complete denture prosthodontics

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Planning and Decision-Making

Yasemin K. Özkan Editor

Complete Denture Prosthodontics

Yasemin K. ÖzkanEditor


Planning and Decision-Making

EditorYasemin K. ÖzkanFaculty of Dentistry, Department of ProsthodonticsMarmara UniversityIstanbulTurkey

This work has been first published in 2017 by Quintessence Yayıncılık, Turkey with the following title: Tam protezler: problemler ve çözüm yollarıISBN 978-3-319-69031-5 ISBN 978-3-319-69032-2 (eBook)https://doi.org/10.1007/978-3-319-69032-2

Library of Congress Control Number: 2018961732

© Springer International Publishing AG, part of Springer Nature 2018This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed.The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

This Springer imprint is published by the registered company Springer Nature Switzerland AGThe registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

https://doi.org/10.1007/978-3-319-69032-2

I had dedicated my first book published in 2012, “Complete Dentures and Implant-Retained Removable Dentures,” to my brother, Air Force Lieutenant Pilot Adnan Mücahit Kulak, who reached martyrdom in 1989 and to my dearest beloved father Bahri Kulak who passed away in 2006.

When my mother read the dedication section of the book, she felt rejoice and delight but also was grievingly melancholic and then I had promised her that I would dedicate the second edition to her.

And I kept my promise my dear mother.

I dedicate this publication to my mother who showed unlimited loyalty to my family, made endless sacrifices for her loved ones, provided immeasurable amount of love in every stage of my life, and who is more or less similar to other mothers but special because she is mine.

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Preface

The second edition of our book consists of 19 chapters and more than 1500 colorful pictures of our own clinical cases.

This book will continue to be a guidebook not only for dentistry students but also for den-tists. It will both help the clinicians to offer the most proper treatment options to the patients and give practical information about the solutions of the problems occurring before and after the use of dentures.

As Leonardo da Vinci said, “He who loves practice without theory is like the sailor who boards ship without a rudder and compass and never knows where he may cast.”

In this book, we tried to give theoretical information that can be adapted to the clinic rather than giving theoretical information that cannot be applied practically.

I would like to thank everyone who contributed during the writing and publishing of the book.

Istanbul, Turkey Yasemin K. Özkan

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Contents

Part I Introduction to Complete Dentures

1 Anatomical Landmarks and Age- Related Changes in Edentulous Patients . . . . . 3Yasemin K. Özkan, Buket Evren, and Alisa Kauffman

2 Evaluation of the Edentulous Patient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49Yasemin K. Özkan, Zeliha Sanivar Abbasgholizadeh, and Şükrü Can Akmansoy

Part II Pre Prosthetic Planning and Impression Procedures

3 Pre-prosthetic Mouth Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89Yasemin K. Özkan and Yasar Ozkan

4 Impression Material Selection According to the Impression Technique . . . . . . . . 111Yilmaz Umut Aslan and Yasemin K. Özkan

5 Diagnostic Impressions and Custom- Made Trays . . . . . . . . . . . . . . . . . . . . . . . . . . 133Şükrü Can Akmansoy, Zeliha Sanivar Abbasgholizadeh, and Yasemin K. Özkan

6 Anatomical Landmarks and Impression Taking in Complete Dentures . . . . . . . . 189Yasemin K. Özkan

Part III Establishing Occlusal Relationship

7 Recording Maxillomandibular Relations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267Yasemin K. Özkan, Begum Turker, and Rifat Gozneli

8 Movements and Mechanics of Mandible Occlusion Concepts and Laws of Articulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293Yasemin K. Ozkan

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Contributors

Zeliha Sanivar Abbasgholizadeh Faculty of Dentistry, Department of Prosthodontics, Marmara University, Istanbul, Turkey

Şükrü Can Akmansoy Faculty of Dentistry, Department of Prosthodontics, Marmara University, Istanbul, Turkey

Yilmaz Umut Aslan Faculty of Dentistry, Department of Prosthodontics, Marmara University, Istanbul, Turkey

Buket Evren Faculty of Dentistry, Department of Prosthodontics, Marmara University, Istanbul, Turkey

Rifat Gozneli Faculty of Dentistry, Department of Prosthodontics, Marmara University, Istanbul, Turkey

Alisa Kauffman Penn Dental Family Practices, Philadelphia, PA, USA

Yasar Ozkan Faculty of Dentistry, Department of Oral and Maxillofacial Surgery, Marmara University, Istanbul, Turkey

Yasemin K. Ozkan Faculty of Dentistry, Department of Prosthodontics, Marmara University, Istanbul, Turkey

Faculty of Dentistry, Department of Oral and Maxillofacial Surgery, Marmara University, Istanbul, Turkey

Begum Turker Faculty of Dentistry, Department of Prosthodontics, Marmara University, Istanbul, Turkey

Part I

Introduction to Complete Dentures

3© Springer International Publishing AG, part of Springer Nature 2018Y. K. Özkan (ed.), Complete Denture Prosthodontics, https://doi.org/10.1007/978-3-319-69032-2_1

Anatomical Landmarks and Age-Related Changes in Edentulous Patients

Yasemin K. Özkan, Buket Evren, and Alisa Kauffman

1.1 Anatomical Landmarks and Age-Related Changes in Edentulous Patients

When fabricating a new denture, your success will depend on making the correct diagnosis and the correct treatment plan. Gathering necessary information by careful examination of the patient, determining the requests by asking questions, examin-ing the negative or positive sides of their current prosthesis and observing the psychological status of the patient are the most important aspects for making the correct diagnosis.

Current research states that up to more than 50% of elderly people may become edentulous. The population of those wearing complete dentures are often individuals over the age of 60. A careful analysis and clinical observation is required for determining the prosthetic treatment needs and demands of elderly patients. Some changes occur with age in human physiology, and these changes are not widely accepted by individuals. Therefore, when the patients go to the dentist for the fabrication of a new prosthesis, they think that the new dentures will completely eliminate all the prob-lems and this affects the prognosis of prosthesis negatively.

Ageing is the sum of the irreversible structural and func-tional changes in the molecules, cells, tissues, organs and the systems of the organism occurring in course of time (Figs. 1.1 and 1.2).

The oral changes that are generally associated with age-ing include increase in tooth loss, decrease in salivary flow and atrophy of the oral mucosa and the muscles. These func-tional changes cause differences in eating habits and chew-ing functions leading to pathological changes. Loss of teeth,

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Y. K. Özkan (*) · B. Evren Faculty of Dentistry, Department of Prosthodontiscs, Marmara University, Istanbul, Turkeye-mail: [email protected]

A. Kauffman Penn Dental Family Practices, Philadelphia, PA, USAe-mail: [email protected] Figs. 1.1 and 1.2 Age-related structural changes

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mailto:[email protected]

mailto:[email protected]

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problems in eating and speaking with the new dentures are worrying for the elderly individuals. Therefore, the approach of dentist to the patient should be supportive and reassuring.

You must also be patient and tolerant and focus the patient to become acclimated to a new prosthesis that will take some time and will require adjustments to get used to the patients will over time issue. As the patient gets older, alveolar resorption, decrease in chewing efficiency, variations in muscular balance, decrease in vertical height and aesthetic and phonetic deficiencies will be observed in chewing sys-tem related to teeth lost. As most of these changes are physi-ological, they can be compensated within the system, but some of them are irreversible because of elderliness.

When determining the need and desire of prosthetic treat-ment for elderly patients, medical history and a careful clinical observation are required. Before the decision to fabricate a new denture, the patient’s previous dentures, if exists, should be taken into account as well as the local and systemic factors.

For a successful treatment, the existing denture should be evaluated at first. The evaluation of the existing denture will be a guide for new dentures in accordance with the patient’s wishes and complaints.

1.1.1 Age-Related Changes

1.1.1.1 NutritionMalnutrition in the elderly can result from chronic diseases, use of medicine, chewing and swallowing problems, loss of taste, physical disorders, inadequate dietary intake and some psychological and social factors. Studies about the effects of edentulism on nutrition indicate that there is direct propor-tion between malnutrition and edentulism. In some elderly patients, intake of some essential minerals and food may be insufficient. As a result of this, decrease in the amount of plasma concentrated thiamine, riboflavin or folic acid is observed, and this can lead to reduced tolerance of the tis-sues and poor adaptation of dentures (Table 1.1).

Therefore, it is important to do an initial evaluation of the nutritional quality of the patient and, then if necessary, rec-ommend to them a proper diet.

1.1.1.2 Systemic DiseasesSystemic diseases such as diabetes mellitus, gastrointestinal disorders and atherosclerosis may be directly related to weight loss. As a result, patients can completely neglect their oral and prosthetic care. In such cases, the dentist must wait until the general health of the patient is improved.

1.1.1.3 Neurophysiologic ChangesDegeneration in the functional structures of the central ner-vous system and reduction in visual and auditory perception occurs with advancing age. Due to the decrease in visual per-ception, individuals hardly respond to rapid images and movements. Same situation is valid for the auditory percep-tion. Touching sensitivity decreases and a coordinated per-ception is not present. Physical changes in perception require a different patient approach. If the clinician wants to gain the confidence of a patient, we must speak calmly and act slowly during treatment. Since the patient’s understanding ability is inhibited by the changes in perception, it is hard for the patient to follow the stages of the treatment. If the clinician has a commanding style, the patient may feel uncomfortable. Because the pain threshold is too close to the auditory thresh-old for these types of patients, talking loudly may not be understood by the patients and may cause discomfort. Besides the decrease in the perceptions of elderly patients, the reactions are also delayed. Regressive changes in the cerebrum begin to decline after age 65 and one’s ability to produce reflexes become restricted. Despite the ideal form of alveolar ridges and perfect dentures, the adaptation may be difficult or impossible because of the decrease in learning ability. Degeneration in functional structures of central ner-vous system takes place with the increasing age. These changes in the central nervous system will inhibit new mus-cle activities which in turn causes slow adaptation to the new prostheses.

Degeneration occurs in neuromuscular system and mus-cles. The size and power of muscles decrease, contraction intervals increase and due to the loss of teeth, contraction in muscles is accelerated. Related to the contraction in muscles, functional chewing capacity reduces. Previous prostheses may be used as a model for the design of the new ones in this type of patients to make the adaptation easier.

1.1.1.4 Physiologic ChangesMany geriatric patients have some form of depression. Sometimes, a consultation with patients’ physician may give your insight as to how to help your patient.

It is possible to analyse geriatric patients in four groups according to their physiological characteristics.

Table 1.1 Deficiency of nutrients, minerals and vitamins causing pathological changes in the oral cavity and possible symptoms

Deficiency Possible oral symptomsWater Xerostomia, dry mucous membranes, tissue fragilityProtein Tissue fragility, cheilitis, inability to use the prosthesisIron Pallor of oral mucosa, glossitis, burning tongue, pale

and smooth tongueB12 Pallor of oral mucosa, cheilitis, glossitis, burning

tongueFolate Red and pale smooth tongue, mucosal ulcerationsNiacin Cheilitis, rough or granular tongue, purple coloured

tongueVitamin C Desquamation of oral mucosa, soft bleeding gingivaVitamin A Keratosis in oral mucosa, decreased salivary flow rateVitamin K Increase in the prothrombin time and spontaneous

haemorrhage

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1. Philosophical-rational; reasonable, organized and far from contradiction (expectations are realistic)

2. Meticulous-organized; obey the rules, careful, quite per-sistent (every step has to be described before the treatment)

3. Careless-unconcerned; hard to cooperate and lost motiva-tion, blame the clinician because of his health problems, do not pay enough importance to the information (unde-sirable prognosis)

4. Hysterical-emotional; unbalanced, nervous and anxious people (physiological support may be needed)

If the non-adaptive patients have their natural teeth, the clinician has to make an effort to keep those teeth in the mouth and if possible overdentures may help the patient for the transition to complete dentures. Unless there is no alter-native to conventional complete dentures, transitional pros-thesis can be fabricated. At first, this prosthesis has only the base plate. Then, by adding occlusal walls, anterior teeth, premolars and finally molars, respectively, transition to com-plete denture can be performed. If they have a clinically acceptable previous denture, duplicate prosthesis can be used for this kind of patients. In duplication prosthesis, pres-ent prosthesis’ dimensions and contours are imitated and patient’s adaptation is enhanced by the patient’s functional habits. The most important point in tooth arrangement is to maintain patient’s original tongue position again.

Patients who have knowledge about geriatric changes, who are open-minded and who are cooperative for dental treatment will be more understanding of the clinician’s approach and desires. The difficulty of prosthetic treatment in that group of patients is related to the oral conditions and the degree of patient cooperation.

1.1.1.5 Oral Physiological ChangesRelated to ageing, situations like decrease in muscle tonus and fatigue during chewing can be observed. Oral mucosa is more sensitive to thermal and chemical irritants. Submucosa gets thinner and due to the fibrous interstitial tissue increase, its elasticity decreases.

As the skin loses its elasticity, so elderly patients cannot open their mouth wide. Decreasing the vertical height in complete dentures and moisturizing the margins of the mouth with Vaseline is recommended. This situation makes provid-ing the mechanical sufficiency difficult after the insertion of the prosthesis (Fig. 1.3).

The increasing atrophy of the masticatory muscles is also a sign of ageing. This situation is usually accelerated for people using dentures. As a result of the atrophy of the mas-ticatory muscles, sufficient chewing efficiency cannot be provided. Therefore, it will be useful to recommend a suit-able diet, which can be easily chewed by the patient. The atrophy of the buccal muscles may cause food accumulation

especially on the buccal flanges of the dentures. To overcome this situation, the buccal flanges of the dentures can be thick-ened if tolerated. Such an application can contribute to the stability of the dentures.

Changes in tongue anatomy occur with ageing. In elderly patients, besides the functions in speaking and swallowing, the tongue contributes to the stability of the prosthesis (Fig. 1.4). The formation of the fissures may change with ageing, and

Fig. 1.3 Submucosa gets thinner and the skin loses its elasticity

Fig. 1.4 Unlike the masticatory muscles, the tongue is not affected from ageing

1 Anatomical Landmarks and Age-Related Changes in Edentulous Patients

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with the atrophy of the papillae comes a decrease in the sensa-tion of taste. The tongue becomes widespread and loses its moving ability resulting in abnormal movements and the loss of denture retention. Patients only become aware of their tongue’s role and changes when they begin wearing dentures.

Insufficient functioning of the salivary glands increases the sensitivity of the mucosa. Some medications such as diuretics, antihypertensives and antidepressants commonly used by the elderly may cause xerostomia. Xerostomia also reduces the retention of the prosthesis. Decrease in salivary secretion, xerostomia, physic pharmacological medical treat-ment or diseases like diabetes mellitus are just a few of the factors that make the prosthetic treatment difficult. Xerostomia is a major cause of rampant caries, loss of den-ture retention, traumatic lesions and infections of the oral mucosa. The functions of the saliva are for moisturizing the oral mucosa, providing the continuity of the microbial eco-logical balance, cleaning the oral structures mechanically, antibacterial or antifungal activity, preserving the oral pH and remineralization of the teeth. Medications used by the elderly have a direct link to salivary gland hypofunction.

The direct results of decreased salivary secretions, decrease in the resistance of the mucosal tissues against mechanical irritations, decrease in the retention of prosthetic restorations, atrophy of the taste cells, decrease in the taste sensitivity, burning of tongue, itching and pain may often cause an infection like candida.

In order to decrease the complications of denture usage in patients with xerostomia, the oral hygiene which will be pro-vided by mouthwashes with chlorhexidine and daily artifi-cial saliva makers is very important. Even so, complications can be expected and if possible, the use of dentures continu-ously should be limited. If the patients complain that they cannot use their prosthesis because their mouth is too dry, then dentures with reservoir are recommended.

1.1.1.6 Anatomical and Physiological FactorsFor the construction of a successful complete denture, deter-mining the correct anatomical structures of the edentulous maxilla and the mandible are very important. Together with ageing, changes in the alveolar bone and in the maxillo-man-dibular relations occur. The resorption of the alveolar ridge depends on anatomical, metabolic and mechanical factors. The resorption of the alveolar ridge increases due to the tooth loss. As a result of this resorption, the support of denture base is reduced, the prosthesis remains defenceless against lateral forces and difficulties can arise regarding dental implantology.

For the construction of a successful complete denture, anatomical structures of the edentulous maxilla and the man-dible are very important. After age 35–40 years, approxi-mately 1% of bone mass is lost per year in both men and women. Alveolar bone is one of the first bones to be affected by loss of mass. In both the maxilla and the mandible, the

amount, extent and uniformity of the bone loss differ with varying aetiologies and health status. It is now recognized that alveolar bone or residual ridge resorption is confounded by such factors as age, sex, race and health status of the patient when the teeth are extracted; the tooth extraction technique; the diet of the patient; the presence of local fac-tors; and the frequency of denture use.

Osteoporosis may occur in women who are in menopause with a decrease in calcium release from the bone. Since the ridge resorption is greater than normal, these patients should be kept under control with periodic recalls.

The lingual width of the edentulous mandible narrows initially and this situation affects the support. Afterwards the height reduces and the support, retention and stability are adversely affected. Vertical size decreases, the coro-noid process shrinks, condylar growth occurs, mandible moves forward, and mandibular canal becomes more supe-rior. The mental foramen may be exposed, and in this case pain occurs depending on the pressure of the prosthesis. In these patients, care should be taken and if necessary soft denture relining materials should be applied (Fig. 1.5).

The resorption pattern affects the stability at first in the edentulous maxilla. Following tooth extraction, resorption occurs from the buccal-labial area to the lingual area, and this effects the prosthetic support negatively. Severe resorp-tion of the alveolar bone causes the loss in vertical direction. As a result:

(a) The stability of the prosthesis is affected negatively. (b) Pseudo-Class III jaw relationship occurs. (c) Secondary effect: Retention is adversely affected due to

the deterioration of stability. The seal of the edges of the prosthesis will deteriorate easily, because the resistance against lateral forces during function will be minimal.

Fig. 1.5 The lingual width of the edentulous mandible narrows initially and this situation affects the support

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The maxilla shows a volumetric shrinkage, maxillary sinus is separated by only a thin layer of bone from the oral mucosa. The mandibular bone loss is four times more than the loss in the maxilla. This situation cause collapses in the face and lips, shrinkage in the mouth and wrinkles starting from the corners of the lips in elderly patients who do not use denture (Fig. 1.6).

The harmony of the present denture with the anatomical structures and the health of the soft tissues informs us in advance about the prognosis of the treatment. In addition, detailed knowledge of the anatomical structures will help to provide stability, retention, aesthetics and comfort success-fully during impression taking.

1.1.2 Anatomical Landmarks in Relation to Complete Denture

As an architect tries to get information about the place of the building that will be constructed, a skilled dentist should evaluate the anatomy of the face and mouth before fabricat-ing a denture. In this section, anatomical structures in rela-tion to complete denture will be discussed.

1.1.2.1 Mucous MembraneDenture base plate is placed over mucous membrane acting as a pillow between supportive bone and denture base plate. Mucous membrane consists of two layers: mucosa and sub-mucosa layers. Mucosa is formed of an outer layer of strati-fied squamous epithelium and an underlying layer of dense connective tissue (lamina propria).

Submucosa is formed of connective tissue containing fat, glands and muscle cells and provides the transition of blood and nerve cells to support the mucosa. The thickness and

density of the submucosa directly support the soft tissues under the prosthesis, and in many cases submucosa forms the larger part of the mucous membrane. In a healthy mouth, submucosa adheres to the bone by means of the periosteum and is generally resistant against the pressure of the denture (Fig. 1.7). If the submucosa is tight, it resists the pressures; if it is loose, thin, traumatized and mobile, it will be weak against pressures.

Oral mucosa is examined in three groups:

1. Masticatory mucosa 2. Lining mucosa 3. Specialized mucosa

Attached gingiva, residual ridge and hard palate are cov-ered by masticatory mucosa which is covered by a keratin-ized layer changing due to the thickness of the outer surface (Figs. 1.8 and 1.9). Specialized mucosa covers the dorsal surface of the tongue and it is keratinized (Fig. 1.10). Lining mucosa is lacking in keratinized mucosa. Lips, cheeks, ves-tibular spaces, alveololingual sulcus, soft palate and unat-tached gingiva on the slopes of the residual ridge are covered by lining mucosa (Fig. 1.11).

Fig. 1.6 The maxilla shows a volumetric shrinkage and maxillary sinus are separated by only a thin layer of bone from the oral mucosa

Bone

Periost

Submucosa

Mucosa

Fig. 1.7 Mucous membrane


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The hard palate keratinized tissue and the median palati-nal raphe are rather thin and need relief to not cause pressure from the denture. The horizontal parts of the hard palate are the primary stress-bearing areas, while the rugae regions cre-ate an angle with the residual ridge and the secondary stress-bearing area. The part in the rest of the lingual gingival margin is called palatal gingival vestige. This region assists in the position of the posterior teeth during denture fabrication.

On residual ridges, the mucous membrane is keratinized tissue and is tightly attached to bone. There are no glands but there are dense collagen fibers. It is relatively thin but still sufficient for the prosthetic support. The residual crest is prone to resorption and is commended a secondary stress-bearing area. The inclined facial surfaces are loosely attached, cannot resist the pressures and provide little sup-port to the denture.

1.1.3 Anatomical Landmarks in Relation to Mandibular Denture

Anatomical landmarks in relation to mandibular denture are explained in details in Figs. 1.12, 1.13 and 1.14. The consid-erations for the mandibular impressions are generally similar to those of maxillary impressions with a few inceptions. The basal seat of the mandible is different in size and forms its maxillary counterpart. The submucosa in some parts of the mandibular basal seat contains anatomic structures different from those in the upper jaw. The nature of the supporting bone on the crest of residual ridge usually differs between the two jaws. The presence of the tongue complicates the impression procedures for the lower denture.

The available area of support from an edentulous mandi-ble is 14 cm2 while the same for the edentulous maxilla is

Figs. 1.8 and 1.9 Masticatory mucosa on maxilla and mandible

Fig. 1.10 Specialized mucosa

Fig. 1.11 Lining mucosa

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24 cm2. Supporting tissues of the mandibular jaw are shown in Figs. 1.15 and 1.16.

1.1.3.1 Crest of the Mandibular RidgeThe crest is covered by the fibrous connective tissue, but in many mouths the underlying bone is of the cancellous type without a cortical bony plate covering. The fibrous connec-tive tissue is favourable for resisting the externally applied forces, such as the denture. However, with the underlying cancellous bone, this advantage is lost (Fig. 1.17).

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Fig. 1.12 1: Retromolar pad, 2: buccal shelf, 3: posterior alveolar ridge, 4: anterior alveolar ridge, 5: lingual frenum, 6: labial frenum, 7: buccal frenum, 8: labial vestibule, 9: buccal vestibule, 10: masseter muscle area, 11: lingual vestibule

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Fig. 1.13 Mandibular ridge (lateral view): 1: retromolar pad, 2: buccal shelf, 3: posterior alveolar ridge, 4: anterior alveolar ridge, 5: lingula frenum, 6: labial frenum, 7: buccal frenum, 8: labial vestibule, 9: buccal vestibule

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Fig. 1.14 Mandibular ridge (lingual view): 1: retromolar pad, 3: poste-rior alveolar ridge, 4: anterior alveolar ridge, 5: lingual frenum, 6: labial frenum, 11: lingual vestibule, 12: mylohyoid ridge, 13: submandibular fossa

Figs. 1.15 and 1.16 Supporting tissues of the mandibular jaw: 15 Buccal shelf and 16 alveolar ridge

Fig. 1.17 Mandibular crest


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1.1.3.2 Retromolar Pad (Pear-Shaped Pad)The retromolar pad, as described by Sicher, is described as the soft elevation of mucosa that lies distal to the third molar (Figs. 1.18 and 1.19a). It contains loose connective tissue with an aggregation of mucous glands and is bounded posteriorly

by the temporalis tendon, laterally by the buccinators and medially by the pterygomandibular raphe and the superior constrictor muscle. The retromolar pad is quite important for the support and the peripheral seal. The mucosa of the retro-molar pad is usually attached gingiva. When dried with a

a

c

b

d

e

Fig. 1.18 Retromolar pad. (a) In the mouth, (b) on the impression, (c, d) on the model, and (e) on the denture

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gauze pad and examined, the mucosa is hard, smooth and dull. The lower denture should reach the distal side of the retromo-lar pad since it is important for the support and the peripheral seal. The upper border of the retromolar pad or the 2/3 upper part determines the occlusal plane (Fig. 1.19b). Approximately 2/3 of the retromolar pad should be covered by the denture; on the distal 1/3 is a loose tissue covered by salivary glands. Since the retromolar pad is rarely resorbed and decisive for the occlusal plane, it is an important element design.

If the residual ridge is weak and the peripheral seal is dif-ficult, it will be advantageous to extend the denture as a drop shape through the distal side of the pear-shaped pad. The drop shape is achieved by carving the model 1.5 mm in depth and 1.5 mm in width.

1.1.3.3 Buccal Shelf AreaThe buccal shelf is the bone area between the extraction sites of the molars and the external oblique line. In other words, the area between the mandibular buccal frenum and the anterior edge of the masseter is known as the buccal shelf. It is bounded medially by the crest of the residual ridge, anteriorly by the buccal fre-num, laterally by the external oblique line and distally by the retromolar pad. The buccal shelf forms the primary support for the mandibular denture as it is made primarily of cortical bone and generally lies perpendicular to the occlusal plane. The width of the buccal shelf area can range from 4 to 6 mm on an average mandible (Figs. 1.20 and 1.21) to 2–3 mm or less in a narrow mandible (Fig. 1.22). The buccal shelf is resistant to resorption due to the durable cortical bone structure and the stimulation of

Fig. 1.19 (a) Retromolar pad, (b) the relation between occlusal plane and retromolar pad

a b

Figs. 1.20 and 1.21 Buccal shelf is 4–6 mm in width on an average maxilla


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buccinator muscle attachments (Fig. 1.23). When the alveolar ridge is flat, the buccinator muscle mostly adheres to the crest of the ridge. Since the buccinator muscle is relatively resilient and inactive and the fibers of the muscle lie horizontally, it is cov-ered by the denture in this region. The buccal shelf area is a key factor for the stability of the mandibular dentures due to its large support area. Although all the slopes of the alveolar ridges are essential, buccal shelf area which is large, flat and more resistant to occlusal forces is the most important of all the regions. As the masticatory forces reach a right angle to the buccal shelf area,

the load-bearing capacity of the buccal flange is great and pro-vides excellent support against the occlusal forces (Fig. 1.24). Some of the fibers of the buccinator muscle are under the buccal flange; the insertion area of this muscle is close to the crest of the ridge. The attachment of the buccinator muscle lies parallel to the bone; therefore the denture is not effected by the contrac-tions of the muscle.

1.1.3.4 Posterior Alveolar RidgeThe posterior alveolar ridge is considered the primary area of support. However, when the residual ridge is weak, the buccal shelf plays a major role for support (Fig. 1.25).

1.1.3.5 Anterior Alveolar RidgeThe anterior alveolar ridge lies between the extraction sites of canines. This area is prone to resorption under forces and should be considered as a secondary support area (Fig. 1.26).

Fig. 1.22 Buccal shelf area in a narrow mandible

Fig. 1.23 Buccal shelf area

OCCLUSAL FORCES

TRANSFER OFTHE FORCES

Buccal raphe

Fig. 1.24 Masticatory forces reach the buccal shelf area with a right angle

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a

b

c

Fig. 1.25 (a–c) Posterior alveolar ridge area in different cases

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b

c

Fig. 1.26 (a–c) Anterior alveolar ridge area in different cases


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1.1.3.6 Lingual FrenumLingual frenum is a formation connecting the floor of the mouth to the alveolar mucosa and is located over the Genioglossus muscle. As the frenum consists of fibrotic con-nective tissue, they do not contract and expand as the mus-cles. They attach closely to the crest of the ridge. The lingual frenum is usually composed of a single narrow band, but

sometimes two or more bands and wider frenum can be observed (Fig. 1.27). The related area of the mandibular den-ture is prepared accordingly. The dentist should pay attention to this area during taking impression and adjusting the den-tures. Labial frenum is mostly single narrow fibrotic band but occasionally may consist of two or more bands (Fig. 1.28). On the other hand, lingual flange closure is rather important for the retention of the denture. Large opening of the frenum area on the denture will disrupt retention. When the lingual frenum is short, the patient cannot move his tongue anteriorly. In this case, a surgical procedure called frenectomy can be necessary.

1.1.3.7 Labial FrenumLabial frenum is a single narrow fibrotic band but occasion-ally may consist of two or more bands (Fig. 1.29). It is shorter, larger and less prominent when compared to the

a

b

c

Fig. 1.27 (a–c) Lingual frenum in different structures

Fig. 1.28 Short lingual frenum and irritation caused by insufficient reduction

Fig. 1.29 Labial frenum

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maxillary labial frenum. The activity of this area tends to be vertical, so the labial notch on the denture should be narrow (Fig. 1.30).

1.1.3.8 Buccal FrenumBuccal frenum is a single or double, wide or sharp V-shaped connection starting from the posterior of the canine and lying anteroposteriorly. It is closely related to the triangularis mus-cle (Fig. 1.31). Buccal frenum is generally on the level of first premolar, and it is the tendon attachment of the buccina-tor muscle. It is a single fibrotic band but occasionally may consist of two or more bands (Fig. 1.32a–e). The oral activi-ties in these areas are horizontal as well as vertical (i.e. grin-ning and puckering), thus needing wider clearance (Figs. 1.33, 1.34, 1.35, and 1.36). The contour of the denture should be a little narrow in this area due to the activity of the depressor anguli oris muscle (Fig. 1.37).

1.1.3.9 Labial VestibuleLabial vestibule is the area between the buccal frenums. If the frenum is lacking or the locations are different, then it is the area between the first premolars (Fig. 1.38). The lips should be supported by the artificial teeth and acrylic resin in the labial vestibule area. The posterior border of the area

extends through the buccal frenum. Labial vestibule area is limited with the connection area of the mobile and immobile mucosa inferiorly, alveolar ridge medially and lip laterally.

Fig. 1.31 Buccal frenum

LABIAL FRENUM

Fig. 1.30 Widening the labial area on the denture

Fig. 1.32 (a–e) Buccal frenum in different positions

a

c

e


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Fig. 1.33 Sufficient reduction on the buccal frenum area

Fig. 1.34 Insufficient reduction on the buccal frenum area

BUCCAL FRENUM

Fig. 1.35 The space prepared on the buccal frenum

Labial space

Buccal space

Fig. 1.36 The space prepared on the labial and buccal frenum

Fig. 1.37 Thinly prepared buccal flange border of the denture

Fig. 1.32 (continued)

b

d

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İncisive labii inferioris, the mentalis and the orbicularis oris muscles are in that region so the denture should not be thick-ened. The major muscle in this area is the orbicularis oris muscle. Since the fibers of this muscle lie horizontally, the borders of the impression should not be extended (Figs. 1.39 and 1.40). Mental muscle originating from the mental tuber-cule unites with the orbicularis muscle in the lower lip. It is a vertical muscle and is very active in some cases. This activ-ity is very important for the border moulding procedures. During taking impression, the lower lip should be slightly pulled anteriorly. Pulling the lip severely will cause taking the impression inaccurately, short labial flanges and loss of the hermetic seal due to the narrowing of the area. The for-mation of the other muscles effecting the mandibular flange is also in this region, but they are considerably thin and have minimal effect. The structure of the alveolar ridge is signifi-cant for the border moulding. If the ridge is normal and fine, the labial flange should be 1–2 mm (thick flange will inhibit the lips) (Fig. 1.41). If the ridge is flat, the flanges should be prepared thicker in order to provide hermetic seal and buccal support (Fig. 1.42).

Fig. 1.38 Labial vestibule area

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135 6 4

7

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Fig. 1.39 The muscles in relation to complete dentures. 1 Buccinator, 2 modiolus, 3 orbicularis oris, 4 levator anguli oris, 5 zygomaticus major, 6 zygomaticus minor, 7 levator labii superioris, 8 levator labii superioris alaeque nasi, 9 depressor anguli oris, 10 depressor labii infe-rioris, 11 mentalis, 12 risorius, 13 masseter

Fig. 1.40 The muscles in relation to complete dentures


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1.1.3.10 Buccal VestibuleThe width of this area depends on the buccal shelf and the buc-cinator muscle. It is also known as buccal pouch or buccal cavity, and the external oblique line which is a bony formation is situated in this area. The buccal shelf which is also present in the same area is a flat region and is used as a support area in severely resorbed alveolar ridges (Figs. 1.43, 1.44, 1.45, and 1.46). In order to provide proper support in the buccal flange area, the denture should be extended up to the outer border of the buccal shelf and the external oblique line. This area can be determined easily with palpation. In the external oblique area, the denture flange border can be extended only 1–2 mm (Fig. 1.47). The length of the buccal flange is not that much critical for the peripheral seal. The force of the cheeks pro-

Fig. 1.41 Labial border on a normal ridge

Fig. 1.42 Labial border on a flat ridge

Figs. 1.43 and 1.44 Buccal vestibule area

Fig. 1.45 Buccal vestibule area on the model

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vides the facial seal. In some cases, buccinator muscle can be active or strained; in this instance the entire buccal shelf can-not always be covered. Buccinator muscle consists of three muscles anatomically that have different innervations (Fig. 1.48). The middle fibers form the most active muscle as their main function is to control the food bolus during mastica-tion. The middle fibers unite diagonally in the corner of the mouth and named as modulus forming the orbicularis oris. The superior and inferior fibers are rather loose especially in the beginning area. Buccinator muscle starts from the buccal edges of the maxillary and mandibular ridges posteriorly and from the pterygomandibular raphe distally. Therefore, buccal shelf is completely covered in most instances.

1.1.3.11 The Effect Area of Masseter MuscleIt is the area behind the buccal region through the retromolar pad. The effect area of the masseter muscle lies on the lateral side of the retromolar pad (Fig. 1.49). This is being called as the “masseter groove”. This large and strong elevator muscle is located over the buccinator muscle and when the masseter mus-cle goes into action, it forms a straight line from the floor of the retromolar pad to the distobuccal area of the denture (Fig. 1.50). Border moulding should be made accurately in this area; other-wise excessive length may cause pain. Thus, the denture base should be narrow through the retromolar pad according to the anatomy of this area. The masseter muscle is an elevator mus-cle and closes the jaw; in such a situation, the denture should not move. Short flanges will cause the loss of support and sta-bility of the denture against lateral movements. An active mas-seter muscle will form a concavity on the distobuccal border, and a less active muscle will end up with a convex border.

Fig. 1.46 Buccal vestibule area supported by the lips

Buccinator Muscle

External Oblique Line

Fig. 1.47 The relation of buccal vestibule area with buccinator muscle and external oblique line

1

2

2

3

1a

1b

1c

5 4

Fig. 1.48 Major muscles effecting the labial and buccal flanges. 1 Buccinator muscle. a Superior fibers, b middle fibers, c inferior fibers, 2 orbicularis oris muscle, 3 modiolus, 4 depressor anguli oris, 5 mental muscle


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1.1.3.12 Mylohyoid RidgeThe mylohyoid ridge is the origin of the mylohyoid muscle. The distal end of the ridge is close to the crest of the alveo-lar ridge while the anterior part is close to the lower border

of the mandible. Determining the acuteness and promi-nency of the mylohyoid ridge is important. A prominent mylohyoid ridge may prevent making a correct lingual flange and may cause pain during mastication (Figs. 1.51, 1.52, and 1.53).

1.1.3.13 Pterygomandibular RaphePterygomandibular raphe or ligament originates from the pterygoid hamulus of the medial pterygoid lamina and adheres to the distal edge of the mylohyoid ridge (Fig. 1.54). It originates partially from the buccinator muscle laterally and from superior constructor muscle mediolaterally. This raphe which has features of a tendon is covered by a mucous membrane called plica pterygomandibularis.

When the mouth is opened wide, it is stretched and a tense plica comes out between pterygoid hamulus and the retro-molar pad. The stretched raphe results in the rising of the upper parts of the retromolar pad, and this is one of the fac-tors effecting the stability of the mandibular denture nega-tively. The pterygomandibular raphe may be very prominent in some cases, so in the maxillary denture, a small notch can be prepared (Fig. 1.55).

a b c

Fig. 1.50 The effect of the masseter muscle on the distobuccal flange. a Middle level activity will form a straight line, b active muscle will form a concavity, c inactive muscle will form a convexity

Figs. 1.51 and 1.52 The appearance of mylohyoid ridge area in the mouth

Fig. 1.49 Masseter muscle effect area

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Fig. 1.53 Mylohyoid ridge area

Fig. 1.54 Pterygomandibular raphe

Fig. 1.55 Prominent pterygomandibular raphe attached to the buccal frenum

Fig. 1.56 Submandibular fossa

Figs. 1.57–1.59 Submandibular fossa located under the mylohyoid ridge


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1.1.3.14 Submandibular FossaSubmandibular fossa is a concave area which is located dis-tally under the mylohyoid ridge in the mandible (Figs. 1.56, 1.57, 1.58, and 1.59).

1.1.3.15 Lingual VestibuleIt is impossible to achieve peripheral seal without an accu-rate lingual flange. Many dentists are not aware of the sig-nificance of the peripheral seal. The mandibular denture can have a retention as much as the maxillary denture by provid-ing an accurate peripheral seal. Therefore, learning the anat-omy of the related area in details and using the most suitable impression technique for the best seal in the lingual flange area of the denture are required (Figs. 1.60, 1.61, and 1.62). Figure 1.63 shows the old denture with short flanges and the new denture with the extended flanges.

The big differences between lingual vestibular view and the denture flanges emphasize on knowing the oral anatomy and the necessity of using this information during taking impression (Figs. 1.64 and 1.65). It can be easily examined when divided into three areas.

1. Anterior VestibuleSublingual crest area or anterior sublingual gland area (Fig. 1.66)

2. The Middle VestibuleMylohyoid area (Fig. 1.67)

3. The Distolingual Vestibule Lateral throat form or retromylohyoid fossa (Fig. 1.68)

In order to understand the lingual area of the denture, pro-vide retention and use the accurate impression techniques, the anatomy of this area should be well-known.

1. Anterior Lingual Vestibule Sublingual Crest Area or Anterior Sublingual Gland AreaThis area extends from the lingual frenum to the mylohy-oid ridge which curves down below the level of sulcus. The depression of the premylohyoid fossa can be pal-pated here. This area is mainly influenced by the genio-glossus muscle, lingual frenum and the anterior portion of

Figs. 1.60 and 1.61 Lingual vestibule area

Fig. 1.62 The appearance of lingual vestibule on the modelFigs. 1.57–1.59 (continued)

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a

d

b

c

Fig. 1.63 (a) A patient with a flat ridge, (b) old denture, (c) new denture, and (d) two different dentures


complete denture prosthodontics

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