Dental sleep medicine series 7: The dental examination

This post covers the physical and visual dental examination that can be done to screen for evidence of obstructive sleep apnoea. A thorough medical, dental and sleep history is necessary for a clear diagnostic direction. However, the clinical examination is invaluable to strengthen your diagnosis and to educate the behaviour on their risk factors and consequences of their diagnosis. The history and questionnaires will be covered in a separate post.

Extraoral examination

• Blood Pressure measurement: High blood pressure is a common comorbidity in obstructive sleep apnoea. Screening patients for blood pressure is a good way to start the conversation leading to their diagnosis.
• Pulse oximeter reading: This measures the percentage of oxygenated hemoglobin in blood. This can indicate poor perfusion in an awake patient at rest. Ideal readings are above 95%. You would expect a person with poor perfusion to have comorbidities such as COPD, emphysema or a poor breathing pattern and this will worsen during sleep.
• Neck measurement: An increased neck circumference due to increased fat or muscle deposits will constrict the airway. Men are at particular risk of this as when they increase in weight they tend to do so in the belly and neck area. Women tend to gain weight around the hips and thighs away from the respiratory system. Risk is higher with neck circumference measurements in males  17 inches (43cm) and in females 16 inches (41cm) or larger
• BMI: Body mass index measurements is calculated by dividing the weight in kg by the square of the height in metres. It is an estimate tool to gauge the patient's weight range into a category of health vs unhealthy. A BMI> 35kg/M^2 is considered risky for OSA
• Nasal Collapse on inspiration: The nasal valve is a dynamic area at the entrance to the nose and cannot be observed on any radiographic examination. Clinically, the nasal valve collapse generally on inspiration when the ala of the nose occluding the nasal passage due to the suction effect of breathing. This is more common in patients with narrow nares and can be tested by getting the patient to inspire through their nose quickly and observing the movement of their alae. Collapse can simply be a structural issue with a more fluid tissue and cartilage being present in the walls of the nostrils but may also be a sign of nasal obstruction and increased turbulence causing higher velocity in the nasal airflow. Nasal valve collapse can also be the cause of airway obstructions or airway resistance and can force the patient into a mouth breathing patter at night.
• TMJ range of motion: It is important to evaluate the TMJ including presence of abnormal joint sounds and range of motion. Patients with OSA and bruxism often have TMJ complaints as a comorbidity and this should be screened for.
• Venous pooling: Swelling in the skin under the eyes is a good sign of poor perfusion and a sign of poor quality sleep. It is caused by a lack of venous drainage. 
• Nasal examination: Short of nasal endoscoping the patient, we as dentists are limited to the examination of the nasal valve, anterior nasal septum and inferior turbinates. This limited view does give us a wealth of information that could lead to an ENT referral for further investigation. The anterior nasal septum can be an indication of a further deviation in cartilage or bone inside the nasal cavity. This will cause a physical obstruction and can leave the patient with poor airflow in one or both nostrils. 
• Facial/Skeletal type: High angle facial types and retrognathic mandibles or maxillae are signs of a retruded airway. Short pace patients tend to be the ones who brux and clench and have generally high muscle forces.

Intraoral

• Size and shape of tongue: Weight gain results in an increase in tongue size which in turn will be instrumental in causing base of tongue obstructions. A V shaped posterior dorsal tongue is a sign that there is insufficient tongue space and the tongue is forced posteriorly into the pharynx. scalloping in the lateral surface of the tongue corresponding with the lingual surface of the teeth are a sign that the tongue is being compressed into the teeth due to insufficient tongue space and as it is a compressible soft tissue, the imprints are left in place. 
• Oropharyngeal airway space (Mallampati Index): An index of the visibility of pharyngeal structures that estimates the relative size of the tongue relative to the oral cavity originally used to determine the difficulty of intubation. It is a good estimate of the risk of obstructive sleep apnoea. The examiner sits directly oppopsite the patient and gets them to maximally extrude their tongue without any vocalisation

• Size and colour of Uvula: Snoring is a sign of increased airway resistance which results in increased turbulence that can cause tissue vibration. Not every patient with sleep disordered breathing will present with snoring but there is a high correlation of snorers with sleep disordered breathing. Vibration of the uvula and soft palate is the most common cause of snoring. This chronic nightly irritation will result in a uvula that is red and enlarged. These are invariably the patients who will admit to heavy snoring on questioning.
• Size of tonsils: Grading of tonsils was something we weren't taught at university. In fact, anything behind the third molars was an area we have probably turned a blind eye to. However, as the health professionals who are most likely to examine a patient's tonsils most regularly it is our duty to have a good working knowledge of the area. Size, colour and texture are important but size is the largest determinant of obstruction. The size of the palatine tonsils can be graded into 4 levels.  There is no proper guideline to know what size of tonsil is detrimental to health but we must focus more on the functional aspect of the tisuation. Many patients with enlarged tonsils have little to no obstructions due to their condition and many with fairly innocuous tonsils can have obstructions on respiration.
• Grade 0/1: Tonsils not visible or within the tonsillar fossa
• Grade 2: Tonsils larger than the confines of the tonsillar fossa but <50% towards the midline
• Grade 3: Tonsils past 50% towards the midline
• Grade 4: Tonsils touching or almost touching (kissing tonsils)

• Size of adenoids: The adenoids or pharyngeal tonsils sit in the posterior aspect of the nasopharynx. These aren't immediately visible without endoscopy but if you get the patient to elevate the soft palate by saying "aah", soft palates that do not elevate well may be physically obstructed by enlarged adenoids.
• Lingual Frenum: Testing the mobility of the tongue and restriction by the lingual frenum can be tested by getting the patient to open as wide as possible and lift the tongue as high as they can. Ideally they should be able to reach at least 50% of the way to the upper teeth. Again we must focus on functional deficits in speech, eating and swallowing to determine the need for intervention. the issue with tongue ties is that it does not allow the tongue to easily rest on the roof of the mouth at rest which forces it to sit downwards and backwards into the oropharynx.
• Wear facets, abfractions, erosions: Non carious tooth loss in teeth can occur  due to numerous reasons. Attrition is a result of tooth to tooth contact. I like to show the patient in the mirror how their wear facets line up. Often, the canine facets occur in extreme laterotrusion. I ask the question "Do you chew your food like this" Obviously they don't and it opens the question in their mind how the facets occurred. Abfractions are cervical lesions that occur from heavy lateral forces on teeth. These two lesions are signs of bruxism which is commonly associated with OSA. Erosions tend to appear as loss of surface texture i.e smooth enamel and cupping lesions into dentine. This can be a sign of GORD which is a common companion to increased intrathoracic pressure in OSA.
• Tori and exostoses: Lingual tori and buccal exostoses are buttresses in bone designed to deal with high forces on the teeth. They are a sign that the patient is likely a bruxer. 
• Periodontal evaluation: Periodontal disease can commonly be found in OSA patients. Mouth breathing may lead to increased plaque accumulation on the anterior teeth which can hasten attachment loss. Bruxism on a reduced periodontium can accelerate the loss of supportiive bone and lead to early loss of teeth
• Width of Palate: A narrow maxillary arch form can be a sign of a narrow nasal cavity as the palate is the floor of the nasal cavity. A kicked in maxillary arch signifies poor tongue posture as the tongue didn't rest on the palate at a young age to develop the arch form. Both of these should prompt an ENT investigation.
• Depth of Palate: A high arch palate will encroach into the nasal cavity and can be a sign of poor nasal airflow. developing the form of the palate at an early age is important to drop the height of the palate.
• Muscle palpation: Sore masseters, temporalis and pterygoid muscles can be a sign of muscle overuse in bruxism especially if the patient complains of muscle pain on waking that slowly improves during the day. They may complain of sore jaw joints, muscles or a headache.