Evaluation of enamel roughness after the removal of brackets bonded with different materials: In vivo study

The aims of this in vivo study were to evaluate the effect of bonding with resin-modified glass ionomer cement (RMGIC) and to assess enamel surface roughness before and after the removal of brackets bonded with composite or RMGIC from the maxillary central incisors. Fifteen orthodontic patients were selected for the study. For each patient, the teeth were rinsed and dried, and brackets were bonded with composite (Transbond XT) and RMGIC (Vitremer Core Buildup/Restorative). At the conclusion of orthodontic treatment, their brackets were removed. Dental replicas were made of epoxy resin in initial conditions (before bonded) and after polishing with an aluminum oxide disc system. Adhesive remnant index (ARI) and surface roughness was measured on the dental replicas and data were evaluated statistically by Mann-Whitney and paired t-test, respectively. No bracket debonding occurred during patients' treatment periods. It was verified that the ARI values of the two maxillary central incisors were similar (p = 0.665). For both bonding materials, the ARI value of 3 was predominant. After polishing, surface roughness was similar in the composite and RMGIC groups (0.245 μm and 0.248 μm, respectively; p = 0.07). In both groups, enamel surface roughness values were significantly lower after polishing compared with the initial condition (p < 0.001). RMGIC promoted efficiency in cementing brackets without fail during treatment; the choice of composite or RMGIC materials was not a factor that influenced the roughness of the enamel surface, however, polishing led to smoother surfaces than those found at the beginning of the treatment.

Evaluation of the Physical-Mechanical Properties of Type IV Gypsum

AbstractThe purpose of this study was to evaluate a physical property (surface roughness) and a mechanical property (microhardness) of four type IV gypsum. 40 specimens were prepared from a metal matrix that reproduced an edentate upper alveolar ridge. They were divided into 4 groups (n = 10 Clone (G3), Durone(G4), SSWhite (G2), Asfer (G1) and submitted to roughness and microhardness tests . The obtained data were submitted to statistical analysis. By the Kolmogorov-Smirnov test it was verified that there was non-parametric distribution of the samples. The non-parametric Kruskal-Wallis and Mann-Whitney-U tests were applied in hardness and roughness data. In microhardness group 3(Clone) presented the best values (103.0 HV). In surface roughness (Ra), group 3(Clone) and Group 2 (SSWhite) showed the lowest values (1.8 m) and all evaluated groups presented higher values than those found in metallic matrix (baseline). It was concluded that gypsum models obtained from molds with irreversible hydrocolloid are rougher than molded surface, regardless of the commercial brand. The samples made with the Clone gypsum (G3) have the highest microhardness. Keywords: Calcium Sulfate. Hardness. Dental Materials. ResumoO objetivo desse trabalho foi avaliar uma propriedade física (rugosidade superficial) e uma propriedade mecânica (microdureza) de quatro marcas comerciais de gesso tipo IV. Foram confeccionados 40 corpos de prova a partir de uma matriz metálica que reproduzia um rebordo alveolar superior edentado. Os mesmos foram divididos em 4 grupos (n=10), de acordo com as marcas comerciais (Clone, Durone, SSWhite, Asfer), e submetidos aos testes de rugosidade e microdureza superficial utilizando um rugosímetro e um microdurômetro respectivamente. Os dados obtidos foram computados e submetidos à análise estatística. Pelo teste de Kolmogorov-Smirnov verificou-se que não houve distribuição Normal das amostras. Dessa forma foram aplicados os testes não paramétricos de Kruskal-Wallis e Mann-Whitney-U em ambas as análises. Na microdureza, a marca comercial Clone apresentou os melhores valores (103,0). Já na rugosidade superficial as marcas comerciais Clone e SSWhite apresentaram os menores valores (1,8). Ainda em relação à rugosidade superficial, as marcas comerciais avaliadas apresentaram valores maiores que os encontrados na matriz metálica. Concluiu-se que modelos em gesso obtidos a partir de moldes com hidrocolóide irreversível apresentam-se mais rugosos que a superfície moldada, independente da marca comercial avaliada. Os modelos em gesso confeccionados com a marca Clone apresentam melhor microdureza superficial. Palavras-chave: Sulfato de Cálcio. Dureza. Materiais Dentários.

Evaluation of Internal Adaptation and Degree of Porosity of Total Crowns After Cementation

AbstractThe present study evaluated the marginal fit, the internal filling volume and the degree of porosity in cemented metallic total crowns. Then, 12 metal crowns cast in titanium (Ti) were made on bovine teeth with total preparations and 90° shoulder terminal line. The samples were divided into 4 groups according to the type of cement used and the cementation techniques, 2 groups were used Zinc phosphate (SS White) with the partial insertion of the cementing agent filling the inner crown surface (FP) and total filling (FT), and in the other 2 groups, dual resin cement (RelyX ARC 3M) with the partial insertion of cement (RP) and total insertion (RT) were used. The results showed that cervical marginal fit after cementation was clinically adequate in all groups (<100μm), and for the internal filling volume and porosity were: FP - 99.14% / 0.86%; FT = 98.82% / 1.18%; RP - 97.06% / 2.94% and RT - 97.76% / 2.24%. The statistical analysis was performed by Mann-Whitney test. In conclusion, the two types of cements obtained acceptable values of marginal fit, however, the zinc phosphate cement had better internal fill and lower porosity than the resin cement. Regarding the insertion technique, only the FP and FT groups had a statistically significant difference (p < 0.05) compared to the RP group. Keywords: Fixed Partial Denture. X-Ray Microtomography. Dental Cements. ResumoO presente trabalho avaliou o desajuste marginal, o volume de preenchimento interno e o grau de porosidade em cimentações de coroas totais metálicas. A partir de dentes bovinos com preparos periféricos totais e términos cervicais do tipo ombro de 90º, foram confeccionadas 12 coroas metálicas fundidas em titânio (Ti). As amostras foram divididas em 4 grupos de acordo com o tipo de cimento utilizado e as técnicas de cimentação, dentre estes, em 2 grupos foram usados Fosfato de zinco (SS White) com inserção parcial do agente cimentante preenchendo a superfície interna da coroa (FP) e preenchimento total (FT), e nos outros 2 grupos foram usados Cimento resinoso dual (RelyX ARC 3M) com inserção parcial do cimento (RP) e total (RT). As análises foram feitas por microtomografia computadorizada por raios X. Os resultados mostraram que o desajuste marginal cervical após a cimentação estava adequado clinicamente em todos os grupos (<100µm), e para o volume de preenchimento interno e porosidade foram respectivamente: FP – 99,14%/0,86%; FT – 98,82%/1,18%; RP – 97,06%/2,94% e RT – 97,76%/2,24%. Na análise estatística utilizou-se o teste de Mann-Whitney para amostras independentes. Concluiu-se que os dois tipos de cimentos obtiveram valores aceitáveis de desajuste marginal, contudo o cimento de fosfato de zinco apresentou melhor preenchimento interno e menor porosidade que o cimento resinoso. Em relação à técnica de inserção, apenas os grupos FP e FT tiveram diferença estatística significativa (p<0,05) comparado ao grupo RP. Palavras-chave: Prótese Parcial Fixa. Microtomografia por Raio-X. Cimentos Dentários.  

Effect of different surface treatments on the ceramic veneer surface: morphological analysis

Objective: The aim of this study was to evaluate the effect of different surface clinical treatments on the roughness (Ra) of a lithium disilicate ceramic veneer. Material and Methods: Forty-eight lithium disilicate discs with ceramic veneer and glaze layer were manufactured and distributed into six groups (n=8) according to the surface treatment performed: G1, glaze layer (control group); G2, diamond bur 4138F; G3, diamond bur 4138F + 4138FF; G4, diamond bur 4138F + new glaze layer; G5, diamond bur 4138F + ceramic polishing kit; G6, diamond bur 4138F + rubber cup with diamond paste + felt with diamond paste. Surface Ra measurement (µm) was performed using a profilometer before and after surface treatments, and one specimen from each group was subjected to Scanning Electron Microscopy (SEM) after treatment. Two-way ANOVA and Tukey's test (5%) were used for data analysis. Results: Group 2 (3,00 ± 0,61)b showed higher values of Ra, followed by Group 3 (1,93 ± 0,45)c, Group 6 (1,56 ± 0,22)ac, Group 5 (1,14 ± 0,68)a and Group 4 (0,90 ± 0,26)a. G4, G5 and G6 were not different between each other and control group (1,11 ± 0,21)a. SEM imaging revealed surface smoothness in G1, G4 and G5, and presence of irregularities in G2, G3 and G6. Conclusion: it is possible to conclude that different surface clinical treatments influences the roughness of a lithium disilicate ceramic veneer. Keywords: Ceramics; Dental porcelain; Dental polishing.

Associação Radiográfica entre Ponticulus Posticus e as Alterações Morfológicas Condilares

O ponticulus posticus (PP) é definido como uma pequena ponte óssea formada entre a porção posterior do processo articular superior e a porção posterolateral da margem superior do arco posterior da vértebra atlas. A fisiopatologia do PP pode ser relatada pela compressão vascular da artéria vertebral e nervo suboccipital, levando a isquemia circulatória e dor de cabeça cervicogênica, ou por disfunção mecânica da articulação atlanto-occiptal, resultando no tracionamento da dura máter ou iniciando um processo neurodinâmico. O objetivo deste estudo foi avaliar a associação entre PP e alterações morfológicas condilares, por meio das radiografias panorâmicas e teleradiografia lateral. Foram selecionados 1200 pacientes que realizaram documentação ortodôntica em uma clínica de radiologia. O PP foi avaliado e classificado em parcial ou completo. Os dados foram tabulados no SPSS e analisados por regressão logística multinomial. Houve diferença estatística significativa na prevalência do PP parcial entre homens e mulheres (P< 0,001), com odds ratio de 1,91 (95% IC 1,34-2,71), e na prevalência do PP complete (P = 0,002), com odds ratio de 1,72 (95% IC 1,21-2,43). Diferença estatística também foi encontrada na associação entre alteração morfológica condilar e PP complete (P = 0,004). Concluiu-se que o PP é mais prevalente em homens e que existe correlação entre a presença do PP completa e alterações morfológicas condilares.Palavras-chave: Radiografia. Atlas cervical. Côndilo Mandibular.AbstractThe ponticulus posticus (PP) is defined as an abnormal small bony bridge formed between the posterior portion of the superior articular process and the posterolateral portion of the superior margin of the posterior arch of the atlas. The pathophysiology may be related to pressure applied on the vertebral artery and the suboccipital nerve root, and may be a possible cause of posterior circulation ischaemia and cervicogenic headache, or mechanical dysfunction at the atlanto-occipital joint resulting in traction of the dura mater or initiation of neurodynamic processes. The objective was to determine the prevalence of PP and to assess whether there is an association between this condition and changes in condylar morphology, evaluated using digital panoramic and lateral cephalometric radiographs. A sample of 1200 patients was selected. The patients were referred to a radiology clinic for orthodontic evaluation. PP was classified as either partial or complete PP. Data were entered into an SPSS spreadsheet and analysed by multinomial logistic regression. There was a significant difference in the prevalence of partial PP between males and females (P< 0.001), with an odds ratio of 1.91 (95% CI 1.34-2.71), and in the prevalence of complete PP (P = 0.002), with an odds ratio of 1.72 (95% CI 1.21-2.43). A significant difference was found for the association between condylar morphological changes and complete PP (P = 0.004). It was concluded that PP is more prevalent in men, and there is a correlation between the presence of complete PP and changes in condylar morphology.Keywords: Radiography. Cervical atlas. Mandibular condyle. 

The influence of mold temperature on the fit of cast crowns with commercially pure titanium

Commercially pure titanium (CP Ti) has been widely applied to fabricate cast devices because of its favorable properties. However, the mold temperature recommended for the manufacture of casts has been considered relatively low, causing inadequate castability and poor marginal fit of cast crowns. This study evaluated and compared the influence of mold temperature (430°C - as control, 550°C, 670°C) on the marginal discrepancies of cast CP Ti crowns. Eight bovine teeth were prepared on a mechanical grinding device and impressions were used to duplicate each tooth and produce eight master dies. Twenty-four crowns were fabricated using CP Ti in three different groups of mold temperature (n = 8): 430°C (as control), 550°C and 670°C. The gap between the crown and the bovine tooth was measured at 50 X magnification with a traveling microscope. The marginal fit values of the cast CP Ti crowns were submitted to the Kruskal-Wallis test (p = 0.03). The 550°C group (95.0 µm) showed significantly better marginal fit than the crowns of the 430°C group (203.4 µm) and 670°C group (213.8 µm). Better marginal fit for cast CP Ti crowns was observed with the mold temperature of 550°C, differing from the 430°C recommended by the manufacturer.

Fit of cast commercially pure titanium and Ti-6Al-4V alloy crowns before and after marginal refinement by electrical discharge machining

STATEMENT OF PROBLEM

Titanium has been suggested as a replacement for alloys currently used in single-tooth restorations and fixed partial dentures. However, difficulties in casting have resulted in incomplete margins and discrepancies in marginal fit.

PURPOSE

This study evaluated and compared the marginal fit of crowns fabricated from a commercially pure titanium (CP Ti) and from Ti-6Al-4V alloy with crowns fabricated from a Pd-Ag alloy that served as a control. Evaluations were performed before and after marginal refinement by electrical discharge machining (EDM).

MATERIAL AND METHODS

Forty-five bovine teeth were prepared to receive complete cast crowns. Stone and copper-plated dies were obtained from impressions. Fifteen crowns were cast with each alloy (CP Ti, Ti-6Al-4V, and Pd-Ag). Marginal fit measurements (in micrometers) were recorded at 4 reference points on each casting with a traveling microscope. Marginal refinement with EDM was conducted on the titanium-based crowns, and measurements were repeated. Data were analyzed with the Kruskal-Wallis test, paired t test, and independent t test at a 1% probability level.

RESULTS

The Kruskal-Wallis test showed significant differences among mean values of marginal fit for the as-cast CP Ti crowns (mean [SD], 83.9 [26.1] microm) and the other groups: Ti-6Al-4V (50.8 [17.2] microm) and Pd-Ag (45.2 [10.4] microm). After EDM marginal refinement, significant differences were detected among the Ti-6Al-4V crowns (24.5 [10.9] microm) and the other 2 groups: CP Ti (50.6 [20.0] microm) and Pd-Ag (not modified by EDM). Paired t test results indicated that marginal refinement with EDM effectively improved the fit of CP Ti crowns (from 83.9 to 50.6 microm) and Ti-6Al-4V crowns (from 50.8 to 24.5 microm). However, the difference in improvement between the two groups was not significant by t test.

CONCLUSION

Within the limitations of this study, despite the superior results for Ti-6Al-4V, both groups of titanium-based crowns had clinically acceptable marginal fits. After EDM marginal refinement, the fit of cast CP Ti and Ti-6Al-4V crowns improved significantly.