Spray mist reduction by means of a high-volume evacuation system—Results of an experimental study

Abstract

Objectives High-speed tooth preparation requires effective cooling to avoid thermal damage, which generates spray mist, which is a mixture of an aerosol, droplets and particles of different sizes. The aim of this experimental study was to analyze the efficacy of spray mist reduction with an intraoral high-volume evacuation system (HVE) during simulated high-speed tooth preparation for suboptimal versus optimal suction positions of 16 mm sized cannulas and different flow rates of the HVE. Material and methods In a manikin head, the upper first premolar was prepared with a dental turbine, and generated particles of 5–50 microns were analyzed fifty millimeters above the mouth opening with the shadow imaging technique (frame: 6.6×5.3×1.1 mm). This setup was chosen to generate a reproducible spray mist in a vertical direction towards an imaginary operator head (worst case scenario). The flow rate (FR) of the HVE was categorized into five levels (≤120 l/min up to 330 l/min). The number of particles per second (NP; p/s) was counted, and the mass volume flow of particles per second (MVF; μg/s*cm3) was calculated for 10 sec. Statistical tests were nonparametric and two-sided (p≤0.05). Results With increasing flow rate, the NP/MVF values decreased significantly (eta: 0.671/0.678; p≤0.001). Using a suboptimally positioned cannula with an FR≤160 l/min, significantly higher NP values (mean±SD) of 731.67±54.24 p/s (p≤0.019) and an MVF of 3.72±0.42 μg/s*cm3 (p≤0.010) were measured compared to those of the optimal cannula position and FR≥300 l/min (NP/MVF: 0/0). No significant difference in NP and MVF was measurable between FR≥250 l/min and FR>300 l/min (p = 0.652, p = 0.664). Conclusion Within the limitations of the current experimental study, intraoral high-flow rate suction with ≥300 l/min with an HVE effectively reduced 5–50 μm sized particles of the spray mist induced by high-speed tooth preparation with a dental turbine.

Influence of flow rate and different size of suction cannulas on splatter contamination in dentistry: results of an exploratory study with a high-volume evacuation system

“…Also, we could show that a smaller line diameter and a saliva ejector lead to measurable flow rate limited by 150l/min in our study. This is not surprising, as without correction of the HVE’s suction pressure power, a smaller diameter will reduce the flow rate in total in a physical manner, and so, significantly higher SCON values will be occurring [ 8 , 15 ]. There is no dispute that a saliva ejector could aspirate saliva and coolant fluid in the mouth, but them failed to eliminate spray mist and should use in addition to a suction cannula for high-flow rate suction.…”

“…There is no dispute that a saliva ejector could aspirate saliva and coolant fluid in the mouth, but them failed to eliminate spray mist and should use in addition to a suction cannula for high-flow rate suction. But oftentimes, HVE are optimized for vacuum and not for flow rate [ 15 ] or were limited for higher power as it will cause more noise [ 16 ]. But the flow rate at the opening end of each suction cannula is the crucial physical parameter for reducing spray mist [ 15 ].…”

“…But oftentimes, HVE are optimized for vacuum and not for flow rate [ 15 ] or were limited for higher power as it will cause more noise [ 16 ]. But the flow rate at the opening end of each suction cannula is the crucial physical parameter for reducing spray mist [ 15 ]. In detail, the intraoral suction generates a counterflow, which in turn slows down the emitted splatter generated by AGP and has to be so strong that no spray mist leaves the mouth opening.…”

“…In detail, the intraoral suction generates a counterflow, which in turn slows down the emitted splatter generated by AGP and has to be so strong that no spray mist leaves the mouth opening. Only a few studies could show such 100% mitigation of spray mist [ 3 , 15 ], whereat the majority of studies including the current investigation failed to do so and recommended further interventions to control contamination [ 8 , 14 , 17 , 18 ]. This includes among others rubber dam application, pre-procedural antimicrobial oral rinses, and an HVE as tested in our study [ 2 , 19 ].…”

“…In addition to the efforts to improve the effectiveness of intra-/extraoral suction equipment [ 15 , 25 , 26 ], there is also an idea of reducing the amount of fluid spray during AGPs [ 27 ]. When HSP and ADP are used according to manufacture/our internal treatment guidelines, we measured lower water/powder fluid for ADP versus HSP—but that is not equivalent to the subjective sensation of the majority of the user and special equipment or techniques to control spray mist have been described [ 23 , 28 ].…”