Adhesive Bridge

Adhesive bridges (synonyms: adhesive bridges, Maryland bridges), like conventional bridges, are used for the fixed closure of a tooth-limited gap in the dental arch. They are attached adhesively (by bonding) to one or both neighboring teeth without the need for extensive preparation (grinding). Unlike conventional bridges, whose abutment teeth have to be prepared all around to create a common insertion direction for the anchor crowns and to avoid undercutting areas at risk of caries, the preparation for adhesive bridges is minimally invasive: Only the oral (tooth surface facing the oral cavity) enamel, and in the case of posterior bridges also the occlusal (forming the occlusal surface) enamel, is slightly reduced so that interference with occlusion (final bite and chewing movements) can be excluded. Parallel grooves and occlusal rests can improve the mechanical retention (hold) of the adhesive bridge. However, bonding strength is primarily achieved via the micromechanical bond of an adhesive luting composite (resin adhesive), which adheres to both the chemically pre-treated enamel on one side and the bridge material on the other side in microscopically fine surface roughness. Materials

Ceramic veneered metal frameworks and all-ceramic constructions are used as bridge materials.

Indications (areas of application)

Adhesive bridges are now a scientifically recognized therapeutic method that can be used to restore gaps in the adolescent dentition in particular, while preserving tooth structure. However, as desirable as minimally invasive restorations are, adhesive bridges can only be planned within narrow indication limits:

Anchor teeth must be largely free of caries and fillings: small composite fillings (plastic fillings) are possible, but must be completely covered by the wings of the bridge construction.
In the maxillary anterior region, a maximum of one incisor may be replaced.
In the posterior region, a maximum of one tooth may be replaced.
In the mandibular anterior region, up to four incisors may be replaced.
Single incisors may be adhesively fixed with only one wing. This does not usually apply to canines.
Two-wing adhesive bridges may only be used after tooth eruption has been completed.
For an adhesive bridge in the maxillary anterior region, the vertical anterior step must not exceed 3 mm, unless there is also a large horizontal anterior step at the same time, which precludes overloading of the bridge during occlusion (final bite and chewing movements).
Long-term provisional before planned gap restoration with an implant: implants should be placed only after bone growth is complete. For girls, this is about 17 years, for boys at 21 years.

Contraindications

Degree of destruction of abutment teeth (decayed teeth and teeth with fillings).
Gap over more than one tooth in the maxillary anterior region.
Gap over more than one tooth in the posterior region of the upper or lower jaw.
Gap over more than four mandibular anterior teeth.
Vertical anterior tooth step over 3 mm
Pronounced parafunctional stresses such as bruxism (grinding) increase the risk of failure.
Inadequate oral hygiene
Intolerance to luting composite
In case of incompatibility against alloy components: Switch to all-ceramic material

The procedure

First appointment – situation models before preparation:

Plaster models are made on the basis of alginate impressions (impression of the dentition) to plan the preparation and for a better overview of the space available, which can also be prepared (ground) as a study model if necessary. Second appointment – preparation:

Minimally invasive preparation: oral and proximal surfaces (towards the oral cavity and in the interdental space) are parallelized, small bearing surfaces are incorporated into occlusal (chewing) surfaces, oral surfaces of incisors are reduced to allow undisturbed occlusion (tooth contacts during final bite and chewing movements). Parallel grooves and retention pins improve the mechanical adhesion of the design to the tooth.
Impressions of both jaws and bite registration after preparation: to transfer the positional relationship of the upper and lower jaws, the dental laboratory requires models of the upper and lower jaws and a so-called bite registration (e.g. made of silicone or plastic).
Facebow system: for transferring the temporomandibular joint position to the articulator (dental device for imitating the movements of the temporomandibular joint).
Shade selection

Dental laboratory:

Fabrication of the metal or ceramic bridge framework on the working model (plaster model based on the impressions). For a metal framework, non-precious metal alloys are used due to the more suitable modulus of elasticity.
Ceramic veneer (raw firing) in the previously determined tooth color.
Completion (glaze firing)
Abrasive blasting of the bonding surfaces of both metallic and oxide ceramic frameworks with aluminum oxide powder (Al2O3) in a grain size of 50 to 110 μm at 1 to 2.5 bar.

Third (to fifth) appointment – try-in and incorporation:

The final appointment may be preceded by two separate appointments for framework try-in and raw firing try-in before final completion in the dental laboratory. When cementing with adhesive luting systems, the principle is that the manufacturer’s instructions for use must be followed in detail.

Try-in: check color, fit and, as far as possible before cementation, occlusion.
Conditioning of the bonding surfaces of the bridge framework to improve adhesion (bonding): etching with hydrofluoric acid and silanizing (coating the surface with a silane compound as a bonding agent).
Rubber dam: placing a tension rubber in the patient’s mouth prevents saliva from entering during the luting procedure. It must lie in the gap area without tension or wrinkles and must not cover the preparation margins.
Conditioning the abutment teeth: the prepared enamel is etched with 35% phosphoric acid (H3PO4) for 30 sec, then sprayed with water for approx. 30 sec. The resulting retentive etching pattern receives a bonding (thin flowing plastic), which fills the.
Application of a dual (two-part) curing luting composite to the prepared tooth and bridge surfaces and positioning of the bridge under pressure.
Removal of excess cement before final curing.
The chemical curing of the material is accelerated by a polymerization lamp. Purely light-curing luting composites can also be used for all-ceramic bridges.
Occlusion control
Finishing of the margins with ultra-fine grit diamond instruments and polishers.
Instruction of the patient to adequately clean the bridge.

After the procedure

especially two-wing bridges should be checked at regular intervals, e.g., as part of the semi-annual routine examination, because sometimes the partial detachment of only one wing goes unnoticed by the patient and is associated with a high risk of caries.

Possible complications

Loosening of the adhesive fixation, e.g., due to parafunctions (incorrect stresses such as grinding)
If a two-wing anchored bridge loosens only on one side, the risk of caries formation between the bridge wing and tooth surface is high.
Behavior of jaw growth with too early inserted two-wing bridge.
Behavior of the length growth of an abutment tooth with too early inserted two-wing bridge.