Stress distribution and microgap formation in angulated zirconia abutments with a titanium base in narrow diameter implants: A 3D finite element analysis.

This in vitro study aimed to use failure stress and implant abutment interface (IAI) microgap size to find the compromised axial angle range of angulated zirconia abutments with a titanium base in narrow diameter implants in the esthetic region. A three-dimensional (3D) finite element model of maxillary central incisor implant prosthesis was reconstructed. Angulated zirconia abutments (0°, 15°, 30°, and - 15°) with a titanium base in narrow diameter implants (3.3 × 12 mm, Bone level, Roxolid SLActive, Straumann AG, Switzerland) were designed to simulate clinical scenarios of buccal inclination 0°, 15°, and 30°, and palatal inclination 15° of the implant long axis. Straight titanium abutment and pure titanium implant were used as two control groups. An oblique force at 30° inclination to the long axis of the crown was applied 3 mm below the incisal edge on the palatal surface of the prosthesis. Under simulated dynamic chewing force, the stress distribution of the implant components and surrounding bone were investigated. The relative micromotion displacement between the implant and abutment models at the IAI area was recorded, and the influence of tightening torque on the IAI microgap was evaluated. The angulation of the zirconia abutment could affect the stress value and IAI microgap of implant restorations. When the zirconia abutment angle increased from -15° to 30°, the stress on the central screw, titanium base, and surrounding bone tissue gradually increased by 9%, 20%, and 23%, respectively. The stress levels of the 30° zirconia abutment group showed the risk of exceeding the threshold. When the long axis of the implant was inclined in the palatal direction, the -15° angle abutment reduced the stress by 3% and reduced the strain level of the implant system by 17% and the surrounding bone tissue by 26%. Under simulated dynamic chewing load, the displacement between the implants and the abutment occurred in each group of the implant system, and the amplitude of the micromotion fluctuated with the change in the load. The horizontal displacement caused a 0.075-1.459 µm palatal microgap and 0.091-0.945 µm distal microgap in the IAI. The microgap between the lip and palate was more evident, and the vertical displacement difference was manifested as the abutment sliding down the implant. In cases of upper implant restoration with difficulties such as small gaps and axial defects in the esthetic zone, the abutment angle is highly recommended to be in a slightly palatal-inclined direction or to not exceed 15° when the implant is inclined to the labial side to avoid mechanical damage and leakage caused by the appearance of excessively large micromotion gaps.

Novel bendable abutments as a solution to correct unfavorable implant inclination. A clinical report.

OBJECTIVE: This clinical case report describes a novel bendable abutment as a prosthetic solution for implants presenting with an unfavorable inclination. CLINICAL CONSIDERATIONS: A metal-ceramic screw-retained single crown was made on this novel bendable abutment in a patient presenting with a pronounced buccal inclination of an implant. A plastic reference guide is used to define the correct inclination and then this inclination is transferred to the abutment using a specific bending device at the same appointment. CONCLUSIONS: Bendable abutments can be used as a solution to correct unfavorable implant inclinations. This abutment can be customized at the same appointment considering a case-specific inclination rather than conventional pre-angled abutments. CLINICAL SIGNIFICANCE: Bendable abutments can be customized according to each case specificities while conventional pre-angled abutments may not be adequate for all patients. Also, the abutment customization could be easily done by dentists at their own practices using a specific bending device with hand pressure only, saving time, and the need to order pre-angled abutments or having it in stock.

Angled Abutment Transfer Jig: A Technical Report.

AIM: To introduce an angled abutment transfer jig that splints abutments securely together to facilitate easy and quick orientation. BACKGROUND: Transferring angled abutments from cast to patients' mouth could be tasking and time-consuming. Transfer jigs are often used to facilitate orientation of abutments into implant fixtures. However, with the available jigs, abutments could move out of place and thus pose a hassle in repositioning. TECHNIQUE: This technical report introduces an angled abutment transfer jig that consists of two impression copings screwed onto angled abutments which are splinted together with red acrylic resin. Access to abutment screws is feasible through slots created in the impression copings. CONCLUSION: The introduced jig is rigid and thus ensures very accurate and easy transfer of abutments into implants followed by accurate prosthesis seating. CLINICAL SIGNIFICANCE: This transfer jig design allows clinicians to transfer the orientation of angled abutments from cast to patients' mouth with optimal speed and precision.

Managing maxillary proclination with novel designed angulated implants.

Implant-supported removable dental prostheses may be supported by a variety of splinted (bar and clip) attachment systems or nonsplinted abutment-based attachments (ball, magnets, and resilient stud attachments such as locators [Zest Anchors], ERA [Sterngold], and nonresilient-stud attachments such as ANKYLOS SynCone [Dentsply Implants]). Nonsplinted attachments are preferred as they are more economical, less technique sensitive, easier to clean, repair, and maintain than splinted (bar and clip) attachment systems, but they work favorably only when implants in the arch are placed parallel to each other. Often implants in the anterior maxilla have to be placed with a labial inclination (due to the proclination of the premaxilla), resulting in lack of parallelism between the anterior and posterior implants, making it challenging to fabricate a removable dental prostheses supported by nonsplinted attachments, and necessitating the use of angled abutments. Recently, a novel implant design with a 12° restorative platform angulation has been introduced by Southern Implants (Co-axis, Keystone Dental, Inc., Burlington, MA, USA). These new angulated implants aid in minimizing the divergence between the anterior and posterior maxillary implants without using angled abutments. The purpose of this article was to report a case utilizing the novel angulated implants (Co-axis, Keystone Dental, Inc., Burlington, MA, USA) in the premaxilla for fabrication of maxillary removable dental prostheses supported and retained by nonsplinted attachments.

Effects of abutment angulation and type of connection on the fracture strength of zirconia abutments / 대한치과보철학회지

PURPOSE: The purpose of this study was to evaluate the fracture strength of straight and angled zirconia abutments for internal hex and external hex implants. MATERIALS AND METHODS: Twenty internal hex implants and 20 external hex implants were prepared. The prefabricated straight zirconia abutments and 17-degree-angled zirconia abutments were connected to those 40 implants. The specimens were classified into 4 groups depending on the connection type and abutment angulation; internal hex implant/straight abutment, group INS; internal hex implant/angled abutment, group INA; external hex implant/straight abutment, group EXS; external hex implant/angled abutment, group EXA. All specimens were loaded at a 30-degree angle with a crosshead speed of 1 mm/min using universal testing machine. The fracture loads were analyzed using 2-way ANOVA and independent t-test (α= .05). RESULTS: The mean fracture load for INS was 955.91 N, 933.65 N for INA, 1267.20 N for EXS, and 1405.93 N for EXA. External hex implant showed a significantly higher fracture load, as compared to internal hex implant (P < .001). No significant differences in fracture loads were observed between the straight and angled abutment in internal hex implants (P = .747) and external hex implants (P = .222). Internal hexes of abutments were fractured horizontally in internal connection implants, while lingual cervical neck portions were fractured in external connection implants. CONCLUSION: The zirconia abutments with external hex implants showed significantly higher fracture strength than those with internal hex implants. However there was no difference in fracture strength between the straight and 17-degree-angled zirconia abutment connected to both implant systems.

Three-dimensional finite element analysis of angled abutments in anterior maxilla implant restoration / 西安交通大学学报(医学版)

Objective To explore the effects of angled abutments on the anterior maxilla implant restoration. Methods We analyzed the biomechanical properties of implants of different sizes (Φ3.5 mm,4.0 mm and 4.5 mm in diameter;L11.5 mm and L13 mm in length)after connecting different angled abutments (0°,10°,20°,and 30°) using finite element method.Results The stresses and strains of loading parts of restorations increased and their distribution became more concentrated as the angle of abutment increased.Cortical bone of Φ3 .5 implants with smaller angle (10°or less)andΦ4.0 implants with abutments had the risk of overpassing the bone elastic threshold when the angle approached 30°.However,the cortical bone elastic deformation was within a safe range at all angles inΦ4.5 group.Conclusion We should consider the diameter of the implant when selecting angled abutments.The angled abutments are not suitable for small diameter implants.The bite force should be under control when needed. The larger angled abutments can be applied in the standard and major diameter implants and it is necessary to avoid occlusal overloading.

The effects of angled abutments with small diameter implant restoration in anterior maxilla:A finite ele-ment analysis / 实用口腔医学杂志

Objective:To study the influences of angled abutments connected with small diameter implants in anterior maxilla restora-tion.Methods:Simulation models of angled abutment with small diameter restoration in anterior maxilla were established,the biome-chanical properties of the models were studied by finite element method(FEM)analysis.Results:Following the increase of the abut-ment angle,the stress and strain of all parts increased linearly and more concentrated,while appropriate prosthetic crown could share some load.Cortical bone elastic deformation exceeded the threshold when the abutment angle was bigger than 8 °.Conclusion:With abutment angle increase,stresses and strains will increase and will be more concentrated,which is unfavorable for load conduction.Ap-propriate crown can reduce the adverse effects of angled abutment.Angled abutment should not be used for d 3.5 implant.

The Effect of Implant Angulation on the Transfer Accuracy of External-Connection Implants.

BACKGROUND: Accurate recording of implant location is required in every implant-supported prostheses. Implant angulation, which is inevitable in various clinical situations, could affect the impression accuracy. PURPOSE: The purpose of this in vitro study was to compare the transfer accuracy of straight and tilted implants of All-on-4 protocol with implant or abutment level impression making and different techniques of direct and indirect. MATERIALS AND METHODS: One reference model of edentulous maxilla with four external connection implants (Brånemark) inserted according to All-on-4 protocol was made. Forty impressions of this model were made at implant (groups 1 and 2) or abutment (groups 3 and 4) levels with different techniques of direct or indirect, respectively. Impressions were poured with type IV dental stone. Coordinate measuring machine was used to record x, y, and z coordinates and also angular dislocation of implants. These measurements were compared with the equals calculated on the reference model. Data were analyzed with univariate analysis of variance and t-test at α = 0.05. RESULTS: The results showed that abutment level impression making (groups 3 and 4), either with direct or indirect technique, produced the same results for straight and tilted implants of Δr variable (p > .05), though in implant level groups (groups 1 and 2), it was statistically significant (p < .05). However, only implant level impression making with direct technique (group 1) had the same results of angular accuracy for straight and tilted implants. CONCLUSION: Impression technique (direct or indirect) had significant effect on the impression accuracy of tilted implants, and direct technique produced less inaccuracy. Also, abutment level impressions showed more accuracy than implant level impressions.

Three dimensional finite element analysis of stress distribution around implant with straight and angled abutments in different bone qualities.

The aim of the study was to compare the stress distribution around implant in different bone qualities of D1, D2, D3, and D4 with straight and angled abutments using three dimensional finite element analysis. A three dimensional finite element model of the premaxilla region, and two solid 4.3 × 10 mm implant, one with a straight abutment and the other with an angled abutment was done. Four distinctly different bone qualities of D1, D2, D3, and D4 were made. A static load of 178 N was applied at the centre of incisal edge along the long axis of each abutment. The maximum equivalent von Misses stress values around the implants were recorded. The distribution of stresses changed considerably with abutment angulation. As angulation increased from 0° to 15° the concentration of Von Misses stresses shifted to the cortical layer of bone on the facial side of the fixture. Although Von Misses stress increased in straight abutment as the bone quality changed from D1 to D4, it was more noticeable under the loading side of the angulated abutments. The high stresses induced through angled abutments at the cervical zone of the implant due to forces and moments could be a dominant factor that may aggravate the peri-implant bone loss or changes the existing peri-implantitis direction.