[Implications of choice of products and impression technique on the thickness of the dento-prosthetic interface of the CAD-CAM crowns]. / Incidences du choix des produits et de la technique d'empreinte sur l'épaisseur de l'interface dento-prothétique des couronnes CAD/CAM.

The purpose of this study is to find out what type of impression material is able to achieve a CAD-CAM (Procera) crown with minimal thickness at the dental-prosthetic interface, taking into account the effect of the oversize replica and dimensional variations of the impression materials over time. The accuracy of the marginal adaptation will therefore depend on the oversize replica of clinical preparation controlled by the constant K. Three different types of impression materials: medium viscosity polyether (Impregum 3M-ESPE, Germany), silicones polyvinyl siloxane A (Putty + Very Light) and (Heavy + Light) (Express 3M-ESPE, Germany), were used for making impressions of fifteen initial prototype maxillary teeth made of nickel chrome. The cast of the impressions were poured with plaster type IV (Zhermack, Italy), on which thirty Procera crowns were fabricated. The thickness of the dental-prosthetic interface was then studied at three levels: 0, 1 and 2 mm. The results show that the impression material has a statistically significant impact on the thickness of the dental-prosthetic interface at all three levels. The most compressive impression technique, Putty + Very Light gave the best results at the three levels pre-cited. The results analyzed under optical microscopy show a statistically significant difference between the three impression material products (p-value < 0.05). The calibration constant K, according to each clinical situation, can therefore lead to optimal dental-prosthetic inter-face.

Natural, polarized light and the choice of composite: a key to success in shade matching of direct anterior restorations- Part I.

The biggest challenge while restoring anterior teeth is shade matching. Hue, chroma, value, opacity, translucency, intensity and anatomy must be seen to be reproduced. To see we need light, knowing that there is a strong relation between the nature of light and the components of natural teeth. This article enlightens the way to do the shade matching and the stratification of anterior teeth by choosing the relevant materials to mimic the nature. The physical properties of natural and polarized light will be studied to understand their correlation with dental materials and natural teeth to use them in the best combination.

Natural, polarized light and the choice of composite: a key to success in shade matching of direct anterior restorations- Part II.

With time, natural and polarized light proved their importance and utility in dental photography. After studying the physical properties of natural and polarized light, in the first part of this article, to understand their correlation with dental materials and natural teeth and how to use them in the best combination, this second part will illustrate the importance of a polarized image in color matching, how to manipulate it and how to apply it in clinical cases.

[An 18 month evaluation of MM-MTA pulpotomy on primary decayed molars]. / Evaluation sur 18 mois de la pulpotomie au MM-MTA sur des molaires temporaires cariées.

Pulpotomy is the most performed and controversial therapeutic in pediatric dentistry. Formocresol is known to have a toxic effect on living tissues, a mutagenic and carcinogenic potential with a systemic uptake of formocresol via pulpotomized teeth, other alternative products have been investigated. 40 molars were pulpotomized using Micro Mega Mineral Trioxide Aggregate (MM-MTA), which eliminates the need for the use of formocresol. The effects of this material were evaluated both clinically and radiographically. Post-operative control examinations were performed at 1, 6, 12, and 18 months trying to detect spontaneous or stimulated pain, pathological tooth mobility, abscesses or fistulas, internal or external pathological tooth resorption, periapical bone destruction, or canal obliteration. Pain was absent at 18 months post operatively. Thirty six molar treated with the MM-MTA didn't show any mobility or pain, one molar presented a pathological resorption and one molar presented an abscess without a fistula at 12 month. The observations were compared to others related to formocresol, ferric sulfate, MTA, and laser pulpotomies, using the Chi-square test x2. The abundance of positive result strongly demonstrate that the MM-MTA pulpotomy on carious temporary molars is a promising technique.

Stratification in anterior teeth using one dentine shade and a predefined thickness of enamel: a new concept in composite layering--Part II.

While restoring an anterior tooth, shade matching is one of the crucial points that we can face to have an esthetic final outcome. After studying the physical and optical characteristics of enamel and dentine in the first part of this article, the second part will propose a new method for color matching and a clinical stratification using a simple and reproducible procedure for anterior restorations with only one dentine and one enamel shade.

Stratification in anterior teeth using one dentine shade and a predefined thickness of enamel: a new concept in composite layering--Part I.

Restoring an anterior tooth has always been a challenge, regarding the shade matching, the choice of colors, opacities, translucencies of our composites and the final anatomical outcome. This article proposes a new method for color matching and a clinical stratification using a simple and reproducible procedure for anterior restorations. The physical and optical characteristics of enamel and dentine will be studied and applied to our dental materials that we are using to restore anterior teeth.

[Amalgam, composite and compomer: microbiological study]. / Amalgames, composites et compomères. Etude microbiologique comparative.

Restorative materials have different consequences on the periodontium. The surface of these materials may influence gingival health and cause in some instances gingival inflammation. The purpose of this study was to investigate and compare, in a healthy periodontium, intracrevicular plaque bacteria (Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythensis and Treponema denticola), at day 0 and at 6 months, around subgingivally located amalgam, composite and compomer fillings. All the tests were negative (less than 0.1% of the sum of 103 cells), since none of the investigated pathogens were detected. It has been concluded that the material used does not have direct effect on the bacteria species developed around the restorations at this short time period.

Effect of different modes of light curing and resin composites on microleakage of Class II restorations--Part II.

INTRODUCTION: To reduce the polymerization shrinkage of the composite resins and after the introduction of the "slow and gradual polymerization" by GORACCI et al. in 1992, many light curing units (LCU) presented the "soft-start polymerization" in addition to the classical high light intensity mode. This study investigated whether this slow and gradual polymerization has the ability of reducing the marginal debonding, by minimizing the internal stress of the composite, knowing that rare are the studies which compared this mode of polymerization. MATERIAL AND METHODS: One hundred twenty Class II cavities were prepared at the mesial and the distal side of human extracted premolars. The teeth were randomly divided into four groups (n = 15). In each tooth the mesial Class II cavities were restored with the micro-hybrid resin composite Filtek Z250 (3M ESPE) and the distal Class II cavities were restored with the nano-filled resin composite Filtek Supreme (3M ESPE). The light curing unit used in this study was a conventional quartz tungsten halogen (QTH) curing light, the QHL 75 (Dentsply) modified by adding a regulating electronic device, controlled by a special software that gives 4 different modes of polymerization as follows: Group A: Standard polymerization: Exposure for 20 seconds at 700 mW/cm2, this group was used as control. Group B: Modified pulse-delay polymerization: Exposure for 2 seconds at 700 mW/cm2, 5 seconds at 0 mW/cm2, then 20 seconds at 700mW/cm2. Group C: Modified ramp polymerization: Exposure for 20 seconds with a slow rise of the intensity to reach the 700 mW/cm2 then 20 seconds at 700 mW/cm2. Group D: Slow and Gradual polymerization: Exposure for 4 minutes with a slow rise of the intensity to reach 700 mW/cm2. The teeth were stored in water at 37 degrees C for 48 hours, then finished and subjected to thermocycling (3000 cycles between 5 degrees C and 55 degrees C). All the teeth were immersed in 2% methylene blue solution for 12 hours at 37 degrees C, sectioned, and evaluated at the gingival margins. Data were statistically analyzed by two-way analysis of variance followed by Tukey HSD multiple comparisons. RESULTS: The main effect for the type of composites (p = 0.682), and the interaction effect (p = 0.678) did not reach statistical significance. There was a statistically significant main effect for the type of polymerization used (p = 0.014). Post-hoc comparisons using the Tukey HSD test indicated that the mean score for the Group A (M = 2.40, SD = 1.102) was significantly different from the group D (M = 1.30, SD = 1.393, p = 0.010). The group D did not differ significantly from group B (M = 1.63, SD = 1.351, p = 0.767), and group C (M = 1.60, SD = 1.404, p = 0.819). There was a difference between the group A (M = 2.40, SD = 1.102), group B (M = 1.63, SD = 1.351) and group C (M = 1.60, SD = 1.404). However, when the Tukey HSD was used, no statistically significant differences between Group A, B and C were found (p = 0.122 and p = 0.098). CONCLUSIONS: There was a statistically significant difference in microleakage between the "slow and gradual polymerization" and the standard polymerization, however no significant differences were found when using the nano-filled or the micro-hybrid composite materials cured with different polymerization regimens.

Effect of different modes of light curing and resin composites on microleakage of Class II restorations.

INTRODUCTION: In an attempt to reduce polymerization shrinkage of composites, some light curing units (LCU) presented "soft-start polymerization" in addition to the classical high light intensity mode. This study investigated whether those soft-start polymerization modes delivered by those LCUs are suitable to minimize the internal stress by increasing the time available for the flow of the material and decreasing the marginal debonding. MATERIAL AND METHODS: One hundred twenty Class II cavities were prepared at the mesial and the distal side of human extracted premolars. The teeth were randomly divided into four groups (n = 15). In each tooth the mesial Class II cavities were restored with the micro-hybrid resin composite Filtek Z250 (3M ESPE) and the distal Class II cavities were restored with the nano-filled resin composite Filtek Supreme (3M ESPE). The light curing unit used in this study was a conventional quartz tungsten halogen (QTH) curing light, the QHL 75 (Dentsply) modified by adding a regulating electronic device, controlled by a special software that enabled us to have 4 different modes of polymerization as follows: Group A: Standard polymerization: Exposure for 20 seconds at 700 mW/cm2, this group was used as control. Group B: Step polymerization: Exposure for 10 seconds at 100 mW/cm2 then 20 seconds at 700 mW/cm2. Group C: Pulse polymerization: Exposure for 20 cycles, each cycle consists in: 1 second at 700 mW/cm2 then 0.25 second at 0 mW/cm2. Group D: Ramp polymerization: Exposure for 10 seconds with a slow rise of the intensity to reach 700 mW/cm2 then 20 seconds at 700 mW/cm2. The teeth were stored in water at 37 degrees C for 48 hours, then finished and subjected to thermocycling (3000 cycles between 5 degrees C and 55 degrees C). All the teeth were immersed in 2% methylene blue solution for 12 hours at 37 degrees C, sectioned, and evaluated at the gingival margins. Data were statistically analyzed by two-way analysis of variance followed by Tukey HSD multiple comparisons. RESULTS: The main effect for the type of restoration (p = 0.185), and the interaction effect (p = 0.640) did not reach statistical significance. There was not a statistically significant main effect for the type of polymerization used (p = 0.082). There was a difference between the group A (M = 2.40, SD = 1.102), and group C (M = 1.67, SD = 1.348). However, when the Tukey HSD test was used, no statistically significant differences between group A and group C were found (p = 0.103). CONCLUSIONS: There were no statistically significant differences in microleakage between the different soft-start polymerization modes tested, even between the nano-filled and micro-hybrid composite materials cured with different polymerization regimens.