A screw lock for single-tooth implant superstructures

Novel Esthetic Technique for Restoring Dental Implant Access Holes: A Case Report

Background/Objectives: For dental implant treatment to be successful, esthetics, functionality, and cleanability are all required of the superstructure, which is the final prosthesis. Screw fixation and cementation have been the conventional methods of choice for the crown prosthesis of implants, but these individual methods cannot fulfill all the requirements. Methods: As a solution to this problem, we have devised a new implant superstructure restoration method called the inlay covering esthetic technique, which uses computer-aided design/computer-aided manufacturing inlays. Results: It involves the placement of an inlay covering the access hole in a highly translucent partially stabilized zirconia crown. Conclusions: This technique, demonstrated in this clinical case study, expands the indications for implant treatment and improves the oral quality of life of patients. This case report describes a novel esthetic technique for restoring dental implant access holes.

Effect of implant‒abutment connections on abutment screw loosening: An in vitro study

Background

The widespread use of dental implants as a predictable treatment choice has drawn attention to their complications as a major challenge despite their high clinical success rates. In this context, loosening of the abutment screw in posterior single crowns is the most common problem; the use of adequate preload and proper anti-rotational features at implant‒abutment interface appear to be two main solutions to such a problem. The present study evaluated the effect of implant‒abutment connections in four different implant systems before and after cyclic loading.

Methods

Intra-Lock, Dentis, Xive, and Dio implant systems were used in this study. Each system underwent one million cycles of dynamic forces eight times with a magnitude of 110 N. For each specimen after tightening the screw with a torque of 32 Ncm, the detorque values were measured and recorded by a digital torquemeter after and before cyclic loading. Data were analyzed by Kolmogorov-Smirnov, Levene's, one-way ANOVA, and post hoc Tukey tests.

Results

Initial detorque values between the study groups showed significant differences (P<0.0001). Pairwise comparisons showed significantly lower primary detorque values in the Dentis system compared to the three other systems (P<0.0001). After cyclic loading, significant differences were observed between the study groups (P<0.0001). Pairwise comparisons of the groups showed significant differences between all the systems after loading.

Conclusion

The type of implant‒abutment connection is an essential factor influencing the amount of abutment screw loosening.

Effect of Application of a Bio-Adhesive on the Removal Torque Value and Rotational Misfit at the Implant-Abutment Junction: An In Vitro Study

The aim of this study was to assess the effect of application of a recently developed bio-adhesive (Impladhesive) to abutment screw threads on the removal torque value and rotational misfit at the implant–abutment junction. This in vitro study evaluated 20 implant fixtures and 20 straight abutments. Specimens were randomly divided into two groups (n = 10) with/without adhesive application. In the adhesive group, the abutment was dipped in Impladhesive before torquing. In the control group, the abutment was torqued conventionally without adhesive application. The removal torque value was recorded after completion of the cyclic loading of 500,000 cycles with 2 Hz frequency and 75 N load. Rotational misfit was recorded using a video measuring machine. After applying the torque, the change in the bisector angle on the abutment hex was recorded for each implant. The biocompatibility of Impladhesive was evaluated using a MTT cell vitality assay. Normal distribution of data was assessed using the Kolmogorov–Smirnov test. Data were analyzed using a t-test and Pearson’s correlation coefficient The application of Impladhesive at the implant–abutment interface resulted in significantly greater mean removal torque value compared to the control group (p = 0.008). In addition, the mean rotational misfit at the implant–abutment interface was significantly lower in the use of Impladhesive compared to the control group (p = 0.001). In addition, the cell vitality was found to be greater than 80% at all evaluated time points. It can be concluded that the application of Impladhesive on the abutment screw significantly decreased rotational misfit and increased the removal torque value. Future studies are needed to evaluate the efficacy of this bio-adhesive an in vivo setting.

Effect of implant abutment connection designs, and implant diameters on screw loosening before and after cyclic loading: In-vitro study

AIMS

The purpose of this in-vitro study was to evaluate the screw loosening of two different forms of implant abutment connection designs, and two implant diameters by measuring removal torque value (RTV) before and after cyclic loading.

MATERIALS AND METHODS

Twenty implant fixtures were divided equally into 2 groups (N=10): group I fixture with conical hybrid connection (CH), and group II fixture with internal hex connection (IH). Each group was divided equally into two subgroups according to implant diameters: subgroup A (3.3mm), and subgroup B (4.2mm). Each fixture was vertically placed in the center of an acrylic resin block. The samples were fixed to the jig, and an implant abutment connected it with a 20 Ncm tightening torque. The samples were subjected to eccentric cyclic loading (at a distance of 5mm) away from center of abutment at 100,000 cycles. A digital torque gauge was used to evaluate screw loosening by measuring RTVs in (Ncm) before and after cyclic loading. The removal torque loss ratio before and after cyclic loading and the removal torque loss ratio between before and after cyclic loading were calculated and analyzed using the SPSS statistical analysis.

RESULTS

For GI the initial removal torque loss ratio measurement was (14.45±3.18) and decreased significantly after loading, it was (11.47±3.64). For GII the initial removal torque loss ratio measurement was (20.47±4.99) and increased significantly after loading, being (35.35±4.26). There is no significant effect upon screw loosening for two implant diameters.

CONCLUSION

Within the limitations of this study, the results suggested that conical hybrid connections showed a better screw stability than an internal hex connection. Therefore, the use of conical implants can be promoted as they have better screw stability compared to other systems.

Effect of cyclic loading and retightening on reverse torque value in external and internal implants

PURPOSE

The aim of this study was to evaluate the effect of cyclic loading and screw retightening on reverse torque value (RTV) in external and internal type implants.

MATERIALS AND METHODS

Cement-retained abutments were connected with 30 Ncm torque to external and internal type implants. Experimental groups were classified according to implant connection type and retightening/loading protocol. In groups with no retightening, RTV was evaluated after cyclic loading for 100,000 cycles. In groups with retightening, RTV was measured after 3, 10, 100 cycles as well as every 20,000 cycles until 100,000 cycles of loading.

RESULTS

Every group showed decreased RTV after cyclic loading. Before and after cyclic loading, external type implants had significantly higher RTVs than internal type implants. In external type implants, retightening did not affect the decrease in RTV. In contrast, retightening 5 times and retightening after 10 cycles of dynamic loading was effective for maintaining RTV in internal type implants.

CONCLUSION

Retightening of screws is more effective in internal type implants than external type implants. Retightening of screws is recommended in the early stage of functional loading.

Management of abutment screw loosening: review of literature and report of a case

Dental implant restoration has been widely accepted as one of the treatment modalities to replace missing teeth and to restore human masticatory function. The use of root form endosseous implant has increased considerably and this restorative option has become more refined with the introduction of newer designs and concepts. Long term post placement studies have reported prosthetic complications, including screw loosening, screw fracture, framework and implant fracture. Abutment screw loosening is the second most common cause of failure of implant supported restoration, next to loss of osseointegration. This is more seen in single implant supported restoration. Management of screw loosening is challenging and this clinical report describes the management of an implant abutment screw loosening of upper anterior teeth with minimal damage to the existing restoration making it possible to be reused and a literature review on the various factors associated with abutment screw loosening.

Screw- vs cement-implant-retained restorations: an experimental study in the Beagle. Part 1. Screw and abutment loosening

The causes of implant failures can be biological or mechanical. The mechanical causes include fracture of the implant, fracture of the abutment, and loosening of the abutment. Numerous studies show that abutment loosening constitutes one of the marked implant postsurgery complications requiring clinical intervention. The aim of the present study was to evaluate the incidence of the screw loosening in screwed or cemented abutments. Six adult male Beagles were used. In each dog, the first molars and 2 premolars were extracted. The sutures were removed after 7 days. After 3 months, 10 implants were placed in each dog, 5 in the right mandible and 5 in the left mandible. The abutments either were screwed in (n=30) by applying a total strength of 30 N/cm or were cemented (n=30). After 12 months, 8 (27%) loosened screws were present in screwed abutments, whereas no abutment loosening was observed in cemented abutments (P = .0001). Screwed abutments are often submitted to nonaxial loads that determine screw and abutment loosening.

Stability of the Implant/Abutment Joint in a Single-Tooth External-Hexagon Implant System: Clinical and Mechanical Review

Rigorous efforts have recently been made to reduce the recurrence of implant/abutment joint failure in single-tooth implant restorations. However, the current knowledge about the stability of implant/abutment joints in an external hexagon implant system is incomplete. We reviewed clinical data regarding single-tooth implant treatment with Brånemark implants, specifically the CeraOne abutment system (Nobel Biocare AB, Göteborg, Sweden). In vitro studies on joint stability were systematically assessed. Bending overload and the presence of misfit at the implant/abutment joint interface are the critical mechanical conditions that can make the joint unstable. Appropriate joint fitness and proper alignment of the implant should be assessed, and occlusal adjustment by narrowing the restoration width and flattening cuspal inclination should be applied to avoid bending moments caused by the lateral component of occlusal forces. Sufficient clinical reports of longer duration that evaluate and verify longer-term success of the newly manufactured joint components were unavailable.

Implant abutment screw rotations and preloads for four different screw materials and surfaces

STATEMENT OF PROBLEM

Chronic implant screw loosening remains a problem in restorative practices. Some implant manufacturers have introduced abutment screws with treated surfaces in an effort to increase preload and reduce potential loosening. Purpose. This study evaluated the materials and surfaces of 4 commercially available abutment screws on preload generation.

MATERIAL AND METHODS

Twenty of each of the following abutment screws-Gold-Tite (Gt), TorqTite (Tt), gold alloy (Ga), and titanium alloy (Ta)-were divided into 2 groups. Measurements were recorded for each abutment screw on a mounted 3.75 x 18 mm external hex implant with a titanium abutment. Rotational angle measurements were conducted on the 4 abutment screws at 20 and 32 Ncm. Removal torque values were recorded and used to indirectly generate preload values. Random implant block specimens were sectioned and qualitatively evaluated with an SEM.

RESULTS

At 20 and 32 Ncm, the largest rotational angles were recorded for the Tt groups: 21.2 +/- 3.1 degrees and 38.1 +/- 8.7 degrees, respectively. The greatest preload values at 20 and 32 Ncm were calculated for the Gt groups: 596.8 +/- 101.2 N and 1015.3 +/- 191.2 N, respectively. SEM analysis of the 4 implant block specimens revealed mating thread contacts located in the middle portion of the superior surface of the abutment screw thread. The greatest number of mating thread contacts were seen in the Gt implant block specimen (14 of 20 possible thread contacts).

CONCLUSION

The Gt and Tt abutment screws with enhanced surfaces that help reduce the coefficient of friction produced greater rotational angles and preload values than the conventional gold alloy and titanium alloy screws.