superior and anterior position, resting against the posterior slope of the articular eminence (cr) note that the anterior teeth should also be occluding, but the contact should be lighter than the posterior contacts 2. freedom in co this means the mandible is still able to move slightly in the sagittal and horizontal plane in centric occlusion this is also part of the pms theory of occlusion mentioned earlier in organisation of occlusion. 3. immediate and lasting posterior disocclusion upon mandibular movement during lateral excursive movements, the working side contacts act to disclude the non-working side immediately during protrusive movements, the anterior tooth contact and guidance acts to disclude the posterior teeth immediately 4. canine guidance is considered the best anterior guidance system this is due to their ability to accept horizontal forces as they have the longest and largest roots as well as a desirable crown/root ratio they are also surrounded by dense compact bone unlike the posterior teeth which makes them more suited to tolerate horizontal forces canine guidance is also easier to manage restoratively than group function however, if the patient’s canines are not positioned correctly for canine guidance, group function (involving the canines and premolars) is the most favourable alternative it is necessary to understand the concepts that influence the function and health of the masticatory system in order to prevent, minimise or eliminate any breakdown or trauma to the tmjs or teeth. patient adaptability there are various factors that play a role in the adaptive capability of a patient with regards to changes in occlusion. factors such as the central nervous system and the mechanoreceptors in the periodontium, mucosa and dentition are all of importance here. it is in fact, the somatosensory input from these sources that determines whether an individual is able to adapt to changes in the occlusion, opposed to the occlusal scheme itself. failure of adaptation to minor changes in the occlusion can occur, although rare. it is thought that patients who are increasingly vigilant to any changes in the oral environment are less likely to adapt to any occlusal changes. psychological and emotional stress can also contribute to the patient's ability to adapt as these factors have an impact on the central nervous system. occlusal examination in individuals with unexplained pain, fracture, drifting, mobility and tooth wear, a full occlusal examination is vital. similarly when complex restorative work is planned it is also essential to identify whether any occlusal changes are required prior to the provision of definitive restoration in some people even minor discrepancies in the occlusion can lead to symptoms involving the tmj or acute orofacial pain so it is important to identify and eradicate this cause. occlusal examination instruments: willis gauge, mosquito forceps with shim stock, miller's forceps with thin blue and red articulating paper, college tweezers, dental probe. dental mirror (from left to right) by university of aberdeen. instruments required miller’s forceps articulating paper shimstock mosquito forceps mirror dental probe willis gauge the examination should be carried out using a systematic approach whilst assessing the following: facial appearance musculature tmj each arch individually intercuspal position (icp) retruded contact position (rcp) rcp-icp slide lateral excursions protrusion ovd extra-oral examination 1) facial appearance the facial symmetry of the patient should be observed. the skeletal relationship of the patient should then be identified and noted. class i: the maxilla and mandible are in harmony and coincide class ii: the maxilla lies anterior to the mandible and is retrognathic class iii: the maxilla lies posterior to the mandible and is prognathic the facial height of the patient should be considered and it should be noted where there may have been a loss. 2) muscles begin by simply palpating the muscles concerned with the occlusion of the teeth. these muscles include the muscles of mastication and other muscles within the head and neck area, such as the supra-hyoid muscles. it is best to palpate the muscles simultaneously and bilaterally. the temporalis, masseter, medial and lateral pterygoids, geniohyoid, mylohyoid and digastric muscles alongside the trapezius, posterior cervical muscles, occipitalis muscle and the sternocleidomastoid should all be checked for any signs of wasting or tenderness. temporomandibular dysfunction commonly presents with muscular tenderness, but pain or palpable soreness associated with the muscles can also be linked to parafunctional activity. 3) tmj tmj disorders can be detected through occlusal examination. ask the patient to open and close whilst placing two fingers over the space of the tmj. opening of less than 35mm in the mandible is considered to be restricted and such restriction may be associated with intra-capsular changes within the joint. following this, ask the patient to move their jaw to the right and following this, to the left. note any clicking, crepitus, pain or deviation. intra-oral examination 4) maxillary / mandibular arch assess each arch and identify whether there are any signs of occlusal disharmony, overloading, tooth migration, wear, craze lines, cracking or mobility (not due to periodontal causes). abfraction, faceting and possible vertical enamel fracture lesions should also be noted if present. 5) contacts in icp begin by assessing the incisor and molar relationship as described above. similarly examine the overbite and overjet. an overbite of 3-5mm and an overjet of 2-3mms are considered to be within the range of normal. to look at the icp, articulating paper should be placed on the occlusal surface and the patient asked to bite together, which will mark their occlusal contacts. it is best to check these whilst the teeth are dry. during icp, most opposing teeth should be contacting close examination of these contacts marked by the articulating paper help to identify the nature of the tooth contacts good stable contacts often appear as small and not very prominent markings when articulating paper is used and there are multiple contacts on each tooth broad and rubbing contacts identified in icp may be associated with disturbances in function and may indicate occlusal instability these contacts can be verified using shimstock (a 12.5μm thick mylar strip) and the stability of the contacts can be checked the operator should pull the shimstock through the teeth, whilst the patient is biting together this should be carried out for each set of teeth and will highlight if there is adequate contact to hold the shimstock this material is appropriate as it is thinner and will eliminate any false contacts that may occur with even thin articulating papers that are roughly 20μm thick one is also able to pull shim stock through when patients are biting together unlike other articulating paper, which will tear 6) rcp the patient may be guided into cr using one of the follow methods; bimanual manipulation- manipulating the patient's condyles so they are in cr the operator should lightly rest their fingers along the inferior border of the mandible and their thumbs should lie lightly on the anterior aspect of the chin when the patient is relaxed place light downward pressure on the chin and light upward pressure under the angle of the mandible deprogramme the jaw by guiding the opening and closing of the jaw and once the patient is relaxed, ask them to close gently and stop when they feel teeth first contacting chin point guidance- one hand is used to apply pressure to the chin guiding the chin posteriorly with some force in some patients it may be difficult to guide the mandible into cr, for example in those with muscle tension, muscle splinting, occlusal disharmony or parafunctional habit. for these patients a lucia jig or deprogramming appliance can be constructed at chair-side. mark rcp tooth contacts using articulating paper, note the teeth which are contacting and identify whether this rcp position is causing problems related to the occlusion. for example if there is a heavy contact or interference in rcp this may be the cause of occlusal disturbance. it is important to be able to guide the patient into rcp, as a registration may need to be taken in this position particularly if the occlusion is being reorganised, the ovd is being changed or even just for diagnostic and treatment planning purposes. 7) rcp-icp slide the patient should be supine and relaxed. they should be placed into rcp by the operator and then asked to bite together “normally”, this is moving them from rcp into their position of maximum intercuspation (icp). ask the patient to feel the slide and identify whether this is small or large. the slide should be smooth and the direction should be recorded. the operator should evaluate from both the side of the patient and the front of the patient, how far the mandible travels both forward and laterally (however this is difficult and it may be easier to observe by mounting casts onto an articulator). this can be done by observing the maxillary and mandibular incisors during the slide. the rcp-icp slide for most dentate patients tends to be roughly 1–2 mm in an anterior and upward direction. a deflective rcp-icp slide, can have some relation to an anterior thrust. an anterior thrust, which is likely to be associated with the anterior teeth or other teeth involved in guidance such as canine teeth, often causes the teeth to exhibit fremitus. 8) protrusive movements the patient is asked to move their mandible forward from icp. this is commonly around a distance of 8-10mm and would normally be until the lower incisors slide anterior to the incisal edges of the maxillary anteriors. observe the contacts during this movement. mark the contacts using coloured articulating paper alongside the icp contacts, which should be in a different colour - any teeth providing guidance and any interferences should be noted. 9) lateral excursions the patient is also asked to move their lower jaw to one side. lateral movements should be measured and measurements of 12mm are thought to be normal. both working side and non-working side should be observed during this movement. record any teeth that are providing guidance during this movement and any interferences that are present (and the location of these). smooth and unbroken contacts should be identified when these excursive movements are recorded 10) ovd if occlusal wear can be seen, a willis gauge is used to measure the occlusal-vertical dimension and the resting vertical dimension of an individual. take a measurement by placing two reference points on the patients face, one under the nose (usually the columella) and one under the chin. take one measurement whilst the patient is resting (teeth should not be contacting) and one with the patient biting together i.e. in icp and take this measurement away from the resting measurement to give the freeway space. the normal freeway space is usually 2-4mm. patients with considerable tooth wear may have lost occlusal vertical dimension (ovd). when restoring the dentition, it is important to be aware of the exact ovd the patient has and by how much you may be increasing this. patient’s may not be able to adapt to a large increase in ovd and therefore this may have to be done in phases. summary table 1: summary of key aspects of occlusal examination aspect of examination what to look for facial appearance this involves assessing the face for symmetry and categorising the patient into the appropriate skeletal relationship. musculature palpate and ensure normal muscle mass with no signs of wasting. temporomandibular joint any pain, clicking, crepitus or deviation should be noted and appropriate questions asked to find out more. maxillary and mandibular arch examine each arch individually and note any signs of occlusal loading, faceting and microfractures within the teeth. intercuspal position (icp) note overbite and overjet. assess where the teeth contact in icp and whether these contacts are stable or not. retruded contact position (rcp) put the patient into their rcp using bimanual manipulation, or chin point guidance. assess their rcp and if any problems in relation to the occlusion exist note these. rcp-icp slide assess both the quality and the quantity of the slide. the slide from rcp to icp should be smooth and is usually about 1–2 mm in length, this should be confirmed during examination and any issues recorded. protrusive movement any teeth providing guidance should be noted. similarly any interferences should be made note of. right lateral excursion it is important to examine which teeth the guidance is