• The Journal of Korean Academy of Prosthodontics
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• v.35 no.3
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• pp.486-503
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• 1997

The purpose of this study was to evaluate the stress patterns developed in abutment and residual ridge according to removable denture design in case of remaining mandibular canines. The removable denture designs in this study were as foolows : 1. Removable partial denture with non-splinted abutment 2. Removable partial denture with splinted abutment 3. Overdenture with telescopic crown 4. Overdenture with O-Ring attachment 5. Overdenture with combination bar attachment Photoelastic stress analysis was used to record the isochromatic fringe patterns and to calculate principal stress components at measuring points. The results were as follows : 1. In case of removable partial denture with non-splinted abutment, stress of root area at the loaded side was the largest. No significant differences in stress of root area were observed between loaded side and unloaded side. 2. No significant differences in stress of residual ridge at the loaded side were observed between removable partial denture with splinted abutment and removable partial denture with non-splinted abutment. 3. In case of combination bar attachment retained overdenture, stress of root area was the largest and in case of telescopic crown retained overdenture, stress of root area was the lowest. 4. In case of attachment retained overdenture, stress of residual ridge was lower but stress of root area was larger than in case of removable partial denture.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.3
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• pp.577-608
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• 1997

The purpose of this study is to evaluate the stress distribution in the bone around dental implants supporting mandibular overdenture according to the number of implant and the type of attachment. Two or four implants were placed in an edentulous mandibular model and three dimensional photoelastic stress analysis was carried out to measure the fringe order around the implant supporting structure and also to calculate principal stress components at cervical area of each implant. The attachments tested were rigid and resilient type of Dolder bar, Round bar, Hader bar and Dal-Ro attchment. The results were as follows ; 1. In 2-implant supported overdenture using Round bar, Hader bar, and Dal-Ro attachment, compressive stress pattern was observed on the supporting structure of implant on loaded side, while tensile stress pattern in unloaded side. 2. In 2-implant supported overdenture using Dolder bar, the rigid Dolder bar shared the occlusal loads between 2 implants in a more favorable manner than was exhibited by the resilient type, while the resilient type placed a more stress on the distocervical area of the implant on the loaded side. But compressive stress pattern was observed in both the loaded and unloaded sides in either case. 3. In 2-implant supported overdenture, rigid and resilient type of Dolder bar exhibited more cross arch involvement than the Round bar, Hader bar, or Dal-Ro attachment. 4. In 4-implant supported overdenture using resilient Dolder bar and Hader bar, stress turned out to be distributed evenly among the implants between loaded and unloaded side, but thor was no reduction in the magnitude of the stress in the surrounding structure of implant contratry to 2-implant supported overdenture. 5. The stress pattern at cervical area of implant was different with the number of implant or the type of attachment but the overload, harmful to surrounding structure of implant, was not observed.

• The Journal of Korean Academy of Prosthodontics
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• v.31 no.4
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• pp.661-678
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• 1993

The purpose of this study was to analyze the stress distribution at supporting bone according to the types of endosseous implants. This investigation evaluated the stress patterns in rectangular photoelastic models produced by four different types of dental implants such as $Br\ddot{a}nemark$, screw type of Steri-Oss, blade type of Steri-Oss, IMZ with IMC and resin tooth using the techniques of quasi-three dimensional photoelasticity. All prostheses were casted in the same nonprecious alloy and were cemented or screwed on their respective implants and abutments. 20 kg of vertical load was applied on the central fossa of casted crown and 16 kg of inclined had was applied on the top third of distal surface of casted crown respectively. The results were as follows : 1. Under the vertical load, screw implants of Steri-Oss and $Br\ddot{a}nemark$ showed increasing stress condition between and around the screw threads along the implant lateral surface and cylindrical implant of IMZ showed the less stress condition along the lateral surface with concentration of stress mostly near the root apex. 2. Under the vertical load, the stress of Steri-Oss blade was distributed uniformly at the alveolar bone under the broad blade. 3. Under the inclined load, the stress concentration of Steri-Oss screw and $Br\ddot{a}nemark$ was developed highly around the mesiocervical bone area on the contralateral side to force application. The stress of $Br\ddot{a}nemark$ with flexible gold glod was more concentrated in the cervical bone area than that of Steri-Oss with stiff screw. 4. Under the inclined load, the stress of Steri-Oss blade broadly was distributed around the mesioceivical bone area and the lower and mesial bone area of the blade. 5. Under the Inclined load, IMZ implant showed the gap between c개wn and fixture due ta deformation of the IMC and IMZ was lower in stress concentration developed around the mesiocervical bone area than $Br\ddot{a}nemark$ and Steri-Oss screw. 6. Under the inclined load, the stress magnitude induced in the mesiocervical bone area of implants was in order of $Br\ddot{a}nemark$, Steri-Oss strew, IMZ and Stsri-Oss blade. 7. Tilting forces as compared to axial forces exerted greater magnitude of stress in the cervical bone area of the implant. 8. In respect of stress distribution, Steri-Oss blade was superior than any other implants and in respect of the stability by horizontal lone, IMB and $Br\ddot{a}nemark$ was inferior than any other implants.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.1
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• pp.31-69
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• 1996

The purpose of this investigation was to analyze stress distribution in implant supporting tissue according to different types of attachments such as combination bar attachment, Hader bar attachment, O-Ring attachment and Dal-Ro attachment that are used in mandibular overdenture by using two osseointegrated implants, to study the influence that POM IMC used in bar type attachment has in implant supporting tissue and compare the preceding analyses to find out an effective stress distribution method. Three dimensional photoelastic method was used to obtain the following results. (A) Analysis of stress distribution according to attachment type 1. Under vertical load condition, compressive stress was seen at implant supporting area of working side on all the photoelastic models but in Hader bar attachment tensional stress was seen at distal upper area of implant supporting area. Relatively Hader bar and O-Ring attachment showed even stress distribution pattern. 2. Under vertical load condition, compressive stress at implant apex area and tensional stress at implant lateral supporting area were seen at nonworking side of all models. 3. Under $25^{\circ}$ lateral load condition, general compressive stress was seen at working side implant supporting area in most of the models, especially at distal upper supporting area higher compressive stress concentration was seen in combination bar attachment and tensional stress concentration, in Hader bar attachment. 4. Under $25^{\circ}$ lateral load condition, compressive stress at implant apex area and tensional stress at implant lateral supporting area were seen at nonworking side of all models, except O-Ring model which showed compressive stress only. (B) Influence of POM IMC to stress distribution in bar type attachment 5. Under vertical load condition, better stress distribution pattern was seen at working side of combination bar and Hader bar attachment model using POM IMC. 6. Under vertical load condition, stress value was increased at nonworking side of combination bar attachment model using POM IMC and tendency of increasing compression was seen at nonworking side of Hader bar attachment model using POM IMC. 7. Under $25^{\circ}$ lateral load condition, better stress distribution pattern was seen at working side of combination bar attachment model using POM IMC but tendency of increasing stress was seen on working side of Hader bar attachment model using POM IMC. 8. Under $25^{\circ}$ lateral load condition, stress reduction was seen at nonworking side of combination bar attachment model using POM IMC but tendency of increasing stress was seen at nonworking side of Hader bar attachment model using POM IMC.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.4
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• pp.425-442
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• 2004

Statement of problem: A difficulty in achieving a passive-fitting prosthesis can be overcome by individual crown restoation of multiple implants. But individualized crown has another difficulty in control of contact tightness and stress distribution. Purpose: This in vitro study is to evaluate the stress distribution and the magnitude in the supporting tissues around Endopore implants with different crown lengths, interproximal contact tightness, and the splinting effects. Material & methods: Three Endopore implants($4.1{\times}9mm$) were placed in the mandibular posterior edentulous area distal to the canine and photoelastic model was made with PL-2 resin(Measurements Group, Raleigh, USA). Restorations were fabricated in two crown lengths: 9, 13 mm. For non-splinted restorations, individual crowns were fabricated on three custom-milled titanium abutments. After the units were cemented, 4 levels of interproximal contact tightness were evaluated: open, ideal($8{\mu}m$ shim stock drags without tearing), medium($40{\mu}m$), and heavy($80{\mu}m$). For splinted restorations, 3-unit fixed partial dentures were fabricated. This study was examined under simulated non-loaded and loaded conditions(6.8 kg). Photoelastic stress analysis was carried out to measure the fringe order around the implant supporting structure. Results: 1. When restorations were not splinted, the more interproximal contact tightness was increased among the three implants, the more stress was shown in the cervical region of each implant. When crown length was increased, stresses tended to increase in the apex of implants but there were little differences in stress fringes. 2. When nonsplinted restorations were loaded on the first or third implant, stresses were increased in the apex and cervical region of loaded implant. Regardless of interproximal contact tightness level, stresses were not distributed among the three implants. But with tighter interproximal contact, stresses were increased in the cervical region of loaded first or third implant. 3. When the nonsplinted restorations were not loaded, there were little stresses on the supporting structure of implants, but low level stresses were shown in the splinted restorations even after sectioning and soldering. 4. With splinted restorations, there were little differences in stresses between different crown lengths. When splinted restorations were loaded, stresses were increased slightly on the loaded implant, but relatively even stress distribution occurred among the three implants. Conclusions: Splinting the crowns of adjacent implants is recommended for Endopore implants under the overloading situation.

• The Journal of Korean Academy of Prosthodontics
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• v.30 no.1
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• pp.25-42
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• 1992

The purpose of this study was to analyze the magnitude and distribution of stress using a photoelastic model from a unilateral distal extention removable partial dentures with five kinds of the direct retainers, that is, the bilaterally designed bar clasp of the cross-arch lingual bar and the unilaterally designed bar clasp, circumferential clasp, mini-Dalbo attachment, and telescope retainer. A photoelastic model for mandible was made of the epoxy resin(PL-1) and hardner (PLH-1) with the acrylic resin teeth used and was coated with plastic cement-1 at the lingual surface of the model, and then five kinds of removable partial dentures were set, A unilateral vertical load of about 16Kg was applied on the first molar and the stress pattern of the photoelastic model under each condition was analyzed by the reflective circular polariscope. The following results were obtained: 1. The conventional removable partial denture with the bilaterally cross arch lingual bar produced the most favorable stress distribution on the residual ridge and supporting structure of abutment teeth than the unilaterally designed removable partial dentures. 2. The unilaterally designed removable partial denture with the bar clasp produced the stress distribution on the residual ridge, except sligtly higher stress concentration on the supporting structure of the abutment teeth, similar to the conventional removable partial denture with the bilaterally designed cross arch lingual bar. 3. On the unilaterally designed removable partial dentures, the bar clasp produced greater stress distribution on the residual ridge and supporting structure of the abutment teeth than the circumferential clasp. 4. On the unilaterally designed removable partial dentures, the mimi-Dalbo attachment produced relatively higher stress concentration on the residual ridge, but produced lesser stress concentration on the supporting structure of the abutment teeth than the other direct retainers. 5. On the unilaterally designed removable partial dentures, the telescope retainer produced uniform stress distribution on the residual ridge, but produced higher stress concentration at the root apex of the terminal abutment tooth than the other direct retainers. 6. On the unilaterally designed removable partial dentures the circumferential clasp and telescope retainer produced slightly higher stress concentration on the residual ridge and supporting structure of the abutment teeth than the bar clasp and mini- Dalbo attachment.

• The Journal of Korean Academy of Prosthodontics
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• v.28 no.2
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• pp.183-197
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• 1990

The purpose of this study was to analyse the magnitude and distribution of stresses using a Photoelastic model from and distal - extension removable partial dentures With four designed indirect retainers. The designs of the indirect retainers were as follows : Design No. 1 : Aker's clasp on 1st bicuspid with no indirect retainer. Design No. 2 : Aker's clasp on 1st bicuspid with indirect retainer on canine. Design No. 3 : Extension of the reciprocal arm of Aker's clasp toward incisal rest on canine. Design No. 4 : Connection with the indirect retainer as in No. 2 and extension of reciprocal arm of Aker' s clasp. A photoelastic model was made of the epoxy resin(PL - 1) and hardner(PLH - 1) and coated with plastic cement -1(PC -1) at the lingual surface of the epoxy model and set with chrome - cobalt partial dentures. A unilateral vertical load of 10kg to the right 1st molar and a vertical load of 10kg to the middle portion of the metal bar crossing both the 1st molars of the right and left, were applied. With the use of specially designed jig, fixture; loading device and the reflective circular polariscope, we obtained the following results : 1. When the unilateral vertical load and the vertical load of the middle portion of the metal bar were applied, design No. 2, 3 and 4 exhibited the higher stress concentration at the root apices and their surrounding tissues of the primary and secondary abutment teeth. 2. When the unilateral vertical load applied to design No. 2,3 and 4 the root apices of the primary and secondary abutment teeth and their surrounding tissues and the nonloaded side of edentulous area exhibited and even stress distribution. 3. When the vertical load was applied, the stress concentration fringe in the primary and secondary abutment teeth was in the order of No. 1,4,2 and 3. 4. No.1 and 4 exhibited the higher distrorted stress concentration at the primary teeth and the edentulous area in the nonloaded side. 5. No.2 design reduced the stresses at the apices of the alveoli of the primary abutment teeth bilaterally as well as on the crest of the residual ridge on the nonloaded side. 6. No. 2 design exhibited the most favorable stress distribution.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.1
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• pp.120-131
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• 2005

Statement of problem. More than 70% of patients who need the implant supported restoration are parially edentulous. The principles of design for implant supported fixed partial denture in mandibular posterior region are many and varied. Jurisdiction for their use is usually based on clinical evaluation. There are several areas or interest regarding the design of implant supported fixed partial denture in mandibular posterior region. 1) Straight and tripod configuration in implant placement, 2) Two restoration types such as individualized and splinted restorations. Purpose. The purpose of this study was to compare the amount and distribution of stress around the implant fixtures placed in the mandibular posterior region with two different arrangements and to evaluate the effects of splinting using the photoelastic stress analysis. Material & methods. 1) Production of study model: Mandibular partially edentulous model was waxed-up and duplicated with silicone and two models were poured in stone. 2) Fixture installation and photoelastic model construction: Using surveyor(Ney, USh), 3 fixtures(two 4.0 $\times$13 mm, one 5.0$\times$10 mm, Lifecore, USA) were insta)led in straight & tripod configurations. Silicone molds were made and poured in photoelastic resin (PL-2. Measurements group, USA). 3) Prostheses construction: Four 3-unit bridges (Type III gold alloy, Dongmyung co., Korea) were produced with nonhexed and hexed UCLA abutments and fitted with conventional methods. The abutments were tightened with 30 Ncm torque and the static loads were applied at 12 points of the occlusal surface. 4) Photoelastic stress analysis : The polarizer analyzer system with digital camera(S-2 Pro, Fujifilm, Japan) was used to take the photoelastic fringes and analysed using computer analysis program. Results. Solitary hexed UCLA restoration developed different stress patterns between two implant arrangement configurations, but there were no stress transfer to adjacent implants from the loaded implant in both configurations. However splinted restorations showed lesser amount of stresses in the loaded implants and showed stress transfer to adjacent implants in both configurations. Solitary hexed UCLA restoration with tripod configuration developed higher stresses in anterior and middle implants under loading than implants with straight configurations. Splintied 3 unit fixed partial dentures with tripod configuration showed higher stress development in posterior implant under loading but there were no obvious differences between two configurations. Conclusions. The tripod configuration of implant arrangement didn't show any advantages over the straight configuration. Splinting of 3 unit bridges with nonhexed UCLA abutments showed less stress development around the fixtures. Solitary hexed UCLA restoration developed tilting of implant fixture under offset loads.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.4
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• pp.526-552
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• 1994

The extent and direction of movement of removable partial dentures during function are influenced by the nature of the supporting structures and and the design of the prosthesis. Since forces are transmitted to the abutment teeth through occlusal rests, guide planes and direct retainers during functional movements, proper design based on the avaialble research data will maintain the health of abutment teeth and their supporting structures. The purpose of this in vitro study is evaluating stress distribution clinically around the abutment teeth prepared following 4-type clasping systems for unilateral free-end removable partial dentures. Three-Dimensional Photoelastic Stress Analysis method was used because it shows a visual display of stresses of the simulated abutment teeth and residual ridges and reveals stress concentration that can be read at any given points in terms of direction and magnitude. For this study, the author fabricated 4 mandibular photoelastic epoxy models missing left 1st and End molar. Epoxy models were duplicated and 4 unilateral removable partial dentures were construe- ted in accordance with 4-type direct retainers. Unilateral free-end removable partial dentures were positioned on their own models. 6kg force was loaded on the every removable partial dentures of the epoxy model on the central fossa of mandibular left 1st molar vertically by the loading device. After the stress was frozen in a stress freezing furnace, 6 specimens of 6-mm thickness were made from every epoxy model and examined with the circular polariscope. The results were as follows : 1. Generally I-bar clasp revealed the most favorable stress distribution around the abutment teeth. 2. At the end portion of the free-end ridge, Back action clasp showed the highest stress concentration at the bucco-lingual and top portions of the residual alveolar ridge. 3. At the distal area of the abutment teeth, Akers clasp and Roach clasp showed higher stress concentration bucco-lingually and apically than the others. 4. To the abutment tooth, I-bar clasp showed the least stress distribution bucco-lingually but the others showed irregular stress distribution. 5. At the mesial area of the abutment teeth, the order of effective stress distribution was I-bar clasp, Back-action clasp, Akers clasp and Roach clasp. There was big difference of stress distribution between them. 6. At the right 2nd premolar and 1st molar, the stress concentration of Akers clasp was a little high but that of I-bar clasp was low.