Matrix metalloproteinases (MMPs) in dentistry

Matrix metalloproteinases (MMPs) are a family of zinc- dependent endopeptidases that degrade a variety of extracellular matrix components. They play important roles in tissue morphogenesis, development and remodelling. The MMPs are secreted in latent forms (pro-MMP) and activated extracellularly. Their expressions and activities are regulated by the interaction with specific tissue inhibitors of metalloproteinases (TIMPs).

Imbalance between activated MMPs and their TIMPs results in pathological destruction or accumulation of the extracellular matrix.Certain MMPs and TIMPs have been identified in human tooth structures and reported to play different roles in various physiological and pathological processes during human dentine—pulp complex formation and maintenance. Among these MMPs, the distribution of gelatinases with collagen-degrading ability (i.e., MMP-2 and MMP-9) and their inhibitors is of particular interest because of their important roles in tooth formation and mineralization, as well as in the process of caries progression and degradation of dentine hybrid layers.

                           REF : JOURNAL OF DENTISTRY 39 , 2011.

methods to determine polymerisation shrinkage

1. Dilatometry,
2. modified bonded disk,
3. strain gage,
4. linear transducer,
5. gas pycnometer

REF: Dental Materials (2004) 20

irrigation system ( soni care canal brush )

The Sonicare CanalBrush is a combination of a newly designed intra-canal polypropylene brush inserted into a Philips Sonicare Elite toothbrush (Philips, Amsterdam, Netherlands). The sonic toothbrush operates at a frequency of 50 Hz and performs 31 000 strokes per minute. The head of the original Sonicare Elite toothbrush was altered to hold the CanalBrush. The Sonicare achieves brush velocity with a combination of high frequency and high amplitude brush motion. This velocity generates dynamic action but is gentle on the root canal walls. The Canal Brush has a total length of 41 mm. Its contra angle shaft of 15.34 mm includes the acting 16 mm component that contains the bristles. The 30 bristles are <0.40 mm long and arranged opposite to each other with an inter-bristle distance of 0.50 mm. The bristle tip has a diameter of 0.25 mm, and the core increases with a taper of 2%. The acting part of the bristle starts approximately 1 mm behind the tip.

Technique for measuring root canal curvature (schneider method )

 The angle of the curvature was first determined by Schneider (1971). He determined by marking certain points like point A which denotes the apical foramen. The point where the canal begins the curvature is marked as point B. A line is then drawn parallel to the long axis of the canal through point B, and a point C is chosen on this line such that the distance between B and C is equal to that between A and B. The angle formed by lines AB and BC is the angle of curvature.

From E and F, the midpoints of AB and BC, respectively, two lines are drawn perpendicular to the lines AB and BC, which would meet at the circumcentre 0 of triangle ABC. The distance between 0 and A, B or C is the radius (K) of the circumference, which determines the magnitude of the curve.