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ProsthodonticsSept 2012prosthodontiCs ProsthodonticsgolDen proportIon In

prosthoDontICspart-1

1Dr. Parul Singh P.G Student

2Dr. Manish RaiConsultant

1Dr. Ajay Singh Prof. & H.O.D.

1Department of Prosthodontics1Sardar Patel Postgraduate Institute of Dental and Medical Sciences,

Lucknow, India2SGPGI Lucknow, India

There is substantial evidence that even in Pre-Civilization era; human beings were conscious and strongly aware of beauty. Crude cave paintings point out this fact and so does old civilizations across the globe eg. Mayan, Egyptian, Mesopotamian, Greek, Indian, and Chinese.Esthetics, proportion, form and function go hand-in-hand. This was realized by humans very early, since, the inception of civilization, and the very fact was appreciated by great artists like Leonardo da Vinci and Michelangelo. This mystical (1:1.618) proportion was, for long, termed as Magical/Divine Proportion and later on Golden Proportion, which was appreciated in nature, both in plants and animals. It was also used in architecture. Attention to existence of Golden Proportion in dental arches was drawn by Lombardi1 and Levin2 (1978). Marquardt discovered the Golden Rectangle i.e., height of central incisor is in Golden Proportion to the width of the two central incisors. This Golden Proportion is also used in reconstruction of maxillofacial defects eg., eye, ear, nose, and fingers. The Golden Proportion principle is also used to design implant supported prostheses. Ward3 demonstrated the Recurring Esthetic Dental Proportion (RED) claiming it to be more consistent and practical to use in prosthodontic rehabilitation. This paper traces the origin of the Divine Proportion and gives an overview of the adaptation of the Golden Proportion in art and architecture in the middle ages. The paper also gives us an insight of how the Golden Proportion has been used in dentistry, particularly Prosthodontics, in the fabrication of Removable, Fixed, Maxillofacial, and Implant supported prostheses; and also been adapted in newly developed

electronic techniques like 3-D imaging and interactive software.

keywords: Golden Proportion, Divine/Magical Proportion, RED Proportion, Nature, Art/Architecture, Golden Rectangle, Esthetics,

Perception, Dental Arch, Prostheses, Interactive software.

IntroductIonBeauty and esthetics have a strong psychic correlation with health, power, success, and wealth. This can easily explain the thriving global multimillion beauties and esthetic industry.

If we closely observe the beauty of nature, art or teeth, we can easily discover a common link, that of a “Divine/Golden/Magical proportion”.

The “Golden Proportion”, has been suggested as a possible mathematical analysis or tool to measure or analyze beauty, and to evaluate smile esthetics. Hence, the Golden Proportion serves as a cornerstone of smile design and forms the basic elements of esthetic dentistry.

Esthetics is defined as the restitution of form and function in harmony with the biologic environment. Dental esthetics is based on simple mathematical principles, dating back to antiquity.

The two main objectives in dental esthetics are-

To create teeth of pleasing inherent proportion, in themselves, a. as well as, to each other.

To create a pleasing tooth arrangement in harmony with the lips, b. gingiva, and face.

In the current scenario, it is imperative for a Prosthodontist, or for that matter, any esthetic/restorative dentist, to appreciate the elements of smile, and to apply the basic mathematical logic in creation of an esthetic and harmonious restoration.

A) ORIGIN OF THE GOLDEN PROPORTION

AristotleXX 2, the great Greek Philosopher, is credited with the earliest recorded appreciation of the power of the Magical Proportion in esthetics, in the 4th century B.C.

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PythagorasXX 1, in the 6th century B.C., is considered the creator of the Golden Proportion-1:1.618 or 0.618 which was also confirmed by Euclid, another Greek geometrician.PhidiasXX 2 in approximately 400 B.C. gave the concept of the Golden Mean and the letter “phi” or 1.618.Leonardo PisanoXX 4, the Italian mathematician, nicknamed “Fibonacci”- gave a complementary view of the Golden Proportion- in his number series (the enigmatic Fibonacci sequence). In this number series, each subsequent number is the sum of the previous two numbers eg. 0 1 2 3 5 8------.Division of any two numbers yields the Magical/Golden proportion 1.618 or phi. The Fibonacci series represents the exponential growth of all living things eg. Living cells.Ancient Greek architecture, eg. classic Parthenon temple uses the XX

Golden Proportion in its archways, as does, the drawings of Leonardo da Vinci eg. Pentacle :-the formation by the outstretched limbs5.The Golden Proportion 1.618:1 is that the smaller part is about 62% of XX

the larger portion. The ratio is unique, in that, the ratio of the smaller part to the larger part is the same as the ratio of the larger part to the whole.This Divine Proportion was very much recognized and appreciated by XX

the Pagan tribes in ancient Europe and Asia, in the Pre Constantinople Era (the Dark Ages)5.

Kepler was the first to coin the term “Divine Proportion”XX 5.

Lombardi was the first to propose the application of the Golden XX

Proportion in dentistry-an optimized dentofacial composition from the frontal aspect, the width of central incisor and lateral incisor to canine are in Golden Proportion1.

Levin (1978) also demonstrated the widths of the central incisor, XX

lateral and canine, to be in Golden Proportion2.

Marquardt discovered the “Golden Rectangle” i.e., the height of the XX

two central incisors5 (Fig no. 1).

B) RELATIONSHIP WITH NATURE AND HUMAN

Golden Proportion is everywhere around us, in the plant (Fig no. 2) and XX

animal kingdoms2 (Fig no.3)

eg. In the wings of a butterfly, spirals of the Sunflower, Pine cones, Mollusc shells, and even the DNA molecule2.

Geometric progressions are commonly seen in the Snail shellXX 5 (Fig no. 4).

Fig 1: The Golden Rectangle. Fig 2: Photograph of flower with Golden Mean Gauge superimposed on the dominant landmarks.

Fig 3: Golden Proportion in Peacock’s feather, insect’s wing and leaves of Rose.

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Fig 4: Geometric progression and the spiral.

Geometric progressions are evident in the octave progression in XX

music, as also, in the coils of a ship’s rope5.

The connections between the Fibonacci series, the Golden Proportion, XX

polygons, Vedic Hindu Square, Cabbala number system and Islamic art are illustrated beautifully in the Language of Pattern5.

Leonardo da Vinci, by his drawings of human cadavers, demonstrated XX

that the human body, the masterpiece of God’s creation, obeyed the Divine Proportion5.

Artists ranging from Da Vinci to Michelangelo have used the Golden XX

Proportion on their art5 (Fig no. 5).

pictures to illustrate the Golden Proportion. He proposed the following concepts establishing the existence of a universal standard of Facial Beauty based on Golden Proportion.

There is a universal standard for facial beauty regardless of a. race, age, gender etc.

The universal standard is based on a Golden Proportion which is b. universal and synonymous with beauty.

All living organisms, including human beings, are genetically c. encoded to develop and conform to the Golden Proportion.

Facial and body disproportions occur more due to environmental d. factors than to genetic factors3.

In a relaxed face, when the teeth are not touching together, the lip line XX

divides the lower third of the face into the Golden Proportion-i.e., the chin to lip line distance (larger portion) to the lip line to the bottom of the nose (smaller portion). This is the Willis method to determine the length of the central incisor, when selecting size of the artificial teeth and to determine RR3(Fig no. 6).

Fig.5: Drawing of Mona Lisa.

C) RELATIONSHIP WITH THE FACEMack M.R. discussed the use of Golden Proportion in treating the XX

dentition and esp. in the lower third of the face3.

Jefferson Y. used cephalometric tracings and computer generated XX

Fig.6: The Golden Mean Gauge showing the lip line as well as the incisal edge of the incisors.

Greber’s embryogenetic philosophy states that the nose is the most XX

essential guide in selecting the proper size for the maxilaary incisors (because the four maxillary incisors have a common Frontonasal origin as the nose).

One of the proportions suggested in this philosophy is the proportion of the interalar width (IAW) and the width of the root of the nose (WRN)-as to that, of the central incisor width (CIW) to the lateral incisor width (LIW)1.

The width of the smiling lips (between the two corners of the mouth) XX

is equal to the distance between the bridge of the nose and the width of the eye1.

The white part of the eye is in Golden Proportion to the distance XX

between the eyes across the bridge of the nose, and als to the white of the teeth1.

D) RELEVANCE OF GOLDEN PROPORTION IN PROSTHODONTICS

Individual tooth size is the building block of a smile. Intra arch tooth XX

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relationship proportions eg. RED proportion can be used to arrange the teeth in a pleasing smile. It is easier in Removable prostheses, where the artificial teeth are being selected and arranged. However, in natural dentition, combined (multidisciplinary) approach eg. Orthodontics, Periodontics, Oral Surgery-may be required prior to esthetic restorative dentistry6.

Ricketts, (1954) was the first to devise the Golden Proportion Calipers, XX

to validate the existence of the magical proportion in natural dentition3 (Fig no.7).

Levin devised the Golden Proportion Grid to evaluate and to develop XX

well proportioned teeth1 (Fig no.8 &9).

Esthetic tooth dimensions can be evaluated and treated by similar XX

numerical analysis6 (Fig no. 12-a, b, c,&d).

Fig 9: The Golden Proportion Grid.

La Corbusier developed the Golden Proportion Scale (Fig no. 10) based XX

on the golden sections of the human body1.

3 4Fig.7: Calipers showing that the central incisor is in golden proportion with the lateral and the lateral incisor is in golden proportion with the

canine.

Fig No. 12(a)-Prototype proportion gauge; a Siamese twin instrument tip with preset markings notched into the surface with measurements indicating a

predetermined 78% width to length proportion.

Fig No.12 (b)-Surgical crown lengthening was provided additional clinical crown exposure; the proportion gauge was used to position the FGM of the soft tissue flap

apicocoronally.

Fig No.12 (c)-Preoperative smile of patient requiring aesthetic crown lengthening to restore proper individual tooth dimensions / proportion and decrease gingival

display.

Fig no.8- Golden Proportion grid illustrating how well the teeth fit the Golden Proportion spaces. Note that the neutral buccal space

is in the Golden Proportion to the teeth showing in the smile

Fig no.10- Golden Proportion ruler.

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The Proportion Gauge represents a mathematical evaluation of tooth XX

size ranges. The Proportion Gauge is designed as a double ended instrument with a T-bar and In-line tip screwed into the handle at opposing ends6. (Fig no. 13).

The T-bar tip features an incisal edge position (incisal stop), when the XX

tooth is oriented with the tip accordingly, the evaluation of its length and width dimension can be done6.

Utility gauges enable the clinician to diagnose and correct tooth size XX

discrepancies. The color coded marks on the horizontal axis (width) of the T-bar tip are aligned to the corresponding color markings on the vertical axis (length) of the instrument6 (Fig no. 14 b&c).

Fig 13: T Bar Proportion Gauge.

height and width, gingival shape and contour, connectors and embrasures, black triangular holes and tooth shade7.

Sarver reinforces the view of Frush and Fisher, in that, the ideal smile XX

arc, have the maxillary incisal edges at a parallel curvature with that of the lower lip7.

Husley –first quantified the smile arc as a ratio to the lower lip, with XX

the perfect/ideal ratio being one7.

Frush and Fisher-drew attention to the presence of the Buccal Corridor XX

space-a negative space created between the buccal surfaces of the posterior teeth and the inner wall of the cheek. Optimizing the amount of buccal corridor is critical to complete denture esthetics7.

Husley-also attempted a ratio for the buccal corridor space i.e., a ratio XX

between the corners of the mouth7.

Roden, Johnson et. al studied computer simulations of Husley’s XX

finding’s, on a visual analog scale7.

Contrary to the Golden Proportion concept, Lombardi and Ward XX

described a “continuous proportion” or “repeated ratio”, established between the width of the central and lateral incisors3 (Fig no. 15 a&b).

Fig.14: (b)-In-Line tip width utility. (c) I n-Line tip length utility.

E) BUCCAL CORRIDOR, SMILE ELEMENTS, SMILE CONTENTS

Sarver and AckermanXX 7 gave three basic requirements for assessing dental and facial esthetics.

A dynamic and static 3 dimensional evaluation of the face.a.

Determination of the lip-tooth relationships and anterior tooth b. display at rest and during facial animation (computer simulation using digital imaging methodology).

Analysis of the dental and skeletal volume of the face and its c. effects on the soft tissue facial mask7.

The esthetic issues should be matching with the patient’s concerns XX

and priorities. The hierarchy of esthetic issues would be –

The face in all 3 spatial planes (Macro esthetics) eg. Facial a. asymmetry, excess or diminished face height, advanced or receeded mandible.

Smile framework (Mini esthetics)-bordered by the lips on smile b. animation, amount of gingival showing in smile, excess buccal corridors.

The teeth (Micro esthetics)- assessment of tooth proportions in c.

Fig.15: (a)& (b)- RED Proportion.

Ward termed it as the “Recurring Esthetic Dental (RE) proportion”, XX

recommending it to be more consistent than the Golden Proportion, when moving distally in the arch3.

rEfErEncEsMinoo Mashid, DDS, MS, Alireza Khoshcaghti, DDS, Masoud 1. Varshosaz, DDS, MS, Naser Vallaei, MS-Evaluation of “Golden Proportion”in Individuals with an Esthetic Smile, Journal of Esthetic and Restorative Dentistry-2004; 16(4):185-192.

A Gopinadh, Sreedevi, I. Premanandan, G. Manmohan-Fixed Prosthetic 2. Rehabilitation in Esthetic Zone-Report of Two Cases, Journal of Orofacial Sciences-November 2009; 1(2):21-24.

Ravudai Singh, Kusum Datta-The Golden Proportion-God’s building 3. block for the world, The Journal of Indian Prosthodontic Society -2008; 8(1):6-9.

Edwin I. Levin, B.Ch.D. - Dental esthetics and the golden proportion, J 4. Prosthet Dent-September 1978; 40(3):244-252.

Tongue Sulun, Dr Med Dent/Ugur Ergin, Dr Med Dent/Necat Tuncer, 5. Dr Med Dent-The nose shape as a predictor of maxillary central and lateral incisor width, Quintessence International-September 2005; 36(8):603-607.

More references are available on request

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