docElasticke¬ moduly v ortodoncii Elastic modules in orthodontics
download 
Stížnost Transkript
Elasticke¬ moduly v ortodoncii Elastic modules in orthodontics
Cyan Magenta Yellow Black ORTODONCIE Odborna praÂce rocÏnõÂk 23 cÏ. 2. 2014 Elasticke moduly v ortodoncii Elastic modules in orthodontics MUDr. Alena FormaÂnkovaÂ, MUDr. Magdalena Kot'ovaÂ, Ph. D. OddeÏlenõ ortodoncie a rozsÏteÏpovyÂch vad Stomatologicke kliniky 3. LF UK FNKV Praha Department of Orthodontics and Cleft Defects, Clinic of Stomatology, 3rd Medical Faculty of Charles University, University Hospital KraÂlovske Vinohrady, Prague Souhrn JednõÂm ze zaÂkladnõÂch prÏedpokladuÊ uÂspeÏsÏne ortodonticke leÂcÏby je kontrolovane puÊsobenõ ortodontickyÂch sil. CõÂlem praÂce je analyÂza silovyÂch charakteristik beÏzÏneÏ pouzÏÂõvanyÂch ortodontickyÂch elastickyÂch rÏetõÂzkuÊ. Byl zkoumaÂn vliv ruÊznyÂch parametruÊ (tvar rÏetõÂzku, vyÂrobce, prestretching) na produkci sil v zaÂvislosti na cÏase. Byl vytvorÏen soubor 18 typuÊ beÏzÏneÏ pouzÏÂõvanyÂch elastickyÂch rÏetõÂzkuÊ od 7 ruÊznyÂch vyÂrobcuÊ. RÏetõÂzky byly rozdeÏleny do 3 skupin, podle deÂlky mezicÏlaÂnku. NaÂsledneÏ byly protazÏeny o 50 % a 100 % jejich puÊvodnõ deÂlky a byl meÏrÏen pokles sõÂly v cÏase ve zvolenyÂch cÏasovyÂch intervalech ve standardizovanyÂch podmõÂnkaÂch. Studie prokaÂzala, zÏe sõÂly produkovane elastickyÂmi rÏetõÂzky jsou velke a znacÏneÏ se lisÏÂõ dle vyÂrobce. BeÏhem prvnõÂch 24 hodin dochaÂzõ k vyÂrazneÂmu poklesu sil, pote sõÂly klesajõ uzÏ jen velmi pomalu. Vliv prestretchingu na snõÂzÏenõ vyÂchozõÂch sil byl patrny pouze u naÂsledneÂho protazÏenõ rÏetõÂzku o 50 %, prÏi 100 % protazÏenõ tento vliv prokaÂzaÂn nebyl (Ortodoncie, 23, cÏ. 2, s. 97-108). Abstract Controlled delivery of orthodontic forces is one of the preconditions for successful orthodontic treatment. The work aims to give the analysis of common orthodontic elastic chains force characteristics. The study focuses on the effect of individual parameters (chain shape, manufacturer, prestretching) on time-related delivery of forces. Our sample included 18 types of common elastic chains produced by 7 manufacturers. The chains were subdivided into 3 groups according to the length of their connecting link. Subsequently, the chains were elongated by 50% and 100% of their original length, and the decrease of force over a period of time was measured at given intervals under standardized conditions. The study proves that forces delivered by elastic chains are big, and that products of individual manufacturers are different. Within the first 24 hours forces decrease significantly, afterwards they lessen very slowly. The effect of prestretching on the decrease of initial forces was evident only in subsequent stretching of a chain by 50%. In case of 100% stretching the effect was not proved (Ortodoncie, 23, No. 2, p. 97-108). KlõÂcÏova slova: elasticky rÏetõÂzek, pokles sõÂly, mezicÏlaÂnek, prestretching Key Words: elastic chain, force degeneration, connecting link, prestretching UÂvod Introduction Elasticke rÏetõÂzky se staly neodmyslitelnou, trvalou a beÏzÏneÏ pouzÏõÂvanou soucÏaÂstõ nasÏich ortodontickyÂch praxõÂ. Elasticke rÏetõÂzky a ligatury jsou vyrobeny z polyurethanuÊ. Je pro neÏ charakteristickeÂ, zÏe vykazujõ elasticitu kaucÏuku. To znamenaÂ, zÏe v jednom ze svyÂch prÏechodowww.orthodont-cz.cz e-mail: [email protected] Cyan Magenta Yellow - Elastic chains have become an inherent and integral part of orthodontic practices. Elastic chains and ligatures are made of polyurethane. They are as elastic as natural rubber; after substantial deformation with a relatively light force they rapidly return to their original di97 Cyan Magenta Yellow Black rocÏnõÂk 23 cÏ. 2. 2014 Odborna praÂce vyÂch stavuÊ - stavu kaucÏukoviteÂm, je lze pomeÏrneÏ malou silou vratneÏ deformovat azÏ o stovky procent. Nesmõ se ale prÏekrocÏit mez elasticity, to by jizÏ vratna deformace elastickeÂho rÏetõÂzku nebyla mozÏna [1, 2]. ChovaÂnõ elastickyÂch rÏetõÂzkuÊ a zejmeÂna pokles sil, ktery nastane po jejich natazÏenõÂ, je oblastõÂ, na kterou byla zameÏrÏena pozornost v mnoha studiõÂch. Byly zaznamenaÂny signifikantnõ rozdõÂly v poklesu sil mezi rÏetõÂzky jednotlivyÂch znacÏek. DuÊvody, procÏ by tomu tak mohlo byÂt, spocÏõÂvajõ ve variabiliteÏ prÏidanyÂch aditiv, ktera se inkorporujõ do vyÂsledne struktury elastomeru, a take v morfologicke variabiliteÏ rÏetõÂzku. Mnoho studiõ poklesu sil produkovanyÂch rÏetõÂzky bylo provaÂdeÏno in vitro. DuÊvoduÊ, procÏ studie degradace sil probõÂhajõ veÏtsÏinou in vitro a ne in vivo, je võÂce a lze je shrnout do konstatovaÂnõÂ, zÏe standardizace podmõÂnek pro experiment v dutineÏ uÂstnõ je velmi obtõÂzÏnaÂ, ne-li nemozÏnaÂ. SÏõÂrÏe testovacõÂch podmõÂnek prÏi experimentech in vitro byla velika (vlhkost, pH, protazÏenõ vzorkuÊ ...). I prÏes vsÏechna tato rozdõÂlna kriteria lze rÏõÂci, zÏe dosÏlo k vyÂrazne shodeÏ zaÂveÏruÊ ruÊznyÂch studiõ v tom, zÏe beÏhem prvnõÂch 24 hodin dojde k strmeÂmu poklesu sil v rozsahu o 4060 % vyÂchozõ hodnoty sõÂly. NaÂsledny pokles beÏhem dalsÏõÂch dvou azÏ trÏõ tyÂdnuÊ je jizÏ vyÂrazneÏ pomalejsÏõ [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]. JednõÂm z faktoruÊ, ktery ovlivnÏuje produkci sil rÏetõÂzkuÊ, je fenomeÂn ªstaÂrnutõª rÏetõÂzkuÊ in vivo. Hlavnõ faktor odlisÏujõÂcõ prostrÏedõ dutiny uÂstnõ je prÏõÂtomnost oraÂlnõ floÂry a jejõÂch vedlejsÏõÂch produktuÊ a rovneÏzÏ akumulace zubnõÂho plaku. V studiõÂch in vitro se v soucÏasne dobeÏ nedajõ tyto podmõÂnky simulovat. Je oveÏrÏeno, zÏe vystavenõ ruÊznyÂch materiaÂluÊ podmõÂnkaÂm dutiny uÂstnõ muÊzÏe vyvolat podstatne zmeÏny v jejich strukturÏe a povrchovyÂch vlastnostech. CõÂlem teÂto praÂce, provedene in vitro, je analyÂza silovyÂch charakteristik beÏzÏneÏ pouzÏõÂvanyÂch ortodontickyÂch elastickyÂch rÏetõÂzkuÊ. Chceme odpoveÏdeÏt na otaÂzky, zda jsou vyÂchozõ hodnoty sil produkovanyÂch rÏetõÂzky stejneÂ, nebo sõÂly klesajõ ruÊznou rychlostõÂ, zda ovlivnõ prÏõÂtomnost a deÂlka mezicÏlaÂnku sõÂly produkovane rÏetõÂzky a zda bude mõÂt provedenõ prestretchingu (¹prÏednatazÏenõª) vliv na uÂrovenÏ vyÂchozõÂch sil a jejich pokles ve srovnaÂnõ s rÏetõÂzky, u kteryÂch prestretching proveden nebyl. MateriaÂl Nejprve byl analyzovaÂn a meÏrÏen uÂbytek sõÂly v cÏase po natazÏenõ u 18 typuÊ ortodontickyÂch rÏetõÂzkuÊ od 7 ruÊznyÂch vyÂrobcuÊ: Dentaurum, Ispringen, Germany; American Orthodontics, Sheboygan, WIS, USA; G&H Wire Company, Franklin, IN, USA; Ormco, Glendora, CA, USA; Highland Metals Inc., San Jose, CA, USA; Ortho-Care /UK/ Ltd, Saltaire, UK; 3M/Unitek, Monrovia, CA, USA. 98 ORTODONCIE mensions, i.e. the deformation is reversible. However, the elastic limit must not be exceeded [1, 2]. Elastic chains behaviour, especially decrease of forces occurring after they are stretched, has been the focus of many studies. There were reported significant differences in force decrease between chains by individual producers. The reasons may be seen in various additives incorporated into the resulting structure of elastomer, and in morphological variability of chains. The majority of studies focusing on force degradation have been conducted in vitro. There are several reasons for the research to be done mostly in vitro, not in vivo, the primary one being that to achieve standard conditions for the experiment in oral cavity is very demanding, if not impossible. There is a number of parameters examined during experiments in vitro (humidity, pH, stretching of samples, etc.). Most studies agree in that within the first 24 hours there is significant amount of force degradation - 40-60%. Subsequent force degradation, i.e. during the following two or three weeks, is significantly slower [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]. One of the factors affecting delivery of chain force is the ¹ageingª of chains in vivo. Differences in the mouth cavity conditions are mainly due to oral flora and its side effects, as well as plaque accumulation. This artificial environment can not be exactly duplicated in studies in vitro. It has been proved that the exposure of different materials to mouth cavity environment can provoke significant changes in their structure and surface characteristics. The aim of the presented study, performed in vitro, is the analysis of force characteristics of common orthodontic chains. We strive to answer the following questions: Are the initial forces delivered by chains identical or do they decrease at different rate? Do the presence and length of the connecting link affect forces induced by chains? Does prestretching affect the level of the initial force and its degradation in comparison with chains without prestretching? Material First we analyzed and measured force decrease over a period of time after stretching in 18 types of orthodontic chains by 7 manufacturers: Dentaurum, Inspringen, Germany; American Orthodontics, Sheboygan, WIS, USA; G&H Wire Company, Franklin, IN, USA; Ormco, Glendora, CA, USA; Highland Metals Inc., San Jose, CA, USA; Ortho-Care /UK/ Ltd., Saltaire, UK; 3M/Unitek, Monrovia, CA, USA. The sample of 18 chains was subdivided according to whether a chain has a connecting link or not, and according to the connecting link length. As the length of connecting links and description given by individual manufacturers are different and do not correspond to www.orthodont-cz.cz e-mail: [email protected] Cyan Magenta Yellow - Cyan Magenta Yellow Black ORTODONCIE Odborna praÂce Soubor 18 rÏetõÂzkuÊ byl rozdeÏlen podle toho, zda rÏetõÂzek meÏl cÏi nemeÏl mezicÏlaÂnek a daÂle podle deÂlky mezicÏlaÂnku. ProtozÏe deÂlka mezicÏlaÂnkuÊ a slovnõ oznacÏenõ rÏetõÂzkuÊ jednotlivyÂch vyÂrobcuÊ se lisÏõ a vzaÂjemneÏ si neodpovõÂdaÂ, byla stanovena hranice 0,9 mm, kterou se rÏõÂdilo zarÏazenõ rÏetõÂzku bud'do skupiny rÏetõÂzkuÊ s kraÂtkyÂm nebo s dlouhyÂm mezicÏlaÂnkem. Sedm rÏetõÂzkuÊ bylo zarÏazeno do skupiny rÏetõÂzkuÊ bez mezicÏlaÂnku: Dyna-Link Continuous (G&H), Plastic Chain Closed (AO), Memory Chain Closed (AO), Dura Chain Close Link (Ortho-Care), Power Chain Closed Space (Ormco), Alastik Chain CK Blue Met (3M/Unitek), Elasto Force Closed (Dentaurum). CÏtyrÏi rÏetõÂzky byly zarÏazeny do skupiny rÏetõÂzkuÊ s kraÂtkyÂm mezicÏlaÂnkem: Dyna-Link Short (G&H) - deÂlka mezicÏlaÂnku 0,2 mm, Chain Elastic Short (Highland Metals) - deÂlka mezicÏlaÂnku 0,2 mm, Plastic Chain Short (AO) - deÂlka mezicÏlaÂnku 0,3 mm, Power Chain Open Space (Ormco) - deÂlka mezicÏlaÂnku 0,5 mm. Sedm rÏetõÂzkuÊ bylo zarÏazeno do skupiny rÏetõÂzkuÊ s dlouhyÂm mezicÏlaÂnkem: Dyna-Link Long (G&H) - deÂlka mezicÏlaÂnku 0,9 mm, Plastic Chain Long (AO) - deÂlka mezicÏlaÂnku 0,9 mm, Elasto Force Connector (Dentaurum) deÂlka mezicÏlaÂnku 1 mm, Dura Chain Medium Link (Ortho-Care) - deÂlka mezicÏlaÂnku 1,2 mm, Power Chain Wide Space (Ormco) - deÂlka mezicÏlaÂnku 1,7 mm, Memory Chain Long (AO) - deÂlka mezicÏlaÂnku 1,8 mm, Dura Chain Wide Link (Ortho-Care) - deÂlka mezicÏlaÂnku 1,8 mm. DaÂle byla provedena analyÂza tvaru ocÏek u vsÏech rÏetõÂzkuÊ zahrnutyÂch do experimentu, protozÏe jednotlive rÏetõÂzky se mohou lisÏit i tvarem ocÏek. Bylo zjisÏteÏno, zÏe vsÏechna ocÏka u vsÏech rÏetõÂzkuÊ majõ kruhovy tvar. Take byl porovnaÂn tvar pruÊrÏezu rÏetõÂzku. VsÏechny zkoumane rÏetõÂzky majõ obdeÂlnõÂkovy tvar pruÊrÏezu. DalsÏõÂm uÂkolem bylo zhodnotit vliv prestretchingu elastickeÂho rÏetõÂzku na hodnotu vyÂchozõ sõÂly a jejõ naÂsledny pokles v cÏase. V tomto experimentu byly pouzÏity trÏi rÏetõÂzky od jednoho vyÂrobce: Power Chain Closed Space, Power Chain Open Space a Power Chain Wide Space, vsÏechny od firmy Ormco. Metodika K prvnõÂmu experimentu bylo od kazÏdeÂho rÏetõÂzku zhotoveno 20 vzorkuÊ v deÂlce 11 a puÊl ocÏek. Vzorky byly oddeÏleny bez natazÏenõ pomocõ skalpelu. Na jedne straneÏ vzorku byla ponechaÂna polovina ocÏka, aby prÏi oddeÏlovaÂnõ skalpelem nedosÏlo k posÏkozenõ krajnõÂho ocÏka, ktere se v experimentu navleÂkalo na ocelovy trn urcÏeny k natazÏenõ rÏetõÂzku. Na druhe straneÏ vzorku bylo ponechaÂno ocÏko celeÂ. To pak slouzÏilo k meÏrÏenõ a do neÏj byl zasouvaÂn hrot silomeÏru. Vzorky byly rozdeÏleny do dvou skupin po 10 kusech v kazÏde skupineÏ. Bylo rozhodnuto, zÏe v prvnõ skupineÏ budou vzorky jednoraÂzoveÏ natazÏeny o 50 % jejich puÊvodnõ deÂlky a ve www.orthodont-cz.cz e-mail: [email protected] Cyan Magenta Yellow - rocÏnõÂk 23 cÏ. 2. 2014 each other, we set out the limit of 0.9 mm according to which a chain was classified as the one with short or long connecting link. Seven chains were in the group of chains without connecting link: Dyna-Link Continuous (G&H), Plastic Chain Closed (AO), Memory Chain Closed (AO), Dura Chain Close Link (Ortho-Care), Power Chain Closed Space (Ormco), Alastik Chain CK Blue Met (3M/Unitek), Elasto Force Closed (Dentaurum). Four chains were in the group of chains with a short connecting link: Dyna-Link Short (G&H) - the connecting link length 0.2 mm; Chain Elastic Short (Highland Metals) - the connecting link length 0.2 mm; Plastic Chain Short (AO) - the connecting link length 0.3 mm; Power Chain Open Space (Ormco) - the connecting link length 0.5 mm. Seven chains were in the group of chains with a long connecting link: Dyna-Link Long (G&H) - the connecting link length 0.9 mm; Plastic Chain Long (AO) - the connecting link length 0.9 mm; Elasto Force Connector (Dentaurum) - the connecting link length 1 mm; Dura Chain Medium Link (Ortho-Care) - the connecting link length 1.2 mm; Power Chain Wide Space (Ormco) the connecting link length 1.7 mm; Memory Chain Long (AO) - the connecting link length 1.8 mm; Dura Chain Wide Link (Ortho-Care) - the connecting link length 1.8 mm. Individual chains may differ in a unit shape; therefore the shapes of units of all the chains included in the experiment were analyzed. In all chains the units were circular, and the crossection oblong. Further effects of prestretching on the amount of the initial force and its subsequent decrease over a period of time were evaluated. For this experiment three chains by the same manufacturer were used: Power Chain Closed Space, Power Chain Open Space, and Power Chain Wide Space by Ormco. Methods For the first experiment there were 20 samples of each chain, of 11.5 units. Samples were cut with a lancet. On one end of the sample a half of a unit was left in order that a lancet would not damage an outside unit that was attached to the steel pin for stretching. On the other side a whole unit was left, that was used for measurements a dynamometer was inserted into it. Samples were divided into two groups of 10. The samples in the first group were stretched by 50% of their initial length, in the second group by 100%. First, in each chain we measured the length of ten units before elongation. The length of each chain after stretching by 50%, and 100% was calculated. To stretch all samples, measurement plastic (PHS) plates were produced width of 3 mm. At the calculated distances corresponding to a given stretching, holes were pred99 Cyan Magenta Yellow Black rocÏnõÂk 23 cÏ. 2. 2014 Odborna praÂce druhe skupineÏ o 100 % puÊvodnõ deÂlky. Nejprve byla u kazÏdeÂho rÏetõÂzku zmeÏrÏena deÂlka deseti ocÏek v klidu prÏed natazÏenõÂm. Byla spocÏõÂtaÂna deÂlka kazÏdeÂho rÏetõÂzku prÏi protazÏenõ o 50 % jejich puÊvodnõ deÂlky a prÏi protazÏenõ o 100 % puÊvodnõ deÂlky. Pro standardnõ natazÏenõ vsÏech vzorkuÊ byly vyrobeny meÏrÏõÂcõ plastove desticÏky (materiaÂl PSH) tlousÏt'ky 3 mm. Ve vypocÏtenyÂch vzdaÂlenostech odpovõÂdajõÂcõÂch zvoleneÂmu natazÏenõ byly prÏedvrtaÂny otvory a do nich byly zafixovaÂny ocelove trny o pruÊmeÏru 1,1 mm pro uchycenõ vzorkuÊ. Prvnõ ocÏko rÏetõÂzku bylo navlecÏeno na jeden ocelovy trn, pomocõ peaÂnu byl rÏetõÂzek jednoraÂzoveÏ protazÏen do nastavene vzdaÂlenosti a desaÂte ocÏko rÏetõÂzku bylo navlecÏeno na druhy ocelovy trn. MeÏrÏenõ u vsÏech rÏetõÂzkuÊ probeÏhlo ve zvolenyÂch cÏasovyÂch intervalech: 0, 2, 8, 24 hodin, 7 dnuÊ a 21 dnuÊ. CelkoveÏ probeÏhlo 2160 meÏrÏenõÂ. Cely experiment probõÂhal in vitro za prÏesneÏ specifikovanyÂch podmõÂnek. RÏetõÂzky, po natazÏenõ na meÏrÏõÂcõÂch desticÏkaÂch, byly vlozÏeny do polyfunkcÏnõÂho inkubaÂtoru Cultura M, vyÂrobce ALMEDICA AG, Guglera1, 1735 Giffers, Switzerland. Po celou dobu experimentu byla zajisÏteÏna konstantnõ teplota 37°C, teplotnõ prÏesnost teplomeÏru je ± 1°C. Cely experiment probõÂhal za vlhka. Vlhkost prostrÏedõ zajisÏt'oval pruh gaÂzy vlhcÏeny kazÏdyÂch 12 hodin 20 ml vody pokojove teploty. K meÏrÏenõ sõÂly, kterou produkovaly natazÏene rÏetõÂzky v jednotlivyÂch cÏasovyÂch intervalech, byl pouzÏit rucÏnõ analogovy silomeÏr SHITO DGD-8 s meÏrÏõÂcõÂm rozsahem 0-600 gramuÊ s prÏesnostõ 2 %, vyÂrobce Huatest Electronic Co, Ltd, Shenzhen, China. MeÏrÏenõ bylo provedeno tak, zÏe hrot silomeÏru byl zasunut do poslednõÂho jedenaÂcteÂho ocÏka rÏetõÂzku. Hodnota sõÂly byla odecÏtena v okamzÏiku, kdy se desaÂte ocÏko rÏetõÂzku nedotyÂkalo oceloveÂho trnu a trn byl v okamzÏiku meÏrÏenõ uprostrÏed ocÏka (Obr. 1). Pro druhy experiment bylo zhotoveno 20 vzorkuÊ v deÂlce 11 a puÊl ocÏka ze vsÏech trÏõ rÏetõÂzkuÊ a byly rozdeÏleny do dvou skupin po 10 kusech v kazÏde skupineÏ. RÏetõÂzky byly opeÏt natazÏeny na meÏrÏõÂcõ desticÏku na vzdaÂlenost odpovõÂdajõÂcõ protazÏenõ o 50 a o 100 % puÊvodnõ deÂlky. PrÏed tõÂmto natazÏenõÂm bylo nejprve provedeno ªprÏednatazÏenõª rÏetõÂzkuÊ na 180 % puÊvodnõ deÂlky 5x po sobeÏ. Na meÏrÏõÂcõ desticÏku byla zakreslena linie odpovõÂdajõÂcõ 180 % vyÂchozõ deÂlky deseti ocÏek rÏetõÂzku. Krajnõ ocÏko bylo navlecÏeno na ocelovy trn. PeaÂnem byl zachycen konec rÏetõÂzku (jedenaÂcte ocÏko) a 5x po sobeÏ byl rÏetõÂzek natazÏen k vyznacÏene linii. Toto 5x opakovane ªprÏednatazÏenõª trvalo celkem 5 vterÏin. Pote byly rÏetõÂzky definitivneÏ umõÂsteÏny do pozic a vzdaÂlenostõ odpovõÂdajõÂcõÂch stanovenyÂm podmõÂnkaÂm experimentu. MeÏrÏenõ probõÂhalo podle stejneÂho protokolu jako u prvnõÂho experimentu. V druheÂm experimentu bylo provedeno 360 meÏrÏenõÂ. 100 ORTODONCIE rilled into which steel pins, the diameter of 1.1 mm, were inserted (they served for a sample attachment). The first unit of a chain was attached to one steel pin, the chain was stretched to the set distance with the help of a clamp, and the tenth unit of the chain was attached to the other steel pin. Measurements were performed at the given time intervals: 0, 2, 8, 24 hours, 7 days, and 21 days. There were 2160 measurements performed. The experiment was carried out in vitro under specific conditions. After stretching on measurement plates, the chains were put into polyfunctional incubator Cultura M, fy ALMEDICA AG, Guglera1, 1735 Giffers, Switzerland. During the experiment there was the constant temperature 37°C, the accuracy of a thermometer ± 1°C. The experiment was performed in a humid environment. The humidity was ensured with a band of gauze that was moistened every 12 hours with 20 ml of water of room temperature. To measure forces induced by stretched chains at individual intervals a manual analogue force gauge SHITO DGD-8 was used, the range of measurement 0 - 600 g, the accuracy of 2%, fy Huatest Electronic Co., Ltd., Shenzhen, China. The point of the force gauge was inserted into the last (eleventh) chain unit. The force was read at the moment when the tenth unit did not touch the steel pin, and the pin was in the middle of the unit (Fig. 1). For the second experiment 20 samples were prepared, the length of 11.5 units, of all the three chains, and they were divided into two groups of 10 samples each. Again, the chains were stretched on the measuring plate - elongated by 50% and by 100% of the initial length. Prior to that, ¹prestretchª to 180% of the initial length was carried out 5 times in a row. On the measure plate the line representing 180% of the original length of ten units was drawn. An outside unit was attached to the steel pin. The end of the chain (the eleventh unit) was held with a clamp, and the chain was 5 times stretched according to the line drawn. This prestretching Obr. 1. UkaÂzka meÏrÏenõ sõÂly silomeÏrem SHITO DGD-8 Fig. 1. Force measurement with SHITO DGD-8 force gauge www.orthodont-cz.cz e-mail: [email protected] Cyan Magenta Yellow - Cyan Magenta Yellow Black ORTODONCIE Odborna praÂce VsÏechna meÏrÏenõ byla statisticky zhodnocena. Nejprve byly hodnoty popsaÂny pomocõ popisne statistiky (aritmeticky pruÊmeÏr, mediaÂn, minimaÂlnõ a maximaÂlnõ hodnoty, smeÏrodatna odchylka). NaÂsledneÏ byly jednotlive soubory nameÏrÏenyÂch hodnot testovaÂny na normaÂlnõ rozlozÏenõÂ. Pokud meÏly hodnoty normaÂlnõ rozlozÏenõÂ, byly podrobeny parametrickyÂm testuÊm (Studentovy t-testy, paÂrove t-testy s Bonferroniho korekcõÂ), v opacÏneÂm prÏõÂpadeÏ byly podrobeny testuÊm neparametrickyÂm (FriedmanuÊv test, Wilcoxonovy testy s Bonferroniho korekcõÂ, Mann-Whitney U-testy). VyÂsledky byly zpracovaÂny do tabulek s vyznacÏenõÂm statisticky vyÂznamnyÂch hodnot na hladineÏ statisticke vyÂznamnosti 0,05. VyÂsledky VyÂsledky vsÏech provedenyÂch meÏrÏenõ sõÂly produkovane rÏetõÂzky ve zvolenyÂch cÏasovyÂch intervalech v prvnõÂm i druheÂm experimentu byly zaznamenaÂny do tabulek a grafuÊ a zpracovaÂny v programu Microsoft Excel. Byly vypocÏteny aritmeticke pruÊmeÏry pro kazÏde meÏrÏenõ sõÂly a procentuaÂlnõ poklesy sil. PrÏi protazÏenõ rÏetõÂzkuÊ o 50 % puÊvodnõ deÂlky se pocÏaÂtecÏnõ hodnoty sil v cÏase 0 pohybovaly v rozmezõ od 2,5 N (Dura Chain Wide Link, Ortho-Care) do 5,8 N (Dyna Link Continuous, G&H). Po 21 dnech bylo rozmezõ sil produkovanyÂch rÏetõÂzky od 1,5 N (Dura Chain Wide Link, Ortho-Care) do 2,4 N (Dyna Link Continuous, G&H; Power Chain closed space, Ormco; Plastic chain, AO; Elasto Force with connector, Dentaurum). ProcentuaÂlnõ pokles sil se pohyboval od 24 % do 62 % po 24 hodinaÂch a od 31 % do 70 % po 21 dnech. NejmensÏõ procentuaÂlnõ pokles sil s ohledem na vyÂchozõ poskytovanou uÂrovenÏ sõÂly meÏly rÏetõÂzky Memory chain closed, AO; Elasto Force with connector, Dentaurum a Dura Chain close link, Orthocare. rocÏnõÂk 23 cÏ. 2. 2014 took 5 seconds. Then the chains were placed into positions and distances according to the set conditions of the experiment. The measurement followed the same protocol as in the first experiment. There were 360 measurements performed. All measurements were statistically processed. First, the data obtained were described by means of descriptive statistics (arithmetic mean, median, minimum and maximum values, standard deviation). Further the individual sets of measured values were tested for normal distribution. In case the values showed normal distribution, they were subjected to parametric tests (Student's t-tests, pair t-tests with Bonferroni's correction), otherwise they were subject of non-parametric tests (Friedman's test, Wilcoxon tests with Bonferroni's correction, Mann-Whitney U-tests). The results were plotted in tables, statistically significant values on the level of statistical significance of 0.05 were highlighted. Results The results of all measurements of chain induced forces at given intervals in both experiments were plotted in tables and graphs, and processed with Microsoft Excel software. Arithmetic means for each force measurement and percentage of force degeneration were calculated. After stretching of chains by 50% of their initial length, the initial values of forces at time 0 fluctuated between 2.5 N (Dura Chain Wide Link, Ortho-Care) and 5.8 N (Dyna Link Continunous, G&H). After 21 days the range was between 1.5 N (Dura Chain Wide Link, Ortho-Care) and 2.4 N (Dyna Link Continuous, G&H; Power Chain Closed Space, Ormco; Plastic Chain, AO; Elasto Force with connector, Dentaurum). The Tab. 1. PruÊmeÏrne hodnoty sil a procentuaÂlnõ poklesy sil pro protazÏenõ o 50 % puÊvodnõ deÂlky ve zvolenyÂch cÏasovyÂch intervalech Tab. 1. Mean values of forces and forces degeneration in per cents after stretching by 50% of the initial length at given time intervals www.orthodont-cz.cz e-mail: [email protected] Cyan Magenta Yellow - 101 Cyan Magenta Yellow Black rocÏnõÂk 23 cÏ. 2. 2014 Odborna praÂce ORTODONCIE Tab. 2. PruÊmeÏrne hodnoty sil a procentuaÂlnõ poklesy sil pro protazÏenõ o 100 % puÊvodnõ deÂlky ve zvolenyÂch cÏasovyÂch intervalech Tab. 2. Mean values of forces and forces degeneration in per cents after stretching by 100% of the initial length at given time intervals Obr. 2. Pokles pruÊmeÏrnyÂch sil v cÏase prÏi protazÏenõ o 50 % vyÂchozõ deÂlky rÏetõÂzku Fig. 2. Mean forces degeneration over a period of time after stretching by 50% of the initial length Obr. 3. Poklesu pruÊmeÏrnyÂch sil v cÏase prÏi protazÏenõ o 100 % vyÂchozõ deÂlky rÏetõÂzku Fig. 3. Mean forces degeneration over a period of time after stretching by 100% of the initial length Na obr. 2 je patrny rozptyl vyÂchozõÂch hodnot sil produkovanyÂch elastickyÂmi rÏetõÂzky. PruÊbeÏh krÏivek pro vsÏechny rÏetõÂzky i charakter jejich poklesu je si velmi podobnyÂ. NejstrmeÏjsÏõ pruÊbeÏh je v prvnõÂch 24 hodinaÂch. PrÏi protazÏenõ o 100 % puÊvodnõ deÂlky se pocÏaÂtecÏnõ hodnoty sil produkovanyÂch v cÏase 0 pohybovaly v rozmezõ od 3,2 N (Dura Chain Wide Link, Ortho-Care) do 6 N (Dyna Link Continuous, G&H). Po 21 dnech bylo rozmezõ sil produkovanyÂch rÏetõÂzky od 1,6 N (Dura Chain Wide Link, Ortho-Care) do 3,2 N (Dyna Link Continuous, G&H). ProcentuaÂlnõ pokles sil se pohyboval od 28 % do 60 % po 24 hodinaÂch a od 39 % do 68 % po 21 dnech. NejmensÏõ procentuaÂlnõ ztraÂtu sil oproti vyÂchozõ sõÂle meÏly rÏetõÂzky Power Chain open space, Ormco; Memory chain closed, AO a Elasto Force with connector, Dentaurum. Na obr. 3 je videÏt podobny charakter poklesu sõÂly a pruÊbeÏhu krÏivek jako prÏi protazÏenõ o 50 %, opeÏt s nejstrmeÏjsÏõÂm poklesem v prvnõÂch 24 hodinaÂch. KrÏivka po- percentage of force degeneration oscillated between 24 and 62 per cents after 24 hours and between 31 and 70 per cents after 21 days. The least force degeneration in per cents was recorded for Memory Chain Closed, AO; Elasto Force with connector, Dentaurum; and Dura Chain close link, Orthocare. In Figure 2 we can observe an obvious distribution of initial values of forces induced by elastic chains. Shapes of curves for all chains as well as their decline are very similar. The steepest shape is observed within the first 24 hours. After stretching of chains by 100% of their initial length, the initial values of forces induced by chains at time 0 fluctuated between 3.2 N (Dura Chain Wide Link, Ortho-Care) and 6N (Dyna Link Continuous, G&H). After 21 days the range was between 1.6 N (Dura Chain Wide Link, Ortho-Care) and 3.2 N (Dyna Link Continuous, G&H). The percentage of force degeneration oscillated between 28 and 60 per cents after 24 hours and bet- 102 www.orthodont-cz.cz e-mail: [email protected] Cyan Magenta Yellow - Cyan Magenta Yellow Black ORTODONCIE Odborna praÂce rocÏnõÂk 23 cÏ. 2. 2014 Tab. 3. PruÊmeÏrne hodnoty sil a procentuaÂlnõ poklesy sil pro protazÏenõ o 50 % a 100 % puÊvodnõ deÂlky ve zvolenyÂch cÏasovyÂch intervalech u rÏetõÂzkuÊ s prestretchingem a bez neÏho (rÏetõÂzky s prestretchingem oznacÏeny barevneÏ a v oznacÏenõ rÏetõÂzku jsou oznacÏeny P ( CP, MP, WP) ) Tab. 3. Mean values of forces and forces degeneration in per cents after stretching by 50% and 100% of the initial length at given time intervals for the chains with prestretching, and without prestretching. Chains with prestretching have the letter P in the name/acronym of their type (CP, MP, WP). Obr. 4. RÏetõÂzky s prestretchingem a bez neÏho prÏi vyÂchozõÂm protazÏenõ o 50 % vyÂchozõ deÂlky. RÏetõÂzky s prestretchingem jsou oznacÏeny prÏidaÂnõÂm P v typu ( CP, MP, WP). Fig. 4. Chains with and without prestretching at stretching by 50% of the initial length. Chains with prestretching have the letter P in the name/acronym of their type (CP, MP, WP). Obr. 5. RÏetõÂzky s prestretchingem a bez neÏho prÏi vyÂchozõÂm protazÏenõ o 100% vyÂchozõ deÂlky. RÏetõÂzky s prestretchingem jsou oznacÏeny prÏidaÂnõÂm P v typu ( CP, MP, WP). Fig. 5. Chains with and without prestretching at stretching by 100% of the initial length. Chains with prestretching have the letter P in the name/acronym of their type (CP, MP, WP). klesu sõÂly jednoho rÏetõÂzku se ale svyÂm pruÊbeÏhem vymykaÂ. PrÏi 100 % protazÏenõ hodnoty sil tohoto rÏetõÂzku klesajõ pomalu a i v zaÂveÏru experimentu se pohybujõ na hodnoteÏ 3,2 N. ween 39 and 68 per cents after 21 days. The least force decrease in per cents was recorded for Power Chain Open Space, Ormco; Memory Chain Closed, AO; and Elasto Force with connector, Dentaurum). V experimentu zkoumajõÂcõÂm vliv prestretchingu byly do tabulky 3 zapsaÂny pruÊmeÏrne hodnoty sil a procentuaÂlnõ poklesy sil prÏi protazÏenõ o 50 % a 100 % vyÂchozõ deÂlky rÏetõÂzkuÊ s prestretchingem a hodnoty pro tyteÂzÏ rÏetõÂzky, ktere prestretchingem neprosÏly. In Figure 3 we can observe similar force degeneration as in stretching by 50%; the steepest shape is observed within the first 24 hours. However, the shape of curve representing force degeneration of one chain is different. After stretching by 100%, forces of this chain decline slowly, and at the end of the experiment they are still at 3.2 N. Z pruÊbeÏhu krÏivek (obr. 4) lze usuzovat, zÏe provedeny prestretching, prÏi naÂsledneÂm protazÏenõ o 50 % vyÂchozõ deÂlky, ovlivnil produkci sil rÏetõÂzkuÊ. Dle pruÊbeÏhu krÏivek (obr. 5) muÊzÏeme v tomto prÏõÂpadeÏ usuzovat, zÏe provedeny prestretching, prÏi naÂsledneÂm protazÏenõ o 100 % vyÂchozõ deÂlky sõÂly produkovane rÏetõÂzky neovlivnil. www.orthodont-cz.cz e-mail: [email protected] Cyan Magenta Yellow - In the experiment on prestretching, mean forces values and percentage of forces degeneration after stretching by 50 and 100% of the initial length of chains with prestretching were plotted in Table 3; there were plotted also values for the same brands of chains that did not undergo prestretching. 103 Cyan Magenta Yellow Black rocÏnõÂk 23 cÏ. 2. 2014 Odborna praÂce Souhrn statistickeÂho hodnocenõ Pro obeÏ vyÂchozõ protazÏenõ (50 i 100 %), bylo signifikantneÏ prokaÂzaÂno, zÏe pruÊmeÏrna sõÂla v cÏase klesaÂ, stoupa hodnota procentuaÂlnõÂho poklesu sõÂly a rychlost poklesu sõÂly v cÏase klesaÂ, prÏicÏemzÏ v prvnõÂch 24 hodinaÂch je pokles sõÂly nejveÏtsÏõÂ. PrÏi vzaÂjemneÂm porovnaÂnõ pruÊmeÏrnyÂch sil prÏi protazÏenõ o 50 % se silami prÏi protazÏenõ o 100 % byla ve vsÏech cÏasech statisticky vyÂznamneÏ vysÏsÏõ hodnota pruÊmeÏrnyÂch sil prÏi protazÏenõ o 100 % vyÂchozõ deÂlky rÏetõÂzku. Rychlost poklesu sõÂly byla signifikantneÏ vysÏsÏõ prÏi protazÏenõ o 100% pouze v cÏasoveÂm intervalu 0-2 hodiny. PrÏi posouzenõ vlivu deÂlky mezicÏlaÂnku na produkci sil elastickyÂmi rÏetõÂzky se nepodarÏilo jednoznacÏneÏ prokaÂzat, zÏe deÂlka mezicÏlaÂnku tuto produkci ovlivnõÂ. Byl pouze zachycen trend, ktery naznacÏuje, zÏe hodnota pruÊmeÏrnyÂch sil pro obeÏ protazÏenõ je statisticky vyÂznamneÏ nizÏsÏõ u rÏetõÂzkuÊ s dlouhyÂm mezicÏlaÂnkem oproti rÏetõÂzkuÊm s kraÂtkyÂm mezicÏlaÂnkem a bez mezicÏlaÂnku. PrÏi protazÏenõ o 100 % vyÂchozõ deÂlky rÏetõÂzku pak byl zachycen i trend vysÏsÏõ rychlosti poklesu sõÂly u rÏetõÂzku bez mezicÏlaÂnku. PrÏi srovnaÂnõ sil rÏetõÂzkuÊ, u kteryÂch byl proveden prestretching s teÏmi, u kteryÂch prestretching proveden nebyl, byl prokaÂzaÂn prÏi protazÏenõ o 50 % vyÂchozõ deÂlky rÏetõÂzku ve vsÏech cÏasech statisticky vyÂznamny procentuaÂlnõ pokles sõÂly u rÏetõÂzkuÊ, ktere prestretching nepodstoupily. Hodnota pruÊmeÏrnyÂch sil a rychlost poklesu sõÂly byly signifikantneÏ vysÏsÏõ pouze v cÏase 0 u rÏetõÂzkuÊ bez prestretchingu. PrÏi protazÏenõ o 100 % vyÂchozõ deÂlky nebyl prokaÂzaÂn vliv prestretchingu ani na pruÊmeÏrnou hodnotu sil ani na procentuaÂlnõ pokles sil ve vsÏech cÏasech. Rychlost poklesu sõÂly byla signifikantneÏ vysÏsÏõ pouze v intervalu 2-8 hodin u rÏetõÂzkuÊ s prestretchingem. Diskuse PouzÏitõ elastickyÂch rÏetõÂzkuÊ skyÂta ortodontistuÊm rÏadu vyÂhod. Pro jejich pouzÏitõ hovorÏõ jednoznacÏneÏ jejich jednoducha aplikovatelnost, nenõ nutna spolupraÂce pacienta a jsou relativneÏ levneÂ. Jejich uzÏitõ ma i nevyÂhody. Po vlozÏenõ do dutiny uÂstnõ absorbujõ vodu a slinu, zbarvujõ se a dochaÂzõ k posÏkozenõ vnitrÏnõÂch vazeb vedoucõ k trvale deformaci aplikovanyÂch rÏetõÂzkuÊ. NavõÂc na povrchu rÏetõÂzkuÊ dochaÂzõ k precipitaci iontuÊ a tvorbeÏ proteinoveÂho filmu. Z toho pak pramenõ rychla ztraÂta sõÂly vedoucõ k postupneÂmu snizÏovaÂnõ efektivity [2, 15, 16, 17]. KvuÊli teÂto ztraÂteÏ je pro ortodontistu obtõÂzÏne urcÏit aktuaÂlnõ sõÂlu prÏenaÂsÏenou na zuby. NavõÂc je sõÂlu nutno posuzovat individuaÂlneÏ dle prostrÏedõ dutiny uÂstnõ jednotlivyÂch pacientuÊ. Navzdory probõÂhajõÂcõÂm debataÂm, zda lze aplikovat vyÂsledky experimentuÊ provedenyÂch in vitro na podmõÂnky dutiny uÂstnõÂ, kde musõÂme vzõÂt v uÂvahu dalsÏõ vlivy 104 ORTODONCIE Shapes of curves (Fig.4) suggest that prestretching affected forces induced by chains. Shapes of curves (Fig.5) suggest that prestretching did not affect forces produced by chains. Summary of statistical evaluation For both elongations (by 50 and 100 per cents) it was proved that the mean force decreases over a period of time, the value (in per cents) of force degeneration increases, and the rate of force degeneration decreases with time, and that the force degeneration is the greatest within the first 24 hours. Comparison of mean forces stretched by 50% and mean forces stretched by 100% showed that mean forces value was always statistically higher in case of stretching by 100%. In case of 100% stretching the rate of force degeneration was significantly higher only at the interval 0-2 hours. The effect of connecting link length on the delivery of force by elastic chains was not proved. There is only a tendency suggesting that mean force value for both stretchings is significantly lower in chains with a long connecting link (unlike in chains with a short connecting link or chains without a connecting link). In case of stretching by 100% there was recorded a tendency to more rapid force degeneration in chains without a connecting link. Comparison of forces in chains with or without prestretching proved significant percentage of force degeneration in chains without prestretching (they were stretched by 50% at all intervals). Mean forces values and the rate of force degeneration were significantly higher only at time 0 in chains without prestretching. In case of stretching by 100% there was not proved any impact of prestretching with regard either to mean forces value or percentage of forces decline at all intervals. The rate of force degeneration was significantly higher only at interval 2-8 hours in chains with prestretching. Discussion Elastic chains bring a number of advantages for orthodontists - they are easy to use, the cooperation of a patient is not necessary, and they are relatively cheap. However, their application may also have weak points: after they are inserted into mouth cavity they absorb water and saliva, they change in colour, and their internal bonds may be damaged which results in their permanent deformation. Moreover, on the surface of chains there occurs ion precipitation and protein film is formed. That leads to rapid force degeneration resulting in a gradual decrease of effectiveness [2, 15, 16, 17]. Due to this loss, it is difficult for an orthodontist to determine actual force delivered on teeth. In addition, it is necessary to judge the force individually according to individual patients' mouth cavity conditions. Despite the www.orthodont-cz.cz e-mail: [email protected] Cyan Magenta Yellow - Cyan Magenta Yellow Black ORTODONCIE Odborna praÂce jako je mikrobiaÂlnõ flora, enzymy, vyÂzÏivove faktory atd., ma experiment provedeny in vitro mnoho vyÂhod, pokud jde o charakteristiky materiaÂluÊ dõÂky mozÏnosti standardizace prostrÏedõÂ. Studie srovnaÂvajõÂcõ vyÂsledky experimentu provedeneÂho in vitro na vzduchu a provedeneÂho in vivo ukaÂzaly pomeÏrneÏ velke rozdõÂly [8, 10, 12]; naopak srovnaÂnõ vyÂsledkuÊ experimentu provedeneÂho in vitro ve vlhkeÂm prostrÏedõ a experimentu provedeneÂho in vivo ukaÂzalo rozdõÂly nepatrne [8]. VyÂsledky experimentaÂlnõ cÏaÂsti teÂto praÂce potvrdily velkou variabilitu uÂrovneÏ vyÂchozõ sõÂly produkovane elastickyÂmi rÏetõÂzky danou typem rÏetõÂzku a vyÂrobcem. PrÏi natazÏenõ o 50 % vyÂchozõ deÂlky se hodnoty sõÂly pohybovaly v rozsahu 2,5 N do 5,8 N a prÏi natazÏenõ o 100 % vyÂchozõ deÂlky v rozsahu 3,2 N do 6 N.Toto zjisÏteÏnõ je v souladu s vyÂsledky mnoha publikovanyÂch studiõ [3, 4, 5, 6, 7, 8, 10, 11, 12, 13]. RovneÏzÏ se naÂm podarÏilo prokaÂzat a uprÏesnit uÂbytek produkovane sõÂly v cÏase, prÏicÏemzÏ rychlost poklesu sõÂly produkovane rÏetõÂzky je nejveÏtsÏõ v prvnõÂch 24 hodinaÂch a daÂle se v cÏase snizÏuje po celou dobu testovacõÂho obdobõ 3 tyÂdnuÊ. Take tento poznatek se shoduje s dostupnou literaturou [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]. Dle dostupne literatury delsÏõ testovacõ obdobõ ukaÂzalo jen nepatrny pokles uÂrovneÏ produkovane sõÂly, nejdelsÏõ sledovana testovacõ perioda byla 100 dnuÊ [14]. Pro nasÏõ klinickou praxi to znamenaÂ, zÏe uÂrovenÏ sõÂly poskytovane elastickyÂm rÏetõÂzkem prÏi kontrole pacienta v intervalu 4-6 tyÂdnuÊ, by meÏla byÂt pravdeÏpodobneÏ velmi podobna sõÂle nameÏrÏene po 3 tyÂdnech. Pokud se zabyÂvaÂme posouzenõÂm vlivu deÂlky mezicÏlaÂnku na sõÂlu produkovanou elastickyÂmi rÏetõÂzky, zde jizÏ naÂzory jednotne nejsou. NaprÏõÂklad De Genova, Stevenson a Kusy ve svyÂch studiõÂch potvrdili, zÏe rÏetõÂzky s kraÂtkyÂm mezicÏlaÂnkem produkujõ vysÏsÏõ uÂrovenÏ sil nezÏ rÏetõÂzky s dlouhyÂm mezicÏlaÂnkem [9, 14]. V nasÏem experimentu se naÂm jednoznacÏneÏ nepodarÏilo prokaÂzat ovlivneÏnõ produkce sil deÂlkou mezicÏlaÂnku. Pouze jsme zachytily trend, ktery naznacÏil, zÏe sõÂly produkovane rÏetõÂzky bez mezicÏlaÂnku a s kraÂtkyÂm mezicÏlaÂnkem jsou vysÏsÏõ nezÏ ty, ktere produkujõ rÏetõÂzky s dlouhyÂm mezicÏlaÂnkem. Eliades a kol. tvrdõÂ, zÏe rÏetõÂzky s kraÂtkyÂm mezicÏlaÂnkem a bez mezicÏlaÂnku budou ztraÂcet sõÂlu rychleji, protozÏe zbytkove napeÏtõ v modulu se po jeho natazÏenõ koncentruje do ocÏka rÏetõÂzku, cozÏ ho oslabuje, a navõÂc je zde veÏtsÏõ riziko posÏkozenõ ocÏka prÏi navleÂkaÂnõ na zaÂmek. To je dalsÏõ rizikovy faktor, ktery muÊzÏe ovlivnit produkci sil [2, 16]. NaÂzory na efekt prestretchingu jakozÏto mozÏneÂho zpuÊsobu ovlivneÏnõ produkce sil elastickyÂmi rÏetõÂzky jsou jesÏteÏ võÂce kontroverznõÂ. VeÏtsÏina studiõ dospeÏla ke zjisÏteÏnõÂ, zÏe prestretching vyÂslednou hodnotu sil produkovanyÂch elastickyÂmi rÏetõÂzky neovlivnõ [18, 19, 20]. Pokud neÏktere z nich prestretching doporucÏily, nedokaÂzaly www.orthodont-cz.cz e-mail: [email protected] Cyan Magenta Yellow - rocÏnõÂk 23 cÏ. 2. 2014 current debate on application of results of the experiments carried out in vitro in the conditions of mouth cavity, where we have to consider other impacts, e.g. microbial flora, enzymes, nutrition, etc., the experiment carried out in vitro has many advantages with regard to materials characteristics - this is possible thanks to standardized conditions. The study comparing results of the experiment performed in vitro in the open air and the experiment carried out in vivo showed relatively great differences [8, 10, 12]. On the contrary, comparison of results of the experiment performed in vitro in a damp environment and the experiment done in vivo showed only slight differences [8]. Results of the experimental part of the presented study proved a great variability in the value of the initial force induced by elastic chains - it is due to the type and manufacturer of a given chain. When stretched by 50% of the initial length, the force values were between 2.5 N and 5.8 N; when stretched by 100% of the initial length, the values oscillated between 3.2 N and 6 N. This agrees with the results of many studies published [3, 4, 5, 6, 7, 8, 10, 11, 12, 13]. We also proved and specified the force degeneration over a period of time; the rate of the force degeneration is higher within the first 24 hours, and then it gradually decreases during the whole period of 3 weeks. This conclusion agrees with the literature available [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]. According to the published works a longer testing period showed only a minute decline in the amount of the force induced by chains; the longest testing period took 100 days [14]. For our clinical practice this means that the force delivered by elastic chain measured at the interval of 4-6 weeks during a patient's check-up should be very close to the value obtained after 3 weeks. The views on the impact of a connecting link length on the force induced by elastic chains are not uniform. E.g. De Genova, Stevenson, and Kusy state that chains with a short connecting link produce bigger force than those with a long connecting link [9, 14]. Our experiment did not prove the relationship between force delivery and the connecting link length. However, there is a tendency suggesting that the forces induced by chains without a connecting link or with a short connecting link are bigger than those induced by chains with a long connecting link. Eliades et al. conclude that chains with a short connecting link or without a connecting link lose the force more quickly because a residual strain in the module concentrates into a chain unit which makes the module weaker, and additionally, there is also a higher risk of damage to the unit during the process of its attachment to a bracket. This is another risk factor that may affect delivery of forces [2, 16]. The views on the effect of prestretching on the production of forces by elastic chains are even more con105 Cyan Magenta Yellow Black rocÏnõÂk 23 cÏ. 2. 2014 Odborna praÂce stanovit mõÂru prestretchingu [6]. Dle nasÏeho experimentu se zdaÂ, zÏe prestretching ovlivnõ vyÂslednou produkci sõÂly rÏetõÂzkuÊ, pokud vzdaÂlenost, na kterou rÏetõÂzek nataÂhneme, bude vyÂrazneÏ mensÏõ nezÏ vzdaÂlenost, na kterou jsme provedli prestretching. ZaÂrovenÏ tõÂm muÊzÏeme ovlivnit pocÏaÂtecÏnõ neprÏõÂjemne pocity vnõÂmane pacientem. PodobneÏ se k teÂto problematice ve sve studii stavõ Stevenson a Kusy [14]. S ohledem na vyÂsledky experimentu je pomeÏrneÏ zajõÂmave zhodnotit problematiku prÏenosu sil rÏetõÂzku na zub jako prostrÏedku produkujõÂcõÂho sõÂly kontinuaÂlnõ nebo, jak tvrdõ Proffit, sõÂly prÏerusÏovane [21]. UkaÂzalo se, zÏe prÏi protazÏenõ o 100 % vyÂchozõ deÂlky se produkce sil neÏkteryÂch rÏetõÂzkuÊ pohybuje v hodnotaÂch prÏesahujõÂcõÂch ªbezpecÏneª uzÏitõ rÏetõÂzkuÊ. PrÏi tomto protazÏenõ by mohly prÏevaÂzÏit nechteÏne a nezÏaÂdoucõ uÂcÏinky elastickeÂho rÏetõÂzku. Dle teÏchto vyÂsledkuÊ bychom tyto sõÂly produkovane elastickyÂmi rÏetõÂzky zarÏadili do kategorie sil nevhodnyÂch. ZaÂveÏr 1. PodarÏilo se prokaÂzat, zÏe sõÂly produkovane rÏetõÂzky protazÏenyÂmi o 50 a 100 % jejich vyÂchozõ deÂlky nejsou stejne a podleÂhajõ sÏiroke variabiliteÏ dle typu rÏetõÂzku a vyÂrobce. Pohybujõ se v rozmezõ 2,5 N - 5,8 N pro protazÏenõ o 50 % a v rozmezõ 3,2 N - 6 N pro protazÏenõ o 100 % vyÂchozõ deÂlky rÏetõÂzkuÊ. 2. Bylo potvrzeno, zÏe beÏhem prvnõÂch 24 hodin dochaÂzõ k nejveÏtsÏõÂm ztraÂtaÂm sõÂly produkovane rÏetõÂzky a rychlost poklesu sil v cÏase se daÂle snizÏuje. SrovnaÂme-li rychlosti uÂbytku sõÂly prÏi protazÏenõ o 50 % a prÏi protazÏenõ o 100 %, statisticky vyÂznamneÏ vysÏsÏõ rychlost poklesu najdeme pouze v intervalu 0 - 2 hodiny. Velikost pruÊmeÏrneÏ puÊsobõÂcõÂch sil vyvinutyÂch rÏetõÂzky je ve vsÏech cÏasovyÂch intervalech vysÏsÏõ prÏi protazÏenõ o 100 % vyÂchozõ deÂlky. 3. PrÏi protazÏenõ rÏetõÂzkuÊ o 50 i 100 % jejich vyÂchozõ deÂlky se nepodarÏilo jednoznacÏneÏ prokaÂzat vliv deÂlky mezicÏlaÂnku na uÂrovenÏ produkovane sõÂly ani na rychlost jejõÂho naÂsledneÂho poklesu. 4. PrÏi testovaÂnõ vlivu prestretchingu na uÂrovenÏ vyÂchozõ sõÂly a jejõ naÂsledny pokles v cÏase se podarÏilo jednoznacÏneÏ prokaÂzat, zÏe vyÂchozõ sõÂla prÏi prestretchingu a naÂsledneÂm protazÏenõ o 50 % jejich vyÂchozõ deÂlky je nizÏsÏõ nezÏ vyÂchozõ sõÂla u rÏetõÂzkuÊ, ktere prestretching nepodstoupily. NaÂsledny procentuaÂlnõ pokles sõÂly v cÏase je pak rovneÏzÏ nizÏsÏõ u rÏetõÂzkuÊ, ktere prosÏly prestretchingem ve srovnaÂnõ s rÏetõÂzky, u kteryÂch jsme prestretching neprovedly. 5. U rÏetõÂzkuÊ, kde prestretching nebyl proveden a naÂsledneÏ byly protazÏeny o 100 % jejich vyÂchozõ deÂlky, nebyly vyÂrazne rozdõÂly ani ve vyÂchozõ uÂrovni sõÂly ani v naÂsledneÂm procentuaÂlnõÂm poklesu sõÂly v cÏase. 106 ORTODONCIE troversial. The majority of studies conclude that prestretching does not influence the resulting amount of force induced by elastic chains [18, 19, 20]. The works recommending prestretching did not give the extent of elongation [6]. Our experiment suggests that prestretching can influence resulting force delivery by chains only in case that the distance to which the chain is stretched is significantly shorter than the length of prestretching. At the same time, we can also alleviate the initial discomfort of a patient. Stevenson and Kusy maintain the same position [14]. With respect to the results of our experiment, it is interesting to assess the problem of chain induced forces transfer on a tooth as the means producing continual forces or, as Proffit states, interrupted forces [21]. It turned out that after stretching by 100% of the initial length, the force delivery by some chains reached values exceeding ªsafeªchains application. In such cases the unwanted and undesirable effects of elastic chain might prevail. According to these results we would classify such forces induced by elastic chains as unsuitable. Conclusion 1. The study proved that forces induced by chains stretched by 50 and 100% of their initial length are not identical; they differ considerably according to the chain type and brand. The values oscillate between 2.5 N and 5.8 N after 50% stretch and between 3.2 N and 6 N after 100% stretch. 2. The study proved that within the first 24 hours the forces induced by chains degenerate rapidly, and the rate of force degeneration slows down over a period of time. Comparison of the force degeneration after 50% stretching and 100% stretching showed significantly more rapid decline only at the interval 0-2 hours. The mean value of forces induced by chains is higher at all intervals after stretching by 100% of the initial length. 3. In chains stretched by 50 and 100% we could not prove the effect of a connecting link length on the amount of the force induced or on the rate of its subsequent decline. 4. Testing of prestretching effects on the amount of initial force and its subsequent decline over a period of time proved that the initial force in prestretching and subsequent stretching by 50% is lower than the initial force in chains that did not undergo prestretching. The following decline of force in time (given in per cents) is also lower in chains that underwent prestretching. 5. In chains without prestretching that were stretched by 100% of their initial length, there were found no significant differences in the initial amount of force or in force decline (given in per cents) over a period of time. The above given findings may be reflected in the following clinical recommendations: www.orthodont-cz.cz e-mail: [email protected] Cyan Magenta Yellow - Cyan Magenta Yellow Black ORTODONCIE Odborna praÂce Uvedena zjisÏteÏnõ mohou veÂst k teÏmto klinickyÂm doporucÏenõÂm: 1. Vzhledem k rozdõÂlnosti uÂrovneÏ iniciaÂlnõ sõÂly produkovane rÏetõÂzky ruÊznyÂch vyÂrobcuÊ zvaÂzÏit vyÂbeÏr odpovõÂdajõÂcõÂho rÏetõÂzku podle pozÏadovaneÂho uÂcÏinku. Nejde totizÏ pouze o prÏõÂpadne prÏetõÂzÏenõ zubuÊ, u nichzÏ ocÏekaÂvaÂme, zÏe puÊsobenõÂm rÏetõÂzku zmeÏnõ sve postavenõÂ, ale take o prÏõÂpadne negativnõ ovlivneÏnõ kotevnõ jednotky. NasÏõÂm cõÂlem je dosaÂhnout pohybu zubu co nejmensÏõÂ, avsÏak uÂcÏinnou aplikovanou silou, abychom eliminovali v nejvysÏsÏõ mozÏne mõÂrÏe riziko nechteÏnyÂch a nezÏaÂdoucõÂch uÂcÏinkuÊ spojenyÂch s pouzÏitõÂm elastickyÂch rÏetõÂzkuÊ. 2. UkaÂzalo se, zÏe neÏktere rÏetõÂzky prÏi nadmeÏrneÂm natazÏenõ budou produkovat sõÂly, ktere toto riziko vyÂrazneÏ zvysÏujõÂ. Proto je na mõÂsteÏ urcÏita obezrÏetnost prÏi leÂcÏbeÏ nasÏich pacientuÊ i prÏi pouzÏitõ tak beÏzÏne pomuÊcky jako je elasticky rÏetõÂzek. 3. Pokud budeme chtõÂt leÂpe kontrolovat sõÂly produkovane elastickyÂmi rÏetõÂzky, je na mõÂsteÏ vyÂchozõ kontrola sõÂly na silomeÏru a dle tohoto uÂdaje naplaÂnovat dalsÏõ kontroly pacienta v ordinaci. 4. PouzÏitõÂm prestretchingu muÊzÏeme pozitivneÏ ovlivnit vyÂchozõ hodnotu aplikovane sõÂly, tõÂm zmõÂrnõÂme neprÏõÂjemne subjektivnõ pocity nasÏich pacientuÊ a naÂsledny pokles sõÂly v cÏase bude meÂneÏ vyÂraznyÂ. rocÏnõÂk 23 cÏ. 2. 2014 1. With regard to different amounts of the initial force induced by chains of different brands, the appropriate chain should be chosen according to the effect required. The problem is not only an eventual overload of teeth that should alter their positions due to chain force delivery, but also the potential negative effect on the anchorage. Our aim is to move a tooth with as light force applied as possible, in order to eliminate potential risks of unwanted and undesirable effects arising from the use of elastic chains. 2. It turned out that during excessive stretching some chains would produce forces that raise the risk significantly. Therefore, we should always be very cautious when treating our patients even if we use as common a tool as an elastic chain. 3. In case we want to better control forces induced by elastic chains, we should set the initial amount of force with a force gauge, and then - depending on the data obtained - plan further check-ups of a patient. 4. Prestretching may positively affect the initial amount of the force applied, and thus can alleviate subjective discomfort of our patients, and the subsequent force decline over a period of time will be less noticeable. PodeÏkovaÂnõÂ: Autorky deÏkujõ Mgr. KaterÏineÏ LangoveÂ, Ph. D. za pomoc prÏi zpracovaÂnõ statistickyÂch vyÂsledkuÊ. Acknowledgment: The authors want to express their gratitude to Mgr.KaterÏina LangovaÂ, Ph.D., for her help in statistical processing of the data. Autorky nemajõ komercÏnõÂ, vlastnicke nebo financÏnõ zaÂjmy na produktech nebo spolecÏnostech popsanyÂch v tomto cÏlaÂnku. The authors have no commercial, proprietary or financial interest in products or companies mentioned in the article. Literatura/ References 1. Mleziva, J.: Polymery-vyÂroba, struktura, vlastnosti a pouzÏitõÂ, Praha: SobotaÂles, 1993. 2. Brantley, W. A.; Eliades, T.: Orthodontics Materials, Scientific and Clinical Aspects, 1st ed. New York: Thieme Stuttgart, 2001. 3. Baty, D. L.; Storie, D. J.; von Fraunhofner, J. A.: Synthetic elastomeric chains: a literature review. Amer. J. Orthodont. dentofacial Orthop. 1994, 105, s. 536-542. 4. Bishara, S. E.; Andreasen, G. F.: A comparison of timerelated forces between plastic alastics and latex elastics. Angle Orthodont. 1970, 40, s. 319-328. 5. Hershey, G.; Reynolds, W.: The plastic module as an orthodontic tooth moving mechanism. Amer. J. Orthodont. 1975, 67, s. 554-662. 6. Wong, A. K.: Orthodontic elastic materials. Angle Orthodont. 1976, 46, s. 196-205. 7. Kovatch, J.; Lautenschlager, D.; Keller, J.: Load extension-time behavior of orthodontic alastiks. J. dent. Res. 1976, 55, s. 783-786. 8. Ash, J.; Nikolai, R.: Relaxation of orthodontic elastic chains and modules in vitro and in vivo. J. dent. Res. 1978, 57, s. 685-690. 9. De Genova, D. C.; McInnes-Ledoux, P.; Weinberg, R.; Shaye, R.: Force degradation of orthodontic elastomeric www.orthodont-cz.cz e-mail: [email protected] Cyan Magenta Yellow - chains-a product comparison study. Amer. J. Orthodont. 1985, 87, s. 377-384. 10. Rock, W.; Wilson, H.; Fisher, S.: A laboratory investigation of orthodontic elastomeric chain. Brit. J. Orthodont. 1985, 12, s. 202-207. 11. Killiany, D.; Duplessis, J.: Relaxation of elastomeric chains. J. clin. Orthodont. 1985, 19, s. 592-593. 12. Kuster, R.; Ingervall, B.; Burgin, W.: Laboratory and intraoral test of the degradation of elastic chains. Eur. J. Orthodont. 1986, 8, s. 202-208. 13. Buchmann, N.; Senn, Ch.; Ball, J.; Brauchli, L.: Influence of initial strain on the force decay of currently available elastic chains over time. Angle Orthodont. 2012, 82, s. 529-535. 14. Stevenson, J. S.; Kusy, R. P.: Force application and decay characteristics of untreated and treated polyurethane elastomeric chains. Angle Orthodont. 1994, 64, s. 455-464. 15. Huget, E. F.; Patrick, K. S.; Nunez, L. J.: Observations on the elastic behavior of a synthetic orthodontic elastomer. J. dent. Res. 1990, 69, s. 496-501. 16. Eliades, T.; Eliades, G.; Watts, D. S.: Structural conformation of in vitro and in vivo aged orthodontic elastomeric modules. Eur. J. Orthodont. 1999, 21, s. 649-658. 107 Cyan Magenta Yellow Black rocÏnõÂk 23 cÏ. 2. 2014 Odborna praÂce 17. Ferriter, J.; Meyers, C.; Lorton, L.: The effect of hydrogen ion concentration on the force degradation rate of orthodontic polyurethane chain elastics. Amer. J. Orthodont. dentofacial Orthop. 1990, 98, s. 404-410. 18. Hershey, H.; Brooks, D.: Effect of heat and time on stretched plastic orthodontic modules. J. Dent. Res. 1976, 55B, s. 363. [Cit. in: Baty, D. L.; Storie, D. J.; von Fraunhofner, J. A.: Synthetic elastomeric chains: a literature review. Amer. J. Orthodont. dentofacial Orthop. 1994, 105, s. 536-542.] ORTODONCIE 19. Young, J.; Sandrik, J. L.: The influence of preloading on stress relaxation of orthodontic elastic polymers. Angle Orthodont. 1979, 49, s. 104-109. 20. von Fraunhofner, J. A.; Coffelt, M.-T. P.; Orbell, G. M.: The effects of artificial saliva and topical fluoride treatments on the degradation of the elastic properties of orthodontic chains. Angle Orthodont. 1992, 62, s. 265274. 21. Proffit, W. R.; Fields, H. W.: Contemporary orthodontics. 5th ed., St. Louis: Mosby, 2013. MUDr. Alena FormaÂnkova Stomatologicka klinika FNKV Praha SÏrobaÂrova 50, 100 34, Praha 1 Stomatologicka klinika a Klinika plasticke chirurgie 3. LF UK FNKV Praha porÏaÂdajõ dne 28. 11. 2014 od 9 do 17 hodin v posluchaÂrneÏ Kliniky plasticke chirurgie (pavilon N) mezioborovy seminaÂrÏ RozsÏteÏpy 2014. Dopolednõ blok 9.00-12.00: urcÏen prÏedevsÏõÂm pro postgraduaÂlnõ studenty. Odpolednõ blok 13.30-17.00: zveme vsÏechny zaÂjemce o problematiku rozsÏteÏpuÊ z rÏad odborne verÏejnosti. Vstup volnyÂ. BlizÏsÏõ info 267163283, p. BrÏezinova SeminaÂrÏ se kona pod zaÂsÏtitou CÏeske ortodonticke spolecÏnosti. 108 www.orthodont-cz.cz e-mail: [email protected] Cyan Magenta Yellow -
± intruze hornõÂch prvnõÂch molaÂruÊ;