A risk-based decision making tree for managing fractured abutment and prosthetic screws: A systematic review

Resistance to Torsion of Cement vs Screw-Retained Abutments Under a Tangential Load: A Pilot Study

The aim is to compare the resistance to torsion between 2 implant systems with internal hexagon connection: one using screw-retained abutments (Titanium Fix) and the other using cementable abutments (ITEC) under a tangential load. An in vitro experimental study was carried out. Fourteen implants, 7 implants from each system, were included in this study. The implants were placed at a 45° angle into metal blocks to simulate their position in the maxilla. Then, implants were subjected to a resistance test on a CMT5L universal testing machine, and the maximum load was applied to each sample. The maximum force with which the torsion was achieved in each sample was analyzed. The data were tested using the Shapiro-Wilk test and showed normal distribution. Student t test was used to examine statistical significance between the two groups, and the P value was set at P < .05. There was a statistically significant difference between the two groups (P = .001). ITEC implants with a cementable abutment showed greater flexural strength compared to the Titanium Fix with a screwed abutment implant system. The cemented abutment showed more resistance to torsion against a tangential load compared with the screwed abutment.

Resistance to loosening of intentionally shortened screws used to solve the unsuccessful removal of fractured prosthetic screws

STATEMENT OF PROBLEM

Fractured prosthetic implant screws cannot be removed in all patients, ultimately leading to the removal of the implant. Whether an intentionally shortened prosthetic implant screw (SPIS) can provide adequate retention is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the resistance to loosening of SPISs engaging the remaining coronal internal threads as a possible solution to maintaining both implant and restoration.

MATERIAL AND METHODS

Fifty grade V titanium SPISs were used to tighten 50 titanium transepithelial abutments on implants to 30 Ncm. The specimens were distributed into 5 groups (n=10) according to the conditions under which the screws were secured to manufacturer-recommended preload: dry (D), moistened in saliva (AS), moistened in chlorhexidine (CLHX), wrapped in polytetrafluoroethylene tape (PTFE), and resin cemented (RE). All groups were subjected to a cyclic loading test (240 000 cycles). The reverse torque value (RTV) of the SPIS was registered twice: 24 hours after initial tightening (T1); and after retightening and the cyclic loading test (T2). The resultant RTV was compared with the 30-Ncm tightening torque to assess torque loosening. The Kruskal-Wallis and Mann-Whitney tests were used for the comparisons between groups and the Wilcoxon test for the intragroup comparisons (α=.05 with Bonferroni correction).

RESULTS

At T1, all groups found lower mean±standard deviation RTVs than the reference tightening torque (30 Ncm) (D 24.82±2.34 Ncm, AS 25.56±2.89 Ncm, PTFE 26.02±2.26 Ncm, CLHX 26.26±1.82 Ncm), except the resin-cemented group, which increased its RTV (RE 44.01±19.94 Ncm). At T2, all the groups found lower RTVs than the reference tightening torque, and the torque values at T1 (D 19.81±6.59 Ncm, CLHX 18.98±6.36 Ncm, AS 21.28±7.32 Ncm), with the exception of PTFE (24.07±3.41 Ncm) and RE (41.47±21.68 Ncm), where RTV was similar to that recorded at T1. At T1, significant differences were found among the groups (P=.024). At T2, after cyclic loading, the RE group found the highest RTV, reporting significant differences with the D and CHLX groups (P<.05) and statistically similar to the AS group (P=.068).

CONCLUSIONS

PTFE-wrapped screws found similar RTVs after the fatigue test than dry, moistened with saliva, and moistened with chlorhexidine screws. Resin-cemented shortened prosthetic implant screws were found to be the most resistant to loosening after cyclic loading.

An in vitro evaluation of 2 methods for retrieving fractured abutment screw fragments from the intaglio of 4 different implant systems

STATEMENT OF PROBLEM

When an abutment screw fractures, there is no standardized technique for retrieving it from the intaglio of the dental implant.

PURPOSE

The purpose of this in vitro study was to assess the relative efficacy of a commercially available screw fragment retrieval kit with a range of standard dental instruments in regard to success and retrieval time. In addition, the effects of other variables on the success rate of screw fragment retrieval and the retrieval time required were also investigated. Finally, the integrity of the intaglio screw channel of the dental implant was also assessed following retrieval.

MATERIAL AND METHODS

The abutment screws from 4 dental implant systems: Osseotite Certain, Ø4.1 mm (Zimmer Biomet); Osseotite External hexagonal connection micromini, Ø3.25 mm (Zimmer Biomet); Standard Plus Tissue Level, Ø4.8 mm (Institut Straumann AG); and Brånemark Mark III TiUnite, Ø4.1 mm (Nobel Biocare) had notches placed between the first and second coronal threads before being placed in their respective abutments, positioned in the dental implants (n=128), and tightened until the screws fractured. The dental implant specimens were placed in maxillary and mandibular casts at the lateral incisor and first molar sites on both sides. The casts were placed in mannequin heads on a dental chair and assigned to 2 experienced and 2 inexperienced operators who used 2 different retrieval kits to retrieve the screw fragments. Chisquared tests were used to determine the association between the success rate of screw fragment retrieval and the other factors recorded (α=.05), and a binary logistic regression was used to determine the association between the retrieval event and all of the independent variables. Regression models were developed to determine the factors effecting retrieval time.

RESULTS

An overall success rate of 88.3% was achieved for screw fragment retrieval. No statistically significant difference (P>.999) was found in the relative efficacy of the retrieval kits. Univariate analysis identified a statistically significant association (P<.01) in the success of abutment screw fragment retrieval between the Osseotite Certain and the Osseotite External hexagonal connection micromini implant systems. Gamma regression analysis identified significant differences between the time taken to retrieve the screw fragments and the type of dental implant (P<.001), (P<.01). The time taken to retrieve screw fragments in the maxillary arch was significantly longer than for the mandibular arch (P<.05).

CONCLUSIONS

The commercially available screw fragment retrieval kit and the standard dental instruments were equally effective in retrieving the screw fragments. Less time was required to retrieve screw fragments in the mandibular arch than the maxillary arch. The level of experience of the operator had no effect on the ability to successfully retrieve fractured abutment screws.

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.

Evaluation of different debridement strategies for implant-abutment connections: An in vitro study

STATEMENT OF PROBLEM

Technical complications, including abutment fracture, are a clinical reality. After retrieving failed components, re-establishing a reliable implant-abutment connection is essential, but recommendations on how to clean the interface are lacking.

PURPOSE

The purpose of this in vitro study was to evaluate different clinical debridement strategies for removing titanium powder from an implant-abutment interface with regard to their efficacy and associated risk of damaging the interface.

MATERIAL AND METHODS

Specimens (n=5) were assembled from previously cut implant halves, which were then contaminated by placing titanium powder inside the implant-abutment connection. Activated rinsing, airflow, and an ultrasound scaler, as well as combinations thereof, were then used to clean the implant-abutment connections. Both parts of each specimen were rated under a light microscope with respect to contamination and damage. In addition, abutments were placed in intact implants (n=10), which had previously been contaminated and cleaned, to record torque curves and abutment stability. Statistical analysis of ratings was based on Kruskal-Wallis tests and the Nemenyi All Pairs test with single-step P value correction, while abutment stability and torque were analyzed using analysis of variance and Tukey HSD tests (α=.05).

RESULTS

Erythritol as an abrasive medium led to significantly greater contamination than the scaler (P=.002), activated rinsing (P=.021), and airflow with sodium bicarbonate combined with either conventional (P=.002) or activated rinsing (P=.007). Greater damage was also observed with erythritol because of accumulations of the abrasive media, while scratches were seen after scaler application. Airflow using sodium bicarbonate in combination with activated rinsing showed the lowest level of damage (versus scaler P=.030). Using conventional (P=.010) or activated (P=.029) rinsing, airflow treatment led to a significant reduction in contamination. The scaler led to a significant decrease in abutment stability (P=.048), while activated rinsing and the combination of airflow and activated rinsing did not significantly affect abutment stability. Abutments placed in implants previously contaminated and cleaned required greater torque as compared with original implants (versus activated rinsing, P=.009).

CONCLUSIONS

Activated rinsing constituted the best technique for cleaning implant-abutment connections. Cleaning efficiency can be enhanced with airflow using sodium bicarbonate as an abrasive medium.

Retrieval of a fractured implant abutment using a modified cover screw removal instrument: A clinical report

Implant abutment fractures are an uncommon mechanical complication, and the removal of the abutment fragment and replacement with a new prosthesis is the best solution. However, successful retrieval of the fractured abutment fragment from the implant is challenging, and effective rescue kits are lacking. This clinical report describes the retrieval of a fractured implant abutment in a conical connection implant using a modified manufacturer-specific instrument.

A method of removing the stripped abutment screw from the angled screw channel: Technical details and a clinical report

An angled screw channel (ASC) avoids a facial screw hole by correcting the pathway of the screwdriver. However, the structure of the specially designed screw is prone to mechanical complications, including screw-head stripping. Removing an angled screw is challenging because regular screw-removal tools cannot access the ASC. A safe and convenient method for the retrieval of the stripped screw is reported.

Retrieval of a fractured implant abutment screw using a microtube extraction device: A dental technique

Abutment screw fracture is a mechanical complication associated with the failure of dental implant-supported restorations. Retrieval of fractured abutment screws without damaging the internal surface of implants is challenging and can be time-consuming. Microtube extraction devices are used to remove separated endodontic instruments. This article presents a conservative method of retrieving a fractured implant abutment screw using a microtube device.

A retrospective study of 12,538 internal conical connection implants: focused on the long-term integrity of implant-abutment complexes

OBJECTIVES

To evaluate the long-term integrity of implant-abutment complexes in implant systems with two internal conical angles.

MATERIAL AND METHODS

12,538 bone-level implants of two systems placed between January 2012 and December 2018 were retrospectively analyzed. Cumulative abutment/implant fracture rates in systems with larger (LA, 7.5°) and smaller (SA, 5.7°) internal conical angles were estimated using Kaplan-Meier analysis and compared between groups. The association between implant systems and jammed abutment retrievability was evaluated by multivariable generalized estimating equation logistic regression modelling.

RESULTS

For LA, the 8-year cumulative incident rate was 0.10% (95% confidence interval (CI): 0-0.24%) for implant fracture and 0.26% (95% CI: 0.11%-0.41%) for abutment fracture, demonstrating a significant difference in gender (p = 0.03), implant diameter (p = 0.01), jaw (p = 0.006) and antagonist tooth (p < 0.001). For SA, the 8-year cumulative incident rate was 0.38% (95% CI: 0-0.79%) for implant fracture and 2.62% (95% CI: 0.05%-5.13%) for abutment fracture, which was influenced by implant diameter (p < 0.001) and site (p = 0.03). The cumulative implant/abutment fracture rate was lower for LA implants, particularly for LA implant-supported single crowns (SCs) (p < 0.05). The abutment-retrieval success rate was 92.8% for LA, and 57.1% for SA (p = 0.055).

CONCLUSION

LA implants exhibited a lower incidence of fracture in abutment-implant complexes and a relatively higher retrievability success rate for jammed abutments.

Management of perishing implants with abutment screw fracture - A systematic review

Aim:

To systematically review the reported techniques, for evaluating the risk and difficulty encountered in the management of fractured abutment screw in accordance with the location of fracture, and to develop a logical sequence in managing an implant abutment screw fracture.

Settings and Design:

Systematic review following PRISMA guidelines.

Materials and Methods:

A systematic search of the PubMed/MEDLINE database for articles published between January 2000 and March 2020 was performed by 2 independent reviewers. Case reports and case series that described the management of fractured implant abutment screw were included. Published articles were qualitatively analyzed employing CARE guidelines and were classified according to the location of screw fracture with respect to implant platform, risk of damage to the implant, and intervention for managing the fractured screw.

Statistical Analysis Used:

Qualitative analyisis.

Results:

A total of 28 articles were included in the review. Two of them explained the management of screw fracture at or above the implant platform and required only mild approach with low risk while the others explained the management of screw fracture below the level of implant platform. Among them, 6 were considered mild approach with low risk, 13 moderate approach with moderate risk, and 8 of them severe approach with high risk.

Conclusion:

Irrespective of the technique, any attempt to retrieve abutment screw fragment poses some risk to the implant which is varying from mild to severe. As the location of fracture is more gingival to the implant platform, difficulty of retrieval as well as risk to the implant increases. The proposed decisionmaking tree will be a useful tool in helping clinicians to manage abutment screw fracture.

Screw stability of CAD-CAM titanium and zirconia abutments on different implants: An in vitro study

BACKGROUND

Limited information is available regarding the removal torque values (RTVs) of screws of different abutment materials when used with different implants.

PURPOSE

To evaluate the effect of implant type and abutment material (zirconia; Zir and titanium; Ti) on the RTVs of abutment screws after cyclic loading.

MATERIALS AND METHODS

Internal conical connection implants (CC, OsseoSpeed TX) and modified internal conical connection implants (MCC, OsseoSpeed EV) (n = 10) were clamped in resin dies. Zir and Ti (N = 20) custom abutments were tightened to implants (20 Ncm for CC and 25 Ncm for MCC) as specified by their manufacturers. The abutments were cyclically loaded by using a sequentially increased loading protocol; 2-million cycles under 100 N, 3-million cycles under 200 N, and 2-million cycles under 300 N loads with 2 Hz. After 7 million cycles, RTVs (Ncm) were measured by using a torque gauge. The data were analyzed with ANOVA by using the restricted maximum likelihood estimation method. Tukey-Kramer adjustment was used for any significant interaction of implant-abutment pairs (α = 0.05).

RESULTS

Two CC implants, 1 with Ti and 1 with Zir abutment, fractured during cyclic loading (under 300 N loads within the 6th and 7th million cycles) and discarded for statistical analysis. Only implant type had a significant effect on RTVs (p <0.001). Screws of Ti abutments on MCC implants had significantly higher RTVs than the screws of Ti (p = 0.003) and Zir (p = 0.005) abutments on CC implants.

CONCLUSIONS

Implant type affected the RTVs, however, the RTVs were higher than the initial torque values for all groups. Screws of Ti abutments on implant, which required greater initial torque values had higher RTVs than the screws of Ti and Zir abutments on the implant that required smaller initial torque values. RTVs were similar for Zir and Ti abutment screws within each implant type.

In vitro comparison of the efficacy of two fractured implant-prosthesis screw extraction methods: Conventional versus mechanical

STATEMENT OF PROBLEM

Implant-supported prostheses may be subject to esthetic, biological, or mechanical complications. Protocols for dealing with these mechanical problems are sparse.

PURPOSE

The purpose of this in vitro study was to compare the efficacy of a mechanical system for extracting fractured implant-prosthesis screws with the conventional method.

MATERIAL AND METHODS

A total of 60 screws were divided into 2 groups according to their morphology (flat screws with a smooth shaft and threaded apical area and screws with a completely threaded body) and subjected to fatiguing and static load testing until fracture. The specimens were assigned to 3 operators with varying levels of clinical experience (high, medium, low) in extracting fractured screws by using the conventional method (explorer and ultrasound device) and a mechanical method (extractor kit). The extraction event (whether the screw fragment was extracted or not within 10 minutes) was recorded, and the time taken to perform the extraction was measured for each method in relation to screw type, operator experience, and damage to the threads. The influence of screw morphology, extraction method, operator experience, and fracture type on the time needed to extract a screw fragment was assessed with the Mann-Whitney and Kruskal-Wallis tests. Thread damage was compared by using the Fisher's exact test and the Kruskal-Wallis test (α=.05).

RESULTS

The mechanical method was more effective for screw extraction than the conventional method (P=.032). Screw morphology also had a significant influence on extraction, whereby the screw design with apical thread took less time to extract (P=.022). Coronal fractures had a higher probability of extraction than apical fractures (P=.05).

CONCLUSIONS

Mechanical extraction is more effective for extracting fractured implant-prosthetic screws, showing a higher probability of extraction than the conventional method. Prosthetic fixing screws with a smooth shaft and threaded apical area are the easiest to extract.

A modified implant abutment holder fabricated with fused deposition modeling to improve the transfer process for implant-supported restorations

Ingestion or aspiration of an implant abutment can occur in patients during the process of abutment transfer for implant-supported restorations, especially in the posterior region. A technique of fabricating an abutment holder is described to prevent ingestion or aspiration by computer-aided design (CAD) and fused deposition modeling (FDM). The modified abutment holder has a serrated handle for a firm grip and a barrel-shaped fixed portion that firmly secures the abutment. The modified holder is more secure than the conventional hexagon screwdriver. Furthermore, abutment holders can be easily manufactured by using 3D printers and repeatedly used for multiple implants restoration without substitution.

Rescue of an implant-supported fixed complete prosthesis after the failure of an implant: A dental technique

This technique article describes the rescue of an existing implant-supported fixed complete prosthesis after the failure of a supporting implant. To achieve this, a system able to rescue the fixed prosthesis after placement of a new implant was used, and the protocol for performing this procedure is described.

Systematic review versus structured critical analysis

Objective: This analysis discusses common problems with systematic reviews (SRs) and presents a novel solution, the structured critical analysis (SCA) that can be incorporated into a SR or used as an alternative literature review design.Methods: A cross-sectional survey of current SRs related to interdisciplinary restorative dentistry was obtained by evaluating 100 current SRs for their self-reported methodological quality and its effect on scientific validity.Results: The preferred reporting items for systematic reviews and meta-analyses protocol (PRISMA) was used in 99/100 SRs, but only 8/100 reported a low risk of bias. High statistical heterogeneity precluding meta-analysis was found in 44/100 SRs. Only 94 paragraphs/100 SRs provided critical analysis.Discussion: Significant problems were found with current SRs that can compromise their reliability as the premier level of evidence for clinical science research. The reader must be aware of these deficiencies to correctly interpret the SR and cannot rely on the format alone.

An accessory technique for the intraoral removal of a fractured implant abutment screw

As the use of dental implants becomes more prevalent, mechanical complications become more common. When an implant abutment screw fractures, it can be difficult to retrieve the retained fragment. The purpose of this article is to describe a technique to remove the abutment screw fragments without damaging the implant body or its screw threads.