[Clinical outcome of single posterior implant-supported monolithic zirconia crowns fabricated using full digital workflow and conventional workflow: a 3-year follow-up].

Objective: To compare the clinical performance of posterior single implant-supported monolithic zirconia crowns fabricated by full digital workflow and that of those fabricated by conventional workflow. Methods: This is prospective clinical research. Thirty-five patients who participated in a previous study during August 2017 to October 2018 at Department of Prosthodontics, Peking University School and Hospital of Stomatology were included in this 3-year follow-up study. The 35 patients, 17 females and 18 males, aged (49.0±15.4) years (24-86 years old), was allocated into two groups. In the full digital workflow group, intraoral scanning was taken immediately after implant placement, and a full zirconia implant crown was fabricated using model-free computer aided design/computer aided manufacturing (CAD/CAM) procedure (n=14). In the conventional group, a conventional impression was taken 3 months after implant placement and the stone model was produced. A full zirconia implant crown was fabricated using conventional model-based procedure (n=21). Three years following crown delivery, all the prostheses were evaluated in the aspect of color, surface roughness, contour and marginal integrity using modified US Public Health Service criteria (MUSPHS criteria). The soft and hard tissue around implant was evaluated using modified plaque index, probing depth (PD), number of implants with bleeding on probing, marginal bone loss (MBL). The biological and mechanical complication were also recorded. Statistical analysis was performed using independent samples t test, Mann-Whitney U test and Fisher's exact test. Results: The total survival rate of prosthesis and implant was 100% (35/35). No significant difference in MUSPHS criteria ratings on color, surface roughness, contour and marginal integrity of these crowns were found between the full digital workflow group and the conventional group (P>0.05). Sixteen out of the 35 crowns had a contour score of B due to loss of interproximal contact. Ten out of the 35 crowns had the screw hole sealing resin sinking or falling off, four in the full digital workflow group and six in the conventional group. There was no significant difference in the rate of prostheses mechanical complications between the two groups (P=1.000). For all the implants, there was no significant difference in MBL, PD, the modified plaque index, and number of implants with bleeding on probing between the two groups (U=119.50,133.00,142.50, t=-0.53, P>0.05). Conclusions: The clinical performance of implant-supported posterior single monolithic zirconia crowns fabricated by full digital workflow was stable. There was no significant difference in the clinical performance of the single implant crowns between the full digital workflow group and the conventional group.

[Comparison of the registration methods for the three-dimensional facial scans applied to the design of full-arch implant supported restoration].

OBJECTIVE: To compare the registration accuracy of three-dimensional (3D) facial scans for the design of full-arch implant supported restoration by five methods and to explore the suitable registration method. METHODS: According to the criteria, ten patients with maxillary edentulous jaw or end-stage dentition requiring implant supported restorations were enrolled in this study. A special rim with individual feature marks reflected appropriate occlusal relationship and esthetic characteristics was made for each patient. Both 3D facial scan data of natural laughter and with opener traction to expose the teeth or occlusal rim of each patient were acquired by facial scan and input to the digital analysis software Geomagic Qualify 2012. The dataset was superimposed by five different methods: seven facial anatomical landmark points alignment, facial immobile area alignment (forehead and nasal area), facial anatomical landmark points and immobile area combining alignment, facial feature points alignment, facial and intraoral feature points alignment with the same local coordinate system. The three-dimensional deviation of the same selected area was calculated, the smaller the deviation, the higher the registration accuracy. The 3D deviation was compared among the three registration methods of facial anatomical landmark points, facial immobile area alignment and the combination of the above two methods. Friedman test was performed to analyze the difference among the three methods (α=0.05). The effect of the aid of the facial and intraoral feature points were evaluated. Paired t test were performed to analyze the difference (P<0.05). RESULTS: The average three-dimensional deviation of the selected area after alignment with the facial anatomical landmarks was (1.501 2±0.406 1) mm, significantly larger than that of the facial immobile area best-fit alignment [(0.629 1±0.150 6) mm] and the combination of the two methods[(0.629 1±0.150 6) mm] (P < 0.001). The aid of the facial feature points could significantly reduce the deviation (t=1.001 3, P < 0.001). There was no significant statistical difference in the remaining groups. CONCLUSION: The forehead area of the 3D facial scan can be exposed as much as possible. The establishment of facial characteristic landmark points and the use of the invariant area alignment can improve the accuracy of registration. It should be clinically feasible to apply three-dimensional facial scan to the design of full-arch implant supported restoration with the registration of the immobile area on the face especially the forehead area.

[A clinical analysis of 27 cases of simultaneous bilateral sudden sensorineural hearing loss].

Objective:To compare the clinical characteristics and therapeutic effects between simultaneous bilateral sudden sensorineural hearing loss（Si-BSSHL） and unilateral sudden sensorineural hearing loss（USSHL）. Method:The clinical data of 27 cases of Si-BSSHL were retrospectively analyzed, including the characteristics of the disease, clinical manifestations, audiological examination, hematological examination, and therapeutic effect, and compared with those of 139 cases of USSHL. Result:There was a statistically significant difference in the age（65.85±9.17 vs 56.95±13.18, P<0.01） and no significant difference in sex ratio（P>0.05） between the two groups. The proportion of Si-BSSHL patients with vertigo, ear fullness, hypertension, diabetes, coronary heart disease and stroke had no statistical difference compared with those of USSHL（P>0.05）, the proportion of patients with tinnitus in Si-BSSHL group was significantly lower than that in USSHL group（P<0.05）. The distribution of hearing loss degree and the type of audiometry in Si-BSSHL group were significantly different from those in USSHL group, PTA before treatment and the proportion of profound hearing loss in Si-BSSHL group was significantly lower than that in USSHL group（P<0.05）, descending audiometry type was more common in Si-BSSHL group compared to USSHL（P<0.01）. Fibrinogen in Si-BSSHL group was significantly higher than that in USSHL group（P<0.05）. No significant difference was found between the two groups with respect to mean platelet volume, blood lipid and folic acid（P>0.05）. The total treatment effective rate in Si-BSSHL group was 44.44%, while that in USSHL group was 41.73%, there was no significant difference between the two groups（P>0.05）. Conclusion:Si-BSSHL has a female preponderance and tends to occur in advanced age in our cohort. Compared to USSHL patients, Si-BSSHL patients have less profound hearing loss and more descending audiograms, and the proportion of patients with extremely severe deafness is relatively small. There is no significant difference in the therapeutic effect between the two groups.