Oral Structure & Biology

Ralf J. Radlanski

• Publisher: Quintessence Publishing Co, Inc
• Year: 2019
• ISBN:
  9780867159059
• Topic: Medizin
• Subtopic: Zahnmedizin

Knowledge of the structures of the orofacial region from the macroscopic scale to the molecular level and pathologic changes to those structures enables practitioners to successfully treat patients or seek treatment options. This book presents the structural biologic foundations underpinning dental and oral medicine. Beginning with an overview of the anatomy of the mouth and moving on to the evolution of the oral structures and pre- and postnatal development of the oral cavity, related facial structures, and the teeth, this book describes each part of the orofacial region in terms of its morphology, tissue structure, cellular properties, and development. Functioning as both a textbook for dental students and a reference manual for experienced clinicians, this compendium of the structural biologic foundations of clinical work in dental and oral medicine allows practitioners to integrate current research in molecular biology into a solid framework of knowledge.

CHAPTER 1

Definitions, Objectives, and Clinical Relevance

The difference between health and sickness can be seen even in the mouth, based on changes in form and structure from the macroscopic to the microstructural. Knowledge of the structures and pathologic changes to those structures enables practitioners to successfully treat patients or seek treatment options. This book presents the structural biologic foundations underpinning dental and oral medicine.

The mouth encompasses the area between the lips and the throat. All the parts are described in terms of their form, composition, tissue structure, and cellular properties. In many cases, the structural makeup only becomes comprehensible once its origins are understood. This is why aspects of development are described, ranging from embryonic development to changes in old age.

Clinical examination and treatment are influenced by patient morphology as understood through visual and haptic impressions. However, these aspects are based on the microstructure of the organs and tissues. Because this structure is not visible to the naked eye in most cases, our knowledge relies on rigorous examination using radiology, light microscopy, and electron microscopy. Knowledge is also gained through objective experiments. However, patience and sometimes substantial investment in laboratory equipment are needed to bring patterns and connections to light.

When dealing with a patient, the full range of knowledge and all available facts may not be needed. Nevertheless, the more fundamental knowledge practitioners have on which to base their work, the more successful they will be. People should not be frustrated if the odd fact escapes them every now and then. Understanding the connections between the facts is what matters most. However, these connections are only revealed after a thorough study of the facts. It is our duty to our patients to know exactly what we are doing. Patients will rarely go along with suppositions and a trial-and-error approach.

A large proportion of the material presented in this book is based on knowledge that was gained using human subjects. However, some experiments can only be done in animals. Not all findings are transferable to humans; where statements in the text apply only to a specific experimental animal, a note is given to that effect. To show links between fundamental knowledge about structural biology and patients, clinical notes are given where appropriate. Because our knowledge is still incomplete, reference is made in several places to unanswered questions.

Nevertheless, most morphologic and microstructural knowledge can be regarded as accepted fact. New findings in this sphere are rare. While modern research focuses on questions of molecular biology, structural biology remains the foundation. Furthermore, we can only meaningfully integrate biochemical knowledge if we know where the reactions take place, the physical distances that promote or inhibit a reaction, and the structural settings nature has provided for this purpose.

At present, we are witnessing a virtual explosion of knowledge about the signaling molecules cells use to communicate with each other during embryologic development and postnatal remodeling and healing. The same transcription and growth factors crop up time and again in relation to diverse tasks in different tissues and organs and at different phases of development. Table 4-1 presents a selection of these factors. Though research in the field of molecular developmental biology is very much in a state of flux, it seemed necessary to incorporate this aspect of structural development into this textbook, despite its potential to soon be outdated and deemed incorrect because of more recent findings. However, at least a fundamental understanding of molecular-oriented medicine has been established and is already being applied to some extent in dental and oral medicine on questions of bone formation, osseointegration of implants, and regeneration of the periodontium.

The more we intervene in the biology of the cell at the molecular level, however, the more side effects and difficult-to-manage repercussions come to light. Therefore, everyone who works in this area must act responsibly. The content of the individual chapters sometimes overlaps with that of other chapters, and in places cross references to other chapters are given. The chapters describing the individual structures in detail are preceded by a few introductory overview chapters.

Chapter 2 first explains the macroscopic anatomy of the mouth and its surrounding cranial structures and deals with orientation in the oral cavity. Each individual tooth is described here. Chapter 3 presents a brief assessment of the importance of evolutionary theory to explain the orofacial structures. Chapter 4, which explores general principles of morphogenesis, should be regarded as an introductory overview. Chapter 5 describes in detail the prenatal and postnatal development of the orofacial region. Tooth development is the subject of chapter 6. The reader will discover here that much more is known about the formation of the dental crown than about the formation of the roots. These gaps in knowledge are only partially filled by current research.

The structural makeup of dental enamel, dentin, root, and pulp is described in chapters 7, 8, and 9. Although dentin and pulp are structurally connected, each is assigned its own chapter because the structural similarity mainly relates to the odontoblasts as the outermost layer of the pulp and to the apposition of predentin as the innermost layer of dentin. Innervation of the dentin also involves a structural overlap with the pulp because the nerves extend from the pulp into the dentinal tubules and the content of the dentinal tubules may transmit stimuli from the periphery of the dentin into the pulp. Apart from these overlapping aspects, dentin and pulp are such different tissues that separate chapters were preferable. Chapter 10 is another introductory overview, dealing with the different structures of the periodontium that functionally form a unit, but they are discussed in their own chapters (chapters 11 to 13 on the cementum, periodontal ligament, and alveolar bone) because of their specific composition.

Chapter 14, concerning the oral mucosa, inevitably became a sizeable chapter; this shows how differently structured the various regions of the lining of the oral cavity are. The gingiva, as part of the marginal periodontium, is discussed in this chapter because it is part of the lining of the mouth. The salivary glands are given their own chapter 15. Because the mouth region is an extensive opening of the body to the outside world, the immune system has particular importance in this region, as is reflected structurally in the tissues. This is why a detailed description of the immune system warrants its own chapter, 16. In chapter 17 on the development of the dentition and eruption of the teeth, aspects of tooth development are picked up again from chapter 6. However, because aspects of the periodontium, jawbone, and oral mucosa play roles in eruption of the teeth, it makes sense to describe these toward the end of the book. Chapter 18, about the temporomandibular joint (TMJ), stands alone in terms of the description of its structure, but in terms of its formation the TMJ can only be understood in connection with the development of the face. Functionally, it is closely connected to development of the dentition and occlusion, so this chapter usefully concludes the description of oral structural and developmental biology.

CHAPTER 2

The Mouth and Its Parts

This chapter provides a brief introductory guide. References in the text direct the reader to other chapters in the book that contain detailed descriptions. In addition, reference is made to textbooks for further reading and to atlases of anatomy. It can also be helpful when reading this chapter to hold a mirror in your hand and look at the structures being described in your own mouth.

Directional Terms

The nomenclature used in medicine and dentistry primarily has a Latin/Greek origin. Before embarking on an anatomical description, it is important to explain the positional and directional terms as well as the fundamental concepts (Fig 2-1 and Table 2-1). These positional and directional terms are clear and unambiguous because they pertain to the body and apply regardless of whether the patient is standing, sitting, or lying down.

Fig 2-1 Oral cavity with the most important directional terms identified (see Table 2-1).

Table 2-1Positional and directional terms

Face and Mouth

The human face has general characteristics that are common among all members of the species. Nonetheless, there is so much variation in facial features among individuals that we are able to recognize people purely from their faces. The interaction of anatomical structures and the extent to which they vary contribute to this individuality.

The bony structures form the facial skeleton that supports the overlying soft tissue. The contour and sturdiness of the masticatory and facial muscles and the distribution of the subcutaneous fatty tissue make a huge contribution to the shape of the face. The teeth also have a significant influence on the human face. The lips lie against the anterior teeth, while the posterior teeth support the mandible against the maxilla and, in so doing, determine the height of the lower face.

Sizeable deviations in tooth position and tooth loss can thus have an adverse effect on facial esthetics. The increased wrinkling of the facial skin in old age is due not merely to the aging of the skin itself but also to age-related changes affecting the teeth, including positional changes, abrasion, and tooth and bone loss.

Externally, the mouth is bounded by the lips. Anatomically, the lips are the area above and below (cranial and caudal to) the vermilion border. The vermilion border itself appears red because there is no thick horny layer of skin in this area and thin blood vessels are able to show through the thin epithelium (see chapter 14). A vertical furrow known as the philtrum runs down the middle of the upper lip below the nose. At its lower edge, the margin of the lip describes a curve known as the Cupid’s bow. The angles of the mouth are indented to varying degrees depending on muscle tension.

To the right and left of the wings of the nose, the nasolabial groove (or sulcus) forms the border between the cheeks and the top lip. The labiomental groove runs crosswise, usually in a slightly sweeping curve, between the lower lip and the chin. How pronounced these grooves are differs from one individual to another and varies with soft tissue thickness, muscle tension, and age.

Oral Cavity

Oral vestibule

The dental arches with their alveolar processes delineate the oral vestibule (vestibulum) from the actual oral cavity (Figs 2-1 and 2-2). Roughly level with the premolars, a buccal (cheek) frenum spans each quadrant. In the maxilla and mandible, a corresponding labial frenum runs from the area between the two central incisors to the inside of the corresponding lip. The formation of the oral vestibule is described in chapter 6.

Fig 2-2 View of the occluding dental arches with the adjacent soft tissue parts of the oral cavity: anterior view (a) and right lateral view (b).

Clinical note

Orthodontic plate appliances, which extend into the vestibule, and fu...

Table of contents

• Cover
• Halftitle Page
• Title Page
• Copyright Page
• Contents
• Preface
• 1 Definitions, Objectives, and Clinical Relevance
• 2 The Mouth and Its Parts
• 3 Evolution
• 4 Morphogenesis
• 5 Development of the Oral Cavity in Relation to Facial Development
• 6 Tooth Development
• 7 Dental Enamel
• 8 Dentin
• 9 Pulp and Root
• 10 Periodontium
• 11 Cementum
• 12 Periodontal Ligament
• 13 Alveolar Bone and Jawbone
• 14 Oral Mucosa
• 15 Salivary Glands
• 16 Immune System
• 17 Development of the Dentition and Teeth Eruption
• 18 Temporomandibular Joint
• Index