Fixed prosthesis and periodontium
Introduction
1. Reminder
- The periodontium
- The gingivo-dental groove
- The biological space
- Emergence profile
2. Pre-prosthetic periodontal diagnosis
Before moving on to prosthetic rehabilitation, it is necessary to assess:
- Periodontal health
- The height and thickness of keratinized tissue
- The biological space
2.1 Clinical examination in joint prosthesis: Aims to assess:
- The patient’s level of dental hygiene.
- The severity of periodontal disease.
- Tooth integrity and quality of endodontic care.
- Functional integrity of the masticatory system
The parameters to consider during this examination are:
- The presence of plaque or other deposits.
- Absence or presence of: gingival inflammation – Periodontal pockets – Interradicular alveolysis – dental mobility.
- Functionally, the pathological signs of possible dysfunction of the masticatory system are: Facet wear of the teeth – joint cracking – Pain when opening the mouth – Muscle spasm.
2.2 Review of models:
- The occlusion is analyzed to decide whether the prosthesis can fit into the existing occlusal pattern or to make corrections if necessary.
- If a fixed prosthesis is designed on an occlusal imbalance that has not been resolved beforehand, this imbalance will be aggravated, hence the need for a pre-prosthetic occlusal analysis.
2.3 Radiological examination : to confirm what the clinic was able to detect.
- The condition of the deep periodontium and the contour of the mucosal tissues.
- The appearance of bone trabeculation.
- The shape, depth and direction of the roots.
- The crown to root ratio.
- Caries damage and the quality of endodontic treatments.
- Presence of residual roots or cyst.
3. Evaluation of the pre-prosthetic periodontal state
- After a thorough periodontal examination, two clinical situations can be encountered:
3.1 Diseased periodontium
- If the clinical examination reveals periodontal disease: no prosthetic reconstruction should be considered before periodontal treatment for the following reasons:
- Reduces the longevity of teeth and prostheses.
- Tooth mobility hinders chewing and retention of prostheses.
- Inflammation and degeneration of the periodontium can prevent abutment teeth from coping with the functional demands of prosthetics.
- Dentures built on models taken from diseased gums will not fit properly after periodontal treatment, which will leave spaces under the pontics (plaque buildup and inflammation).
- An adequate periodontal treatment plan with a clinical radiological evaluation session is necessary before determining the indication or contraindication of a fixed prosthetic restoration.
Fixed prosthesis and periodontium
3.2 Healthy periodontium
- Even if the periodontium is healthy, there may be defects that prevent a satisfactory prosthetic result from being obtained and that must be restored before the fixed prosthesis is placed.
- These corrections can be summarized as:
- Coronary elongation.
- Frenulumectomy.
- Recession recovery.
- Augmentation of attached gingiva.
- Alignment of the gingival scallop.
- Treatment of edentulous ridges by addition or subtraction of tissues.
4. Influence of periodontal status on prosthetic treatment
- Any prosthetic treatment is conditioned by the disappearance of signs of inflammation. A healing period of at least 12 weeks before any prosthetic restoration in order to guarantee durability.
5. Impact of the creation of the joint prosthesis on the periodontium:
1. When performing dental preparation:
- Generates a great many attacks on the pulp and periodontal tissues of the supporting teeth linked to both the instrumentation and the materials used.
- The attacks that biological structures may face at this stage are mechanical, bacterial and chemical.
- The delicate maintenance of the biological space requires that the prosthetic edges be at least 0.4 mm from the bottom of the sulcus (safety zone) and 2 to 2.5 mm from the bony crest.
- Indeed, any intra-sulcular preparation carries an effective periodontal risk, particularly if the preparation or an accidental slippage of the bur reaches the cementum (Sharpey fibers).
- This traumatic gesture results in the appearance of inflammatory periodontal lesions resulting in deep bone resorption, or the formation of marginal tissue recessions, depending on whether the periodontium is thin or thick.
- Precautions to take
- Avoid intrasulcular LC as much as possible. However, the aesthetic demand and mechanical requirements require their indication.
- The distance between the intended prosthetic limit and the bone crest must be assessed clinically using a probe and an X-ray.
- Regular, precise and sufficiently wide LC to accommodate the different materials of the prosthetic element; over-contours, which are detrimental to periodontal health, are thus avoided.
- Access to the LC : The cord allows the practitioner to create a limit at a regular distance from the bottom of the gingival sulcus, and constitutes a depth gauge for locating the LC, without interference with the biological space.
- Magne and Belser , for their part, recommend the use of oscillating instruments. Due to their non-rotating action and their non-working guide surface, oscillating insert tips allow for rapid minimal preparations; the precision of the limit is significantly better, without risk to the adjacent tooth and without damage to the soft tissues when creating intra-sulcular limits.
Fixed prosthesis and periodontium
2. When developing temporary prostheses:
- Although temporary prostheses provide a protective role for dental tissues, both mechanically and physically (thermal shocks) or chemically and biologically, they can nevertheless be the cause of attacks on pulp and periodontal tissues, due to the nature of the materials they are made of and their setting reaction.
- According to histological studies by Dragoo and Williams, clinical inflammation of the marginal gingiva around temporary crowns is observed after 4 weeks.
- Thermal aggression : This is due to the exothermic reaction of polymerization of the resins which can cause burn lesions of the mucous membranes.
- Chemical aggression : Manifestations of intolerance at the level of the mucous membranes are rare
- Bacterial aggression : linked to poor surface condition or imprecise cervical adjustment should be investigated first.
- Mechanical aggression : A temporary prosthesis not integrated into the occlusal context (overload in the guides, prematurity, etc.) can cause pulp reactions and most frequently desmodontal reactions, in the same way as poorly adjusted fillings in occlusion and during functional mandibular movements.
Fixed prosthesis and periodontium
Precautions to take
- Respect for Morphology : the creation of proximal contacts and embrasures, the shapes of axial contours.
- Surface condition : The prosthetic element must be polished and have a smooth surface condition.
- Cervical adaptation : check for overextension, overhang, withdrawal or hiatus
- Occlusion : respect for occlusal morphology and the occlusal schema
5.3 When taking the print:
- It is divided into 2 phases: on the one hand, access to the cervical limits, using deflection or gingival eviction methods; on the other hand, insertion of the material.
5.3.1 Aggression Related to methods of access to cervical limits:
- The objective is the precise recording of the emergence profile (According to Armand the impression material must invest the 0.2-0.3 mm of unprepared tissue, located apically to the preparation limit).
- This requires, particularly in the case of an intra-sulcular limit, a prior opening of the gingival sulcus of at least 0.2 mm, which can be achieved using gingival deflection methods (soaked or unsoaked cords – Expasyl®, etc.) or gingival eviction (electrosurgery, rotary curettage, laser). The choice between the various techniques is subject to various clinical parameters, including the depth of the sulcus and the type of healthy periodontium encountered (thick and more resistant or thin and fragile). Each of these methods is likely to present, to a greater or lesser extent, a pathogenic risk for the supporting tissues of the tooth.
Deflection by cord(s):
- The diameter of the inserted wire should be a function of the depth of the sulcus and the thickness of the marginal gingiva.
- Insertion of a single cord may pose a risk of epithelial attachment injury and bleeding upon removal.
- The double cord deflection technique (initially, and before clinical preparation, insert a small diameter, non-impregnated cord at the bottom of the sulcus, ensuring apical deflection of the gingiva. Then, in a second step, once the dental preparation has been carried out and before taking the impression, a second, larger diameter, impregnated cord is inserted to ensure horizontal deflection of the marginal gingiva), for its part, appears to be one of the least traumatic methods for the soft tissues.
Tissue removal by electrosurgery:
- This method remains, by its nature, traumatic for the soft tissues. Indeed, according to Blanchard and a, the observation under a scanning electron microscope of a sulcus (healthy periodontium) after electro-section confirms a deep attack on the sulcular epithelium and the connective tissue in different areas.
- Contact with a metal surface (metal filling, inlay core, etc.) can cause burns and pulp pain.
5.3.2 Related to the nature of the imprint material:
- Thermal aggression
- Mechanical aggression: lesions can be induced by the retention of small particles of silicone or alginate in the gingival sulcus.
- Chemical aggression: It depends on the type of material used.
- Irreversible hydrocolloids: It is generally accepted that alginates do not have any adverse biological effects. This is due, in particular, to the fact that the contact time with the tissues remains relatively short. However, if debris of material stagnates in the gingival-dental sulcus, an inflammatory reaction may occur.
- Elastomers: for this material, a contact time corresponding to the duration of an imprint (even repeated) does not induce significant irritation, however care must be taken to remove any excess that may be retained in the sulcus.
- Grégoire and Guyonnet, for their part, consider that the components of the accelerators contained in silicone elastomers (polyvinyls, polysiloxanes) are irritants and allergens which should not come into direct contact with skin tissues and mucous membranes, particularly in the case of insufficiently mixed and non-homogeneous mixtures.
Fixed prosthesis and periodontium
Precautions to take
- Access to LC : The Expasyl system and the double cord technique appear to present the greatest safety with regard to periodontal tissues
- Compliance with the implementation protocol
- Choice of impression technique (compressive, etc.)
5.4 When assembling the fixed prosthesis and the dental preparation:
- Delicate step whose objective is to obtain a joint as thin as possible, with elimination of cement debris at the SGD level.
- For Bonding: the cervical limit must be supragingival with the use of the dam.
- The attacks which can then be generated are largely a function of the nature of the biomaterial used; the assembly itself constitutes a maneuver which is detrimental to biological structures.
- Mechanical aggression : results from the retention of material debris in the gingival sulcus after setting. The resulting mechanical irritation then leads to an inflammatory reaction.
- Thermal aggression : linked to the exothermic setting reaction of zinc phosphate cements.
- Bacterial aggression : Dissolution of the cement seal is accompanied by an increase in plaque retention at this level, responsible for tissue inflammation.
- Chemical aggression : according to Bœver et al, the immediate toxic effect, as opposed to the delayed toxic effect of these materials which is linked to the degradation of the cement joint over time and responsible for the release of possible harmful products.
Zinc phosphate cements
- The acidity and exothermicity of the setting reaction are responsible for an antigenic reaction involving macrophages. The degradation of the cement joint then induces a chronic reaction of a slightly inflammatory nature.
- However, the release of zinc ions would be rather beneficial for the tissues.
Glass ionomer cements
- The biocompatibility of these cements varies depending on the nature of the product, ranging from an absence of significant cytomorphological changes in gingival fibroblast cultures to complete cell death.
- Furthermore, the cytotoxic reaction of expired glass ionomers is much stronger than fresh products, this being probably related to a very incomplete conversion in vivo.
- Nevertheless, all glass ionomers appear to be well tolerated by tissues.
Glues
- The toxic effect of these elements (observed during in vitro studies) is almost non-existent in vivo if the requirements specific to this type of material are respected : supra-gingival preparation – use of the dam.
Fixed prosthesis and periodontium
Precautions to take
- The thermal and chemical aggressions of zinc phosphate cements are limited by the rules for implementing this material .
- Whatever the cement used, the placement of a very small diameter cord in the sulcus before sealing prevents the material from flowing into the depth of this groove, the excess is thus easily deposited, and mechanical irritation due to the retention of material debris is non-existent.
Conclusion
Fixed prosthesis and periodontium
Deep cavities may require root canal treatment.
Interdental brushes effectively clean between teeth.
Misaligned teeth can cause chewing problems.
Untreated dental infections can spread to other parts of the body.
Whitening trays are used for gradual results.
Cracked teeth can be repaired with composite resins.
Proper hydration helps maintain a healthy mouth.