Retence premolaâruê Unerupted premolars

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Retence premolaÂruÊ

Unerupted premolars

MUDr.Hana BenesÏovaÂ, MUDr.Magdalena Kot'ovaÂ, Ph.D.

OddeÏlenõ ortodoncie a rozsÏteÏpovyÂch vad, stomatologicka klinika 3. LF UK, FN KraÂlovske Vinohrady Praha Department of Orthodontics and Cleft Defects, Clinic of Dental Medicine, 3rd Medical Faculty of Charles Univer-sity, University Hospital KraÂlovske Vinohrady Prague

Souhrn

Sledovany soubor tvorÏilo 75 pacientuÊ s retinovanyÂm premolaÂrem a kontrolnõ soubor tvorÏilo 80 pacientuÊ s fyzio-logickou vyÂmeÏnou chrupu. CõÂlem studie byla analyÂza znakuÊ vyskytujõÂcõÂch se v chrupu pacientuÊ s retencõÂ/impaktacõ premolaÂruÊ.

Na ortopantomogramech pacientuÊ jsme sledovaly odchylky erupcÏnõ draÂhy premolaÂruÊ a porÏadõ prorÏezaÂvaÂnõ la-teraÂlnõÂch staÂlyÂch zubuÊ beÏhem druhe faÂze vyÂmeÏny chrupu. Na saÂdrovyÂch modelech jsme sledovaly ztraÂtu mõÂsta v opeÏrne zoÂneÏ. DalsÏõÂmi znaky sledovanyÂmi v souvislosti s retencõ premolaÂruÊ byla ageneze jednoho z premolaÂruÊ, prÏõÂtomnost nadpocÏetnyÂch zubuÊ v oblasti premolaÂruÊ a reinkluze docÏasnyÂch molaÂruÊ. SnazÏily jsme se urcÏit nej-cÏasteÏjsÏõ kombinace sledovanyÂch znakuÊ, ktere se u retinovanyÂch/impaktovanyÂch premolaÂruÊ vyskytovaly a z jejichzÏ manifestace by prÏõÂpadneÏ bylo mozÏne vcÏas usuzovat na poruchy erupce premolaÂruÊ.

NejcÏasteÏji retinovanyÂm zubem byl levy dolnõ druhy premolaÂr, a nejcÏasteÏjsÏõ kombinacõ znakuÊ, ktera se vyskyto-vala v chrupu pacientuÊ s retencõÂ/impaktacõ premolaÂruÊ, byla ztraÂta mõÂsta v opeÏrne zoÂneÏ a odchylka uÂhlu sklonu erupcÏnõ draÂhy premolaÂru.

Velmi pravdeÏpodobneÏ je tedy retence nebo impaktace premolaÂruÊ vyÂsledkem võÂce potenciaÂlneÏ patologickyÂch jevuÊ a teprve jejich soucÏasnyÂm vyÂskytem v dane oblasti dochaÂzõ k retenci nebo impaktaci premolaÂru(Ortodoncie 2008, 17, cÏ. 3, s. 22-33).

Abstract

The sample involved 75 patients with an unerupted premolar; the control sample included 80 patients with physiological transition of dentition. The aim was to make the analysis of characteristic features in the dentition of patients with unerupted/impacted premolars.

In panoramic X-ray pictures we observed deviations of the eruption paths of premolars, and sequence of erup-tion of lateral permanent teeth during the second phase of transierup-tion of dentierup-tion. In casts we observed the loss of space in the area. Further we observed agenesis of premolar, supernumerary teeth in the premolar area, submer-ged deciduous molars. We tried to establish the most frequent combinations of features observed in unerupted premolars, which may help in the early diagnosis of premolar eruption problems.

The lower second premolar was the most frequent impacted tooth; the loss of space in the area together with deviation in the inclination of eruption path of premolar was the most frequent combination of characteristic fea-tures.

It is highly probable, that unerupted or impacted premolars are the result of several potentially pathological phenomena, and that the uneruption and/or impaction occur only if these phenomena co-occur (Ortodoncie 2008, 17, No. 3, p. 22-33).

KlõÂcÏova slova:retence premolaÂruÊ, impaktace

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UÂvod

Retence zubu je tehdy, kdyzÏ zalozÏeny zub neprorÏe-zal ve fyziologickeÂmobdobõ jeho prorÏezaÂvaÂnõ a zub ma ukoncÏeny vyÂvoj korÏene. NaÂzev retence se vsÏak uzÏõÂva i v pruÊbeÏhu obdobõÂ, kdy zub jesÏteÏ m uÊzÏe fyziologicky prorÏezat, ale jeho ulozÏenõ je tak anomaÂlnõÂ, zÏe mozÏnost prorÏezaÂnõÂdo dutiny uÂstnõÂje velmi nepravdeÏpodobna [2, 3].

Definice zadrzÏene erupce, cÏi impaktace zubu je naÂ-sledujõÂcõÂ: zub neprorÏezal pro urcÏitou prÏekaÂzÏku, naprÏ. prÏespocÏetne zuby, cÏi uzaÂveÏr prostoru sousednõÂmi zuby [2].

VyÂznampremolaÂruÊ spocÏõÂvaÂ, vedle jejich mastikacÏnõ funkce, v udrzÏenõ vyÂsÏky skusu [1], podle jejich interku-spidace se diagnostikuje I. klõÂcÏ okluze podle Andrewse [2]. PremolaÂry jsou z hlediska protetickeÂho pilõÂrÏe II. trÏõÂdy. Dojde-li ke sblokovaÂnõ sousednõÂch premolaÂruÊ, lze je povazÏovat za proteticky pilõÂrÏ I. trÏõÂdy [1]. Nezaned-batelna je take jejich uÂloha v oblasti estetiky tzv. bukaÂl-nõÂch koridoruÊ [3, 4, 5, 6, 7, 8].

SledovaÂnõÂmjednotlivyÂch znakuÊ a kombinacõ znakuÊ, ktere by mohly veÂst k retenci/impaktaci premolaÂruÊ, jsme se snazÏily odhalit mozÏnou prÏõÂcÏinu retence/impak-tace premolaÂruÊ.

ZajõÂmalo naÂs rovneÏzÏ, zda lze vyÂvoj neprÏõÂznive si-tuace prÏi erupci premolaÂruÊ ovlivnit ortodonticky.

MateriaÂl

NasÏe pozorovaÂnõÂ bylo provaÂdeÏno na souboru pa-cientuÊ s retencõÂ/impaktacõÂ premolaÂruÊ (soubor B) a na souboru pacientuÊ s fyziologickou vyÂmeÏnou chrupu (soubor A).

Soubor A (kontrolnõÂ) zahrnoval 80 pacientuÊ s fyziolo-gickyÂmpruÊbeÏhemvyÂmeÏny chrupu, cozÏ bylo mozÏno dokladovat na ortopantomogramech.

Pro zarÏazenõÂ do kontrolnõÂho souboru A byla stano-vena naÂsledujõÂcõÂ kriteÂria:

1. minimaÂlneÏ 3 na sebe navazujõÂcõÂ ortopantomo-gramy v dobeÏ vyÂvoje a erupce premolaÂruÊ,

2. prvnõ rentgenovy snõÂmek byl zhotoven po skon-cÏenõ I. faÂze vyÂmeÏny chrupu,

3. zaÂrodky premolaÂruÊ byly v odpovõÂdajõÂcõÂmstadiu vyÂvoje zubu a nachaÂzely se ve fyziologickeÂmposta-venõÂ,

4. na dalsÏõÂch rentgenovyÂch snõÂmcõÂch bylo mozÏno prokaÂzat pokracÏujõÂcõ fyziologicky pruÊbeÏh erupce pre-molaÂruÊ.

Soubor B (retence/impaktace premolaÂruÊ) zahrnoval 75 pacientuÊ, u kteryÂch bylo mozÏno dokladovat na saÂd-rovyÂch modelech chrupu a na ortopantomogramech retenci/impaktaci premolaÂru.

Pro zarÏazenõÂ do sledovaneÂho souboru B byla stano-vena naÂsledujõÂcõÂ kriteÂria :

Introduction

Unerupted tooth occurs when the germinated tooth did not erupt in the physiological phase of its eruption and its root development is finished. However, the termis used also for the period when a tooth may still erupt physiologically but its location is so abnormal that the potential eruption into the oral cavity is very im-probable [2, 3].

The definition of arrested eruption, or impaction of a tooth, is the following: the tooth did not erupt due to some obstacle, e.g. supernumerary teeth, or closure of its eruption path by adjacent teeth [2].

Apart from mastication, premolars play an impor-tant role in maintaining the overbite [1], their occlusion serves in diagnostics of the 1st key of occlusion ac-cording to Andrews [2]. Fromthe prosthetic view-point, premolars serve as the prosthetic pillar of the 2nd grade. In case the adjacent premolars create a block, they may be considered a prosthetic pillar of the 1st grade [1]. They also play an important role in the esthetics of the so-called buccal corridors [3, 4, 5, 6, 7, 8].

We monitored individual features and their combi-nations that may result in uneruption/impaction of pre-molars, and thus we wanted to find out potential cause of premolars uneruption/impaction. We were also inte-rested in whether the development of unfavorable si-tuation may be affected with orthodontic treatment.

Material

We worked with the sample of patients with unerup-ted/impacted premolars (sample B), and with the sam-ple of patients with physiological change of dentition (sample A).

The sample A (control) included 80 patients with na-tural change of dentition (which was documented with panoramic X-ray pictures - OPG).

The sample A met the following criteria:

1) minimum of 3 OPG taken during the development and eruption of premolars;

2) the first OPG was taken after the 1st phase of den-tition change had been finished;

3) premolar teeth had normal stage of tooth deve-lopment and their location was physiological;

4) following OPG proved the on-going physiological eruption of premolars.

The sample B (unerupted/impacted premolars) in-cluded 75 patients in which unerupted/impacted pre-molars were found in casts and OPG.

The sample B met the following criteria:

1) there exists at least one OPG for each patient; OPG may help in diagnostics of premolar uneruption and may help to identify that the development of the

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1. pacient ma zhotoveny minimaÂlneÏ jeden ortopan-tomogram, kde je mozÏno diagnostikovat retenci pre-molaÂru a urcÏit, zÏe vyÂvoj retinovaneÂho zubu je, dle mor-fologie korÏene skutecÏneÏ ukoncÏen, nebo, zÏe se jedna o impaktaci,

2. pacient ma zhotoven saÂdrovy model chrupu sou-cÏasneÏ s analyzovanyÂmrentgenovyÂm snõÂmkem.

Za duÊlezÏite povazÏujeme upozorneÏnõÂ, zÏe rentgenove snõÂmky nebyly zhotoveny pro uÂcÏely teÂto studie.

Metodika

Na rentgenovyÂch snõÂmcõÂch a saÂdrovyÂch modelech chrupu jsme sledovaly potenciaÂlneÏ patologicke znaky retence/impaktace premolaÂruÊ (uÂhel sklonu erupcÏnõ draÂhy, ztraÂta mõÂsta v opeÏrne zoÂneÏ, porÏadõ erupce zubuÊ v lateraÂlnõÂmuÂseku, ageneze premolaÂruÊ, nadpocÏetne zuby v oblasti remolaÂruÊ, reinkluze docÏasneÂho molaÂru). PrÏi pozorovaÂnõ jednotlivyÂch znakuÊ jsme sledovaly take jejich kombinace.

VyhodnocovaÂnõÂ erupcÏnõÂ draÂhy zaÂrodkuÊ premo-laÂruÊ (Obr. 1, 2) bylo provaÂdeÏno na ortopantomogra-mech. Byl meÏrÏen uÂhel sklonu erupcÏnõÂdraÂhy premolaÂru vuÊcÏi okluznõÂlinii, kteraÂbyla urcÏena distaÂlnõÂm ruÊzÏkem dolnõÂho centraÂlnõÂho rÏezaÂku a distaÂlnõÂm hrbolkem plneÏ prorÏezaneÂho prvnõÂho staÂleÂho dolnõÂho molaÂru. PodeÂ-lnou osu zaÂrodku premolaÂru tvorÏila kolmice na spojnici dvou protilehlyÂch boduÊ, ktereÂse nachaÂzely naproti sobeÏ v nejsÏirsÏõÂm mõÂsteÏ klinickeÂkorunky. ProdlouzÏenõÂ konstruovaneÂosy zaÂrodku premolaÂru prÏedstavovalo erupcÏnõÂdraÂhu a protõÂnalo konstruovanou okluznõÂ linii. UÂhel erupcÏnõÂdraÂhy premolaÂru byl meÏrÏen k distaÂlnõÂmu konci okluznõÂlinie.

Na saÂdrovyÂch modelech chrupu pacientuÊ byla meÏ-rÏenõÂmzjisÏt'ovaÂna prÏõÂpadna ztraÂta mõÂsta v opeÏrne zoÂneÏ. Toto meÏrÏenõÂbylo provaÂdeÏno standardnõÂm zpuÊ-sobem pomocõÂposuvneÂho meÏrÏidla. Pro zjisÏteÏnõÂztraÂty mõÂsta v opeÏrneÂzoÂneÏ byly pouzÏity zjednodusÏeneÂta-bulky podle Moyerse k odhadu mõÂsta potrÏebneÂho pro lateraÂlnõÂskupinu zubuÊ (staÂle sÏpicÏaÂky a premolaÂry).

unerupted tooth is (according to the root morphology) finished, or that it is the case of impaction;

2) casts and analyzed OPG for each patient are present.

We want to emphasize the fact that the OPG were not taken for the purpose of the presented study.

Method

In OPG and casts we observed potentially patholo-gical features of uneruption/impaction of premolars (inclination of eruption path, loss of space for canines and premolars, sequence of teeth eruption in lateral segment, missing premolars, supernumerary teeth in the premolar area, submerged deciduous molar). We also paid attention to the combinations of individual factors.

Evaluation of eruption path of premolar teeth (Fig. 1, 2) was made in OPG picture. We measured the inclination of premolar eruption path to the occlusal line. The occlusal line was determined by the distal cor-ner of the lower central incisor, and distal cusp of the fully erupted first lower permanent molar. Long axis of the premolar germ was represented by the perpen-dicular to the connecting line of two opposite points lo-cated in the widest part of clinical crown. Prolongation of the constructed axis of the premolar represented eruption path and crossed constructed occlusal line. The angle of eruption path of premolar was measured with regard to the distal end of occlusal line.

The potentialloss of space in area of canines and premolarswas measured in the casts. The measure-ment was performed with a calliper rule. Simplified ver-sion of Moyers tables was used to assess the loss of space in the area that is required for the group of lateral teeth (permanent canines and premolars).

Thesequence of teeth eruption in the lateral se-gment of dentition was assessed according to the position of tooth germs, or clinical crowns, in OPG. We focused especially on the eruption of second

per-Obr.1:MeÏrÏenõÂuÂhlu erupcÏnõÂdraÂhy - hornõÂcÏelist

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PorÏadõÂ erupce zubuÊ v lateraÂlnõÂm uÂseku chrupu jsme hodnotily podle polohy zaÂrodkuÊ resp. klinickyÂch korunek na ortopantomogramech pacientuÊ. V centru nasÏeho zaÂjmu byla zejmeÂna erupce druheÂho staÂleÂho molaÂru, pokud nastala prÏed erupcõÂdruheÂho premolaÂru.

SledovaÂnõÂ ageneze premolaÂru bylo provaÂdeÏno opakovanyÂm pozorovaÂnõÂm na ortopantomogramech pacientuÊ.

PrÏedmeÏtemnasÏeho zaÂjmu se staly rovneÏzÏ prÏespo-cÏetne zuby v oblasti premolaÂruÊ, ktereÂjsme pozoro-valy na ortopantomogramech pacientuÊ.

VyhodnocenõÂ reinkluze docÏasneÂho molaÂru bylo provaÂdeÏno pozorovaÂnõÂm na ortopantomogramech pa-cientuÊ a na saÂdrovyÂch modelech chrupu.

ZõÂskana data u jednotlivyÂch souboruÊ byla zpraco-vaÂna oddeÏleneÏ a vyhodnocena metodou popisne sta-tistiky. Statisticke vyhodnocenõ bylo provedeno Stu-dentovyÂmt-testemrovnosti strÏednõÂch hodnot.

VyÂsledky

Soubor A (kontrolnõÂ)

U kazÏdeÂho z 80 pacientuÊ v kontrolnõÂmsouboru byly hodnoceny angulaÂrnõ charakteristiky podeÂlne osy zaÂ-rodkuÊ vsÏech osmi premolaÂruÊ vuÊcÏi konstruovane oklu-znõ linii. U kazÏdeÂho pacienta kontrolnõÂho souboru bylo nameÏrÏeno 8 hodnot. ZõÂskaly jsme tak 640 nameÏrÏenyÂch hodnot (n=640).

Pro kazÏdy premolaÂr byla stanovena strÏednõ hodnota (mediaÂn) vzestupneÏ serÏazenyÂch nameÏrÏenyÂch hodnot uÂhluÊ jejich erupcÏnõ draÂhy. Takto zõÂskanou hodnotu u kazÏdeÂho premolaÂru jsme povazÏovaly za ¹ideaÂlnõ uÂhelª erupcÏnõÂdraÂhy pro sledovany zub. Pro prÏesne novenõ ¹ideaÂlnõÂho uÂhluª erupcÏnõ draÂhy bylo pouzÏito stisticke vyhodnocenõÂ, jehozÏ vyÂsledky uvaÂdõÂme v ta-bulce 1. Hodnotu ¹ideaÂlnõÂho uÂhluª jsme pouzÏily k po-souzenõ uÂhlu sklonu erupcÏnõ draÂhy zaÂrodkuÊ premolaÂruÊ u souboru retinovanyÂch/impaktovanyÂch premolaÂruÊ.

Tato hodnota slouzÏila take jako rozhranõ pro stano-venõ meziaÂlnõÂho nebo distaÂlnõÂho sklonu erupcÏnõ draÂhy premolaÂruÊ v souboru retinovanyÂch/impaktovanyÂch premolaÂruÊ.

Pro dalsÏõ hodnocenõ byla pouzÏita hodnota mediaÂnu uÂhlu erupcÏnõ draÂhy zjisÏteÏna pro kazÏdy premolaÂr zvlaÂsÏt'. Tuto hodnotu lze povazÏovat za fyziologickou hodnotu uÂhlu erupcÏnõ draÂhy pro kazÏdy jednotlivy premolaÂr (v Ta-bulce cÏ. 1 oznacÏeno silneÏ).

Soubor B (retence/impaktace premolaÂruÊ)

U 75 pacientuÊ, kterÏõ splnÏovali stanovena kriteria souboru B bylo nalezeno 108 retinovanyÂch nebo im-paktovanyÂch premolaÂruÊ (n=108).

manent molar in case it preceded the eruption of se-cond premolar.

Missing premolar (agenesis)was assessed by re-peated examination of OPG.

We also paid attention tosupernumerary teeth in the premolar area- we assessed the situation with the help of OPG.

Submerged deciduous molar was assessed by examination of OPG and casts.

The data obtained for individual samples of patients were processed separately, and evaluated with de-scriptive statistics. Statistic processing involved the t-tests.

Results

Sample A (control group)

Inclination of long axes of the germs of all eight pre-molars to the constructed occlusal line was evaluated in 80 patients of the control group. For each patient 8 values were measured. The overall number was 640 (n=640).

There was set the middle value (median) for each premolar - ascending sequence of the inclinations of their eruption paths. The middle value was taken as a ¹ideal inclinationª of the eruption path for the tooth observed. To state the ¹ideal inclinationª accurately, we use the statistical evaluation (the results are given in Table 1). The value of the ¹ideal inclinationª was used to assess the eruption path inclination of the germs of premolars in the group of impacted premolars. The va-lue also served as the dividing line for setting of mesial or distal inclination of premolar eruption paths in the sample of impacted premolars. The median value of eruption path inclination set for each premolar separa-tely was used. The value may be considered as the physiological inclination of eruption path for each indi-vidual premolar (in Table 1 in bold letters).

Tabulka 1: StatistickeÂvyhodnocenõÂsledovanyÂch hodnot uÂhlu erupcÏnõÂdraÂhy kontrolnõÂho souboru

Table 1:Statistical evaluation of eruption path inclinations in the control group

Tabulka 2:Skupiny souboru B. Znaky a kombinace znakuÊ v textu

Table 2:Groups of sample B. Characteristic features and their com-binations in text

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Sledovane znaky a jejich kombinace

V souboru B byly zjisÏteÏny naÂsledujõÂcõÂ znaky a jejich kombinace vytvorÏily naÂsledujõÂcõÂ skupiny B1 - B9 (pocÏty zubuÊ ve skupinaÂch v tabulce 2):

B1 ZtraÂta mõÂsta v opeÏrneÂzoÂneÏ a odchylka uÂhlu sklonu retinovaneÂho premolaÂru

B2 ZtraÂta mõÂsta v opeÏrneÂzoÂneÏ, odchylka uÂhlu sklonu retinovaneÂho premolaÂru a erupce druheÂho staÂ-leÂho molaÂru prÏed druhyÂm premolaÂrem

B3Odchylka uÂhlu sklonu retinovaneÂho premolaÂru, ageneze sousednõÂho nebo druhostranneÂho premolaÂru a ztraÂta mõÂsta v opeÏrneÂzoÂneÏ

B4ZtraÂta mõÂsta v opeÏrneÂzoÂneÏ a odchylka uÂhlu sklonu retinovaneÂho premolaÂru a reinkluze docÏasneÂho molaÂru

B5 Erupce druheÂho staÂleÂho molaÂru prÏed druhyÂm premolaÂrem a odchylka uÂhlu sklonu retinovaneÂho pre-molaÂru

B6Odchylka uÂhlu sklonu retinovaneÂho premolaÂru B7Odchylka uÂhlu sklonu retinovaneÂho premolaÂru a reinkluze docÏasneÂho molaÂru

B8Odchylka uÂhlu sklonu retinovaneÂho premolaÂru, erupce druheÂho staÂleÂho molaÂru prÏed druhyÂm premolaÂ-rem a reinkluze

B9Odchylka uÂhlu sklonu retinovaneÂho premolaÂru, ageneze sousednõÂho nebo druhostranneÂho prelaÂru, ztraÂta opeÏrneÂzoÂny a erupce druheÂho staÂleÂho mo-laÂru prÏed druhyÂm premolaÂrem.

PrÏi zpracovaÂnõÂ vyÂsledkuÊ nameÏrÏenyÂch hodnot u jed-notlivyÂch skupin B1 - B9 jsme vyhodnocovaly uÂdaje oddeÏleneÏ pro kazÏdou cÏelist pacienta.

U pacientuÊ souboru B jsme roztrÏõÂdily nameÏrÏene uÂhly erupcÏnõ draÂhy jednotlivyÂch premolaÂruÊ podle jejich inkli-nace. Za rozhranõ jsme povazÏovaly strÏednõ hodnotu (median) uÂhlu erupcÏnõ draÂhy zjisÏteÏnou pro jednotlive premolaÂry v kontrolnõÂmsouboru (soubor A).

UÂhly s hodnotou nizÏsÏõÂnezÏ je strÏednõÂhodnota uÂhlu erupcÏnõÂdraÂhy zjisÏteÏnaÂv kontrolnõÂm souboru jsme daÂle povazÏovaly za uÂhly sveÏdcÏõÂcõÂ o meziaÂlnõÂm sklonu erupcÏnõÂdraÂhy.

UÂhly s hodnotou vysÏsÏõÂnezÏ je strÏednõÂhodnota uÂhlu erupcÏnõÂdraÂhy zjisÏteÏnaÂv kontrolnõÂm souboru jsme daÂle povazÏovaly za uÂhly sveÏdcÏõÂcõÂ o distaÂlnõÂm sklonu erupcÏnõÂdraÂhy.

ZaÂkladnõÂ vyhodnocenõÂ souboru B

Ze 75 pacientuÊ souboru B meÏlo 49 pacientuÊ (65 %) jen jeden retinovanyÂ/impaktovany premolaÂr, u 22 pa-cientuÊ (29 %) jsme nalezly dva retinovaneÂ/impakto-vane premolaÂry. TrÏi retinoretinovaneÂ/impakto-vane premolaÂry byly u 2 pa-cientuÊ, daÂle byly registrovaÂny cÏtyrÏi (1 pacient) a peÏt re-tinovanyÂch premolaÂruÊ (1 pacient).

Retence/impaktace jednoho premolaÂru se u pa-cientuÊ v souboru B vyskytovala dvakraÂt cÏasteÏji v dolnõÂ cÏelisti nezÏ v hornõÂ cÏelisti.

Sample B (unerupted/impacted premolars)

In 75 patients included in the sample B, there were 108 unerupted or impacted premolars (n=108).

The features monitored, their combinations

In the sample B the following features and their combinations were found and the following groups B1 - B9 were formed (number of teeth in groups are in Table 2):

B1Loss of space in area of canine and premolars, and deviation in inclination of unerupted premolar.

B2Loss of space in area of canine and premolars, deviation in inclination of unerupted premolar, and eruption of the second permanent molar preceding the second premolar.

B3Deviation in the inclination of unerupted premo-lar, missing neighbouring or opposite premopremo-lar, and the loss of space in area of canine and premolars.

B4Loss of space in area of canine and premolars, deviation in inclination of unerupted premolar, and submerged deciduous molar.

B5Eruption of the second permanent molar prece-des that of the second premolar, and deviation in incli-nation of unerupted premolar.

B6Deviation in inclination of unerupted premolar. B7Deviation in inclination of unerupted premolar, and submerged deciduous molar.

B8Deviation in inclination of unerupted premolar, eruption of the second permanent molar preceding that of the second premolar, and submergence.

B9Deviation in inclination of unerupted premolar, agenesis of the neighbouring or opposite premolar, loss of space in area of canine and premolars, and eruption of the second permanent molar preceding that of the second premolar.

The results were processed for each group (B1-B9) and each jaw separately.

The eruption path angles of individual premolars were classified according to their inclination. The bor-derline was the median of eruption path angle of indi-vidual premolars in the control sample (group A).

Angles belowthe middle value of the eruption path angle found in the control sample, manifestmesial in-clination of eruption path.

Angles overthe middle value of the eruption path angle found in the control sample, manifestdistal incli-nation of eruption path.

Basic evaluation of the sample B

From the sample B (75 patients) one unerupted/im-pacted premolar was found in 49 (65 %) of them. 22 patients (29 %) had two unerupted/impacted premo-lars, three unerupted premolars were in 2 patients. There were registered also 4 (1 patient) and 5 (1 patient) unerupted premolars.

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ZhodnocenõÂmsouboru pacientuÊ s retinovanyÂmi/im-paktovanyÂmi premolaÂry bylo zjisÏteÏno, zÏe nejcÏasteÏji re-tinovanyÂ/impaktovany premolaÂr byl zub 35 (38%) naÂ-sledovany zubem45 (28,7%). V premolaÂrove oblasti hornõ cÏelisti dosÏlo nejcÏasteÏji k retenci/impaktaci zubu 25 (14,8%).

VyhodnocenõÂznakuÊ a jejich kombinacõÂv souboru B

Z celkoveÂho pocÏtu vyhodnocovanyÂch znakuÊ a jejich kombinacõ (n=108) bylo nejvõÂce (44,4%) zarÏazeno do skupiny B1 (ztraÂta mõÂsta v opeÏrne zoÂneÏ a odchylka uÂhlu sklonu erupcÏnõ draÂhy premolaÂru). Druhou vyÂznamnou skupinu znakuÊ prÏedstavovala skupina oznacÏena B2 (vyÂskyt ztraÂty mõÂsta v opeÏrne zoÂneÏ, odchylka uÂhlu sklonu erupcÏnõ draÂhy premolaÂru a erupce druheÂho staÂ-leÂho molaÂru prÏed druhyÂmpremolaÂrem) jejõÂzÏ podõÂl byl 35,2 % souboru (Tab. 2).

U skupin B4 - B9 je pocÏet znakuÊ v kazÏde skupineÏ mensÏõ nebo roven trÏem(n£3). Z tohoto duÊvodu jsme v dalsÏõÂmzpracovaÂnõ tyto skupiny v souboru B samo-statneÏ nevyhodnocovaly, ale jsou zastoupeny v hod-nocenõ jevuÊ u jednotlivyÂch premolaÂruÊ.

AnalyÂza skupin znakuÊ a kombinacõÂ znakuÊ v sou-boru B

Skupina B1

Do teÂto skupiny pacientuÊ seztraÂtou mõÂsta v opeÏrne zoÂneÏ a odchylkou uÂhlu sklonu erupcÏnõ draÂhy pre-molaÂru (B1)bylo zarÏazeno 48 retinovanyÂch/impakto-vanyÂch zubuÊ. NameÏrÏeneÂhodnoty uÂhluÊ erupcÏnõÂdraÂhy retinovanyÂch/impaktovanyÂch premolaÂruÊ vykazujõÂvel-kou variabilitu. Lze rÏõÂci, zÏe retinovaneÂpremolaÂry v teÂto skupineÏ vyÂrazneÏ cÏasteÏji dosahovaly meziaÂlnõÂho sklonu.

V teÂto skupineÏ B1 byl nejcÏasteÏji retinovanyÂ/impakto-vany zub 35 a vykazoval meziaÂlnõ sklon erupcÏnõ draÂhy. V hornõ cÏelisti byl v nasÏempodsouboru cÏasteÏji retino-vanyÂ/impaktovany zub 25 a take byl meziaÂlneÏ skloneÏn.

In sample B the unerupted/impacted one premolar in the mandible was two times more frequent than that in maxilla.

The most frequent unerupted/impacted premolars were (in order of prevalence): the tooth 35 (38 %) and the tooth 45 (28.7 %). In the premolar area of the ma-xilla the tooth 25 was the most often unerupted/impac-ted one (14.8 %).

Evaluation of features and their combinations in the sample B

Within the total number of characteristic features evaluated, including their combinations (n=108), the group B1 prevailed (44.4 %), i.e. loss of space in area of canine and premolars and deviation of the premolar eruption path inclination. The group B2 (loss of space in the area, deviation of premolar eruption path inclina-tion, and eruption of second permanent molar prece-ding that of the second premolar) represented 35.2 % (Table 2).

In groups B4-B9 the number of features is three or below three (n£3). Therefore, these groups of the sam-ple B were not evaluated separately. However, they are included in the evaluation of the phenomena in indivi-dual premolars.

Analysis of the features and their combinations in the sample B

Group B1

48 unerupted/impacted teeth were included in this group of patients withloss of space in area of canine and premolars and deviation of premolar eruption path inclination (B1). The values of angles of eruption path of unerupted/impacted premolars show great va-riability. Unerupted/impacted premolars inclined me-sially most frequently.

Obr.3.RozdeÏlenõÂpacientuÊ podle pocÏtu retinovanyÂch/impaktova-nyÂch premolaÂruÊ (soubor B)

Fig.3.Patients according to the number of unerupted/impacted

pre-molars (sample B) Obr.4.Fig.4.Number of unerupted/impacted teeth in individual premolarsCÏetnost retencõÂ/impaktacõÂ u jednotlivyÂch premolaÂruÊ - soubor B - sample B

(7)

K nejveÏtsÏõÂztraÂteÏ mõÂsta v opeÏrne zoÂneÏ dosÏlo v kvadrantu 3, kde hodnota maxima cÏinila 9,2 mm a pocÏet prÏõÂpaduÊ vyÂ-skytu ztraÂty mõÂsta v opeÏrne zoÂneÏ byl rovneÏzÏ nejvysÏsÏõ v tomto kvadrantu. PruÊm eÏrna hodnota ztraÂty opeÏrne zoÂny u vsÏech kvadrantuÊ se pohybovala okolo 5 mm.

Skupina B2

Ve skupineÏ pacientuÊ se ztraÂtou mõÂsta v opeÏrne zoÂneÏ, odchylkou uÂhlu sklonu erupcÏnõ draÂhy premo-laÂru a erupcõ druheÂho staÂleÂho mopremo-laÂru prÏed druhyÂm premolaÂrem (B2)jsme sledovaly 38 prÏõÂpaduÊ retinova-nyÂch/impaktovanyÂch premolaÂruÊ.

Znaky skupiny B2 se nejcÏasteÏji vyskytovaly v dolnõÂm zubnõÂmoblouku. V hornõÂmzubnõÂmoblouku byl zazna-menaÂn pouze jeden vyÂskyt v kvadrantu 2, kvadrant 1 nebyl zastoupen vuÊbec. NejveÏtsÏõ vyÂskyt byl zazname-naÂn v kvadrantu 3. Maximum ztraÂty mõÂsta v opeÏrne zoÂneÏ bylo nameÏrÏeno v dolnõÂmzubnõÂmoblouku a cÏinilo 7,1 resp. 7,2 mm.

Skupina B3

Do skupiny pacientuÊ s odchylkou uÂhlu sklonu erupcÏnõ draÂhy premolaÂru, agenezõ sousednõÂho nebo druhostranneÂho premolaÂru a ztraÂtou mõÂsta v opeÏrne zoÂneÏ (B3)bylo zarÏazeno 9 prÏõÂpaduÊ retinova-nyÂch/impaktovanyÂch premolaÂruÊ.

Kombinace znakuÊ teÂto skupiny se vyskytla nejcÏa-steÏji v kvadrantu 2.

Ve trÏech prÏõÂpadech ageneze nebyl zalozÏeny premolaÂr, ktery by sousedil s premolaÂremretinovanyÂm/impaktova-nyÂm. CÏasteÏji jsme vsÏak nalezly prÏõÂpady retinovaneÂho/im-paktovaneÂho premolaÂru spojene s agenezõ protilehleÂho premolaÂru dane cÏelisti. U dvou trÏetin pacientuÊ ze skupiny B3 se vyskytla ageneze jednoho premolaÂru a retence/im-paktace druhostranneÂho premolaÂru.

V jednomprÏõÂpadeÏ retinovaneÂho zubu 25 se druho-stranneÏ vyskytla nejen ageneze druheÂho premolaÂru, ale take transpozice staÂleÂho sÏpicÏaÂku a prvnõÂho premo-laÂru.

PrÏedcÏasna ztraÂta mõÂsta v opeÏrne zoÂneÏ postihla vyÂra-zneÏji hornõ zubnõ oblouk.

The prevailing unerupted/impacted tooth in the group B1 was 35. The tooth also showed mesial incli-nation of its eruption path. In the group, the most fre-quent unerupted/impacted tooth in the maxilla was 25. The tooth also inclined mesially.

The greatest loss of space in area was found in the quadrant 3, with the maximum value of 9.2 mm. The loss of space in area of canine and premolars was also most frequently found in this quadrant. The mean value of the loss of space reached approximately 5 mm.

Group B2

38 unerupted/impacted teeth were included in this group of patients withloss of space in area of canine and premolars, deviation of premolar eruption path, and the eruption of second permanent molar preceding that of second premolar (B2).

Characteristic features for B2 were found especially in the lower dental arch. We recorded only one in the upper dental arch, quadrant 2; there were no features recorded in quadrant 1. The highest incidence was re-corded in quadrant 3. The maximum loss of space in area of canine and premolars was measured in the lo-wer dental arch - 7.1 mm, 7.2 mm respectively.

Group B3

9 unerupted/impacted premolars were included in this group of patients with deviation of premolar eruption path, loss of adjacent or opposite lar, and loss of space in area of canine and premo-lars (B3).

The highest incidence of combinations of characte-ristic features was found in quadrant 2.

Tab.3:ZtraÂta mõÂsta a odchylka erupcÏnõÂdraÂhy premolaÂru - skupina B1

Table 3:Lost space and deviation of eruption path of premolar -group B1

Tabulka 4:Erupce druheÂho staÂleÂho molaÂru prÏed druhyÂm premolaÂ-rem - skupina B2

Table 4:Eruption of second permanent molar before the second premolar - group B2

Tabulka 5:Ageneze, ztraÂta mõÂsta a odchylka erupcÏnõÂdraÂhy

- skupina B3

(8)

Sklon erupcÏnõÂ draÂhy u retinovaneÂho/ impaktova-neÂho premolaÂru vykazuje v prÏõÂpadeÏ zubuÊ 24, 25 a 35 meziaÂlnõÂ tendenci, u premolaÂruÊ 14 a 44 naleÂzaÂme di-staÂlnõÂ sklon.

NejcÏasteÏji retinovanyÂmi/impaktovanyÂmi zuby sou-boru B byly dolnõ druhe premolaÂry, proto jsme u teÏchto prÏõÂpaduÊ vyhodnotily znaky (skupiny znakuÊ), ktere se podõÂlely na vzniku retence zubuÊ 35 a 45.

Retence/impaktace dolnõÂch premolaÂruÊ

Retence/impaktace leveÂho dolnõÂho druheÂho premolaÂru prÏedstavovala v souboru B nejcÏasteÏji se vyskytujõÂcõ retinovanyÂzub (41 prÏõÂpaduÊ). Na retenci/im-paktaci zde participovalo 7 skupin znakuÊ, z nichzÏ 50% zaujõÂmala kombinace znakuÊ - ztraÂta mõÂsta v opeÏrne zoÂneÏ, odchylka uÂhlu sklonu erupcÏnõÂdraÂhy premolaÂru a erupce druheÂho staÂleÂho molaÂru prÏed druhyÂm premo-laÂrem. DruhaÂnejcÏasteÏji zastoupenaÂkombinace znakuÊ (29%) byla ztraÂta mõÂsta v opeÏrneÂzoÂneÏ a odchylka uÂhlu sklonu erupcÏnõÂdraÂhy premolaÂru.

Z dalsÏõÂch pozorovanyÂch znakuÊ se ve trÏech prÏõÂpa-dech objevila reinkluze docÏasneÂho prÏedchuÊdce a v peÏti prÏõÂpadech se prÏidruzÏila ageneze protilehleÂho zubu 45. ZtraÂta opeÏrne zoÂny cÏinila pruÊm eÏrneÏ 4,54 mm. Sklon erupcÏnõÂdraÂhy vykazoval prÏevahu meziaÂlneÏ skloneÏnyÂch retinovanyÂch/impaktovanyÂch premolaÂruÊ (58,54% prÏõÂ-paduÊ). NameÏrÏene angulaÂrnõ parametry vykazovaly velky rozsah mezi minimaÂlnõÂm a maximaÂlnõÂmuÂhlem sklonu erupcÏnõ draÂhy.

Druha nejpocÏetneÏjsÏõ skupina retinovanyÂch/im-paktovanyÂch premolaÂruÊ prÏipadala na zub 45(31 pa-cientuÊ). Na patologickeÂerupcÏnõÂsituaci se zde podõÂlelo 6 skupin znakuÊ, nadpolovicÏnõ veÏtsÏina (56%) prÏipadala na kombinaci znakuÊ - ztraÂta mõÂsta v opeÏrneÂzoÂneÏ, od-chylka uÂhlu sklonu erupcÏnõÂdraÂhy premolaÂru a erupce druheÂho staÂleÂho molaÂru prÏed druhyÂm premolaÂrem.

Ve 32% prÏõÂpaduÊ byla pozorovaÂna kombinace ztraÂty mõÂsta v opeÏrne zoÂneÏ a odchylky uÂhlu sklonu erupcÏnõ draÂhy premolaÂru.

Hodnota pruÊm eÏrne ztraÂty mõÂsta v opeÏrne zoÂneÏ cÏinila 4,34 mm. PrÏi sledovaÂnõ soucÏasneÂho vyÂskytu ageneze a ztraÂty mõÂsta byl nalezen pouze jeden pacient s neza-lozÏenyÂmprotilehlyÂmpremolaÂrem. Hodnoty uÂhlu erupcÏnõ draÂhy ukazujõ na velmi vyrovnanou tendenci k meziaÂlnõÂmu i distaÂlnõÂmu sklonu retinovaneÂho/impak-tovaneÂho premolaÂru 45.

UÂhel sklonu erupcÏnõÂ draÂhy premolaÂruÊ jevil nejvõÂce nepravidelnostõÂ u zubuÊ 35 a 45.

Pro statisticke vyhodnocenõ byl proveden vyÂbeÏr ze vsÏech nameÏrÏenyÂch hodnot uÂhlu sklonu erupcÏnõ draÂhy zubuÊ 35 a 45 u kontrolnõÂho souboru a u souboru B.

PaÂrovyÂmt-testemrovnosti strÏednõÂch hodnot bylo zjisÏteÏno, zÏe rozdõÂl pruÊm eÏrneÂho uÂhlu sklonu erupcÏnõÂ

Three cases of agenesis were represented by the absence of premolar that would neighbour with the unerupted premolar. However, the unerupted premo-lar accompanied with the loss of the opposite premopremo-lar was more frequent. In 2/3 of patients in group B3 the agenesis of one premolar together with unerupted opposite premolar was found.

In one unereupted tooth 25 there occurred agenesis of the second premolar together with the transposition of permanent canine and first premolar.

The early loss of space in area of canine and premo-lars affected more often the upper dental arch.

Inclination of the eruption path of the unerupted/im-pacted premolar shows mesial tendency in case of teeth 24, 25 and 35, while distal inclination is found in premolars 14 and 44.

Lower second premolars were the most frequently unerupted/impacted teeth in group B. Therefore, in these cases we evaluated features (or groups of featu-res) contributing to the uneruption of the teeth 35 and 45.

Unerupted/impacted lower premolars

Unerupted/impacted left lower second premolar represented the most frequently unerupted tooth in group B (41 patients). 7 groups of features contributed to the uneruption/impaction; 50% represented combi-nation of the features - loss of space in area of canine and premolars, deviation of the eruption path of pre-molar, and eruption of second permanent molar prece-ding that of second premolar. The second most fre-quent combination of features (29%) included loss of space in the area, and deviation of the inclination of the eruption path of premolar.

We should also mention three cases of submerged deciduous tooth, and five cases with agenesis of the opposite tooth 45.

The average loss of area of canine and premolars was 4.54 mm. Inclination of eruption path was mostly represented by mesially inclined unerupted/impacted premolars (58.54%). Angular parameters showed great range between the maximum and minimum angle of inclination of the eruption path.

The second most frequent group of unerupted/ impacted premolars was represented by the tooth 45(31 patients). 6 groups of features contributed to the abnormal eruption. 56% represented combination -loss of space in area of canine and premolars, devia-tion of premolar erupdevia-tion path, and erupdevia-tion of second permanent molar preceding that of second premolar.

The average loss of space in the area of canine and premolars was 4.34 mm. Only one patient with agene-sis of opposite premolar was recorded. Angular para-meters show balanced tendency to both mesial and

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di-draÂhy souboru B a kontrolnõÂho souboru je statisticky nevyÂznamny na hladineÏ vyÂznamnosti 5% (p¬0,5).

UÂhel sklonu erupcÏnõ draÂhy sledovany ve skupinaÂch souboru B (retence/impaktace premolaÂru) vykazoval v hornõ cÏelisti tendenci k distaÂlnõÂmu sklonu erupcÏnõ draÂhy, pro dolnõ cÏelist byl pomeÏr tendence k meziaÂl-nõÂmu nebo distaÂlmeziaÂl-nõÂmu sklonu 1:1.

Diskuse

Problematikou uÂhlu sklonu erupcÏnõ draÂhy premolaÂru se zabyÂval ve sve studii Wasserstein v Izraeli v roce 2002, kdyzÏ m eÏrÏil na ortopantomogramech angulaÂrnõ pa-rametry druheÂho dolnõÂho premolaÂru u 85 deÏtõ s prÏedcÏas-nou ztraÂtou docÏasneÂho druheÂho molaÂru. V teÂto studii zji-stil, zÏe po prÏedcÏasne ztraÂteÏ dolnõÂho docÏasneÂho druheÂho molaÂru druhy dolnõ premolaÂr vykazuje veÏtsÏõ variabilitu v uÂhlu sklonu sve erupcÏnõ draÂhy, ale tento rozdõÂl oproti kontrolnõ skupineÏ nenõ statisticky vyÂznamny (pacienti s prÏedcÏasnou ztraÂtou - druhy dolnõ premolaÂr prorÏezaÂval pod uÂhlem79,6°, u pacientuÊ, kde nedosÏlo k prÏedcÏasne ztraÂteÏ druheÂho dolnõÂho docÏasneÂho molaÂru - druhe dolnõ premolaÂry prorÏezaÂvaly pod uÂhlem83,2°) [10]. MediaÂn uÂhlu erupcÏnõ draÂhy v kontrolnõ skupineÏ nasÏeho souboru pro zuby 35 a 45 cÏinil 87°(tedy rozdõÂl 3,8°oproti Wasse-steinoveÏ skupineÏ kontrolnõÂ).

DalsÏõ Wassersteinova studie z roku 2003 je zameÏ-rÏena opeÏt na uÂhel sklonu erupcÏnõ draÂhy druheÂho dol-nõÂho premolaÂru v souvislosti s jeho opozÏdeÏnyÂmvyÂvo-jem. V teÂto praÂci m eÏrÏil na ortopantomogramech u 101 pacientuÊ uÂhel sklonu erupcÏnõ draÂhy vuÊcÏi mandibulaÂrnõ linii ve trÏech staÂdiõÂch vyÂvoje zaÂrodku druheÂho dolnõÂho premolaÂru [11]. KriteÂriempro zarÏazenõ do souboru byl nejmeÂneÏ devõÂtimeÏsõÂcÏnõÂcÏasovy odstup dvou ortopanto-mogramuÊ. Tohoto kriteria v nasÏemsouboru nebylo do-sazÏeno, nebot'se pro snõÂmkovaÂnõ pacientuÊ v cÏasoveÂm odstupu 9 meÏsõÂcuÊ nenasÏlo klinicke opodstatneÏnõÂ.

stal inclination of the unerupted/impacted premolar 45.

The angle of premolar eruption path showed irregu-larities especially in teeth 35 and 45.

For statistical processing, we selected out of all an-gular parameters (eruption path of 35 and 45) measu-red in the control sample and in sample B.

The pair t-test of equal mean values revealed that the difference in angle of inclination in sample B and in control sample is statistically insignificant, the level of significance being 5% (p ¬ 0.5).

The angle of eruption path monitored in individual groups of sample B (retention/impaction of premolar) showed tendency to distal inclination in the maxilla, while mesial and distal inclination was equally repre-sented in the mandible.

Discussion

Wasserstein discussed the angle of premolar erup-tion path inclinaerup-tion in his study in 2002. He measured angular parameters of the second lower premolars in OPG in 85 children with early loss of the deciduous se-cond molar. He found out that after the early loss of the lower temporary second molar, the second lower pre-molar showed greater variability of the angle of its eruption path. However, the difference was not statisti-cally significant in comparison with the control group (patients with early loss - the lower second premolar erupted in 79.6°, in the control group - the lower se-cond premolar erupted in 83.2°) [10]. Median of the of the eruption path angle in our control sample (teeth 35 and 45) was 87° (i.e. in comparison with Wasserstein's control group there was a difference of only 3.8°).

Another Wasserstein's study focuses on the angle of the second lower premolar eruption path connected with the late development of the tooth. In OPG of 101

Obr.5.Retence/impaktace 35 - kombinace znakuÊ

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MeÏrÏenõÂmztraÂty mõÂsta v opeÏrne zoÂneÏ v sledovanyÂch skupinaÂch u souboru B (retence/impaktace premolaÂru) bylo zjisÏteÏno rozmezõ pro hornõ zubnõ oblouk 1,5-7,6 mm (pruÊm eÏrna hodnota 4,97 mm) a pro dolnõ zubnõ oblouk 0,7 - 9,2 mm (pruÊm eÏrna hodnota 4,67 mm).

Je patrneÂ, zÏe pruÊm eÏrne hodnoty ztraÂty mõÂsta v opeÏrne zoÂneÏ v souboru B se pohybujõ do 5 mm, tzn. meÂneÏ nezÏ je meziodistaÂlnõ rozmeÏr premolaÂru.

DaÂle byla sledovaÂna erupce druheÂho staÂleÂho molaÂru prÏed druhyÂmpremolaÂrem. Zde jsme take m eÏrÏily, jak se tato skutecÏnost projevõ na prostorovyÂch parametrech v oblasti opeÏrne zoÂny. V souboru B byla zjisÏteÏna pouze jedna hodnota pro hornõ zubnõ oblouk (2,5 mm), pro-tozÏe v hornõ cÏelisti byl nalezen pouze jeden druhy staÂly molaÂr prorÏezaÂvajõÂcõÂprÏed druhyÂmpremolaÂrem. Hledane rozmezõ mohlo byÂt zjisÏteÏno v dolnõÂmzubnõÂmoblouku, protozÏe zde je vyÂskyt erupce druheÂho staÂleÂho molaÂru prÏed druhyÂmpremolaÂrempodstatneÏ cÏasteÏjsÏõÂ. PruÊ-meÏrna hodnota ztraÂty prostoru pro dolnõ zubnõ oblouk cÏinõ 4,1 mm (rozmezõ 0,2 mm - 7,2 mm).

Je zrÏejmeÂ, zÏe pruÊm eÏrne hodnoty ztraÂty mõÂsta v opeÏrne zoÂneÏ zpuÊsobene tlakemprorÏezaÂvajõÂcõÂho dru-heÂho staÂleÂho molaÂru a hodnoty ztraÂty mõÂsta v opeÏrne zoÂneÏ zpuÊsobene prÏedcÏasnou ztraÂtou docÏasnyÂch zubuÊ opeÏrnou zoÂnu tvorÏõÂcõÂch, jsou velmi podobneÂ.

PrÏedmeÏtemnasÏeho zaÂjm u daÂle byly ageneze pre-molaÂruÊ.

V souboru B mõÂrneÏ zde prÏevazÏoval vyÂskyt ageneze v hornõÂcÏelisti. Take bylo zjisÏteÏno, zÏe v souboru B z devõÂti pacientuÊ s agenezõ premolaÂru se v 6 prÏõÂpadech objevila retence premolaÂru protilehleÂho (skupina B3), tedy u 2/3 souboru .

V roce 2002 Shalish v Bostonu publikoval studii, kde se zabyÂval souvislostõ ageneze premolaÂru a odchylkou uÂhlu sklonu erupcÏnõ draÂhy premolaÂru druhostranneÂho [12]. Zkoumal druhe dolnõ premolaÂry a jejich angulaÂrnõ parametry v pruÊbeÏhu erupce. Ve sve praÂci Shalish na-lezl souvislost ageneze druheÂho dolnõÂho premolaÂru a distaÂlnõÂho sklonu erupcÏnõ draÂhy druhostranneÂho pre-molaÂru. PrÏedpoklaÂdaÂ, zÏe distaÂlnõ odchylka uÂhlu sklonu druheÂho dolnõÂho premolaÂru a ageneze premolaÂru dru-hostranneÂho m a genetickou souvislost.

V nasÏõ praÂci se souvislost ageneze premolaÂru a pa-tologicka erupce premolaÂru projevila takteÂzÏ. Patolo-gicka erupce se projevila u premolaÂru druhostranneÂho nebo sousednõÂho. Skupina, kde se tato souvislost kli-nicky projevila (B3) vsÏak byla maÂlo pocÏetna pro po-trÏeby statistickeÂho vyhodnocenõÂ.

DaÂle jsme se zabyÂvaly souvislostmi mezi kombino-vanou manifestacõÂ potenciaÂlneÏ patologickyÂch defino-vanyÂch znakuÊ u retencõÂ/impaktacõÂ premolaÂruÊ.

V souboru B (retence/impaktace premolaÂru) se ve veÏtsÏineÏ prÏõÂpaduÊ objevujõÂ kombinace dvou a võÂce poten-ciaÂlneÏ patologickyÂch znakuÊ.

patients he measured the angle of eruption path incli-nation to the mandible line during three stages of the development of the germ of second lower premolar [11]. There were two OPG made for each patient, the second one after 9 months. Our sample did not meet the criterion - there were no clinical reasons to make OPG after nine months in our patients.

We measured the loss of space in the area of canine and premolars in the individual groups of the sample B (retention/impaction of premolar): in the upper dental arch the interval was 1.5 - 7.6 mm (mean value = 4.97 mm), in the lower dental arch the interval was 0.7 - 9.2 mm (mean value = 4.67 mm). The mean loss of space in the area of canine and premolars within the sample B was less than 5 mm, i.e. less than the me-siodistal parameter of the premolar.

Further, we monitored the eruption of the second permanent molar that preceded that of the second pre-molar. We considered spatial parameters in the area of canine and premolars. In the sample B only one value was found for the upper dental arch (2.5 mm), because we found only one permanent second molar erupting prior to second premolar in the maxilla. The range of values was found in the lower dental arch - the occur-rence of second permanent molar erupting prior se-cond premolar was much more frequent there. The mean value of lost space for the lower dental arch is 4.1 mm (range from 0.2 mm to 7.2 mm).

The mean values of lost space in the area of canine and premolars due to the pressure of the erupting se-cond permanent molar, and values of lost space in the area due to the early loss of temporary dentition crea-ting the area, are very similar.

We also paid attention to the premolar agenesis. In the sample B the agenesis in maxilla prevailed. Out of the nine patients with premolar agenesis six showed unerupted opposite premolar (sample B3), i.e. 2/3 of the sample.

In Boston 2002, Shalish published his study about the association between premolar agenesis and devia-tion of the erupdevia-tion path inclinadevia-tion of the opposite pre-molar [12]. He focused on second lower prepre-molars and their angular parameters during eruption. He found the link between the missing second lower premolar and the distal inclination of the opposite premolar eruption path. Shalish assumes that the distal deviation of the second lower premolar and agenesis of the opposite premolar are genetically conditioned.

The agenesis of premolar and pathological eruption of other premolar occurred in our work, too. Abnormal eruption was found in the opposite or adjacent premo-lar. However, the group in which this connection was found (B3) was not large enough for the statistical eva-luation.

(11)

Toto zjisÏteÏnõ by naÂs mohlo do urcÏite mõÂry prÏiblõÂzÏit k osveÏtlenõ prÏõÂcÏiny retence/impaktace premolaÂru.

Pro vznik retence/impaktace premolaÂruÊ musõÂ byÂt velmi pravdeÏpodobneÏ zastoupeno neÏkolik neprÏõÂzni-vyÂch okolnostõÂ. VyÂskyt jen jednoho potenciaÂlneÏ patolo-gickeÂho znaku ve veÏtsÏineÏ prÏõÂpaduÊ nevede k retenci/im-paktaci premolaÂru.

V souboru B byla nejcÏasteÏjsÏõ kombinace ztraÂty mõÂsta v opeÏrne zoÂneÏ a odchylky uÂhlu sklonu erupcÏnõ draÂhy (skupina B1). Tuto kombinaci lze pravdeÏpodobneÏ pova-zÏovat za jednu z prÏõÂcÏin retence/impaktace premolaÂru.

Druha nejcÏasteÏjsÏõ kombinace, ktera vedla k retenci/ impaktaci premolaÂru byla ztraÂta mõÂsta v opeÏrne zoÂneÏ, odchylka uÂhlu sklonu erupcÏnõ draÂhy zaÂrodku premo-laÂru a erupce druheÂho staÂleÂho mopremo-laÂru prÏed druhyÂm premolaÂrem (soubor B2). I tato kombinace vede k ma-nifestaci retence/impaktace premolaÂru.

DomnõÂvaÂme se, zÏe je duÊlezÏite prÏedchaÂzet ztraÂteÏ mõÂsta v opeÏrne zoÂneÏ pecÏlivou sanacõ docÏasnyÂch zubuÊ tvorÏõÂ-cõÂch opeÏrnou zoÂnu, a tak udrzÏovat jejõ meziodistaÂlnõ roz-meÏr. Tento pozÏadavek je trÏeba akcentovatzejmeÂnau pa-cientuÊ, kde na ortopantomogramu nachaÂzõÂme tendence k odchylkaÂmv erupcÏnõ draÂze zaÂrodku premolaÂru (sklon, vzaÂjemna kolize) a u pacientuÊ s atypickyÂmporÏadõÂm erupce zubuÊ v lateraÂlnõÂmuÂseku chrupu.

Z potenciaÂlneÏ patologickyÂch znakuÊ vedoucõÂch k re-tenci/impaktaci premolaÂruÊ dokaÂzÏeme vcÏasnou orto-dontickou intervencõ efektivneÏ ovlivnit pouze ztraÂtu m õÂ-sta v opeÏrne zoÂneÏ. DomnõÂvaÂme se, zÏe pro dalsÏõÂstudium tohoto probleÂm u je trÏeba hledat dalsÏõ souvislosti mezi puÊsobenõÂmjednotlivyÂch potenciaÂlneÏ patologickyÂch erupcÏnõÂch faktoruÊ premolaÂruÊ a mezi jejich vyÂvojem.

ZaÂveÏr

Absence premolaÂruÊ zubuÊ v zubnõÂch obloucõÂch prÏed-stavuje probleÂm, ktery je v rÏadeÏ prÏõÂpaduÊ m ozÏne uÂspeÏsÏneÏ ortodonticky vyrÏesÏit. Jednou z cest je co nej-drÏõÂve odhalit potenciaÂlneÏ patologicke prÏõÂcÏinne faktory retence premolaÂruÊ.

U pacientuÊ s retencõ nebo impaktacõ premolaÂruÊ do-chaÂzelo k sumaci võÂce znakuÊ. V tomto souboru byla ve 44% zastoupena kombinace ztraÂty mõÂsta v opeÏrne zoÂneÏ a odchylky uÂhlu sklonu prorÏezaÂvajõÂcõÂho premo-laÂru a v 35% byla zastoupena kombinace ztraÂty mõÂsta v opeÏrne zoÂneÏ, odchylky uÂhlu sklonu prorÏezaÂvajõÂcõÂho premolaÂru a erupce druheÂho staÂleÂho molaÂru prÏed dru-hyÂmpremolaÂrem.

MõÂra odchylek v erupcÏnõÂ draÂze nebyla pro retenci premolaÂruÊ statisticky vyÂznamnaÂ.

Velmi pravdeÏpodobneÏ je tedy retence nebo impak-tace premolaÂruÊ vyÂsledkemvõÂce potenciaÂlneÏ patologic-kyÂch jevuÊ a teprve jejich soucÏasnyÂmvyÂskytemv dane oblasti dochaÂzõ k retenci nebo impaktaci premolaÂru.

We also considered the links between the combi-ned manifestations of potentially abnormal features in impacted premolars.

In the sample B (unerupted/impacted premolars) there were usually found combinations of two or more potentially pathological features. Therefore, we could try to explain the cause of unerupted/impacted premo-lars.

Several unfavorable conditions must be probably present for the unerupted premolars. In most cases the occurrence of one potentially abnormal feature does not result in the uneruption/impaction of a premolar.

Loss of space in the area of canine and premolars together with deviation of the eruption path was the most frequent combination in the sample B (B1). The-refore, the combination seems to be one of the causes of premolar uneruption/impaction.

Loss of space in the area, deviation of the inclination of eruption path, and eruption of second permanent molar prior to that of second premolar represented the second most frequent combination (B2). It also re-sulted in premolar uneruption/impaction.

We believe that a thorough care of temporary denti-tion is the best prevendenti-tion of loss of space in the area. This should be emphasized especially in the patients whose OPG suggest tendency to deviation of the erup-tion path of a premolar germ (inclinaerup-tion, mutual colli-sion), and in the patients with atypical order of eruption in the lateral segment.

The early orthodontic intervention may effectively influence only the loss of space in the area. We are sure that it is necessary to search for other links between in-dividual factors influencing abnormal eruption of pre-molars and their development.

Conclusion

Missing premolars in dental arches pose the pro-blemthat can be successfully solved by the orthodon-tic treatment. It is essential to discover potentially pa-thological factors resulting in unerupted premolars as soon as possible.

Several factors contributed to the unerupted/im-pacted premolars. The combination of the loss of space in the area and deviation of erupting premolar represented 44%; the combination of the loss of space in the area, deviation in inclination of premolar, and eruption of the second permanent molar preceding that of the second premolar represented 35%.

The deviations of eruption path were not statistically significant for the unerupted premolars. Therefore, we assume that uneruption/impaction of premolars is the result of more potentially pathological phenomena, and only their co-occurrence may lead to the premolar uneruption/impaction.

(12)

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2. KamõÂnek, M.; SÏtefkovaÂ, M.: Ortodoncie I. Olomouc: Uni-verzita PalackeÂho, 2001.

3. Proffit, W. R.; Fields, H. W.: Contemporary Orthodontics. 3rd ed., St. Louis: Mosby, 2000.

4. Capelozza Filho, L.; Cardoso, Mde. A.; An, T. L.; Bertoz, F. A.: Maxillary canine-first premolar transposition. Angle Orthodont. 2006, 77, cÏ. 1, s. 167-175.

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8. Moore, T.; Southard, K. A.; Casko, J. S.; Qian, F.; Sou-thard, T. E.: Buccal corridors and smile esthetics. Amer. J. Orthodont. dentofacial Orthop. 2005, 127, cÏ. 2, s. 207-213.

9. Kot'ovaÂ, M.: Ortodonticky pruÊvodce praktickeÂho zubnõÂho leÂkarÏe. Praha: Grada Publishing, 2006.

10. Wasserstein, A.; Shalish, M.: Adequacy of mandibular premolar position despite early loss of its deciduous mo-lar. ADSC J. Dent. Child. 2002, 69, cÏ. 3, s. 254-258, 233-234.

11. Wasserstein, A.; Brezniak, N.; Shalish, M.; Heller, M.; Ra-kocz, M.: Angular changes and their rates in concurrence to developmental stages of the mandibular second pre-molar. Angle Orthodont. 2004, 74, cÏ. 3, s. 332-336. 12. Shalish, M.; Peck, S.; Wasserstein, A.; Peck, L.:

Malposi-tion of unerupted mandibular second premolar associa-ted with agenesis of its antimere. Amer. J. Orthodont. dentofacial Orthop. 2002, 121, cÏ. 1, s. 53-56.

MUDr.Hana BenesÏovaÂ

Stomatologicka klinika 3.LF UK Praha SÏrobaÂrova 50, 100 34 Praha 10

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