|Year : 2015 | Volume
| Issue : 1 | Page : 46-53
The perio-restorative interrelationship-expanding the horizons in esthetic dentistry
Priya John, Majo Ambooken, Anu Kuriakose, Jayan Jacob Mathew
Department of Periodontics, Mar Baselios Dental College, Thankalam, Kothamangalam, Kerala, India
|Date of Web Publication||12-Aug-2015|
Department of Periodontics, Mar Baselios Dental College, Thankalam, Kothamangalam, Kerala
Source of Support: None, Conflict of Interest: None
| Abstract|| |
The astute clinician strives to create a beautiful smile paying due heed not only to the gleaming white teeth, but also to the health of the surrounding tissues. A sound periodontium provides a firm foundation for an esthetic and functional prosthesis. Conversely, when restorations are designed to be self-cleansing and promote gingival health, the tissues present a harmonious esthetic blend at the restorative -gingival interface. This review paper aims at exploring the potential of an interdisciplinary approach to achieve this end. This involves incorporating a comprehensive treatment plan, paying close attention to both soft and hard tissues around teeth and implants before, during, and after restorative procedure. Key aspects of the restoration and partial denture design that have a direct effect on the periodontium include restoration contour, margin adaptation, margin placement, prosthetic and restorative materials, design of fixed and removable partial dentures, restorative procedures and occlusal function. Special emphasis is paid to the consequences of violation of biologic width, that leads to incessant inflammation, possible recession and unsightly exposure of crown margin. Periodontal considerations include control of periodontal inflammation, correction of the gingival architecture, and periodontal maintenance. A search of articles from "Pubmed" and "Medline" with the keywords restorative-alveolar interface, methods of gingival retraction and biologic width was conducted. A total of 430 abstracts were collected, of which most relevant articles were included in this paper.
Clinical Relevance to Interdisciplinary Dentistry
- To promote restoration and pontic designs that promote favorable tissue response.
- To stress the importance of preserving biologic width to all dental practitioners
- To shed light on iatrogenic damage to the periodontium from certain materials and procedures.
- To unveil the potential of periodontal plastic surgery techniques like augmenting attached gingiva and esthetic crown lengthening prior to restorative procedures when indicated.
- To emphasize the need for recall and maintenance therapy.
All the above concepts can be successfully implemented into clinical practice.
Keywords: Methods of gingival retraction, biologic width, restorative-alvelolar interface
|How to cite this article:|
John P, Ambooken M, Kuriakose A, Mathew JJ. The perio-restorative interrelationship-expanding the horizons in esthetic dentistry. J Interdiscip Dentistry 2015;5:46-53
|How to cite this URL:|
John P, Ambooken M, Kuriakose A, Mathew JJ. The perio-restorative interrelationship-expanding the horizons in esthetic dentistry. J Interdiscip Dentistry [serial online] 2015 [cited 2019 Jun 18];5:46-53. Available from: http://www.jidonline.com/text.asp?2015/5/1/46/162745
| Introduction|| |
Abeautiful smile can be crafted only against a backdrop of healthy gingiva. A sound periodontium provides a firm foundation for an esthetic and functional prosthesis. The practice of restorative dentistry has a reciprocal relationship with the maintenance of periodontal health. Poor restorative treatment may have adverse effects on the periodontium by increasing accumulation of plaque while untreated periodontal disease will compromise the success of restorative dentistry.  When restorations are designed to be self-cleansing and promote gingival health, the tissues present a harmonious esthetic blend at the restorative-gingival interface. The purpose of this review is to explore the effects of contemporary restorative procedures and materials on the periodontium. On the other hand, the clinical relevance of some periodontal plastic surgery procedures for a healthier restorative-alveolar interface is outlined.
| Restorative considerations that impact the periodontium|| |
- Restoration contour and contact areas
- Margin adaptation and defects
- Location of margin
- Role of provisional restorations
- Design of fixed and removable partial dentures (RPDs)
- Occlusal function
- Prosthetic and restorative materials and alloy hypersensitivity
- Iatrogenic damage from restorative procedures.
Contour and contact areas
Clinical longevity of any prosthesis is directly related to achieving proper restorative contours.  It is the function of the axial form of teeth to afford protection and stimulation to the marginal periodontium. ,
Physiologic tooth contouring
- Allows for self-cleansing mechanisms of cheek, tongue, etc. For instance, the bucco-lingual bulge should be <0.5 mm wider than the cemento-enamel junction ,,
- There must be sufficient space: Cervically to create the correct contour that facilitates plaque removal, occlusally to allow the restoration of a proper occlusion, and axially to provide a proper thickness of veneering material to achieve an esthetically acceptable prosthesis.
Insufficient preparation of abutment teeth is often done to preserve sound tooth structure, but often results in over contouring.
Problems with over contouring
- "Food traps" from open contacts, overhangs, or plunger cusps may occur
- Poor occlusal design, and poor esthetics ,
- When the coronal contour of a restoration prevents access for oral hygiene or creates mechanical pressure on the gingival tissue, gingival health is likely to be compromised 
- Plaque accumulation, inflammation, bleeding, and potential bone loss. Plaque is the primary factor in gingivitis 
- An unesthetic emergence profile of a restoration is created. The emergence profile is the shape of the restoration in relation to the gingival tissues. Stein and Kuwata described the part of the axial contour that extends from the base of the gingival sulcus past the free margin of the gingiva as the emergence profile that was straight in the gingival third. 
Schluger et al. felt the cervical bulge overprotects the microbial plaque. Schluger et al. have advocated "flat" not "fat" contours.  Over contouring is potentially more detrimental to the periodontium than under contouring. 
- Should be in the coronal third of the crown and buccal in relation to the central fossa
- Proximal contact points are buccal to the central fossa line, except for maxillary molars founds at the middle third. This creates a large lingual embrasure for optimum health of the lingual papilla. ,
Problems with misplaced contacts
- Horizontal food impaction is produced by the action of the tongue, lips, cheeks and results from poorly contoured interproximal surfaces. Lower fixed partial dentures usually collect more food than upper dentures, particularly in the molar region
- Lifting and rotating forces on dentures
- Deflective occlusal contacts. 
Marginal adaptation and defects
- Scientific data indicate that even clinically successful crowns have margins that are open. The average opening is about 100 nm, which tends to harbor bacterial plaque even around the best fitting margins of a restoration causing inflammation ,
- Roughness of the tooth-restoration interface from scratches in the surface of carefully polished acrylic and ceramic crowns, inadequate marginal fit of the restoration, dissolution and disintegration of the luting material causing crater formation between the preparation and the restoration and inflammation of gingiva 
- Sharp edges or corners in the preparation not reproduced accurately on the stone die can create marginal discrepancies. Dentists must ensure that the crowns completely seat on the tooth.
Preparation margin designs for metal ceramic crowns
- The chamfer: The thin metal collar may distort during the firing of porcelain, thus producing inaccurate margins
- Feather-edge margin: Used for cast crowns and veneers. But finish line is hard to read and not amenable to thorough finishing and polishing
- A shoulder with bevel is more conservative than a full shoulder preparation, but the presence of the metal collar necessitates an intra-crevicular preparation in esthetic areas
- A shoulder preparation allows for sufficient bulk for porcelain to produce esthetically pleasing restorations. ,
Location of margin: The clinical significance of margin placement
Eissman et al.'s design criteria for fixed partial dentures state that crown margins should be placed on tooth surfaces that are fully exposed to cleansing action, preferably supragingival or slightly into the sulcus.  Vigorous tooth brushing was effective up to 0.7 mm below the gingival margin, suggesting that the submarginal extension of restorations should be limited to no more than this distance.  Restorative requirements frequently necessitate subgingival margin placement in order to gain resistance or retention form to alter tooth contour, for caries for subgingival tooth fracture removal, in furcation involvement and to hide the tooth-restorative interface or have contacts that need to be lengthened apically to avoid black triangles.  In such cases, subgingival margin placement is necessary, marginal fit should be optimal because rough restorations or grossly open margins lead to an accumulation of bacterial plaque. 
Advantages of supragingival margins over subgingival margins
- Supragingival margins improved periodontal health 
- Subgingival margins demonstrated increased plaque, gingival index score, and probing depths 
- Furthermore, more spirochetes, fusiforms, rods and filamentous bacteria were found to be associated with subgingival margins ,,
- Violation of the connective tissue attachment; and greater pathogenicity of the subgingival plaque are documented with subgingival margins 
- Supragingival margins stay away from the periodontal tissues, and thus, they are easier to prepare, record and maintain. ,
Current trends favor equigingival margins over older concepts of subgingival margins for crowns, which are kinder to the periodontium. Furthermore, advances with emerging translucent restorative materials adhesive dentistry, and resin cements, promote polished margins that esthetically blend with the tooth for a healthy tooth-restorative interface even when placed equigingival. 
The concept of biologic width, and its applications in placement of gingival margins
Understanding and clinically managing the concept of biological width is the key to creating gingival harmony with dental restorations. The biologic width is defined as the dimension of space occupied by the soft tissues above the level of the alveolar crest. The connective tissue attachment occupied 1.07 mm above the level of the crestal bone, junctional epithelium attachment below the base of the gingival sulcus to be 0.97 mm, and an average sulcus depth of 0.69 mm. In the average human, this 2-3-mm distance remains constant in health and disease. , Encroachment on the biological width by tooth preparation, caries, fracture, restorative materials or orthodontic devices can lead to bacterial accumulation, persistent gingival inflammation eventually resulting in increased probing depths, gingival recession or pocket formation.
Assessment of biologic width
Wilson and Maynard have described the concept of intra-crevicular restorative dentistry. Intra-crevicular margins are defined as those confined within the gingival crevice.  The restorative dentist must be able to determine the base of the sulcus for intra-crevicular margin location. Kois suggested that the restorative dentist must determine the total distance from the gingival crest to the alveolar crest.  This procedure is termed bone sounding. The tissues are anesthetized, and the periodontal probe is placed in the sulcus and pushed through the attachment apparatus until the tip of the probe engages alveolar bone. Based on this measurement, the three categories of biologic width described are: 
- Normal crest: A biologic width of 3 mm on the labial aspect allows for a crown margin that is placed 0.5 mm subgingivally
- High crest: Measurement lesser than 3 mm does not allow for subgingival margins without bone removal
- Low crest: Measurement of more than 3.0 mm. It is most susceptible to recession secondary to the placement of an intra-crevicular crown margin in the presence of a thin periodontium.
This is an attempt of the body to recreate room above the alveolar crest for tissue reattachment.
Correction of violation of biologic width
To restore gingival health, it is necessary to reestablish the space clinically between alveolar bone and the gingival margin. For this purpose, either surgery to alter bone level , or orthodontic extrusion of the tooth to move the restoration margin away from the bone level.
Margin placement guidelines
- Rule I: If the sulcus probes 1.5 mm or less, place the restoration margin 0.5 mm below the gingival tissue crest
- Rule II: If the sulcus probes more than 1.5 mm, place the margin one-half the depth of the sulcus below the tissue crest. This places the margin enough below tissue so that it is still covered if the patient is at higher risk of recession
- Rule III: If the sulcus >2 mm is found, especially on the facial aspect of the tooth, then evaluate to see whether a gingivectomy could be performed to lengthen the teeth and create a 1.5 mm sulcus. Then the patient can be treated as mentioned in rule I. 
It can be achieved mechanically using retraction cords, copper bands or cords.
- A single-cord technique is the least traumatic option than two cord technique and is normally employed when the sulcus, is shallow, and the margin is placed only minimally in the crevice in areas of root proximity. ,
Chemicals used for the treatment of chords diffuse in blood circulation through crevicular epithelium, help to control seepage of blood or gingival fluid but Can cause damage to gingiva if used injudiciously. , Newer and safer materials like biocompatible polymer - hydroxylate polyvinyl acetate (Merocel) absorbs intraoral fluids and is soft and adaptable. Expasyl is a paste that not only opens the sulcus but also leaves the field dry. It is mainly composed of micronized kaolin, aluminum chloride and water. 
Role of provisional restorations
Provisional restorations are needed to protect the prepared teeth, to reduce the sensitivity of the vital abutments, and to prevent tooth migration. They are used to correct esthetics, phonetics and occlusal scheme before fabrication of the definitive restoration. Provisionals should have good marginal fit and polish. This prevents plaque accumulation and related inflammatory gingival overgrowth or recession. ,,
Design of fixed and partial dentures and crowns for root-resected teeth
A bridge should be designed to minimize accumulation of dental plaque and food debris and to maximize access for cleansing by the patient. It should also provide embrasures for the passage of food and protection of gingival crevices.  Stein concluded that the pontic design was more important than the material used in the pontic construction. The undersurface of pontics in fixed bridges should barely touch the mucosa. When the contact is excessive, it prevents cleaning. The "modified ridge-lap" pontic has pinpoint, pressure-free contact on the facial slope of the ridge, and all surfaces should be convex, smooth, and highly polished or glazed. ,, The sanitary pontic is most hygienic, but ovate pontic combines both esthetics and hygiene.
Crowns for root-resected teeth
Root resection may be indicated in multirooted teeth with advanced Grade II to III furcation involvements.  Crowns that are placed on upper molars that have undergone root resection must be contoured in a specific way to ensure that the patient has access for oral hygiene measures. The preparation eliminates residual ledges, roots, furcation lips or horizontal components or the furcation. , The gingival embrasure form created in the restoration must be fluted into these areas so that the surfaces can be accessed an interdental brush, a knife edge or chamfer margin is indicated  [Figure 1].
|Figure 1: Treatment of Grade II furcation involvement with root resection. Contour of crown modified to prevent ledge formation. Occlusal platform reduced|
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A cast post and core may be indicated to create an adequate foundation for the final restoration.  When palatal root has been resected, re-contouring of the crown results in a much thinner crown buccopalatally. After root separation, close proximity of the roots should be relieved using one of the following options.
- Partial instead of full-coverage restorations to avoid preparing and restoring the side of the tooth with the proximity problem
- More apical placement of the restorative margin if the root trunk tapers apically or an odontoplasty with a flame-shaped bur to increase the separation
- Orthodontic movement to separate the teeth; and strategic extractions. 
Lateral forces are controlled by minimizing cuspal inclines on the resected molar and the teeth stabilizing it. Bergman et al. (1982) also reported that RPDs did not compromise long-term dental health. Conventional RPDs were designed and fabricated to keep denture bases, clasps, and bars as far from the gingiva as possible. 
Occlusal discrepancies in a restoration appear to be a significant risk factor that contributes to more rapid periodontal destruction and that treatment of occlusal discrepancies seemed to slow periodontal destruction.  Cantilever designs often result in fractures of casting and roots and periodontal inflammation around abutment tooth. Occlusal evaluation is to be done after inflammation due to periodontitis has subsided due to changes in tooth-tissue relationship. Occlusal appliance therapy may be used before occlusal adjustment for acute issues. Use cantilevers sparingly and with light occlusal contact if needed with multiple abutments. 
Restorative materials and alloy sensitivity
Self-curing acrylics are less tissue friendly. Improperly finished composites may become rough. Phosphate cements and silicates are irritant. Lab cast and high polish of restorations is important in preventing plaque accumulation.  Unfavorable gingival reactions to alloys used in the oral environment have been documented.  The fine marginal fit of glass ceramics and porcelain veneers have least gingival irritation.
Iatrogenic damage from procedures
Special care should be directed to minimize mechanical and chemical trauma to the natural dentition and to the periodontium during restorative procedures. Injudicious use of electrosurgery, cryosurgery and laser can cause excessive necrosis of the gingiva and in extreme cases, the underlying bone. Excessive pressure while trimming and fitting bands may sever or traumatize the gingival attachment and lead to irreversible gingival recession.  The residual material of retraction cords left in the crevice can lead to periodontal abscess later. Injury from rubber dam clamp and disks can lead to gingival inflammation.
| Current trends in periodontal aspects of restorative dentistry|| |
- Supragingival placement of margins of restorations
- Avoidance of over contoured restoration, and minimal concern with lack of contour
- Occlusal stability through precise occlusal adjustment and accurate reconstruction of occlusal anatomy in single restorations
- Restricted indications for splinting of mobile teeth
- Hemisection with fixed bridges in cases of extensive bifurcation involvement. 
The purpose of restorative dentistry is to restore and maintain health and functional comfort of the natural dentition combined with satisfactory esthetics. Thus, all dental restorations should comply with established requirements for periodontal physiology and health, both with regard to surface and functional characteristics. 
| Periodontal considerations|| |
Periodontal therapy to resolve inflammation must be completed before restorative dentistry.
Importance of a healthy periodontium: A firm foundation for precise and lasting restorations
- Healthy gingival margins do not shrink after tooth preparation and enable accurate impressions ,
- There are less chances of bleeding after preparation, which aids visibility and making impressions 
- Stable tissues, free of inflammation ensures predictable restorations 
- Trauma from occlusion on teeth with untreated periodontitis may increase tooth mobility and rate of attachment loss 
- Quality and topography of the periodontium should be improved to prevent negative changes once the restorations have been placed.  For instance, a wider zone of attached gingiva is needed around abutment teeth and in those with subgingival restorations as less inflammation is reported than in teeth with narrow zones.  It is useful in areas of esthetic margin placement, to facilitate impressions, and in some cases, to increase patient comfort. Thicker tissues have been found to provide adequate protection against recession.
- A thorough periodontal evaluation is indicated in the planning stages prior to fabrication of the prosthesis. Selection of abutment teeth is based on prosthodontic and periodontal considerations, including bone support and architecture, width of attached gingiva, tooth mobility, root anatomy, and tooth position
- Controlling or eliminating periodontal disease with cause-related therapy and surgical therapy to eliminate pockets
- Correction of the gingival architecture that may favor disease, impair esthetics, or impede placement of prosthesis with preprosthetic surgery
- Periodontal maintenance and motivation for oral hygiene should be given during treatment and interim periods. 
Plaque control, calculus removal, and the removal of any inadequate dental restorations in the gingival environment, treatment of food impaction, correction of trauma from occlusion, and orthodontic tooth movement, motivation for oral hygiene, as well as extraction of hopeless teeth can be done.
- Periodontal flap surgery may be necessary to gain access for debridement, to reduce pockets and for periodontal regenerative therapy with bone grafts [Figure 2]
- Preprosthetic surgery: Gingival augmentation: It can be done using a free gingival graft or connective tissue graft or acellular dermal matrix 
- A vestibuloplasty may be required in areas where a shallow vestibule complicates oral hygiene. Correction of shallow vestibule also facilitates gain in attached gingiva. Vestibuloplasty by periosteal fenestration [Figure 3], and vestibuloplasty with free gingival graft [Figure 4]. Removal of aberrant frena improves vestibular depth, attached gingiva and eliminates tension on marginal gingiva in the area of a frenum
|Figure 3: Vestibuloplasty with periosteal fenestration for treatment of shallow vestibule and insufficient width of attached gingiva|
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|Figure 4: Vestibuloplasty with free gingival graft. Incision given, recipient bed, and template for graft prepared. Free gingival graft harvested and sutured in place|
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- Removal of gingival excess and maintaining biologic width: In situations in which a tooth has a short clinical crown deemed inadequate for retention of a required cast restoration, it is necessary to increase the size of the clinical crown using periodontal surgical procedures [Figure 5].
|Figure 5: Crown lengthening with osteoplasty done for unesthetic gingival margins and reduced height of clinical crown. Vertical and internal bevel incisions are given. Flap raised and bone recontoured to prevent violation of biologic width|
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This can be done surgically or orthodontically while maintaining the biologic width. To select the proper treatment approach for crown lengthening, an analysis of the individual case with regard to crown-root alveolar bone relationships should be done.
- External bevel gingivectomy: This can be done when there is more than adequate attached gingiva and at least 5 mm excessive suprabony gingival tissue is present and no bone involvement [Figure 6]
|Figure 6: Esthetic gingival recontouring with external bevel incision for unesthetic gingival margins. Gingival margins established in golden proportions|
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- Internal bevel gingivectomy: Reduction of excessive pocket depth and exposure of additional coronal tooth structure in the absence of a sufficient zone of attached gingiva with or without the need for correction of osseous abnormalities requires a surgical procedure, wherein the flap must always be internally beveled so as to expose the supporting alveolar bone [Figure 7]
|Figure 7: Internal bevel gingivectomy with osseous contouring for prosthetic restoration of fractured tooth. Core buildup done and crown is in place|
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- Apically positioned flap with bone re-contouring: It is used to expose sound tooth structure in cases of tooth fracture or caries. As a general rule, at least 4 mm of sound tooth structure must be exposed at the time of surgery. It is indicated for multiple teeth in the nonesthetic zone. , Esthetic crown lengthening can be done using flap surgery with bone removal using a surgical guide. The golden proportion has been recommended as a guide for an esthetic tooth/restoration: The mesial-distal width of a tooth is approximately 75% of its height. Allen recommended having the gingival margins on incisors peak slightly distal to the midline of the teeth. Central incisors, with an average length of 11-12 mm, should be 1.5 mm longer than laterals 
- Pontic - soft tissue relationships: If soft tissue form and surface characteristics are deemed unacceptable, corrections should precede fabrication of the restoration. Pontics should preferably be placed over keratinized tissue rather than alveolar mucosa. Ridge augmentation may be accomplished by internal connective tissue grafts, free soft tissue onlay-autografts, or ridge transposition. When the ridge is covered by excessive amounts of soft tissue, ridge reduction can be accomplished by gingivoplasty or internal soft tissue wedge reduction (e.g., tuberosity reductions).  Osseous respective surgery may be indicated when a bony portion of the ridge is covered by a thin layer of soft tissue. Ridge reduction surgery may be required to increase the vertical clearance between the residual ridge and opposing occlusion.
| Supportive periodontal therapy|| |
Maintenance recalls are essential to the long-term success of fixed and removable prosthesis especially overdenture abutments. Hygiene adjuncts using end-tufted brushes and daily application of fluoride are beneficial.
| Conclusion|| |
An interdisciplinary approach requiring coordinated efforts by the restorative dentist and periodontist is the need of the hour. Close attention paid to both soft and hard tissues around teeth and implants before, during, and after restorative produces a successful outcome. It also gives the patient the benefit of comprehensive treatment with precise and lasting and restorations.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]