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International Poster Journal of Dentistry and Oral Medicine



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Int Poster J Dent Oral Med 14 (2012), No. 2     15. June 2012

Int Poster J Dent Oral Med 2012, Vol 14 No 2, Poster 595

Retention characteristics of semi-precise bar attachments in implant dentistry

Language: English

Dr. Sonia Mansour, Kristin Schlenz, Dipl.-Ing. Christin Arnold, Prof. Dr. Jürgen M. Setz, PD Dr. Arne F. Boeckler,
Martin-Luther-University Halle-Wittenberg, Department of Prosthodontics, Halle (Saale), Germany

March 16-19, 2011
89th General Session & Exhibition of the IADR
San Diego, USA


Bar attachments have been established in implant dentistry. Only bar attachments realize primary splinting of the implants. For different bar designs various patterns with different crass sections are usable. [1] Contrary to prefabricated or individual fabricated matrices from metal or electroplated gold, semi-precise resin friction inserts are economical and easily replaceable. [2, 3, 4] (Fig. 1). These inserts determine the retention of the prosthesis and are embedded by metal friction patterns (matrices). Manufacturers offer various and colour-coded inserts with different retention forces often specified only as 'smooth', 'normal' and 'strong'. (Tab. 1) Clinical reproducibility of the retention forces of semi-precise bar inserts is not yet investigated.


The aim of this in vitro study was to analyze and compare retention characteristics of different prefabricated resin inserts in implant dentistry.

Material and Methods

4 bar systems were tested for retention of the corresponding specific resin inserts. For each system a bar (10mm long) was casted (Heraenium P, Heraeus Kulzer, Hanau, D) using prefabricated acrylic components. Specimen were connected rigidly to a titanium abutment by laser and torqued to an implant (SP-RN, Straumann, Basel, CH). Matrices for the friction inserts were prefabricated (Cendres & Métaux) or casted from a prefabricated resin pattern which burns out without residues (Bredent). All inserts (polyacetal-copolymer resins) were tested as delivered by the respective manufacturers. For each bar system and the respective color-coded retention forces (n=3) 10 resin inserts were tested (n=12x10; Tab. 1) Retention forces of 3 systems were indicated by the manufacturers (4/6/8N). Dolder bar attachment quotes only 'light'/'middle'/'heavy'. In an universal-testing-machine (Zwick, Ulm, D) matrices were removed 10 times from the patrices (v=50mm/min, axial, salivary solution 22°C; Fig. 3). Force-deflection-graphs were made. If possible mean retention forces were compared to manufacturer's data and statistically analyzed (p < 0,05).

Fig. 1a-b: Snap bar attachment with friction-snap matrice vsp-fs 'yellow'
Fig. 1c-d: Snap bar attachment with friction-snap matrice vsp-fs 'yellow'
Fig. 1e-f: Snap bar attachment with friction-snap matrice vsp-fs 'yellow'
Fig. 1g-h: Snap bar attachment with friction-snap matrice vsp-fs 'yellow'
Product Friction inserts Color code Retention force
Manufacturer's data [N]
Parallel bar attachment Friction matrice vsp-f green 4 Bredent, Senden, D
yellow 6
red 8
Snap bar attachment Friction-snap matrice vsp_fs green 4 Bredent, Senden, D
yellow 6
red 8
Resilient snap bar attachment Joint snap-in matrice vsp-gs green 4 Bredent, Senden, D
yellow 6
red 8
Friction matrice green not reported Cendres & Métaux, Biel/Bienne, CH
yellow not reported
red not reported
Tab. 1: Tested bar attachment systems
Fig. 2a-b: Construction principles of the tested bar systems
Fig. 2c-d: Construction principles of the tested bar systems
Fig. 3 Fig. 4


Mean retention forces differed within the groups (Welch- und Brown-Forsythe Test, p < 0,05, Fig. 4). Differences were not significant for all groups. The graduation in different retention force levels given by the manufacturers could only be proven in one system. However, the system produced retention forces about 100% above the other three tested systems. Retention force information by the manufacturer was not provided. Lowest deviation from manufacturer's inforrnation was found in the red friction inserts of the parallel bar attachment (-0,9%). Highest deviation of 44% was shown by the green friction inserts of the resilient snap bar attachment.
In three groups the inserts with the declared lowest retention force (green) produced comparable higher retention forces.
Owing to the influence on long term success and patients' satisfaction retention force is important for choosing the adequate insert. So, precise labeling by the respective manufacturers is clinically important. All tested inserts offered initially adequate retention forces. The forces of 11 of 12 inserts met the requirements for attachments (4-12N) postulated by Lehmann and Armin [5]. The resulted data are beneath the retention forces of alternative semi-precise single resin attachments (12N to 25N). [7] Reasons for deviation of measured data maybe be found in various insert resin materials, the retentive design and subsequent manipulation of the casted bars. Long term investigations to the retention properties of the tested systems are initiated.


Within some systems differences in retention forces between the color coded friction inserts were small. Retention forces of the inserts of most systems showed significant differences to the manufacturer's information. A purposeful application of some tested inserts according to their guaranteed retention force seems to be clinically doubtful and unpractical.


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This Poster was submitted by Dr. Sonia Mansour.

Correspondence address:
Dr. Sonia Mansour
Martin-Luther-University Halle-Wittenberg
Department of Prosthodontics
Grosse Steinstrasse 19
06108 Halle (Saale)