Framing the teeth, within the confines of the gingival architecture, has a tremendous impact on the aesthetics of the smile. A gummy smile is as unaesthetic as a patient with severe recession. The impact on the beauty of a smile from an uneven gingival contour height can be dramatic and although the position of the zenith of the gingival tissue seems like a small detail, it can greatly influence the axial inclination and emergence profile of the teeth. These factors, some major and some minor all add up to determine how pleasing the smile will be. It is our responsibility to understand the ramifications of these details and how they impact on the smiles we create.
The concept of periodontal health has been a mainstay in restorative dentistry long before cosmetic dentistry had become defined to the levels we know today. These concepts of healthy tissue still hold true today, however the scope of these concepts has been expanded along with our knowledge.
Not only must we be concerned with the overall health of the tissue, but the concept of the aesthetics of the tissue as well. We must concern ourselves with the various factors of gingival architecture and understand how these and other factors so critically affect the overall aesthetic result of our restorative efforts.
When considering tissue health, we must understand how the margin placement and fit, the provisional restorations, the contours and the tooth preparations will affect the ultimate tissue health and position. Watchwords like “Biological width,” “Ovate Pontics” and concepts of “crestal bone to contact point distance” guide our preparation and design so we are able to achieve the desired aesthetic tissue results.
SMILE DESIGN
“Smile design” is the architectural blueprint we as Cosmetic Dentists use to plan the smile we are about to create. This list of factors (Table 1) which are desirable to achieve a healthy and aesthetic smile must be applied to each patient in order to achieve the highest predictability of an aesthetic result.
The list of gingival considerations are of equal importance with the other set of factors on this list of smile design characteristics. Often ignored, these gingival factors will definitively affect the aesthetic outcome of every case.
AESTHETIC GINGIVAL SMILE DESIGN
“You don’t know what you don’t know.” Unless we know what constitutes a beautiful smile we will be unable to achieve it. Learning the ideal design features (Table 2) and how our treatment is influenced by, and influences these parameters, will enable us to raise the level of care we can give our patients. It’s time to achieve the results that will become the new standard of care by raising the bar.
I) GINGIVAL HEIGHT OF CONTOUR (GHOC)
Undoubtedly the easiest way to create a more aesthetic smile is to adhere to the smile design principle of the GHOC. Figure 1 shows the ideal relationship of the GHOC A straight line, level with the horizontal plane (sometimes the interpupillary line if level) will join the gingival margin of the centrals and cuspids, this line will be harmonious with the upper lip which should just cover 1mm of the margin during full smile. This ranges from 2mm to -2mm. The gingival margin of the lateral incisor can range from being on the GHOC line to 1mm below while maintaining an aesthetic result (Figs. 2 – 4).
Factors affecting GHOC:
1. Active and Passive Eruption:
During tooth eruption, the tooth actively erupts through the bone so that the CEJ is 2mm above the level of crestal bone. After eruption, the gingival complex will gradually recede to create a sulcus depth 1 to 2.5mm from the CEJ. This is called the passive eruption phase. This normal recession causes the gingiva to recede to the CEJ resulting in a sulcus depth, which ranges from 1 to 2.5mm. The additional 2mm from the gingival epithelial attachment to bone combined with the sulcus depth is referred to as the Biological width.1
If during the eruption phase there is a lack of movement, the result may be that the CEJ will remain partially covered by bone. In this case of delayed active eruption, the tooth will also be covered with excess gingival tissue. Sounding to bone will indicate a normal biological width and the sounding will not be able to detect the CEJ. In this case, crown lengthening with osseous recontouring will need to be undertaken.
If the tooth appears short, with excess gingival tissue, a long sulcus (Fig. 4), and sounding indicates the presence of the CEJ, then this is a case of delayed passive eruption. Simple sculpting away of the excess gingival tissue will result in a normal sized tooth and restoration of a more ideal GHOC.2
Other factors involve tooth position such as under eruption, over eruption, linguo and labioversion and rotations (Fig. 5). Most of these situations can best be treated orthodontically to properly position the tooth within the arch form. Trying to mask these situations with veneers will create difficulties at the gingival margin due to the emergence profile dictated by the malpositioned tooth.
2. Maxillary Incisal Edge position and tooth height:
When treatment planning any cosmetic or reconstruction case, the first step is the determination of the ideal maxillary incisal edge position. Following the determination of the ideal incisal edge position using the various factors involved (beyond the scope of this article alone) the desired tooth size, height and width will be determined according to the ideal formula of 78% H:W ratio. By measuring from the newly determined incisal edge position to the gingival margin, determine if excess gingival tissue must be added or removed to achieve the ideal tooth height or if the tissue is already in the correct position.3
II) GINGIVAL DISPLAY
The gummy smile is caused by excess gingival display. Where the GHOC generally refers to one or two teeth out of alignment within the aesthetic zone. Gingival excess or gummy smile generally refers to several teeth or the entire arch which shows a gingival excess.
A gummy smile can be classified as occurring when there is too much gingival display with short teeth, normal size teeth, or long teeth.
1a. Teeth short — teeth are worn (Fig. 6). It is likely that these teeth have now over-erupted. If the Crown to root ratio is favorable, crown lengthening procedures will be undertaken to lengthen the tooth reveal by doing a gum lift (gingivectomy). If the Crown to root ratio is unfavorable, orthodontic intrusion should be undertaken and then the incisal edge of the tooth lengthened to restore the tooth to proper height and placement of ideal incisal edge position.
1b. Teeth short — teeth not worn. Likely we are now dealing with a delayed passive or delayed active eruption. If sounding indicates the presence of CEJ and excess gingival tissue, then simple gingivectomy procedure will be indicated. If the sounding to bone is in the biological width and the CEJ is not probable, this is a case of delayed active eruption and crown lengthening with osseous recontouring is necessary.
2. Teeth normal height — in the situation where there is excess gingival display and the teeth are the correct height, there will be a problem with vertical maxillary excess and orthodontic intrusion or surgical correction is required.
3. Teeth are long — with excess gingival display. Orthodontic intrusion, surgery and mucogingival grafts may be required. This type of situation is often encountered in patients with extreme Class II malocclusions.4
III) GINGIVAL ZENITH
Directly related to the aesthetics of the smile is the position of the gingival zenith. (Figure 1 shows the proper placement of the gingival zenith.) The zenith of the central incisor should be at the distal third, the lateral incisor in the middle, and the cuspid can range from anterior third through to the distal third5 (Fig. 7). The position of the zenith will help create the desired axial inclination of the tooth by changing the line angle position of the long axis of the tooth (Fig. 8).
IV) RECESSION
Recession will negatively a
ffect the GHOC by falling above the ideal line of the GHOC. Numerous surgical methods are available to create grafts to cover these areas of recession. There are many factors which can result in recession other than periodontal disease (Fig. 9).
Iatrogenic Tissue Trauma
Tissue trauma, especially during tooth preparation and impression taking plays a large role in the recession which can occur post treatment, resulting in unsightly exposed margins.
Special care must be taken during tooth preparation to eliminate any tissue trauma. Supragingival margins can be the answer in some cases, however, careful consideration to case aesthetics and restorative materials, must be determined when deciding on margin placement.6
When tucking the margin subgingival, start by outlining the gingival margin at or slightly above the gingival margin using a very small round diamond bur. Gently reflecting the tissue away from the tooth surface with a special instrument called a Zekrya gingival retractor, (Pollard Dental Products, West Lake Village California) this instrument will allow the practitioner to create the subgingival margin without traumatizing the sulcular tissues. Carry the margin subgingivally using a narrow end cutting diamond. Once the prep is done, the tissue is released and gently falls back over the prepared margin.
Impressions
Impression taking must be done very gently.7 Packing cord with excess haemostatic agent will likely cause recession. Packing of cord is still recommended by some clinicians; however the use of Expasyl (Kerr Corp, Orange Ca.) especially in the anterior is much kinder to the tissues. If using cord, little or no haemostatic agent should be needed as any tissue trauma will be eliminated during the preparation technique. The cord must be placed very gently into the sulcus without disturbing the attachment. Instead of using a two cord technique, triple zero cord is placed first, and Expasyl can be applied over top. Placing this clay based material can be difficult. A “Goodlin number 1” instrument (the practitioner’s index finger) is used to gently putty the material around the preparation, and then using a disposable micro brush bent at a 45-90 degree angle, the expasyl is gently pushed into the sulcus. After 2 minutes, the expasyl is washed off with copious water, the prep is dried and the impression taken.
V) PAPILLA HEIGHT AND SYMMETRY
Papillary height of contour (PHOC)
The interproximal papillae should be symmetrical and level across the arch form (Fig. 1). Perhaps the most difficult area to achieve success and the easiest area in which to create an aesthetic disaster, the papillae should always be treated with the utmost care and precision during all phases of the treatment process.
Papilla height and position is dependant on several factors including the contact point position root approximation, and tooth form.
Interproximal contact point
In the case of the Papilla, the same rule applies, with an additional important concept. The height of the interproximal contact point must be 4.5mm from the height of the crestal bone8 (Fig. 10).
If the contact area is greater than 4.5mm from crestal bone, a black hole between the teeth will be the result (Fig. 11) as there is too much volume for the papilla bag to fill. Even if we were to squeeze the bag by adding porcelain to the emergence profile, if there is more than 4.5mm, the black hole will usually be the result.
If there is less than 4.5mm from the crest of bone to the contact, we will encroach on the biological width of the papilla setting up a chronic disease state resulting in a red bleeding swollen papilla.
If the papilla is traumatized during the restorative procedure or encroached upon with ill fitting or designed temporaries, the papilla will blunt resulting in the dreaded black hole (Fig. 12). If the contact area is now recontoured so that it falls within the recommended guidelines, chances are excellent that the papilla will bounce back and the black hole will eventually (2 – 8 months) fill back in.
For the purposes of lab communication, measure the interproximal distance from crown margin to crestal bone, for example let us assume that this measurement is 2.5mm. Subtract this number (2.5) from 4.5 and tell the lab they need to make the interproximal contact that distance (2.0mm) from the crown margin.
Root Angulation and approximation
Papilla height is greatly influenced by root angulation and tooth rotations. Think of the papilla as a fluid filled bag. If squeezed from the sides, the bag will expand lengthways. If the support is released, the bag will sag and become more round and blunted. Similarly with the papilla, If the roots are divergent apically, the volume between the roots will be increased. As the papilla bag cannot increase the volume and the support has been lost, the papilla will slump resulting in a black hole9 between the teeth (Fig. 13).
In the case when the roots are too close together the papilla should according to this theory expand up between the teeth. However, the impingement on the papilla can create strangulation of the papilla which again may result in chronic inflammation, or blunting of the papilla (Fig. 14).
In cosmetic situations where the papilla has slumped, by preparing the tooth well to the lingual the restored tooth can be bulked out from the lingual supporting the papilla and thus creating a fuller papilla labially.
The maintenance of papilla height will be greatly affected during tooth preparation. Care must be taken to avoid traumatizing the interproximal col during preparation. The placement of the interproximal margin below the level of the col will usually result in loss of papilla height.
VI) EMERGENCE PROFILE
Ideal tooth morphology indicates that the transition from crown to root will show a convexity in the crown contour, flowing gently into a straight or very slightly concave root form.10 Duplicating this morphology is critical in the development of the ideal papilla height and shape (Fig. 15).
Often the practitioner and lab technician will overbuild the mesial emergence profile (Fig. 16). The resulting impingement on the available volume for the papilla will result in a lost or blunted papilla and chronic gingivitis.
In clinical situations where there is a black hole, carefully measure the crestal bone to contact height. Make sure there is the ideal 4.5mm measurement and that the emergence profile follows biological principles. Leave the case in provisional restorations for 3-8 months and allow the papilla to grow back before finishing the case. Completing the case prematurely will not allow enough time for the papilla to regrow and overbuilding will be required to eliminate the black hole (Table 3).
VII) TISSUE HEALTH
Tissue health is measured by a series of ten separate parameters listed in Table 4. It is not sufficient to solely justify tissue health on periodontal pocket measurements. Many factors are involved in the tissue health and are listed in Table 5.
Review of Biological Factors
Understanding the underlying biological principles is essential to achieving the ultimate goal of tissue health and aesthetics (Table 5).
Many factors will affect the health of the tissues. Any of these can result in compromised tissue health and decreased overall aesthetics and case success (Table 4). Many of the factors listed in Table 5, have been addressed and understood by most practitioners for many years, however others deserve another look.
Oral Hygiene
Poor oral hygiene resulting in plaque accumulation has been well documented as a factor in the inflammatory process of gingival and periodontal disease (Fig. 17). We must be very careful however to not blame all the marginal gingivitis we see on hygiene issues. Several other factors such as encroachment of biological width, improper tooth form and margin placement and integrity will also result in sore, discoloured and inflamed gingival tissues. Careful determination of the cause of these symptoms must be undertaken in order to alleviate the problem.
Margin placement and integrity
In t
he case of a patient with an uneven gingival height of contour, (GHOC) it is very easy to take an electrosurg or laser and sculpt the gum tissue so the GHOC is even. Often the tissue will grow back to reform the natural 1 – 2.5mm sulcus unless it is prevented from doing so by the placement of a restoration on the tooth.
If the tooth involved is to have a crown or veneer placed, then the tissue will grow back to the point of the restorative margin. If the gingival recontouring and subsequent placement of the restorative margin encroaches on the biological width, the result will be a chronic marginal gingivitis with swollen red and bleeding gums (Fig. 18).
Provisional restorations are often overlooked when dealing with marginal integrity. The importance of proper margins cannot be over emphasized as the tissue health is dependant on these margins during the tissue healing phase prior to final impressions and cementation.11
Biological Width
As we are all aware, there is a comfort zone when speaking with someone face to face. There is a certain distance the faces are apart which when encroached upon will create a discomfort level causing the other person to back away. As seen in the “Seinfeld” episode called “the close talker,” when one person gets too close to the other and invades his or her personal space, the other person becomes very uncomfortable and backs away.
Similarly with teeth, gums and restorative margins, the biological width refers to the comfort zone between the restoration margin and the distance to the bony crest. (Fig. 19). If this distance is encroached upon, it will set up a chronic periodontal reaction usually resulting in marginal gingivitis, indicated by red, inflamed bleeding gums which are not improved upon even with meticulous oral hygiene (Fig. 20).
Much research has been done in these areas with the works of Tarnow,8 Gargiulo,5 Van Der Velden12 and Spear and Kokich,13 to quantify and qualify these biological principles, providing the practitioner with guides in which to operate in order to achieve biological success as well as aesthetic success (Table 6).
The natural periodontal complex comprises a sulcus depth ranging from 1 to 2.5mm, measured from the gingival margin to the attachment. A further 2mm of attachment will be found before sounding to crestal bone1 (Fig. 21).
There are three areas where biological width can be disturbed, Restorative margins, Pontics and papillary biological widths.
In the case of the restorative margin, there must be a minimum of 3.0 mm of space between the margin and the crestal bone.
In the case of the pontic, on odd occasion, a patient will complain that a bridge is sensitive to chewing in the pontic area. There must be a minimum of 2.0 mm of attached gingival tissue overlying the bone or pressure sensitivity may occur14 (Figs. 22 & 31).
As discussed above, when confronted with the situation of a restoration encroaching on the biological width, it will be necessary to do a crown lengthening procedure with osseous recontouring to attain the proper level of the GHOC and restorative margin and therefore maintain the biological width of 3.0mm minimum.
Restoration Contours
Over contoured restorations at the gingival third will result in a chronic marginal gingivitis. Under contoured restorations rarely result in gingival irritation however there is often a lack of support to the gingival tissue.15 (Figs. 23-25)
As discussed previously, under contouring of the emergence profile may result in a black hole, and over contouring can create a biological width issue with the interproximal papilla.
VIII) GINGIVAL COLOUR
Normal gingival colour is different for patients of differing ethnic backgrounds. This can range from light coral pink to pink with melanotic pigmentations from light to heavy.
Endodontic Discolouration
Dark teeth due to past endodontic disease and treatment will often show through the gingival tissue and show up as a dark discoloured gingival display. In these situations three options are available (Fig. 28).
First, careful treatment of the tooth by utilizing a ditch within the confines of the preparation margin subgingivally, and then filled with an opaque resin prior to impressions and temporization, will often completely mask the discoloured gingival display.
The second method is to use bleaching (tooth whitening) gel, which is light activated, and place the gel into the ditch and onto the prepped abutment surface. Light activation of the gel for a period of 15-20 minutes will often greatly reduce the discoloration. Removing some or all of the core buildup of the tooth and internal bleaching using superoxol or light activated bleaching gels will also help reduce the discoloration.
Thirdly, periodontal connective tissue grafting can be done to thicken the overlying tissue thereby masking the discoloration of the root.
Shadowed Root
Light transmission through the natural tooth creates a translucency not only of the crown but of the root. With placement of metal based or opacious based ceramic restorations, the light transmission is lost, creating a shadow in the root structure. This shadowing can result in a darkening of the marginal gingival tissues and those tissues overlying the root surface itself (Fig. 29).
When at all possible, the restoration of choice from a purely aesthetic standpoint will be an all ceramic restoration. It is understood that is not always possible to use this type of restoration, however when the clinician analyzes the case, careful consideration must be made according to all parameters of smile design.
IX) OVATE PONTIC DESIGN
In cases of missing teeth, the creation of an ovate pontic or implant site, is critical in order to achieve an aesthetic result. A small round depression in the gingival tissue along the ridge is created, allowing the pontic or implant to be embedded within the “crater” so as to appear to be emerging from the ridge as would be seen in a natural emergence profile.
The outer edges of the crater are raised 3mm from the floor of the crater. These outer raised edges represent the papilla height and the interproximal col, which surrounds the natural tooth. The shape of the crater has been best described as the larger rounded end of an egg. Remembering biological principles, there must be at least 2mm of gingival tissue between the bottom of the crater and the underlying alveolar ridge. (Figs. 30-31)
There are two scenarios we will be dealing with: the case of an immediate extraction, and the case of long term edentulous space.
Tooth to be extracted scenario
When faced with a situation where an anterior tooth must be extracted either from traumatic causes, periodontal concerns, hopeless decay, root fracture or failed endodontic procedure….the practitioner has been presented a rare and unique opportunity, a gift so to speak.
The gift is the presence of the papilla. The papilla cannot be regenerated, and in the scenario of a tooth to be extracted, the papilla must be maintained at all costs. The papilla is a very fragile gingival component, which will be lost at the slightest bit of trauma or loss of support.
If a tooth is extracted, the loss of support to the papilla will result in a slumping of the papillary tissues immediately. Within 30-60 minutes that papilla will have slumped to the point of no return. The worst thing that can happen, is for the patient to bite on the gauze immediately after extraction, forcing the papilla down into the socket site. Remember, that supporting the papilla is of utmost importance.
Meticulous care during surgery so as not to disturb the interproximal crestal bone, damage the buccal or lingual plate of bone or the soft tissue is crucial to the formation of a natural looking ovate pontic site.
By creating a preoperative temporary bridge for the socket area with an ovate pontic design, the papillae will be supported during the healing phase postoperatively.
The design of this supporting bridge must include a 3mm projection into the socket site from gingival crest to the floor of the ovate crater, a very smooth and hig
hly polished gingival surface to the pontic, 4.5 mm or more of contact point space to interproximal crestal bone with wide cervical embrasures to allow for swelling.
The temporary can be in the form of a resin bonded bridge, a full coverage bridge, an immediate insertion thumb partial denture or even using the extracted tooth, root cut off, sealed and polished, and bonded into position.
In all of these cases, the insertion of the temporary bridge as soon as possible following the extraction is imperative in maintaining the papilla and the formation of the healing ovate pontic site.
X) RIDGE AUGMENTATION
In the case of the anterior tooth, which has been missing for some time, generally there will be a loss of ridge support creating a deficiency or depression in the ridge overlying the missing root. This will result in a pontic that looks like it is hanging from thin air and a very un-natural appearance (Fig. 32).
It must be noted at this point that the papillae will have been lost. There is no way to regenerate a papilla, however by building up the ridge with soft tissue, and then sinking a round diamond into the soft tissue buildup, a simulated papilla can be created.16
Ridge augmentation can be achieved in various ways,17 bone grafting, and connective tissue grafts are the most common. Once the ridge augmentation and ovate pontic site has been developed and supported during healing with a temporary bridge, the final bridge or implant can be fabricated. (Figs. 33 – 37).
Orthodontic Considerations
Orthodontics plays an increasing role in the development of cosmetic dentistry. Simple rotations, arch form alignment, root angulations and gingival heights of contour can be corrected with simple orthodontic treatment. This type of treatment greatly enhances the final result and often minimizes the amount of tooth structure which has to be removed, as well as the risks associated with cosmetic treatment. Simple orthodontics before restorative procedures will simplify the treatment and greatly improve the predictability of a case. Orthodontics is an invaluable part in the treatment of the gingival aesthetics of many cases and is not to be overlooked or undervalued.
CONCLUSION
Smile design is the architectural blueprint on which to base treatment planning decisions. Many factors are involved, and the gingival component plays a very strong role in the final aesthetic result.
Careful attention to the biological and iatrogenic factors which greatly influence the health and appearance of the gingival tissues is necessary to maintain the integrity of the tissue and the gingival architecture that frames the teeth in the beautiful smile patient’s have come to expect.
Patient expectations have raised the bar; we as Cosmetic Dentists must rise to the challenge, keep up with the advances in techniques and materials so as to provide our patients with the highest quality care.
Dr. Goodlin is a general dentist with a special interest in cosmetic dentistry. He serves on the executive board of the Toronto Academy of Cosmetic Dentistry and is actively completing his Accreditation with the American Academy of Cosmetic Dentistry.
Oral Health welcomes this original article.
REFERENCES
1.Ingber, F.J.S., Rose, L.F., Coslet, J.G., Biologic Width – A Concept in Periodontics and Restorative Dentistry. Alpha Omegan, 1977;10:62-65
2.Coslet, J.G., Vanarsdall, R.L., Weisgold, A. Diagnosis and Classification of Delayed Passive Eruption of the Dento-Gingival Junction in the Adult. Alpha Omegan, 1977;70(3):24-28
3.Kokich,V.G., Spear, F.M., Maximizing anterior aesthetics: An interdisciplinary approach: Aesthetics and Orthodontics, JA McNamara, Ed., Craniofacial Growth Series, Center fro Human Growth and Development, University of Michigan, Ann Arbor, 2001.
4.Spear, F.W., The State of the Art in Aesthetics Presentation of the Seattle Institute for Advanced Dental Education 20015.Gargiulo,R., The Concepts, Contours and Cosmetics of Periodontics and Restorative Dentistry for the General Practitioner. CDS Review,1983;76(8):26.
6.Newcomb,G.A., The Relationship Between the Location of Subgingival Crown Margins and Gingival Inflammation. J.Periodontol 1974;45:151
7.Kois,J.C., Vakay R.T., Relationships of the Periodontiumt Impression Procedures. Compendium of Continuing Education in Dentistry, August 2000/Vol. 21, No.8 pp 684-692.
8.Tarnow, D.P., Mabner A.W., Fletcher, P.: The effect of the distance from the contact point to the crest of bone on the presence or absence of interproximal papilla. J.Periodontol 1992 Dec., 63(12)
9.Spear, F.W., Winter, R. Black Holes: Presentation to the American Academy of Cosmetic Dentistry Annual Convention, San Fransisco 2000.
10.Maynard, G.T., Wilson R.D., Physiologic Dimensions of the Periodontium Fundamental to Successful Restorative Dentistry. J.Periodontol 1979;50:107
11.Kois, J.C., The Restorative-Periodontal interface:biological parameters. J.,Periodontol 1996;11:29-38.
12.Van Der Velden, J.C.Perio Nov 1982l
13.Kokich, V.A., Spear.F.W., Maximizing Anterior Aesthetics: Perio-Ortho-Restorative Connection Presentation to the Toronto Academy of Cosmetic Dentistry, Feb 2001. Toronto Canada.
14.Spear,F.W., Tooth Replacement in Clinical Practice Seattle Institute for Advanced Dental Education, 2001.
15.Kois,J.C., The Gingiva is Red Around My Crown – A Differential Diagnosis Dent Econ 1993:4:101-105.
16.Han, T.J., Takei H.H., Progress in Gingival Papilla Reconstruction. J.Periodontol 1996 Vol 11;65-68.
17.Seibert, Salama, M.A., Alveolar Ridge Preservation and Reconstruction J.Periodontol Vol 11, 70-82.
18.Kois,J.C. Altering Gingival Levels:The Restorative Connection I. Biological Variables J.Ethet Dent 1994: 6: 3-9
19.Garber, D.A., Salama, M.A., The Aesthetic Smile: Diagnosis and Treatment J. Periodontol,1996 11:18-28
20.Miller, Allen, Development of periodontal plastic surgery J.Periodontol 1996 Vol 11 11-17
21.Winter,R. Technical Parameters for Anterior Aesthetics Presentation to the Toronto Crown and Bridge Study Club, Toronto Ontario Canada, January 24, 2003.
22.Chiche, G.J. Pinault, A. Aesthetics of Anterior Fixed Prosthodontics Quintessence Publishing 1994, pp.143-159.
23.Flores-de-Jacoby, L. Ziafiropoulos,G.C., Ciancio,S. The Effect of Crown Margin Location on Plaque and Periodontal Health Int J Perio-Rest Dents. 1989:9: 197-205.
