Initial Retentive Force Research Articles

임플란트 피개의치를 위한 Locator 어태치먼트: 문헌 고찰

The Locator attachment is used widely for implant retained overdenture. It can be used solitary and needs small vertical space. Locator can be applicable for parallel implants and divergent implants. Nylon male cap allow personalized retention for each case. In this literature review, initial retention force and changes in retention force of various attachments were evaluated. Rotation freedom and stress distribution around the attachment were reviewed. Moreover, patient satisfaction and maintenance care of Locator attachment were described. From all of the researches, it was drawn that Locator attachment can be used successfully and widely in several clinical situations.

Effect of corrosive environments and thermocycling on the attractive force of four types of dental magnetic attachments

Background/purposeOne of the problems that has limited magnets’ wide acceptance by clinicians is their low corrosion resistance. The purpose of this study was to determine the effect of corrosive environments and thermocycling on the attractive force of different types of new generation magnetic attachments. Materials and methodsWe measured the attractive forces of 60 magnetic attachment systems (Hyper slim, Hicorex slim, Dyna, and Steco) with a universal test machine. We then immersed 40 of the magnetic attachment systems in two media, namely, 1% lactic acid solution (pH 2.3), and 0.9% NaCl solution (pH 7.3). The remaining magnetic attachments were put through 10,000 thermal cycles (5 °C/55 °C). We measured the attractive forces of the magnetic attachment systems again after immersion and thermocycling to compare data. The data were statistically evaluated with one-way analysis of variance, paired samples t-test, and post hoc Tukey–Kramer multiple comparison tests (α = 0.05). ResultsWe found significant differences between the mean values before and after immersion in corrosive environments (P < 0.05). In contrast to the Dyna and Steco systems (P < 0.001), the differences between the attractive forces before and after thermocycling were not statistically significant for the Hicorex slim and Hyper slim systems (P > 0.05). ConclusionMagnetic attachments showed lower attractive force after immersion in corrosive environments compared to their initial retentive force. In addition, closed-field systems were not affected by the thermocycling procedures and were more resistant than open-field systems to thermal variations characteristic of the oral cavity.

Retentive forces and fatigue resistance of thermoplastic resin clasps

ObjectivesThe objective of this study was to evaluate the retentive force of clasps made from three thermoplastic resins and cobalt–chromium (CoCr) alloy by the insertion/removal test simulating 10 years use. MethodsOn standardized premolar metal crowns 112 clasps were fabricated, including 16 CoCr (1.0mm thick) clasps and 32 clasps (1.0 or 1.5mm thick) from each of the following thermoplastic resins: polyetheretherketon (PEEK), polyetherketonketon (PEKK) and polyoxymethylene (POM). Specimens were divided in subgroups with clasp undercuts of 0.25mm and 0.5mm, respectively. Each clasp assembly was subjected to an insertion/removal test on its abutment crown for 15,000cycles. To analyze the retention over the course of insertion/removal test, retention was measured every 1500cycles. Data were statistically analyzed using 3-way ANOVA (α=0.05). ResultsResin clasps with 1.5mm thickness showed higher retention (4.9–9.1N) than clasps with 1.0mm thickness (1.2–3.1N; P≤0.001). Resin clasps of both dimensions had significantly lower retentive force than CoCr clasps (11.3–16.3N; P≤0.001). Clasps with 0.25mm undercut showed significantly less retention than clasps with 0.50mm (P≤0.001). All clasps exhibited an increase in retentive force during the first period of cycling followed by continuous decrease till the end of the cycling but it was still significantly not different compared to the initial retentive force (P=0.970). SignificanceThermoplastic resin clasps maintained retention over 15,000 joining and separating cycles with lower retention than CoCr clasps. However, the retention of adequately designed resin clasps might be sufficient for clinical use.

Evaluation of the retentive characteristics of semi-precision extracoronal attachments

The aims of this in vitro study were: to evaluate the repeatability of producing the semi-precision attachment; to establish their estimated longevity by a simulated, repeated denture placement/removal procedure of denture; and to investigate the wear of their components. Four types of semi-precision attachments were evaluated. The attachments represented polymer-to-metal type of friction: Vario-Kugel-Snap, Vario-Soft, Strategy OT and ASC-52, which exhibited metal-to-metal type of friction. Tensile dislodging force was applied to sample to register peak load-to-dislodgment and also to determine the displacement curve. Then the cyclic axial loading tests were performed with insertion/separation machine. To detect worn areas, the surface of each sample was examined under a scanning electron microscope. The large variability of initial retentive force and shape of displacement curves was noted within Vario-Soft and Vario-Kugel-Snap group. After the first period of loading (up to 300 cycles), the mechanical properties of all samples were stabilised. The mean retention force of attachments with polymer matrix after 3000 cycles was approximately half the recommended value, while samples of ASC-52 (with metal-to-metal friction) withstood 8000 cycles. Results suggest that the inaccuracies of casting and laboratory procedure have only limited influence on the fit of the semi-precision attachments. The attachment with metal-to-metal type of friction exhibits the highest wear resistance (simulated up to 8 years of usage) compared to attachments with polymeric matrix (up to 3 years). All attachments exhibited wear of metal patrix, what can minimise the chance of re-activation in a long run.

The in Vitro Effect of Different Implant Angulations and Cyclic Dislodgement on the Retentive Properties of an Overdenture Attachment System

The retentive capacity of ball attachments may be altered by a change in implant angulations. The purpose of this in vitro study was to investigate the effect of cyclic dislodgement on the retention of an overdenture attachment system when 2 implants were placed at angulations of 0, 5, 10, 15, and 20 degrees. Twelve acrylic resin blocks were fabricated and divided into 6 groups of 2 pairs each. In each of the 6 groups, 1 acrylic resin block was used to house the implants (block A), while the other (block B) was used to house the overdenture attachments. Two implants positioned at 0/0 degrees, with a standard plastic component(white) designed for 0-degree angulations, served as a control (CTRL), while the other 5 pairs of implants were placed in 5 different angulations: 0D: 0/0 degrees, 5D: 5/5 degrees, 10D: 10/10 degrees, 15D: 15/15 degrees, 20D: 20/20degrees (n=5). The extended range (green color) attachment was used for all groups except the control group. Implants(4.3 mm x 13 mm, internally hexed) were placed in blocks B. All angled implants were mesially tilted. Thirty pairs of attachments (Locator) were used. Dislodging cycles were applied to the overdenture attachment system. The initial retentive forces among the groups were not identical. The cycles required for the retentive forces of the attachments to decrease from the initial values to 60 N, and then to 40 N and 20 N, were recorded for standardization purposes.One-way ANOVA and Tukey HSD tests were used to analyze the difference in retention loss among the 6 groups(alpha=.05). A regression analysis (alpha=.05) was also performed to investigate the relationship between the implant angulation,the retentive force, and the logarithm of the number of cycles required for ball attachment retention decrease. The 1-way ANOVA and the Tukey HSD tests revealed significant differences for the number of cycles required by different implant angulation groups for the initial retentive values to decrease to 60 N, 40 N, and 20 N (P<.001).The 0D and 5D groups required the longest time for retention loss, while 20D and CTRL groups demonstrated the shortest time for retention loss. The results of the regression analysis of the logarithmic number of cycles on retentive force and implant angulation demonstrated a significant effect (P<.001). Implant angulations negatively affect attachment retention longevity. (J Prosthet Dent 2009;102:140-147)

Mechanical Properties of Magnetic Attachments for Removable Prostheses on Teeth and Implants

Magnetic attachments on teeth and implants may be used to improve stability, support, and retention of removable prostheses. Various forms of magnetic attachments are available, divided according to the design, the mechanical properties of the attachments, and the clinical indication. Recently developed attachment systems are small and promise improved retentive capacity, while existing magnetic attachments continue to be technologically modified and improved. This investigation reviewed and compared maximum retentive forces and characteristic curves for magnetic attachments indicated for use as root anchors and on implants. Twenty-four samarium-cobalt (SmCo) and neodym-iron-boron (NeFeB) magnetic attachments (12 tooth- and 12 implant-borne) were evaluated. Specimens were delivered by the manufacturers or fabricated according to their instructions. Five magnet pairs of each product and each combination were tested 10 times in a calibrated universal testing machine using a nonmagnetic test device (s = 40 mm, v = 20 mm/min). Results were recorded electronically and compared to manufacturers' details. Maximum retentive forces for root keepers ranged from 1.4 to 6.6 N. Maximum retentive forces for magnetic attachments on implants ranged from 0.7 to 5.8 N. After a distance of 0.1 mm, a complete reversed distribution of the different systems became obvious. The retentive force provided by the manufacturer was achieved in one implant abutment, with retentive force (as compared to those provided by the manufacturers) for root keepers ranging between 42.5% and 92.9% and for implant abutments between 43.0% and 99.4%. There were differences between magnetic attachments for both the initial retentive capabilities and the characteristic curves. Recently introduced products provided relatively high initial retentive forces despite their small size. The measured retentive forces and the manufacturer's information differed in the majority of magnetic systems evaluated.

Comparison of cast Ti-Ni alloy clasp retention with conventional removable partial denture clasps

Statement of problem The elastic property of Ti-Ni alloy may be a desirable property for cast removable partial dentures. However, little is known about the retentive properties of cast Ti-Ni alloy clasps. Purpose This in vitro study investigated the retentive force of various types of clasps during repeated cycles of placement and removal to determine whether Ti-Ni alloy clasps maintain their initial retentive force under varied conditions, including different retentive undercut depths and clasp size (thickness and width). Material and methods The test models were developed using a mandibular dentiform with a horizontal plane of occlusion. Two complete metal abutment crowns were made for the left second molar, differing only in retentive undercut depths. A total of 98 clasps (n=7) were fabricated, including 14 wrought wire clasps and 28 clasps from each of the following alloys: Co-Cr alloy (Biosil), Type IV gold alloy (Cast-4), and Ti-Ni alloy (TN-10). Clasps were made to engage one of 2 retentive undercut depths (0.25 mm or 0.75 mm) and were made in 2 sizes (0.8 mm or 1.4 mm). Each clasp was radiographically examined for casting defects and porosity. The force (N) required to remove the clasps was measured using a universal testing machine with a crosshead speed of 10 mm/min. After measuring the retentive force, a masticatory simulator was used to cycle the clasps on and off the metal crown 500 times, simulating the insertion and removal of a removable partial denture clasp. The cycling sequence was repeated 10 times, and retention force was measured after each sequence. The internal surface of the clasp arms was examined for evidence of metal fatigue using scanning electron microscopy. Data were subjected to 2-way and 4-way analysis of variance, followed by Scheffe's multiple comparison test (α=.05). Results Co-Cr alloy and gold alloy clasps in the 0.25-mm retentive undercut groups experienced a gradual decrease in retentive force measurements ( P<.001). In contrast, the Ti-Ni alloy clasps maintained a retentive force of approximately 1.8 N and 2.6 N for the 0.8 mm and 1.4 mm clasp groups, respectively. Although Ti-Ni alloy clasps' retentive force was reduced slightly after the first cycling sequence, it was negligible compared with other clasps tested. The wrought wire clasps also retained their retentive force until the final cycling sequence. A similar trend was found in the clasp groups engaging 0.75-mm retentive undercuts. Conclusion Although the end-point retention for all the clasps was similar, there was less change in the retentive force of the cast Ti-Ni alloy clasps after repeated cycling sequences of simulated placement and removal.

Retention and postinsertion maintenance of bar‐clip, ball and magnet attachments in mandibular implant overdenture treatment: an in vivo comparison after 3 months of function

It could be hypothesised that attachments, which provide more retention against vertical and horizontal dislodgement, will be associated with more favourable parameters of oral function. This in vivo study is designed to provide data regarding initial retention force, loss of retention force after 3 months of function and postinsertion maintenance and complications associated with the use of magnet, bar-clip and ball attachments in mandibular overdenture treatment. Eighteen edentulous subjects received two permucosal implants in the inter-foramina region of the mandible, a new denture and three successive suprastructure modalities (magnet-, bar-clip and ball attachments). The retention force of the attachments at baseline and after 3 months was measured in a standardised way. The amount and type of postinsertion maintenance that was related to the attachment were evaluated. No differences in retention force at baseline and after 3 months of loading were observed for all three attachment types. The mean retention forces of magnet attachments, bar-clip attachments and ball attachments were 8.1, 31.3 and 29.7 N respectively. Functional maintenance complications related to the attachments were predominantly observed in 11/36 magnet attachments. Functional problems in the ball attachment group were relatively rare, easily manageable and seen in 4/36 attachments. The bar-clip attachments exhibited no maintenance problems at all.

Retention of prefabricated attachments for implant stabilized overdentures in the edentulous mandible: An in vitro study

Statement of problem.Bar and stud attachments are widely used to stabilize overdentures on implants in the mandible. There is strong evidence that retention of the attachment is an important factor for a patient’s satisfaction. Purpose. This study describes retentive forces and wear of commercially available attachments of 4 implant systems (3I, IMZ, Nobel Biocare, ITI Straumann) and 2 magnets (Steco). Methods.Forces while removing the keyway portion of an attachment in its path of insertion were measured with a platform load cell. A total of 15,000 removals were performed to simulate fatigue. Results. Retentive forces ranged between 3 and 85 N. The fatigue test revealed an initial increase of forces with some attachments. After 15,000 cycles, most of the attachments showed little loss of retention compared with the initial retentive forces. It is suggested that conventional fatigue tests with application of axial loads do not simulate clinical fatigue adequately. (J Prosthet Dent 1998;80:323-9.)

Laboratory-made stud attachment. Report II. Effect of cycle of engaging and disengaging on fatigue

A number of engaging and disengaging of retainers induce those fatigue and consequent decrease in retentive force. In this study on the laboratory-made stud attachment consisting of a male (Type IV gold) like a snap and a female with semi-loop and linear portion made by bending a wrought gold wire, the maximum buldges of males, the distances between the female tips, and the retentive forces were measured before and after each stage of engaging and disengaging of predetermined cycles (10: initial, 1, 000, 3, 000, 5, 000, 10, 000). The males had 0.25 mm undercut. The females were 0.8mm in diameter and 3, 5, 7 and 10mm in length from the contact points with the males at the semi-loop portion to the points fixed in the resin base at the linear portion.Results:1. The initial retentive force, the abrasion of male, the permanent deformation of female and the decrease in retentive force all increased with the shorter female.2. 5mm-length female kept the most amount of retentive force of approximately 380 to 190g during 1, 000 to 10, 000 cycles.