biologic width & emergence profile
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INTRODUCTIONTo maintain or enhance the patients esthetic appearance, the tooth/tissue interface must present a healthy natural appearance with gingival tissue framing the restored teeth in a harmonious manner.
Consideration regarding periodontal restorative interrelationship
BIOLOGIC CONSIDERATIONMARGIN PLACEMENT & BIOLOGIC WIDTH
IT IS THE DISTANCE BETWEEN GINGIVAL MARGIN AND THE BASE OF THE POCKET.
There are 3 options:-
Sub gingival position
Restorative consideration frequently dictate the placement of restoration margins beneath the gingival tissue crest. Restoration may need to be extend gingivally To create adequate resistance and retentive form in the perpotion. To make significant contour alterations because of caries and other tooth deficiency. To mask the tooth/restoration interface by locating it subgingivally.
margin is too far from crest bone loss Tissue Recession In deep margin placement bone level appears to remain unchanged. but gingival inflammation develops and persist.
Evaluation of Biologic WidthRadiographic ally interpretation can identify interproximal violation of biologic width. But more common location is mesio-fascial & distofascial line angle of teeth which cannot be diagnosed because of superimposition. An other method for accessing the width clinically by measuring the distance between bone and restoration margin using a periodontal probe. The anaesthetized attachment tissue from the sulcus to underlying bone
The biologic width or attached width can be identified for each individual patient by probing under anesthesia to the bone level and then subtracting the sulcus depth from the resulting measurement . This measurement must be performed on teeth with healthy gingival tissue and should be repeated on one or more teeth to ensure an accurate assessment. Such information is then used to definitively diagnose biologic width violation, the extent of correction needed and the parameters for placement of future restoration.
Correction of Biologic Width
Biologic width violation can be corrected either :-
surgically orthodontic ally
Crown lengthening procedure
It is done to achieve an effective increase in crown length by gingivectomy or by removal of gingiva by electosurgery. There is also osseous recountouring is most often needed to prevent encroachment of the prosthesis on biologic width For this procedure full thickness flap is reflected and the osseous resection creates 3.5-4.0mm between gingival crest and the margin of the existing restoration or carious lesion.
There are some factors which should be considered during the procedure
Estheticwhen surgically crown lengthening procedure is indicated it may be difficult to achieve a harmonious transition from the tissue around the lengthened tooth to that around adjacent teeth. if surgery is under taken most of osseous reduction should be on the lingual or palatal side where there is usually no esthetic problem with blending on the labial or buccal side only as necessary
Root length within bone-if there is limited osseous support it may better to remove the tooth and replace it with prosthesis than to have the patient undergo surgery on a tooth with a doubtful prognosis . Effect on adjacent teeth often a fracture or defect on such depth cannot be eliminated without severely endangering the adjacent teeth
Root furcation espouser in a posterior teeth-in this situation cannot be remedied by osteoplasty and /or odontoplasty. the tooth may require removal.
Mobility-post surgical mobility of a tooth with small or conical root is a valid concern. if such tooth cannot support it self or cannot be supported by the adjacent teeth, removal may be necessary.
Extent of the defect-the severity and complication of any fracture, root caries or cervical wear must be carefully evaluated during the treatment planning phase.
Root perforation-this is uncommon but if it occur during endodontic therapy its location determines whether to remove the tooth Orthodontically extruded or lengthen the root surgically
Thickness of soft tissue in some instance thick gingival tissue may effect a regrowth of tissue in a coronal direction .an increased removal of osseous support may be needed at the time of crown lengthening surgery to regret this potential problem
When all tooth structure has been lost to the level of the alveolar crest or beyond , because of either fracture or caries, the tooth cannot be satisfactorily resorted without some extraordinary measure. Even if dowel core is placed in the tooth ,the root will remain susceptible to fracture with out crown encircling the tooth apical to the core. This ferrule effect around the tooth protect it from fracture by the dowel from within. If tooth structure is lost only to the level of the epithelial attachment, minor extrusion may be desirable to permit access to enough tooth structure apical to the finish line to produce a ferrule effect. Orthodontic extrusion has been used to move
brackets has been described for this purpose
there are some disadvantages :Bulky and unaesthetic. Difficult to place apically. Unwanted movement of the abutment. High degree of patient compliance.
Margin placement guideline The
first is using sulcus in depth as a guide in margin placement is to manage gingival health Then following 3 rules can be used to place intracreviular margins:RULE I:if the sulcus probe 1.5mm or less, place the margin 0.5mm below the gingival tissue crest.
RULE II: If sulcus probe more than 1.5mm, place the margin half the depth of the sulcus below the tissue crest. RULEIII: If a sulcus grater than 2mm is found especially fascial aspect of the tooth ,evaluate to see if a gingivectomy could be performed to lengthen the tooth and creates a 1.5mm sulcus. Then patient is treated using rule 1.
Provisional RestorationThree critical areas must be managed to produce favorable biologic response to provisional restorationMarginal fit Contour Surface finish of the interim restorations must be appropriate to maintain the health and position of the gingival tissues during the time interval until the final restoration are delivered
Poorly adapted restoration at the margins, are over or under contoured and have rough or porous surface can cause inflammation ,overgrowth or recession of gingival tissues
Marginal FitMarginal fit has been implicated in producing an inflammatory response in the periodontium .It has been seen that level of gingival inflammation can increase, corresponding with the level of marginal opening. Open margins are capable of harboring large number of bacteria and may be responsible for
Crown contour Restoration
contour has been described as extremely important to maintenance periodontal health. Ideal contour provides access for hygiene and has the fullness to create the desired gingival form and a pleasing visual tooth contour in esthetic areas Most frequent cause is inadequate tooth preparation. In areas where esthetic are not critical, a flatter contour is always acceptable.
Sub gingival DebrisLeaving debris below the tissue during restorative procedure can create an adverse periodontal response. Cause can be :Retraction cord Impression material Provisional material Temporary or permanent restoration
Hypersensitivity to dental materialInflammatory response have been reported related to the use of nonprecious alloy in the dental restoration. The response have occurred to alloys containing nickel. More importantly tissue respond more to the differences in the surface roughness of the material rather than composition of material.
Rougher the surface of the restoration subgingivally, the grater are the plaque accumulation and gingival inflammation.
In clinical research, porcelain, highly polished gold, and highly polished resin
The part of the axial contour that extends from the base of the gingival sulcus past the free gingiva has been described as the emergence profile. Given by STEIN & KUWATA. It extends to the height of contour producing a straight profile in the, gingival third of the axial surface. Production of a straight profile should be a treatment objective in restoring a tooth, because it facilitates access for oral hygiene measures
Straight profile is easily evaluated with a periodontal probe. The most common error relating to axial contour is the creation of a bulge or excessive convexity. According to PARKINSON:FACIOLINUAL WIDTH METAL CERAMIC CROWNS >0.71mm FULL GOLD CROWN 0.36mm If over contoured restoration with large convexity causes accumulation of food debris and plaque, and which causes gingival inflammation.