Preparation Protocol To Ensure Predictable Aesthetic Restorations"
Dr. Shannon
Abstract:
Advances in adhesive dentistry have created higher bond strengths. Higher bond strength has allowed for greater predictability in the utilization of ceramic-based restorations to restore damaged teeth back to their original pre-operative strength. Dentists have been slow to accept both direct and indirect posterior esthetic restorations despite improvements in flexural strength, esthetics, margin fit and wear to opposing dentition.
This article is meant to familiarize clinicians with the proper diagnostic and preparation principles for ceramic onlays, and to review finishing and polishing procedures to obtain an optimal clinical result. These are critical steps in creating functionally sound and esthetically pleasing restorations. If strict adherence to the protocol is not followed, clinical failure can occur for both direct and indirect restorations.
Indications and Contraindications
A healthy periodontium and a balanced occlusion are vital whenever the utilization of esthetic materials is considered to restore deteriorating posterior dentition. If complete isolation from blood and saliva cannot be achieved, adhesive dentistry is contraindicated. In cases where margins are supragingival or slightly subgingival and complete isolation is possible bonded procedures are an option. If margins are too far subgingival because of decay or previous restorations, the treatment of choice would be a conventional cemented gold inlay/onlay/crown restoration or a cementable all ceramic crown (esthetic inlay/onlays cannot be used with conventional cements).
Resistance, retention and optimal physical strength of bonded ceramic restorations are maximized by the adhesive process. Bonded restorations are said to restore the dentition to near pre-restoration strength. [1] [2] [3] It is difficult to quantify the amount of bondable surface area, but it can be said that the greater the bonded surface area, the stronger the restoration is and the greater it’s ability to withstand normal functional occlusal loads. Facial margins need not be placed subgingivally to achieve esthetic success; proper lab and color communications ensure supragingival margins and are virtually undetectable.
Various Onlay Preparations Designs
Onlays are indicated when you are required to extend the preparation into more than 50% of both the buccal and lingual cusps. The cusp may be severely weakened with decay, fractured or have a wall thickness of less than 1 mm. It is critical to have a good balanced occlusion for onlay preparations. Four different preparation designs predominate. These classifications are the author’s opinion only, as he assessed each given clinical situation.
The design principles for bonded onlays are quite different from those of cemented gold onlay restorations. Bonded onlay preparation guidelines state that these restorations should have a 5o to 15o flaring of the axial walls. The gingival box should have a butt joint finish and all internal line angles must be rounded. All visible margins should be finished with a butt joint and a heavy chamfer. Beveled and feather edges should be avoided. The minimum isthmus width required is 2.5 - 3.0 mm; the minimum thickness of material from the opposing supporting cusp is 2.5 - 3.0 mm. For onlays, all cusps should be covered with 1.5 - 2.0 mm of material and the minimum wall thickness of 1 - 1.5 mm is required for optimal strength.
Case Presentation
When assessing any clinical situation, proper clinical diagnosis and a discussion of treatment alternatives with the patient is of the utmost importance prior to beginning treatment. A pressed ceramic onlay was the treatment of choice. Pressed ceramic onlays offer increased strength, excellent esthetic appearance and demonstrate very good wear compatibility with the opposing arch. [5] [6] [7] [8] [9] As with all technique sensitive procedures, strict adherence to protocol is a must. If not followed, clinical failure can and will occur with both direct and indirect restorations. [10] [11] [12] [13] [14] [15] [16] With the patient’s informed consent, treatment commenced.
Shade Selection
Shade selection prior to isolation and preparation is critical because dehydration of the teeth will alter the value. Any variance in the value will be a cause for esthetic failure. Teeth are visually broken down into sections for color mapping: developmental groove, cuspal incline and incisal tip for the occlusal color development. The color communicated allows the technician to create depth perception along with necessary special characterization. This procedure is then completed with the facial surface. The facial surface is divided into three sections; the gingival third, the mid third and the incisal third. This grid system is then further evaluated for hue, chroma and value to create the best esthetic results. Along with this mapping, clinicians should also send 35 mm slides or photographs to the ceramist so that the most life-like restorations with invisible margins can be produced. This point of the procedure shows how critical shade matching is. In thiscase, because the patient was going through orthodontic care to better align his teeth, the author already determined that the end shade the patient wanted was Vita B1. The author and patient opted to restore the tooth in a Vita B1 shade explaining why the author did not have a polychromatic restoration.
A polyvinyl preoperative impression was taken using Position Penta Quick (3M ESPE) [Figure 2], which allows the author to make a quick, easy precise fitting provisional restoration in less than 5 minutes.
Preparation
To insure proper reduction in high stress areas of the cusp tips, depth cuts of 1.5 mm were made using a Great White #557 carbide bur. The cuts were first placed on the facial aspect followed up by going through the bulk of the cusp [Figure 4A and 4B].
GWU#856 -020 round end taper bur is used to ensure smooth internal line angles that provide a minimum material thickness of 2.0 to 2.5 mm from the opposing cusp tips [Figure 6]. The GWU#856-020 was used on all preparations in both the perpendicular and the horizontal positions to be sure a minimum material thickness of 2.0 to 2.5 mm from the opposing cusp tip was present. The GWU#845-018KR bur was used to finish the preparation and to create more natural margin blending while eliminating any existing internal line angles [Figure 7]. Caries indicator solution (Seek, Ultradent) is use throughout the preparation phase. This insures that all infected tooth structure is removed and will not interfere negatively in regard to future bond strength integrity [17] Figure 8A and 8B show a completed view of the preparations from both the occlusal and facial aspect showing the clear definite interocclusal clearance.
Preparations were completed using the before mentioned protocol. By following this strict protocol, we are able to provide uniform material thickness giving optimal material strength. [18] [19] [20] [21] xxii[22] Upon completion of the preparation, both a light and heavy body vinyl polysiloxane impression (Take 1, Kerr, California) was taken along with a rigid vinyl polysiloxane bite registration (Take One Bite, Kerr). [23] [24] This allows the technician to articulate the models so the completed result not only has accurate marginal fit and interproximal contact but also accurate occlusion. Once the impressions are complete, the placement of the temporaries (Fill In, Kerr) takes place. This was done to provide interproximal and occlusal stability, which upon removal ensured an exacting fit of the lab restorations [Figure 9A, 9B, 9C]. There are five separate pieces of data that are sent to the lab for the technician to use to insure the creation of the desired esthetic results:
Attention to detail is essential; a lab-manufactured restoration may have great esthetics, sound occlusion and contacts, but if the restoration is not properly seated, it is destine to fail. The two most common complaints heard from clinicians in the cementation phase of the restorative procedure are; accomplishing complete resin removal and completely isolating the tooth. First and foremost, always isolate the tooth using a rubber dam and try-in the restoration prior to seating using a water-soluble try-in paste to insure color and to verify the fit.
Removal of the try-in paste from the ceramic restoration is done when both dentist and patient are happy with the look and fit of the restoration. The bondable surface must be cleaned and treated. Historically, we have used 37% phosphoric acid. Clinicians now have new options available to clean and treat the bondable surfaces. Two of these new options are Cojet (ESPE 3M) which is sandblasted onto the restoration and then air dried or Ceramic primer, (ESPE 3M), which is a fresh silane and is applied chair side for 1 minute [25] followed by a layer of adhesive. The tooth should be thoroughly rinsed to get rid of any remaining debris. Once the ceramic is treated, prepare the tooth. The total etch is completed by placing etch over the dentin for 10 second. [26] [27] [28] [29]
In the past, the preparation and cementation phase consisted of a series of technique specific steps. Failure to adhere properly these steps occasionally created results (assuming the pulp is still vital), which could lead to management issues such as heat and bite pressure sensitivity. Today, due to the creation of self etch bond resin cements, we are able to consistently replicate clinically predictable bonds with superior strength.
Clinical Steps for Restoration Cementation
Some clinicians still avoid using tooth colored direct and indirect restorations in the posterior dentition because of associated historical deficiencies. By following a strict protocol, a large portion of these deficiencies can be eliminated. Clinical unpredictability such as poor marginal fit and inadequate flexural strength, which inherently made many of yesterday’s ceramic restorations clinically unpredictable, [30] has greatly been reduced with advances made in ceramic strength and esthetics, predictable seating protocol and advances with 5th generation adhesive systems. Highly esthetic restorations are now the norm. A pressed ceramic system was used in this case presentation. This was done to insure that like materials are used when restoring teeth from opposing arches, this safeguards against occlusion/contact issues that could arise as a byproduct of the use of different materials. [31] [32]
Conclusion
Today’s patients are educated consumers; they demand esthetic excellence and most often, metal free restorations. Esthetic onlays have been shown to satisfy even the most discerning patient. It is imperative not to forget there will be clinical situations where the new ceromer materials cannot be used because proper isolation cannot be achieved. In these situations rely on cementable restorations for predictable clinical results. A true understanding of current restorative materials and attention to detailed procedural protocols will enable clinicians the opportunity to provide metal free esthetic dentistry on a predictable basis.
Dr. Shannon
Abstract:
Advances in adhesive dentistry have created higher bond strengths. Higher bond strength has allowed for greater predictability in the utilization of ceramic-based restorations to restore damaged teeth back to their original pre-operative strength. Dentists have been slow to accept both direct and indirect posterior esthetic restorations despite improvements in flexural strength, esthetics, margin fit and wear to opposing dentition.
This article is meant to familiarize clinicians with the proper diagnostic and preparation principles for ceramic onlays, and to review finishing and polishing procedures to obtain an optimal clinical result. These are critical steps in creating functionally sound and esthetically pleasing restorations. If strict adherence to the protocol is not followed, clinical failure can occur for both direct and indirect restorations.
Indications and Contraindications
A healthy periodontium and a balanced occlusion are vital whenever the utilization of esthetic materials is considered to restore deteriorating posterior dentition. If complete isolation from blood and saliva cannot be achieved, adhesive dentistry is contraindicated. In cases where margins are supragingival or slightly subgingival and complete isolation is possible bonded procedures are an option. If margins are too far subgingival because of decay or previous restorations, the treatment of choice would be a conventional cemented gold inlay/onlay/crown restoration or a cementable all ceramic crown (esthetic inlay/onlays cannot be used with conventional cements).
Resistance, retention and optimal physical strength of bonded ceramic restorations are maximized by the adhesive process. Bonded restorations are said to restore the dentition to near pre-restoration strength. [1] [2] [3] It is difficult to quantify the amount of bondable surface area, but it can be said that the greater the bonded surface area, the stronger the restoration is and the greater it’s ability to withstand normal functional occlusal loads. Facial margins need not be placed subgingivally to achieve esthetic success; proper lab and color communications ensure supragingival margins and are virtually undetectable.
Various Onlay Preparations Designs
Onlays are indicated when you are required to extend the preparation into more than 50% of both the buccal and lingual cusps. The cusp may be severely weakened with decay, fractured or have a wall thickness of less than 1 mm. It is critical to have a good balanced occlusion for onlay preparations. Four different preparation designs predominate. These classifications are the author’s opinion only, as he assessed each given clinical situation.
- When a large restoration with an occlusal isthmus width extends approximately two thirds the way up the cusp inclines and does not have extensive undercuts present in the proximal box area (but still has a good sound 2mm of enamel at the cusp tip area), then the onlay will be performed without sacrificing the cusp tips. This scenario calls for the onlay to sit on top of the cusp incline and once bonded in place will restore the tooth back to ideal strength.
- The second scenario presents itself when one or more of the cusp tips are severely weakened through decay or when the wall thickness is less than 1mm. In this situation, an onlay restoration is required which will allow for the proper reduction of the weakened tip that is necessary to create a sound restoration that utilizes no unsupported enamel.
- The third scenario is present when the proximal box has extensive undercuts that extend more than two-thirds the gingival incisal height of either the buccal or lingual cusp. To restore this weakened state, blockout technique would be contraindicated, therefore the preparation design would need to be modified to conserve tooth while also properly supporting the weakened cusp with the restoration. The modification is to prepare from the proximal box area occlusally while reducing the amount of unsupported cusp tip needed to render a well-supported cusp.
- The final onlay design applies if a patient presents with an isolated cusp fracture. Follow the onlay design principles but keep the onlay isolated to the compromised area. Abandon the traditional GV Black guidelines. The damaged cusp can be replaced by itself with no other tooth structure being removed. [4]
The design principles for bonded onlays are quite different from those of cemented gold onlay restorations. Bonded onlay preparation guidelines state that these restorations should have a 5o to 15o flaring of the axial walls. The gingival box should have a butt joint finish and all internal line angles must be rounded. All visible margins should be finished with a butt joint and a heavy chamfer. Beveled and feather edges should be avoided. The minimum isthmus width required is 2.5 - 3.0 mm; the minimum thickness of material from the opposing supporting cusp is 2.5 - 3.0 mm. For onlays, all cusps should be covered with 1.5 - 2.0 mm of material and the minimum wall thickness of 1 - 1.5 mm is required for optimal strength.
Case Presentation
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Shade Selection
 Figure 2 |
A polyvinyl preoperative impression was taken using Position Penta Quick (3M ESPE) [Figure 2], which allows the author to make a quick, easy precise fitting provisional restoration in less than 5 minutes.
Preparation
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Preparations were completed using the before mentioned protocol. By following this strict protocol, we are able to provide uniform material thickness giving optimal material strength. [18] [19] [20] [21] xxii[22] Upon completion of the preparation, both a light and heavy body vinyl polysiloxane impression (Take 1, Kerr, California) was taken along with a rigid vinyl polysiloxane bite registration (Take One Bite, Kerr). [23] [24] This allows the technician to articulate the models so the completed result not only has accurate marginal fit and interproximal contact but also accurate occlusion. Once the impressions are complete, the placement of the temporaries (Fill In, Kerr) takes place. This was done to provide interproximal and occlusal stability, which upon removal ensured an exacting fit of the lab restorations [Figure 9A, 9B, 9C]. There are five separate pieces of data that are sent to the lab for the technician to use to insure the creation of the desired esthetic results:
- The 35 mm slide of the natural teeth taken pre-treatment
- Completed color mapping imagery
- The bite registration
- The impression
- A detailed lab prescription
Attention to detail is essential; a lab-manufactured restoration may have great esthetics, sound occlusion and contacts, but if the restoration is not properly seated, it is destine to fail. The two most common complaints heard from clinicians in the cementation phase of the restorative procedure are; accomplishing complete resin removal and completely isolating the tooth. First and foremost, always isolate the tooth using a rubber dam and try-in the restoration prior to seating using a water-soluble try-in paste to insure color and to verify the fit.
Removal of the try-in paste from the ceramic restoration is done when both dentist and patient are happy with the look and fit of the restoration. The bondable surface must be cleaned and treated. Historically, we have used 37% phosphoric acid. Clinicians now have new options available to clean and treat the bondable surfaces. Two of these new options are Cojet (ESPE 3M) which is sandblasted onto the restoration and then air dried or Ceramic primer, (ESPE 3M), which is a fresh silane and is applied chair side for 1 minute [25] followed by a layer of adhesive. The tooth should be thoroughly rinsed to get rid of any remaining debris. Once the ceramic is treated, prepare the tooth. The total etch is completed by placing etch over the dentin for 10 second. [26] [27] [28] [29]
In the past, the preparation and cementation phase consisted of a series of technique specific steps. Failure to adhere properly these steps occasionally created results (assuming the pulp is still vital), which could lead to management issues such as heat and bite pressure sensitivity. Today, due to the creation of self etch bond resin cements, we are able to consistently replicate clinically predictable bonds with superior strength.
Clinical Steps for Restoration Cementation
- The restoration and the tooth is filled with MaxCem (Kerr) [Figure 10]
- With the aid of Pic-n-sticks (Pulpdent), the onlay is seated with firm pressure being applied [Figure 11]
- Excess resin is removed with a Benda-Brush (Centrix) and/or rubber tip prior to curing
- Spot tack the restoration using the LED Demetron (Kerr) to minimize clean up after curing
- Clean the interproximals with floss and an explorer prior to curing
- Cure the restoration in place (10 seconds per surface). We use both our LED and Optilux 501, (Kerr Corp California). If needed, remove any interproximal resin with Interproximal Contact Discs (Almore)
- Remove the rubber dam upon completion of curing
- Check occlusion with articulating ribbon (both centric and lateral excursions)
- Remove all unwanted occlusal interference
- Polish the finishing surface to a high luster with either Pogo (Dentsply) or Diamondpaste (Kerr).
Minimizing chairside adjustments is accomplished by utilizing accurate impressions and sending detailed restoration requirements to your lab. This results in a restoration that exhibits the proper aesthetic and morphological features [Figures 12A, 12B].
Some clinicians still avoid using tooth colored direct and indirect restorations in the posterior dentition because of associated historical deficiencies. By following a strict protocol, a large portion of these deficiencies can be eliminated. Clinical unpredictability such as poor marginal fit and inadequate flexural strength, which inherently made many of yesterday’s ceramic restorations clinically unpredictable, [30] has greatly been reduced with advances made in ceramic strength and esthetics, predictable seating protocol and advances with 5th generation adhesive systems. Highly esthetic restorations are now the norm. A pressed ceramic system was used in this case presentation. This was done to insure that like materials are used when restoring teeth from opposing arches, this safeguards against occlusion/contact issues that could arise as a byproduct of the use of different materials. [31] [32]
Conclusion
Today’s patients are educated consumers; they demand esthetic excellence and most often, metal free restorations. Esthetic onlays have been shown to satisfy even the most discerning patient. It is imperative not to forget there will be clinical situations where the new ceromer materials cannot be used because proper isolation cannot be achieved. In these situations rely on cementable restorations for predictable clinical results. A true understanding of current restorative materials and attention to detailed procedural protocols will enable clinicians the opportunity to provide metal free esthetic dentistry on a predictable basis.
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