Skip to main content

Novel CAD–CAM fabrication of a custom-made ball attachment retentive housing: an in-vitro study



This study aims to evaluate the digitally designed ball attachment housing in its initial retentive force and after 2 years of simulated clinical use and to compare it with the regular nylon ball attachment housing.

Materials and methods

Twenty implants with their corresponding ball abutments (diameter 4.5 × 4.0 mm) were inserted in resin blocks. They were divided into two groups. In Group I, ten ball abutments each received their corresponding conventional attachment with nylon rings. In Group II, ten ball abutments received the novel CAD–CAM polyetheretherketone ball attachment housing. A universal testing machine was used to measure the retention force. The achieved maximum values of retention force were recorded at the beginning of the study (initial retention) and after 2 years of artificial ageing (2000 cycles of insertion and removal). Results were statistically analyzed using an independent sample T test.


The PEEK attachment housing showed high retention forces (25.12 ± 0.99 N) compared to the conventional attachment with a nylon ring (15.76 ± 0.93 N) in the initial dislodgement test. There was a statistically significant difference in mean retention at the initial retention test and after 2 years of stimulated usage between the two studied groups, p = 0.000.


Within the limitations of this study, the novel CAD–CAM–PEEK attachment showed high retention characteristics compared to the conventional attachment with nylon rings, initially and after simulated long-term use.


Overdenture prostheses have high success rates, as they offer increased retention, stability, esthetic, comfort, bone preservation, and patient acceptance [1]. The attachment is a mechanical device used for the stabilization and retention of the prosthesis. It is composed of two interlocking matrix and patrix parts [2, 3].

A proper attachment selection depends on many factors such as interarch distance, the amount of desired retention force, prosthesis type, inclination and number of implants, and financial options. [4,5,6]. The attachments are classified as bars, magnets, telescopes, and studs, such as locator, ball and socket, and equator [2, 7,8,9,10].

The ball and socket attachment type is widely used in implant overdentures, removable partial dentures, and maxillofacial prostheses. However, there are several inherent deficiencies and shortcomings within this approach. One of which is the loss of retention due to wear of the retaining mechanism of these attachments that require replacement over time [7, 11,12,13].

The success of implant-retained overdentures depends on many factors to maintain their long-term function. Among these factors is the retentive force of its attachment component. The inevitable movement between the retentive surfaces of an attachment during insertion and removal of the overdenture leads to wear, decreasing retentive forces with time [14,15,16].

This study adopted a new digital technology workflow for the fabrication of these attachments. Reviewing the literature, none of the previous research has documented CAD–CAM–polyetheretherketone (PEEK) fabrication of the ball attachment housing itself.

The aim of this study was to evaluate the retentive quality of a digitally designed PEEK Ball attachment housing after repeated use. This study compared the retention characteristics of the conventional ball and socket attachment system (housing with nylon ring) with the CAD–CAM–PEEK housing design after 2 years of simulated use. The null hypothesis is that there is no significant difference in retention between the two designs.

Materials and methods

Model preparation

A stone model of 4 cm in length, 2 cm in width, and 3 cm in height was constructed in Type III dental stone. This model was duplicated using laboratory addition silicone (REPLISIL 22N, dent-e-con) using a metal flask to build a master mold. This master model was used for subsequent duplication.

Forty identical heat-cured acrylic resin blocks (Acrostone Manufacturing and Import Co.) were constructed. Half of these rectangular heat-cured acrylic resin blocks represent the ridge to which the ball abutment is connected, and the other half simulates the overdenture fitting surface to which the ball attachment housing is connected.

An implant drilling hole was prepared in the resin block with the aid of the dental parallelometer (Ney Surveyor, Dentsply) to ensure that the ball abutment is perpendicular to the horizontal plane. This was done to avoid discrepancies from malalignment of attachment components, which accelerates wear mechanisms [17].

Twenty implants with their corresponding ball abutments were inserted into the standardized resin blocks. A chemically processed acrylic resin (Acrostone Manufacturing and Import Co.) was used to seal the space between the implant and the sidewalls of the drilled hole. Another depression in the simulating overdenture fitting surface blocks was made for the pick-up of the attachment housing.

Digital ball attachment housing fabrication

The digital workflow began with the acquisition of the ball abutment geometry (Ball abutment ISABA 400 diameter 4.5 × 4.0 mm by NeoBiotech Co. Ltd.) by optical scanner (MEDIT i500; MEDIT Corp) (Fig. 1).

Fig. 1
figure 1

STL file acquired by an optical scanner and representing the ball abutment geometry which is composed of the ball abutment head and ball surface undercut

The housings were virtually designed using free CAD software (MeshMixer, Autodesk, Inc.). The housing outline was drawn using the select software tool. The housing was given an offset of 0.035 mm to compensate for shrinkage that occurs in the printing of polymethylmethacrylate (PMMA). A 1-mm thickness was given to the attachment housing and then exported in the form of a Standard Tessellation Language (STL) file. A 3D printer (Phrozen sonic mini 4K) was used to print a resin housing which was pressed into a polyetheretherketone (PEEK) housing [5, 18,19,20,21,22,23,24,25,26,27,28] (Figs. 2,3) (Additional file 1: Video S1).

Fig. 2
figure 2

STL file of the outer surface of digitally designed ball attachment housing, the outer surface contains many surface undercuts which will facilitate the future pickup of the housing into the denture

Fig. 3
figure 3

STL file of the inner surface of digitally designed ball attachment housing, the inner surface is a negative replication of the ball abutment housing


Two ball attachment retentive housings were examined in this study; the first is the conventional attachment nylon ring (Group I). The second is the novel digitally designed PEEK attachment retentive housings (Group II).

Ten ball abutments were used for each studied group. This study adopted the methodology utilized by other researchers [5, 10] for the evaluation of the retention force of the selected attachments. The sample size was calculated by G-power software and confirmed by many recent previous studies [5, 10, 29, 30].

The Instron universal testing machine (Instron, model 3345) was used to measure the retention forces. The abutment base blocks were attached to the lower compartment of the universal testing machine, while overdenture-simulating blocks were attached to the upper compartment of the machine. (Fig. 4) The test was carried out at a crosshead speed of 50 mm/min with a 500 N load cell with removal parallel to the axis of the implant abutment, in the presence of artificial saliva between the abutment and attachments to simulate intraoral conditions.

Fig. 4
figure 4

Two resin blocks, one with the ball abutment and the top one with the tested attachments attached to the Instron universal testing machine for measuring retention values

The retention values were recorded at the initial stage and after 1 and 2 years of simulated clinical use. Each year is simulated with 1000 insertion and removal cycles according to three daily insertion and removal by the patient [5, 10].

Statistical methodology

Data were collected and processed on the computer using the SPSS (Statistical Package for Social Science) program for statistical analysis (ver. 25). The parametric statistics were used as the Kolmogorov–Smirnov test of normality showed no significant difference in variable distribution. An independent sample t test was used to compare the two studied groups.


The results of this study showed that the maximum dislodgement force required to pull the novel CAD–CAM–PEEK attachment was 5–6 times that of the conventional nylon ring (25.12 ± 0.99 N) in PEEK housing compared to (15.76 ± 0.93 N) in conventional nylon housing in the initial dislodgement test (Table 1).

Table 1 Retention in (Newton) between the studied groups at different times of measurement

The retention values were reduced after 1 year to be 21.84 ± 0.73 for PEEK housing and 13.64 ± 0.70 (N) for conventional nylon housing, and then further reduced to be 16.76 ± 1.38 for PEEK housing and 12.56 ± 0.69 (N) for conventional nylon housing after 2 years of simulated use.

Comparisons in retention between the studied groups showed a statistically significant difference in mean retention at the initial retention test (p = 0.000*) (Table 1).

CAD–CAM–PEEK attachment housing showed a decrease in retention by 33.28% after 2 years of use, while nylon caps showed a reduction in retention after 2 years of use by 20.30% compared to primary retention (Table 2) (Fig. 5).

Table 2 percentage of retention loss in (Newton) between the studied groups at different times of measurement primary retention vs 1, 2 years of use
Fig. 5
figure 5

Retention in (Newton) comparing the PEEK and nylon ball attachment housing at different time intervals


Two challenges in the fabrication of the digital PEEK ball attachment retentive housing were faced. The first was the use of computer-aided design (CAD) to design a virtual attachment retentive housing that conforms to the actual geometry of the existing ball abutment and provides acceptable retention of the prosthesis. The second was how to use the currently available computer-aided manufacturing (CAM) techniques for the attachment fabrication with suitable material [5].

Multiple digital technologies have also emerged in the perspective of the digitization, modeling, designing, and fabrication of different implant-anchored prosthetic components. Despite the great progress and popularity gained by CAD and CAM technology in most dental specialties, such as fixed and removable prosthodontics, aesthetics, and dental implantology, its role in fabricating small and complex geometry components has been, to date, limited [24].

According to the author’s knowledge, none of the previous studies in the literature have dealt with digital fabrication of the ball attachment housing itself. This novel study used digital technology to fabricate a customized ball attachment retentive housing to solve the problem when these attachments are no longer available in stock due to production policies of the manufacturing companies.

The designed attachment housing was 3D printed in resin then pressed into PEEK as 3D printing technologies have many advantages, such as the ability to manufacture complex geometries of small items with no waste of the materials [27]. While this technology has certain limitations, such as the need for a skilled professional with good computing skills [28, 31].

The attachment housing was fabricated from PEEK material as PEEK has many advantages, such as excellent mechanical properties, wear resistance, stability at high temperatures, and biocompatibility [32]. Several in vitro studies and clinical reports suggested that PEEK could be suitable for CAD–CAM fabrication of many fixed and removable dental prosthetics [25]. In a study by Qin et al., it was reported that the use of PEEK material as an attachment reduces the stresses around the abutment teeth and on the edentulous ridge. However, PEEK has an opaque and greyish color, reducing its aesthetic quality [32,33,34,35].

The retentive force for each design was measured using a Universal Testing Machine (Instron), which is an evidence based valid method used by many previous studies to measure the retentive forces of different attachments [5, 10, 17, 23].

The results of this study showed that the novel CAD–CAM–PEEK attachment showed higher retention forces than the conventional attachment in the initial testing condition and after simulated use of 2 years. However, both showed a significant reduction in the recorded values after 2 years of use. This could be due to wear and surface topography changes due to continuous friction between the ball abutment and the attachment housing [5, 36, 37].

The significant reduction of retentive values by 33.28% in PEEK attachment after 2 years of use, while nylon caps showed a decrease in retention after 2 years of use by 20.30% compared to primary retention. This could be attributed to the properties of the material from which the attachment housing is fabricated. In elastic materials such as nylon, the wall of the cap is compressed and then returns to its original shape, while in rigid materials such as PEEK, there is outward flex of the wall of the cap. These results are in agreement with previous studies [5, 36,37,38].

The result of our study agrees with the results of a previous study conducted by Nassar and Abdelaziz [5] who compared the retention force of PEEK and nylon retentive clip of bar attachments and concluded that PEEK clips have comparable or even better retention in comparison to nylon ones due to its high resistance to surface alteration and wear.

On the contrary, a study conducted by Abdelaziz [3] have proved that PEEK locator attachments showed higher retention loss in comparison to Nylon one and this could be attributed to the type of PEEK used in their study and the amount of filler incorporated in this material.

Optimal retention is the level of retention that allows a patient to easily manipulate a prosthesis into position and remove it without dislodgment during normal use [39, 40]. The minimum accepted retention force of different attachment systems for implant-retained overdentures was reported to range from 3 to 8 N [41]. The retention values of PEEK attachment housing recorded in this study were higher than the minimum accepted attachment retentive values. This is in accordance with a study conducted by Abdelaziz et al., who tested the initial retentive values of ball and socket and locator attachments and recorded 15 N and 14 N, respectively [10]. Another study conducted by Nassar and Abdelaziz reported that the initial retentive force of PEEK and Nylon bar attachment clips were 42 N and 16 N, respectively [5]

In this study, lateral forces affecting the retention throughout the chewing process were not simulated in the testing conditions, which is considered as one of the limitations of this study [42]. However, Tehini et al. tested different attachment retentive values after chewing simulation cycles and concluded that chewing simulation did not demonstrate any significant effect or correlation to the attachment retentive values [43].

Clinical significance

The introduced ball attachment retentive housing could be indicated when a small custom-made attachment is essential to use due to space limitations, unavailability in stock, and in situations when the prosthesis requires high retention qualities, as in a minimum number of implants or in maxillofacial obturator prosthesis.


Within the limitations of this study, it could be concluded that both attachment housings fabricated from PEEK and Nylon differed in retention values at initial delivery and after simulated use of 2 years. However, the CAD–CAM-fabricated PEEK attachment housing demonstrated the highest retentive values. Both retentive housings exhibited reduced retention after simulated use.

Data availability

The data sets used and/or analyzed during the current study are available from the corresponding author on reasonable request.


  1. Hakeem AA, Shah AS, Shazana QN, Bali KS. Evaluation of patient satisfaction in precision attachment-supported overdentures and conventional overdentures through verbal rating system. Int J Adv Res. 2021;9:963–7.

    Article  Google Scholar 

  2. Salehi R, Shayegh SS, Johnston WM, Hakimaneh SMR. Effects of interimplant distance and cyclic dislodgement on retention of LOCATOR and ball attachments: an in vitro study. J Prosthet Dent. 2019;122:550–6.

    Article  PubMed  Google Scholar 

  3. Abdelaziz MS, Fawzy AM, Ghali RM, Nassar HI. Retention of different attachment systems for digitally designed mandibular implant overdenture. J Prosthodont. 2023;32:162–9.

    Article  PubMed  Google Scholar 

  4. Yilmaz B, Ozkir E, Johnston WM, McGlumphy E. Dislodgement force analysis of an overdenture attachment system. J Prosthet Dent. 2020;123:291–8.

    Article  PubMed  Google Scholar 

  5. Nassar HI, Abdelaziz MS. Retention of bar clip attachment for mandibular implant overdenture. BMC Oral Health. 2022;22:1–8.

    Article  CAS  Google Scholar 

  6. Abdelaziz MS, Fawzy A, Ghali RMNH. Retention loss of locator attachment system different retention caps for two implant retained mandibular overdenture. Futur Dent J. 2022;7:120–6.

    Google Scholar 

  7. Stock V, Wagner C, Merk S, Roos M, Schmidlin PR, et al. Retention force of differently fabricated telescopic PEEK crowns with different tapers. Dent Mater J. 2016;35:594–600.

    Article  CAS  PubMed  Google Scholar 

  8. Maryod WH, Taha ER, Alkaranfilly GA, El-anwar MI. Finite element study on short implants retaining mandibular overdentures with different denture materials in severely resorbed ridge. Int J Dent Oral Heal. 2020;6:1–7.

    Google Scholar 

  9. Kutkut A, Rezk M, Zephyr D, Dawson D, Frazer R, Al-Sabbagh M. Immediate loading of unsplinted implant retained mandibular overdenture: a randomized controlled clinical study. J Oral Implantol. 2019;45:378–89.

    Article  PubMed  Google Scholar 

  10. Abdelaziz MS, Tella EAESAEM. Digital fabrication of polyetheretherketone retentive bar attachment inserts as overdenture maintenance: a dental technique. J Prosthet Dent. 2022.

    Article  PubMed  Google Scholar 

  11. Dantas IDS, de Souza MBC, de Siqueira Torres Morais ST, da Fonte Porto Carreiro A, Barbosa GAS. Success and survival rates of mandibular overdentures supported by two or four implants: a systematic review. Braz Oral Res. 2014;28:74–80.

    PubMed  Google Scholar 

  12. Matthys C, Vervaeke S, Besseler J, Doornewaard R, Dierens M, De Bruyn H. Five years follow-up of mandibular 2-implant overdentures on locator or ball abutments: Implant results, patient-related outcome, and prosthetic aftercare. Clin Implant Dent Relat Res. 2019;21:835–44.

    Article  PubMed  Google Scholar 

  13. Choi J-W, Yun B-H, Jeong C-M, Huh J-B. Retentive properties of two stud attachments with polyetherketoneketone or nylon insert in mandibular implant overdentures. Int J Oral Maxillofac Implants. 2018;33:1079–88.

    Article  PubMed  Google Scholar 

  14. Marin DOM, Leite ARP, de Oliveira Junior NM, Paleari AG, Pero AC, Compagnoni MA. Retention force and wear characteristics of three attachment systems after dislodging cycles. Braz Dent J. 2018;29:576–82.

    Article  PubMed  Google Scholar 

  15. Li P, Hasselbeck D, Unkovskiy A, Sharghi F, Spintzyk S. Retentive characteristics of a polyetheretherketone post-core restoration with polyvinylsiloxane attachments. Polymers (Basel). 2020;12:1–9.

    Google Scholar 

  16. Yue Q, Yilmaz B, Abou-Ayash S, Zimmermann P, Brägger U, Schimmel M. Use of an attachment system with angulated abutments and polyetheretherketone inserts to retain a maxillary overdenture: a clinical report. J Prosthet Dent. 2020;124:129–34.

    Article  CAS  PubMed  Google Scholar 

  17. Atashrazm P, Dashti MH, Alavijeh LZ, Azarmaeh SMS. The influences of implant angulations in one and two directions on the retentive properties of overdenture attachments: an in vitro study. J Indian Prosthodont Soc. 2014;14:72–7.

    Article  PubMed  Google Scholar 

  18. da Fontoura Frasca LC, Castro Mattia PR, Botega DMRE, Da Fontoura Frasca LC, Castro Mattia PR, Botega DM, Rivaldo EG. Evaluation of retention forces and resistance to fatigue of attachment systems for overdentures: plastic and metal components. Implant Dent. 2014;23:451–5.

    PubMed  Google Scholar 

  19. Schweiger J, Edelhoff DGJ. 3D printing in digital prosthetic dentistry: an overview of recent developments in additive manufacturing. Clin Med. 2021;10:2010.

    CAS  Google Scholar 

  20. Khorsandi D, Fahimipour A, Abasian P, Saber SS, Seyedi M, Ghanavati S, Ahmad A, De Stephanis AA, Taghavinezhaddilami F, Leonova A, Mohammadinejad R, Shabani M, Mazzolai B, Mattoli V, Tay FRMP. 3D and 4D printing in dentistry and maxillofacial surgery: printing techniques, materials, and applications. Acta Biomater. 2021;1:26–49.

    Article  Google Scholar 

  21. El Aziz MSA, El Sattar Abd El Megid Tella EA. Fully digital workflow for reinforced mandibular implant overdenture – a novel method. J Indian Prosthodont Soc. 2022;22:205–9.

    Article  PubMed  PubMed Central  Google Scholar 

  22. Kuo H, Kuo P, Bittner N, Cavallaro J. Assessment of the changes in retention and surface topography of attachments for maxillary 4-implant-retained overdentures. J Prosthet Dent. 2021;5:413.

    Google Scholar 

  23. Ramadan RE, Mohamed FS. Retention of mandibular implant-retained overdentures with two different attachment designs: an in vitro study. J Prosthet Dent. 2020;1:738.

    Google Scholar 

  24. Cristache CM, Tudor I, Moraru L, Cristache G, Lanza A, Burlibasa M, Cristache CM, Tudor I, Moraru L, Cristache G, Lanza A, et al. Digital workflow in maxillofacial prosthodontics—an update on defect data acquisition, editing and design using open-source and commercial available software. Appl Sci. 2021;11:1–19.

    Article  Google Scholar 

  25. Oancea L, Burlibasa M, Petre AE, Panaitescu E, Cristache CM. Predictive model for occlusal vertical dimension determination and digital preservation with three-dimensional facial scanning. Appl Sci. 2020;10:7890.

    Article  CAS  Google Scholar 

  26. Cristache CM, Totu EE, Iorgulescu G, et al. Eighteen months follow-up with patient-centered outcomes assessment of complete dentures manufactured using a hybrid nanocomposite and additive CAD/CAM protocol. J Clin Med. 2020;9:324.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  27. Tian Y, Chen C, Xu X, Wang J, Hou X, Li K, Lu X, Shi H, Lee E-S, Jiang HB. A review of 3D printing in dentistry: technologies, affecting factors, and applications. Scanning. 2021;2021:1.

    Article  Google Scholar 

  28. Pillai S, Upadhyay A, Khayambashi P, et al. Dental 3D-printing: transferring art from the laboratories to the clinics. Polym. 2021;13:157.

    Article  CAS  Google Scholar 

  29. Unkovskiy A, Spintzyk S, Brom J, Huettig FKC. Direct 3D printing of silicone facial prostheses: a preliminary experience in digital workflow. J Prosthet Dent. 2018;120:303–8.

    Article  CAS  PubMed  Google Scholar 

  30. Reda KM, El-Torky IR, El-Gendy MN, Reda KM, El-Torky IR, El-Gendy M. In vitro retention force measurement for three different attachment systems for implant-retained overdenture. J Indian Prosthodont Soc. 2016;16:380–5.

    Article  PubMed  PubMed Central  Google Scholar 

  31. Koutsoukis T, Zinelis S, Eliades G, Al-Wazzan K, Rifaiy M, Al Jabbari YS. Selective laser melting technique of Co-Cr dental alloys: a review of structure and properties and comparative analysis with other available techniques. J Prosthodont. 2015;24:303–12.

    Article  PubMed  Google Scholar 

  32. Yu W, Zhang H, Lan A, Yang S, Zhang J, Wang H, Zhou Z, Zhou Y, Zhao J, Jiang Z. Enhanced bioactivity and osteogenic property of carbon fiber reinforced polyetheretherketone composites modified with amino groups. Colloids Surf B Biointerfaces. 2020;193:111098.

    Article  CAS  PubMed  Google Scholar 

  33. Qin L, Yao S, Zhao J, Zhou C, Oates TW, Weir MD, Wu J, Xu HHK. Review on development and dental applications of polyetheretherketone-based biomaterials and restorations. Materials (Basel). 2021;14:408.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  34. Papathanasiou I, Kamposiora P, Papavasiliou G, Ferrari M, Papathanasiou I, Kamposiora P, Papavasiliou G, et al. The use of PEEK in digital prosthodontics: a narrative review. BMC Oral Health. 2020;217:1–11.

    Google Scholar 

  35. Chen T, Chen Q, Fu H, et al. Construction and performance evaluation of a sustained release implant material polyetheretherketone with antibacterial properties. Mater Sci Eng C, Mater Biol Appl. 2021;126:112109.

    Article  CAS  PubMed  Google Scholar 

  36. Kobayashi M, Srinivasan M, Ammann P, Perriard J, Ohkubo C, Müller F, et al. Effects of in vitro cyclic dislodging on retentive force and removal torque of three overdenture attachment systems. Clin Oral Implant Res. 2014;25:426–34.

    Article  Google Scholar 

  37. Rutkunas V, Mizutani H, Takahashi HIN. Wear simulation effects on overdenture stud attachments. Dent Mater J. 2011;30:845–53.

    Article  PubMed  Google Scholar 

  38. Rhein 83. product catalogue. 2019.

  39. Guttal SS, Nadiger RKAS. Effect of insertion and removal of tooth supported overdentures on retention strength and fatigue resistance of two commercially available attachment systems. Int J Prosthodont Restor Dent. 2012;2:47–51.

    Google Scholar 

  40. Gujjalapudi M, Verma AK, Magar SM, Balaji DL, Dang GSBA. An in vitro assessment of retention force for implant retained overdentures using all polyetheretherketone, zirconia, and titanium attachments. Int J Curr Res Rev. 2021;13:75.

    Article  CAS  Google Scholar 

  41. Burns DR, Unger JW, Elswick RK, Beck DA. Prospective clinical evaluation of mandibular implant overdentures: Part I-retention, stability, and tissue response. J Prosthet Dent. 1995;73:354–63.

    Article  CAS  PubMed  Google Scholar 

  42. Kamal Emera R, Elgamal M, Altonbary G. Retention force of all-zirconia, all-polyetheretherketone, and zirconia-polyetheretherketone telescopic attachments for implant-retained overdentures: in vitro comparative study. J Dent Implant. 2020;10:78.

    Article  Google Scholar 

  43. Tehini G, Baba NZ, Majzoub Z, Nahas P, Berberi A, Rifai K. In vitro effect of mastication on the retention and wear of locator attachments in a flat mandibular ridge model. J Prosthodont. 2019;28:e744–51.

    Article  PubMed  Google Scholar 

Download references


The authors thank Professor Mohamed Farouk Abdallah professor of prosthodontics, Cairo University.


Open access funding provided by The Science, Technology & Innovation Funding Authority (STDF) in cooperation with The Egyptian Knowledge Bank (EKB). This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Author information

Authors and Affiliations



HGEC: build up the study design—wrote the main manuscript text—reviewed the manuscript—conduct the experiment testing. MSA: conduct digital workflow—prepared figures—reviewed the manuscript—conduct the experiment testing.

Corresponding author

Correspondence to Hussein G. El Charkawi.

Ethics declarations

Ethics approval and consent to participants

Not applicable.

Consent to publication

Not applicable.

Competing interests

The authors declare that they have no conflict of interest.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary Information

Additional file 1. A video demonstrating the digital workflow of the design of the ball attachment retentive insert.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

El Charkawi, H.G., Abdelaziz, M.S. Novel CAD–CAM fabrication of a custom-made ball attachment retentive housing: an in-vitro study. Eur J Med Res 28, 520 (2023).

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: