Anterior Crowns in Reestablishing Vertical Dimension of Occlusion: Overcoming Fear of Heights

by Nathan Blitz, B.Sc., DDS

As we age, our teeth become worn and shortened and less and less visible when we speak or smile. As the teeth become smaller in this way, the lower portion of the face decreases in height which further contributes to an aged appearance. This article describes the aesthetic and functional benefits and method of rebuilding the teeth to their original size and shape.

Restoring vertical dimension of occlusion allows the rejuvenation of a dentition ravaged by Attrition. The underlying causes of the presenting condition must be thoroughly evaluated prior to the commencement of any irreversible treatment, Proper assessment is essential in order to arrive at the right diagnosis. This in turn will dictate appropriate treatment. The following case illustrates the relationships among certain, fundamental principles of dentistry involving function, phonetics and esthetic.

Chief Complaint

This patient expressed a desire to have his anterior teeth "slightly lengthened." He believed that in his youth a "somewhat greater amount of tooth" was visible in his smile.

History

This 47 year old Caucasian male is in excellent health. He is a busy real estate salesman who is active in sports and community work.

Past dental treatment has consisted of extraction, minor restorative procedures and regular maintenance. A regurgitation problem was treated successfully ten years ago. There has been no relapse. Medical history is uneventful in all other respects.

Clinical Examination

A thorough clinical examination together with radiological interpretation of all film records revealed no abnormalities or pathology. Periodontal health is indicated by the firm, pink, stippled gingiva and the absence of any pocket depth greater than 2-3 mm Lamina dura is distinct and good bone height is present. All incisal enamel of the maxillary an mandibular centrals, laterals and cuspids is worn or missing. Enamel is also completely worn away on the lingual of the maxillary incisors. The length of the centrals is 6 mm.

Their width is 8.6 mm. Maxillary first bicuspids are over erupted. Tooth 2.4 is rotated 90 degrees toward the distal. There is a diastema between maxillary cuspids and bicuspids. A 4.6 mm space exists between 4.3 and 4.4. Missing teeth are 1.8, 1.6, 2.6, 2.8, 3.4, 3.6, 4.6 and 4.8. A reverse smile line is present. There is a 1.0 in diastema between the centrals. Generalized wear facet are present on all posterior teeth. There is a 3.3 in overjet and a 50% overbite. During formation of the sibilant "s" sound there is a 3 mm. interincisal opening.

Diagnosis

The patient exhibits posterior occlusal collapse in a mutilated Class II occlusion caused by multiple tooth loss. Severe attrition, induced by bruxing has resulted in three interrelated conditions:

  1. Loss of vertical dimension of occlusion (VDO)
  2. Reverse smile line
  3. Aged central incisors of poor proportions. The width to length ratio is almost 3:2 instead of the ideal 4:51

Regurgitation problems many years ago may have caused chemical erosion of some lingual enamel (maxillary centrals and laterals) and thus also contributed to the present condition.

Figure 1

Figure 2

Fig. 1 Severe attrition, induced by bruxing has resulted in three interrelated conditions. The loss of vertical dimension of occlusion is in this case accompanied by a reverse smile line and central incisors of poor proportions.

Fig. 2 The maxillary first bicuspids must be contoured to correct their over-eruption and create a more even plane of occlusion.

Treatment Plan

The increase of interincisal clearance (from the normal 1 mm) during formation of the sibilant "s" sound confirms a decreased VDO.2 An increase in the vertical dimension of occlusion must be reestablished. The unopposed maxillary first bicuspids will be contoured to correct their over-eruption and create a more even plane of occlusion. A bite plane will then be fabricated to open the bite. This appliance has three functions:

  1. It will enable us to determine if the patient can tolerate in comfort an increased vertical to accommodate the requirements of reconstruction.
  2. This appliance will give the patient an opportunity to break the neuromuscular pattern that has resulted in his attrition.
  3. Once stability is evident, we can use the bite plane to record the patient's centric relation at the new vertical.

In this case, because of the severe bruxing, the strongest possible restorations are required. These teeth will be restored with porcelain fused to metal (P.F.M.) crowns and bridges fabricated to the reestablished vertical dimension. Due to financial limitations, Phase I of treatment will restore only the six maxillary anteriors with P.F.M. crowns. A removable mandibular temporary partial overdenture with a metal occlusal surface will provide posterior stability at the new vertical. In the future, the patient will proceed with Phase II of treatment and replace the removable partial with fixed partials. A night guard appliance will also be fabricated.

Figure 3

Figure 4

Fig. 3 A bite plane will open the patient's bite, give him an opportunity to break his destructive neuromuscular patterns and can be useful in recording occlusal records at the new vertical.

Fig. 4 These aged incisors exhibit poor proportions. Their width to length ratio is almost 3:2 instead of the ideal 4:5 and their colour is monochromatic.

Discussion of Treatment

Previously, alginate impressions were taken and two sets of study models poured. These diagnostic casts help determine the extent of contouring required for the over erupted teeth in order to create a more even plane of occlusion. The occlusal contouring is accomplished with a medium grit diamond and completed with rubber cups (Mini-Identoflex, Centrix, Shelton, CT) followed by composite polishing paste (Prisma-Gloss, Caulk, Milford, DE). Topical fluoride can now be applied.

Study models were previously mounted on an adjustable articulator. The six anteriors were waxed up to the ideal dimensions using the width to length formula (4:5) to calculate the ideal crown length of the centrals. Throughout attrition, the width of the centrals (8.6 mm) remained stable. Therefore their length should be 10.75 mm. An evaluation was made that the increased dimension of vertical opening needed to accommodate these idealized (wax) anteriors is 2.0 mm.

Interincisal clearance during sibilant "s" sound formation is 3 mm for this patient. Normal clearance is 1 mm. The 2 mm discrepancy is compensation for a corresponding loss in vertical dimension. Thus esthetics and phonetics help determine and confirm the extent of increase in vertical opening.

Alginate impressions are now taken and working models are poured. These will be used for the fabrication of the bite plane. Bite registration is taken with the condyles in their terminal hinged axis position and the bite open 2.5 mm. This will allow room for adjustments to the bite plane.

Figure 5

Figure 6

Fig. 5 Reestablishing the vertical dimension has allowed restoration of pleasing proportions to the centrals. This has led to the reassertion of the dominance of the centrals and thus corrected the reverse smile line.

Fig. 6 Correct lncisal Edge Placement is critical because it influences anterior guidance, lingual and labial contours, the pitch of the anterior teeth and proper lip support.

In this case the bite plane is fabricated for the mandibular arch. It covers all occlusal and incisal surfaces. The occlusal splint therapy was uneventful. A few minor adjustments were required. The patient wore his appliance at all times except when eating. He functioned comfortably over a two month period.

Now centric relation registration is taken at this vertical using the bite plane. New impressions are taken and models poured. The bite registrations, bite plane, the model on which it was made and the new models are sent to the laboratory.

A temporary, cast mandibular partial overdenture is fabricated. It replaces the missing 3.4, 3.6 and fills the space (4.6 mm) between 4.3 and 4.4. It provides posterior occlusal contact at our new vertical. Now, the laboratory, on the mounted, working cast, prepares the six maxillary anteriors at this new vertical and fabricates provisional shells that duplicate the wax up of our ideal anteriors for this patient.

A try-in appointment is required to evaluate the fit of the temporary mandibular partial overdenture. At the next visit, the maxillary anterior teeth are anesthetized. The patient participates in shade selection under various pertinent lighting conditions.3 The basic shade of the centrals and laterals will be shade A3 of the Vita shade guide The cuspids will be closer to shade A3.5. The gingival area will be richer in chroma. The body will be more uniform and the incisal will have blue, violet and gray. Some incisal clouds will also be present. A colour map is provided for the laboratory.4

Plain braided "ooo" cord is gently inserted into the sulcus. Since there is no enamel on the incisal and lingual surfaces of the centrals and laterals, there is no incisal reduction for these teeth. The lingual of the incisors is only "freshened up" with a football shaped diamond. A chamfer margin is placed 0.5 mm apical to the gingival crest. During margin instrumentation, the gingiva is protected (deflected) with an 8A plastic instrument. The labial and interproximal surfaces are reduced 1.5 mm. On the mesial and distal surfaces of the short centrals vertical grooves are placed. This increases surface area, provides some parallelism to the preparation and thus enhances retention.

The finished mandibular partial overdenture is inserted to provide stable posterior occlusion at the new vertical. At this time the provisionals (shells) are tried in. Phonetics help determine the incisal edge position (IEP). The incisal edges should lightly touch the vermilion border of the lower lip when making F and V sounds. This location then helps verify the length of each tooth. The pitch of each anterior tooth is determined by the combination of correct lip support and the lingual labial position of the incisal edge.5 These factors play a dominant role in both esthetics and function. Correct Incisal Edge Position is crucial because it:

  1. determines the pitch of the anterior teeth
  2. contributes to establishing labial contours
  3. provides proper lip support
  4. influences anterior guidance
  5. together with anterior guidance determines lingual contours
  6. delineates our restorations by following the curvature of the superior border of the lower lip

Adjustments to the shells and preparations are made on the basis of these and other parameters. The teeth are lubricated and the temporaries are relined. After the initial set of acrylic, it is advantageous to reline just the margins with a very wet mix. Then the provisionals are removed and the teeth are cleaned of any lubricant or acrylic. The cord is removed and a polyvinylsiloxane impression is taken. Bite registration records are obtained. The provisionals are trimmed. Occlusion together with anterior and cuspid guidance is further developed and refined. The esthetics are evaluated and adjusted. Once the patient is pleased, the provisionals are cemented. The temporaries should display excellence of:

  1. fit
  2. marginal adaptation
  3. emergence profile
  4. gingival contour
  5. incisal contour
  6. a properly developed occlusion in centric and during excursive movements.

If standards of excellence are not maintained during temporization then we will have recession, inflammation and disease and our final restorations will be doomed to failure even before they are inserted.

At the next appointment, the status of the gingival tissue is checked. If the margin is exposed it must be repositioned and a new polyvinylsiloxane impression is taken. Occlusion together with anterior and cuspid guidance of the temporary is again reevaluated and refined. Alginate impressions are taken of the provisionals. The laboratory is instructed to use the new study cast as a guide in the fabrication of six P.F.M. Crowns.

At the next appointment the crowns are evaluated separately for fit. Marginal adaptation and gingival tissue position is checked. All the crowns are then seated and the margins are reevaluated. The contacts are checked and adjusted. At this time the occlusion is checked and refined. The crowns and smile are now assessed with the patient for final approval.

The teeth are anesthetized. Crowns and preparations are cleaned with chlorhexidine and the restorations are cemented. Excess cement is removed and the patient is reappointed in one week for reevaluation, fine adjustments and slides.

Summary and Conclusion

The rejuvenation of this dentition is initiated with the placement of six anterior crowns. Reestablishing the vertical dimension has allowed the restoration of pleasing proportions to the centrals. This has led to the reassertion of the dominance of the centrals and thus corrected the reverse smile line.

The restoration of these teeth demands harmonious accommodation of the requirements of esthetics, phonetics and function. These considerations are inseparable and are in fact, determinants of each other. Esthetics and phonetics help determine the degree of vertical opening and incisal edge placement. This location influences anterior guidance, lingual and labial contours, the pitch of the anterior teeth and proper lip support. The principles of proportion, so important in esthetics, allow us, to calculate incisor length. Thus, function, phonetics and esthetics are intimately intertwined and enhance one another in the restoration of vertical dimension of occlusion.

Figure 7

Fig. 7 The provisionals as well as the final restorations must display excellence of fit, marginal adaptation, emergence profile, gingival and incisal contour and occlusion.

References

  1. Chiche G. Pinault A. Srnile Rejuvenation A Methodic Approach. Practical Periodontics and Aesthetic Dentistry Vol. 5 No. 3 April 1993:37-43
  2. Rubinoff M. Attrition/Bruxism Diagnosis and Treatment. Ontario Dentist March 1993 17-22 3
  3. Glick K. Color and Shade Selection in Cosmetic Dentistry: Part III AACD Journal Summer 1994:14-20
  4. Materdomini D. Communicate Visually With Your Laboratory. AACD Journal March 1994: 32-34
  5. Dawson E. P. Evaluation Diagnosis and Treatment of Occlusal Problems Chapter 13 Restoring Upper Anterior Teeth C.V. Mosby 1974: 173-189

Sources Consulted

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