axial/occlusal surface in each impression were recorded. The impression quality of each abutment was evaluated. The overall quality distribution and the pass rate of abutments between the two methods were analyzed.@*RESULTS@#The impressions made by conventional method had more defects at shoulder than those made by digital individual tooth tray technique. No difference of the number of defects at axial/occlusal surface between the two methods was observed. The digital individual tooth tray technique for the full-arch abutment impression exhibited higher pass rate of abutments and better quality of impression, compared with conventional methods.@*CONCLUSION@#A new method for the production of digital individual tooth tray based on digital scanning, CAD and 3D printing was established. Compared with conventional method, using digital individual tooth tray technique for impression taking of full-arch abutments can achieve better effect.

Characteristics of orofacial operant test for orofacial pain sensitivity caused by occlusal interference in rats / 北京大学学报(医学版)

OBJECTIVE@#To compare the orofacial pain sensitivity with operant test and mechanical hyperalgesia with von Frey filaments of two orofacial pain models (EOI: experimental occlusal interference; pIONX: partial infraorbital nerve transection). To investigate the operant and evoked characteristics of EOI-rats.@*METHODS@#The orofacial operant behaviors were tested by Ugo Basile Orofacial Stimulation Test System. The mechanical thresholds of vibrissal pads were tested by von Frey filaments. Male Sprague-Dawley rats were randomly divided into eight groups: von Frey group: sham-EOI, EOI, sham-pIONX, pIONX (sham: sham-operated group); operant test group: sham-EOI, EOI, sham-pIONX, pIONX (sham: sham-operated group). The mechanical thresholds and orofacial operant behaviors were tested on pre-operation and post-operation days l, 3, 7, 10, 14 and 21.@*RESULTS@#In pIONX of von Frey group, the mechanical withdrawal threshold decreased from days 1 to 21 (P<0.05), peaking from days 7 to 10, and lasted until the end of the experiment. There was no significant difference between the bilateral sides. In pIONX of operant test group, the total contact time decreased from days 10 to 21 (P<0.05), peaking from days 10 to 14, and lasted until the end of the experiment. In EOI of von Frey group, the mechanical withdrawal threshold decreased from days 3 to 21 (P<0.05), peaking on day 7, and lasted until the end of the experiment. There was no significant difference between the bilateral sides. In EOI of operant test group, the total contact time decreased from days 1 to 21 (P<0.05), peaking from days 7 to 10, and lasting until the end of experiment.@*CONCLUSION@#Orofacial operant test is a stable method to evaluate orofacial pain behaviors, which could discriminate the feature of neuropathic and EOI orofacial pain. In these two animal models, both of the operant behaviors and the mechanical hyperalgesia exhibited different time courses. Orofacial operant test provides a novel method for evaluating the orofacial pain sensitivity and studying the orofacial pain mechanism thoroughly.

Quantitative analysis of occlusal changes in posterior partial fixed implant supported prostheses / 北京大学学报(医学版)

OBJECTIVE@#To analyze changes in occlusal force distribution and occlusal contact in posterior partial fixed implant-supported prostheses over time, and to provide reference for the precise occlusion design, adjustment and maintenance of implant prostheses.@*METHODS@#According to certain inclusion and exclusion criteria, patients were recruited from partially edentulous patients who had received implant-supported single crown or fixed bridge in the posterior region. The patients were collected since the implant prostheses settling and scheduled for the routine examination of implant prostheses and the occlusal examinations of complete dentition after 2 weeks, 3, 6, and 12 months. Occlusal examinations were taken with the articulating papers and T-Scan III (Tekscan, South Boston, USA), which could check and measure the occlusal contact condition of complete dentition. The occlusion time and relative occlusal forces of implant prostheses, mesial adjacent teeth and control teeth were recorded at the same time.@*RESULTS@#Thirty-seven posterior partial fixed implant prostheses in 33 patients (17 women and 16 men, aged 24-70 years) were followed up for 3-12 months (average 8.3 months). At baseline, the relative occlusal forces of implant prostheses were significantly lower than those of the corresponding control teeth (P<0.001). However, after 3 months, the relative occlusal forces of implant prostheses had significantly increased (P<0.05), while control teeth decreased significantly (P<0.05), resulting in no statistical significance between them. The implant prostheses occlusion time ratio also increased significantly from 2 weeks to 3 months (P<0.05). There was no significant difference from the third month to the sixth month, or from the sixth month to the twelfth month (P>0.05).@*CONCLUSION@#Light contact and time-delayed occlusion of posterior implant prostheses changes significantly in the first three months after settling implant prostheses. These changes mainly include the advance of the time point of the implant prosthesis to start the occlusion contact, and the increase of the occlusal force of the implant prosthesis. The occlusion of posterior implant prostheses should be carefully monitored at end of the third month follow-up clinically.

Effect of long-term resistance exercise on masseter muscle mechanical hyperalgesia in rats / 北京大学学报(医学版)

OBJECTIVE@#To investigate the effect of long-term resistance exercise of hindlimb on mechanical hyperalgesia of bilateral masseter muscle in rats with or without occlusal interference.@*METHODS@#Six-teen male Sprague-Dawley rats (220-250 g) were randomly divided into four groups: the naive control group, naive exercise group, occlusal interference control group, and occlusal interference exercise group. The rats in occlusal interference groups (occlusal interference control group and occlusal interference exercise group) obtained occlusal interference with 0.4 mm-thick crowns bonded to the right maxillary first molars. The rats in exercise groups (naive exercise group and occlusal interference exercise group) performed squat-type resistance exercises for 30 minutes, once a day, 5 days/week, lasting for 14 weeks. Resistance exercise was recorded every day. Mechanical withdrawal thresholds of bilateral masseter muscle were tested per week by use of modified electronic von-frey anesthesiometer. The rats were weighed per week. After the 14-week exercise, the muscle strength of the hindlimb was tested with a grip strength meter. Muscle (gastrocnemius and soleus) weight of bilateral hindlimb and length of bilateral fibula of the rats were obtained. The muscle-mass/body-mass ratios and muscle-mass/fibula-length ratios were calculated.@*RESULTS@#Between the naive control group and naive exercise group, there was no significant difference in the mechanical withdrawal thresholds of bilateral masseter muscle for the 0-4 weeks (P>0.05). During the 5-14 weeks, the mechanical withdrawal thresholds of the rats in the naive exercise group were higher than those in the naive control group (P<0.05). Between the occlusal interference control group and occlusal interference exercise group, there was no significant difference in the mechanical withdrawal thresholds of bilateral masseter muscle for the 0-6 weeks (P>0.05). During the 7-14 weeks, the mechanical withdrawal thresholds of rats in the naive exercise group were higher than those in the occlusal interference control group (P<0.05). After the 14week exercise, the body mass of the rats in nonexercise group (the naive control group and occlusal interference control group) were larger than those in exercise group [(462±6) g vs. (418±14) g, P<0.05]. And the muscle strength of hindlimb of the rats in exercise group were bigger than those in non-exercise group [(6.75±0.13) N vs. (5.41±0.15) N, P<0.01].@*CONCLUSION@#long-term resistance exercise can increase mechanical withdrawal thresholds of the bilateral masseter muscle in rats with or without masseter muscle mechanical hyperalgesia.

Preliminary study on tactile function of implant-supported single crowns / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To measure passive tactile threshold of implant-supported single crowns (ISSC) in six orthogonal orientations, to analyze impact factors, and to guide the occlusal adjustment in a personalized manner.</p><p><b>METHODS</b>The passive tactile thresholds of 24 implant-supported single crowns (5 maxillary anterior teeth, 7 maxillary posterior teeth and 12 mandibular posterior teeth) from 19 ISSC patients (8 men and 11 women, from 25 years old to 56 years old) were measured in six orthogonal orientations (four horizontal orientations of labial or buccal, lingual, mesial and distal, and two axial orientations of apical and coronal) using a digital test system for tactile function of teeth.SPSS 19.0 for windows was used to analyze impact factors, using double-sided test, with a significance level of 0.05. Paired-samples t test was used to test the difference between implant-supported single crowns and the controlled natural teeth, and between different time points. One-way ANOVA was used to test the difference between different orientations, maxilla-mandibular anterior-posterior, and men-women.</p><p><b>RESULTS</b>The passive tactile thresholds of ISSC and control teeth were (1282 ± 709) and (40 ± 40) mN respectively. The difference was of statistical significance (P < 0.001). The passive tactile thresholds of buccal-lingual, mesial-distal and axial of ISSC were (1334 ± 696), (1102 ± 605) and (1412 ± 791) mN respectively, of which, the difference between mesial-distal and axial was of statistical significance (P < 0.05). The passive tactile thresholds of ISSC of maxillary anterior teeth, posterior teeth and mandibular posterior teeth were (1003 ± 616), (1302 ± 620) and (1386 ± 769) mN respectively, of which, the difference between maxillary anterior teeth and posterior teeth was of statistical significance (P < 0.05). The passive tactile thresholds of ISSC of men and women were (1751 ± 784) and (946 ± 393) mN respectively, the difference was of statistical significance (P < 0.001). The passive tactile thresholds of ISSC of one-week and one-month after wearing the teeth were (1421 ± 826) and (1411 ± 814) mN respectively, the difference was of no statistical significance (P > 0.05).</p><p><b>CONCLUSIONS</b>The passive tactile threshold of ISSC was more than 65 times as much as that of the natural teeth. There was statistical significance between different orientations, between maxillary anterior and posterior teeth, and between men and women. No statistical significance was found between maxillary and madibular posterior teeth and between one-week and one-month after wearing the teeth.</p>

Classification and clinical characteristics of masticatory myospasm / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To determine the classification of masticatory myospasm by analyzing characteristics of clinical appearances.</p><p><b>METHODS</b>Thirty-six cases of masticatory myospasm from 2000 to 2010 were included. The clinical data of these patients were analyzed, including patient information, patient history, clinical characteristics, severity and the frequency of myospasmodic movement, electromyogram (EMG), and the efficacy of botulinum toxin injection treatment.</p><p><b>RESULTS</b>There were 11 males and 25 females, aged from 15 to 71. According to the clinical manifestation and EMG findings, patients could be divided into two groups: 18 cases were classified as jaw closing type which involved masseter and/or temporalis muscles presenting as trismus and acute pain, the other 18 cases were jaw opening type which involved lateral pterygoid muscles complaining difficulty in jaw closing and teeth clenching. The jaw closing type was often seen in patients of 20 to 50 years old, the jaw opening was frequently seen in patients over 50 years old. Jaw closing type was attacked intermittently and unilaterally, but jaw opening was often attacked continually and bilaterally. The rating scale of the severity of spasmodic movement was not different between the two types, but the frequency of spasmodic attack was much higher for jaw opening type (P < 0.05). The EMG of jaw closing type was classified into persistent, rhythmic and irregular type. The EMG of jaw opening type was classified into spontaneous and exercise-induced type. Twelve cases were treated by botulinum toxin injection that could significantly relieve symptoms.</p><p><b>CONCLUSIONS</b>Masticatory myospasm can be classified into jaw closing and jaw opening types. Jaw closing type involves masseter and/or temporalis muscles and jaw opening type involves lateral pterygoid muscles. Botulinum toxin injection was the most effective therapy for the masticatory myospasm.</p>

Measurement of tactile threshold of natural teeth and its clinical significance / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To measure passive tactile threshold of natural teeth in six orthogonal orientations, to analyze impact factors, and to guide the occlusal adjustment in a personalized manner.</p><p><b>METHODS</b>The passive tactile thresholds of 218 natural teeth from 20 healthy subjects were measured in six orthogonal orientations using a digital test system for tactile function of teeth. The subjects were composed of 10 males and 10 females, with a mean age of 25 years. The natural teeth were tested from central incisors to first molars in maxilla and mandible. The passive tactile thresholds of teeth were measured respectively in the four horizontal orientations of labial (buccal), lingual, mesial and distal, and the two axial orientations of apical and coronal. The multilevel modeling (MLM) was used to analyze impact factors.</p><p><b>RESULTS</b>The passive tactile thresholds of anterior teeth, premolars and molars were 16 (18), 38(57) and 105 (115) mN respectively. The difference between subjects was of statistical significance (P < 0.05). The three factors of tooth, gender and orthogonal orientation were disclosed to influence the passive tactile threshold of natural teeth (P < 0.01). The influence level of the factors was tooth > gender > orthogonal orientation.</p><p><b>CONCLUSIONS</b>A force level of 10 mN could be detected by natural teeth. There was statistical difference in the passive tactile threshold between subjects. The passive tactile threshold was affected with tooth, gender and orthogonal orientation.</p>

Electrical pain thresholds of face and finger in patients with chronic masticatory muscle pain / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To compare electrical sensory threshold (EST) and electrical pain threshold (EPT) of bilateral masseters, temporal muscles and finger region of chronic masticatory muscle pain (MMP) patients and the controls, and to analyze the mechanism of pain threshold change.</p><p><b>METHODS</b>Twelve patients with MMP and 12 matched controls participated in this study. EST and EPT of bilateral masseters, bilateral temporal muscles, and left middle finger were recorded and compared within group and between groups.</p><p><b>RESULTS</b>Compared to the controls, the EPTs of patients significantly decreased [left masseter (5.9 +/- 1.1) mA,right masseter (5.7 +/- 1.0) mA, left temporal muscle (5.3 +/- 1.4) mA, right temporal muscle (5.5 +/- 1.7) mA,finger (5.2 +/- 1.0) mA] (P < 0.001). There was no significant difference in EST between patients and the controls. No relationship was found among VAS, ESP, and EPT.</p><p><b>CONCLUSIONS</b>Decreased pain thresholds of masseters, temporal muscles and fingers in MMP indicated that peripheral sensitization was induced in MMP patients. Decreased pain threshold in patients meant that MMP might influence the central modulation of nervous system.</p>

Clinical application of anterior all-ceramic cantilevered resin-bonded fixed partial dentures / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To explore a fabricating method of incisor all-ceramic cantilevered resin-bonded fixed partial denture (RBFPD) and evaluate their clinical performances.</p><p><b>METHODS</b>All-ceramic cantilevered RBFPDs were made to replace 1 missing incisor in each of 10 patients. The RBFPDs with lingual surface retainer were made of Empress II ceramic materials and luted with resin cement. The prostheses were examined at 2 weeks, 1 year and 2 years after denture insertion. Examining criteria included: fracture of bridge, marginal adaptation, secondary caries, and color match.</p><p><b>RESULTS</b>The average follow-up period was 14. 7 months. No framework fracture and retainer debonding were observed and marginal adaptation was evaluated as good. Seven RBFPDs matched the color of adjacent teeth, and other three did not match well but within the acceptable range of tooth shade difference.</p><p><b>CONCLUSIONS</b>The results of this preliminary study suggest that the clinical performances of all-ceramic cantilevered RBFPDs are good in short-term evaluation, but their long-term success needs to be further investigated.</p>

Evaluation of trigeminal somatosensory evoked potential of patients with chronic masticatory muscle pain / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate trigeminal function of patients with chronic masticatory muscle pain (MMP) using trigeminal somatosensory evoked potential (TSEP) and analyze mechanism of changes compared to the controls.</p><p><b>METHODS</b>Twelve chronic MMP patients and 12 matched controls participated in this study. TSEPs of bilateral masseter regions and inferior alveolar nerves were measured and compared between patient and control groups. The collected waves were concluded and those with appearance rate over 75% - 100% were selected. The latencies of waves were analyzed by use of the paired t test and independent-samples t test.</p><p><b>RESULTS</b>Five stable-appearing waves were obtained and named P1, N1, P2, N2, P3. The latency of P1 was significant reduced in patients (P < 0.05). The latencies of other waves were prolonged, but only P2 and N2 in left were significantly changed (P < 0.05).</p><p><b>CONCLUSIONS</b>TSEP latencies of chronic MMP patients changed in certain regular pattern and TSEP could be used as a parameter to disclose the trigeminal system abnormalities of the patients. The reduced latency of P1 might indicate the increasing conductivity of trigeminal nerves under level of ganglion Gasseri and the prolongation of latency of P2 was possibly related to inhibitory effects of the brain stem.</p>

Influence of fiber framework design on fracture strength of posterior glass fiber-reinforced-composite resin-bonded fixed partial dentures / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To analyze influence of fiber framework design on fracture strength of posterior glass fiber-reinforced-composite resin-bonded fixed partial dentures (GFRC-RBFPD).</p><p><b>METHODS</b>Based on established three-dimensional finite element models of GFRC-RBFPD for restoring the second mandibular premolar or the first mandibular molar, traditional fiber framework design and modified fiber framework design were analyzed. Two types of load, including cusp-fossa load and buccal-lingual cusp load, were selected. Load values were 400 N on premolar and 600 N on molar respectively. The fracture strength of GFRC-RBFPD was calculated.</p><p><b>RESULTS</b>Under cusp-fossa load, the fracture strength was 1340 N for both types of fiber frameworks of premolar GFRC-RBFPD, and 864 N for traditional framework and 875 N for modified framework of molar GFRC-RBFPD. Under buccal-lingual load, the fracture strength of premolar GFRC-RBFPD was 792 N for traditional framework and 1019 N for modified framework; that of molar GFRC-RBFPD was 645 N for traditional framework and 652 N for modified framework.</p><p><b>CONCLUSIONS</b>The modified fiber framework obviously improved the strength of premolar GFRC-RBFPD and only slightly improved that of molar GFRC-RBFPD.</p>

Influence of fiber framework design on stress distribution in posterior glass fiber reinforced composite resin-bonded fixed partial dentures / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To compare the difference of stress distribution among models with different fiber frameworks.</p><p><b>METHODS</b>Four models were generated in Marc 2003 software. Four types of loads simulating normal mastication were selected. The stress within models was calculated, and output by means of graph and data.</p><p><b>RESULTS</b>There was stress concentration around connectors and retainers near connectors under cusp -fossa load, occlusal even load, and lateral load. When dentures were reinforced with fiber framework, area of stress concentration and principal stress max could decrease in comparison with pure composite resin bonded fixed partial denture. Under buccal-lingual load, there was another stress concentration around central fossa beside above two stress concentration areas. Only modified fiber framework constructed with both mesial-distal and lingual-buccal directional glass fiber could markedly reduce principal stress under buccal-lingual cusp loads.</p><p><b>CONCLUSION</b>Under 4 types of loads simulating normal mastication, three critical regions were disclosed at the area of retainers adjacent connectors, connectors and occlusal central fossa and fissures. Only modified fiber framework constructed with both mesial-distal and lingual-buccal directional glass fiber could markedly reduce stress concentration under buccal-lingual cusp loads.</p>

Mechanical properties of preimpregnated glass fiber reinforced composite resins / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the mechanical properties of two kinds of composite resins reinforced by preimpregnated glass fibers.</p><p><b>METHODS</b>Sinfony and belleGlass composite resins were used to make standard samples (25 mm x 2 mm x 2 mm) with and without glass fibers. After all specimens were stored for 24 hours in distilled water at (37 +/- 1) degrees C, the flexural strength and flexural modulus were measured on a universal test machine.</p><p><b>RESULTS</b>Both flexural strength and flexural modulus of Sinfony composite reinforced by the glass fibers became significantly increased, which were (555.76 +/- 67.31) MPa and (12.59 +/- 3.06) GPa respectively, and 4.5 and 2.5 times much more than those of the specimens without glass fibers (P = 0); the flexural modulus of belleGlass composite became significantly increased, which was (14.10 +/- 2.88) GPa, and 0.9 time much more than the specimens without glass fibers (P = 0), but the improvement of flexural strength was not significant.</p><p><b>CONCLUSION</b>Glass fibers can improve the mechanical properties of composite resins, but the reinforcement effect is different between different resins.</p>

Association of mandibular angle size with cortical thickness and residual ridge height of the edentulous mandible / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the mandible angle and to investigate the relationship of angle size to gender, age-group, cortical thickness at the mandibular angle (CTMA), height of mandibular residual body, and edentulous period in the elderly edentulous subjects.</p><p><b>METHODS</b>A total of 356 panoramic radiographs of three groups of subjects were evaluated: the young dentate group, 131 subjects (mean age: 27); the older dentate group, 97 (mean age: 64); and the elderly edentulous group, 128 (ages 76, 81, or 86). Mandibular angle size, CTMA, and height of mandibular residual body were measured from panoramic radiographs. A structured questionnaire was used to determine the history of edentulousness.</p><p><b>RESULTS</b>Difference in angle size was found between dentate men and women (P < 0.05, P < 0.001), but not between the elderly edentulous men and elderly women. The elderly edentulous subjects had larger mandibular angles than did older dentate subjects (P < 0.001). The angle size was negatively related to CTMA only among 76-year-old edentulous women (P < 0.01) and negatively associated with average height of the mandibular residual body in the edentulous men and women (P < 0.01). No association existed between angle size and duration of edentulousness.</p><p><b>CONCLUSIONS</b>Elderly edentulous subjects have large mandibular angles and the angle size is correlated with low-height of the mandibular residual body, which suggests that masticatory function of natural dentition and complete denture may influence change of the mandibular angle. The significant relationship of mandibular angle size to CTMA probably indicates the effect of systemic factors on change in the mandibular angle.</p>

The study of natural head posture in edentulous patients before and after oral rehabilitation / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To study the natural head posture (NHP) of edentulous patients compared with dentate people and to understand NHP shift immediately inserting complete dentures and three months after denture wearing.</p><p><b>METHODS</b>The NHPs of twenty edentulous patients and twenty-two dentate subjects were recorded with cephalometric technique. The NTPs of edentulous patients were exposed three times, before inserting, right after inserting and three months after inserting dentures. The NHPs of dentate subjects were recorded once as a controlled group. Six angles measured from the radiographs were evaluated for the NHP and three angles and two linear measures for the mandibular position.</p><p><b>RESULTS</b>Compared with dentate subjects, the craniomandibular angles of the edentulous patients increased and the camber of the cervical columns decreased, but changes of the NHP were not significant. The mandible showed a significant upward moving (P < 0.05) and an insignificant forward moving. At the time of denture insertion, the camber of the cervical columns significantly increased (P < 0.05). Three months after using the dentures, the craniomandibular angles of the patients obviously decreased. (P < 0.05).</p><p><b>CONCLUSION</b>The shift of NHP after denture inserting does exist. The shifted NHP of the patients with dentures is a new balanced posture and closer to the normal position than the NHP of them without dentures.</p>

A comparative study of masticatory efficiency and mandibular movement pattern among patients with CD, COD and IOD / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To compare the masticatory efficiency and the character of mandibular movement trace of the patients with complete denture (CD), complete overdenture (COD) and implant-supported overdenture (IOD).</p><p><b>METHODS</b>A total of 42 subjects were rehabilitated with CD, COD and IOD respectively and wore the dentures at least half a year. Each study group was composed of 14 subjects. The masticatory function of patients were investigated by means of masticatory efficiency and mandibular movement trace. The characters of mandibular movement trace were evaluated from four aspects: the regulation of chewing cycle, centralization of end traces, the type of the contact slides and the type of the trace on the frontal plane.</p><p><b>RESULTS</b>The average chewing efficiency of almond and jujube in the IOD patients was higher than that in the CD group (P < 0.01), and the chewing efficiency of almond in COD group was higher than that in the CD group (P < 0.01). In the IOD group, there were more patients with regular chewing cycle (P < 0.05) and centralized end traces (P < 0.01) in mandibular movement than those in the CD group and COD group.</p><p><b>CONCLUSIONS</b>IOD and COD benefit the fully or partially edentulous patients with a relatively good masticatory function. The patients with IOD have more regular mandibular movement than those with CD.</p>