Essentials of minimally invasive operative dentistry

All members of the oral healthcare team have a part to play in patient management, and the team is comprised of the lead dentist (plus other colleagues in the dental practice), the dental nurse, hygienist, receptionist, laboratory technician, and possibly a dental therapist. In the UK, registered dental nurses can take further qualifications in teaching, oral health education, and radiography, and can specialize in other aspects of dentistry, including orthodontics, oral surgery, sedation, and special care. If the dentist wishes to have a second specialist opinion regarding a difficult diagnosis, formulating a care plan or even executing it, they may refer the patient to a specialist dentist working in another practice, or to a hospital-based consultant specialist in restorative dentistry. These specialists have undergone further postgraduate clinical and academic training and gained qualifications enabling them to be registered as specialists with the General Dental Council (GDC) in the UK in their specific trained fields (e.g. endodontics, periodontics, prosthodontics), or have further specialist training in restorative dentistry. The lead dentist will act as a central hub in the coordinating wheel of patient management, possibly outsourcing different aspects of work to relevant specialist colleagues, as spokes of that wheel. This is the clinical environment in which patients are diagnosed and treated. This room has traditionally been known as the ‘dental surgery’, but a more appropriate modern description might be the ‘dental clinic’, as much of the more holistic care offered to patients within its four walls will be non-surgical in the first instance. The operator and nurse must work closely together. To be successful, each must build up an understanding of how the other works. The clinic consists of a dental operating chair with an attached or mobile bracket table carrying the rotary instruments and 3-1 air/water syringe (and possibly the light-cure unit and ultrasonic scaler), work surfaces (which should be as clutter-free as possible for good-quality infection control; see later), cupboards for storage, and two sinks, one for normal hand washing and another for decontaminating soiled instruments prior to sterilization. Often the surgery will also house an X-ray unit for taking intra-oral radiographs. Most clinics are designed to accommodate right-handed practitioners, in terms of the location of many of the instruments and controls.

Long-term management of direct restorations

As has been emphasized throughout this book, minimum intervention oral/dental care involves more than just the minimally invasive operative treatment of the consequences of dental disease. It involves identifying and predicting disease patterns, and concerns the control/ prevention of disease by modifying aetiological factors and reassessing the adherence to changes in patient behaviours, attitudes, and responsibility. Monitoring the oral cavity and restored dentition ensures that the treatment undertaken, and subsequently improved oral health, is maintained. This should be accomplished through individualized strategic recall regimes. Restorations need to be reviewed regularly and occasionally refurbished, resealed, repaired, or replaced (see Figures 9.1, 9.2, and 9.3, and Section 9.5). Therefore periodic recall appointments, once an episode of treatment has been completed, are just as important as the treatment itself. It is critical that the patient understands the importance of these recall consultations as part of the ongoing care that is being offered to help to maintain their oral health. Three aspects of dental care need to be assessed at recall visits:… • the overall state of the patient’s oral and dental health (review) • the individual patient’s longer-term response/adherence to previous preventive advice and/or treatment, in moderating any aetiological factors that could cause future dental disease (reassessment) • the status and quality of the restorations present (monitoring and maintenance)…. The potential causes of restoration failure have been identified and outlined in Table 9.1. It is important to appreciate that the causes of restoration and tooth failure (see Table 9.2) are often multifactorial in nature. Indeed, as the causes of both tooth and restoration failure are inextricably linked, it is wise to consider them together, as a tooth–restoration complex. The multifactorial aetiology of restoration failure is often due to manifestations of inherent long-term weaknesses in the mechanical properties of different restorative materials (e.g. poor edge strength, wear, compressive strength, water absorption, etc.) and/or problems with the technical application of the restorative material for the chosen clinical situation (i.e. incorrect choice of material and poor placement technique). The chemistry and physical properties of the different direct, plastic restorative dental materials at a dentist’s disposal have been discussed in Chapter 7.

Principles of management of the badly broken down tooth

This textbook has covered the common causes of broken down teeth: dental caries, tooth wear, and trauma. In addition, long-term failure of parts, or all, of the existing tooth–restoration complex can be significant and may require further operative intervention for its successful management (see Chapter 9). Many intra-coronal defects can be repaired with direct adhesive restorations, as discussed in Chapters 5 and 9. However, the situation can be complicated by the loss of significant portions of existing restoration or tooth structure (e.g. cusps, buccal/lingual walls), which influence the restorative procedures used in an attempt to maintain the tooth longevity, as well as pulp viability, for as long as possible. For direct restorations to succeed clinically, they require healthy dental tissues to aid support, retention, and ideally provide an element of protection from excessive occlusal loads. With diminishing amounts of tooth structure to work with, greater thought and care are required to manage and prepare the remaining viable hard tissues to support and retain the larger restoration. The core restoration describes the often large direct plastic restoration used to build up the clinically broken down crown. It is retained and supported by remaining tooth structure wherever possible (sometimes including the pulp chamber and posts in root canals of endodontically treated teeth). These large restorations often benefit from further overlying protection to secure their clinical longevity, by means of indirect onlays, and partial or full coverage crowns. Before carrying out a detailed clinical examination of the individual tooth and the related oral cavity, it is always important to justify your clinical decisions, for both operative and non-operative preventive interventions. The five key reasons for minimally invasive (MI) operative intervention are:… • to repair hard tissue damage/cavitation caused by the active, progressing caries/tooth-wear process (where non-operative prevention has failed repeatedly) • to remove plaque stagnation areas within cavities/defects which will increase the risk of caries activity due to the lack of effective plaque removal by the patient • to help to manage acute pulpitic pain caused by active caries by removing the bacterial biomass and sealing the defect, thereby protecting the pulp • to restore the tooth to maintain structure and function in the dental arch • aesthetics.

Clinical detection: ‘information gathering’

The oral healthcare team (dentist, nurse, hygienist/therapist/oral health educator, laboratory technician, receptionist, practice manager), led by the principal dental practitioner, should all be involved in the decision-making processes and dental management of the patient, as part of the minimum intervention philosophy of oral/dental healthcare (see Figure 1.1 in Chapter 1). This care rationale is patientcentred, engaging with the patient to encourage them to take responsibility for their own oral health. The role of the oral healthcare team is to provide advice and guidance to help the patient to maintain oral health, as well as providing operative treatment to repair damaged hard and soft tissues. Sometimes the dentist will refer difficult cases to a specialist dentist for their opinion as to what the diagnosis and care plan should be. To manage patients successfully, there are five stages that must be followed (see Figure 2.1):… 1. Detecting clinical problems and their aetiology (see Chapter 2): • This involves detective work to help to gather clinically relevant and useful information, primarily using the skills of verbal history taking, oral examination, and relevant special investigations. 2. Diagnosis and risk assessment (see Chapter 3): • The art of interpretation of signs and symptoms/results from investigations to conclude with identifying the cause of the problem and the potential the individual patient has of developing further disease in the future or responding to treatment. Both aspects are critical to planning the overall care of the patient. 3. Prognosis (see Chapter 3): • The art of forecasting the course of a disease or problem, whether treated or not. 4. Formulation of an individualized patient care plan (see Chapters 3 and 4): • This must be underpinned by the non-invasive control of disease and lesion prevention, following the principles of minimum intervention oral care. • The care plan will also include itemized, costed, minimally invasive operative treatments when required. 5. Recall/re-assess/review (see Chapter 9): • Reviewing the outcomes of any care provided, re-assessing the patient’s response to evaluate whether knowledge/behavioural adaptations and adherence have helped to control and/ or prevent disease reoccurrence, and developing adaptive recall strategies/ intervals that are patient-centred, rather than generic and guideline-driven.

Clinical operative procedures: a step-by-step guide

This chapter illustrates several minimally invasive operative dentistry procedures used for the successful placement of direct plastic restorations in the posterior and anterior dentition. The procedure list cannot be and is not exhaustive, but has been chosen to give the reader the broadest application of the techniques described. The techniques shown are not exclusive—there are many varied operative techniques for removing caries and placing suitable restorations (see Chapters 5 and 6), but the authors feel that the methods described are simple and achievable for most clinical abilities and in most clinical situations. The experienced skilled clinician is able to adapt the myriad of skills outlined in these examples to best fit the developing clinical situation presented to them. There are several classifications of cavities in the dental literature that attempt to correlate site, size of lesion, and disease activity. The oldest, simplest, and probably most universally accepted is Black’s classification (see Table 8.1). This classification was originally used to denote the most common sites for caries to develop, so helping to formulate an idea of the individual’s caries risk. Nowadays it is used to describe the site of the cavity or restoration, and is useful for descriptive purposes, communicating between dentists, or annotations in dental records. It must be understood that cavities should not be cut with predetermined geometric shapes according to this classification, but the classification should be used according to the final restoration placed, which will be governed by the biological extent of the caries, the type of material used, and other factors (e.g. amount/strength of tooth structure retained, occlusal factors, etc.). The remainder of this chapter will be dedicated to describing and illustrating the practical stages involved in placing certain types of restoration, outlining in detail the clinical procedures involved (see Tables 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 8.10, and 8.11). Discussion of the separate steps will be found throughout the preceding chapters, and these links are highlighted throughout. It is assumed that the clinical need for intervention has been appropriately ascertained and that any necessary local analgesia has been administered prior to commencement of the restorative procedures outlined.

Restorative materials and their relationship to tooth structure

Modern restorative materials can be classified in several ways, in terms of their retention (chemically adhesive, macro-, micro- or even nanomechanical), their chemistry (e.g. resin-based vs. acid–base reaction, filler particles), or their clinical properties (e.g. aesthetics, strength, handling). It is essential that these materials are considered closely with the histological substrate to which they will adhere or with which they will interact, in order to understand the complexities of each system and their potential clinical uses. This chapter will outline and discuss aspects of dental materials science to enable the reader to understand and appreciate the links with relevant histology and relate this to the clinical aspects of minimally invasive operative dentistry. Also discussed is dental amalgam, still a popular restorative material among many dentists worldwide, although clinical indications for its use are becoming more limited as treatment rationales change and adhesive materials improve. This text will require supplementation from suitable dental histology and detailed dental material science texts. Dental resin composites are aesthetic, plastic adhesive restorative materials that consist of co-polymerized methacrylate-based resin chains embedding inert filler particles (conferring strength and wear resistance) and requiring a separate adhesive (bonding agent) to micro-/ nano-mechanically bond them to either enamel or dentine, respectively. However, not all modern dental composites are based purely on this methacrylate resin chemistry (see Section 7.2.6). Therefore the term ‘composite resin’ is inappropriate and should not be used. Resin composites have developed over the past 50 years, after the introduction of the acid-etch technique (Buonocore, 1955) and methacrylate monomers (Bowen’s resin—Bis-GMA (1971); see Section 7.2.2). The unset (or uncured) material consists of a mixture of several different types of resin methacrylate monomers, most of which are hydrophobic (water-hating) in nature (see Figure 7.1). The monomer chain length affects certain properties of the resin composite:… • Viscosity (or flowability) of the material. This is important in order to minimize voids trapped within the uncured composite during placement and packing within the depths of a cavity (the stiffer the consistency, the greater the risk of trapping air voids). The shorter the uncured monomer length (and therefore the lower the molecular weight), the lower is its viscosity. Often shorter-length, lower-molecular- weight methacrylate monomers form the basis of the resin chemistry of flowable resin composites, and other diluent molecules may be added.

Disease control and lesion prevention

From the previous chapter it can be seen that in all cases of caries and tooth wear, minimum intervention disease control and lesion prevention are key aspects of the management strategy, often commencing in the stabilization phase of the care plan, but continuing throughout the full course of treatment and beyond in order to maintain lifelong oral health. Neither the dentist, as part of the oral healthcare team, nor the patient has the power to prevent the caries or tooth-wear process. These ubiquitous processes occur at the ionic, metabolic, and microscopic level at the tooth surface/biofilm interface, and are made pathological by other factors in combination. If these factors are controlled or modified by the patient (with help from the oral healthcare team), then the processes can be regulated. The term primary prevention is sometimes used in this context. The term prevention has been commonly used, but actually it is only the manifestation of the pathological process (i.e. the lesion in caries or tooth wear) that can be prevented if the disease process is controlled. The term secondary prevention has been used in this context to slow down or stop (arrest) incipient, progressing lesions. Tertiary prevention is a term sometimes used to describe the care offered to the patient in an attempt to control or reduce the pattern of future disease. On the basis of the history and examination, the patient may be allocated to one of the following in terms of caries activity/risk status:… • Caries inactive/caries controlled/low risk: no active lesions and no history of recurrent active restorations in the past 2 to 3 years. A level of control (maintenance) is still required to remain in this stable condition. • Caries active/modifiable risk factors/moderate risk (plaque control, fluoride, diet): presence of active lesions and a yearly increment of more than two new/progressing/filled lesions in the preceding 2 to 3 years. Caries control may be achieved by changing/ modifying risk factors. • Caries active/unmodifiable or unidentifiable risk factors/ high risk (dry mouth, medications): this category will always be high risk, although it may still be possible to control caries by optimal moderation of such risk factors. Presence of active lesions and a yearly increment of more than two new/progressing/filled lesions in the preceding 2 years.

Diagnosis, prognosis, and care planning: ‘information processing’

Once a general and targeted history, examination, and investigations have been carried out (‘information gathering’), it is time for the dentist and their oral healthcare team to assimilate all of the relevant information in order to formulate a diagnosis, prognosis, and care plan for the individual patient (‘information processing’). Although the detection and diagnostic phases are each discussed separately in this book, an experienced clinician will often accomplish both phases simultaneously. It is vital to remember that diagnosis precedes treatment in all cases. Diagnosis is the art or act of inferring, from its signs and symptoms or manifestations, the nature or cause of an illness or condition. This stage is critical in order to allow the dental team and the patient to appreciate the nature, cause, and severity of the illness or condition. The prognosis is the forecast of the course of a disease or the patient’s response to treatment of the disease. This stage helps the dentist and the patient to understand how easy or difficult the treatment will be to carry out, and it allows assessment of the patient’s motivation to cure the problem. In dentistry, the oral healthcare team can only start the patient off on the road to recovery by restoring form and function to their dentition as well as helping the patient to prevent or control the disease process, so preventing its return. It is then up to the patient whether they follow this advice and maintain their oral health in the future. This plan is the formal itemized management strategy, developed by the dentist and their oral healthcare team, for the individual patient to treat the manifestations of a disease and to control it or prevent it from recurring. It can be divided into phases of therapy (e.g. prevention or control, stabilization or definitive treatment, and review, reassessment, or recall), and it should be adapted and modified during its execution for maximum benefit to the patient. It should take into account unforeseen developments in the course of the disease or the patient’s response to care. It should be written down and made clear to all parties for discussion, so that informed consent can be gained prior to implementation.

Dental hard tissue pathologies, aetiology, and their clinical manifestations

Minimally invasive operative dentistry is that aspect of restorative dentistry which repairs and/or restores damaged and defective tooth structure directly in order to maintain pulp vitality, function, and aesthetics (see Figure 1.1). The primary goal is to respect tooth structure during this process, retaining viable and biologically repairable tissues to maintain tooth vitality for as long as possible. The hard tissue damage or defects can be caused by one or more of the following:… • caries • tooth wear • trauma • developmental conditions…. Minimum intervention oral healthcare is that approach to patient management where the oral healthcare team (comprised of the dentist, nurses, oral health educators, hygienists, therapists, technicians, reception staff, and practice managers), led by the dentist, act as one to provide individualized patient-centred care and advice to encourage the patient to take responsibility for and maintain their own oral health. Minimum intervention care revolves around methods of detection/ diagnosis/risk assessment of oral disease, non-operative control/ prevention of these conditions, minimally invasive operative repair of tissue damage, and review/maintenance/recall of the patient and the advice/care offered by the dentist/team (see Figure 1.1). The process of care planning involves the patient, including disease prevention by behaviour change and adherence, not just listing those operative procedures offered to restore damaged or defective teeth in isolation. It must be understood from the outset that even though minimally invasive operative dentistry has a pivotal role in the ‘surgical’ repair of damaged teeth, it alone does not provide the actual cure for dental disease— please understand that ‘drilling and filling teeth does not cure caries!’ The following sections will provide an overview of the four conditions mentioned previously with respect to their aetiology, histopathology, and microbiology where relevant. An attempt will be made to relate these features to the clinical manifestations of each condition, namely carious lesions and tooth-wear lesions.