Direct to implant vs. abutment

Advantages of abutment-supported prostheses

• When implants are not parallel to each other, the use of angulated abutments can "correct" for the non-parallelism. 
• Angulated abutments are available for a screw-retained prosthesis. 
• Custom abutments can be fabricated for a cemented prosthesis.
• Placement of abutments permits the abutment-prosthesis interface to be placed crestally or supra-crestally making impression-taking and trial placement much easier and less invasive for the soft tissues. 

Disadvantages of abutment-supported prostheses

• When there is limited interarch space, placing abutments reduces the size and hence the strength of the prosthesis framework. 
• The typical implant to prosthesis system involves two retentive interfaces of implant-abutment and abutment-prosthesis meaning that in the case of cement-rertained prostheses, access to the abutment screw may be difficult.
• Cement excess is a major cause for peri-implant inflammation and peri-implant crestal bone loss.

Advantages of implant-supported prosthesis

• When there is limited interarch space, this type of prosthesis allows for the necessary size and strength of the prosthesis framework. 
• With the typical implant-prosthesis-prosthetic screw system, retrievability is enhanced. 
• There is only one retentive mechanism to manage.

Disadvantages of implant-supported prosthesis

• Cannot be used with a cement-retained prosthesis. 
• Non-parallelism of implants may lead to compromised esthetics due to the position of the access holes for the prosthetic screws. 
• Impressions and trial placement procedures may traumatize the peri-implant soft tissues.
• Connection and disconnection of the prosthesis may influence the periimplant tissue condition/crestal bone levels.
• Connection and disconnection of the restoration may be more uncomfortable for the patient in comparison to an abutment supported prosthesis.