CERVICAL LIMITS

CERVICAL LIMITS

1. INTRODUCTION :

•  To meet all the conditions and respect the principles of anchorage preparation, it is of prime importance to know and master the different types of relationships between the cervical end of the reconstruction and that of the preparation on one side, and on the other side their relationship with the superficial periodontium.    

2. ANATOMICAL REMINDER OF THE BIOLOGICAL SPACE: 

– Any injury caused by rotating instruments or by reconstitution after delivery may damage the integrity of the biological space.

3. DEFINITION OF THE CERVICAL LIMIT:

•  It is a finishing line separating the prepared tissues (a) 

and the unprepared (b) still nearby 

gingival contours. Or even the place where it should 

stop preparing outline shapes 

means of anchoring prostheses.

4. ROLES OF THE CERVICAL LIMIT: 
   1. Ensured a perfect junction of reconstruction and the unprepared part. 
   2. Ensures a watertight seal by preventing the dissolution of the sealing cement.
   3. Provides strength to the reconstruction due to the thickness of the metal by supporting the forces of mastication.
   4. Allows better visibility and readability of the peripheral contour of the preparation both in the clinic and in the lab.

5. CLASSIFICATION OF CERVICAL LIMITS:
6. Depending on the situation: it can be supra-gingival or supra-gingival , juxta-gingival and sub-gingival, according to several criteria: 

– Aesthetic considerations: position of teeth, age of the patient.

– Biological considerations: Periodontal health, levels of patient motivation.

– Biomechanical considerations: tooth anatomy (crown height and width)

1. Supra or supragingival limit: It does not present any contact with the marginal periodontium, located above the gingival margin, at a distance of 1 mm.

-Indications: Posterior teeth , sufficient crown height , good hygiene 

buccal

-Advantage: reduced risk of gingival irritation , good visibility , easy adjustment  

and finishing, Economy of dental tissue , Accessibility to cleaning.

-Contraindications: Smile teeth, Insufficient crown height, poor oral hygiene.

-Disadvantages: Risk of caries due to exposure of the dento-prosthetic joint , unaesthetic

2. Juxta-gingival cervical limit: this limit is at the same level as the marginal edge of the gum, without exceeding it apically; it presents almost the same parameters as the previous one, apart from its probable influence on the anterior teeth which can become a disadvantage over time with the passage to the supragingival situation due to the passive eruption of the teeth.
3. Subgingival or intra-sulcular limit: The finishing line is located in the sulcus, The cervical edge of the preparation is not in direct contact with the oral environment, This limit should not exceed half the depth of the sulcus, and should respect the biological space.

-Indications: All teeth may be affected, particularly anterior teeth , Insufficient coronal height, Healthy and stabilized periodontium.

– Advantages: preserves aesthetics , improves retention by increasing contact surface , prophylactic limit.

– Disadvantages: Delicate execution , risk of damage to the superficial  periodontium ,

difficulty in finishing and polishing the joint.

– Contraindications: Thin marginal gingiva , prosthesis stuck due to fluid

 gingival, haemostasis disorder and major haemorrhagic risk.

2. According to the shape : There are several types of finishing lines chosen according to several criteria:

– Better quality of the denture joint .

– Anchor type  

– Infrastructure, whether metallic or cosmetic material

– Possibility of better registration when imprinting 

– Better flowability of the metal

1. Long bevel: or simple cervical limit (A, B) made with a conical burr.
   1. Advantage  : Better Advantages: Less mutilating preparation, Ease of execution, Better sealing
   2. Disadvantage: fragility of the edge of the reconstruction at the cervical level, does not allow the use of cosmetic material, difficulty of visibility in the mouth , difficulty of reading on the MPU illegible on the model, possibility of over-contouring of the reconstruction
   3. Indication: case of cast crown (metal), on the lingual faces of cuspid teeth
2. Shoulder: the cervical limit is a sidewalk delimiting the preparation, made with a flat-ended conical bur.
   1. Disadvantages  : significant tissue mutilation , poor flowability of the metal, poor flow of the cement thus giving a poor dento-prosthetic joint thus giving insufficient coverage of the shoulder surfaces.
   2. Advantage: ease of reading in the mouth and on the unitary positive model ”MPU”, Resistance of the prosthetic edges
   3. Indication: Ceramic crown , vestibular inlay crown ”CIV”, metal-ceramic crown ”CCM”

-Chamfered       shoulder  : the chamfer is a bevel made on     

 the shoulder, thus giving a sharp prosthetic edge, Good dento-prosthetic seal, good flow of cement

    -Rounded internal angle shoulder: improved flowability,            

                                              It is obtained with a tungsten carbide finishing cutter.

                                           – Chamfered shoulder with rounded internal angle

3. The leave: cervical limit in a ¼ circle made with a round-end preparation bur

1. Advantages: Less mutilating limit , better distribution of constraints , Readable , resistance of the infrastructure, better flow of cement , better flowability of the metal
2. Indications: metal crown, crown with vestibular inlay 

6. CERVICAL LIMITS ACCESS PROCESSES: this is the set of techniques, equipment and materials allowing gingival clearance in order to facilitate the preparation of cervical limits and their recording. 
   1. Mechanical processes  : These processes act by releasing the gingival contour by means which can be:
      1. Ring collar: or resin coping which is used for taking impressions
      2. Dry cords: made of silk or cotton, they come in several shapes and diameters, inserted into the gingival sulcus using a special spatula allowing a temporary deflection of the gum. The choice between the single cord or double cord technique depends on the clinical situation and the patient’s periodontium.
      3. Temporary prosthesis.
   2. chemical processes:
      1. The Expasyl concept: involves the use of a paste, based on kaolin containing aluminum chloride, a process consisting of injecting the paste into the sulcus using a syringe and then rinsing after setting.
      2. Soaked cords  : Consists of placing in the sulcus a cord impregnated with a chemical solution that is astringent (aluminum chloride or alum), hemostatic (ferric sulfate), vasoconstrictive (adrenaline) or caustic (sulfuric acid) allowing: to control the hemorrhage , and limit the time the cord is in place.
   3. Surgical procedures: With electric scalpels under local anesthesia (healing occurs after 10 to 15 days) or during rotary curettage.
7. CONCLUSION 

A good indication of each type of LC according to clinical data requires a good mastery of different LCs, and supports the success of prosthetic restorations. 

CERVICAL LIMITS

                                                     BIBLIOGRAPHY: 

1. EXBRAYAT Fixed Dental Prosthesis Manual
2. Fundamental bases in fixed prosthesis
3. Book fixed prosthesis and periodontium FRANCOIS UNGER

CERVICAL LIMITS

  Sensitive teeth react to hot, cold or sweet.
Sensitive teeth react to hot, cold or sweet.
Ceramic crowns perfectly imitate the appearance of natural teeth.
Regular dental care reduces the risk of serious problems.
Impacted teeth can cause pain and require intervention.
Antiseptic mouthwashes help reduce plaque.
Fractured teeth can be repaired with modern techniques.
A balanced diet promotes healthy teeth and gums.
 

CERVICAL LIMITS