MR Microscopy in Dental Research

Glass Ionomer Cements (GIC) are widely used dental materials. They adhere to hard dental tissues, release fluoride ions and are bio-compatible. GIC are obtained from the reaction during the hardening process between a polymeric acid and acid-degradable glass. Water plays a crucial role in this reaction; its absence retards or even prevents the reaction while high concentrations results in improper glass matrix formation. In either case, the resulting cement has poor mechanical properties. A potential problem that may manifest itself in clinical applications is the migration of water from the oral cavity into the still hardening cement. To prevent this process, special surface coatings (varnishes) were proposed. Magnetic resonance microscopy is a convenient tool for studying water migration into dental cements and other porous materials because of its good spatial resolution and high sensitivity. The aim of our MR microimaging study was to evaluate the effect of surface coating on the reduction of water contamination in glass GIC restorations [1].

water migration in dental cement

Water concentration in glass ionomer dental cement 36 hours (a, b) and 192 hours (c, d) after immersion in water measured by MR microscopy (a, c) and computer simulated (b, d).

Precise assessment of anatomical features of a human tooth pulp chamber is essential for a successful endodontical treatment. The shape of dental pulp anatomy is often difficult to predict correctly. In many cases dental pulps of first, second, third molars, premolars or even incisors or canines have different number of root channels, which may be irregularly shaped and may have pulpo-periodontal communications. A standard X-ray radiograph of human tooth is obtained by absorption of X rays in hard dental tissues, such as dentine or enamel. Therefore, it yields an image of pulp’s projection in 2D in one orientation only. The X-ray image is also an inverse image of the pulp and the pulp’s shape can be judged just from its outline. X-ray radiographs therefore do not provide sufficient information on pulp’s anatomy, which makes the outcome of the endodontical treatment unpredictable. An efficient 3D imaging technique could minimize these problems as it would enable precise assessment of pulp anatomy in 3D and enable visualization of all root channels and fine anatomical details. Therefore MR microscopy has great potentials to become future standards for dental pulp imaging [2].

X-ray and MR image of a tooth

Images above show a first molar imaged by the conventional X-ray radiography (left) and by the volume rendered 3D MR microscopy (right). In MR microscopy signal comes from the pulp directly and the pulp can be therefore much better visualized than by X-ray radiography. Unfortunately, due to limitations of the present hardware, high-resolution MR imaging of human teeth can be done in vitro only as the scanning time is too long and there is no dedicated hardware for in-vivo tooth MR microscopy. In spite of that, MR microscopy is very promising tool for studying the pulp anatomy. It enables precise determination of a number and a shape of root channels; it can visualize communications between the channels and can even reveal fine anatomical details such as pulpo-periodontal communications.

  1. JEVNIKAR, Peter, SERŠA, Igor, SEPE, Ana, JARH, Orest, FUNDUK, Nenad. Effect of surface coating on water migration into resin-modified glass ionomer cements : a magnetic resonance micro-imaging study. Magn. reson. med., 2000, vol. 44, no. 5, p. 686-691. [PDF]
  2. ŠUŠTERČIČ, Dušan, SERŠA, Igor. Human tooth pulp magnetic resonance microscopy. Period. biol., 2005, vol. 107, p. 275-278. [PDF]
  3. ŠUŠTERČIČ, Duąan, SERŠA, Igor, FUNDUK, Nenad. Prikaz zobne pulpe izdrtega zoba z magnetnoresonančno mikroskopijo (Dental pulp visualisation by magnetic resonance microscopy of extracted teeth). Zobozdrav. vestn., 2006, vol. 61 (1), p. 19-23. [PDF]
  4. SCHARA, Rok, SERŠA, Igor, SKALERIČ, Uroš. T1 relaxation time and magnetic resonance imaging of inflamed gingival tissue. Dentomaxillofacial Radiology, 2009, vol. 38, p. 216-223. [PDF]
  5. ŠUŠTERČIČ, Duąan, SERŠA, Igor. Human tooth pulp anatomy visualization by 3D magnetic resonance microscopy. Radiol. Oncol., 2012, vol. 46, p. 1-7. [PDF]
  6. VIDMAR, Jernej, CANKAR, Ksenija, NEMETH, Lidija, SERŠA, Igor. Assessment of the dentin-pulp complex response to caries by ADC mapping. NMR biomed., 2012, vol. 25, issue 9, p. 1056-1062. [PDF]
  7. CANKAR, Ksenija, NEMETH, Lidija, BAJD, Franci, VIDMAR, Jernej, SERŠA, Igor. Discrimination between intact and decayed pulp regions in carious teeth by ADC mapping. Caries Research, 2014, vol. 48, no. 5, p. 467-474. [PDF]
  8. CANKAR, Ksenija, VIDMAR, Jernej, NEMETH, Lidija, SERŠA, Igor. T2 mapping as a tool for assessment of dental pulp response to caries progression : in vivo MRI study. Caries Research, 2020, vol. 54, no. 1, str. 24-35. [PDF]