System and method for ablation of dental hard tissue through adjustable annular water mist mediated laser

Abstract

The invention provides a system and a method for ablation of dental hard tissue through adjustable annular water mist mediated laser. The system comprises a laser, a water supply system, a double-path gas supply system and a waste liquid recovery system. The nozzle is characterized by being provided with a coaxial three-layer nozzle which is composed of an outer-layer air cavity, a middle-layer water pipe and an inner-layer air cavity in sequence from outside to inside; the outer-layer air cavity and the middle-layer water pipe are sealed by a first light-transmitting window, and the middle-layer water pipe and the inner-layer air cavity are sealed by a second light-transmitting window; micro-pores are formed in the center of the first light-transmitting window; a central water hole is formed in the center of the second light-transmitting window; a laser beam sequentially penetrates through the two light-transmitting windows along the axis of the nozzle. By independently adjusting the inner-layer air pressure (0.1-1 MPa), the water pressure (0.2-1 MPa) and the outer-layer air pressure (0.05-1 MPa), annular water mist with the controllable geometric dimension can be formed at the front end of the nozzle, laser is focused in a central dry air column area to achieve high-precision ablation, and meanwhile the annular water mist cools surrounding tissues. The problems of low cooling efficiency, large laser scattering loss and deep heat damage in existing water mist-assisted laser ablation are solved, and the water mist-assisted laser ablation device is suitable for dental minimally invasive surgeries such as decayed tooth hole preparation and root canal cleaning.

Description

Technical Field

[0001] This invention relates to the field of laser ablation of biological hard tissue, specifically a system and method for ablation dental hard tissue using a laser as energy and a controllable annular water mist. Background Technology

[0002] With the development of the times, more and more people are paying attention to their oral health. Dental diseases are the most serious threats to human oral health, and efficient and comfortable treatment of dental diseases aligns with the national strategy of "Healthy China".

[0003] In dental treatment, hard tissues such as teeth are typically treated, including cavities, periodontitis, and tartar removal. Traditional surgical instruments like drills and saws were commonly used, but these instruments generate noise and vibration during operation; they also produce significant pressure and heat when handling hard dental tissues; and they can cause significant bleeding, susceptibility to fungal infections, and severe pain, making patients hesitant to undergo treatment. Furthermore, these instruments are inflexible, time-consuming, and physically demanding for the operator.

[0004] The aforementioned issues have a certain impact on patients' physical and mental health, and also place higher demands on medical staff's operations. However, this has also promoted the development and application of various new medical devices, especially the application of lasers in various medical devices, which has brought great convenience to life.

[0005] In clinical practice, laser ablation offers advantages such as minimal vibration in the surgical field, non-contact operation, precise cutting, good compatibility, and minimal invasiveness, making it a promising technique for dental surgery, including tooth ablation, cosmetic dentistry, caries prevention, and tooth sensitivity treatment. Er:YAG (2.94μm) lasers have high absorption properties for hydroxyapatite, effectively cutting dentin and enamel. However, the interaction between Er:YAG lasers and teeth is often accompanied by thermal damage, causing overheating of the enamel and dentin, leading to carbonization, melting, and cracking. Excess heat is also conducted through the dentin to the dental pulp, causing irreversible damage to healthy pulp tissue. Therefore, developing low-thermal-damage Er:YAG laser ablation methods for hard dental tissues is particularly important.

[0006] Water-mediated laser ablation has become a hot topic in the field of biological hard tissue ablation over the past decade. Currently, water-mediated methods mainly focus on water spray and water film layers, but these two water supply methods cannot effectively cool the ablation depth direction. However, tissue remains active below 5.6℃ in the medullary cavity, while most tissues lose activity above 16℃, thus requiring strict control of the medullary cavity temperature. Coaxial water spray and water jets can better achieve cooling effects in the ablation depth direction. As the laser ablation depth increases, the water jet can still effectively flush the inside of the ablation incision, ensuring continuous cooling. In addition, water jet flushing ensures the cleanliness of the ablation surface and reduces the interference of debris on the laser beam, thereby improving ablation efficiency. However, the absorption coefficient of water for Er:YAG laser is 12500 (1 / cm). According to the Beer-Lambert law, Er:YAG laser can only penetrate a water layer of a few micrometers thickness.

[0007] The "channel effect" allows Er:YAG lasers to penetrate water films up to the centimeter level, but this requires sacrificing some Er:YAG laser energy to form "cavitation channels." The formation mechanism of these channels is unclear and unstable, thus reducing laser energy utilization efficiency. Furthermore, forming stable "cavitation channels" through laser vaporization in flowing water is difficult and unstable.

[0008] Inspired by the "cavitation channel" effect, this invention proposes a coaxial annular water jet design that forms a stable air column channel through central ventilation, reducing water absorption of the laser while ensuring that the annular water jet effectively cools the area surrounding the laser processing. An outer ring ventilation is used to form an air curtain to prevent excessive diffusion of water mist, thus realizing a system and method for controllable annular water mist-mediated Er:YAG laser ablation of dental hard tissue. Summary of the Invention

[0009] The purpose of this invention is to provide a system and method for adjustable annular water mist-mediated laser ablation of dental hard tissues, so as to solve the problems of high cooling efficiency and large absorption of laser energy during ablation in the prior art.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A system for adjustable annular water mist-mediated laser ablation of dental hard tissue includes a laser, a water supply system, a dual-channel air supply system, a coaxial three-layer nozzle, and a waste liquid recovery system.

[0012] The laser is preferably an Er:YAG laser generator with a wavelength of 2.94 μm and adjustable pulse energy.

[0013] The water supply system includes a water tank, a flow sensor, a flow regulating valve, a filter device, and a medical pump. The medical pump draws water from the water tank, filters it through the filter device, and then delivers it to the middle layer of the water pipe.

[0014] The dual-supply system includes two air compressors, a pressure regulating valve, and a pressure sensor. The first gas, after pressure regulation, enters the inner gas chamber to generate a central gas column, preventing water from entering the laser path and forming a drying channel. The second gas enters the outer gas chamber to generate an outer gas curtain, preventing excessive diffusion of the annular water mist and ensuring sufficient water for cooling at the edge of the ablation zone.

[0015] The coaxial three-layer nozzle is the core component of the invention, consisting of an outer air chamber, a middle water pipe, and an inner air chamber, arranged sequentially from the outside in. The outer air chamber and the middle water pipe are sealed by a first light-transmitting window, and the middle water pipe and the inner air chamber are sealed by a second light-transmitting window. A micro-pore is located in the center of the first light-transmitting window, and a central water hole is located in the center of the second light-transmitting window. Both the first and second light-transmitting windows are made of annular high-transmittance glass (such as sapphire glass or quartz glass), and the edges of their central openings are chamfered and polished to reduce laser scattering and absorption. The laser beam passes sequentially through the central holes of the two light-transmitting windows along the nozzle axis and is then focused onto the target material.

[0016] The waste liquid recovery system includes a water pump, a filter device, and a waste water tank, which are used to recover and treat the accumulated water and residue generated during the ablation process.

[0017] By independently adjusting the air pressure in the inner air chamber (0.1-1 MPa), the water pressure in the middle water pipe (0.2-1 MPa), and the air pressure in the outer air chamber (0.05-1 MPa), a geometrically controllable annular water mist zone can be formed at the nozzle tip. The inner air pressure determines the diameter of the central drying air column (corresponding to the inner diameter of the annular water mist), the water pressure affects the flow rate and velocity of the water mist, and the outer air pressure constrains the outer edge of the water mist. The laser is focused within the drying air column zone at the center of the annular water mist, achieving high-precision ablation, while the annular water mist effectively cools the surrounding tissue. Beneficial effects

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) By actively supplying air through the inner air cavity, a stable dry air column channel is formed in the center of the annular water mist, which avoids the laser energy being absorbed by the water. Compared with traditional coaxial water mist, the laser energy utilization rate is improved.

[0020] (2) The inner and outer diameters of the annular water mist can be independently adjusted, and the cooling range can be optimized in real time according to different laser power and ablation depth, so as to control the temperature rise of the pulp cavity within a safe threshold and avoid thermal damage.

[0021] (3) The central opening structure of the light-transmitting window ensures that the laser transmission path is unobstructed, and the chamfering treatment at the edges reduces scattering loss.

[0022] (4) The waste liquid recycling system is separated from the water supply system, which reduces the risk of cross-infection and meets medical and health requirements.

[0023] (5) The ablation process is non-contact and vibration-free, with clear ablation boundaries and minimal damage to surrounding healthy tissues. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the system of the present invention.

[0025] Explanation of reference numerals in the attached figures: Laser-1, Reflector-2, Water Tank-3, Flow Control Valve-4, Filter Device-5, Focusing Lens-6, Inner Air Chamber-7, Middle Water Pipe-8, Outer Air Chamber-9, First Light Transmitting Window-10, Second Light Transmitting Window-11, Air Compressor (Inner Layer)-12, Inner Pressure Regulating Valve-13, Outer Pressure Regulating Valve-14, Air Compressor (Outer Layer)-15, Workbench-16, Waste Liquid Filter Device-17, Wastewater Tank-18, Annular Water Mist-19, Medical Pump-20, Micro-pores-21, Central Water Hole-22, Outer Air Channel-23, Water Suction Pump-24. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the implementation of the present invention is not limited thereto. Example

[0027] See Figure 1 A system for adjustable annular water mist-mediated laser ablation of dental hard tissue includes a laser (1), a reflector (2), a focusing lens (6), a water supply system, a dual-path air supply system, a coaxial three-layer nozzle, and a waste liquid recovery system.

[0028] The laser (1) is an Er:YAG laser with a wavelength of 2.94 μm, a maximum pulse energy of 400 mJ, and a maximum frequency of 20 Hz.

[0029] Water supply system: Deionized water in water tank (3) is driven by medical pump (20), and enters the middle layer water pipe (8) after passing through flow regulating valve (4) and filter device (5). Water pressure is controlled by medical pump speed and back pressure valve, and the adjustment range is 0.2-1MPa.

[0030] Dual-path air supply system: The inner air path is supplied by the air compressor (12), and the pressure is adjusted to 0.1-0.3MPa by the inner pressure regulating valve (13) before entering the inner air chamber (7); the outer air path is supplied by the air compressor (15), and the pressure is adjusted to 0.05-1MPa by the outer pressure regulating valve (14) before entering the outer air chamber (9).

[0031] The three-layer coaxial nozzle is made of aluminum alloy 6063 or stainless steel. The inner air chamber (7) has an inner diameter of 5 mm, and its end is sealed to the first light-transmitting window (10). The first light-transmitting window (10) is made of sapphire glass with a diameter of 6 mm and a thickness of 2 mm, and has a micro-hole (21) with a diameter of 0.2 mm to 0.5 mm in the center. The second light-transmitting window (11) is made of sapphire glass with a diameter of 11 mm and a thickness of 2 mm, and has a central water hole (22) with a diameter of 0.5 mm to 1 mm in the center. The edge of the hole is chamfered and polished. The middle water pipe (8) is fitted on the outside of the inner air chamber and is sealed to the first light-transmitting window (10). The outer air chamber (9) is fitted on the outermost side. The three-layer structure is coaxially installed.

[0032] Waste liquid recovery system: The workbench (16) collects waste liquid, which is then pumped to the waste liquid filtration device (17) by the water pump (24), and the filter residue enters the waste water tank (18).

[0033] The following steps were taken to perform an in vitro bovine tooth enamel ablation experiment using this system:

[0034] (1) Start the medical pump (20), adjust the water pressure to 0.3MPa, and a stable water column flows out of the central water hole (22).

[0035] (2) Start the waste liquid recovery system.

[0036] (3) Start the dual-line air supply system: adjust the inner layer air pressure to 0.2MPa and the outer layer air pressure to 0.1MPa. At this time, an annular water mist is formed below the nozzle.

[0037] (4) Start the laser: Set the pulse energy and frequency, the focal length of the focusing lens is 50mm, and the laser focus is located on the enamel surface. The laser beam passes through the central drying gas column area (with an inner diameter of about 0.5mm) and acts on the target point.

[0038] (5) After ablating for 30 seconds, turn off the laser, gas supply system, water supply system in sequence, and finally turn off the waste liquid recovery system. Industrial applicability

[0039] The system of this invention has a compact structure and is easy to control. It can be integrated into a dental treatment unit and is suitable for minimally invasive oral hard tissue surgeries such as cavity preparation, root canal cleaning, and cortical bone incision. It has clear industrial applicability and market prospects.

Claims

1. A system for adjustable annular water mist-mediated laser ablation of dental hard tissue, characterized in that, include: Laser (1) is used to generate a laser beam; water supply system is used to provide water medium; dual-channel gas supply system is used to provide the first channel gas and the second channel gas; coaxial three-layer nozzle is composed of an outer gas cavity, a middle water pipe and an inner gas cavity from the outside to the inside. The outer air cavity and the middle water pipe are sealed by a first light-transmitting window (10). The middle water pipe and the inner air cavity are sealed by a second light-transmitting window (11); the first light-transmitting window The center of the first light-transmitting window (21) has a micro-pore (21), and the center of the second light-transmitting window (11) has a micro-pore (21). Central water hole (22); The laser beam is arranged along the axis of the coaxial three-layer nozzle, and acts on the target material after passing through the first light-transmitting window (10) and the second light-transmitting window (11) in sequence; The dual-supply gas system is connected to the outer air chamber and the inner air chamber respectively, and the water supply system is connected to the middle water pipe.

2. The system according to claim 1, characterized in that, The laser (1) is an Er:YAG laser generator with a wavelength of 2.94 μm.

3. The system according to claim 1, characterized in that, The dual-supply gas system includes: The first air passage is connected to the inner air cavity and is used to generate a central air column to form a drying channel at the center of the annular water mist. The second air passage is connected to the outer air cavity and is used to generate an outer air curtain to constrain the diffusion range of the annular water mist.

4. The system according to claim 1, characterized in that, The water supply system includes a water tank (3), a flow regulating valve (4), a filter device (5), and a medical pump (20). The medical pump (20) delivers the filtered water from the water tank to the middle water pipe.

5. The system according to claim 1, characterized in that, The first light-transmitting window (10) and the second light-transmitting window (11) are both annular high-transmittance glass, and the edges of the central opening are chamfered and polished to reduce laser scattering.

6. The system according to claim 1, characterized in that, It also includes a waste liquid recovery system, which includes a water pump (24), a filter device (17) and a waste water tank (18) for recovering waste liquid and debris generated during the ablation process.

7. A method for adjustable annular water mist-mediated laser ablation of dental hard tissue using the system described in any one of claims 1 to 6, characterized in that, Includes the following steps: (1) Start the water supply system and adjust the water pressure to 0.2-1MPa so that water is discharged from the central water hole (22) to form a stable water flow; (2) Start the waste liquid recovery system; (3) Start the dual-line air supply system, adjust the air pressure of the inner air chamber to 0.1-1MPa and the air pressure of the outer air chamber to 0.05-1MPa, and form a stable annular water mist below the nozzle; (4) Start the laser, adjust the laser energy and frequency, so that the laser beam is focused and passes through the central drying air column area to focus on the surface of the hard tooth tissue for ablation; (5) After the ablation is completed, first turn off the laser, then turn off the gas supply system and the water supply system, and finally turn off the waste liquid recovery system.

8. The method according to claim 7, characterized in that, By independently adjusting the inner air pressure, water pressure, and outer air pressure, the inner and outer diameters of the annular water mist can be controlled to adapt to different ablation depths and rates: when deep ablation is required, the inner air pressure is increased to expand the drying channel; when enhanced peripheral cooling is required, the outer air pressure is increased to close the outer edge of the water mist.

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