TAP CHi NGHIEN CLPU Y HQC •
M 6 | LIEN QUAN GIU'A HJNH THAI THAN RANG Vai TiNH TRANG CHEN CHUC RANG TREN CUNG HAM
Hodng Viet Hai, Tdng Minh San Vidn ddo tao Ring Ham Mat, tnrong dai hpc Y Hi Ndi Nghien ciru nhim dinh gia mdi lidn quan giu'a kich thwdc thin rang chiiu gin xa, chidu ngoii tmng vi ft' Id thin ring vdi muc dg chen chuc rang Tiin hanh do kich thude gin xa vi ngoii trong thin mng cua tit ci cie ring (trir rang him Idn thir hai va thw ba) d 100 miu thach cao hai him, sau do tinh ti Ig than rang. Cdc cung rang dwgc xip thanh ba nhdm tiiy theo mOc dd chen chuc rang- chen chOe vira, chen chen nh^ vi khdng chen chuc. So sinh kich thwdc thin ring vi ti 1$ than rang cua cac ddi tuang nghien ciru cOa ba nhdm trdn. Kit qua nghien cuv cho thay cac cung rSng cd muc dd chen chuc ring khic nhau co sw khic nhau c6 y nghTa d hau hit vi kich thwdc gin xa cua thin ring va ti 1$ than rang, nhung sw khic nhau l^i khdng rd rang ve kich thwdc ngoai trong cua than rang. Sw khic bidt vi kich thwdc gin xa giira cdc nhdm tdn tai d tit ca cac rang (thr rang ham nho thw hai) d ham tren vi ring cwa giwa, rang cCra bdn, ring him nho thir nhat d him dudi Vdi t! Id thin ring, sw khic bidt giira cac nhdm ton tai d nhdm ring cira, ring nanh. ring him nhd thw nhit ham trdn va rang cwa bdn, ring nanh, rang ham nhd thw nhat ham dudi.
TCr kh6a: kich thude gSn xa than rang, Kich thude ngoHi trong than rang, chen chuc rang
I. OAT
V A N D ^Tinh trgng chen ehue rang Id mdt trong nhdng d$e dilm nil bat vd pho bien nhit cOa Idch lgc khdp cdn [1]. Theo nghien cuu eua Buschangvd Suhulman ndm 2003, khoang 78% ddn s l Hoa Ky cd chen chuc d vung rdng trude d cdc mCre dd khac nhau [2]. Khi ddnh gid thim my ny cudi cua mdt ngudi, yeu t l dd nhdn biit nhat eua Idch lac khdp eIn Id su chen chCie rdng, dde biet la d vCing rang phia trudc Trong dilu trj chinh nha, tinh trang chen ehCie rdng phia trudc thudng duae xem • Id mdt van d l tham mT quan trpng, [3],
Ldeh lgc khdp edn khd pho bien d trdn thi gidi cQng nhu d Vidt Nam. Theo nghidn cuu cua Dong Khic Tham vd Hoang TCr Hung, ti l§
ldeh lac khdp edn d ngudi Vidt Nam d ICra tuoi
Bia chi liin hd: Hoing Viet Hal, -Vien Bio tao Ring Him Mit. Tmtng Bai hoc Y Hi NQI
Eemair hoanghairhm@gmail com Ngiy nhin: 20/3/2014 Ngiy duvc chip thuin 29/8/2014
17 - 27 Id 83,2% [4]. Nguydn nhdn gdy ra tinh trang ldeh lac khdp edn nhin chung khd da dgng. bao gom cdc ylu t6 di truyen vd yeu to mdi trudng. trong dd ed su khde nhau v l kich thude vd hinh dgng rdng.
Vide xdc djnh nguydn nhdn gdy ldeh lgc khdp eIn Id mpt dieu kidn quan trpng eho vi§c chin dodn vd dieu tn chinh nha [5]. Moi lidn quan gida chen chCie rdng vd kieh thude rdng dd 6ur?c nhilu tde gia trdn thi gidi nghidn cdu, tuy nhidn cdc kit lu$n vSn ehua thong nhat. [6; 7, 8; 9].
Trdn thi gidi dd cd nhieu nghidn cuu ddnh gid tinh trgng chen ehue rdng cQng nhu mli lidn quan eua nd vdi hinh thdi rdng. tuy nhidn d nude ta cho din nay vln chua ed nghidn edu ndo d l edp den van d l ndy. Vi v^y. ehCIng tdi thyc hign nghidn edu ndy nhim muc tidu.
Ddnh gid moi lidn quan giCra kieh thude
thdn rdng ehiiu gan xa, chieu ngodi trong vd ti
Id thdn rdng vdi myc dO chen chuc rdng
V ' W CHl NGHlfiN CIHJ Y Hpc It. D 6 | TU'aNG VA PHU'aNG PHAP
Ddy Id mdt nghidn cCru md ta cdt ngang trdn 100 ngudi lua tuoi 17 - 27, d y o c thyc hidn tai vidn Dao tao Rdng Hdm Mdt - Trudng Dai hpe Y Hd Ndj trong thdi gian t u thdng 9/2012 d i n thang 9/2013.
I.Ddi tuang Tirdu chuin lira chon - Cac rang vTnh v i i n dd mpc du.
- Khdng cd rang phge hinh.
- Khdng ed rang-vd ho^e hdn rdng d ria c i n rdng eu'a va d nOm ngodi rdng hdm.
- Khdng ed bat thudng v l so lyyng rdng, kich thude ho^e hinh dgng rdng,
Tieu chuan loai tru-
- NhCrng ngudi dd tdng d u a c d i l u tri chinh nha,
- Nhung ngudi cd di tdt b i m smh vung ham m0t.
- Nhung ngudi ed t i l n sir c h i n thuang vCing ham mat,
- NhCrng ngudi khdng hpp tdc, 2. Phu'ang phap
2.1. Kham lam s^ng, lay khudn vd do mSu hai ham rang
Doi tupng d u o c thdm khdm Idm sdng, ddnh gid tinh b^ng cua rdng vd vung quanh rdng.
Lay khudn hai hdm rdng b l n g alginate. Do m i u b l n g thach cao nha khoa.
2.2. Xac dinh kich thuvv va ty If thSn rang - Do ede kich thude g i n xa vd ngodi trong cua tCrng rang M l i kich thude dupe do ba l l n bdi cung mdt ngudi, eCing mdt dyng cy, trong eCing mdt dieu kign dnh sdng t y nhidn, nhidt dd phdng. Kieh thude d u o c chpn ghi vdo phidu la trung binh cdng cua ba lan do. Ty Id than rang: tinh ty le cua kich thude GX/NT cho tCrng rdng.
H i n h l . D o kich t h u ' d c than rdng g i n xa (A) va ngodi t r o n g (B)
2.3. Xac djnh muv dg chen chuc rang tr6n cung ham
a. Do kieh thude ehu vi cung hdm, xdc dmh khoang hien ed trdn cung hdm vd t i n g kich thude g i n xa cua cdc rdng.
b, Ddnh gia mCrc dd thieu khoang, chen chuc rdng trdn cung hdm.
Dua vdo mdc dp khde bidt tinh theo mm gida kich thude cung rdng vdi tong kich thude g i n xa eua cdc rdng:
JfiP CHi NGHIEN CO'U Y HpC •
- Tmng binh thieu khoang tCr 5,1 mm trd len, - Nhe: thieu khoang tCr 0,1 den 5 mm - Khdng ed chen ehue rang- thilu khoang 0 mm hodc thda khoang,
Cdc cung rdng hdm tren vd hdm dudi dype phdn loai mdt cdch ddc Idp,
3. Xir ly sd lieu
Tat ea cdc philu nghien cuu sau khi kiem tra lln culi, cdc ddy so lieu se dupe Idm sgeh, md hda vd nhdp vdo mdy tinh theo phin mem thong kd SPSS 11 5
Su dyng test thing kd kilm dmh phuang sai da biln (Test MANOVA) vd kilm dmh phuang sai dan biln (test ANOVA),
4. Oao dire nghien CIFU
Tit ea ede ddi tuong nghidn cuu deu ty nguydn tham gia vd duac khdm danh gid tinh trgng rdng midng, tu vln vd hudng din phuang phdp chdm sdc sdc khde rdng midng D0e bidt, nhO'ng trudng hpp cd Idch lac rdng - hdm sd duoc hudng ddn vd cd the phdi hap d l dilu tri nin chlnh rdng niu can thilL
Kit qud cua nghien edu dupe cdng bl rdng rdi, ding thdi cQng dua ra cdc kiln nghj, khuyen cdo d l gdp phin ndng eao hi$u qua chdm sdc sue khde rdng midng, dde bi$t id trong cdng tde dy phdng vd dieu trj nin chlnh rdng.
I. K^T QUA
1. Tinh trang chen chlic rang tren cung ham
" HSm dir6i
Chen chlic vira Chen chiic nhe Khdngchen chlic
Bieu dd 1. Ty Id cac nhdm chen chuc rang d hai ham
0 ea hai hdm, nhdm cd rang chen chCie nhe chiem ty Id eao nhat, tilp theo Id nhdm khdng cd
Chen chuc rdng vd thap nhat Id nhdm cd chen ehCic rang d mdc dd trun^ blnh,
2. Tuang quan cua cac kich thu'dc rdng vdi mu'c dp chen chuc rang
2.1. Kich thuvc than rang theo chiiu gan xaPhdn tieh blng test MANOVA eho tit ea cdc kieh thude cho thiy ed sy khde bidt trung blnh
cd y nghTa thong kd gida ede nhdm cung rdng (p < 0.01). Nhu vgy, it nhit cd mdt trong s6 ede
kieh thude gin xa cua rdng ed sy khde nhau trong s l ede nhdm ndy (bang 1},
• TjflkPCH(NGHIEN CI>U Y H Q C Bang 1. K i c h thu'dc: gdn xa cua than rang ham tren a cac n h o m (mm)
Rang Rang eu'a gi&a Rang ci>a ben Rang nanh RHN thif nhSl RHN thiJ hai RHL t h * nhSt
Khong Chen chuc 8,32 ±0,51 6,67 ± 0,46 7,62 ± 0,47 7,05 ± 0,38 7,01 ± 0,41 10,42 ±0,55
Ham tren Chen chuc nhe 8,68 ± 0,47 6,79 ± 0.60 7.66 ± 0,46 7.16 ±0.42 7,12 ±0.38 10.51 ±0,52
Chen chuc vira 8,74 ± 0,54 6,94 ± 0.49 7,78 ± 0,52 7,33 ± 0,45 7,19 ±0.42 10.56 ±0.53
Khdng Chen chuc 5,13 ± 0 3 2 5,73 ± 0,40 7,02 ± 0,44 7,15 ±0,39 7,21 ± 0,42 11,26 ±0,56
Ham d u ^ i Chen chuc nh?
5,21 ± 0 3 7 5,86 ± 0,42 7,21 ±0,45 7,26 ± 0,37 7,27 ± 0,39 11,31 ± 0 5 5
Chen chOc vira 5,27 ± 0,35 6,04 ±0,43 7,26 ± 0,47 7,34 ± 0.40 7,49 ± 0,43 11,52 ±0,63
So sdnh cdc kich t h u d e cua than rang giCra cdc nhdm b l n g phdn tieh phuong sai dan b i l n (test ANOVA) cho thay cd s y khde bidt ed ^ nghTa thdng ke eho t i t ca cdc rdng: d hdm trdn, t d rdng eCra gida d i n rdng hdm ldn thCr nhat (trCr rdng hdm nhd thy hai). Cf hdm d y d i . Id rdng cira gida, rdng cua bdn vd rdng hdm nhd thCr nhat,
Mdc dCi kfch t h y d c gan xa cua ede rdng trong nhdm ed chen ehue trung binh ludn ldn hon so vdl nhdm cd chen chCie nhg va nd cung ldn hon nhdm khdng cd chen ehue, khde bidt cd y nghTa thong ke ton tai giua cdc cung rang ed mCre dd chen ehue rdng trung binh vdi cung rdng khdng ed chen chuc.
2.2. Kich thuKK than rang theo chieu ngoai trong
Bang 2. K i c h t h u d e ngoai t r o n g cua t h a n rang d ham tren (mm)
Rang
Rang cCra giCra Rang eu'a bgn Rang nanh RHN thii nhat RHN thij hai RHL Ihii nhat
Khong Chen chuc 7,08 ± 0,35 6,10 ±0.41 8,05 ± 0,49 9,12 ±0,56 9,15 ±0,47 11,22 ±0,57
Ham tren Chen chOc
nh^
7.12 ± 0 3 7 6,09 ± 0,40 8,07± 0,52 9,18 ±0,53 9,20 ± 0,48 11,21 ±0,55
Chen chuc vi!ra 7,05 ± 0,33 6,02 ± 0,41 7,92 ± 0.51 9.27 ± 0.55 9,23 ± 0,46 11,24 ±0,58
Khong Chen chuc 6,02 ± 0,31 6,70 ± 0,38 7.61 ± 0.48 7,75 ± 0,47 8,32 ±0,51 10,93 ± 0 5 6
Ham du'di Chen chijc nh^
5,98 ± 0,35 6.73 ± 0.40 7.60 ± 0,46 7,78 ± 0,46 8,30 ± 0,49 10,91 ±0,58
Chen chijc vi!ra 6,04 ± 0,34 6,74 ± 0,37 7,57 ± 0,45 7,80 ± 0,48 8,37 ± 0,50- 10,95 ±0,54
SCr dyng phuang phdp kiem dinh thong kd, so sdnh cac kich thude rdng ngodi trong eho thay khdng cd s y khde bidt eo y nghTd ihoiig kd giun e t c ••'hd^ (t hdrr trdn- p > 0 20; d hdm dudi.
p > 0 , 1 8 ) .
TCNCYH 89 (4) - 2014
TAP CHi NGHIEN CCTU Y HQC •
3. T u a n g quan t i le t h a n rang (GX/NT) v d l mu-c dp chen chtic rang Bang 3. T i Id t h a n rang ctja cac rSng ham tren giira cac n h d m
Ham tren Ti le than rang: GX/NT (%)
R3ng Khong
chen chuc
Chen chuc nhe
Chen chuc vCra
Khong Chen chuc
Chen chuc Chen chlic vira Rang oia giira
R§ng cira bgn Rang nanh RHN thij nhat RHN thii hai RHL thii nhat
117,8 ±6,84 109,6±6,11 93,7 ±5.16 77,6 ±4,15 76,9 ± 4.26 93,0 ± 5,03
122,1 ±6,87 111,7±6,23 95,2 ± 5,21 78,3 ± 4,09 77.7 ±4,35 93,9 ±5,14
124,2 ± 7,02 115,8 ±6,27 98,6 ± 5,32 79,4 ± 4,37 78,1 ±4,41 94,4 ± 5,36
85,6 ± 4,32 85,8 ± 4,67 92,7 ±5,12 92,5 ± 5.23 86,9 ±4.17 103,2 ±6,12
87,4 ± 4,58 87,3 ± 4,73 95.1 ± 5.41 93,6 ± 5,36 87,8 ± 4,90 103,8 ±6,35
87,5 ± 4,45 89,9 ±4,52 96,3 ± 5,68 94,4 ±5,19 89,7 ±4,86 105,6 ±6,46 0 hdm trdn. phdn tich bang test MANOVA eho t h i y ti Id thdn rdng cd s u khde nhau giO'a cdc nhdm cung rdng chen ehue rang trung blnh, chen ehCie nhg, vd khdng chen ehCie rang (p < 0,01), Sy khde bigt (khi kiem dinh ANOVA) trong so cdc nhdm d i i t u p n g d rang eua giua (p = 0,005), rdng cua ben (p < 0.002), rang nanh (p = 0,005) vd rdng hdm nhd t h d nhat (p < 0,002)
0 hdm dudi, phdn tich bdng test MANOVA cho t h i y ti Ig thdn rang cd s y khde nhau gida cdc nhdm cung rdng chen chuc rang trung blnh, chen ehiJc nhg, vd khdng chen chCie rang (p < 0,001 vd p = 0,012 tuong Crng cho cung rdng tren vd cung rdng dudi). S u khde bidt (khi kiem djnh ANOVA) trong so ede nhdm doi tuong d rdng eua bdn (p < 0,002), rSng nanh (p < 0,002) vd rdng hdm nhd thd n h i t , (p < 0,01).
IV. BAN LUAN
Tinh trang chen chuc rdng tren cung hdm:
nghidn cCru ndy eho thay ty Id chen chuc rdng trdn cung ham d ede nhdm ddi tuong nghidn eCru Id khd eao. 0 cung ham trdn, tinh trang Chen ehue nhe chiem nhidu nhat vdi ty Id 45%, Cf cung hdm dudi, t u o n g t y nhu d hdm trdn, cung rdng d u d i ed muc dd chen chCie nhg chiem ty 10 cao nhdt (44%}, Vide ehia mdc dd Chen ehue rdng thanh ba nhdm nhy vay dd dupe nhilu tdc gia trdn thd gidi dp dyng vd nd cd y nghia trong chan dodn va Idp ke hoach d i l u tri ehinh hinh rdng mdt [8].
Tinh trgng chen chuc rdng xay ra khi khoang e I n thiet eho s y s i p x i p hop ly cua
rdng tren cung hdm Idn hon khoang cd s i n cua cung hdm. Didu ndy t h u d n g dan den tinh trang rdng xoay. nghidng, rang lac chd ho§e rdng mpc kgl Tuy nhidn. ngdy nay van chua ed mdt s y c h i p nhdn rdng rai ve mdt phuang phdp phdn logi ey the hay mdt ea s d de phdn loai chen ehue rdng. VI vdy, trong ede nghidn eCru tryde day, chen ehCJc rdng t h u d n g dype y d e tinh dua vdo cdc can c u khde nhau nhy:
Mdc dd sai ldeh eua ede rdng ridng le so vdi s u s i p xep Chung cua ea cung rdng Mdc dd khac bigt gida khoang sdn cd vd khoang c i n cd (su mat edn xu*ng rang - x u a n g o rdng).
Mdc dd khap khenh, chen chuc cua ede rdng eua hdm dudi...
• TAP CHl NGHIEN CChJ Y HQC Trong nhdm ed chen chiic rdng, chCing tdi
nh|n thay c h i l m n h i l u n h i t Id nhdm ed chen chuc d vCing rdng trudc (cdc rdng cua vd rdng nanh), edn chen chiJe d vOng rang sau (rdng hdm Idn vd rdng hdm nhd) c h i l m ti Id it han.
Nhu vdy, da s6 d l l t u o n g nghidn cdu ed chen chCic rdng d vCing rdng trudc, trong khi rat It d l l tupng ed chen ehCic vCing rdng hdm Idn vd rdng hdm nhd K i t qua ndy eOng phCi hop vdi nghidn cdu eua Noriko vd cpng s y [10]. Theo nghidn cdu eua Little vd cdng s u , tinh trang chen ehCic rdng x u i t hi^n vd tdng Idn d vCing rdng trudc theo t u l i [1],
M i l lldn quan giCra kich thude thdn rdng vdl tinh trgng chen ehCie rdng: theo nhieu tdc gid, sy khde bi$t ve kich t h u d e eua ede rdng d cung rdng bdn phai. vd cung rdng bdn trdi Id khd nhd vd khdng ed ^ nghTa t h i n g kd Dieu ndy eho t h i y r i n g kieh thude eua rdng a ea hai bdn phai vd trdi d i u cd t h i l i y ldm dai dien eho kich thude eho mdu nghidn eCru [8], Trong nghidn cCru ndy, chCing tdi cung nhan thay khdng cd s y khde bidt ndo d u o c phdt hidn giO'a hai nCra cung rdng (trdn eCing mpt cung rdng), vl v^y, gid trj trung blnh eua ea hai nCra cung rdng, ca kieh t h u d e gan xa vd ngodi trong cua rdng, d i u d u a e s u dyng trong t i t ea cdc phdn tieh t h i n g kd.
M l i lidn quan gida cdc kieh thude eua rdng trong mdt cung rdng dd 6wac n h i l u tdc gia trong vd ngodi nude cdng bo vd nd cijng dd dupe cdc nhd Idm sdng s u dyng rdng rdi d l d y dodn kieh t h u d e rdng khi Idp k l hoach d i l u trj. Dieu ndy cho thay s u tuang quan da chieu cOa mdi rdng trong cung rdng tuong Crng. Vi vdy, nghidn edu ndy dd str dyng phuang phdp thong kd nhdm so sdnh cdc kfch thude eua t i t ea cdc rdng gida ede cung rdng khdng chT d mCrc dd tCrng rdng ndng le md edn k i t hpp d i n g thdi vdi nhdng rdng khde.
Hidn nay. nguyen nhdn gdy ra chen chOc rang vdn chua thuc s y sdng td hodn todn, ed tdc gia eho r i n g tinh trang chen chuc rdng ed t h i Id k i t qua eua xu hudng tien hda trong dd kieh t h u d e xuong mdt giam khdng kdm theo s y giam tuong Crng eua kieh thude rdng. Cd nhieu y l u td cd the anh hudng den tinh trgng chen chuc rdng trdn cung hdm, trong dd kich thude rang d u o c nhidu tae gia xem Id mdt yeu td quan trpng va da cd n h i l u nghidn cuu so sdnh kich thude eua rang giCra ede cung rdng cd vd khdng cd chen ehue rang.
Theo k i t qua cua nghidn cu'u ndy, cdc kich thude cua than rang theo chieu gan xa a hdm trdn vd hdm d u d i cd s u khde nhau giua ba nhdm ddi tupng nghidn edu. 0 hdm trdn, s y khde nhau k i t hop trong cdc nhdm Id do t i t ca cdc kich thude gan xa eua thdn rdng (cCia t i t ea ede rdng, trCr rdng hdm nhd thd hai), trong khi dd d hdm dudi, s u khde nhau ndy chi do kieh thude cua rdng cCra giu'a, rdng cua bdn vd rang hdm nhd thu nhat. Chung tdi dd nhdn thdy mdt md hinh gia tdng d tat ea ede rdng dupe danh gid; Khi kieh thude gan xa cua than rang tang len, muc dd chen chuc rdng d mdi cung rang cung tdng ldn T r u d c ddy dd cd mpt sd nghidn eCru so sdnh kieh thude g i n xa eua t i t ca cac rdng d hdm trdn va ham dudi.
K i t qua cua chung tdi phu hop vdi nghidn c d u eua Doris [7] nhung khdng phu hap vdi nghidn c u u eua Howe [9]. Trong dd, d h i u h i t nhO'ng nghien c u u t r u d c ddy, s u so sdnh ehi d u o c thyc hidn giO'a hai nhdm (cung rdng ed chen ehue rang vd cung r§ng khdng ed chen ehue rang). Nghidn eCru nay dd so sdnh vd eho t h i y s y khde bidt v l kich thude gan xa eua than rdng giua cae nhdm doi typng ed mCrc dd chen chuc rdng khde nhau. Tde gia Bernabe cung da nghidn cuu v l van d l ndy vd eCtng ed ket luan t u a n g t y .
TCNCYH 89 (4) - 2014
TAP CHI NGHIEN CU'U Y HQC •
Khi so sdnh kich thude than rdng theo ehiiu ngodi trong giCra ede nhdm ddi tuang cd mdc dd chen ehue rang khde nhau, chung tdi nhdn t h i y khdng ed s y khde biet v l kich thude thdn rdng theo chieu ngodi trong khi phoi hpp tat ea cdc kich t h y d c ndy d mdi cung rdng.
Ddnh gid v l tT Id than rdng giua ede nhdm eho t h i y ed s u khac nhau eho ea hai cung rdng. Nhdng khac bidt nay la do s u bdt tuong xCrng eua rdng eua giua, rang eua bdn, rdng nanh vd rdng ham nhd thCr n h i t d hdm trdn;
vd do rdng eCra ben, rang nanh vd rang hdm nhd thCr nhat d ham d u d i Mae du ed mdt md hlnh tdng ti Ig thudn, nhyng nd khdng rd rdng nhy md hinh ndy d kich thude g i n xa cua thdn rdng
Bernabe eho r i n g e I n phai cd them ede thdng s l ngodi kich thude gan xa cua thdn rdng vi theo nhu'ng ket qua nghien eCru eua tdc gia ndy thi ti le than rang eua rdng nanh eho thgy ed s u khde biet d ea hai cung rdng, trong khi kieh thude gdn xa eua than rdng ndy lai khdng cd s y khde bidt cd y nghTa thdng kd d hdm d y d i [8]. Tae gia Bernabe cung dd khuyen cdo r i n g hlnh thdi rdng ( d day bao g i m kich thude rdng vd ti le than rdng) ehi Id mdt trong nhdng y l u to cd the bao g i m trong nhdm nguydn nhdn gdy chen ehCie rang trdn cung hdm,
V. K^T LUAN
Ti Id chen ehue rdng trdn cung ham d cdc nhdm doi typng nghidn cCru la khd eao. Cdc cung rdng ed muc dp ehenchCie rdng khde nhau (trung blnh, nhe vd khdng chen chCic} cd s y khde nhau cd y nghTa d hau h i t ve kieh thude g i n xa eua thdn rang vd ti Id thdn rdng, nhung s u khde nhau Igi khdng rd rdng ve kieh thude ngodi trong cOa t+idn rang.
S y khde bidt ve kieh thude gan xa gida cdc nhdm t i n tgi d t i t ca ede rdng (trCr rdng hdm nhd thCr hai) d ham tren vd rdng eua giCra. rdng cira bdn, rdng ham nhd thd n h i t d hdm dudi. Vdi t i le than rdng, s y khde bidt gida ede nhdm ton tgi d nhdm rang cua, rdng nanh, rdng hdm nhd thCr nhdt ham trdn vd rdng eCra bdn, rang nanh, rang ham nhd thCr nhat hdm dudi.
Lo'i
came n
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Summary
THE RELATIONSHIP BETWEEN TOOTH MORPHOLOGY AND DENTAL CROWDING
This study compares the mesiodistal, bueeolingual tooth sizes and their respective crown proportions in the moderate, mild, and nonerovk^ded dental archs. The mesiodistal and bueeolin- gual tooth sizes of all permanent teeth except the second and third molars were measured from 100 dental casts and their crown proportion was calculated Tooth size measurements were made with a sliding caliper. Each dental arch was classified as presenting moderate dental arch, mild dental arch and noncrowded dental arch The comparisons among the three groups for the tooth sizes and crown proportions were performed. The results showed that mesiodistal tooth sizes and crown proportions from almost individual teeth are significantly different between moderate, mild, and noncrowded arches, but no significant difference was observed among crowding groups for the bueeolingual tooth sizes The compansons indicated differences for mesiodistal tooth size of all upper teeth (except second premolars) and for lower central incisors, lateral incisors and first premolars. Differences were also detected for crown proportions of the upper central incisors, lateral incisors, canines, first premolar, as well as for the lower lateral incisors, canines and first premolars.
Keywords: mesiodistal tooth size, bueeolingual tooth size, dental crowding
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