___ Detailed analysis of
Tap Phenomenon_______________________________

Main concern of every prosthetic dentist is to take all measures while imprinting to avoid tap phenomenon.In order to achieve that, he/she must: - properly and in exact dosage to use impression masses - to pay attention of application time while working with impression masses - to pay attention on impression`s compression towards oral tissues. - to cut preliminary impression, thus can be done in two ways:

- with extending the lumen of imprinted dental crown - with making channels for leaking the surplus of imprint mass.

But, if this TAP PHENOMENON occurs, dentist must:
1. Take whole new impression, all over again (when there are more taps in the impression)
2. To cut out existing tap with neighboring imprint mass, and to place new second imprint mass and to perform taking a new impression just on that tooth ( rest of the impression remains the same)
3. To cut out the tap without any further correction.

Cutting off the tap phenomenon without doing any further correction of the impression is main aim of this analysis, because in that way we will achieve: - saving of impression material - not leaving patient with thoughts of doubt about the quality of our work, because "we are not taking the same impression for the second time"

When we can remove tap phenomenon without new correction of the impression ?

1. Horizontal ( incisal or occlusal ) tap phenomenons - they occur lineal to incisal line or occlusal (horizontal) surface of lumen of imprinted dental crown. These tap phenomenons depend of their size, can be: -total, when fully cover incisal line or occlusal surface of the lumen.It`s impossible to remove these phenomenons, and in this case re-impression is inevitable.
- partial, when partially cover incisal and occlusal surface and in this case it is possible with small technician's knife or scalpel to remove this phenomenon, because incisal or occlusal surface is partially unaltered and it would be quite easy to restore it fully on the casting model. Although, if we don't pay attention, with knife or scalpel we could harm unaltered surface, and then we must perform re-impression.
2. Vertical Tap phenomenons   - aproximal ; sinistral and dextral, - vestibular or - lingual These are phenomenons that occur on vertical surfaces of lumen of imprinted dental crown. a. also they can occur in the shapes, depends of their size: - total, when they fully line on vertical surface and it is very difficult to extract them with a knife or scalpel. - partial, when they partially cover vertical surface of the lumen.These phenomenons are easiest for removal b. if they cover more aproximal sides of the lumen, they can be: - one-sided ( covers only one aproximal side) - multi-sided (covers more then one aproximal side)
3. Combined ( horizontal-vertical, occlusal-aproximal)   When tap phenomenon covers incisal or occlusal and more vertical surfaces of the lumen. Impossible to remove.

Summary : There is no theoretic possibility to remove combined tap phenomenons without correction of impression. There, correction is ultimate. Occlusal tap phenomenons are hardest to remove, because it is almost impossible with scalpel or knife ( that is in vertical position) to remove some formation that lays horizontally, without altering the shape of the whole horizontal surface (ocllusal surface of the lumen). Altered shape of horizontal surface can be reconstructed later on casting model only in case when we will have two agonistic teeth next to the prepared tooth, which will show us the average clinical height of the crowns, and afterwards, we could reconstruct occlusal surface of prepared tooth, placing it 2 milliliters below occlusal surfaces of neighboring (not-prepared) teeth. This is not-precise method and it goes towards theory of ultimate correction of any impression that contains total tap phenomenons.
At vertical tap phenomenons, if they are multi-sided, it's rare to have success in removing tap phenomenons without correction of the impression, while at one-sided vertical tap phenomenons, correction is not necessary, because it's easier to remove formation on vertical surface with a knife or scalpel who is vertically positioned. Also, afterwards on casting model we could easily reconstruct vertical surface that was covered with tap phenomenon, because we know the shapes of other three unaltered vertical surfaces.

Pseudo-tap phenomenon is oval, rubbed formation inside of dental lumen of the impression. Reason for existence of this pseudo-tap phenomenon is caries cavity existing on prepared tooth, which was not treated (filled) by dentist. Usually dentist knows that this pseudo-tap phenomenon is due to caries cavity.

Dentist is not treating (filling) this caries cavity:

1. When it can be used as add to prepared space between prepared tooth and antagonist tooth, a space in which new artificial crown will take place.
2. When caries cavity is positioned on vertical surface of prepared tooth.This lesion was not filed with phosphate cement material before impression, because it will be filled during the cementation of a new artificial crown, in order to extend retention of the crown. When these pseudo tap phenomenons came in front of dental technician's eyes, and when they are not informed of pseudo existence of that cystic formation, they think that it is real tap phenomenon, so it is highly important for dentists to inform dental technicians about any unusual formations inside of dental impression.
if dental technician was not informed he/she can still make difference between real and pseudo tap phenomenons. Real tap phenomenons have clean sharp surface, and pseudo's don't.

Author : Dr.Boban Fidanoski, DT, DDS

Doctor of Dentistry, 2000 - Skopje, Republic of Macedonia.
Dental Technician, 1992 - Skopje, Republic of Macedonia

Date of on-line publishing : 01-th January 2002

© 2002 Copyright - Text and photographs by Boban Fidanoski- Skopje,Macedonia

Thanks to Dr.Natali Dimovska, M.D. , Dr.Dusan Velkoski, D.D.S. and Dr.Liljana Velkoska, D.D.S.

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