Surface Processing: An Elegant Way to Enhance the Femtosecond Laser Ablation Rate and Ablation Efficiency on Human Teeth

Abstract

Background and Objectives The employability of the non‐invasive femtosecond laser ablation technique for dental treatment has been severely limited by its low ablation rate despite the advantage of minimal tissue damage. The study explores a means of improving the femtosecond laser ablation rate and efficiency by physiochemical surface modification. Materials and Methods Surface modification of dental hard tissues has been carried out by food graded orthophosphoric acid and Carie care gel pretreatment. The laser ablation characteristics were studied by using a Ti:Sapphire laser (10 kHz, 10 mm/s, 100 fs, 800 nm) to ascertain the influence of pretreatment. Surface morphology and chemical composition were obtained by using an optical profiler, SEM and EDAX. Results The ablation threshold fluence decreased by almost one‐third whereas the ablation rate and ablation efficiency nearly tripled upon pretreatment. The microstructural and compositional analysis clearly reveals that surface modification and demineralization reduce the threshold fluence and increase the ablation rate by effective utilization of the laser beam energy. The pretreatment effect is more pronounced in orthophosphoric acid as compared with Carie care gel. Conclusions Physiochemical surface modification can be an efficient method to improve the laser ablation rate and ablation efficiency. Compositional analysis can be an elegant tool for pre‐surgery determination of laser ablation characteristics. Clinical Significances Pretreatment surface modification can be an effective way to overcome the limitation of the femtosecond laser for tooth preparation in the clinical setting by strongly enhancing the ablation rate. An enhanced ablation rate along with de nova prediction of ablation characteristics will enable the clinician to perform dental surgery in real time with minimal tissue damage. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Physiochemical characteristics: A robust tool to overcome teeth heterogeneity on predicting laser ablation profile

“…For example, Al‐batayneh et al, 34 reported that the laser ablation threshold of primary teeth (200 mJ) is lower than that of permanent teeth (250–350 mJ) due to the variation of chemical composition and microstructure. Also, in our previous study, 26 the demineralized dentin ablates readily at lower ablation threshold fluence (0.48 J/cm 2 ) than healthier dentin (1.50 J/cm 2 ).…”

“…In addition, the variation of threshold fluence with % area of dentin tubules can also be explained with the help of defect model and heat accumulation model (Figure 4). According to the defect model, 26,35 the presents of defects on the target surface causes large entrapment of laser light. As a result, the focused laser beam is effectively utilized at the target surface, which in turn reduces the ablation threshold fluence.…”

“…Likewise, the presence of dentin tubules act as a defect and enhances the entrapment of focused laser light. According to the heat accumulation model, 26,35 increasing the number of pulses hitting ( N eff ) on the target surface improves the transient temperature of the target above single pulse value which results in reduction of ablation threshold. Conversely, as the number of defects enhance the laser entrapment, the value of ω 0 and D eff increases with increase in % area of dentin tubules.…”

“…The precise dental treatment requires complete knowledge of the ablation profile. Though there are numerous experimental studies attempt to predict the laser ablation profile are quite far and few 15,18,26 . Most of the studies 27‐32 are computational model which requires complete knowledge of thermophysical properties and extensive computational resources 5 .…”

Characteristics of Bubble Oscillations During Laser‐Activated Irrigation of Root Canals and Method of Improvement

“…Finally, it is worth noting that recently published studies with novel laser systems [32–34] suggest that laser ablation may be used also as an alternative to standard mechanical instrumentation in order to reduce generated debris and smear layer.…”