Angled Abutments Research Articles

Biomechanical Comparative Analysis of Abutment Screw Head Designs on Preload Stability Under Oblique Compressive Forces: An In Vitro Pilot Study.

To examine the impact of abutment screw head sizes on preload stability when secured to a standard external hex implant under oblique compressive forces. Fifteen metal crowns were divided into three equal groups. The first group had five angulated cemented crowns connected to a 3 mm tall straight hexagonal abutment with an external hex abutment screw. The second and third groups each had five straight cemented crowns attached to a tapered abutment with flat slotted and internal hex abutment screws, respectively. Samples were subjected to a static cyclic load until failure. Kruskal-Wallis H, Dunn's, and one-way ANOVA with Tukey HSD tests were performed. Cemented straight crown supported by an angled abutment connected to implants with flat slotted and internal hex abutment screw heads failed at an average of 4.24 x 106 cycles ± 3.31 SD and 12.67 x 106 cycles ± 5.47 SD, respectively. Cemented angled crowns supported by a straight abutment connected to identical implants with an external hex abutment screw survived 18.02 x 106 cycles ± 4.49 SD. Periotest value (PTV) rate of change increased at a higher rate in crowns supported by angled abutments compared to straight abutments (p < 0.05). No cement failure was observed. Under the experimental conditions, larger abutment screw head sizes demonstrated greater stability of the abutment screw joint interface. Based on the in vitro findings, no cement failure was observed between the cemented crown and abutment connection. Future research with standardized comparative setups and larger sample sizes is needed.

Peri-implant stress distribution in maxillary All-on-4 prosthesis fabricated on multi-unit angled abutment with cobalt chromium framework versus those with titanium framework: A 3D Finite Element Analysis

Peri-implant stress distribution in maxillary All-on-4 prosthesis fabricated on multi-unit angled abutment with cobalt chromium framework versus those with titanium framework: A 3D Finite Element Analysis

Assessment of the Impact of Bone Quality and Abutment Configuration on the Fatigue Performance of Dental Implant Systems Using Finite Element Analysis (FEA).

The aim of this study was to evaluate the influence of abutment angulation, types, and bone quality on fatigue performance in dental implant systems. Three-dimensional models of maxillary 3-unit fixed implant-supported prostheses were analyzed. Abutments with different angles and types were used. Healthy bone (Hb) and resorbed bone (Rb) were used. Conducted on implants, a force of 150 N was applied obliquely, directed from the palatal to the buccal aspect, at a specific angle of 30 degrees. The stress distribution and fatigue performance were then evaluated considering the types of bone used and the angles of the three different abutments. The simulation aspect of the research was carried out utilizing Abaqus 2020 software. In all models, fatigue strengths in healthy bone were higher than in resorbed bone. Maximum stress levels were seen in models with angled implants. In almost all models with resorbed bone, fatigue performances were slightly lower. Increasing the abutment angle has been shown to increase stress levels and decrease fatigue performance in the adjacent bone and along the implant-abutment interface. In general, implants applied to healthy bone were found to have a higher success rate. It has also been suggested that multiunit abutments have beneficial effects on stress distribution and fatigue performance compared to resin cemented abutments. The type or angle of abutment and the quality of the bone can lead to biomechanical changes that affect the force distribution within the bone structure surrounding the implant. Clinicians can influence the biomechanical environment of the implant site by varying the abutment angle and type to suit the condition of bone health, potentially affecting the long-term success of implant treatment.

Investigation of Phase Transformation and Fracture Pattern as a Result of Long-Term Chewing Simulation and Static Loading of Reduced-Diameter Zirconia Implants.

While zirconia implants exhibit osseointegration comparable to that of titanium, concerns arise regarding low-temperature degradation and its potential impact on fracture strength. This study investigated the phase transformation and fracture characteristics of zirconia dental implants after aging through chewing simulation and subsequent static loading. The experimental setup involved 48 one-piece monobloc zirconia implants with diameters of 3.0 mm and 3.7 mm that had straight or angled abutments, with crown restorations, which were divided into six groups based on intraoral regions. The specimens underwent chewing simulation equal to five years of oral service, which was followed by static loading. Statistical analyses were performed for the data obtained from the tests. After dynamic and static loadings, the fractured samples were investigated by Raman spectroscopy to analyze the phase composition and micro-CT to evaluate fracture surfaces and volume changes. According to the results, narrow-diameter zirconia implants have low mechanical durability. The fracture levels, fracture patterns, total porosity, and implant fracture volume values varied according to the implant diameter and phase transformation grade. It was concluded that phase transformation initially guides the propagation of microcracks in zirconia implants, enhancing fracture toughness up to a specific threshold; however, beyond that point, it leads to destructive consequences.

Comparison of Aesthetic, Mechanical Outcome, and Bone Loss in Angulated Screw Channels (ASCs) and Cement-Retained Implant-Supported Prosthesis: A Case-Control Study.

Angulated-screw channels (ASCs) allow the clinician to employ screw-retained restorations in almost all cases, as the access hole can be moved away from the vestibular portion of the crown, where it would jeopardize the final esthetic result. The objective of this study was to compare screw-retained restorations employing ASCs with restorations cemented on angled abutments. In this study, 30 subjects, equally divided into two groups: group 1 (cemented restorations on angulated abutments) and group 2 (screw-retained restorations adopting ASCs), were treated and retrospectively compared after 2 years using the pink esthetic score (PES) and the white esthetic score (WES). All restorations were in use at the last follow-up, with a survival rate of 100%. Three mechanical complications were observed (2 chippings and 1 crown came loose), with a success rate of 93% in group 1 and 87% in group 2 (p > 0.05). No statistically significant differences were reported regarding the esthetic outcome; the marginal bone loss (MBL) showed better results for the screw-retained restorations, both at the distal aspect (group 1 = 0.98 mm ± 0.16; group 2 = 0.45 mm ± 0.06; p = 0.006) and at the mesial aspect (group 1 = 1.04 ± 0.27; group 2 = 0.45 ± 0.005; p < 0.001). From an esthetical perspective, screw-retained restorations with ASCs and cemented restorations on angulated abutments are both effective means of restoring implants; both have excellent esthetic outcomes, but screw-retained restorations have reduced bone loss when compared to cemented ones but are more prone to mechanical complications. Still, our results must be cautiously observed given the reduced dimension of our sample. Larger studies are needed to confirm our findings.

Design and Biomechanical Analysis of Customized Angled Abutment Based on Tooth Inclination Angle for Immediate Implant Placement on Maxillary Anterior Region.

Finite element analysis and an in vitro experiment were employed to investigate the loading effects of angled abutments, comparing various customized angled abutments derived from the average angle of incisors in patients with a commercial 15°∆ angled abutment, on both the implant and surrounding bone. Four customized angled abutment models (21.9°∆, 24.15°∆, 20.22°∆, 33°∆) were developed using cone-beam computed tomography (CBCT) images of incisor inclination from various age groups of patients. 3D maxillary bone models were created from CBCT images of four individual patients. Finite element analysis and in-vitro strain gauge experiments were conducted, applying 100N or 50N of axial or oblique force, to assess the differences in stress/strain between the customized and the commercial 15°∆ angled abutments in both the implants and surrounding bone. Under axial loading, the stress values in the dental implant and surrounding bone were elevated due to the relatively higher angles of the customized angled abutments (21.9°∆, 24.15°∆, 20.22°∆, 33°∆) when compared to the commercial 15°∆ angled abutment; however, under oblique loading the commercial 15°∆angled abutment exhibited higher stress values in both the implant and surrounding bone. For in vitro experiment, there is no statically difference in bone strain between the customized (21.9°∆) and the commercial 15°∆ angled abutments in axial loading. Nevertheless, in oblique loading using a commercial 15°∆ angled abutment induced the higher bone strains. Customized angled abutments offer lower stress/strain under oblique loads but higher stress/strain under axial loads compared to commercial ones. Therefore, in the design and application of angled abutments, careful consideration of the occlusal load direction is paramount for achieving biomechanical success of dental implant.

The Effect of Different Angled Abutments with Peripheral Groove and Vent Hole on the Retention of Cement Retained Implant – Supported Restorations

Background: The purpose of this study was to analyze the effect of vent hole or peripheral groove on retention of differently angled (15 ° and 30 o) abutments in of cement retained implant supported restorations. Methods: A total of sixty standart implant abutments were used. Abutments were divided into two groups at 15 ° and 30 ° angles on CNC. According to the modification, each group were divided into 3 subgroups; (1) no modifications, (2) with peripheral groove and (3) with vent hole. Sixty metal frameworks were prepared using laser sintering to fit all abutments. All laser sintered frameworks were cemented with eugenol-free provisional cement. Then, all specimens were thermocycled. The frameworks were removed from the abutments by using the universal test machine and the peak removal force was recorded. Statistical analysis were performed with two-way ANOVA, post hoc Tukey’s (HSD) test-adjusted independent samples t-tests. Results: According to the results, there were significant differences between 15 ° and 30 ° groups in terms of retention values (p &amp;lt; 0.001). Additional hole and grooves enhanced retention in both groups. The highest mean value of vertical pull-out strength (185.00 ± 23.08 N) was showed in 15 ° additional grooves group, and the lowest mean value of vertical pull-out strength (27.60 ± 14.84 N) was showed in 30° control group. Means values of additional groove specimens had the highest scores in both groups. In all groups, there were significant differences between all subgroups (p &amp;lt; 0.05). Conclusion: Increased abutment angle decreases retention, while addition of hole and groove increases.

Effect of angled abutments in the posterior maxillary region on tilted implants: a 3D finite element analysis.

The aim of this study was to evaluate the bone tissue effects under dynamic loading using finite element analysis (FEA) for four angled abutments with different deviated palatal lateral tilt angles. A three-dimensional model of the posterior maxillary region and an implant crown model were reconstructed and assembled with a three-dimensional model of the implant, angled abutment, and central screw to create a total of 10 three-dimensional finite element models tilted at , , , and in three groups, and the dynamic loads simulating oral mastication were loaded on the implant crown to analyze the equivalent stresses and strains in the peri-implant bone tissues. Under the dynamic loading, the cortical bone on the buccal side of the implant neck showed different degrees of stress concentration, and the cortical bone stress was much higher than the cancellous bone, and the strain concentration area of each model was located in the bone tissue around the implant neck and base. For the use of angular abutment, under the premise that the cortical bone stresses and strains of the 10 models meet the requirements for use, the peak stresses of 2.907 MPa, 3.018 MPa, and 2.164 MPa were achieved by using the angular abutment to achieve the tilt angles of , , and implantation, which is more advantageous compared with other models.

The Use of a New Safe Angle Concept for Immediate Implant Placement in the Anterior Maxilla: A Cross-Sectional CBCT Study

To introduce a new method for labiopalatal positioning and angulation of immediately placed dental implants in the anterior maxilla with relation to the type of abutment used (straight/angled abutment). CBCT scans from the database of a private practice were searched for patients who received immediate implants in the anterior maxilla. After superimposition of the initial and postoperative scans, the incisor root angle (IRA), incisor implant angle (IIA), and the difference between these angles were measured. An assessment was then made about whether the implant position would be within the safe angle or not. Age, sex, tooth/implant site, and type of prosthetic abutment (straight/angled) were retrieved from the patients' records. A total of 74 patients with 95 immediate implants altogether were selected for analysis. In regard to the type of abutment, 76 (80%) were straight, and 19 abutments (20%) were angled. Regardless of abutment type, 72 implants (75.8%) were placed within the safe angle, while 23 implants (24.2%) were placed outside it. All 19 implants with angled abutments were placed outside the safe angle. There were statistically significant associations between placement within the safe angle and type of abutment (P < .001; OR = 19), IRA (P < .001; effect size = 0.904), difference between IIA and IRA (P < .001; effect size = 1.209), and sex (P < .001; OR = 2.995). There was no statistically significant association between placement within the safe angle and IIA (P = .757, effect size = 0.063), site (P = .200; effect size = 0.184 ), or age (P = .387; effect size = 0.208). There was a statistically significant association between the type of abutment and the IRA (P = .001; effect size = 0.762) as well as the difference between IIA and IRA (P < .001; effect size = 1.056). The safe angle concept can be used as a reliable planning tool to determine the correct implant positioning for immediate implant placement in the anterior maxilla. Applying the safe angle concept will reduce the need for angled abutments for prosthetic correction.

Evaluating Angled Abutments: Three-Dimensional Finite Element Stress Analysis of Anterior Maxillary Implants

Restorative dentistry is the repairing of damaged teeth and restoring oral health and function. Dental implants are typically placed within the cortical bone of the jaw to provide stability and support for prosthetic restorations. The successful restoration of complex anatomical features of the maxillary anterior is difficult for prosthodontists. Using a 3D slicer, CT scan images were used to create a detailed three-dimensional model of the maxilla bone. This study utilizes ANSYS Workbench, a finite element software program, to analyze the abutment angles, ranging from 0° to 25°, and the impact stress distribution within peri-implant bone. The outcomes of our studies align with and substantiate certain evidence in the literature documenting bone resorption, specifically at the level of the implant neck and near the cortical bone. The study aims to provide a comprehensive understanding of angled abutment stress patterns in the bone surrounding dental implants, offering valuable insights for clinical applications in critical areas of the mouth.

Does the index in Morse taper connection affect the abutment stability? An in vitro experimental study.

The present study compared three different implant and abutment sets of type Morse taper (MT) connection, with- and without-index, were analyzed regarding their mechanical behavior without and with cyclic load application simulating the masticatory function. Ninety implant and abutment (IA) sets were used in the present study, divided into three groups (n = 30 samples per group): Group A, Ideale solid straight abutment (one piece) without index; Group B, Ideale abutment with an angle of 30-degree (two pieces) without index; Group C, Ideale abutment with an angle of 30-degree (two pieces) with index. The abutment stability quotient (ASQ) values, detorque value and rotation angle were measured before and after the cycling load. Twenty IA sets of each group were submitted to mechanical load at 360,000 cycles. The ASQ without load were 64.7 ± 2.49 for the group A, 60.2 ± 2.64 for the group B, 54.4 ± 3.27 for the group C; With load were 66.1 ± 5.20 for the group A, 58.5 ± 6.14 for the group B, 58.9 ± 2.99 for the group C. Detorque values were lower in groups B and C compared to group A (p < 0.05). In conclusion, the presence of the index did not influence the stability values. However, solid straight abutments (group A) showed higher values of stability compared to groups of angled abutments (groups B and C).

The Impact of Implant Abutment Angle and Height on Peri-implant Tissue Health: Retrospective Analyses from a Randomized Controlled Clinical Trial.

To examine the influence of abutment emergence angle and abutment height on marginal peri-implant bone stability in patients not considered susceptible to peri-implantitis. Furthermore, it was analyzed whether titanium-base (Ti-base) abutments lead to wider abutment emergence angles compared to one-piece abutments. A total of 48 abutments (ie, 24 Ti-base and 24 one-piece abutments in 24 patients) were evaluated at abutment installation, after 1 year, and thereafter on a yearly basis for up to 5 years. Clinical and radiographic outcome variables were assessed. With regard to peri-implant marginal bone stability, only moderately negative, albeit significant, correlations were found on the mesial sides of the one-piece abutments after 4 and 5 years for an abutment emergence angle > 30 degrees. No statistically significant negative correlations were found for distances of ≤ 1.5 mm between the restoration margin and the crestal peri-implant bone level for either Ti-base or for one-piece abutments. Furthermore, abutments bonded to Ti-bases were not associated with larger emergence angles than one-piece abutments. For patients at low risk of developing peri-implantitis, it can be concluded that neither a larger abutment emergence angle (> 30 degrees) nor a distance of ≤ 1.5 mm between the restoration margin and the crestal peri-implant bone level are associated with marginal peri-implant bone loss. Furthermore, abutments bonded to Ti-bases are not associated with wider emergence angles than one-piece abutments.

Impact of type and position of abutment connection on microstrain distribution: an in vitro study.

The aim of this study was to investigate microstrains around two non-parallel implant-supported prostheses and different abutment connections and positions under vertical static load using strain gauges. 4 models simulating the mandibular unilateral free-end were fabricated. 8 implants (4.0 × 10 mm and 5.0 × 10 mm) were inserted in the second premolar, perpendicular to the occlusal plane, and the second molar, tilted at 15°. Four groups were analyzed: engaging and angled abutments (control group), both non-engaging abutments, both screw-and cement-retained prosthesis (SCRP) abutments, and engaging and non-engaging abutments. Strain gauges were placed buccally, lingually, mesially, and distally adjacent to each implant. The restoration was cement-retained in the control group and screw and cement-retained in the rest. Zirconia bridges were fixed on the abutment with NX3, and a 300 N vertical static load was applied. Microstrains were recorded and analyzed. Both non-engaging abutments showed the highest compressive microstrains (-52.975), followed by engaging, angled abutment (-25.239). SCRP-SCRP abutments had the lowest compressive microstrains (-14.505), while the engaging, non-engaging abutments showed tensile microstrains (0.418). Microstrains in SCRP-SCRP and engaging, non-engaging groups were significantly lower than in the control group (α = .05). Premolar areas showed compressive microstrains (-47.06), while molar sites had tensile microstrains (+0.91), with microstrains in premolars being significantly higher than in molar area (α = .05). The types of abutment connections and positions may have a potential effect on microstrains at the implant-bone interface. SCRP-SCRP abutments could be an alternative to use in non-parallel implant-supported prostheses when two implants make an angle of no more than 20 degrees.

A dental technique to reseat an angled nonhexagon multiunit abutment in a complete arch fixed prosthesis

When an angled abutment lacking an antirotation structure within a complete arch implant- supported fixed prosthesis becomes loose, the conventional approach typically involves replacing the entire prosthesis because of the difficulty of reseating the abutment at its original angle. To address this predicament, this technique article describes a novel solution in the form of a resin verification guide that replicates the maxillary prosthesis. The modified cylinder enables tightening of the abutment screw of the reseated multiunit abutment in place, eliminating the need for replacing the prosthesis and reducing treatment costs and duration.

On the fatigue life of dental implants: Numerical and experimental investigation on configuration effect

Dental implants have seen widespread and successful use in recent years. Given their long-term application and the critical role of geometry in determining fracture and fatigue characteristics, fatigue assessments are of utmost importance for implant systems. In this study, nine dental implant system samples were subjected to testing in accordance with ISO 14801 standards. The tests included static evaluations to assess ultimate loads and fatigue tests conducted under loads of 270 N and 230 N at a frequency of 15 Hz, aimed at identifying fatigue failure locations and fatigue life. Fatigue life predictions and related calculations were carried out using Fe-safe software. The initial model featured a 22° angle for both the fixture and abutment. Subsequently, variations in abutment angles at 21° and 23° were considered while keeping the fixture angle at 22°. In the next phase, the fixture and abutment angles were set as identical, at 21° and 23°. The results unveiled that when the angles of the abutment and fixture matched, stress values decreased, and fatigue life increased. Conversely, models featuring abutment angles of 21° and 23°, with a 22° angle for the fixture, led to a 49.1 % increase in stress and a 36.9 % decrease in fatigue life compared to the primary model. Notably, in the case of the implant with a 23° angle for both abutment and fixture, the fatigue life reached its highest value at 10 million cycles. Conversely, the worst-case scenario was observed in the implant with a 21° abutment angle and a 23° fixture angle, with a fatigue life of 5.49 million cycles.

Effect of Dynamic Cycles and Abutment Angle on The Screw Stability of Standard and Narrow Implants: An In vitro Study

Objective: Screw loosening in implant-supported crowns is a common issue, leading to potential mechanical and biological complications. This study aimed to evaluate the combined influence of cyclic loading, abutment angulation, and implant diameter on screw torque loss in dental implants. Material and Methods: A total of 80 bone-level implants, divided into standard and narrow diameters, underwent cyclic loading protocols. These implants were paired with straight and 15-degree angled abutments. The study assessed the reverse torque values (RTV) before and after loading, with a primary focus on the effects of cyclic loading, abutment angulation, and implant diameter on screw torque loss. Results: Cyclic loading protocols and screw diameter significantly influenced screw torque loss. Standard diameter implants exhibited higher RTV compared to narrow diameter implants. . While the role of abutment angulation was less definitive, narrow diameter implants with angled placements showed a pronounced decrease in RTV. The study also highlighted that even with optimal preload values, a percentage of the initial preload is lost, potentially leading to screw loosening Conclusion: Cyclic loading and screw diameter are pivotal determinants of screw torque loss in dental implants. The study underscores the need for careful consideration of implant diameter and abutment angulation, especially in narrow diameter implants with angled abutments, to ensure optimal implant stability.

Comparison of electronic versus mechanical torque-limiting devices for dental implants: An in vitro study.

To determine the accuracy of new electronic torque-limiting devices (ET) when compared to new and used conventional-style beam-type (BT) mechanical torque-limiting devices and hand-piece style (HS) mechanical torque-limiting devices. The secondary purpose was to compare any difference in accuracy between new and used mechanical torque-limiting devices, and any difference in accuracy when used on a straight versus an angled screw channel abutment. A total of five torque-limiting devices were used to obtain 2000 readings under standardized conditions. An implant analog was fastened into a digital torque meter, to which an abutment was connected. Pre-determined torque values of 15 Ncm and 35 Ncm were applied, and actual torque values were recorded. A straight and an angled abutment were used to record 1000 readings each using the five torque-limiting devices. An overall Kruskal-Wallis test was applied to compare the median deviation among devices followed by a pairwise comparison ( = 0.05). For a target torque value of 15 Ncm on a straight abutment, the electronic device (ET) was statistically more accurate than the beam type (BT) new (p < 0.001) and used (p < 0.048) devices but less accurate than the hand-piece style (HS) used device (p < 0.001). On an angled abutment for a target value of 15 Ncm, the electronic device (ET) was statistically more accurate than hand-piece style (HS) new and used devices (p < 0.001). For a target torque value of 35 Ncm on a straight abutment, the ET was statistically more accurate than the HS new device (p < 0.001) but less accurate than the BT new device (p < 0.001). On an angled abutment for a target value of 35 Ncm, the electronic device (ET) was statistically less accurate than the beam-type (BT) new device (p < 0.001), the beam-type (BT) used device (p = 0.001), and the hand-piece style (HS) used device (p < 0.001). The electronic device (ET) was the only device accurate within the ISO standard of accuracy of 6% for each of the target torque value/abutment design combinations. There was no statistically significant difference related to the type of abutment used (angled vs. straight). Electronic torque limiting devices (ET) are an acceptable method for delivering torque for implant restorations for straight and angled abutments at 15 Ncm and 35 Ncm torque values. Conventional style beam-type (BT) mechanical torque-limiting devices are a simple, predictable, validated, and inexpensive tool for delivering accurate torque at 15 Ncm and 35 Ncm torque values. The hand-piece style (HS) mechanical torque-limiting devices are predictable to deliver 15 Ncm torque values.

A Comparative Evaluation of Vertical Marginal Gap for Vented and Precemented Cad-Cam Zirconium Copings on Angulated Abutments: An In vitro Study.

To evaluate vertical marginal gap after cementation of Zr (zirconium) copings with palatal vent, open vent, and precementation technique on angulated abutments resulting from cement entrapment between intaglio surface of copings and angulated abutments. Twenty-four angled abutments and 24 CAD-CAM Zr copings were assigned to three groups depending on the type of cementation technique, comprising eight copings with palatal vent, open vent, and no vent, respectively. Vertical marginal gaps between abutment shoulder and coping margin were evaluated at four points: buccal, palatal, mesial, and distal. The readings were statistically analyzed. The average mean value of vertical marginal gap at all sites for Group A with palatal vent was 158.45, for Group B with open vent was 151.84, and for Group C using precementation technique was 163.58. A statistically non-significant difference was seen for values between all sites (P > 0.05) for all groups. The average vertical marginal gap for Group B was comparatively lower compared to Groups A and C.

Three-dimensional Finite Element Stress Pattern Analysis in Bone around Implant-supported Abutment with Different Angulations under Axial and Oblique Load.

The goal of this research was to compare the stress distribution in the bone adjacent to the implant where three different angled abutments were loaded in both the axial and oblique directions. The premaxilla region was digitally recreated in 3-dimension (3D) using a finite element model, with a solid 4.2 mm by 13 mm implant and abutments at 0°, 15°, and 25° of rotation. Axial load (100 N) and oblique load were also applied to the abutments (178 N). Six models were made and used with a fixed bases. The coefficient of friction was set at a constant value of 0.02. The CITIA program was used for the stress analysis. In this investigation, we employed linear static analysis. Each abutment and crown in the model has subjected to an arbitrary vertical load as well as the oblique load. The cortical bone around the implant with a 25° angled abutment experienced a maximum von Mises stress of 187.692 Mpa under oblique load. This stress was increased with the degree of abutment angulation. As abutment angulation was increased, axial and oblique burdens were also increased. In both cases, we were able to identify the source of the observed growth. When we looked at the effect of stress on angulation, we found that the peaks were seen in the area of abutment and cortical bone. Since it was difficult to predict the stress distribution around implants with varying abutment angles in a clinical setting, finite element analysis (FEA) was chosen for this investigation as a more cutting-edge approach. It is a herculean task calculating the prompted forces clinically, FEA has opted for this study as it's a progressively wielded tool to prognosticate the stress allocation in the region of the implants with different angled abutments.

EXPERIMENTAL COMPARISON OF THE DEGREE OF FIXING SCREW TIGHTENING FOR FULL ZIRCONIA CROWNS SUPPORTED BY STRAIGHT IMPLANTS, STRAIGHT IMPLANTS WITH ANGLED ABUTMENTS, AND ANGLED IMPLANTS WITH DIFFERENT PLATFORM INCLINATIONS. IN VITRO STUDY

ABSTRACT&#x0D; Background: Success of immediate implant placement in the area of maxillary central incisor greatly depends on the degree of tightening of the fixing screw of the fully zirconia crowns. For treatment of this kind, clinicians use implants of various designs and implants with angled abutments to bypass anatomical limitations, achieve primary implant stability, and fabricate a screw-retained crown. However, the crown fabricated for the implant placed can experience non-axial loads during occlusion, which can lead to screw loosening and adversely affect treatment success, especially in the early post-operative period.&#x0D; &#x0D; Objective: to perform a comparative analysis of the effect of cyclic loading on the reliability of the fixing screw in full zirconia crowns supported by angled implants with platform inclination of 12, 24, 36, by straight implants and straight implants with angled abutments.&#x0D; &#x0D; Materials and methods: the degree of the prosthetic screw tightening was studied in 30 samples, 6 groups of 5 implants (straight implants, straight implants with standard 17 angled abutments and 12 custom abutments, angled implants with platform inclination of 12, 24, and 36. A full zirconia crown of maxillary central incisor was fabricated and fixed on every implant and subsequently exposed to cyclic loading up to 1*106 cycles. Afterwards, the maximum unscrewing torque was determined for each group. Statistical analysis was carried out.&#x0D; &#x0D; Results: the minimum values of the maximum torque were 20.8040.01 N/cm for the group of straight implants with 17 angled abutments, and the maximum values for the group of straight implants were 22.820.04 N/cm. There was no significant difference in values between the straight and angled implant groups. However, the values in these groups were higher compared to the groups of implants with angled abutments.&#x0D; Conclusion: the study showed that fixing screws are more reliable in crowns supported by straight implants and angled implants with different platform inclinations. Therefore, these implants are the most preferred option for immediate implant placement in the anterior region.