A patient in his early 20s with teeth badly discoloured by tetracycline was seeking treatment to improve his esthetics. Because retreatment and cost were important considerations, porcelain veneers were the treatment of choice. The challenge in this case was to mask the underlying tetracycline stain before the final cementation and thus gain more control over the final shade of the veneers. (+info)
The marginal-ridge rest seat.
Natural canine crowns are preferred as abutments for removable partial dentures because of their root morphology and bony support. However, preparing the rest seat on the lingual surface of a mandibular canine risks perforating the enamel. An alternative rest-seat preparation, on the marginal ridge of the canine crown, conserves tooth structure and provides a rest seat of adequate length and depth to ensure support for a cast framework. To illustrate why this little-discussed rest-seat preparation has endured locally, the rationale and preparation of the marginal-ridge rest seat is discussed from both historical and clinical perspectives. (+info)
This final article in the series describes the modification of teeth to improve their shape for the support and retention of RPDs. (+info)
The use of real time video magnification for the pre-clinical teaching of crown preparations.
OBJECTIVE: To investigate the effect on the undergraduate learning process of using an alternative method designed to enhance the visual demonstration of taper on full veneer crown preparations (better understanding of the value of taper on preparations early in the teaching programme in restorative dentistry). DESIGN: A comparison between the conventional teaching of full veneer crown preparations and the same teaching with the additional use of a magnified real time video display using a surgical microscope was investigated in this study. OUTCOME MEASURES: The degree of taper was measured for replica full crown preparations and results compared between different cohorts of undergraduates and experimental conditions. RESULT: Undergraduates taught using the real time video produced more accurately tapered preparations. This ability was retained over one year. CONCLUSIONS: A possible explanation for the result was that the use of magnification improved the undergraduates' precise understanding of taper by enhancing their ability to evaluate this critical measurement during the teaching process. (+info)
Integrating posterior crowns with partial dentures.
This article outlines those considerations which are important in integrating posterior crowns with partial dentures. Planning the support and retention of the denture prior to crown construction will enhance patient treatment. Modification of the crown preparation to incorporate rest seats, retentive areas, guide planes and a planned path of insertion may be necessary. (+info)
Variations in tooth preparations for resin-bonded all-ceramic crowns in general dental practice.
OBJECTIVE: To investigate variations in tooth preparations for resin-bonded all-ceramic crowns (RBCs) in general dental practice (GDP). DESIGN: Laboratory-based retrospective analysis of dies for RBCs. SETTING: General dental practices in the UK and Ireland (2000). METHODS: A sample (n = 132) of laboratory models containing 180 tooth preparations for RBCs, featuring work from different general dental practitioners was obtained from four commercial dental laboratories. Aspects of the preparations were quantified and compared with accepted criteria defined following a review of the literature. RESULTS: The teeth found to be most frequently prepared for RBCs were maxillary incisors (41%). Margin positions were variably positioned with 29% of the preparations on the buccal aspect having subgingival margins. There were many tooth preparation dies for low fusing RBCs (47%) and Chameleon Fortress RBCs (62%) demonstrating overpreparation in the mesiodistal plane. The majority of the margins (84% buccally and 79% lingually) of the dies examined exhibited appropriate shoulder or chamfer finishes. Of the Chameleon Fortress preparations analysed, 86% had been underprepared occlusally. 42% of the teeth had been prepared with no regard to tooth morphology and demonstrated just one plane of reduction. The majority (93%) of the clinicians failed to provide any information regarding the shade of the prepared tooth stump. CONCLUSIONS: On the evidence of this survey of this sample of general dental practitioners' work, it was found that relevant guidelines for the preparations of RBCs are not being fully adhered to. (+info)
A technique for using maxillary anterior soft-tissue undercuts in denture placement: a case report.
Restoring a large edentulous space in the anterior maxilla presents many challenges, including how to utilize and manage a deep anterior soft tissue undercut. In the case reported here, a partial denture was constructed that incorporated a semi-rigid exterior flange and a soft liner to help the denture to engage the depth of the undercut. The denture was placed after extraction of the anterior teeth, and there was very little postoperative tissue trauma. With this combination of materials, known as "triple lamination", the prosthesis was able to engage the soft-tissue undercut, the undercut was actively involved in retaining the prosthesis, the denture could be placed immediately, and the prosthesis was very comfortable. Triple lamination should be considered when a deep soft-tissue undercut must be engaged to ensure retention of a prosthesis. (+info)
Crowns and other extra-coronal restorations: try-in and cementation of crowns.
Having successfully negotiated the planning, preparation, impression and prescription of your crown, the cementation stage represents the culmination of all your efforts. This stage is not difficult, but a successful outcome needs as much care as the preceding stages. Once a restoration is cemented there is no scope for modification or repeat You have to get it right first time. Decemented crowns often have thick layers of residual cement suggesting problems with either initial seating or cement handling. When the fate of restorations costing hundreds of pounds depends on correct proportioning of cements and the quality of the mix, the value of a well-trained and experienced dental nurse is easy to see. Both dentist and nurse need a working knowledge of the materials they are handling. (+info)