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RESTS AND REST SEATS Denture Base Artificial Teeth Supporting Rests Retainers Direct retainers Indirect Retainers Connectors : Major Connectors Minor.

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Presentation on theme: "RESTS AND REST SEATS Denture Base Artificial Teeth Supporting Rests Retainers Direct retainers Indirect Retainers Connectors : Major Connectors Minor."— Presentation transcript:

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3 RESTS AND REST SEATS

4 Denture Base Artificial Teeth Supporting Rests Retainers Direct retainers Indirect Retainers Connectors : Major Connectors Minor Connectors The Component Parts of Removable Partial Dentures

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7 Clasp assembly

8 REST

9 Rests: - Are rigid extensions of a Partial Denture, Placed in Rest Seats, Which are prepared on either the Occlusal, Lingual surfaces or Incisal edges of the teeth, providing Support to the Partial Denture

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11 The Quality of the Prosthesis to Resist Displacement Towards Denture Supporting Structures Support

12 Functions Of The RestsFunctions Of The Rests 1. Support 2. Transmitting vertical stress along the long axis of the tooth 3. Secure the clasp in its proper position 4. Distributing the Occlusal Load 5. It May Act As Indirect Retention.

13 1-Support SUPPORT & FORCE TRANSMISSION

14 Transmitting Vertical Stress Along The Long Axis Of The Tooth

15 3-Secure the clasp arms in their proper position

16 Secure the Clasp in Its Proper Position

17 4-Distributing the Occlusal Load

18 5-May Act As Indirect Retention

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20 6-Restore occlusion of the abutment that show tilting or infra-occlusion (overlay rest)

21 Tipped molar (Mesially inclined mandibular molar)

22 Onlay (reduce cusp angle)

23 7-Direct food away from tooth contact and embrasure area

24 Embrasure Rest A Gap Between Two Molars

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27 8-Resistance to Lateral Displacement of the Prosthesis but applying damaging horizontal forces on abutment teeth

28 Assembly ( A- Rests are either a part of a Clasp Assembly (primary rest) Or Auxiliary Rest An Auxiliary Rest Types of rests:-

29 Clasp assembly

30 Auxiliary rest

31 B-According to the relations to edentulous span: - B-According to the relations to edentulous span: - 1. Adjacent to the saddle 2. Away from the saddle

32 C- According to positions: - C- According to positions: - 1. Occlusal rest{ molars- premolar} 2. Lingual rests{ cingulam of canines-or casted lingual restorations} 3. Incisal rests {canines- incisors}

33 A Rigid Extension of a RPD That Contacts the Occlusal Surface of a Posterior Tooth or Restoration, on a Rest Seat Specially Prepared to Receive it. I- Occlusal Rest

34 Forms and Requirements of Rest Seat Preparation 1- Should Be Rounded Triangular in Shape the Base of the Triangle at the Marginal Ridge About 2.5 mm in Width, and Its Rounded Apex Is Directed Towards the Center of the Tooth 2.5m.m.

35 Rest Seat 2 -The Marginal Ridge Is Lowered Approximately 1 to 1.5 Mm of Teeth in Relation to a Vertical Line (permit sufficient bulk ) 1mm1mm

36 3- The floor of the rest seat should be spoon shaped

37 Forms and Requirements of Rest Seat Preparation Prevent Slippage of the Prosthesis Creating an Orthodontic Like Force The angle between the minor connector and the rest should be less than 90˚ To Direct the Forces Along the Long Axis of the Tooth

38 Rest Seat 4- Spoon Shaped Inclined Apically As It Approaches the Center of the Tooth 1mm1mm

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40 Forms And Requirements Of Rest Seat Preparation 5- 5-Rest seats are prepared in sound enamel, existing restorations or in crowns and inlays 6-If an amalgam restoration is present, it could be replaced by a cast restoration (Occlusal rests can be prepared in an old amalgam restoration 7-Preparations for the occlusal rest must precede making master cast and follow proximal preparation (guiding planes and elimination of undesirable undercuts)

41 GUIDING PLANES

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43 Requirements of the Occlusal Rest I- I-O.R. must fit the tooth ( minimize food collection and preserve their location in relation to the tooth 2- It must be strong enough to withstand the loads without deform 3- 3-It must not raise the vertical dimension of occlusion

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46 Not Raise the Vertical Dimension

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48 Employed Only on a Perfectly Periodontally Healthy Tooth Special Considerations Helps in Preventing Lateral Movement of the Denture 1- Boxed shaped occlusal rest

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50 II- Lingual Rests I- Occlusal Rest III. Incisal Rest Rests

51 II-Lingual Rests C. Canine Ledge A- Cingulum Rest (inverted V Rest) B. Ball Rest

52 II-Lingual Rests C. Canine Ledge A- Cingulum Rest ( V Rest ) B. Ball Rest

53 Lab Ling M D 2 mm A mm Half -Moon Shaped V- Shaped

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56 Adequate Tooth Preparation Directs Forces Down the Long Axis of Tooth

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58 III- Incisal Rest seat 1.5mm 2mm

59 1.5mm

60 III- Incisal Rest Used Predominantly As Auxiliary Rests or As Indirect Retainers Rigid Extension More Applicable on Mandibular Teeth 2.5 mm Wide and 1.5 mm Deep

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62 The Lingual Rest Is Preferable to an Incisal Rest Less Bothersome to a Curious Tongue More Esthetic Placed Closer to the Center of Rotation of the Abutment Tooth

63 Lingual Rest Will Exert Less Leverage and Reducing Its Tendency to Tipping

64 Post Is More Readily Removed by Application of Force Near Its Top Than by Applying Same Force Nearer Ground Level

65 IV- Embrasure Hooks Placed in Embrasures Between Teeth Extending Over the Buccal or Labial Surface but Never Extend Below Survey Line.

66 IV- Embrasure Hooks Act As Indirect Retainer Resistance to Lateral and Anteroposterior Movement

67 IV- Embrasure Hooks Poor Esthetics and Wedging Action on Teeth

68 THANK YOU


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