Dental luting plays a vital role in ensuring the long-term success and stability of various dental prostheses used in restorative dentistry.
It is the technique used to secure indirect dental restorations, such as crowns, bridges, inlays, onlays, and veneers, to the natural tooth structure. It involves the use of a dental cement which acts as an adhesive between the restoration and the tooth.
However, Dr RL Castillo, Professional Development Manager at GC Australasia Dental, explains there is a critical difference between cementation and bonding that all dentists must understand.
“Cementation is typically used when your preparations allow mechanical retention,” she says. “Bonding is typically used when extra adhesion is required or when aesthetics are of the utmost importance.”
Understanding the key differences between cementation, retention, bonding and adhesion as they apply to securing indirect restorations is an important first step to select the right luting agent.
Cementation: Cementation is the overall process of attaching a dental restoration to the tooth structure. It encompasses the selection of an appropriate luting agent, preparation of the tooth surface, application of the cement, and final seating of the restoration. Cementation ensures the proper fit, retention, and stability of the restoration
Retention: Retention refers to the resistance of a restoration to displacement along the path of insertion. It relies on the shape and preparation of the tooth, the material properties of the restoration, and the luting agent used. Retention is critical in preventing dislodgement or failure of the restoration during normal oral functions.
Bonding: Bonding involves the formation of a chemical or micromechanical bond between the luting agent and the tooth structure or the restoration material. It enhances the strength and stability of the cemented restoration, reducing the likelihood of failure or debonding.
Adhesion: Adhesion is the molecular attraction or force of attraction between two dissimilar materials, such as the tooth structure and the luting agent or the restoration material and the luting agent. Adhesion contributes to the retention and bonding of the restoration.
Misconceptions about luting can hinder proper dental treatment planning and compromise the longevity of restorations. Understanding that luting cement is not permanent, that different types of cements have distinct properties, and that alternative bonding methods may be more appropriate in certain cases is crucial. It’s also essential to recognise that luting cement does not eliminate the need for proper tooth preparation.
Luting cement is permanent: One misconception is that once a dental restoration is cemented in place, it becomes permanent and cannot be removed. While luting cement provides a strong bond, it is not considered a permanent attachment. Dental restorations may need to be adjusted, repaired, or replaced over time, and the cement can be carefully removed by a dental professional when necessary.
All luting cements are the same: Another misconception is that all luting cements are similar and can be used interchangeably. In reality, different types of luting cements have distinct properties, strengths, and applications. The choice of luting cement depends on factors such as the type of restoration, the material being bonded, the desired bond strength, and the clinical situation.
Any type of cement will work: While resin modified glass ionomer cements are widely used and appropriate for many dental restorations, it may not always be the best choice in certain situations. Alternative bonding methods, such as adhesive resin cements, may be more suitable depending on the specific restoration, tooth condition, and patient factors. The selection of the bonding method should be based on a comprehensive evaluation by the dentist.
Luting cement eliminates the need for proper tooth preparation: Some may mistakenly believe that luting cement can compensate for inadequate tooth preparation. However, proper tooth preparation is still essential for achieving a good fit, retention, and longevity of the restoration. Luting cement is not a substitute for proper tooth preparation and restoration design.
There are several types of dental luting agents available, each with its unique properties and indications. The choice of luting agent depends on various factors such as the type of restoration, the material of the restoration and the tooth structure, aesthetic requirements, and clinical conditions. Common types of dental luting agents include:
Zinc Phosphate Cement: Zinc phosphate cement has been widely used in dentistry for many years. It is a powder-liquid system that chemically bonds to the tooth structure through an acid-base reaction. It offers good strength and durability, making it suitable for cementation of crowns, bridges, inlays, and onlays. However, it may cause some degree of pulp irritation due to its acidity.
Glass Ionomer Cement (GIC): Glass ionomer cement is a versatile luting agent that can chemically bond to both tooth structure and certain restoration materials. It releases fluoride, which helps in preventing secondary caries and remineralising tooth structure. GIC has good biocompatibility and is often used for cementing crowns, bridges, inlays, onlays, and orthodontic bands. It exhibits lower strength compared to other luting agents, making it more suitable for non-load-bearing restorations.
Resin-Modified Glass Ionomer Cement (RMGIC): RMGIC is a hybrid luting agent that combines the benefits of resin-based materials and glass ionomer cement. It offers the best balance of ease of use, speed and tooth protection with the strength of a resin cement. RMGICs offer moisture tolerance with excellent chemical adhesion to the tooth. RMGIC is commonly used for cementing metal and porcelain-fused-to-metal crowns, inlays, onlays, and orthodontic brackets. It offers good aesthetics, fluoride release, and adhesion to tooth structure.
Adhesive Resin Cement: Resin-based luting agents are widely used in esthetic dentistry. They provide excellent aesthetics, high bond strength, and low solubility, and are commonly used for cementing all-ceramic crowns, veneers, inlays, onlays, and implant-supported restorations. Resin cements are composed of resin and filler material, such as glass or quartz particles. They can be classified as dual-cure or light-cured, and utilise a bonding agent applied to the tooth prior to the luting procedure. It is recommended to use a universal bonding agent as this features excellent bond to tooth structure.. Depending on the substrate, a universal primer that contains silane coupling agent, MDP and MDTP can be used to bond to various materials, including ceramics, zirconia, non-precious and precious metal, and composite. It’s important to note that resin cements require proper isolation during the procedure as moisture can compromise the adhesion of the restoration to the tooth.
Zinc Oxide Eugenol Cement (ZOE): ZOE cement is a temporary luting agent commonly used for short-term cementation of provisional restorations or as an intermediate cement during endodontic treatment. It has sedative properties, soothing the pulp and protecting it from irritation. ZOE cement has low strength and is not suitable for long-term use or load-bearing restorations.
Polycarboxylate Cement: Polycarboxylate cement is a powder-liquid system that provides good adhesion to tooth structure and certain restorative materials. It releases fluoride and has a moderate strength. It is commonly used for cementing cast restorations, such as crowns and bridges, as well as orthodontic bands. Polycarboxylate cement has good biocompatibility and low pulpal irritation.
It’s important to note that advancements in dental materials continue to introduce new luting agents, such as universal self-adhesive resin cements, which simplify the cementation process while maintaining good bond strength and aesthetics. The selection of a luting agent should be based on the specific clinical situation, with consideration of factors such as retention requirements, material compatibility, and the desired clinical outcome.
Luting dental restorations can present certain challenges that dentists need to consider and address. Achieving an ideal marginal fit, controlling moisture, working within limited setting time, ensuring proper cement cleanup, and addressing aesthetic concerns can impact the success and longevity of the restoration.
Marginal fit: Achieving an ideal marginal fit between the restoration and the prepared tooth surface can be challenging. If the restoration does not fit properly, it can lead to gaps or open margins where luting cement may not adequately seal the restoration. This can result in microleakage, bacterial infiltration, and potential complications. It is essential that the tooth preparation and proper impression or scan are properly executed.
Moisture control: Moisture control is crucial during the luting process. Luting cement requires a dry environment to achieve optimal bonding. Moisture contamination, such as saliva or blood, can compromise the bond strength and longevity of the restoration. Achieving proper isolation and maintaining a dry field can be challenging, especially in areas with significant salivary flow or bleeding.
Time sensitivity: Luting cement typically has a limited working time or setting time before it starts to harden. This means that dentists need to work efficiently to ensure the restoration is properly seated and aligned before the cement sets. It requires careful coordination and timing to complete the luting process within the given working time.
Cement cleanup: After luting a restoration, excess cement needs to be carefully removed to prevent irritation or inflammation of the surrounding gum tissue. However, removing the cement without disrupting the restoration or causing trauma to the tooth or soft tissues can be challenging, especially in areas with limited visibility or difficult access.
Aesthetic challenges: Achieving optimal aesthetics with luting cement can be challenging, especially when dealing with restorations in highly visible areas of the mouth. Matching the colour and translucency of the cement to the natural tooth shade and ensuring a seamless blend with the surrounding teeth can require skill and precision.
To overcome these challenges, dentists must focus on meticulous preparation and isolation techniques to achieve a precise marginal fit and maintain a dry field. Efficient coordination and timing are crucial to ensure proper seating of the restoration before the luting cement sets. Careful attention should be given to removing excess cement without causing damage to the surrounding tissues.
Addressing aesthetic challenges requires expertise in selecting luting cements that provide optimal colour matching and translucency to blend seamlessly with natural teeth.
Optimising dental luting requires careful assessment and decision-making. Dr Castillo emphasises the importance of proper patient assessment, balancing aesthetics and function, selecting the right curing type, and paying attention to viscosity.
“Understanding these key considerations is vital for dental professionals to provide reliable and long-lasting restorations that meet the unique needs of each patient,” she says.
Dental luting begins with a comprehensive patient assessment. This involves evaluating the patient’s requirements and the current condition of the oral cavity. Factors such as tooth preparation, aesthetic demands, and substrate selection should be considered.
“The choice of restoration material, its placement in the mouth, and the patient’s treatment priorities will all impact the choice of luting cement,” Dr Castillo explains. “Additionally, decisions on when to bond or cement the restoration should consider factors like retentive preparation, isolation, caries susceptibility, and aesthetic demands.”
The balance between aesthetics and function is a critical consideration in dental luting. Anterior teeth, being prominently visible during a smile, often prioritise aesthetics. For posterior teeth, where aesthetics may be less critical, functional aspects like chewing efficiency take precedence. Materials such as zirconia or porcelain-fused-to-metal may be viable options for posterior restorations.
Dr Castillo says universal cements like GC’s G-CEM ONE universal self-adhesive resin cement offer the versatility to address both aesthetic and functional needs.
“Depending on the preparation, with G-CEM ONE you could choose from either a simplified self-adhesive cementation or full adhesive application,” she explains. “In the case of full adhesive application, G-CEM ONE offers two simple options – Adhesive Enhancing Primer (AEP) with our unique touch cure technology, or G-Premio BOND for all direct and indirect workflows.
“The advantage of using AEP is that the use of a rubber dam is optional. The surfactant included in AEP will transform the salivary proteins into micelles, which will be blown away during the strong air drying step. This means that in the case of saliva contamination, AEP will be able to dissolve the salivary proteins and avoid a negative impact on the bonding performance.
“Also, the difference between AEP and G-Premio BOND is that AEP is not light-cured and G-Premio BOND must be light-cured.”
Choosing the appropriate curing method is an essential aspect of dental luting. Light-only curing and dual-cured cements are the two primary options. Dr Castillo explains that light curing is effective for thinner restorations – such as veneers – while dual-cured cements are suitable for thicker restorations that require a reliable set.
“Light-only curing allows for extended working time, making it preferred for veneers and aesthetic procedures,” she says. “Dual-cured cements offer the advantage of setting even in areas where light penetration is limited, such as beneath opaque restorations. Considering the opacity of the restoration material is crucial in selecting the appropriate curing type.
“G-CEM ONE has a strong dark cure reaction and offers a high degree of conversion so the adhesion is excellent.”
Viscosity plays a vital role in the cementation process, ensuring proper flow and easy cleanup. Proper cleanup prevents issues such as staining or marginal wearing over time. The stability of the cement and its wear resistance are also crucial, especially when dealing with non-retentive preparations or exposed margins.
“The ideal cement should have a balance of viscosity that allows it to flow under pressure without excessive flowing or thickness,” Dr Castillo explains. “The excess cement should be easily removable to achieve a precise fit and patient comfort. It’s always best to use a cement that has excellent wear and stain resistance around the margins. It should offer simplicity without compromise. ”
Mastering the art of dental luting requires a comprehensive understanding of the techniques involved, dispelling common misconceptions, and addressing the challenges that may arise.
Through meticulous patient assessment, balancing aesthetics and function, selecting the right curing method, and paying attention to viscosity, dental professionals can achieve reliable and long-lasting restorations.
Watch our webinar: How to select the correct dental luting agent
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Main image credit: Dr Otani, Japan