Potentially carcinogenic effects of hydrogen peroxide for tooth bleaching on the oral mucosa: A systematic review and meta-analysis.

STATEMENT OF PROBLEM: Little is known about the extent to which hydrogen peroxide as used for tooth bleaching could be carcinogenic to the oral mucosa. PURPOSE: The purpose of this systematic review and meta-analysis was to evaluate whether hydrogen peroxide as used for tooth bleaching has carcinogenic effects on the oral mucosa. MATERIAL AND METHODS: PubMed, Web of Science, Scopus, and Embase electronic databases were searched. Studies evaluating different outcomes potentially related to the carcinogenic effects of hydrogen peroxide for tooth bleaching on the oral mucosa were included. Risk of bias was assessed by the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE), Risk Of Bias in Non-randomized Studies of Interventions (ROBINS-I), or Risk of Bias 2 (RoB 2) tools. The strength of the evidence was assessed by using the Grading of Recommendation, Assessment, Development, and Evaluation (GRADE) protocol. The quantitative analysis was performed with means, standard deviations, and 95% confidence intervals (CIs). Heterogeneity was analyzed by using I-squared statistics. RESULTS: Thirteen articles comprising 5 animal and 8 clinical studies met the inclusion criteria. Three of the 5 animal studies associated the bleaching agents with a carcinogen and demonstrated an enhancement of the carcinogenic effect, but probably with the bleaching agent acting only as a promoter. Five clinical studies concluded that the bleaching agents did not cause mutagenic stress on the oral mucosa by using the micronucleus test. The meta-analysis demonstrated that the frequency of micronuclei did not differ significantly between baseline and 30 days after bleaching (mean difference: 0.48; 95% CI, -1.49, 2.46; P=.63). CONCLUSIONS: This systematic review indicated that hydrogen peroxide does not appear to have carcinogenic effects on the oral mucosa.

Adaptation and penetration of resin-based root canal sealers in root canals irradiated with high-intensity lasers.

This research analyzed the quality of resin-based sealer adaptation after intracanal laser irradiation. Extracted teeth (n = 168) were root canal treated and divided into four groups, according to dentin surface treatment: no laser; Nd:YAG laser (1.5 W, 100 mJ, 15 Hz); diode laser (2.5 W in CW), and Er:YAG laser (1 W, 100 mJ, 10 Hz). The teeth were divided into four subgroups according to the sealer used: AH Plus, EndoREZ, Epiphany, and EpiphanySE. For testing the sealing after root canal obturation, the penetration of silver nitrate solution was measured, whereas to evaluate the adaptation and penetration of the sealer into the dentin, environmental scanning electron microscopy (ESEM) was used. The ESEM images were analyzed using a four-grade criteria score by three evaluators. The inter-examiner agreement was confirmed by Kappa test and the scores statistically compared by the Kruskal-Wallis' test (p < 0.05). Both adaptation and sealer penetration in root canals were not affected by the laser irradiation. Nd:YAG and diode laser decreased the tracer penetration for AH Plus, whereas EndoREZ and EpiphanySE performances were affected by Nd:YAG irradiation (p < 0.05). It can be concluded that intracanal laser irradiation can be used as an adjunct in endodontic treatment; however, the use of hydrophilic resin sealers should be avoided when root canals were irradiated with Nd:YAG laser.

Comparison of the effectiveness of 3 irrigation devices for the cleaning of root canal walls instrumented with oscillatory and rotary techniques.

In this study, scanning electron microscopy (SEM) was used to evaluate the smear layer removal of 3 irrigation devices. The study hypothesis was that more contemporary side-vented needles and brush-covered needles are more efficient for smear layer removal of root canals than traditional needles. The aim of this study was to compare the effectiveness of these irrigation devices in the cleansing of root canals instrumented with oscillatory and rotary systems. Sixty single-rooted teeth were divided according to instrumentation and irrigation techniques into 6 groups. The teeth were prepared for SEM analysis to evaluate the cleansing of cervical, middle, and apical thirds. For all groups, the cleansing of the cervical and middle thirds was better than that of the apical third (P < 0.05). Regardless of the instrumentation technique, no statistically significant differences were found between the groups regarding the cleansing of root canal walls (P > 0.05).

CT study of the performance of reciprocating and oscillatory motions in flattened root canal areas

Root canal preparation is an important step in endodontic treatment. The anatomical complexity of the middle third of the root compromises the effective cleaning of this area. Thus, advances have been made in instrumentation techniques and instruments for this purpose. The aim of this study was to evaluate the effects of three different instrumentation systems on the enlargement of the middle thirds of root canals in mandibular incisors. The preparation methods used were the reciprocating systems Reciproc (Group I) and WaveOne (Group II) and the oscillatory system Tilos (Group III). Comparisons were made by three-dimensional image reconstruction with cone-beam computed tomography before and after instrumentation. Changes in area, perimeter, centering ability, and pattern of preparation were analyzed. The results were subjected to ANOVA complemented by the Tukey’s test. Changes in area, perimeter, and tendency of transportation showed similar results among groups. The transportation index of the Tilos system was significantly lower than that of the other groups. Qualitative analysis of the preparation pattern showed that the Tilos system had a more uniform preparation, although Reciproc and WaveOne preparations appeared more rounded, incompatible with the original canal anatomy. There was similarity in the systems’ performance on flattened areas, although the Tilos system presented a better pattern of root canal preparation and a lower index of transportation.

Changes in irradiance and energy density in relation to different curing distances

The present study aimed to assess the influence of curing distance on the loss of irradiance and power density of four curing light devices. The behavior in terms of power density of four different dental curing devices was analyzed (Valo, Elipar 2, Radii-Cal, and Optilux-401) using three different distances of photopolymerization (0 mm, 4 mm, and 8 mm). All devices had their power density measured using a MARC simulator. Ten measurements were made per device at each distance. The total amount of energy delivered and the required curing time to achieve 16 J/cm2 of energy was also calculated. Data were statistically analyzed with one-way analysis of variance and Tukey’s tests (p < 0.05). The curing distance significantly interfered with the loss of power density for all curing light devices, with the farthest distance generating the lowest power density and consequently the longer time to achieve an energy density of 16 J/cm2 (p < 0.01). Comparison of devices showed that Valo, in extra power mode, showed the best results at all distances, followed by Valo in high power mode, Valo in standard mode, Elipar 2, Radii-Cal, and Optilux-401 halogen lamp (p < 0.01). These findings indicate that all curing lights induced a significant loss of irradiance and total energy when the light was emitted farther from the probe. The Valo device in extra power mode showed the highest power density and the shortest time to achieve an energy density of 16 J/cm2 at all curing distances.

Micro-CT assessment of two different endodontic preparation systems

The aim of this study was to compare two endodontic preparation systems using micro-CT analysis. Twenty-four one-rooted mandibular premolars were selected and randomly assigned to two groups. The samples (n = 12) of Group 1 were prepared using the ProTaper Universal rotary system, while Group 2 (n = 12) was prepared using the EndoEZE AET system complemented by manual apical preparation with K-type hand files up to #30. A 2.5% sodium hypochlorite solution was used in both groups for irrigating. Both groups were scanned by high-resolution microcomputed tomography before and after preparation (SkyScan 1172, SkyScan, Kontich, Belgium). The root canal volume and surface area was measured before and after preparation, and the differences were calculated and analyzed for statistically significant differences using ANOVA complemented by the Tukey test (p < 0.05). The results showed no statistically significant differences between the mean volumes of dentin removal by the two systems. However, the EndoEZE AET system presented a significantly greater mean surface area compared to the ProTaper system (p < 0.05). The EndoEZE AET system enabled preparation of a greater root canal surface area when compared to the ProTaper Universal system. There seemed to be no difference in dentin volume loss between the two systems used.

Influence of prior 810-nm-diode intracanal laser irradiation on hydrophilic resin-based sealer obturation

Dentin wall structural changes caused by 810-nm-diode laser irradiation can influence the sealing ability of endodontic sealers. The objective of this study was to evaluate the apical leakage of AH Plus and RealSeal resin-based sealers with and without prior diode laser irradiation. Fifty-two single-rooted mandibular premolars were prepared and divided into 4 groups, according to the endodontic sealer used and the use or non-use of laser irradiation. The protocol for laser irradiation was 2.5W, continuous wave in scanning mode, with 4 exposures per tooth. After sample preparation, apical leakage of 50% ammoniacal silver nitrate impregnation was analyzed. When the teeth were not exposed to irradiation, the RealSeal sealer achieved the highest scores, showing the least leakage, with significant differences at the 5% level (Kruskal-Wallis test, p = 0.0004), compared with AH Plus. When the teeth were exposed to the 810-nm-diode laser irradiation, the sealing ability of AH Plus sealer was improved (p = 0282). In the RealSeal groups, the intracanal laser irradiation did not interfere with the leakage index, showing similar results in the GRS and GRSd groups (p = 0.1009).

Nd:YAG laser irradiation effect on apical intracanal dentin - a microleakage and SEM evaluation

The purpose of this in vitro study was to evaluate the effect of neodymium:yttrium-aluminum-garnet (Nd:YAG) laser irradiation on intracanal dentin surface by SEM analysis and its interference in the apical seal of filled canals. After endodontic treatment procedures, 34 maxillary human incisors were randomly assigned to 2 groups. In the negative control group (n=17), no additional treatment was performed and teeth were filled with vertically condensed gutta-percha; in the laser-treated group (n=17), the root canals were irradiated with Nd:YAG laser (1.5 W, 100 mJ, 15 Hz) before filling as described for the control group. Two specimens of each group were prepared for SEM analysis to evaluate the presence and extent of morphological changes and removal of debris; the other specimens were immersed in 0.5 percent methylene blue dye (pH 7.2) for 24 h for evaluation of the linear dye leakage at the apical third. SEM analysis of the laser-treated group showed dentin fusion and resolidification without smear layer or debris. The Student’s t-test showed that the laser-treated group had significantly less leakage in apical third than the control group. Within the limitations of this study, it may be concluded that the morphological changes on the apical intraradicular dentin surface caused by Nd:YAG laser resulted in less linear dye apical leakage.

Avaliação da variação da temperatura intrapulpar após o uso de agentes clareadores e ativação por fontes de luz / Evaluation of the variation of intrapulpal temperature after the use of bleaching agents and activation by light sources

Introdução e objetivo: Buscou-se avaliar in vitro o grau de aquecimento promovido no interior da câmara pulpar após o uso de diferentes agentes clareadores, com ou sem ativação por fontes de luz. Material e métodos: Foram utilizados 60 dentes incisivos bovinos, que receberam acesso ao canal radicular pela face lingual, com a parede vestibular padronizada em 2 mm. Os espécimes foram divididos em 6 grupos (n = 10), de acordo com o agente clareador e a fonte de ativação utilizada: G1 - ausência de agente clareador e aplicação de luz halógena; G2 - ausência de agente clareador e aplicação de LED; G3 - aplicação do agente clareador Whiteness HP Maxx (peróxido de hidrogênio 35%) e ativação com luz halógena; G4 - aplicação do agente clareador Whiteness HP Maxx (peróxido de hidrogênio 35%) e ativação com LED; G5 - aplicação do agente clareador Opalescence Xtra Boost (peróxido de hidrogênio 38%) e ativação com fotopolimerizador; G6 - aplicação do agente clareador Opalescence Xtra Boost (peróxido de hidrogênio 38%) e ativação com LED. A variação da temperatura na câmara pulpar foi mensurada com um aparelho termopar. Resultados: Os valores de temperatura foram medidos pelo aparelho durante 10 minutos, com alguns intervalos selecionados: t1 - temperatura inicial; t2 - após 25 segundos de aplicação do gel e 20 segundos de ativação; t3 - após 10 minutos. Os valores obtidos foram registrados pela máquina no software, e os dados foram submetidos à análise estatística pelo teste Anova. Verificou-se que o aumento da temperatura não foi significante em todos os grupos testados. Conclusão: Não foram encontradas diferenças estatisticamente significantes entre os grupos com e sem ativação por fontes de luz ou entre os diferentes clareadores.

Introduction and objective: To evaluate in vitro the degree of warming promoted within the pulp chamber, after the use of bleaching agents, with or without activation by light sources. Material and methods: Sixty bovine teeth were used, which had received access to the root canal by the side lingual, with the wall vestibular standardized at 2 mm. The specimens were divided into 6 groups (n = 10), according to the bleaching agent and the source of activation used: G1 - absence of bleaching agent and application of halogen light; G2 - absence of bleaching agent and application of LED; G3 - application of the Whiteness HP Maxx (35% hydrogen peroxide) and activation with halogen light; G4 - application of Whiteness HP Maxx (35% hydrogen peroxide) and activation with LED; G5 - application of the Opalescence Xtra Boost (38% hydrogen peroxide) and activation with photopolymerizer; G6 - application of the Opalescence Xtra Boost (38% hydrogen peroxide) and activation with LED. The change of temperature in the pulp chamber was measured using a Termopar apparatus. Results: The values of temperature were measured by the device during an interval of 10 minutes, with some selected intervals: t1 - initial temperature; t2 - after 25 seconds of application of the gel and 20 seconds of activation; t3 - after 10 minutes. The values were registered by the machine in the software and the data were subjected to statistical analysis using the Anova test. Conclusion: There were no statistically significant differences between groups with and without activation or between different bleaching.

O uso do ultra-som na remoção de retentores intra-radiculares com diferentes tipos de retenção / The use of ultrasound for removal of cast posts with different types of retention

Objetivo: O objetivo deste trabalho foi avaliar o uso do ultra-som na remoção de retentores intra-radiculares metálicos fundidos (RI). Metodologia: Foram utilizados 30 dentes humanos unirradiculados tratados endodonticamente e divididos em três grupos: grupo G1 - retentores intra-radiculares do tipo convencional, sem nenhum tipo de retenção mecânica adicional (tipo liso); grupo G2 - retentores intra-radiculares com sulcos longitudinais (tipo canaleta) e grupo G3 - retentores intra-radiculares com sulcos transversais (tipo anelado). Os retentores foram cimentados nos canais radiculares com cimento fosfato de zinco e os espécimes armazenados por 24 h em temperatura ambiente. Para a remoção dos retentores utilizou-se o ultra-som e a tração manual com pinça hemostática. Foi medido o tempo necessário para remoção dos retentores; os dados foram analisados por ANOVA e teste de Tukey (5% de significância). Resultados: Houve diferença estatisticamente significante entre G1(3,7±1,5 min) e G2 (1,4±0,5 min) (P<0,001) e entre G1 e G3 (2,3±1,2 min) (P=0,041). Não houve diferença significante entre G2 e G3 (P=0,207). Conclusão: Concluiu-se que os pinos metálicos fundidos lisos apresentaram maior dificuldade para remoção.

Purpose: The objective of this study was to evaluate the use of ultrasound for removal of cast posts (CP) with different characteristics. Methods: Thirty uniradicular human teeth were endodontically treated and divided into three groups: G1 - conventional post (no additional mechanical retention); G2 - post with longitudinal groove; and G3 - post with transversal grooves. The posts were cemented inside the root canal using zinc phosphate cement, and the specimens were stored in room temperature for 24 h. The procedures for post removal included the use of ultrasonification (ultrasound equipment Multisonic S) and manual pushing with haemostatic tweezers. The period of time necessary for post removal was recorded, and data were analyzed by ANOVA and Tukey tests (5% level of significance). Results: Time for post removal was statistically different between groups G1 (3.7±1.5 min) and G2 (1.4±0.5 min) (P<0.001) and between G1 and G3 (2.3±1.2 min) (P=0.04). No difference was found between G2 and G3 (P=0.207). Conclusion: It was concluded that conventional cast posts were more difficult to remove in comparison with posts with additional mechanical retention.

Tratamento não-cirurgico de patologias com imagens radiográficas sugestivas de cisto radicular / No-surgical treatment of pathologies with suggestive radiographic images of radicular cyst

São consideradas periapicopatias verdadeiras de origem inflamatória a pericementite apical aguda e crônica, abscesso dentoalveolar agudo e crônico, granuloma periapical e cisto periapical. Casos de lesões periapicais com imagens radiográficas sugerindo cistos podem ser tratados de forma não-cirúrgica com um índice de sucesso bastante elevado. Este trabalho teve como objetivo apresentar três casos clínicos de tratamento não-cirúrgico para lesões com aspecto radiográfico sugestivo de cisto. Foi realizado o preparo químico mecânico e a medicação intracanal com pasta de hidróxido de cálcio associado ao paramonoclorofenol canforado com trocas mensais de seis e sete meses ou ao gel de clorexidina 2% com trocas mensais durante dez meses. Medicação sistêmica também foi utilizada como complemento do tratamento. Em dois casos, houve regressão da lesão somente com o tratamento endodôntico. No terceiro caso, na proservação de dois anos, foi observada a recidiva da imagem sendo indicada a complementação cirúrgica do caso. Conclui-se que lesões periapicais, com imagens radiográficas sugestivas de cistos, podem ser tratadas da forma convencional, com trocas periódicas da medicação intracanal à base de hidróxido de cálcio associado ao paramonoclorofenol canforado ou ao gel de clorexidina 2%, com um índice de sucesso bastante elevado.

Acute and chronic apical pericementitis, acute and chronic dentoalveolar abscess, apical granuloma and apical periodontal cyst are considered real periapical diseases of inflammatory original. Cases that present periapicallesions with cyst-like radiographic images may be treated non-surgically with significantly high index of success. The purpose of this report was presented three clinical cases reports which were performed non-surgical treatment for lesions with a cyst-like radiographic aspect. In these clinical cases, the root canal was prepared by chemical mechanic treatment using intra-canal medication based on calcium hydroxide paste associated with camphorated paramonochlorophenol changing during 6 and 7 months or 2% chlorhexidine gel changing during 10 months. Systemic medication had also used to complement the treatment. It was verified that two cases revealed regression of the cyst-like lesion using only the root canal treatment. After two years following, the third case showed the recidivate image and it was recommended the surgical procedure for the treatment. In conclusion, periapical lesions with a cyst-like radiographic can be treated by conventional way using periodic changes of intra-canal medication based on calcium hydroxide associated with camphorated paramonochlorophenol or 2% chlorhexidine gel promoting a high index of success.

Passagens de ions peróxido para a superfície dentária externa após clareamento com peróxido de hidrogênio / Peroxide íons passage throug external dental surface after internal bleaching with hydrogen peroxide

O objetivo deste trabalho foi avaliar a quantidade de peróxido que passa da câmara pulpar para a superfície dentária externa durante o clareamento interno no esmalte, cemento e dentina. Foram utilizados 50 incisivos bovinos extraídos que receberam aberturas coronárias, as raízes foram cortadas a 5 mm da junção amelo-cementária e foi realizado um tampão de 2mm de ionômero de vidro selando a entrada do canal. A extremidade apical dos espécimes foi isolada externamente com resina composta fotoativada. Os dentes foram então impermeabilizados completamente, deixando exposto somente as áreas a serem estudadas. As câmaras coronárias foram preenchidas com peróxido de hidrogênio a 35%. Os dentes foram divididos em três grupos experimentais e dois grupos controles, com 10 espécimes cada. GE – esmalte exposto a ser avaliado; GC – cemento exposto a ser avaliado; GD – dentina exposta a ser avaliada; e dois grupos Controle: GC1 – sem a presença de clareador internamente e sem impermeabilização e GC2 – câmara pulpar preenchida com clareador e impermeabilização total. Cada amostra foi colocado no interior de reservatórios individuais com 1000μl de solução tampão de acetato 2M (pH 4,5). Após 7 dias a 37±1ºC a solução foi transferida para um tubo de ensaio onde foram adicionados 100μl do corante violeta leucocristal e 50 μl de peroxidase, resultando em uma solução de coloração azul. A mensuração da absorbância foi feita em um espectrofotômetro e convertida em μg/ml de peróxido. Para avaliar se houve diferença entre os grupos experimentais e controle, realizou-se os testes de Kruskall-Walis e Dunn-Bunferroni e os resultados mostraram os íon passaram mais pela dentina exposta, seguida da dentina recoberta pelo esmalte e dentina recoberta pelo cemento, sem diferenças estatísticas. Todos os grupos experimentais foram diferentes dos controles...

The aim of this study was evaluated the pulp chamber penetration of peroxide bleaching agent to the root surface during the internal bleach technique in the enamel, dentin and cement. Bovine teeth were sectioned 5mm apical of the cemento-enamel junction and was performed a 2mm cervical seal with glass ionomer cement. The external apical part of samples was filled with composite resin. The teeth were divided into three experimental groups and two control groups: GE – exposition of enamel; GC – exposition of cement; GD – exposition of dentin and control groups: GC1 – no presence of internal agent bleaching e no waterproof and GC2 – pulp chamber filled with bleaching agent and total waterproof. Each sample was placed inside of individual flasks with 1000μl of acetate buffer solution 2M (pH 4.5). After 7 days, the buffer solution was transferred to a glass tube where leuco crystal violet and horseradish peroxidase were added, producing a blue solution. The optical density of the blue solution was determined by spectrophotometer and converted into microgram equivalents of hydrogen peroxide. Data were submitted to Kruskal-Wallis, and Dunn-Bunferroni tests. The results showed that the ions penetration was higher in dentin followed by enamel and cement. All experimental groups presented statistical differences to the control groups.

Avaliação do desgaste das paredes internas de canais radiculares de molares / Evaluation of the internal wall wear in molar root canal

Para avaliar o desgaste interno do terço cervical de raízes de molares, comparando-se instrumentos rotatórios em níquel e titânio com oscilatórios em aço inoxidável e brocas Gates-Glidden, 30 raízes de molares humanos foram padronizadas e radiografadas. As radiografias foram digitalizadas e mediu-se a espessura dentinária na entrada do canal radicular e 3 mm abaixo da entrada, em relação à parede de risco e a de segurança. As amostras foram aleatoriamente divididas nos grupos: G1 (Pré-Race), G2 (Gates-Glidden) e G3 (Endo-Eze). Radiografou-se novamente e as radiografias foram digitalizadas. Foi feita a redução percentual e os dados submetidos ao teste "t" pareado. Concluiu-se que não houve diferença significante entre os grupos, havendo, no entanto, um maior desgaste da parede de risco quando as brocas de Gates-Glidden foram utilizadas.

To evaluate the internal wear of the cervical third of molar root canal, comparing rotary nickel-titanium instruments with stainless steel oscillatory instruments and Gates-Glidden burs, 30 human molar roots were slandered and radiographed. The radiographs were digitalized and the dentin width was measured at the entrance of the root canal and 3 mm down from the entrance, in relation to the risk and safety walls. The samples were randomly divided the groups: G1 (Pré-Race), G2 (Gales-Glidden) e G3 (Endo-Eze). Radiographs were taken again and digitalized. Percentual reduction made and the data were submitted to pared t test. It was concluded that there was no significant difference among the studied groups, thus a higher wear was found on the risk walls when Gates-Glidden burs were used.