Comparison of retention and stability of two implant-retained overdentures based on implant location.

STATEMENT OF PROBLEM: The location of dental implants and the choice of retentive attachments for implant-retained overdentures are selected based on clinician preference, expert opinion, or empirical information. Limited information is available regarding implant position and the effect on the retention and stability of 2-implant mandibular implant overdentures. PURPOSE: The purpose of this investigation was to evaluate the effect of implant location on the in vitro retention and stability of a simulated 2-implant-supported overdenture and to examine the differences among different attachment systems. MATERIAL AND METHODS: A model that simulates a mandibular edentulous ridge with dental implants in positions that approximate tooth positions, and a cobalt-chromium cast framework attached to a universal testing machine was used to measure the peak load (N) required to disconnect the attachments. Four different types of attachments (Ball/Cap, ERA, Locator, and O-Ring) were used in sequence in various positions on the model to evaluate the effect of implant location on the retention and stability of a simulated 2-implant-retained overdenture. Means were calculated, and differences among the systems, directions, and groups were identified by using a repeated measured ANOVA (α=.05). For differences observed between measurements, the Bonferroni post hoc method at the 5% level of significance was used to determine the location and magnitude of difference. RESULTS: The interactions between the attachment system, direction of force, and implant location were statistically significant (P=.01). The vertical retention and horizontal stability of a simulated overdenture prosthesis increased with the distal implant location up to the second premolar, and the anteroposterior stability increased with distal implant location. The attachment type affected retention and stability differently by location. Ball attachments produced the highest levels of retention and stability, followed by Locator (pink), O-Ring, and ERA (orange). CONCLUSIONS: The retention and stability of a 2-implant simulated overdenture prosthesis is significantly affected by implant location (P=.01) and abutment type (P=.01).

Comparison of retention and stability of implant-retained overdentures based upon implant number and distribution.

PURPOSE: The purpose of this investigation was to evaluate the effects of number and distribution of implants upon in vitro dislodging forces to a simulated implant-supported overdenture and to examine differences between several different attachment systems. MATERIALS AND METHODS: An experiment was undertaken utilizing a model simulating a mandibular edentulous ridge with dental implants in positions on the model approximating tooth positions in the natural dentition. A cobalt-chromium-cast testing framework was used to measure the peak load required to disconnect an attachment. Four different types of commercially available attachments were used in various positions on the model in sequence to evaluate the effects of retention and stability of overdentures based on implant number and distribution: (1) ERA, (2) O-Ring, (3) Locator, and (4) Ball. For each group, 10 measurements were made of peak dislodging forces. Means were calculated and differences among the systems, directions, and groups were identified using a repeated measured analysis of variance (α = .05). RESULTS: The interactions between the attachment system, direction of force, and implant number and distribution were statistically significant. Vertical dislodging forces of the simulated overdenture prosthesis increased with additional widely spaced implants. Oblique dislodging forces of the simulated prosthesis increased with additional widely spaced implants except in the two-implant model with all attachments, and in the four-implant groups with Locator attachments. Anteroposterior dislodging forces of a simulated overdenture prosthesis increased with additional widely spaced implants except in the four-implant groups with Ball and Locator attachments. Ball attachments reported the highest levels of retention and stability followed by Locator, O-Ring, and ERA. CONCLUSIONS: Within the limitations of this study, retention and stability of an implant overdenture prosthesis are significantly affected by implant number, implant distribution, and abutment type.

Conversion of a partial removable dental prosthesis from Kennedy class II to class III using a dental implant and semiprecision attachments.

This article presents a design to convert a partial removable dental prosthesis (PRDP) from Kennedy class II to class III using a dental implant. Incorporating semiprecision attachments, this design provides desired esthetics, phonetics, and function.

An accelerated clinical chairside technique for casting overdenture attachment copings.

An accelerated technique for casting a direct-pattern post and core restoration for use in fixed prosthodontics has been previously described. Similar techniques for use in removable prosthodontics show potential for clinical use, specifically for the fabrication of radicular stud overdenture attachments and their corresponding copings. The procedure uses a chairside technique and readily available components to fabricate a direct, acrylic resin pattern combining the elements of a cast coping with a fixed radicular attachment. This pattern can subsequently be invested, cast, finished and polished, luted, and attached to the removable prosthesis in a single clinical appointment.

Effect of axial height and palatal wall on the resistance form of a maxillary anterior metal-ceramic crown preparation.

The effect of palatal wall modifications and height of a maxillary central incisor on the resistance form of metal-ceramic crowns are compared. Dies with adequate preparation height show no crown dislodgement in groups with a palatal wall, palatal wall/groove, and no palatal wall. This study suggests the use of a palatal groove improves the resistance to dislodgement in short maxillary anterior tooth preparations.

Linguoaxial wall and cervicoincisal dimension of anterior crown preparation: effect on retention.

This study sought to evaluate the effect of the linguoaxial wall, a lingual auxiliary groove, and the cervicoincisal dimension of the anterior tooth preparation on retention. A simulated maxillary central incisor was prepared following "ideal" guidelines. The linguoaxial wall of these preparations was modified and the samples were divided into three groups: preparations with a linguoaxial wall (Group 1), preparations with a linguoaxial wall and groove (Group 2), and preparations with no linguoaxial wall (Group 3). Ten metal dies and crowns were fabricated from each preparation group. A universal testing machine subjected cemented crowns to force along the long axis of the dies and load-to-dislodgement was measured. All preparations were shortened by 3.0 mm and crowns for the reduced-height groups were fabricated, cemented, and subjected to similar force. The preparations with the groove produced higher mean retention than the other groups. Among the reduced-height groups, the preparations with the groove also produced higher mean retention than the other groups. There were no differences in mean retention for the short and long preparation heights of each group.

Peri-implant tissue response of immediately loaded, threaded, HA-coated implants: 1-year results.

STATEMENT OF PROBLEM: Although high success rates have been reported with immediately loaded implants, the peri-implant tissue response has not been well documented. PURPOSE: This study evaluated implant success and peri-implant tissue response of immediately loaded, threaded, hydroxyapatite (HA)-coated root-form implants supporting mandibular bar overdentures with opposing conventional maxillary complete dentures in humans. MATERIAL AND METHODS: Five patients (3 men, 2 women; mean age 61 years) each received 4 HA-coated endosseous root-form implants in the interforaminal region in the mandible. The implants were rigidly splinted with a metal framework within 24 hours. The final EDS clip prosthesis was placed 1 to 2 weeks thereafter. The implants and peri-implant tissues were evaluated clinically and radiographically 0, 1, 3, 6, and 12 months after prosthesis placement. Data were analyzed with a repeated measures 1-way analysis of variance (P<.05). RESULTS: All implants were stable at the end of the observation period (mean Periotest value = -5.9 +/- 1.4). No peri-implant radiolucencies were noted, and no implants were lost. The mean marginal bone changes were -0.42 plus minus 0.34, -0.84 +/- 0.55, -1.14 +/- 0.80, and -1.16 +/- 0.89 mm at the 1-, 3-, 6-, and 12-month follow-ups, respectively (P<.001). Significant declines in the rates of marginal bone changes at each time interval were noted (P<.001). In addition, there were significant decreases in probing depth (P<.001) and plaque index (P<.001) but no significant difference in the frequency of bleeding upon probing (P=.64). CONCLUSION: Within the limitations of this study, the peri-implant tissue response of immediately loaded, HA-coated implants was favorable and comparable to that of conventional, delayed-loaded implants after 1 year.