OBJECTIVE: To evaluate the bone changes around equicrestal and subcrestal implants, analyzing the effect of abutment height [short abutments (SA < 2 mm) and long abutments (LA > 2 mm)] and the three components of the peri‑implant soft-tissue phenotype.
METHODS: Twenty-six patients received 71 implants that were placed according to supracrestal tissue height (STH) in an equicrestal (n = 17), shallow subcrestal ≈1 mm (n = 33), or deep subcrestal ≈2 mm (n = 21) position. After 3 months of healing, rehabilitation was completed using metal-ceramic crowns on multi-unit abutments of 1.5 mm, 2.5 mm, or 3.5 mm in height, depending on the prosthetic space and STH. Longitudinal clinical parameters (STH, mucosal thickness, and keratinized mucosa width) and radiographic data [bone remodelling and marginal bone loss (MBL)] were collected at 3, 6, 12, and 24 months postsurgery.
RESULTS: The gain in STH was significantly greater around the implants placed in a subcrestal ≈2 mm position. After 2 years, the mean change in bone remodelling in the SA group was significantly greater than in the LA group. According to the multiple linear regression, bone remodelling depends primarily on abutment height (β = -0.43), followed by crestal position (β = 0.34), and keratinized mucosa width (β = -0.22), while MBL depends on abutment height (β = -0.37), and the patient\'s age (β = -0.36).
CONCLUSIONS: Implants placed in an equicrestal or subcrestal ≈1 mm position with LA undergo less bone remodelling, while the lowest level of MBL occurs in subcrestal ≈2 mm implants with LA. Differing soft-tissue thicknesses combined with the use of either SA or LA produced significant intergroup differences in bone remodelling and MBL.
CONCLUSIONS: Abutment height is the most powerful predictor variable affecting bone remodelling and MBL. Depending on the dimensions of the peri‑implant soft-tissue phenotype, placing the implants subcrestally may also be a viable option to decrease bone remodelling and, consequently, reduce MBL.
BACKGROUND: identification number: NCT05670340.

OBJECTIVE: The study aimed to assess the impact on the mechanical strength and failure patterns of implant-abutment complexes of choosing different abutment types, designs and manufacturers, aiding in selecting the optimal restorative solution. Stock and custom abutments from original and aftermarket suppliers were subjected to thermomechanical aging.
METHODS: Stock and custom abutments from the implant manufacturer (original) and a aftermarket supplier (nonoriginal) were connected to identical implants with internal connection. Custom abutments were designed in a typical molar and premolar design, manufactured using the workflow from the respective suppliers. A total of 90 implants (4 mm diameter, 3.4 mm platform, 13 mm length) equally divided across 6 groups (three designs, two manufacturers) underwent thermo-mechanical aging according to three different regimes, simulating five (n = 30) or 10 years (n = 30) of clinical function, or unaged control (n = 30). Subsequently, all samples were tested to failure.
RESULTS: During aging, no failures occurred. The mean strength at failure was 1009N ± 171, showing significant differences between original and nonoriginal abutments overall (-230N ± 27.1, p < .001), and within each abutment type (p = .000), favoring original abutments. Aging did not significantly affect the failure load, while the type of abutment and manufacturer did, favoring original and custom-designed abutments. The most common failure was implant bending or deformation, significantly differing between original and nonoriginal abutments and screws. All failure tests resulted in clinically unsalvageable implants and abutments.
CONCLUSIONS: Within the limitations of this study, original abutments exhibited a higher mechanical strength compared to the nonoriginal alternative, regardless of the amount of simulated clinical use. Similarly, custom abutments showed higher mechanical strength compared to stock abutments. However, mechanical strength in all abutments tested was higher than average chewing forces reported in literature, thus components tested in this study can be expected to perform equally well in clinical situations without excessive force.

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。.

BACKGROUND: Placement of an implant in the maxillary anterior region is challenging due to the angulation of bone in this area. Angled abutments may be used to achieve proper restorative contours. The present study was undertaken to examine and compare the stress levels of implants in the maxillary anterior region having different types of internal connections and different abutment angulations.
METHODS: Implants with three types of abutment connections, internal conical, Morse taper, and internal hex, were modeled using SolidWorks software. Three abutment angulations of 0, 15, and 30 degrees were used for each type of implant. A 100 N axial load was applied to the implants, and the stresses on the implant, abutment, and bone were analyzed by finite element analysis.
RESULTS: Among the straight abutments, the most stress was in model 3A (62.60 MPa). The stress value among angled abutments was highest with 30-degree angled abutments. The value was highest in model 3C (94.83 MPa). Internal hex connection showed the highest stress levels in all degrees of angulation of the abutment, and Morse taper connection showed the least amount of stress in all three abutment angles. The most stress concentration was seen in the cortical bone on the buccal surface in the implant-abutment junction.
CONCLUSIONS: The Morse taper design of implant exhibited the least-highest stress levels on the alveolar bone. The stress levels increased with the increasing angulation of the implant or implant-abutment connection.

OBJECTIVE: The aim of this in vitro study was to investigate whether and to what extent different scenarios of rotational freedom in different IAC designs affect the vertical dimension of a three-part fixed partial denture (FPD). At the same time, the experimental setup should simulate all clinical and laboratory steps of the implementation of such an FPD as accurately as possible.
METHODS: Twenty identical pairs of jaw models were fabricated from aluminum, each lower-jaw model holding two implants with conical or flat IACs. Three impressions of each model were taken to fabricate stone casts and three-unit FPDs. Three assembly scenarios were compared for the vertical position stability they offered for these FPDs, differing by how the sequential implant components (impression posts > laboratory analogs > abutments 1 > abutments 2) were aligned with the positional index of the IAC. In this way, a total of 60 stone casts and FPDs were fabricated and statistically analyzed for changes in vertical dimension (p < 0.05).
RESULTS: Regardless of whether a conical/flat IAC was used (p > 0.05), significantly greater mean changes in vertical dimension were consistently (all comparisons p < 0.0001) found in a \"worst-case scenario\" of component alignment alternating between the left- and right-limit stop of the positional index (0.286/0.350 mm) than in a \"random scenario\" of 10 dentists and 10 technicians with varying levels of experience freely selecting the alignment (0.003/0.014 mm) or in a \"best-case scenario\" of all components being aligned with the right-limit stop (-0.019/0.005 mm).
CONCLUSIONS: The likelihood of integrating a superstructure correctly in terms of vertical dimension appears to vary considerably more with assembly strategies than with IAC designs. Specifically, our findings warrant a recommendation that all implant components should be aligned with the right-limit stop of the positioning index.

The optimal configuration of a customized implant abutment is crucial for bone remodeling and is influenced by various design parameters. This study introduces an optimization process for designing two-piece zirconia dental implant abutments. The aim is to enhance bone remodeling, increase bone density in the peri-implant region, and reduce the risk of late implant failure. A 12-month bone remodeling algorithm subroutine in finite element analysis to optimize three parameters: implant placement depth, abutment taper degree, and gingival height of the titanium base abutment. The response surface analysis shows that implant placement depth and gingival height significantly impact bone density and uniformity. The taper degree has a smaller effect on bone remodeling. The optimization identified optimal values of 1.5 mm for depth, 35° for taper, and 0.5 mm for gingival height. The optimum model significantly increased cortical bone density from 1.2 to 1.937 g/cm3 in 2 months, while the original model reached 1.91 g/cm3 in 11 months. The standard deviation of density showed more uniform bone apposition, with the optimum model showing values 2 to 6 times lower than the original over 12 months. The cancellous bone showed a similar trend. In conclusion, the depth and taper have a significant effect on bone remodeling. This optimized model significantly improves bone density uniformity.

BACKGROUND: This case report outlines a novel prosthodontic approach for managing a broken screw inside an implant screw channel, emphasising the importance of innovative solutions in implant dentistry.
METHODS: A 57-year-old male patient sought restoration for implant-supported crowns (#46 and #47). A broken screw inside the implant screw channel posed a significant concern for both the patient and the dental team.
METHODS: Utilising an impression pickup technique of the inner surface of the implant body, a custom titanium abutment was fabricated in the laboratory and restoration was successfully replaced. A follow-up of 6 months was performed, ensuring optimal function and patient satisfaction.
RESULTS: The custom titanium abutment with a zirconia crown was placed, leading to a successful restoration. The patient reported no discomfort, demonstrating improved function and aesthetics.
UNASSIGNED: This case highlights the effectiveness of tailored prosthodontic interventions in addressing complex implant-related complications.

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 evaluate the potential of laser-microtextured abutments (LMAs) compared to machined abutments (MAs) in peri-implant clinical and radiographic outcomes.
METHODS: Eligible studies consisted of randomized clinical trials (RCTs) retrieved from MEDLINE, Web of Science, Scopus, and Embase databases. The study adhered to the PRISMA statement, and the protocol was registered at the PROSPERO (registration number CRD42023443112). The risk of bias was evaluated according to version 2 of the Cochrane risk of bias tool (RoB 2). Meta-analyses were performed using random effect models. Afterward, the GRADE approach was used to determine the certainty of evidence.
RESULTS: Four RCTs were included from a total of 2,876 studies. LMAs had lower peri-implant sulcus depth at 6-8 weeks (WMD: -0.69 mm; 95% CI: -0.97, -0.40; p = 0.15, I2 = 53%) and at one year (WMD: -0.75 mm; 95% CI: -1.41, -0.09; p = 0.09, I2 = 65%), but the certainty of evidence was low. In addition, the marginal bone loss favored the LMAs group (WMD: -0.29 mm; 95% CI: -0.36, -0.21; p = 0.69, I2 = 0%) with moderate evidence. There were fewer sites with bleeding on probing in the LMAs group (WMD: -1.10; 95% CI: -1.43, -0.77; p = 0.88, i2 = 0%). There was no statistical difference between groups for the modified gingival index and modified plaque index. Furthermore, all studies were classified as having some concerns risk of bias.
CONCLUSIONS: There was low to moderate certainty evidence that LMAs can favor peri-implant clinical and radiographic parameters compared to MAs.
CONCLUSIONS: Laser-microtextured abutments may benefit peri-implant clinical and radiographic outcomes.

OBJECTIVE: To assess the reliability of implant stability measurements recorded with the Periotest device and to investigate the differences in values when these measurements were taken on implant retained crowns and healing abutments.
METHODS: Fifty-six implants in eight synthetic bone blocks were used to carry out implant stability measurements using the Periotest device by two different operators. Each block constituted an example of bone of density D1, D2, D3, or D4, and two blocks of each density were used. The healing abutments placed were of a height to allow approximately 6 mm of the implant-abutment complex to be supracrestal and temporary crowns were made to match the dimensions of an average central incisor. Descriptive statistics were used to describe the perio test values (PTVs) at each of the different heights on the implant abutments and implant crowns. Means for each site were calculated and distribution of data assessed using the Kruskal Wallis test. The interclass correlation coefficient (ICC) was used to determine the relationship between the PTVs recorded on the implant abutments and implant crowns.
RESULTS: The mean PTV (±standard devidation) recorded across all sites was 5.57 ± 11.643 on the implant abutments, and 12.27 ± 11.735 on the temporary crowns. Excellent/good inter-operator ICCs were recorded for the mid-abutment site in all bone blocks D1-D4 (ICC = 0.814, p < 0.001, ICC = 0.922, p < 0.001, ICC = 0.938, p < 0.001, ICC = 776, p < 0.001). For mid crown sites, ICC between operators was excellent/good only for recordings in D2 bone (ICC = 0.897, p < 0.001).
CONCLUSIONS: Periotest device seems to be able to reliably measure implant stability across all types of bones when the implant stability is assessed at approximately 3 mm coronal to the implant platform for abutments and 4.5 mm for implant supported single crowns.