A novel tray for recording maxillomandibular relationship of edentulous patients based on dimensional surveying of complete dentures / 北京大学学报(医学版)

OBJECTIVE@#To measure the dimensional data of complete dentures and to design a novel tray for recording maxillomandibular relationship of edentulous patients.@*METHODS@#For the measurement, 100 pairs of complete dentures from the clinic were surveyed for the following parameters: a1, the distance between the middle fossa of the upper left and right first molars; a2, the anterior-posterior distance between the middle fossa of the upper first molars and the incisal edge; a3, the width of the upper denture; a4, the anterior-posterior length of the upper denture; a51, the height from the mesio-lingual cusp of the right upper first molar to the saddle surface; a52, the height from the central fossa of the right lower first molar to the saddle surface; a6, the height from the notch of the upper lip frenulum to the upper central incisor edge; a7, the least thickness of the labial saddle base in the upper central incisor region. Based on the data, the trays with different sizes were designed and fabricated, and the key parameters were: b1, the distance between the foramina of screw posts, b2, the anterior-posterior distance between the foramina of the screw posts and the incisal edge; b3, the width of the tray; b4, the anterior-posterior length of the tray; b51, the height of the posterior platform with the screw nut; b52, the height of the screw post; b6, the height of the anterior tray handle; b7, the thickness of the anterior tray handle.@*RESULTS@#The minimum, average and maximum data for each parameter were (in millimeter): a1: 37.1, 44.5, and 59.6; a2: 22.6, 29.0, and 38.1; a3: 48.5, 58.2, and 76.6; a4: 37.4, 50.8, and 61.0; a51: 5.6, 9.5, and 14.7; a52: 3.8, 9.9, and 18.8; a6: 8.9, 16.6, and 24.7; a7: 1.2, 2.8, and 5.9. Based on the data, the trays in small, medium and large sizes were designed and fabricated. In clinical application, the putty silicone rubber impression material was used to reline the tray, meanwhile the posterior platform and anterior tray handle were set as the occlusal plane, then the screw posts were added and adjusted till the proper vertical dimension, after that, the putty silicone rubber impression material was added around the screw posts to record the horizontal maxillomandibular relationship, finally, the anterior surface of the tray handle was used to record the midline of the face and lower edge of the upper lip at rest and with smile.@*CONCLUSION@#The dimensional data offered reference for the analysis of restoration space in edentulous patients. The tray designed and fabricated in this study may serve as a new tool for recording the maxillomandibular relationship.

Detection of EDA gene mutation and phenotypic analysis in patients with hypohidrotic ectodermal dysplasia / 北京大学学报(医学版)

OBJECTIVE@#To detect the ectodysplasin A (EDA) gene mutation in patients with hypohidro-tic ectodermal dysplasia (HED), and to analyze the distribution pattern of missing permanent teeth and the systemic manifestation of HED patients with EDA gene mutation.@*METHODS@#Twelve HED families were enrolled from clinic for genetic history collection, systemic physical examination and oral examination. Peripheral blood or saliva samples were collected from the probands and the family members to extract genomic DNA. PCR amplification and Sanger sequencing were utilized to detect the EDA gene variations, which were compared with the normal sequence (NM_001399.5). The functional impact of EDA gene variants was then evaluated by functional prediction of mutation, conservation analysis and protein structure prediction. The pathogenicity of each EDA gene variation was assessed according to the stan-dards and guidelines of the American College of Medical Genetics and Genomics (ACMG). The systemic phenotype and missing permanent tooth sites of HED patients with EDA gene mutations were summarized, and the missing rate of each tooth position was analyzed and compared.@*RESULTS@#Eight out of twelve HED families were identified to carry EDA gene mutations, including: c.164T>C(p.Leu55Pro); c.457C>T (p.Arg153Cys); c.466C>T(p.Arg156Cys); c. 584G>A(p.Gly195Glu); c.619delG(p.Gly207Profs*73); c.673C>T(p.Pro225Ser); c.676C>T(p.Gln226*) and c.905T>G(p.Phe302Cys). Among them, c.164T>C(p.Leu55Pro); c.619delG(p.Gly207Profs*73); c.673C>T(p.Pro225Ser); c.676C>T(p.Gln226*) and c.905T>G(p.Phe302Cys) were novel mutations. The HED patients with EDA gene mutations in this study were all male. Our results showed that the average number of missing permanent teeth was 13.86±4.49, the average number of missing permanent teeth in the upper jaw was 13.14±5.76, the missing rate was 73.02%. And in the lower jaw, the average number of missing permanent teeth was 14.57±3.05, the missing rate was 80.95%. There was no significant difference in the number of missing teeth between the left and right sides of the permanent dentition (P>0.05). Specifi-cally, the maxillary lateral incisors, the maxillary second premolars and the mandibular lateral incisors were more likely to be missing, while the maxillary central incisors, the maxillary and mandibular first molars had higher possibility of persistence.@*CONCLUSION@#This study detected novel EDA gene pathogenic variants and summarized the distribution pattern of missing permanent teeth of HED patients, thus enriched the variation and phenotype spectrum of EDA gene, and provided new clinical evidence for genetic diagnosis and prenatal consultation.

Detection and functional analysis of BMP2 gene mutation in patients with tooth agenesis / 北京大学学报(医学版)

OBJECTIVE@#To screen for BMP2 mutation with functional impact in patients with congenital tooth agenesis and to make oral and skeletal phenotype record and functional analysis with in vitro experiments.@*METHODS@#We enrolled eighteen patients with congenital tooth agenesis. The medical and dental history was collected,and clinical and dental examinations including the X-ray examination of oral-facial and skeletal bone were performed for the phenotypic analysis. Blood samples were collected to extract DNA and whole exome sequencing was conducted. The genes involved in oral-facial development and congenital skeletal diseases were investigated for mutation screening. The mutations with functional impact were then investigated. In one patient, the BMP2 mutation with putative functional impact was selected for functional analysis. Wild type and mutant BMP2 plasmids with green fluorescent protein (GFP) tag were constructed and transfected into HEK293T cells. Subcellular protein distribution was observed under laser scanning confocal microscope. The activation of downstream SMAD1/5/9 phosphorylation by BMP2 was detected by Western blotting to investigate the functional impact and genetic pathogenicity.@*RESULTS@#BMP2 mutation NM_001200.3:c.393A>T (p.Arg131Ser), rs140417301 was detected in one patient with congenital tooth agenesis, while for other genes involved in oral-facial development and congenital skeletal diseases, no functionally significant mutation was found. The proband's parents didn't carry this mutation. The father had normal dentition, while the mother lacked one premolar, and both the parents showed normal palate and maxilla. The patient also had maxillary hypoplasia in both sagittal and coronal planes, palatal dysmorphology, and malocclusion, and was diagonsed with osteopenia after the X-ray examnination of his skeletal bone. Functional analysis showed this mutation had normal subcelluar localization but reduced phosphorylation of SMAD1/5/9 (reduction by 32%, 22%, and 27% in three independent replicates). Taken together with family co-segregation, this mutaion was considered as "likely pathogenic".@*CONCLUSION@#BMP2 mutation c.393A>T (p. Arg131Ser) affects bone morphogenetic protein signaling activity, and may affect the number of teeth, growth of maxilla and palate, and bone mineral density.

Analysis of edge morphology of partial veneers made by different processing techniques and materials / 北京大学学报(医学版)

OBJECTIVE@#To compare the edge morphology of partial veneers made of different materials by slurry molding, heat-pressed and computer aided design/computer aided manufacturing (CAD/CAM) techniques.@*METHODS@#Thirty premolars with smooth surface and intact enamel were selected and randomly divided into five groups, 6 specimens for each group. Group A were made from feldspathic porcelain (Noritake®) by slurry molding, while Group B were made from lithium disilicate glass ceramic (IPS E.max® Press) by heat-pressed. Group C/D/E were respectively made from feldspar porcelain block (VITA Mark II®), zirconia-reinforced glass ceramic (VITA Suprinity®) and hybrid ceramic with a ceramic-polymer network (VITA Enamic®) by CAD/CAM techniques. All the partial veneers luted with light-cured composite resin. Then the partial veneers were trimmed and polished to achieve the smooth finishing margin, clinical polishing sets were used according to the product descriptions. Scanning electron microscope (SEM) was used to observe the edge morphology of prostheses and the exposure of resin cements.@*RESULTS@#The smooth surface and knife-like edge of the partial veneers could be obtained after bonding, trimming and polishing. The edges of Group A were slightly rough and the width of the exposed adhesive was (106.00±9.17) μm. In Group B, the edges were smoother than Group A, and the exposed wide adhesive strip was visible, which was (138.33±20.59) μm. In Group E, the edges were smooth too, and the width of exposed adhesive strip was (186.00±5.66) μm. The edges of Group C and Group D were rough and uneven, and the adhesive was rarely exposed, they were (50.67±7.51) μm and (65.67±17.90) μm. There were all significant differences between two groups, except Group C and Group D.@*CONCLUSION@#After trimming and polishing in accordance with clinical procedures, the expected knife-like edge can be obtained in all groups. The width of the exposed resin adhesive of each group is different, the order: Mark II/Suprinity < Noritake < E.max Press < Enamic. The edge morphology of partial veneers in different processing technic and materials are different.

Oral hygiene maintenance of locator attachments implant overdentures in edentulous population: A longitudinal study / 北京大学学报(医学版)

OBJECTIVE@#To investigate the oral hygiene status of edentulous patients with locator attachments implant overdentures (IOD) and to analyze the relationship among daily hygiene behavior, oral hygiene status and peri-implant diseases.@*METHODS@#Edentulous patients who received IOD treatment with locator attachments from January 2012 to May 2016 were recruited. Clinical and radiographic examinations were conducted to assess the peri-implant tissue status. Modified plaque index (mPLI), sulcus bleeding index (SBI), gingival index (GI), and probing depth (PD) were recorded and peri-implant marginal bone loss (MBL) was measured using paralleling projection technique. Patients' peri-implant oral hygiene maintainence habits were investigated. The correlation between peri-implant diseases and oral hygiene status and behaviors was analyzed.@*RESULTS@#Fifty patients (125 implants) with an average follow-up time of 22 months (6-54 months) were enrolled. The mean values of mPLI, SBI, and GI were 1.4±1.2, 0.8±0.7, and 0.7± 0.6, respectively. Average PD was (2.2±0.7) mm. Mesial and distal maginal bone resorptions were (1.1±1.1) mm and (0.9±0.9) mm, respectively. The prevalance of mucositis and peri-implantitis of the implants were 49.6% and 0. The prevelance of mucositis in the patients with poor oral hygiene (mPLI≥2) was 11.9 times as much as that of those with adequate oral hygiene (mPLI<1). The patients who performed oral hygiene procedure on attachments at least twice a day achieved much lower mPLI scores than those who cleaned less than twice a day.@*CONCLUSION@#Oral hygiene condition in the group of patients with implant overdentures was poor, and it contributed to increased risk of peri-implant mucositis. The prevelance of musositis of the paitients with poor oral hygiene was 11.9 times as much as that of those with proper oral hygiene. Patients wearing IOD should pay more attention to the hygiene of the attachments.

Influence of implants prepared by selective laser melting on early bone healing / 北京大学学报(医学版)

OBJECTIVE@#To evaluate the influence of the rough surface of dental implants prepared by selective laser melting (SLM) on early bone healing around titanium implants.@*METHODS@#A total of sixteen titanium implants were involved in our research, of which eight implants were prepared by SLM (TIXOS Cylindrical, Leader-Novaxa, Milan, Italy; 3.3 mm×10 mm, internal hex) and the other eight were sandblasted, large-grit and acid-etched (SLA) implants (IMPLUS Cylindrical, Leader-Novaxa, Milan, Italy; 3.3 mm×10 mm, internal hex). All of the dental implants were inserted into the healed extraction sockets of the mandible of two adult male Beagle dogs. Half of the dental implants were designed to be healed beneath the mucosa and the other half were intended to be healed transgingivally and were immediately loaded by acrylic resin bridge restoration. Three types of tetracycline fluorescent labels, namely calcein blue, alizarin complexone and calcein, were administered into the veins of the Beagle dogs 2, 4, and 8 weeks after implant placement respectively for fluorescent evaluation of newly formed bone peri-implant. Both Beagle dogs were euthanized 12 weeks after implant insertion and the mandible block specimens containing the titanium implants and surrounding bone and soft tissue of each dog were carefully sectioned and dissected. A total of 16 hard tissue slices were obtained and stained with toluidine blue for microscopic examination and histomorphometric measurements. Histological observation was made for each slice under light microscope and laser scanning confocal microscope (LSCM). Comparison on new bone formation around titanium implants of each group was made and mineral apposition rate (MAR) was calculated for each group.@*RESULTS@#Dental implants prepared by selective laser melting had achieved satisfying osseointegration to surrounding bone tissue after the healing period of 12 weeks. Newly formed bone tissue was observed creeping on the highly porous surface of the SLM implant and growing into the pores of surface structure. Higher MAR values were shown for SLM implants compared with SLA implants (P<0.01).@*CONCLUSION@#Dental implants prepared by selective laser melting could promote early bone healing and improve mineral apposition rate.

Genetic variants analysis and histological observation of teeth in a patient with hereditary opalescent dentin / 北京大学学报(医学版)

OBJECTIVE@#To analyze the clinical characteristics and the genetic cause of a Chinese patient with hereditary opalescent dentin, and to make an observation of the histologic and elemental features of the affected teeth.@*METHODS@#We enrolled a patient affected with hereditary opalescent dentin. The medical history was collected and clinical examinations were performed for the phenotypic analyses. The blood sample was collected for DNA extraction and PCRs of the coding sequence of DSPP were done for sanger sequencing. The teeth samples were collected for histological evaluation and elemental analysis.@*RESULTS@#The patient showed typical clinical manifestations of opalescent dentin and had enamel dysplasia and skeletal class III malocclusion. Several polymorphisms (c.727G>A, c.897A>G, c.2053_2054ins18bp, c.2548G>A, c.2645_2646ins9bp, c.2706T>C, c.2878A>G, c.3004A>G, c.3069_3086del18bp, c.3249A>C, c.3264T>C, c.3266_3400del135bp, c.3418A>G, c.3454G>A, c.3461_3462ins18bp, c.3606C>T) but no pathogenic mutations were identified in DSPP. The histological analyses of the patient's teeth showed characteristic abnormalities that were significantly different from normal teeth. The dentin tubules of the affected teeth were decreased in number and sparsed in arrangement, while in the control teeth, they were more regular. The enamel-dentin junction of the affected teeth was abnormal in its less scallopped outline compared with the control teeth under the scanning electronic microscopy. The Mg proportion of the patient's teeth (0.615 0%±0.261 6%) was lower than that of the control teeth (1.283 3%±0.322 1%), the P value was 0.040. The Ca proportion was the higher compared with the control teeth (34.865 0%±0.388 9% vs. 29.221 7%±2.248 4%), the P value was 0.015. The Ca/P ration of the patient's teeth was 1.981 2±0.019 3, which was higher than that of control teeth (1.775 9±0.111 6), the P value was 0.049. The differences of Mg, Ca proportion and Ca/P ration between the affected teeth and the control teeth were significant. The C and O proportion of the patient's teeth were lower and the P proportion was higher compared with the control teeth, however, the differences were not significant.@*CONCLUSION@#Our study of clinical manifestation analysis, genetic variants sequencing and histological observation has enlarged the phenotypic spectrum of hereditary opalescent dentin, and the genetic and histological results would contribute to further studies.

Evaluation of the fabrication deviation of a kind of milling digital implant surgical guides / 北京大学学报(医学版)

OBJECTIVE@#To evaluate the deviation of digital implant surgical guides during fabrication process in the Organical Dental Implant (ODI) system.@*METHODS@#This study included two parts. The first part was the in vitro study. A resin block with a diagnostic template was used for the planning. After cone beam computed tomography (CBCT) scanning, a surgical guide with eight implants was virtually designed using the ODI system. The guide was milled by a 5-axial numerical controlled milling machine, and an optical scanning was taken to digitalize the guide to a standard tessellation language (STL) form. The STL data were then imported into an ODI software and registered with the original design. The deviation of the sleeves between the design and the STL was measured in the ODI software and set as the golden standard. Then the ODI examination table was used to measure the deviation of the guide during fabrication. Examiners A and B measured 10 times separately. The reliability and the validity of the examination table was calculated. The second part was the in vivo study: The deviation during fabrication of 12 guides designed and fabricated by the ODI system were measured using the examination table.@*RESULTS@#The standard deviation of the deviation measured using the examination table by examiners A and B were all below 0.40 mm (for the shell reference points) and 0.71 degree (for the angles). No significant difference was found between the two examiners for any implant sites. The result of the examination table was larger than that of the software for the shell reference point (t-test, P<0.05), but no significant difference was found for the angle deviation (t-test, P>0.05). The 45 implants positions in the 12 guides for the in vivo study were examined using the examination table. The deviations at the shell reference points were (1.06±0.29) mm (0.42-1.75 mm), and at the implant tip were (1.12±0.48) mm (0.41-2.44 mm). The angle deviations were (1.42±0.70) degree (0.29-2.96 degree).@*CONCLUSION@#Deviation is unavoidable during the fabrication process of the guides. The examination table of the ODI system is a reliable and valid tool to measure the deviation during fabrication of the ODI guides. More studies should be designed to research the relationship between the fabrication deviation and the implant insertion deviation.

Short-term clinical observation of modified resin-bonded fixed partial denture utilizing tooth undercuts / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To observe a short-term clinical result of modified resin-bonded fixed partial denture(MRBFPD) utilizing tooth undercuts.</p><p><b>METHODS</b>One hundred and twenty-nine patients received restoration and totally 196 missing teeth were restored with 148 MRBFPD. According to the positions of abutments in the dental arch, all the MRBFPD were divided into three groups, namely anterior prostheses (40), posterior prostheses (95) and prostheses spanning anterior and posterior (13). The prostheses were examined at 2 weeks, 1 month, 3 months, 6 months, and every year after denture delivery. Retention and marginal integrity of MRBFPD, sensibility, secondary caries and gingival bleeding index were clinically evaluated. The evaluation results were graded as good, acceptable, and bad according to modified United States Public Health service (USPHS) criteria. Survival in this study was defined at two levels: "complete" survival (survival without any debonding), and "functional" survival (survival including loss of retention on one occasion and successful rebonding of the original MRBFPD without further debonding).</p><p><b>RESULTS</b>The average follow-up period was 26 months. Fifteen prostheses failed and were rated as bad with USPHS criteria, and ten prostheses were evaluated as "acceptable" because the gingival bleeding index has been rated as 3 or more at one appointment but reduced to 1 or 0 after treatment. The results of the other 123 prostheses were evaluated as "good". The "complete" survival rates were 80% (32/40) for anterior prostheses, 11/13 for prostheses spanning anterior and posterior, and 95% (90/95) for posterior prostheses, while the "functional" survival rates were 80% (32/40), 11/13 and 99% (93/95) respectively. The "complete" survival rate of posterior prostheses was statistically higher than that of anterior prostheses (χ(2) = 5.433, P < 0.05). The "functional" survival rate of posterior prostheses was not only higher than that of anterior prostheses (χ(2) = 13.179, P < 0.01)but also higher than that of prostheses spanning anterior and posterior (χ(2) = 4.143, P < 0.05) statistically.</p><p><b>CONCLUSIONS</b>The results of this preliminary study suggest that short term survival rate of MRBFPD in posterior area was statistically better than that in anterior area. The outstanding advantage of MRBFPD is the minimum need of dental tissue reduction. However, their long-term success needs further investigation.</p>

Adoption of the condyle position of patients with extensive tooth wear during occlusal rehabilitation / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the adoption of the condyle position of patients with extensive tooth wear during occlusal rehabilitation, and the correlation between increased vertical dimensions and the changes of joint spaces.</p><p><b>METHODS</b>Twenty-seven patients (five from Beifang hospital, others from Peking University School and Hospital of Stomatology) with extensive tooth wear were selected and received occlusal rehabilitation treatment. The radiographs of standard Schüllers position were taken before treatment (stage 1), 1 month following delivery of temporary restoration (stage 2), and 1 month following delivery of permanent restoration (stage 3).</p><p><b>RESULTS</b>The superior, anterior and posterior joint spaces were (3.24 ± 0.16), (2.06 ± 0.11), (1.89 ± 0.13) mm at stage 1; (3.61 ± 0.15), (1.94 ± 0.10), (2.52 ± 0.11) mm at stage 2; (3.49 ± 0.19), (1.93 ± 0.10), (2.40 ± 0.13) mm at stage 3. The posterior joint spaces at stage 2 and stage 3 were significantly larger than that at stage 1(P < 0.01). The superior spaces at stage 2 were significantly larger than that at stage 1 (P < 0.05). No correlations between the increased vertical dimensions and the changes of joint spaces were found in the three stages (P > 0.05).</p><p><b>CONCLUSIONS</b>The condyle positions in the patients with extensive tooth wear changed after occlusal rehabilitation.</p>

Inhibition of retinoblastoma binding protein 2 promotes osteogenic differentiation of human adipose-derived stromal cells / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To explore the effect of retinoblastoma binding protein 2 (RBP-2), a histone H3K4 demethylase, on osteogenic differentiation of human adipose-derived stromal cell (hASC).</p><p><b>METHODS</b>According to the GenBank sequence information of RBP-2, four different small interfering RNAs (siRNA) targeting RBP-2 gene were designed and the corresponding short hairpin RNAs (shRNA) were cloned into pLL 3.7 lentivirus RNA interference vector. The lentivirus with RBP-2-siRNA was packaged in 293T cells. The effective sequence was examined and selected by Western blotting and real-time PCR. The lentiviruses with efficient knockdown effects were used to infect hASC. On the 14th day after osteogenic differentiation, alkaline phosphatase (ALP) activities of hASC were quantitatively tested and at the same time, ALP staining and alizarin red staining were performed to assess the difference of osteogenic differentiation between the knockdown group and the control group.</p><p><b>RESULTS</b>The recombinant lentivirus siRNA targeting RBP-2 was successfully constructed and the expression of RBP-2 mRNA and protein were dramatically suppressed by infection with RBP-2-siRNA lentivirus. On the 14th day after osteogenic induction, ALP activity of hASC in the knockdown group [(299.2 ± 22.7), (224.3 ± 17.7) U/g] was much stronger than that in the control group [(129.9 ± 12.9) U/g, P < 0.05] and the same result was achieved for the ALP staining and alizarin red staining.</p><p><b>CONCLUSIONS</b>The constructed RBP-2-siRNA lentivirus could markedly decrease the expression of RBP-2 and promote osteogenic differentiation of hASC. It indicated that RBP-2 can repress the osteogenic differentiation of hASC.</p>

Heterozygous TP63 mutation in a Chinese patient with ectrodactyly-ectodermal dysplasia clefting syndrome without clefting / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To determine if alteration in TP63 is responsible for a Chinese patient with ectrodactyly-ectodermal dysplasia clefting (EEC) syndrome, but without cleft palate/lip.</p><p><b>METHODS</b>Screening of TP63 gene was performed in the patient with EEC syndrome and his family members using PCR-single strand conformational polymorphism (SSCP) analysis, then performed by direct sequencing of the coding region.</p><p><b>RESULTS</b>A C > T substitution at nucleotide position 838 in exon 7 was detected in the patient, and the change predicted a heterozygous missense mutation, Arg280Cys. His parents showed the wild type.</p><p><b>CONCLUSIONS</b>The results indicate that the de novo mutation Arg280Cys of the TP63 gene observed in the patient maybe contribute to his EEC syndrome.</p>

Double scanning method for computer aided design and computer aided manufacture all-ceramic restorations / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To introduce the double scanning for producing computer aided design and computer aided manufacture (CAD-CAM) zirconia crowns, and to compare Procera with Everest CAD-CAM system by observing clinical effects of the crowns.</p><p><b>METHODS</b>Forty CAD-CAM zirconia crowns (10 crowns by Procera, and 30 crowns by Everest) were evaluated, and the examination criteria included: marginal fit, aesthetics, gingival health, retention, and fracture. All of the zirconia copings were produced using double scanning. Procera system and Everest system use contact scanner and optical scanner respectively.</p><p><b>RESULTS</b>The observation time for the crowns ranged from 6 to 24 months. The results of clinic evaluation were acceptable in all restorations.</p><p><b>CONCLUSIONS</b>Double scanning could be used to produce complicated zirconia copings by CAD-CAM in order to get proper symmetrical porcelain length. It was easier to make complicated coping with contact scanner than with optical scanner.</p>

The accuracy of occlusal simulation of virtual craniofacial movement simulation system / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the accuracy of occlusal contacts simulated by virtual craniofacial movement simulation system, and to provide theoretical basis for its application.</p><p><b>METHODS</b>Ten pairs of plaster dental casts were fabricated, and mounted on Kavo PROTA 7 articulator. Lateral movement was produced on the articulator. Then each pair of the casts on the articulator was scanned three dimensionally and used as the reference model. The movement of the articulator was simulated using the virtual craniofacial movement simulation system. Then, the digital casts were established on the simulation system and used as the test model. To evaluate the accuracy of the simulation system, positional differences between the simulated and the reference lower dentition were compared.</p><p><b>RESULTS</b>The mean value of the absolute average distance between the simulated and reference lower dentition was (0.18 ± 0.05) mm. Among the left, right, anterior and posterior areas of the dentition, the maximum mean value of the absolute average distance between the simulated and the reference model was found in the right posterior area, which was (0.19 ± 0.07) mm.</p><p><b>CONCLUSIONS</b>The in vitro accuracy of occlusal contacts simulated by virtual craniofacial movement simulation system is 0.19 mm, and this could be a reference data for the practical application of this system.</p>

Application and comparison of two shade guide training systems / 中华口腔医学杂志

<p><b>OBJECTIVES</b>To evaluate the effect of shade guide training box and shade guide training software on shade matching ability of observers when used separately. To find out the difference between two training plans when the two training methods were used in combination, and to provide information on shade matching training system.</p><p><b>METHODS</b>Sixty-two postgraduate dental students who specialized in prosthodontics with 1 to 5 year clinical experience were enrolled in this study. At base line, each participant were asked to match 7 standard shade tabs which have been randomly chosen from Vita 3D-Master shade guide and 7 intermediate shade tabs from Vita bleached guide 3D-Master. Then the subjects were allocated to 2 groups [Toothguide Training Box (TTB) group and Toothguide Training (TT) group] according to the baseline data. Participants in group TTB received training session once a week for 3 weeks, while those in group TT received TT training session once a week for 3 weeks. All participants took a middle term shade-matching test. Then the two groups exchange the training methods and repeat the whole process, a final test was given to each participant. The elapsed time and number of accurate shade matching were recorded for each training session. Wilcoxon signed ranks test and ANOVA were used in data analysis.</p><p><b>RESULTS</b>There were no significant differences in the number of accurate shade matching (standard shade tab and the sum) between group TTB (4.4 +/- 1.3 and 5.3 +/- 1.6) and TT (4.0 +/- 1.4 and 4.9 +/- 1.5) in the middle term test with higher value found in group TTB. In the final test, the number of accurate shade matching (standard shade tab and the sum) in group TT (4.9 +/- 0.8 and 6.4 +/- 0.8) was higher than that in group TTB (4.7 +/- 1.1 and 5.8 +/- 0.9), but significant difference was found only when the sum number of accurate shade matching was compared between the two groups (P < 0.05). There was no significant difference between data from middle term test and from final test in group TTB; while in group TT, the number of accurate shade matching in the final test was significantly increased compared with that in the middle term test (P < 0.05).</p><p><b>CONCLUSIONS</b>When used in combination, TT training followed by TTB training is recommended.</p>

Comparison of shade matching accuracy of tabs of shadeguide and tabs out of shadeguide / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To compare the shade matching accuracy between tabs of shade guide and tabs out of shade guide by prosthodontists.</p><p><b>METHODS</b>Sixty-two graduate students who had 1 to 5 years clinical experience without color blindness were included in this study. Twenty-nine tabs from Vita 3D-Master shadeguide and 7 tabs out of Vita 3D-Master shade guide but from Vita Bleachedguide 3D-Master were taken as the targets of shade matching and observed under the standard light. Subjects' shade matching accuracy on tabs of shadeguide and tabs out of shadeguide was recorded. Frequency of right match was analyzed using Monte Carlo exact probability-test. Wilcoxin test was used to analyze the difference between each group on ranked data of value, chroma and hue.</p><p><b>RESULTS</b>The shade matching accuracy of tabs of shade guide [45.9% (199/434)] was significantly higher than that of tabs out of shade guide [9.0% (39/434)]. There was significant difference between the two kinds of tabs of ranked data of value [0.2 (0.1 - 0.3), 0.4 (0.4 - 0.5)] and chroma [0.2 (0.1 - 0.4), 0.5 (0.4 - 0.6), P < 0.01, but there was no significant difference in hue data [0.3 (0.1 - 0.4), 0.3 (0.1 - 0.4)].</p><p><b>CONCLUSIONS</b>The shade matching ability of prosthodontists on tabs out of shade guide is lower than that on tabs of shadeguide. To fulfill clinical need, more training is necessary.</p>

Analysis of the difference in the tissue surfaces between the old and new upper complete dentures / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the reduction in residual ridges of maxillary edentulous models duplicated from old and new complete dentures using the 3-D data analysis.</p><p><b>METHODS</b>Twenty-six pairs of maxillary edentulous models copied from the fitting surfaces of new and old upper complete dentures were selected for this study. The 3-D data were collected with a laser scanning system. The data were matched using Geomagic Studio 8 and Rapidform2006 software and then the fitting surfaces of new complete dentures were analyzed in comparison with old ones.</p><p><b>RESULTS</b>The total amount of morphologic change of fitting surface [(39.8+/-14.2)%] was greater than the change of width [(28.2+/-16.0)%]; the area reduction of the residual ridge in anterior region [(43.0+/-15.2)%] was larger than that in posterior region [(36.1+/-14.1)%]; and the area reduction of residual ridge in buccal aspect [(42.9+/-13.8)%] was larger than that in lingual aspect [(35.5+/-15.2)%]. All the differences were statistically significant (P<0.05).</p><p><b>CONCLUSIONS</b>The results of this study reveal that 3-D analysis of the whole change of the residual ridge is significant and verify that the residual ridge resorption of edentulous maxilla in three dimensions is greater in buccal aspect than in lingual aspect and greater in anterior region than in posterior region.</p>

Analysis of the fracture processes in all-ceramic crowns by finite element analysis / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To analyze the effects of core material and design on the fracture mechanism of veneered all-ceramic crowns.</p><p><b>METHODS</b>The fracture process of 6 veneered alumina or zirconia crowns with different core design (well-distributed core, not well distributed core, and core with cervical ring) under load was analyzed by RFPA'2D finite element analysis software.</p><p><b>RESULTS</b>All the six tested crowns fractured due to tension failure, and the crack started at the porcelain in the cusp and spread along the interface between core and porcelain. Under the conditions of this test, the break was only related to the porcelain and not the core, and the crack of porcelain took place earlier in zirconia crowns than in alumina crowns. Minimum stress distribution in cervical ring core design crown and maximum stress distribution in not well distributed core design crown could be seen at the neck area.</p><p><b>CONCLUSIONS</b>Zirconia crowns presented greater stress at the interface between core and porcelain than alumina crowns. The not well distributed core design did not increase the rise of break. The neck area was the weak area with tensile stress concentration in the cervical ring core design.</p>

Silver-ion release and particle distribution of denture base resin containing nanometer-sized silver-supported antimicrobial agent / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the distribution of antimicrobial agent STR-1 of nanometer level which was incorporated with ball-grinding method in the polymethylmethacrylate (PMMA) denture base, and to study the release mode of silver ions from the base.</p><p><b>METHODS</b>The distribution of the antimicrobial agent in the PMMA denture base containing STR-1 at concentrations of 0 g/L, 5 g/L, and 10 g/L was examined with scanning electronic microscopy. Then, PMMA resin bases containing STR-1 at the three concentrations were respectively immersed in artificial saliva at 37 degrees C for 54 days. The release of silver ions from the resin bases was surveyed with inductively coupled plasma-mass spectroscopy (ICP-MS) every 24 hours.</p><p><b>RESULTS</b>The antimicrobial agent incorporated by ball-grinding method was even-distributed with individual particles of nanometer level in the PMMA resin base. The release of silver ions from the PMMA resin with antimicrobial agent was extremely slow during the test, a very small fraction of the silver ions released. At the beginning of the test, the release speed was extremely slow, the speed increased rapidly in the middle of the test, and at the end of the test, the speed returned to slow and steady. The cumulative release curve of silver ions was of "S" type.</p><p><b>CONCLUSIONS</b>STR-1 can be even-distributed in the denture base, and the silver ions release from the base with extremely slow speed. It also indicates that biological safety and long-term antimicrobial efficacy of denture base containing silver-supported antimicrobial agents of nanometer level are possibly obtained based on their slow release of silver ions.</p>

Effects of occlusal rehabilitation on chewing patterns of patients with severe tooth wear / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effects of occlusal rehabilitation on chewing patterns of patients with extensive tooth wear.</p><p><b>METHODS</b>29 patients with severe tooth wear were selected and divided into two groups: Group I with complete posterior tooth support (15 cases) and group II with one-side or both side posterior support lost (14 cases). 15 normal old persons were also selected as control group. The surface electromyography (EMG) of masseter(MM), anterior temporalis (TA) and posterior temporalis (TP) during chewing movement were recorded in the stage of pre-treatment, 1 month after temporary restoration and 1 month after permanent restoration. The EMG activity, total cycle duration (TCD) and ratio of activation period to relaxation period (AP/RP) of chewing cycles were measured and compared.</p><p><b>RESULTS</b>1) Before treatment, the TCD of these two groups were longer than normal group, but the differences were not significant (P > 0.05). All of the AP/RPs of MM, TA and TP in group II were significantly higher than that of normal group (P < 0.01), and EMG activity of TA of group II was group I were both significantly lower than that in pre-treatment stage. 3)After permanent restoration, the TCD of group I were significantly lower than that in temporary restoration stage (P < 0.01). In group II, the TCD was continuously slightly shortened, while the AP/RP were significantly lower (P < 0.01) and EMG activities were significantly higher(P < 0.01) than that in the temporary restoration stage.</p><p><b>CONCLUSION</b>Occlusal rehabilitation could obviously change the chewing patterns and the EMG activities of patients with severe tooth wear.</p>