Synthesis and biocompatibility of an experimental glass ionomer cement prepared by a non-hydrolytic sol-gel method

The aims of this study were to demonstrate the synthesis of an experimental glass ionomer cement (GIC) by the non-hydrolytic sol-gel method and to evaluate its biocompatibility in comparison to a conventional glass ionomer cement (Vidrion R). Four polyethylene tubes containing the tested cements were implanted in the dorsal region of 15 rats, as follows: GI - experimental GIC and GII - conventional GIC. The external tube walls was considered the control group (CG). The rats were sacrificed 7, 21 and 42 days after implant placement for histopathological analysis. A four-point (I-IV) scoring system was used to graduate the inflammatory reaction. Regarding the experimental GIC sintherization, thermogravimetric and x-ray diffraction analysis demonstrated vitreous material formation at 110oC by the sol-gel method. For biocompatibility test, results showed a moderate chronic inflammatory reaction for GI (III), severe for GII (IV) and mild for CG (II) at 7 days. After 21 days, GI presented a mild reaction (II); GII, moderate (III) and CG, mild (II). At 42 days, GI showed a mild/absent inflammatory reaction (II to I), similar to GII (II to I). CG presented absence of chronic inflammatory reaction (I). It was concluded that the experimental GIC presented mild/absent tissue reaction after 42 days, being biocompatible when tested in the connective tissue of rats.     

Cervical impalement injury

Impacted injuries of the head and neck are uncommon. Associated injuries can be present and can be a serious problem. We present an unusual clinical case and discuss the management of this complex injury. Head and neck injuries deserve special attention because of their enormous functional and esthetic significance. Contusion, abrasion, retained foreign bodies, laceration, and avulsion are some of the most frequent injuries. Impalement injuries are not so common. These lesions combine aspects of blunt and penetrating trauma and usually result from penetration by a large, rigid, blunt-tipped object that traverses a certain body area in a through-and-through fashion and often remains in situ at the time of presentation. There have been many case reports describing these injuries in the trunk and extremities; however, cases of head and neck impalement are still lacking in number. A case of an unusual cervical impalement is presented, together with a discussion of the management of this complex injury.     

Microleakage at sealant/enamel interface of primary teeth: effect of Er:YAG laser ablation of pits and fissures

PURPOSE: The objective of this study was to assess microleakage at sealant/enamel interface after treatment of primary teeth occlusal surfaces with 3 etching techniques. METHODS: Thirty sound primary molars were randomly assigned to 3 groups (N = 10): (1) group I = acid etching for 30 seconds; (2) group II = Er:YAG laser (120 mJ; 4 Hz) plus acid-etching; and (3) group III = Er:YAG laser (120 mJ; 4 Hz). Pits and fissures were sealed with a resin-based sealant (Fluroshield, Dentsply/Caulk). Teeth were isolated, thermocycled, immersed in a 0.2% rhodamine B solution for 24 hours, and serially sectioned. Cuts were analyzed for leakage using an optical microscope connected to a video camera. The images were digitized, and a specific software (Axion Vision) assessed microleakage quantitatively (millimeters). The sealant extension on buccal/lingual cusp heights was measured separately, and the percentage of dye penetration along enamel/sealant interface, in relation to the sealant extension, was calculated. Means of dye penetration were: (1) group I = 2%(+/- 3.75); (2) group II = 2%(+/- 3.38); and (3) group III = 4%(+/- 6.26). Data were submitted to ANOVA and Tukey test. RESULTS: A statistically significant difference (P < .05) was observed between the nonetched lased specimens (group III) and those in the other groups. No significant difference (P >.05) was found between the acid-etched and lased/acid-etched groups (I and II). Fissures prepared with Er:YAG laser alone showed the highest degree of microleakage. All specimens exhibted some degree of leakage. CONCLUSIONS: Laser irradiation did not eliminate the need for acid etching enamel prior to the placement of a pit-and-fissure sealant. The ablation of pits and fissures with an Er:YAG laser device did not yield significantly better marginal sealing at primary enamel/sealant interface, compared to conventional acid etching.     

Cytotoxicity of denture base acrylic resins: a literature review

Acrylic resins are widely used in the fabrication of denture bases and have been shown to be cytotoxic as a result of substances that leach from the resin. The primary eluate is residual monomer. Numerous reports suggest that residual monomer may be responsible for mucosal irritation and sensitization of tissues. This information is important, not only to assess the biologic effects of such materials, but also to enable a comparison among the different polymerization methods, thus assisting the clinician in selecting a material with minimal cytotoxicity. This article reviews the literature published from 1973 to 2000, selected by use of a Medline search, associated with cytotoxic effects usually ascribed to acrylic denture base materials.     

Comparative study of the effects of two bleaching agents on oral microbiota

This study evaluated the in vivo effects of bleaching agents containing 10% carbamide peroxide (Platinum/Colgate) or 7.5% hydrogen peroxide (Day White 2Z/Discus Dental) on mutans Streptococcus during dental bleaching. The products were applied on 30 volunteers who needed dental bleaching. In each volunteer, one of the two bleaching agents was used on both dental arches one hour a day for three weeks. Analysis of the bacterial counts was made by collecting saliva before (baseline values), during (7 and 21 days) bleaching treatments and 14 days posttreatment. The Friedman non-parametric analysis (alpha=0.05) found no differences in microorganism counts at different times for each group for both agents (p>0.05). The Mann Whitney nonparametric test (alpha=0.05) showed no differences in micro-organism counts for both agents (p>0.05). Different bleaching agents did not change the oral cavity mutans Streptococcus counts.     

Retention force of T-bar clasps for titanium and cobalt-chromium removable partial dentures

The objective of this study was to evaluate the retention force of T-bar clasps made from commercially pure titanium (CP Ti) and cobalt-chromium (Co-Cr) alloy by the insertion/removal test simulating 5 years use. Thirty-six frameworks were cast from CP Ti (n=18) and Co-Cr alloy (n=18) with identical prefabricated patterns on refractory casts from a distal extension mandibular hemi-arch segment. The castings were made on a vacuum-pressure machine, under vacuum and argon atmosphere. Each group was subdivided in three, corresponding to 0.25 mm, 0.50 mm and 0.75 mm undercuts, respectively. No polishing procedures were performed to ensure uniformity. The specimens were subjected to an insertion/removal test and data was analyzed statistically to compare CP Ti and Co-Cr alloy in the same undercut (Student's t-test for independent samples) and each material in different undercuts (one-way ANOVA) (p=0.05). Comparisons between materials revealed significant differences (p=0.017) only for the 0.50-mm undercut. No significant differences (p>0.05) were found when comparing the same material for the undercuts. It may be concluded that for different undercuts, both Co-Cr alloy and CP Ti had no significant differences for T-bar clasps; CP Ti showed the lowest retention force values when compared to Co-Cr alloy in each undercut, but with significant difference only for the 0.50-mm undercut; and both materials maintained the retentive capacity during the simulation test.     

Surgical planning for resection of an ameloblastoma and reconstruction of the mandible using a selective laser sintering 3D biomodel

Ameloblastoma is a benign locally aggressive infiltrative odontogenic lesion. It is characterized by slow growth and painless swelling. The treatment for ameloblastoma varies from curettage to en bloc resection, and the reported recurrence rates after treatment are high; the safety margin of resection is important to avoid recurrence. Advances in technology brought about great benefits in dentistry; a new generation of computed tomography scanners and 3-dimensional images enhance the surgical planning and management of maxillofacial tumors. The development of new prototyping systems provides accurate 3D biomodels on which surgery can be simulated, especially in cases of ameloblastoma, in which the safety margin is important for treatment success. A case of mandibular follicular ameloblastoma is reported where a 3D biomodel was used before and during surgery.