In-vitro Investigations on Suitability of Light-cured Resins for Interocclusal Splints

OBJECTIVE: It was the aim of the present study to investigate the material properties of different resins and their suitability for the fabrication of occlusal and intermaxillary splints. MATERIAL AND METHOD: We subjected auto-polymerized resins (Palapress, Orthocryl, Steady-Resin M) and light-polymerized resins (Acrylight, Primosplint, Triad TranSheet Colorless and Pink) to investigation. The Targis Power light oven was used to polymerize the light-cured resins. After the auto-polymerized resins had been mixed by hand and filled into the forms, they were polymerized for 15 minutes in a high-pressure polymerization machine (Palamat) at 2 bar. The parameters examined were flexural strength, water adsorption, and polymerization shrinkage. Tests carried out according to DIN EN ISO 1567 served to determine flexural strength, flexural modulus, and water adsorption. Polymerization shrinkage was determined via the buoyancy test. RESULTS: The resins' flexural strength ranged from 60 to 101 MPa. Flexural moduli lay between 1.3 and 5.3 GPa. The water adsorption noted in light-cured resins amounted to 2.1-4.6 mass percent. Palapress and Steady-Resin displayed the lowest water adsorption with 2.0 mass percent. The light-polymerized resins revealed significantly less shrinkage (p < 0.05) than the autopolymerized resins tested in this study. CONCLUSION: Our results demonstrate that the light-cured resins-with the exception of Acrylight -easily match and even exceed the material properties of the cold-polymerized resins regarding flexural strength, flexural modulus, water adsorption and polymerization shrinkage. The light-cured resins examined thus seem suitable for use as splint material.     

Treatment of noncomminuted zygomatic fractures with percutaneous screw reduction and fixation

The standard treatment modality of zygomatic fractures is open reduction and rigid fixation of the fractured segments. Although most of the zygomatic fractures deserve this attentive surgical manipulation to prevent late residual asymmetry, minimally depressed noncomminuted zygomatic fractures can be reduced and fixed percutaneously. Percutaneous intervention causes minimal scarring and morbidity than open techniques and it is possible to align fragments precisely by using high-quality three-dimensional computed tomography (3-D CT) imaging. Six patients with noncomminuted fractures of the zygomaticomaxillary skeleton were evaluated with plain radiographs of facial bones, axial, coronal and 3-D CT. Reduction of the displaced bone segments were achieved by traction of percutaneously applied screw. Either reduced segments were not fixated at all or one of the two new fixation techniques, described in detail in the article, were used for stabilization of reduced segments. In all patients, accurate reduction was obtained. None of the patients showed any recurrent displacement or infection during the follow-up period of six months. The screws were removed in the clinical settings without difficulty. Although percutaneous reduction and external fixation of noncomminuted zygomatic fractures has limited indications, it has its own advantages over open techniques. This method is a less invasive technique and can be performed without any problem in selected cases. Our technique is not suitable for complex zygomatic and periorbital fractures.     

The effect of antibacterial compounds on glucosyltransferase activity from Streptococcus mutans.

The effect of several plaque-inhibiting and/or antibacterial compounds on glucan synthesis by glucosyltransferases purified from the cariogenic bacterium Streptococcus mutans strain 6715 was determined. Drugs were tested at concentrations of 0.2–2.0 mM at pH values between 6.5 and 6.8. Bis-biguanides, quaternary ammonium salts and aliphatic amines were found to be potent inhibitors of enzyme activity. The strong anionic detergent, sodium lauryl sulphate and the phenol derivative, hexylresorcinol, also caused significant inhibition. Basic nitrogen compounds lacking a functional hydrophobic group were less inhibitory or stimulated enzyme activity. Both electrostatic and hydrophobic interactions appear to be occurring between the cationic test-agents and the glucosyltransferases, with hydrophobic interaction being more important for enzyme inhibition.     

Assessment of correlation between computerized tomography values of the bone, and maximum torque and resonance frequency values at dental implant placement

summary The aim of this study was to determine the bone density in the designated implant sites using computerized tomography (CT), the fastening torque values of dental implants, and the implant stability values using resonance frequency analysis. Further aim was to evaluate a possible correlation between bone density, fastening torque and implant stability. Eighty‐five patients were treated with 158 Brånemark System implants. CT machine was used for preoperative evaluation of the jawbone for each patient, and bone densities were recorded in Hounsfield units (HU). The fastening torque values of all implants were recorded with the OsseoCare equipment. Implant stability measurements were performed with the Osstell machine. The average bone density and fastening torque values were 751·4 ± 256 HU and 39·7 ± 7 Ncm for 158 implants. The average primary implant stability was 73·2 ± 6 ISQ for seventy implants. Strong correlations were observed between the bone density, fastening torque and implant stability values of Brånemark System TiUnite MKIII implants at implant placement (P < 0·001). These results strengthen the hypothesis that it may be possible to predict and quantify initial implant stability and bone quality from pre‐surgical CT diagnosis.     

The development of plate osteosynthesis for the treatment of fractures of the mandibular body - a literature review.

PURPOSE: Today plate and screw osteosynthesis of mandibular fractures is a standard procedure in routine clinical practice. In this review, the breakthroughs and drawbacks of the development of this important aspect of maxillofacial surgery are followed-up. METHODS: Medline search of relevant English and German literature. RESULTS: In 1886, Carl Hansmann was the first who applied steel screws and plates. Until today the material, the types of plates and applications have been continually improved. Over the last two decades miniplate osteosynthesis has induced a revolution in mandibular fracture treatment. The modern systems provide better handling, higher stability and less pressure on the bone. CONCLUSION: Modern miniplates have great advantages, like the intra-oral approach and the easy adaptability. In addition, it is no longer necessary to expose bone as extensively.     

Selection of restorative materials in permanent teeth in general dental practice

In this study, we recorded the type of restoration and the materials used in 24,429 restorations in permanent teeth by 243 Norwegian clinicians in general practice. Demographic information included patient's gender and age, and clinician's gender, years since graduation, and practice setting (private or salaried). The overall recorded use of restorative materials in permanent teeth shows that 32% are amalgams, just over 40% composites, and about 25% glass ionomer type materials. Three percent are "other" materials. A marked shift away from amalgam restorations is noted both in the clinician's estimated use during the last 2 decades and by comparing the present use of materials with that in failed restorations. Tooth-colored materials are more commonly used in adolescents, especially glass ionomer materials, and in female patients. In patients < or = 18 years, amalgam is used in 25% of all restorations. The use of amalgam is similar in private practice and in public health service practice, but private practitioners use more composites and salaried dentists more glass ionomers. The clinician's gender does not have any effect on the selection of restorative materials. The change from amalgam to tooth-colored material is particularly noticeable for Class I and Class V restorations. Amalgam is the predominant material in 2- and 3-surface Class II restorations.     

NO-cGMP signaling molecules in cells of the rat molar dentin-pulp complex

By the formation of cyclic guanosine 3',5'-monophosphate (cGMP), nitric oxide (NO)-sensitive enzyme-soluble guanylate cyclase (sGC) plays a receptor role for NO within the NO-cGMP signaling cascade, which is involved in vasodilatation and neurotransmission. The hypothesis that NO-cGMP signaling molecules modulate cells of the dentin-pulp complex was investigated in rat molars by histochemical, immunohistochemical, immuno-ultrastructural, and organ bath techniques. NO synthase (NOS) I-III, the sGC alpha(2)-subunit/beta(1)-subunit, and cGMP were detected in odontoblasts and blood vessels. NOS I, sGC alpha(2), and cGMP were identified in nerve fibers. Treatment of rat molars with the NO donor NONOate (10(-5) M) increased cGMP staining intensities in blood vessels and odontoblasts, while NO synthase inhibitor L-NAME (10(-4) M) attenuated intensity of the reaction products for cGMP, suggesting an effect of endogenous NO on sGC. These correlations of patterns and alterations of cGMP staining intensities after treatment with the NO donor or NO inhibitor might represent an NO-sGC-cGMP signaling-dependent modulation of odontoblasts, blood vessels, and nerve fibers in the dentin-pulp complex.