Undercuts on teeth
Natural undercuts on teeth are important for the retention of partial dentures, dental appliances and rubber dam clamps. It is undesirable interproximally next to denture saddle areas and when preparing a tooth for a crown or other indirect restoration.
When assessing a patient for a partial denture or before rubber dam placement it is important to use your eyes to survey around the teeth to check for useful undercuts. Some molars have exceedingly straight buccal and lingual walls which makes retention of clasps and clamps difficult. Lingually tilted molars can make denture design difficult as it will result in a large open space under the lingual flange. You may want to design the denture so it sits anterior to teeth like this or fiddle with the path of insertion. Alternatively, mouth preparations can reduce these undesirable undercuts.
With rubber dam placement, lack of undercuts may force you to use subgingival clamps or to clamp the soft tissue. You should be able to pick the teeth that are unsuitable for regular clamping if you consider the undercuts on the buccal and lingual walls as well as the degree of eruption. cases where there is excess gingiva will hinder clamping as the undercut of the tooth is not exposed. The same goes for sectional matrix rings, lack of undercuts will cause them to pop off. You may want to supplement tooth separation with a wooden wedge and consider using a material such as flowable composite, GIC or dental compound to tack your rings and clamps down after placement.
When assessing a patient for a partial denture or before rubber dam placement it is important to use your eyes to survey around the teeth to check for useful undercuts. Some molars have exceedingly straight buccal and lingual walls which makes retention of clasps and clamps difficult. Lingually tilted molars can make denture design difficult as it will result in a large open space under the lingual flange. You may want to design the denture so it sits anterior to teeth like this or fiddle with the path of insertion. Alternatively, mouth preparations can reduce these undesirable undercuts.
With rubber dam placement, lack of undercuts may force you to use subgingival clamps or to clamp the soft tissue. You should be able to pick the teeth that are unsuitable for regular clamping if you consider the undercuts on the buccal and lingual walls as well as the degree of eruption. cases where there is excess gingiva will hinder clamping as the undercut of the tooth is not exposed. The same goes for sectional matrix rings, lack of undercuts will cause them to pop off. You may want to supplement tooth separation with a wooden wedge and consider using a material such as flowable composite, GIC or dental compound to tack your rings and clamps down after placement.
Yeah okay thanks for that mate
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