Cárie de radiação: efeitos da radioterapia na estrutura dentária / Caries de radiación: efectos de la radiación en la estructura dental / Radiation caries: effects of radiotherapy on dental structure

Introdução: Pacientes submetidos à radioterapia para tratamento de neoplasias malignas na região de cabeça e pescoço são propensos a desenvolver complicações orais como a cárie de radiação, que evolui rapidamente e é altamente destrutiva.É reconhecido que o seu desenvolvimento está associado a alterações pós-radioterápicas nas glândulas salivares maiores, o que resulta em hipossalivação e alteração nos constituintes salivares. No entanto, tem sido aceito que danos diretos causados pela radiação à estrutura dentária podem acelerar a progressão da cárie e estudos têm demonstrado alterações morfológicas e físicas em dentes humanos após radioterapia. Objetivo: Propõe-se apresentar um caso de cárie de radiação e os efeitos diretos da radioterapia na estrutura dentária. Relato de caso: Paciente masculino, 60 anos de idade, com queixa principal de fragilidade dentária; relatou história de carcinoma epidermóide em língua há 18 meses e que o protocolo de tratamento aplicado foi quimioterapia (38 sessões), radioterapia (38 sessões) e cirurgia. Ao exame físico, dentre as alterações observadas, destacou-se a presença de regiões cervicais dentárias enegrecidas com coroas bastante fragilizadas em todos os dentes remanescentes, características de cárie de radiação. Foi realizado um tratamento atraumático, que está em acompanhamento. Conclusões: A cárie de radiação tem como principal fator etiológico alterações salivares qualitativas e quantitativas. A discussão sobre os efeitos diretos da radioterapia sobre a estrutura dentária ainda é bastante polêmica na literatura odontológica. Desta forma, sugere-se que mais estudos sejam realizados de forma sistemática, de maneira mais completa e padronizada(AU)

Introducción: Los pacientes sometidos a radioterapia para el tratamiento de tumores malignos en la cabeza y el cuello son propensos a desarrollar complicaciones bucales, tales como caries de radiación que evoluciona rápidamente y es altamente destructiva. Se reconoce que el desarrollo se asocia con cambios posradioterapia en las glándulas salivales, que resulta en hiposalivación y el cambio en los componentes salivales. Sin embargo, se ha aceptado que los daños por radiación directa a la estructura dental puede acelerar la progresión de la caries y los estudios han demostrado cambios morfológicos y físicos en los dientes humanos después de la radioterapia. Objetivo: presentar un caso de caries de radiación y los efectos directos de la radiación en la estructura dental. Presentación del caso: Paciente masculino de 60 años de edad, se quejaba de fragilidad dental, con historia notificada de carcinoma de células escamosas en la lengua hace 18 meses y con protocolo de tratamiento aplicado de quimioterapia (38 sesiones), terapia de radiación (38 sesiones) y cirugía. En el examen físico, de los cambios observados, se destacó la presencia de regiones cervicales dentarias negruzcas con coronas bastante frágiles en todos los dientes restantes, características de caries de radiación. El tratamiento atraumático se realizó y el paciente está bajo observación. Conclusiones: los cambios cuantitativos y cualitativos salivales actúa como el factor causal principal de la caries por radiación. La discusión acerca de los efectos directos de la radiación sobre la estructura del diente es todavía muy controvertido en la literatura dental. Por lo tanto, se sugiere que se realicen estudios adicionales de manera sistemática, más completa y estandarizada(AU)

Introduction: Patients undergoing radiotherapy as treatment for malignant head and neck tumors are prone to develop oral complications such as radiation caries, which evolves rapidly and is highly destructive. Such development is known to be caused by post-radiotherapy alterations in salivary glands resulting in hyposalivation and changes in salivary components. However, it has been accepted that damage by direct radiation to the dental structure may hasten the progress of caries development, and studies have shown the morphological and physical changes occurring in human teeth after radiotherapy. Objective: Present a case of radiation caries and the direct effects of radiation on dental structure. Case presentation: A 60-year-old male patient complains of dental fragility. The patient was diagnosed with squamous-cell carcinoma of the tongue 18 months ago and indicated chemotherapy (38 sessions), radiotherapy (38 sessions) and surgery. Physical examination revealed among other changes the presence of blackish cervical areas with quite fragile crowns in all remaining teeth, which are characteristic of radiation caries. Non-traumatic treatment was performed and the patient is now under observation. Conclusions: Salivary quantitative and qualitative changes are the main cause of radiation caries. Discussion about the direct effects of radiation on dental structure is still quite controversial in the literature on the topic. It is therefore suggested to conduct further studies in a more systematic, complete and standardized manner(AU)

Effect of carbon dioxide laser irradiation on enamel surface microhardness around orthodontic brackets.

INTRODUCTION: In this study, we aimed to determine the effect of carbon dioxide laser irradiation on enamel surface microhardness. METHODS: In this single-blind interventional clinical trial, 16 patients needing at least 2 premolars extracted for orthodontic purposes participated. In each subject, 1 premolar was treated with the carbon dioxide laser (beam diameter, 0.2 mm; power, 0.7 W); the other was exposed to a visible guiding light as the control. A t-loop was ligated to the bonded brackets to increase caries risk. After at least 2 months, the teeth were extracted, and the surface microhardness was measured. Scanning electron microscope evaluation was performed on 1 sample from each group. Normal distribution of the data was assessed by the Kolmogorov-Smirnov and Shapiro-Wilks tests. Mean microhardness values of the 2 groups were compared using paired t tests. RESULTS: The data had normal distributions. Means and standard deviations of the microhardness in the laser-treated and control groups were 301.81 ± 94.29 and 183.9 ± 72.08 Vickers hardness numbers, respectively; this was different significantly (P <0.001). Scanning electron microscopy showed the enamel surface melting in the laser-treated specimens. CONCLUSIONS: Carbon dioxide laser treatment results in higher enamel surface microhardness around orthodontic brackets. Patients at high risk of caries might benefit from this intervention. Exact control of the laser irradiation parameters is recommended.

Fluoride plus CO2 laser against the progression of caries in root dentin.

PURPOSE: To evaluate the effect of a 1.23% acidulated phosphate fluoride (APF) gel combined with CO2 laser in protecting carious root dentin against further cariogenic challenges. METHODS: After a 7-day lead-in period, 12 volunteers wore an intraoral palatal device containing four carious root dentin slabs, treated with APF and APF+CO2 or placebo and placebo+CO2. After a 14-day wash-out period, volunteers were crossed-over to the other treatment arm. During both intraoral phases, specimens were submitted to cariogenic challenges and then evaluated for cross-sectional Knoop microhardness. RESULTS: Two-way ANOVA demonstrated that there was significant effect for both main factors: CO2 laser irradiation (P < 0.0001) and gel treatment (P < 0.0001), and that there was no interaction between them (P = 0.4706). Protection of carious root dentin against further cariogenic challenges may be provided by APF fluoride gel and CO2 laser, but no additive benefit was found by combining such strategies.

CO2 Laser (10.6 microm) parameters for caries prevention in dental enamel.

Although CO(2) laser irradiation can decrease enamel demineralisation, it has still not been clarified which laser wavelength and which irradiation conditions represent the optimum parameters for application as preventive treatment. The aim of the present explorative study was to find low-fluence CO(2) laser (lambda = 10.6 microm) parameters resulting in a maximum caries-preventive effect with the least thermal damage. Different laser parameters were systematically evaluated in 3 steps. In the first experiment, 5 fluences of 0.1, 0.3, 0.4, 0.5 and 0.6 J/cm(2), combined with high repetition rates and 10 micros pulse duration, were chosen for the experiments. In a second experiment, the influence of different pulse durations (5, 10, 20, 30 and 50 micros) on the demineralisation of dental enamel was assessed. Finally, 3 different irradiation times (2, 5 and 9 s) were tested in a third experiment. In total, 276 bovine enamel blocks were used for the experiments. An 8-day pH-cycling regime was performed after the laser treatment. Demineralisation was assessed by lesion depth measurements with a polarised light microscope, and morphological changes were assessed with a scanning electron microscope. Irradiation with 0.3 J/cm(2), 5 micros, 226 Hz for 9 s (2,036 overlapping pulses) increased caries resistance by up to 81% compared to the control and was even significantly better than fluoride application (25%, p < 0.0001). Scanning electron microscopy examination did not reveal any obvious damage caused by the laser irradiation.

Influence of cavity preparation with Er:YAG Laser on enamel adjacent to restorations submitted to cariogenic challenge in situ: a polarized light microscopic analysis.

BACKGROUND AND OBJECTIVES: Er:YAG laser has been used for caries removal and cavity preparation, using ablative parameters. Its effect on the margins of restorations submitted to cariogenic challenge has not yet been sufficiently investigated. The aim of this study was to assess the enamel adjacent to restored Er:YAG laser-prepared cavities submitted to cariogenic challenge in situ, under polarized light microscopy. STUDY DESIGN/MATERIALS AND METHODS: Ninety-one enamel slabs were randomly assigned to seven groups (n = 13): I, II, III-Er:YAG laser with 250 mJ, 62.5 J/cm2, combined with 2, 3, and 4 Hz, respectively; IV, V, VI-Er:YAG laser with 350 mJ, 87.5 J/cm(2), combined with 2, 3, and 4 Hz, respectively; VII-High-speed handpiece (control). Cavities were restored and the restorations were polished. The slabs were fixed to intra-oral appliances, worn by 13 volunteers for 14 days. Sucrose solution was applied to each slab six times per day. Samples were removed, cleaned, sectioned and ground to polarized light microscopic analysis. Demineralized area and inhibition zone width were quantitatively assessed. Presence or absence of cracks was also analyzed. Scores for demineralization and inhibition zone were determined. RESULTS: No difference was found among the groups with regard to demineralized area, inhibition zone width, presence or absence of cracks, and demineralization score. Inhibition zone score showed difference among the groups. There was a correlation between the quantitative measures and the scores. CONCLUSION: Er:YAG laser was similar to high-speed handpiece, with regard to alterations in enamel adjacent to restorations submitted to cariogenic challenge in situ. The inhibition zone score might suggest less demineralization at the restoration margin of the irradiated substrates. Correlation between the quantitative measures and scores indicates that score was, in this case, a suitable complementary method for assessment of caries lesion around restorations, under polarized light microscopy.

Influence of Er:YAG laser on microhardness of enamel adjacent to restorations submitted to cariogenic challenge in situ.

OBJECTIVE: This study assessed the effect of the Er:YAG laser on enamel adjacent to restorations submitted to cariogenic challenge in situ, by microhardness analysis. BACKGROUND DATA: The influence of Er:YAG laser energy on secondary caries formation has been investigated in vitro. However, no research involving demineralization around cavities prepared with the Er:YAG laser under intra-oral conditions has yet been described. MATERIALS AND METHODS: Slabs of enamel were randomly assigned to seven groups (n = 12), according to the cavity preparation technique: groups I, II, and III--Er:YAG laser, 250 mJ, at 2, 3, and 4 Hz, respectively; groups IV, V, and VI--350 mJ, at 2, 3, and 4 Hz, respectively; group VII--high-speed handpiece (control). Cavities were restored and the specimens were fixed in intra-oral appliances and worn by 12 volunteers for 14 d. Sucrose solution was applied to each slab 6 times/d. Samples were removed, sectioned, and examined for microhardness at 100, 200, and 300 microm (factor distance), and 30, 60, and 90 microm (factor depth), from the restoration and enamel surface, respectively. RESULTS: Analysis of variance according to a split-plot model showed no difference among the cavity preparation techniques, among distances, or among depths, as well as no difference in the interaction between the factors of cavity preparation and distance. A significant difference was found in the interaction of cavity preparation and depth (p < 0.0001), as identified by contrast technique. CONCLUSION: The results revealed that the Er:YAG laser did not differ from conventional cavity preparation with regard to enamel microhardness.

In vitro evaluation of enamel demineralization after Er:YAG and Nd:YAG laser irradiation on primary teeth.

OBJECTIVE: This in vitro study evaluated the influence of both Er:YAG and Nd:YAG laser irradiation on deciduous enamel demineralization. BACKGROUND DATA: Although there are still few studies on the use of the high-intensity laser for caries prevention in deciduous teeth, it is believed that its use on the dental structure can lead to a more acid-resistant surface. METHODS: Forty enamel samples obtained from 22 deciduous first molar teeth were ground and randomly divided into four groups (n = 10): group 1 (G1), no treatment (negative control); G2, fluoride (positive control); G3, Er:YAG laser (2 Hz, 60 mJ, 40.3 J/cm(2)); G4, Nd:YAG laser (80 mJ, 10 Hz, 0.8 W). After the surface treatment, the samples were submitted to an acid challenge that consisted of a 5-day immersion in demineralizing (3 h) and remineralizing solution (21 h). Next, a microhardness test was preformed. RESULTS: Analysis of variance (ANOVA) and Student Newman Keuls tests were performed (alpha = 5%). The percentage of lesion inhibition for each group was as follows: G2, 59.4%; G3, 35.7%; and G4, 40.4%. As regards the percentage loss of mineral volume, there was no statistical difference between groups G2 (444.37 +/- 146.42) and G3 (441.81 +/- 207.08) when compared with group G1 (281.03 +/- 134.57). All experimental groups presented a lower mineral loss compared with the non-irradiated samples (G4). CONCLUSION: The findings of the present study revealed that both Nd:YAG and Er:YAG lasers can be an alternative tool for enhancing deciduous enamel acid resistance.

Dissolution studies of bovine dental enamel surfaces modified by high-speed scanning ablation with a lambda = 9.3-microm TEA CO(2) laser.

BACKGROUND AND OBJECTIVES: Previous studies have demonstrated that lasers can be used to modify the chemical composition of dental enamel to render the mineral phase more resistant to acid dissolution with minimal peripheral thermal damage. Transverse excited atmospheric (TEA) CO(2) lasers tuned to the strong mineral absorption of hydroxyapatite (HAP) near lambda = 9 microm are well-suited for the efficient ablation of dental hard tissues if the laser-pulse is stretched to greater than 5-10 microseconds to avoid plasma shielding phenomena. Moreover, TEA CO(2) lasers can be operated at very high repetition rates and are inherently less expensive and more versatile than Er:YAG and Er:YSGG solid-state lasers. In this study a lambda = 9.3-microm TEA CO(2) with a pulse duration of 8 microseconds and a repetition rate of 300 Hz was used to uniformly treat bovine enamel surfaces at ablative irradiation intensities. We hypothesized that a uniform surface layer of modified enamel of improved crystallinity and CaP phase composition would be formed with an enhanced resistance to acid-dissolution in the ablated areas at higher scanning rates used with the water spray. Such a modified layer of enamel formed at the base and walls of a cavity preparation under the irradiation conditions employed in this study have the potential to inhibit secondary caries under sealants and restorations. STUDY DESIGN/MATERIALS AND METHODS: The surfaces of bovine enamel blocks (3 x 3 mm(2)) were rapidly scanned across the laser beam at rates of 2, 3, and 6 mm/second with and without a water-spray at an incident fluence of 30 J/cm(2). The resistance to acid dissolution was evaluated using controlled surface dissolution experiments on laser-irradiated and control samples. RESULTS: The groups irradiated at a fluence of 30 J/cm(2) with a repetition rate of 300 Hz and a high scan rate of 6 mm/second with and without water-cooling significantly reduced the overall surface dissolution rates (P < 0.001). At low scan rates (2-3 mm/second) excessive heat deposition resulted in the formation of an outer layer of asperities containing non-apatitic CaP phases that were more susceptible to acid-dissolution. At a scanning rate of 6 mm/second even without the water spray a layer of purer phase HAP was formed without thermal damage, indicating that a high scanning rate can be used to avoid excessive thermal damage during ablation. The best results (80% inhibition) were attained for the higher scanning speed 6-mm/second combined with a water spray. CONCLUSION: This study demonstrates that an enamel surface with enhanced resistance to acid dissolution is produced after ablation with lambda = 9.3-microm TEA CO(2) laser pulses delivered at high-repetition rates if sufficiently high scanning rates are used with or without a water-spray.

In vitro caries formation in primary tooth enamel: role of argon laser irradiation and remineralizing solution treatment.

BACKGROUND: The authors evaluated the effects of argon laser (AL) diation and remineralizing solution (RS) treatment alone and in combination on carieslike lesion formation in primary tooth enamel in an in vitro study. MATERIALS AND METHODS: The authors divided 10 caries free primary tooth enamel surfaces into four segments and assigned them to one of four treatment groups: no treatment control, AL irradiation alone at 13.5 joules per square centimeters (0.270 watts, 5-millimeter beam, 10 seconds), RS treatment alone for two minutes and AL irradiation before RS treatment. The authors created in vitro caries using a modified ten Cate solution. They evaluated longitudinal sections (three per tooth segment, 30 per treatment group) for mean lesion depth. RESULTS: After lesion formation, mean lesion depths (+/- standard deviation) were 179 +/- 16 micrometers for the no treatment controls, 137 +/- 19 microm for AL irradiation alone, 87 +/- 9 microm for RS treatment alone and 68 +/- 12 microm for AL irradiation before RS treatment. All treatment groups had mean lesion depths that were significantly less than those for the matched no-treatment control group (analysis of variance [ANOVA], Duncan multiple range [DMR] test, P < .05). AL irradiation before RS treatment significantly reduced lesion depth compared with AL irradiation alone or RS treatment alone (ANOVA, DMR test, P < .05). CONCLUSIONS: The maximum reduction in lesion depth in primary tooth enamel was achieved when the RS--which contained calcium, phosphate and fluoride in a carbopol base--was combined with AL irradiation. CLINICAL IMPLICATIONS: It would appear that to improve clinical caries resistance to enamel dissolution, AL irradiation before RS treatment could be used.

Effect of diode laser and fluoride varnish on initial surface demineralization of primary dentition enamel: an in vitro study.

INTRODUCTION: Previous investigations have demonstrated improved enamel caries resistance after laser irradiation. The purpose of this in vitro study was to assess the caries-preventive potential of 809 nm diode laser treatment of the enamel of primary teeth compared to topical fluoride application. METHODS: Eighty samples of sound primary teeth were embedded in plastic and stored in saline solution. The enamel surface of 80 samples was polished in an area of 2 x 2 mm. These tooth specimens were randomly assigned to one control and three test groups: (1) no treatment/control; (2) application of 0.1 mg of fluoride varnish (Duraphat) for 6 h; (3) diode laser application (809 nm, 140 mJ, 50 Hz, Ø 600 micro m fibre, contact mode, absorber, 1 min; ORA-LASER01 I.S.T.); and (4) combined application - laser/fluoride varnish. Caries-like lesions were created by pH-cycling. After lesion formation, longitudinal sections were taken and examined by polarized light microscopy. RESULTS: In the control group, all samples showed lesions up to 30 micro m in depth. After laser application, lesions could be identified in 15 out of 20 samples. Topical fluoride treatment in groups 2 (varnish) and 4 (laser/varnish) completely inhibited the development of caries-like lesions in all samples. CONCLUSION: In this in vitro investigation, topical fluoride treatment enhances the resistance of sound enamel of primary teeth more effectively than diode laser application.

In vitro enamel caries formation: argon laser, light-emitting diode and APF treatment effect.

PURPOSE: To evaluate argon laser irradiation (AL), light-emitting diode exposure (LED), and acidulated phosphate fluoride treatment (APF) in vitro effects on caries-like enamel caries formation. METHODS: Sound teeth (n = 18) were divided into four tooth quarters and coated with an acid-resistant varnish, leaving an enamel window exposed per tooth quarter. The tooth quarters were assigned to: (1) no treatment (control, mesiobuccal); (2) 1.23% APF (4 minutes, distolingual); (3) LED (Ultradent Ultra-Lume LED2 20 seconds, mesiolingual); and (4) AL (HGM Model 8, 11.5 J/cm2, 231 mW, 5mm beam size, 10 seconds, distobuccal). Following caries-like lesion formation (modified ten Cate solution), longitudinal sections (three per tooth quarter, 54 lesions per group) were obtained and evaluated for mean lesion depths (water imbibition, polarized light microscopy, ANOVA, DMR). RESULTS: Mean lesion depths were: 198 +/- 21 microm for controls; 186 +/- 17 microm for LED; 117 +/- 19 microm for AL; and 104 +/- 23 microm for APF. Lesion depths were statistically significantly decreased for AL (41%) and APF (47%) groups (P < 0.05), compared with controls. A slight lesion depth reduction for LED (6%) was present compared with controls; however this was not statistically significantly different (P > 0.05).

Effect of Er:YAG laser on CaF2 formation and its anti-cariogenic action on human enamel: an in vitro study.

OBJECTIVE: The objective of this study was to evaluate the effect of Er:YAG laser on the formation of CaF(2), after the application of acidulated phosphate fluoride (APF), and its influence on the anti-cariogenic action in human dental enamel. BACKGROUND DATA: Er:YAG laser was designed to promote ablation of the enamel. However, the possibility of using this energy to increase the enamel's resistance to caries has hardly been explored, and neither has its interaction with the use of fluorides. MATERIALS AND METHODS: One hundred and twenty blocks of enamel were allocated to four groups of 30 blocks each: (1) C, control group; (2) Er:YAG, laser; (3) APF; and (4) Er:YAG+APF. Of these, 80 blocks were submitted to pH cycling for 14 days. In the other 40 blocks, fluoride (CaF(2)) was measured before cycling. After pH cycling, surface microhardness (SMH), microhardness in cross-section (converted to mineral contents % vol. min.), and fluoride after cycling (40 blocks) were also determined. RESULTS: SMH decreased in all groups. The control group showed the highest decrease, and Er:YAG+APF showed the lowest decrease (p < 0.05). Groups APF and Er:YAG showed the same results (p > 0.05). Mineral content at depths 10, 20, and 40 microm was lower in the control and Er:YAG groups, and higher in groups APF and Er:YAG+APF. CaF(2) (microgF/cm(2)) deposited before pH cycling was higher in the APF group when compared to the Er:YAG+APF group. Control and Er:YAG groups showed the lowest values (p > 0.05). CONCLUSION: It was concluded that Er:YAG laser influenced the deposition of CaF(2) on the enamel and showed a superficial anti-cariogenic action, but not in depth.

Enamel caries initiation and progression after argon laser irradiation: in vitro argon laser systems comparison.

OBJECTIVE: The purpose of this in vitro laboratory study was to determine the effect of low-fluence argon laser (AL) irradiation delivered from two different argon laser systems on enamel caries-like lesion initiation and progression. BACKGROUND DATA: Previous in vitro investigations and a recent in vivo pilot study have shown that AL irradiation of enamel provided a protective effect against in vitro and in vivo cariogenic challenges. MATERIALS AND METHODS: Twenty extracted human molars were selected, and 10 teeth were assigned to the HGM argon laser group and 10 were assigned to the LaserMed argon laser group. The exposed buccal windows of sound enamel were exposed to low-fluence irradiation, while the lingual windows of enamel were not exposed to laser irradiation and served as the no-treatment (control) group. Enamel caries-like lesions were created using an acidified gel. Two longitudinal sections were taken per sample (n = 20 lesions per group) and evaluated by polarized light microscopy for body of the lesion depths after lesion initiation (8 weeks) and progression (12 weeks) periods. RESULTS: After lesion initiation and progression, the body of lesion depths were similar for both argon-irradiated groups (p > 0.05). With the no-treatment (control) group, there were significant increases in lesion depth with a 61-78% increase for the lesion initiation period and a 50-69% increase for the lesion progression period when compared with the argon laser-treated groups. CONCLUSION: Argon laser irradiation provides a certain degree of protection against in vitro enamel caries initiation and progression. Resistance to a continuous caries challenge was similar with either argon laser delivery systems (HGM and LaserMed). Argon laser irradiation may prove to be beneficial in reducing the caries susceptibility of sound enamel and white spot lesions in the clinical environment.

Sparing of contralateral major salivary glands has a significant effect on oral health in patients treated with radical radiotherapy of head and neck tumors.

BACKGROUND: Has a conscious exclusion of the contralateral major salivary glands (parotid, submandibular, and sublingual glands) a significant impact on the milieu of the oral cavity (saliva flow, pH, buffer capacity, and colonisation with Streptococcus mutans) in patients with ENT tumors receiving radical radiotherapy? PATIENTS AND METHODS: 20 consecutive consenting patients with ENT tumors were evaluated once before, weekly during, and 6 weeks after the end of treatment in regard to saliva flow, ph, buffer capacity, and colonisation with Streptococcus mutans. In 13 patients the major salivary glands on both sides were included in the treated volume, in seven patients the treatment portals excluded consciously the contralateral major salivary glands. RESULTS: The stimulated saliva flow decreases already during the 1st week of radiotherapy, the decrease follows the dose exponentially; the saliva flow is further reduced in the weeks after the end of treatment. The effect is less pronounced in patients with sparing of contralateral major salivary glands. The majority of patients with unilateral sparing of the major salivary glands retain the baseline value of buffer capacity, whereas buffer capacity of all patients with inclusion of all major salivary glands is markedly reduced with 20 Gy already, without signs of recovery when treatment has stopped. With unilateral salivary gland sparing the pH always remains basic, in bilaterally irradiated patients the pH changes from a mean of 7.3 to 5.8 during treatment. The colonisation with Streptococcus mutans varies little in both groups during the radiotherapy; after the end of therapy, it is higher in bilaterally irradiated patients. CONCLUSIONS: The conscious arrangement of irradiation portals in order to spare contralateral major salivary glands in patients with radical radiotherapy of ENT tumors has a significant influence on the oral environment: the stimulated saliva flow is higher, the buffer capacity retains the baseline value, the saliva pH remains basic, and the colonisation with Streptococcus mutans is reduced.

Microradiographic and microscopic studies on in situ induced initial caries in irradiated and nonirradiated dental enamel.

The objective of this study was to evaluate the onset of initial demineralization in irradiated and nonirradiated human enamel. Enamel specimens were prepared from the lingual and buccal surfaces of 48 freshly extracted, caries-free third molars. Either the lingual or the buccal enamel specimen of each tooth was irradiated with 60 Gy. The remaining enamel sample was not irradiated. Two irradiated and two nonirradiated enamel specimens were inserted into both buccal aspects of each 12 intraoral mandibular appliances. The appliances were worn by 12 persons for 6 weeks throughout day and night. One side was brushed daily with a fluoride-free toothpaste. On the other side plaque was allowed to grow. Individual oral hygiene techniques were performed without any fluorides. During meals, the appliance was stored in 10% sucrose solution. The enamel specimens were cut perpendicular to the enamel surface. Subsequently, the slabs were ground to a thickness of 90 microm, and studied by means of TMR and microscopic techniques. Evaluated data did not show any differences between irradiated and nonirradiated enamel lesions (ANOVA). The onset of caries in irradiated enamel can be hampered by regularly performed oral hygiene techniques.

Correlation of transversal microradiography and microhardness on in situ-induced demineralization in irradiated and nonirradiated human dental enamel.

The objective was to evaluate whether a correlation exists between microhardness (MH) and transversal microradiographical (TMR) data for in situ-induced caries lesions in irradiated and nonirradiated human enamel. Enamel specimens were prepared from the lingual and buccal surfaces of 20 freshly extracted, caries-free third molars. The surfaces were polished (4000 grit). Either the lingual or the buccal specimen of each tooth was irradiated with 60 Gy; the other sample was not irradiated. Two irradiated and two nonirradiated specimens were inserted into both buccal aspects of each of five intraoral mandibular appliances. The appliances were worn by five persons for 6 weeks day and night. One side was brushed daily with a fluoride-free toothpaste; on the other side, dental plaque was allowed to grow. Individual oral hygiene was performed without any fluorides. During meals, the appliance was stored in 10% sucrose solution. Then the enamel specimens were cut perpendicular to their oral surface. The cut surface was polished (4000 grit) and the Knoop hardness number (KHN) was measured across the lesions, at 25, 50 and 75 microm from the oral surface. After MH testing the samples were polished again, thereby reducing the surface by about 10 microm. Subsequently, the slabs were ground to a thickness of 90 microm, and studied by means of TMR. Mineral loss was calculated with dedicated software at the locations corresponding to the MH testing. A total of 120 paired data was submitted to linear-regression analysis. Neither MH nor TMR showed significant differences between irradiated and nonirradiated enamel lesions. A linear relation was found between square root of KHN and the mineral volume percent. In naturally induced caries lesions, MH values can be converted to mineral volume percent using the equation [21.19 + 3.66 x square root of KHN]. This equation fits the data with a reliable correlation coefficient (r2=0.915).

Effect of resin/fluoride and holmium:YAG laser irradiation on the resistance to the formation of caries-like lesions.

PURPOSE: This study compared the effects of a combination of a topical application of resin/NaF mixture and holmium-doped yttrium aluminum garnet (HO:YAG) laser energy with untreated control sites for their resistance to acid destruction/mechanical challenges of root surfaces adjacent to restorative margins. MATERIALS AND METHODS: Forty-eight extracted human teeth were prepared for restorations with coronal margins in enamel and the apical margins on root surfaces. Four types of restorative materials were used. One half of the restorative/root surface margins were treated with an application of nonfilled resin/fluoride mixture and holmium-doped yttrium aluminum garnet laser irradiation; the remaining portion served as the untreated control for each tooth. Acid (10% formic) and mechanical (air sandblaster) challenges were used to test the effects of these treated sites to their controls and to other types of restorative/root surface margins. The depth of root surface loss within 0 to 2 mm apical from the restorative margins was measured and evaluated after 24, 48, and 72 hours of acid exposures. RESULTS: The measurements of tooth loss for the 24- and 48-hour acid-exposure cycles were subjected to statistical analysis (ANOVA) using a paired t test for the variables. The variables, depth of tooth surface loss for the control sites was compared with the depth of loss of the treated sites on opposing sides of each tooth. The depth of tooth surface loss for the control sites had an average mean of 0.35 (0.25) mm for the 24-hour acid exposures, with the opposing treated sides having a mean of 0.053 (0.05) mm (significant at the 0.05 level). The 48-hour acid-exposure results showed significant increased tooth loss for the control sites, but minimum additional loss on the treated sites. The control sites showed an average mean of 1.16 (0.24) mm and a mean of 0.095 (0.103) mm for the treated areas, significant at the 0.05 level. No measurements were made for the 72-hour cycle groups of composite and amalgam alloy restorations because of the loss of most of the filling materials in the control sites. The control groups of crowns showed an average mean loss of 2.06 (0.37) mm with only 0.20 (0.19) mm surface loss for the treated sites. The paired t test for variables indicated no significant differences of tooth surface loss between various types of restorative margins used in this study. CONCLUSIONS: HO:YAG laser energy irradiation after application of resin/NaF to restorative margins and adjacent areas showed a significant increased resistance to acid/mechanical destruction on cementum-dentin root surfaces. The integrity of the restorative/dentin margins were maintained after extended exposures to formic acid and mechanical challenges.

The patients with cariogenic high-risk after the cervico-facial radiotherapy and their management.

Studying through clinical and laboratory means the bucco-dental status of the 28 patients who followed radiotherapeutical cures in the cervico-facial territory, the authors establish the apparition, at different periods of time, of the rampant caries. The rampant caries have been found in 46.42 percent of the cases, especially in patients exposed to prolonged or repeated cures of cervico-facial radiotherapy (88.88 percent) and concern the cervical zones, incisal edges and cusps, zones that are usually resistant at caries. The appearance and the severity of these types of caries are correlated with: a) the degree of reduction of the repose and stimulated salivary flow; b) the maintaining time of the low salivary flow that is dependent on the received X-ray dose and the number of cures; c) the association with sweet-drinks intake; d) the manner of effectuation of the bucco-dental hygiene; e) the setting-up or not of the some prevention measures. There are presented some preventive measures that must be set-up in this category of patients and treatment-protocols, that can be applied in the clinical situations of appearance of rampant caries after the irradiant treatment of the head and neck. The authors recommend the compulsory use of the prophylactic treatment and suggest a suitable plan of treatment that includes the reduction of microbial flora, the change of the alimentary diet, and salivary stimulates and substitutes. These measures can avoid the apparition of rampant caries, which will require ample restoration. The conclusions emphasize the fact that exists real possibilities of protection and treatment for these types of caries, depending on the clinical status of patient and the disease prognosis, when exists a tight collaboration between the radiotherapist, patients, and dentist.

[Caries prevention in radiotherapy of the head-neck area]. / Kariesprophylaxe bei Strahlentherapie im Kopf-Hals-Bereich.

Following radiotherapy of malignant head and neck tumours, tooth damage is observed in many cases, which is frequently referred to as "radiation caries". This is not the immediate result of radiation, but has a number of causes. The damage to the salivary glands caused by radiation leads to xerostomia, which affects the self-cleaning capacity in the mouth. As a result of the very painful mucositis which occurs during the course of radiotherapy as well as the restricted mastication caused by the operation, patients prefer a soft diet, which in turn promotes plaque formation. The acidogenic coating causes erosion of the enamel. If preventive measures are not taken, all of the teeth can be completely destroyed within a short time. All efforts should be made to prevent this from happening, particularly in young patients who have undergone curative radiotherapy. This should include intensive fluoride treatment and meticulous oral hygiene.