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This is an open access journal, and articles are distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms.
A conventional fixed partial denture is the most common method for replacement of missing anterior teeth. However, it often produces pulpal stress on abutment teeth and usually not indicated for young patients. Implants though considered to be the better treatment option, but they are not feasible in every clinical situation due to high cost. Thus, in such cases, resin-bonded bridges (RBBs) are considered to be a better treatment option. It can be used as a permanent as well as an intermediate prosthesis while planning for implants and fixed partial denture.
RBBs have micromechanical bonding with the tooth surface and the metal alloy surface and it requires minimal or no tooth reduction. Various types of RBBs are Rochette bridge, Virginia bridge, and Maryland bridge, among which Maryland bridge is commonly used.
The requirement for tooth preparation for RBBs is debatable. Previously, more comprehensive preparations were utilized to improve retention. However, most practitioners now recommend minimum preparation, within enamel, or no preparation at all.
Various techniques available for fabrication of Maryland bridge are conventional casting, computer-aided designing and computer-aided manufacturing (CAD-CAM) and 3D printing. The materials used are metal, porcelain-fused metal, ceramics, more recently zirconia and graphene. The present case reports discus the conventional and digital technique for the fabrication of Maryland bridge for the replacement of missing anterior maxillary teeth.
Case examination1
A 25-year-old female patient reported with chief complaint of unesthetic smile due to missing tooth in upper front teeth region for 6 months. History revealed that the patient had grossly decayed maxillary left central incisor, for which she underwent root canal treatment in 2018. She got the same tooth extracted 6 months back due to fracture of the coronal structure that could not be restored. There was no relevant medical history was given by the patient. Extraoral examination revealed no abnormalities. Intraoral examination revealed missing maxillary left central incisor (21) with moderate generalized fluorosis (according to dean fluorosis index) (a, c and e) Case 1 (prerehabilitative view, inter-arch relation, maxillary intraoral view), (b, d, and f) Case 2 (prerehabilitative view, inter-arch relation, maxillary intraoral view.
Case examination 2
A 23-year-old female reported with a chief complaint of unpleasant smile due to missing teeth in upper front tooth region since a year. Patient gave a history of trauma 2 years back in which her maxillary left lateral incisor got fractured and she got the same tooth extracted after 6 months of trauma. No relevant medical history was given by the patient. No extraoral abnormalities were noted. Intraoral examination revealed maxillary left lateral incisor (22) with mild generalized fluorosis (according to dean fluorosis index)
Treatment plan
Various treatment options such as fixed dental prosthesis, implant retained prosthesis, and removable partial dentures, were explained to the patient but later excluded due to various reasons such as patient desire for fixed restoration, extensive tooth preparation, and high cost. Considering the patient's age and financial status, a RBB (Maryland bridge) was planned and explained to the patient. For Case 1, a porcelain-fused-to-metal hybrid Maryland bridge was planned and fabricated by conventional casting technique. For Case 2, a graphene Maryland bridge was fabricated by CAD/CAM technique.
Treatment progress
Case 1
Diagnostic impression was made using irreversible hydrocolloid (Algitex Alginate Impression Material-Dental Product of India) (a, c, and e) Case 1 (diagnostic impression and cast, maxillary and mandibular cast mounted in an articulator), (b, d, and f) Case 2 (diagnostic impression and cast, maxillary and mandibular cast mounted in an articulator). (a) Putty index, (b) Tooth preparation (full veneer preparation in 22 and lingual window preparation in 11), (c) Final impression, (d) Provisional restoration (e). Metal try in (f). Final prosthesis after porcelain firing and glazing.
The wax pattern was prepared using inlay wax over the die cast. It was removed carefully from the die, then sprue wax was attached followed by investing it in the casting ring. The conventional de-waxing and casting procedure was done in an induction casting machine followed by finishing of metal coping. The metal try in was carried out in the patient's mouth (a) Final prosthesis in master cast (b) Final prosthesis in situ, (c) Final prosthesis
Case 2
The diagnostic impression, cast, articulation, and wax-up were done same as Case 1. The lingual window preparation was done in maxillary left central incisor and canine, followed by final impression and fabrication of master cast same as in Case 1 (a) Putty index cut in the middle to replace with Chemi-sil, (b) Chemi-sil application (c) Provisional restoration composite material, (d) Tooth preparation (window preparation in 21 and 23), (e) Injecting the flowable composite after placing putty index in prepared tooth, (f) Provisional restoration.
In laboratory, the master cast was scanned using Dentsply Sirona – in Eos X5 scanner (Dentsply Sirona Global headquarters, Charlotte, NC 28277, USA) and after that designing was done using EXOCAD software (exocad GmbH, Darmstadt, Germany) After scanning of master cast, the maxillary scanned model in EXOCAD software, (b) CAD Designing of pontic, (c) Designing of two wings on prepared tooth, (d) Final prosthesis after Milling in CAM machine, (e) Final prosthesis in situ, (f) Postrehabilitative view. CAD: Computer-Aided Designing, CAM: Computer-Aided Manufacturing.
The post rehabilitative instructions were given to both the patients and they were recalled for periodic follow-up visit after a week, month, and 3 months.
There are several treatment options available for replacing missing anterior teeth, including removable partial dentures, fixed partial dentures, and implant retained prostheses. Removable partial dentures are the simplest and most cost-effective method of replacement, but they have several drawbacks, including underlying bone resorption, an unpleasant look, and a negative psychological impact in young patients. Fixed partial dentures are a useful treatment option, but it involves greater tooth reduction, which should be avoided in young patients as they have large pulp chambers in the abutments, predictable gingival transition, and patient age also limits the use of conventional fixed prostheses. Implants are the most acceptable treatment alternatives for long-term success, however owing to the bone development in young people, they are not recommended as well as they are more expensive, and failure rates are higher if not placed appropriately.
A conventional cantilever bridge is another treatment option, but according to ante's law, lateral incisors cannot be used as abutment teeth for replacement of central incisor and also bridge cannot be cantilevered across the midline. Hence, resin-bonded Maryland bridges was planned because according to Prasanna et al. the success rate of resin-bonded cantilever bridges was more when compared to conventional cantilever bridges.
The main advantage of a resin-bonded Maryland bridge is that it is a minimally invasive procedure that causes less damage to the abutment teeth, requires less chair time, and is less expensive.
Therefore, graphene was used as a choice of material in Case 2. It is an allotropic carbon based material which will be nano-reinforced with polymethyl methacrylate acrylic resin as a biopolymer for dental use. They can be used as a material of choice for dental fillings, bridges and implants. The major advantage of this material is high mechanical strength, flexibility, low cost, nontoxicity, impermeability to liquid and gases, and transparency. Furthermore, CAD/CAM technology has the advantage of high quality, reproducibility, high efficiency, ability to store data from a standardized chain of production, industrial prefabrication and controlled materials, and increased popularity when compared to conventional techniques. However, it also has disadvantage of difficulty in fabrication and compromised esthetics in terms of color when compared to all-ceramic restoration. Hence, a long-term comparative studies has to be conducted to evaluate the success rate of graphene with other crown materials.
RBBs can be highly effective in replacing missing anterior teeth, restoring oral function and esthetics, thereby increasing patient's satisfaction. In the following case reports two things were tried. A hybrid Maryland bridge was fabricated in first case which had a full veneer crown in maxillary left lateral incisor for adequate tooth coverage and not violating the ante's law and single wing on maxillary right central incisor of contralateral arch. The graphene was tried as a material of choice in second case and was fabricated by CAD/CAM technique which has an advantage of high strength and flexibility. Although the durability of RBBs is not much extended, a careful case selection, judicious designing of the preparation, and meticulous cementation regimen all can ensure the long-term success of Maryland Bridges.
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Conflicts of interest
The authors of this manuscript declare that they have no conflicts of interest, real or perceived, financial or nonfinancial in this article.