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L N E T IPCRS O S T H O D O N T I C S R E M O V A B L E RPER M O SOTVHA OB DO The Swing-Lock Denture: Its Use in Conventional Removable Partial Denture Prosthodontics CHRISTOPHER D. LYNCH AND P FINBARR ALLEN Abstract: This article describes the uses of the swing-lock retained removable partial denture in partially dentate patients where the potential for achievable retention with a conventionally designed removable partial denture is less than adequate. The article presents two case reports detailing effective use of the swing-lock concept in removable partial denture design and it is hoped that this article will increase the awareness of practitioners to the use of this prosthesis type when planning removable partial dentures. Dent Update 2004; 31: 506–508 Clinical Relevance: The swing-lock removable partial denture is a useful treatment option for patients who lack clinical features for adequate retention of conventional removable partial denture therapy, or for those patients
who, for a variety of reasons, are not suitable for fixed prosthodontics or implant-retained prostheses. natural teeth is such that there is poor tooth support for the prosthesis; The remaining teeth are periodontally compromised – the swing-lock design is thought to act as a splint, distributing forces evenly among the remaining teeth (the use of clasps on a conventional prosthesis would subject periodontally compromised abutment teeth to damaging forces); Implant-retained prostheses are contra-indicated owing to financial or clinical reasons. Contra-indications for its use include scenarios where: I mprovements in dental health in developed countries have led to an increase in the prevalence of partially dentate adults.1 Rehabilitation of partially dentate patients place considerable demands on the diagnostic, clinical and technical skills of those involved in their rehabilitation. The swing-lock denture is useful in partially dentate patients where the configuration of the
remaining teeth is such that either the retention or stability available for a conventional removable partial denture is less than ideal. Its development can be credited to two people; it was first documented by Simmons in 1963,2 though previous work by Ackerman3 in 1955 makes reference to a prosthesis type that utilized a similar mechanism for retention. While the use of Christopher D. Lynch, BDS, MFD RCSI, Registrar in Restorative Dentistry and P. Finbarr Allen, BDS, MSc, FDS RCPS, PhD, Senior Lecturer/Consultant, Department of Restorative Dentistry, National University of Ireland, Cork, Ireland. 506 a swing-lock component has been documented in the retention of maxillofacial prostheses,4,5,6 the purpose of this article is to bring its use to the attention of dental practitioners for partially dentate patients where adequate retention is not readily achievable. The design of this prosthesis incorporates a conventional removable partial denture design with a ‘swing-lock’
component consisting of a preformed metal hinge and locking precision attachments in a single casting – a ‘hinge’, ‘gate’ and ‘clasp’ (Figure 1). This additional component is usually placed in the labial sulcus. Indications for the use of a swing-lock component include scenarios where: Existing dental or alveolar undercuts do not provide sufficient retention for conventional removable partial dentures; The use of retentive clasps will lead to compromised aesthetics; The configuration of the remaining The patient’s manual dexterity is such that they cannot correctly manipulate the clasping mechanism of the swinglock portion; The patient has consistently demonstrated poor oral hygiene, or inadequate dietary control, or advanced unstabilized periodontal disease (the prosthesis covers the gingival margins of many teeth); The patient has a shallow sulcus or Figure 1. The swing-lock removable partial denture with the ‘hinge’, ‘gate’ and ‘clasp’
identified. Dental Update – November 2004 R E M OVA B L E P R O S T H O D O N T I C S Figure 2. A mandibular swing-lock removable partial denture. Note the use of metal struts on the remaining teeth. Figure 3. A maxillary swing-lock removable partial denture with an acrylic flange added to the labial bar. large frenal attachment in the area where the position of the bar is planned; For a maxillary prosthesis, the patient has a high smile-line. Original descriptions2 of the swing-lock prosthesis used small metal ‘struts’ beneath undercut areas of abutment teeth (similar to gingivally approaching clasps on conventional prostheses) (Figure 2). While this is feasible in mandibular prostheses, it may compromise aesthetics and limit patient acceptance of maxillary prostheses, particularly if the patient has a tendency towards a high smile-line. This can be overcome by placing an acrylic flange on the metal bar, which is also useful in masking unaesthetic gingival recession –
a common feature in such aged dentitions (Figure 3). Struts also have the potential to trap food, hence the need for meticulous oral hygiene is clear. The following case reports demonstrate effective uses of swing-lock removable partial dentures. CASE REPORT 1 A 71-year-old partially dentate female was referred to the Department of Restorative Dental Update – November 2004 Dentistry of the Cork University Dental School and Hospital (Cork, Ireland) for specialist treatment regarding her prosthodontic rehabilitation. The patient reported difficulty wearing several maxillary removable partial dentures that had been made for her in the past. The patient was a retired dental assistant and had extensive fixed prosthodontic work, fitted during her lifetime, that was now disintegrating. An intra-oral photograph of this patient is shown in Figure 4. The endodontically treated root of an upper right canine was present, and the patient’s referring practitioner suggested that this tooth was
suitable for restoration with a dowel-retained crown. The patient’s existing prosthesis was examined. It was clear that the main difficulty with retention of the prosthesis was in the upper left quadrant, with no teeth present distal to the upper left central incisor. Treatment options discussed with the patient included implant-retained prostheses (fixed or removable), conventional removable partial dentures, or a swinglock removable partial denture. As the patient was elderly and limited by financial constraints, an implant-retained prosthesis was not suitable. As previous removable prostheses had been unsuccessful, it was decided to fabricate an upper swing-lock removable partial denture, with a prosthetic ‘overdenture’ abutment tooth to be placed over the root of the upper right canine. Diagnostic casts were made in the usual fashion and mounted on a semi-adjustable articulator. The upper cast was surveyed and a chrome-cobalt framework designed. Following tooth preparation, a
master impression was made in silicone. The impression was sent to the technician with written instructions for the fabrication of the designed prosthesis to include a labial swing-lock component with an acrylic flange to disguise the appearance of the metal bar. The metal framework was tried in the mouth and found to fit accurately. The patient’s dexterity in manipulating the clasp was assessed at this stage and found to be satisfactory. Following occlusal registration and tooth selection, the denture was completed in the normal manner and delivered to the patient (Figure 5). At subsequent review Figure 4. Intra-oral photograph showing the dental configuration of the patient described in Case Report 1. Figure 5. Intra-oral photograph showing the swing-lock denture in situ for the patient in Case Report 1. appointments, the patient reported satisfaction with the aesthetics, function and retention of the prosthesis. CASE REPORT 2 A 55-year-old female was referred to the Department
of Restorative Dentistry of the Cork University Dental School and Hospital (Cork, Ireland) for provision of an implant-retained prosthesis. On discussion with the patient, she reported that she had several upper partial dentures fabricated for her that she found difficult to control. She was also concerned about the cost of an implant-retained prosthesis. On examination, the patient was found to be partially dentate, with five teeth present in her upper arch (3|, 2|, 1|, |1, |3) (Figure 6). The upper left canine was over-erupted and periodontally compromised (Grade III mobility); however, the patient reported that she wanted to retain this tooth. When the upper cast was surveyed it was found the labial surface of the upper right canine was non-retentive. In view of the patient’s clinical and financial considerations, it was agreed that an upper swing-lock removable partial denture would be fabricated. Following tooth preparation (which included the addition of some adhesive composite
resin on the labial surface of the upper right canine to enhance retention), a master impression was 507 R E M OVA B L E P R O S T H O D O N T I C S DISCUSSION Figure 6. Intra-oral photograph showing the dental configuration of the patient described in Case Report 2. Figure 7. Intra-oral photograph showing the swing-lock denture in situ for the patient in Case Report 2. Figure 8. View of the fitting surface of the swinglock denture for Case Report 2 made in silicone. The prosthesis was designed to include a labial swing-lock component with an acrylic flange to mask the gingival recession around the remaining upper teeth, and fabrication continued in the fashion described in the previous case report. At the final ‘try-in’ stage, the patient reported that the upper right canine had become quite uncomfortable and requested its extraction. It was decided to do this at the delivery stage. The upper left canine was removed from the master cast and added to the final prosthesis
prior to processing of the acrylic component. At the denture delivery stage, the upper right canine was extracted and the prosthesis fitted (Figures 7 and 8). At subsequent review appointments the patient reported satisfaction with the aesthetics, function and retention of the prosthesis. 508 The swing-lock concept is a useful method of improving retention of removable prostheses where conventional retention is absent. The cases presented in this paper demonstrate how to achieve a satisfactory result for those dentitions where the possibilities for clasp-retained removable partial dentures are limited by utilizing a concept which has been often used in maxillofacial prosthodontics.4,5,6 Neither patient in the described case reports was able to afford implantretained prostheses, and the chances of success of a conventional removable prosthesis were clearly limited. The materials and techniques used are not dissimilar from conventional removable partial denture construction. It is
critical that the patient’s dexterity is assessed at an early stage as poor manual dexterity will clearly limit the success of the prosthesis. Swing-lock dentures may also be used in association with other retentive factors such as implants.7 There is little scientific evidence in the literature regarding patient satisfaction with swing-lock prostheses or the effect of swing-locks on the oral environment. Most recommendations regarding its use seem to be based on opinion rather than scientific evidence – for example, its use as a splint for periodontally involved teeth.8 The only evidence available is published as case reports with varied follow-up times9,10 and a study by Smith and Schulte11 that examined a population of swing-lock dentures provided in a dental school. After an average follow-up period of 2.5 years, they found this prosthesis had no adverse effect on the periodontium. It is noteworthy that, in this study, subjects were exposed to a rigorous oral hygiene programme.
It is worth remembering the potential risks to the periodontal tissues caused by the extensive coverage of gingival margins by this prosthesis. There is a need for further well-designed scientific investigation of this area. In terminal dentitions, the swing-lock denture can be useful as a transitional denture. Transitional dentures are recommended for patients who are progressing to an edentulous state, enabling the patient to control and become accustomed to removable prostheses prior to being rendered edentulous. SUMMARY The clinical scenarios described demonstrate the usefulness of the swinglock concept in providing conventional prostheses where retention is compromised. The operational techniques and materials utilized are similar to those used in conventional removable prosthodontics. Coupled with the knowledge and skills of the dentist, this technique can overcome this particular clinical difficulty in a simple fashion, while avoiding invasive and expensive procedures.
ACKNOWLEDGEMENT The authors are indebted to Mr Tim Clark and the staff of the ‘Dentacast of Exeter’ laboratory (PO Box 21, 18B Cowick Rd, Exeter, EX2 9BE, UK ) for technical support in the cases described. REFERENCES 1. O’Mullane D, Whelton H. Oral Health of Irish Adults.The Stationery Office, Dublin, 1992 2. Simmons JJ Swing-lock stabilization and retention A preliminary clinical report. Tex Dent J 1963; 81: 10–12. 3. Ackerman AJ The prosthetic management of oral and facial defects following cancer surgery. J Prosthet Dent 1955; 5: 413–432. 4. Sigurgeirsdottir E, Minsely GE, Rothenberger SL Incorporation of an ERA attachment for obturator framework design: a clinical report. J Prosthet Dent 2002; 87: 477–480. 5. Javid NS, Dadmanesh J Obturator design for hemimaxillectomy patients. J Prosthet Dent 1976; 36: 77–81. 6. Black WB Surgical obturation using a gated prosthesis. J Prosthet Dent 1992; 68: 339–342 7. McAndrew R Prosthodontic rehabilitation with a swing-lock
removable partial denture and a single osseointegrated implant: A clinical report. J Prosthet Dent 2002; 88: 128–131. 8. Bolender CL, Becker CM Swinglock removable partial dentures: where and when. J Prosthet Dent 1981; 45: 4–10. 9. Talbot TR Review of the swinglock removable partial denture. Int J Prosthodont 1991; 4: 80–88 10. Barclay CW, Russell MD, Murphy P A three-part bilateral swinglock design denture revisited. Br Dent J 2001; 190: 538–540. 11. Smith JK, Schulte DE Clinical evaluation of swinglock removable partial dentures. J Prosthet Dent 1980; 44: 595–603. Dental Update – November 2004
who, for a variety of reasons, are not suitable for fixed prosthodontics or implant-retained prostheses. natural teeth is such that there is poor tooth support for the prosthesis; The remaining teeth are periodontally compromised – the swing-lock design is thought to act as a splint, distributing forces evenly among the remaining teeth (the use of clasps on a conventional prosthesis would subject periodontally compromised abutment teeth to damaging forces); Implant-retained prostheses are contra-indicated owing to financial or clinical reasons. Contra-indications for its use include scenarios where: I mprovements in dental health in developed countries have led to an increase in the prevalence of partially dentate adults.1 Rehabilitation of partially dentate patients place considerable demands on the diagnostic, clinical and technical skills of those involved in their rehabilitation. The swing-lock denture is useful in partially dentate patients where the configuration of the
remaining teeth is such that either the retention or stability available for a conventional removable partial denture is less than ideal. Its development can be credited to two people; it was first documented by Simmons in 1963,2 though previous work by Ackerman3 in 1955 makes reference to a prosthesis type that utilized a similar mechanism for retention. While the use of Christopher D. Lynch, BDS, MFD RCSI, Registrar in Restorative Dentistry and P. Finbarr Allen, BDS, MSc, FDS RCPS, PhD, Senior Lecturer/Consultant, Department of Restorative Dentistry, National University of Ireland, Cork, Ireland. 506 a swing-lock component has been documented in the retention of maxillofacial prostheses,4,5,6 the purpose of this article is to bring its use to the attention of dental practitioners for partially dentate patients where adequate retention is not readily achievable. The design of this prosthesis incorporates a conventional removable partial denture design with a ‘swing-lock’
component consisting of a preformed metal hinge and locking precision attachments in a single casting – a ‘hinge’, ‘gate’ and ‘clasp’ (Figure 1). This additional component is usually placed in the labial sulcus. Indications for the use of a swing-lock component include scenarios where: Existing dental or alveolar undercuts do not provide sufficient retention for conventional removable partial dentures; The use of retentive clasps will lead to compromised aesthetics; The configuration of the remaining The patient’s manual dexterity is such that they cannot correctly manipulate the clasping mechanism of the swinglock portion; The patient has consistently demonstrated poor oral hygiene, or inadequate dietary control, or advanced unstabilized periodontal disease (the prosthesis covers the gingival margins of many teeth); The patient has a shallow sulcus or Figure 1. The swing-lock removable partial denture with the ‘hinge’, ‘gate’ and ‘clasp’
identified. Dental Update – November 2004 R E M OVA B L E P R O S T H O D O N T I C S Figure 2. A mandibular swing-lock removable partial denture. Note the use of metal struts on the remaining teeth. Figure 3. A maxillary swing-lock removable partial denture with an acrylic flange added to the labial bar. large frenal attachment in the area where the position of the bar is planned; For a maxillary prosthesis, the patient has a high smile-line. Original descriptions2 of the swing-lock prosthesis used small metal ‘struts’ beneath undercut areas of abutment teeth (similar to gingivally approaching clasps on conventional prostheses) (Figure 2). While this is feasible in mandibular prostheses, it may compromise aesthetics and limit patient acceptance of maxillary prostheses, particularly if the patient has a tendency towards a high smile-line. This can be overcome by placing an acrylic flange on the metal bar, which is also useful in masking unaesthetic gingival recession –
a common feature in such aged dentitions (Figure 3). Struts also have the potential to trap food, hence the need for meticulous oral hygiene is clear. The following case reports demonstrate effective uses of swing-lock removable partial dentures. CASE REPORT 1 A 71-year-old partially dentate female was referred to the Department of Restorative Dental Update – November 2004 Dentistry of the Cork University Dental School and Hospital (Cork, Ireland) for specialist treatment regarding her prosthodontic rehabilitation. The patient reported difficulty wearing several maxillary removable partial dentures that had been made for her in the past. The patient was a retired dental assistant and had extensive fixed prosthodontic work, fitted during her lifetime, that was now disintegrating. An intra-oral photograph of this patient is shown in Figure 4. The endodontically treated root of an upper right canine was present, and the patient’s referring practitioner suggested that this tooth was
suitable for restoration with a dowel-retained crown. The patient’s existing prosthesis was examined. It was clear that the main difficulty with retention of the prosthesis was in the upper left quadrant, with no teeth present distal to the upper left central incisor. Treatment options discussed with the patient included implant-retained prostheses (fixed or removable), conventional removable partial dentures, or a swinglock removable partial denture. As the patient was elderly and limited by financial constraints, an implant-retained prosthesis was not suitable. As previous removable prostheses had been unsuccessful, it was decided to fabricate an upper swing-lock removable partial denture, with a prosthetic ‘overdenture’ abutment tooth to be placed over the root of the upper right canine. Diagnostic casts were made in the usual fashion and mounted on a semi-adjustable articulator. The upper cast was surveyed and a chrome-cobalt framework designed. Following tooth preparation, a
master impression was made in silicone. The impression was sent to the technician with written instructions for the fabrication of the designed prosthesis to include a labial swing-lock component with an acrylic flange to disguise the appearance of the metal bar. The metal framework was tried in the mouth and found to fit accurately. The patient’s dexterity in manipulating the clasp was assessed at this stage and found to be satisfactory. Following occlusal registration and tooth selection, the denture was completed in the normal manner and delivered to the patient (Figure 5). At subsequent review Figure 4. Intra-oral photograph showing the dental configuration of the patient described in Case Report 1. Figure 5. Intra-oral photograph showing the swing-lock denture in situ for the patient in Case Report 1. appointments, the patient reported satisfaction with the aesthetics, function and retention of the prosthesis. CASE REPORT 2 A 55-year-old female was referred to the Department
of Restorative Dentistry of the Cork University Dental School and Hospital (Cork, Ireland) for provision of an implant-retained prosthesis. On discussion with the patient, she reported that she had several upper partial dentures fabricated for her that she found difficult to control. She was also concerned about the cost of an implant-retained prosthesis. On examination, the patient was found to be partially dentate, with five teeth present in her upper arch (3|, 2|, 1|, |1, |3) (Figure 6). The upper left canine was over-erupted and periodontally compromised (Grade III mobility); however, the patient reported that she wanted to retain this tooth. When the upper cast was surveyed it was found the labial surface of the upper right canine was non-retentive. In view of the patient’s clinical and financial considerations, it was agreed that an upper swing-lock removable partial denture would be fabricated. Following tooth preparation (which included the addition of some adhesive composite
resin on the labial surface of the upper right canine to enhance retention), a master impression was 507 R E M OVA B L E P R O S T H O D O N T I C S DISCUSSION Figure 6. Intra-oral photograph showing the dental configuration of the patient described in Case Report 2. Figure 7. Intra-oral photograph showing the swing-lock denture in situ for the patient in Case Report 2. Figure 8. View of the fitting surface of the swinglock denture for Case Report 2 made in silicone. The prosthesis was designed to include a labial swing-lock component with an acrylic flange to mask the gingival recession around the remaining upper teeth, and fabrication continued in the fashion described in the previous case report. At the final ‘try-in’ stage, the patient reported that the upper right canine had become quite uncomfortable and requested its extraction. It was decided to do this at the delivery stage. The upper left canine was removed from the master cast and added to the final prosthesis
prior to processing of the acrylic component. At the denture delivery stage, the upper right canine was extracted and the prosthesis fitted (Figures 7 and 8). At subsequent review appointments the patient reported satisfaction with the aesthetics, function and retention of the prosthesis. 508 The swing-lock concept is a useful method of improving retention of removable prostheses where conventional retention is absent. The cases presented in this paper demonstrate how to achieve a satisfactory result for those dentitions where the possibilities for clasp-retained removable partial dentures are limited by utilizing a concept which has been often used in maxillofacial prosthodontics.4,5,6 Neither patient in the described case reports was able to afford implantretained prostheses, and the chances of success of a conventional removable prosthesis were clearly limited. The materials and techniques used are not dissimilar from conventional removable partial denture construction. It is
critical that the patient’s dexterity is assessed at an early stage as poor manual dexterity will clearly limit the success of the prosthesis. Swing-lock dentures may also be used in association with other retentive factors such as implants.7 There is little scientific evidence in the literature regarding patient satisfaction with swing-lock prostheses or the effect of swing-locks on the oral environment. Most recommendations regarding its use seem to be based on opinion rather than scientific evidence – for example, its use as a splint for periodontally involved teeth.8 The only evidence available is published as case reports with varied follow-up times9,10 and a study by Smith and Schulte11 that examined a population of swing-lock dentures provided in a dental school. After an average follow-up period of 2.5 years, they found this prosthesis had no adverse effect on the periodontium. It is noteworthy that, in this study, subjects were exposed to a rigorous oral hygiene programme.
It is worth remembering the potential risks to the periodontal tissues caused by the extensive coverage of gingival margins by this prosthesis. There is a need for further well-designed scientific investigation of this area. In terminal dentitions, the swing-lock denture can be useful as a transitional denture. Transitional dentures are recommended for patients who are progressing to an edentulous state, enabling the patient to control and become accustomed to removable prostheses prior to being rendered edentulous. SUMMARY The clinical scenarios described demonstrate the usefulness of the swinglock concept in providing conventional prostheses where retention is compromised. The operational techniques and materials utilized are similar to those used in conventional removable prosthodontics. Coupled with the knowledge and skills of the dentist, this technique can overcome this particular clinical difficulty in a simple fashion, while avoiding invasive and expensive procedures.
ACKNOWLEDGEMENT The authors are indebted to Mr Tim Clark and the staff of the ‘Dentacast of Exeter’ laboratory (PO Box 21, 18B Cowick Rd, Exeter, EX2 9BE, UK ) for technical support in the cases described. REFERENCES 1. O’Mullane D, Whelton H. Oral Health of Irish Adults.The Stationery Office, Dublin, 1992 2. Simmons JJ Swing-lock stabilization and retention A preliminary clinical report. Tex Dent J 1963; 81: 10–12. 3. Ackerman AJ The prosthetic management of oral and facial defects following cancer surgery. J Prosthet Dent 1955; 5: 413–432. 4. Sigurgeirsdottir E, Minsely GE, Rothenberger SL Incorporation of an ERA attachment for obturator framework design: a clinical report. J Prosthet Dent 2002; 87: 477–480. 5. Javid NS, Dadmanesh J Obturator design for hemimaxillectomy patients. J Prosthet Dent 1976; 36: 77–81. 6. Black WB Surgical obturation using a gated prosthesis. J Prosthet Dent 1992; 68: 339–342 7. McAndrew R Prosthodontic rehabilitation with a swing-lock
removable partial denture and a single osseointegrated implant: A clinical report. J Prosthet Dent 2002; 88: 128–131. 8. Bolender CL, Becker CM Swinglock removable partial dentures: where and when. J Prosthet Dent 1981; 45: 4–10. 9. Talbot TR Review of the swinglock removable partial denture. Int J Prosthodont 1991; 4: 80–88 10. Barclay CW, Russell MD, Murphy P A three-part bilateral swinglock design denture revisited. Br Dent J 2001; 190: 538–540. 11. Smith JK, Schulte DE Clinical evaluation of swinglock removable partial dentures. J Prosthet Dent 1980; 44: 595–603. Dental Update – November 2004
