A study on the fit of the implant-abutment-screw interface / 대한치과보철학회지

STATEMENT OF PROBLEM: There have been previous studies about considerable variations in machining accuracy and consistency in the implant-abutment-screw interfaces. PURPOSE: The purpose of this study was to evaluate the machining accuracy and consistency of implant/abutment/screw combinations on two randomly selected implants from each of four manufactures. MATERIAL AND METHODS: In this study, screws were respectively used to secure a cemented abutment to a hexlock implant fixture; teflon coated titanium alloy screw(Torq-Tite) and titanium alloy screw in Steri-Oss system, gold-plated gold-palladium alloy screw(Gold-Tite) and titanium alloy screw in 3i system, gold screw and titanium screw in AVANA Dental Implant system, and titanium screws in Paragon System. The implants were perpendicularly mounted in polymethyl methacrylate autopolymerizing acrylic resin block(Orthodontic resin, Densply International Inc. USA) by use of dental surveyer. Each abutment screw was secured to the implant with recommended torque value using a digital torque controller. Each screw was again tightened after 10minutes. All samples were cross sectioned with grinder-polisher unit(Omnilap 2000 SBT Inc) after embeded in liquid unsaturated polyester (Epovia, Cray Valley Inc). RESULTS: There were the largest gaps in the neck areas of screws in hexagonal extension implants which were examined in this study. The leading edge of the abutment screw thread (superior surface) was in contact with the implant body thread, and the majority of the contacting surfaces were localized to the middle portion of the mating threads. Considerable variation in the contacting surfaces was noted in the samples evaluated. Amounts of contact in the abutment screw thread were larger for assemblies with Gold-Tite screw, gold alloy screw, Torq-Tite screw than those with titanium screws. The findings of intimate contact between the screw and screw seat were seen in all samples, regardless of manufacturers. However, microgap between the head and lateral neck surface of the screw and the abutment could be dectected in all samples. The findings of intimate contact between the platform of the implant and the bottom of the abutment were consistent in all samples, regardless of manufacturers. However, microgaps between the lateral surface of external hex of the fixture and the abutment could be dectected in all samples. CONCLUSION: Considerable variations in machining accuracy and consistency were noted in the samples and the implant-abutment-screw interfaces were incomplete. From the results of this study, further development of the system will be required, including improvements in pattern design.

Preliminary Study on the Design of Implant Abutment Screw Head for Rapid Fastening & loosening / 대한치과보철학회지

For the purpose of decreasing the chair time in implant cases,the time needed to loosening and fastening the screw must be shortened.Nowadays,the two typical designs of screw head are slot and hexa form.This study aimed at the shortening of loosening and fastening time by modifying the slot and hexa form.Total of twelve dentists participate in these experiments,four of them were experienced and eight of them were novice dentists. 1.There were many differences in the speeds of screw loosening and fastening between personal experiences.Experienced dentists are faster than novice dentists. 2.There were many differences in the speeds by angulation of the implant,by the conditions of the muscle tonicity. 3.Revised slot and hexa heads show the slightly shortened time for screw looseing and fastening.

Relaltionship Between The Depth Access Hole And Prosthetic Components In Screw Retained Implants / 대한치과보철학회지

A total of 605 implant fixture prosthesis delivered by 3 clinics and 2 laboratories were examined in this study. The object of this study was to determine the proper length of screw head. The depth of access hole were measured and compared to the type of fixture, abutment, gold screw and prosthesis. The results were as follows: 1. The average number of fixtures per patient were 2.97. 2. The number of fixture installed in the lower posterior area are 327(55.56 %), the upper posterior area 171(28.25%). 3. The depth of access hole is 4.23 mm in shallow area, and 5.46 mm in deep area and the differences were 1.23 mm. 4. The average depth of the aceess hole of the UCLA abutment were 5.02 mm. 5. The number of 4-5 mm access hole depth were 60(22.39%)in abutment screw level and the number of 4-5 mm depth in fixture level were 101(29.19%). 6. In the shape of screw head, hexed type were 576(95.21%), slotted type were 29(4.79%).

Effect of the surface modifications and the use of washer on the reverse torque of the implant prosthetic gold retaining screw / 대한치과보철학회지

The screw loosening is one of the complications that happen frequently in dental implant prostheses. The purpose of this study was to evaluate the changes of reverse/loosening (opening) torque of the screw according to the surface modifications by sandblasting and 24K gold electroplating as well as to determine the possibility of the clinical use of a washer in dental implant. The reverse torque of 4 experimental conditions(control, sandblasted, use of washers, electroplasted) was measured by digital torque gauge (Model MGT50Z, Mark-10 Corp., 458 West John Street Hicksville, NY 11801 USA). Electronic torque controller (Nobel Biocare DEA 020) was used in fastening the gold screws into abutment replicas. Mixed Linear Model Analysis method was used for statistical analysis. To examine the changes of screw thread surface, microphotographs were taken by Olympus PME-3 metallurgic microscope (Olympus Optical Co. Ltd., Tokyo, Japan). Within the limitations of this study, the following results were drawn: 1. The surface modifications of the gold screws and the use of a washer have significantly affected the reverse torque value compared to the control group (p<0.01). 2. Sandblasting and electroplating treatments demonstrated significantly higher reverse torque val-ue than that of control group. 3. The use of a washer may be one of the useful clinical methods that prevent the screw loosening. However, further studies are necessary for the material selection and design of the washer.

THE EFFECTS OF FABRICATION AND TIGHTENING METHODS OF GOLD CYLINDER ON THE PRELOAD OF THE IMPLANT ABUTMENT / 대한치과보철학회지

The purpose of this study was to evaluate the effects of fabrication and tightening methods of gold cyliner on the preload of the standard abutment. Three linear strain gauges (KFR-02N-120C1-23, Kyowa, Japan) were mounted longitudinally on the 5.5mm Standard abutment (Nobel Biocare, Sweden) and three kinds of gold cylinders such as, as-received gold cylinder, gold cylinder after casting, and plastic cylinder after casting with type IV gold alloy were connectedd over the top of the standard abutment. Two kinds of tightening methods, such as manual torque with handheld screwdriver and electronic torque using Electronic torque controller were used to generate preload on the abutment. The result were as follows 1. The preload generated by tightening cast plastic cylinder with handheld screw driver, was the lowest among the six groups. 2. The preload generated by cast plastic cylinder was lower than those by gold cylinders regardless of the tightening methods. 3. The electronic torque controller produced higher torque values than the handheld screwdriver.