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1、部分牙冠,1,Section 4 Partial crown,部分牙冠,2,Definition ：Partial crown is a kind of fixed prosthetic restoration which cover part of the dental surface. Characteristics ：Less cutting of the tooth, short cervical margin, less stimulus to the gingival margin, easily be inserted, etc.,部分牙冠,3,Classification ：
2、3/4 crown of anterior tooth 3/4 crown of posterior tooth window crown half crown,部分牙冠,4, 3/4 crown 3/4 crown of anterior tooth Indication Tight occlusion, the anterior tooth with little defect in the proximal surface or incisal angle which is not suitable for full crown or veneering. The retainer of
3、 anterior fixed bridge that doesnt fit for other kinds of retainers . Those cases that need fixed splint or occlusal reconstruction.,部分牙冠,5,2. Contraindication The cases that defect is so much that enough resistance form and retention form can not be prepared The cases that the pulposis and periapic
4、al diseases have not been cured.,部分牙冠,6,3. Tooth preparation of anterior 3/4 crown （1）Preparation of proximal surface Purpose Cutting out enough proximal space for 3/4 crown, remove the undercut, guarantee the smooth insertion of crown.,部分牙冠,7,Requirement Two proximal surfaces should be parallel wit
5、h each other or polymerize toward the incisal end at 25and the space should not be less than 0.5mm. For those teeth with short crown and little proximal undercut, the crown margin should be at the level of gingival margin and the shoulder should be prepared. On the contrary, for those with long crow
6、n and obvious undercut, the crown margin may be above the gingival margin and no undercut exists in the crown-covered area. Method Slice cut and preparation by diamond bur,部分牙冠,8,Method of proximal slice cutting With one-side carbide disc, cut from the incisal end to gingival end and the disc should
7、 incline to the lingual surface according to the width of mesio-distal distance of the labial and lingual surfaces. Avoiding excessive cutting at the incisal angle.,部分牙冠,9,Method of proximal preparation by carbide bur The virtues of this method are safety, easy to control the dimension. Column-shape
8、d bur and cone-like carbide bur with the diameter less than 1mm is first used to cut out the space from the lingual-proximal surface and remove the undercut.,部分牙冠,10,The preparation method and dimension for proximal surface of 3/4 crown,部分牙冠,11,（2）The preparation of incisal bevel： Purpose To protect
9、 the incisal end of 3/4 crown, keep enough thickness of the restoration and avoid interference when protrusion. Requirement The incisal surface should incline from labial surface to lingual surface for upper incisors and from lingual surface to labial surface for lower incisors. Plane of 45 should b
10、e prepared on mesio-distal dimension Method The width of incisal bevel relates to the labial-lingual dimension and space more than 0.35mm should be prepared. For canine, two bevels should be prepared.,部分牙冠,12,The preparation of incisal bevel of 3/4 crown,部分牙冠,13,（3）The preparation of lingual surface
11、 Requirement Space of 0.5mm on the lingual surface and no undercut on the axial wall Method Space of 0.5mm from the lingual protuberance to gingival and 0.5mm from incisal bevel to lingual protuberance. Column-shaped stone and wheel-shaped stone are required.,部分牙冠,14,Two stages preparation of lingua
12、l surface,Section 2,Section 1,部分牙冠,15,（4）The preparation of proximal groove Purpose Avoid lingual-towards dislocation of 3/4 crown. Requirement Parallel to the incisal 2/3 of labial surface, between labial 1/3 and middle 1/3 of proximal surface. The depth of groove is 1mm and two grooves should be p
13、arallel to each other or polymerize to the incisal end. The groove is arch-like in shape and the incisal end should be wider than gingival end. The line angle between the groove and proximal surface should be clear. Method Fissure bur or fine carbide bur should be used to prepare the proximal groove
14、.,部分牙冠,16,The position and dimension of proximal groove （1）the position is correct （2）the groove is too close to labial surface （3）the starting point is too close to lingual surface （4）the groove is too close to lingual surface,部分牙冠,17,（5）Refinement The line angle should be continuous and round and
15、no undercut is permitted.,部分牙冠,18,（6）The preparation of incisal groove Role increase the marginal strength of 3/4 crown and promote the retention. Method the apex angle of the groove is 90, the height of labial wall is twice that of lingual wall and the end of incisal groove should be connected with
16、 the proximal grooves.,部分牙冠,19,The position and shape of incisal groove,部分牙冠,20,4. The manufacture of anterior 3/4 crown （1） Wax pattern preparation （2） Casting （3） Examination and cementation,部分牙冠,21,(二）3/4 crown of posterior tooth Indication Those cases with lingual and occlusal surface defect tha
17、t are not fit for full crown and filling. Those cases with occlusal surface defect or require occlusion reconstruction Retainer of fixed bridge Stabilization splint,部分牙冠,22,Contraindication The same with anterior 3/4 crown,部分牙冠,23,3. The tooth preparation of posterior 3/4 crown Basically same with t
18、he anterior 3/4 crown, the difference is： （1）Preparation of occlusal surface： Space of 0.51.0mm should be prepared on the occlusal surface，the margin of crown should be below the occlusal marginal crest in order to protect the dental cusps.,部分牙冠,24,The preparation of occlusal surface of posterior 3/
19、4 crown,部分牙冠,25,（2）The preparation of occlusal groove Purpose Avoid the lingual-towards dislocation of crown. Method The dimension of the groove should be 1.5mm1.5mm, the margin is round and the groove should be connected with the axial groove on the proximal surface.,部分牙冠,26,（3）The preparation of proximal groove Between the buccal 1/3 and middle 1/3 of proximal surface, parallel to the axial wall, and 1mm in depth and width.,部分牙冠,27,The manufacture of posterior 3/4 crown The same with anterior 3/4 crown,