The effect of oral antiseptics on the corrosion of nickel-titanium (NiTi) alloys with various coating was investigated. Uncoated, titanium nitride-coated and rhodium-coated NiTi archwires (0.020 × 0.020″) were tested in interaction with artificial saliva pH 4.8 and oral antiseptics based on hyaluronic acid (Gengigel), chlorhexidine (Curasept) and essential oils in alcohol base (Listerine). The dynamics of nickel and titanium ions release were recorded during 28 days. Springback ratio and modulus of resilience were assessed by three-point bending test. The results showed that corrosion of NiTi is related to type of antiseptic mouth rinse and coating formulations. Exposure to an artificial saliva and antiseptics tend to reduce flexibility and resilience of NiTi archwires. The influence of the media is more significant than the influence of the type of the alloys coating. The largest release of nickel ions is in the first 3 days. Antiseptics do not cause further deterioration of the elastic properties in uncoated NiTi compared to saliva. As a result of exposure of nitrified NiTi wires in Listerine, there is bigger release of nickel ions, decrease in elastic properties and lower force delivery in unload. Listerine tends to reduce elastic properties of rhodium-coated wires also. In conclusion, except for Listerine, changes of mechanical characteristics induced by antiseptics are small and would not have a clinically important impact. Generally, Curasept would be the most suitable option.

Hypodontia or tooth agenesis is a condition at which the patient is missing one or more teeth due to a failure of those teeth to develop. This is not only an aesthetic, but also a functional deficiency. The incidence of congenitally missing teeth depends on etiological factors that affect tooth development, as well as which dentition is concerned, sex or race and geographic distribution. The tooth agenesis is mostly seen in teeth that are formed last in a given class (lateral incisors, second premolars and third molars). The aim of this study was to calculate the prevalence of congenitally missing teeth in population of FYROM and, through a review of the literature, to compare these results to other populations in the world.For this purpose a retrospective, transversal and cross-sectional study was made, where dental history and anamnesis of 8160 patients (3671 males and 4489 females) were examined, as well as their panoramic radiographs. The patients were 8-18 years old. The data was statistically analyzed with programme Statistica 7.0. The prevalence of hypodontia population of FYROM was 7.52%. Most commonly congenitally missing tooth in patients with hypodontia was mandibular second premolar (35.5% left and 34.53% right). Tooth agenesis predominated in females and in ethnic Albanian population, without significance.

Dental treatment introduces titanium-and nickel-containing biomaterials (implants, crowns, bridges and orthodontic appliances) which can induce a late hypersensitivity reaction. 1 A nickel allergy occurs more frequently than allergies to other metals altogether. 2 Due to its high biocompatibility, titanium was previously considered to have no allergic potential; however, titanium can erode when it co-exists with other metals or is exposed to fluoride ions in the acidic environment, such as in the oral cavity. 3,4 The aims of this study were to assess the prevalence of the allergic sensitization to titanium and nickel in patients undergoing orthodontic treatment with fixed appliances containing titanium and nickel and to evaluate whether subjects experiencing hypersensitivity have an altered sense of smell and taste. 2 | MATERIAL S AND ME THODS A total of 250 subjects undergoing orthodontic treatment in three orthodontic offices in Croatia were invited to participate and 245 accepted. Assuming a prevalence of hypersensitivity of 15%-20% (95% confidence intervals 10%-25%) and precision of 5%, the estimated sample size was calculated to be 196-246. The inclusion criterion

The aims of this study were: (a) to determine if the presence of probiotic bacteria in an aging medium, that is, artificial saliva in this study, has relevant effects on the surface roughness and the chemical composition of two main alloys used in dentistry (NiTi and stainless steel [SS]) and (b) in the case of NiTi, if these effects are influenced by the coating of the alloy (rhodium and titanium nitride). Atomic force microscopy and Raman spectroscopy were used to study the surface morphology and identify metal oxides formed on the surface of the alloys. Experiments demonstrated that the probiotic bacteria Lactobacillus reuteri can induce processes that alter some features of the surface such as roughness and chemical composition. The effect is dependent on the type of alloy and coating. The bacteria increased roughness in the case of uncoated NiTi more than saliva alone (pH = 4.8). Probiotic bacteria tend to decrease the corrosive influence of saliva on NiTi when the alloy is coated with rhodium or titanium nitride and this effect was also evidenced on SS. Raman spectroscopy confirmed that only SS samples are prone to oxidation processes, predominantly associated with exposure to saliva rather than probiotic bacteria.

The aim of this study was to evaluate the influence of the acidity of saliva on changes to the surface roughness, friction and microhardness of NiTi alloys with various coatings. Three types of commercially available NiTi archwires: uncoated, rhodium coated and nitrified (dimension 0.508×0.508 mm, 10 cm long) were immersed in 10 mL of artificial saliva with the pH ranging from 4.8 to 6.6 for a period of 28 d. Surface roughness, friction and microhardness were analyzed and compared to the unexposed as-received wires. These mechanical properties were influenced by the wire coating with a moderate-to-high effect size (p£0.005; h 2 =0.132-0.309). The uncoated wire had a lower maximum roughness depth after exposure to pH 6.6 and 5.5 than the unexposed wire (p=0.026; h 2 =0.346). The friction was significantly increased only in the rhodium-coated NiTi at pH 4.8 compared to the lower acidities and the unexposed wire (p=0.005; h 2 =0.437). No correlation was found between pH, surface roughness, friction and microhardness, respectively. The coating of a NiTi alloy has a greater impact on the mechanical properties than the acidity does. A rhodium coating makes the alloy harder, induces a rougher surface and more friction. Nitrification does not alter the alloy as much. The relation between acidity and mechanical properties is not linear. A high acidity of 4.8 induces a high friction, but only in rhodium-coated NiTi. A lower acidity does not change the friction significantly.Cilj {tudije je bil ovrednotiti vpliv kislosti sline na spremembe povr{inske hrapavosti, trenja in mikrotrdote biokompatibilne NiTi zlitine z razli~nimi opla{~enji. Avtorji so za svoje preiskave uporabili tri vrste komercialno dosegljivih NiTi ortodontskih pritrjevalnih`ic: neopla{~eno, opla{~eno z rodijem in nitrificirano (dimenzij 0,508 mm × 0,508 mm, dol`ine 10 cm). @ice so 28 dni potapljali v 10 ml umetne sline s pH vrednostjo med 4,8 in 6,6. Nato so izvedli analize povr{inske hrapavosti, trenja in mikrotrdote v slino namo~enih`ic in jih primerjali z nenamo~enimi izhodnimi`icami. Na mehanske lastnosti je imelo opla{~enje`ic zmeren do znaten vpliv (p£0.005; h 2 =0,132-0,309). Neopla{~ena`ica je imela manj{o maksimalno globino hrapavosti po izpostavitvi pH 6,6 in 5,5 kot`ica, ki slini ni bila izpostavljena (p=0,026; h 2 =0,346). Trenje se je znatno pove~alo samo pri z rodijem opla{~eni NiTi`ici pri pH 4,8 v primerjavi z manj{imi kislostmi in pri s slino neizpostavljeni`ici (p=0,005; h 2 =0,437). Avtorji niso na{li nobene povezave med pH, povr{insko hrapavostjo, trenjem in mikrotrdoto. Opla{~enje NiTi zlitine ima ve~ji vpliv na mehanske lastnosti kot kislost. Opla{~enje z rodijem naredi zlitino tr{o, inducira bolj grobo povr{ino in pove~a trenje. Nitrifikacija bistveno ne spremeni zlitine. Zveza med kislostjo in mehanskimi lastnostmi ni linearna. Velika kislost 4,8 inducira trenje, vendar samo pri z rodijem opla{~enih NiTi`icah. Manj{a kislost pomembno ne spremeni trenja.