A Survey of Modern Dental Care Among MIT Freshmen

Owen W. Kite,* DMD, and Lennard T. Swanson,f DMD, Boston

A survey of modern dental care among MIT freshmen

Of 913 students from 16 to 20 years old who were given dental examinations, one in four had incipient gingival disease, and the overall average DMFT rate was 9.6. Only 42 per cent of the students had de­ tectable tooth decay controlled, and few had received needed periodontal care. Of these students, 167 had received or­ thodontic care for an average of 2.9 years. Malocclusion in a group having all per­ manent teeth was from 61 to 71 per cent, depending on the criteria used.

Almost 1,000 freshman students from 16 to 20 years old are admitted each year to the Massachusetts Institute of Tech­ nology (MIT) from throughout the United States and some foreign countries. They are a social and economic cross sec­ tion,1 the major bias being intellectual selection. Their total dental status is also a cross section and reflects their past den­ tal problems and the care they have re­ ceived. Their status reflects the success or failure of today’s approaches to oral health. At this age, decay has been active on the permanent dentition for four to ten years; early periodontal disease exists, and the adult occlusion is established. This study is an attempt to compare the

practical results of modem dentistry with the theoretical problems. Previous reports on college groups have described dental decay,2'6 gingival conditions7 and occlu­ sion.8-9 METHODS

We obtained the data by participating in the physical examination of the en­ tering freshman class. We used mirror and explorer in a fully equipped two-unit dental clinic with adequate lighting. Standard bitewing roentgenograms were taken with a commercial dental roentgenographic unit. W e completed all exami­ nations, roentgenograms and questions. The DMF count, based on 28 teeth, is a recognized method for assessing decay rates.10 Unanimity does not exist, how­ ever, in assessing the periodontal status. Whereas decay is a destruction of one specialized tissue, periodontal disease in­ volves epithelium, connective tissue and alveolar bone with great variation in rate and degree of tissue involvement. Many methods for recording periodontal disease have been proposed,9'19 and there has been much discussion20'26 of the disad­ vantages of these methods and the need for a uniform epidemiologic index for periodontal disease. This study required a qualitative estimate. Because inflamma­

K ite and Swanson: M O D ER N DENTAL CARE • 1143

T a b le 1 • G e o g ra p h ic a l distribution o f D M F T rates o f M IT freshmen

N o. of students

Mean DMFT scores

Standard deviation

Students with 0 DMFT (% !

Students with fluoride experience (no. & % l

N e w England

141

11.3

5.59

2

20 (12%)

Middle Atlantic

263

10.0

5.05

3

48 (15%)

Southern

107

8.9

5.5)

8

20 (16%)

Midwestern

Region*

134

9.3

5.42

9

40 (23%)

Western

86

8.5

5.42

8

13 (13%)

Foreign

41

8.1

6.50

9

9.6+

5.32+

6+

772

Total

0 141 (1 5 % t)

*New England—Maine. Vermont, Massachusetts, Rhode Island, New Hampshire; Middle Atlantic—New York, New Jersey, Pennsylvania, Delaware, Maryland, District of Columbia; Southern—Virginia, West Virginia, North Carolina, South Carolina, Georgia, Florida, Alabama, Mississippi, Kentucky, Tennessee, Louisiana, Arkansas, Texas, Oklahoma; Midwestern—Ohio, Indiana, Illinois, Wisconsin, Michigan, Minnesota, Iowa, Missouri; Western—North Dakota, South Dakota, Nebraska, Kansas, New Mexico, Colorado, Wyoming, Montana, Idaho, Utah, Arizona, California, Oregon, Washington, Nevada; Foreign—countries outside United States. fAverage.

tion is the prime gingival disturbance in youths, we estimated its presence or absence and degree of redness, swelling and bleeding. A score of 0 was given to absence, 1 to mild and 4 to severe degrees of each, and the three values for redness, swelling and bleeding were totaled to pro­ vide a 0 to 12 scale. Our scale corre­ sponds to a 0 to 2 value of the Russell Index or a 1 to -6 value of the papillary marginal attached (PMA) Index. Debris and calculus also were recorded as absent, slight or severe. Bitewing roentgenograms were exam­ ined to determine the condition of inter­ dental bone. The configuration was classi­ fied as arched, flat or concave, and the amount of resorption from cementoenamel junction was measured in milli­ meters. The following were observed directly: Angle classification of molar and cuspid teeth, anterior crowding, horizontal and vertical overbites and cross bites. Students were asked about their orthodontic and periodontal treatment experience. RESU LTS

A total of 913 freshmen, over 90 per cent of whom were 17 to 18 years old, had completed DMFT counts.

Table 1 summarizes the results accord­ ing to geographical region. The overall average DMF rate is 9.6. The New England and Middle Atlan­ tic states have the highest decay rates and, by far, the smallest number of per­ sons with decay-free teeth. The small number and widely scattered origin of the foreign students make comparisons difficult, and their lower decay rate may be due to the high number of caries-free individuals. Listed separately are 141 students (15 per cent) who had some exposure to fluoride. Information concerning the type of fluoride exposure was so varied and in­ definite that a further analysis was im­ possible. The reported caries experience of MIT freshmen could differ from reports of others because of differences in data col­ lection and evaluation.26 Knutson27 pointed out that DMF counts are, at best, general approximations. Surveys of similar groups show DMF rates of 9.70 to 13.8 with 1.17 to 3.22 per cent decay-free individuals.4'6,28 The M IT group with a DMF of 9.6 and a standard deviation of ± 5.32 is com­ parable. The geographical distribution of the M IT students’ decay rate is comparable

! 144 • J. A M ER . DENT. AS S N .: V ol. 70, M ay 1965

Table 2 • Comparison of clinical and bltewing d e ­ tection of dental caries of M IT freshmen without fluoride exposure Decay clinically present

Decay clinically absent

Total

Decay present radiographically

150 (21%)

180 (26% )

338 (48%)

Decay absent radiographically

73 (10%)

300 (42% )

373 (52% )

Total

223 (31%)

488 (69% )

711* (100%)

*Slxty-one refused roentgenograms.

to other reports. Nizel and Bibby29 and Dunning30 found that New England and the Middle Atlantic states had the highest decay rates, whereas southern, midwestem and western regions have three to four times the percentage of caries-free individuals found in the New England and Middle Atlantic states. The highest single frequency in the group exposed to fluoride is at zero DMFT, whereas the zero DMFT in the group without fluoride exposure is the sixth largest. Table 2 compares the decay found by clinical examination alone with that

Table 3 • Ratios of filled and missing teeth, by region, of M IT freshmen without fluoride exposure Filled ratio FsDMF

Region

No. of stud­ ents

Less than 100%

%

Missing ratio M:DMF O ne or more miss­ ing

%

N e w England

141

69

49

24

17

Middle Atlantic

263

97

37

12

5

Southern

107

27

25

10

9

Midwestern

134

46

34

8

6

Western

86

27

31

3

4

Foreign

41

21

51

5

12

772

287

Total ‘ Average.

37 *

62

8*

found by roentgenographic examination alone. Most significant is the number of students free of active decay by clini­ cal examination who had active lesions on the roentgenograms. One hundred and eighty-eight students would have had higher DMF counts if roentgenographic examinations had been included in the total—an increase of 84 per cent. The use of roentgenograms alone in detecting decay would have shown a total of 338 individuals with decay as opposed to 223 by clinical methods alone. Table 3 indicates the care received ac­ cording to geographical regions. The filled ratio is the proportion of filled lesions to the total DMF scores and should have a value of 1 if the count is above 0. Clini­ cal examination showed approximately 37 per cent had teeth to be filled, and 8 per cent had teeth missing—both figures indicating needed care. A total of 12 per cent had none of their DMF count in the filled category. New England and for­ eign students figured most prominently in the 8 per cent with missing teeth. The foreign students had less decay but higher D and M scores than their American counterparts. New England had twice the number of students with teeth missing as well as the highest decay rate among American students. Periodontal Evaluation • The completed periodontal records of the freshmen class number 789. Graduate students who were entering MIT for the first time had simi­ lar examinations at the same time and, when pertinent, their results were com­ pared with those from the freshmen. The age of the graduates was from 21 to 35, the majority being in the early twenties. Five hundred and thirty-nine graduate students had completed clinical records. Roentgenograms were not taken of this group. Figure 1 summarizes the spread of the gingival score. The score would tend to understate the actual condition because periodontal scaling of the normal group would detect more, not less, trouble. The

K ite end Swenson: M O D ER N DENTAL CARE • I 145

percentage of the freshmen with healthy gingiva was 73.4 as contrasted to 56 per cent of the graduates. T he incidence of severe gingivitis was two and a h alf times greater among the graduate students. T he regional breakdown of the gingi­ vitis scores did not follow the same trend as the D M F count. Table 4 indicates that the South had the highest propor­ tion of healthy gingiva; the M iddle A t­ lantic region, the lowest. Most severe cases were seen where prevalence of de­ cay was highest—New England and M iddle A tlantic states. Figure 2 shows that high calculus deposits and poor oral hygiene had the same distribution as gin­ givitis am ong the freshmen. Only 21 of the 539 graduate students had consulted a dentist about painful or bleeding gingiva. Of these, nine had re­ ceived no active treatm ent for their symptoms; nine had received sympto­ m atic treatm ent, such as mouthwash, penicillin or aspirin; only three had re­ ceived a scaling. To correlate the gingivitis scores with oral hygiene and calculus, we selected 355 students who had had no extractions and who had not undergone any ortho­ dontic treatm ent. T he pattern appears to be consistent throughout. As the gin­ givitis becomes more severe, the calculus and oral hygiene worsens. In the group with no gingivitis, the calculus and oral hygiene figures are normal in 80 to 90 per cent of the students. T able 5 sum­ marizes the results. T able 6 shows the level of alveolar bone in the m olar and bicuspid region of the bitew ing roentgenograms.31 R itchey and Orban32 concluded that a flat plane interdentally is normal and depends on the convexity of the teeth— anterior teeth tend to have pointed crests. Of the 723 case studies, 5.1 per cent show more than norm al resorption. T he pre­ ponderant profile of the interdental alve­ olar crest was flat in 77.9 per cent and arched in 20.5 per cent. Resorption in­ dicating active disease was found in 1.5 per cent of the students.

80

i&’l l i Freshmen

70

Groduotes

60 50 40 30 20 10 Free

Mild

Severe

G in gival

S c o re s

Fig. 1 * Percentage com parison o f g ing ival scores fo r freshmen and gra d u a te students

C o m p a r is o n o f D e c a y a n d G in giva l Dis­ e a s e ' The relation of dental caries and periodontal disease has been the subject of m any investigations.33'41 The consen­ sus is that decay and periodontal disease have no relationship unless both exist to­ gether in the extreme. Periodontal dis­ ease does not have a geographical pattern and varies inversely w ith the quality of oral hygiene. To compare our data w ith the afore­ mentioned findings, the students with no extractions and no history of orthodontic treatm ent were allotted to two groups: one w ith 0 to 6 D M FT , and the other with 13 to 22 D M FT. T able 7 shows no difference in either group as to gingival

Table 4 • Geographical distribution of MIT freshmen with gingivitis Score Region

No. of students

0

1-4

5-12

New England

140

75.0%

20.7%

4.3%

Middle Atlantic

260

66.5%

30.0%

3.5%

Southern

142

86.6%

12.7%

0.7%

•Midwestern

130

78.5%

20.8%

0.7%

Western

85

72.8%

23.6%

3.6%

Foreign

41

51.2%

41.5%

7-3%

1146 • J . A M ER . DENT. A S S N .: V o l. 70, M ay 1965

E&l&j F r e sh me n

I I

None

Slight

Severe

Excel lent

CALCULUS

I Graduates

Fair

ORAL

Poor

HYGIENE

Fig. 2 • Percentage com parison o f calculus and oral hygiene fo r freshmen and gra d u a te students.

condition, oral hygiene or calculus de­ posits.

is to determ ine the incidence and inter­ relationship of recordable dental irregu­ larities. Students were placed in the fol­ lowing categories: ( 1 ) Individuals with a full complement of teeth who had not received orthodontic treatm ent (3 6 1 ), (2) Individuals with a full complement of teeth who had received orthodontic treatm ent ( 1 1 8 ) and (3) Individuals who had orthodontic treatm ent and had

O cc lu s a l E va lu a tion ’ T he occlusion of 772 students forms the basis of this sec­ tion. In the exam ination performed, den­ tal relationships were described, but the functional adequacy of occlusion could not be determined. The purpose of the occlusal evaluation

5

Table • Comparison of gingival score with calculus and oral hygiene among freshmen with no missing teeth and no orthodontic treatment Oral hygiene

Gingi­ vitis score

Excellent

Fair

No.

%

No.

226

89.7

22

24.1

5-12

1

8.4

Total

249

0 1-4

Per cent

Poor %

No.

26

10.3

0

63

69.4

8

66.6

97 70.1

Calculus

None

%

Severe

No.

%

No.

0

214

84.9

37

14.7

1

6

6.5

23

25.3

62

68.1

6

6.6

3

25.0

2

16.7

6

50.0

4

33.3

9 27.3

Mild

239 2.5

%

105 67.3

No.

% 0.4

11 29.6

3.1

K ite and Swanson: M O D ER N DENTAL CARE • ! 147

Table 6 • Alveolar bone resportion in millimeters below cemenfoenamel {unction in 723 M IT freshmen Millimeters from cemenfoenamel ¡unction

Per cent

0

27.2

1

67.6

2

4.7

M ore

0.4

teeth removed for orthodontic purposes (53). Not included are 240 students who had had teeth extracted for reasons other than orthodontic treatment or whose rec­ ords were incomplete. Of the 118 students no longer wearing appliances, 20 per cent had been treated for one year or less; 30 per centior 1 to 2 years; 16 per cent for 2 to 3 years, and 34 per cent for 4 to 7 years. None re­ ceived treatment before age six years. Treatment was started in the early mixed dentition (6 to 10 years old) in 15.2 per cent of the students. The mean duration of appliance use (active and passive treat­ ment) was 2.9 years. Pretreatment rec­ ords were not available. Fifty-three students still are wearing appliances. Twenty-six of these started treatment between 7 and 13 years of age. Of those who completed treatment, 81 per cent were satisfied with the results. Of those who were still wearing appli­ ances, 30 per cent thought the results were satisfactory. Table 8 summarizes the Angle classifi­ cation which indicates the relationship

of the upper to the lower dentition. Both cuspid and molar relationships are listed with no differentiation being made be­ tween the right and left sides. Of the 532 students, 68 per cent had Glass I molar and cuspid interdigitation. Of those who had had orthodontic treatment without extractions, 74 per cent had a Glass I relationship, but only 63.5 per cent of students in the treated groups who had had teeth removed had Class I molar and cuspid relationship. Three hundred and eighty-seven, or 73.2 per cent, had bi­ laterally symmetrical posterior occlusion in all classifications. Because the goal of orthodontic treat­ ment is normal anatomical interdigita­ tion, we should expect groups 2 and 3 to have better posterior interdigitation than the untreated group. A total of 122, or 71.2 per cent, of the treated students had a Class I relationship; 66.5 per cent of the untreated group were so classified. The incidence may be lower when retain­ ers are removed from the 30 per cent now wearing them. A comparison of the alignment of up­ per and lower anterior teeth is given in Table 9. Of the entire group, 46.1 per cent had straight anterior teeth. Align­ ment of anterior teeth was better in the orthodontically treated groups: 50 per cent in those treated without extractions and 58.5 per cent among those who had had teeth removed in the course of or­ thodontic treatment. This compares with 42.9 per cent among the untreated stu­ dents with a full complement of teeth. Orthodontic treatment had increased the incidence of straight anterior teeth by

Table 7 • Gingivitis score, oral hygiene and calculus of M IT freshmen with no missing teeth and no ortho­ dontic treatment. Comparison of individuals with low and high DMFT range Gingivitis score

DMFT range

O ral hygiene

-----------------------N one

Mild

Severe

Calculus

-----------------------Excellent

Fair

Poor

----------------------None

Mild

Severe

0-6

73

28

4

72

30

3

70

31

4

13-22

79

22

5

77

28

1

81

24

1

1148 • J . A M E R . DENT. AS S N .: V o l. 70, M ay t% 5

Table 8 • Angle Classification« cuspid and moiar relationships compared I bilaterally Class

I bilaterally

I & II

II bilaterally

Group*

No.

%

No.

%

No.

%

1 2 3

240 88 34

66.5 74.0 63.5

17 3 2

4.7 2.6 3.8

6 2 0

1.7 1.7 0

3 2 0

Total

362

68.0

22

4.1

8

1.5

1 2 3

6 1 0

1.7 0.9 0

46 8 2

12.7 7.0 3.8

2 1 0

Total

7

1.3

56

10.6

1 2 3

5 0 7

1.4 0 13.5

2 0 3

12

1.9

1 2 3

3 0 0

Total I & III

II & III

No

I & III

II & III

%

No.

%

No.

0.8 1.7 0

3 4 0

0.8 3.5 0

0 0 0

0 0 0

5

0.9

7

1.3

0

0

0.6 0.9 0

0 0 0

0 0 0

0 1 0

0 0.9 0

0 0 0

0 0 0

3

0.6

0

0

1

0.2

0

0

0.6 0 5.8

14 5 2

3.9 4.3 3.8

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

5

0.96

21

3.9

0

0

0

0

0

0

0.8 0 0

0 0 0

0 0 0

1 0 0

0.3 0 0

5 0 2

1.4 0 3.8

1 0 0

0.3 0 0

0 0 1

0 0 0.2

3

0.77

0

0

1

0.2

7

1.3

1

0.2

1

0.2

1 2 3

4 1 0

1.1 0.9 0

1 0 0

0.3 0 0

0 0 0

0 0 0

0 0 0

0 0 0

2 0 0

0.6 0 0

0 0 0

0 0 0

Total

5

0.77

1

0.2

0

0

0

0

2

0.4

0

0

1 2 3

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 0

0 0 1

0 0 0.9

Total

0

0

0

0

0

0

0

0

0

0

1

0.2

Total III

CUSPID INTERDIGITATION II III bilaterally

I & II

%

*Group I, students with no missing teeth {third molars excluded) and no orthodontic treatment (total 361). Group 2, students having had orthodontic treatment with a full complement of teeth (total 118). Group 3, students having had teeth removed for orthodontic reasons (total 53). {No differentiation has been made between righi and left sides.

7.1 per cent and 15.6 per cent in groups 2 and 3 over the untreated group 1. The interrelationship of vertical and horizontal overbites as shown in Table 10 confirms general clinical experience as well as findings of others.42,43 There is a wider latitude in horizontal overbite when the vertical overbite is either ex­ tremely deep or extremely shallow (open). The highest incidence of hori­ zontal overbite was from 2 to 4 mm., with the mean ranging from 4.1 mm. in the closed bite group to 3.7 mm. and 3.0 mm. in the two groups where the verti­ cal overbite fell within the limits of the upper incisors and at 2 mm. in the open bite group. The proportion of students

with a normal vertical overbite was simi­ lar whether they had been treated. Lower anterior teeth were crowded in a third of the students, regardless of vertical overbite. Students who had had teeth removed but no orthodontic treatment had more horizontal overbite than other groups. Posterior crossbite was found among 33 students of the untreated group. Nine students had crossbite of a single tooth; 15 had two teeth in crossbite, whereas 5 students had three and 3 students had four teeth in crossbite. One student had a unilateral posterior crossbite involving all the posterior teeth. Twenty-five first mo­ lars, 22 bicuspids, 7 second molars and 3

K ite and Swanson: M O D ERN DENTAL CARE • ! 149

first bicuspids were in crossbite relation­ ships. Of the 33 students, 7 had bilateral crossbite of individual teeth. The data describe individual occlusal variations and are, therefore, of no value in determining the overall incidence of malocclusion in this population. When students with abnormal molar and cuspid relationships, excessive horizontal and vertical overbite, spacing or much crowd­ ing of upper or lower incisors or both and crossbites were eliminated from the

group of 361 students who had received no orthodontic treatment, there were only 104 students or 29 per cent of the group with normal occlusion. The DMF counts and periodontal scores were compared with the occlusal findings. In the group of 361 students who had had no orthodontic treatment, there was no significant difference in DMF count or periodontal score between the normal and those classified as having malocclusion.

Table 9 • Alignment of upper and lower anterior teeth

UPPER ANTERIOR Spaced Teeth

Spaced t

+ Aligned +

Mildly s crowded s

Crowded H

Aligned

Group*

Crowded

%

No.

%

No.

9 14 3

2.5 1.9 5.6

0 7 3

0 5.9 5.6

0 0 0

0 0 0

3.4

26

4.9

10

1.9

0

0

33 3 2

9.1 2.5 3.8

155 59 31

42.9 50.0 58.5

13 22 5

3.6 18.6 9.4

0 1 2

0 0.9 3.8

Total

38

7.1

245

46.1

40

7.5

3

0.6

1 2 3

26 1 2

7.2' 0.9 3.8

55 4 3

15.2 3 .4 5.6

44 2 1

12 .2 1.7 1.9

2 0 0

0.6 0 0

Total

29

5.5

62

11.6

47

9.0

2

0.4

1 2 3

0 0 0

0 0 0

5 0 0

1.4 0 0

1 0 •0

0.3 0 0

5 1 0

1.4 0.9 0

Total

0

0

5

0.9

1

0.2

6

1.1

No.

%

1 2 3

13 4 1

3.6 3.4 1.9

Total

18

1 2 3

No.

Mildly crowded

%

*Group I, students with no missing teeth (third molars excluded) and no orthodontic treatment. Group 2, students who had orthodontic treatment and have full complement of teeth. Group 3, students having had teeth removed for orthodontic reasons. No differentiation has been rriade between right and left sides. fSpaced incisors—individual anterior teeth not in contact. JAIigned incisors—normal arrangement with mesiodistal contacts and no rotations. §Mildly crowded incisors—rotations of individual teeth with lack of intercuspid spaces no greater than one half width of lower incisor. HCrowded incisors—space loss greater than one half width of incisor.

! 150 • J . A M ER . DENT. AS SN .: V o l. 70, M ay 1965

Table 10 • Interrelationship of vertical and horizontal overbites of 569 individuals (Means + standard errorsl HORIZONTAL Overbite (in mm.)

Untreated

Treated

No extraction

Extractions

No extraction

Deep*

3.9 + 0.47

4.1 ± 0.90

5.0 ± 1.27

4.6 ± 1.07

4.1 ± 0.39

Deep normali"

3.4 ± 0.11

4.0 + 0.27

4.0 + 0.27

4.0 Í 0.27

3.6 ± 0.08

4* Shallow normal+

3.0 ± 0.09

3.4 ± 0.26

3.1 ¿ 0.17

2.7 ± 0.28

3.0 ± 0.08

Open §

2.0 + 0.43

2.8 + 0.92

2.8 ± 1.13

0.8 ± 0.92

2.0 ± 0.36

Extractions

Combined

*Deep, the lower incisors contacting the palate. fDeep normal, the lower Incisors in contact with or in projection at the level of the gingival half of the lingual surface of the upper incisors. {Shallow normal, the lower incisors in contact with or in projection at the level of the incisal half of the upper teeth. §Open, no overlap in the vertical plane.

DISCUSSION

Our findings on dental decay rates, gin­ gival conditions and occlusal needs are comparable to other studies on similar groups. There are no standards for evaluating the adequacy of dental care. At the time of examination, 58 per cent of the mem­ bers of this class needed restorations. Roughly 21,616 teeth were susceptible to decay and, of these, clinical examina­ tion without the use of roentgenograms indicated that 7,517 (35 per cent) had been affected by dental decay. There were 677 teeth in need of restorations, and 131 teeth had been extracted. Thus 91 per cent of the lesions found by clini­ cal examination had been treated. The 1929 Minnesota study showed 86 per cent of the decayed teeth had been filled, whereas 90 per cent had been filled according to the 1959 study. This rate was achieved in spite of an increased decay rate over the same period. The fluoride experience of a geographi­ cally random sample like this has not been reported. The campaign for fluori­ dation has been waged throughout this country for over a decade. Only 141 of the 913 students reported any contact with fluoride, and most of this was by sporadic topical application or toothpaste with fluoride additive or both. The dental profession cannot treat

gingival disease with the positive and im­ mediate results achieved by restorative dentistry. The students’ response to ques­ tions on gingival care indicated neglect. One freshman in 4 showed evidences of disease; 1 in 25 had severe, generalized gingivitis; 1 of 2 of the graduate students had signs of gingival disease, and 1 of 10 had severe gingivitis. Calculus deposits and poor oral hygiene followed a similar pattern and were in the same proportion to the gingivitis. Schour and Massler44 found 42.4 per cent free of gingivitis and 6 per cent with severe gingivitis in a group comparable to our graduate stu­ dents. Alveolar bone resorption was found in 0.4 per cent and signs of active periodon­ tal disease in 1.5 per cent of the freshmen. Studies on the relationship of alveolar bone to periodontal disease confirm that bone loss is not expected to any significant extent in the younger population.11’13’45 Schei and others17 report that bone loss increases with age and poor oral care. Our study reaffirms these findings. The relation of poor oral hygiene and gingivitis suggests a need for better care of the soft tissues in the younger age groups—a need that goes beyond home care34 and rests with education and treat­ ment of individuals by their own dentists. Scaling may be an even more important preventive measure during the early years of adult dentition because it is in this

K ite and Swanson: M O D ER N DENTAL CARE -1151

age group that the early stages of perio­ dontal disease occur. Occlusal surveys by others as sum­ marized by Haryett46 show large varia­ tions in percentage of malocclusions in different populations. One of the most important reasons for the variation is lack of agreement on the criteria for de­ termining what is normal or abnormal. Normal as applied to an anatomical char­ acteristic may mean the common or usual and, therefore, would be related to inci­ dence or frequency of occurrence in the population. Normal also could mean ideal. Diagnostic technics currently in use are little help in determining the need for correction. We should assess and treat the functionally inadequate occlusion, which we now cannot define. Anatomical normality per se should not be the basis for judging the results of orthodontic treatment, and many untreated dentitions with apparent malocclusion are function­ ally sound. Certainly, more than 29 per cent of this group have functionally and esthetically satisfactory occlusions. We believe, therefore, that additional corre­ lations must be made from factors that determine the arrangement of teeth. SU M M A R Y

A dental examination of 913 students of varied social background and geographi­ cal distribution showed that their dental decay rate and distribution corroborated other reports on the 16- to 20-year-old age group. One student in four had demonstrable incipient gingival disease. Gingivitis was related to poor oral hygiene and calcu­ lus deposits but not to decay. One hundred and sixty-seven students received orthodontic treatment for an average of 2.9 years. Students who had orthodontic treatment had better align­ ment of anterior teeth and slightly im­ proved posterior interdigitation. Maloc­ clusion in a group with all permanent teeth present ranged from 61 to 71 per cent, depending on the criteria used for

determining normality. Occlusal abnor­ malities do not affect DMFT counts or gingival status. The students are not receiving opti­ mum dental care: only 42 per cent have detectable decay controlled, few have received any periodontal care and the incidence of malocclusion is similar in orthodontically treated and untreated groups.

From the medical department, Massachusetts Institute of Technology, Cambridge, Mass. *Assistant dentist, medical department, Massachusetts Institute of Technology. {Orthodontist, Children's Hospital Medical Center; clinical associate in orthodontics, Harvard School of Dental Medicine. 1. Gleicher, D., Sussman, L., and Levine, G. N. Fresh­ man student study codebook, institute committee report No. 108, 1957. 2. Brekhus, P. J. A report on dental caries in 10,445 university students (1928-1930). JADA 18:1,350 July 1931. 3. Brekhus, P. J. A second census of dental conditions in University of Minnesota freshmen students. JADA 28:1,126 July 1941. 4. Bartholdi, W. L., Petersen, E. E., and Crawford, W. H. Fourth census of dental conditions in University of Minnesota freshmen students. JADA 63:868 Dec. 1961. 5. Healey, H. J., and Cheyne, V. D. Comparison of caries prevalence between freshman students in two Midwestern universities. JADA 30:692 May I, 1943. 6. Hadpmarkos, D. M., and Storvick, C. A. Incidence of dental caries among freshman students at Oregon State College. J. D. Res. 27:299 June 1948. 7. Heylings, R. T. Study of the prevalence and se­ verity of gingivitis in undergraduates at Leeds Univer­ sity, I960. Practitioner and Records 12:129 Dec. 1961. 8. Huber, R. E., and Reynolds, J. W. Dentofacial study of male students at the University of Michigan in the physical hardening program. Am. J. of Orthodont. & Oral Surg. 32:1 Jan. 1946. 9. Hixon, E. H., Maschka, P. J., and Fleming, P. T. Occlusal status, caries and mastication. J. D. Res. 41:514 May-June 1962. 10. Klein, H., and Palmer, C. E. On the epidemiology of dental caries, University of Penn. Bicentennial con­ ference. Philadelphia, U. of Penn. 1941. 11. Marshall-Day, C. D., and Shourie, K. L. Roentgenographic survey of periodontal disease in India. JADA 39:572 Nov. 1949. 12. Schour, I., and Massler, M. Gingival disease in postwar Italy. (1945) 1. Prevalence of gingivitis in vari­ ous age groups. JADA 35:475 July I, 1947. 13. Belting, C. M., Massler, M., and Schour, 1. Prevalence and incidence of alveolar bone disease in men. JADA 47:190 Aug. 1953. 14. Massler, M., and Schour, I. PMA index of gingi­ vitis. J. D. Res. 28:634 Dec. 1949. 15. Russell, A. L. System of classification and scoring for prevalence surveys of periodontal disease. J. D. Res. 35:350 June 1956. 16. Sandler, H, C., and Stahl, S. Measurement of periodontal disease prevalence. JADA 58:93 March 1959. 17. Schei, O., and others. Alveolar bone loss as re­ lated to oral hygiene and age. J. Periodont. 30:7 Jan. 1959. 18. Dunning, J. M., and Leach, L. B. Gingival bone count: a method for epidemiological study of perio­ dontal disease. J. D. Res. 39:506 May-June I960. 19. Greene, J. C., and Vermillion, R. Oral hygiene

1152- J . A M ER . DENT. A S S N .: V o l. 70, M ay 1965

Index: a method for classifying oral hygiene status. JADA 61:172 Aug. I960. 20. Chilton, N. Some public health aspects of perio­ dontal disease. JADA 40:28 Jan. 1950. 21. Marshall-Day, C. D. Epidemiology of periodontal disease. J. Periodont. 22:13 Jan. 195). 22. Sandler, H. C. Testing the uniformity of the PMA index as a measurement of periodontal diseases. J. D. Res. 31:323 June 1952. 23. Ramfjord, S. P. Indices for prevalence and inci­ dence of periodontal diseases. J. Periodont. 30:51 Jan. 1959. 24. Parfitt, G. J. Five year longitudinal study of the gingival condition of a group of children inEngland. J. Periodont. 28:26 Jan. 1957. 25. Belting, C. M. Review of the epidemiology of periodontal diseases. J. Periodont. 28:37 Jan. 1957. 26. Berggren, H., and Welander, E. Unreliability of caries recording methods. Acta Odont. 'Scandlnavlca 18:409 Dec. I960. 27. Knutson, J. W. Epidemiological trend patterns of dental caries prevalence data. JADA 57:821 Dec. 1958. 28. Dunning, J. M. Dental status of midshipmen. U.S. Navy Med. Bull. 43:895 Nov. 1944. 29. Nizel, E., and Bibby, B. G. Geographic variations in caries presence in soldiers. JADA 31:1,619 Dec. 1944. 30. Dunning, J. M. Incidence and distribution of den­ tal caries in the United States. D. Clinics of N. America 291 July 1962. 31. Theilade, J. Evaluation of the reliability of radio* graphs in the measurement of bone loss in periodontal disease. J. Periodont. 31:143 April I960. 32. Ritchey, B., and Orban, B. Crests of the inter­ dental alveolar septa. J. Periodont. 24:75 April 1953. 33. Bibby, B. G. Apparent antagonism between carles and periodontal disease. J. Periodont. 24:42 Jan. 1953. 34. Miller, J., and Hobson, P. Relationship between

malocclusion, oral cleanliness, gingival conditions, and dental caries in school children. Brit. D. J. 111:43 July 18, 1961. 35. Schwartz, J. Teeth of the Masai. J. D. Res. 25:17 Feb. 1946. 36. Miller, S. C., and Seidler, B. B. Correlation be­ tween periodontal disease and caries. J. D. Res. 19:549 Dec. 1940. 37. Massler, M., Ludwic-k, W.f and Schour, I. Dental caries and gingivitis in males 17 to 20 years old. J. D. Res. 31:195 April 1952. 38. Massler, M., and Ludwick, W. Relation of dental caries experience and gingivitis to geographic location and size of community in males 17 to 21 years old. J. D. Res. 31:313 June 1952. 39. Green, A. G. Survey of the dental condition of I9-year-old youths. Brit. D. J. 94:213 April 21, 1953. 40. Muhler, J. C., and Ennever, J. Occurrence of den­ tal calculus through several successive periods in a selected group of subjects. J. Periodont. 33:22 Jan. 1962. 41. Trubman, A. Oral hygiene: Its association with periodontal disease and dental caries in children. JADA 67:348 Sept. 1963. 42. Bjork, A. Face in profile. Svensk Tandla KareTidskrlft. Sweden. Berlingska Boktryckeriret. 1947. 43.> Baume, L. J. Physiological tooth migration and its significance for the development of occlusion. IV. Biogenesis of over-bite. J. D. Res. 29:440 Aug. 1950. 44. Schour, I., and Massler, M. Prevalence of gingi­ vitis in young adults. J» D. Res. 27:733 Dec. 1948. 45. Marshall-Day, C. D., Stephens, R. G., and Quig­ ley, L. F., Jr. Periodontal disease: prevalence and inci­ dence. J. Periodont. 26:185 July 1955. 46. Haryett, R. D. Malocclusion in public health. J. Canad. D. A. 28:372 June 1962. 47. Tweed, C. H. Philosophy of orthodontic treatment. Am. J; Orthodont. & Oral Surg. 31:74 Feb. 1945.

D ru g Safety and A n im a l S tudies • T o assure m aximum safety, tests are made on m illions of

animals each year. T h e pharm aceutical industry research programs made studies o f the effects of drugs on nearly nine m illion animals in 1962, including 6.1 m illion mice, 1.5 m illion rats, 471,000 chickens, 94,000 guinea pigs, 51,000 rabbits, 36,000 dogs, 17,000 cats and thousands of other animals. By using animals, scientists can obtain some idea o f how a drug w ill act in man— its usefulness and possible side effects. Many compounds can be ru led ou t strictly on the strength of anim al studies. T his work is absolutely essential, and there is no reasonable alternative. Nonetheless, there always comes a point where fu rther anim al work w ill yield no additional data, and careful investigations w ith human patients must begin. P h a rm a ceu tica l M an u fa ctu rers A ssocia tion , W a sh in g to n , D C .