Resin-Bonded bridges- History
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.
Design improvements from Dr. Yamashita in Japan were popularized by Dr. Ray Bertolotti in the 80s and 90s. These were still enamel-bonded metal flanges, but with parallel proximal grooves, much like the 3/4 anterior gold crown designs of the 1950s and 1960s. Retention improved, and 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 managing greying and metal show were still an important if not paramount limitation. The use of 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 a new playing field. While Porcelain Veneers were the new kid on the block, bonding to labial enamel, these corresponded to the inverse, bonding to lingual enamel.
In the early 2000s, 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 intermediate flexural strength of this porcelain. Interproximal greying and shine-through became history.
in 2001 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 exceeding that to enamel. The extremely high flexural strength of correctly-selected Zirconium permitted smaller connectives and hence more realistic embrasures.
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
Resin bonded bridges now and in the future
What is missing in Dr. Kern’s wonderful method is the possibility of larger span adhesive prosthodontics. These requires a different retainer. This is what I 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.
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 retainers and caries can develop. However, 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.
As a failure rate, this is better than implants.It is also a better rate than convention full coverage prosthodontics.
So, to my mind, it is an attitude simply born out of unfamiliarity. Airplane travel once seemed impossible, you know. Do this procedure right, and 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 have succeeded. Multiple tooth prosthetics have become possible. Patients prefer them 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.
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 – a simple root amputation can eliminate a hopeless root while retaining the clinical crown and the prosthesis. For the short term, weak teeth can be retained. When needed, roots can be amputated. For the long term, the whole prosthesis is retained, needing only short and effective intervention if a tooth fails.
It is particularly valuable in lower arch reconstruction, because an anterior 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, , avoiding the endodontic morbidity of heavily-reduced mandibular incisors in lower sextant full coverage. This method accomplishes the same end at less than half the fee, yet cost-effectively for the practice.
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. Once united into an arch form, roots stabilize their mobility. Free of mobility, regenerative periodontal therapies optimize osseus quality and re-attachment, and offer a vastly improved prognosis.
My handbooks describe these methods, applications with case examples, precautions, lab instructions, and suggested fees.
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. Bulky fiber-reinforced splints, or fragile and short-lived splinting with un-reinforced composite can be superceded by a laboratory framework that is compact, 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 material covers Posterior Adhesive Bridges (Yamashita -design Resin-Bonded Fixed Partial Dentures). 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 existing fee guide entry for dental plans. See the photos below for a typical impression of the inlay/flange abutment, and 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 because the enamel is full-thickness in the interproximal, not thinned by a proximal groove.Note the abutment -the upper right cuspid, 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 bicuspids as well as the 6 anteriors, to spans up to 10 teeth, provided the path of insertion and integrity of abutments allow. The only insurmountable contraindication is insufficient lingual bonding enamel area.
CATEGORIES OF INLAY FLANGE BRIDGES: See Categories of Inlay Flange Bridges
CLINICAL CASE TO ILLUSTRATE:
Look at the before and after photos of this case below replacing missing lateral incisors. 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 patient was referred to me for treatment.The cuspids were destroyed: they presented with advanced lingual decay under the double-abutment bridges.The centrals were intact.
- The destruction of the cuspids made them unusable as abutments, necessitating cantilever pontics from the central incisors if the patient wished to retain his natural facial surfaces and be treated with Inlay-Flange retainers
- The patient refused full coverage restoration
- There were size dissimilarities in the edentulous spaces.
- from radiographs, implants were clearly not possible due to root convergences.
- The patient fortunately had
- shallow overbite
- large root volume of the central incisors
- no signs of periodontal disease in the mouth at age 40
- robust physique
- This rendered the choice of central incisors feasible.
- His dental plan would cover the bulk of the treatment costs, a deciding factor for a father of two young children building a new house.
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 on the cuspid. Convincing pontics were fabricated in low noble alloy,with an ovate undersurface which was inserted under a mini-flap raised at the time of insertion. A small amount of crestal bone was removed to create biological width for differentiation of bone, connective tissue and epithelium on the pontic area. The pontic was thus able to emerged realistically from the alveolus, increasing bulk of the interproximal papilla, in a way that is not possible with a ridgelap design.
- The patient suffered no pain from these procedures and was very pleased with the result, despite the compromise of pontic size discrepancy . The 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.