Clinical and Radiographic Assessment of Periodontal Infrabony Defect Depth and Width and Their Correlation

Brief Background There is preliminary evidence of periodontal defect depth, number of walls and the width of infrabony defects exerting influence on the regenerative potential of particular therapeutic modality. Aim: To assess defect width and defect depth and their influence on pretreatment defect angle in patients affected with periodontal disease. Materials and Methods 60 untreated severe chronic or aggressive periodontitis patients were selected for the study. Digital intraoral periapical radiograph of defects in all patients were taken using RVG. First auxiliary line was drawn to represent tooth axis (AUX1). Perpendicular to this, a second auxiliary line (AUX2) was drawn that ran through most coronal margin of defect (M3). The depth of defect was measured as the distance between the base of bony defect and AUX2. The width of defect was the distance from coronal margin of bony defect to the root surface perpendicular to AUX1. Results In a total of 67 defects, the radiographic defect depth, defect width and defect angle for maxillary arch was 3.19 ± 1.19 mm , 2.82 ± 0.63 mm and 37.34 ± 9.47 ° respectively while these values for mandibular sites were 3.69 ± 0.92 mm, 2.87 ± 0.76 mm and 35.62 ± 7.08 ° respectively. Multilevel regression analysis revealed narrow defect angles to be related to deep infrabony defects, whereas the width of the interdental space to wide defects. Summary and Conclusion Defect dimensions are determined by the radius of action of microbial biofilm and the baseline defect angle of an infrabony defect would be a function of defect depth. Key Words: Periodontitis, periodontal therapy, vertical defects, radiography

Effects of Grease Types on Vibration and Acoustic Emission of Defective Linear-Guideway Type Recirculating Ball Bearings

This paper deals with effects of grease types on vibrations and acoustic emissions (AEs) of linear-guideway type recirculating ball bearings with a millimeter-sized artificial defect in the carriage. First, the vibration and AE of one normal bearing without a defect (Type N) and six defective bearings (Types D1–D6) were measured using a linear velocity of 1 m/s. Three types of grease are used for the lubrication of test bearings. The experimental results show that the vibration and AE amplitudes (the pulse amplitudes, the root-mean-square (RMS) values, and component amplitudes in the spectra) of both the normal and defective bearings have a tendency to be reduced when a grease with higher base oil viscosity is used. Under the same type of grease, the RMS values of the vibrations and AE of the defective bearings increase as the defect angle increases. However, the increases of the RMS values due to increased defect angle (the increasing rates of the RMS values) are reduced when a grease with higher base oil viscosity is used. To explain these experimental results, grease impact tests are carried out. The grease impact tests show that a grease with higher base oil viscosity reduces the impact velocity and the maximum impact forces. This implies that a grease with higher base oil viscosity generate greater viscous resistance to balls in the test bearings then reduces the ball impact forces in the ball circulation collisions and ball-defect collisions. Because of the reduction of the ball impact forces, both the vibration and AE amplitudes as well as the increasing rate of the RMS values are reduced.

Effects of Grease Types on Vibration and Acoustic Emission of Defective Linear-Guideway Type Recirculating Ball Bearings

In this paper, vibrations and acoustic emissions (AEs) of defective linear-guideway type recirculating ball bearings under grease lubrication were measured. The experimental results show that the vibration and AE amplitudes (the pulse amplitudes, the RMS values) of both the normal and defective bearings have a tendency to be reduced when a grease with higher base oil viscosity is used. Under the same type of grease, the RMS values of the vibrations and AE of the defective bearings increase as the defect angle increases. However, the increases of the RMS values due to increased defect angle are reduced when a grease with higher base oil viscosity is used.

Vibration and Acoustic Emission of Linear-Guideway Type Recirculating Ball Bearings With a Millimeter-Sized Artificial Defect in the Carriage

This paper deals with vibrations and acoustic emissions (AEs) of linear-guideway type recirculating ball bearings with a millimeter-sized artificial defect in the carriage. The vibration and AE of one normal bearing without a defect (Type N), and six defective bearings (Types D1–D6) were measured using a linear velocity of 1 m/s. The defects in the bearings range from 1.87 mm to 6.77 mm in length, 2.45 mm to 3.80 mm in width, and 23.3 μm to 68.0 μm in depth. The experimental results show that the pulse amplitudes of the vibrations and AE (both the peak-to-peak and RMS values) of the defective bearings have a tendency to be greater than those of the normal bearing. Both the measured vibration and AE components over 30 kHz increased in the carriages with defects. To explain these increases in the defective bearings, a collision model with balls and one defect in the carriage is presented. That collision model shows that the increases in both the vibrations and AE of the defective bearings are caused by increases in the defect angle. A reasonable correlation exists between the presented collision model and the measured vibrations or AE of the defective bearings.