Real‐time confocal imaging, during active air abrasion – substrate cutting

Abstract

Air abrasion cutting, using particulates accelerated in a controlled compressed gas stream, is currently being re‐evaluated as a precision tissue removal technique for dental cavity preparation. The minimal vibrations and heat generated during cutting commend the technique for use in the shaping of fragile or brittle materials that are vulnerable to vibrations and thermal stresses. Traditional air abrasion studies have relied solely upon post‐procedure imaging, and cutting process details have been inferred from the nature of the residual surface. In this paper, however, a real‐time confocal microscopic imaging method is described, which for the first time has allowed prior target structure characterization with subsequent imaging of cutting interactions and substrate failure patterns. Using internally focusing long working distance Hill objective lenses, focusing deep to a protective microscope slide and adhesive interfaces, unhindered remote image sampling within the bulk of specimens such as tooth tissue, acrylic and brittle ceramics was possible. Moreover, areas of active cutting and inactive regions were identified within air abraded cavities during their creation. The characteristics of the finished cut surfaces were demonstrated and confirmed the findings of previous SEM studies. The method allowed direct control over all the known variables influencing cutting with particulate streams.

In Vitro Effect of Air-abrasion Operating Parameters on Dynamic Cutting Characteristics of Alumina and Bio-active Glass Powders

“…Since the increase in air pressure does not increase the PFR in the Aquacut unit, as proved in the PFR evaluation study, this finding may be explained based on the dependency upon the increased kinetic energy of the particles, a finding consistent with those of previous studies. 7,27 It is important to be aware that when low air pressure was applied, the difference in air-abrasion cutting efficiency between the two powders more than doubled, implying that at low air pressure settings, the cutting efficiency of air-abrasion depends mainly on the nature of the abrasive powder rather than on the physics of airabrasion unit itself.…”

Operative Dentistry and the Abuse of Dental Hard Tissues: Confocal Microscopical Imaging of Cutting

“…However, devices have been made that allow for the observation of air abrasion as it is cutting into enamel and dentin, using confocal microscopy. 37 The sample is held in a static relationship to the air abrasion nozzle and the cavity is imaged as it is cut.…”

“…Centrally cut access windows allowed for specimen imaging and alignment of the air abrader nozzle to the specimen. 37 Thus, the design allowed for the viewing of serial specimens through a glass window, and the flexible handpiece seal (dental rubber dam) allowed for realignment and several cutting attempts into each specimen. Flat polishing the air abrader head allowed the 450 µm bore nozzle orifice to come within 500 µm of the glass base plate, maximizing the depth of focus into the cut substrate.…”

Influence of air abrasion tips and operation modes on enamel-cutting characteristics

“…1 This technique uses the kinetic energy of aluminum oxide particles that are propelled by compressed air to cut or abrade the target material, and there is no noise to cause discomfort to the professional and to the patient. [2][3] The efficiency of tooth tissue removal is relative to the operating parameters of the air abrasion device. Clinicians have to understand the effect of these parameters because they affect the manner in which the tooth tissue is abraded.…”