Mandibular Major Connectors Prepared by: 1-Naif Alqunfidi 201405181 2-Mohammad Ajeely 201403648 Contents • Introduction • Definition • Basic Requirements of mandibular major connectors • Types of mandibular major connectors •Design sequence for mandibular major connector •Non Rigid Connectors •Summary •Conclusion •References “No component of a Removable Partial Denture should be added arbitrarily or conventionally. Each INTRODUCTION component should be added for a good reason and to serve a definite purpose”. - WL McCracken Major Connector The part of a partial removable dental prosthesis that joins the components on one side of the arch to those on the opposite side (GPT 8) Glossary of prosthodontic Basic requirements of Mandibular major connectors. o Rigid & provides cross-arch stability - broad distribution of stress. o Should not interfere with & non irritating to the tongue. o Should not alter the contour of the lingual surface of the mandibular alveolar ridge. o Should not impinge on the oral tissues when the prosthesis is inserted or rotate in function. o Cover no more tissue than is absolutely necessary. o Does not contribute to the retention or entrapment of food particles. o Has support from other elements of the framework to minimize rotational tendencies during function. o Made from an alloy compatible with the oral tissues. Design Specifications Placement of borders: The superior borders are placed atleast 3 mm from the gingival margins. Relief: To prevent tissue impingement at rest & during function. 1) Tooth-borne prostheses: 30 guage,0.010 inches. 2) Tooth/tissue-borne prostheses: More relief is required. Relief required for tooth/tissueborne prostheses depends upon: a) Relationship of fulcrum line to major connector: 1) When the fulcrum line is posterior to the major connector, less relief is required (28 guage,0.013 inches to 26 guage, 0.016 inches) 2) When the fulcrum line is anterior to the major connector, more relief is required (26 guage,0.016 inches to 24 guage,0.020 inches) 3) Shape of adjacent alveolar ridge: The lingual slope of the alveolar ridge influences the amount of relief required, due to the rotation of the prosthesis tissue-wards. Quality of supporting structures: 1) Periodontal status of abutment teeth 2) Quality of the supporting soft tissues 3) Bone index 4) Movement of the dento-alveolar segment 5) Lingual tori Recording the Height of floor of the mouth o Using a Periodontal probe Recording the Height of floor of the mouth o Make a custom tray 3mm short of elevated floor of the mouth. o Then using an impression material record the area by asking the patient to lick the upper lip. Types Of Mandibular Major Connectors LINGUAL BAR SUBLINGUAL BAR CINGULUM BAR (Continuous bar) LINGUAL BAR WITH CINGULUM BAR (Continuous bar) LINGUOPLATE LABIAL BAR HINGED CONTINUOUS LABIAL BAR Lingual Bar Lingual Bar Major Connector ▪ Indications: 8mm vertical space between gingival margin and floor of the mouth. Lingual Bar Lingual Bar Major Connector ▪ Indications: 8mm vertical space between gingival margin and floor of the mouth. Lingual Bar Contraindications: oInoperable lingual tori. oHigh lingual frenum attachment. oInterferences during functional omovements of the floor of the mouth . Lingual Bar Major Connector Characteristics and location o Half-pear shaped with bulkiest portion inferiorly located. o Superior border tapered to soft tissue. o Superior border located at least 3mm inferior to gingival margins. o Inferior border located at the ascertained height of the alveolar lingual sulcus when the patients tongue is slightly elevated. Lingual Bar At least 8mm of vertical space between the active tissues of the floor of the mouth and the gingival margins of the teeth is required. ADVANTAGES • Lingual bar connector has minimal tissue coverage and has minimal contact with oral tissues. • It does not contact the teeth, so decalcification of the tooth surface is minimized. • It may be flexible if poorly construct • Rigidity is less compared to a well constructed lingual plate. DISADVANTAGES Lingual Bar Major Connector Block out & relief of master cast o All tissue undercuts parallel to path of placement. o An additional thickness of 32-gauge wax when the lingual surface of the alveolar ridge is either undercut or parallel to the path of placement. o No relief is necessary when the lingual surface slopes inferiorly and posteriorly. Lingual Bar Major Connector Waxing Specifications - 6 gauge, half-pear shaped wax form reinforced by 2224 gauge sheet wax adapted to the design width. ▪ Long bar require more bulk than short bar. ▪ Finish lines ▪ Butt joints with minor connectors for retention of denture bases. Linguoplate Lingual plate Indications: o o o o High lingual frenum , shallow vestibule. Severe vertical resorption Presence of lingual tori. Stabilization of periodontally weak teeth. Contraindications: o In lingually inclined mandibular anterior teeth. o Wide embrassures and diastema Linguoplate Characteristics and location o Half-pear shaped with bulkiest portion inferiorly located. o Thin metal apron extending superiorly to contact cingula of anterior teeth and height of contour of posterior teeth; and interproximally to contact points. o Scalloped contour of apron as dictated by interproximal blockout. Linguoplate oThe superior border should be knife edge and contoured to intimately contact lingual surface above the cingula. oClose inter proximal space to level of contact points. Linguoplate ADVANTAGES o Provides more support and stabilization when compared to other connectors. o Can be used in stabilizing the periodontally weakened teeth. o When it is supported at each end by a rest it contributes to the action of indirect retention. o Provision to include more teeth in the design Linguoplate DISADVATAGES o It covers the tooth structure and the gingival tissue. o The metal coverage of the free gingival tissue prevents physiological stimulation and self-cleansing of these areas by saliva. British Dental Journal 189, 414 - 424 (2000) Linguoplate Modifications Interrupted Lingual Plate o It is a type of the lingual plate recommended in wide interproximal areas. Here the upper border of the lingual plate is cut longitudinally to prevent its display through the wider interproximal spaces Linguoplate BLOCKOUT & RELIEF •All involved undercuts of contacted teeth parallel to the path of placement. •All involved gingival crevices. •Lingual surface of alveolar ridge. WAXING SPECIFICATIONS •Inferior border 6-gauge, half pear shaped wax form reinforced with 24-gauge sheet wax. •Apron 24-gauge sheet wax. FINISH LINE: Butt joint Double Lingual Bar Double lingual bar • This type of major connector is also called “Kennedy bar” it distribute stresses to all of the teeth with which it comes in contact there by reducing the stresses to the underlying tissues. • It is also referred as “continuous lingual clasp” major connector, because of series of clasp arms connected on the lingual surfaces of lower anterior teeth. Double Lingual Bar Characteristics and location o The lower component displays same charecteristics as that of a lingual bar. o The upper bar should be half oval ,2-3mm in height and 1mm thick, presenting scallopped appearance. o Two bars joined by minor connectors on each end Double Lingual Bar ADVANTAGES oEffectively extends indirect retention in an anterior direction. oContributes to horizontal stabilization. oIt helps in minor amount of support to the prosthesis. oThe gingival tissues and inter-proximal embrassures are not covered by the connector, which helps in free flow of saliva. Double Lingual Bar DISADVATAGES oPatient may feel discomfort because it alters the normal position of the tongue. oIf connector does not maintain intimate contact with tooth surface there will be food entrapment British Dental Journal 189, 414 - 424 (2000) Double Lingual Bar BLOCKOUT & RELIEF •Same as for lingual bar. •No relief for continuous bar except blockout of interproximal spaces WAXING SPECIFICATIONS •Same as lingual bar. •Continuous bar pattern found by adapting two strips (3 mm wide) of 28-gauge sheet wax over the cingula and into interproximal embrassures. FINISH LINE: Butt joint Sublingual Bar Sublingual Bar Indications oThe height of the floor of the mouth in relation to the free gingival margin is less than 6mm. oIf it is desired to keep the free gingival margins of anterior teeth exposed and there is inadequate depth of the floor of the mouth. Contraindications: oLingually tilted remaining natural teeth. oInoperable lingual tori. oHigh attached lingual frenum. Sublingual Bar o Accurately record the functional depth and width of the lingual sulcus o These sulcus dimensions are retained on the master cast resulting in a bar whose maximum cross-sectional dimension is oriented horizontally. o Rigidity Height ~ Rigidity2 Width ~ Rigidity3 o The increased width of the sublingual bar connector therefore ensures that the important requirement of rigidity is satisfied. Cingulum Bar Continuous bar (cingulum bar) • Indication: Improper axial alignment of the anterior teeth requiring excessive blockout of interproximal undercuts. • Contraindications: – In lingually tilted anterior teeth. – Wide diastema between mandibular anterior teeth. Cingulum Bar Characteristics and location o Thin narrow metal strap located on cingula of anterior teeth, scalloped to follow interproximal embrassures. o Originates bilaterally from rests of the adjacent principle abutments. Cingulum Bar BLOCKOUT & RELIEF •No relief for cingulum bar except interproximal spaces. WAXING SPECIFICATIONS •A cingulum bar pattern formed by adapting two strips of 28gauge, 3mm wide over the cingula and into interproximal embrassures. FINISH LINE: Butt joint Labial Bar Indication: o Large inoperable lingual tori. o Severe & abrupt lingual undercuts. o Lingually inclined lower anterior & premolars. Characteristics and location o Half-pear shaped with bulkiest portion inferiorly located on the buccal aspect. o Superior border tapered to soft tissue and 4mm inferior to labial gingival margins. o Inferior border located in the labial buccal vestibule; at the junction of attached & mobile mucosa. BLOCKOUT & RELIEF •All tissue undercuts parallel to path of placement and when the labial surface is either undercut or parallel to the path of placement. •No relief if labial surface of alveolar ridge slopes inferiorly. WAXING SPECIFICATIONS •6-gauge half-pear shaped wax form reinforced with 22-24 gauge •Long bar more bulkier than shorter bar. •Minor connector joined with occlusal or other superior components by a labial approach. FINISH LINE: Butt joint Hinged continuous labial bar • Indications: – – – – Missing key abutments. Unfavorable tooth contour. Unfavorable soft tissue contours. Teeth with questionable prognosis. • Contraindications: – Poor oral hygiene. – Shallow buccal labial vestibule. – High frenal attachment. Hinged continuous labial bar Characteristics and location • This type of major connector is the modification of linguoplate which is incorporated in the “Swing-lock” • Design consists of labial bar i.e. connected to the major connector by hinge on one end and latch at the other end. Hinged continuous labial bar o Support is provided by multiple rests on the remaining natural teeth while stabilization and reciprocation is by ingual plate. o Retention is provided by bar type retentive clasp arms projecting from the labial bar & contacting the infrabulge areas on the labial surfaces Sequence of design considerations Design of Mandibular Major Connectors Step I-Outline the basal seat areas on the diagnostic cast. Step II-Outline the inferior border of the major connector. Step III-Outline the superior border of the major connector. Step-IV-Connect the basal seat area to the inferior and superior borders of the major connector and add minor connectors to retain the acrylic resin base. NON RIGID CONNECTORS Split Bar major Connector Ticonium Hidden Lock Partial Denture The 12 Gauge Chrome Wire Stress Breaker Disjunct Dentures NON RIGID CONNECTORS Split Bar Major Connector Split is provided between the denture base area and the major connector . When occlusal forces are applied they are transferred more towards the tissue supported base and then they are transmitted to the abutment teeth. NON RIGID CONNECTORS Ticonium Hidden Lock Partial Denture This is a two piece casting, the top half, which is the major connector supporting the direct retainers and other rigid components, is cast first. The bottom half, which is the connector between the denture bases, is cast to the major connector next. NON RIGID CONNECTORS The hidden lock is created by mechanical means, and the split between the two connectors is made possible by the thin oxide shell that forms during the making of the two sections. What appears to be a conventional lingual bar or linguoplate actually is two bars connected by a movable joint at the midline Chrome NON RIGID CONNECTORS Wire Stress Breaker The 12 gauge chrome wire stress breaker avoids the complexities of most stress breaker designs and yet offers many clinical advantages. 1. The 12 gauge wire is adapted to the refractory cast. The wire is coated with die lubricant and the wax up is completed. 2. The wax must not go beyond the maximum convexity of the wire. 3. The wire is removed and the casting is completed. 4. After recovering the casting the wire is welded or soldered. 5. Then the connection between the denture base and the main major connector is separated to activate 12 gauge chrome wire. ADVANTAGES: 1. The rigidity of the 12 gauge wire avoids overloading the mucosa. 2. The mucosa is also more evenly loaded 3. It is easy to splint teeth with this design. 4. The fabrication is relatively simple. 5. Repairs are rarely needed and are also simple. NON RIGID CONNECTORS Disjunct Dentures (Geissler, Watt 1965 ) Principle: oTooth borne & mucosa-borne parts of denture are disjoined. oTooth borne part providing splinting of remaining teeth & only retention for mucosa borne part. Structural details: •The tooth borne part is a lingual plate and thus provides stabilization for the remaining teeth. •The tissue borne part is a lingual bar which consists of denture bases along with the teeth at its terminals. Advantages: o Independent movement between the tooth supported and tissue supported parts decreases the forces on periodontally weakened remaining teeth. Disadvantages : oIt is technically difficult to fabricate oPatient may complains of rattlingof the framework during mastication. Disadvantages of non rigid major connectors: 1. The broken stress denture is usually more difficult to fabricate and therefore more costly. 2. Vertical and horizontal forces are concentrated on the residual ridge, resulting in increased ridge resorption.Many stress breakers designs are not well stabilized against horizontal forces. 3. If relining is not done when needed, excessive resorption of the residual ridge may result. Summary •For a tooth supported removable partial denture the lingual bar is the suitable major connector. •Long span edentulous ridges in which there is posterior abutment and indirect retention is needed, the lingual plate is indicated. •When anterior teeth are periodontally treated and needs support and stabilization, the lingual plate or double lingual bar may be used. •When the tissue of the floor of the mouth are active and <8mm space available between tissue and marginal gingiva, a lingual plate is preferred. Conclusion •Major connectors by uniting the other components of a removable partial dentures acts like a foundation bringing about bilateral distribution of forces which depends on the rigidity of the connector. •Although there are many variations in major connector, a thorough comprehension of all factors influencing their design will lead to the best design for each patient. Refrences •McCracken’s Removable Partial Prosthodontics. A.B. Carr, G.P. McGivney, D.T. Brown. Elsevier.11th ed. •Stewart’s Clinical Removable Partial Prosthodontics. Rodney D. Phoenix, David R. Cagna, Charles F. DeFreest. Quintessence 3rd ed. •Clinical Removable Partial Prosthodontics. Stewart, Rudd, Kuebker. Ishiyaku EuroAmerica.2nd ed. •David Henderson. Major connectors for mandibular removable partial dentures: Design & function. J Prosthet Dent.1973; 30(4): 532-548 •David Henderson : Major connectors for mandibular removable partial dentures: Design and function. J Prosthet Dent 1973; 30: 530-549. •Carl A. Hansen, Donald J. Campbell : Clinical comparison of two-mandibular major connector designs: The sublingual bar and the lingual plate. J Prosthet Dent 1985; 54: 805-808 • Z. Ben-Ur, S. Matalon, I. Aviv : Rigidity of major connectors when subjected to bending and torsion forces. J Prosthet Dent 1989; 62: 557-562. • Mansuang Arksornnukit,Hisashi Taniguchi and ▪ Takashi Ohyama.Rigidity of three different types of mandibular major connectors through vibratory observation.Int J Prosthodont 2001;14: 510-516 • Todd Pienkos, Jack Morris, Peter Gronet, Stephan Cameron and Stephen Looney: The stength of multiple major connector designs under simulated loading.J Prosthet Dent 2007;97:299-304 • Robert Walter, James Brudvik, Ariel Raigrodski, Lloyd Mancl, Kwok-Hung Chung: A comparision of the rigidity of five mandibular major connectors for partial removable dental prostheses via load deflection.J Prosthet Dent 2010;104:182-190 THANK YOU !
