The different types of single-unit restorations In fixed prosthesis
Introduction
Metallic, ceramic or metal-ceramic prosthetic elements make it possible to replace large volumes of dental substance while preserving and protecting those that are not affected.
They restore functional activity and can satisfy certain aesthetic requirements.
Definition of fixed unit restorations
Any prosthetic design that involves only one tooth, with the aim of restoring or replacing it without modifying the neighboring teeth.
Indications and contraindications of single fixed prosthesis
Directions:
Fixed prosthesis is essential whenever the lasting restoration of function and aesthetics makes it the solution of choice:
- Congenital dental anomalies (anomalies of location, direction, volume and shape);
- Hereditary diseases;
- Acquired diseases dominated by dental caries;
- Trauma, hypoplasia, dysplasia, dystrophy as well as abrasions.
Contraindications
- Lack of hygiene;
- Bleeding problems;
- Progressive and advanced pathological conditions;
- Contraindications to locoregional or local anesthesia;
- Certain pathologies of the temporomandibular joint;
- Mouth opening limitations;
- Terminal periodontal disease;
- Malpositions that cannot be corrected orthodontically;
- Contraindications of a psychological or economic nature.
Preparation strategy
The approach consists of giving oneself a reference to guide the reduction. It can be done in three ways:
- Controlled penetration: recess grooves with a depth equal to half the diameter of the cutter ensure a regular thickness during reduction.
- Progressive reduction: carried out by referring to a reduction guide, mold
sectioned in silicone of intact or reconstituted teeth.
The different types of single-unit restorations In fixed prosthesis
- Reference to a collateral tooth
An intraoperative retractor cord to better visualize the cervical limit.
Classification of single-unit restorations in fixed prosthesis
The different types of single-unit restorations In fixed prosthesis
1. Instrumentation
1- Turbine / counter angle red ring: Rotation speed greater than 100,000 rpm
2-Spray: will allow you to
- Avoid overheating
- Clear debris from the cutter relief
3-Aspiration that brings
- Patient and practitioner comfort
- Save time
4-strawberries:
Diamond burs :
Small diamond chips of various shapes and sharp angles are electroplated onto the sides of a steel instrument.
They work by abrasion by removing material with a thickness of a diamond with each pass.
Tungsten Carbide Burrs: CT
- These are the instruments best suited to the precise realization of certain elements of the preparations and to the polishing of the surfaces.
They perform a cutting and piercing action.
- It is important to know the shape characteristics of the strawberry
- Base diameter
- End diameter
- The cutting length
- Conicity (cylindrical/conical)
- The shape and convergence of the end (round plate)
5-Choosing strawberries
- Depending on the shape of the working part
Cylindrical strawberries
Conical cutters
Flaming strawberries
Strawberry balls
Rugby ball or “button” strawberries
The different types of single-unit restorations In fixed prosthesis
- Depending on the shape of the end:
Plates (right-angled shoulder)
Plate with rounded external angles (shoulder with rounded internal angle)
Rounds (quarter round fillet)
Ogival/elliptical (quarter oval fillet)
Angled (bevels and chamfer)
Pointed (proximal faces)
- Depending on the grain size/No. of blades
The different types of single-unit restorations In fixed prosthesis
Clinical expressions of single-unit fixed prosthesis
The crown has total coverage
The crown that covers all the axial walls of the occlusal face of the tooth is the sealed prosthetic element that has the best retention and stabilization.
Indications for full-reconstitution crowns
Cast crown
It is described in operative dentistry as “the extreme solution to save a tooth.”
Indicated when the aesthetic damage is secondary, on a vital or devitalized tooth,
little dilapidated or reconstructed.
The different types of single-unit restorations In fixed prosthesis
The different types of single-unit restorations In fixed prosthesis
Metal-ceramic crown (MCC)
The ceramic is made by firing, first a thin opaque layer to hide the metal, then a thicker layer.
- The thickness of a non-precious alloy is 0.2mm;
- The preparation for CCM must be done taking into account the difference in reduction of the supporting tooth depending on whether it is covered with ceramic or metal. Any ceramic surface corresponds to a greater thickness of tooth reduction.
Directions:
- Marked to deep overbite;
- Aesthetic requirements;
- Pulped or depulped tooth;
- Milling and/or attachment support.
The different types of single-unit restorations In fixed prosthesis
Anterior tooth reduction features:
- Reduction on the vestibular face: 1 to 1.5 mm;
- Reduction of the lingual face: 0.5 to 1mm;
- Reduction of the proximal faces: 0.5 to 0.7mm.
The choice of limits is between the shoulder with rounded internal angle, the fillet and their variants.
Several types of limits can coexist on the same preparation in order to match aesthetic and mechanical requirements.
The reduction of the vestibular face is done in two directions: one is parallel to the axis of insertion, the other parallel to the incisal 2/3 of the tooth (A).
If the reduction of the vestibular face is not done in two planes, the ceramic thickness is too thin. The opaque is visible at the incisal edge of the preparation. This is the case on this crown and for the left maxillary central incisor
The different types of single-unit restorations In fixed prosthesis
CCM on posterior tooth
Reduction features:
- Vestibular face: 1 to 1.2 mm.
- Lingual face: 0.5 to 1 mm.
- Proximal faces: 0.5 to 0.8 mm.
- Occlusal surface: 1.2 to 1.5 mm
necessarily homothetic to the original anatomy
A low coronal height leads the practitioner to make occlusal contacts on the metal, without interposing ceramic, in order to limit coronal reduction during preparation. Bruxism could constitute a contraindication:
the choice of cast metal crowns on the posterior teeth is sometimes preferable
Vestibular inlay crown
It is identical to the metal crown except that a vestibular recess of 1 to 1.2 mm must be created to accommodate the aesthetic material.
The different types of single-unit restorations In fixed prosthesis
- Reduction features
Crown jacket Ceramic-ceramic crown
Restoration of the natural appearance of a smile cannot be conceived without the use of all-ceramic systems” John MacLean 1975.
Directions:
- Very high aesthetic requirements;
- Pulped tooth with shallow overbite;
- Absence of parafunctions;
- Single element or small span bridge;
Young tooth, large pulp volume
Materials used:
- Reinforced feldspathic ceramics injected under high pressure.
- Sintered then infiltrated aluminous ceramics.
- High density pure polycrystalline ceramics, zirconium dioxide also called zirconia is the most advanced in the field of fracture resistance.
The different types of single-unit restorations In fixed prosthesis
Jacket crown on anterior tooth
- Reduction features:
- Vestibular face: 0.7 to 1mm.
- Lingual face: 0.8 to 1.2mm
- Proximal faces: 0.4 to 0.5mm
- The cervical limit is a shoulder
peripheral with rounded internal angle.
On a central incisor the vestibular and palatal shoulders: 0.8 to 1 mm. The width of the proximal shoulder is 0.5 mm.
Ceramic-ceramic crown on posterior tooth
Indicated on a pulped tooth in single restoration with significant aesthetic requirements.
Reduction feature:
- Vestibular face: at least 1 mm.
- Lingual face: 1 to 1.2 mm
- Proximal faces: 0.5 to 0.7 mm
- Occlusal surface: at least 1.5 mm
With chamfer on the external slope of
the support cusp.
- The cervical boundary is a shoulder with a rounded internal angle
The different types of single-unit restorations In fixed prosthesis
Conclusion
Making a fixed prosthesis is a delicate job
requiring multidisciplinary knowledge . The success of the
Long-term prosthesis begins with a clinical examination
in-depth.
We must never forget that a prosthesis is always a
added part, foreign to the masticatory system. It is this which must
adapt to the stomatognathic system by respecting the various
imperatives and not the other way around.
Good oral hygiene Regular scaling at the dentist Dental implant placement Dental x-rays Teeth whitening A visit to the dentist The dentist uses local anesthesia to minimize pain