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3.2 The SAC Classification as a Risk Management Tool

The SAC classification is essentially a tool that assists practitioners to identify risks so that they can educate their patients about these potential problems as part of the informed consent process. Clinicians then use their understanding of these risks to plan treatments that minimize risk. Patients are then monitored after the completion of treatment to identify problems that might arise as early as possible, thus allowing intervention to minimize the impact of the problem on the ongoing quality of treatment outcomes.

This review of the SAC classification system incorporated this risk-management focus on risk identification, the likelihood of this problem arising, and the potential impacts of these risks on treatment outcome. Three subgroups in the review team each looked at one major area of risk factors. A “Systems” group reviewed general patient-related risk factors and worked to develop concepts in the SAC Assessment Tool workflow and algorithm. The “Surgical” and “Prosthetic” groups looked at surgical and restorative risk factors respectively, concentrating on risks associated with the treatment approach and technologies. The results from the deliberations of these groups represent a consensus opinion of the risk factors most likely to influence dental implant treatments.

3.3 General Risks

A. DAWSON, J. KLEINHEINZ, A. MURAT KÖKAT, D. WISMEIJER

A structured approach to patient assessment and treatment planning aims to identify all factors that have the potential to have some impact or influence on our treatment. Such a structured approach has been promoted by the ITI in its Academy Learning Module “Structured Assessment and Treatment Planning” (Weber, 2015), and the sequence and steps in this process are illustrated in Figure 2.

ITI Learning Module Structured Assessment and Treatment Planning by Hans-Peter Weber.

Identification of potential risk factors occurs relatively early in this process—during the information-gathering phase that incorporates anamnesis, clinical examination, imaging, and other investigations.

Identification of general risk factors is almost always done in the anamnesis and clinical examination. These factors relate to potential problems arising out of the patient’s medical and dental history and their presenting condition. These general factors fall into three main clusters:

• Patient medical factors

• Patient-related attitudinal/behavioral factors

• Site-related factors

3.3.1 Patient medical factors

Most implant patients present with a range of historical and ongoing medical issues that may have an impact on implant treatment. The following were considered the most significant.

3.3.1.1 MEDICAL FITNESS

A patient’s current health status has the potential to influence their fitness to undergo treatment, and also how well they will heal after implant surgery.

The American Society of Anesthesiologists (ASA) has developed a physical status classification and risk management tool that is widely used to assess patients’ fitness for surgical interventions. The ASA Physical Status classification system (Doyle et al, 2019) is detailed in Table 2.

Fig 2. A structured approach to patient assessment and treatment planning.

Table 2 The ASA Physical Status Classification.

ASA PS Classiciation	Definition
ASA I	A normal healthy patient
ASA II	A patient with mild systemic disease
ASA III	A patient with severe systemic disease
ASA IV	A patient with severe systemic disease that is a constant threat to life
ASA V	A moribund patient who is not expected to survive without the operation
ASA VI	A declared brain-dead patient whose organs are being removed for donor purposes

Healthy patients (ASA I) and those with mild, well-controlled systemic disease (ASA II) are generally good candidates for implant surgery. Some patients identified as ASA III (severe systemic disease that may or may not be well controlled) can be treated with care but have higher risk and might best be managed by highly trained and experienced clinicians. While there may be some occasional indications for implant treatment in ASA IV cases, these treatments are high risk and should be restricted to specialist facilities where emergency medical care is readily available, and by highly experienced surgical teams.

ITI Learning Module Patient Medical Factors by Simon Storgård Jensen

Medical status may also impact the speed of implant healing (usually a slowdown) and the esthetic outcome of treatments. For example, conditions associated with abnormal scarring after surgery, such as the development of keloid scars, may impact esthetic outcomes.

3.3.1.2 MEDICATIONS

Pharmaceutically active substances include prescription medications, over-the-counter medicines, herbal remedies, dietary supplements, and recreational substances. All of these may have an influence on implant treatment either directly through their influence on implant healing and/or peri-implant tissue health, or indirectly through their effects on the patient’s behavior.

Review article from the 6th ITI Consensus Conference on Medication-Related Dental Implant Failure by Vivianne Chappuis and coworkers (2017).

ITI Learning Module Pharmacology with Relevance to Dental Implant Therapy by Stephen Barter.

Possibly of most importance relating to implant surgery are the antiresorptive drugs used to manage osteoporosis. These medications have been linked to a condition known as medication-related osteonecrosis of the jaws (MRONJ) that can also arise following surgical interventions involving the facial skeleton (Figure 3). The risk of MRONJ arising is related to the type of medication (usually biphosphonates), the dosage used and the duration of therapy (as some types of antiresorptives accumulate in facial bones). Antiresorptives with higher potency are usually administered via intravenous route, and hence they are associated with greater risk. This condition can be very difficult to treat and is usually associated with significant discomfort and disfigurement. In cases where there is a history of intravenous treatment, such as in patients with metastatic bone disease or Paget’s Disease, the risks are such that implant treatment would normally be contraindicated.

Fig 3. MRONJ associated with an implant in the mandibular left molar region.

3.3.1.3 RADIATION

Radiotherapy can have a dramatically adverse effect on bone healing. Osteoradionecrosis can arise following surgery in irradiated bone due to the reduction in blood supply to affected bone. This effect is dose related. The dosage to the area where implant placement is planned is the significant consideration, rather than the dosage used to treat the cancer. Doses of less than 50 Gray may allow implant placement with care. Doses of greater than 50 Gray to the area of interest would likely contraindicate implant placement. Time after radiation therapy, and presence of other coadjutant factors, such as smoking and oral hygiene can also impact the rate of occurrence of osteoradionecrosis of the jaws (Aarup-Kristensen et al, 2019).

3.3.1.4 GROWTH STATUS

Implants act in a similar way to ankylosed teeth to retard the development of surrounding bone. As such, placement of implants in growing individuals is normally contraindicated. These implant-supported prostheses can become unesthetic and/or nonfunctional due to apparent infraocclusion as a result of the continued growth of the alveolar bone supporting adjacent teeth. This issue can also arise in older patients, as facial growth can continue—albeit at a very slow rate—well into maturity. The following case demonstrates the esthetic issues that can arise. An implant-supported crown replacing the maxillary right central incisor 5 years after placement in a 24-year-old male patient is seen in Figure 4. Ten years later, there is a significant difference in incisal edge position between the implant-supported crown and the adjacent natural teeth, due to continuous growth and extrusion of natural teeth. The implant crown remained stable (Figure 5).

Fig 4. Five-year follow-up of an implant-supported crown replacing the maxillary right central incisor.

3.3.2 Patient attitudes/behaviors
3.3.2.1 SMOKING HABIT

Tobacco smoking is related to increased risks of implant failure and peri-implant disease (Heitz-Mayfield & Huynh-Ba, 2009). There is some evidence of a dose-related effect, and that this is mediated by nicotine and other tobacco-derived chemicals that compromise wound healing, the immune response, and increase the risk of scarring. Ideally, patients should cease smoking prior to implant placement, as there is evidence that reducing their smoking habit acts to reduce risk. There is a paucity of evidence relating cannabis use or vaping (electronic cigarettes) to implant failure, but caution is advised when treating patients practicing these habits.

Review article from the 4th ITI Consensus Conference on History of Treated Periodontitis and Smoking as Risks for Implant Therapy by Lisa J. A. Heitz-Mayfield and Guy Huynh-Ba (2009).

3.3.2.2 COMPLIANCE

A patient’s willingness and/or ability to comply with instructions is an important factor in any complex treatment where maintenance is vital to long-term success, and where following instructions is essential for optimal treatment outcomes in the short term. Noncompliant patients are more likely to experience problems with treatment and are less likely to follow the necessary steps to overcome these issues. Poor compliance might best be considered relative contraindication for implant therapy until the patient can become motivated to support their treatment.

Fig 5. 15-year follow-up. Note the difference in incisal edge between implant-supported crown and adjacent natural teeth, due to continuous growth and extrusion of natural teeth.

3.3.2.3 ORAL HYGIENE

Bacterial biofilm accumulation has been associated with the development of peri-implant mucositis and peri-implantitis (Salvi & Zitzmann, 2014), and measures to regularly remove these deposits are the prime strategy for preventing the development of these biologic complications. If patients are unwilling or unable to perform these oral hygiene procedures, implant therapy should be delayed until they can do so. Alternatively, other forms of prosthetic reconstruction might best be considered.

Review article from the 5th ITI Consensus Conference on the Effects of Anti-infective Preventive Measures on the Occurrence of Biologic Implant Complications and Implant Loss by Giovanni E. Salvi and Nicola U. Zitzmann (2014).

3.3.2.4 PATIENT EXPECTATIONS

Unrealized expectations are often the trigger of patient complaints to statutory bodies, or to initiation of legal proceedings against treating practitioners. This risk is only amplified by the expense and invasiveness of implant treatment.

Communicating realistic expectations to patients, and managing their desired outcomes, is an important part of the ongoing consent process. A patient may have high and realistic expectations due to their social position or employment, and managing these situations can be challenging. Patients may also have unrealistic expectations, and managing these can often be virtually impossible. An extreme example of such a situation might involve a patient with body dysmorphic disorder. Unless these expectations can be managed, it is best not to proceed with implant rehabilitation.

3.3.3 Site-related factors
3.3.3.1 PERIODONTAL STATUS

A history of treated periodontal disease has been associated with an increased risk of biologic complications (Heitz-Mayfield & Huynh-Ba, 2009), as has the presence of active periodontal disease with periodontal pockets greater than 5 mm in depth. As an elective rehabilitative treatment, an implant-supported prostheses should not be considered until all active oral diseases are under control. Where implant treatment is planned, treatment to manage the periodontal disease prior to implant placement is mandatory.

Review article from the 4th ITI Consensus Conference on the History of Treated Periodontitis and Smoking as Risks for Implant Therapy by Lisa J. A. Heitz-Mayfield and Guy Huynh-Ba (2009).

3.3.3.2 ACCESS

Implant treatment involves the use of instruments that can occupy more physical space than conventional handpieces. During surgical procedures, the use of templates in conjunction with the surgical handpiece, twist drills, and drivers can consume more vertical space, requiring a large mouth opening by the patient. If there is insufficient space, treatment cannot proceed without changes to instrumentation. Limited (but adequate) space can make treatment more difficult, but insufficient space will need adjunctive treatment to make more space if implant placement and restoration is still desired. The use of a measuring device (such as the Straumann Diagnostic-T; Figure 6) during the consultation visit can assist in identifying situations where access will be difficult. This device identifies the amount of space needed to fit the head of the handpiece with the shortest Straumann kit twist drill (33 mm) at the site of planned implant placement.

3.3.3.3 PREVIOUS SURGERIES IN THE PLANNED IMPLANT SITE

Previous surgeries in the site of a planned implant can result in hard and soft tissue changes that may complicate implant placement and healing. Scarring from these surgeries (Figures 7 and 8) is also often associated with reduced vascularity that may have a negative influence on healing. While a single previous surgical treatment in a site may only have a small impact, multiple surgeries are likely to significantly increase the risk of problems.

Fig 6. Clinical use of a Diagnostic-T (Straumann, Basel, Switzerland) to assess available space for surgical instrumentation.

Fig 7. Clinical evaluation of patient missing maxillary central and lateral incisors with evidence of previous surgical procedures.

Fig 8. Clinical evaluation of patient missing tooth 21 with evidence of previous surgical procedures.

Fig 9. An apical infection adjacent to a recently placed implant can infect this site as well.

3.3.3.4 NEARBY PATHOLOGY

As a general rule, elective treatments such as implant therapy are only provided once all other pathologic conditions have been managed. However, there are situations where this may not be either possible or practical. Notwithstanding this, pathologies that may have an adverse effect on implant healing, or the risk of biologic complications, must be managed before implants are placed. For example, apical periodontitis affecting a tooth in another quadrant might be managed simultaneously with implant treatment. However, apical periodontitis related to a nonvital tooth adjacent to the planned implant site (Figure 9) must be managed prior to implant placement.

3.4 Esthetic Risk

W. MARTIN, V. CHAPPUIS, D. MORTON, D. BUSER

Esthetic issues apply where the implant restoration and the surrounding mucosal margin will be visible during normal functional activity or when the patient smiles. Smiles are as unique to individuals as the treatment necessary to maintain their natural appearance. Implant therapy in the esthetic zone can be a challenging process, as patient demands on esthetics coupled with preexisting deficiencies in the anatomy can present obstacles to obtain ideal results. Failure to achieve esthetic and functional results with dental implants could lead to disastrous situations that would require additional surgical and restorative procedures in an attempt to correct the compromise (Buser et al, 2004; Levine et al, 2014).

Consequently, not all implant treatments will have associated esthetic risk. It is therefore important for clinicians to understand their patient’s desires and to perform a thorough initial clinical examination to highlight any potential obstacles that may present as a challenge in achieving an ideal esthetic outcome. Clinicians performing a rehabilitation must have a thorough understanding of tissue biology and the knowledge of all treatment modalities for a given clinical situation, as dental implants may not always be the primary choice. This series of modifiers has been discussed in detail in Chapter 3: “Preoperative Risk Assessment and Treatment Planning for Optimal Esthetic Outcomes” (W. Martin, V. Chappuis, D. Morton, D. Buser) found in “The ITI Treatment Guide, Volume 10: Implant Therapy in the Esthetic Zone: Current Treatment Modalities and Materials for Single-tooth Replacements” (Chappuis & Martin, 2017).

ITI Treatment Guide Vol. 10 Extended Edentulous Spaces in the Esthetic Zone: Current Treatment Modalities and Materials for Single-tooth Replacements by Vivianne Chappuis and Will Martin.

ITI Learning Module Esthetic Risk Assessment by William Christopher Martin.

Table 3 lists the factors that determine esthetic risk in the partially edentulous patient. The esthetic risk assessment (ERA) table was developed to assist clinicians in the diagnosis and planning of treatment in the esthetic zone and to identify clinical situations that could contribute to an esthetic compromise, thus assisting the clinician in determining the SAC classification of the case. It should be noted that, by definition, a case for which there is some esthetic risk (ie, the restoration margin is visible) would have a classification of at least Advanced.