Evaluation of antibacterial activity of propolis on regenerative potential of necrotic immature permanent teeth in dogs.

BACKGROUND: This study evaluated the antibacterial efficiency and ability of propolis to promote regeneration of immature permanent non-vital dogs' teeth. METHODS: Ninety six immature permanent premolars teeth in 6 mongrel dogs were divided randomly into: experimental teeth (N = 72) and control teeth (N = 24). Periapical pathosis was induced in all experimental and positive control teeth. Experimental teeth were classified according to the used intra-canal medication into: group I (N = 36), propolis paste was used and group II (N = 36), triple antibiotic paste (TAP) was used. Bacteriologic samplings were collected before and after exposure to intra-canal medicaments. After the disinfection period (3 weeks), revascularization was induced in all experimental teeth. Each group was subdivided according to the root canal orifice plug into: subgroup A (N = 18), propolis paste was used and subgroup B (N = 18), mineral trioxide aggregates (MTA) was used. Each subgroup was further subdivided according to the evaluation period into 3 subdivisions (6 teeth each): subdivision 1; after 2 weeks, subdivision 2; after one month and subdivision 3; after 2 months. Positive control group had 12 teeth with induced untreated periapical pathosis. Negative control group had 12 untouched sound teeth. All teeth were evaluated with radiography and histology. The bacteriologic and radiographic data were analyzed using repeated measures ANOVA and post-hoc Tukey tests. The histologic data were analyzed using Kruskal-Wallis test, Mann-Whitney U test with Bonferroni's adjustment and Chi-square test. The significance level was set at P ≤ .05. RESULTS: There was no significant difference in the antibacterial effectiveness between TAP and propolis groups (P > .05). In all subdivisions, there was no significant difference between the experimental groups in terms of increase in root length and dentin thickness, decrease in apical closure, new hard tissue formation, vital tissue formation inside the pulp canal and apical closure scores (P > .05). CONCLUSION: Propolis can be comparable with TAP as a disinfection treatment option in regenerative endodontic. As a root canal orifice plug after revascularization of necrotic immature permanent teeth in dogs, propolis induces a progressive increase in root length and dentin thickness and a decrease in apical diameter similar to those of MTA.

Use of platelet-rich plasma for regeneration in non-vital immature permanent teeth: Clinical and cone-beam computed tomography evaluation.

Objective This study was performed to assess the clinical and radiological outcomes of a revascularization procedure in immature teeth with apical periodontitis using platelet-rich plasma (PRP). The PRP protocol and conventional revascularization protocol, which used a blood clot as the scaffold, were compared. Methods Thirty non-vital immature permanent teeth were randomly categorized into two groups. After disinfecting the root canal space with triple antibiotic paste (1:1:1 ciprofloxacin, metronidazole, and cefaclor), a tissue scaffold was created using either PRP or a blood clot (control) and covered with white mineral trioxide aggregate. All cases were followed up clinically and radiographically for 12 months. Differences in bone density, root length, and lesion size were calculated using preoperative and postoperative computed tomography images. The means of the differences in individual parameters in the blood clot and PRP groups were compared using the Mann-Whitney U test. Results After 5 months, sensitivity tests (cold and electric pulp tests) elicited a delayed positive response in 23 sites. At 12 months, cone-beam computed tomography revealed resolution or a decrease in lesion size and an increase in bone density in all 30 (100%) teeth. Additionally, continued root development was observed in 22 (73%) teeth and early root growth was observed in the test group (mineral trioxide aggregate with PRP). Conclusions The results of this study suggest that PRP can serve as a successful scaffold for regenerative endodontic treatment. With the exception of a significant increase in root length, the results of treatment with PRP were not significantly different from those of the conventional protocol using a blood clot as the scaffold.

Regenerative potential of immature permanent non-vital teeth following different dentin surface treatments.

This study evaluates the regenerative potential of immature permanent non-vital teeth following different dentin surface treatments in dogs. Periapical lesions and necrotic pulps were induced in 288 roots of 144 teeth in twelve dogs. Teeth were randomly divided into 3 equal groups according to the evaluation period. Each group was subdivided into 8 subgroups according to the treatment modalities including; blood clot, blood clot and collagen, blood clot and Ethylenediaminetetraacetic acid (EDTA), blood clot, collagen and EDTA, blood clot and Mixture Tetracycline Citric Acid and Detergent (MTAD), blood clot, collagen and MTAD, positive control and negative control. Apart from control subgroups, all infected root canals were cleaned with sodium hypochlorite solution and triple antibiotics paste before different treatment protocols. After different treatments, the root length, thickness and apical diameter were evaluated by radiographic examination. Histopathological examination was carried out to evaluate the inflammation, bone/root resorption, tissue in-growth in pulp space, new hard tissue formation and apical closure. Using EDTA solution as a surface modifier showed significantly higher levels of tissue in-growth in the pulp space after 6 weeks and 3 months. Addition of collagen as a scaffold caused significantly more bone/root resorption than the other subgroups while EDTA caused significantly lower inflammatory cell counts only after 2 weeks. Final rinse with 17% EDTA solution before blood clot induction has positive impact on tissue interaction along dentinal walls without modification of the cell type. Moreover, the use of collagen as a scaffold material and MTAD as a surface modifier did not improve the quality of the regenerative process.

Action Mechanism of Fibroblast Growth Factor-2 (FGF-2) in the Promotion of Periodontal Regeneration in Beagle Dogs.

Fibroblast growth factor-2 (FGF-2) enhances the formation of new alveolar bone, cementum, and periodontal ligament (PDL) in periodontal defect models. However, the mechanism through which FGF-2 acts in periodontal regeneration in vivo has not been fully clarified yet. To reveal the action mechanism, the formation of regenerated tissue and gene expression at the early phase were analyzed in a beagle dog 3-wall periodontal defect model. FGF-2 (0.3%) or the vehicle (hydroxypropyl cellulose) only were topically applied to the defect in FGF-2 and control groups, respectively. Then, the amount of regenerated tissues and the number of proliferating cells at 3, 7, 14, and 28 days and the number of blood vessels at 7 days were quantitated histologically. Additionally, the expression of osteogenic genes in the regenerated tissue was evaluated by real-time PCR at 7 and 14 days. Compared with the control, cell proliferation around the existing bone and PDL, connective tissue formation on the root surface, and new bone formation in the defect at 7 days were significantly promoted by FGF-2. Additionally, the number of blood vessels at 7 days was increased by FGF-2 treatment. At 28 days, new cementum and PDL were extended by FGF-2. Moreover, FGF-2 increased the expression of bone morphogenetic protein 2 (BMP-2) and osteoblast differentiation markers (osterix, alkaline phosphatase, and osteocalcin) in the regenerated tissue. We revealed the facilitatory mechanisms of FGF-2 in periodontal regeneration in vivo. First, the proliferation of fibroblastic cells derived from bone marrow and PDL was accelerated and enhanced by FGF-2. Second, angiogenesis was enhanced by FGF-2 treatment. Finally, osteoblastic differentiation and bone formation, at least in part due to BMP-2 production, were rapidly induced by FGF-2. Therefore, these multifaceted effects of FGF-2 promote new tissue formation at the early regeneration phase, leading to enhanced formation of new bone, cementum, and PDL.

Nicotine effect on bone remodeling during orthodontic tooth movement: histological study in rats.

INTRODUCTION: Nicotine is harmful to angiogenesis, osteogenesis and synthesis of collagen. OBJECTIVE: The aim of this study was to investigate the effect of nicotine on bone remodeling during orthodontic movement in rats. METHODS: Eighty male Wistar rats were randomly divided into three groups: Group C (control), group CM (with orthodontic movement) and group NM (nicotine with orthodontic movement) groups. The animals comprising groups C and CM received 0.9% saline solution while group NM received nicotine solution (2 mg/kg). A nickel-titanium closed-coil spring was used to induce tooth movement. The animals were euthanized and tissue specimens were histologically processed. Blood vessels, Howship's lacunae and osteoclast-like cells present in the tension and compression areas of periodontal ligaments were quantified. The extent of bone formation was evaluated under polarized light, to determine the percentage of immature/mature collagen. RESULTS: It was observed lower blood vessel densities in the NM group in comparison to the CM group, three (p < 0.001) and seven (p < 0.05) days after force application. Osteoclast-like cells and Howship's lacunae in the NM group presented lower levels of expression, in comparison to the CM group, with significant differences on day 7 (p < 0.05 for both variables) and day 14 (p < 0.05 for osteoclast-like cells and p < 0.01 for Howship's lacunae). The percentage of immature collagen was increased in the NM group in comparison to the CM group, with a statistically significant difference on day 3 (p < 0.05), day 7 (p < 0.001), day 14 (p < 0.001) and day 21 (p < 0.001). CONCLUSIONS: Nicotine affects bone remodeling during orthodontic movement, reducing angiogenesis, osteoclast-like cells and Howship's lacunae, thereby delaying the collagen maturation process in new bone matrix.

Nicotine effect on bone remodeling during orthodontic tooth movement: Histological study in rats

Introduction: Nicotine is harmful to angiogenesis, osteogenesis and synthesis of collagen. Objective: The aim of this study was to investigate the effect of nicotine on bone remodeling during orthodontic movement in rats. Methods: Eighty male Wistar rats were randomly divided into three groups: Group C (control), group CM (with orthodontic movement) and group NM (nicotine with orthodontic movement) groups. The animals comprising groups C and CM received 0.9% saline solution while group NM received nicotine solution (2 mg/kg). A nickel-titanium closed-coil spring was used to induce tooth movement. The animals were euthanized and tissue specimens were processed histologically. We quantified blood vessels, Howship's lacunae and osteoclast-like cells present in the tension and compression areas of periodontal ligaments. The extent of bone formation was evaluated under polarized light to determine the percentage of immature/mature collagen. Results: We observed lower blood vessel densities in the NM group in comparison to the CM group, three (p < 0.001) and seven (p < 0.05) days after force application. Osteoclast-like cells and Howship's lacunae in the NM group presented lower levels of expression in comparison to the CM group, with significant differences on day 7 (p < 0.05 for both variables) and day 14 (p < 0.05 for osteoclast-like cells and p < 0.01 for Howship's lacunae). The percentage of immature collagen increased in the NM group in comparison to the CM group with a statistically significant difference on day 3 (p < 0.05), day 7 (p < 0.001), day 14 (p < 0.001) and day 21 (p < 0.001). Conclusions: Nicotine affects bone remodeling during orthodontic movement, reducing angiogenesis, osteoclast-like cells and Howship's lacunae, thereby delaying the collagen maturation process in developed bone matrix. .

Introdução: a nicotina apresenta efeito prejudicial sobre a angiogênese, osteogênese e síntese de colágeno. Objetivo: investigar a ação da nicotina sobre a remodelação óssea durante o movimento dentário induzido em ratos. Métodos: oitenta ratos machos Wistar foram divididos em três grupos: grupo C (sem indução de movimento dentário e sem a ação da nicotina - controle); grupo CM (indução de movimento dentário) e grupo NM (indução de movimento dentário associado à ação da nicotina). Os animais dos grupos C e CM receberam solução salina a 0,9% e os animais do grupo NM receberam nicotina (solução PA a 98% diluída em solução salina a 0,9% estéril) por via subcutânea (2mg/kg). Após a eutanásia dos animais, com 3, 7, 14 e 21 dias de uso da mola ortodôntica, os espécimes teciduais foram processados histologicamente e quantificou-se o número de vasos sanguíneos, lacunas de Howship e células osteoclásticas nos lados de tração e compressão do ligamento periodontal. A neoformação óssea foi avaliada por meio de luz polarizada, para determinar a porcentagem de colágeno maduro e imaturo. Resultados: observou-se que a quantidade de vasos sanguíneos diminuiu no grupo NM, quando comparado ao grupo CM, nos períodos de três (p < 0,001) e sete (p < 0,05) dias. Quanto às células osteoclásticas e lacunas de Howship, o grupo NM apresentou menores níveis de expressão em relação ao grupo CM, com diferença estatisticamente significativa nos períodos de 7 e 14 dias. A porcentagem de colágeno imaturo apresentou-se aumentada no grupo NM, quando comparado ao grupo CM, em todos os períodos analisados, com diferença e...

[Revascularization? Only as the last resort!].

Revascularization has been suggested for treatment of necrotic immature permanent teeth. The desirable outcome of the treatment is continuous growth of the root, maturation of the dentin walls underneath the cervical seal and apical closure. Despite of increasing numbers of case reports, a uniform treatment protocol has not been set. This procedure has many shortcomings of which tooth discoloration is the most prevalent and easy to observe. The severe discoloration is attributed to the use of Mincocycline in the antibiotic dressing, or to the use of MTA for the seal. The maturation of the root is not predictable and does not always occur. The outcome should be evaluated radiographically and clinically. Sensibility testing may not be possible due to the large MTA plug in the root canal. It is recommended only when alternative procedures such as apexificaiton, pulpotomy or pulp capping are impossible. The patient and his parents should be aware of the potential discoloration and must be committed to routine follow ups. Currently, this procedure should be limited to incisor or premolar teeth in which the crown is longer than the root, or the canal's width is larger than that of the dentinal wall.

Mahidol study 1: comparison of radiographic and survival outcomes of immature teeth treated with either regenerative endodontic or apexification methods: a retrospective study.

INTRODUCTION: There are numerous challenges in treating immature permanent teeth with a diagnosis of pulp necrosis. Three general treatment options are calcium hydroxide apexification, mineral trioxide aggregate (MTA) apexification, and revascularization. The objective of this retrospective study was to evaluate radiographic and clinical outcomes of immature teeth treated with 1 of these 3 methods. METHODS: Clinical outcome data and radiographs were collected from 61 cases (ie, 22 calcium hydroxide apexification cases, 19 MTA apexification cases, and 20 revascularization cases). Both tooth survival and clinical success rates were analyzed. In addition, the preoperative and recall radiographs were analyzed to calculate the percentage increase in root width and length. RESULTS: The percentage change of root width was significantly greater in the revascularization group (28.2%) compared with the MTA apexification (0.0%) and calcium hydroxide apexification groups (1.5%). In addition, the percentage increase of root length was significantly greater in the revascularization group (14.9%) compared with the MTA (6.1%) and calcium hydroxide apexification groups (0.4%). Moreover, the survival rate of the revascularization-treated teeth (100%) and MTA apexification-treated teeth (95%) were greater than the survival rates observed in teeth treated with calcium hydroxide (77.2%). CONCLUSIONS: In this study, revascularization was associated with significantly greater increases in root length and thickness in comparison with calcium hydroxide apexification and MTA apexification as well as excellent overall survival rates.

Regenerative endodontic treatment (revascularization) for necrotic immature permanent molars: a review and report of two cases with a new biomaterial.

INTRODUCTION: Revascularization is a valuable treatment in immature necrotic teeth that allows the continuation of root development. In this article we describe successful revascularization treatment of 2 necrotic immature first mandibular molars. METHODS: The clinical and radiographic examinations showed extensive coronal caries, immature roots, and periapical radiolucencies in mandibular first molars of a 9-year-old boy and an 8-year-old girl. The exam findings suggested revascularization treatment in both cases, which was started with irrigation of the canals by using NaOCl 5.25% for 20 minutes, followed by 3 weeks of triple antibiotic (metronidazole, ciprofloxacin, and minocycline) paste dressing. Next, the antibiotic paste was removed, bleeding was induced in the canals, and calcium enriched mixture (CEM) cement was placed over blood clots. RESULTS: In radiographic and clinical follow-ups both cases were asymptomatic and functional, periapical radiolucencies were healed, and roots continued to develop. CONCLUSIONS: Revascularization is a realistic treatment in immature necrotic molars. In addition, placing CEM cement as a new endodontic biomaterial over the blood clot formed inside the canals provided good seal and favorable outcomes.

Revascularization of an immature permanent tooth with periradicular abscess after luxation.

An immature permanent mandibular central incisor with periapical involvement in a 7-year-old boy was treated to promote revascularization. The tooth suffered from acute apical periodontitis after periodontal treatment by a general practitioner. An access cavity was prepared in the tooth and the cavity was left open until the next visit to achieve drainage through the canal. The root canal was not mechanically cleaned during the treatment period, but was irrigated with hydrogen peroxide and sodium hypochlorite. Calcium hydroxide compound was used for disinfection. At the fifth visit vital tissue appeared in the canal near the apical region, and calcium hydroxide compound was placed in contact with the soft tissue in the root canal. The access cavity was sealed with glass-ionomer cement followed by an adhesive composite resin filling. Radiographic examination 30 months after the initial treatment confirmed closure of the apex and thickening of the root wall. The case was observed for up to 13 years and root development was confirmed.

Management of the immature apex tooth: an online study guide.

The Editorial Board of the Journal of Endodontics has developed a literature-based study guide of topical areas related to endodontics. This study guide is intended to give the reader a focused review of the essential endodontic literature and does not cite all possible articles related to each topic. Although citing all articles would be comprehensive, it would defeat the idea of a study guide. This section will cover apexogenesis, revascularization/regeneration, apexification, and artificial apical barriers.

Rare courses of the mandibular canal in the molar regions of the human mandible: a cadaveric study.

The inferior alveolar artery, vein and nerve send some branches to the molar teeth via the mandibular canal to the mental foramen. The present study attempted to define the presence and course of the mandibular canal in the mandible with the alveolar process by macroscopic cadaveric dissection and computerized tomography (CT) in order to provide information that might prevent injuries to vessels and nerves at risk during root canal treatment. We identified the position of the mandibular canal within a 30% ratio of the distance from inferior border of mandible to the apices of the root for 39 out of 131 sides (mesial root of first molar, 20%; distal root of first molar, 22.6%; mesial root of second molar, 27.8% and distal root of second molar, 47%) on panoramic X-ray observation. In one cadaver (male, 64 years old), the root apex of the second molar was in close proximity to the upper bony mandibular canal. Macroscopic dissection and computerized tomography showed that the main trunks of the inferior alveolar artery, vein, and nerve were in tight contact with the apex of the second molar. These observations of the anatomic course of the mandibular canal will be important to consider during root canal treatment of mandibular teeth.

Distribution of the epithelial rests of Malassez and their relationship to blood vessels of the periodontal ligament during rat tooth development.

BACKGROUND: There is some evidence that the epithelial cell rests of Malassez partition the root surface from the periodontal ligament blood vessels, and may protect the root from resorption. OBJECTIVE: The aim of the present study was to determine the distributions of the epithelial rests of Malassez (ERM) and blood vessels in the periodontal ligament (PDL) of the developing rat first molar before, during and after emergence. METHODS: Four Sprague-Dawley rats were sacrificed at two days, one week, two weeks, three weeks, four weeks and six weeks of age. After processing, the maxillae were embedded in paraffin, and sectioned longitudinally and transversely. The sections were stained with a double immuno-histochemical technique which utilised a keratin antibody AE1-AE3 (1:2,000) and an endothelial antibody Factor VIII (1:10,000) to enable simultaneous labelling of ERM and blood vessels. ERM and blood vessel counts were obtained from the mesio-buccal roots of three week, four week and six week-old rats, whilst qualitative observations were made for the earlier developmental stages. RESULTS: ERM cells and cell clusters were found in the tooth third of the PDL width at the three, four and six week stages. Cells and cell clusters increased in number with age, especially in the upper third of the mesio-buccal root. The largest numbers of cells and clusters were found on the distal surfaces of the roots in all age groups. Cells and clusters in all root surfaces increased from three to four weeks, but decreased from four to six weeks. The greatest number of blood vessels was found in the bone-side third of the PDL. The distal surface had the highest proportion of blood vessels, and the palatal surface the least proportion. The number of blood vessels in all surface quadrants did not vary much from three to four weeks of age, but increased from four to six weeks of age, possibly as a reaction to tooth emergence and occlusal function. Physiological root resorption was only observed after tooth emergence, and appeared to be related to loss of continuity of the ERM network and the incursion of blood vessels. CONCLUSIONS: Orthodontic root resorption can be regarded as an exaggerated response to loss of PDL homeostatic control, possibly mediated by the epithelial rests of Malassez.

Clinical management of the avulsed tooth: present strategies and future directions.

The aim of this review article is to supplement the recently published International Association of Dental Traumatology (IADT) guidelines on treatment of the avulsed tooth. A thorough discussion on the reasoning behind each guideline is presented. In addition, the author's views on alternate treatment strategies and future directions, along with recent research on the subject of the avulsed tooth, are also presented.

Ultrastructural changes in postcapillary-sized venule morphology in aged mouse periodontal ligament.

The aim of this study was to compare the postcapillary-sized venule (PCV) morphology of four young ALCA mice (35 days) and four colony-related aged mice (365 days) using the transmission electron microscope (TEM). Right and left mandibular first molar mesial roots with associated periodontal ligament (PDL) and bony socket, were used for TEM assessment. Five PCV profiles were selected at each 160 microm interval, from the alveolar crest to the tooth apex. PCV profile dimensions were measured on standardised micrographs magnified x2900. Age affects were tested using multiple regression analysis. The number of PCV profiles in the tooth third of the PDL was higher in aged mice (p < 0.01) and comprised predominantly apericytic vessels (p < 0.001). The number of PCV profiles increased significantly (p < 0.001) in aged mice in the PDL middle circumferential third halfway down the molar root. Age had no significant affect on PCV diameter. Aged PDL permeability studies are needed to investigate whether the changes in aged PCV profile number are associated with functional modification of the PDL microvasculature.

Conductos radiculares artificiales: análisis de su confiabilidad para el estudio de diferentes técnicas de instrumentación / Artificial root canals: analysis of its reliability for the study of differents instrumentation techniques

En la primera parte de esta experiencia, se utilizaron 30 conductos radiculares curvos artificiales, contenidos en bloques de acrilico estandarizados, los que no fueron instrumentados y se conservaron tal como fueran provistos por el fabricante. En la segunda parte de la experiencia se utilizaron 10 conductos artificiales similares a los anteriores, los que fueron instrumentados por medio de limas de niquel-titanio rotatorias pertenecientes al sistema Quantec (Grupo1) y una tecnica de instrumentacion escalonada con instrumentos manuales convencionales (Grupo 2). Todos los especimenes se cortaron transversalmente a 1,5 y 10 mm del limite de trabajo previamente establecido y se analizo el porcentaje de circularidad en cada uno de los niveles preseleccionados por medio de un Fotomicroscopio anexado a un analizador de imagenes y un programa de software apropiado. Los canales sin instrumentar presentaron un porcentaje de circularidad significativamente alto, y no hubo diferencias significativas entre todos los especimenes analizados. Los conductos pertenecientes al Grupo 1 presentaron valores de circularidad significativamente mayores (p<0,01) que aquellos pertenecientes al Grupo 2. El alto indice de regularidad presentada por los especimenes analizados en este trabajo indica que el uso de conductos artificiales contenidos en bloques de acrilico, cuya estandarizacion este garantizada por controles de calidad adecuados, constituye un modelo experimental apropiado para el estudio comparativo de la accion de diferentes instrumentos y/o tecnicas de instrumentacion endodontics. (AU)

Conductos radiculares artificiales: análisis de su confiabilidad para el estudio de diferentes técnicas de instrumentación / Artificial root canals: analysis of its reliability for the study of differents instrumentation techniques

En la primera parte de esta experiencia, se utilizaron 30 conductos radiculares curvos artificiales, contenidos en bloques de acrilico estandarizados, los que no fueron instrumentados y se conservaron tal como fueran provistos por el fabricante. En la segunda parte de la experiencia se utilizaron 10 conductos artificiales similares a los anteriores, los que fueron instrumentados por medio de limas de niquel-titanio rotatorias pertenecientes al sistema Quantec (Grupo1) y una tecnica de instrumentacion escalonada con instrumentos manuales convencionales (Grupo 2). Todos los especimenes se cortaron transversalmente a 1,5 y 10 mm del limite de trabajo previamente establecido y se analizo el porcentaje de circularidad en cada uno de los niveles preseleccionados por medio de un Fotomicroscopio anexado a un analizador de imagenes y un programa de software apropiado. Los canales sin instrumentar presentaron un porcentaje de circularidad significativamente alto, y no hubo diferencias significativas entre todos los especimenes analizados. Los conductos pertenecientes al Grupo 1 presentaron valores de circularidad significativamente mayores (p<0,01) que aquellos pertenecientes al Grupo 2. El alto indice de regularidad presentada por los especimenes analizados en este trabajo indica que el uso de conductos artificiales contenidos en bloques de acrilico, cuya estandarizacion este garantizada por controles de calidad adecuados, constituye un modelo experimental apropiado para el estudio comparativo de la accion de diferentes instrumentos y/o tecnicas de instrumentacion endodontics.

Pulsed Nd:YAG laser irradiation of the tooth pulp in the cat: I. Effect of spot lasing.

BACKGROUND AND OBJECTIVE: The purpose of the present study was to evaluate physiologically pulpal nerve responses and to elucidate histopathologically the pulp tissue reactions to "spot irradiation" with a pulsed Nd:YAG laser. STUDY DESIGN/MATERIALS AND METHODS: Antidromic compound action potentials and the pulpal blood flow (PBF) were recorded from the canine tooth of a sodium pentobarbitone-anesthetized cat. The laser irradiation-induced pulp tissue changes were histologically investigated. RESULTS: The coronal antidromic compound action potentials disappeared in all the teeth tested during lasing, and the time needed to erase them was significantly shortened with increases in lasing power (P < 0.05). The radicular PBF increased when spot irradiation was performed, and the coronal PBF also temporarily increased with low-powered lasing. Histologic investigation revealed that spot irradiation with the laser produced severe damage in the pulp tissue in a dose-dependent manner. CONCLUSION: The present study suggests that spot irradiation with a pulsed Nd:YAG laser risks producing nerve injury and irreversible tissue damage in the pulp with lasing for the purpose of desensitizing hypersensitive dentin.