Until implants became predictable a conventional complete denture was the only means of restoring missing dentition in the edentulous mandible.  Implant retain overdentures improve the stability and support provide for complete dentures but have the become the standard of care.  If not, which patients are likely to benefit from implant retained overdentures?  When overdentures are fabricated, which retention system is best, implant connected bars, individual attachments, magnetic attachments etc.?  These questions are addressed as well as a thorough description of the techniques used in fabricating these prostheses.

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Edentulous Mandible – Overlay Dentures — Course Transcript

  • 1. 4. Edentulous Mandible OverdenturesJohn Beumer III DDS, MS, Robert Faulkner DDS and Hiroaki Okabe CDTDivision of Advanced Prosthodontics, Biomaterials and Hospital Dentistry, UCLA This program of instruction is protected by copyright ©. No portion of this program of instruction may be reproduced, recorded or transferred by any means electronic, digital, photographic, mechanical etc., or by any information storage or retrieval system, without prior
  • 2. Table of Contents!  Conventional dentures vs implant retained dentures. !  Which patients benefit from implant retention !  Patient satisfaction: Conventional dentures vs implant retained dentures!  Treatment choices!  Clinical outcomes studies!  Fixed vs removable!  Issues of concern!  O Rings and similar type attachments !  Advantages vs disadvantages !  Prosthodontic procedures !  Complications!  Hader bars Prosthodontic procedures !  Prosthodontic procedures !  Complications!  Magnetic attachments!  Mini-Implants!  Implant supported tissue bars!  Treatment of the severely resorbed mandible!  The 4 implant assisted tissue bar
  • 3. Conventional Dentures: Pt. SatisfactionMost patients are satisfied with their dentures in spiteof the difficulties referred to in the previous slides. Dissatisfied 7.7 % Moderately Satisfied Fully Satisfied 25.6 % 66.7 % Berg E (1998); Smedley TC et al (1989); Kapur KK et al (1997)
  • 4. Problems with mandibular dentures!  Lack of stability, lack of retention, poor support and poor neuromuscular control make it difficult for many patients to efficiently manipulate the food bolus along with the lower denture sufficiently well to masticate at levels consistent with their expectations. ! Implants can overcome these problems in many patients ! However implants may not be necessary and may not improve the overall level of function if the patients present with favorable mandibular denture bearing surfaces.
  • 5. Edentulous Mandible-Overlay Dentures Conventional dentures vs implant retained overdentures. 1.  Which patients will most likely be capable of functioning effectively with conventional dentures? 2.  Which patients will benefit from implant retention? 3.  Does the addition of implants improve the mastication efficiency of patients using complete upper and lower dentures?
  • 6. Characteristics of favorable denture bearing surfaces Floor of Mouth Posture and Tongue Position 1.  Which patients will most likely be capable of functioning effectively with conventional dentures?! Floor of mouth posture and tongue position (depth of retromylohyoid space) affect stability and retention! Broad – rounded alveolus covered with attached keratinized mucosa enhance support! Patients with favorable floor of mouth contours and anterior tongue position as seen above permits development of a longer lingual flange.! Result: Improved stability and retention of the mandibular denture! Such patients have a good prognosis for effective use of conventional dentures
  • 7. Characteristics of favorable denture bearing surfaces Floor of Mouth Posture and Tongue Position!  Patients presenting with a favorable floor of mouth contour, and anterior tongue position and a reasonable zone of attached keratinized mucosa available to engage for support as seen in these patients are excellent candidates for conventional complete dentures.!  In such patients significant lingual flange extensions can be developed facilitating stability and retention. With coverage of the retromolar pad, proper extensions onto the buccal shelf and good adaptation with attached keratinized mucosa of the alveolus, sufficient support will be provided.!  Implant retention will most probably not enhance the functionality of such patients as compared to conventional complete dentures.
  • 8. Characteristics of unfavorable denture bearing surfaces Floor of Mouth Posture and Tongue Position Which patients benefit from implant retention?Patients with unfavorable floor of mouth posture and tongue position (a, b).The tip of the tongue has lost its definition and is retruded and the floor ofmouth is elevated. a bResult:! Length of the lingual flange of the denture will be limited, compromising stability, retention and the ability of the patient to control the lower denture and compromising the prognosis for conventional complete dentures.! Such patients will benefit the most from implant retained overlay dentures.
  • 9. Which patients benefit from implant retention? Patients with unfavorable floor of mouth contours and retruded tongue position!  In such patients retention and stability is provided by the implants.!  Support anteriorly is provided by the implants!  Support posteriorly is provided by engagement of the retromolar pad and buccal shelf (dotted line)
  • 10. Which patients benefit from implant retention? ! This patient presented with a retruded tongue position, unfavorable floor of mouth contours but a wide zone of keratinized attached mucosa on the alveolus. Support is excellent but stability and retention will not be ideal because the length of the lingual flange will be relatively short.! Such patients will probably derive functional benefit from implant retention.! The implant will enhance support but the primary benefit is improved stability and retention,! In addition maintenance of healthy peri-implant soft tissues will be relatively easy because of the wide zone of keratinized attached mucosa.
  • 11. Which patients benefit from implant retention? Unfavorable floor of mouth contours lacking keratinized attached mucosaPatient (a) presented with retruded tongue position, unfavorable floor of mouthcontours and a very narrow zone of keratinized attached mucosa on thealveolus.Such patients would stand to gain significant functional improvement with theaddition of implants to retain and stabilize the lower denture. However with solittle attached keratinized tissue remaining, widening the zone of keratinizedattached tissue with a palatal graft should be considered in such patients.
  • 12. DefinitionsImplant assisted prosthesis The forces of occlusion are shared betweenthe implants and the mucoperiosteum. Always removable overlay dentures.Implant supported prosthesis All the forces of occlusion are borne bythe implants. Can be either fixed partial dentures or removable overdentures.
  • 13. Which patients benefit from implant retention? Neuromuscular ControlSome patients have the ability to manipulate their lowerdenture and control the food bolus simultaneously, regardlessof the quality of the design and construction of the denture orthe quality of the denture bearing surfaces.The opposite is also true and those with poor neuromuscularcontrol will benefit from implant retention. Such patients canfocus their attention exclusively on manipulation of the foodbolus since the denture is effectively retained and positionedwith the implants.
  • 14. Conventional Dentures: Masticatory Performance Effect of Improvements in Fit or New Dentures!  Improvements in chewing function were perceived by most pts. despite the lack of improvement in masticatory performance. Denture wearers may perceive chewing ability in terms of chewing comfort rather than the ability to comminute food, an objective measure of chewing performance. Garrett et al. 1996!  Results indicate that dentists cannot rely on asking denture wearers about chewing problems and clinical responses with respect to oral conditions and denture quality for predicting patient s , masticatory abilities. Masticatory ability is determined by many factors. Slagter et al. 1992
  • 15. Conventional Dentures: Pt. Satisfaction” Outcome from the pt s point of view is only in part related to technical aspects of the treatment modality Vervoorn 1988, Van Waas 1990″ The technical denture quality accounts for less than half of the total success Miller, 1960; Devan, 1963″ Denture satisfaction is influenced by various factors, including denture quality, the denture bearing area available, the quality of dentist-patient interaction, previous denture experience and the patient s personality & psychologic well being. Berg, 1991Patient satisfaction is primarily based on denture retention
  • 16. Treatment choicesImplant Supported Implant Assisted Fixed Edentulous Bridge Overdentures Overdentures
  • 17. Evidence Based Dentistry!  Aremandibular dentures retained with dental implants the best treatment for the edentulous patient (better than conventional dentures)?!  Functional (objective) and perceptual (subjective) outcomes of treatments !  Conventional dentures !  Implant assisted overlay dentures !  Implant supported overlay dentures !  Fixed implant supported prostheses
  • 18. A Randomized Clinical Trial Comparing Implant Overdentures and Conventional Dentures in Diabetic Patients
  • 19. Purpose!  To determine whether a two implant mandibular overdenture (IOD) is an effective treatment alternative to a conventional complete denture (CD) in diabetic edentulous patients treated with insulin and/or dietary therapy.Two implants•  Hader Bar•  2 clips•  Experienced denture wearers (15 yrs)•  Good ridge height (20 mm)
  • 20. Purpose !  To determine whether a two implant mandibular overdenture (IOD) is an effective treatment alternative to a conventional complete denture (CD) in diabetic edentulous patients treated with insulin and/or dietary therapy.Treatment effectiveness was based on improvements intreatment success rates, masticatory efficiency, food selectionpatterns, dietary intake, patient satisfaction, and cost of initial andmaintenance care.
  • 21. ! !
  • 22. ! It is important to not that the patients selected for this studywere excellent candidates for successful outcomes withconventional complete dentures.! They were experienced denture wearers and did not presentwith advanced resorption of the mandible! In the following studies not that the patients selecteddemonstrated more severe resorption of the mandibular body.It is therefore not surprising that the outcomes with the implantretained overlay dentures were more favorable.
  • 23. ”  95 pts., balanced allocation method, including a control groupInclusion criteria “  Severely resorbed mandible (<15 mm) “  Persistent problems in wearing a conventional denture (>90% of patients dissatisfied at entry)Results “  Increasedsatisfaction with IOD (2 implant overdenture) “  Improved masticatory performance with IOD Geertman et al, 1994, 1996
  • 24. Patient Selection and Treatment Planning Treatment Options Implant assisted ” Fixed Edentulous Bridge overlay denture ” Overdenture ” Implant Supported ” Implant Assisted Fixed edentulous bridge Implant supported overlay denture (Fixed hybrid prosthesis)Which is the best option from a functional perspective?
  • 25. Implant Assisted Overdentures vs Implant Supported Overdentures”  95 pts., balanced allocation method, including a controlgroup Results ” The differences with respect to satisfaction, complaints & subjective chewing ability were not significant. ” No significant difference in chewing ability were noted between the implant assisted and implant supported groups Geertman et al, 1994, 1996
  • 26. Within-subject Comparison Of Mandibular Long-bar andHybrid Implant-supported Prostheses: Evaluation OfMasticatory Function. Tang et al. J Dent Res 1999Conclusion: No change in function with increased implant support,but some perceptual changes are reported
  • 27. Within-subject Comparisons of Implant-supported Mandibular Prostheses: Choice of Prostheses Feine et al. J Dent Res 1994! ! ! !
  • 28. Summary of Clinical Outcome Data!  The primary factor in impaired mastication is tooth loss, which will continue to be a problem and require prosthetic restoration for the immediate future!  Neither conventional, implant-assisted or implant-supported mandibular dentures restore masticatory function to dentate levels.!  Most patients with reasonable denture bearing surfaces can function effectively with conventional complete dentures.!  Little well-controlled evidence exist to support a functional benefit of increased implant support.
  • 29. Summary of Clinical Outcome Data!  Mostpatients with reasonable denture bearing surfaces can function effectively with conventional complete dentures.!  Thereare only limited advantages of one type of implant treatment over the other for the general population. !  The two implant assisted overlay denture will improve mastication efficiency in patients with severe resorption and compromised mandibular denture bearing surfaces.
  • 30. Summary of Clinical Outcome Data!  The two implant assisted overdenture will improve mastication efficiency in patients with severe resorption and compromised mandibular denture bearing surfaces.!  There is no difference in implant success rates between tissue bar clip retention systems and O ring type attachments without splinting.!  Most bone loss around implants used with this application take place the first year. Thereafter, bone levels appear to stabilize.!  There is no evidence to indicate that the bone loss around implants is affected by the type of implant assisted attachment systems used.
  • 31. Indications for Implant Supported Overlay Denture!  Replacement for a fixed prosthesis as age and dexterity make it difficult to properly manipulate hygiene aids!  Patients with exposure of the inferior alveolar nerve
  • 32. Fixed vs RemovableDictated by: ! Estheticdemands ! Psychological demands ! Need for hygiene access ! Oralcompliance ! Quality of the soft tissues ! Cost
  • 33. Fixed vs Removable EstheticsSome patients require the presence of a properlycontoured and extended denture flange in order toestablish proper lip contours.
  • 34. Fixed vs Removable EstheticsNote the poor facial contours because of lack ofsupport for the lower lip in this patient who wasfitted with a fixed hybrid prosthesis.
  • 35. Fixed vs RemovableNeed for hygiene access ” Quality of soft tissues surrounding the implants When implants emerge through poorly keratinized unattached mucosa removable overlay dentures are recommended because oral hygiene access is easier.
  • 36. Fixed vs Removable Amount of Keratinized Attached Mucosa!  Both these patients have little or no attached keratinized mucosa! Oral hygiene procedures are much easier to perform when the implants are surrounded by keratinized attached mucosa.! Creating a zone of attached keratinized tissues anteriorly would be beneficial regardless of whether the patient chose fixed or removable
  • 37. Fixed vs Removable Amount of Keratinized Attached Mucosa!  Thispatient presented with ample residual keratinized attached mucosa. Note that almost both of these implants have well formed gingival cuffs. If the patient is capable and willing to properly use the hygiene aids, fixed also would have been a suitable choice.
  • 38. Fixed vs Removable Amount of Keratinized Attached Mucosa!  These implants emerge through poorly keratinized unattached mucosa. Previously the patient had been fitted with a fixed edentulous bridge. Hygiene measures were difficult to perform because of tissue sensitivity. A removable overlay denture was eventually fabricated. The enhanced hygiene access allowed by tissue bars design permitted the patient to maintain healthy peri-implant soft tissues.
  • 39. Fixed vs Removable Oral Compliance!  It is difficult to manipulate the hygiene aids used in patients with fixed edentulous bridges. If the patient has impaired vision or impaired motor skills, removable overlay dentures are recommended.
  • 40. Fixed vs Removable Oral Hygiene!  Oral hygiene must be maintained meticulously. Otherwise chronic peri-implant gingival infections develop which can result in considerable morbidity and may even lead to loss of the implants.
  • 41. Hypertrophy of peri-implant tissuesSecondary to a combination of:!  Plague!  Poor quality peri-implant tissues
  • 42. Implants in the Edentulous Mandible Issues of concern”  Severe resorption •  Buccal-lingual dimension most important. Less than 5-6 mm requires bone augmentation” Lack of attached keratinized tissue •  Hygiene compromised when the implants are surrounded by poorly keratinized unattached mucosa •  Palatal grafts are favored over skin grafts” Lack of interocclusal space •  Limits design choices •  Compromises prosthodontic procedures •  Commonly encountered when a patient still retains residual dentition in either the maxilla or mandible •  Seen in some recently edentulated patients
  • 43. Severe ResorptionAnatomic Limitations Severely resorbed mandibular body a)Vertical height – less than 7 mm b)Buccal lingual dimension – less than 5 mmMandibles that are smaller than the above are at risk forfracture during or immediately after implant placementand should be augmented with a bone graft.
  • 44. Severe ResorptionMandibles that are smaller than the aboveare at risk for fracture during or immediatelyafter implant placement and should beaugmented with a bone graft. Courtesy Dr. H Davis
  • 45. Severe Resorption Mandibular FracturesThe mandible fractured through the left posterior implant site two weeks following implant placement. It was reduced and repaired as shown and healing progressed normally. An implant assisted overlay denture was later fabricated and used successfully by the patient.
  • 46. Severe Resorption Mandibular fractures !  The use of 5mm diameter implant was a poor choice for this patient !  Nothing was to be gained from the use of a wide diameter implant in a patient scheduled to receive an implant assisted overlay denture !  The appropriate choice would have been an implant 3.75 mm in diameter This patient illustrates the consequences of poor communication between the surgeon and the referring dentist and a lack of understanding of by the surgeon of the primary means of support provided implant assisted overlay dentures.
  • 47. Lack of Keratinized Attached Tissue”  Palatal grafts are preferred over skin grafts”  They are best performed at second stage implant surgery
  • 48. Lack of Keratinized Attached TissueA palatal graft was used to establish a zone of keratinizedattached tissue around these implants. The procedure wasperformed at the time of implant uncovering. A surgical stent,secured to the implants with gold screws, held the graft inposition during the healing period.
  • 49. Lack of interocclusal space”  Recently edentulated patients”  Patients to be fitted with an immediate denture followed by an implant supported fixed edentulous bridge”  Patients with supereruption of anterior teeth prior to extraction ! Note the supereruption of the mandibular teeth. ! When these teeth are removed an aggressive alveolectomy needs to be performed prior to placement of implants. ! Implants should be placed combatable with the plane of occlusion.
  • 50. Cost Advantage The most bang for the buck for edentulous patients is obtained with a two implant assisted overlay denture. The edentulous maxilla is restored with a conventional complete denture. Advantages: a)  Predictability – Implant failure rates for this application are virtually zero b)  Patient acceptance is very favorable c)  Cost effective d)  Simplicity
  • 51. Types of attachment systems!  Bar clip (tissue bar) !  Hader !  Dolder Bar clip!  Individual attachments !  “O” ring O Ring !  Individual attachments !  ERA !  Locator Locator!  Magnetic attachments Magnetic!  Mini-implants Mini-implants
  • 52. Individual attachments and O Rings (ball type) Advantages “  Favorable stress distribution patterns (ball type only) minimize the risk of implant loss secondary to implant overload “  Simple to use “  Less initial cost than a tissue bar Note: Implants must parallel to one another
  • 53. Individual attachments and O Rings (ball type)Disadvantages !  Less retention and stability !  Implants must be parallel or constant insertion and removal accelerates attachment fatigue and wear !  Higher profiles may prevent proper positioning of the lower anterior teeth and predispose to fracture of the overlying acrylic resin. !  Misaligned implants difficult to overcome and require custom abutments !  More maintenance required which leads to higher costs (Walton, 2003)
  • 54. Tissue barsAdvantages !  Better support anteriorly !  Less attachment fatigue !  Less maintenance cost !  Easier to accommodate divergent implants or a labially inclined implantDisadvantages !  Higherinitial cost !  More complex prosthodontic procedures
  • 55. Tissue bars vs individual attachmentsWe favor bar clip type attachments. Why? !  Lower maintenance costs (Walton, 2003; Stoker et al, 2007) !  Less attachment fatigue leads to better long term retention !  Can easily accommodate diverging or labially inclined implants !  Anterior support is provided with the bar extension when the implants are placed to far posteriorly or when the arch is severely tapered. !  Since the implants are splinted together there is less chance of implant overload.
  • 56. O ring (ball) and individual attachments!  Two types !  “O” ring type ! They permit a pure rotation !  Individualattachments such as the “ERA” or “Locator type” ! Moe retentive but do not permit a pure rotation
  • 57. Types of O ring (ball) attachmentsBall types are preferred because they allow a pure rotationaround the patrix portion of the attachments. Straumann gold clip Straumann 2.25 mm (matrix) retentive anchor (patrix) Straumann titanium matrix with stainless steel spring (matrix) Steri-Oss ball patrix Steri-Oss rubber matrix ! Less wear of patrix portion of the attachments ! Less stress on the implants with less chance of mechanical or implant failures.
  • 58. O Rings (ball type)Plastic or rubber attachment matrix is preferred over the metal type. Why? ! Less wear of matrix and patrix. Brånemark 2.25 Brånemark gold mm ball patrix matrix Southern 3.25 mm Southern plastic ball patrix matrix
  • 59. Individual attachments ! Locators ! Single tooth ERA!  Initial retention at delivery is good with these two attachments a but after a couple of hundred insertions and removals attachment fatigue significantly decreases the retention!  If the implants are divergent and not parallel to one another as in these patients, excessive wear during functional rotation, insertion and removal will lead to excessive wear of the abutment portion of the attachment.
  • 60. Individual attachments Locators!  When occlusal forces are applied unilaterally in the posterior region these forces are concentrated around the implant on that side.!  In patients with poor support the risk of implant overload becomes greater.!  This phenomenon increases the risk of implant overload as seen in this photo-elastic study assessing locator attachments.
  • 61. Prosthodontic ProceduresIndividual attachments and O Rings (ball type)Requirements ! Implants must be placed anteriorly (20 mm apart from center to center) ! Implants must be parallel to one another ! Impressions must be border molded to extend the denture to cover the retromolar pad and the buccal shelf
  • 62. Prosthodontic Procedures Individual attachments and O Rings (ball type)Support provided by: !  Implantsanteriorly !  Buccal shelf and retromolar pad posteriorly Properly extended denture Under-extended denture Therefore impressions must be border molded
  • 63. Prosthodontic Procedures Individual attachments – O Rings (ball type) Upper denture mounted with facebow transfer jig.The dentures arecompleted and deliveredin the usual manner. Lower denture with remount cast
  • 64. Prosthodontic Procedures Individual attachments – O Rings (ball type)Delivery and Post-Insertion Care !  Pressure indicating paste !  Disclosing wax !  Clinical remount !  24 and 48 hour followup !  Leave dentures out at night !  Educate the patient
  • 65. Prosthodontic Procedures Individual attachments – O Rings (ball type) Clinical RemountOcclusion is refined in centric, and to permit unencumberedsliding functional tracking between working, balancing andprotrusive.
  • 66. Prosthodontic ProceduresIndividual attachments – O Rings (ball type) Clinical RemountWhy is bilateral balanced occlusion so importantwhen a patient is fitted with an implant assistedoverdenture?!  Thesetypes of dentures move during function. The more the dentures move and rock during function the more rapidly the attachments wear.
  • 67. Prosthodontic Procedures Individual attachments – O Rings (ball type) Design of the surgical template! The implants must be parallel to one another so it isimperative that the surgeon use a surgical template (drill guide)while inserting the implants. ! The mandibular denture is duplicated and altered as shown to create the surgical template. Courtesy Dr. S. Esposito
  • 68. Surgical Templates Individual attachments – O Rings (ball type)Implants must be positioned anteriorly –approximately 20 mm from center to center
  • 69. Connecting the matrix portion of the attachment to the denture baseWhen the implants are osseointegrated they canbe either related to the denture by one of twomethods !  Directly intra-orally !  By means of a reline impression.
  • 70. Pick up attachments directly!  Healing abutment is removed and a depth gauge used to select an attachment – abutment (patrix) of proper length.!  The abutment must project 1-2 mm above the level of the tissue.
  • 71. Pick up attachments directly!  Secure the abutments (the patrix portion of the attachment), to the implant fixtures!  Tighten to 20 Newton Cm but no more. Why? !  These attachment systems are subject to wear and periodically need to be replaced. If they are tightened to an excessive degree the screw may become swedged to the abutment6 and it may not be possible to remove them.
  • 72. Pick up attachments directly !  Secure O rings as shown to the abutments in order to block out the undercuts. !  Secure the metal housing of the matrix portion to the abutment !  In some situations wax may need to be added.
  • 73. Pick up attachments directly!  In this instance the abutment projected far above the tissue levels. Wax was added beneath the washier to insure all undercuts have been effectively blocked out.
  • 74. Pick up attachments directly!  Using PIP or disclosing wax as an indicator, room is created in the denture base for the metal housing of the matrix portion of the attachment.!  Pressure indicating paste is used to ensure that the denture is properly seated before the attachments are picked up.
  • 75. Pick up attachments directly!  Separating medium is applied the denture base adjacent to where the metal housing will be positioned!  Resin is applied to the metal housing and the denture base.
  • 76. Pick up attachments directly!  Thedenture is seated and the resin allowed to polymerize.
  • 77. Pick up attachments directly Attachment!  Resin flash is removed with a sharp instrument!  There should no contact between the acrylic resin and the peri-implant tissues.!  The processing attachments are replaced by the plastic attachments of desired retention
  • 78. Pick up attachments directly! Attachment systems come in varying degrees of retention as indicated bythe color. However, studies indicate after the initial period of use,attachment fatigue occurs and little difference in retention is noted betweenattachments of different colors.! Some clinicians recommend that at delivery the denture be inserted andremoved 15-20 times so the patient has a realistic view of the retention aftera few weeks of wear.
  • 79. Impression MethodA reline impression can be used to secure thefemale portion of the O ring to the denture base. Retentive Anchor AnalogFinal Rubber Base Impression with LaboratoryRetentive Anchor Analogs Positioned in Impression. Courtesy Dr. S. Esposito
  • 80. Prosthodontic Procedures O ring retained overlay dentures Completed Denture! Relined Denture deflasked with analogs and acrylic flash still present.! Completed Denture with the female portion imbedded within the denture base. Courtesy Dr. S. Esposito
  • 81. ComplicationsIndividual and ball type attachments!  Wear, attachment breakage and fatigue!  Diverging implants and labially positioned implants!  Poor oral hygiene!  Tissue hypertrophy!  Rocking of the denture
  • 82. Complications Individual attachments and O Rings (ball type)Wear !  Note the wear (as indicated by the shiny surfaces) associated with these “Locator” type attachments. When implants are divergent (not parallel to one another) wear and loss of retention is accelerated when individual attachments are used (Al-Ghafli et al, New attachment- Worn attachment- 2009; Evtimovska et al, 2009)) abutment abutment
  • 83. Complications Individual attachments – the Locator type!  Note the significant wear on the anterior portion of the Locator attachments!  This is caused by the movement of the denture when occlusal forces are applied posteriorly.!  The Locator attachment does not permit as free a rotation as the O ring type and as a result will wear more rapidly than other attachments.!  It is best used for implant supported type tissue bars where there is no movement of the overdenture during function.
  • 84. Complications Individual attachments – the Locator type Delrin matrix!  Note the wear (as indicated by the shiny surfaces) associated with these “Locator” type attachments. When implants are divergent (not parallel to one another) wear and loss of retention is accelerated when individual attachments are used (Al-Ghafli et al, 2009; Evtimovska et al, 2009). Locator type attachments are particularly prone to wear.!  Why does the “Locator” wear so rapidly when used to retain implant assisted overdentures? !  The plastic matrix attachment is made of “Delrin” a very hard plastic !  The “Locator” type attachment does not permit a free rotation like “O” ring type designs.
  • 85. Complications Individual attachments – the Locator typeLocator type attachments are best used with milled tissuebars that are designed to be implant supported. Why?!  There is no movement of the overdenture during function since this is an implant supported design!  The “Locator” attachments have a low profile and permit the proper positioning of the denture teeth.!  The “Locator” attachments have excellent retention.
  • 86. Complications Individual attachments and O Rings (ball type)!  When implants are divergent or an implant is positioned or inclined to the labial it will not be possible to properly position the denture teeth without excessively thinning the acrylic resin over the attachment. !  This will predispose the resin to crazing and fracture!  Solution !  Tissue bars – the tissue bar can be tapered anteriorly to accommodate the denture teeth as seen in this example.
  • 87. Complications Individual attachments and O Rings (ball type)!  Attachment fatigue !  Withina very short period of use, retention values are reduced by up to 50% and then stabilize.!  Attachment fracture !  Fracture of the plastic portion of the attachment, as shown here, is relatively rare
  • 88. Complications Individual attachments and O Rings (ball type)Poor oral hygiene and food impaction !  Predisposes to peri-implantitis !  Damages the attachments !  Accelerates wear of the abutment and the attachments Dental plague Note accumulation of plague and food debris
  • 89. ComplicationsIndividual attachments and O Rings (ball type)Tissue irritation and hypertrophy – Secondary to: !  The acrylic resin in contact with the peri-implant mucosa !  Poor oral hygiene !  Wearing the dentures at night
  • 90. Complications Individual attachments and O Rings (ball type) Tapered arch Tapered archPatient complaint: Anterior–posterior rocking of the denture due to lack of anterior support!  Reason: Implants placed to far posteriorly!  This is a common problem in tapered arches when individual attachments are used
  • 91. Complications Individual attachments – O Rings (ball type) Solution !  Tissue bar with an anterior cantileverNote: This solution is less than ideal biomechanically but fortunately theanterior forces are only ¼ to 1/5 of those delivered posteriorly during chewingand so risk of implant overload and mechanical failures is very low.
  • 92. Immediate loading Overdentures using Individual attachments or O Rings (ball type) This procedure is easily accomplished but should not be used (contra-indicated) !  Implant loss rates the first year after placement approach 20% (Kronstrom et al, 2010)If you permit the implants to osseointegrate before employingthe attachments the implant success rates are close to 100%.
  • 93. Prosthodontic Procedures Tissue Bars
  • 94. Tissue Bar DesignWe favor two implants splinted together with a Hader bar,with the bar aligned parallel to the axis of rotation. The denturerotates around the bar when the patient generates a posteriorocclusal load. With this design the implant loss rates afterloading are virtually zero.The anterior, or incisal forces are borne by the implants whilethe posterior occlusal loads or born by the primary denturesupport areas (retromolar pad and the buccal shelf).
  • 95. Tissue Bar Design Hader bar design In cross section the “Hader” bar is a complete circle and permits the denture to rotate around it. Hader clip rotates Clip around the bar housing Plastic burnout pattern for the Hader barThis is an implant assisted type tissue bar design. When posterior occlusal forces areapplied, the denture rotates around the bar. As a result the posterior occlusal forcesare supported by the buccal shelf and retromolar pad. The anterior forces aresupported by the tissue bar. Hence support is shared between the implants and thedenture bearing surfaces. The bar provides retention and stability for the denture.
  • 96. Implant position – Hader Bar Design!  In most patients there are five implant positions available in the anterior mandible anterior to the mental foramen.!  We prefer to place implants in the cuspid positions or between the cuspid and the 1st premolar so that the bar can be configured parallel to the axis of rotation with little or no cantilever extension.
  • 97. Implant position – Hader Bar DesignThese implants are too posterior and too far apart. Since thedenture is only connected to the bar via the clips no clinicaladvantage is gained. The tissue bar fabricated will have an excessive anterior cantilever.
  • 98. Implant position These implants are in ideal positionThe implants are wide enough apart to accept twoHader clips and an anterior cantilever is notnecessary to fit the tissue bar within the contours ofthe denture.
  • 99. Implant position and angulation!  These implants are in ideal position. They are at least 20 mm apart but are far enough anteriorly minimize the anterior cantilever.!  They exit through the crest of the ridge.!  Implants must not emerge through the mobile tissues of the floor of the mouth. The tissue mobility at this site is such that the peri-implant tissues will be in a perpetual state of irritation.!  Angulation is less important than when O ring or similar type attachments are employed for retention.
  • 100. Implant positionThese implants are a bit too close together eventhough room is available for the use two Hader clips. The wider the Hader segment of the bar, the better the stability of the denture. Ideally, the Hader segment should be at least 14 mm.
  • 101. Implant position – Hader Bar DesignThese implants are too close together. Roomis available for only one Hader clip. Stability of the overlay denture was not ideal and retention was also suboptimal
  • 102. Soft tissue problems following 2nd stage surgery: Solutions:Peri-implant tissues excessively thick lacking keratinized mucosa “  Repeat submucosal resection “  Free palatal grafts can be used to replace poorly keratinized tissue with keratinized mucosa Graft 1 week postop 1 month postop
  • 103. Impressions Types of impression copings!  Transfer type (closed tray) !  Bordermolded impression with corrected impression made with silicone impression material.!  Pickup type (open tray) !  Impressioncopings are linked permitting the use of a corrected impression made with polysulfide.
  • 104. Preliminary ImpressionsPreliminary impressions are made with transfer type copingsand stock trays. After the impression is made abutment analogues or fixture analogues, as appropriate, are connected to the transfer impression copings and positioned in the impression.
  • 105. Preliminary ImpressionsPreliminary impressions are made with transfer type copingsand stock trays. Removed the transfer copings from the mouth and attach them to a fixture analogue. The impression analogue with the fixture analogue attached is inserted into the impression and the preliminary cast is made.
  • 106. Preliminary Cast!  Thetransfer impression copings are removed from the preliminary cast in preparation for making the master impression tray.
  • 107. Pickup type ( open tray) Impression copings are linked permitting the use of a corrected impression made with polysulfide.Impression copings are secured tothe fixture analogues imbedded inthe preliminary cast
  • 108. Pickup type ( open tray) Impression copings are linked permitting the use of a corrected impression made with polysulfide.The impression copings are linked together with floss andDuralay*. They are sectioned and then reconnected intra-orally with Duralay or cyanoacrylate.
  • 109. Pickup type ( open tray) !  A separating disc is used to separate each of the impression copings from one another. !  They are labeled. !  They will be reunited with pattern resin in mouth just prior to making the final master impression.
  • 110. Pickup type ( open tray) Impression copings are linked permitting the use of a corrected impression made with polysulfide.The copings, undercuts and reliefareas are blocked out with wax.
  • 111. Pickup type ( open tray) Impression copings are linked permitting the use of a corrected impression made with polysulfide.The master impression tray iscompleted in the usual manner. Theguide pins must project 1-2 mmabove the level of the tray.
  • 112. Master Impression Linked pickup type impression copingsClinical steps: !  The impression tray is border molded in the usual fashion !  The pick up impression copings are screwed onto the fixtures and linked together with pattern resin !  The impression is corrected in the usual manner Completed border molded impression
  • 113. Master Impression Linked pickup type impression copings A light body polysulfide impression material can be used to refine the border molded impression when linked imbedded type copings are used.Appropriate analogues are nowsecured to the pickup typeimpression copings that areimbedded in the master impression.The impression is boxed andpoured in the usual fashion.
  • 114. Impressions with transfer type copings!  When transfer copings for master impressions they must be inspected carefully to ensure they are free of imperfections.!  When transfer copings are used the corrected impression must made with silicone. Polysulfide is insufficiently accurate if transfer coping are used.
  • 115. Pouring the Master Cast !  !  !
  • 116. Master CastThe master cast.The land of the castis slightly wider thannormal.Why?”   A silicone template with the denture teeth imbedded withinthe template will need to be fabricated and this is supportedby the land of the cast .
  • 117. Record Bases!  Secure healing abutments of identical lengths found in the patient, to the master cast.!  Block out undercuts around the healing abutments and master cast as needed.
  • 118. Record Bases!  Fabricate the record base and wax rims in the usual manner.!  The record bases will positively engage the healing abutments in the patient helping to stabilize the record base during the making of the centric relation records.
  • 119. Facebow Transfer RecordMake the facebow record and secure the maxillarycast to the articulator.
  • 120. Maxillo-mandibular recordsMake the centric relationrecord and mount themandibular cast onto thearticulator in the usualmanner
  • 121. Occlusion – Bilateral Balance Working position! ! !
  • 122. Try-in Appointment”  Verify the vertical dimension of occlusion”  Prove centric relation record”  Make protrusive record and transfer to the articulator”  Address the esthetic concerns of the patient
  • 123. Try-in appointmentProve centric relation record With the record in position the condyles should be locked in their fossae.
  • 124. Try–in AppointmentThe protrusive record is made and transferred to thearticulator.The condylar inclination isestablished and recordedin the patient s chart.
  • 125. Fabricating the Tissue Bar A silicone template is made using a silicone puttyOnly the anterior teeth needbe recorded in the siliconetemplate.
  • 126. Fabricating the Tissue BarThe anterior teeth are removed from the record baseand attached to the silicone template. A small amountof sticky wax will help connect the denture teeth to thetemplate.
  • 127. Fabricating the Tissue BarIn this examplethe tissue bar willbe fabricated withthe use of theUcla abutment.Begin by attaching the Ucla abutment to a fixture analogue with along guide pin (screw). Apply a thin layer of of pattern resin to theUcla abutment and extend it 2-4 mm onto the guide pin.
  • 128. Fabricating the Tissue Bar Secure the Ucla abutments to the fixture analogues in the master cast with an abutment screw.
  • 129. Fabricating the Tissue BarThe silicone template can be repositioned asnecessary when developing the wax patternfor the tissue bar.
  • 130. Fabricating the Tissue Bar!  The cast is surveyed and a proper path of insertion is selected!  The plastic pattern is attached to a specially designed instrument that in turn is attached to the surveyor.!  The plastic pattern can then be secured to the Duralay so as to be compatible with the chosen path of insertion
  • 131. Fabricating the Tissue Bar!  A plastic burnout Hader bar pattern is cut and shaped to fit between the two implants!  The bar should be positioned beneath the denture teeth so as. not to displace them or alter the contours of the denture base
  • 132. Tissue Bars Summary of Design PrinciplesThe tissue bar is designed to be implant assisted !  The denture should rotate freely around the bar when posterior occlusal forces are delivered !  To idealize this rotation the bar should be perpendicular to the midline and parallel to the plane of occlusionThere should be space beneath the bar and thetissue to ensure appropriate hygiene access !  If the bar touches the tissue bar bacterial plagues will form on the undersurface of the bar which will irritate the tissue and ultimately lead to hypertrophy of these tissuesThe portion directly associated with the implants mayneed to be tapered anteriorly to allow for properplacement of denture teeth
  • 133. Design of the Tissue BarConfiguration of the bar “  Parallel to the plane of occlusion “  Perpendicular to the midline “  There should be ample space beneath the bar to provide for proper hygiene access Occlusal plane Midline
  • 134. Design of the Tissue Bar”   Parallel to the plane of occlusion”   Perpendicular to the midline”   There should be ample space beneath the bar to provide for proper hygiene access
  • 135. Design of the Tissue Bar The left implant is slightly more posterior than desiredHowever the configuration of the bar remains the same “  Parallel to the plane of occlusion “  Perpendicular to the midline “  There should be ample space beneath the bar to provide for proper hygiene access
  • 136. Design of the Tissue Bar The left anterior implant is more labial than desired The basic configuration of the bar remains the same ! Parallel to the plane of occlusion ! Perpendicular to the midline ! There should be ample space beneath the bar to provide for proper hygiene accessHowever, the tissue bar portion over the left implant is taperedto accommodate the positioning of the denture teeth.
  • 137. Fabrication of the Tissue Bar Tissue bars must be parallel to the plane of occlusion and perpendicular to the midline.Note how the labial portion of the bar is tapered over the leftimplant bar. This allows for proper positioning of denture teeth.
  • 138. Fabrication of the Tissue Bar!  When implants are positioned or inclined excessively to the labial the area over the implants can be tapered to allow for proper positioning if the denture teeth!  Note the hygiene access below the tissue bar
  • 139. Fabrication of the Tissue Bar Completed tissue bar.Note the hygiene access beneath the bar.
  • 140. Processing !  Priorto processing the clip housings are secured to the bar and the rest of the bar is blocked out with plaster or stone.! This will ensure that the denture rotates freely around the tissuebar when occlusal forces are applied posteriorly during function.
  • 141. Completed dentures-Delivery Sequence!  Insert clips into the denture.!  Orange clips are more retentive initially but after a couple of weeks of wear retention becomes the same as the yellow clips
  • 142. Completed dentures-Delivery Sequence!  Ensure that the denture rotates properly around the tissue bar as designed!  Connect the tissue bar to the implants !  Two stage tightening procedure – At delivery and 1-2 weeks later!  Pip denture bases!  Use disclosing wax to verify border extensions!  Clinical remount and refine the occlusion
  • 143. Delivery Sequence Check to ensure the bar fits properly within the denture baseMake sure the bar rotates freely within the retentive clips.This ensures that the overly denture will indeed be implantassisted rather than implant supported.
  • 144. Connect the tissue bar to the implants !  Use gold alloy screws (Do not use titanium screws because they tend to loosen and have a propensity to fracture) !  Torque to no more than 20 Neuton cm. Why? !  The tissue bars wear over time and may need to be removed and replaced.Note: Mechanical Torque drivers are notoriously inaccurate
  • 145. Delivery Sequence Pressure Indicating Paste (PIP)Using pressure indicating paste (PIP) to eliminate areas ofexcessive tissue displacement or undercut areas that may betraumatized during insertion and removal of the denture.The most critical undercuts relative to the path of insertion in animplant retained denture are generally located anteriorly.
  • 146. Delivery Sequence Pressure Indicating Paste (PIP)The mylohyoid area is always an area ofconcern and must be carefully adjusted.
  • 147. Delivery SequenceDisclosing wax is used to check the length, thicknessand contour of the denture border This border slightly This border is of overextended and proper length but a little thick excessively thick
  • 148. Clinical Remount Using remount casts and a facebow transfer record, mount the upper cast, obtain and new centric relation record and mount the lower cast.
  • 149. Clinical RemountThese are anatomic posterior denture teeth Equilibrate in centric
  • 150. Clinical RemountThese are anatomic posterior denture teeth Balancing position Working position Equilibrate in working, balancing and protrusive. Why is this so important. !  Excessive rocking and tipping of the denture will accelerate wear of the attachments and the tissue bar.
  • 151. Patient instructions ! Leave dentures out at night ! Hygiene of the tissue bar and the dentures ! Follow every 4-6 months!  Clips need to changed about every 12-18 months!  Denture teeth wear out 7-10 years!  Tissue bars wear out 12-15 years.
  • 152. Complications Tissue bars!  Poor oral hygiene and tissue irritation!  Wear of the bar!  Attachment fatigue!  Fracture of the resin of the denture base!  Excessive wear of the denture teeth
  • 153. ComplicationsTissue irritation and hypertrophy secondary to poor oral hygiene Note that the bar does not touch the tissue. As a result, only the tissues around the implants have hypertrophied and the tissues beneath the bar remain healthy.
  • 154. ComplicationsTissue irritation and hypertrophy secondary to poor oral hygiene Note that the bar touches the tissue. As a result, the tissues around the implants and beneath the tissue bar have hypertrophied.
  • 155. Complications Wear of the tissue barTissue bar after21 years of wearNew tissue bar
  • 156. Cracking and fracture of the denture base
  • 157. Cracking and fracture of the denture base Reinforce denture base with metal substructure if resin overlying the tissue bar is thin. !  Impression and cast. Bar is represented by a plastic burn out pattern !  Wax pattern developed with pattern resin and wax !  Note that the metal housings are incorporated with the pattern
  • 158. Cracking and fracture of the denture base Cast framework is incorporated within the denture base.
  • 159. Excessive wear of denture teeth!  Denture teeth wear more rapidly when support is enhanced with implants.!  Solution !  Replace denture teeth as needed (usually every 7-10 years) !  Gold occlusals
  • 160. Excessive wear of denture teethGold occlusals – There are disadvantages !  Highcost !  Technical challenges
  • 161. Other designs Hader – ERA!  This design is implant assisted but the addition of ERA attachments to the posterior extension of the bar will improve retention.!  Risk: !  If followup is not maintained and the denture bottoms out on the ERA attachments cantilever forces are introduced which could lead to mechanical failures
  • 162. Other designs Hader – ERAImplant fracture cause:Functional load exceeds load bearing capacity leading to implantfracture
  • 163. Magnetic attachments Advantages ! Simple to use ! Low cost ! Advantageous when implants are divergent ! Ease of insertion for debilitated patients ! Oral hygiene is simple ! No attachment fatigue
  • 164. Magnetic attachmentsPrevious generation of magnets were less than ideal(Aluminum-nickel-cobalt) ! Retention was poor and the source of patient dissatisfaction ! Corrosion limited their life span (2-3 years)
  • 165. Magnetic attachments New generation of magnets (samarium and neodymium) ! Retention is 4 times as powerful ! Laser welded keepers may eliminate corrosion ! Followup time is limited (1 year, Cerutto et al, 2010) ! Clinicians should be cautious before employing this method until there is longer followup
  • 166. Mini-Implants Courtesy E. LaBarre!  Originally designed to retain transitional (temporary) prostheses
  • 167. Mini-Implants Courtesy E. LaBarre!  Patient presents with mobile, periodontally compromised canine teeth.!  The canines are removed and the existing removable partial denture is adapted to serve as a transitional prosthesis.
  • 168. Mini-Implants Courtesy E. LaBarre!  When the canines are removed the mini-implants are placed!  The matrix portion of the attachment is incorporated within the denture to retain the transitional prosthesis
  • 169. Mini-Implants Courtesy E. LaBarre!  The rubber O rings are incorporated within the metal housing!  The housing is secured to the implants!  The housings are incorporated within the denture base with a chairside pick up procedure
  • 170. Mini-Implants Courtesy E. LaBarre!  Existingremovable partial denture has been altered and can be used as a temporary overdenture.
  • 171. Mini-Implants Courtesy E. LaBarre!  These implants are not recommended for long term use for overdentures!  Failure rates in the edentulous mandible are unacceptably high (10% at two years followup; Krenmair et al, 2003)
  • 172. Single implant placed in the midline Overdenture retained with an O ring type of attachment!  Several authors have suggested this approach in order to reduce treatment times and component costs!  The implant is placed on the midline!  Patient satisfaction appears to be equivalent to the 2 implant retained overdenture (Walton et al, 2009)!  Some clinicians have reported a high risk of the acrylic resin fractures overlying the single implant (Harder et al, 2001).
  • 173. Treatment of the Severely Resorbed MandibleIssues!  Exposure of the inferior alveolar nerve (arrows)!  Pathologic fracture of the mandible
  • 174. Treatment of the Severely Resorbed Mandible Exposure of the inferior alveolar nerveIf the inferior alveolar nerve is exposed andthe mandible is not at risk of fracture animplant supported prosthesis isrecommended.! Two options ! Implant supported overdentures ! Fixed prostheses
  • 175. DefinitionsImplant assisted prosthesisThe forces of occlusion areshared between the implants andthe denture bearing surfaces.Always removable overdentures.Implant supported prosthesisAll the forces of occlusion areborne by the implants. Can beeither fixed prostheses orremovable overdentures.
  • 176. Biomechanical requirements Implant supported prostheses Implant number and arrangementAnterior – Posterior SpreadIf an implant supported prosthesis isplanned, 4-5 implants are required withat least 1 cm of A-P spread.
  • 177. Indications for Implant Supported Overdenture!  Replacement for fixed as patients age and experience difficulty manipulating hygiene aids!  Patients with exposure of the inferior alveolar nerve
  • 178. Implant Supported OverdenturesBiomechanical requirements Minimum of 4 implants Minimum of 1 cm of Anterior Poster A-P) spread
  • 179. Implant Supported Overdentures Design Considerations!  The tissue bar requires more bulk between the implants because of the increased forces delivered.!  Hygiene access between the implants and beneath the bar is required!  We prefer Hader attachments because of their low profile
  • 180. Implant Supported Overdentures Design Considerations!  Bite force of patients with implant supported prostheses is greater!  Therefore it may be advisable to provide metal reinforcement particularly if interocclusal space is compromised
  • 181. Implant Supported Overdentures Design Considerations
  • 182. Implant Supported Overdentures Design Considerations
  • 183. Implant Supported Overlay Dentures ! Anatomic posterior teeth ! Bilateral balanced occlusion
  • 184. Treatment of the Severely Resorbed Mandible Exposure of the inferior alveolar nerve!  Fixed hybrid prosthesis !  In these patients the cantilever extension must be 4 mm above the level of the tissue. Why? 4 mm Deposition of new bone on top of the nerve.
  • 185. Treatment of the severely resorbed mandible! Implants are placed if there is sufficient bone for placement of implants 7 mm in length and 3.75 mm in diameter.! A fixed hybrid prosthesis was fabricated for the patient! In some patients there is a significant increase in bone mass of the mandibular body posterior to the implants Courtesy Dr. H Davis
  • 186. Treatment of the severely resorbed mandible!  Notethe significant increase in bone over the inferior alveolar nerve 8 years following delivery of the prosthesis. Courtesy Dr. H Davis
  • 187. Treatment of the severely resorbed mandible Note the significant increase in bone over the inferior alveolar nerve in another patient 10 years following delivery of the prosthesis. Courtesy Dr. H Davis
  • 188. Treatment of the Severely Resorbed MandibleRole of bone grafting!  To prevent pathologic fracture of the mandible!  If there is insufficient bone volume available to place implants into the anterior region of the mandible bone grafting followed by implant placement is recommended. Placement of implants will prevent resorption of the bone graft
  • 189. Treatment of the severely resorbed mandible preopReconstruction of themandible with bone graftsMany methods have been used!  Rib grafts 3 mths!  Iliac crest grafts!  Visor osteotomyRegardless of the method usedunless implants are placed, the 5 yrsgrafts resorb within a few yearswhen conventional dentures areworn by the patient. This resultis typical.
  • 190. Treatment of the severely resorbed mandibleCourtesy Dr. H Davis If implants are placed and put into function, the graft does not resorb.
  • 191. Treatment of the Severely Resorbed Mandible Preferred method !  Particulatemarrow with HA particles !  The marrow provides the osteogenic potential and the HACourtesy Dr. H Davis provides a scaffold
  • 192. Treatment of the Severely Resorbed Mandible !  Another patient with severe resorption whose mandible was reconstructed prior to placement of implant. !  A fixed hybrid prosthesis was fabricated for thisCourtesy Dr. H Davis patient.
  • 193. The 4 implant assisted overlay denture!  Four implants splinted together with a implant assisted overlay denture.!  In this design the Hader segment anteriorly serves as the axis of rotation. The resilient ERA attachments posteriorly allow the prosthesis to rotate around the Hader segment when posterior occlusal forces are applied.
  • 194. The 4 implant assisted overlay denture Inadequate A-P spread for fixedWe only recommend this approach when there isinadequate A-P spread or when the implant sites aredramatically compromised.!  For example: Patients treated with cancero-cidal levels of radiation!  When there is insufficient A-P spread to fabricate an implant supported prosthesis
  • 195. The 4 implant assisted overlay denture Inadequate A-P spread for fixedNote the minimal A-P spread in thiscase. Therefore the tissue bardesign is implant assisted.
  • 196. The 4 implant assisted overlay denture Inadequate A-P spread for fixedCompleted tissue bar with Hader and ERA typeattachments.
  • 197. The 4 implant assisted overlay denture Inadequate A-P spread for fixedTissue bar is secured to theimplants with gold alloy screws antightened to no more than 20 N/cm.
  • 198. The 4 implant assisted overlay denture Inadequate A-P spread for fixed Completed prosthesis. Note: the support for the prosthesis is shared between the implants in the anterior region and the retromolar pad and buccal shelf in the posterior region. Therefore the master impression was border molded.
  • 199. The 4 implant assisted overlay denture Inadequate A-P spread for fixed Completed and inserted prosthesis.
  • 200. The 4 implant assisted overlay denture Inadequate A-P spread for fixed Inserted prosthesis
  • 201. !  Visitffofr.org for hundreds of additional lectures on Complete Dentures, Implant Dentistry, Removable Partial Dentures, Esthetic Dentistry and Maxillofacial Prosthetics.!  The lectures are free.!  Our objective is to create the best and most comprehensive online programs of instruction in Prosthodontics