EXPERIMENTAL EVALUATION OF TITANIUM REMOVABLE PARTIAL PROSTHESES RETENTION WITH: 0,50 - 0,75 MM UNDERCUTS AND/OR GUIDE PLANES. ABSTRACT

THE PURPOSE OF OUR RESEARCH WAS TO TEST THE RETENTION OF A TITANIUM FRAMEWORK IN AN EDENTULOUS RIDGE WITH DIFFERENT UNDERCUTS WITH OR WITHOUT GUIDE PLANES. WE HAVE MADE FOUR TWIN MODELS REPRODUCING AN EDENTULOUS RIDGE BETWEEN THE MANDIBULAR RIGHT SECOND MOLAR AND FIRST PREMOLAR, AND ON THESE TEETH, TWO ADEQUATELY PREPARED Cr-Co CROWNS HAVE BEEN CEMENTED. WE HAVE PREPARE TWO GROUPS, ONE WITH GUIDE PLANES AND ONE WITHOUT. EACH GRUOP HAS TWO MODELS: 0.50 AND 0.75- MM UNDERCUTS. WE HAVE MADE FIVE Ti1 ALLOY FRAMEWORKS FOR EACH MODEL USING THE Cr-Co PREFORMED CLASPS' SHAPE. EVERY FRAMEWORK IS COMPOSED OF TWO ACKERS CLASP (ONE ON THE FIRST PREMOLAR, THE OTHER ON THE SECOND MOLAR) LINKED TOGETHER BY A SECONDARY CONNECTOR. A LITTLE RING IS JOINED ON THE REST OF EACH CLASP, IN ORDER TO PERMIT THE TRACTION BY AN INSTRON MACHINE HUNG USING A STEEL WIRE. FINALLY, WE HAVE 20 SAMPLES: 10 SAMPLES WITH PROXIMAL PLATES: FIVE WITH 0.50 UNDERCUTS (SERIES 1_ AND FIVE WITH 0.75-MM UNDERCUTS (SERIES 2); 10 SAMPLES WITHOUT PROXIMAL PLATES: FIVE WITH 0.50-MM UNDERCUTS (SERIES 3), FIVE WITH 0.75-MM UDERCUTS (SERIES 4). THE INSTRON MACHINE RECORDED THE MAXIMUM LOAD FOR A COMPLETE SEPARATION OF THE FRAMEWORK FROM MODEL. TEN TRACTION TESTS FOR EACH SAMPLE WERE DONE. THE MACHINE SHOWED US A GRAPHIC (TIME/LOAD APPLIED), THE MAXIMUM LOAD, THE APPLIED LOAD AVERAGE, AND STANDARD DEVIATIONS. THE FOUR AVERAGE DATA ARE 2.668 KG (SERIES 1), 3.571 KG (SERIES 2), 1.37 kg (series 3), and 2.141 kg (series 4). BY ALL TESE DATA, WE CAN SEE THE PROPORTIONAL INCREASE OF RETENTION ACCORDING TO THE UNDERCUT DEPTH AND THE GUIDE PLANES. THE CHOISE WILL DEPEND ON THE CLINICAL SITUATION. IN ANOTHER STUDY WE HAVE TESTED THE RETENTION IN A 0.25-MM MODEL WITH AND WITHOUT GUIDE PLANES, OBTAINING DATA TO HAVE A FULL VIEW FOR AN EASY FRAMEWORK PROJECT OF REMOVABLE PARTIAL PROSTHESES, RESPECTING EVERY PARTICULAR CLINICAL SITUATION.