The effect of thickness of the provisional crown and fixed partial denture materials on the translucency and masking effect / 대한치과보철학회지

STATEMENT OF PROBLEM: Translucency and masking effect of provisional crown and fixed partial denture materials is an important esthetic consideration. But, provisional resin materials differ substantially in their ability to mask underlying colors. PURPOSE: The purpose of this study was to evaluate the translucency differences of provisional resin materials at various thicknesses and the correlation between the translucency and the masking efficiency. MATERIAL AND METHODS: Two polymethyl methacrylate resins (Jet Tooth Shade, Alike) and three resin composites (Protemp 3 Garant, Luxatemp and Revotek LC) were used. Specimens (n=6) were fabricated from each material in 0.3, 0.5, 0.8, 1.0, 1.5, 2.0 and 3.0 mm thickness. The CIELAB parameters of each specimens were measured using a spectrophotometer. The translucency parameter (TP) values and the masking effect (delta ME*(ab)) values were computed and all data were statistically analyzed by one-way ANOVA and the multiple comparisons Scheffe test. The correlation between the thickness and the TP values and the correlation between the thickness and the delta ME*(ab) values were also evaluated by correlation analysis and regression analysis. RESULTS: The TP values and the delta ME*(ab) values were significantly related to the thickness in all specimens. The TP values were more sensitive to the change of thickness than the delta ME*(ab) values. The order of the translucency by brand was different from the order of the masking effect by brand in all thickness groups. CONCLUSION: Within the limitations of this study, the translucency and masking effect of the provisional resin materials investigated were significantly related to their thickness. The masking effect of provisional resin was correlated with the translucency parameter, but the order of the masking effect by brand was different from the order of the translucency parameter.

Biomechanics of abutments supporting removable partial dentures underunilateral loading / 대한치과보철학회지

STATEMENT OF PROBLEM: In distal extension removable partial denture, the preservation of health of abutment teeth is very important, but abutment teeth are subjected to unfavorable stress under unilateral loading specially. PURPOSE: The purpose of this study was to investigate the biomechanical effects of mandibular removable partial dentures with various prosthetic designs under unilateral loading, using strain gauge analysis. MATERIAL AND METHODS: Artificial teeth of both canines were anchored bilaterally in a mandibular edentulous model made of resin. Bilateral distal extension removable partial dentures with splinted and unsplinted abutments were fabricated. Group 1: Clasp-retained mandibular removable partial denture with unsplinted abutments Group 2: Clasp-retained mandibular removable partial denture with splinted abutments by 6-unit bridge Group 3: Bar-retained mandibular removable partial denture Strain gauges were bonded on the labial plate of the mandibular resin model, approximately 2 mm close to the abutments. Two unilateral vertical experimental loadings (30N and 100N) were applied subsequently via miniature load cell that were placed at mandibular left first molar region. Strain measurements were performed and simultaneously monitored from a computer connected to data acquisition system. For within-group evaluations, t-test was used to compare the strain values and for between-group comparisons, a one-way analysis of variance (ANOVA) was used and Tukey test was used as post hoc comparisons. RESULTS: The strain values of group 1 and 2 were tensile under loadings. In contrast, strain values of group 3 were compressive in nature. Strain values increased as the applied load increased from 30N to 100N (P<.05) except for right side in group 1. Under 30N loading, in left side, group 1 showed higher strain values than groups 2 and 3 in absolute quantity (P<.05). And group 2 showed higher strain values than group 1 (P<.05). In right side, group 1 and 2 showed higher strain values than group 3 in absolute quantity (P<.05). Under 100N loading, in left side, group 1 showed higher strain values than groups 2 and 3 in absolute quantity (P<.05). And group 2 showed higher strain values than group 1 (P<.05). In right side, group 1 and 2 showed higher strain values than group 3 in absolute quantity (P<.05). Under 30N loading, group 2 and 3 showed higher strain values in right side than in left side. Under 100N loading, right side strain values were higher than left side ones for all groups. CONCLUSION: Splinting of two isolated abutments by bridge reduced the peri-abutment strain in comparison with unsplinted abutments under unilateral loading. Bar-retained removable partial denture showed the lowest strain of three groups, and compressive nature.

Comparative study of shear bond strength between cp-Ti / Co-Cr alloy and composite resins / 대한치과보철학회지

STATEMENT OF PROBLEM: Composite resin-veneered metal restorations can be used as an alternative to porcelain-fused-metal restorations. But, because of the relatively low bond strength of veneering composite to metal framework, various surface treatment methods have been introduced to improve the bond strength. PURPOSE: The object of this study was to compare the shear bond strength of different combinations of each of the two bonding systems and each of the two composite veneering resins to cp-Ti / Co-Cr alloy. MATERIAL AND METHODS: Two resin bonding systems (metal conditioner containing MEPS monomer, tribochemical silicoating system) and two composite resins (Gradia, Sinfony) were tested on cp-Ti and Co-Cr alloy. Then, according to manufacturers' instructions, resin bonding systems and composite resins were applied. All test specimens were divided into four groups for each alloy; I) sandblast + Metal Primer II+ Gradia (MG), II) sandblast + Metal Primer II + Sinfony (MS), III) Rocatec + Gradia (RG), IV) Rocatec + Sinfony (RS). The shear bond strength was determined using a universal testing machine and all data were statistically analyzed with Mann-Whitney test and Kruskal-Wallis test at the significance level of 0.05. RESULTS: The mean (standard deviations) of shear bond strength according to the combinations of two bonding systems and two composite resins to cp-Ti arranged from 16.44 MPa to 17.07 MPa and the shear bond strength to Co-Cr alloy ranged from 16.26 MPa to 17.70 MPa. The result shows that the difference were not statistically significant. CONCLUSION: The shear bond strengths of composite resins to both cast cp-Ti and Co-Cr alloy were not significantly different between the metal conditioner and the tribochemical silicoating system. And no differences in bond strength were found between cp-Ti and Co-Cr alloy.

The effect of screw tightening sequence and tightening method on the detorque value in implant-supported superstructure / 대한치과보철학회지

STATEMENT OF PROBLEM: The screw detorque value is a measure of the preload remaining in the screw just before detorquing. PURPOSE: This study evaluated the effect of different screw tightening sequences and tightening methods on detorque values for a well-fitting implant superstructure. MATERIAL AND METHOD: An implant superstructure that connected directly to four implants (Astra Tech) was fabricated on a fully edentulous mandibular acrylic resin model. Six wellfitting dental stone casts were made with a pickup impression of the superstructure from the acrylic resin model. To evaluate the effect of three screw tightening sequences (1-2-3-4, 2-4-3-1, and 2-3-1-4) and two tightening methods (2-step and 1-step) on the stability of screw joint, the detorque values for a well-fitting implant superstructure were measured twice after screw tightening using 20 Ncm. Detorque values were analyzed using multi-way analysis of variance and two-way analysis of variance at a .05 level of significance. RESULTS: 1. The mean detorque values for three screw tightening sequences were 12.3 Ncm, 12.6 Ncm, and 12.0 Ncm, respectively. 2. The mean detorque values for two screw tightening methods were 12.0 Ncm, and 12.2 Ncm, respectively. 3. The mean of mimimum detorque values for three screw tightening sequences and for two tightening methods were 10.6 Ncm, 11.1 Ncm, 10.5 Ncm, and 9.8 Ncm, respectively. 4. No statistically significant differences among the variables of screw tightening sequence and tightening method were found (p>.05) for detorque values and for mimimum detorque values. CONCLUSION: Within the limitations of this study, the screw tightening sequence and tightening method did not have a significant effect on the detorque values for a well-fitting implant superstructure.

The comparison of initial retentive force in different double crown systems / 대한치과보철학회지

STATEMENT OF PROBLEM: Various double crown systems have been used with removable partial dentures in the clinical field. Although retentive force between inner and outer crown are affected by several factors, differences between the retentive forces of different double crown system types are expected. PURPOSE: The purpose of this study was to evaluate the initial retentive force of outer crowns fabricated by the conventional casting technique in conus and hybrid double crowns. MATERIAL AND METHODS: Ten double crowns were fabricated. The groups were as follows. Group 1, double crowns of hybrid inner and outer crowns using the conventional casting method; Group 2, double crowns of conus inner and outer crowns using the conventional casting method. Tensile strengths of double crowns when the inner and outer crowns were separated on a universal testing machine were measured. These values of retentive force were then statistically analyzed using the Kruskal-Wallis test. RESULTS: Retentive force in group 2 was significantly higher than that in group 1 (p<.05). CONCLUSION: The initial retentive forces of double crowns were affected by the types of the double crown system.

A tissue response to the titanium alloy (Ti-13Zr-6Nb) in vivo / 대한치과보철학회지

STATEMENT OF PROBLEM: Mechanisms of tissue-implant interaction and the effect of the implant surface on the behavior of cells has not yet been clarified. PURPOSE: This study was performed to investigate the tissue reaction to the titanium alloy submerged into rat peritoneum in vivo. MATERIALS AND METHODS: Titanium alloys (titanium-13Zirconium-6Niobium) were inserted inside the peritoneal cavity of Sprague Dawley rats. After 3 months, the tissue formed around the inserted titanium alloys were examined with a light-microscope. Tissue reaction around the material was analyzed by confocal microscopy to evaluate their biocompatibility in a living body. RESULTS: In in vivo study, foreign body type multinucleated giant cells were found in the fibrous tissue formed as a reaction to the foreign material (4 in 20 cases), but the inflammatory reaction was very weak. After experiment, the contaminants of biomaterials was removed from living tissue. In confocal microscopy, we observed that the staining of vinculin and actin showed mixed appearance. In a few cases, we found that the staining of vinculin and beta-catenin showed the prominent appearance. CONCLUSION: We found that titanium-13Zirconium-6Niobium alloy was an excellent biomaterial.

The effort of various mixing methods on dynamic viscoelasticity of a temporary soft lining material; coe-comfort / 대한치과보철학회지

STATEMENT OF PROBLEM: Temporary soft relining materials are used in a diverse clinical situations such as tissue conditioner, relining material, functional impression by varying its viscoelasticity. However, reproduction of consistent viscoelasticity has been not possible. MATERIALS AND METHODS: Considering setting mechanism of this material, this study has measured the effect of varying amount of void in dynamic viscoelasticity of soft relining material, with three different mixing methods. In each methods 10 specimens were made and subjected to dynamic viscoelastic test which were measured at specific times over period of 72 hours. RESULTS: The analysis of the result shown that there was no statistically significant differences between different mixing methods. CONCLUSION: Different mixing methods had no effect over control of viscoelasticity of soft lining material. Further research is recommended for under similar oral environmental condition.

A novel 3D scan method to quantify teeth wear / 대한치과보철학회지

STATEMENT OF PROBLEM: Tooth wear is physiological phenomenon. Ninety-seven percent of normal people have tooth wear and about 7% has pathologic teeth wear. If we know the amount of tooth surface loss caused by pathologic tooth wear, we may restore it ideally. PURPOSE: Recently, measurement of tooth wear by using 3D scan has been increasing. Therefore, we need to know how accurate 3D scan is. Past accuracy test on 3D scan was about linear change, but as we know that tooth wear is volume change. Thus, the purpose of this study is to know how accurate 3D scan is. MATERIAL AND METHODS: For accuracy test of 3D scanner, volume values measured by 3D scanner and micro-balance were compared. For test I, preliminary, 3 ball samples and 3 circular cones were made with pattern resin. For test II, 10 teeth shape rubber samples were used. RESULTS AND CONCLUSION: 1. The result of the accuracy test on 3D scan with 3 ball samples and 3 circular cones made of pattern resin has no significant difference(p<0.05). 2. The result of the accuracy test on 3D scan with 10 samples of tooth shape rubber has no significant difference(p<0.05). As a result, we may concluded the analysis of quantifying tooth wear used by 3D scan is useful in the clinic.

Double crown retained removable partial denture -4 years in retrospect / 대한치과보철학회지

STATMENT OF PROBLEM: Little in known about the importance of selection of various double crowns as retainer in determining the outcome of treatment with double crown retained removable partial denture. Purpose : To obtain information about the effects and the results of this treatment modality. MATERIAL AND METHODS: This study describes 61 double crown retained removable partial dentures worn by 51 patients from Samsung Medical Center, Seoul a time ranging between 6 and 48 months and evaluate occlusal contacts on the denture teeth, denture movement, incidence of denture relining, denture retention, fracture of dentures and abutments, hygiene, residual ridge inflammatory changes, number of lost abutments, interruption of denture use. RESULTS: One tenth of all the restorations were relined. Restorations in 21 arches fractured repeatedly for various reasons. There was no apparent interrelationship between fractures and the five groups. CONCLUSION: Good prognoses of removable partial dentures were shown in all groups(Kennedy Classes I, II, III, combination and few remaining abutment).

A study on fitness of several domestic implant fixture and abutment screws / 대한치과보철학회지

STATEMENT OF PROBLEM: Several domestic dental implants have been developed since dental treatment being implants are increasing and popularized. However, they have not been used in domestic market like imported goods. MATERIAL AND METHODS: This study was carried out to compare domestic and imported implants in aspect of fitness, dental implant fixture and abutment screw using scanning electron microscope. All experiments were performed under dry condition. RESULTS: 1. Only in aspect of relation of dental implant fixture and abutment screw, except only one group with point contact, good fitness was existed. 2. Home products must presevere in their efforts, so as excellent to fit.

The fracture characteristics of glass fiber post and core on using different types of core resin materials / 대한치과보철학회지

STATEMENT OF PROBLEM: Glass fiber post is one of recent developments to accommodate esthetic restoration for endodontically treated teeth. This has many advantages over conventional post system in physical properties, esthetic factor, risk of root and restoration fracture, adhesion to core, radiopacity, removal and retrievabilty, biocompatibility and chemical stability. PURPOSE: This in vitro study was to evaluate the most suitable type of resin core for the glass fiber post through surveying the fracture modes and the maximum load that fractures the tooth. MATERIAL AND METHODS: 50 sound maxillary premolars restored with glass fiber posts(ParaPost(R) Fiber White) and different types of resin cores(ParaCore, Z100(TM), Rebilda(R) and Admira(R)) were prepared and loaded to faiure in a universal test machine. The maximum fracture load and fracture mode were investigated in the specimens that were restored with resin and those of metal cast and core. With the data, Wilcoxon rank sum test was used to validate the significance between the test groups, and Tukey's studentized range test was used to check if there is any significant statistical difference between each test group. Every analysis was approved with 95% reliance. RESULTS: On measuring the maximum fracture load of teeth specimens, there was a significant difference between the maximum fracture loads of the tooth specimens. ParaCore showed the highest mean maximum fracture load followed by Z100(TM). And, the distribution of fracture mode of tooth specimens showed generally Type D, the three parted fracture of the core around the post was mostly seen(62.5%), and specifically, ParaCore showed 90% and Z100(TM) showed 100% Type D fracture. CONCLUSION. Referring to the values of maximum fracture load and mean compressive fracture load, ParaCore and Z100(TM) had high values and are recommended as tooth colored resin core material for glass fiber post. CLINICAL IMPLICATIONS: This study was carried out intending to be of aid in selecting the appropriate resin core for the glass fiber post. The dual cure type composite resin ParaCore and light cure type composite resin Z100(TM) have good properties and are recommended as tooth colored resin core material for glass fiber post.

Resonance frequency analysis of impl-ants with anodized surface oxides / 대한치과보철학회지

The present experimental study was designed to address two issues. The first was to investigate whether oxidation voltage of titanium implants influenced bone tissue responses after an in vivo implantation. The second aim was to investigate secondary stability change after 1 to 3months period. Screw-shaped implants with a wide range of oxide properties were prepared by electrochemical oxidation methods, where the oxide thickness varied in the range of 3-15micrometer. The micro structure revealed pore sizes of 1-3micrometer, the crystal structures of the titanium oxide were amorphous, anatase and a mixture of anatase and rutile type. Bone tissue responses were evaluated by resonance frequency measurements that were undertaken 1 to 3months after insertion in the rabbit tibia. It was concluded that no statistical difference of RFA values was found between the groups, RFA gains after 1month and 3months were calculated.

Wear behavior of attachments for implant retained overdenture according to material in vitro / 대한치과보철학회지

STATEMENT OF PROBLEM: The proper materials of attachments for implant retained overdenture are unknown, such as the correlation between retention and abrasion, as well as the types of materials that are suitable for patrix and for matrix individually. PURPOSE OF THIS STUDY: The aim of this study was to select a proper clinical attachment system for a successful treatment as well as patient satisfaction. METHOD: Retention and abrasion of 14 commercial attachments were measured during 15,000 removes. RESULT: A retentive part (matrix) which requires elasticity has to be made of gold while the patrix part which does not require elasticity has to be made of titanium. This gold matrix / titanium patrix combination showed the most retentive force and the least retention loss.