Microleakage of the prosthetic abutment/implant interface with internal and external connection: in vitro study

Clinical Oral Implant Research. Vol. 25, Issue 9, 2014: 1078-1083


This study determined the degree of marginal microleakage of the abutment–implant interface on platforms with Morse taper connection and external connection.


For this in vitro study, 42 implants, 21 with external connection and 21 with Morse taper connection, were used, immersed in acrylic resin cylinders. Each implant was joined by a prosthetic abutment screw tightened at different degrees, forming the six study groups: (1) External connection, manual tightening (2) External connection, 20 Newton (N) tightening (3) External connection, 30 N tightening (4) Morse taper connection, manual tightening (5) Morse taper connection, 20 N tightening (6)Morse taper connection, 30 N tightening. All samples were subjected to load cycling and thermocycling. Then, they were submerged in a solution of 0.2% methylene blue for 24 h. Finally, the microleakage was measured via 209 optical microscopy in each study group, average was obtained, and Mann–Whitney test was applied.


Statistically significant differences (P < 0.001) were found between the levels of microleakage presented in the Morse taper connection implants (1.48) and external connection implants (2.8) in all three types of tightening. Microleakage levels decrease when increasing torque is applied to the screws.


However, if only applied torque is analysed, the lower levels of microleakage occur in 30N tightened abutments, where, as shown in the photomicrographs, the gap is virtually nonexistent for Morse taper connections and external connections get an almost perfect seal. This may be due to the strict manufacturing criteria found in the analysed elements.


Morse taper connection implants showed lower levels of microleakage than external connection implants; also, it was observed that microleakage decreases in the way torque increases.

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