Ozone Treatment of Initial Lesions

Karijes je bolest tvrdoga zubnog tkiva za koji je da bi nastao potrebno nekoliko čimebnika od kojih su najvažniji domaćin (zub), uzročnik (mikroorganizmi), utjecaj okoline i vrijeme. Razvojem tehnologije uvedene su nove suvremene metode dijagnostike karijesnih lezija. Među njima važno mjesto zauzima laserska fluorescencija. Usporedno s razvojem dijagnostike klasično “Blackovo načelo” preparacije kaviteta u terapiji karijesnih lezija ispunom zamijenila je ponajprije koncepcija “minimalno invazivne atraumatske stomatologije”, a nedavno je u svrhu terapije karijesa uporabljen i ozon. Baktericidni i dezinfekcijski učinak ozona omogućio je novu koncepciju “bezbolne terapije” karijesnih lezija.Caries is a disease of hard dental tissue caused by the following factors: host (the tooth), cause (microorganisms), environmental influence and time. With improved technology new, contemporary, methods of diagnosing caries lesions have been introduced, one of the most important being laser fluorescence. Parallel with the development of new diagnostic methods, the classical “Black’s principle” of cavity preparation, was replaced, first with “minimally invasive non-traumatic dentistry”, and more recently with “ozone therapy”. Bactericide and disinfective properties of ozone enabled a new concept of “painless therapy” in treatment of caries lesions

The Amount of Bennett-Movement According to Occlusion

Bennett-kretnja je jedan od biomehaničkih čimbenika okluzijskog programa, jer smjer i iznos kretnje utječe na visinu kvržica i položaj fisurnog sustava zuba. Individualno se razlikuje samo ISS (engl. immediate side shift) - početni dio Bennett-kretnje. Iz literature nije potpuno jasan međusobni utjecaj organizacije okluzije i iznosa ISS-a. Stoga je svrha rada bila izmjeriti iznos ISS-a kod ispitanika s okluzijom »vođenom očnjakom« i okluzijom tipa »sloboda u centriku«, te utvrditi postoji li povezanost između iznosa ISS-a, tipa okluzije, te spola i dobi ispitanika. Ispitivani uzorak sastojao se od 988 ispitanika: 68 s očnjakom vođenom okluzijom i 30 ispitanika s okluzijom sloboda u centriku. Registracija Bennett-kretnje izvršena je napravom »Quick Analyzer «, a mjerenje iznosa ISS-a pomičnom mjerkom. Nije nađena razlika iznosa ISS-a u odnosu na dob i spol, kako u ukupnom uzorku tako i unutar pojedinih tipova okluzije. Srednja vrijednost ISS iznosila je 0,79 mm u skupini ispitanika s očnjakom vođenom okluzijom i 0,82 mm u skupini s okluzijom sloboda u centriku.Bennett movement is one of the biomechanical factors of the occlusal program, because the direction and size of the shift influence the height o f the nodules and position o f the tooth fissure system. Individual differences only refer to the immediate lateral shift (ISS), i.e. the initial part o f the Bennett movement. The interrelationship between the occlusion organization and ISS size has not yet been fully clarified in literature reports. Therefore, the aim o f this study was to measure the ISS size in subjects with canine occlusion and centric occlusion, and to determine the possible correlation among the size o f ISS, type o f occlusion, and subject\u27s sex and age. The study sample consisted o f 98 subjects, 68 with canine occlusion and 30 with centric occlusion. Bennett movement was registered employing a Quick Analyzer, whereas the size o f ISS was measured with a sliding caliper.No difference was found in the size o f ISS relative to sex and age, either in the total sample or within particular types o f occlusion. The mean ISS was 0.9 mm and 0.82 mm in the groups o f subjects with canine and centric occlusion, respectively

The Release of Metal Ions in the Gingival Fluid of Prosthodontic Patients

Korozija nadomjestka i njegovo trošenje u funkciji zatvaraju krug koji uzrokuje oštećenje nadomjestka i štetne reakcije na okolnome tkivu ili čak na udaljenim organima. Svrha ovoga istraživanja bila je identificirati ione Au, Pt, Ag i Pd u sulkusnoj tekućini (ST) u fiksnoprotetskih pacijenata i odrediti masu iona u dobivenom uzorku. U istraživanju je sudjelovalo 20 ispitanika, od toga 15 je imalo fiksne nadomjestke i isti stupanj higijene, a 5 nije imalo nikakav protetski rad te su poslužili kao kontrolna skupina. Nadomjesci su bili izrađenih od slitina Au − Pt, Au − Pt, Ag − Pd i Ni − Cr te pričvršćeni u ustima: - od 1-14 dana, i 3-8 godina. Uzorci su dobiveni ulaganjem adsorbcijskoga papirića (AP) u gingivni sulkus (GS) zuba nosača u vremenu od deset minuta. AP s uzorkom ST analizirani su s pomoću spektrometra masa s induciranom združenom plazmom (ICP-MS). Rezultati su statistički obrađeni programskim paketom SPSS, a upotrijebljena je deskriptivna statistika i korelacija uzoraka. U cijelome uzorku statistički se znatno povezane koncentracije Ag, Au i Pt, a koncentracija Pd ponaša se prema vlastitu uzorku. Raščlambom rezultata u kontrolnoj skupini nije utvrđena statistički znatna povezanost za iste međuodnose. U podskupini Ag-Pd slitine utvrđena je statistički znatna povezanost između koncentracija Ag, Au i Pd, a najizrazitija je veza između koncentracija Au i Pd. Postoji statistički znatna razlika u koncentraciji Pt između podskupina s novim radovima s najvišom vrijednosti u skupini slitina Au (P=0,023) u usporedbi s kontrolnom skupinom.Utvrđena je statistički znatna promjena vrijednosti Ag (P=0,011) i Pt (P=0,039) s padom vrijednosti obiju tih kovina u ispitanika sa starim protetskim radovima.Corrosion of prosthetic restorations and simultaneous wear during usage leads to damage of the restoration and harmful reactions on the surrounding tissues or even on distant organs. The aim of this study was to identify the ions Au, Pt, Ag and Pd in the gingival fluid of patients with fixed prosthetic appliances and to determine the mass of ions in the obtained sample . The study included 20 subjects: of which 15 had fixed prosthetic appliances and the same level of hygiene, and 5 without have any prosthetic appliances, who served as a control group. The prosthetic appliances were made from alloy compounds: Au - Pt, Au - Pt, Ag - Pd, Ni - Cr, fixed in the mouths: from 1-14 days, and 3-8 years. Samples were obtained by placing adsorbent paper (AP) in the gingival sulcus (GS) of the abutment tooth for a period of ten minutes. AP with samples gingival fluid (ST) were analysed by means of a mass spectrometer with fused plasma (ICP-MS). The results were statistically analysed by the programme packet SPSS, with descriptive statistics and correlation of samples. In the whole sample statistically significant correlation was found for the concentrations of Ag, Au and Pt, while the concentration of Pd was characteristic for each sample. Analysis of the results in the control group did not reveal statistically significant correlation for the same inter-relations. In the sub-group Ag-Pd alloys statistically significant correlation was established between the concentrations of Ag, Au and Pd, and the most marked correlation found was between the concentrations of Au and Pd. Statistically significant differences were determined in the concentrations of Pt between the subgroups with new appliances, with the highest value in the group of Au alloy (P=0.023) in comparison with the control group. Statistically significant changes were determined in the values of Ag (P=0.011) and Pt (P=0.039), with a fall in the values of both metals in subjects with older prosthetic appliances

Investigation of Contact Allergies to Component and Auxiliary Prosthetic Materials

Kontaktna alergija je odgođena reakcija preosjetljivosti u kojoj se lokalizirana lezija kože ili sluznice javlja zbog opetovanoga doticaja s alergenom. Od fiksnog ili mobilnoga protetskog rada u usnoj šupljini nastaju korozijski procesi na površini nadomjestka te otpuštanja iona koji, kao hapteni, mogu pokrenuti alergijsku reakciju. Svrha ovoga istraživanja bila je epikutanim alergološkim testom ispitati pojavnost alergije na gradivne i pomoćne protetske materijale u pacijenta s lihen ruber planusom, stomatitisom i stomatopirozom. U istraživanju su sudjelovala 32 pacijenta s fiksnim i/ili mobilnim nadomjestkom i 7 pacijenata s jednom od navedenih dijagnoza bez nadomjestaka. Ispitivanje je provedeno standardnom tehnikom (patch testom) na 13 alergena. Rezultati istraživanja pokazuju veću vjerojatnost na pozitivan patch test u osoba s navedenim bolestima i s nadomjestkom u usporedbi s ispitanicima bez nadomjestaka (P = 0,62). Pričvršćenjem fiksnog ili postavljanjem mobilnoga nadomjestka raste vjerojatnost da će se simptomi pogoršati (P = 0,019), a pogotovo ako se radi o nadomjescima od Co-Cr-Mo slitine. Povećanjem broja članova fiksnih nadomjestaka, ili pak postojanjem mobilnih nadomjestaka u objema čeljustima, raste i vjerojatnost pozitivnoga rezultata patch testa na kobaltni klorid (P = 0,05). Lichen ruber planus povećava vjerojatnost na pozitivan patch test u najvećem broju slučajeva (P = 0,05). Najviše pozitivnih rezultata bilo je na alergene nikla, kobalta i kroma (svaki 17,95%), a negativan nalaz dobiven je kod dibutilftalata i HH smjese. Stomatopiroza povećava vjerojatnost da ispitanik ima pozitivan rezultat testiranja na krom (P = 0,019). U žena je pojava pozitivnoga patch testa veća na sve alergene (P = 0,05) osim na epoksidne smole, kod kojih je manja nego u muških ispitanika (P = 0,036). Zbog sve češće kontaktne alergije u populaciji potrebno je provesti potanka ispitivanja protetskih materijala prije nego što ih se uvede u kliničku praksu, a u pacijenata s atopijskom anamnezom alergološka testiranja i imunološke testove prije protetske sanacije.Contact allergy is a delayed reaction to sensitivity in which a localised lesion of the skin or mucous membrane occurs as a result of contact with an allergen. The fitting of a fixed, or placement of a mobile, prosthetic appliance in the oral cavity causes corrosive processes to occur on the surface of the restoration and the release of ions which, as haptens, can induce allergic reaction. The aim of this investigation was to examine the occurrence of allergies to component and auxiliary prosthetic materials by patch test in patients with lichen ruber planus, stomatitis and stomatopyrosis. Thirtytwo patients with fixed and/or mobile restorations and seven patients with one of the above diagnoses without a restoration, participated in the investigation. Testing was carried out by standard technique (patch test) with 13 allergens. The results of the investigation indicate the greater probability of a positive patch test in subjects with the aforementioned diseases and with a restoration, in relation to subjects without a restoration (P = 0.62). The probability of symptoms worsening increased with the insertion/ fitting of a fixed or placement of a mobile restoration (P = 0.019). This was particularly so in the case of restorations made of Co-Cr-Mo alloy. With the increase in the number of units of fixed restorations, or the presence of mobile restorations in both jaws, the probability of a positive patch test to cobalt chloride also increased (P = 0.05). Lichen ruber planus increased the probability of a positive patch test in the majority of cases (P = 0.05). The greatest number of positive results were for the allergens nickel, cobalt and chrome (each 17.95%) and a negative finding was obtained for dibutylphthalate and HH mix. Stomatopyrosis increased the probability that the subject would have a positive result for chrome (P = 0.019). The occurrence of a positive patch test was greater in women for all allergens (P = 0.05), apart from epoxy resin, where it was less than in the male subjects (P=0.036). Because of the greater incidence of contact allergies in the population a more detailed investigation of prosthetic materials is needed prior to their introduction into clinical practice. In the case of patients with atopic history allergological testing and immunological tests should be performed prior to prosthetic treatment

Promjene na površini cakline i dentina nakon dva različita postupka izbjeljivanja

Bleaching agents have effect on chemical/physical and morphological structure of enamel and dentin that must be taken into account when this therapy is used. The aim of this in vitro study was to evaluate the effects of two bleaching agents containing a high concentration of hydrogen peroxide for professional use on human enamel and dentin surface and to evaluate the potential remineralizing effect of amorphous calcium phosphate gel (ACP). Twenty-five human third molars were divided into two groups and dissected in half and both surfaces were bleached with either ZOOM2 or Opalescence BOOST for 3×15 minutes. Vickers microhardness of enamel and dentin was measured before, after the bleaching treatment, and after treatment with artificial saliva and ACP gel or 2-week storage in deionized water. Surface microstructure was evaluated using scanning electron microscopy. The mixed model ANOVA and Wilcoxon Rank Sum test were used. Both bleaching agents showed significant reduction in surface microhardness (p<0.001 for both BOOST and ZOOM2 application). ZOOM2, which had a lower pH value showed greater decrease in surface microhardness (p=0.005) compared to BOOST. Post-treatment with artificial saliva and ACP showed significant increase in surface microhardness (p<0.001). After the bleaching procedure, enamel and dentin surface microstructure showed mild or slight alterations with no loss of superficial structure. In conclusion, both bleaching agents resulted in reduction in surface enamel and dentin microhardness. Treatment with ACP led to increase in surface microhardness, improved surface roughness, and enhanced remineralization of the hard dental tissues.Sredstva za izbjeljivanje zubi mogu utjecati na kemijska i fizička svojstva, kao i na mikromorfološku strukturu cakline i dentina, na što se mora pripaziti prilikom provođenja ovakve terapije. Svrha ovoga istraživanja je bila procijeniti učinak dvaju sredstava za izbjeljivanje koja sadrže visoke koncentracije vodikovog peroksida na površinu cakline i dentina, kao i potencijalni remineralizacijski učinak gela amorfnog kalcijevog fosfata (ACP). Dvadesetpet ljudskih trećih molara podijeljeno je u dvije skupine, raspiljeno napola i obje površine su zatim tretirane gelom ZOOM2 ili Opalescence BOOST u trajanju od 3×15 minuta. Vickersova mikrotvrdoća cakline i dentina izmjerena je neposredno prije, nakon postupka izbjeljivanja i nakon tretmana umjetnom slinom i gelom ACP-a kroz 2 tjedna ili nakon držanja u deioniziranoj vodi kroz isto razdoblje. Površinske promjene su promatrane SEM mikroskopom. Korišteni su Mixed model ANOVA i Wilcoxon Rank Sum test. Oba gela za izbjeljivanje pokazala su značajno smanjenje u površinskoj mikrotvrdoći cakline i dentina (p<0,001 za BOOST i ZOOM2). ZOOM2 koji je imao nižu pH vrijednost je pokazao veće smanjenje površinske mikrotvrdoće (p=0,005) u odnosu na BOOST. Naknadna obrada umjetnom slinom i pripravkom ACP-a pokazla je značajno povećanje površinske mikrotvrdoće (p<0,001). Nakon izbjeljivanja površine cakline i dentina su pokazale blage ili umjerene promjene bez gubitka površinske strukture. U zaključku, oba sredstva za izbjeljivanje dovela su do smanjenja površinske mikrotvrdoće. Tretman ACP-om nakon izbjeljivanja doveo je do povišenja mikrotvrdoće i smanjio površinska oštećenja poboljšavši remineralizaciju tvrdih zubnih tkiva

Efficacy of Ozone on Microorganisms in the Tooth Root Canal

The aim of this study was to examine the effect of ozone gas on the remaining bacteria after chemomechanical instrumentation of tooth root canal. The study was carried out at the Department of Endodontics and Restorative dentistry, School of Dental Medicine, University of Zagreb. A total of 37 tooth root canals from 23 teeth (10 incisors, 2 canines, 8 premolars and 3 molars) with a diagnosis of chronic apical periodontitis (17 untreated teeth and 6 retreatments) from 20 adult patients (11 females and 9 male) were selected. Endodontic samples consisted of 74 swabs from 37 canals. The first root canal swab was taken following a completed chemomechanical instrumentation by a sterile paper point after rinsing the root canal with a sterile saline solution. The canal was dried and treated with ozone gas for 40 seconds (HealOzone, Kavo, Germany). After the ozone treatment the canal was rinsed with a sterile saline solution a second swab was taken. The swabs were stored in transport media until cultivation. Microbiological identification was performed by macromorphological, micromorphological, commercial biochemical test microbiological analysis and bacteria count. A significant decrease in the number of bacteria (p<0.001) was found after the ozone treatment: the total number of bacteria was 82%, 67% of aerobic and 93% of anaerobic bacteria. When analysing individually, a significant decrease was found for Streptococcus mitis and Propionibacterium acnes (p<0.05). The results of this study shows the efficacy of ozone on the bacterial count reduction in the root canal treatment

Rizični čimbenici povezani s nastankom crnih obojenja na zubima

The aim of the study was to show whether there is any influence of food, drink or drug intake on the formation of tooth discoloration. A total of 500 patients aged 15-25 years were examined to take part in the study. Of these, 60 patients were selected and divided into two groups of 30 patients each. Group 1 included patients with blackpigmentation on vestibular/oral tooth surfaces. Group 2 included patients without discoloration (control). Data were recorded in a questionnaire. Atomic absorption spectrometry was used to determine elements in discoloration samples. The Caries Risk Test (CRT) buffer was used to assess buffer capacity of saliva, while CRT bacteria were used to determine the presence of Streptococcus mutans and Lactobacillusspp. Statistically significant betweengroup differences were found for the intake of collard greens and beets (p<0.05), but not for other vegetables. As for drink consumption, patients with pigmentation reported less wine intake (p<0.05) than those without pigmentation. There was no diff erence according to drug intake between patients with and without pigmentation. Patients with pigmentation were older, smoked and had lower saliva pH with lower presence of Streptococcus mutansthan those without pigmentation (p<0.05). In tooth discoloration samples, there were traces of calcium, magnesium, iron, copper and zinc. The appearance of tooth discoloration is influenced by many factors, among which diet and saliva seem to be very important. Our study showed that patients with black pigmentation used to take more beets, while patients without pigmentation were taking more collard greens and red wine.Svrha ovoga istraživanja bila je dokazati postoji li utjecaj konzumacije hrane, pića ili lijekova na nastanak i pojavnost crnihobojenja na zubima. Ukupno 500 pacijenata u dobi od 15-25 godina pregledano je i uključeno u ovu studiju. Od ukupnog broja, 60 pacijenata je odabrano i podijeljeno u dvije skupine od 30 pacijenata. Skupina 1. je uključivala pacijente s crnim obojenjima na vestibularnim/oralnim plohama zuba. Skupina 2. je uključivala pacijente bez crnih obojenja (kontrola). Podaci su prikupljeni korištenjem posebno pripremljenog upitnika. Atomska apsorpcijska spektroskopija je primijenjena za odre-đivanje elemenata koji uzrokuju i nalaze se u sastavu crnih obojenja zubi. Test rizika karijesa (CRT) korišten je za određivanje puferskog kapaciteta sline, dok je CRT test bakterija korišten za određivanje prisutnosti bakterija Streptococcus mutansi Lactobacillusspp. u slini. Statistički značajna razlika između skupina utvrđena je za kelj i ciklu (p<0,05), no ne i za ostalo povrće. Što se tiče konzumacije pića, pacijenti s crnim obojenjima na zubima su pili manje vina (p<0,05) u odnosu na pacijente bez obojenja. Nije zabilježena razlika u konzumaciji lijekova između pacijenata s crnim obojenjima i bez njih. Pacijenti s obojenjima su bili stariji, pušili su i imali su niži pH sline te nižu razinu bakterije Streptococcus mutansnego oni bez obojenja (p<0,05). U diskoloriranim uzorcima pronađeni su tragovi kalcija, magnezija, željeza, bakra i cinka. Na nastanak obojenja zuba utječe niz čimbenika, među kojima se prehrana i slina smatraju jednim od važnijih. Ovo istraživanje je pokazalo da pacijenti s crnim obojenjima na zubima konzumiraju više cikle, dok pacijenti bez obojenja konzumiraju više kelja i crnog vina

Endodontic Treatment of Upper Central Incisors

U radu je prikazano endodontsko liječenje gornjih trajnih sjekutića koji su zbog nepravilna postupka bili dugotrajno bezuspješno liječeni. Pravilnom endodontskom terapijom liječenje je završeno u sedam dana. Tijekom tri mjeseca nakon endodontske terapije zubi su bez simptoma.This paper describes endodontic treatment of first central upper incisors which have been unsuccessfully treated for a long period as a consequence of inadequate procedure. The root canals of the problematic teeth were obturated for seven days, by correct proper endodontic treatment. Three months after root canal obturation, the teeth were without symptoms

Endodontic Morphology of Permanent Teeth

Uspješnost liječenja zubne pulpe uvjetovana je dobrim poznavanjem endodontskoga prostora i njegovih raznolikosti. Najčešći uzrok neuspjeha jest što se ne nađu korijenski kanali, jedan ili više njih, ili pak njihove anatomske osobitosti. Premda svi zubi imaju više-manje određenu građu endodonta, ipak terapeut mora biti spreman i na moguće varijacije. Najrjeđe varijabilnosti u građi endodontskoga prostora pokazuju gornji sjekutići i očnjak. Oni gotovo u 100% slučajeva imaju jedan korijen i korijenski kanal, a u praksi je zabilježeno tek nekoliko slučajeva gornjih sjekutića sa dva korijena ili korijenska kanala. Donji sjekutići i očnjaci najčešće imaju korijen i korijenski kanal, no moguće ih je naći dva, pa čak i tri. Pretkutnjaci i kutnjaci često variraju u građi endodontskoga prostora. Stomatolog mora biti spreman na postojanje dvaju ili triju korijenskih kanala kod pretkutnjaka, te čak četiriju, pet ili više korijenskih kanala kod kutnjaka. Raspored kanala također može biti vrlo raznolik, pa tako u bilo kojem od korijena tih zuba može postojati više korijenskih kanala. Osobitost u građi gornjih i donjih kutnjaka jest da je moguć i tzv. C- -oblik endodonta, a nastaje kao posljedica sraštanja korijena tih zuba. Primjeri iz prakse danomice potvrđuju vrlo složenu morfologiju endodontskoga prostora zuba i zato stomatolog mora biti spreman na te raznolikosti kako bi postigao što bolji uspjeh u endodontskoj terapiji.The prerequisite for successful treatment of dental pulp is a good knowledge of endodontic space and its diversities. The most common reason of not succeeding is failing to notice one or more root canals or their anatomic particularities. Maxillary incisors and canines show least variability in the structure of endodontic morphology. In almost 100% of cases they have one root and one root canal, and in practice only a few cases of maxillary incisors with two roots or root canals have been noted. In mandibular incisors and canine, along with the most often incidence of one, the incidence of two and even three roots and root canals is possible. Premolars and molars often vary in the structure of their endodontic morphology. The stomatologist must be prepared for the existence of two or even three root canals in the premolar and even four, five or more roots canals in the molar. The configuration of canals can also vary a lot and there may exist more roots canals in any of the root of these teeth. The particularity in the structure of maxillary and mandibular molars is the possible occurrence of the socalled C-shaped canals which result as a consequence of the growing into one of the roots in these teeth. Examples from daily practice demonstrate the very complex endodontic morphology of teeth and, therefore, the stomatologist must be prepared for these diversities, in order to achieve the best possible endodontic treatment

The Prevalence of Lateral Incisor Hypodontia and Canine Impaction in Croatian Population

The study investigates the prevalence of second incisor hypodontia and canine impaction in Croatia. The study of incisor hypodontia encompassed 568 examinees (229 boys, 339 girls) aged 6–22 (X = 11.2, SD = 2.8) while for canine impaction, a subsample of 170 examinees older than 13 years was formed (68 boys and 102 girls). The participants were non-selected ambulatory patients of the Dental Clinic Zagreb and the School of Dental Medicine, University of Zagreb who voluntarily participated in the study. Investigated anomalies were registered from panoramic x-rays and dental records and a tooth was diagnosed as congenitally missing when no crown mineralization could be identified on dental panoramic tomogram and no evidence of extraction was found. For each examinee, the final dental panoramic tomogram evaluation was performed at the age of 13 years. Missing lateral incisors are found in 14 out of 568 participants, indicating the prevalence of 2.46%. With the M : F ratio 1 : 6, sex-specific prevalence are 0.87% and 3.54% for males and females respectively. The prevalence of missing lateral incisor is 1.76% in maxilla and 0.70% in mandible. The sex specific pattern as well as overall prevalence of lateral incisor hypodontia is within the range reported in other studies. On the other hand, the findings of bilaterally missing lateral incisor in six out of 14 examinees (or in 42.86% of hypodontia) is certainly the specificity of the here investigated population. The additional peculiarity is the finding of the bilateral aplasia of mandible canines registered in one child. Canine impaction is found in 8 participants of the present study (4.71%) and in all cases it was placed in maxilla. No sex specific differences in prevalence of impactions are found. In one case (or in 12.5%) a canine impaction is found bilaterally. Missing lateral incisors and canine impaction in the same examinee was not found in this study