BACKGROUND: Immediate rehabilitation is a considerable therapeutic challenge but is necessary for edentulous patients with oronasal fistulas, especially those with inadequate residual bone and a history of radiotherapy.
METHODS: We report a rare case of a 63-year-old patient who was missing the majority of his maxillary teeth and who had a defect due to palatal mucoepidermoid carcinoma resection. The patient also received radiotherapy twice within one year postoperatively. An implant-supported prosthesis with an obturator was fabricated immediately.
CONCLUSIONS: This technique improved patients\' oral function, enhanced the aesthetic effect, and increased their confidence.

Objective: To evaluate the clinical outcomes after implant restoration in the posterior region of severe periodontitis patients and to investigate the factors of natural tooth affecting the implant from the perspective of improving natural periodontal health, which may provide a reference for clinical practice. Methods: Fifty-three patients with severe periodontitis who visited the Department of Periodontology at the Affiliated Stomatological Hospital of China Medical University from June 2014 to June 2023 and completed posterior implant treatment with single crown were included, among which were 16 males and 37 females, aged (52.2±8.0) years old, with a total of 136 implants, 135 adjacent natural teeth in the edentulous area. We retrospectively compared the changes of probing depth (PD), bleeding on probing (BOP) and tooth mobility (TM) before and after implant placement. Besides, we explored the effects of the natural periodontal status on PD, BOP and marginal bone loss (MBL) of the implant at the last follow-up examination by univariate analysis and multivariate analysis. Results: Fifty-three patients were followed up for (44.5±14.1) months in average, with longest interval of (8.3±2.7) months. The PD of adjacent natural teeth in the edentulous area improved from 4.3 (3.6, 4.6) mm before implantation to 3.6 (3.2, 4.0) mm in the last review (P<0.01), while the proportion of BOP (+) improved from 69.6% (94/135) before implantation to 46.7% (63/135) in the last review (P<0.01). The proportion of teeth with mobility≥Ⅱ decreased from 15.6% (21/135) to 5.9% (8/135) (P<0.01). The percentage of natural teeth with PD≥4 mm in the same segment improved from 21.0% (13.3%, 26.0%) before implantation to 18.0% (12.0%, 25.0%) in the last review (P<0.05). The BOP (+)% improved from 29.0% (24.0%, 35.0%) before implantation to 23.0% (18.0%, 31.0%) in the last review (P<0.05), and the number of teeth with mobility≥Ⅱ decreased from 0.0 (0.0, 1.0) to 0.0 (0.0, 0.8) (P<0.05). The functional tooth unit score of full natural teeth increased from 8.0 (6.0, 10.0) points before implantation to 12.0 (12.0, 12.0) points in the last review (P<0.01). PD≥4 mm % increased from 11.0% (6.0%, 25.0%) before implantation to 13.0% (3.0%, 21.0%) in the last review (P<0.05) and there was no significant differences in BOP (+)% [(17.0±9.7) % vs (14.6±7.2) %, P>0.05]. The number of teeth with mobility≥Ⅱ decreased from 1.0 (0.0, 1.8) to 0.0 (0.0, 0.8) (P<0.05). Conclusions: Under the premise of regular supportive care, implant restorative treatment in the posterior region of severe periodontitis patients is helpful to improve the PD, BOP and TM of remaining natural teeth. Besides, the stages and grades of periodontitis at initial diagnosis can affect the PD and BOP of implants.
目的： 从改善天然牙牙周健康的角度，评价规律复查的重度牙周炎患者后牙区种植修复治疗对天然牙的影响，以及天然牙牙周状态对种植体的影响，为临床提供参考。 方法： 收集2014年6月至2023年6月于中国医科大学口腔医学院·附属口腔医院牙周病科就诊，并完成后牙单冠种植修复治疗的重度牙周炎者53例，其中男性16例，女性37例，年龄（52.2±8.0）岁，种植体共136枚，缺牙区相邻天然牙135颗。回顾性比较种植前后口内余留天然牙的探诊深度（PD）、探诊出血（BOP）和松动度变化，并通过单因素和多因素分析探讨天然牙对种植体PD、BOP和末次复查时边缘骨丧失（MBL）的可能影响因素。 结果： 53例患者的随访时间为（44.5±14.1）个月，最长复查间隔为（8.3±2.7）个月。缺牙区相邻天然牙PD由种植前的4.3（3.6，4.6）mm显著改善至末次复查时的3.6（3.2，4.0）mm（P<0.01），BOP（+）%由种植前的69.6%（94/135）显著改善至末次复查时的46.7%（63/135）（P<0.01），松动度≥Ⅱ度的牙齿占比由15.6%（21/135）显著降至5.9%（8/135）（P<0.01）；同区段天然牙的PD≥4 mm%由种植前的21.0%（13.3%，26.0%）显著改善至末次复查时的18.0%（12.0%，25.0%）（P<0.05），BOP（+）%由种植前的29.0%（24.0%，35.0%）显著改善至末次复查的23.0%（18.0%，31.0%）（P<0.05），松动度≥Ⅱ度的牙齿数量由0.0（0.0，1.0）颗显著下降至0.0（0.0，0.8）颗（P<0.05）；全口天然牙的功能牙齿单位（FTU）分值由种植前的8.0（6.0，10.0）分显著提升至末次复查时的12.0（12.0，12.0）分（P<0.01），PD≥4 mm%由种植前的11.0%（6.0%，25.0%）显著提升至末次复查时的13.0%（3.0%，21.0%）（P<0.05），种植前BOP（+）%［（17.0±9.7）%］与末次复查时［（14.6±7.2）%］相比差异无统计学意义（P>0.05），松动度≥Ⅱ度的牙齿数量由1.0（0.0，1.8）颗显著降为1.0（0.0，1.0）颗（P<0.05）。 结论： 规律复查的前提下，重度牙周炎患者后牙区种植修复治疗有助于改善余留天然牙的PD、BOP和松动度，同时初诊牙周炎分期分级可影响种植体的PD和BOP。.

To evaluate the influence of intraoral scanning coverage (IOSC) on digital implant impression accuracy in various partially edentulous situations and predict the optimal IOSC.
Five types of resin models were fabricated, each simulating single or multiple tooth loss scenarios with inserted implants and scan bodies. IOSC was subgrouped to cover two, four, six, eight, ten, and twelve teeth, as well as full arch. Each group underwent ten scans. A desktop scanner served as the reference. Accuracy was evaluated by measuring the Root mean square error (RMSE) values of scan bodies. A convolutional neural network (CNN) was trained to predict the optimal IOSC with different edentulous situations. Statistical analysis was performed using one-way ANOVA and Tukey\'s test.
For single-tooth-missing situations, in anterior sites, significantly better accuracy was observed in groups with IOSC ranging from four teeth to full arch (p < 0.05). In premolar sites, IOSC spanning four to six teeth were more accurate (p < 0.05), while in molar sites, groups with IOSC encompassing two to eight teeth exhibited better accuracy (p < 0.05). For multiple-teeth-missing situations, IOSC covering four, six, and eight teeth, as well as full arch showed better accuracy in anterior gaps (p < 0.05). In posterior gaps, IOSC of two, four, six or eight teeth were more accurate (p < 0.05). The CNN predicted distinct optimal IOSC for different edentulous scenarios.
Implant impression accuracy can be significantly impacted by IOSC in different partially edentulous situations. The selection of IOSC should be customized to the specific dentition defect condition.
The number of teeth scanned can significantly affect digital implant impression accuracy. For missing single or four anterior teeth, scan at least four or six neighboring teeth is acceptable. In lateral cases, two neighboring teeth may suffice, but extending over ten teeth, including contralateral side, might deteriorate the scan.

OBJECTIVE: The purpose of this in vitro study was to compare the trueness and precision of complete arch implant impressions using conventional impression, intraoral scanning with and without splinting, and stereophotogrammetry.
METHODS: An edentulous model with six implants was used in this study. Four implant impression techniques were compared: the conventional impression (CI), intraoral scanning (IOS) without splinting, intraoral scanning with splinting (MIOS), and stereophotogrammetry (SPG). An industrial blue light scanner was used to generate the baseline scan from the model. The CI was captured with a laboratory scanner. The reference best-fit method was then applied in the computer-aided design (CAD) software to compute the three-dimensional, angular, and linear discrepancies among the four impression techniques. The root mean square (RMS) 3D discrepancies in trueness and precision between the four impression groups were analyzed with a Kruskal-Wallis test. Trueness and precision between single analogs were assessed using generalized estimating equations.
RESULTS: Significant differences in the overall trueness (p = .017) and precision (p < .001) were observed across four impression groups. The SPG group exhibited significantly smaller RMS 3D deviations than the CI, IOS, and MIOS groups (p < .05), with no significant difference detected among the latter three groups (p > .05).
CONCLUSIONS: Stereophotogrammetry showed superior trueness and precision, meeting misfit thresholds for implant-supported complete arch prostheses. Intraoral scanning, while accurate like conventional impressions, exhibited cross-arch angular and linear deviations. Adding a splint to the scan body did not improve intraoral scanning accuracy.

OBJECTIVE: To evaluate the impact of guide stabilizers and their application sequences on implant placement accuracy of guided implant surgery in multiple teeth loss at free end.
METHODS: In this study, 96 implants were placed in the regions of #34, #36, and #37 of 32 identical mandibular models. The influence of using guide stabilizers or not (group A and group B) and various guide stabilizers application sequences (group B: #34 → #36 → #37; group C: #36 → #34 → #37; group D: #37 → #34 → #36) on implant placement trueness and precision was investigated. Data were analyzed using T-tests and one-way ANOVA.
RESULTS: Group B showed significant benefits in enhancing implant placement precision. Compared to group A, it resulted in reducing 3D-deviation at crest and 2D deviation in vestibular-oral direction at both crest and apex. Furthermore, group D demonstrated greater improvement in global implant placement precision by reducing 2D deviation in mesial-distal direction at both crest and apex. Among the three different stabilizer application sequences, group D exhibited the highest level of implant placement precision.
CONCLUSIONS: In cases of missing teeth at distal free end, the use of guide stabilizers and their application sequences does not have a significant impact on implant placement trueness. However, they do improve implant placement precision compared to methods that do not utilize guide stabilizers. Specifically, applying a guide stabilizer first at the furthest implant site to change teeth loss classification from free end to edentulous space with posterior support is the most reliable sequence.

BACKGROUND: The maintenance of marginal bone integrity around dental implants continues to be a clinical challenge. It is still unclear whether loading multiple implant-supported prostheses that have different implant connections influences bone resorption.
OBJECTIVE: The aim of this in vitro study was to compare stress distribution around residual edentulous ridges supported by external hexagon (EH) and Morse taper (MT) implants with screw-retained frameworks obtained with the use of different methods.
METHODS: Three-element implant-supported prostheses with distal cantilevers were manufactured according to different techniques of obtaining the framework: LAS - framework sectioned and welded with a laser; TIG - framework sectioned and welded with tungsten inert gas (TIG); and CCS - framework obtained using a computer-aided design/computer-aided manufacturing (CAD/CAM) system. Occlusal and punctual loading (150 N) was applied to the cantilevers. In the photoelastic stress analysis, the fringe orders (n) were quanitified using the Tardy method, which calculates the maximum shear stress value (τ) at each selected point.
RESULTS: High stress around the implants and tightening were observed in the TIG group, mainly in the crestal bone region for the EH and MT implant connections. The LAS and CCS frameworks exhibited lower stress for the MT connection under occlusal and punctual loading.
CONCLUSIONS: The comparative analysis of the models showed that the MT connection type associated with the laser-welded or CAD/CAM frameworks resulted in lower stress values in the crestal bone area, suggesting the preservation of bone tissue in this region.

To examine the effect of artificial landmarks of prefabricated auxiliary devices (PAD) located at different arch positions on the accuracy of complete-arch edentulous digital implant scanning.
A reference model containing four analogs and PAD were fabricated by a 3D printer (AccuFab-C1s, 3DShining). 10 digital scans were performed using an intraoral scanner (Aoralscan 3, 3DShining), sv 1.0.0.3115, with artificial landmarks located at different arch positions: group I, without any artificial landmarks; group II, with artificial landmarks at the anterior region; group III, with artificial landmarks at the posterior region. group IV: with artificial landmarks at both anterior and posterior regions. For group V: Conventional open-tray splinted impressions. The reference file and conventional stone casts were digitalized by using a dental laboratory scanner. The related files were imported into inspection software for trueness and precision assessment. Statistical analysis was performed with One-way ANOVA and Kruskal-Wallis test. The level of significance was set at α=0.05.
For the global accuracy assessment, significantly higher global trueness was seen in group II (p < 0.01), III (p < 0.001), IV (p < 0.001) and V (p < 0.001) than group I. Significantly higher global precision was seen in group III (p < 0.001), IV (p < 0.001) and V (p < 0.001) than group I. For the local accuracy assessment, the PAD primarily improved accuracy on the linear deviations.
Artificial landmarks of PAD at different arch positions significantly influenced the scanning accuracy. Applying the PAD in group IV could achieve comparable outcomes to conventional open-tray splinted impressions. Artificial landmarks on the posterior region may be more pivotal than those on the anterior region.
Group IV could achieve comparable accuracy to conventional open-tray splinted impressions.

OBJECTIVE: To evaluate the clinical effect of complete denture restoration in edentulous patients using secondary functional impression.
METHODS: Complete denture restoration was performed in 433 edentulous patients using secondary functional impression. The Geriatric Oral Health Assessment Index (GOHAI) was used to evaluate patients\' oral health-related quality of life before and after restoration. All patients were divided into 3 groups according to whether they had a history of denture restoration: no denture group(ND)，removable partial denture group(RPD), complete denture group(CD). In CD group, 30 patients were asked to chew two-colour gum. The SDhue value was evaluated by using ViewGum software. SPSS 26.0 software package was used for data analysis.
RESULTS: The oral health-related quality of life was improved in all the 3 groups after restoration, and the GOHAI index 1 month after restoration was significantly higher than that before restoration(P＜0.05). In CD group, SDHue value of 30 patients after restoration was significantly lower than that before restoration(P＜0.05).
CONCLUSIONS: Secondary functional impression is simple and fast, and can improve the satisfaction of patients after complete denture restoration.

Premature loss of primary molars can be treated with a band loop space maintainer (SM). However, fabricating a conventional band loop SM requires multiple clinical and laboratory procedures, which can potentially affect the accuracy of the SM. Moreover, the conventional SM is unable to fully restore masticatory function and maintain the vertical dimension of the edentulous space. In this current study, a fully digital workflow to fabricate a semi-rigid bridge SM made from polyetheretherketone (PEEK) has been described and evaluated for its clinical effectiveness.
A total of 15 children (eight males and seven females) between the ages of 4-8 years, who experienced the premature loss of a single primary molar, were included in this study. Digital impressions were taken using the CEREC CAD/CAM chair system and imported into CAD software to design the semi-rigid bridge SM, which was fabricated using PEEK block as the maintainer material. The digital SM was tried-in and bonded to the abutment with resin cement. The edentulous space was measured immediately after bonding (T0) and 1 month (T1), 3 months (T2), and 6 months (T3) after treatment. The periodontal condition and mobility of the SM and abutment were also examined.
The use of digital impressions resulted in a decreased occurrence of the pharyngeal reflex. The digital semi-rigid bridge SM, fabricated with PEEK, was both convenient and aesthetically pleasing, and successfully restored the anatomy and masticatory function of the missing primary molar. None of the 15 semi-rigid bridge SMs or abutments became loose or fell off during the study, and only one child presented with gingivitis. Furthermore, the difference in the edentulous space at T0, T1, T2, and T3 was not statistically significant (all P > 0.05).
The digital semi-rigid bridge SM fabricated with PEEK was clinically effective in maintaining the missing space and had advantages over the traditional band/crown loop SM.

To develop a new post-processing strategy that utilizes an auxiliary device to adjust intraoral scans and improve the accuracy of 3D models of complete-arch dental implants.
An edentulous resin model with 6 dental implants was prepared. An auxiliary device, consisting of an opaque base and artificial landmarks, was fabricated and mounted onto the resin model. Twenty intraoral scans (raw scans) were taken using this setup. A new post-processing strategy was proposed to adjust the raw scans using reverse engineering software (verified group). Additionally, ten conventional gypsum casts were duplicated and digitized using a laboratory scanner. The linear and angular trueness and precision of the models were evaluated and compared. The effect of the proposed strategy on the accuracy of complete-arch intraoral scans was analyzed using one-way ANOVA.
The linear trueness (29.7 µm) and precision (24.8 µm) of the verified group were significantly better than the raw scans (46.6 µm, 44.7 µm) and conventional casts (51.3 µm, 36.5 µm), particularly in cross-arch sites. However, the angular trueness (0.114°) and precision (0.085°) of the conventional casts were significantly better than both the verified models (0.298°, 0.168°) and the raw scans (0.288°, 0.202°).
The novel post-processing strategy is effective in enhancing the linear accuracy of complete-arch implant IO scans, especially in cross-arch sites. However, further improvement is needed to eliminate the angular deviations.
Errors generated from intraoral scanning in complete edentulous arches exceed the clinical threshold. The elimination of stitching errors in the raw scans particularly in the cross-arch sites, through the proposed post-processing strategy would enhance the accuracy of complete-arch implant prostheses.