Er:YAG雷射波長2940 nm，是一種於牙科治療時可用來處置軟、硬組織的雷射。Er:YAG 雷射可交換使用不同型態的雷射尖端，根據不同的尖端設計，對於照射表面預期會有不同切削效果。本研究目的是想探討不同型號的雷射尖端，於不同能量設定下，照射後對於牙本質表面的影響。本研究的牙本質樣本是使用牛的前齒來製作。牛齒拔除後，使用Gracey curettes No. 1/2 和 3/4做牙根整平，室溫下保存於0.9%生理食鹽水中。之後切下牙根，並使用環氧樹脂進行包埋，再利用砂紙研磨露出的牙本質表面。露出的牙本質表面硬度的測量是使用維氏硬度儀。四組不同雷射能量設定為50mJ/20pps, water (+)；100mJ/20pps, water (+)；50mJ/20pps, water (-)；100mJ/20pps, water (-)。三種不同雷射尖端型號分別是C600F, PS600T, R600T。雷射照射是雷射尖端與牙本質表面呈 45°直接接觸，以掃描式移動照射 10秒。照射後牛齒牙本質表面的刻痕深度與型態變化是使用粗度計檢測器、光學同調斷層掃描儀及掃描式電子顯微鏡來進行分析與觀測。組織切片是採用蘇木精-伊紅染色來進行觀測。結果顯示使用相同雷射尖端與不同的能量設定下，牙本質表面硬度較大者，雷射照射後產生的刻痕深度無差異；而硬度較小者，刻痕深度有出現差異。在硬度相近的組別，使用不同雷射尖端進行照射，刻痕型態有差異出現，以PS600T最為明顯。在硬度相近的組別，PS600T 所造成的表面粗糙度比起其他兩組有統計學上的顯著差異(p< 0.05)。掃描式電子顯微鏡結果發現，雷射照射後牙本質表面呈現粗糙、牙本質小管有暴露的現象。在組織切片染色下也發現牙本質表面的切削刻痕。本研究結果發現使用Er:YAG雷射進行牙根表面照射的時候，除了要選擇合適的能量設定外，必須考量到牙齒硬度與不同雷射尖端型號，特別是尖端型號PS600T，也會造成牙本質表面粗糙度、刻痕深度等的型態異。

The Er:YAG laser has a wavelength of 2940 nm, which provides the capability to be used on soft and hard tissues. There are different types of laser tips with different cutting effects for different dental purposes. The aim of this in-vitro study was to analyze the characteristics of dentin surfaces after Er:YAG laser irradiation using 3 different types of tips. Extracted anterior teeth from cattle were used in this study. After extraction, the teeth were root planed with hand instruments (Gracey curets No. 1/2 and 3/4). The teeth were stored in 0.9% normal saline at 25°C. The teeth were cut by high-speed diamond bur and fixed in the resin blocks. The exposed dentin surfaces were ground with silicon carbide abrasive papers. The hardness of teeth was measured using Vickers hardness testing machine. There were 4 laser settings: G1–50mJ/20pps, with water spray 70%; G2–100mJ/20pps, with water spray 70%; G3–50mJ/20pps, without water spray and G4–100mJ/20pps, without water spray. The dentin surface was irradiated with 3 types of tips (C600F, PS600T, R600T) according to the settings mentioned above respectively. The optical fiber was positioned 45 degrees to the surface of the sample with swiping motion. The irradiation time was 10 seconds. The irradiation was carried out manually to simulate clinical conditions. Afterwards, the dentin surfaces were analyzed using optical coherence tomography (OCT), surface roughness measuring instrument and scanning electron microscopy (SEM). Histological analysis was done using hematoxylin-eosin (HE) stain. OCT analysis revealed that PS600T produced the most obvious ablation. Among the groups of similar hardness, the groups of PS600T showed the statistically significant higher in surface roughness (p< 0.05). SEM analysis revealed alterations on the root surfaces. There were different degrees of rough surfaces and sharp-pointed projections resulting from the ablation of dentin. The samples also revealed exposure of dentin tubules without smear layer. The histological analysis of HE staining also revealed the defect of laser irradiation on dentin surface and charring of the dentine tubules. Based on the results of this study, in addition to appropriate laser settings, it can be concluded that the differences between teeth hardness and types of laser tip, especially for PS600T, would also contribute to the differences of surface roughness, ablation depths and morphological alterations.

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