Clinical Corner: Information on Dental Procedures

Articles

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Combating Hidden Decay with Early Detection
Atraumatic Removal of Defective Crowns
Balancing: The Art, Science and Business of Dentistry
Intra-Oral Preparation of Titanium Abutments in Order to Obtain Ideal Angulations and Contours
SS White Express Line High Speed Laboratory Metal Finishing Burs
Direct Preparation Of Preexisting Implant Abutments For Case Rehabilitation
Flextime Xtreme: The 80/20 Rule
Fast and Smooth - Efficient Crown Preparation With Carbide Instruments
When Advancing the Bur, One Can Feel the Presence of Dentinal Caries
Precision Trimming and Finishing of Current Dental Restorations Using the Safe End Bur System
Indirect Restorative Tooth Preparation: Extreme Efficiency and Accuracy
Creating Maximum Efficiency and Accuracy In Indirect Restorative Tooth Preparation
Preparation Protocol To Ensure Predictable Aesthetic Restorations
Tooth Preparation Mastering Quality and Efficiency
Fissurotomy: Proactive Treatment for Incipient Decay
Anatomically Adapted Carbide Finishing Burs - Creating Super-Smooth Composite Surfaces in Two Steps
Directions for Use: Dr. David Clark Kit
Placing Traditional Sealants with Enhanced Magnification: Methodology to Increase Both Short-term and Long-term Success - David Clark, DDS
How to Quickly and Conservatively Restore a Natural Shine after Orthodontic Bracket Removal
SS White Surgical Length Oral Surgery Burs: Atraumatic Removal of Teeth for Maximum Bone Preservation

"Direct Preparation Of Preexisting Implant Abutments For Case Rehabilitation"

Robert A. Lowe, D.D.S., F.A.G.D., F.I.C.D., F.A.D.I., F.A.C.D. 

Dental implants have been used as “root replacements” in oral reconstruction for several years with a great deal of success.  Due to the high predictability of osseointegration 1,2 we are now seeing cases in which the prosthetic components need replacement, either due to functional wear and stress, or due to a patient’s desire for a more esthetic appearance.  As a result during this period of time, many implant systems have come and gone creating some difficulty in finding prosthetic replacement parts for well-integrated, successful dental implants.  Also, some of these earlier implant reconstructions have had the prosthetic components splinted to natural tooth abutments and now the natural teeth are failing.  It has been found through research and experience that this situation can be lead to early failure of the prosthesis due to natural tooth morbidity and differences in occlusal stress tolerance 3.  Advances in implant prosthetic systems and in esthetic materials now allow the dentist and laboratory technician to create beautiful esthetic restorations that are totally implant born.  Most clinicians today recommend that the implant segments of the reconstruction be separate and free standing from remaining natural teeth to allow for retrievably and/or replacement of both implant and tooth born segments 4.  In cases where this is not possible, some sort of “stress breaker” such as a semiprecision male-female connector can be integrated into the design of the case to allow the natural tooth abutments to move freely from the osseointegrated implant segments 5. When replacement prosthetic parts are not available for the preexisting implant system, one solution is to directly reprepare the existing implant abutments and use a superstructure with a cemented prosthesis.  Keeping these two principles in mind may make rebuilding a patient’s old reconstruction easier for the dentist and the patient, with a higher degree of predictability.

Many older implant reconstructions used titanium or titanium/metallic abutments that were “stock-type” abutments and not properly angulated or shaped like prepared teeth.  Often times this could make the prosthetics for the dentist an esthetic and functional challenge.  “UCLA type” custom abutments were developed to correct some of these issues 6, however many times not used because of the increased laboratory costs.  When they were used, often times they were not sufficiently prepared at the restorative margin to allow for a sufficient thickness of ceramic to create an esthetic outcome at the gingival- restorative interface.  Regardless, the restorative dentist would need to reshape the metal implant abutments intraorally to create the environment for a better restorative outcome.  Some of the issues faced when preparing abutments directly in the mouth are 1) Creation of heat that could possibly be transferred to the implant cylinder and interfere with the osseointegrated surface 7, 2) Control of the instrument in preparing precise margins and geometry, and 3) Creating a smooth, polished surface after preparation. 

Figure 1 Two stock cylinder implant abutments are shown after removal of the restorations.  Note the supragingival positions of the restorative margins and the thinness of the gingival tissue above tooth number 12.	Figure 2 The 2S Great White Bur (S.S. White) is used to reprepare the restorative margin at a more esthetic level.  A connective tissue graft will be done after placement of the provisional restoration to create a more esthetic restorative gingival emergence.	Figure 3 After gross preparation, a #881-014F rounded cylinder diamond (SS White) is used to smooth the metal surface.  It is important to remember the axial reduction should be 1.5 millimeters for porcelain fused to metal implant prostheses, which is the same as for natural tooth preparations.
Figure 4 Rubber porcelain abrasives are used to polish metallic abutments to a fine luster.  Remember, the smoother the preparation, the more intimate the fit.	Gross preparation of metal implant abutments can be easily accomplished in a controlled fashion using a #2S Great White Bur (S.S. White) in a high speed or electric handpiece.  The enhanced blade geometrical design (sharp dentated surface) cuts metal smoothly without skipping or gouging the metallic surface.  Once the gross preparation is completed, an 881-014F rounded cylinder finishing diamond (SS White) is used to begin polishing by removing the bur excoriations left by the carbide bur.  Final polishing of the abutment is accomplished using rubber porcelain abrasive points.  A smooth abutment will yield a more precise fit to the superstructure that will be fabricated for the new porcelain-to-metal restoration (Figures 1 to 4).

Case Report # 1: Spatial Repositioning Of Teeth In The Esthetic Zone Involving Malpositioned Preexisting Implant Abutments 

This patient presented requesting a correction of her “crooked smile” (Figure 5).  She also wanted “straighter and whiter teeth”.  Upon examination, the patient had implant restorations replacing tooth numbers 10 and 11.  The lower gingival levels on the right side of her mouth accompanied by the superior labial placement of the implants in the numbers 10 and 11 position made her smile appear as if “it ran downhill” from left to right.  Minor supereruption and crowding of the maxillary right anterior segment further complicated the esthetic and functional outcome of the case (Figure 6).   The implants that were placed 12 years previously for this patient were well integrated, but no longer available for prosthetic replacement parts (Figure 7).  It soon became apparent the implants would be the “esthetic weak link” in the fabrication of this case.  It was recommended to the patient to consider recovery of the implants, bone grafting, and replacement with an updated system in a prosthetically more desirable location.  The patient, however, did not wish to undergo replacement of the implants.  The case was planned to restore the esthetic zone from tooth number 4 to 13.  Tooth numbers 4 and 5 had some occlusal and proximal decay and were planned for inlay veneer restorations.  Tooth numbers 6 through 9 required all ceramic “mini-crowns” (less than 1.0 millimeters of reduction) after incisal plane correction and elimination of crowding.  Tooth numbers 10 and 11 would be porcelain to Captek (Precious Metals, Inc.) restorations, splinted for retention and independent from the dentulous areas.  And, tooth numbers 12 and 13 would require porcelain veneers for color, rotational correction, and diastema closure. 

Figure 5 A preoperative smile view showing a patient with multiple issues.  Both incisal and gingival planes exhibit a left to right superior-inferior cant creating both esthetic and functional problems.  Other problems include color mismatches, proportional discrepancies, and overlap of the maxillary central incisors.

Figure 6 This maxillary arch preoperative view shows the problems previously discussed and also the labial position of the implants, which could make it a problem to restore them esthetically.

Figure 7 This x-ray view shows the existing implants in the 10 and 11 positions, although not in the ideal position to be restored esthetically, are well integrated in the alveolar bone.

The plan for the soft tissue correction was to do crown lengthening with osseous recontouring on tooth numbers 4 through 9.  The goal is to have the cervico-incisal height of the central incisors to be slightly higher than the lateral incisors, and the cervico-incisal height of the cuspids to be slightly higher than both central and lateral incisors.  Again, the area where this will be most difficult to achieve will be over the implant restorations due to the superior, labial position of the fixtures.  Therefore, a connective tissue graft was planned to get as much coverage of the tooth surfaces as possible and to “plump out” the alveolar ridge facially to help create better emergence profiles.

The first step is to outline the surgical plan using an extra fine felt marker.  This is critical in visualizing the end result prior to surgical correction.  The gingiva is marked at the appropriate levels with the height of contour (gingival zenith) located at the distolabial line angles.  Where the biologic dimension is violated, osseous recontouring will be done.  The implant restorations are marked at the gingival area to get an idea of how much root coverage will be needed to balance with the heights of the gingival tissue on the contralateral side.  The incisal edges are also marked to correct the incisal plane discrepancy.  The incisal edges can be shortened if excessive overlap exists, but only as long as protrusive disclusion and canine guidance is not interfered with.  It is desirable to have the maxillary central incisors to be between 10 and 12 millimeters long with a 75 to 80 percent width to length ratio (Figures 8 and 9).   A diode laser (Twilight: Biolase Technologies) is used to do the gingivectomy over the marked areas.  The incisal edges are shortened in the appropriate areas using a high-speed diamond bur (Figure 10 and 11).   The teeth will then prepared for the appropriate restorations to the new gingival margin.  This margin placement is meant to be in the final position for esthetic requirements.  In this case, the bony correction will be done be the surgeon at the time of grafting to save the patient a surgical procedure.  After reflection of the gingival tissues, the surgeon will only have to follow or “mirror” the restorative margin when doing the osseous correction 3 millimeters apical to that position established by the restorative dentist with the provisional restoration 8,9.  This is an excellent way to communicate esthetic parameters to the surgeon if the restorative dentist is not comfortable doing flap surgery.  As tooth preparation proceeds, the old implant restorations must be cut off very carefully, since the type and spatial position of abutment underneath may not be known.  The #2S Great White carbide (S.S.White) is used in a judicious manner to remove the superficial ceramic material and strip away at the metal superstructure until a cement line can be seen (Figures 12).  The superstructure can then be removed with a hemostat once the cement seal is broken.  After modification and polishing of the abutments in the manner previously described, a diode laser (Twilight: Biolase Technologies) is used to sculpt an ovate site around the abutments to help create normal emergence (root) contours in the ceramometallic restoration (Figure 13).

Figure 8 The surgical plan is “mapped” on the gingiva using a fine tipped felt marker.  The goal is to correct the gingival cant by apically repositioning the soft tissue from tooth number 4 to 9 and graft soft tissue above the implant positions 10 and 11 to lessen the cervico-incisal discrepancy in that area.	Figure 9 This smile view shows the soft tissue plan with the incisal edges marked to show where they need to be reduced to correct the incisal-occlusal plane.  Remember, a case like this needs correction at the functional (incisal) end as well as the tissue (apical) end to correct the slant of the teeth without making the teeth look disproportionately long.	Figure 10 Soft tissue correction has been made with a diode laser (Twilight: Biolase Technologies) and the incisal edged reduced with rotary instrumentation.
Figure 11 A full smile view shows immediately how this combined approach corrects the esthetically unpleasing cant to the smile zone.  Areas where biologic width has been violated will require subsequent reduction of the osseous crest to recreate a healthy biologic zone.	Figure 12 The ceramic and metallic superstructure is stripped down to the cement line of the restoration.  At this point, the old restoration can be removed from the implant abutments.	Figure 13 The diode laser (Twilight: Biolase Technologies) is used to develop internal emergence angle around the non-anatomic implant abutment so that the ceramic restorations can have a more natural emergence profile.

The provisional restoration is fabricated in bisacrylic temporary material using a preoperative mockup and a clear stent (Figure 14).  This surgical provisional restoration will serve as a guide for the periodontist when performing the osseous correction as previously described.  After the connective tissue graft and osseous surgery is complete, the patient’s tissues are allowed to heal for about four months.  This is to allow for maturity and stabilization of the grafted tissue.  The gingival tissue around the teeth that underwent osseous surgery will predictably mature to the provisional margins provided the surgeon was meticulous in following the restorative margin 3 millimeters apically when recontouring the alveolar bone. When healing is completed, final impressions are taken using a double cord technique.  Around the natural abutments, one wrap of #00 cord (Ultrapak: Ultradent) is placed followed by a single wrap of #1 (Ultrapak: Ultradent) cord.  A #2 (Ultrapak: Ultradent) cord is used around the implant abutments due to the increased depth of the periimplant sulcular environment.  Care must be taken not to force the cord to deep into the sulcus.  At final placement, the #2 cord (Ultrapak: Ultradent) should not be placed below the restorative margin of the implant abutment (Figures 15 and 16).  The final impression (Honigum: Zenith/DMG) should capture the marginal detail plus .5 millimeters of root (implant abutment) surface apically so that the ceramist can develop correct emergence angles.  Figures 17 and 18 show the retracted view and smile of the patient after completion of the case.  Compare to the preoperative views of Figures 5 and 8.  A much more esthetically pleasing smile and symmetric gingival framework have been created for this patient using some creative planning that included utilization of preexisting implant abutments under less than ideal circumstances.

Figure 14 The surgical provisional restoration is in place.  The patient is then sent to the periodontist for connective tissue grafting and osseous reduction following the restorative plan of the dentist conveyed via the provisional restoration.	Figure 15 Final impressions around the implant abutments are taken using conventional mechanical tissue displacement (cords) in a similar fashion to the natural tooth abutments (Ultrapak: Ultradent).	Figure 16 The final impression (Honigum: Zenith/DMG) shows the marginal detail of the implant abutments and soft tissue correction to allow the ceramist to create more esthetic emergence profiles.
Figure 17 A retracted intraoral view shows the maxillary reconstruction after cementation.  The area of the connective tissue graft will continue to mature for several months.	Figure 18 Compare this postoperative smile view with the preoperative view in Figure 5.  This is truly an example of an “extreme makeover” for the smile of this 28-year-old female patient.

Case Report #2: Preparation Correction Of Preexisting Implant Abutments To Allow For Creation Of Anatomic Tooth Form

This patient presented with a maxillary full arch splinted provisional restoration (Figure 19).  Tooth numbers 2, 6,7, and 8 remained and were in good condition.  Implants were placed in the 10, 12, and 13 positions and had cemented gold abutments on them.  The laboratory-fabricated porcelain to metal prosthesis splinted the natural teeth on the patient’s right side to the implants on the left side.  The patient was never able to gain a state of comfort with this prosthesis.  She stated “the bridge felt tight on the left side since the new abutments on the implants were made.”  Upon clinical inspection, the implant abutments, particularly #’s 12 and 13, appeared excessive in length were not prepared in a proper two-plane fashion on the facial and lingual surfaces.  As a result, there was not sufficient space for metal and porcelain to recreate proper tooth contours.  Therefore, the restoration felt bulky and was not comfortable functionally for the patient (Figure 20).  The #2S Great White carbide (S.S. White) is used to correct preparation geometry.  The abutments are shortened and reduced properly in the central groove areas to allow for enough “negative space” to create proper occlusal anatomy within a desired thickness (1.5-2.0 millimeters) of ceramic material.  They are then polished as previously described using a 30 micron rounded cylinder diamond and porcelain polishing abrasives to smoothed, shiny gold surfaces (Figure 21).  A new provisional restoration (Figure 22) is fabricated at the same vertical dimension of occlusion as the original provisional restoration, since the patient had been comfortable in that position for several months.  The plan for the new prosthesis includes a semiprecision male-female stressbreaker between tooth numbers 9 and 10 allow physiologic movement of the natural abutments yet create the cross arch retention gained from a full arch splint (Figure 23).

Figure 19 A full arch retracted view of this patient who presented in existing provisional restorations.  This restoration was a full arch splint on natural teeth and implant abutments.	Figure 20 Removal of the provisional restorations shows implant abutments which are underprepared and need to be reshaped as part of the operative plan to complete the remake of this reconstruction.	Figure 21 This full arch retracted view shows the prepared and polished implant abutments.
Figure 22 The replacement provisional restoration created from a laboratory wax up and plastic stent is carved chairside in bisacrylic provisional material and cemented with temporary cement.	Figure 23 The completed maxillary reconstruction at delivery time.

Conclusion 

Two cases have been shown that illustrate the preparation and reuse of implant abutments for dental reconstructions.  Direct preparation of metallic structures intraorally demands instrumentation that can be used efficiently and produce the required geometric accuracy without damage to the supporting structures, whether they are natural tooth or implant born.  Often times metallic abutments on well-integrated implants when in the proper position can be modified, polished and be reused, much like previously prepared teeth in a new reconstruction, saving the dentist and patient additional time and expense.  

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