• The Journal of Korean Academy of Prosthodontics
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• v.51 no.4
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• pp.323-331
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• 2013

Soft tissue collapse around prepared teeth and pontic is inevitable after removal of the provisional restoration during the impression taking procedures. When inserting gingival retraction cord, soft tissue is displaced to an undesired contour. Viscosity of impression material also causes gingival displacement. Therefore, the consideration to transfer the prosthetically contoured soft tissue to master cast is required, especially in the esthetic area. In this report, the methods to maintain the soft tissue contour and transfer to the mastercast will be introduced. Harmonious contour of the soft tissue can be achieved with provisional restoration and be transferred to the master cast with two different techniques mentioned in this case report.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.2
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• pp.154-166
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• 2004

Statement of problem: In distal extension removable partial denture, the preservation of health of abutment teeth are very important, but they are always subjected to unfavorable stress. Purpose: The purpose of this study was performed to investigate the effects of abutment splinting and design of direct retainer on the stress distribution of abutments in unilateral distal extension removable partial dentures. Material and method: Abutments were splinted by different method. In group 1, autment teeth were not splinted, in group 2, canine and 1st premolar were splinted, and in group 3, canine, 1st and 2nd premolars were all splinted. Three different types of direct retainer such as Akers clasp, RPI clasp, and wrought wire clasp were designed. Strain was measured with Switch & Balance Unit(SB-10, Measurement Group Instruments Division, Raleigh USA) and Strain Indicator(P-3500, Measurement Group Instruments Division, Raleigh, USA) 15kg of vertical and oblique loads was applied at central fossa of missing 2nd molar area. Results : The strain on lingual side of 2nd premolar was the greatest, and abutment splinting induced decrease of strain on buccolingual side of 2nd premolar. The strain of loaded area was decreased by abutment splinting and there was no statistical difference of strain between Group2 and Group 3, and strain on 2nd premolar in wrought wire clasp was the least. Conclusion: Within the limitations of this study, splinting of two distal abutment teeth is enough for stress distribution widely, and wrought wire clasp was more benefitable than others.

• 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.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.3
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• pp.413-439
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• 1995

The purpose of this study was to evaluate the stress distribution developed in the supporting structures by mandibular distal extension removable partial dentures with 2 different direct retainer designs and with or without indirect retainer and abutment splinting. The examined direct retainers on the second bicuspid abutment tooth were Akers clasp and RPA clasp, the indirect retainer was located on the mesial fossa of the first bicuspid, and the first and second bicuspid were splinted in case of tooth splinting. Total 8 cases were compared and analyzed with 3-dimensional finite element method. 150N were applied vertically on the artificial teeth of the removable partial denture, and then stress distribution patterns were analyzed and compared. The results were as follows : 1. The forces transmitted to the abutment tooth were primarily from the occlusal rests. 2. The abutment tooth was displaced distally when the force was applied. The compressive stress was observed at the distal root surface of the abutment tooth and the tensile stress, at the mesial root surface. 3. The denture base was displaced posteriorly and inferiorly when the force was applied. At the more distal portion of the denture base, the greater displacement was observed.And the anterior portion of the major connector was displaced superiorly. 4. The occlusal rest placed on the distal part of the abutment tooth tended to tip the tooth more posteriorly than did one on the mesial part of that tooth. 5. Severe superior displacement was observed at the anterior portion of the major connector in case of removable partial dentures without indirect retainer. 6. In case of tooth-splinting, the stress was distributed through all the root surface of both abuments. In case of no tooth-splinting, the stress was concentrated on the distal root surface of the primary abutment.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.2
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• pp.241-268
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• 1995

Splint therapy, the immobilization of teeth, has been done for patient's masticatory comforts and an adjunctive aid in periodontal therapy. Mandibular premolars are frequently splinted in many distal extension removable partial denture cases. But splinting is an extensive restoration that may not be conservative of tooth structure and may prove to be quite costly to the patient. The two dimensional finite element analysis method was used to determine the magnitude and mode of distribution of the stresses of the periodontal ligament and supporting alveolar bone when abutments with different periodontal supports were splinted and distal-extension removable partial denture was subjected to different loading schemes. The results were as follows : 1. When abutments were splinted, stresses moved from apico-distal to apico-mesial of terminal abutment on a vertical force and from disto-alveolar crest to apex on a distally directed force. But stresses were generally diminished on a mesially directed force. 2. As vertical bone loss was proceeding, most of stresses were transmitted to residual ridge and the rest of stresses were concentrated on apex of distal abutment. But these apical stresses were minimized when abutments were splinted. 3. As mesially inclined bone loss was proceeding, it seemed to be dangerous that many stresses were concentrated on the distal alveolar crest, especially in the distally directed load case. Abutments splinting decreased the alveolar crestal stresses but not enough. 4. For all vertical stresses were effectively decreased on splinting, stresses were concentrated as highly on apico-mesial area of distal abutment in distally directed load cases as the distal inclination of bone level was severe. 5. The directions and magnitudes of abutment movements were decreased with teeth splinting.

• The Journal of Korean Academy of Prosthodontics
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• v.56 no.1
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• pp.31-39
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• 2018

The collapse of the posterior occlusion destroys the normal occlusal plane and causes excessive wear reducing the vertical dimension. Reduced vertical dimension of occlusion causes not only aesthetic and functional problems but also overloading on the temporomandibular joints and abnormalities of muscle nerve system. In order to improve the collapsed occlusal relationship, it is necessary to consider the change of the vertical dimension. It is necessary to make a precise diagnosis and analysis before the treatment and to evaluate the adaption of patient to the new vertical dimension of occlusion. A patient with excessive overbite often has occlusal problems of tooth wear and tooth eruption. Considering these considerations, overall prosthodontic restoration is required to solve the problem. A patient of 68 year old man in this case who suffered major tooth wear and maxillary posterior teeth loss was treated with elevation of vertical dimension of occlusion by maxillary removable dental prosthesis and mandibular fixed prosthesis.

• The Journal of Korean Academy of Prosthodontics
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• v.21 no.1
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• pp.59-66
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• 1983

Distal extension partial dentures are supported by both the relatively rigid teeth and the resilient mucosa. So impression techniques of residual alveolar ridge in case of distal extension partial denture have particular importance in order to broad distribution of the masticatory force. McLean recognized the need for recording the tissues supporting distal extension partial denture base in functional form to equalize the resilient and non-resilient support, and this was called functional impression. Many investigators proposed various techniques of the functional impression for a distal extension partial denture, but only a little studies were performed about displacement of soft tissue under distal extension partial denture base. The purpose of this study is to investigate the amount of vertical displacement of the soft tissue under distal extension partial denture base by different functional impression techniques. Impression techniques used were Z.O.P. Impression, Selective Tissue Placement Impression, Functional Relining Impression. Measurement of the vertical displacement of soft tissue were made with Depth Gauge and Measuring Platform. A Anatomic Impression was used as a control. The results were tested statistically using 3 way ANOVA and Scheffe test. The followings were the results obtained from this study. 1. The greatest amount of soft tissue displacement was observed in the center of the retromolar pad. 2. No significant differences were found between the crest of alveolar ridge and the buccal shelf area. 3. The greatest soft tissue displacement was observed in Functional Relining Impression using Iowa wax, and the least displacement was observed in Selective Tissue Placement Impression using murcaptan rubber base. 4. No significant differences were found between finger pressure and biting pressure in Z.O.P. Impression, but greater displacement was observed by biting pressure than finger pressure in Functional Reling Impression.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.2
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• pp.235-248
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• 1994

There were many studies that distribute the partial edentulous states and examine the removable partial denture designs in the planning of removable partial denture treatment. This study was performed in the point of removable partial denture prescription to evaluate partial edentulism and its removable partial denture designs. The data was collected from the dental laboratory of each three dental colleges in Seoul and from two dental laboratories only for removable partial dentures as a prescription form. A total of 1411 cases with prescription form collected from dental laboratories were distributed for this study, then 788 cases were selected for this study. The case selection was done according to the contents of prescription form. The selected cases were divided into maxillary arch and mandibular and classified in terms of types of major connector and direct retainer, unbroken anterior teeth, Kennedy classification, the number of remaining teeth, and distribution of age and sex. The analyzed results were as follows : 1. The Kennedy classification I showed highest frequency both in maxilla and mandible. 2. The arch distribution of removable partial denture was 50.08% for maxilla and 49.92% for mandible. 3. The highest frequency in the distribution of direct retainer was the RPA clasp design. 4. The frequency of unbroken anterior 6 was 73.36% for maxilla and 82.30% for mandible. 5. The design of broad palatal strap and lingual bar revealed the highest prevalence in the major connector construction. 6. The mean number of remaining teeth per arch was 8.25 for maxilla and 8.37 for mandible. 7. The mean age of the patients supplied with removable partial denture was 52.25 years for men, 51.68 years for women, 52.11 years for maxilla, and 51.76 years for mandible and women showed more prevalence.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.2
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• pp.296-326
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• 1994

The purpose of this study was to evaluate the mechanical effects when one implant fixture was connected to the natural teeth with reduced alveolar bone height. This study also examined the effects of increasing the number of abutment teeth and the effects of the intramobile connector and the titanium connector as they were inserted between the implant superstructure and the fixture. The distribution and concentration load was applied to the fixed partial denture(FPD) supported by implant and the natural teeth with reduced alveolar bone height. The stress and displacement of each element was observed and compared by the two-dimensional finite element method. The following results were obtained : 1. The greater the loss of alveolar bone in natural teeth area, the greater the displacement of FPD and the stress concentration in alveolar bone around implant, especially at the stress concentration in the mesial alveolar bone crest around implant fixture. 2. The displacement of FPD was increased more and that of implants fixture was decreased more when intramobile connector was used than titanium connector was used. Also the stress concentration in alveolar bone around implant fixture was greater when intramobile connector than titanium connector. One implication of this finding was that the difference in stiffness of implant and the natural teeth with reduced alveolar bone height could be partially compensated in case of the POM intramobile connector. 3. The amount and direction of displacement and the stress distribution of the 4-unit FPD was better than those of the 3-unit FPD. It implied that the difference of stiffness of implant and natural teeth with reduced alveolar bone height could be partially compensated in case of the 4 unit FPD.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.6
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• pp.878-887
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• 1998

Although attachments have been utilized for a retainer of removable prostheses during several decades, there is little information on the force distribution by the attachments. This study was undertaken to evaluate the stress patterns developed by partial dentures employing rigid attachments on the supporting structures. Four types of the mandibular removable partial dentures were designed depending upon the position of the rigid attachment and the existency of lingual bracing. Under 100N of vertical and 25N of lateral loads on the 1st and 2nd lower molar of partial denture, stress distribution patterns and displacement were analysed with three dimensional finite element method by ANSYS version 5.3. 1. The highest stresses were concentrated on the distal alveolar crest of posterior abutment and the second stresses on the apical region of posterior abutment in the models. 2. The greatest displacement were shown on the distal alveolar crest of posterior abutment and the second displacement on the distal alveolar crest of anterior abutment in the models. 3. There was little difference between the models with intraoral attachment and those with extracoronal attachment. 4. There was little difference between the models with and without the lingual bracing.