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KMID : 0362820090280020010
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Journal of the Korean Academy of Implant Dentistry
2009 Volume.28 No. 2 p.10 ~ p.28
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Photoelastic stress analysis of mandible in the case of tooth-implant supported removable partial denture
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Jung Da-Un
Sim Hye-Young
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Abstract
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The purpose of this study was to compare and evaluate the stress distribution of mandible according to five different design of toothimplant supported removable partial denture, designed to prevent the movement around various axis of rotation and distribute the stress in the case of free end partial denture by placement of implant at both 2nd molar area . For this study, a three-dimensional photoelastic stress analysis method was used. In the model which only six anterior tooth are remained, two implants were installed at both 2nd molar area. In all five case, lingual bar was designed as a major connector and Akers clasps were designed for direct retainer of canine which were composed of cingulum rest and casting circumferential clasp using mesio-buccal undercut of canine. At the posterior implant, Akers clasp(A-AIRPD), Konus crown(AKIRPD), Long rest(A-LIRPD), Dalbo abutment(A-DIRPD) and O-ring abutment(A-OIRPD) were designed.. After this five Bilateral removable partial dentures were positioned on the photoelastic epoxy resin models, and In the stress freezing furnace, the vertical and oblique load(15°Δ) of 60 Ncm was applied on the central fossa of mandibular right the 1st molar artificial tooth of the every removable partial dentures. After the stress freezing cycle of 15 hours, these models were sliced mesio-distally with a thickness of 6ßÆ. The sliced specimens were examined with the polariscope and transmission photoelastic device to observe the distribution of stress and the result were as follows.
1. In the vertical loading, stress of alveolar bone around implant was in the decreasing order as follows :
A-KIRPD >A-LIRPD > A-AIRPD, A-DIRPD > A-OIRPD
In the oblique loading, stress of the alveolar bone around implant was in the decreasing order as follows :
A-KIRPD > A-AIRPD, A-LIRPD, > A-DIRPD > A-OIRPD
Mesio-distal distribution of stress is more uniform in A-LIRPD, A-DIRPD and A-OIRPD than A-AIRPD and A-KIRPD.
2. In the vertical loading, stress of alveolar bone around the canine in A-KIRPD, A-LIRPD, A-AIRPD was slightly higher than ADIRPD, A-OIRPD.
In the oblique loading, there were no considerable differences these models.
3. when the distance from loading point was increased, the stress of alveolar residual ridge was decreased in the vertical loading but In the oblique loading, there were no considerable differences in these models.
In the design of tooth-implant supported removable partial denture by installation of one implant at the terminal end of bilateral free end case, it is the desirable design that prevent the movement around various axis of rotation and distribute the stress properly to anterior abutment, residual ridge and implant. In the case of Dalbo or O ring attatchment, the stress on the anterior canine abutment and implant is relatively little, mesio-distal distribution of stress is more uniform and cause of its short occluso-gigival length, power arm is more short. Therefore, when the length of implant is short, supporting bone around implant is weak, periodontal support of anterior tooth is poor or occlusal force is heavy cause of opposing natural dentition, Dalbo or O ring attatchment design is more recommendable on implant than konus design. If the occlusal force is light cause of opposing dentition is removable denture and periodontal support is sufficient around implant and anterior canine abutment, design of akers clasp or long rest on implant can be used. Long rest design is the better for more uniform stress distribution. If the konus crown is used on implant with anterior clasp design, excessive stress can be occurred around supporting bone of implant. Therefore careful choice is required under the consideration of the supporting bone around implant, residual ridge and periodontal support of anterior canine abutment.
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KEYWORD
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axis of rotation, stress pattern, photoelastic stress analysis
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