Dominic Hassall discusses some of the key aesthetic and restorative dentistry materials and techniques and challenges some outdated concepts.
I first published on progressive, clinical, restorative and aesthetic dentistry more than 20 years ago (Hassall et al, 2000; Hassall and Mellor, 2001), the same year I gained my intercollegiate speciality fellowship in restorative dentistry and certificate of completion of specialist training in restorative dentistry.
Since then there have been significant advances in aesthetic and restorative dentistry. I have been fortunate to be at the forefront of many of these developments.
I shall limit this article to a discussion of some of the key materials and techniques that I have incorporated into my practice and clinical teaching over the last two decades. As well as challenge some outdated concepts.
Minimally invasive aesthetic crowns and bridges
With the emergence of zirconia and E.max, minimally invasive all-ceramic crowns and bridges have become a mainstay of aesthetic practice.
You can use zirconia in its monolithic form or veneered. However, we must constantly review the literature. Veneered zirconia proved to be prone to chipping/delamination of the veneering porcelain posteriorly.
Over seven years, success rates revealed only 57.9%. Veneered zirconia can only currently be routinely recommended for anterior use (Hassall, 2017).
Consequently, monolithic zirconia has developed and improved. This allows ultraconservative preparations and improved aesthetics compared to early products.
Over a five-year period, failure rates of only 2.6% for bridges and 0.71% for crowns have been demonstrated (Hassall, 2017).
The newer multi-layered zirconias would generally only be indicated for single anterior crowns, having a strength similar to monolithic E.max.
E.max ceramics can provide superb aesthetics when veneered with E.max Ceram. It can also be used in press-only monolithic form, with excellent aesthetics and strength. I have pioneered these ultraconservative monolithic anterior restorations. I have termed the phrase the 360o veneer to emphasise their minimally invasive nature (Hassall, 2017).
The technique also encompasses the concept of the biologically controlled preparation. This utilises a ‘prep through’ guide formed from the diagnostic wax-up to ensure adequate but minimal preparation (Hassall, 2014).
Single pressed E.max restorations demonstrate good success; a nine-year evaluation of E.max crowns demonstrated 94.8% survival in anterior/posterior positions over nine years (Hassall, 2017).
Bridge performance is variable; for example, only 71% survival has been recorded over 10 years in respect to three unit anterior bridges. The majority of failures being connector fracture (Hassall, 2017).
Minimal preparation ceramics represent a lower risk to the pulp and tooth structure than traditional preparations. They can be combined with the Pashley immediate dentine sealing technique (immediate dentine sealing after preparation with a self-etch primer or etch and bond), which I employ routinely to further minimise pupal irritation (Pashley et al, 1992).
The following case (Figures 1-6) illustrates some of the concepts of contemporary minimally invasive comprehensive aesthetic dentistry and the 360o veneer concept.
The patient suffered near catastrophic fractures to the upper incisors. They were referred with large pin composite repairs in situ. The fractures to the moderately restored incisors occurred due to a lack of protective canine guidance (there was no parafunction).
Pre-restorative short-term orthodontics was undertaken to restore canine guidance before restoring the compromised incisors. A diagnostic wax-up was used to constructed a prep-through guide to biologically control the 360o ultraconservative monolithic E.max preparations. As the arch form was expanded facially this minimises the buccal tooth reduction.
Align, bleach and bond and pre-restorative orthodontics
Minimally invasive treatment options such as the align, bleach and bond philosophy have, fortunately, replaced the misguided philosophy by some that sacrificing large amounts of tooth tissue to satisfy ‘cosmetic demands’ with heavy preparation veneers is acceptable (Hassall, 2014).
Pre-restorative orthodontics to improve functional outcomes is now widely accepted. Also, protective orthodontics to prevent tooth wear and correct occlusal disorders such as the restricted envelope of function (Hassall, 2015).
There have been advances in adhesive bridgework, with highly aesthetic zirconia frameworks (Figure 7) demonstrating success rates of 92% over 10 years in the upper and lower incisor region (Kern et al, 2017).
We must also challenge outdated concepts – for example, the myth of a stress-breaking element in fixed-moveable/jointed bridgework. These bridges are useful to overcome angulation difficulties but there is no credible evidence for any other claims.
During the 1970s, Shillingberg popularised this type of bridge (Shillingberg, 1979; Shillingberg and Fisher, 1973), but more contemporary texts support my opinion and openly question the stress-breaking claims, which are unlikely to have any significant clinical effect as movement can only take place along the long axis of the joint (Ricketts and Bartlett, 2011).
There has been a more away from bimanual manipulation to record centric relation when increasing the vertical dimension. A potentially more physiologically sound, less technique-sensitive and clinically simpler method has evolved using long-term deprogramming and passive muscle contraction to aid recording centric relation (Hassall, 2020).
It overcomes concerns associated with bimanual manipulation, such as the potential for post-restorative anterior mandibular relapse (particularly when rehabilitating advanced tooth wear cases that may have assumed a class III incisor relationship).
Cements, bonding and particle abrasion
Self-adhesive resins have long replaced zinc phosphate and zinc polycarboxylate cements as the first choice for cementation of indirect restorations due to their high bond strength, lack of solubility and ease of use (Hassall and Burgess, 2018). The latest addition is 3M Relyx Universal, you can use this as a self-adhesive resin or a composite luting cement with 3M Scotchbond Universal Plus Adhesive.
The use of particle abrasion to condition dentine and enamel has increased in popularity prior to the provision of composite restorations and fixed prosthodontics as it increases bond strength (Mujdeci and Gokay, 2004). Popular units include the Bioclear blaster and Aquacare unit (Figure 8), which has multiple applications.
Intraoral scanners are becoming an integral part of clinical practice, with the digital workflow having multiple restorative/aesthetic, implant and orthodontic applications.
There have been significant developments in composite materials and techniques.
Composites such as 3M Filtek One Bulk Fill have both reduced shrinkage/stress relief features. They have increased depth of cure up to 5mm, allowing placement in larger increments.
In conjunction with this, there have been dramatic improvements in composite handling and placement techniques with the Bioclear method (developed by Dr David Clark), encompassing the principles of modern composite dentistry (Hassall and Burgess, 2020).
Key principles include:
- Biofilm removal using particle abrasion, improving bond strength and reducing chipping/staining at the tooth restoration interface
- Infinity Edge margin, which combines a modern radius bevel and infinity edge margin, resulting in a more gradual transition from composite to tooth, producing a strong compressive joint and superior aesthetics
- Use of anatomical mylar matrices, developing an ideal emergence profile, excellent marginal adaption and interdental contact points
- Injection bulk-fill over-moulding of warmed composite, resulting in a high strength monolithic composite restoration, with reduced voids, good shine and stain resistance
- Unique finishing protocol.
You can apply the Bioclear method to diastema and black triangle closure (Figures 9-11), anterior composite restorations (including full anatomic anterior crowns) and posterior direct onlays (Figures 12 and 13) with a lower financial and biologic cost than indirect restorations.
It is proving invaluable in the aesthetic and functional rehabilitation of tooth wear cases where traditional composite restorations perform poorly with high maintenance rates in terms of fracture and staining (Hassall, 2014).
To summarise, there have been some truly revolutionary changes in the fields of aesthetic and restorative dentistry over the last two decades. I have incorporated these into my clinical practice and teaching to the benefit of our patients.
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This article was first published in Clinical Dentistry. Read the latest copy here.
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