GAP Australasian Dentist Mar Apr 2020

Category 64 Austràlàsiàn Dentist àhe answer is a resounding àO àraditionally, when a patient presents with a Class malocclusion and associated reverse overjet-they have usually been planned for orthognathic surgery. For many of those patient’s, treatment can involve a far more simple and conservative approach. Firstly, let’s describe a Class malocclusion – this is where the lower arch is positioned anterior to the upper arch. From a technical point of view, the Mesiobuccal cusp of the upper first molar sits posterior to the buccal groove of the mandibular first molar Many of these Class malocclusions also present with a posterior crossbite – as the wider part of the mandible is now more forward to the ideal position, and hence a transverse discrepancy appears in the posterior segment. occlusion will identify the vertical issues more accurately – hence these patients need 2 separate radiographs. àn order to obtain the Cà radiograph-the dentist needs to provide a wax bite with no anterior contact – and this will need to be in the patient’s mouth at the time of that radiograph. On the other hand, if we cannot achieve an edge to edge bite in Centric àelation – this would indicate there is a significant skeletal component to the malocclusion and hence surgery may be the best option. àhere are cases which are diagnosed as a Pseudo Class malocclusion – but the upper incisors are already proclined and/or the lower incisors are retrusive and hence teeth are already dentally compensated for the skeletal malocclusion, and we are unable to orthodontically provide any further compensations – so this type of presentation may also require a combined orthodontic/surgical approach . Assuming the patient has a Pseudo Class malocclusion which is amenable to dental compensation – various options may be available. àhese include but not limited to: Do all class III cases require Orthognathic Surgery? àlàn al Figure 1: A class 3 malocclusion Figure 2: a Teeth in Centric relation and b àCentric occlusion after functional shift Figure 3: Lateral ceph in Centric relation Diagnosing a Class 3 Malocclusion correctly A Class malocclusion can be dental or skeletal in nature. àhe correct diagnosis is essential in providing the correct treatment for an individual patient. ào differentiate between a true skeletal and dental functional malocclusion- patients who present with Class molar relationship and/or anterior crossbite should be checked for the presence of a functional shift. àf we can obtain an edge to edge bite in centric relation, then the diagnosis is a “Pseudo-Class malocclusion”. At that point the patient needs to shift their mandible forwards into Centric Occlusion to obtain a stable and comfortable occlusal scheme. àdeally, the cephalometric analysis also should be performed from Centric àelation to more accurately assess the àagittal discrepancy, whilst the conventional lateral cephalometric radiograph in Centric Figure 4: Non extraction therapy showing upper anterior advancement (before and after) i.à on extraction approach in the upper arch to allow advancement of crowded anterior teeth ii.à Dental extractions in the lower arch eg àxtraction of lower incisor: àspecially appropriate if there is a Bolton tooth size discrepancy (mandibular excess) between the upper and lower incisors. iii.à xtraction of the upper second and lower first premolars: àhis may be indicated in situations where minimal space for correction of upper crowding is required and most of the upper extraction space is utilised for mesial movement of molars to correct molar relationship. iv.à Many of these patients will require Class elastics to aid in anterior movement of the maxillary dentition Hence if we are dealing with a Pseudo Cass malocclusion i.e. one where we can manipulate the mandible into an edge to edge position in Centric àelation – the following questions must be asked: u Are we able to advance the upper anterior teeth/arch? u Are we able to retract the lower anterior teeth? u Or can we do a combination of a and b àf we can answer yes to the above questions – the practitioner has a great chance of being able to provide minimal dental compensations to eliminate the functional shift and hence correct the anterior dental relationship. By Dr Geoffrey Hall Dr Geoffrey Hall