The patient general satisfaction of mandibular single-implant overdentures and conventional complete dentures: Study protocol for a randomized crossover trial.

BACKGROUND: Mandibular overdentures retained by a single implant placed in the midline of edentulous mandible have been reported to be more comfortable and function better than complete dentures. Although single-implant overdentures are still more costly than conventional complete dentures, there are a few studies which investigated whether mandibular single-implant overdentures are superior to complete dentures when patient general satisfaction is compared. The aim of this study is to assess patient general satisfaction with mandibular single-implant overdentures and complete dentures. METHODS: This study is a randomized crossover trial to compare mandibular single-implant overdentures and complete dentures in edentulous individuals. Participant recruitment is ongoing at the time of this submission. Twenty-two participants will be recruited. New mandibular complete dentures will be fabricated. A single implant will be placed in the midline of the edentulous mandible. The mucosal surface of the complete denture around the implant will be relieved for 3 months. The participants will then be randomly allocated into 2 groups according to the order of the interventions; group 1 will receive single-implant overdentures first and will wear them for 2 months, followed by complete dentures for 2 months. Group 2 will receive the same treatments in a reverse order. After experiencing the 2 interventions, the participants will choose one of the mandibular prostheses, and yearly follow-up visits are planned for 5 years. The primary outcome of this trial is patient ratings of general satisfaction on 100 mm visual analog scales. Assessments of the prostheses and oral health-related quality of life will also be recorded as patient-reported outcomes. The secondary outcomes are cost and time for treatment. Masticatory efficiency and cognitive capacity will also be recorded. Furthermore, qualitative research will be performed to investigate the factors associated with success of these mandibular denture types. Clinical outcomes, such as implant survival rate, marginal bone loss, and prosthodontic complications, will also be recorded. DISCUSSION: The results of this randomized crossover trial will clarify whether mandibular single implants and overdentures for edentulous individuals provide better patient general satisfaction when compared to conventional complete dentures. TRIAL REGISTRATION: This clinical trial was registered at the University Hospital Medical Information Network (UMIN) Center (UMIN000017883).

Influence of implant number on the movement of mandibular implant overdentures.

STATEMENT OF PROBLEM: The rotational movement of an implant overdenture (IOD) has a negative effect on the perceived masticatory ability of the denture wearer. However, the influence of implant number on the movement of IODs has not been investigated. PURPOSE: The purpose of this in vitro study was to evaluate the denture movement of mandibular IODs anchored by different numbers of implants. MATERIAL AND METHODS: An edentulous mandibular test model with artificial mucosa and 5 experimental overdentures (N=5) was fabricated. The locator attachment system with blue nylon inserts was chosen for this study. Three implant positions were prepared: anterior midline (1-IOD), bilateral lateral incisor regions (2-IOD), and anterior midline and bilateral canine regions (3-IOD). Vertical loads of 50 N were applied to the mid-anterior region, the left canine region, the left premolar region, and the left first molar region. The vertical and horizontal displacements at the right distal edge and the vertical displacements at the loading point were measured. The displacement values were statistically analyzed using a 1-way analysis of variance and the post hoc Tukey honest significant difference test with the implant number as a factor. In addition, the values of the vertical and horizontal displacements at the distal edge of the overdenture were statistically compared using a paired t test, and the values of the vertical displacement at the distal edge of the overdenture were statistically analyzed by a repeated measures analysis of variance and the post hoc Tukey honest significance difference test with the loading point as a factor (a=.05). RESULTS: Upon anterior loading, the 2-IOD showed significantly larger vertical displacements at the right distal edge than the 1-IOD or 3-IOD (P<.01). The horizontal displacements at the right distal edge were small compared with the vertical displacements at the same point, although the displacement of the 2-IOD was significantly larger than that of the 1-IOD upon anterior loading (P=.03). The magnitude of the vertical displacement at the loading point of the 2-IOD was significantly larger than that of the 3-IOD upon anterior loading (P<.01). No statistically significant differences were shown under the other conditions for each loading (P>.05). CONCLUSIONS: Within the limitations of this in vitro study, the following conclusions were drawn: During mastication with the anterior teeth, the use of 2 implants for anchoring an IOD increased the rotation of the denture base more than the use of 1 or 3 implants. The horizontal movements of the IODs were small compared with the vertical movements. Denture movement under the occlusal force in the molar region was smaller than that in the anterior region.

Effects of clip materials on stress distribution to maxillary implant overdentures with bar attachments.

STATEMENT OF PROBLEM: Fracture of maxillary implant overdentures (IODs) is a frequent complication. However, no studies have examined the effects of clip materials on the stress applied to maxillary IODs. PURPOSE: The purpose of this study was to investigate the effects of clip materials for bar attachments on the stress applied to maxillary IODs without palatal coverage. MATERIAL AND METHODS: This study included finite element analysis and a model study. An edentulous maxillary model with 4 implants and an experimental overdenture with bar attachments was fabricated. Strain gauges were attached on the denture surface adjacent to the end of each clip. Four clip conditions (n=5) were prepared: 3 plastic clips, 1 plastic clip, 3 metal clips, and 1 metal clip. A vertical load of 50 N was applied on the IOD. The maximum principle strain (MPS) was statistically analyzed by 2-way ANOVA and the post hoc Tukey HSD tests with clip materials and clip numbers as factors (α=.05). RESULTS: The greatest stress was observed on the resin surface around the end of the clip on the loaded side. The MPSs between both clip materials (P=.048) and numbers (P<.001) differed significantly on the palatal side of the end of the center clip on the loaded side: the MPSs of the metal clips were significantly larger than those of the plastic clips, and the MPS of 1 clip was significantly larger than for 3 clips. CONCLUSIONS: The stress around plastic clips tended to be lower than that around metal clips.

Stress analysis of mandibular two-implant overdenture with different attachment systems.

This study aimed to investigate the influence of different overdenture attachment systems on the stress generated in peri-implant bone during overdenture dislodgement and loading. Two implants were placed in the canine regions on an acrylic edentulous mandibular model. Four strain gauges were attached to the resin surface adjacent to the left implant. Bar, ball, and magnetic attachments were examined. Three experimental overdentures were fabricated, and the denture parts of the attachment systems were incorporated into the mucosal surface. Retentive forces and strains generated in peri-implant bone during three types of dislodgement (vertical, anterior and posterior) and loading (left first molar region, right first molar region and mid-anterior region) were measured. The bar attachment showed the highest retentive force and reduced strain on posterior dislodgement. The ball attachment demonstrated the largest strain on loading at molar regions. The magnetic attachment showed the smallest retentive force and little strain.