To develop a low cost, compact, open MRI system for dental applications using a Halbach dipole array.It has previously been shown that low field MRI may have an important future role in dentistry (1) although the cost of current MRI systems is prohibitive for this application. Our aim was to develop a specialised prototype, low cost Halbach array magnet (2) which would allow the mouth region to be imaged. The Halbach dipole is a particularly efficient design providing a large homogenous region and a simple mechanical design. The magnet dimensions were scaled to fit over a human head and allow the mouth region to be centred in the magnet with a slight tilt back of the head.A rectangular Halbach four block dipole array consisting of 6x6 and 4x4 sets of M40 50x50x25mm Neodymium blocks mounted on four steel plates was 2D finite element modelled in FEMM 4.2 (Figs. 1, 2). The aperture was 320mm x 210mm. A double layer of blocks was used on the edges to improve the field profile through the magnet. A B0 field prediction along the line shown through the centre of the bare magnet is shown in Figure 2, showing mainly z2 error.The magnet was assembled using a set of stainless steel nuts on four 25mm threaded rods to carefully lower the magnetic plates into position and adjust for parallel alignment and for coarse shimming. The field of the unshimmed magnet, Fig. 5, was measured initially using a gaussmeter (GM05, Hirst, UK) over the line shown in Fig. 2 through iso-centre, agreeing well with the FEMM prediction shown in Fig. 3. To illustrate the potential of the dental magnet system, spin echo images (TR/TE 650/20ms, FOV 160mm, 160x256 matrix, SLT 3mm, NEX =10) of a set of dentures in a CuSo4 doped (1.25 gm/l) water phantom acquired with a 150mm diameter knee coil using the specialised Niche orthopedic MRI system which operates at exactly the same field strength as the prototype magnet, Fig. 6.Low field MRI, with inherently low susceptibility artifacts, could be an important addition to the dentist’s imaging capability if systems can be designed which are sufficiently compact and low cost to be housed in a dental surgery alongside existing X-ray equipment to provide additional soft tissue information. A passive shimming set to suit the magnet geometry as well as a planar gradient set and 50mm intra-oral T/R coil are currently being developed and the magnet will then be integrated with a compact Labview based spectrometer (ISD Ltd., Bradley, UK). The easy to assemble prototype permanent magnet, although requiring further passive and active shimming, has already achieved the field strength, low cost and patient access required.