Comparative study of axial displacement in digital and conventional implant prosthetic components.

Axial displacement of prosthetic components is a major concern in implant dentistry, particularly during screw tightening. However, implant manufacturers provide different recommended torques for tightening implant prosthetic components, which can lead to errors in prosthesis fit before and after impression making. Implant-abutment connection angle or abutment geometries can affect axial displacement. This study aimed to compare the axial displacement between conventional and digital components based on the tightening torque and differences in the implant-abutment connection angles and geometries. The results showed that scan bodies with different implant-abutment connection geometries exhibited smaller axial displacement with increasing tightening torque than other prosthetic components. Except for the scan bodies, there was no difference in the axial displacement of prosthetic components when tightened with the same torque. However, regardless of the use of digital or conventional method of impression making, the axial displacement between the impression making component and the abutment when tightened to the recommended torques were significantly different. In addition, axial displacement was affected by the internal connection angle. The results of this study indicate that the tightening torque and geometry of prosthetic components should be considered to prevent possible misfits which can occur before and after impression making.

Fretting-corrosion at the Implant-Abutment Interface Simulating Clinically Relevant Conditions.

OBJECTIVE: Implant treatment is provided to individuals with normal, idealized masticatory forces and also to patients with parafunctional habits such as grinding, clenching, and bruxing. Dental erosion is a common increasing condition and is reported to affect 32 % of adults, increasing with age. This oral environment is conducive to tribocorrosion and the potential loss of materials from the implant surfaces and interfaces with prosthetic components. Although several fretting-corrosion studies have been reported, until now, no study has simulated clinically relevant micromotion. Therefore, our aim is to investigate fretting-corrosion using our new micro-fretting corrosion system, simulating clinical conditions with 5 µm motion at the implant-abutment interface under various occlusal loads and acidic exposures. METHODS: We simulated four conditions in an oral environment by varying the contact load (83 N and 233 N) and pH levels (3 and 6.5). The commonly used dental implant material, Grade IV titanium, and abutment material Zirconia (ZrO2)/ Grade IV titanium were selected as testing couple materials. Artificial saliva was employed to represent an oral environment. In addition, a standard tribocorrosion protocol was followed, and the pin was controlled to oscillate on the disk with an amplitude of 5 µm during the mastication stage. After the testing, 3D profilometry and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) were utilized to analyze the worn surfaces. Inductively coupled plasma mass spectrometry (ICP-MS) was also used to measure the metal ion release. RESULTS: Energy ratios were below 0.2, indicating a fretting regime of partial slip for all groups. Open-circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) were analyzed to compare the electrochemical behavior among groups. As a result, corrosive damage was observed to be more in the Ti4- Ti4 groups than in Zr-Ti4 ones, whereas more mechanical damage was found in the Zr-Ti4 groups than in the Ti4-Ti4 groups. Possible mechanisms were proposed in the discussion to explain these findings. SIGNIFICANCE: The results observed from this study might be helpful to clinicians with implant selection. For example, for patients with bruxism, a titanium implant paired with a titanium abutment may be preferable, while patients with GERD may benefit more from a titanium implant paired with a zirconia abutment.

Simulating the Entire Clinical Process for an Implant-Supported Fixed Prosthesis: In Vitro Study on the Vertical Implications of Implant-Abutment Connections and Rotational Freedom.

OBJECTIVES: 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. MATERIAL AND 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.

Effect of one-time placement of the definitive abutment versus multiple healing abutment disconnections and reconnections during the prosthetic phase on radiographic and clinical outcomes: A 12-month randomized clinical trial.

OBJECTIVE: The aim of this investigation was to evaluate the effect on clinical and radiological outcomes of the one-abutment, one-time protocol (test) versus placing the definitive abutment on the day of functional loading after having disconnected and connected three times the healing abutment during the prosthetic phase (control). MATERIALS AND METHODS: Forty patients with 80 implants were randomly allocated to either the test or the control group. Changes in the radiographic marginal bone levels (MBLs), clinical outcomes, prosthetic-related outcomes, and patient-reported outcomes measures (PROMs) were assessed and compared 6 and 12 months after functional loading. RESULTS: Thirty-seven patients with 74 implants were followed at 12 months. A statistically significant bone remodeling was observed in both groups following implant placement. MBLs were significantly greater in the control group at the 6- (-0.13 mm vs. -0.61 mm) and 12-month visits (-0.01 mm vs. -0.53 mm). Bone loss was significantly greater in the control group from surgery to 6 and 12 months and from loading to 6 and 12 months. The abutment height was significantly greater in the test group, however, there were no significant differences in the restorative angle. Similarly, there were no statistically significant differences between groups for the measured clinical variables (probing depth, plaque, and bleeding index) and PROMs. CONCLUSIONS: Disconnecting and reconnecting the healing abutment was associated with significantly higher bone loss after 12 months, as compared to the placement of the definitive abutment at implant installation.

The innovative double or triple dental abutment-implant: Case study with a 3-to-12-year follow-up.

BACKGROUND: The aim of this case study is to present the rationality and scientific evidence of a new design for a double (DA) and triple (TA) dental abutment-implant with their specific new concept of biodynamic optimized peri-implant tissue (BOPiT). METHODS: The innovative design of these abutments with a paraboloid geometry was based on BOPiT, simultaneously involving the principles of mechanobiology, biotensegrity, and mechanotransduction. Thus, 37 consecutive individuals/43 cases rehabilitated with single dental implant using the innovative DA (n = 28) and TA (n = 15) on 43 implants were included in this case study. The DA and TA support 2 or 3 dental crowns on a single implant, respectively. Clinic and radiographic examinations were presented at T1 (loading after 4 months) and T2 [final examination with an average follow-up time of 7.2 years (>3 to 12 years)]. RESULTS: At T2, mean scores for plaque index, peri-implant bleeding on probing, and peri-implant probing depth were low, depicting healthy peri-implant conditions. All radiographic images showed insignificant annual marginal bone loss (0.022 ± 0.05 mm) when compared to T1, reflecting great bone stability. CONCLUSION: DA and TA, based on the BOPiT concept, represent an advantageous, simple and non-invasive mechanism for the longevity and healthy regulation of the peri-implant tissues.

Experimental study on implant-abutment locking force and abutment subsidence in a pure Morse taper connection implant system.

OBJECTIVES: 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.

Mechanical strength of stock and custom abutments as original and aftermarket components after thermomechanical aging.

OBJECTIVES: 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. MATERIAL AND 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.

Microbial Leakage through Three Different Implant-Abutment Interfaces on Morse Taper Implants In Vitro.

The objective of this study was to evaluate microbial leakage by means of genome counts, through the implant-abutment interface in dental implants with different Morse taper abutments. Fifty-six samples were prepared and divided in four groups: CMC TB (14 Cylindrical Implants-14 TiBase Abutments), CMX TB (14 Conical Implants-14 TiBase Abutments), CMX PU (14 Conical Implants-14 Universal Abutment) and CMX U (14 Tapered Implants-14 UCLA Abutments). Assemblies had their interface submerged in saliva as the contaminant. Samples were subjected either to thermomechanical cycling (2 × 106 mechanical cycles with frequency of 5 Hz and load of 120 N simultaneously with thermal cycles of 5-55 °C) or thermal cycling (5-55 °C). After cycling, the contents from the inner parts of assemblies were collected and analyzed using the Checkerboard DNA-DNA hybridization technique. Significant differences in the total genome counts were found after both thermomechanical or thermal cycling: CMX U > CMX PU > CMX TB > CMC TB. There were also significant differences in individual bacterial counts in each of the groups (p < 0.05). Irrespective of mechanical cycling, the type of abutment seems to influence not only the total microbial leakage through the interface, but also seems to significantly reflect differences considering individual target species.

Comparative in vitro evaluation of microgap in titanium stock versus cobalt-chrome custom abutments on a conical connection implant: Effect of crown cementation and ceramic veneering.

OBJECTIVE: To compare the implant-abutment connection microgap between computer-aided design and computer-aided manufacturing (CAD/CAM) milled or laser-sintered cobalt-chrome custom abutments with or without ceramic veneering and titanium stock abutments with or without crown cementation. MATERIAL AND METHODS: Six groups of six abutments each were prepared: (1) CAD/CAM cobalt-chrome custom abutments: milled, milled with ceramic veneering, laser-sintered, and laser-sintered with ceramic veneering (four groups: MIL, MIL-C, SIN, and SIN-C, respectively) and (2) titanium stock abutments with or without zirconia crown cementation (two groups: STK and STK-Z, respectively). Abutments were screwed to the implants by applying 30 Ncm torque. All 36 samples were sectioned along their long axes. The implant-abutment connection microgap was measured using scanning electron microscopy on the right and left sides of the connection at the upper, middle, and lower levels. Data were analyzed using the Kruskal-Wallis test (p < .05). RESULTS: Mean values (µm) of the microgap were 0.54 ± 0.44 (STK), 0.55 ± 0.48 (STK-Z), 1.53 ± 1.30 (MIL), 2.30 ± 2.2 (MIL-C), 1.53 ± 1.37 (SIN), and 1.87 ± 1.8 (SIN-C). Although significant differences were observed between the STK and STK-Z groups and the other groups (p < .05), none were observed between the milled and laser-sintered groups before or after ceramic veneering. The largest microgap was observed at the upper level in all groups. CONCLUSIONS: Titanium stock abutments provided a closer fit than cobalt-chrome custom abutments. Neither crown cementation nor ceramic veneering resulted in significant changes in the implant-abutment connection microgap.

Comparative Analysis of Internal Tapered Implant-Abutment Connections: Evaluating the Morse Effect.

The purpose of the present study was to evaluate the Morse effect of different internal tapered implant-abutment connections (ITCs) using a pullout test. Implants with different ITCs were selected: Short (Bicon, USA), G1; Novo Colosso (Medens, Brazil), G2; Epkut (SIN, Brazil), G3; Strong SW (SIN, Brazil), G4; Flash (Conexão, Brazil), G5 and Bone Level (Straumann, Switzerland), G6. The respective computer-aided design (CAD) files were loaded into the analysis software to measure each ITC's taper angle and implant-abutment contact area. Six implants from each group were embedded in acrylic resin blocks, and the respective universal abutments were fixed using a mallet (G1) or by applying 20 Ncm of torque (G2 to G6). After 10 minutes, each abutment's retention screw was removed, and the force necessary for abutment rupture was recorded using a universal testing machine at a crosshead speed of 0.5 mm/min. The groups were compared using a one-way analysis of variance and Tukey's test. Spearman's correlation was used to check the correlation of the taper angle and contacting area with the pullout strength. G1, a no-screw abutment with a 3° taper, and G2, a 10° tapered abutment tightened by 20 Ncm, presented the highest pullout strength (P < .05). The increased taper angle of G4, compared to G3, reduced the Morse effect despite their similar implant-abutment contacting areas (P < .05). The G5 and G6 abutments loosened after screw removal and did not exhibit pullout resistance. The closer the tapered angle (r = -.958) and the higher the implant-abutment contact area (r = .880), the higher the pullout strength (P < .001). Within the limits of this study, the Morse effect is different among tapered implant-abutment connections. The closer the tapered angle and the higher the interface area, the higher the Morse effect between the abutment and the implant.

Longevity of different abutments placed on narrow diameter implants: Assessment of structural damage and loosening.

OBJECTIVES: To evaluate structural damage and loosening of abutments placed on narrow diameter implants after cyclic fatigue. METHODS: Sixty Morse taper narrow diameter implants (Neodent, Brazil) received two types of abutments (1PA- one-piece abutment or 2PA- two-piece abutment), which were randomly divided into 3 fatigue experiments (n = 10). The implants were placed into a customized supporting holder and a software-assisted digital torque wrench secured the manufacturer recommended torque for each abutment. Cone beam computed tomography (CBCT) scans were acquired, before and after fatigue, and post-processed (software e-Vol DX) to assess damage and abutment displacement. The boundary fatigue method was adapted to use 2 × 106 cycles, 2 Hz of frequency and constant peak load of 80 N (first experiment) that varied according to the failure rate of previous specimens (second and third experiments). Failure was evaluated using CBCT scans and removal torque values. Data were used to estimate long-term torque degradation, probability of failure and Weibull modulus (software ALTA PRO9). RESULTS: All 2PA specimens became loosen independently of the applied fatigue load, and structural bending was observed in 14 abutments. Eight 1PA got loosen during the fatigue experiment. The Weibull analysis showed a lower modulus (m = 1.0; 0.7, 1.4) for 1PA than for 2PA (m = 2.6; 2, 3.4) resulting in longer predicted lifetimes and slower torque degradation for 1PA than for 2PA specimens. SIGNIFICANCE: 1PA showed greater long-term survival probability than 2PA. Predicting the lifetime and mechanical behavior of implant-abutment systems are useful information to clinicians during the decision-making process of oral rehabilitations.

Longitudinal Observation of Micromotion upon Loading of Implant-Abutment Connection.

While technological advances have made implants a good treatment option with a good long-term prognosis, peri-implantitis, which results in alveolar bone resorption around implants, has been observed in some cases. Micromotion at the implant abutment connection can cause peri-implantitis. However, the temporal progression of micromotion upon loading remains unclear. Therefore, we aimed to longitudinally measure micromotion upon loading application on an implant. Implants with Morse-tapered connections were prepared. Custom titanium abutments were fabricated and tightened onto implant bodies at 35 N. A 100 N vertical load was applied for 200,000 cycles. Micromotion was measured when the load was applied, as was the total implant length and removal torque before and after loading. The micromotion was measured from the position data of the jig of the testing machine during loading. The average removal torque was 30.67 N after 10 min of tightening and 27.95 N after loading, indicating a decrease due to loading. The implant length reduced by 3.6 µm under the load. The average micromotion was 0.018 mm at 2 cycles, 0.016 mm at 100,000 cycles, and 0.0157 mm at 200,000 cycles, indicating implant length reduction under the load but not reaching 0. The micromotion between the implant and abutment under a cyclic load decreased over time but did not completely cease. These results highlight the relationship between micromotion and loading, underscoring the importance of careful monitoring and management to mitigate potential complications, such as peri-implantitis, and ensure optimal performance and durability of the implant.

A comparative finite element analysis of titanium, poly-ether-etherketone, and zirconia abutment on stress distribution around maxillary anterior implants.

Background: The aim of this study was to investigate the influence of abutment material, alveolar bone density, and occlusal forces on stress distribution around maxillary anterior implants. Materials and Methods: An in-vitro study was conducted. The maxillary anterior implant was modeled using a three-dimensional finite element model in D2 and D3 bones with three different abutment materials: titanium, zirconia, and poly-ether-ether ketone (PEEK). Von Mises stress was evaluated after the application of vertical and oblique loads of 100 N, 175 N, and 250 N. Statistical analysis was done by Friedman-Wilcoxon signed-rank test, Mann-Whitney U test, and Kruskal-Wallis test. The probability value <0.05 is considered a significant level. Results: Stress distribution around D3 bone was higher than D2 bone in all the abutment materials with greater values seen in oblique load than vertical load with insignificant difference (P > 0.05). Statistically insignificant stress values were seen greater in PEEK than titanium or zirconia abutment (P > 0.05). A statistically significant difference was observed between 100 N and 175 N of load (P < 0.05). Conclusion: PEEK, zirconia, and titanium as abutment material in the anterior region showed similar properties. The stress on the bone was proportionately increased during the vertical and oblique loads suggesting the influence of mechanical load in crestal bone loss rather than the type of abutment material.

Marginal changes at bone-level implants supporting dental prostheses with or without intermediate standardised abutments after 36 months: Randomised controlled clinical trial.

OBJECTIVE: The objective of this study is to evaluate the changes at marginal bone level at implants restored with screw-retained prosthesis connected directly to the implants or with an intermediate abutment, after 3-year follow-up. MATERIAL AND METHODS: Thirty-six partially edentulous patients received 72 implants. Each patient received 2 implants and a 2-4-unit screw-retained implant-prosthesis. The test group implants received a screw-retained prosthesis connected directly to the implant shoulder, the control group prosthesis were connected through a 3-mm standardised intermediate abutment. Clinical and radiological data were recorded at baseline and at 6-, 12-, and 36-month follow-up. RESULTS: At 36 months, the mean marginal bone loss was 0.13 ± 0.18 mm for the control group and 0.20 ± 0.24 for the test group, with no significant differences between groups (p > .05). Clinical variables (Probing Pocket Depth, Bleeding on Probing and Plaque Index) at 36 months also showed no significant difference between groups. Minor complications frequency was 6.7% in the control group and 5.3% in test group. None of the groups suffered from mayor complications. Patient Reported Outcomes (PROs) showed a General Satisfaction mean score in the control group of 9.40 (SD 0.82) and 9.37 (SD 1.06) in the test group with no significant differences between groups. CONCLUSIONS: Bone-level implants restored with screw-retained partial prostheses with or without intermediate abutments showed similar radiographic and clinical outcomes after 3 years.

Static and dynamic stress analysis of different crown materials on a titanium base abutment in an implant-supported single crown: a 3D finite element analysis.

BACKGROUND: This Finite Element Analysis was conducted to analyze the biomechanical behaviors of titanium base abutments and several crown materials with respect to fatigue lifetime and stress distribution in implants and prosthetic components. METHODS: Five distinct designs of implant-supported single crowns were modeled, including a polyetheretherketone (PEEK), polymer-infiltrated ceramic network, monolithic lithium disilicate, and precrystallized and crystallized zirconia-reinforced lithium silicates supported by a titanium base abutment. For the static load, a 100 N oblique load was applied to the buccal incline of the palatal cusp of the maxillary right first premolar. The dynamic load was applied in the same way as in static loading with a frequency of 1 Hz. The principal stresses in the peripheral bone as well as the von Mises stresses and fatigue strength of the implants, abutments, prosthetic screws, and crowns were assessed. RESULTS: All of the models had comparable von Mises stress values from the implants and abutments, as well as comparable maximum and minimum principal stress values from the cortical and trabecular bones. The PEEK crown showed the lowest stress (46.89 MPa) in the cervical region. The prosthetic screws and implants exhibited the highest von Mises stress among the models. The lithium disilicate crown model had approximately 9.5 times more cycles to fatique values for implants and 1.7 times more cycles to fatique values for abutments than for the lowest ones. CONCLUSIONS: With the promise of at least ten years of clinical success and favorable stress distributions in implants and prosthetic components, clinicians can suggest using an implant-supported lithium disilicate crown with a titanium base abutment.

Bioactivity and antibacterial effects of zinc-containing bioactive glass on the surface of zirconia abutments.

OBJECTIVES: This study aimed to enhance gingival fibroblast function and to achieve antibacterial activity around the implant abutment by using a zinc (Zn)-containing bioactive glass (BG) coating. METHODS: 45S5 BG containing 0, 5, and 10 wt.% Zn were coated on zirconia disks. The release of silica and Zn ions in physiological saline and their antibacterial effects were measured. The effects of BG coatings on human gingival fibroblasts (hGFs) were assessed using cytotoxicity assays and by analyzing the gene expression of various genes related to antioxidant enzymes, wound healing, and fibrosis. RESULTS: BG coatings are capable of continuous degradation and simultaneous ion release. The antibacterial effect of BG coatings increased with the addition of Zn, while the cytotoxicity remained unchanged compared to the group without coatings. BG coating enhances the expression of angiogenesis genes, while the Zn-containing BG enhances the expression of antioxidant genes at an early time point. BG coating enhances the expression of collagen genes at later time points. CONCLUSIONS: The antibacterial effect of BG improved with the increase in Zn concentration, without inducing cytotoxicity. BG coating enhances the expression of angiogenesis genes, and Zn-containing BG enhances the expression of antioxidant genes at an early time point. BG coating enhances the expression of collagen genes at later time points. CLINICAL SIGNIFICANCE: Adding 10 wt% Zn to BG could enhance the environment around implant abutments by providing antibacterial, antioxidant, and anti-fibrotic effects, having potential for clinical use.

Rotational Load Fatigue Performance of a One-Size Implant- Abutment Connection System.

PURPOSE: One-size implant-abutment (OSIA) connection systems have been developed for simplicity of clinical use and for a range of implant diameters. The aim of this in vitro study was to investigate the rotational load fatigue performance of different implant diameters and abutment platforms of an OSIA connection system. METHODOLOGY: Narrow, regular and wide diameter implants were tested with Regular Base (RB/WB) abutments of an OSIA system (Straumann. BLX). Wide diameter implants were also tested with Wide Base (WB) abutments. This resulted in 4 test groups (n=5): N-RB/WB (Narrow, 3.5mm, RB/WB abutment), R-RB/WB (Regular, 4.0mm, RB/WB abutment), W-RB/WB (Wide, 5.0mm, RB/WB abutment) and W-WB (Wide, 5.0mm, WB abutment). A rotational load fatigue machine applied a sinusoidally varying stress at an angle of 45o, producing an effective bending moment of 35Ncm at a frequency of 10 Hz in air at 20 oC. The number of cycles to failure was recorded. Results were evaluated using ANOVA. Failed specimens were examined with SEM to evaluate the failure mode. Pristine specimens were sectioned to examine the implant-abutment connection. RESULTS: All specimens in the 3 test groups with RB/WB abutments failed within the range of 558,750 cycles to 4,497,619 cycles, while the W-WB test group reached the upper limit of 5 million cycles without failure. Significant difference was found between abutment platforms (P < .001). There were no significant differences found for implant diameters (P =.857). However, with increasing implant diameter, implant fracture was less common and the location of failure was more coronal and consistently at the level of the implant platform for the abutment, and at the screw neck. CONCLUSIONS: For wide diameter implants, WB abutments exhibited a superior fatigue performance than RB/WB abutments, and would be preferred in situations of high mechanical risk. Increasing implant diameter, when used with RB/WB abutments, did not improve fatigue performance due to the one-size prosthetic connection, but failures were less catastrophic, and coronally located, which may be advantageous in managing failures.

Does Implant Placement Below the Ridge Reduce Crestal Bone Loss? A Split-Mouth Randomized Controlled Clinical Trial.

Reducing crestal bone loss (CBL) around implants allows for soft tissue stability and long-term success. The aim of the present study was to evaluate the extent of CBL in implants placed with the implant shoulder at the equi-crestal level and 2 mm below the alveolar ridge at 2, 12, 36, and 60 months. A split-mouth randomized controlled clinical trial was conducted by selecting subjects with Kennedy Class IV partial edentulism of the lower jaw. Two implants were inserted, of equal length and diameter, one equi-crestal and the other sub-crestal, in the site corresponding to the lateral incisor. Intraoral periapical radiographs with Rinn centering devices were performed at the time of implant insertion (T0), at 2 (T1), 12 (T2), 36 (T3), and 60 months (T4). Descriptive statistics and the T-test were used, setting the significance to P⩽ 0.05. Twenty-five subjects were recruited, with a mean age of 65 years (SD 9.88, range 42-82). No subject dropped out. A total of 50 implants were inserted, 25 at crestal and 25 sub-crest level. At the 60-month follow-up, no implant or prosthetic failure was recorded. An average loss of -0.81 mm was recorded in the crestal implant group (n.25; SD: 0.40; max-min: -1.6 - -0.1) while in the implants positioned below the crest the average CBL was -0.87mm (n.25; SD: 0.41; max-min: -2 - -0.2); however, the higher CBL in the sub-crestal implant group was not statistically significant (P=0.65). Comparing the mean CBL values of the two groups at the various follow-ups, a greater crestal bone resorption was recorded in sub-crest implants between T0 and T1 (-0.25 vs -0.1) and between T1 and T2 (-0.39 vs -0.23), while in subsequent follow-ups a greater, statistically significant (P=0.01), crestal bone loss was recorded in ridge implants between T3 and T4 (-0.05 vs -0.18). Over time, therefore, the extent of CBL seems to be reduced in implants placed below the crest, with bone retention above the implant shoulder. Ultimately, although the position of the implant shoulder relative to the crestal ridge doesn't affect the CBL, sub-crestal placement is recommended in order to reduce the risk of exposure of the rough surface of the implant.

Periodontal Tissue Responses to Restorations with and without Cervical Finish Line: A Systematic Review and Meta-analysis.

The purpose of this review was to evaluate the periodontal and peri-implant tissue responses to restorative approaches with and without cervical finish line on teeth and dental implants. An electronic search was performed in PubMed/MEDLINE, Embase, Cochrane Library, LILACS, Web of Science, and Scopus databases, and in the gray literature. Controlled clinical trials and prospective cohort studies were included. Analyzed outcomes included gingival index (GI), bleeding on probing (BOP), probing depth (PD), gingival thickness (GT), marginal stability (MS), and marginal bone loss (MBL). A meta-analysis was then performed in two parts: the first compared results of restorations on teeth with and without cervical finish line, and the second compared results of restorations on implant abutments with and without cervical finish line. Regarding the tooth-based restoration analysis, 7 out of 1,388 selected articles were included in the systematic review, and 2 were selected for the meta-analysis. For implantbased restorations on abutments with and without cervical finish line, 6 out of 707 selected articles were included in the systematic review, and 2 in the meta-analysis. No significant differences in periodontal and peri implant indexes were identified between both prosthetic approaches in situations with and without cervical finish lines.

Dental Implant Abutment Screw Loss: Presentation of 10 Cases.

Re-tightening the loosened dental implant abutment screw is an accepted procedure, however the evidence that such screw will hold sufficiently is weak. The purpose of this study was material analysis of lost dental implant abutment screws made of the TiAlV alloy from various manufacturers, which became lost due to unscrewing or damaged when checking if unscrewed; undamaged screws could be safely re-tightened. Among 13 failed screws retrieved from 10 cases, 10 screws were removed due to untightening and 3 were broken but without mechanical damage at the threads. Advanced corrosion was found on nine screws after 2 years of working time on all surfaces, also not mechanically loaded. Sediments observed especially in the thread area did not affect the corrosion process because of no pit densification around sediments. Pitting corrosion visible in all long-used screws raises the question of whether the screws should be replaced after a certain period during service, even if they are well-tightened. This requires further research on the influence of the degree of corrosion on the loss of the load-bearing ability of the screw.