Maria Fidela de Lima Navarro

Fracture strength of human teeth with cavity preparations

F ailure of dental restorations is a major concern. The most common causes are faulty cavity preparation and improper manipulation of restorative materials. Another cause of failure is the geometric form of the cavity preparation, which may lead to fracture of the tooth. The anatomic forms of posterior teeth with cusps and fossae present a design possessing a tendency to deflect the cusps under stress (Fig. 1, A).’ While sound teeth rarely fracture from the stresses of mastication, fracture of a cusp may occur in teeth which have been weakened by caries and the cavity preparation required for restoration. The typical intracoronal cavity preparation, especially in the maxillary premolars, exaggerates the height of the cusps (Fig. 1, B). The weakened or unsupported cusps are subjected to stresses which tend to deflect or fracture them at the buccopulpal or linguopulpal line angles (Fig., 1, C). While a fracture may not occur, deflection of a weakened cusp may open the tooth-restoration interface and lead to subsequent marginal leakage (Fig. 1, C). It is evident that the buccolingual width of the occlusal preparation may contribute toward weakening of the cusps. Cavity forms have been based on Black’s principles.’ For Class I and II cavity preparations, Black advocated an occlusal width of one-third the buccolingual intercuspal distance. Present-day equipment and restorative materials permit more conservative geometric forms. Modern cavity preparation permits narrow occlusal designs, one-fourth the buccolingual

Cytotoxicity and biocompatibility of direct and indirect pulp capping materials

There are several studies about the cytotoxic effects of dental materials in contact with the pulp tissue, such as calcium hydroxide (CH), adhesive systems, resin composite and glass ionomer cements. The aim of this review article was to summarize and discuss the cytotoxicity and biocompatibility of materials used for protection of the dentin-pulp complex, some components of resin composites and adhesive systems when placed in direct or indirect contact with the pulp tissue. A large number of dental materials present cytotoxic effects when applied close or directly to the pulp, and the only material that seems to stimulate early pulp repair and dentin hard tissue barrier formation is CH.

In vivo effect of a resin-modified glass ionomer cement on enamel demineralization around orthodontic brackets

Because the risk of dental caries increases with the use of orthodontic appliances and its control cannot depend only on the patients self-care, this study evaluated the effect of a glass ionomer cement on reducing enamel demineralization around orthodontic brackets. Fourteen orthodontic patients were randomly divided into 2 groups of 7; they received 23 brackets fitted to their premolars, bonded with either Concise (3M Dental Products, St Paul, Minn), a composite resin (control group), or Fuji Ortho LC (GC America, Chicago, Ill), a resin-modified glass ionomer cement (experimental group). The volunteers lived in a city that has fluoridated water, but they did not use fluoridated dentifrices during the study. After 30 days, the teeth were extracted and longitudinally sectioned; in the enamel around the brackets, demineralization was assessed by cross-sectional microhardness. The determinations were made at the bracket edge cementing limits, and at occlusal and cervical points 100 and 200 microm away from them. In all of these positions, indentations were made at depths from 10 to 90 microm from enamel surface. Analysis of variance showed statistically significant effects for position, material, depth, and their interactions (P<.05). The Tukey test showed that the glass ionomer cement was statistically more efficient than the control, reducing enamel demineralization in all analyses (P<.05). The use of glass ionomer cement for bonding can be encouraged because it decreases the development of caries around orthodontic brackets.

Effect of caries preventive measures directed to expectant mothers on caries experience in their children.

The aim of this prospective study was to determine the effectiveness of caries preventive measures started during pregnancy on the caries experience of first-time mothers and their infants. Eighty-one pregnant women with low social background were selected on the basis of the presence of active carious lesions and were randomly divided into control (38) and experimental (43) groups. The initial dental status (DMFS and white spot lesions) was established through clinical examination. The prophylactic measures were repeated during pregnancy and 6 and 12 months after delivery. Both groups received primary care intervention. They were instructed in relation to the etiologic factors of dental caries and received oral hygiene kits. Oral hygiene instructions were reinforced through interactive brushing. The experimental group also received antimicrobial treatment (topical application of NaF and iodine solution immediately after prophylaxis and 3 and 5 days later) and restorative care using glass ionomer cement. By the time the children were 2 years of age, 33.3% of the infants in the control group and 14.7% in the experimental group had caries activity. A significant difference in caries prevalence was observed between children with and without visible dental plaque. The mean number of tooth surfaces with carious lesions (including areas of demineralization) was higher among the children in the control group compared to the experimental group (6.3 x 3.2), however, with no statistical significance. Maternal caries increase was a significant factor influencing the caries experience of the children. These data support the evidence of an association between caries prevalence in young children and clinical (dental plaque) and maternal factors.

5-year Clinical Performance of Resin Composite Versus Resin Modified Glass Ionomer Restorative System in Non-carious Cervical Lesions

AIM To comparatively assess the 5-year clinical performance of a 1-bottle adhesive and resin composite system with a resin-modified glass ionomer restorative in non-carious cervical lesions. METHOD AND MATERIALS One operator placed 70 restorations (35 resin modified glass ionomer restorations and 35 resin composite restorations) in 30 patients under rubber dam isolation without mechanical preparation. The restorations were directly assessed by 2 independent examiners, using modified USPHS criteria at baseline and 6, 12, 24 and 60 months. RESULTS Twenty-two patients were available for recall after 5 years (73.3% recall rate) and 55 out of 70 restorations were evaluated. Excellent agreement was registered for all criteria between examiners (kappa > or = 0.85). Sixteen composite restorations were dislodged (51.5% retention) and 1 ionomer restoration was lost (96.4% retention). The McNemar test detected significant differences in resin composite restorations between baseline and 5-year recall for marginal integrity (p<0.001) and retention (p=0.004). For resin modified glass ionomer restorations, no significant differences were identified for all criteria (p>0.05). When comparing both materials, the Fisher exact test pointed out significant differences in retention (p=0.002) after 5 years of clinical service. CONCLUSIONS After 5 years of evaluation, the clinical performance of resin modified glass ionomer restorations was superior to resin composite restorations.

Secondary caries around amalgam restorations

Secondary caries is one of the greatest causes for replacement of amalgam restorations. This study verified whether marginal defects in class I restorations could be a determining factor in the development of secondary caries. Fifty-five extracted premolars and molars whose occlusal surfaces were already restored with amalgam were selected. A macroscopic examination of these teeth was carried out to see whether there was a difference in the prevalence of caries beneath ditched and nonditched margins. To assess the presence of caries, a section was ground in each tooth so that the cut passed through a ditched margin and a better margin. This permitted assessment of the two types of margins that had been exposed to the same oral environment. Macroscopic examination revealed caries in 3.6% of the nonditched margins and caries in 20% of the ditched margins. Microscopic examination revealed caries in 47.06% of the nonditched margins and caries in 58.82% of the ditched margins. Statistical analysis supports the conclusion that the marginal defect itself is insufficient to determine the presence of secondary caries that surround the amalgam restoration on the occlusal surface.

Microhardness of resin-based materials polymerized with LED and halogen curing units

The purpose of this study was to evaluate the microhardness of resin-based materials polymerized with a LED (light-emitting diode) light-curing unit (LCU) and a halogen LCU. Twenty cylindrical specimens (3.0 mm in diameter and 2.0 mm high) were prepared for each tested material (Z100, Definite and Dyract). Specimens were light-cured with two LCUs (Ultraled and Curing Light 2500) for either 40 or 60 s on their top surfaces. Hardness was measured on top and bottom surfaces of each specimen. Statistical analysis was done by ANOVA and Tukeys test (p<0.05). There was no significant difference in hardness between LED LCU and halogen LCU for Z100 and Dyract on top surface. Conversely, lower hardness was recorded when Definite was light-cured with the LED LCU than with the halogen lamp. On bottom surface, hardness was significantly lower for all materials light-cured with LED LCU. Z100 was harder than Dyract and Definite regardless of the light curing unit. There was no significant difference in hardness between the exposure times on top surface. Higher hardness was obtained when the materials were light-cured for 60 s on bottom surface. The tested LED was not able to produce the same microhardness of resin-based materials as the halogen LCU.

Compressive and diametral tensile strength of glass ionomer cements

The aim of this study was to compare, in different periods of time, the compressive and diametral tensile strength of a traditional high viscous glass ionomer cement: Fuji IX (GC Corporation), with two new Brazilian GICs: Vitro-Molar (DFL) and Bioglass R (Biodinamica), all indicated for the Atraumatic Restorative Treatment (ART) technique. Fifteen disk specimens (6.0mm diameter x 3.0mm height) for the diametral tensile strength (DTS) test and fifteen cylindrical specimens (6.0mm diameter x 12.0mm height) for the compressive strength (CS) test were made of each GIC. Specimens were stored in deionized water at 37º C and 100% of humidity in a stove until testing. Five specimens of each GIC were submitted to CS and DTS test in each period, namely 1 hour, 24 hours and 7 days. The specimens were tested in a testing machine (Emic) at a crosshead speed of 1.0mm/min for CS and 0.5mm/min for the DTS test until failure occurred. The data were submitted to two-way ANOVA and Tukey tests (alpha=0.05). The mean CS values ranged from 42.03 to 155.47MPa and means DTS from 5.54 to 13.72 MPa, with test periods from 1h to 7 days. The CS and DTS tests showed no statistically significant difference between Fuji IX and Vitro Molar, except for CS test at 1-hour period. Bioglass R had lowest mean value for CS of the cements tested. In DTS test Bioglass R presented no statistically significant differences when compared with all others tested GICs at 1-hour period and Bioglass R presented no difference at 24-hour and 7-day periods when compared to Vitro-Molar. Further studies to investigate other physical properties such as fracture toughness and wear resistance, as well as chemical composition and biocompatibility, are now needed to better understand the properties of these new Brazilian GICs.

Diametral tensile strength and water sorption of glass-ionomer cements used in Atraumatic Restorative Treatment

The purposes of this study were to evaluate the diametral tensile strength and the water sorption of restorative (Fuji IX and Ketac Molar) and resin-modified glass-ionomer luting cements (ProTec Cem, Fuji Plus and Vitremer) mixed at both manufacturer and increased powder: liquid ratio, for their use in the Atraumatic Restorative Treatment. A conventional restorative glass-ionomer (Ketac Fil) was used as control. Specimens (6.0 mm in diameter x 3.0 mm in height) were prepared and stored (1 hour, 1 day and 1 week) for a diametral tensile strength test. Data were subjected to two-way ANOVA and Tukey tests (p<0.05). For the water sorption test, specimens of 15.0 mm in diameter x 0.5 mm in height were prepared and transfered to desiccators until a constant mass was obtained. Then the specimens were immersed in deionized water for 7 days, weighed and reconditioned to a constant mass in desiccators. Data were subjected to one-way ANOVA and Tukey tests (p<0.05). Five specimens of each studied material and consistency were prepared for each test. The resin-modified glass-ionomer cements showed significantly higher strength than the conventional materials. Except for ProTec Cem, the diametral tensile strength of the resin-modified materials significantly increased from luting to restorative consistency. Except for ProTec Cem, the water sorption of the resin-modified glass ionomers was higher than the others. The water sorption of resin-modified materials at restorative consistency was significantly lower than at luting consistency. Resin-modified glass-ionomer luting cements mixed at increased powder: liquid ratio showed better properties than at luting consistency.

Comparasion of two minimally invasive methods on the longevity of glass ionomer cement restorations: short-term results of a pilot study

The purpose of this study was to evaluate the clinical performance of glass ionomer cement (GIC) restorations comparing two minimally invasive methods in permanent teeth after 12 months. Fifty pregnant women (second trimester of pregnancy), mean age 22 ± 5.30 years, were treated by two previously trained operators. The treatment approaches tested were: chemomechanical method (CarisolvTM; MediTeam) and atraumatic restorative treatment (ART). A split-mouth study design was used in which the two treatments were randomly placed in 50 matched pairs of permanent teeth. The chemomechanical method (CM) was the test group and the ART was the control group. The treatments were performed in Public Health Centers. The tested restorative material was a high-strength GIC (Ketac Molar; 3M/ESPE). The restorations were placed according to the ART guidelines. Two calibrated independent examiners evaluated the restorations in accordance with ART criteria. The interexaminer kappa was 0.97. Data were analyzed using 95% confidence interval on the binomial distribution and Fishers exact test at 5% significance level. In a 12-month follow-up, 86% of the restorations were evaluated. In the test group (CM), 100% (CI=93.3-100%) of the restorations were considered successful. In the control group (ART) 97.6% (CI=87.4-99.9%) of the restorations were considered successful and 2.4% unsuccessful (marginal defect >0.5 mm). There was no statistically significant difference between the 12-mounth success rate for both groups (Fishers exact test: P=0.49) and between the two operators (Fishers exact test: P=1.00). Both minimally invasive methods, chemomechanical method and ART, showed a similar clinical performance after 12 months of follow up.