The assembly of prosthetic teeth
- Introduction
The purpose of a prosthesis is to replace missing teeth with artificial teeth. In order to ensure the various functions and safeguard the health of the supporting structures.
- Fitting prosthetic teeth
Definition of assembly: Laboratory stage which consists of making wax models bearing artificial teeth, prefiguring the finished prosthesis.
Definition of the prosthetic occlusal plane
- Surface on which the prosthetic teeth are arranged.
- Plan according to which the 2 arches meet
Definition of the SPEE Curve
The occlusion surface achieves a curve with superior concavity in the sagittal plane, the objective of which is to promote the achievement of occlusion in propulsion.
Definition of the WILSON Curve
The buccal and lingual cusps are aligned in a curve with superior concavity in the frontal plane, this is the result of their axial inclination.
Prerequisites for assembly
- After adjusting the height of the rim, the inter-incisal point is drawn.
- It is the occlusion model which guides the arrangement of the anterior teeth.
- The height of the rim was adjusted to that of the mesio-distal grooves of the proximal teeth
- The projection of the ridge line of the ridges is engraved on their surface
Assembly of the upper anterior teeth
It is guided by aesthetic criteria as well as functional imperatives: elocution, phonation and occlusal contact.
The conventional aesthetic wax assembly of the six anterior teeth is carried out according to the template of the rim of the occlusion base set in the mouth.
| Upper jaw | FRONTAL Plan | SAGITTAL Plan | HORIZONTAL plan | ||
| Central incisor | Free edge in contact with the occlusal plane* Vertical axis | *Tooth is perpendicular to the occlusal plane with a lingual neck. | * On either side of the inter-incisal point.* Free edge 6 to 8 mm of the retro-incisal papilla | ||
| Lateral incisor | * Tooth slightly above the occlusal plane * Major axis distally 10° | Tooth is vestibulated 10° with a lingual neck | * Its free edge is continuous with that of the central one | ||
| Canine | Canine tip in contact with the occlusal plane | Is perpendicular to the occlusal plane | Canine tips and retroincisive papilla are on the same line | ||
View in FRONTAL plane view in SAGITTAL plane view in HORIZONTAL plane
Animation of the assembly : For aesthetic purposes, it is possible to carry out movements, bulk, diastemas, grinding to promote the enhancement of a tooth. Possible modifications concern the position of the necks (out or in), the possible rotations in order to animate the assembly, and the offset of the free edges between the central and lateral incisors.
Assembly of the anterior lower teeth
| Mandible | FRONTAL Plan | SAGITTAL Plan | HORIZONTAL plan |
| Central incisor | *Vertical axis. | * 10° vestibule * Heels placed on the external slope of the ridge. | *The free edges of the anterior lower teeth fit into the curve of the upper free edges. |
| Lateral incisor | *Almost vertical or 5° distal. | * 5° vestibule | |
| Canine | *Canine tip at the same level as the incisors.*Distal by 10 | *Linguo-version of 10° |
View in FRONTAL plane view in SAGITTAL plane view in HORIZONTAL plane
- The coverage of the anterior-inferior teeth is 0.5 to 1 mm.
- The incisal overhang is 1mm.
Upper posterior teeth assembly
It is guided primarily by functional imperatives and, to a lesser extent, aesthetic ones.
He must:
- Re-establish numerous, simultaneous and well-distributed occlusal contacts with the teeth of the opposing arch
- Ensure the balance of the prosthesis during movements of the mandible.
- Be in aesthetic harmony with the previous assembly.
The rules of functional assembly are:
- Mounting the teeth on the ridge line of the edentulous ridges;
- Creation of occlusal curves compatible with the occlusion.
- Obey the Ackermann Rule
- Ackermann’s 3 HM Rule:
3H: Heteronumber, Heteromorphy, Heterotopia
It is respected in order to avoid any risk of tilting and to reduce pressure on the alveolar ridges and supporting teeth.
- M = median pressure : the resultant of the chewing forces must be exerted at the center of the crest; the distal part of the crest therefore does not support any teeth.
- H = Heteronumber: the number of prosthetic teeth is not identical to that of missing teeth
Ex: 3Molar is not replaced,
Mandibular PM can be removed
- H = Heteromorphism: the shape of the prosthetic teeth is not identical to that of the missing teeth
🡪 It is possible to reduce the mesiodistal and vestibulolingual diameters
- H = Heterotopia: The position of the prosthetic teeth does not necessarily match that of the teeth to be replaced.
Ex: sometimes the 2nd molar is replaced by a PM
| FRONTAL Plan | SAGITTAL Plan | HORIZONTAL plan | |
| 1st PM | *perpendicular to the occlusal plane | *Vertical axis*Bicuspid contact with the occlusal plane | *The buccal cusps, lingual cusps and intercuspal grooves must be aligned |
| 2nd PM | idem | idem | |
| 1st molar | *Vestibuloversée of 20° | *6° inclination to initiate the SPEE curve*In contact with the occlusal plane by its mesiopalatine cusp | |
| 2nd molar | *vestibuloversed by 20° | *Same inclination*No contact with the occlusal plane |
Fitting the lower posterior teeth
1st Lower Molar: whose central fossa will receive the mesiopalatine cusp of the upper molar and the median vestibular cusp will be placed in contact with the mesiovestibular cusp of the 1st upper molar 🡪 class I molar
2nd Lower Molar: in contact with the 2nd upper M, its axis will be inclined from bottom to top and from back to front to follow the compensation curve.
2nd lower PM : the vestibular cusp will be placed between the mesio and disto-vestibular slopes of the 1st and 2nd upper PM.
1st Pm lower : should participate in creating the canine class I
🡪 The mesh obtained between the upper and lower teeth should be impeccable
- Conclusion
By respecting these different principles, the definitive prosthesis will succeed in satisfying the patient on an aesthetic and functional level .
The assembly of prosthetic teeth
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