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PubMed1996

Retention force changes in implant-supported titanium telescope crowns over long-term use in vitro.

Titanium is used to fabricate spherical and bar attachments for overdentures on osseointegrated implants. This in vitro study investigated the long-term effects of commercially pure titanium on the retention force of telescope crowns with conical interface. Combinations of various materials for the inner and outer crowns were tested. Telescope crowns of pure titanium showed retention force characteristics comparable to telescope crowns fabricated conventionally in a precious alloy.

Chromium Alloys↗
PubMed2002

Retention mechanisms and prosthetic complications of implant-supported mandibular overdentures: long-term results.

BACKGROUND: Although many studies report high survival rates of mandibular implants supporting an overdenture, complications with prostheses and the need for prosthetic maintenance are not so well documented. PURPOSE: The purpose of the present study was to analyze three categories of prosthetic complications in relation to the type of retention mechanism for overdenture connection to the implants (ie, rigid or resilient). MATERIALS AND METHODS: One hundred nineteen patients with a total of 258 implants participated in the study. They had been monitored regularly during an observation period of 5 to 15 years (mean 9.3 yr). Seventy-five patients had a resilient retention device (ball anchors or a round clip bar); 44 patients had a rigid bar with or without distal extensions. The incidence and rate of complications were calculated for the overall- and for the 2- and 5-year observation periods. Comparisons were made between the three categories of maintenance and the two types of retention. A Kaplan-Meier analysis was applied for calculations of changes of the retention mechanism. RESULTS: The mean number of complications per overdenture during the entire observation period was 3.5; this did not differ statistically between the two retention groups. Some significant differences were found only for the 2- and 5- year period. Broken, loose, or lost female parts were more frequently observed with resilient devices, as were repairs and relining of the resin denture base, whereas tightening of bar retainers was more typical with rigid bars. A change from a resilient retention device to a rigid bar was performed more often than vice versa but not at a statistically significant level. CONCLUSION: Although these long-term results do not indicate a significant difference between the retention groups, a slight superiority of the rigid bar is suggested.

Adult↗
PubMed2000

Effects of abutment size and luting cement type on the uniaxial retention force of implant-supported crowns.

STATEMENT OF PROBLEM: The assumption that increasing the diameter of the abutment/crown components will provide greater resistance to crown loosening forces than standard-sized components has not been reported either with clinical trials or in the laboratory. PURPOSE: This study attempted to determine what effect abutment dimension and type of luting agent have on the retention of the prosthetic crown. METHODS AND MATERIAL: Test specimens consisted of standard, wide, and "experimental" CeraOne titanium abutments and matching CeraOne gold cylinders cemented with a zinc phosphate permanent or a zinc oxide eugenol provisional cement. The mean uniaxial force (Newtons) and the load (MPa) required to dislodge the cylinder from the abutment was determined. Statistical analysis of the sample data was performed using a 2-way analysis of variance test (alpha=.05). RESULTS: Mean uniaxial resistance force (Newtons) was significantly greater for zinc phosphate cement than for zinc oxide cement (P <. 001). Abutment size was a significant factor when permanent luting cement is used (P <.001). Retention strength per unit area (MPa) of the wide abutments was lower than the standard size and "experimental" abutments. CONCLUSION: Permanent luting cement produced uniaxial retention forces approximately 3 times greater than provisional cement. The increase in surface area provided by a wide abutment did not result in an improvement in retention strength over the standard abutment.

Analysis of Variance↗
PubMed1998

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 (31, 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 no simulate clinical fatigue adequately.

Dental Abutments↗
PubMed1994

Effect of preload torque on the ultimate tensile strength of implant prosthetic retaining screws.

The preload concept proposes that an optimal torque exists to which implant prosthetic retaining screws should be tightened. According to this theory, the preload prevents separation of implant components, thus protecting the screw from fracture. Recent research suggests that most implant-retained prostheses in function today were placed using improper preloads. The purpose of this investigation was to determine whether or not improper preloading of prosthetic implant-retaining screws would adversely affect their ultimate tensile strength. Fifteen Nobelpharma-slotted gold screws from one lot were tightened to 6, 10, and 15 N/cm with a torque gauge and ultimate tensile strength values determined. The procedure was duplicated using 15 Nobelpharma gold screws from another lot tightened to 0, 10, and 20 N/cm. Within each of the test groups, there was no significant difference in the ultimate tensile strength among the three preload torques. However, a paired t test (P = 0.005) determined that there was a significant difference between the two lots with respect to the ultimate tensile strength of the screws preloaded to 10 N/cm. Altering the preload torque applied to Nobelpharma gold-retaining screws does not affect their ultimate tensile strength. The ultimate tensile strength of the screws from the two lots differed, suggesting an unannounced change in component specifications.

Dental Implants↗
PubMed2002

Solving the frustrations of crown cementation.

Restoration cementation is a routine procedure, but it commonly is accomplished improperly. In this article, I have discussed several of the most frequently occurring problems with restoration cementation and have made suggestions about how to prevent them.

Cementation↗
PubMed1990

Clinical and microbiologic findings that may contribute to dental implant failure.

Clinical and DNA probe analysis were used to evaluate 36 failing implant sites in 13 patients. Failing implants showed evidence of increased mobility and a high incidence of peri-implant radiolucencies in radiographs. The probing depth was greater than 6 mm in 58% of the sites measured. Moderate levels of Actinobacillus actinomycetemcomitans, Bacteroides intermedius, and Bacteroides gingivalis were detected with DNA probe analysis.

Actinobacillus↗
PubMed1996

Monitoring procedures for the single-tooth implant-stabilized crown with an internally located customized abutment.

Three procedures to ensure the correct location of components in the orifice of a hydroxyapatite-coated implant cylinder are presented. These facilitate recording of an accurate impression and the correct location of a customized abutment supporting a single-tooth crown. A technique is offered for obtaining the reproducible, comparable radiographs necessary for monitoring horizontal bone levels.

Alveolar Bone Loss↗
PubMedDate not supplied

Single tooth replacement using a one-piece screw-retained restoration.

This article reviews and illustrates several options available with single tooth implant prostheses. For use with internal hex implants, the authors prefer one-piece screw-retained restorations due to their easy retrievability, absence of cement, and remarkable aesthetics. The treatment procedure is outlined from presurgical prosthetic planning and surgery to the placement of the final prosthesis. The advantages and disadvantages of the technique are reviewed. The use of wide or narrow screw access channels is discussed. Selection of torque instruments and the proper levels of torque when tightening the screws are evaluated. Three clinical cases are presented to illustrate the principles reviewed in the text. The learning objective of this article is to provide up-to-date information on an implant system for screw-retained single tooth restorations.

Adolescent↗
PubMed2005

Retentive force of O-ring attachment to use Immediate Provisional Implant (IPI)-retained overdenture.

This study evaluated the retentive force of the O-ring attachment to an Immediate Provisional Implant (IPI)-retained overdenture. Two sizes of O-rings (#1, #2) were placed on the IPI abutment head. As the controls, soft relining material, silicone lining material, and the PMMA resin were used to connect the IPI abutment head. The retentive forces (n=5, N) obtained at a crosshead speed of 40 mm/min were analyzed by ANOVA/Tukey's HSD test (alpha=0.05). O-ring #1 showed the significantly greatest force among all materials tested (p0.05). Appropriate retention was obtained using the smaller O-ring#1 for the IPI-retained overdenture.

Analysis of Variance↗
PubMed1997

Implant-supported overdentures: the ZAAG attachment system.

It has been amply demonstrated during the last decade that there are significant advantages to implant-supported overdentures beyond conventional complete dentures. Several attachment systems exist for connecting the overdenture to the implants, and practically all of them present notable benefits to the patients. This article discusses the use of the Zest Anchor Advanced Generation (ZAAG). This system, an outgrowth from the original Zest attachment, uses both individual implant attachments and bar attachments, and is compatible with all major implant systems. In addition to the retention, stability, and resiliency the ZAAG implant attachment system provides, it has the advantage of placing the resistance force of the attachment close to the implant body.

Dental Abutments↗
PubMed1996

3-D in vivo force measurements on mandibular implants supporting overdentures. A comparative study.

Force transmission onto implants supporting overdentures was measured in vivo by means of piezoelectric transducers that allow for simultaneous force registrations in 3 dimensions. The transducers are directly mounted onto the implants, beneath the anchorage device. The force registrations were analyzed with regard to the anchorage device and retention mechanism of overdenture support. The 3 types of denture anchorage were a U-shaped bar, a round clip-bar and single telescopes. Forces were measured in the following test situations: maximum force when biting in centric occlusion, maximum bite force during biting on a bite plate, grinding and chewing bread. Multiple regression showed that the vertical component of maximum forces was dependent on the anchorage device and test situation. The transverse components reached 10 to 50% of the vertical force magnitude. With the bite plate in situ maximum forces measured in vertical direction were significantly higher or the ipsilateral implant with telescopes than with bars (p < 0.01 and p < 0.001). Chewing and grinding resulted in lower vertical forces compared to maximum biting. In transverse dimensions, mainly in the anterior-posterior direction, registered forces reached magnitudes that resembled the vertical component (50 to 100%). Force magnitudes of chewing and grinding were similar for all three anchorage devices. However, differences were observed between bars and telescopes with regard to the direction of transverse force components. The results of this study do not suggest the preference of one specific anchorage system or retention mechanism for overdenture support. However, rigid bars contribute to load sharing and stress distribution onto the implants.

Aged↗
PubMed2004

Resistance to crown displacement on a hexagonal implant abutment.

The purpose of this study was to evaluate the resistance and retention of a hexagonal abutment to crown displacement with varying crown heights (10, 12, and 14 mm) and axis of load. Implants were embedded in resin blocks at a 30 degree angle to the vertical. Crowns were made at heights of 10, 12, and 14 mm. Groups of 5 crowns for each of the 3 crown heights were loaded (200 N) both under the long axis and off axis. The marginal gaps were measured using standardized periapical radiographs before and after loading. The gaps were statistically compared using a 3-way analysis of variance with factors of load, crown height, and point of load. Crowns were loaded to 10 cycles or point of failure. The 10-mm crowns did not show any displacement. The 12-mm and 14-mm groups only showed displacement of the off axis-loaded crowns. The average marginal displacement was 193.56 micro (standard deviation [SD] +/- 138.62 micro) at point of failure (320,717 cycles) and 400.18 micro (SD +/- 644.31) at point of failure (134,278 cycles), respectively. A 1-piece implant with a standardized abutment design can provide sufficient resistance and retention form for crowns of varying dimension if loads are centered over the long axis of the crown.

Crowns↗
PubMed1997

Comparison of screw retention of nine abutment systems: a pilot study.

Fracturing or loosening of abutment and retaining screws is a frequent occurrence. This study was designed to evaluate the retaining ability of nine abutment systems. Abutment and retaining screws were secured to the appropriate implant using a digital torque gauge, with the abutment screws placed at 30 N-cm and the retaining screws at 10 N-cm. Removal torque was recorded three times for each sample 10 minutes after initial placement, 20 minutes after retightening, and 24 hours after retightening. There was no statistical difference in removal torque relative to time or repeated tightening. Of the nine abutment systems, three were statistically less retentive as compared with the most retentive system. The retaining screws were less retentive as compared with the abutment screws. For maximum retention the elimination of retaining screws from the restorative design and using 30 N-cm of torque for the abutment screws is suggested.

Analysis of Variance↗
PubMed2004

Short-term retention properties of cements for retrievable implant-supported prostheses.

This in vitro study compared the retentive ability of 11 materials used to cement cast crowns on one implant system. The crowns were cemented to the abutments and the tensile load necessary to remove each casting was measured 30 minutes after cementation in a dry condition at 22 degrees C and after storage for 72 hours in saline solution at 37 degrees C. The results provide a ranking order of the tested materials according to their ability to retain implant restorations. This information, along with studies that better represent the effect of aging, may assist the clinician in selecting a material that is retentive enough to withstand occlusal forces, yet weak enough to allow easy retrieval of cement-retained implant restorations.

Adhesiveness↗
PubMedDate not supplied

In vivo stress behavior in cemented and screw-retained five-unit implant FPDs.

PURPOSE: When fixing implant-supported fixed partial dentures (FPDs), it is important to achieve passive fit. The objective of the in vivo study presented was to quantify the strain development during the fixation of screw- and cement-retained FPDs. MATERIALS AND METHODS: After informed patient consent had been obtained (Ethics commission Approval No. 2315; FAU Erlangen-Nuremberg, Germany), four groups of five-unit FPDs (five samples per group) were fabricated and investigated in vivo. Group 1: Cementable, repositioning technique impression, burn out plastic coping; Group 2: Screwable, pickup technique impression, burn out plastic coping; Group 3: Screwable, pickup technique impression, cast to gold cylinder; Group 4: Screwable, pickup technique impression, bonded to gold cylinder. Two strain gauges (SG) were attached to the pontics of each bridge (SG-M and SG-D) to measure the strains that occurred during either the cementing or screw-in process. The final values were recorded for analysis. RESULTS: The mean strain values (microm/m) for each SG were: Group 1: SG-M 32 microm/m, SG-D: 89 microm/m; Group 2: SG-M 302 microm/m, SG-D: 197 microm/m; Group 3: SG-M 458 microm/m, SG-D: 268 microm/m; Group 4: SG-M 269 microm/m, SG-D: 52 microm/m. CONCLUSIONS: Although the bridges were clinically acceptable, none of them revealed a truly passive fit with zero microstrain. In contrast to conventional screw-retained bridges, cement retention seems to result in lower strain levels. Bonding bridge pontics to prefabricated implant components seems to allow both the retrievability of a screw-retained bridge and produce moderate strain values.

Aged↗