許多研究結論已經指出牙根發育溝是造成牙周破壞的輔助因子，而大臼齒牙根形態對於牙周並進行也有明顯的影響。對於牙根發育溝在臼齒部位解剖型態與發生原因的報告尚付闕如。本研究樣本收集自1999年9月至2001年2月間，高雄醫學大學附設醫院牙科病患與高雄地區診所拔除之大臼齒為樣本共332顆。上顎第一大臼齒52顆，上顎第二大臼齒91顆，下顎第一大臼齒58顆，下顎第二大臼齒131顆。分析其牙根發育溝之發生率、牙根發育溝之長度、牙根發育溝至牙骨質牙本質交界(CEJ)的距離，以及牙根發育溝最深點的深度、佔牙根長的位置、與到牙根根管的距離，並且將牙根分類為上顎第一大臼齒，僅一種分類。下顎第一大臼齒，區分成Type A：正常分叉牙根近心牙根內側面發育溝。Type B：三牙根近心根內側面發育溝。上顎第二大臼齒區分成Type A：沒有牙根融合。Type B：兩個頰側根融合，Type C：任一個頰側根與顎側根融合。Type D：全融合，Type E：假性融合。上顎第二大臼齒，區分成Type A：沒有牙根融合。Type B：全融合。Type C： C-形牙根對側無發育溝。Type D：C-形牙根對側有發育溝。Type E：假性融合。結果顯示：(1)牙根發育溝的發生率在上下顎第一與第二大臼齒以下顎第二大臼齒最高，上顎第一大臼齒最低。(2)上下顎第一與第二大臼齒牙根發育溝在左右側發生率沒有統計學上的差異(p>0.05)。(3)上顎第二大臼齒次分類發生率以Type D與Type B為最多Type E 為最少下顎第二大臼齒次分類以Type B與Type C為最多Type E為最少。(4)牙根發育溝距離CEJ的距離以上顎第二大臼齒較短下顎第二大臼齒較長。(5)上顎第二大臼齒各個次分類牙根發育溝到CEJ之間的距離，以Type B最長，Type C最短。(6)下顎第二大臼齒次分類牙根發育溝到CEJ之間的距離以右側的Type B最長，最短的是左側的Type B。(7)牙根發育溝(DRG)最深點位於整個牙根中的位置，均是以位於牙根中間三分之一為最多，(8)在牙根發育溝深度方面，無論橫切或是縱切DRG所得到的結果，與直接以數位測微器所測得的結果，有統計學上的差異(橫切：p=0.0317，p<0.05，縱切：p=0.0030，p<0.05)。(9)牙根發育溝(DRG)最深點到牙根根管之間的距離平均為0.95±0.25mm。

Numerous studies concluded that developmental root groove is a cofactor of periodontal breakdown. The shapes of molar roots also have significant influence on the progression. The purpose of the present study were as follows：(1) location of molar developmental root grooves (DRGs), (2) prevalence of molar DRGs, (3) length and depth of molar DRGs, (4) measurement of the root wall thickness at the deepest point of DRG. The totally 332 teeth included maxillary first molar(52), maxillary second molar(91), mandibular first molar(58),and mandibular second molar(131). Maxillary second molar has five subtype, Type A: absence of root fusion, Type B: presence of mesiobuccal and distobuccal root fusion, Type C: palatal root with anyone of buccal root fusion of molar with three roots, Type D:complete root fusion of molar with three roots, Type E:pseudofusion of molar. Mandibular first molar has two subtype, Type A: mesial root with DRG on 2-root molar, Type B: mesial root with DRG on 3-root molar. Mandibular second molar has five subtype, Type A. absence of root fusion, Type B: presence of complete root fusion, Type C: c-shape root without DRG at counterlateral surface, Type D: c-shape root with DRG at counterlateral surface, Type E: pseudofusion of mesial and distal roots fusion. The results were summarized as follows: (1)Mandibular second molar has the highest distribution and maxillary first molar has the lowest distribution of maxillary and mandibular first and second molars. (2)There are no significant difference(p>0.05) between right and left maxillary and amndibular first and second molars. (3)Type D has the highest distribution of maxillary second molars; Type B has the hishest distribution of mandibular second molars. (4) DRG of mandibular second molars is longer than others. (5) Type B has the longest distance from CEJ to DRG and Type C has the shortest distance from CEJ to DRG in maxillary second molars. (6) Most of the DRG deepest points are located in middle third of DRG. (7) There are significantly statistic difference in depth between section and non-section(cross-section: p<0.05; longitudinal-section:p<0.05). (8)Mean distance from DRG to canal is 0.95±0.25mm.

論文目次
第一章 前言……………………………………………………………1
第一節 研究背景………………………………………………….1
第二節 文獻探討………………………………………………….7
第三節 研究目的………………………………………………….9
第二章 材料方法…………………………………………………….10
第一節 樣本收集………………………………………………..10
第二節 研究材料………………………………………………..10
第三節 研究步驟………………………………………………..11
第四節 資料處理與分析………………………………………..19
第五節 研究限制………………………………………………..20
第三章 研究結果………..……………………………………………21
前驅實驗的結果………………………………………………….21
第一節 大臼齒牙根發育溝發生率與臼齒位置之關係………..23
第二節 以游標尺與牙周探針直接測量上下顎第一與第二大臼齒牙根發育溝長度、深度與臼齒之關係………………...27
第三節 以立體顯微鏡測量上下顎第一與第二大臼齒牙根發育溝長度、深度與臼齒關係………………………………..49
第四章 討論…………………………………………………………..51
第一節 上下顎第一與第二大臼齒牙根發育溝發生率…………51
第二節 牙根發育溝研究方法……………………………………55
第三節 CEJ至牙根發育溝起始點之距離JA探討…………….58
第四節 牙根發育溝最深點深度之探討…………………………61
第五節 直接測量與立體顯微鏡測量牙根發育溝之比較………64
第五章 結論……………………………………………….…………..66
第六章 參考資料………………………………………….…………..69
附錄………………………………………………………….………….74
附圖及附表目次
Table 1-1 prevalence and distribution of DRG on molars (1626?)………………………………………………….74
Table 1-2 prevalence and distribution of DRG on molars (3646?)………………………………………………….75
Table 2 prevalence and distribution of DRG classification on molars..76
Table 3-1 Prevalence and distribution of DRG classification on maxillary right and left second molars…………………………………..77
Table 3-2 Prevalence and distribution of DRG classification on mandibular right and left second molars……………………...78
Table 4 Length and depth of DRG on molars…………………………79
Table 4-1 Length and depth of DRG on maxillary right and left first molar………………………………………………………….80
Table 4-2 Length and depth of DRG on maxillary right and left second molar………………………………………………………….81
Table 4-3 Length and depth of DRG on mandibular right and left first molar………………………………………………………….82
Table 4-4 Length and depth of DRG on mandibular right and left second molar………………………………………………………….83
Table 5-1 Length and depth of DRG at different root surface of maxillary right and left second molar……………………………………84
Table 5-2 Length and depth of DRG at different root surface of mandibular right and left second molar……………………….85
Table 6-1 Length and depth of DRG at different classification of mandibular right and left first molar…………………………..86
Table 6-2 Length and depth of DRG at different classification of maxillary right and left second molar…………………………87
Table 6-3 Length and depth of DRG at different classification of mandibular right and left second molar………………………..88
Table 7-1 Length and depth of DRG at different root surfaces in subtype classification of maxillary second molar………………………89
Table 7-2 Length and depth of DRG at different root surfaces in subtype classification of mandibular second molar…………………….90
Table 8 Distribution of the deepest point at root length on maxillary and mandibular molars……………………………………………..91
Table 8-1 Distribution of the deepest point at root length on maxillary first molar………………………………………………………92
Table 8-2 Distribution of the deepest point at root length on mandibular first molar………………………………………………………93
Table 8-3 Distribution of the deepest point at root length on maxillary second molar……………………………………………………94
Table 8-4 Distribution of the deepest point at root length on mandibular second molar……………………………………………………95
Table 9 Relationship in longitudinal section,cross section of root and normal DRG…………………………………………………….96
Table 10 Percentage of root canal system type found in mesio-buccal roots of maxillary first molars in various studies………………97
Table 11 Percentage of root canal system type found in mesio-buccal roots of maxillary second molars in various studies…………...98
流程圖…………………………………………………………………..99
Fig 1 Prevalence and distribution of DRG on maxillary first molar…..100
Fig 1-1 Prevalence and distribution of DRG on maxillary first molar ..101
Fig 1-2 prevalence and distribution of DRG on maxillary second molar…………………………………………………………..102
Fig 1-3 Prevalence and distribution of DRG on mandibular first molar…………………………………………………………..103
Fig 1-4 Prevalence and distribution of DRG on mandibular second molar…………………………………………………………..104
Fig 2 Location of reference points and measurement of DRG………..105
Fig 3-1 Prevalence and distribution of DRG classification on maxillary right and left second molar……………………………………106
Fig 3-2 Prevalence and distribution of DRG classification on mandibular right and left second molars…………………………………..107
Fig8-1 Distribution of the deepest point at root length on maxillary first molar………………………………………………………….108
Fig 8-2-1 Distribution of the deepest point at root length on mandibular first molar subtype A………………………………………….109
Fig 8-2-2 Distribution of the deepest point at root length on mandibular first molar subtype B………………………………………….110
Fig 8-3-1 Distribution of the deepest point at root length on maxillary second molar mesial surface…………………………………..111
Fig 8-3-2 Distribution of the deepest point at root length on maxillary second molar distal surface……………………………………112
Fig 8-3-3 Distribution of the deepest point at root length on maxillary second molar buccal surface……………………………….….113
Fig 8-4-1 distribution of the deepest point at root length on mandibular second molar mesial surface…………………………………..114
Fig 8-4-2 distribution of the deepest point at root length on mandibular second molar distal surface……………………………………115
Fig 8-4-3 distribution of the deepest point at root length on mandibular second molar buccal surface…………………………………..116
Fig 8-4-4Distribution of the deepest point at root length on mandibular second molar lingular surface…………………………………117
Fig A Root formation process of multiple roots teeth…………………118
Fig B-1 直接以數位測微器與牙周探針測量牙根發育溝…………..119
Fig B-2 以立體顯微鏡測量牙根發育溝……………………………..120
Fig B-3 牙根發育溝橫切與縱切圖…………………………………..120
Fig C透射燈光檢查牙根……………………………………………...121
Fig D上顎第一大臼齒………………………………………………..122
Fig E-1 下顎第一大臼齒 type A…………………………………….123
Fig E-2 下顎第一大臼齒 type B…………………………………….124
Fig F-1 上顎第二大臼齒 type A…………………………………….125
Fig F-2 上顎第二大臼齒 type B……………………………………..126
Fig F-3 上顎第二大臼齒 type C……………………………………..127
Fig F-4 上顎第二大臼齒 type D…………………………………….128
Fig F-5 上顎第二大臼齒 type E……………………………………..129
Fig G-1下顎第二大臼齒 type A……………………………………..130
Fig G-2 下顎第二大臼齒type B………………………………….….131
Fig G-3下顎第二大臼齒 type C…………………………………..…132
Fig G-4下顎第二大臼齒 type D…………………………………..…133
Fig G-5 下顎第二大臼齒 type E…………………………………….134

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