Preliminary clinical application of complete digital workflow of design and manufacturing occlusal splint for sleep bruxism / 北京大学学报(医学版)

OBJECTIVE@#To establish a complete workflow of digital design and manufacturing occlusal splint for sleep bruxism, which can be preliminarily applied in clinical use, thus observe the clinical efficacy.@*METHODS@#Twenty-four patients with sleep bruxism were recruited in the study and randomly divided into two groups by using random number tables. Digital-occlusal-splint (experimental group) treatment plan and traditional-occlusal-splint (control-group) treatment plan were carried out for each group, respectively. For experimental group, digital models of patients' both dental arches and the occlusion relationship after elevation were captured using an intraoral scanner. The occlusal splint was carried out by computer aided design/computer aided manufacturing (CAD/CAM), including splint designing and milling. For control group, the traditional soft occlusal splint was fabricated by vacuum laminator. The two kinds of occlusal splints were tried in the patients from each group, and the occlusal contacts were tested respectively by T-scan analysis system, which recorded the changes of occlusal indicators in the two groups. The retention, appearance and occlusal comfort degree were evaluated by the two groups of patients. Mann-Whitney test was performed with IBM SPSS 20.0 software, and bilateral test was performed. P<0.05 was considered to be statistically significant.@*RESULTS@#The complete workflow of digital design and manufacturing occlusal splint was successfully established. During the clinical use, there was no statistical difference in the retention evaluation of two kinds of occlusal splints between the two groups of patients (Z=-0.538, P=0.590). The appearance score (Z=2.038, P=0.042) and the occlusal comfort score (Z=-2.579, P=0.010) of the experimental group were higher than those of the control group, with statistically significant differences. The T-scan analysis results showed that only the second molar on both sides of the traditional occlusal splint had occlusal contact in intercupsal position, while the digital occlusal splint had stable and bilaterally balanced contact between the maxillary and mandibular teeth. Furthermore, the occlusal force was uniformly distributed in the experimental group.@*CONCLUSION@#The complete workflow of digital occlusal splint improves the occlusal design, greatly simplifies and optimizes the traditional process of making occlusal splint. This new method is resource-saving and environmental-friendly, and it is able to serve patients more conveniently and efficiently.

Comparison of the translucency and color masking effect of the zirconia ceramics made by milling and gel deposition / 北京大学学报(医学版)

OBJECTIVE@#Three kinds of zirconia specimens were made respectively by milling of the prisintered blocks and by three dimensional (3D) gel deposition for in vitro evaluation of their optical translucency under three different thicknesses and their color masking effect on discolored teeth. The study aims for establishing the principle for guiding the materials selection in clinical practice.@*METHODS@#Ninety A2-colored zirconia disc specimens with diameter of 14 mm were prepared and were divided into three groups (n=30). (1) Group CZ, by milling of the presintered blanks; (2) Group NZW, by 3D gel deposition, without a color masking opaque inner layer; (3) Group NZY, by 3D gel deposition, with a color masking opaque inner layer. Furthermore, each group was divided into three sub-groups (n=10) according to the sample thickness, i.e., 0.6, 1.0 and 1.5 mm, respectively. The maxillary anterior teeth with severe discoloration, extracted owing to periodontal disease, were collected and embedded. By gentle gridding and polishing a plane, larger than 6 mm2×6 mm2, was generated on the labial surface of each tooth. Chromatic values(CIE1976-L*a*b*) of the zirconia samples in the nine sub-groups were measured by the spectrophotometer Crystaleye in front of the black or white background in a cassette, and the translucency parameter (TP) values were calculated for each sample. Thereafter the zirconia specimens were bonded onto the labial surface of the polished teeth for measuring the chromatic values, using the chromatic value of the medium 1/3 of the standardized Vita A2 as a control. The color aberration ΔE between each zirconia specimen and the control value was calculated, respectively. The results were statistically analyzed by One-way ANOVA and Bonferroni.@*RESULTS@#(1) The optical transparency of the three kinds of zirconia disc specimens with the thickness of 0.6, 1.0 and 1.5 mm was 14.09, 12.31 and 10.45 for group CZ; 19.84, 16.54 and 12.44 for group NZW;14.81, 13.16 and 11.92 for group NZY. In each group, the degree of optical transparency of the specimens showed a clear tendency as in the sub-group 0.6 mm >1.0 mm >1.5 mm. The TP value of the specimens in the three groups with the same thickness showed a tendency of the group NZW >group NZY >group CZ. (2) After bonding onto the polished labial surface of the teeth, the color aberration ΔE of the specimens with the thickness of 0.6, 1.0 and 1.5 mm was calculated to be 10.77, 9.94 and 8.50 for group CZ; 6.84, 5.89 and 5.29 for group NZW; 4.16, 3.92 and 3.67 for group NZY. In each group, the color aberration of the specimens showed a clear tendency as in the sub-group 0.6 mm >1.0 mm >1.5 mm; the color aberration of the three groups with the same thickness was in the order of the group CZ >group NZW >group NZY.@*CONCLUSION@#In all the specimen groups with a fixed specimen thickness, the optical translucency of the specimen was the highest in group NZW made by 3D gel deposition, and the best color masking effect was obtained in specimens with a color masking opaque inner layer in group NZY, where a thickness of 0.6 mm was sufficient enough for obtaining the ideal color masking effect.

The technic and dose evaluation of postoperative (125)I radioactive seeds brachytherapy for malignant tumors of maxilla / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the technique and effect of treating malignant tumors of maxilla with postoperative brachytherapy by digital model obturators containing (125)I radioactive seeds.</p><p><b>METHODS</b>Four patients with adnoid cystic carcinomas and two with squamous cell carcinomas in the maxilla were included in this study. All patients accepted (125)I seeds implantation after operation, and wore digital model obturators containing (125)I seeds. The prescription dose was 80 Gy. All patients were followed up every 2 months after treatment.</p><p><b>RESULTS</b>The total number of seeds used in these six patients was 189, and 105 seeds were contained in obturators. Radioactive seeds and doses distributed very well as designed in all patients. No tumors recurred after follow up of 12-16 months and there were no severe complications.</p><p><b>CONCLUSIONS</b>It's an effective way to treat malignant tumors with positive excision margin in the maxilla by brachytherapy using digital model obturators which contain (125)I radioactive seeds.</p>

Application of computer aided design and rapid prototyping technology for defected maxilla restoration / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To test a new cast-making method based on computer aided design (CAD) and rapid prototyping (RP) technology for defected maxilla.</p><p><b>METHODS</b>Head CT data of 12 patients with defected maxilla were transmitted into a computer. Three-dimensional digital image of the patient's defected maxilla was then obtained based on Mimics 8.11 and Geomagic 7.0 and the plastic cast of the defected region was manufactured by prototyping. The obturator was made on this plastic cast that duplicated the undercut tissue of defected area. The prominent part of the obturator was made of elastic heat-curing resin and it was helpful to gain the retention through the engagement between the obturator and the tissue undercut. After the obturator was finished, the upper removable partial denture was fabricated in conventional method. The combination of these two parts was achieved using magnetic attachment. Clinical effects of obturator and removable partial denture were evaluated and the nasalance value of 5 patients before and after insertion of the obturator was measured using nanometer.</p><p><b>RESULTS</b>The obturator and removable partial denture could be seated into place separately. They all had good retention and stability. After the obturator was seated in place, the nasalance of non-nasal and vowel text decreased from (46.53 +/- 13.86)% to (22.60 +/- 8.52)% (P < 0.001).</p><p><b>CONCLUSIONS</b>The cast-making method based on CAD and RP technology for cast-making of defected maxilla is feasible and practical.</p>

The measurement and comparison of shear fracture strength and shear bond strength between carbon fiber post and some other posts / 中华口腔医学杂志

<p><b>OBJECTIVE</b>The shear fracture strengths of carbon fiber post, IPS-Empress 2 all-ceramic post (without ZrO2 post), cast Ni-Cr alloy post, prefabricated zirconia ceramic post, human dentin and the shear bonding strengths of the first three kinds of post bonded in the human root canals were measured and compared, which are as the reference for dental clinic.</p><p><b>METHODS</b>Standard cylindrical samples were made respectively in each group of carbon fiber post, IPS-Empress 2 all-ceramic post, cast Ni-Cr alloy post, prefabricated zirconia ceramic post, human dentin, three for each group. The shear fracture strengths of these samples were measured by universal testing machine (AUTOGRAPH DCS5000). Standard cylindrical samples were made respectively in each group of carbon fiber post, IPS-Empress 2 all-ceramic post (without ZrO2 post), cast Ni-Cr alloy post, five for each group. They were bonded in extracted human root canals that had been prepared to 3.0 mm length and 2.0 mm diameter with Glass ionomer cement (Japan Shofu). The shear bond strengths were measured by the same universal testing machine.</p><p><b>RESULTS</b>The shear fracture strengths of the carbon fiber post (199MPa), cast Ni-Cr alloy post (210MPa, shear bend strength) and prefabricated zirconia ceramic post (193MPa) were statistically higher than those of IPS-Empress 2 all-ceramic post (109MPa) and human dentin (100MPa). The shear fracture strength of the carbon fiber post was statistically similar to that of cast Ni-Cr alloy post and prefabricated zirconia ceramic post. There were no statistical differences between the shear bond strengths of carbon fiber post (2.4MPa) and cast Ni-Cr alloy post (3.8MPa). IPS-Empress 2 all-ceramic post broke before debonding (2.7, break value).</p><p><b>CONCLUSIONS</b>Carbon fiber post, as well as cast Ni-Cr alloy post and prefabricated zirconia ceramic post, has a comparatively high shear fracture strength. The shear bond strengths of carbon fiber post is similar to cast Ni-Cr alloy post.</p>

The influence of electronic gingivoplasty on the gingival tissue of rats with high blood sugar or with blood coagulating dysfunction / 实用口腔医学杂志

Objective:To study the feasibility of electronic gingivoplasty on the subjects suffering from high blood sugar or blood coagulating dysfunction on rat model.Methods:Electronic gingivoplasty was performed in 10 SD rats with high blood sugar and 10 with blood coagulating dysfunction on the right side of mandible and scalpel gingivoplasty on the left.For each group of diseased rats 10 healthy rats were used as the controls. Gingival tissue slices of the rats with high blood sugar and the controls were obtained 1,24, 72 hours, one and two weeks after operation respectively, and processed for histological observation. The bleeding condition were evaluated with paper tips during the operations on the rats with blood coagulating dysfunction and the controls.Results:The process of histological reaction in the tissues of operation area after electronic gingivoplasty was basically similar to that after scalpel gingivoplasty. Electronic surgery caused more slight inflammatary reaction than scalpel surgery in high blood sugar group. The amount of bleeding during electronic surgery was significantly smaller than that during scalpel surgery in blood coagulating dysfunction group.Conclusion:Electronic surgery is feasible for gingivoplasty on the subjects with high blood sugar or blood coagulating dysfunction.