of therapy may require mutilation of the remaining tooth structure. The biologi-cal and structural outcomes will be compromised from three essential aspects:
endodontic stability regarding questionable pulpal health and long-term prog-nosis of root canal treatment; structural stability of the remaining tooth struc-ture to support the restoration and/or occlusal scheme; and periodontal stability impacted by resultant changes in restorative tooth morphology. Proximal con-tours that impede proper oral hygiene and encourage food impaction and plaque retention are one example of a compromised outcome of overly aggressive tooth reduction.1 If the desired contour requires a tooth preparation that exposes the pulp or amputates the pulp and coronal tooth structure, strong consideration must be given to treating the situation with orthodontics. Additionally, negative gingival and interdental papilla architecture cannot be remediated through RSM treatment.1
K E Y P O I N T S U M M A R Y
In many countries, cutting into dentine and devitalizing pulp tissue for esthetic reasons is frowned upon.
A pure RSM esthetic correction must also take into account the risk of adversely affecting the biology of the periodontium. The potential exists for significant alterations in emergence profile when correcting restoratively a rotated or lin-gually positioned tooth. The impact on gingival health must be considered in these cases. Restorative alignment of severely overlapped teeth also has the potential to have a negative impact on the periodontium as the contacts and supporting bone has moved apically as the overlap developed. The risk of chronic periodontal inflammation increases due to the violation of biological width as a consequence of the required aggressive tooth preparation and the subsequent restoration. In fact, when the teeth are overlapped, the very act of separating the contact with a bur creates a high likelihood that the preparation margin will be placed in the attachment.4
Esthetic Parameters
The use of RSM to treat spatially compromised cases demands that several esthetic factors be considered.10 The elements that make up facial composition must be evaluated. Frontal and lateral examination of the subject, including analysis of the position of the eyes, nose, chin and lips, is required for identifica-tion of the reference points and lines that are indispensable to performing RSM.
Analysis of these features is made using horizontal and vertical reference lines, which allow correlation of the patient’s face with the dentition.11,12
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S pa c e M a n a g e m e n t
The dentolabial analysis is essential for evaluating the correct ratio between teeth and lips during the various phases of speaking and smiling. Maxillary incisor tooth display, with the lips at rest, is a major parameter in justifying incisal edge lengthening.13,14 Appropriate vertical tooth position, incisal edge position and vertical gingival margin control are as important as correcting horizontal and buccolingual deficiencies in achieving an ideal result when treat-ing spatially compromised cases.3 Many of the procedural choices that the clini-cian will make to provide a suitable restoration are significantly affected by the correct incisal edge position.13 This is also covered in detail in Chapters 2 and 3. The key parameter is the determination of the portion of the maxillary teeth that is visible with the lips at rest.14
The smile line analysis evaluates the exposure of the anterior teeth and the display of the gingival margins while smiling.15 In patients with high smile lines, the esthetic considerations for periodontal surgery are as important as those for teeth. In cases where discrepancies in the soft tissues interfere with the proposed tooth proportion, the gingival tissues can be altered via periodontal surgery to accomplish an ideal architecture.3
Measurement of the teeth, through micro-esthetic dental analysis, is the primary building block within the framework of a smile. Anterior tooth display in the finished case must be consistent with the principles of proportion in order to be considered a success.16 When proper tooth proportions are violated, as may happen in RSM therapy, the restored teeth look ‘wrong’.10 The ideal width of the maxillary central incisor should be approximately 80% of its length (Fig. 6.4).
A higher width to height ratio means a squarer tooth, and a lower ratio indicates a longer, more rectangular appearance.9 For greater detail refer to Chapter 1, Esthetic Diagnosis on the proper use of the Esthetic Evaluation Form.
Fig. 6.4 A pleasant width to length proportion for a maxillary central incisor is 75–85%.
75% to 85%
E s t h e t i c P a r a m e t e r s
In patients with diastemata, inappropriately small natural anterior teeth or normal teeth with an excessively large arch form are the primary causes of this condition. For each of these causes, the treatment is very different. The patient with diastemata owing to small teeth is usually best treated with restorative dentistry, regardless of whether orthodontics is also performed.4 At the other end of the spectrum are patients with severely overlapped and crowded teeth. As one might expect, this condition occurs either because of inappropriately large anterior teeth or normally sized teeth within an exces-sively small arch form. The esthetic concern, in both diastemata and crowding cases, is the appearance of the teeth if they are restored in their current position.
There are several articles discussing the use of the ‘golden proportion’17 when planning treatment for patients with malalignment. Although this may be a useful tool for doing a wax-up or setup, it can fall short of creating ideal esthet-ics in patients with diastemata or crowding. Only the relationship between the teeth widths is considered within the golden proportion. As logical as this may seem, there is strong evidence that some anterior teeth, particularly the maxil-lary central incisors, carry more weight than others in the assessment of esthetic outcomes.4 The maxillary lateral incisors, however, can have large variations in their width and still be judged esthetically pleasing as long as they are symmetri-cal. More pleasing esthetic results can be created by designing central incisors with ideal proportions and allowing the laterals to be wider or narrower than the golden proportion would require. Proportionate central incisors create the illusion of a pleasing smile, whereas mis-sized lateral incisors are rarely noticed as long as they are symmetrical to each other.4
Chu18 describes yet another way to relate the width of teeth within the esthetic zone and proposes that the width of the maxillary lateral incisor should be approximately 2 mm less than the central incisor and that the canine should be 1 mm less than the central incisor (Fig. 6.5).
The methods available to compensate esthetically for anatomical crowns that are excessively wide include: restorative lengthening of the crown incisally, increasing the clinical crown length apically with periodontal surgery, using restorative optical illusions that make a wide tooth appear narrow or any com-bination of these methods (Box 6.2).10 When compensating esthetically for teeth with excessively long clinical crowns, the width may be increased, the incisal edge may be shortened if the lip line and phonetics permit or the location of the gingival margins may be altered to a more coronal position through orthodontic extrusion or additive periodontal surgery. Again, restorative optical illusions or any combination of the aforementioned techniques may be employed to make a long tooth appear wider (Box 6.3).
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S pa c e M a n a g e m e n t
Fig. 6.5 The width of the maxillary lateral incisor is approximately 2 mm less than the central incisor and the width of the canine is approximately 1 mm less than the central incisor.
X X-2 X-1
B O X 6 . 2
To compensate esthetically for crowns which are excessively wide:
• Lengthen the clinical crown incisally with a restoration
• Lengthen the clinical crown apically with the use of periodontal surgery
• Move the mesial and distal line angles towards the midline of the tooth to create the illusion of a narrower tooth
• Use a combination of the above techniques
Dlugokinski M, Frazier K, Goldstein R. Restorative treatment of diastema. In: Goldstein R, Haywood V. Esthetics in dentistry, vol. 2: Esthetic problems of individual teeth, missing teeth, malocclusion, special populations. Ontario, Canada: BC Decker, 2001:703–731.