Effect of Nd:YAG, Ho:YAG, Er:YAG, CO2, and GaAIAs laser irradiation on surface properties of endosseous dental implants

PURPOSE: To analyze potential surface alterations in endosseous dental implants induced by irradiation with common dental lasers. MATERIALS AND METHODS: Sandblasted and acid-etched, plasma-sprayed, hydroxyapatite-coated, and smooth titanium discs were irradiated using Nd:YAG, Ho:YAG, Er:YAG, CO2, and GaAIAs lasers at various power settings. The specimens were examined by scanning electron microscopy and energy dispersive spectroscopy. Results: In an energy-dependent manner, the pulsed YAG lasers induced partial melting, cracking, and crater formation on all 4 surfaces. Within the energy range applied, the CO2 laser caused surface alterations on the hydroxyapatite and plasma coatings as well as in the acid-etched surface. GaAIAs laser irradiation did not damage any of the surfaces. Energy dispersive spectroscopy revealed an altered chemical compound of the surfaces with regard to titanium, oxygen, and silicon. DISCUSSION: The clinical application of most common dental laser systems can induce implant surface alterations. Relevant factors are not only the laser system and power setting, but also the application system. CONCLUSION: The results of the study indicate that Nd:YAG and Ho:YAG lasers are not suitable for use in decontamination of implant surfaces, irrespective of the power output. With the Er:YAG and CO2 laser, the power output must be limited so as to avoid surface damage. The GaAIAs laser seems to be safe as far as possible surface alterations are concerned.     

Histologic and histomorphometric comparison of immediately placed hydroxyapatite-coated and titanium plasma-sprayed implants: a pilot study in dogs.

The purpose of this pilot study was to make a histologic and histomorphometric comparison of hydroxyapatite-(HA) coated and titanium plasma-sprayed (TPS) root-form implants that were placed in 2 mongrel dogs immediately after extraction of mandibular premolars. After 8 weeks of healing, the implant-containing segments of the mandible were removed en bloc and bone blocks including implants were sectioned. Histologic and histomorphometric analyses were performed by evaluating bone sections. The mean bone contact percentage of HA-coated implants was 61.84 +/- 7.84%, with a range of 52.09% to 75.7%, and the mean bone contact percentage of TPS implants was 51.35 +/- 12.1%, with a range of 30.1% to 70.6%. This pilot study suggests that HA-coated implants placed into fresh extraction sockets can achieve better bone contact than TPS implants, but there was evidence that the surface of the HA layer can be resorbed, so long-term stability of HA coatings in immediate implantation must be investigated.     

Guided bone regeneration around titanium plasma-sprayed,acid-etched,and hydroxyapatite-coated implants in the canine model

BACKGROUND: Endosseous dental implants with rough surfaces have been designed to improve early healing, especially in areas of poor bone or insufficient bone quantity. The aim of this study was to histomorphometrically assess the bone-to-implant contact on 3 different rough-surfaced implants following guided bone regeneration. METHODS: Mandibular premolars and first molars were extracted in 12 dogs, and healing was allowed for 6 months. Six implant osteotomy sites were prepared, 3 per side, followed by the creation of 7.3 mm wide by 5 mm deep surgical defects in the coronal section of the osteotomy sites. Ten-mm long titanium screw-type implants with titanium plasma-sprayed (TPS), hydroxyapatite-coated (HA), or acid-etched (AE) surfaces were placed; the surrounding defects were filled with canine demineralized freeze-dried bone allograft; implants/grafts were covered with expanded polytetrafluoroethylene membranes; and the tissue was closed. Following a healing period of 4 months, the animals were sacrificed and mandibular blocks were harvested for histomorphometric analysis. RESULTS: The mean percentage of bone-to-implant contact in the defect and non-defect areas for the different implant surfaces was: AE 16.24% defect, and 28.78% non-defect; TPS 25.08% defect, and 16.96% non-defect; and HA 48.25% defect and 26.60% non-defect. Within the defect, the mean difference in the bone-to-implant contact was significant for HA compared to TPS (P < 0.0001) and HA versus AE (P < 0.0001); TPS versus AE was not significant (P = 0.063). In the non-defect areas, the mean difference in the bone-to-implant contact was significant for AE versus TPS (P = 0.010); all other comparisons were not significant. There were 18 membrane exposures in the 72 implant sites. Data were analyzed again to assess the impact of membrane complications. Using a 1-way analysis of variance, the bone-to-implant contact was compared between the sites with and without membrane complications. No significant differences were seen in the defect areas or in the non-defect areas between the sites with and without membrane complications. CONCLUSION: In this study, the bone-to-implant contact in regenerated bone was greatest when an HA-coated implant was used.     

Evaluation of stability of titanium and hydroxyapatite-coated osseointegrated dental implants: a pilot study

An endosseous implant is described as osseointegrated when it is immobile in function. Objective measures of stability testing have been described. The Periotest is a commercially available device that is used for this purpose. This study was designed to measure stability of endosseous implants placed in the mandible. Implants were placed in the mandibular canine or first premolar area to support an overdenture prosthesis. Stability was evaluated through the use of a Periotest device at the time of implant placement and following one year of functional loading. Implant designs were either a screw-shaped titanium alloy or a hydroxyapatite-coated cylinder. A total of 54 implants were placed, 37 were titanium screw-shaped implants, while the remaining 17 were hydroxyapatite cylinders. Initial measurements of stability showed no difference due to implant type. Following one year of functional loading, titanium screw-shaped implants were more stable than hydroxyapatite implants (P < 0.05). The difference in implant rigidity following a period of functional loading may be an indication of a difference in osseointegration between the two implants used in this study.     

改良喷砂表面处理对钛牙种植体骨结合的组织学作用

研究改良喷砂表面处理对钛牙种植体骨结合的影响。方法柱状纯钛种色植分两组（光滑表面和改良喷砂表面组）进行表面处理,植于狗后肢股骨内侧髁,分别于2、4、12周取材、固定、脱钙后常规HE染色,光镜观察。结果：改良喷砂表面组与光滑表面组的骨愈合过程,均为膜内成骨,并形成完全的骨结合。二者的差别主要表现在愈合的早期（割周）,改良喷砂表面组界面成骨较快,愈合中晚期差别不明显。结论：改良喷砂表面处理可以加快钛牙种植体的骨结合速度。     

Nd:YAG laser penetration into cast titanium and gold alloy with different surface preparations

This study investigated the effect of surface preparation on the Nd:YAG laser penetration into cast titanium and gold alloy. Cast blocks of each metal were given four different surface preparations: (i) coloured with black marker; (ii) air-abraded with 50 microm Al2O3; (iii) ground with SiC points and (iv) polished with 1 microm Al2O3 (mirror-polished). Two blocks with each of the surface preparations were abutted and laser-welded at their interface using the voltages of 210-260 V in increments of 10 V. After the welded blocks were mechanically separated, the laser penetration was measured using computer graphics. Regardless of the surface preparation, an increase in voltage increased the laser penetration for both metals. The laser penetration into titanium prepared with black marker and air-abrasion was significantly deeper than into the titanium ground with SiC points and mirror-polished. Although there were no statistical differences in penetration among the surface preparations for the gold alloy, the penetration in the mirror-polished specimens was shallower than any of the other preparation methods at higher voltages of 240-260 V. The results obtained in this study suggested that broken metal frameworks with finished surfaces should be painted with black marker or air-abraded before laser welding.     

The surgical management of osseous defects associated with endosteal hydroxyapatite-coated and titanium dental implants.

As more and more patients choose implant therapies it will be incumbent upon the dentists placing, restoring, and maintaining endosseous implants to be armed with the most current information. There is a need for further research to answer the many significant questions in the management of osseous defects associated with dental implants. Some of these questions include: Which grafting materials yield the greatest repair? If resorbable materials (for example, DFDB) are not replaced by bone, are residual defects and peri-implant tissues similar to those which existed prior to osseous grafting procedures? If so, perhaps the combination of a nonresorbable graft like HA with DFDB may yield the wound-healing potential of both materials; for example, osseoinduction by DFDB and the benefits of a radiographic marker and defect filler provided by HA. Can reintegration occur on previously pathologically exposed implant surfaces? Do biodegradable barriers yield significant GTR, and do they resorb predictably? Is complete detoxification of the infected HA-coated surface possible or necessary for regeneration to occur? Which chemotherapeutic modality detoxifies HA-coated surfaces best clinically and at the histologic level? Or should infected HA coatings be removed before attempting implant repair? Are regenerative techniques (for example, GTR) predictable enough to treatment plan for them when we know there will be residual osseous defects after placing fixtures in their most ideal prosthetic position? If so, what defect types resolve most predictably following surgical correction? Should barriers be used in conjunction with grafting when placing 2-stage blade implants to generate bone in the slot preparation coronal to the shoulder of the blade? It is evident from the growing popularity and acceptance of implant therapies that these and other questions will need to be answered to continue the evolution of the science of this discipline. This author would encourage practitioners to keep abreast of the current research and developments in this field as new techniques, materials, and therapies are in a constant state of flux.     

Histomorphometric analyses of hydroxyapatite-coated and uncoated titanium dental implants in rabbit cortical bone

In this article, we report the results of analyses of bone healing around four types of dental implants. Five implants of each type were inserted into the proximal tibia metaphysis of adult New Zealand rabbits and were analyzed using computerized histomorphometry 12 weeks after implantation. Hydroxyapatite-coated implants showed more direct bone contact and more lamellar bone in the threads than the titanium implants. There was a significant correlation between an increase in the percentage of mineralized tissue in the threads of metallic implants and cellular density around the implant, indicating less lamellar bone in contact with metallic implants.     

Clinical and radiographic experience with a hydroxyapatite-coated titanium plasma-sprayed porous implant.

Recent efforts to improve the interface between implant and bone have involved the use of bioactive materials, specifically hydroxyapatite (HA). HA coatings applied to implants have shown excellent clinical results at 2 years. There have been no radiolucent lines around the HA-coated implants. The long-term strength of the HA coating-substrate bone interface remains a concern as osseointegration of the HA appears to be a consistent phenomenon. This can lead potentially to an interruption between the substrate itself and the osseointegrated coating.     

The pulsed Nd:YAG dental laser: review of clinical applications.

Since the first demonstration of a laser in 1960, numerous applications of this unique form of energy have been developed for the manufacturing, electronic, consumer and medical industries. Recent technological innovations have permitted development of lasers appropriate for use in the dental operatory. The carbon dioxide laser has been used for soft tissue surgery; the Nd:YAG laser has both soft and hard tissue applications. Advantages of laser treatment over conventional methods include minimal cellular destruction and tissue swelling, hemostasis, increased visualization of surgical sites and reduced post-operative pain. Additionally, it is possible to perform many procedures without needing anesthesia. Soft tissue clinical applications of the Nd:YAG laser include gingivectomies, gingivoplasties, operculectomies, biopsies, incising and draining procedures, frenectomies and treatment of aphthous ulcers; hard tissue clinical applications include vaporizing decay, etching enamel and dentin, desensitizing exposed root structure and creating temporary analgesia. As both clinical experiences and scientific investigations expand, possible future applications of the dental laser may well include development of new dental adhesives and composite systems, new methods for managing caries and new endodontic treatments. With its numerous benefits, the laser is having a positive impact on patients and the dental team.     

Clinical comparison of hydroxyapatite-coated titanium dental implants placed in fresh extraction sockets and healed sites.

The placement of hydroxyapatite-coated dental implants in fresh extraction sockets was compared to placement in adjacent healed sites in 14 patients. Systematic sequential documentation was obtained regarding periodontal health, radiographic bone levels, and implant stability at the time of implant placement, at uncovering, and from 8 to 24 months (mean 16 months) after loading and restoration delivery. There were no significant differences in any clinical parameter between those implants placed in fresh extraction sockets and those placed in healed areas. Periodontal health, maintenance of crestal bone levels, and implant stability were excellent for implants placed in both types of recipient sites. The results of this study suggest that hydroxyapatite-coated dental implants can be successfully placed in fresh extraction sockets utilizing otherwise standard implant placement techniques, and that they appear to clinically perform equally well in fresh sockets and healed sites.     

Effects of diode and Nd:YAG laser irradiation on titanium discs: a scanning electron microscope examination

BACKGROUND: Dental lasers have been recommended for uncovering submerged implants as well as decontaminating implant surfaces when treating peri-implantitis. The aim of this study was to show the possible alterations in titanium disc surfaces using an Nd:YAG or a diode laser. METHODS: Three different titanium discs were used (sandblasted, titanium plasma-sprayed [TPS], and hydroxyapatite [HA] coated) to determine the effects of laser irradiation on these surfaces using a scanning electron microscope (SEM). The discs were either irradiated with a pulsed Nd:YAG laser with a contact handpiece and power settings of 2.0, 4.0, and 6.0 W or with a diode laser at 5.0, 10.0, and 15.0 W power settings and continuous wave (cw) in the contact handpiece. Irradiated areas were compared with control titanium sites which were not lased. The specimens were prepared for SEM examination after the disc irradiation. RESULTS: The SEM examination demonstrated extensive melting in all of the Nd:YAG laser irradiated areas. Damage was seen in all TPS- and HA-coated discs even at the lowest power setting. Loss of porosity, coating microfractures, and a relatively smooth surface were observed. In contrast, the diode laser did not cause any damage or modify the disc surface. Regardless of the power setting, there was no visible difference between lased and non-lased surfaces after cw irradiation with the diode laser. CONCLUSIONS: From these findings, it was concluded that the diode laser (980 nm) does not damage titanium surfaces, which should be of value when uncovering submerged implants and treating peri-implantitis.     

脉冲Nd:YAG激光照射对犬牙髓的影响

目的：探讨Nd：YAG激光对牙髓的安全阈值。方法：选择4条健康的本地杂种犬，先进行过敏模型制备，随机分为3组，分别给予：33J／cm^2、56J／cm^2和111J／cm^2激光照射，按照即刻、3d、7d、1个月4个时间段处死试验犬，实验牙经过固定、脱钙后，进行组织切片、光镜观察、病理分级。结果：牙髓反应均在3级以下，随激光照射能量的升高牙髓组织病理变化明显。在33～56J／cm^2之间，牙髓组织正常或反应轻微。结论：应用Nd：YAG激光进行牙齿过敏治疗时，其热效应可能对牙髓组织产生影响，33～56J／cm^2的激光能量不会对牙髓组织产生损害，能量较高将导致牙髓组织炎症，所以33～56J／cm^2的能量密度应为进行当次牙齿过敏治疗的安全阈值。     

An in-vitro study of the sterilization of titanium dental implants using low intensity UV-radiation.

OBJECTIVES: Commercial titanium dental implants are coated with nanostructured TiO2. The aim of the research reported in this paper was to assess whether the TiO2 at the surface of a dental implant is sufficiently photoactive to eradicate bacteria when illuminated with low intensity light. METHODS: The photoactivity of dental implants was established by studies of the photoenhanced decomposition of Rhodamine B. In vitro studies to establish the influence of irradiating with UV light an implant that is immersed in a solution containing Escherichia Coli were performed. RESULTS: It was demonstrated that under low UV intensity irradiation, 49 microW cm(-2), bacteria are killed at a rate of approximately 650 million per cm2 of implant per minute. SIGNIFICANCE: The results indicate that illumination of dental implants with UV light may be a suitable treatment for periimplantitis.     

Nd:YAG激光对猴牙牙髓的影响

目的：观察Nd：YAG激光对猴牙牙髓的影响，比较牙面涂布60g／L美蓝和经常规硝酸银脱敏后对激光照射效果的影响情况。方法：以1592、3185、4777mJ／mm^23种能量水平的Nd：YAG激光照射3只猴的30个牙面，用组织病理学方法观察牙髓变化情况。结果：1592mJ／mm^2照射组，不论牙面经何种处理，牙髓反应均与对照组相似，为0级；3185mJ／mm^2照射组，牙髓出现轻度改变；大能量、高频率的4777mJ／mm^2照射则出现广泛性成牙本质细胞变性、坏死。照射面色素的存在增加了激光对牙髓的刺激，氨硝酸银加丁香油酚还原成银沉淀，隔绝了外界刺激对牙本质和牙髓的影响，同样参数的Nd：YAG激光造成的牙髓损害在3组中最小。结论：大能量Nd：YAG激光可造成牙髓组织损伤性反应，照射面经不同的处理可影响Nd：YAG激光的照射效果。     

脉冲Nd:YAG激光照射后牙髓碱性磷酸酶的活性

目的 :探讨脉冲Nd :YAG激光照射后牙髓碱性磷酸酶 (ALP)的活性。方法 :选择 4条健康的本地杂种犬 ,进行牙齿过敏模型制备 ,随机分为 3组 ,分别给予 :33J/cm2 、5 6J/cm2 、111J/cm2 激光照射 ,按照即刻、3d、7d和 1月 4个时间段处死试验犬 ,实验牙经过固定、脱钙后 ,进行组织切片、染色、光镜观察、灰度值分级。结果 :3组激光能量照射后 ,牙髓成牙本质细胞均有染色 ,以 3d、7d染色较深 ,1月后染色变浅 ,ALP活性降低 ,接近正常牙髓细胞水平。结论 :在本实验条件下 ,牙髓成牙本质细胞碱性磷酸酶活性在不同的观察期相差显著 (P <0 .0 1) ,与激光能量无关 (P >0 .0 5 )。     

脉冲Nd:YAG激光照射牙本质后对光固化树脂充填体边缘微渗漏的影响

目的研究脉冲Nd：YAG激光照射牙本质后对光固化树脂充填体边缘微渗漏的影响，以探讨脉冲Nd-YAG激光在龋病治疗中的临床应用意义。方法选用正畸要求拔除的正常双尖牙30颗，随机分为A。B，C三组，每组10颗，用高速裂钻备洞（洞长、宽为3mm；洞深为2mm），A组为对照组，常规酸蚀树脂充填；B，C两组分别用50mJ，10Hz和100mJ，10Hz的脉冲Nd：YAG激光能量照射窝洞牙本质壁30s后树脂充填，分别用体视显微镜和扫描电镜观察充填体边缘和洞壁结合情况。结果．体视显微镜下观察：A组的牙本质洞壁与光固化树脂充填体间染料渗入较多，着色较深；B、C组的牙本质洞壁与光固化树脂充填体间染料渗入较少，着色较浅。扫描电镜下观察：B、C组的牙本质洞壁与光固化树脂充填体间裂隙明显小于未经激光处理的对照组。结论脉冲Nd：YAG激光处理牙本质后进行光固化复合树脂充填，可以减少充填体微渗漏，有利于充填的成功．     

重症牙本质过敏牙Nd：YAG激光照射后的SEM观察

用脉冲Ｎｄ：ＹＡＧ牙科激光照射３个新鲜离体的重症牙本质过敏牙３０ｍＪ、８０ｍＪ，脉冲数１０／ｓ，１ｍｉｎ，并涂布２％甲紫液。ＳＥＭ显示：照射３０ｍＪ者，牙本质小管口部分或完全封闭，表面密度明显提高，出现＂弹坑＂样结构；照射８０ｍＪ者，牙本质小管口模糊，出现不规则均质化物质；涂布２％甲紫液照射３０ｍＪ区的大部分牙本质小管口封闭，表面密度提高，出现均质化物质和＂弹坑＂样结构，所有的照射区都未发现微裂。提示：牙本质小管口的封闭和牙本质表面的溶融是牙本质过敏症激光脱敏的形态学变化。２％甲紫液可作为该激光的光敏剂使用。