An alternative solution for a complex prosthodontic problem: A modified Andrews fixed dental prosthesis Carly L. Taylor, BDS, MSca and Julian D. Satterthwaite, BDS, MSc, PhDb School of Dentistry, University of Manchester, Oxford Rd, Manchester, UK This report describes the prosthodontic rehabilitation of an alveolar defect in the posterior mandible after the excision of an odontogenic myxoma. A minimally invasive technique that involves a modification of the traditional Andrews fixed dental prosthesis was used to replace both soft and hard tissues. The clinical stages and materials used to provide this treatment are discussed. (J Prosthet Dent 2014;-:---) A significant component of restorative dentistry is the replacement of missing teeth. The congenital absence of a tooth or the extraction of a tooth is associated with the progressive reduction of the surrounding volume of hard and soft tissues.1,2 Loss of such tissues is even more pronounced in situations of trauma and cleft lip and palate, and after the surgical excision of pathoses. The traditional management of such patients requires the use of partial removable dental prostheses to replace the missing dentition and associated structures. This can be associated with problems of patient adaptability, retention, and stability. The Andrews fixed dental prosthesis was first introduced in 1976 by James Andrews, DMD and has been described as a partial fixed removable dental prosthesis that consisted of a bar soldered to retainers at each end onto which a denture is clipped. It has been advocated for use in patients with extensive alveolar bone loss, median diastema, and unfavorable skeletal relationships that preclude the esthetic positioning of pontics.3 Problems with the Andrews fixed dental prosthesis include soft-tissue proliferation after placement of the bar too close to the gingival tissues, which impedes oral hygiene.4 Fracture of the solder joint can also occur if there is insufficient occlusal a

clearance and subsequent inadequate thickness of material.4 Such prostheses also can require greater maintenance because the retentive elements can wear, which necessitates replacement.4 Finally, failure of the luting cement may occur if it is exposed to excessive tensile forces, which results in microleakage and recurrent caries. This may occur if the path of placements for the fixed and removable components of the prostheses are identical.5 The widespread use of dental implants now offers an alternative solution for many patients. Such partial removable dental prostheses can be firmly attached to the underlying fixtures with precision attachments and require no preparation of the adjacent teeth.6 For patients with a significant amount of vertical bone loss, however, implant placement may not be possible. In such patients, traditional techniques may be required to reconstruct the oral tissues. A conventional Andrews fixed dental prosthesis uses complete crowns as retainers. One of the major problems with these restorations is their destructive nature, which results in significant removal of sound tooth tissue. With the increasing predictability of adhesive dentistry, minimally invasive techniques, for example, resin-bonded fixed dental prostheses, are becoming a popular

Clinical Lecturer and Honorary Specialty Trainee, Department of Restorative Dentistry. Senior Lecturer and Honorary Consultant, Department of Restorative Dentistry.

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and predictable method of tooth replacement.7 Although a variety of techniques have previously been reported, current practice involves bonding an airborne-particle abraded base metal alloy wing to tooth tissue with a bifunctional resin. Such procedures are technique sensitive, and, although their lifespan is shorter than traditional alternatives, the biologic cost is lower. Factors that reportedly influence the success of such restorations include the amount of enamel coverage, location, design, number of pontics, and operator experience.7,8 Cantilever designs are now advocated because of the risk of debonding and recurrent caries, which is associated with fixed-fixed designs. The restoration must also be designed to allow sufficient rigidity of the connector and retainer and to direct forces away from the bond.8 Correct occlusal management is key to achieving the latter. This report describes a modification to the traditional Andrews fixed dental prosthesis to replace both soft and hard tissues after resection of an odontogenic myxoma in the posterior mandible.

CLINICAL REPORT A 46-year-old woman was referred to the University Dental Hospital

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Volume of Manchester by her maxillofacial surgeon after the excision of an odontogenic myxoma in the right quadrant of the mandible. Odontogenic myxomas are rare benign tumors that originate from dental mesenchyme. They can be locally invasive, which results in significant loss of bone and resorption of the roots of adjacent teeth.9 It has been estimated that they account for 1% of all tumors found in the jawbones10 and can occur in any part of the jaw but most commonly in the molar and ramus regions of the mandible.11,12 Because of their invasive nature, lesions may be asymptomatic until they reach a considerable size. The patient’s presenting symptom was the inability to clear food from the base of the defect with her tongue. The patient’s medical history was unremarkable, with no known allergies and no medication. Clinical and radiographic examination revealed the loss of the mandibular right first and second premolars and first molar, and an associated defect that extended almost to the floor of the mouth (Figs. 1, 2). Results of radiographic examination showed close proximity of the base of the defect to the mental foramen. In spite of this, the patient did not have paresthesia of the lip or discomfort from the area. The mandibular right canine had no restorations, and the mandibular right second molar had an occlusal amalgam restoration. No apical pathology was present on either tooth, and pulp sensitivity tests gave normal responses. The second molar had good periodontal support. However, the labial and distal aspects of the canine had clinical attachment loss, with the associated loss of bony support that extended halfway down the distal aspect of the root. Due to the significant vertical loss of bone and proximity of the inferior dental nerve, implant placement would not have been possible without significant grafting. Techniques such as onlay grafts and distraction osteogenesis have been used, but they are not without complications.13-15 Achieving soft-tissue closure when grafting large amounts of bone can be challenging, and the vicinity

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1 Panoramic radiograph highlighting depth of lesion and proximity of inferior dental canal and mental foramen.

2 Preoperative photograph. Note resolution of gingival inflammation after oral hygiene instruction that revealed subgingival calculus. of the inferior dental nerve precluded the use of distraction techniques for this patient.15 Unilateral edentulous areas are often amenable to restoration with a sectional partial removable dental prosthesis. Such prostheses have 2 or more components with separate paths of placement. When connected intraorally, a high degree of retention can be achieved from the opposing undercuts. Unfortunately, the excision of the lesion had resulted in a defect with divergent walls (Fig. 2). Adequate undercuts could not have been provided by modifying the proximal surfaces of the abutment teeth because of the height of the lesion and would also have created significant plaque retentive factors. A conventional partial removable dental prosthesis also

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was considered. To provide adequate support, retention, and reciprocation, multiple teeth would need to serve as abutments in conjunction with a lingual plate connector. Such a prosthesis would retain significant plaque, and, given the patient’s history of periodontal disease, this was not deemed an ideal option. A unilateral partial removable dental prosthesis would have overcome the problem of plaque retention but was discounted for several reasons. First, patients have swallowed or inhaled such prostheses,16,17 and 1 study reported that dental prostheses account for 11.5% of all impacted foreign bodies.18 Because such prostheses have sharp clasps, complications such as the perforation of the internal mucous

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membranes can occur with accompanying edema and possible obstruction and potentially fatal consequences.16 Second, given the size of the defect, achieving satisfactory reciprocation and retention of the prosthesis with clasps alone would have been difficult. Significant undercuts would need to be created on the mandibular right canine and second molar with additions of composite resin. Such restorations, in conjunction with an infrabulge clasp on the canine could result in both aesthetic problems and increased plaque retention. Finally, it would be difficult to achieve satisfactory support for such a large prosthesis, particularly on the molar abutment. Excessive force could be placed upon supporting elements, which results in the bending or fracturing of components. A conventional Andrews fixed dental prosthesis was contemplated; however, complete coverage indirect restorations have been associated with a greater increase in pulpal necrosis.19 It has been reported that traditional metal ceramic crown preparations on molar teeth result in 8 times more tissue removal than that required for a retainer in a resin-bonded prosthesis.19 In addition to this, further axial reduction is often required adjacent to the edentulous area to allow sufficient space for soldering the bar to the retainer.2,5 This could result in an even greater risk of pulpal necrosis of the abutment teeth. The preservation of both abutment teeth was considered important in this patient because loss of either tooth would have made restoration of the defect significantly more challenging. It was decided to modify the Andrews fixed dental prosthesis concept by using resin-bonded retainers rather than complete crown retainers. A previous clinical report described a similar technique to restore an alveolar defect that involved a maxillary incisor; however, no details of survival time were presented.20 After periapical radiography and vitality testing of the abutment teeth, initial stabilization treatment was performed. Primary impressions (Xantalgin; Heraeus Kulzer Ltd) and a facebow

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3 registration were made to obtain diagnostic casts. A 2-mmespaced mandibular custom tray was made in addition to a wax trial insertion to assess the tooth position and shade. The amalgam restoration was removed from the mandibular right second molar under a rubber dam and replaced with composite resin (Filtek Z250; 3M ESPE). Tooth preparation confined to enamel was carried out on the abutment teeth. For the mandibular right canine, this included a chamfer finish line, cingulum rest, and proximal grooves to provide resistance to torsional forces and flattening of the distal surface to provide an adequate height of metal for the connector. The preparation of the mandibular right second molar involved mesial and distal rest seats, a 180-degree wrap around, and a chamfer finish line that

extended across the central fissure of the occlusal surface. Because of the lingual inclination of this tooth, occlusal contacts were only present on the buccal cusps, with adequate occlusal clearance on the lingual aspect so as not to require occlusal reduction. A single-stage highviscosity and wash impression in addition polymerized polyvinyl siloxane (Dimension Penta VPS impression material; 3M ESPE) and a registration (Futar D; Optident) were made. A framework was fabricated in a nickelchromium alloy (Wiron 99; Metrodent) with a Hader bar (Cendres þ Metaux) to prevent the rotation of the prosthesis (Figs. 3, 4). The bar was evaluated intraorally for fit and the ability for interproximal brushes to fit between the bar and gingival tissues at the proximal surfaces of the abutments. The occlusal relationships were recorded with acrylic

3 Occlusal view of resin retained bar on definitive cast.

4 Buccal view of bar on definitive cast. Note design to permit adequate space for denture.

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Volume resin (Pattern Resin LS; GC) built up onto the bar with a “brush bead” technique. The denture was processed with a metal housing into which a resilient plastic Hader clip (Cendres þ Metaux) was inserted to engage the bar (Figs. 5, 6). To avoid tensile forces on the cement lute, the lingual cusps of the prosthetic teeth were reduced to ensure canine guidance on natural teeth. The framework was polished, and the fitting surfaces were abraded with alumina. The framework was cemented under a rubber dam. A cement that contained 4-META (Panavia F 2.0; Kuraray Dental) was used to lute the framework by following the manufacturer’s instructions. The denture was evaluated, and occlusal contacts were adjusted (Figs 7, 8). Oral hygiene instruction and demonstration were provided, including interproximal brushes. Upon review, the oral hygiene was satisfactory, and the patient no longer had problems with food accumulating at the base of the defect. After reviews at 2 and 12 weeks, the patient was referred to her general dentist for recall and a maintenance program.

5 Denture component of restoration, showing metal housing and plastic Hader clip.

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6 Denture and bar components connected extraorally.

DISCUSSION This technique, just described, offers a straightforward treatment option for restoring defects that resulted in both hard- and soft-tissue loss. It is a cost-effective procedure that requires no specialist equipment and only minimal clinical time, which makes it suitable for use in general dental practice. The restoration offers a satisfactory esthetic outcome and has the advantage of replacing both teeth and their supporting structures while providing optimal retention, support, and bracing. From a biologic perspective, this type of restoration has a low biologic cost because only minimal tooth preparation confined to enamel is required. The technique does have several potential shortcomings. First, the retention of the prosthesis relies solely on the bond between the retainers and the enamel. Several studies investigated the longevity and causes of failure of resin-bonded

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7 Occlusal view of completed restoration.

8 Frontal view with prosthesis in situ.

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fixed dental prostheses. Location is thought to affect survival rates, with the lowest survival times being reported in the posterior mandible.21,22 This has been attributed to difficulty in achieving adequate moisture isolation during bonding and the unfavorable forces placed on the restoration during function compared with maxillary restorations.21 The length and design of the prostheses could also affect survival times. Fixed-fixed designs and those that exceed 4 units also were found to have higher failure rates in 1 study.7 Given the above information, the risk of debonding could be increased for this restoration, especially as it is opposed by a natural dentition. Fixed-fixed designs also are associated with a high risk of recurrent caries.21 In spite of this, the risk of recurrent caries might be lower for this restoration because of the length of the bar and the presence of single retainers at each end. The debonding of 1 retainer would be noticeable to the patient because the bar would move. Only 1 other study has reported the use of a resin-retained Andrews fixed dental prosthesis.20 In this study, 5 retainers were used to replace a maxillary lateral incisor, with the removable portion of the prostheses being retained by a pin.20 Although the retention of the metal framework would be expected to be better than that of the restoration presented in this article, the risk of recurrent caries after debonding would be a significant risk because the restoration would still remain in situ, even if multiple retainers were to debond. Unfortunately, no information is given regarding the longevity of, or any, complications associated with this prosthesis. A risk of ingestion also is associated with unilateral prostheses. This would be expected to be quite low in this situation because the removable component is large because of the depth of the defect. In addition, positive retention was afforded by the clip attachment to the Hader bar, and the patient was instructed to remove the

Taylor and Satterthwaite

5 prosthesis at night. Unlike a unilateral partial removable dental prosthesis, the prosthesis does not contain any sharp elements, such as clasps, which reduces the risk of damage to internal soft issues if the prosthesis were to be ingested.

SUMMARY The treatment of a mandibular defect was achieved with a modified Andrews fixed dental prosthesis, which comprises a resin-bonded Hader bar and partial removable dental prosthesis. Given the size and location of the restoration, the survival time of the restoration should be somewhat lower than published figures for resin-bonded fixed dental prostheses. In spite of this, the restoration provides a minimally invasive medium-term solution.

REFERENCES 1. Pietrokovski J, Massler M. Alveolar ridge resorption following tooth extraction. J Prosthet Dent 1967;17:21-7. 2. Johnson K. A study of the dimensional changes occurring in the maxilla following tooth extraction. Aust Dent J 1969;14:241-4. 3. Everhart RJ, Cavazos E. Evaluation of a fixed removable partial denture: Andrews bridge system. J Prosthet Dent 1983;50:180-4. 4. Gardner MF, Stankewitz CG. Using removable gingival facades with fixed partial dentures. J Prosthet Dent 1982;47:262-4. 5. Mueninghoff LA, Johnson MH. Fixedremovable partial denture. J Prosthet Dent 1982;48:547-50. 6. Morgano SM, Lima Verde MAR, Haddad MJ. A fixed-detachable implant-supported prosthesis retained with precision attachments. J Prosthet Dent 1993;70:438-42. 7. Djemal S, Setchell D, King P, Wickens J. Long-term survival characteristics of 832 resin-retained bridges and splints provided in a post-graduate teaching hospital between 1978 and 1993. J Oral Rehabil 1993;26: 302-20. 8. Pjetursson BE, Tan WC, Tan K, Brägger U, Zwahlen M, Lang NP. A systematic review of the survival and complication rates of resinbonded bridges after an observation period of at least 5 years. Clin Oral Implants Res 2008;19:131-41. 9. Soames JV, Southam JC. Oral pathology. 4th ed.Oxford: Oxford University Press; 2005. p. 234-5. 10. Wu PC, Chan KW. A survey of tumours of the jaws in Hong Kong Chinese. Br J Oral Maxillofac Surg 1985;23:92-102.

11. Noffke CEE, Raubenheimer EJ, Chabikuli NJ, Bouckaert MMR. Odontogenic myxoma: review of the literature and report of 30 cases from South Africa. Oral Surg Oral Med Oral Pathol Oral Radiol 2007;104:101-9. 12. MacDonald-Jankowski DS, Yeung R, Lee KM, Li TKL. Odontogenic myxomas in the Hong Kong Chinese: clinico-radiological presentation and systematic review. Dentomaxillofac Radiol 2002;31:71-83. 13. Saulacic N, Zix J, Iizuka T. Complication rates and associated factors in alveolar distraction osteogenesis: a comprehensive review. Int J Oral Maxillofac Surg 2009;38: 210-7. 14. Barone A, Ugo C. Maxillary alveolar ridge reconstruction with nonvascularized autogenous block bone: clinical results. J Oral Maxillofac Surg 2007;65:2039-46. 15. Perdijk FBT, Meijer GJ, van Strijen PJ, Koole R. Complications in alveolar distraction osteogenesis of the atrophic mandible. Int J Oral Maxillfac Surg 2007;36:916-21. 16. Gallas M, Blanco M, Martinez-Ares D, Rivo E, Garcia-Gontan E, Canizares M. Unnotices swallowing of a unilateral removable partial denture. Gerodontology 2012;29:e1198-200. 17. Goodacre CJ. A dislodged and swallowed unilateral removable partial denture. J Prosthet Dent 1987;58:124-5. 18. Abdullah BJ, Teong LK, Mahadevan J, Jalaludin A. Dental prosthesis ingested and impacted in the esophagus and orolaryngopharynx. J Otolaryngol 1998;27: 190-4. 19. Edelhoff D, Sorensen JA. Tooth structure removal associated with various preparation designs for posterior teeth. Int J Periodontics Restorative Dent 2002;22: 241-50. 20. Cohen SR, Blitzer RM, Rieger WJ, Mingledorff EB, Songsakul A. Resinbonded retainers with custom-made precision attachment for anterior alveolar ridge defect in patients with cleft. J Prosthet Dent 1987;57:78-81. 21. Chang HK, Zidan O, Lee IK, GomezMartin O. Resin-bonded fixed partial dentures: a recall study. J Prosthet Dent 1991;65: 778-81. 22. De Kanter RJAM, Creugers NHJ, Verzijden CWGJM, Van’t Hof MA. A five year multi-practice clinical study on posterior resin-bonded bridges. J Dent Res 1998;77: 609-14.

Corresponding author: Dr Carly Taylor First Floor, Coupland III Building University of Manchester Oxford Rd, Manchester, M13 9PL UNITED KINGDOM E-mail: [email protected] Copyright ª 2014 by the Editorial Council for The Journal of Prosthetic Dentistry.

An alternative solution for a complex prosthodontic problem: a modified Andrews fixed dental prosthesis.

This report describes the prosthodontic rehabilitation of an alveolar defect in the posterior mandible after the excision of an odontogenic myxoma. A ...
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