Effect of Placement of Magnetic Attachment on Retentive Force of Overdenture

Y. Umekawa^1,2, Y. Ogawa¹, K. Ohtani^1,2, S. Ohno¹, T. Ishigami^1,2

¹Department of Partial Denture Prosthodontics, Nihon University School of Dentistry

²Division of Clinical Research, Dental Research Center, Nihon University School of Dentistry

Introduction

 Mandible complete denture for edentulous fail out when losing border seal at precipitous tongue movement or open mouth. Implant with attachment is useful for retaining overdenture.Lot of magnetic overdenture cases are reported with good results. But most of experimental report for retentive force is magnetic attachment independently.Experimental report for retentive force of magnetic overdenture clinical situation is few.

 

Objective

The aim of this study is to evaluate retentive force of mandible overdenture with various layout of implants with magnetic attachments by using universal testing machine.

Materials and Methods

1.   Experimental model

 Mandible model (H3-402L, Nissin) was used for master model.Mandibular bone model and overdenture model was made by acryl resin (Acron, GC) and residual mucous membrane model was made by silicone rubber impression material (Exahiflex regular, GC).Artificial saliva was made by moisturizing gel (Oralbalance, Laclede).Magnetic attachment (Gigauss D600, GC) was placed median mandibular, canine and molar (fig. 1).

 

1.   Tensile test

 Tensile test was performed at incisor point (A), left second molar (B) and center of second molars (C) of overdenture model by original testing jig¹⁾ and universal testing machine at 5.0 mm/min of cross head speed²⁾.The test was repeated five times each condition and averaged(fig. 2,3).

 

 

Statistical analysis

 Statistical analysis was performed using SPSS ver.12 software. Statistical comparison was performed using Tukey’s test (P<.05).

Results

 Largest retentive force at A point was measured from design 3 (6.3N), at B point was measured from design 4 (5.0N) and at C point was measured from design and 4 (4.9N) (fig. 3-6).Largest retentive force was found at traction point C at design 0 (fig. 7).No significant difference was found between traction points at design 1 and design 4.Largest retentive force was found at traction point A at design 2 and design 3.

 

Conclusions

1. Magnetic attachment significant increases retentive force of mandible overdenture.

2. Median mandible magnetic attachment significant increases of retentive force against anterior dislodgement of overdenture.

3. Three front placement or four square placement of magnetic attachment increases retentive forces against posterior dislodgement of overdenture.

 

References

1.  Y. Umekawa, T. Ishigami, Influence of keeper tilt angle on retentive force, J J Mag Dent 17(2):98-100, 2008.

2.  Y. Ogawa, Y. Umekawa, T. Ishigami, Y. Takeuchi, N.Tsukimura, K. Ohtani, and S. Ohno. Effect of Crosshead Speed on Magnetic Retentive Force, Natsume S, J J Mag Dent 18(2):39-41, 2009.