Review of literature: Orban F et al. (Dimensions and Relations of the Dentogingival Junction in Humans. J. Periodontol (1961 32:261)) In their study measured dimensions of tissues involved in Biological Width considerations. Used histologic sections to measure average dimensions of biologic width. These are not clinically accurate due to distortion with histologic processing. This study said width of junctional epithelium plus connective tissue width was Biologic width; i.e.approximately 2 mm. If a subgingival crown margin is placed in the middle of the gingival sulcus, the crest of bone should be a minimum of 2 mm apically positioned. mean depth of the histologic sulcus is 0.69 mm,mean junctional epithelium measures 0.97 mm (0.71 to 1.35 mm),mean supraalveolar connective tissue attachment is 1.07 mm (1.06 to 1.08 mm).The total of the attachment is therefore 2.04 millimeters (1.77 to 2.43 mm) and is called the biologic width.
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Review of literature:
Orban F et al. (Dimensions and Relations of the Dentogingival Junction in
Humans. J. Periodontol (1961 32:261))
In their study measured dimensions of tissues involved in Biological Width
considerations. Used histologic sections to measure average dimensions of
biologic width. These are not clinically accurate due to distortion with
histologic processing. This study said width of junctional epithelium plus
connective tissue width was Biologic width; i.e.approximately 2 mm. If a
subgingival crown margin is placed in the middle of the gingival sulcus, the
crest of bone should be a minimum of 2 mm apically positioned. mean depth
of the histologic sulcus is 0.69 mm,mean junctional epithelium measures 0.97
mm (0.71 to 1.35 mm),mean supraalveolar connective tissue attachment is
1.07 mm (1.06 to 1.08 mm).The total of the attachment is therefore 2.04
millimeters (1.77 to 2.43 mm) and is called the biologic width.
James s Marcum et al, J Prosthet Dent. 1967 May;17:479-487
studied the effect of crown marginal depth upon gingival tissue.,
Sixty six crowns were placed and finished above, below, and even with the
gingival crest in 6 dogs. the crowns were left in place until the dogs were put to
death at time intervals of one ,two, and three months. two dogs were sacrificed
at each interval, block specimens of the teeth and gingiva were taken at this
time. Control specimens of unoperated teeth were also taken. The block
specimens were decalcified,sectioned,stained,histologically examined,and
graded for severity of inflammatory response.six hundred histological slides of
the tissue sections were graded as having evidence of none,slight,moderate or
severe gingival inflammation.
The investigation showed that crowns with margins located at or even with the
gingival crest caused the least inflammatory response; that crowns with margins
located above and below the crest cause the most severe inflammatory response.
The length of time a restoration was in place had little if any effect upon the
severity or degree of inflammation.
Choosing the proper crown marginal depth depends upon many factors.however
it appears from the results of this investigation that crowns with the gingival
crest would be least likely to cause gingival inflammation.
Yuodelis et al,
J Prosthet Dent. 1973 jan;29:61-6
Studied about the esthetics and hygiene in crowns given after periodontal
therapy that involves osseous resection procedures or following gingival
recession,we are often confronted with longer than normal clinical
crowns.these lengthened clinical crowns are much more difficult to keep
plaque free due to the exposed furcations and root flutings. If plaque is
allowed to accumulate for long periods of time ,demineralization of the
cemental surfaces will rapidly cause increased sensitivity and root caries. If
root portions must be covered by complete artificial crowns ,the gold castings
should not frustrate the oral hygiene efforts of patients.
The final restoration should not follow the original anatomic crown and should
recreate the original contours of the root portion.the modification of the
anatomic coronal form entails reduction of unnecessary bulges in order to
create additional accessibility to gingival third of the fluted and furcation
regions.this will eliminate the triangular region that is created by the roots and
cervical bulge and which is the area most difficult to maintain in a plaque-free
condition by normal brushing.for this reason we endeavour to flatten the facial
and lingual contours of restorations and have observed excellent gingival
response.most probably the cervical region is made more accessible for
routine home care.
D. Tarnow et al( Journal of Clinical Periodontology Volume 13, Issue 6, pages
563–569, July 1986)
Studied Human gingival attachment responses to subgingival crown placement
and marginal gingival remodelling.
13 teeth in block were extracted from 2 patients. Their facial periodontal
condition was essentially within normal clinical limits. Temporary crowns
covering the bevel were placed below the base of the crevice 1 to 8 weeks prior
to extraction. At time of extraction, all blocks were decalcified, the temporary
crown dissolved, and the blocks prepared for histologic examinations using
bucco-lingual cut, step serial sections.
Histologic data revealed reformation of a new supracrestal attachment unit
within 1 week following crown placement. The reformation of the gingival unit
consisted of marginal recession with apical and lateral migration of the
junctional epithelium to the level of remaining cementum inserted fibers. With
gingival recession and migration of junctional epithelium, resorption of crestal
portions of the facial plate occurred. However, periodontal fibers anchored into
cementum opposite the resorbed bone were not lysed. Rather, the attached
fibrillar ends appeared to interdigitate with fibers from the corium of the facial
gingiva at this site, thereby forming a more apically located crestal attachment.
This response may be one mechanism of reformation of the gingival attachment
unit taking place following mechanical and/or surgical injury to this site and is
completed often, within 2 weeks after injury.
Geoffrion J.et al 1989.
[Transformation of a lateral incisor to a central incisor with a ceramometal
crown].
They gave guidelines to change a maxillary lateral incisor into a central incisor
by using a ceramo-metallic crown. It is required to schedule a rational plan of
treatment. All the different pre-prosthetic (orthodontic, periodontic, and
endodontic) and prosthetic steps are described and justified. In order to
achieve a compromise between esthetic and a stable periodontium the mesial
profile of emergence of the ceramic should be conceived to prevent any
overcontour.
Croll BM.et al
(J Prosthet Dent. 1990 Apr;63(4):374-9.)
In their study showed that Selection of the straight emergence profile in
designing artificial crowns for teeth has been shown to improve the
effectiveness of oral hygiene near the gingival sulcus. The axial profile of teeth
can be viewed as a series of straight lines with curved transitions.
Reproduction of these geometric patterns facilitates fabrication of restorations
that appear natural.
Ferencz JL.
(J Prosthet Dent. 1991 May;65(5):650-7.)
Reviewed about Maintaining and enhancing gingival architecture in fixed
prosthodontics.
The long-term success of fixed prosthodontic restorations is greatly dependent
upon the health and stability of the surrounding periodontal structures. This
article deals with the interrelationship between fixed prosthodontic
procedures and the stability and health of the periodontium. The commonly
encountered problem of alterations in gingival architecture is examined in
relation to tooth preparation as well as soft tissue preparation. In addition, the
ability of the provisional restoration to guide soft tissue form is discussed as
well as the role of the final restoration in providing long-term tissue
maintenance. Key factors such as margin placement, tissue damage during
tooth preparation, the role of the provisional restoration, tissue injury during
impression procedures, crown contour, pontic design, and embrasure design
are all important factors to be considered to achieve a good emergence profile.
Donald F. Reikie et al (J Prosthet Dent 1993;70:433-7)
Did a review of esthetic and functional considerations for the partially
edentulous implant candidate. Stated that with the availability of adjunctive
grafting procedures, it is time for the implant team to change the traditional
treatment planning approach that allows patient anatomy to dictate implant
position and prosthesis design. Dimensions of the edentulous space and
evaluation of occlusal relationships are discussed by the author. Soft tissue
ridge contour and creation of favorable cervical harmony are also reviewed.
Functional demands unique to the partially edentulous patient are outlined in
addition to the challenges of creating a prosthesis with natural cervical form
and emergence profile.
David Neale et al (J Prosthet Dent 1994;71:364-8)
Describes a technique to help predict, develop, and evaluate implant
prostheses and their soft tissue contours at the provisional restoration stage.
This technique records the planned and subsequently proven contours, which
are then used to guide fabrication of the final prosthesis and produce a