Marie-France Bertrand

Scanning Electron Microscopy Analysis of Experimental Bone Hacking Trauma

The authors report on their macro- and microscopy study of bone lesions made by a sharp force instrument (a single blade knife), and a sharp-blunt instrument classified as a chopping weapon (a hatchet). The aim of this work was to attempt to identify the instrument by analyzing the general class characteristics of the cuts. Each weapon was used on human bones. The results indicate that macroscopic analysis is more problematic. The microscopic analysis assessed that characteristics examined were effective in distinguishing sharp from sharp-blunt injury to the bone. The microscope facilitates analysis unachievable with macroscopic methods, some three-dimensional characteristics not visible to the naked eye being clearly defined with its use. Emphasis has been placed on the value of SEM as an anthropologists tool in bone lesion injuries.

In vitro action of Bordeaux red wine on the microhardness of human dental enamel

Several studies have demonstrated that the regular and large consumption of wine is associated with increased risk of tooth erosion. Here, the effect of Bordeaux red wine on enamel was estimated by measuring changes in its Vickers microhardness. Thirty premolars were used; microhardness tests were performed on buccal areas before and after 10, 30, 90 and 120 s immersion in the wine (pH=3.9). Enamel surfaces were also observed by scanning electron microscopy. No statistically significant difference was found between the mean Vickers microhardness obtained at t=0 and 90 s, but slight signs of enamel demineralisation were observed with the scanning electron microscope. It appears that wine has no disastrous effect on the microhardness of dental enamel when the two are in contact for less than 90 s. When the exposure is for at least 120 s, it may become harmful, as the decrease in the microhardness of enamel was then significant (P<0.05).

Morpho-structural Aspects of Er:YAG-Prepared Class V Cavities

OBJECTIVE The aim of this study was to evaluate the ability of an Er:YAG laser (2960nm) to prepare class V cavities as compared with rotary instruments. MATERIALS AND METHODS Twenty-six freshly extracted human molars were selected and randomly distributed in two groups. Non standardized class V cavities were prepared using (group 1) a diamond bur for enamel, plus a tungsten bur for dentin with water irrigation and (group 2) an Er:YAG laser (output parameters, enamel: 1000 mJ, 12Hz, dentin: 500 mJ, 20Hz) with a continuous flow of water. RESULTS The SEM examination revealed characteristic micro-irregularities of the lased samples as compared with the conventional prepared cavities: group 1, the walls of the cavities were slightly curved and a smear layer plus muds covered peripheric walls as well as the depth of the cavity; rare dentinal tubules were opened; linear and circular surface irregularities were observed on the dentin; and group 2, the walls of the cavities were irregular, jagged; photo-ablation creates a real cleavage of hydroxyapatite prisms with respect to the enamel prism pathway; an homogeneous dentin with opened dentinal tubules covered the depth of the cavities; intertubular dentin is selectively more ablated than Er-YAG the peritubular dentin. CONCLUSIONS Jagged outline as well as opened dentinal tubules are the main characteristics of the Er-YAG prepared class V cavities. Further investigations (ulstrastructural, histochemical properties of the lased dentin, resistance to traction of bonded resins) should be conducted.

Removal of Thermafil root canal filling material.

The aim of this study was to evaluate if removal of Thermafil plastic carriers and reestablishment of working length were possible in single rooted teeth filled with the Thermafil system. Twenty freshly extracted maxillary central incisors were prepared and filled with #30 Thermafil plastic obturators according to manufacturers recommendations. Teeth were divided in two groups: Group I: 10 teeth were retreated using dimethylformamide as a solvent. Group II: 10 teeth were retreated using chloroform as a solvent. Removal of filling material was performed manually using K files and H files alternately between carrier and dentinal walls. The average time needed to remove the plastic carrier was 7 min for group I and approximately 6 1/2 min for group II. No deformation of the plastic carrier was observed after removal from the canal. Removal of plastic carriers and measurement of the proper working length were easily performed using manual endodontic instruments. Chloroform greatly enhanced this procedure.

Shear Bond Strength of Self-Etching Adhesive Systems to Er:YAG Laser-Prepared Dentine with and without Pulpal Pressure Simulation

OBJECTIVE This study was conducted to study the role of pulpal pressure on the shear bond strength of composite resin bonded to Er:YAG laser-prepared or bur-prepared dentine surfaces using a self-etching adhesive system. MATERIALS AND METHODS The occlusal surfaces of 80 human third molars were ground flat to expose the dentine. The dentine was prepared using either a carbide bur or an Er:YAG laser at 350 mJ/pulse and 10 Hz (fluence 44.5 J/cm(2)). Clearfil SE Bond was then applied with or without pressure. Rods of composite resin were bonded to dentine surfaces and shear bond tests were carried out. RESULTS When the Clearfil SE Bond was used without pressure, the difference between the shear bond strength values of bur-prepared and laser-prepared dentine surfaces was significant. When the Clearfil SE Bond was used with pressure, the difference of shear bond strength values was not significant between the two types of surface preparation. CONCLUSION The absence of smear layer formation during the preparation of the dentine by the Er:YAG laser did not improve the adhesion values of self-etching adhesive systems.

Scanning electron microscopy analysis of experimental bone hacking trauma of the mandible.

The authors report on a macroscopic and microscopic study of human mandible bone lesions achieved by a single-blade knife and a hatchet. The aim of this work was to complete the previous data (scanning electron microscopy analysis of bone lesions made by a single-blade knife and a hatchet, on human femurs) and to compare the lesions of the femur with those of the mandible. The results indicate that the mandible is a more fragile bone, but the features observed on the mandible are quite similar to those previously observed on the femur. This work spells out the main scanning electron microscopy characteristics of sharp (bone cutting) and blunt (exerting a pressure on the bone) mechanisms on human bone. Weapon characteristics serve to explain all of these features.

Er:YAG Laser Cavity Preparation and Semi-Direct Composite Resin Restoration: A Microleakage Study

OBJECTIVE This study was performed to assess the microleakage of composite resin restorations bonded in Er:YAG laser-prepared cavities using a semi-direct technique, in comparison with diamond bur-prepared cavities. BACKGROUND DATA Previous in vitro studies assessed the performance of total-etch and self-etch adhesive systems by investigating the microleakage of direct composite resin restorations. MATERIALS AND METHODS Class V cavities were randomly prepared in buccal and lingual surfaces of 20 human molars using a diamond bur and an Er:YAG laser (fluence 50 J/cm2). Composite resin inlays were bonded using a self-curing adhesive system and a composite resin luting cement. Microleakage was assessed using a methylene blue dye penetration method. The length of dye penetration along the occlusal margin, the length of dye penetration along the cervical margin, and the total length of the interface were recorded in millimeters. The total length of infiltration and the ratio of infiltration were then calculated. RESULTS The ratio of dye infiltration was 0.20 +/- 0.22 for bur-prepared cavities and 0.27 +/- 0.30 for Er:YAG laser-prepared cavities, with no significant difference (Wilcoxon test, p = 0.77). CONCLUSION In terms of microleakage, our results supported the use of the Er:YAG laser to remove carious tissues and prepare cavities in clinical practice.

Comparison of macroscopic and microscopic (stereomicroscopy and scanning electron microscopy) features of bone lesions due to hatchet hacking trauma

This experimental study examined the lesions produced by a hatchet on human bones (tibiae). A total of 30 lesions were produced and examined macroscopically (naked eye) and by stereomicroscopy. 13 of them were also analyzed using scanning electron microscopy. The general shape of the lesion, both edges, both walls, the kerf floor and the extremities were described. The length and maximum width of the lesions were also recorded. The microscopic analysis of the lesions led to the description of a sharp-blunt mechanism. Specific criteria were identified (lateral pushing back, fragmentation of the upraising, fossa dug laterally to the edge and vertical striae) enabling the forensic expert to conclude that a hacking instrument was used. These criteria are easily identifiable using scanning electron microscopy, but can also be observed with stereomicroscopy. Overall, lateral pushing back and vertical striae visible using stereomicroscopy and scanning electron microscopy signal the use of a hacking tool.

Inter- and Intra-Operator Reliability of Facial and Dental Measurements Using 3D-Stereophotogrammetry.

OBJECTIVES The goal of this study was to assess the reproducibility of an innovative method for facial analysis with three-dimensional-stereophotogrammetry (3D-spg). METHODS Twelve subjects with no obvious malocclusion participated in this study. For each of them, four photographs were acquired using the LifeViz(TM) , an absolute calibration 3D-spg system. The facial reconstructions were analyzed with the DermaPix(TM) image management software. Two different operators recorded distances between landmarks and each operator repeated the measurements after one week. The intra- and inter-examiner reproducibilities were assessed using the Intraclass Correlation Coefficient (ICC). RESULTS This study showed reproducible intra and inter-examiners results for facial measurements (ICC comprised between 0.732 and 0.976) except for measurements that involve the inner part of the dental corridor (ICC comprised between 0.598 and 0.914). CONCLUSION The measurements recorded by 3D-LifeViz(TM) system are accurate and reliable for research and clinical use. Moreover, it is simple and inexpensive compared with other 3D methods (laser scanner, 3D Computed Tomography, and 3D Cone Beam CT). CLINICAL SIGNIFICANCE The inter- and intra-operator reliability of the LifeViz(TM) 3D-spg method was demonstrated. The LifeViz(TM) 3D-spg method might be a useful method to accomplish indirect 3D measurements that are relevant to dental and facial diagnosis. (J Esthet Restor Dent, 2016).

Esthetic rehabilitation of the smile with partial laminate veneers in an older adult

Bonded partial ceramic veneer is an interesting alternative to full buccal restoration in terms of tissue economy. However, its usage is restricted to patients with a low smile line (such as the elderly) due to the visibility of the tooth/restoration limit which is a key to the therapeutic decision.