HANDBOOK OF ADHESIVE BRIDGES

Early Resin-Bonded  bridges- Failures and disappointment

Resin-bonded bridges in North America were developed in the 70s as the “Maryland Bridge”, and  were intended to replace single missing anterior teeth. The honeymoon phase of this new method  soon passed, as simple enamel bonded flanges, utilizing two anterior abutments, de-bonded with alarming frequency.

The bridge featured in the header photo above is a 6-unit non-precious splint in a negligent periodontal patient which is 15 years old. The teeth were so mobile that the patient could not eat an apple.

After splinting, the teeth were treated non-surgically with SRP, inflammation reduced and comfort returned. Hygiene was never ideal. Nonetheless it has this beat the odds of early failure seen with outwardly identical flanges in the “Maryland Bridge” design camp?

The secret is six precision guitar-shaped inlays, similar to this framework below. They positively engage with tooth structure to guarantee full seating at cementation and anti-rotation features in use, even with mobile teeth.

I have placed over 600 units of this design over 20 years. There are no failures unless grossly neglected hygiene is at play, and still, this amounts to less than 20 units in this practice span.

This is a typical laboratory cast.

More historical inprovements in adhesive anterior bridges -proximal grooves

in the 80s and 90s, design improvements from Dr. Yamashita in Japan were popularized by Dr. Ray Bertolotti. These were still enamel-bonded metal flanges, but with parallel proximal grooves, much like  3/4 anterior gold crown designs of the 1950s and 1960s. Retention improved. Cantilever anterior designs proved to be superior to two-abutment  bridges. The luting  choice was opaque Panavia, which reduced shine-through of the metal to the facial, although greying of the proximal margins in abutments and metal show were still  a paramount limitation.

What we learned from this iteration:

Proximal grooves illustrated an emerging axiom of the adhesive world; that mechanically sound preparations with resistance and retentive form, once combined with robust resin-enamel adhesion, were the new playing field.

During this period, Porcelain Veneers were the new kid on the block, bonding to labial enamel. With little mechanical forces in function, success was high. If the veneer design involved displacement forces at the incisal edges, retention dropped.

Ceramic adhesive anterior prosthetics in the  early 2000s

A German researcher,  Professor Dr. Mattias Kern pioneered the use of milled In -Ceram as the flange and pontic material. A meticulous operator, he was able to achieve highly esthetic and reliable prosthetic results despite the fracture-prone nature  and only intermediate flexural strength of  this porcelain. Interproximal greying and shine-through became history.

The next step Dr. Kern’s work

in 2010 Dr. Kern took the next step forward in materials, milled 3Y zirconium,  with fused labial porcelain. With chairside air-abrasion he was able to exceed 35 mPa  bond strengths to zirconium equaling that of a well-executed enamel bond. The extremely high flexural strength of correctly-selected Zirconium permits smaller connectives and hence more realistic embrasures than Inceram.

This is a  proven and viable option where occlusal loads are reasonable and high-quality lab work is available. It is easier to persuade patients to accept a white material rather than metal in a cosmetic setting. A seen from the lingual, it is less intrusive than metal.

However, it is more expensive to fabricate than non-precious frameworks and proximal disturbance is more likely than the inlay-flange bridge design, which never thins the proximal surfaces of abutments.

Dr. Kern’s text can be found on Amazon at https://www.amazon.com/RBFDPs-Resin-Bonded-Fixed-Dental-Prostheses/dp/1786980207

As well, he presents a very organized review of his method through Dentaltown by subscription at https://www.dentaltown.com/blog/post/16372/dentaltown-learning-onlineresin-bonded-fixed-dental-prostheses-minimally-invasive-esthetic-and-reliable-by-dr-matthias-kern?st=matthias%20kern

This Handbook’s alternative-Resin bonded bridges developed by Dr. Peter Walford

What is missing in Dr. Kern’s wonderful method  is the possibility of larger span adhesive prosthodontics. These requires  a different retainer. The periodontal splint case above- invented, developed. and deployed over the last 20 years, and the method is available though my handbooks.

In the early 2000s, I sidestepped the parallel-groove design in favor of a precision lingual inlay, still mated to metal flanges. The inlay penetrates into dentin, generating a depth of about 1.25 to 2.0 mm. in an anterior tooth, of which 0.25 to 0.5 mm is in dentin. I have placed over 600 in a 20 year span.

Conventional pushback

Some prosthodontists object to entering dentin with an adhesive design. These are the same people that will strip a whole mouth of enamel without hesitation for full crown coverage. Perhaps their reasoning is based on the historical expectation that de-bond is inevitable with bonded flanges and hence caries can develop. But if you know they are not going to debond, that fear is moot.

My experience has been, in over 600 insertions, less than 3% de-bonds over 20 years. Essentially, everything I  placed is still there, unless the abutments suffered wholesale periodontal collapse and came out as a unit.

Be objective. As a failure rate, this is better than implants. It is also a  better rate  than convention full coverage prosthodontics. It also is applicable where bony architecture  is not suitable for implants, due to alveolar concavity, inviting dehiscence. It also is applicable where periodontal disease has robbed the alveolus of bone  height, bone  quantity, and as we are learning, invites implant collapse from peri-implantitis from the same microbes  and host factors that generate periodontal disease.. It also is far more economical, and quick to complete.

So, to my mind, professional  resistance to this design is an attitude born out of unfamiliarity. The goal of this handbook is to familiarize the reader with the design and develop the reader’s skill in applying the method. problems. Then you can fly with it. Airplane travel once seemed risky, even impossible, you know.

Why this retainer is a breakthrough

If you do this procedure right,  it proves to be a breakthrough in versatility and reliability.

Changing the  path of insertion from vertical to lingual or linguo-incisal is a game changer. Splints of up to 10 units, including first bicuspids as well as anterior sextants, and have succeeded for decades. Multiple tooth prosthetics have become possible. Patients prefer them over full coverage and can afford them more readily. The facial enamel is retained, and all stages of the prosthesis from prep to insertion become faster, easier and less invasive than any other laboratory procedure.

Splinting with dubious abutments

A whole new class of periodontal splints with or without pontics results. A photo of a six unit splint placed in 2004 is found at the header of this page. This latter method provides a transition for future loss of dubious abutments without scrapping the whole prosthesis.  If a root fails periodontally, a simple root amputation can eliminate a hopeless root while the clinical crown and the prosthesis carry on. Two months after amputation the clinical crown can be returned to full length  with a composite extension, a procedure that requires no anesthetic.

For other patients facing one or more dubious abutments, in the short term, weak teeth can be retained.   Once united into an arch form, roots often re-stabilize. Free of mobility, regenerative periodontal therapies optimize osseus quality  and re-attachment, and offer a vastly improved prognosis for teeth once routinely doomed to extraction. Do you suppose patients are grateful for this?

Advantages in lower arch reconstruction

It is particularly valuable in lower arch reconstruction, because an anterior fixed splint/bridge separates the anterior sextant from the posterior arches, eliminating the never-satisfactory option of a Kennedy Class IV RPLD,  i.e., the Teeter-Totter Partial”.

Also, if the teeth are caries-free, the seldom satisfactory six-unit full-coverage lower fixed bridge is bypassed. Endodontic morbidity of heavily-reduced mandibular incisors is bypassed. This method accomplishes the same end at less than half the fee, yet profitably for the practice because it is so easy and quick. An hour is more than enough time to prepare six inlays, capture an impression, desensitize the dentin on the abutments, and temporize them with a LC soft temp material.

Finally, a lingual path of insertion permits sound engagement with crowded and malposed teeth around an arch; sufficient enamel bonding area becomes the dominant restriction, limited by having the necessary skill to find a retentive inlay variant if  the lingual guitar shapes cannot fit a path of insertion for all the abutments.

My handbooks describe these methods, applications with case examples, precautions, lab instructions, and suggested fees.

Digital design evolution

The evolution is not over. The next stage of RBFPD development is a digital-based workflow, permitting in-office zirconium milling and same-day placement. Improved esthetics in 3Y milling blocks is the next frontier, one that is sure to be very attractive to mainstream dental offices. 3D printing of temporaries can also be visualized if laboratory fused porcelain delays fabrication.

Handbook of Adhesive Bridges

  • Adhesive Bridges- Anterior- Inlay-Flange
  • Named the ” Inlay-Flange Bridge” , this new retainer was originated  by Dr. Walford in 2003.After a few trial cases, its promise was evident and development began.
  • Excellent applications for periodontal splinting, which is so poorly-accomplished in today’s dental office, has reached maturity. The lousy alternatives- bulky  fiber-reinforced splints, or fragile and short-lived splinting with un-reinforced composite are superseded by a laboratory framework that is compact, strong, durable, retentive, and versatile. This treatment carries the patient forward with minimal tooth loss and maximum versatility when heavily diseased anterior sextants  contain several teeth with uncertain periodontal prognosis.
  • Adhesive Bridges- Posterior
  • This section covers  Posterior Adhesive Bridges (Yamashita -design Resin-Bonded Fixed Partial Dentures) and describes how to fabricate adhesion bridges, usually with less or no anesthesia, retraction cord or pulpal  involvement.

WHY CONSIDER LEARNING THIS MODALITY?

  • 97% retention over a 20 year period with over 600 retainer placements.
  • Simplicity  in concept and execution: a lingual inlay is mated to a flange of metal covering lingual enamel. Normal burs are used, little time is taken to prepare, impression is simple and conventional, temporization is quick and straightforward, lab prescription is simple,  insertion follows conventional approaches, and there is an fee guide for dental plans. See the photos below for a typical impression of the inlay/flange abutment. In this case the lateral incisor was being lost due to external root resorption.
  • Note below the attractive 18-year result of replacement of the upper right lateral incisor, mimicking the labioversion of the contralateral upper left incisor.
  • No interproximal greying is seen on the right cuspid because the enamel is full-thickness in the interproximal, not thinned by a proximal groove. The abutment looks untouched.
  • Application is almost without restriction:  The Maryland bridge was contraindicated if teeth were mobile, were recently treated orthodontically,  or were rotated and malposed. Deep overbite would also contraindicate a Maryland Bridge. These restrictions are absent in the inlay-flange design.
  • The prosthesis can be extended to longer spans, to include first  bicuspids in addition to 6 anterior teeth, for spans of 10 teeth,  provided the path of insertion and integrity of abutments allow. The only insurmountable contraindication is insufficient  lingual bonding enamel area. This may be because of restorations on the abutments orbecause of malpositions of the teeth.

CATEGORIES OF INLAY FLANGE BRIDGES: See Categories of Inlay Flange Bridges

 A BEAUTIFUL CLINICAL CASE TO ILLUSTRATE:

Look at the before and after photos of this case below replacing  missing lateral incisors. The patient was referred to me for treatment by a study club member. The patient refused full coverage. Previous Maryland bridges were placed 20 years prior in another dental practice and had de-bonded and been re-luted numerous times. There was advanced caries under the de-bonded flanges.

The cuspids were destroyed: they presented with advanced lingual decay under the double-abutment bridges. No lingual enamel was present. Their use as abutments was contraindicated. The centrals were intact.

  • If the patient wished to retain his natural facial surfaces and be treated with Inlay-Flange retainers,  cantilever pontics from the central incisors  would be necessary due to the destruction of the cuspids.
  • The patient refused full coverage restoration
  • There were size dissimilarities in the edentulous spaces visible in the post op photos
  • From radiographs, implants were clearly not possible due to root convergences.
  • The prognosis for the patient was favorable
    • shallow overbite
    • large root volume of the central incisors
    • no signs of periodontal disease in the mouth at age 40
    • robust physique and health
  • This  rendered  the choice of central incisors feasible where ordinarily one might shy away from their use.
  • We would follow a cantilever design to avoid the higher failure rate of 3-unit flange bridges, because the cuspid and centrals move in differing vectors, leading, according to retrospective studies, to earlier failure than  single abutment cantilever pontics.
  • His dental plan would cover the bulk of the treatment costs, a deciding factor for a father of two children building a new house.

TREATMENT RENDERED

The  decay on the cuspids was treated with composite resin. The centrals were prepared with inlays into the lingual surfaces, and an anti-rotation dimple was placed into the resin restorations on the cuspids. Convincing pontics were fabricated in low noble alloy, with an ovate undersurface. It was fabricated folowing the instruction to the lab to fabricate it to 1 mm below the edentuous ridge.

At the time of insertion , a mini-flap raised to allow the pontic to insert sub-tissue . A small amount of crestal bone was removed through the miniflap to create biological width for healing, which requires differentiation to bone, connective tissue and epithelium under the pontic. The pontic thus emerged realistically from the alveolus. This approach increasing bulk of the interproximal papilla, to fill in black triangles in a way that is not possible with a ridgelap design.

Hemostasis in the insertion into a fresh surgical field was achieved using Hemostatic Etch and Retraction Cord . Cementation with the very durable Panavia F2.0 opaque cement took place under proper conditions of isolation

  • The patient suffered no pain from these procedures and was very pleased with the result, despite the built-in compromise of pontic size discrepancy  His pontics are flossable because floss passes under the rounded anti-rotation dimple set against the cuspids.
  • He reports that his friends could not believe the teeth were not real.
  • The lack of inflammation around the pontic emergence, the bulk to the pontics at the  cervix, healthy response of the tissues to the adjacent porcelain, and the almost normal tissue line combine to form a convincing end result.
  • Of course there is  a lot of innovation to consider;
    • The preparation itself, outline form, inlay form
    • Capturing the prep with great precision in the impression.
    • Making a suitable temporary
    • Ensuring the lab gives you what you asked for
    • Raising a miniflap and removing subjacent bone
    • Achieving hemostasis sufficient to prevent contamination of bond and cement in placement
    • Ensuring that cuspid disclusion relieves the prostheses of occlusal loads that might de-bond them
  • This is the meat of the Handbook, to learn how to do these steps with confidence and without errors.
  • BEFORE
  •  

 

  • AFTER
  •