Oral Biology Research, 2018; March 31, 42(1):37-44 Copyright c 2018, Oral Biology Research Institute DOI: 10.21851/obr.42.01.201803.37 Original Article ORAL BIOLOGY RESEARCH An analysis of temporomandibular joint vibration about the balancing side occlusal contacts and temporomandibular joint noises Se-Jin Joo 1, Dong-Wan Kang 2,3, and Gyeong-Je Lee 2,3 * 1 Apple tree Dental Clinic, Pyeongtaek 17936, Republic of Korea 2 Department of Prosthodontics, School of Dentistry, Chosun University, Gwangju 61452, Republic of Korea 3 Oral Biology Research Institute, Chosun University, Gwangju 61452, Republic of Korea (Received Jan 17, 2018; Revised version received [1] Jan 29, 2018 [2] Feb 8, 2018; Accepted Feb 12, 2018) ABSTRACT The purpose of this study is to investigate the effect of balancing side occlusal contacts on temporomandibular joints (TMJ) through sonography. In this study, 100 adults with no symptoms of temporomandibular disorder (TMD) such as pain or opening disorder but with the possibility of clicking sounds were investigated. Subjects were checked for occlusal interferences with articulating paper, and the presence of clicking sounds with TMJ palpation and stethoscopy. Subsequently, they were classified into four groups according to their status of occlusal interferences or clicking sounds for each category. The joint vibration of the subjects was recorded using joint vibration analysis (JVA). JVA indexes (total integral, integral 300 Hz, peak amplitude, peak frequency, >300/<300 ratio, med. frequency, max. opening) were measured and compared. All JVA indexes showed no statistically significant difference between the groups. Only JVA index of > 300/< 300 ratio, med. frequency showed a statistically significant difference in the group with both interference and clicking sound. If there are balancing side interferences and clicking sounds at the same time, a larger >300/<300 ratio, med. frequency showed that the interferences and the TMJ clicking sounds were chronic and affected the TMJ vibration. KEY WORDS: Balancing side occlusal contact, Temporomandibular joints (TMJ) clicking sound, Joint vibration analysis (JVA) 서 론 측두하악장애 (Temporomandibular disorder; TMD) 는양측턱관절과근육, 여기에분포하는혈관및신경에나타날수있는모든문제로정의할수있으며, 저작근및악관절의통증, 악관절잡음, 하악운동의제한등의증상을보인다. 측두하악장애를쉽게일으킬수있는기여요인으로는외상, 정서적스트레스, 심부통증의유입, 이상기능활동, 교합이상이있다 [1]. 이중교합이측두하악장애의원인이라는것에는여전히많은이견이존재한다. Molin 등 [2] 은측두하악장애의유무와상관없이교합장애의발현빈도에서큰차이가없다고한반면 Pullinger 등 [3] 은근골격적안정위와치아의최대교두간접촉위사이의불일치가관절낭내장증의발 *Corresponding author: Gyeong-Je Lee Department of Prosthodontics, School of Dentistry, Chosun University, 303 Pilmun-daero, Dong-gu, Gwangju 61452, Republic of Korea Tel.: +82-62-220-3827, Fax: +82-62-220-3827 E-mail: lkj1998@chosun.ac.kr 생가능성을증가시킨다고보고하였고, Williamson [4] 은측방운동시의양측성교합접촉을보이는경우해당운동시좌우측측두근과교근네개의근육을모두활성화한다고하였다. Solberg 등 [5] 은이러한두가지의견을절충하였는데, 교합이상이다른요인들과복합적으로작용시악영향을미친다고하였다. 측두하악장애의흔한증상중하나인악관절잡음은 clicking, popping, crepitus로분류되며, 이중 clicking sound는동통이나기능이상의증상을동반하지않을경우병적으로간주하지않는다 [6,7]. 그러나 Widmalm 등 [8] 에의하면악관절잡음은어린나이에서부터발생하고측두하악장애의초기증상일가능성이있으며악관절잡음이존재하는경우측두하악장애의임상적발현빈도가높을수있다고보고하였다. clicking sound을포함한악관절잡음을측정하는방법에있어촉진및청진을이용할수있으나이는측두하악장애가심하게진행된경우를제외하고정확도가낮은방법으로악관절잡음에의한진동이아닌조직의진동을악관절잡음으로오인할가능성이존재한다 [9]. 이러한임상적한계를극복하기위해악관절잡음을측정하는장치가 - 37 -
Se-Jin Joo et al. Fig. 1. Sensor design (A) Sonography Sensor Design. When a vibration occurs in the TMJ, it must be strong enough to create a pressure wave that will transmit to the air in the sensor and make it to the microphone. 개발되었는데음파촬영술 (sonography) 과전자진동술 (electrovibratography) 이이에해당한다. 음파촬영술은악관절잡음이발생할때생기는악관절자체의진동을측정하는것이아니며, 악관절의진동으로인해일어나는조직의진동을측정한다. 반면에전자진동술은악관절잡음에의해발생하는악관절자체의진동을측정하고더불어주변의소음을차단하여보다정확한측정이가능하다. 전자진동술의원리를이용한장치로는대표적으로 Joint Vibration Analysis (JVA) (BioResearch. Inc., Milwaukee, Wisconsin, USA) 가있으며이러한장치들과음파촬영술의차이는센서의디자인차이로발생한다. 음파촬영술에사용되는센서는센서안에마이크로폰이내장되어있는며마이크로폰의빈공간이공기로채워져있는반면전자진동술의센서는빈공간이실리콘으로채워져있어악관절의진동을그대로전달하게된다 [10](Fig. 1). 측두하악장애와교합과의관계에관한기존의많은연구들은임상적증상, 저작근의활성및교합력등을측정하는방법을이용하였으나악관절잡음을이용한연구는부족한실정이다. 더불어이미심한측두하악장애를갖고있는환자가아닌잠재적인환자군에서의교합과의관계를입증한연구또한부족한실태이다. 앞서 Widmalm 등 [8] 이언급한것과같이 clicking sound는측두하악장애의발현빈도를높일수있다고하였다. 이는교합과 clicking sound의관계를파악하는것이, clicking sound를갖고있는경우측두하악장애로진행하는데있어하나의예방법으로서교합조정이가능할지판단케할것이다. 그래서본연구의목적은전자진동술의하나인 JVA 를이용하여측방운동시의균형측간섭과악관절잡음의관계를알아보는것이다. 재료및방법 연구대상및분류 20 30 대 ( 평균 28.5 세 ) 의조선대학교치과병원에내원한 Table 1. Classification of each group Balancing side Clicking Number of Total number Classification interference sound subjects of subjects Group 1 No No 24 Group 2 No Yes 17 90 Group 3 Yes No 32 Group 4 Yes Yes 17 환자및모집공고에지원한조선대학교치의학전문대학원학생중측두하악장애병력과현재동통및운동제한과같은측두하악장애를보이지않고, 정상개구량을보이며, 3대구치를제외한상실치가없는유치악환자 100명을대상으로하였다. 류마티스관절염과같은만성전신질환이있는경우, JVA 의개폐구운동을잘따라하지못하는경우대상자에서제외하였다. 실험진행에앞서조선대학교치과병원임상시험심사위원회의심의 (CUDHIRB 1608 036) 를거쳐진행하였다. 대상자들은측방운동시의좌우구치부의균형측간섭유무와환자의문진과촉진에의해측정되는측두하악관절의 clicking sound의유무에따라그룹으로분류하였다. 총 100명의대상자중측방운동시구치부균형측교합간섭이편측에존재하는경우 (10명) 는대상자에서제외하였다 (Table 1). 연구방법 측방운동시간섭유무측정 측방운동시의균형측간섭유무를판단하기위해측정에앞서측방운동반복훈련을시행하였다. 상악중철치를기준으로최대교두감합위에서좌우로 3 mm까지운동시켰으며 T-Scan II system (T-Scan system, TekScan Inc., Boston, MA, USA) 을이용하여측방운동시의구치부간섭유무를판단하였다. T-Scan sensor 두께로인한측정오차를줄이기위해교합지 (AccuFilm II, Parkell Inc., Edgewood, NY, - 38 -
An analysis of temporomandibular joint vibration Fig. 2. Sample Joint Vibration. Middle line of JVA is the metronome (A) normal JVA Screening Trace (B) abnormal JVA Screening Trace USA) 를사용하여검증하였다. T-scan 측정시에간섭이존재한다고측정되었으나측방운동시구치부에서교합지가물리지않는경우간섭이존재하지않는것으로간주하였다. 악관절잡음의측정 JVA 는최대개구시와폐구시에발생하는측두하악관절의진동을센서를통해측정하고측정된진동의파장을증폭하여컴퓨터상의프로그램 (BioPAKTM, BioResearch. Inc., Milwaukee, Wisconsin, USA) 으로수치가구현한다 [10]. 실험은다른소리에영향을받지않는실험실에서진행하였고, 피실험자들을편안한상태로의자에앉히고좌우측과두상방에센서를위치시켜 JVA 측정을진행하였다. 피실험자들의최대개구량을측정하여프로그램상에입력하고악관절잡음의측정에앞서개폐구운동의재현성을위해 60초간반복적인개폐구운동을연습시켰다. 폐구시에는치아의접촉음이확실히발생하도록연습시켰다. 일정한개폐구운동을위해컴퓨터모니터상의개폐구운동동영상및메트로놈소리에맞춰 1.5초당 1회운동의빈도로진행하였다. 60초간의연습후개폐구운동을중단하지않은채로이어서바로악관절잡음을측정하였다. 각각의피실험자들은적어도 6회이상의개폐구운동을시행하여악관절잡음을측정하였다. JVA 분석개폐구시에발생하는잡음은진동의진폭으로표현된다. 폐구시에발생하는치아접촉에의한진동을제외하고운 Fig. 3. Parameters were calculated within the BioPAK program. 동중발생하는가장큰진폭을보이는지점을선택하였다 (Fig. 2). 각각의수치는좌 / 우진동중 mirror image 와 >300/<300 ratio를고려하여원인관절로감별되는쪽을선택하였다 [11]. 개폐구운동의 4-6회째구간에서가장큰진폭을보이는 3 지점을선택하였고이 3 지점에서의평균을이용하여다음항목들을측정하였다 [12](Fig. 3). Total integral : 악관절잡음에의해발생하는진동의총에너지로 0에서 500 Hz 사이의에너지의총량을의미한다. Integral<300 Hz : 300 Hz 이하에해당하는에너지총량으로이영역은디스크의변위및정복, 관절의과 - 39 -
Se-Jin Joo et al. 운동영향을받는다. Integral>300 Hz : 300 Hz 이상에해당하는에너지총량으로관절의파괴적인변화와연관된다. >300/<300 ratio : 고주파수영역에너지에대한저주파수영역에너지의비율로관절의파괴적인변화와연관된다. Peak amplitude : 진폭이가장클때의진폭값을의미한다. Peak frequency : 가장높은진폭을가질때의주파수값을의미하며관절및디스크변위의만성화와연관된다. 통계학적분석 SPSS Ver. 20.0 (SPSS Inc, Chicago, IL, USA) 프로그램을이용하여통계처리하였으며, 각그룹간의측방운동시에발생하는구치부교합간섭과 clicking souund의연관정도를확인하기위해 Kruskall-Wallis test (P<0.05) 와 t-test (P<0.05) 를사용하였다. 결과 악관절잡음에의해발생하는진동의총에너지를의미 하는 total integral은모든그룹에서 20 Hz이하의적은에너지총량을보였으며, 대부분의피실험자에서 300 Hz이하에집중된에너지분포를보였다. >300/<300 ratio는모두평균 0.2 이하의낮은값을보였다 (Table 2). 각각의그룹간비교시모든항목에서통계적으로유의할만한차이를보이지않았다 (Table 3). 간섭유무에따른항목간비교를위해그룹 1, 2 대그룹 3, 4 간비교시통계적으로유의할만한차이를보이지않았고, (Table 4) clicking sound에따른항목간비교를위해그룹 1, 3 대그룹 2, 4 간비교시에도통계적으로유의할만한차이를보이지않았다. 다만 med. frequency는통계적으로유의할만한수준은아니나 clicking sound가존재하는경우다소크게나타나는경향을보였다 (Table 5). 고찰 측방운동시의교합간섭을포함한교합접촉양상에대한많은문헌들이존재하는데, Ogawa 등 [13] 은측방운동시작업측의견치에서가장많은교합접촉빈도를보인다고하였고 Song 등 [14] 의연구도이와비슷한결과를보였다. 한국인을대상으로한 Song 등의실험은, 측방운동시작업 Table 2. Mean (SD) vibration values of each group Group 1 Group 2 Group 3 Group 4 Total integral 12.28 ± 4.330 17.83 ± 12.30 18.96 ± 15.08 19.48 ± 18.29 Integral<300 10.99 ± 3.930 16.40 ± 11.02 17.29 ± 13.66 17.16 ± 16.05 Integral>300 1.33 ± 1.06 1.84 ± 1.56 1.78 ± 2.03 2.28 ± 2.58 >300/<300 ratio 0.16 ± 0.09 0.19 ± 0.08 0.16 ± 0.10 0.19 ± 0.09 Peak amplitude 1.90 ± 1.03 2.05 ± 1.13 2.38 ± 1.74 2.29 ± 1.99 Peak frequency 43.58 ± 15.09 54.59 ± 28.71 48.56 ± 19.77 45.18 ± 14.51 Med. frequency 84.29 ± 36.43 99.18 ± 30.88 89.47 ± 37.35 105.41 ± 39.340 Max. opening 52.63 ± 5.420 53.12 ± 5.010 51.20 ± 4.740 52.50 ± 7.710 Table 3. Correlation between groups on vibration values Total integral Integral<300 Integral>300 >300/<300 ratio p-value 0.507 0.427 0.325 0.411 Peak Amplitude Peak frequency Med. frequency Max. opening p-value 0.940 0.591 0.113 0.747 a) Statistically significant difference (P<0.05) (Kruskall-Wallis test). Table 4. Correlation between groups (group 1, 3 vs group 2, 4) according to clicking sound Total integral Integral<300 Integral>300 >300/<300 ratio p-value 0.093 0.100 0.283 0.922 Peak Amplitude Peak frequency Med. frequency Max. opening p-value 0.208 0.858 0.561 0.378 a) Statistically significant difference (P<0.05) (t-test). - 40 -
An analysis of temporomandibular joint vibration Table 5. Correlation between groups (group 1, 2 vs group 3, 4) according to occlusal interference Total integral Integral<300 Integral>300 >300/<300 ratio p-value 0.383 0.408 0.239 0.186 Peak Amplitude Peak frequency Med. frequency Max. opening p-value 0.979 0.428 0.058 0.518 a) Statistically significant difference (P<0.05) (t-test). 측에서견치유도보다군기능유도가더큰빈도를보였으나개개의치아접촉빈도는견치에서 34% 로가장높은접촉빈도를보이고구치부로갈수록낮은접촉빈도를보인다고하였다. 피실험자의 44.8% 에서측방운동시균형측에서의교합접촉이관찰되었으며, 작업측및균형측양쪽에서교합접촉이나타나는경우는 40.2%, 오직균형측에서만교합접촉이관찰되는경우는 4.6% 의비율을보였고균형측에서의치아접촉은주로제 2대구치에서관찰되었다. 본실험에서균형측에서의교합접촉빈도는약 45% 로 Song 등 [14] 의실험과유사한결과를나타내었다. 다른문헌들을살펴보면 De Laat 등 [15] 은 61% 에서 Sadowsky 등 [16] 은 88-91% 에서 Agerberg 등 [17] 은 23-25% 에서측방운동시균형측의교합접촉을보인다고하였다. 이러한논문들은연구대상이나연구방법에따라차이를보이나상당수의사람들에서균형측에서의교합접촉이존재한다는것을의미한다. 균형측에서의교합간섭이측두하악관절에부정 적인영향을미친다는것에는많은이견이존재하나, Mohlin 등 [18] 은측두하악장애를보이는환자들에서더많은균형측교합간섭이존재한다고하였다. 본실험에서는한국인의교합에서발현빈도가높으며측두하악장애를일으킬가능성높은경우를대상으로진행하고자하였으며실제로측방운동시작업측과더불어균형측에서도교합접촉이존재하는피실험자를대상으로진행하였다. Ishigaki 등 [19] 은측두하악장애가있는경우악관절잡음이정상적인범주의진동을보일지라도정상범주보다큰진동을보인다고하였다. 또한 total integral을이용한진단시민감도는 75%, 특이도는 77% 라고하였으며 [20] 특히초기정복성관절원판변위시민감도는 96.6%, 후기정복성관절원판변위시민감도는 91.8% 의높은민감도를보인다고하였다 [21]. 본연구의피실험자들은일부몇몇을제외하고대부분 20 Hz이하의낮은 total integral 을보였고일부에서만 80 Hz 이상의수치를보였다. Huang Fig. 4. JVA flow chart provided by BioResearch. Inc. - 41 -
Se-Jin Joo et al. 등 [22] 은 total integral에있어 20 Hz를기준으로정상과정복성관절원판변위로구분시그민감도는 85.7% 이며특이도는 84.6% 라고하였다. 이러한결과는 BioResearch. Inc. 에서제공하는 JVA flow chart에서도확인할수있으며 [23] 정상의경우대개 20 Hz의이하의 total integral을보인다 (Fig. 4). 피실험자들을 flow chart를이용하여잠정진단할경우모두정상범주에해당했으며 80 Hz의이상의 total integral 을보이는경우도단순 eminence click에의한것으로진단되었다. JVA 데이터를분석하기위해개폐구시에발생하는잡음의진폭중폐구시에발생하는치아접촉에의한진동을제외하고운동중발생하는가장큰진폭을보이는지점을선택하였다. Radke 등 [24] 에의하면대개개폐구운동의 4-6회째구간에서가장큰진동을보인다고하였으며이를토대로 4-6회째구간에서가장큰진폭을보이는 3 지점을선택하였다. Radke 등 [25] 은한쪽관절에서발생한진동은반대쪽관절에전달되며반대쪽관절에서는진동이발생하는관절에서의파장과반대로나타는 mirror image가나타난다고하였다 (Fig. 5). Widmalm 등 [26] 은진동의전달이하악골을통해전달되고반대쪽관절에서는약간의시간차를두고진동이나타나며연령이나골밀도, 골질에따라전달되는비율은다르게나타난다고한반면 Radke 등 [25] 은관절원판의변위의의한하악골의튕김현상에의한것으로방향에따라서도진동이전달되는정도가달라지며관절원판이전후방이아닌좌우측방변위시에더큰전달을보인다고하였다. 본연구에서는이러한원리를기반으로 mirror image를참고하여진동을일으키는원인관절을결정하였으며 mirror image가명확하지않는경우 >300/<300 ratio 수치를참고하였다. Jung 등 [11] 은명확한 mirror image를보이지않는경우진동이전달된관절에서 10이하의낮은 total integral을보 이며진동이발생한관절에비해더큰 >300/<300 ratio 값을보인다고하였다. 이는 300 Hz 이상의에너지를갖는진동의경우 300 Hz 이하의에너지를갖는진동에비해골전도가더잘일어나며이로인해 300 Hz 이상의진동이원인관절의반대측으로전달되기때문이다. JVA 는 500 Hz 이하의에너지를측정하며이를 300 Hz를기준으로에너지총량을산출한다. 높은 integral<300 Hz 값은관절원판의과운동을의미한다. 그래서일반적으로인대가더느슨하며관절낭이더큰여성에서남성보다큰수치를보인다 [12]. 이에반해높은 integral>300 Hz 값은측두하악관절의퇴행성변화를의미한다 [25]. Ishigaki 등 [19] 에의하면정상군과측두하악장애병력이있는실험군간의비교시 integral<300 Hz 값은차이를보이지않으나병력이있는군에서정상군에비해더높은 Integral>300 Hz 값을보인다고하였고또다른연구 [27] 에서는측두하악관절의퇴행성변화시 350-450 Hz의높은에너지를보이는진동이일어난다고하였다. Huang 등 [28] 에의하면측두하악장애가없는정상군에서는 >300/<300 ratio 중앙값이 0.1인반면정복성관절원판변위가있는군에서는 0.58의높은중앙값을보인다고보고하였는데본연구에서는모든그룹에서 0.2 이하의값을보였다. 이는 0.1 보다는약간큰값을가지나정상그룹에서작은 >300/<300 ratio 값을보인다는많은연구들의결과와일치한다 [19, 27, 28]. 본연구결과, 측방운동시존재하는구치부교합간섭은측두하악관절의병적인음파변화를일으키지않았으며모든피실험자들은정상적인파형을보였다. Tsolka 등 [29] 은측두하악장애와교합간섭이모두있는환자군에서교합간섭을제거하였으나측두하악장애의증상을현저하게개선시키지는못했다고하였으며, Rugh 등 [30] 에의하면조기접촉의존재가야간이갈이를증가시키지는않았다고하였다. 즉구치부의조기접촉이반드시근활성을증가시키지는않는다고하였는데이러한결과는앞에서 Fig. 5. Mirror image. There is transferred vibration in right side overlapped in lower waveform of left side vibration. - 42 -
An analysis of temporomandibular joint vibration 언급한 Widmalm 등 [8] 의연구와는반대되는결과를보인다. Seligman 등 [31] 도비슷한결과를보였는데교합간섭의발현빈도는측두하악장애환자와정상인간에차이를보이지않으며측두하악장애증상과밀접한관계를보이지않는다고하였다. 위에서언급한것과같이많은연구에서교합간섭과측두하악장애가관련이없음을보이며본연구의결과와일치한다. 실험의결과에의하면교합간섭이 clicking sound와연관이없으며, 교합간섭이존재할경우교합조정이 clicking sound의치료혹은하나의예방법이될수없음을간접적으로보여준다. 본실험은단순 clicking sound와교합간섭간의관계를규명하였으며교합간섭과측두하악장애의관계에있어더많은연구가필요할것으로사료된다. Randolph 등 [6] 은 110명의측두하악장애를환자를대상으로진행한장기간연구에서단순 clicking sound가존재한경우단 7% 만이 1-7.5년후 TMJ의병적인상태로진행하였고, Widmalm 등 [32] 은 clicking sound의존재유무가 TMD의감별기준이되지는않는다고하였으며, Kononen 등 [33] 에의하면 clicking sound의발현빈도는연령이증가함에따라증가하나 locking으로의진행은보이지않는다고하였다. 이러한연구결과와비슷하게본연구에서 clicking sound가측두하악관절의병적인음파변화를야기하지않았다. 본연구에서는피실험자의크기가크지않고성별이나나이를고려하지않은점, 교합간섭이나 clicking sound가존재한경우시간의경과에따른측두하악관절의음파변화를고려하지않는등의한계점이존재하는바이에관한추가적인연구가필요할것으로사료된다. 감사의글 This study was conducted with the research grant of Chosun University Dental Hospital in 2016. Conflict of Interest The authors declare that they have no competing interests. ORCID Se-Jin Joo 0000-0002-1814-661X Dong-Wan Kang 0000-0001-9455-4706 Gyeong-Je Lee 0000-0002-3545-2280 Reference 1. Okeson JP. Management of temporomandibular disorders and occlusion. 7th ed. Elsevier Health Sciences. 2013. 2. Molin C, Carlsson G, Friling B, Hedegaard B. Frequency of symptoms of mandibular dysfunction in young Swedish men. J Oral Rehabil 1976;3:9-18. doi: 10.1111/ j.1365-2842.1976.tb00925.x. 3. Pullinger AG, Seligman DA. The degree to which attrition characterizes differentiated patient groups of temporomandibular disorders. J Orofac Pain 1993;7:196-208. 4. Williamson EH. The role of craniomandibular dysfunction in orthodontic diagnosis and treatment planning. Dent Clin North Am 1983;27:541-560. 5. Solberg WK, Seligman DA. Temporomandibular orthopedics a new vista in orthodontics In Johnston LE (ed) ; New vista in orthodontics. Philadelphia Lea & Febiger. 1985;148-183. 6. Randolph CS, Greene CS, Moretti R, Forbes D, and Perry HT. Conservative management of temporomandibular disorders : A post treatment comparison between patients from a university clinic and from private practice. Am J Ortho Dentofac Orthop 1990;98:77-82. doi: 10.1016/ 0889-5406(90)70035-B. 7. Greene CS, Laskin DM. Longterm status of TMJ clicking in patients with myofacial pain dysfunction. JADA 1998;117:461-465. doi: 10.1016/S0002-8177(88)73018-4. 8. Widmalm SE, Christiansen RL, Gunn SM. Crepitation and Clicking As Signs of TMD in Preschool Children. Cranio 1999;17:58-63. doi: 10.1080/08869634.1999.11746078. 9. Hardison JD, Okeson JP. Comparison of three clinical techniques for evaluating joint sounds. J Creaniomandib Pract 1990;8:307-311. doi: 10.1080/08869634.1990. 11678329. 10. Christensen LV. Physics and the sounds produced by the temporomandibular joints. Part I. J Oral Rehabil 1992; 19:471-483. doi: 10.1111/j.1365-2842.1992.tb01111.x. 11. Jung DU, Kang DW. Study for discriminating method of origin side vibration from non-symptomatic clicking group. J Dent Rehabil Appl Sci 2016;32:38-46. doi: 10.14368/jdras.2016.32.1.38. 12. Gupta B, Thumati P, Radke J. Temporomandibular joint vibration from totally asymptomatic subjects. Cranio 2016;34:169-175. doi: 10.1179/2151090315Y.0000000013. 13. Ogawa T, Ogimoto T, Koyano K. Pattern of occlusal contacts in lateral positions: canine protection and group function validity in classifying guidance patterns. J Prosthet Dent 1998;80:67-74. doi: 10.1016/S0022-3913(98) 70093-9. 14. Song JH, Joo SJ, Lee HS, Kang DW, Lee GJ. An occlusal contact analysis of lateral mandibular movement - 43 -
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