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Prosthodontics prep manual for UG. sample chapter-mouth preparation. To order call us at +91 8527622422


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Prosthodontics prep manual for ug. sample chapter-mouth preparation

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  • 1. CHAPTER Mouth Preparation of Complete Denture Patients 3 QUESTION 1 Enumerate the methods to prepare the mouth to receive complete dentures. Write the objectives of these methods. ANSWER Methods commonly used to prepare the mouth to receive complete dentures are as follows: (i) Nonsurgical method. (ii) Surgical method or pre-prosthetic surgery. Objectives of Mouth Preparation Improves denture foundation. Improves the ridge relations. Enhances support. Restoration of form and function of stomatognathic system. Improves aesthetics. QUESTION 2 Describe the nonsurgical methods to prepare mouth for complete dentures. ANSWER Nonsurgical methods of preparing mouth for complete dentures are as follows: Rest for denture bearing areas: The most preferred method to allow the deformed material to return to a state of good health is to give rest to the tissues. This is accomplished by asking the patient to remove the dentures from the mouth for an extended period of time or by the use of temporary soft liners. The condition of the oral tissues will determine the time the dentures are to be left out of the mouth. A rest of 48–72 h is usually advised before final impression can be made for new dentures. If the dentures cannot be removed for extended period of time then alternatives such as the use of tissue conditioning material should be advised.Chapter-03.indd 43 11/9/2011 5:55:43 PM
  • 2. 44 Sec. I Complete Dentures Correcting occlusion: Faulty occlusion is most commonly found in the faulty dentures. Generalized redness or bone loss with the hyperplastic tissue formation may be the result of faulty occlusion. Optimum occlusal vertical dimension occlusion (VDO) should be restored using interim resilient lining material. Heavy anterior occlusal contacts are common in old dentures because changes have usually occurred in the denture bearing areas and in the VDO due to wearing of the teeth. This heavy contact should be eliminated as it will cause excessive pressure on the anterior ridge resulting in increased resorption of the residual ridge. Extension of denture: Correctly extended denture borders provide improved retention and stability of the dentures. Mostly the old dentures are underextended. Correct extension of all usable supporting tissues is achieved using resin border moulding materials combined with the tissue conditioners. Good nutrition: All the edentulous patients should be educated and motivated to follow good nutritional programs. Good healthy food is advised to such patients as their metabolic and masticatory efficiency is decreased. Conditioning of the patient’s musculature: Jaw exercises are advised to the edentulous patient as they help in relaxation of the muscle of mastication and to strengthen their coordination. It is important in patients who have difficulty in responding to the instructions of relaxing and coordinating mandibular movements. Such exercises are important during recording of the jaw relations. QUESTION 3 Describe the role of tissue conditioners in treating abused tissues. ANSWER Tissue conditioners are used to treat abused and compromised tissues due to congenital or acquired abnormalities, parafunctional habits, systemic deficiencies, or faulty dentures. The softness and flexibility of these materials help in protecting the supporting tissues from functional and parafunctional occlusal stresses. Uses Temporary reline of dentures following oral surgery. Conditioning the denture bearing areas to healthy state. Aid in treatment of chronic soreness from dentures. As impression material to reline complete dentures. Final impression material for new complete dentures. Temporary relining of loose immediate dentures. For temporary obturation and protection of surgical areas. As a stabilizer for baseplates or surgical stents.Chapter-03.indd 44 11/9/2011 5:55:44 PM
  • 3. Ch. 3 Mouth Preparation of Complete Denture Patients 45 Composition and Characteristics Composed of poly(ethyl methacrylate) and an aromatic ester ethyl alcohol mixture. When these materials are mixed, they form a cohesive, resilient gel. The material does not adhere to the wet mucosa but readily adhere to dry acrylic resin, to skin or to old tissue conditioning material. Flow of the material can be improved by adding plasticizing liquid. It continues to flow under pressure for several days. To obtain good results, the material should be changed after every 72 h. The material usually remains plastic but will become grainy and discoloured if in contact with denture for more than 2 weeks. Causes of Abused Tissues Hyperaemic or traumatized oral mucosa because of ill-fitting dentures. Poor occlusion. Bruxism. Papillary hyperplasia. Depressed area with suction cups. Nutritional disorders. General debilitating patients. Treatment of Abused Tissues For patients who cannot remain without dentures over an extended period of time, tissue conditioners are used. Before the fabrication of new dentures, the hypertrophic, irritated, hyperaemic, and abused oral tissues should be conditioned to a healthy state. Self-curing, slowly polymerizing material provides excellent medium to aid in conditioning of the abused tissues. After occlusal adjustments and correction of the underextended or overextended borders, tissue conditioning material is applied. Tissue side of the denture and the borders are reduced by approximately 2 mm. Posterior palatal seal and the buccal shelf region are not reduced as they act as posterior stops. Also, anterior stops are provided by reducing a small area of 3 × 3 mm in the cuspid region during initial relief. Anterior and posterior stops are necessary to correctly orient the dentures to the ridges during placement of the material and to maintain a correct vertical dimension. Material is mixed following the manufacturer’s instructions. Material is spread evenly on the tissue surface and border areas of the denture. Dentures are placed in the mouth and the patient is instructed to tap the dentures lightly together. The dentures are left in the mouth for several minutes for setting. Any excess material is trimmed using a sharp BP blade. Pressure spots are relieved using acrylic trimmer or vulcanite bur. Dentures are placed back on the ridges, appearance is checked, and the vertical dimension is verified.Chapter-03.indd 45 11/9/2011 5:55:44 PM
  • 4. 46 Sec. I Complete Dentures The centric relation position should coincide with the centric occlusion. Patient is recalled after 72 h and he/she is instructed not to brush the tissue surface of the denture. The denture should be cleaned with lukewarm water. When the patient returns, the dentures and the tissues are examined and necessary corrections are made. Once the tissues return to normal health, preliminary impressions are made. QUESTION 4 Define pre-prosthetic surgery and describe minor pre-prosthetic surgical procedures in the treatment of completely edentulous patient. ANSWER Pre-prosthetic surgery is defined as “surgical procedures designed to facilitate fabrication of prosthesis or to improve the prognosis of prosthodontic care”. —GPT 8th Ed Pre-prosthetic surgery attempts to create an environment that can support the complete dentures and enhances its longevity and patient satisfaction. It is aimed to prepare the edentulous jaw to accept best possible complete denture prosthesis. The edentulous jaw is aimed to provide an ideal shape and form. MINOR PRE-PROSTHETIC SURGICAL PROCEDURES Alveoloplasties Least amount of bone resorption takes place if the sockets are digitally compressed after simple extraction. Surgical technique of alveoplasty is to reflect the mucoperiosteal flap and reduce of the bone with rongeurs or a rotary bur. When there is adequate ridge height but bony undercut occurs on the buccal aspect of the jaw, intraseptal alveoloplasty with cortical bone repositioning is indicated. Frenectomy It is defined as surgical excision of the frenum. Frenectomy or frenotomy is indicated when a band of fibrous tissue attaches near the crest of residual ridge or the thick frenum continuously displaces the denture during function. Hypertrophic maxillary labial frenum most commonly interferes with denture function followed by lingual frenum and maxillary buccal frenum. Different techniques for frenectomy include Diamond excision, Z-plasty technique, and V–Y advancement technique. Diamond excision is the most commonly used technique to release maxillary and mandibular labial frena. Z-plasty technique is used when frenum is broad and short (Fig. 3.1). V–Y advancement technique is used when concomitant decrease in nasal base width is desired.Chapter-03.indd 46 11/9/2011 5:55:44 PM
  • 5. Ch. 3 Mouth Preparation of Complete Denture Patients 47 (a) (b) (c) Fig. 3.1: Diagram to show Z-plasty technique used in frenectomy: (a) ‘Z’ shaped incision. (b) Reflection and detachment of frenum from alveolar process. (c) Sutures closing the wound. During mandibular frenectomy it is advisable to give tongue traction suture in order to improve visibility and control of tongue. Broad frena in the maxillary bicuspid molar region is best treated by localized vestibuloplasty. Excision of Redundant Soft Tissues, Papillary Hyperplasia, or Epulis Fissuratum Surgical excision may be required to remove excess noninflammatory tissues caused due to long-term wearing of a poorly fitting prosthesis. Care should be taken that there is minimal trauma to the remaining tissues. Epulis fissuratum is surgically removed by sharp excision, electrocautery, cryosurgery, and laser excision. Laser excision offers better haemostasis and reduced postoperative pain. Cryosurgery may require several appointments. Palatal papillary hyperplasia is caused by poorly fitting complete denture and sometimes caused by candidal infection. Attempt should be made to reduce the size of the lesion pre-operatively by providing relief of the denture and using tissue conditioners and antifungal agents. Soft tissue removal can be accomplished by surgical excision, curettage, electrosurgery, reduction using large rotary bur or laser ablation. Maxillary Tuberosity Reduction and Exostosis Removal Excess tissue in the region of maxillary tuberosity commonly interferes with the construction of denture. This excess tissue may be soft redundant tissue or a bony undercut. Articulated casts are valuable to plan the amount and location of tissue removal. The excessive soft tissue is surgically excised and sutured to obtain primary closure. To remove excessive bony undercut, an ellipsoid incision is made and the mucoperiosteum is reflected and rongeur or rotary bur is used to remove the bone. Tori removal Tori can be palatal or lingual. Palatal tori Usually located at the centre of the palate and is more common in the females. Composed of entirely cortical bone and occasionally may have cancellous components.Chapter-03.indd 47 11/9/2011 5:55:44 PM
  • 6. 48 Sec. I Complete Dentures Removal of palatal tori is indicated when the following are noticed: Extremely large torus fills the palatal vault. Torus extending beyond the posterior dam area. Mucosa is traumatized over the torus. Deep bony undercut. Interferes with functions such as speech, swallowing. Psychological reasons (fear of malignancy). Smaller torus does not require removal and relief in the denture is sufficient. However, large torus requires surgical removal. Technique Anteroposterior incision is made over the middle of the torus with a Y-shaped realizing incision at each end. Full thickness mucoperiosteal flap is raised carefully and the torus is sectioned with a bur. Sectioned torus is removed in pieces with chisel. A large rotary bur may also be used to grind the torus away. Mucosal tissues are approximated and sutured to achieve primary closure. A stent or denture is used to support the palatal tissues to avoid haematoma formation. Possible complications: Nasal perforation, oronasal or antral fistula formation, palatal tissue necrosis and haematoma. Mandibular tori (Fig. 3.2) Can be single, multiple, or lobulated. Commonly located on the lingual aspect of the premolar region. Osteotome is used to remove the torus by creating a groove in the lingual cortex with a fissure bur. Alternatively large rotary bur can also be used. Bone is smoothened with bone file and the primary closure is obtained. Possible complications: haemorrhage of the floor of the mouth, infection. Mylohyoid Ridge Reduction Vertical bone resorption of the bone in the posterior mandible results in prominent ridge. Superior grooving (a) (b) (c) Fig. 3.2: Diagram to show removal of lingual torus: (a) Lingual torus. (b) Grooving and removal of torus. (c) Sutures placed.Chapter-03.indd 48 11/9/2011 5:55:44 PM
  • 7. Ch. 3 Mouth Preparation of Complete Denture Patients 49 It limits the extension of the lingual flange of the lower denture. Incision is made in the posterior aspect of the mandible on the crest of the ridge. Mucoperiosteal flap is reflected and a rotary bur or bone file is used to reduce the prominence of the ridge. Primary closure is achieved after suturing and a stent or modified denture is immediately placed to position the muscle inferiorly. QUESTION 5 Describe the rationale and technique of ridge augmentation for the complete dentures. ANSWER Augmentation is defined as “to increase in size beyond the existing size. In alveolar ridge augmentation, bone grafts or alloplastic materials are used to increase the size of an atrophic alveolar ridge”. —GPT 8th Ed Rationale of Ridge Augmentation To recreate an edentulous ridge having features compatible with the requirements of denture wearing. Factors Affecting Ridge Augmentation Success Type of augmentation material, i.e. autografts, allograft or alloplast. Augmentation site. Surgical and prosthodontic design. Willingness of patient. Prosthodontic follow-up. Physical and mental condition of the patient. Skill of the surgeon and prosthodontist. Diagnosis and Treatment Planning Through medical and dental history. Complete radiographic evaluation. Frontal and profile photographs. Radiographs and photographs are obtained after satisfactory jaw relations. Properly mounted casts. Mock surgery performed on the cast to determine the surgical approach to be used and the amount of desired correction. Minimum of 16–18 mm of interarch space is required to construct complete dentures. The techniques commonly used for ridge augmentation are as follows: Visor Osteotomy In this technique, the buccolingual dimension of the mandible is split and the lingual cortical bone is repositioned superiorly.Chapter-03.indd 49 11/9/2011 5:55:44 PM
  • 8. 50 Sec. I Complete Dentures Some authors have suggested decreased postoperative bone resorption and good vertical bone augmentation. Incidence of paraesthesia of the mandibular nerve is high. Postoperative ridge form following this technique is poor. Onlay Bone Grafting Indications When bony support in the maxilla and mandible is inadequate. When the residual vertical bone height between the mental foramen is less than 7 mm. In this technique, autogenous bone from the iliac crest has been used to augment the atrophic maxilla or mandible. Drawback is high rate of resorption of the onlay graft. Secondly, another surgery is performed to increase the depth of the vestibule. Interpositional Bone Grafts In this technique an osteotomy is performed by splitting the superior–inferior dimension of the residual jaw and bone is grafted within this osteotomy. In the maxilla, Le Fort osteotomy is performed with interpositional grafting. The advantage of this technique is that it shows less resorption in comparison to the onlay grafting procedure. After grafting, secondary soft tissue procedure to increase the vestibular depth is usually necessary. Horizontal sandwich technique is used to augment the anterior mandible. Advantage is that it shows less incidence of nerve paraesthesia when compared to visor osteotomy. Allogenic bone graft can be used instead of autogenous graft. Procedure of choice for mandibular ridge augmentation as it includes a combination of osteotomy techniques (horizontal or vertical). This procedure involves the movement of the pedicle of the bone along with blood supply. Inferior Bone Grafts (Fig. 3.3) First described by Marx and Saunders (1986) for reconstruction of the mandible following resection. Modified by Quinn et al. (1991). Indications Severely atrophic mandible. Mandible has 5–8 mm of bone and there are chances of pathological fracture. Procedure A supralaryngeal incision is made from the Fig. 3.3: Inferior border bone grafting technique. mastoid process to the mastoid process on the other side.Chapter-03.indd 50 11/9/2011 5:55:44 PM
  • 9. Ch. 3 Mouth Preparation of Complete Denture Patients 51 Subsequently, the inferior border of the mandible is dissected. A freeze-dried allogenic mandible is hollowed out and is used as a tray to hold the autogenous cancellous graft harvested from the iliac crest. If needed, hydroxyapatite or allogenic particulate bone is used as graft expander. Graft is secured in place using sutures or wires. The freeze-dried allogenic bone crib is replaced by a process called creeping substitution over a period of several months. Implants can be placed into the graft after 4 months post surgery. Advantages of this technique is consistent 11–17 mm of bone augmentation is achieved with a resorption rate of only 5%. QUESTION 6 Define vestibuloplasty. Write its indications and contraindi- cations. Describe briefly about the various techniques used for vestibuloplasty. ANSWER Vestibuloplasty is defined as “a surgical procedure designed to restore alveolar ridge height by lowering muscles attachment to the buccal, labial, and lingual aspects of the jaws”. —GPT 8th Ed Indications When other conservative procedures fail. Healthy patient who is highly motivated. Cooperative patient. Contraindications Medically unfit. Under-motivated patient. Geriatric patient who is debilitated or medically compromised. When vertical ridge height is inadequate. Severely prognathic patient. Patient who cannot bear the cost and time of the treatment. Techniques Mucosal advancement First described by McIntosh and Obwegeser (1967). Indicated when maxillary denture is unstable due to shallow vestibular depth or high muscle attachment but there should be sufficient healthy mucosa in the vestibule. Mouth mirror test is used to assess the amount of mucosa. Mouth mirror is used to reflect the soft tissue to the desired vestibular depth; if abnormal shortening of the lip is not noticed, then sufficient mucosa exists to do the procedure. A subperiosteal tunnel is created by dissecting any underlying submucosal connective tissue away from the periosteum.Chapter-03.indd 51 11/9/2011 5:55:44 PM
  • 10. 52 Sec. I Complete Dentures The intervening submucosal tissues are then excised or repositioned anteriorly. An overextended surgical stent or overextended denture is placed to the new vestibular area. Stent is removed after complete healing. New denture is then fabricated to a new maxillary form and vestibular depth. Secondary epithelialization (Fig. 3.4) Involves the use of apically repositioned flap sutured to the periosteum to the desired sulcus depth. Exposed tissues are allowed to heal by granulation and secondary intention. This can be used when hypermobile and hyperplastic ridges are present and can be reduced while the ridge is extended. Overcorrection is advised beyond the desired sulcus depth as chances of relapse are very high. Splint (a) (b) (c) Fig. 3.4: Diagram to show secondary epithelialization procedure: (a) Incision of the ridge. (b) Supraperiosteal reflection. (c) Suturing of flap at new sulcus depth and placement of splint. Epithelial Graft Vestibuloplasty It is a secondary epithelization procedure which uses skin or mucous membrane graft to cover the exposed tissues. It was first described by Esser (1917) and later developed by Obwegeser (1967). It is used to enhance retention, stability, and support of a denture in highly resorbed maxilla or mandible. It is used when there is high muscle attachment that interferes with development of adequate border seal. Adequate vertical height of the bone is required to allow relocation of the vestibule. This technique is the most preferred and predictable of all the vestibular procedures. Lip Switch Procedures (Transitional Flap Vestibuloplasty) (Fig. 3.5) First described by Kazanjian (1935).Chapter-03.indd 52 11/9/2011 5:55:45 PM
  • 11. Ch. 3 Mouth Preparation of Complete Denture Patients 53 Indicated for patients with insufficient vestibular depth owing to mandibular atrophy and high muscle and soft tissue attachments. This technique effectively increases the vestibular depth in patients having bone height more than 15 mm. If the bone height is less than 15 mm, then the prosthetic results are compromised and other procedures such as ridge augmentation are advised. A submucosal dissection is made from the inner lower lip to the mucogingival junction. Then supraperiosteal dissection is done to remove the muscle and connective tissue attachments inferiorly to the desired vestibular depth. Periosteal flap is dissected from the bone and sutured to the raw lip bed. Raised mucosal flap is adapted to the exposed bone to the depth of the new vestibule and is fixed with sutures or stent. Possible complication includes pain, oedema and/or transient mental nerve paraesthesia. (a) (b) (c) Fig. 3.5: Lip switch technique of vestibuloplasty: (a) Incision made in labial mucosa or periosteal flap. (b) Flap is reflected to the depth of vestibule. (c) Flap sutured. QUESTION 7 Describe the role of soft liners in the management of edentulous patients. ANSWER Resilient liners are elastomeric polymers which are used to prevent chronic soreness from complete dentures and to preserve the supporting structures. Types of resilient liners based on their composition are as follows: (i) Velum rubber (ii) Vinyl or acrylic resin (iii) Silicones (iv) Polyurethane (v) Ethyl methacrylate elastomers Ideal Requirements of Resilient Liners Material should be durable. Should have adequate hardness and strength and its hardness should not change with time.Chapter-03.indd 53 11/9/2011 5:55:45 PM
  • 12. 54 Sec. I Complete Dentures Should adhere well to the denture base. Should recover well from deformation. Should be easily cleaned and adjusted. Should not be affected by the microorganisms and their metabolites. Should be colour stable, odourless, tasteless, nonirritating, and nontoxic. Should be dimensionally stable and accurate. Should not distort the denture base. Should have good surface wetability. Composition Vinyl and acrylic polymers are made resilient by adding oily or alcohol type of plasticizer. Hydrophilic polymer is a mixture of polyethylene glycol methacrylate with diacetins. Once hardened, the material can be polished by conventional means. It becomes flexible when placed in water or in moist environment of the oral cavity. Role in Edentulous Patient Resorbed or atrophied edentulous ridges which require protection (e.g. in knife-edged ridges, mental foramen region, dehiscent mandibular canal, or surgically excised soft or bony tissues). Resilient liners provide excellent protection to underlying soft tissues. When surgical correction of bony undercuts is contraindicated. Resilient liners are useful in patients who cannot afford or undergo surgery for correction of bilateral undercuts. These materials owing to their flexibility facilitate insertion and removal without compromising retention. Patients with parafunctional habit such as bruxism. The constant grinding of the occlusal surfaces of the denture teeth transmit intermittent shear stress to the basal seat which results in mucosal irritation and subsequent bone resorption. Resilient liners protect the supporting tissues from excessive stress. Used in the relief area such as mid-palatal raphe or anterior nasal spine. The soft flexible material provides relief to these regions. When congenital or acquired oral defects are to be restored. Resilient liners are valuable in fabricating prosthesis such as obturator to restore congenital or acquired oral defects. It can be indicated in xerostomic patients. However, it should be avoided in severe xerostomic patients as they too can cause mucosal irritation. In cases where the edentulous arch opposes the natural dentition. Resilient liners prevent the problems of chronic soreness from complete dentures and thus help in preserving the supporting tissues. Drawbacks Plasticizer leaches out over the period of time making it hard and discoloured.Chapter-03.indd 54 11/9/2011 5:55:45 PM
  • 13. Ch. 3 Mouth Preparation of Complete Denture Patients 55 Silicone elastomers do not adhere well with the acrylic resin denture base and thus are prone to get discoloured, difficult to finish and polish, dimensionally unstable, and affected by the metabolites of Candida albicans. Polyurethanes are ultra soft and comfortable but are difficult to processes. Ethyl methacrylates can be processed by compression moulding technique and can be easily finished and polished by conventional means. Key Facts Epulis fissuratum is caused due to overextension of the labial flanges. Generalized soreness of the denture bearing area in new denture wearer is due to increased vertical dimension. Mandibular tori are most commonly located lingual to the premolar region. Maxillary tori are most commonly located in the mid palatal region.Chapter-03.indd 55 11/9/2011 5:55:45 PM