Changes in periapical status of root canal-treated teeth after head and neck IMRT: a retrospective study

The objective of this retrospective study was to analyze the effect of the intensity modulated radiotherapy (IMRT) of the head and neck region on root canal-treated teeth and their periapical changes due to radiation. Patients undergoing IMRT of the head and neck region were evaluated. Different types of teeth (molars, premolars, incisors and canines) were compared. Panoramic and dental radiographs were used to assess the periapical region of root canal-treated teeth using the periapical index (PAI) before and after radiotherapy (RT) and put in relation to the radiation dose per tooth. Further parameters (patient-, therapy- and tooth-related factors) were included in this study. One hundred and twenty-four root canal-treated teeth (maxilla and mandible) of 51 patients were observed. A radiolucency in the periapical region was seen in 34.7% of the samples before IMRT and an increasing number of 46% after IMRT (p-value 0.092). Clinical or radiological signs of osteoradionecrosis could not be determined. The only statistically significant difference was detected in regions irradiated with less than 40 Gy (p-value 0.045). In regions irradiated with higher doses (>40 Gy), comparable pathologies increased in non-significant numbers. A statistically significant increase of periapical pathologies was detected in premolars of the maxilla. The observations reported here suggest that a high radiation dose during IMRT has no significant consequences on root canal-treated teeth. To compare the success of endodontic treatment before versus after IMRT, further research needs to be done.

Highly efficient optical fiber sensor for instantaneous measurement of elevated temperature in dental hard tissues irradiated with an Nd:YaG laser

In this in vitro experiment, the effect of 1.064 µm pulsed laser on both enamel- and dentin-dental tissues has been investigated. A total of fifty-five dental hard tissue samples were exposed to Nd:YAG laser that possesses a pulse width of 9 ns and 850 mJ of total energy. An optical fiber sensor was put behind the samples to measure the temperature instantaneously. A novel, to the best of our knowledge, fiber sensor has been proposed and used to measure the heat generated in dental hard tissues instantaneously after the application of laser irradiation on the tissue surface. This optical sensor exhibits a fast response time of about 1 ms and high sensitivity with about 1.975 nm/°C. The findings of this study in decreasing the probability of pulpal necrosis structure while handling the tooth, whether for ablation, welding, or tooth resurfacing purposes, may establish standards for dentists and laser manufacturers (healthcare professionals) that should be followed.

Influence of Nd:YAG laser on the penetration of a bioceramic root canal sealer into dentinal tubules: A confocal analysis

OBJECTIVE

The aim of this in vitro study, is to evaluate the penetration of a bioceramic root canal sealer into dentinal tubules at 3 mm and 5 mm from the apex after Nd:YAG laser irradiation.

METHODS

Forty freshly extracted human mandibular premolars were prepared using Reciproc® and irrigated with 17% ethylenediaminetetraacetic acid (EDTA). Teeth were divided into 4 groups: group 1, obturated with control sealer (AH Plus®); group 2, obturated with bioceramic sealer (Endosequence BC Sealer®); group 3, Nd:YAG laser + control sealer (AH Plus®); and group 4, Nd:YAG laser + bioceramic sealer (Endosequence BC Sealer®). The samples were transversely sectioned 3 mm and 5 mm from the apex and examined using confocal laser scanning microscopy. Two parameters were measured: 1) sealer penetration into dentinal tubules of the root canal and 2) sealer penetration into the perimeter of the root canal walls.

RESULTS

Penetration analysis showed that bioceramic sealer had a higher penetration at depths of 3 and 5 mm than that of the control sealer, regardless of laser use (p <0.05). Perimeter analysis showed that there was no difference between both sealers at a depth of 3 mm (p <0.05), regardless of laser use. At a depth of 5 mm, bioceramic sealer and laser showed a greater perimeter of penetration (p <0.05) than the control sealer.

CONCLUSION

The use of Nd:YAG laser did not compromise the penetration of bioceramic sealer into dentinal tubules of root canals at 3 mm and 5 mm from the apex.

The local anaesthetic effect of a dental laser prior to cavity preparation: a pilot volunteer study

OBJECTIVES

It has been suggested that laser preconditioning can produce dental anaesthesia. This study aimed to assess the response of the dental pulp to laser preconditioning.

METHODS

The effects of laser preconditioning, sham laser (negative control), and composite curing light (positive control) on the response of the dental pulp to electric pulp testing was investigated in this double-blind crossover trial with six volunteers. The Er,Cr:YSGG laser or curing light was shone on a premolar tooth in a sweeping motion for 30 seconds (in the sham treatment, the laser was not activated) in blindfolded volunteers subjected to a consistent aural stimulus. Treatment method at each visit was randomized and performed by a researcher not involved in pulp testing. Teeth were pulp tested twice initially by another member of the research team to get baseline readings, immediately following the treatment, and thereafter every two minutes for 10 minutes. Results were analyzed using analysis of variance and an independent-sample t-test.

RESULTS

There were no significant differences in pulpal response between treatments (p>0.05).

CONCLUSION

Laser preconditioning did not affect pulpal response as measured by an electronic pulp tester. Laser preconditioning did not result in any pain or noticeable symptoms for both teeth and soft tissues.

Measurements of erbium laser-ablation efficiency in hard dental tissues under different water cooling conditions

Laser triangulation measurements of Er:YAG and Er,Cr:YSGG laser-ablated volumes in hard dental tissues are made, in order to verify the possible existence of a "hydrokinetic" effect that has been proposed as an alternative to the "subsurface water expansion" mechanism for hard-tissue laser ablation. No evidence of the hydrokinetic effect could be observed under a broad range of tested laser parameters and water cooling conditions. On the contrary, the application of water spray during laser exposure of hard dental material is observed to diminish the laser-ablation efficiency (AE) in comparison with laser exposure under the absence of water spray. Our findings are in agreement with the generally accepted principle of action for erbium laser ablation, which is based on fast subsurface expansion of laser-heated water trapped within the interstitial structure of hard dental tissues. Our measurements also show that the well-known phenomenon of ablation stalling, during a series of consecutive laser pulses, can primarily be attributed to the blocking of laser light by the loosely bound and recondensed desiccated minerals that collect on the tooth surface during and following laser ablation. In addition to the prevention of tooth bulk temperature buildup, a positive function of the water spray that is typically used with erbium dental lasers is to rehydrate these minerals, and thus sustaining the subsurface expansion ablation process. A negative side effect of using a continuous water spray is that the AE gets reduced due to the laser light being partially absorbed in the water-spray particles above the tooth and in the collected water pool on the tooth surface. Finally, no evidence of the influence of the water absorption shift on the hypothesized increase in the AE of the Er,Cr:YSGG wavelength is observed.

Short-term effect of low-intensity pulsed ultrasound on an ex-vivo 3-d tooth culture

We investigated the short-term effect of LIPUS on human dentin-pulp complex in vitro. We collected sixty-three premolars from patients who needed the extraction. The premolars were sectioned transversely into 600-μm-thick slices, and then divided into five groups according to LIPUS application time (control, 5, 10, 15 and 20 min). LIPUS transducer produced an incident intensity of 30 mW/cm(2). After 24 h, tissue was harvested for histomorphometrical analysis and RT-PCR (Genes of interest: Collagen I, DMP1, DSPP, TGF β1, RANKL and OPG). Histomorphometric analysis showed no significant difference among the five groups in the odontoblast count and predentin thickness. RT-PCR demonstrated no expression of TGF β1, low amounts of DSPP, a twofold increase in collagen I expression in the 5- and 10-minute LIPUS groups and a threefold increase in DMP1 expression in the 10-minute LIPUS group. LIPUS application was stimulatory to the dentin-pulp complex in vitro and increased the expression of collagen I and DMP1.

Temperature change, dentinal fluid flow and cuspal displacement during resin composite restoration

Dentin-bonding agents and resin composite materials typically require light activation for polymerization. Light curing generates heat, which may influence dentinal fluid flow (DFF) and cuspal displacement. This study investigated the relationship among temperature increase, DFF and cuspal displacement in extracted human maxillary premolars with a mesial occlusal distal (MOD) cavity preparation. Two types of curing light were compared. Temperature changes were measured using thermocouples located on the occlusal cavity floor and at the pulp-dentine junction, during polymerization of bonding agent and resin composite material. DFF and cuspal displacement were measured simultaneously using automated flow measurement apparatus and direct current differential transformers respectively. Temperature increases of up to 15 degrees C were recorded during the restoration procedures. A quartz tungsten halogen (QTH) unit produced a significantly greater temperature increase than a light-emitting diode unit and curing of the bonding agent generated less temperature increase than curing of the resin composite. Heating due to exothermic reaction during polymerization of bonding agent and resin was not significantly different between light sources or between bonding and curing (P > 0.05). The QTH unit produced both greater inward fluid flow and cuspal displacement during the irradiation of bonding agent and resin composite than the light-emitting diode unit. There was not a simple relationship between temperature increase, fluid movement and cuspal displacement. From a clinical point of view, the light-emitting diode unit can be considered preferable to the QTH light, because it caused significantly smaller temperature increase, fluid shift and cuspal displacement.

Effect of GaAIAs laser on reactional dentinogenesis induction in human teeth

OBJECTIVE

This study investigated the biomodulatory effect of the gallium- aluminum-arsenate laser (GaAlAs) in pulp cells on reactional dentinogenesis, and on the expression of collagen type III (Col III), tenascin (TN), and fibronectin (FN) in irradiated dental tissues and controls (not irradiated).

BACKGROUND DATA

Several studies suggest a biomodulatory influence of low-intensity laser radiation in the inflammatory and reparative processes of biological tissues.

METHODS

Sixteen human premolar teeth were selected (after extraction due to orthodontal reasons) and divided into irradiated and control groups. Black class V cavity preparations were accomplished in both groups. For the irradiated group, GaAlAs laser (670 nm, 50 mW) with an energy density of 4 J/cm2 was used. Soon after, the cavities were restored with a glass ionomer and the extractions made after 14 and 42 days.

RESULTS

Histological changes were observed by light microscopy; less intense inflammatory reaction in the irradiated group was found when compared to the controls. Only the irradiated group of 42 days exhibited an area associated with reactional dentinogenesis. After immunohistochemical analysis by the streptoavidin-biotin complex (SABC) method, the expression of Col III, TN, and FN was greater in the irradiated groups.

CONCLUSION

Our results suggest that a GaAlAs laser with energy density of 4 J/cm2 and wavelength of 670 nm caused biomodulation in pulp cells and expression of collagen, but not collagen of the extracellular matrix, after preparation of a cavity.

Temperature rise during orthodontic bonding with various light-curing units--an in vitro study

The purpose of this in vitro study was to investigate the temperature changes in the pulp chamber during bracket bonding using three different light sources. Bracket bonding was performed on one lower first premolar and one lower central incisor at two different distances (surface and 10 mm). The measurements were taken with a J-type thermocouple wire, placed in the pulp chamber and connected to a data logger. Analysis of variance revealed that pulp chamber temperature changes were influenced by the light source, the tooth type, and the distance from the tip of the light guide to the bracket surface. Halogen induced significantly higher intrapulpal temperature changes than light-emitting diode and Xenon Plasma Arc (PAC) (P = .000). The temperature increase was significantly higher when the light-guide tip was positioned at the surface of the teeth than at the 10-mm distance with all light-curing units (P = .000). All light-curing units produced higher intrapulpal temperature increase in the mandibular incisor than in the premolar. Power PAC produced significantly higher heat changes in the incisor than in the premolar. Orthodontic bonding with different light-curing units did not exceed the critical 5.5 degrees C value for pulpal health.

Effects of 2.94 microm Er:YAG laser radiation on root surfaces treated in situ: a histological study

BACKGROUND

Previous scanning electron microscopy (SEM) studies using extracted teeth have shown the potential of infrared Er:YAG laser radiation to remove subgingival calculus without causing severe thermal changes, e.g., charring or fusion, to the irradiated root surface. The purpose of the present study was to examine the morphologic changes on root surfaces following Er:YAG laser irradiation in situ using histological observation.

METHODS

The periodontal pockets of 6 premolars, canines, and incisors that remained in situ in the jaws of human corpses were irradiated with Er:YAG laser radiation at 60 mJ, 100 mJ, or 180 mJ. The pockets were treated in a similar manner to normal clinical circumstances with a total amount of either 50 or 100 laser pulses. Following laser treatment, the entire tooth, marginal gingiva, and underlying alveolar bone were removed from the jaw. The sections were embedded in methyl-methacrylate, serially cross-sectioned, stained with hematoxylin and eosin or gallamine blue, and examined under a light microscope. Additionally, the extension of the thermally changed tissue areas was determined using digital images and histometry.

RESULTS

The histological examination revealed two kinds of thermal changes within the laser-treated root surface. Firstly, a thin superficial layer 5 to 10 microm in width was observed. The surface of this layer showed ultrastructural irregularities. Secondly, a semicircular more deeply stained area close to the apical end of the scaling track beneath the irradiated cementum was observed. The depth of this area ranged from 255 microm to 611 microm and appeared to be independent of the radiation energy.

CONCLUSION

In contrast to previous SEM studies, the histological examination indicated thermal changes within the hard tissue bordering the periodontal pocket following Er:YAG laser irradiation.

Sensitivity of whole human teeth to fast neutrons and gamma-rays estimated by L-band EPR spectroscopy

This paper reports the first attempt to use L-band spectroscopy for estimating the sensitivity of whole teeth to fast neutrons and gamma-rays. Three teeth were successively irradiated first with fast neutrons with a wide energy spectrum (mean energy around 30 MeV) up to approximately 160 Gy and then with gamma-rays up to approximately 14 Gy. After each irradiation, L-band (approximately 1 GHz) EPR spectra of each whole tooth surrounded by the surface-coil resonator were recorded, yielding a single composite line principally due to CO2- and native radicals. The sensitivities are estimated by the slopes of the linear dose response curves of the dosimetric CO2- radicals. The ratios of the gamma/neutron sensitivities were found to be in the range 8-9 (+/- 2) for the three teeth.

An in vitro L-band electron paramagnetic resonance study of highly irradiated whole teeth

Regarding in vivo L-band dosimetry with human teeth, a number of preliminary experiments were carried out that were linked to the resonators response and the relative contribution of enamel to the EPR signal intensity of irradiated whole teeth. The sensitivity of the extended loop resonator varies in the antenna plane, but this variation tends to vanish when the sample is moved away from this plane. When the loop antenna is placed just above the highly irradiated molar, around 88% of the dosimetric signal is due to the crown enamel. The sensitivity inside a birdcage cavity is approximately equal over the volume of a molar; only 30% of the molar's total dosimetric signal results from enamel. Some decrease in the intensity of the dosimetric signal from enamel is observed after irradiation. At room temperature, the signal is reduced by about 20% within 90 days and approaches a plateau with a time constant of about 35 days.

In vivo caries-like lesion prevention with argon laser: pilot study

OBJECTIVE

This clinical pilot study was conducted to investigate the effectiveness of argon laser irradiation to reduce demineralization or loss of tooth structure in vivo.

SUMMARY BACKGROUND DATA

In vitro research previously demonstrated the ability of argon laser irradiation to reduce demineralization or loss of tooth structure.

METHODS

Using the Ogaard model of producing demineralization, the experimental teeth were irradiated with argon laser of 250 mW (producing approximately 12 J/cm2) prior to banding. Polarized light evaluation of the sectioned, extracted teeth was used to determine the amount of demineralization.

RESULTS

Results showed a 29.1% reduction in demineralization in the experimental teeth as compared to the bilateral control teeth.

CONCLUSION

Low-power argon laser irradiation significantly reduced demineralization clinically.

Autofluorescence in human dentine in relation to age, tooth type and temperature measured by nanosecond time-resolved fluorescence microscopy

Stationary and dynamic characteristics of autofluorescence in human dentine were examined with a nanosecond time-resolved fluorescence microphotometer. With ageing, the intensity of the fluorescence increased whereas the decay time decreased. There were no differences in fluorescence intensity, decay time or spectral profile among tooth types taken from the same individuals or from individuals of the same age. Fluorescence intensity was enhanced after the application of heat (37 and 50 degrees C), but remained unchanged when specimens were kept at 4 degrees C. These results suggest that the increase in fluorescence intensity was partially due to a temperature-dependent physicochemical mechanism.

Susceptibility of Nd:YAG laser-irradiated root surfaces in replanted teeth to external inflammatory resorption

Nd:YAG laser-induced modification of the root surface may inhibit development of external inflammatory resorption in replanted teeth. This study tested this hypothesis in vivo. The pulp chambers of six mandibular premolars in each of two dogs were accessed, inoculated with plaque, and sealed (Groups 1, 2). Two additional premolars in each dog were endodontically treated without inoculation (Groups 3, 4). After 2 weeks, teeth were hemisected and extracted. Each root had a 2 x 3 mm surface area denuded of cementum on the buccal and lingual surface. In Groups 1 (n = 12 roots) and 3 (n = 4), the denuded surfaces were wiped with 15% EDTA, coated with black ink, and irradiated with Nd:YAG laser (0.75 W, 15 pps, 300 microns tip, 20 s). In Groups 2 (n = 12) and 4 (n = 4), the surfaces were wiped with 15% EDTA, and rinsed with sterile saline for 20 s. Roots were replanted within 5 min. The dogs were perfusion-euthanised 10 weeks after replantation. Block specimens were removed, decalcified, embedded and horizontally sectioned (6 microns) at 180-microns intervals, resulting in 10 to 14 cross-sections of each root. From these, the middle five consecutive sections were stained with hematoxylin and eosin, and observed by light microscopy for occurrence of surface, inflammatory and replacement resorption on the denuded surfaces. No obvious differences were noted between the laser-irradiated and non-irradiated surfaces. Inflammatory resorption was frequent in Groups 1 and 2, and absent in Groups 3 and 4. Replacement resorption was minimal in Groups 1 and 2, and frequent in Groups 3 and 4. Differences between Groups 1 and 2, and between Groups 3 and 4 were not significant, whereas the differences between the two pairs of groups were statistically significant (chi-square and two-way ANOVA, P < 0.006). These results did not support the hypothesis, and questioned the clinical validity of the surface modification in Nd:YAG laser-irradiated dentin. Therefore, the clinical application of Nd:YAG laser to the root surfaces of replanted teeth is not warranted.

Nd:YAG laser irradiation of infected root canals in combination with microbiological examinations

In this in vivo study, 30 subjects with infected root canals were treated with the neodymium: yttrium-aluminum-garnet, or Nd:YAG, laser using standard laser settings and procedures. In microbiological examinations conducted before irradiation, the authors found streptococci in 30 cases and staphylococci in 15 cases. After the first irradiation, the authors found that 19 root canals showed minimal streptococcal growth and 10 root canals showed minimal staphylococcal growth.

Long-term dental development in children after treatment for malignant disease

A radiographic dental examination was performed in 16 children conditioned with total body irradiation (TBI) and cyclophosphamide (CY) prior to bone marrow transplantation (BMT), and in 52 children treated with multiagent chemotherapy. For each child, three age- and sex-matched healthy controls were selected. Evaluation of disturbances in dental development and tooth size was based on planimetric measurements of mandibular teeth on panoramic radiographs. Short V-shaped roots were diagnosed in 94 per cent of the children treated with TBI/CY compared with 19 per cent in the chemotherapy group (P < 0.001). Children receiving TBI/CY also exhibited a pronounced reduction in tooth size compared with the controls. Reductions varied from 19 per cent in incisors to 39 per cent in the second molars. In the chemotherapy group the corresponding values were 7 and 15 per cent respectively. When comparing crown/root ratios, the indices for incisors, canines (P < 0.05) and molars (P < 0.01) in the BMT group were significantly higher than the corresponding values in the control group. This indicates that the reduction in root size was more pronounced than the reduction in crown size. The premolars in the BMT group exhibited a similar reduction in crown and root size. All developing teeth were affected by multiagent chemotherapy and radiation therapy. The most severe disturbances were found in children treated with TBI/CY at a young age.

Enamel etching by carbon dioxide laser. An in-vitro comparative evaluation

The enamel surfaces etched with carbon dioxide laser and 37% phosphoric acid were compared with regard to surface topography. The shear bond strengths of composite bonded to enamel etched by laser and acid were also compared in the study. Out of the 72 human healthy premolars selected for the study, 12 teeth were used for studying the surface topography using scanning electron microscope. The shear bond strengths were evaluated using a Hounsfield Tensometer in the remaining 60 teeth. Under scanning electron microscope, carbon dioxide laser etching of enamel produced a poor etch pattern. The shear bond strengths of composite bonded to laser etched enamel appeared inferior as compared to those on acid etched enamel. Paired t-test gave a statistically significant difference between the shear bond strengths of composite bonded to laser etched and acid etched enamel surfaces.

Surface treatment of enamel with laser--a potential alternative for acid etching--an in vitro study

An in-vitro study was carried out on 80 human premolars to study the use of Nd:YAG laser as a potential alternative for acid etching in the surface treatment of enamel prior to sealant application. The determination of bond strength using Universal Testing Machine, Model 1011 and marginal leakage using the spectrophotometric dye recovery method showed no statistically significant difference between the groups with laser and acid surface treatments. But, there was a significantly lower bond strength and increased dye penetration in the group with no surface treatment. Scanning electron microscopic study of the interface between sealant and enamel surface of the acid and laser treated specimens was also carried out.

[Pulp-dentin reactions after CO2 laser treatment of the dentin]

The use of a CO2 laser in the treatment of dentinal caries in vital teeth seemed to be an important therapeutical progress compared to traditional means of carious tissue removal with rotary mechanical instruments. Forty sound premolars from patients with a mean age of twelve years were prepared according to a standard method for biological controls and submitted to the action of a CO2 laser of 3 Watts, equipped with a convergent lens of a 38 mm focal distance. The pulpal reactions were observed on day 15, 30, 50 and 80. No clinical post-operative symptomatology was observed in all treated teeth. The pulpal reactions related to the thickness of residual dentine consisted in the presence of reversible inflammatory changes, in the absence of degenerative processes and in an important production of tertiary dentine. The structural modifications occurring on the dentinal walls in these experimental conditions seemed not to induce a barrier totally tight to bacterial penetration.