The applications of the plasma matrix in the treatments of dental pulp and periapical diseases / 口腔疾病防治

@#The plasma matrix is a kind of autologous blood conduct. It has been widely used in maxillofacial tissue regeneration, skin cosmetology and some other fields. Recently, to preserve the dental pulp as well as the teeth, pulp regeneration therapy and apical surgery have become increasingly important as well as the applications of bioactive materials. As a kind of autologous bioactive material, the plasma matrix has some natural advantages as it is easy to obtain and malleable. The plasma matrix can be used in the following cases: ①pulp revascularization of young permanent teeth with open apical foramina that cannot stimulate apical bleeding; ② apical barrier surgery with bone defects and large area perforation repair with bone defects or root sidewall repair surgery; ③ apical surgeries of teeth with large area of apical lesions, with or without periodontal diseases. The plasma matrix is a product derived from our blood, and there are no obvious contraindications for its use. Several systematic reviews have shown that the plasma matrix can effectively promote the regenerative repair of dental pulp in patients with periapical diseases. However, the applications of plasma matrix are different because its characteristics are affected by different preparation methods. In addition, there is still a lack of long-term clinical researches on the plasma matrix, and the histological evidences are difficult to obtain, so a large number of in vitro and in vivo experimental studies are still needed. This article will describe the applications of different kinds of plasma matrix for dental pulp regeneration and bone tissue regeneration in apical surgeries to provide references for clinicians in indication selection and prognosis evaluation.

Research progress on the effect of radiotherapy of nasopharyngeal carcinoma and head and neck cancer on dental hard tissues and oral microbiota / 中华放射肿瘤学杂志

Nasopharyngeal carcinoma and head and neck cancer are the most common malignant tumors in clinical practice. As the most common treatment for nasopharyngeal carcinoma and head and neck cancer, radiotherapy will inevitably cause damage to normal structures such as dental hard tissues and affect the composition of oral microbiota, although it exerts high inhibitory effect against tumor cells. To provide theoretical basis for preventing or reducing the side effects of nasopharyngeal carcinoma and head and neck cancer after radiotherapy and improving the quality of life in patients, related research progress on the effect of radiotherapy of nasopharyngeal carcinoma and head and neck cancer on dental hard tissues and oral microbiota was reviewed.

Clinical management of endo-perio lesion through guided tissue regeneration: a 5 year follow-Up / Manejo clínico de una lesión endo-perio a través de la regeneración tisular guiada: control post-operatorio de 5 años

ABSTRACT: Progressive periodontal disease causes loss of supporting structures of teeth resulting in deep bony defects. In this case a report of 22-year old female patient is being presented with clinical findings of vertical bone loss in two adjacent teeth, on distal surface of 2nd upper right premolar and mesial surface of upper right 1st molar. Root canal treatment, non-surgical periodontal therapy followed by guided tissue regeneration was carried out using decalcified freeze-dried bone allograft (DFDBA) and collagen membrane. Analysis of clinical and radiographic findings showed marked reduction in pocket depth up to 12mm with hard tissue repair on 3-month, 2-year and 5- year follow ups.

RESUMEN: La enfermedad periodontal progresiva provoca la pérdida de las estructuras de soporte de los dientes, lo que resulta en defectos óseos profundos. En este caso clínico se presenta un informe de una paciente de 22 años con pérdida ósea vertical en la superficie distal del segundo premolar superior derecho y en la superficie mesial del primer molar superior derecho. El tratamiento del conducto radicular, la terapia periodontal no quirúrgica seguida de la regeneración tisular guiada se llevó a cabo utilizando aloinjerto óseo liofilizado descalcificado (DFDBA) y membrana de colágeno. El análisis de los hallazgos clínicos y radiográficos mostró una marcada reducción en la profundidad de la bolsa de hasta 12 mm con reparación de tejido duro en seguimientos de 3 meses, 2 años y 5 años.

Primary cilia in hard tissue development and diseases / 医学前沿

Bone and teeth are hard tissues. Hard tissue diseases have a serious effect on human survival and quality of life. Primary cilia are protrusions on the surfaces of cells. As antennas, they are distributed on the membrane surfaces of almost all mammalian cell types and participate in the development of organs and the maintenance of homeostasis. Mutations in cilium-related genes result in a variety of developmental and even lethal diseases. Patients with multiple ciliary gene mutations present overt changes in the skeletal system, suggesting that primary cilia are involved in hard tissue development and reconstruction. Furthermore, primary cilia act as sensors of external stimuli and regulate bone homeostasis. Specifically, substances are trafficked through primary cilia by intraflagellar transport, which affects key signaling pathways during hard tissue development. In this review, we summarize the roles of primary cilia in long bone development and remodeling from two perspectives: primary cilia signaling and sensory mechanisms. In addition, the cilium-related diseases of hard tissue and the manifestations of mutant cilia in the skeleton and teeth are described. We believe that all the findings will help with the intervention and treatment of related hard tissue genetic diseases.

Research progress on Er: YAG lasers applied for tooth bleaching / 口腔疾病防治

@#Er: YAG laser bleaching is a new tooth bleaching method compared with traditional bleaching technology. The Er: YAG laser significantly improves the bleaching efficiency, has the advantages of high safety, short treatment time and excellent bleaching effect and is widely used in clinical operations. This paper summarizes the working principle and bleaching characteristics of Er: YAG laser bleaching technology and its effect on tooth structure. The existing literature suggests that the high absorption of water and hydroxyapatite by the Er: YAG laser makes it work well on water-bearing tissues and dental tissues. When it is absorbed by the bleaching agent on the tooth surface, it accelerates the catalytic oxidation-reduction reaction and selectively acts on the pigment particles deposited on the tooth, thereby achieving the effect of tooth bleaching. Er: YAG laser bleaching can be applied to most discolored teeth. The bleaching process is rapid and effective. During the bleaching process, for the dental pulp tissue, the temperature of the pulp cavity is lower than the critical value of 5.6 ℃, causing no pathological damage to the dental pulp tissue. For the hard tissues of the teeth, laser irradiation will cause changes in the chemical composition of calcium and phosphorus. The enamel presents a unique lava-like shape, and the bonding strength of the tooth increases after bleaching. Compared with other lasers, the Er: YAG laser has a wavelength close to the peak of water, and adding other ingredients to the bleaching agent is not required. Almost all the energy is used for the bleaching agent, with no damage to the surrounding tissues.

Advances in biomimetic modification of materials for oromaxillofacial bone regeneration and dental implant / 华西口腔医学杂志

Oromaxillofacial hard tissue defects is still a difficult problem in clinical treatment. Regeneration of oromaxillofacial hard tissue based on tissue engineering technology has a good clinical application prospect. The functional modification of scaffolds is one of key factors that influence the outcome of tissue regeneration. The biomimetic design of biomaterials through simulating the natural structure and composition of oromaxillofacial hard tissue has gradually become a research hotspot due to its advantages of simplicity and efficiency. In this article, the biomimetic modification of biomaterials for oromaxillofacial hard tissue regeneration is reviewed, expecting to provide a new idea for the treatment of oromaxillofacial hard tissue defect.

Preparation and mechanical properties of zirconia-based nano-hydroxyapatite functionally graded material / 中国组织工程研究

BACKGROUND: Studies have shown that the nano-hydroxyapatite coating on the surface of zirconia has not only high strength and toughness, but also good biocompatibility. It is an ideal substitute for hard tissue. However, the coating is easy to fall off from the surface of zirconia, which is a fatal defect. OBJECTIVE: To prepare functionally graded bioceramics with pure zirconia as matrix, gradient layer in the middle and nano-hydroxyapatite on the surface by gradient composite technology and to screen the optimal mechanical properties and sintering temperature. METHODS: Using zirconia and nano hydroxyapatite powder as raw materials, ceramic specimens were prepared by the lamination method in powder metallurgy. According to the thickness of zirconia layer, three groups A (40 mm), B (30 mm) and C (20 mm) were designated. Each group was sub-divided into three subgroups 1 (3 layers), 2 (5 layers) and 3 (7 layers). Thus, there were 162 ceramic specimens in nine subgroups. The ceramic specimens were sintered at different temperatures (1 300,1 350,1 400,1 450,1500, and 1 550°C) and then processed into rectangular specimens for mechanical property testing. RESULTS AND CONCLUSION: The zirconia-based nano-hydroxyapatite functionally graded material can be formed by 10 MPa single side vertical pressure. With the increases in the number of gradient layers and sintering temperature, the mechanical properties of the functionally graded bioceremics in each group were enhanced. The functionally graded bioceramics had the optimal mechanical properties when sintering temperature was 1 550°C, the number of gradient layers was 7, and substrate thickness was 40 mm. The optimal mechanical property of the functionally graded bioceramics produced at above parameter was significantly superior to that produced at other eight sets of parameters (P<0.05). According to the optimal gradient design, the zirconia-based nano-hydroxyapatite functionally graded ceramic specimens prepared by high temperature sintering technique have stronger mechanical properties.

Evaluation of Hard Tissue Cephalometric Norms for Maharashtrian Population using Downs Analysis

Aim: Based on Downs analysis, the present study aims to evaluate hard tissue cephalometric norms for the Maharashtrianpopulation.Materials and Methods: The digital lateral cephalograms of 100 subjects with Maharashtrian ethnicity within the age rangeof 18–30 years with normal occlusion were obtained. Downs analysis was performed using Dolphin software. The obtainedvalues were statistically analyzed to evaluate hard tissue norms for the Maharashtrian population.Results: Statistically significant differences were observed in hard tissue norms between Maharashtrian population andCaucasian norms.Conclusion: Ethnic differences exist between Maharashtrian population and Caucasian population, which should be consideredwhen formulating an orthodontic treatment plan.

Research progress in bone interface tissue engineering for ligament and tendon injury / 国际生物医学工程杂志

The interface of ligaments, tendons, and bones are susceptible to damage, often fail to heal themselves, and even cannot achieve a good prognosis after surgery. Interface tissue engineering is a comprehensive strategy to functionally connect soft and hard tissues to regenerate original anatomical functions and structures, thereby improving clinical efficacy. In this paper, the interface tissue engineering and composite tissue regeneration in soft tissue healing were systematically reviewed. The recent advances in interface engineering were summarized, based on the treatment of structural damage from two common soft tissue-bone connections (ligamentous bone connections, tendon bone connections), from the development of single tissue to composite tissue structures. The latest interface tissue engineering innovation structure design and potential clinical applications in recent years were reviewed. For future research, in-depth research on the mechanisms of interface development, regeneration, and internal environment balance, structure-function relationships, and biological processes that drive interface development, regeneration, and internal environment balance are still necessary. The innovative studies on interface tissue engineering have promoted the significance of the integration of tissue engineering and clinical, and the construction of complex tissues, so that it has broader significance for the future regeneration of total joints.

Research progress in bone interface tissue engineering for ligament and tendon injury / 国际生物医学工程杂志

The interface of ligaments, tendons, and bones are susceptible to damage, often fail to heal themselves, and even cannot achieve a good prognosis after surgery. Interface tissue engineering is a comprehensive strategy to functionally connect soft and hard tissues to regenerate original anatomical functions and structures, thereby improving clinical efficacy. In this paper, the interface tissue engineering and composite tissue regeneration in soft tissue healing were systematically reviewed. The recent advances in interface engineering were summarized, based on the treatment of structural damage from two common soft tissue-bone connections (ligamentous bone connections, tendon bone connections), from the development of single tissue to composite tissue structures. The latest interface tissue engineering innovation structure design and potential clinical applications in recent years were reviewed. For future research, in-depth research on the mechanisms of interface development, regeneration, and internal environment balance, structure-function relationships, and biological processes that drive interface development, regeneration, and internal environment balance are still necessary. The innovative studies on interface tissue engineering have promoted the significance of the integration of tissue engineering and clinical, and the construction of complex tissues, so that it has broader significance for the future regeneration of total joints.

Animal experimental study of tooth transplantation into artificial tooth socket / 实用口腔医学杂志

Objective: To observe morphological change and diversity of periodontium and alveolar bone after tooth transplantation into artificial tooth socket. Methods: 6 dogs were divided randomly into 2 groups: 2 dogs were used as the controls and 4 used for the experiment. In the control group 4 teeth were autotransplanted into the inherent sockets. In the experiment group 4 teeth were autotransplanted into the artificial sockets. The dogs were sacrificed at the 16th week after operation. The healing condition of periodontal tissue and the remodeling of alveolar bone were examined. Results: None of the transplanted teeth in both groups was loosen or dropped. Mircro-CT examination showed that cancellous bone and bone trabecula around the transplanted teeth lined tightly,no significant difference of bone trabecula thickness was observed between the 2 groups. Hard tissue slice examination revealed that parodontium of both groups grew and adhered to the teeth,and the quantity of new-born bone between the top of alveolar ridge and the neck of transplanted teeth was fundamentally the same in the 2 groups. Conclusion: Autotransplantation of teeth into the artificial socket is similar to that into inherent socket.

Comparsion of soft and hard tissue profiles of adolescent patients with class II division 1 malocclusion between before and after treated with two different kinds of tooth extraction methods / 吉林大学学报(医学版)

Objective: To compare the changes of soft and hard tissue profiles of the adolescent patients with class II division 1 malocclusion between before and after treated with two different kinds of tooth extraction methods, and to provide the reference for clinical treatment. Methods: A total of 60 adolescent patients with class II division 1 malocclusion were included, and they were divided into 44/44 group (n=30) and 44/55 group (n= 30) based on different kinds of tooth extraction methods. Four first premolars of the patients in 44/44 group were extracted and 2 maxillary first premolars and 2 mandibular second premolars of the patients in 44/55 group were extracted. The measurement indexes of pre-treatment (Tl) and post-treatment (T2) and their difference values (T2 -Tl) of soft and hard tissues of the adolescent patients were detected by lateral cephalometric radiographs. Results: As for the hard tissue, compared with before treatment, the Overjet, SNA, ANB, Ul-NA, distance of Ul-NA, Ul-SN, NA-PA, and A-NP of the adolescent patients in two groups after treatment were decreasd (P0. 05). Conclusion: The changes of soft and hard tissue profiles of the adolescent patients after treated with two different kinds of tooth extraction methods are not significant.

Feasibility of integrating 3D photos and cone-beam computed tomography images used to evaluate changes of soft and hard tissue after orthognathic surgery / 北京大学学报(医学版)

Objective:To evaluate the feasibility of integrating 3D photos and cone-beam computed tomography (CBCT)images and to assess the degree of error that may occur during the above process,and to analyze soft and hard tissue changes after orthognathic surgery using this new method.Methods:Ten patients with maxillofacial deformities were chosen.For each patient,CBCT scans and stereophotographic images were taken before and 3 months after surgery.3D photos were superimposed onto the CBCT skin im-ages using relatively immobile areas of the face as a reference.3D color maps and mean distances were used to evaluate the errors that might occur during the process.Two reference planes were set up using cer-tain points.The distances between Prn (pronasale),Sn (subnasale),Ls (labrale superior),ANS (anterior nasal spine),A (subspinale),UIE (upper incisor edge)to the coronal plane were calculated before and af-ter surgery.In order to verify the repeatability of this method,we examined the distances twice at two-week intervals.Paired t test was used to evaluate the reproducibility.Results:CBCT and 3D photos could be successfully fused with clinically acceptable errors.This new method could be used to evaluate soft and hard tissue changes after orthognathic surgery.The 3D color maps showed that the two images could be fused with minimal errors.The mean distances were within 0.3 mm,and the locations of landmarks on maxilla and mandible such as Ls,ANS,A,UIE changed significantly after orthognathic surgery (P 0.1 ).The paired t test showed that the mean value and standard deviation were (0.08 ±0.98)mm.Conclusion:Fusing of CBCT and 3D stereophotographic images used as a new method in evaluating soft and hard tissue changes after orthognathic surgery was feasible and accurate.The virtual 3D composite craniofacial models permitted concurrent assess-ment of hard and soft tissues during diagnosis and treatment planning.Maxillary and mandibular locations had significant association with orthoganthic surgery while the nasal tissue was not simp affected by surgery.

Advances in Three-Dimensional Bioprinting for Hard Tissue Engineering

The need for organ and tissue regeneration in patients continues to increase because of a scarcity of donors, as well as biocompatibility issues in transplant immune rejection. To address this, scientists have investigated artificial tissues as an alternative to transplantation. Three-dimensional (3D) bioprinting technology is an additive manufacturing method that can be used for the fabrication of 3D functional tissues or organs. This technology promises to replicate the complex architecture of structures in natural tissue. To date, 3D bioprinting strategies have confirmed their potential practice in regenerative medicine to fabricate the transplantable hard tissues, including cartilage and bone. However, 3D bioprinting approaches still have unsolved challenges to realize 3D hard tissues. In this manuscript, the current technical development, challenges, and future prospects of 3D bioprinting for engineering hard tissues are reviewed.

Changes of soft and hard tissues of patients with Angle classⅡdivision I malocclusion following orthodontic treatment with extraction / 天津医药

Objective To investigate changes in craniomaxillofacial soft and hard tissues following orthodontic treatment by MBT edgewise technique with fix appliance in patients with Angle classⅡdivisionⅠmalocclusion. Methods Fifty patients with Angle classⅡdivisionⅠmalocclusion were selected in this study. All patients were treated with MBT edgewise technique. Cephalometrics tracings were performed before treatment and after treatment. Cephalometrics measurements were statistically analysed by t-test. Results After the orthodontic treatment, the main changes were the reduction of maxillary and mandibular prominence and the increasement of the Pg′B′-FH and Pog-Pog′and upper-lower prominence as well. The appearance of uncovered teeth by their lips was obviously improved. The changes of soft issue profile are the increment of nasolabial angle and the changes among UL-U1, LL-L1 and the E-line. Conclusion Patients with Angle classⅡdivisionⅠmalocclusion have normal overjet and overbite, and also have a better appearance of soft tissue after the extraction treatment.

Lasers in Operative Dentistry-A Review

Laser equipment represents surely one of the most captivating technologies in the practice of dental medicine. Over the last two decades, numerousscientific publications have emerged in literature, concerning laser equipments and their applications in the field of dental medicine. Presently, in accordancewith their specific wavelength, laser equipments are available on a large scale. This material reviews the most common, most current newly emerged applications of laser in dental medicine. The applications of laser therapy are presented on soft as well as hard tissues. Although laser cannot fully replace all the conventional techniques of dental medicine, the progress is obvious, and laser is expected to become an essential component of conservatory dental medicine.

Características cefalométricas en jóvenes con oclusión normal y perfil armónico en población chilena / Cephalometric characteristics in young individuals with normal occlusion and harmonic profiles in Chilean population

Las normas cefalométricas facilitan el diagnóstico y planificación terapéutica en ortodoncia, siendo estas obtenidas primariamente de población caucásica adulta. Dichas normas variarían entre etnias siendo escasa la información respecto de las de población chilena en crecimiento. Se obtuvo una muestra de 48 telerradiografías de perfil de individuos en crecimiento (23 mujeres y 25 hombres) con oclusión normal y perfil armónico de los registros de la Universidad de los Andes tomados entre Enero y Julio del año 2012, incluyendo 414 individuos. Las radiografías fueron analizadas cefalométricamente, obteniéndose valores de parámetros verticales y sagitales en tejidos blandos y duros. Se obtuvieron estadísticas descriptivas, y las diferencias entre sexos se analizaron con la prueba t de Student. Al compararse con normas caucásicas, los sujetos de la muestra tienen una tendencia a la Clase II esqueletal, por una mandíbula retrognática, eje facial abierto, y biprotrusión incisiva. También mostraron labios superiores e inferiores protruidos respecto de las normas caucásicas. Existen diferencias entre las medidas cefalométricas de la muestra y las de las normas internacionales, manifestadas a nivel mandibular, dentario y labial.

Cephalometric norms facilitate diagnosis and treatment planning in orthodontics. These are obtained primarily from adult Caucasian population. It has been suggested that these norms may vary between different ethnic groups, and there is still little information about Chilean cephalometric norms in growing individuals. A sample of 48 lateral radiographs was obtained from growing individuals (23 women and 25 men) with normal occlusion and harmonious profile taken between January and July 2012 at Universidad de los Andes, including 414 individuals. Radiographs were analyzed cephalometrically, obtaining soft and hard tissue values for vertical and sagittal parameters. Descriptive statistics were obtained, and differences between sexes were analyzed with student´s t-test. When compared to Caucasian standards, subjects in the sample present with a Class II skeletal tendency due to a retrognathic mandible, an open facial axis, with upper and lower incisor protrusion. They also showed more protruded upper and lower lips with respect to Caucasian standards. There are differences between the cephalometric measurements observed on the individuals of the sample compared to international standards, which are evidenced at mandibular, dental and labial structures.

Implant-supported maxillary full-arch fixed prosthesis opposing mandibular natural dentition: A clinical report / 대한치과보철학회지

When an implant-supported maxillary full-arch fixed prosthesis is planned for patients with the horizontal and vertical bone resorption induced by periodontal disease, it is necessary to consider the masticatory function, esthetics and phonetics when placing implants. For this reason, thorough clinical and radiological diagnosis is necessary. Extensive bone and soft tissue grafting may be required as well. Since there is no clear guideline for proper number of implants, segment or splinting of substructure and method of retaining prosthesis, these should be considered during diagnostic process. This clinical report describes a patient who has experienced several tooth extractions and periodontal treatment due to severe periodontitis on maxilla and mandible. With bone and soft tissue graft before dental implant placement, the patient have satisfactory result in esthetic and functional aspect with the implant-supported maxillary full-arch fixed prosthesis opposing mandibular natural dentition.

Impacto da profundidade da agulha de irrigação na remoção de debris dentinários / Impact of the needle insertion depth on the removal of hard-tissue debris

O presente estudo avaliou o efeito da inserção da agulha de irrigação max-i-probe 30G em duas profundidades diferentes na remoção de debris após a instrumentação endodôntica. Raízes mesiais de molares inferiores com a presença de istmos foram escaneadas em um microtomógrafo de raios-X em uma resolução isotrópica de 14.16 µm. Cada dente foi aleatoriamente designado para um dos dois grupos experimentais (n = 10) de acordo com a profundidade de inserção da agulha durante a irrigação do sistema de canais radiculares: 1 ou 5 mm aquém do comprimento de trabalho. Todas as amostras foram instrumentadas com o sistema Reciproc (VDW, Munique, Alemanha) e o mesmo protocolo de irrigação foi usado, diferindo apenas na profundidade de inserção da agulha. O segundo escaneamento foi realizado após os procedimentos de limpeza e modelagem e, depois disso, as imagens registradas, antes e após o preparo, foram examinadas a partir do nível da bifurcação até o ápice para identificar volumetricamente, medir e mapear a quantidade de debris acumulados. O teste de Mann-Whitney comparou estatisticamente o volume percentual de debris acumulados entre os grupos de irrigação. Os resultados mostraram que a profundidade de inserção da agulha teveinfluência relevante na remoção de debris (P< 0,05). Uma redução significativa na percentagem de debris foi observada quando a agulha foi inserida a 1 mm do comprimento de trabalho (P< 0,05). A profundidade de inserção da agulha de irrigação tem uma marcante influênciasobre o montante final de debris acumulados. Infere-se, desta maneira, que quanto mais próximo ao ápice é levada a agulha de irrigação, menor é a quantidade final de debris gerados após a instrumentação endodôntica.

The present study evaluated the effect of the insertion of the irrigation needle (max-i-probe, Smith and Nephew MPL, Franklin Park, IL) at two different depths on the removal of hard tissue debris. Mandibular molarswith isthmuses in the mesial root canalsystem weremicro-CT scanned at an isotropic resolution of 14.16 µm. Each tooth was randomly assigned to 2 experimental groups (n = 10) according to the depth of needle insertion during irrigation of the root canal system: 5 or 1 mm short of working length. All teeth were instrumented with the Reciproc system (VDW, Munich, Germany) and the very same irrigation protocol was used, differing only by the depth of needle insertion. Second micro-CT scans were performed after cleaning and shaping procedures and after that, the matched images, before and after preparation, were examined from the furcation level to the apex to volumetrically identify, measure and map the amount of accumulated hard-tissue debris. Mann-Whitney test was used to statistically compare the percentage volume of accumulated hard tissue debris between the irrigation groups. The result showed a significant influence of the depth of needle insertion on removal of debris (P < .05). A significant reduction in the percentage of hard tissue debris was observed when the needle was inserted up to 1 mm from the apex (P < .05). The depth of needle insertion has a significant influence on the final amount of the accumulated hard-tissue debris. It is fair to conclude that the nearest to the apex the irrigation needle is, the less is the final amount of hard-tissue debris generated.

Effect of different parameters Er: YAG laser irradiation on the structure of dental hard tissue / 中国基层医药

Objective To investigate the effect of Er:YAG laser irradiation on the structure of dental hard tissue.Methods 2 teeth (8 samples) were randomly selected from 26 teeth enamel group(104 samples) for blank control(group C).The remaining 24 teeth (96 samples) were randomly divided into A group (irradiation 10 s) and B group (20 s irradiation),each group according to power were randomly divided into 1,2,3,4,5,6 W six subgroups,each subgroup had 8 samples.Using a Er:YAG laser at 20 Hz frequency,according to the corresponding packet (with different power and different irradiation time) were irradiated for each sample.Dentin grouped with enamel group.To observe the changes of different energy and the pit diameter and depth.Results The enamel surface pit diameter was compared by different irradiation time and power,different power within the same irradiation time (t =1.89,2.02,2.76,1.98,1.37,1.42,all P ＜ 0 05) ; compared between B group and the A group under the same power (t =1.23,3.23,2.04,1.45,1.42,1.87,all P ＜ 0.05).The enamel surface pit depth was compared by different irradiation time and power,different power within the same irradiation time (t =1.15,3.09,2.32,1.76,1.51,1.59,all P ＜ 0.05) ;compared between B group and the A group under the same power (t =1.15,3.09,2.32,1.76,1.51,1.59,all P ＜0.05).The dentin surface pit diameter was compared by different irradiation time and power,different power within the same irradiation time (t =1.15,3.09,2.32,1.76,1.51,1.59,all P ＜ 0.05) ; compared between B group and the A group under the same power(t =1.15,3.09,2.32,1.76,1.51,1.59,all P ＜ 0.05).The dentin surface pit depth was compared by different irradiation time and power,diffe rent power within the same irradiation time (t =2.12,2.04,1.82,1.43,1.31,1.76,all P ＜ 0.05) ; compared between B group and the A group under the same power(t =2.34,3.13,2.76,1.45,1.34,1.62,all P＜0.05).Conclusion With the increase in the laser energy and the irradiation time,the diameter and depth of enamel pits produced also continuously increase;With the increase in the laser energy and the irradiation time,dentin diameter and depth of the pits produced constantly increased.The different parameters of Er:YAG laser irradiation of dental hard tissues have different effects on the structure.