Infective endocarditis

Infective endocarditis (IE) is a serious condition characterized by colonization or invasion of the heart valves or mural endocardium by a microbiological agent, following a transient entry into the bloodstream (bacteraemia). A number of factors can put a patient at high risk of developing an endocarditis:

A number of invasive medical procedures have been causally associated with bacteraemia and endocarditis in susceptible patients and these include dental treatment. The British Society for Antimicrobial Chemotherapy previously recommended the use of antibiotic prophylaxis for any form of dentogingival manipulation in high-risk patients. These recommendations have now changed in the UK.

The National Institute of Health and Clinical Excellence (NICE) now advise that antibiotics to prevent IE should not be given to adults and children with structural cardiac defects at risk of IE who are undergoing dental interventional procedures and this includes orthodontic treatment. According to NICE, current evidence suggests that such antibiotic prophylaxis is not cost effective and may lead to a greater number of deaths through fatal anaphylactic reactions than from not using preventive antibiotics.

Bleeding disorders

Severe bleeding disorders such as haemophilia A do not contraindicate orthodontic treatment, but factor transfusion will be required to achieve haemostasis if dental extractions are necessary. Any risks of potential bleeding in the oral cavity during orthodontic treatment can be kept to a minimum by:

These minor intraoral bleeds are an irritation to most patients, but can be a serious problem in this group. The orthodontist should also be aware of the increased risk of these patients being carriers for hepatitis or the human immunodeficiency virus (HIV).

Childhood malignancy

The commonest malignancies in childhood are the leukaemias, and amongst these, acute lymphoblastic leukaemia accounts for around 80% of cases. This condition mostly occurs in early childhood, before orthodontic treatment is routinely carried out. Treatment for a variety of malignancies in children often involves the use of radiotherapy, which can affect the tooth-bearing tissues. This may result in tooth agenesis and root shortening (Fig. 6.1). Orthodontic treatment should be delayed for these patients until they are in a period of remission and if diagnosis occurs during orthodontic treatment it is usually advisable to suspend treatment and remove the appliances. For patients with severe root shortening orthodontic treatment is contraindicated.

Figure 6.1 Localized root shortening in the upper right quadrant following cranial radiotherapy for treatment of a retinoblastoma.

Diabetes

Patients with insulin-dependent diabetes are more susceptible to periodontal disease and therefore excellent oral hygiene accompanied by regular periodontal maintenance is essential during orthodontic treatment.

Immunosuppression

Immunosuppressant drugs such as cyclosporin, which are routinely used in transplant patients to prevent rejection of the donor organ, can cause gingival hyperplasia, which can be exacerbated by orthodontic appliances. Excellent oral hygiene needs to be maintained during treatment and this can be reinforced with a chlorhexidine mouthwash. Gingivectomy of hyperplastic tissue may be necessary before or even during treatment.

Epilepsy

Removable orthodontic appliances should be avoided in the poorly controlled epileptic as there is a potential risk to the airway from displacement during seizures. These patients can also be at risk from gingival hyperplasia due to the use of certain anticonvulsant drugs; therefore a high standard of oral hygiene must be maintained during treatment.

Asthma

The regular use of steroid-based inhalers can result in oral candida infections on the palate, which can be made worse by the use of palate-covering removable appliances. Patients with autoimmune and hyper-allergenic conditions can also be more prone to root resorption during orthodontic treatment.

Allergies

A patient may present with a reported history of allergic reaction. Although many materials used in orthodontics are capable of inducing an allergic response, the most relevant are natural rubber latex and nickel.

Allergy to latex was first recognized in the 1970s and its occurrence has increased in recent years, particularly amongst healthcare workers following the universal adoption of wearing protective gloves. Latex allergy has been reported in orthodontic practice in relation to gloves and orthodontic elastics. The most common allergic response is a type IV delayed hypersensitivity reaction triggered by the chemical accelerators used in the manufacture of latex. This causes a localized contact dermatitis, typically associated with a pruritic eczematous rash. The IgE-mediated type I reaction is less common but has more serious consequences, including anaphylaxis. Amongst the general public, type I sensitivity has been estimated to occur in around 6% of the population (Ownby et al, 1996). Investigation is via skin prick testing or immunoassay. Patients with a confirmed type I allergy should be treated in a ‘latex-screened’ environment where potential exposure to any allergens is minimized. Synthetic gloves composed of vinyl or nitrile are available as an alternative to latex gloves, whilst the use of orthodontic elastomeric auxiliaries containing natural rubber latex should be avoided. Latex-free silicone elastics are available but show greater force decay and as such, require more frequent replacement.

Orthodontic wires and brackets contain nickel and nickel allergy is thought to be present in approximately 10% of Western populations and more common in females. It is usually a type IV allergic reaction related to the wearing of jewellery or watches and body piercing. Fortunately, oral reactions are rare, although prolonged exposure to nickel-containing oral appliances may increase sensitivity to nickel (Bass et al, 1993). Intraoral signs are nonspecific and have been reported to include erythema, soreness at the side of the tongue and severe gingivitis, despite good oral hygiene. Definitive diagnosis is usually achieved via patch testing. Stainless steel wires and brackets contain a relatively low proportion of nickel and are considered safe to use in a patient with diagnosed nickel allergy although titanium or cobalt chromium nickel-free brackets are available. In contrast, nickel titanium archwires have a much higher content, and should be avoided in these patients.

Frontal view

The frontal view of the face should be assessed vertically and transversely, with attention being paid to the presence of any asymmetry. In addition, the relationship of the lips within the face is examined in detail.

Vertical relationship

Vertically the face is split into thirds, with these dimensions being approximately equidistant. Any discrepancy in this rule of thirds will give an indication of disharmony within the facial proportions and where this lies. Of particular relevance is an increase or decrease in the lower face height. The lower third of the face can be further subdivided into thirds, with the upper lip falling into the upper third and the lower lip into the lower two-thirds (Fig. 6.2).

Figure 6.2 The face can be divided into thirds.

The upper face extends from the hairline or top of forehead (trichion) to the base of the forehead between the eyebrows (glabellar). The midface extends from the base of the forehead to the base of the nose (subnasale). The lower face extends from the base of the nose to the bottom of the chin (menton). The lower third of the face can be further subdivided into thirds, with the upper lip in the upper one-third and the lower lip in the lower two-thirds.

Lip relationship

The relationship of the lips should also be evaluated from the frontal view (Fig. 6.3):

• Competent lips are together at rest;

• Potentially competent lips are apart at rest, but this is due to a physical obstruction, such as the lower lip resting behind the upper incisors; and

• Incompetent lips are apart at rest and require excessive muscular activity to obtain a lip seal.

Figure 6.3 Competent (left), potentially competent (middle) and incompetent (right) lips.

Lip incompetence is common in preadolescent children and competence increases with age due to vertical growth of the soft tissues, especially in males (Mamandras, 1988).

Incisor show at rest

In adolescents and young adults, 3 to 4-mm of the maxillary incisor should be displayed at rest (Fig. 6.4). In general, females tend to show more upper incisor than males, with the amount of incisor show reducing with age in both sexes. An increased incisor show is usually due to an increase in anterior maxillary dentoalveolar height or vertical maxillary excess. Occasionally it is due to a short upper lip. The average upper lip length is 22-mm in adult males and 20-mm in females.

Figure 6.4 Normal upper incisor shown at rest (upper) and on smiling (middle). Increased upper incisor shown on smiling (lower panel).

Incisor show on smiling

Ideally 75 to 100% of the maxillary incisor should be shown when smiling (Fig. 6.4), but this also reduces with age. Some gingival display is acceptable, although excessive show or a ‘gummy smile’ is considered unattractive (Fig. 6.4).

Smile aesthetics is also an important component of orthodontic treatment planning and should be formally assessed (Box 6.2).

Box 6.2 Aesthetics of the smile

During examination of an orthodontic patient the soft tissues should be assessed in animation and not just at rest. A key component of this is the smile. Smiling is an important part of communication and an unattractive smile can be a considerable social handicap, often providing a reason to seek treatment. Creating a pleasing smile is therefore a fundamental aim in orthodontics. Three principle characteristics of the smile need to be assessed (Sarver, 2001):

• Incisal and gingival show—the full height of the maxillary incisor crowns should be visible on smiling. Some gingival show is acceptable, but this should not be excessive. Generally, males show less tooth substance and gingiva then females on smiling, and in both groups this reduces with age; therefore, a full smile gives a youthful appearance. In addition, the gingival margins of the maxillary central incisors and canines should be level, with those of the maxillary lateral incisors being around 1-mm more incisal.

Pleasing gingival aesthetics. The gingival margin of the maxillary central incisors and canines are level, with the lateral incisor margin situated slightly below this. The embrasure spaces between the teeth (dotted lines) increase in size from the maxillary central incisors back. The connector areas (where the teeth appear to meet and indicated by red arrows) should be approximately 50, 40 and 30% of the maxillary central incisor crown length for the maxillary central incisors, central-lateral incisors and lateral incisors-canines, respectively (left panel). The maxillary incisor edges should also lie parallel to the curvature of the lower lip to produce a consonant smile arc (right panel) (Gill et al, 2007).

• Width—the lips should correctly frame the maxillary dentition with bilateral buccal corridors (the space between the buccal surface of the distal-most maxillary molar and the angle of the mouth on smiling) visible but not excessive. This relationship is affected by both the width of the dental arch and its anteroposterior position. However, excessive orthodontic expansion can result in complete elimination of the buccal corridors and an artifical denture-like smile.

• Relationship of the upper incisor edges with the lower lip—the upper incisor edges should be parallel to the curvature of the lower lip on smiling. This is known as the smile arc. Flattening of the smile arc will result in a less attractive smile, which can also be associated with premature aging.

Transverse relationship and symmetry

The transverse proportions of the face should divide approximately into fifths (Fig. 6.5). No face is truly symmetrical; however, any significant facial asymmetry and the level at which it occurs should be noted. This can be done by assessing the patient from the front and also from behind and above, looking down the face (Fig. 6.6). The relative position of each dental midline to the relevant dental base should be recorded. Asymmetries of the lower face are particularly common in class III malocclusion with mandibular prognathism.

Figure 6.5 Transverse facial proportions should divide approximately into fifths (each one the width of the eye).

Figure 6.6 Facial asymmetry viewed from above and behind.

Mandibular asymmetry has been described as primarily of two types (Obwegeser & Makek, 1986):

• Hemimandibular hyperplasia—characterized by three-dimensional enlargement of the mandible, which terminates at the symphysis. There is an increase in height on the affected side, usually accompanied by a marked cant of the occlusal plane. This can be seen by asking the patient to bite onto a wooden tongue spatula.

• Hemimandibular elongation—characterized by a horizontal displacement of the mandible and chin-point towards the unaffected side. There is usually a marked centreline shift and a crossbite on the contralateral side, but no occlusal cant.

Profile view

The facial profile should be assessed anteroposteriorly and vertically.

Anteroposterior relationship

An assessment should be made of the skeletal dental base relationship between the upper and lower jaws in the anteroposterior plane (Fig. 6.7). This can be achieved by mentally dropping a true vertical line down from the bridge of the nose (often called the zero meridian). The upper lip should rest on or slightly in front of this line and the chin slightly behind. Alternatively, the dental bases can be palpated labially.

Figure 6.7 Skeletal class I (left), class II (middle) and class III (right) profiles.

Facial convexity can also be described in relation to the angle between the upper and lower face.

• In a normal or skeletal class 1 relationship, the upper jaw should be approximately 2 to 4-mm in front of the lower;

• In a skeletal class 2 relationship the lower jaw is greater than 4-mm behind the upper; and

• In a skeletal class 3 relationship the lower jaw is less than 2-mm behind the upper.

An assessment can also be made of the angle between the middle and lower third of the face (Fig. 6.7), with the profile being described as:

• Normal or straight;

• Convex; or

• Concave.

Nasolabial angle and lip protrusion

The nasolabial angle is formed between the upper lip and base of the nose (columella) and should be between 90° and 110° (Fig. 6.8). It gives an indication of upper lip drape in relation to the upper incisor position. A high or obtuse nasolabial angle implies a retrusive upper lip, whilst a low or acute angle is associated with lip protrusion.

Figure 6.8 Normal nasolabial angle.

The lips should be slightly everted at their base, with several millimetres of vermillion show at rest, although they do tend to become more retrusive with age. Protrusion of the lips varies between ethnic groups, with patients of African origin being more protrusive than Caucasians. Lip protrusion is also relative to the size and shape of the chin. Generally, lips are considered too protrusive when both are prominent and incompetent.

Vertical relationship

The face can also be divided into thirds as described earlier and direct measurements made of the facial heights (Fig. 6.9).

Figure 6.9 Facial profile divided into thirds.

The angle of the lower border of the mandible to the cranium should also be assessed. This can be done by placing an index finger along the lower border and approximating where this line points. If it points to the base of the skull around the occipital region, the angle is considered average. If it points below this, the angle is reduced, whilst above it the angle is increased (Fig. 6.10). This usually, but not always, correlates with measurements made of the anterior face height.

Figure 6.10 Clinical assessment of the vertical facial relationship.

Dental health

The teeth present clinically should be noted and an assessment made of the general dental condition, including the presence of untreated caries, existing restorations and the standard of oral hygiene. Evidence of previous dentoalveolar trauma, such as chipped or discoloured incisor teeth, should also be recorded. Previous trauma will warrant further investigation in the form of vitality testing and radiographs. Other pathological signs, such as erosion or attrition, should also be noted.

Dental arches

Each dental arch is assessed independently, with the mandible usually described first. The following features should be recorded for both arches:

Figure 6.11 Upper and lower dental arch crowding.

Figure 6.12 Mandibular canine angulation. Mesial (left); upright (middle); distal (right).

Figure 6.13 The normal occlusal plane of the maxillary and mandibular dental arches follows a curve in the anteroposterior plane, producing the curve of Spee.

Any significant increase or decrease of the curve along either occlusal plane can influence the vertical dental relationship.

Static occlusion

When each dental arch has been assessed the patient is asked to occlude in intercuspal position (ICP) and the static occlusal relationship is recorded.

Overjet

The overjet should be measured from the labial surface of the most prominent maxillary incisor to the labial surface of the mandibular incisors (Fig. 6.14). The normal range is 2 to 4-mm. If there is a reverse overjet, as can occur in a class III incisor relationship, this is also measured and given a negative value.

Figure 6.14 Occlusal variation.

Class I occlusion; reduced overjet associated with a class II division 2 incisor relationship (the buccal segment relationship is half a unit class II); increased overjet associated with a class II division 1 incisor relationship (the buccal segment relationship is a full unit class II); reverse overjet associated with a class III incisor relationship.

Overbite

The normal range is for the maxillary incisors to overlap the mandibular by 2 to 4-mm vertically, or one-third to one-half of their crown height (Fig. 6.15). Overbite is described as:

• Increased if the maxillary incisors overlap the mandibular incisor crowns vertically by greater than one-half of the lower incisor crown height;

• Decreased if the maxillary incisors overlap the mandibular incisors by less than one-third of the lower incisor crown height. If there is no vertical overlap between the anterior teeth, this is described as an anterior open bite and a measurement should be made of the incisor separation;

• Complete if there is contact between incisors, or the incisors and opposing mucosa; and

• Incomplete if there is no contact between incisors, or the incisors and opposing mucosa.

Figure 6.15 Variation in overbite.

Normal (upper left), reduced (upper right), increased (lower left) and anterior open bite (lower right).

If the overbite is complete to the gingival tissues, it is described as traumatic if there is evidence of damage. This is most commonly seen on the palatal aspect of the upper incisors or labial aspect of the lower (Fig. 6.16).

Figure 6.16 Traumatic overbites causing palatal (left panels) and labial (right panels) gingival trauma.

Anterior crossbite

Teeth in anterior crossbite should also be noted along with the presence and size of any displacement of the mandible that may occur when closing in the retruded contact position (RCP) into the intercuspal position (ICP) (Fig. 6.17). An anterior crossbite with displacement can cause labial gingival recession associated with the lower incisors in traumatic occlusion, which if present, should be recorded.

Figure 6.17 Anterior crossbite with a forward mandibular displacement on closing, which worsens the class III incisor relationship.

Centrelines

Maxillary and mandibular dental centrelines are assessed in relation to the facial midline and to each other. Displacement of a centreline can be due to:

• Asymmetric dental crowding (Fig. 6.18);

• Buccal crossbite with a mandibular displacement on closing (Fig. 6.19); and

• Skeletal asymmetry of the jaws (Fig. 6.20).

Figure 6.18 Centreline discrepancies due to asymmetric crowding.

Figure 6.19 Lower-centreline displacement to the right, secondary to a mandibular buccal crossbite associated with a mandibular displacement to the right.

Figure 6.20 Skeletal asymmetries of the mandible producing centreline discrepancies to the right.

Posterior crossbite

The transverse relationship of the dental arches is described in occlusion. Crossbites are described in relation to the arch, whether they are localized or affect the whole segment of the dentition and if they occur uni- or bilaterally:

• A mandibular buccal crossbite exists when the buccal cusps of the mandibular dentition occlude buccally to the buccal cusps of the maxillary dentition (Fig. 6.21);

• A mandibular lingual crossbite exists when the buccal cusps of the mandibular dentition occlude lingually to the palatal cusps of the maxillary dentition (this can also be referred to as a scissors bite) (Fig. 6.22);

• A unilateral crossbite affects one side of the dental arch; and

• A bilateral crossbite affects both sides of the dental arch.

Figure 6.21 Mandibular buccal crossbite.

Figure 6.22 Mandibular lingual crossbite.

Teeth in crossbite should be recorded and any associated displacement of the mandible on closing from RCP to ICP. This can be achieved by ensuring the mandible is fully retruded by placing gentle pressure on the chin and asking the patient to put the tip of their tongue up towards the soft palate until initial occlusal contact is made on closing.

Functional occlusion

Any discrepancy between RCP and ICP should be recorded. The patient should also be asked to slide from ICP to the left and right, and the following should be detailed for each lateral excursion:

The patient should also be asked to slide the mandible forwards to check for disclusion of the posterior teeth.

Temporomandibular joint

The patient should be questioned about and examined for any signs and symptoms associated with both temporomandibular joints. These include:

Although some occlusal traits have a weak correlation with temporomandibular dysfunction, orthodontic treatment should be regarded as being neutral in relation to this condition. Treating a malocclusion is unlikely to have any long-term effect on symptoms, either positive or negative. However, a baseline record of temporomandibular joint health should be taken and any signs or symptoms should be recorded. If these represent the main complaint, they should be investigated further and managed before orthodontic treatment is considered.

Study models

Impressions showing all the erupted teeth, full depth of the palate and good soft tissue extension are needed. These can be taken in alginate for study models and poured in dental stone (Fig. 6.23). A wax or polysiloxane bite should be taken with the teeth in ICP (Box 6.4). Orthodontic models should be trimmed with the occlusal plane parallel to the bases, so the teeth are in occlusion when the models are placed on their back. The bases are also trimmed symmetrically so the archform can be assessed and they are neat enough to be used for demonstration to the patient.

Figure 6.23 Angle trimmed cast stone orthodontic study models.