Clinical
Principles of tooth preparation
Dr Paul A. Tipton BDS, MSc, DGDP UKlooks at the various tooth preparation techniques that are avilable to modern GDPs keen to improve their techniques in restorative and aesthetic dentistry
T
his series of articles is dedicated to proper prepara- tion techniques
for all types of cast metal and porcelain restorations and for practical restorative techniques including amalgam and composite. Tooth preparation is often
underexplained and not taught well at dental hospital, due to time restraints and lack of clinical expertise – even though the longevity, occlusal stability, strength, aesthetics and periodontal condition depend upon the correct preparation protocol. Thus, newer graduates can often be lacking in these basic skills.
This series of articles is for them and for practitioners wishing to revise and review their own techniques in light of recent scientific changes. Much of this work was first described by Shillingburg in his classic text book Fundamentals of Tooth Preparation (1988) and has been updated by myself using contemporary scientific criteria and literature. The late Lloyd Miller stated: “No other clinical procedure in fixed prosthodontics reveals the care, skill and judgement used by a dentist than the quality of tooth preparation.” I use all these techniques during the phantom head series of courses to be held in
Dublin in 2011 for dentists wanting to improve their techniques in restorative and aesthetic dentistry. Throughout the series of articles we will explore and teach preparation techniques, not only conventional porcelain fused to metal crowns (Fig 1), but porcelain veneers, inlays/onlays, conventional bridge preps (Figs 2-4) adhesive bridge preps (Fig 5) and also the often forgotten science of the cast gold partial veneer preparation including the three quarter crown and gold onlay(Fig 6)as well as the seven eighths crown and full gold crown, which despite the growth of cosmetic and aesthetic
dentistry is still the longest lasting and often least invasive posterior restoration. This type of preparation has now almost been forgotten in dental schools and needs to be refocused on. The design and preparation
of a tooth for a cast metal or porcelain restoration is governed by five principles (Shillingburg 1991): 1. Preservation of tooth structure
2. Retention of resistance form
3. Structural durability 4. Marginal integrity 5. Preservation of the periodontism
For the optimal fitted restoration, preparation must
Fig 1 Traditional bonded crown prep with wings
Fig 2 Long span bridge preps with distal inclination
Fig 3 Groove in posterior abutment
30 Ireland’s Dental magazine
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