The insertion axis and the parallelizer
1-Definition of the insertion axis
The insertion axis is the trajectory that the prosthesis follows from its first contact with the teeth to its final seating position.
Each clinical case admits several possible axes of insertion.
How to choose an insertion axis?
2-The parallelizer:
a-Definition: it is a diagnostic and treatment instrument which is intended to highlight a relative parallelism between the different mucosal dental surfaces which support a prosthesis .
- 1/ Largest contour line: Q LA
It is defined as: the set of most salient points / a the longitudinal axis of the tooth
- Qqq2/ Guide line:
e This is the set of most salient points of the crown / insertion axis
So: There are an infinite number of guide lines along the chosen zWwef axis while there is only one line of greatest contour along the longitudinal axis of the tooth.
Exceptionally when:
Insertion axis = Tooth axis
LG= LPC
b-Role of the parallelizer:
- At the dental office
Study of the clinical case and the modifications to be made to the different support fabrics.
- In the laboratory
The development of the hooks and the metal frame
At the dental office
To highlight obstacles to prosthesis insertion: highly inclined tooth, soft tissue with a strong undercut
To guide modifications to be made to dental crowns (grinding, fixed prosthesis)
c-Description:
Accessories:
3-Factors involved in choosing the insertion axis:
a-undercut area or withdrawal area:
* clearance area : this is the area above the guide line
*undercut (removal) area:
This is the area below the guide line
b -Guide surface : the parallelism of the teeth allows the rigid elements of the prosthesis to slide along the insertion axis.
c-Interferences : misplaced teeth, exostoses, etc.
d- Aesthetics : positioning of the hooks.
4-Determination techniques
The bisector insertion axis
It results from a bisector of the bisectors of the axes of the supporting teeth
Conclusion
The therapy of partial edentulation is surely one of the most delicate to apply, the objective of which is to replace the missing organs , but above all to respect the integrity of those that remain.
The insertion axis and the parallelizer
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