The restoration of a patient's tooth or teeth often includes the replacement of natural tooth structure by a manufactured dental restoration or dental prosthesis. Typically a tooth that is to be restored is first prepared by a dentist, for example by being abraded or ground to an appropriate shape to remove undesired tooth substance, and to provide the tooth with a shape appropriate to receive the dental restoration.
The dental restoration is typically mated precisely with the remaining tooth shape prepared by the dentist on the basis of an impression of the prepared tooth. Therefore the dental impression should be very precise, and should represent all tooth structure required to determine the shape of the mating surface of the later dental restoration. In particular the dental impression should represent the transition or the “margin” between the shape prepared in a tooth and the natural tooth shape. For dental restorations that extend below a patient's gingiva (or gums) the dentist also should make the part of the margin accessible for the dental impression that would normally be covered by the gingiva. The procedure of displacing the gingiva from the tooth to make the margin accessible is also known as “gingival retraction” in the field of dentistry. A common gingival retraction procedure includes the insertion of a so called retraction cord in the gingival sulcus. The gingival sulcus refers to an area between a tooth and the gingiva, as indicated for example in FIG. 1 at reference number 3.
One way of performing a gingival retraction procedure includes the use of a so-called gingival retraction cord which typically is pushed in the gingival sulcus to mechanically displace the gingiva from the tooth. A dentist may for example push a gingival retraction cord into the gingival sulcus by use of an appropriate dental instrument, for example by a Heinemann spatula. However, the insertion of a retraction cord (reference number 5, shown in FIG. 2) is relatively time consuming and is generally perceived as being relatively inconvenient for the dentist and uncomfortable for the patient. Therefore there has been a strong desire for viable alternatives for many years.
As an alternative for the retraction cord so-called gingival retraction pastes have been suggested. Typically retraction pastes are very high viscosity pastes which—instead of a cord—are typically squeezed in the gingival sulcus in a patient's mouth. In one example a paste is provided which is supposed to be brought into a patient's gingival sulcus to displace the gingival tissue from a tooth. A known paste is for example available under the designation Expasyl, from the company Pierre Roland, Acteon Group, France.
Such gingival retraction paste in one example is provided in a syringe that is connectable with a bendable metal dispensing cannula for dispensation of the paste. A technique has been proposed in which the high viscosity gingival retraction paste is dispensed around a tooth towards the entry of the gingival sulcus, and thereby is squeezed into the gingival sulcus. It has also been suggested to use auxiliary equipment for deeper insertion of the paste into the gingival sulcus in case the paste only has insufficiently penetrated the gingival sulcus during normal dispensation.
DE-A 37 37 552 discloses a composition for insertion into the gingival sulcus which is supposed to expand in volume and thereby to displace the gingiva from the tooth. The composition is intended to be injected into the gingival sulcus.
EP-A 1 693 022 discloses a process for gingival retraction. The process includes the application of an expanding and curing elastomeric material onto and/or the vicinity of the gingival sulcus, and restricting the expansion of the elastomeric material using a cap placed over the tooth. Pressure built up in the chamber due to the expansion of the elastomeric material is supposed to force the material into the gingival sulcus.
US2007259313 discloses a gingival tissue retraction device and method including a dam shaped to be fitted around a tooth. The well of the dam can be filled with a flowable retraction material having a high viscosity. The filled dam is fitted to a prepared tooth so that when pressure is applied onto the dam the retraction material is displaced under pressure and forced into the gingival sulcus, causing the gingival tissue to retract from the tooth.
WO 2008/021740 discloses a curable gingival retraction composition for retracting the gingiva from a tooth.
Although some developments particularly in the field of chemical compositions have been made, there is still a need for a procedure and a device allowing for convenient insertion of a composition for gingival retraction into the gingival sulcus. It is particularly desirable that a gingival retraction composition is made applicable in an acceptably short time, and with relatively little effort by the dentist. Further there is a need for a procedure that provides a treatment that is reliable, acceptable for a patient, and has few adverse side-effects or after-effects. Particularly a gingival retraction procedure desirably provides limited or low risk of damaging the epithelial attachment between the gingiva and the tooth. It is further desirable to provide a gingival retraction device and composition that are rather inexpensive and easy to use.