BACKGROUND: The purpose of this in vitro study was to investigate the effect of polishing post-treatment process on the torque loss ratio and microgap of Selective Laser Melting (SLM) abutments before and after mechanical cycling test through improving the surface roughness of the implant-abutment interface.
METHODS: Forty SLM abutments were fabricated, with 20 underwent minor back-cutting, designated as polishing, in the implant-abutment interface. The abutments were divided into three groups: SLM abutments (group A), original abutments (group B), and polished SLM abutments (group C), each containing 20 abutments. Surface roughness was evaluated using a laser microscope. Implant-abutment specimens were subjected to mechanical cycling test, and disassembly torque values were measured before and after. Scanning electron microscope (SEM) was used to measure microgap after longitudinal sectioning of specimens. Correlation between surface roughness, torque loss ratio, and microgap were evaluated. LSD\'s test and Tamhane\'s T2 comparison were used to analyze the data (α = 0.05).
RESULTS: The Sz value of polished SLM abutments (6.86 ± 0.64 μm) demonstrated a significant reduction compared to SLM abutments (26.52 ± 7.12 μm). The torque loss ratio of polished SLM abutments (24.16%) was significantly lower than SLM abutments (58.26%), while no statistically significant difference that original abutments (18.23%). The implant-abutment microgap of polished SLM abutments (2.38 ± 1.39 μm) was significantly lower than SLM abutments (8.69 ± 5.30 μm), and this difference was not statistically significant with original abutments (1.87 ± 0.81 μm). A significant positive correlation was identified between Sz values and the ratio of torque loss after cycling test (r = 0.903, P < 0.01), as well as Sz values and the microgap for all specimens in SLM abutments and polished SLM abutments (r = 0.800, P < 0.01).
CONCLUSIONS: The findings of this study indicated that the polishing step of minor back-cutting can lead to a notable improvement in the roughness of SLM abutments interface, which subsequently optimized the implant-abutment fit. It can be seen that the application of minor back-cutting method has advanced the clinical use of SLM abutments.

OBJECTIVE: This test aimed to investigate the factors affecting the locking force between the implant and abutment and the amount of abutment subsidence in pure Morse taper connection implant systems.
METHODS: With reference to the Bicon implant abutment connection design, different types of implant specimens and their corresponding types of abutments were fabricated. The implant-abutment locking taper was uniformly 1.5°. The locking depths were 1.0, 2.0, and 3.0 mm. The diameters of the locking column were 2.5, 3.0, and 3.5 mm. The thicknesses of the outer wall of the implant were 0.15 and 0.30 mm. The loading forces of the testing machine were 200, 300, and 400 N. At least 10 specimens of each group of implant-abutment were used. All specimens were loaded in the same manner using a universal testing machine (finger pressure + specified loading force, five times). The total height of the implant-abutment was measured before finger pressure, after finger pressure, and after the testing machine was loaded for five times to calculate the amount of sinking of the abutment. Finally, the implant and abutment were pulled apart using the universal testing machine, and the subluxation force was observed and recorded.
RESULTS: The test loading force, locking depth, and locking post diameter had an effect on the implant-abutment locking force and abutment subsidence. The implant-abutment locking force increased with the increase in the test loading force, locking depth, and locking post diameter (R=0.963, 0.607, and 0.372, respectively), with the test loading force having the most significant effect. Abutment subsidence increased with the increase in test loading force (R=0.645) and decreased with the increase in locking depth and locking post diameter (R=-0.807 and -0.280, respectively), with locking depth having the most significant effect on abutment subsidence. No significant correlation was found between the thickness of the outer wall of the implant and the change in the magnitude of the implant-abutment locking force. However, an increase in the thickness of the outer wall of the implant decreased the amount of abutment subsidence, which was inversely correlated.
CONCLUSIONS: The locking force of the implant-abutment can be increased by adjusting the design of the pure Morse taper connection implant⁃abutment connection, increasing the locking depth and locking post diameter, and increasing the amount and number of times the abutment is loaded during seating. Problems, such as loosening or detachment of the abutment, can be reduced. The recommended abutment to be loaded should be no less than five times during seating to prevent the abutment from sinking and causing changes in the occlusal relationship in the later stages. Preliminary occlusal adjustments should only be conducted in the early stages of the use of temporary restorations, and final restorations and occlusal adjustments are recommended to be performed after using the abutment for a period of time.
目的: 探究纯莫氏锥度连接种植系统种植体与基台锁结力大小及基台下沉量的影响因素。方法: 参考Bicon种植体基台连接设计，制作不同型号的种植体试件及其对应型号的基台，种植体—基台锁结锥度统一为1.5°，锁结深度分别为1.0、2.0、3.0 mm，锁结柱直径分别为2.5、3.0、3.5 mm，种植体外壁厚度分别为0.15、0.30 mm，实验机加载力分别为200、300、400 N，每组至少10枚种植体—基台试件。所有试件均采用万能实验机进行同样的加载方式（指压+指定加载力5次），分别于指压前、指压后、实验机加压5次后测量种植体—基台总高度，计算基台下沉量，最后采用万能实验机拉开种植体与基台，观察并记录其锁结力。结果: 实验加载力、锁结深度、锁结柱直径对种植体—基台锁结力及基台下沉量均有影响，种植体—基台锁结力随实验加载力、锁结深度、锁结柱直径的增加而增加（R=0.963、R=0.607、R=0.372），其中实验加载力对种植体—基台锁结力的影响最为显著。基台下沉量随着实验加载力的增加而增加（R=0.645），随锁结深度、锁结柱直径的增加而减少（R=-0.807、R=-0.280），锁结深度对基台下沉量的影响最为明显。种植体外壁厚度与种植体—基台锁结力大小的变化无明显的相关性，但种植体外壁厚度的增加会减少基台的下沉量，两者呈反比关系。结论: 通过调整纯莫氏锥度连接种植体—基台连接设计，增加锁结深度及锁结柱直径，增加基台就位时的加载力大小及加载次数，可以增加种植体—基台锁结力，减少基台松动甚至脱落等问题。同时为防止基台下沉导致后期咬合关系的改变，建议基台就位时加载次数不少于5次，同时建议使用临时修复体及早期只行初步咬合调整，在使用一段时间后再行最终修复及最终的咬合调整。.

OBJECTIVE: To investigate the effect of different abutments and crowns on the color of implant-supported restorations.
METHODS: Zirconia and lithium disilicate (e.max) disks with A2 shade were fabricated to represent two crowns. The implant abutments were untreated titanium, opaqued titanium, anodized titanium, A2 shade zirconia and white zirconia. 4.0 mm-thickness zirconia and e.max specimens were used as references respectively. The crowns were placed on tested abutments with a drop of clear glycerin between them and the color was measured using a digital spectrophotometer. CIELab values were recorded to evaluate color differences (ΔE) between tested specimens and the references.
RESULTS: Titanium abutments presented higher color differences than zirconia. The ΔE values with untreated titanium were higher than those with opaqued titanium. No differences were found between untreated titanium and anodized titanium for zirconia crowns. The ΔE values of zirconia crowns showed no significant differences between shade A2 zirconia and white zirconia abutments; e.max crowns showed a significant difference. The zirconia crown ΔE values were lower than those of e.max for all titanium and A2 zirconia abutments. Lithium disilicate crowns and zirconia abutments may be more suitable for implant-supported restorations. Opaqued titanium abutment may improve color in esthetic regions when a ceramic abutment cannot be used.
CONCLUSIONS: Lithium disilicate crowns and zirconia abutments may be an effective method to achieve excellent color matching in esthetic regions with implant-supported restorations.

Objective: To compare and evaluate the clinical esthetic effect of angle screw channel abutment and personalized zirconia adhesive abutment for single crown restoration in esthetic area. Methods: A total of 44 patients (21 males and 23 females), aged (37.4±13.5) years (18-67 years) who completed single crown restoration in the esthetic area of the Department of Oral Implantology, Dalian Stomatological Hospital from January 2018 to June 2022 were retrospectively selected. A total of 44 implants were inserted. According to the abutment selected for final restoration, the patients were divided into angle screw channel abutment group and personalized zirconia bonding abutment group, with 22 patients and 22 implants in each group. The implant survival rate, complication rate, pink and white esthetic score and marginal bone resorption were compared between the two groups. Results: Follow-up to 12 months after final restoration, implant survival rates were 100% (22/22) in both groups, and there was no statistically significant difference in the incidence of mechanical complications between the two groups [9% (2/22) in the angle screw channel abutment group and 0(0/22) in the personalized zirconia bonding abutment group, χ2=2.10, P=0.148]. In the follow-up appointment 12 months after final restoration, the pink esthetic score of the angle screw channel abutment group (12.95±1.05) was significantly better than that of the personalized zirconia bonding abutment group (11.45±2.02) (t=3.10, P=0.003). There was no significant difference in white esthetic scores between the two groups (t=1.27, P=0.212). There was no significant difference in the marginal bone resorption between the two groups (t=0.32, P=0.749). Conclusions: When a single implant supported restoration is delivered in the esthetic area of the anterior maxilla, high implant survival rate and stability of the marginal bone can be obtained by using the angle screw channel abutment or the personalized zirconia bonding abutment. The clinical efficacy of the angle screw channel system is reliable, and it will provide clinicians with a new treatment option.
目的： 对比评价上颌前牙种植单冠修复时应用角度螺丝通道基台与个性化氧化锆粘接基台的临床美学效果，为临床提供参考。 方法： 回顾性选择2018年1月至2022年6月于大连市口腔医院种植科完成上颌前牙种植单冠修复的患者44例（男性21例，女性23例），年龄（37.4±13.5）岁（18~67岁），共植入44枚种植体，根据最终修复时选用的基台分为角度螺丝基台组（使用角度螺丝通道基台）和氧化锆基台组（使用个性化氧化锆粘接基台），每组各22例患者（22枚种植体）。比较两组种植体存留率、并发症发生率、粉白美学评分结果及边缘骨吸收量。 结果： 随访至修复完成后12个月，两组种植体存留率均为100%（22/22），两组机械并发症发生率差异无统计学意义［角度螺丝基台组9%（2/22），氧化锆基台组0（0/22）］（χ2=2.10，P=0.148）。修复完成后12个月角度螺丝基台组粉色美学评分［（12.95±1.05）分］显著大于氧化锆基台组［（11.45±2.02）分］（t=3.10，P=0.003），两组白色美学评分差异无统计学意义（t=1.27，P=0.212）。两组边缘骨吸收量差异无统计学意义（t=0.32，P=0.749）。 结论： 前牙美学区种植单冠修复时采用角度螺丝通道基台或个性化氧化锆粘接基台均能获得良好的种植体存留率，边缘骨水平稳定，角度螺丝通道系统的临床疗效可靠，为临床提供了新的治疗选择。.

OBJECTIVE: To assess the impact of a two-piece abutment workflow on enhancing the stability of the alveolar bone and gingiva surrounding the dental implant, and to determine the level of patient satisfaction.
METHODS: A total of 48 patients with dentition defect in the posterior region were included and divided into two groups: the two-piece abutment workflow (TAW) and the sealing screw with submerged healing workflow (SHW). Marginal bone level (MBL), soft tissue indicators, oral hygiene indicators, and patient satisfaction were assessed and recorded partially at 0, 3, 6, and 12 months after surgery. The primary outcome was the change of MBL in different time periods. A generalized linear mixed model (GLMM) was used to take into account the correlated nature of the data, and adjust for potential confounding factors within inter-group differences.
RESULTS: The survival rate of implants and prosthesis reached 100% at 12-month follow-up, with an average decrease of 0.25 mm (SD 0.23 mm) of MBL in the TAW group and 0.48 mm (SD 0.45 mm) in the SHW group. The change of MBL in the TAW group (0.15 ± 0.31 mm) was significantly lower than the SHW group (0.41 ± 0.41 mm) through the analysis of GLMM within 6 months, while no significance was found in 12 months. Moreover, less gingival pain and oppression during prosthesis loading, and less time consumption overall duration were showed in the TAW group through Visual Analogue Scale (VAS, p < 0.05).
CONCLUSIONS: Within a 6-month period, the two-piece abutment workflow showed superior efficacy in preserving the integrity of the marginal bone level. Furthermore, it streamlined treatment procedures and mitigated discomfort, hence increasing patient satisfaction.

OBJECTIVE: This study aimed to investigate the influence of titanium base (ti-base) abutment macro- and micro-geometry on the mechanical stability of polymer-infiltrated ceramic network (PICN) screw-retained implant-supported single crowns (iSCs).
METHODS: Twelve specimens per group were used, comprising six different implant/ti-base abutment combinations restored with PICN iSCs: Nb-T (gingival height [GH]: 1.5 mm, prosthetic height [PH]: 4.3 mm), CC (GH: 0.8 mm, PH: 4.3 mm), CC-P (GH: 0.8 mm, PH: 7 mm), Nb-V (GH: 1.5 mm, PH: 6 mm), St (GH: 1.5 mm, PH: 5.5 mm), and Th (GH: 0.5 mm, PH: 9 mm). The specimens underwent thermo-mechanical aging, and those that survived were subsequently subjected to static loading until failure. The data were analyzed using a one-way ANOVA test followed by Tukey post hoc test (α = .05).
RESULTS: All specimens survived thermo-mechanical aging without complications, namely, visible cracks, debonding, or screw loosening. Th group demonstrated the highest strength values among all the groups, with significant differences compared to Nb-T (p < .05), CC (p < .001), and St (p < .001). Additionally, CC-P group exhibited significantly superior fracture strength results compared to CC (p < .05) and St (p < .05).
CONCLUSIONS: The choice of ti-base, particularly prosthetic height, had a significant influence on fracture resistance of PICN iSCs. Nevertheless, the height or geometrical features of the ti-base did not exhibit a significant influence on the mechanical behavior of the iSC/ti-base assembly under thermomechanical loading, as all specimens withstood the aging without complication or failure.

OBJECTIVE: To compare the clinical, radiographic, and immunological outcomes between one-piece versus two-piece zirconia abutments supported single implant crowns in the esthetic region.
METHODS: The study followed a split-mouth, double-blind, and randomized controlled clinical design for a duration of 3 years. Twenty-two eligible patients with 44 implants were randomly assigned to two groups: Group 1 (one-piece zirconia abutment with zirconia base, n = 22) and Group 2 (two-piece zirconia abutment with titanium base, n = 22). The primary outcome was the technical complication rate. Additionally, survival rates, cytokines concentrations in peri-implant crevicular fluid (PICF), peri-implant conditions, marginal bone loss, and pink/white esthetics score (PES/WES) were assessed as secondary outcomes.
RESULTS: Twelve of 22 patients attended the 1-year follow-up (due to the COVID pandemic), and 19 patients attended the 3-year examination. Two abutments in Group 1 were fractured after 10 and 12 months in function. Additionally, one screw loosening occurred in Group 1 at 1-year follow-up. The 3-year technical complication rate was significantly higher in Group 1 than that in Group 2 (15.79% vs. 0%, p < .001). The 3-year implant survival rate was 100% in both groups. The concentration of IFN-γ in PICF was significantly upregulated in Group 2 (p = .018). Furthermore, the IL-6 concentration was positively correlated with BOP% (p = .020).
CONCLUSIONS: Two-piece zirconia abutments exhibited superior technical performance compared to one-piece designs during a 3-year follow-up in the anterior region. However, further long-term research is necessary to verify the immunological stability of two-piece zirconia abutments.

Zirconia materials have been increasingly used in implant rehabilitation due to their excellent physical and esthetic properties. Stable peri-implant epithelial tissue adhesion to the transmucosal implant abutment may significantly enhance the efficacy of implant long-term stability. However, it is difficult to form stable chemical or biological bindings with peri-implant epithelial tissue due to the strong biological inertia of zirconia materials. In the present study, we investigated whether calcium hydrothermal treatment of zirconia promotes sealing of peri-implant epithelial tissue. In vitro experiments were performed to analyze the effects of calcium hydrothermal treatment on zirconia surface morphology and composition by scanning electron microscopy and energy dispersive spectrometry. Immunofluorescence staining of adherent proteins, namely, F-actin and integrin β1, in human gingival fibroblast line (HGF-l) cells was performed. In the calcium hydrothermal treatment group, there was higher expression of these adherent proteins and increased HGF-l cell proliferation. An in vivo study was conducted by extracting the maxillary right first molars of rats and replacing them with mini-zirconia abutment implants. The calcium hydrothermal treatment group showed better attachment at the zirconia abutment surface, which inhibited horseradish peroxidase penetration at 2 weeks post-implantation. These results demonstrated that calcium hydrothermal treatment of zirconia improves the seal between the implant abutment and surrounding epithelial tissues, potentially increasing the long-term stability of the implant.

Studies have confirmed that tooth loss is closely related to systemic diseases, such as obesity, diabetes, cardiovascular diseases, some types of tumors, and Alzheimer\'s disease. Among many methods for tooth restoration, implant restoration is the most commonly used method. After implantation, long-term stability of implants requires not only good bone bonding but also good soft tissue sealing between implants and surrounding soft tissues. The zirconia abutment is used in clinical implant restoration treatment, but due to the strong biological inertia of zirconia, it is difficult to form stable chemical or biological bonds with surrounding tissues. In this study, we investigated synthesized zinc oxide (ZnO) nanocrystal on the zirconia abutment surface by the hydrothermal method to make it more beneficial for soft tissue early sealing and the molecular mechanism. In vitro experiments found that different hydrothermal treatment temperatures affect the formation of ZnO crystals. The crystal diameter of ZnO changes from micron to nanometer at different temperatures, and the crystal morphology also changes. In vitro, scanning electron microscopy, energy dispersive spectrometry, and real-time polymerase chain reaction results show that ZnO nanocrystal can promote the attachment and proliferation of oral epithelial cells on the surface of zirconia by promoting the binding of laminin 332 and integrin β4, regulating the PI3K/AKT pathway. In vivo, ZnO nanocrystal ultimately promotes the formation of soft tissue seals. Collectively, ZnO nanocrystal can be synthesized on a zirconia surface by hydrothermal treatment. It can help to form a seal between the implant abutment and surrounding soft tissue. This method is beneficial to the long-term stability of the implant and also can be applied to other medical fields.

OBJECTIVE: To study on the accuracy of implant-borne single restoration by two production processes with Ti-base to provide experimental data for proper processes of single implant-borne restoration.
METHODS: Thirty patients were selected with single posterior teeth missing from the Department of Oral Implantology of Shanghai Putuo District Eye Disease and Dental Disease Prevention and Treatment Institute. The patients were taken 2 traditional impressions clinically for two plaster model equipped with implant analogue. These models were then divided into 2 groups according to different production processes. The experimental group was scanned with the scan body installed in the model implant analogue, while the control group was scanned directly on the Ti-base abutment installed in the model implant analogue. The implant-borne single restorations of the two groups were cut along the buccal-lingual side and the distance between the measuring point to the Ti-Base abutment was observed by electron microscopy. In addition, the breaking limit of zirconia crown was observed, universal test machine was used to load direct force to the crown. SPSS 22.0 software package was used for data analysis.
RESULTS: The gap between the implant-borne single restoration to the Ti-base abutment of the experimental group was significantly smaller than that of the control group. The difference between the two groups was statistically significant (P<0.05). However, by testing the breaking limit of zirconia crown, there was no significant difference(P>0.05).
CONCLUSIONS: Using scan body to transfer the implant position and Ti-base abutment data information to the digital dental design software is more accurate and reliable than directly scanning the Ti-base on the model analogue. Using scan body is recommended for processing and manufacture of implant-borne singe restoration.