• The Journal of Korean Academy of Prosthodontics
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• v.46 no.3
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• pp.261-268
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• 2008

STATEMENT OF PROBLEM: Detachment of the magnetic assembly from the denture base has been a problem in magnetic overdenture patients. PURPOSE: The objectives of this study were to compare the dislodging force by the fixing materials and the designs of the magnetic assembly, and to compare the effect between the fixing materials and the designs of the magnetic assembly. MATERIAL AND METHODS: Two fixing materials, Jet denture repair $acrylic^{(R)}$ and Super-$Bond^{(R)}$ C&$B^{(R)}$ and two types of magnetic assembly designed with or without wing were used. Each magnetic assembly was fixed in the chamber of the denture base resin block ($Lucitone^{(R)}$199) with each fixing material respectively. These specimens were thermocycled 2,000 cycles in the water held at $4^{\circ}C$ and $60^{\circ}C$ with a dwell time of 1 min each time. Each specimen was seated in a testing jig and then a push-out test was performed with a universal testing machine at a cross head speed of 0.5 mm/min to measure the maximum dislodging forces. RESULTS: Comparing the fixing materials, Super-Bond C&$B^{(R)}$ showed superior dislodging force than Jet denture repair $acrylic^{(R)}$. Comparing the design of the magnetic assemblies, the wing design magnetic assembly showed better dislodging force. Combination of the Super-Bond C&$B^{(R)}$ as a fixing material and wing design magnetic assembly revealed a greatest dislodging force. The kind of fixing material was more influential than the type of magnetic assembly. CONCLUSION: The dislodging force of Super-Bond C&$B^{(R)}$ was significantly higher than Jet denture repair $acrylic^{(R)}$. And the dislodging force of magnetic assembly which have wing design was significantly higher than magnetic assembly which have no wing design.

• The Journal of Advanced Prosthodontics
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• v.9 no.1
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• pp.14-21
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• 2017

PURPOSE. The aim of this study was to compare the retention of mini implant overdenture by the number, the type of magnetic attachment, and the directions of applied dislodging force. MATERIALS AND METHODS. The experimental groups were designed by the number and type of magnetic attachment. Twenty samples were tested with Magden implants. Each attachment was composed of the magnet assembly in overdenture sample and the abutment keeper in a mandibular model. Dislodging forces were applied to the overdenture samples (50.0 mm/min) in 3 directions. The loading was repeated 10 times in each direction. The values of dislodging force were analyzed statistically using SPSS at 95% level of confidence. RESULTS. The retentive force of group 2 was greater than that of group 1 in both types of attachment in every direction (P < .05). Oblique retentive force of flat type magnetic attachment was higher than that of cushion type attachment in both groups (P < .05). In group 1, oblique retentive force showed the highest and anterior-posterior retentive force showed the lowest value in both attachment types (P < .05). In group 2, both types of attachment showed the lowest retentive force with anterior-posterior direction of dislodging force (P <.05). CONCLUSION. Proper retentive properties for implant overdenture were obtained, regardless of the number and type of magnetic attachment. In both types of magnetic attachment, the greater retentive force was attained with more implants. Oblique retentive force of flat type magnetic attachment was greater than that of cushion type. Among all subgroups, anterior-posterior retentive force was the lowest among three different directions of dislodging force.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.3
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• pp.415-430
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• 1996

The purpose of this study was to evaluate the stress distributions in the surrounding tissues of the teeth seated by indirect retainers in three different teeth of unilateral distal extension partial denture when the dislodging forces were applied on denture bases. Three dimensional photoelastic models were made. The teeth on which indirect retainers were seated were mandibular left lateral incisor (Model I), canine (Model II), and first premolar (Model III). The dislodging force with 860mg at $45^{\circ}$ angulation to occlusal plane was applied to each model. Three dimensional photoelastic stress analysis was done, and the records were diagramed and analysed. The results were as follows : The compressive stresses were shown the most on neck portions of buccal, mesial, and distal sides in all three models. Slight tensile stresses were shown on neck portions of lingual sides in all three models. The compressive stresses on buccal side were shown in strength in such order as model I, model II, and model III. The compressive stresses were shown on neck portion of mesial and distal sides of model I and mode II, with model I more than Model II. The compressive stresses were shown only on neck portion of mesial side on Model III. The general overall magnitude of compressive stresses were shown in strength in such order as Model I, Model II, and Model III.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.1
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• pp.150-165
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• 1998

For the purpose of evaluating the effect of both direct retainer design and bony absorption degree around abutment of indirect retainer on the supporting tissue of abutment of indirect retainer, dislodging force was transmitted to unilateral distal extension RPD bases. Analysis of stress distributed within the supporting tissue around abutment of indirect retainer was carried out. Using three-dimensional photoelastic stress analysis method and the conclusion is a follows. 1. According to the extent of force which the direct retainer of the most distal abutment tooth, the amount of force transmitted to the abutment tooth of indirect retainer was small. 2. Of all the cases, Mandibular first premolar which was used abutment tooth of indirect retainer, buccal, mesial and distal sides represented compression stress and lingual side represented tensile stress. 3. The more bone resorption of abutment tooth of indirect retainer, the more distortion of buccal and distal side of abutment tooth was existed and the extent of compression stress which was existed and distal side to abutment tooth was large. 4. When the alveolar bone around the abutment with indircet retainer is normal. The amount of force transmitted on abutment with indirect retainer was small in the order of Akers clasp, RPA clasp, RPI clasp. 5. When the alveolar bone around the abutment with indirect retainer has been absorbed 20% and 30%, the amount of force transmitted on abutment with indirect retainer was small in the order of RPA calsp, RPI clasp, Akers clasp. 6. When denture is displaced, shape of the direct retainer reciprocating abutment affect much the function of indirect retainer.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.2
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• pp.169-181
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• 2008

The aim of this study was to compare the retention and stability of implant overdenture according to the shape and the number of magnetic attachment. The experimental groups were designed for the number of implants(1, 2, 4) and shape of magnetic attachments(flat, cushion, dome type) resulting in 9 subgroups. 45 attachments were tested attached to $Br{\aa}nemark$ system implants which were planted on a mandibular model. Each attachment was composed of the magnet assembly embedded in a overdenture sample and the abutment keeper screwed into the implants. Dislodging tensile forces were applied to the overdenture samples using an Instron(cross-head speed 50.80mm/min) in 3 directions simulating function: vertical, oblique, and anterior-posterior. The loading was repeated 10 times in each direction for 45 samples. The values of maximum dislodging force of each subgroup were processed statistically using SPSS V. 12.0 at the 0.05 level of significance. The results of this study were as follows: 1. Flat type magnetic overdenture was the most retentive when subjected to vertically directed forces and dome type was the lest retentive when subjected to obliquely directed forces(p<0.05). 2. In case of planting one implant, flat type had a higher vertically retentive force than anterior-posteriorly retentive force. In case of planting two implants, flat type and dome type had a higher vertically retentive force and in case of planting four implants, flat type and cushion type had a higher vertically retentive force than anterior-posteriorly retentive force(p<0.05). 3. The incremental number of dental implant, without regards to the three types of magnetic attachment shapes, showed higher retention of overdenture(p<0.05). From the results, if a patient need much more retention of implant overdenture, flat type magnetic overdenture would be a good treatment. In case of the bruxism where excessive lateral forces are already present, dome type could be expected to produce better results. In case of planting one implant, flat type is more stable than the other shape of magnet and in case of two implant, flat type and dome type are more stable and in case of four implants, flat type and cushion type are more stable. Planting more than two implants and using flat type magnetic attachment would provide better retention and stability of implant overdenture

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.2
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• pp.87-93
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• 2010

Purpose: The purpose of this study was to compare the retention of the two denture adhesives with a silicone edentulous model and a resin denture base in vitro study. Material and methods: The experimental groups were used two denture adhesives and classified into 5 subgroups each. Subgroups were divided by the number of times the saliva sprayed. The control group was used synthetic saliva only. Dislodging tensile strengths were applied to the resin denture base using Instron in 3 directions ; vertical, lateral, and anterior-posterior. Results: The retention of two denture adhesives was increased significantly than saliva alone (P <.05). In each denture adhesives, the retention of saliva sprayed first was decreased than denture adhesive alone, but it didn't have significant differences. Whenever saliva sprayed repeated, the retention was decreased significantly than saliva sprayed first (P <.05). In each denture adhesives, vertical retentive force was highest than lateral and anterior-posterior retentive forces, and anterior-posterior retentive force was higher than lateral retentive force. This results were significantly different (P < .05). Significant differences of the retentive ability among two denture adhesives were not observed. Conclusion: From the results, use of the denture adhesives resulted in improved retentive ability of denture. Especially retentive force was highest in vertical direction.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.1
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• pp.33-38
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• 2010

Maxillectomy is a treatment option for maxillary cancer, which leaves the patient with a palatal defect. It may cause problems with facial deformation, swallowing, mastication, and speech. These functional problems and changes in appearance may result in psychological problems. To control these deficits after maxillectomy, surgical reconstruction or prosthodontic treatment can be chosen as a treatment option. Obturator prosthesis has been used as a preferred method of rehabilitation for most maxillectomy patients. This case is a patient who was classified Aramany classification II hemi-maxillectomy patient with residual teeth from #11-25, whose teeth had substantial labioversion and clinically lengthened from alveolar bone involution, thus making it hard to select proper framework design and resist to the rotational dislodging force of the obturator. Therefore we selected swing-lock attachment design to remain pre-existing crown and bridges and obtain retention and stability of obturator. The swing-lock RPD is economical than the conventional RPD because we can remain pre-existing crown and bridges. And residual teeth which have mobility and poor prognosis can be successfully retained through properly designed swing-lock RPD as it is functioning as a removable splint on the teeth.

• The Journal of Korean Academy of Prosthodontics
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• v.58 no.2
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• pp.130-136
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• 2020

Fabrication of complete denture with suction mechanism was introduced to enhance the retention and stability of denture by sealing around the denture border by forming negative pressure on the inner side of denture base during functional movement such as swallowing or masticating. Mandibular suction dentures reduce denture dislodging force during opening by taking preliminary impression without pressure on retromolar pad area in rest position. In this case, fabrication of complete denture using suction mechanism for an edentulous patient with severe alveolar bone resorption allowed us to clinically enhance retention and stability of denture and improve satisfaction of patient.