Cavity Adaptation for Class II Composite Restorations

Contents:

• Cavity Adaptation and Clinical Outcomes
• Factors Influencing Cavity Adaptation
• Composite Restorative Material
• Operator Technique
• Light-curing the Composite
• Cavity Adaptation with Bulk Fill Flowable Composite
• Achieve Excellent Cavity Adaptation with Help from Dentsply Sirona

Cavity adaptation refers to the ability of a restorative material to seamlessly adapt to the preparation. What’s more, based on a recent survey, two thirds of dentists consider cavity adaptation the most important factor in clinical success. In Class II restorations, the proximal box presents particular challenges for cavity adaptation. Here we’ll look at the impact of poor cavity adaptation on clinical outcomes for Class II composite restorations, the factors influencing cavity adaptation and how to achieve gap-free cavity adaptation.  

Cavity Adaptation and Clinical Outcomes  

Poor cavity adaptation causes gaps and voids at the interface of the restorative material and the tooth structure, as well as internal voids. Adverse clinical outcomes of poor cavity adaptation include:²

• Marginal leakage.
• Post-operative sensitivity.
• Pulpal irritation.
• Recurrent caries.
• Restoration failure.   

While a patient’s caries risk influences the development of recurrent caries, poor adaptation also plays a significant role.³ The main reason for Class II restoration failure is recurrent caries, and up to 90% of recurrent caries lesions occur at the gingival margins.^3,4 Given that 50% of all direct restorations are Class IIs,⁵ it’s crucial to understand the factors that influence cavity adaptation and how to achieve gap-free restorations.

Factors Influencing Cavity Adaptation 

Factors influencing cavity adaptation include the shape of the preparation, the properties of the restorative material, and operator technique. 

Preparation Shape 

Cavity adaptation is influenced by the shape of the preparation and the number of surfaces involved.⁶ The ratio of bonded surfaces (walls) to unbonded surfaces - known as the configuration factor or C-factor – affects cavity adaptation. Challenging sites include the depth of a proximal box and areas with sharp line angles between the floor of the preparation and the axial wall. Procedures involving replacement of amalgam restorations also represent challenges because the preparations frequently have surface irregularities.² In particular, the cavity depth, width and volume are found to be related to the quantity of gaps and voids when using high viscosity composites.⁷

Operator Technique

Poor operator technique significantly affects clinical outcomes.

In the case of universal/posterior composites, which have a high viscosity, applying insufficient or misplaced pressure during placement reduces ‘packing’ of the composite, thereby increasing the likelihood of gaps at the margins and along the walls of the preparation. Methods used to reduce the viscosity of composites during placement include vibration and pre-heating of the material. Both of these techniques are controversial due to variability in the effect across composites (unless recommended by the manufacturer) and, in the case of pre-heating, the potentially unfavorable influence of heated composite on pulpal health.⁶

Low viscosity flowable composites are advantageous for cavity adaptation. Nonetheless, attention to detail is necessary. Placement is optimized when the material is initially syringed into the preparation at the deepest part of the proximal box and then gradually withdrawn while still syringing and keeping the application tip within the flowable material as it fills the preparation. Holding the tip within the flowable composite only intermittently can cause air to be trapped within the material and lead to the formation of gaps and voids.  

Light-curing the Composite 

Failure to obtain an adequate degree of conversion and depth of cure negatively impacts clinical outcomes such as marginal leakage or, in some cases, wash-out of composite material, resulting in gaps.³ The floor of the proximal box in Class II restorations is often as much as 8 mm or more away from the tip of the curing light, making it particularly vulnerable.

Additionally, universal/posterior composites require the placement of small increments of material of up to 2 mm to allow for adequate curing and to properly manage polymerization shrinkage stress.  It may be tempting to take short cuts, but exceeding the recommended thickness of an incremental layer is an error that can result in undercuring and failure. One of the advantages of bulk fill composites is the ability to obtain adequate depth of cure up to 4-5 mm, thanks to their formulation and the use of specific photoinitiators.

It goes without saying that for all composites, the composite manufacturer’s recommendations for curing should be followed.

Achieve Excellent Cavity Adaptation with Help from Dentsply Sirona

Choosing a suitable composite, adhesive system and curing light is crucial for the success of composite restorations. With Dentsply Sirona’s SDR® flow+ Bulk Fill Flowable and Prime&Bond active® Universal Dental Adhesive, together with the SmartLite® Pro Modular LED Curing Light, you can reliably achieve gap-free cavity adaptation.  

SDR^® flow+ material and the bulk fill technique is proven to be safe, effective and clinically durable compared to conventional layering techniques^9-10. What’s more, it’s the most researched bulk fill material available¹⁰. This flowable bulk fill composite makes it possible to achieve excellent marginal adaptation, with the following features:

• Low viscosity and flowability result in reliable filling.
• Self-leveling material provides for easy and faster application without agitation, helping to ensure excellent marginal integrity.
• Easy and controlled delivery with a precise application tip for access to the site, accurate and void-free placement.
• Fast bulk fill placement of up to 4 mm in depth, resulting in fewer steps and up to 40% reduced placement time.¹¹
• Patented SDR® Technology that effectively dissipates energy during polymerization and results in a more relaxed polymer network, minimizing polymerization stress even with a 4 mm increment. 

SDR® flow+ Bulk Fill Flowable also offers versatility. It can be used for Class 1 and II restorations as a base layer in an open or closed sandwich technique, together with an overlay of universal/posterior composite. As a stand-alone bulk fill restorative material, it can be used for Class I, III and V restorations

Using Prime&Bond active® Universal Dental Adhesive together with SDR® flow+ Bulk Fill Flowable material further alleviates the challenges of adaptation. This low viscosity and low film thickness material seamlessly adapts to cavity walls and flows easily into every nook and cranny. What’s more, Prime&Bond active® Universal Dental Adhesive offers high bond strength under varying moisture levels, for a reliable bond and virtually no post-operative sensitivity.

Adequate light-curing is always a must have and that’s where the SmartLite® Pro Modular LED Curing Light comes in! It’s designed to offer leading quality of cure thanks to excellent beam collimation, a large 10 mm active curing diameter, and state of the art optics with an optimized 4 LED design that provides for a homogeneous beam over the entire active curing area. Ergonomics is built in with a slim pen-style design that provides for excellent intraoral access and makes it easier to maintain the proper curing angle. 

Selecting Dentsply Sirona’s SDR® flow+ Bulk Fill Flowable and Prime&Bond active® Universal Dental Adhesive together with the SmartLite® Pro Modular LED Curing Light is a win-win for you, your patients and your practice!  

Here at Dentsply Sirona we want to support you further with our entire online dental academy complete with webinars, how-to videos, and real-world examples on how to create streamlined solutions with efficient procedures and even greater patient satisfaction. Contact us now and let’s get started!