ABSTRACT
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*9 mm) 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 micrometershim stock drags without tearing), medium(40 micrometer), and heavy(80 micrometer). 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.
Subject(s)
Crowns , Denture, Partial, Fixed , Prostheses and Implants , Splints , TitaniumABSTRACT
STATEMENT OF PROBLEM: Recently various implant components such as premachined gold cylinder, plastic cylinder, gold UCLA abutment and plastic abutment were developed and used clinically without clinical investigation. PURPOSE: The purpose of this study was to evaluate the effects of fabrication of gold cylinder on the fitness and preload of the standard abutment and also the effects of fabrication of UCLA gold abutment on the fitness and stress transfer around the implant fixture. MATERIAL AND METHOD: Three kinds of gold cylinders such as, as-received gold cylinder((Nobel Biocare, Sweden), gold cylinder after casting, and plastic cylinder after casting with type IV gold alloy were tested over the top of the standard abutment. At the same time, three types of abutments such as, gold UCLA abutment before and after casting, and plastic abutment after casting were tested. The cylinder and abutment was secured over the fixture with conventional preload values using an electronic torque controller (Nobel Biocare Sweden). The fitness of the abutment on the fixture and gold cylinder over the standard abutment were measured using the microhardness tester (MXT 70, Matsuzawa, Japan). Preload and the strain values were recorded using the strain balance unit (SB-10, Measurement group, Raleigh, USA) and strain indicator (P-3500, Measurement group, Raleigh, USA) systems. RESULTS AND CONCLUSION: 1. Significant differences were found in the fit between the gold cylinder and plastic cylinder. 2. There were significant differences between the preload of the gold cylinder and that of the plastic cylinder. 3. Significant differences were found in the fit between the gold UCLA abutment and plastic UCLA abutment. 4. There were no significant differences in the stress generated on the supporting structure of the fixture among different cylinder and abutment groups.
ABSTRACT
STATEMENT OF PROBLEM: Removable partial denture and complete denture often require denture base relines to improve the fittness against tissue-bearing mucosa because of the gradual change in edentulous ridge contour and resorption of underlyng bony structure. Self-curing hard reline resins offers the immediate and relatively inexpensive means to be recondition the surface of denture base directly. However weak bond between denture base resin and reline material can harbor bacteria, promote staining, or result in complete separation of the two materials. PURPOSE: The purpose of this study was to evaluate the effect of denture cleansers on bond strength and surface hardness of reline resin to denture base resin Denture base resin beams(60.0x15.0x3.0 mm) were made with Lucitone 199. MATERIAL AND METHODS: 10mm section was removed from the center of each specimen. The samples were replaced in the molds and the space of 10mm sections were packed with Tokuso Rebase reline material. The specimens were immersed in denture cleansers(Polident, Cleadent) and were evaluated after 1week, 2weeks, and 4weeks. The bond strength and surface hardness of self-curing hard reline materials to heat-curing denture base resin were measured using an UTM(universal testing machine). RESULTS AND CONCLUSION: 1) There was no significant difference of usage, kind, and denture cleaner by application time on the bonding strength of self-curing hard reline resin to denture base resin. 2) There was no significant difference of usage, kind, and denture cleaner by application time on the surface hardness, but the surface hardness showed decreasing tendency, as the time of immersion was extended 3) The failure modes of the specimens was initially adhesive failure and finally cohesive failure of self-curing hard reline resin.