This in vitro study evaluated the effect of biofilms on abutment torque loss and wear of implant internal connection surfaces. Materials and Methods: Morse taper abutments were torqued to corresponding implants and then the implant-abutment assemblies were immersed in a biofilm medium for 72 hours. After detorque evaluation, the abutments were removed and the inner implant surfaces were observed via scanning electron microscopy and profilometry. Results: The removal torque values and the implant damaged areas decreased after contact with biofilms. Conclusion: The lubricating effect of biofilms decreased the friction between contacting surfaces, negatively affecting the mechanical integrity of the implant-abutment connection.

The aim of this in vitro study was to evaluate the removal torque values on abutments and the morphological wear aspects of two different dental implant joints after immersion in a medium containing biofilm from human saliva. Twenty implant-abutment assemblies were divided into four groups in this study: (A) Morse taper free of medium containing biofilm, and (B) after contact with a medium containing biofilm from human saliva; (C) External Hexagon free of medium containing biofilm, and (D) after contact with medium containing biofilm from human saliva. The abutments were firstly torqued to the implants according to the manufacturer´s recommendations, using a handheld torque meter. Groups B and D were immersed into 24 well-plates containing 2 ml BHI medium with microorganisms for 72 h at 37 °C under microaerophilic conditions. After detorque evaluation, the abutments were removed and the implants were analyzed by scanning electron microscopy (SEM) and profilometry. On the detorque evaluation, the torque values decreased for the external hexagon implants and increased for the Morse taper implants. However, the values were lower when both implant-abutment assemblies were in contact with a medium containing biofilm from human saliva. The wear areas of contacting surfaces of the implants were identified by SEM. The highest average roughness values were recorded on the surfaces free of biofilm. The medium containing biofilm from human saliva affected the maintenance of the torque values on Morse taper and external hexagon abutments. Additionally, the removal of abutment altered the inner implant surfaces resulting in an increase of wear of the titanium-based connection.

The subject of occlusion has been deemphasized by academia over the last 30 years. This marginalization in turn has negatively impacted recent graduates who are largely unfamiliar with the use of occlusal adjustment by selective reshaping as a treatment modality. Use of proper occlusal therapy enables clinicians to more effectively help patients recover from parafunctional wear of the anterior and posterior teeth. In addition, familiarity with this field enhances the correction of progressive posterior and anterior reverse articulations. This article aims to highlight the importance of occlusal principles in treatment planning. In addition, we illustrate the benefits of occlusal adjustment by using a conservative technique, selective reshaping, as an option to correct anterior reverse articulation in a 20-year-old patient. The knowledge of occlusal principles enhances diagnosis of malocclusion in the development of a treatment plan. When properly employed, the technique of occlusal adjustment by selective reshaping may be used to correct an adaptive anterior reverse articulation with a high degree of predictability for select patients.

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Background: The implant–abutment micro-gap has been investigated as a potential etiological factor for peri-implant diseases. Purpose: The aim of this study was to determine the marginal accuracy of different zirconia CAD/CAM abutments placed on external hex implants. Materials & methods: Twelve external hex implants (4.1mm) were used from the same company. The samples were divided into four groups: group 1) 4 mm diameter anti-rotational (AR) stock titanium abutments (n = 4); group 2) scanned (3Series, Dental Wings) and milled (RCS-1, Röders GmbH) 4 mm diameter zirconiaabutments (n = 4); group 3) scanned (3Series, Dental Wings) and milled (CNC 240, Lava) 4mm diameterzirconia abutments (n = 4); and, group 4) two piece 4.1 mm diameter stock abutments (Ti-base, CEREC, Sirona) (n=4), and torqued according with the manufacturer’s instructions (30Ncm, 20Ncm, 20Ncm & 35 Ncm, respectively). The samples were placed in a sample holder and segmented longitudinally. The implant-abutment gap was measured in 6 different pre-determined locations using optic microscopy. Results: One-way ANOVA statistical analysis was conducted and showed that the micro-gaps in the group 1 samples were not significantly different when compared with the micro-gaps in group 4 samples. However, a significant difference (p < 0.05) was found between the micro-gaps when using titanium abutments (groups 1 & 4) compared to zirconia abutments (group 3). Conclusion: Within the limits of this study, it was concluded that zirconia abutments cannot be milled with the same degree of precision as the metal abutments. The mechanical effects of marginal implant-abutment microgap and risk of microbial infiltration should be evaluated in clinical investigations. Keywords: Dental implant; Abutment interface;Microleakage.