METHODS
Occlusal Characteristics and Tooth Mobility in Periodontally Healthy Young Males Classified Orthodontically by TIMOTHY J. O ' L E A R Y , M I C H A E L C.
AND
MATERIALS
The study population was made up of male dental students at Indiana University School of Dentistry. Each subject was evaluated for gingival and periodontal health before entering the study. Subjects were excluded if they had moderate or severe gingival inflammation or loss of supporting alveolar bone, except for slight crestal loss associated with gingival recession. Additional causes for exclusion were caries, other dental problems necessitat ing treatment or completion of orthodontic therapy, including retention, within the past two years. Subjects were classified as to orthodontic status by the Handicapping Labio-Lingual Deviations Index ( H L D ) proposed by Draker and modified slightly for this study. One modification was in the measurement of Item N o . 5 (mandibular protrusion in millimeters). A few participants, although they had a "fairly normal" incisor relation, displayed some degree of Class III tendency in the cuspid and/or molar areas. In no case where there was a Class III relationship of the incisors was there a "normal" cuspid or molar relationship. Therefore, the cuspid relationship seemed to be a better indicator of mandibular prognathism than the incisor relationship. The measurement was made intraorally from the cusp tip of the mandibular cuspid to the cusp tip of the maxillary cuspid with orthodontic dividers while the patient was in centric relation. This measurement was then transferred to a millimeter rule, and scored. The second modification was in Item N o . 9 (labial-lingual spread scored in millimeters). This was scored as the sum in millimeters of the deviations of each anterior tooth from the "normal" arch alignment. The final modifica tion was in the score used to determine the need for orthodontic care. Draker has suggested that a score of 13 or more constitutes a physical handicap. For this study, the score was changed to 14 or more.
D.M.D.*
BADELL, D.D.s.†
11
RICHARD S . BLOOMER, D . D . S . ,
M.S.D.J
T H E L I T E R A T U R E contains limited information on the specific objectives of orthodontic therapy. Jackson stated: "Objectives of orthodontic treatment can be clearly and simply defined as structural balance, func tional efficiency, and esthetic harmony." Clements has said: "Facial balance and a functional occlusion have always been major goals of orthodontic treatment." According to Hixon and Klein, "The objective of treatment is the 'ideal' occlusion (perhaps minus four premolars) which is stable, that is, with little or no retention." 1
2
3
When the concept of an ideal result is limited to the dentition, one frequently mentioned criterion is that centric occclusion and centric relation should be one and the s a m e . Other investigators, however, have re ported that centric occlusion and centric relation do not usually coincide after orthodontic therapy. 4 6
7-9
The stability of the individual teeth after orthodontic therapy has not been extensively studied. J e k k a l s used a periodontometer to assess tooth mobility in 18 patients who had completed orthodontic therapy 10 or more years previously. Because of the small number of subjects and because of the presence of varying degrees of periodontal disease, his results appear inconclusive. The study had a twofold purpose: (1) To determine how frequently certain occlusal characteristics, generally thought of as normal or ideal, were present in a popula tion classified as to orthodontic status, and (2) to determine whether the orthodontic classification affected the variables being considered. 10
The Angle classification of occlusion was determined for each subject. The type of lateral excursive function, either "group" or "cuspid-protected," was then recorded for each participant. When an individual's lateral excursions could not be definitely categorized as either a "group" or "cuspid-protected" type, the type was re corded as "other." The presence and extent of anterior displacement of the mandible from centric relation to the intercuspal position were recorded for each subject. With the sub ject's head seated firmly against the head rest, the mandible was gently guided in opening and closing hinge-like movements until it was felt that the mandible was in "centric relation." The maxillary and mandibular teeth were permitted to make light contact in the retruded contact position and then to close into full intercuspation. Anterior displacement, if present, was recorded to the nearest millimeter. When the data were collated, the subjects were divided into two groups: Those with no anterior displacement or less than 1 mm of displacement, and those with more than 1 mm. 12
Presented at the Orthodontic Periodontic Continuing Education Conference sponsored by the American Association of Orthodontists and the American Academy of Periodontology in Saint Louis, Mis souri, March 24-26, 1974. * Department of Periodontics, Indiana University School of Den tistry. †Department of Orthodontics, University of Washington School of Dentistry, Seattle, Wash. ‡Department of Periodontics, Indiana University School of Den tistry.
13
553
554
O'Leary, Badell,
J. Periodontol. September, 1975
Bloomer
The subjects who had received orthodontic therapy were asked if their occlusion had been adjusted by grinding after orthodontic therapy. All participants were questioned as to any present or past bruxing, grinding or clenching habits and the information was recorded. The mobility of the teeth in the maxillary left quadrant (central incisor through second molar, N o s . 9 through 15) was determined with the U S A F S A M Periodontometer, which permits readings as small as 0.0001 inch (Fig. 1). The instrumentation and technique have been de scribed in previous p u b l i c a t i o n s . 14-17
Each tooth in the maxillary left quadrant was dried and inspected for occlusal facets. Facets were recorded as to their position on the involved teeth. Data from the examinations were analyzed by several B . M . D . programs on a C D C 6600 computer. All contin uous variables were analyzed with analysis of variance procedures, whereas the relationships among the categor ical variables were tested by the chi-square technique. RESULTS
A total of 124 subjects were selected for participation. Mean age of the subjects was 25.6 years, with a standard deviation of ±2.06 years and a range of 23 to 30 years. Forty subjects were classified as orthodontically nor mal (Group I). 43 were classified as needing orthodontic therapy (Group II), and 41 had received comprehensive orthodontic care (Group III). The mean Draker Index scores for Groups I and III are similar and are signifi cantly different from Group II scores at the 0.01 level (Table I). The standard deviations, median scores, and ranges for Groups I and III are somewhat similar and differ considerably from those of Group II. The results of classifying the groups according to the
Angle criteria are seen in Table II. A much larger percentage of the subjects in Group I had a Class I type of occlusion that in Groups II or III (95%, 60.5%, and 63.4%, respectively). There is, in fact, a rather close similarity between Groups II and III except in the number of individuals categorized as having a Class III type occlusion (8 vs. 3, respectively). Table III shows the results of classifying the partici pants within each group as to the type of lateral excursive function. Although there are no statistically significant differences between the three groups, a considerably larger number of subjects in the normal and orthodonti cally treated groups had a "cuspid-protected" type o f occlusion than in the group requiring orthodontic ther apy. Table IV gives the results of categorizing the subjects in each group according to the presence and amount of anterior displacement of the mandible from centric relation to the intercuspal position. Each group is quite evenly divided between subjects having less than 1 ml of anterior displacement and those having more than that. Only 12 individuals had no displacement: 2 in Group I, 6 in Group II, and 4 in Group III. Anterior displacement of the mandible of more than 2 mm was also an TABLE I. Draker Index Scores for the Test Group 2
Group 1
Group 3
9.8*
23.4
10.8*
±2.62 11.0 3.0-13.0
±9.26 20.0 14.0±53.0
±4.99 11.5 3.0±20.5
Mean Standard deviation Median Range
Groups
* Significantly different from Group 2 at the 0.01 level.
TABLE II. Angle Classification Group No. 1 Class I
No. %
Class II
No. %
Class III
No. %
by Group Group No. 2
Group No. 3
38
26
26
95.0 0 0 2 5
60.5 9 20.9 8 18.6
63.4 12 29.3 3 7.3
TABLE III. Type of Lateral Excursive Function by Group Group No. 1 Cuspid Protection
FIGURE 1. Periodontometer positioned to measure the mobil ity of the maxillary left first molar (tooth No. 14).
No. %
Group Function
No. %
Other*
No. %
Group No. 2
Group No. 3
22
11
19
55.0 12 30.0 6 15.0
25.6 20 46.5 12 27.9
46.3 16 39.0 6 14.6
* Includes all subjects that could not be classified as h a v i n g a " t r u e " cuspid protected or "true" group function o c c l u s i o n .
Volume 46 Number 9
Occlusal
uncommon finding (Group I = 6, Group II = 13, and Group III = 4). Only one of the 41 subjects who had undergone comprehensive orthodontic treatment re ported that his occlusion had been adjusted by grinding after tooth movement. Little difference was found between the three groups in mean mobility values for teeth N o s . 9 through 12—cen tral incisor through first bicuspid (Table V). The mean mobility value for tooth N o . 13 (maxillary left second bicuspid), 0.00275, is significantly less ( < 0.05) for Group I than the value of 0.00308 for the same tooth in Group II (requiring orthodontic care). The mean values for tooth N o . 14 (first molar) in Groups I and III are quite similar and are significantly lower (at the 0.01 level) than the mean value for the subjects requiring orthodontic care (Group II). In the case of tooth N o . 15 (second molar), the mean values for Group I and III again differ significantly, at the 0.05 and 0.01 levels, respectively, from the mean value for Group II subjects. The range of tooth mobility values for the three groups is shown in Table VI. The lower end of the mobility range for all three groups is similar, except for three teeth. The extremely low values for tooth N o . 9 (central incisor) in Group II and for teeth N o s . 13 and 14 (second bicuspid and first molar) in Group III are due to ankylosis of individual teeth. It is noteworthy that the upper limit of the mobility range for the test teeth in Group I subjects is considerably lower than the upper limit in Group II subjects and in Group III subjects, except for teeth N o s . 9, 14, and 15. In Group III, 27 subjects were treated without removal of the first premolar, whereas treatment of the other 14 individuals included extraction of the first premolar. A comparison of tooth mobility values between the two subgroups shows that the mobility value of 0.00318 for TABLE I V . Amount
of Anterior
Displacement
Group
Group
Group
No. 1
No. 2
No. 3
Characteristics 5 5 5
tooth N o . 10 (lateral incisor) in the subgroup which had had a premolar removed was considerably lower than the value (0.00385) for the lateral incisor in the other group (Table VII). N o significant differences were seen between the groups when the data on the presence or absence of a tensional occlusal habit were collated. The possible relationships between orthodontic group ing, the presence or absence of a tensional habit, and tooth mobility values were also investigated. The maxil lary left lateral incisor (tooth N o . 10) displayed signifi cantly less mobility (P < 0.05) for the subjects in each group without occlusal tensional habits. Table VIII gives the mean mobility values for Group I subjects with and without a history of occlusal habits. The relationship between treatment group and the presence of facets was analyzed for the test teeth. In the case of tooth N o . 13 (maxillary left second bicuspid), chi-square analysis showed a significant relationship at the 0.05 level between groups and facets. The number of facets on the test tooth in Group I was significantly smaller than the number found on the test tooth in Groups II and III. The individual teeth were examined for differences in mobility while controlling for treatment group and anterior displacement of the mandible. The results of the analysis were erratic. There appeared to be a significant interaction (P < 0.05) between group and displacement on teeth N o s . 10, 12, and 13 only. Significant mobility differences between groups were found only for teeth N o s . 14, and 15 and at the 0.05 probability level. The teeth were also examined for differences in mobility while controlling for treatment group and facets. A few significant results were found, but they were not consistent and sometimes seemed to contradict themselves.
by Group DISCUSSION
0 < 1 mm > 1 mm
No. % No. %
18
20
22
45.0 22 55.0
46.5 23 53.5
53.7 19 46.3
The population used in this study was unique in that all participants had a high level of periodontal health. The objective was to eliminate possible variables resulting from inflammatory periodontal disease. A number of measurement indices are available for assessing malocclusion. Three widely used systems are
TABLE V . Mean Tooth Mobility for Test
Groups
Tooth No.
Group I
Group II
Group I I I
9
0.00397
0.00398
0.00391
10 11 12 13 14 15
0.00361 0.00234 0.00292 0.00275* 0.00212t 0.00265*
0.00370 0.00248 0.00300 0.00308 0.00256 0.00311
0.00361 0.00247 0.00297 0.00291 0.00217* 0.00254t
* Significantly different from Group II score at 0.05 level, t Significantly different from Group II score at 0.01 level.
556
O'Leary, Badell,
J. Periodontol. September, 1975
Bloomer TABLE V I . Range of Tooth Mobility for Subjects
9 10 11 12 13 14 15
Groups Group III
Group II
Group I Tooth N o .
in the Three Test
Min
Max
Min
Max
Min
Max
0.00265
0.00675
0.00050
0.00740
0.00235
0.00675
0.00235 0.00150 0.00180 0.00125 0.00120 0.00110
0.00580 0.00370 0.00515 0.00375 0.00420 0.00500
0.00210 0.00145 0.00195 0.00115 0.00135 0.00175
0.00755 0.00515 0.00545 0.00500 0.00535 0.00570
0.00210 0.00150 0.00145 0.00045 0.00055 0.00140
0.00670 0.00440 0.00835 0.00725 0.00415 0.00535
the Handicapping Labio-Lingual Deviations Index, Or thodontic Treatment Priority Index, and the Handicap ping Malocclusion Assessment. All three systems have similarities with respect to the factors evaluated and the methods of assessment. The latter two systems are widely accepted, do not require millimeter measure ments, and account for deviations such as missing teeth, open spacing, cross bites and posterior problems. How ever, the systems require diagnostic casts and take a considerable time to accomplish. The Draker Handicapping Labio-Lingual Deviations ( H L D ) Index was selected for this study because of its simplicity, reliability and validity, and also because the assessment takes little time. Further, for research pur poses, a rigid set of measurement criteria and definite end points was desirable to minimize examiner variability. The modifications made in the H L D Index for the study permitted more precise definition of certain categories, thus increasing reliability of our measurements over time. The relatively high H L D scores, standard deviations, and range of scores for the subjects who had received orthodontic treatment may be accounted for by a number of factors, including notably the severity of malocclusion which had been present before orthodontic treatment, and the cooperation of the patient. Since the subjects had been treated by various practitioners, there undoubtedly had been differences in treatment objectives, as well as biologic differences between the patients. The fact that a rather large number of subjects did not achieve an Angle Class I relationship after orthodontics, may be due in large measure to the same factors that resulted in the H L D Index findings. In many instances, orthodontists strive to achieve an Angle Class II relation ship. M a n y dentists hold that the posterior teeth should be disoccluded in lateral excursions so they cannot be stressed by premature f o r c e s . This type of occlusion is said to prevent wear of the teeth and ultimate malarticulation. Group I (orthodontically normal) had the largest number and highest percentage (22, 55%) of participants with a cuspid-protected type of occlusion. The group requiring orthodontic care had the smallest number and lowest percentage (11, 25.6%) of subjects 11,
20-22
18,
TABLE V I I . Mean Tooth Mobility of Group III Subjects According Presence or Absence of Maxillary First Premolar
to
1 9
N o . of Subjects Tootn INO. 9 10 11 12 13 14 15
27
14
0.00400
0.00374
0.00385* 0.00255* 0.00297 0.00289 0.00219 0.00261†
0.00318 0.00232 0.00297 0.00214 0.00245
* N = 26. †N = 25.
TABLE V I I I . Mean Mobility Values for Group I Subjects and Without Occlusal Tensional Habits
With
Habit
N o Habit
9
0.00417
0.00377
10 11 12 13 14 15
0.00374 0.00247 0.00307 0.00284 0.00225 0.00276
0.00347* 0.00221 0.00276 0.00266 0.00198 0.00253
Tooth N o .
* Significantly lower (P < 0.05) than the value for subjects with a history of an occlusal habit.
with cuspid protection. It would be interesting to reevalu ate the subjects in the three groups after several years to determine the possible significance of the type of lateral excursive function. A number of investigators have studied the occlusion of subjects after orthodontic therapy. Cohen evaluated 4 0 patients who had received orthodontic care and 36 who, in his opinion, had satisfactory occlusions. He reported that 75% of the treated patients and 80.7% of the group with satisfactory occlusion had a displacement from centric relation to centric occlusion. Ahlgren and Posselt reported that 14 of 23 postorthodontic patients in their study exhibited cuspal interferences. Jekkals evaluated 18 patients who had completed orthodontic therapy and 23
7
Volume 46 Number 9
Occlusal 10
retention at least ten years previously. Seventeen individuals had an anterior displacement from centric relation to centric occlusion. Only three subjects had less than 1 mm of slide. Ten had displacements between 1 and 2 m m , two had displacements between 2 and 3 m m , and two had displacements of more than 3 mm. In the present investigation, centric relation and centric occlusion coin cided in relatively few subjects (Group I = 2, Group II = 4, Group III = 6). However, a considerably larger percentage of subjects exhibited an anterior slide of less than 1 mm than Jekkals found in his study. Although many orthodontists state that the occlusion should be adjusted after tooth movement, only one of the 41 orthodontically treated subjects in this study had received this type of t h e r a p y . This would indicate that not all orthodontists routinely carry out this proce dure. Jekkals, using a U S A F S A M Periodontometer, ob tained mobility values for the teeth of 18 patients who had been out of retention for 10 or more years and compared them with the values compiled for periodontally healthy young males by Rudd, O'Leary and Stumpf. Except for three teeth, his values were some what higher. The differences between the two studies may be due to the varying degrees of periodontal disease in Jekkals' subjects. In the present study, there were statistically significant differences in the mean values for some teeth between Groups I and III subjects and the Group II subjects. In no instance was there a significant difference between the mean values for Group I and III subjects. 24-27
10
A tooth mobility value is considered to be in the pathologic range when it exceeds the mean established for healthy individuals plus two standard deviations. In all three groups, there were individuals with mobility values in the pathologic range for one or more teeth. The elevated readings could not be ascribed to any single factor. In some individuals, an occlusal prematurity appeared to be the cause and in others, an occlusal tensional habit, whereas in the orthodontically treated subjects root resorption was sometimes associated with an elevated value. There is no clear-cut explanation for the significantly lower mean mobility for the maxillary lateral incisor tooth in the subgroup whose treatment included removal of the first premolar. It could be hypothesized that the lateral incisor was placed in a more stable position with respect to basal bone, function, and the surrounding musclature. The presence or absence of a tensional occlusal habit (clenching, bruxing, or clamping) was determined by questioning the patient. The validity of data obtained in this way is always open to question. However, since all three groups were made up of dental students, the probability of obtaining a correct answer was enhanced. Further, in cases where the subject was doubtful as to the existence of a tensional habit, it was always recorded as
Characteristics
567
absent. A few more of the orthodontically normal subjects (Group I) indicated the presence of such a habit than the subjects in Group II or in group III. The finding that Group I subjects without an occlusal habit displayed lower mean tooth mobility values than subjects in the same group with a habit is in accordance with the findings of a previous study by O'Leary et a l . Facets are generally regarded as a sign of abnormal tooth wear. It might be reasoned that an orthodontically treated group should show fewer signs of abnormal wear than a group requiring orthodontic therapy. However, this was not the case here. Indeed, for tooth N o . 13, the orthodontically treated subjects had more facets than the normals (Group I). It is possible that most of these facets were present prior to orthodontic therapy. However, one cannot discount the possibility of a cause and effect relationship between the presence of facets and the centric prematurities found in the treated subjects. 28
SUMMARY
Three groups of periodontally healthy young males classified as to orthodontic status by the Handicapping Labio-Lingual Deviations Index were evaluated for vari ous occlusal characteristics. A much larger proportion (95%) of the orthodontically normal subjects (Group I) had an Angle Class I type of occlusion than the Group II subjects requiring orthodontic care (60.5%), or the Group III subjects who had received orthodontic care (63.4%). The percentages of subjects with a "cuspid-protected" type of occlusion were larger in the orthodontically normal and orthodontically treated groups than in the group requiring orthodontic care. Anterior displacement of the mandible in closing from centric relation to the intercuspal position was found in the majority of subjects in each group. Displacement of more than 2 mm was most common in the subjects requiring orthodontic care. Only 1 of the 41 orthodonti cally treated subjects reported that his occlusion had been adjusted by grinding after tooth movement. There were no statistically significant differences in mean tooth mobility values between the orthodontically normal and orthodontically treated subjects. The lateral incisor tooth had a significantly lower mean mobility value in subjects whose orthodontic care included re moval of the first premolar than in subjects treated without removal of the first premolar. Wear facets were common in all three groups. Based on the findings, one can conclude that orthodon tic therapy was only partially successful in obtaining the objectives described as part of an ideal result. It should be noted, however, that the status of the dentition and occlusion prior to orthodontic treatment could not be determined for more than a few subjects. REFERENCES
1. Jackson, A. F.: Art of orthodontic practice. Am J Orthod 34: 383, 1948.
J. Periodontol. September, 1975
O'Leary, Badell Bloomer
EE 2. Clemento,
B. S.: Treatment objectives. Bull Pac Coast Soc Orthod 46: 27, 1971. 3. Hixon, E., and Klein, P.: Simplified mechanics: A means of treatment based on available scientific information. Am J Orthod 6 2 : 113, 1972. 4. Poulton, D. R.: An orthodontic view of normal occlusion. J Calif Dent Assoc 45: 2, 1969. 5. Sandusky, W. E.: Treatment goals in orthodontics. Bull Pac Coast Soc Orthod 46: 19, 1971. 6. Roth, R. H.: Gnathologic concepts and orthodontic treatment goals in "technique and treatment with light-wire edgewise appliances", 2ed. Jarabak, J. R. and Fizzell, J. A., eds, St. Louis, The C. V. Mosby Co. 1972. 7. Ahlgren, J., and Posselt, U.: Need for functional analysis and selective grinding in orthodontics: A clinical and elec tromyographic study. Acta Odontol Scand 2 1 : 187, N o . 3, 1963. 8. Cohen, W. E.: A study of occlusal interferences in orthodontically treated occlusions and untreated normal occlu sions. Am J Orthod 5 1 : 647, 1965. 9. Stallard, H.: Survival of the periodontium during and after orthodontic treatment. Am J Orthod 50: 584, 1964. 10. Jekkals, V.: Periodontal and occlusal status of patients' ten years after orthodontic treatment. Thesis, Univ. of Wash ington School of Dentistry, 1970. 11. Draker, H. L.: Handicapping labio-lingual deviations: A proposed index for public health purposes. Am J Orthod 46: 295, 1960. 12. Glickman, I.: Clinical periodontology, 4 ed. pp. 838, 839, Philadelphia, W. B. Saunders Company, 1972. 13. Posselt, U.: Physiology of occlusion and rehabilitation, p. 125, Oxford, Black well Scientific Publication, 1972. 14. O'Leary, T. J., and Rudd, K. D.: An instrument for measuring horizontal tooth mobility. Periodontics 1: 249, 1963. 15. Rudd, K. D., O'Leary, T. J., and Stumpf, A. J., Jr.:
Horizontal tooth mobility in carefully screened subjects. Perio dontics 2: 65, 1964. 16. O'Leary, T. J., Rudd, K. D. and Nabers, C. L.: Factors affecting horizontal tooth mobility. Periodontics 4: 308, 1966. 17. O'Leary, T. J.: Tooth mobility. Dent Clin North Am 13: 567, 1969. 18. Grainger, R. M.: Orthodontic treatment priority index. P H S Publication N o . 1000, Series 2, N o . 25. Washington, U.S. Government Printing Office, 1967. 19. Salzman, J. A.: Handicapping malocclusion assessment to establish treatment priority. Am J Orthod 54: 749, 1968. 20. D'Amico, A.: The canine teeth-normal functional rela tion of the natural teeth of man. J South Calif Dent Assoc 26: 6, 49, 127, 175, 194, 239, 1958. 21. Stallard, H., and Stuart, C. E.: Concepts of occlusion: What kind of occlusion should recusped teeth be given? Dent Clin North Am p. 591, 1963. 22. Scott, M. E., and Baum, L.: Procedures and techniques for restoring 'canine function' for abraded teeth. J. South Calif Dent Assoc 32: 23, 1964. 23. Cohen, W. E.: A study of occlusal interferences in orthodontically treated occlusions and untreated normal occlu sions. Am J Orthod 5 1 : 647, 1965. 24. Rothner, J. D.: Occlusal equilibration—A part of ortho dontic treatment. Am J Orthod 38: 530, 1952. 25. Blume, D. G.: A study of occlusal equilibration as it relates to orthodontics. Am J Orthod 44: 575, 1958. 26. Perry, H. T.: Principles of occlusion applied to modern orthodontics. Dent Clin North Am 13: 581, 1969. 27. Williams, R. L.: Occlusal treatment for the postortho dontic patient. Am J Orthod 59: 431, 1971. 28. O'Leary, T. J., Rudd, K. D., Nabers, C. L., and Stumpf, A. J., Jr.: The effect of a "tube type" diet and stress inducing conditions on tooth mobility. J Periodontol 38: 322, 1967.
Abstracts EXPERIMENTAL CONTACT HYPERSENSITIVITY IN THE GINGIVA OF DOGS Nobréus, N., and Attstrbm, R. J Periodont
Res 9: 245, N o . 4, 1974.
l-dinitro-2,4-chlorbenzene ( D N C B , 0.05% in Orabase) was applied to the gingiva on one side daily for six days in a group of seven beagle dogs while on the control side (contralateral side of jaw) only the vehicle (orabase) was applied. Duration of each application was two hours on days 0 and 3, and 30 minutes on days 1, 2, 4, 5. Antithymocyte serum (ATS) was injected subcutaneously in dogs on day 3. Biopsies from the D N C B sites on day 3 indicated a high number of mononuclear inflammatory cells indicative of hypersensitivity towards D N C B whereas the control site had low counts of inflammatory cells. Measurements of crevicular leukocytes, gingival fluid and acid phos phatase activity in crevicular samples (gingival crevice parameters) were also high compared to the control site. Immunosuppression with A T S affected all parameters on day 6. Gingival contact hypersensitivity to D N C B can be elicited in beagle dogs; therefore, this study supports earlier observations on the role of cellular immunity in the pathogenesis of plaque-induced gingival inflammation. School of Dentistry, Carl Gustavs väg 34, S-214 21 Malmo, Sweden
CLINICAL AND STEREOLOGIC ANALYSIS OF THE COURSE OF EARLY GINGIVITIS IN DOGS Lindhe, J., Schroeder, H. E., Page, R. C , Munzel-Pedrazzoli, S., and Hugoson, A . J Periodont Res 9: 314, N o . 5, 1974. In order to observe the sequence of events occurring in gingival tissues of dogs following the accumulation of plaque, five German Pointers were placed on a 2% chlorhexidine mouthrinse for five months during the eruption of their permanent teeth. Clinical examinations of gingival index, plaque index and measurement of gingival exudate as well as biopsies from various areas for stereologic analysis were done. Tests were repeated on various days and lasted 28 days. The plaque and exudate accumulation was relatively constant within the first two weeks but increased in the last two weeks. There was no marked change in the cellular infiltration of the junctional epithelium except for the so-called "X-Lymphocytes'' The total collagen content of the gingival connec tive tissue remained constant. The tests showed that the histopathological alterations did not parallel clinical observations and one of the reasons given was the influence of the chlorhexidine on the gingival tissues. Department of Periodontology, Faculty of Odontology, Pack, S-400 33 Goteborg 33, Sweden
Occlusal Characteristics and Tooth Mobility in Periodontally Healthy Young Males Classified Orthodontically by TIMOTHY J. O ' L E A R Y , M I C H A E L C.
AND
MATERIALS
The study population was made up of male dental students at Indiana University School of Dentistry. Each subject was evaluated for gingival and periodontal health before entering the study. Subjects were excluded if they had moderate or severe gingival inflammation or loss of supporting alveolar bone, except for slight crestal loss associated with gingival recession. Additional causes for exclusion were caries, other dental problems necessitat ing treatment or completion of orthodontic therapy, including retention, within the past two years. Subjects were classified as to orthodontic status by the Handicapping Labio-Lingual Deviations Index ( H L D ) proposed by Draker and modified slightly for this study. One modification was in the measurement of Item N o . 5 (mandibular protrusion in millimeters). A few participants, although they had a "fairly normal" incisor relation, displayed some degree of Class III tendency in the cuspid and/or molar areas. In no case where there was a Class III relationship of the incisors was there a "normal" cuspid or molar relationship. Therefore, the cuspid relationship seemed to be a better indicator of mandibular prognathism than the incisor relationship. The measurement was made intraorally from the cusp tip of the mandibular cuspid to the cusp tip of the maxillary cuspid with orthodontic dividers while the patient was in centric relation. This measurement was then transferred to a millimeter rule, and scored. The second modification was in Item N o . 9 (labial-lingual spread scored in millimeters). This was scored as the sum in millimeters of the deviations of each anterior tooth from the "normal" arch alignment. The final modifica tion was in the score used to determine the need for orthodontic care. Draker has suggested that a score of 13 or more constitutes a physical handicap. For this study, the score was changed to 14 or more.
D.M.D.*
BADELL, D.D.s.†
11
RICHARD S . BLOOMER, D . D . S . ,
M.S.D.J
T H E L I T E R A T U R E contains limited information on the specific objectives of orthodontic therapy. Jackson stated: "Objectives of orthodontic treatment can be clearly and simply defined as structural balance, func tional efficiency, and esthetic harmony." Clements has said: "Facial balance and a functional occlusion have always been major goals of orthodontic treatment." According to Hixon and Klein, "The objective of treatment is the 'ideal' occlusion (perhaps minus four premolars) which is stable, that is, with little or no retention." 1
2
3
When the concept of an ideal result is limited to the dentition, one frequently mentioned criterion is that centric occclusion and centric relation should be one and the s a m e . Other investigators, however, have re ported that centric occlusion and centric relation do not usually coincide after orthodontic therapy. 4 6
7-9
The stability of the individual teeth after orthodontic therapy has not been extensively studied. J e k k a l s used a periodontometer to assess tooth mobility in 18 patients who had completed orthodontic therapy 10 or more years previously. Because of the small number of subjects and because of the presence of varying degrees of periodontal disease, his results appear inconclusive. The study had a twofold purpose: (1) To determine how frequently certain occlusal characteristics, generally thought of as normal or ideal, were present in a popula tion classified as to orthodontic status, and (2) to determine whether the orthodontic classification affected the variables being considered. 10
The Angle classification of occlusion was determined for each subject. The type of lateral excursive function, either "group" or "cuspid-protected," was then recorded for each participant. When an individual's lateral excursions could not be definitely categorized as either a "group" or "cuspid-protected" type, the type was re corded as "other." The presence and extent of anterior displacement of the mandible from centric relation to the intercuspal position were recorded for each subject. With the sub ject's head seated firmly against the head rest, the mandible was gently guided in opening and closing hinge-like movements until it was felt that the mandible was in "centric relation." The maxillary and mandibular teeth were permitted to make light contact in the retruded contact position and then to close into full intercuspation. Anterior displacement, if present, was recorded to the nearest millimeter. When the data were collated, the subjects were divided into two groups: Those with no anterior displacement or less than 1 mm of displacement, and those with more than 1 mm. 12
Presented at the Orthodontic Periodontic Continuing Education Conference sponsored by the American Association of Orthodontists and the American Academy of Periodontology in Saint Louis, Mis souri, March 24-26, 1974. * Department of Periodontics, Indiana University School of Den tistry. †Department of Orthodontics, University of Washington School of Dentistry, Seattle, Wash. ‡Department of Periodontics, Indiana University School of Den tistry.
13
553
554
O'Leary, Badell,
J. Periodontol. September, 1975
Bloomer
The subjects who had received orthodontic therapy were asked if their occlusion had been adjusted by grinding after orthodontic therapy. All participants were questioned as to any present or past bruxing, grinding or clenching habits and the information was recorded. The mobility of the teeth in the maxillary left quadrant (central incisor through second molar, N o s . 9 through 15) was determined with the U S A F S A M Periodontometer, which permits readings as small as 0.0001 inch (Fig. 1). The instrumentation and technique have been de scribed in previous p u b l i c a t i o n s . 14-17
Each tooth in the maxillary left quadrant was dried and inspected for occlusal facets. Facets were recorded as to their position on the involved teeth. Data from the examinations were analyzed by several B . M . D . programs on a C D C 6600 computer. All contin uous variables were analyzed with analysis of variance procedures, whereas the relationships among the categor ical variables were tested by the chi-square technique. RESULTS
A total of 124 subjects were selected for participation. Mean age of the subjects was 25.6 years, with a standard deviation of ±2.06 years and a range of 23 to 30 years. Forty subjects were classified as orthodontically nor mal (Group I). 43 were classified as needing orthodontic therapy (Group II), and 41 had received comprehensive orthodontic care (Group III). The mean Draker Index scores for Groups I and III are similar and are signifi cantly different from Group II scores at the 0.01 level (Table I). The standard deviations, median scores, and ranges for Groups I and III are somewhat similar and differ considerably from those of Group II. The results of classifying the groups according to the
Angle criteria are seen in Table II. A much larger percentage of the subjects in Group I had a Class I type of occlusion that in Groups II or III (95%, 60.5%, and 63.4%, respectively). There is, in fact, a rather close similarity between Groups II and III except in the number of individuals categorized as having a Class III type occlusion (8 vs. 3, respectively). Table III shows the results of classifying the partici pants within each group as to the type of lateral excursive function. Although there are no statistically significant differences between the three groups, a considerably larger number of subjects in the normal and orthodonti cally treated groups had a "cuspid-protected" type o f occlusion than in the group requiring orthodontic ther apy. Table IV gives the results of categorizing the subjects in each group according to the presence and amount of anterior displacement of the mandible from centric relation to the intercuspal position. Each group is quite evenly divided between subjects having less than 1 ml of anterior displacement and those having more than that. Only 12 individuals had no displacement: 2 in Group I, 6 in Group II, and 4 in Group III. Anterior displacement of the mandible of more than 2 mm was also an TABLE I. Draker Index Scores for the Test Group 2
Group 1
Group 3
9.8*
23.4
10.8*
±2.62 11.0 3.0-13.0
±9.26 20.0 14.0±53.0
±4.99 11.5 3.0±20.5
Mean Standard deviation Median Range
Groups
* Significantly different from Group 2 at the 0.01 level.
TABLE II. Angle Classification Group No. 1 Class I
No. %
Class II
No. %
Class III
No. %
by Group Group No. 2
Group No. 3
38
26
26
95.0 0 0 2 5
60.5 9 20.9 8 18.6
63.4 12 29.3 3 7.3
TABLE III. Type of Lateral Excursive Function by Group Group No. 1 Cuspid Protection
FIGURE 1. Periodontometer positioned to measure the mobil ity of the maxillary left first molar (tooth No. 14).
No. %
Group Function
No. %
Other*
No. %
Group No. 2
Group No. 3
22
11
19
55.0 12 30.0 6 15.0
25.6 20 46.5 12 27.9
46.3 16 39.0 6 14.6
* Includes all subjects that could not be classified as h a v i n g a " t r u e " cuspid protected or "true" group function o c c l u s i o n .
Volume 46 Number 9
Occlusal
uncommon finding (Group I = 6, Group II = 13, and Group III = 4). Only one of the 41 subjects who had undergone comprehensive orthodontic treatment re ported that his occlusion had been adjusted by grinding after tooth movement. Little difference was found between the three groups in mean mobility values for teeth N o s . 9 through 12—cen tral incisor through first bicuspid (Table V). The mean mobility value for tooth N o . 13 (maxillary left second bicuspid), 0.00275, is significantly less ( < 0.05) for Group I than the value of 0.00308 for the same tooth in Group II (requiring orthodontic care). The mean values for tooth N o . 14 (first molar) in Groups I and III are quite similar and are significantly lower (at the 0.01 level) than the mean value for the subjects requiring orthodontic care (Group II). In the case of tooth N o . 15 (second molar), the mean values for Group I and III again differ significantly, at the 0.05 and 0.01 levels, respectively, from the mean value for Group II subjects. The range of tooth mobility values for the three groups is shown in Table VI. The lower end of the mobility range for all three groups is similar, except for three teeth. The extremely low values for tooth N o . 9 (central incisor) in Group II and for teeth N o s . 13 and 14 (second bicuspid and first molar) in Group III are due to ankylosis of individual teeth. It is noteworthy that the upper limit of the mobility range for the test teeth in Group I subjects is considerably lower than the upper limit in Group II subjects and in Group III subjects, except for teeth N o s . 9, 14, and 15. In Group III, 27 subjects were treated without removal of the first premolar, whereas treatment of the other 14 individuals included extraction of the first premolar. A comparison of tooth mobility values between the two subgroups shows that the mobility value of 0.00318 for TABLE I V . Amount
of Anterior
Displacement
Group
Group
Group
No. 1
No. 2
No. 3
Characteristics 5 5 5
tooth N o . 10 (lateral incisor) in the subgroup which had had a premolar removed was considerably lower than the value (0.00385) for the lateral incisor in the other group (Table VII). N o significant differences were seen between the groups when the data on the presence or absence of a tensional occlusal habit were collated. The possible relationships between orthodontic group ing, the presence or absence of a tensional habit, and tooth mobility values were also investigated. The maxil lary left lateral incisor (tooth N o . 10) displayed signifi cantly less mobility (P < 0.05) for the subjects in each group without occlusal tensional habits. Table VIII gives the mean mobility values for Group I subjects with and without a history of occlusal habits. The relationship between treatment group and the presence of facets was analyzed for the test teeth. In the case of tooth N o . 13 (maxillary left second bicuspid), chi-square analysis showed a significant relationship at the 0.05 level between groups and facets. The number of facets on the test tooth in Group I was significantly smaller than the number found on the test tooth in Groups II and III. The individual teeth were examined for differences in mobility while controlling for treatment group and anterior displacement of the mandible. The results of the analysis were erratic. There appeared to be a significant interaction (P < 0.05) between group and displacement on teeth N o s . 10, 12, and 13 only. Significant mobility differences between groups were found only for teeth N o s . 14, and 15 and at the 0.05 probability level. The teeth were also examined for differences in mobility while controlling for treatment group and facets. A few significant results were found, but they were not consistent and sometimes seemed to contradict themselves.
by Group DISCUSSION
0 < 1 mm > 1 mm
No. % No. %
18
20
22
45.0 22 55.0
46.5 23 53.5
53.7 19 46.3
The population used in this study was unique in that all participants had a high level of periodontal health. The objective was to eliminate possible variables resulting from inflammatory periodontal disease. A number of measurement indices are available for assessing malocclusion. Three widely used systems are
TABLE V . Mean Tooth Mobility for Test
Groups
Tooth No.
Group I
Group II
Group I I I
9
0.00397
0.00398
0.00391
10 11 12 13 14 15
0.00361 0.00234 0.00292 0.00275* 0.00212t 0.00265*
0.00370 0.00248 0.00300 0.00308 0.00256 0.00311
0.00361 0.00247 0.00297 0.00291 0.00217* 0.00254t
* Significantly different from Group II score at 0.05 level, t Significantly different from Group II score at 0.01 level.
556
O'Leary, Badell,
J. Periodontol. September, 1975
Bloomer TABLE V I . Range of Tooth Mobility for Subjects
9 10 11 12 13 14 15
Groups Group III
Group II
Group I Tooth N o .
in the Three Test
Min
Max
Min
Max
Min
Max
0.00265
0.00675
0.00050
0.00740
0.00235
0.00675
0.00235 0.00150 0.00180 0.00125 0.00120 0.00110
0.00580 0.00370 0.00515 0.00375 0.00420 0.00500
0.00210 0.00145 0.00195 0.00115 0.00135 0.00175
0.00755 0.00515 0.00545 0.00500 0.00535 0.00570
0.00210 0.00150 0.00145 0.00045 0.00055 0.00140
0.00670 0.00440 0.00835 0.00725 0.00415 0.00535
the Handicapping Labio-Lingual Deviations Index, Or thodontic Treatment Priority Index, and the Handicap ping Malocclusion Assessment. All three systems have similarities with respect to the factors evaluated and the methods of assessment. The latter two systems are widely accepted, do not require millimeter measure ments, and account for deviations such as missing teeth, open spacing, cross bites and posterior problems. How ever, the systems require diagnostic casts and take a considerable time to accomplish. The Draker Handicapping Labio-Lingual Deviations ( H L D ) Index was selected for this study because of its simplicity, reliability and validity, and also because the assessment takes little time. Further, for research pur poses, a rigid set of measurement criteria and definite end points was desirable to minimize examiner variability. The modifications made in the H L D Index for the study permitted more precise definition of certain categories, thus increasing reliability of our measurements over time. The relatively high H L D scores, standard deviations, and range of scores for the subjects who had received orthodontic treatment may be accounted for by a number of factors, including notably the severity of malocclusion which had been present before orthodontic treatment, and the cooperation of the patient. Since the subjects had been treated by various practitioners, there undoubtedly had been differences in treatment objectives, as well as biologic differences between the patients. The fact that a rather large number of subjects did not achieve an Angle Class I relationship after orthodontics, may be due in large measure to the same factors that resulted in the H L D Index findings. In many instances, orthodontists strive to achieve an Angle Class II relation ship. M a n y dentists hold that the posterior teeth should be disoccluded in lateral excursions so they cannot be stressed by premature f o r c e s . This type of occlusion is said to prevent wear of the teeth and ultimate malarticulation. Group I (orthodontically normal) had the largest number and highest percentage (22, 55%) of participants with a cuspid-protected type of occlusion. The group requiring orthodontic care had the smallest number and lowest percentage (11, 25.6%) of subjects 11,
20-22
18,
TABLE V I I . Mean Tooth Mobility of Group III Subjects According Presence or Absence of Maxillary First Premolar
to
1 9
N o . of Subjects Tootn INO. 9 10 11 12 13 14 15
27
14
0.00400
0.00374
0.00385* 0.00255* 0.00297 0.00289 0.00219 0.00261†
0.00318 0.00232 0.00297 0.00214 0.00245
* N = 26. †N = 25.
TABLE V I I I . Mean Mobility Values for Group I Subjects and Without Occlusal Tensional Habits
With
Habit
N o Habit
9
0.00417
0.00377
10 11 12 13 14 15
0.00374 0.00247 0.00307 0.00284 0.00225 0.00276
0.00347* 0.00221 0.00276 0.00266 0.00198 0.00253
Tooth N o .
* Significantly lower (P < 0.05) than the value for subjects with a history of an occlusal habit.
with cuspid protection. It would be interesting to reevalu ate the subjects in the three groups after several years to determine the possible significance of the type of lateral excursive function. A number of investigators have studied the occlusion of subjects after orthodontic therapy. Cohen evaluated 4 0 patients who had received orthodontic care and 36 who, in his opinion, had satisfactory occlusions. He reported that 75% of the treated patients and 80.7% of the group with satisfactory occlusion had a displacement from centric relation to centric occlusion. Ahlgren and Posselt reported that 14 of 23 postorthodontic patients in their study exhibited cuspal interferences. Jekkals evaluated 18 patients who had completed orthodontic therapy and 23
7
Volume 46 Number 9
Occlusal 10
retention at least ten years previously. Seventeen individuals had an anterior displacement from centric relation to centric occlusion. Only three subjects had less than 1 mm of slide. Ten had displacements between 1 and 2 m m , two had displacements between 2 and 3 m m , and two had displacements of more than 3 mm. In the present investigation, centric relation and centric occlusion coin cided in relatively few subjects (Group I = 2, Group II = 4, Group III = 6). However, a considerably larger percentage of subjects exhibited an anterior slide of less than 1 mm than Jekkals found in his study. Although many orthodontists state that the occlusion should be adjusted after tooth movement, only one of the 41 orthodontically treated subjects in this study had received this type of t h e r a p y . This would indicate that not all orthodontists routinely carry out this proce dure. Jekkals, using a U S A F S A M Periodontometer, ob tained mobility values for the teeth of 18 patients who had been out of retention for 10 or more years and compared them with the values compiled for periodontally healthy young males by Rudd, O'Leary and Stumpf. Except for three teeth, his values were some what higher. The differences between the two studies may be due to the varying degrees of periodontal disease in Jekkals' subjects. In the present study, there were statistically significant differences in the mean values for some teeth between Groups I and III subjects and the Group II subjects. In no instance was there a significant difference between the mean values for Group I and III subjects. 24-27
10
A tooth mobility value is considered to be in the pathologic range when it exceeds the mean established for healthy individuals plus two standard deviations. In all three groups, there were individuals with mobility values in the pathologic range for one or more teeth. The elevated readings could not be ascribed to any single factor. In some individuals, an occlusal prematurity appeared to be the cause and in others, an occlusal tensional habit, whereas in the orthodontically treated subjects root resorption was sometimes associated with an elevated value. There is no clear-cut explanation for the significantly lower mean mobility for the maxillary lateral incisor tooth in the subgroup whose treatment included removal of the first premolar. It could be hypothesized that the lateral incisor was placed in a more stable position with respect to basal bone, function, and the surrounding musclature. The presence or absence of a tensional occlusal habit (clenching, bruxing, or clamping) was determined by questioning the patient. The validity of data obtained in this way is always open to question. However, since all three groups were made up of dental students, the probability of obtaining a correct answer was enhanced. Further, in cases where the subject was doubtful as to the existence of a tensional habit, it was always recorded as
Characteristics
567
absent. A few more of the orthodontically normal subjects (Group I) indicated the presence of such a habit than the subjects in Group II or in group III. The finding that Group I subjects without an occlusal habit displayed lower mean tooth mobility values than subjects in the same group with a habit is in accordance with the findings of a previous study by O'Leary et a l . Facets are generally regarded as a sign of abnormal tooth wear. It might be reasoned that an orthodontically treated group should show fewer signs of abnormal wear than a group requiring orthodontic therapy. However, this was not the case here. Indeed, for tooth N o . 13, the orthodontically treated subjects had more facets than the normals (Group I). It is possible that most of these facets were present prior to orthodontic therapy. However, one cannot discount the possibility of a cause and effect relationship between the presence of facets and the centric prematurities found in the treated subjects. 28
SUMMARY
Three groups of periodontally healthy young males classified as to orthodontic status by the Handicapping Labio-Lingual Deviations Index were evaluated for vari ous occlusal characteristics. A much larger proportion (95%) of the orthodontically normal subjects (Group I) had an Angle Class I type of occlusion than the Group II subjects requiring orthodontic care (60.5%), or the Group III subjects who had received orthodontic care (63.4%). The percentages of subjects with a "cuspid-protected" type of occlusion were larger in the orthodontically normal and orthodontically treated groups than in the group requiring orthodontic care. Anterior displacement of the mandible in closing from centric relation to the intercuspal position was found in the majority of subjects in each group. Displacement of more than 2 mm was most common in the subjects requiring orthodontic care. Only 1 of the 41 orthodonti cally treated subjects reported that his occlusion had been adjusted by grinding after tooth movement. There were no statistically significant differences in mean tooth mobility values between the orthodontically normal and orthodontically treated subjects. The lateral incisor tooth had a significantly lower mean mobility value in subjects whose orthodontic care included re moval of the first premolar than in subjects treated without removal of the first premolar. Wear facets were common in all three groups. Based on the findings, one can conclude that orthodon tic therapy was only partially successful in obtaining the objectives described as part of an ideal result. It should be noted, however, that the status of the dentition and occlusion prior to orthodontic treatment could not be determined for more than a few subjects. REFERENCES
1. Jackson, A. F.: Art of orthodontic practice. Am J Orthod 34: 383, 1948.
J. Periodontol. September, 1975
O'Leary, Badell Bloomer
EE 2. Clemento,
B. S.: Treatment objectives. Bull Pac Coast Soc Orthod 46: 27, 1971. 3. Hixon, E., and Klein, P.: Simplified mechanics: A means of treatment based on available scientific information. Am J Orthod 6 2 : 113, 1972. 4. Poulton, D. R.: An orthodontic view of normal occlusion. J Calif Dent Assoc 45: 2, 1969. 5. Sandusky, W. E.: Treatment goals in orthodontics. Bull Pac Coast Soc Orthod 46: 19, 1971. 6. Roth, R. H.: Gnathologic concepts and orthodontic treatment goals in "technique and treatment with light-wire edgewise appliances", 2ed. Jarabak, J. R. and Fizzell, J. A., eds, St. Louis, The C. V. Mosby Co. 1972. 7. Ahlgren, J., and Posselt, U.: Need for functional analysis and selective grinding in orthodontics: A clinical and elec tromyographic study. Acta Odontol Scand 2 1 : 187, N o . 3, 1963. 8. Cohen, W. E.: A study of occlusal interferences in orthodontically treated occlusions and untreated normal occlu sions. Am J Orthod 5 1 : 647, 1965. 9. Stallard, H.: Survival of the periodontium during and after orthodontic treatment. Am J Orthod 50: 584, 1964. 10. Jekkals, V.: Periodontal and occlusal status of patients' ten years after orthodontic treatment. Thesis, Univ. of Wash ington School of Dentistry, 1970. 11. Draker, H. L.: Handicapping labio-lingual deviations: A proposed index for public health purposes. Am J Orthod 46: 295, 1960. 12. Glickman, I.: Clinical periodontology, 4 ed. pp. 838, 839, Philadelphia, W. B. Saunders Company, 1972. 13. Posselt, U.: Physiology of occlusion and rehabilitation, p. 125, Oxford, Black well Scientific Publication, 1972. 14. O'Leary, T. J., and Rudd, K. D.: An instrument for measuring horizontal tooth mobility. Periodontics 1: 249, 1963. 15. Rudd, K. D., O'Leary, T. J., and Stumpf, A. J., Jr.:
Horizontal tooth mobility in carefully screened subjects. Perio dontics 2: 65, 1964. 16. O'Leary, T. J., Rudd, K. D. and Nabers, C. L.: Factors affecting horizontal tooth mobility. Periodontics 4: 308, 1966. 17. O'Leary, T. J.: Tooth mobility. Dent Clin North Am 13: 567, 1969. 18. Grainger, R. M.: Orthodontic treatment priority index. P H S Publication N o . 1000, Series 2, N o . 25. Washington, U.S. Government Printing Office, 1967. 19. Salzman, J. A.: Handicapping malocclusion assessment to establish treatment priority. Am J Orthod 54: 749, 1968. 20. D'Amico, A.: The canine teeth-normal functional rela tion of the natural teeth of man. J South Calif Dent Assoc 26: 6, 49, 127, 175, 194, 239, 1958. 21. Stallard, H., and Stuart, C. E.: Concepts of occlusion: What kind of occlusion should recusped teeth be given? Dent Clin North Am p. 591, 1963. 22. Scott, M. E., and Baum, L.: Procedures and techniques for restoring 'canine function' for abraded teeth. J. South Calif Dent Assoc 32: 23, 1964. 23. Cohen, W. E.: A study of occlusal interferences in orthodontically treated occlusions and untreated normal occlu sions. Am J Orthod 5 1 : 647, 1965. 24. Rothner, J. D.: Occlusal equilibration—A part of ortho dontic treatment. Am J Orthod 38: 530, 1952. 25. Blume, D. G.: A study of occlusal equilibration as it relates to orthodontics. Am J Orthod 44: 575, 1958. 26. Perry, H. T.: Principles of occlusion applied to modern orthodontics. Dent Clin North Am 13: 581, 1969. 27. Williams, R. L.: Occlusal treatment for the postortho dontic patient. Am J Orthod 59: 431, 1971. 28. O'Leary, T. J., Rudd, K. D., Nabers, C. L., and Stumpf, A. J., Jr.: The effect of a "tube type" diet and stress inducing conditions on tooth mobility. J Periodontol 38: 322, 1967.
Abstracts EXPERIMENTAL CONTACT HYPERSENSITIVITY IN THE GINGIVA OF DOGS Nobréus, N., and Attstrbm, R. J Periodont
Res 9: 245, N o . 4, 1974.
l-dinitro-2,4-chlorbenzene ( D N C B , 0.05% in Orabase) was applied to the gingiva on one side daily for six days in a group of seven beagle dogs while on the control side (contralateral side of jaw) only the vehicle (orabase) was applied. Duration of each application was two hours on days 0 and 3, and 30 minutes on days 1, 2, 4, 5. Antithymocyte serum (ATS) was injected subcutaneously in dogs on day 3. Biopsies from the D N C B sites on day 3 indicated a high number of mononuclear inflammatory cells indicative of hypersensitivity towards D N C B whereas the control site had low counts of inflammatory cells. Measurements of crevicular leukocytes, gingival fluid and acid phos phatase activity in crevicular samples (gingival crevice parameters) were also high compared to the control site. Immunosuppression with A T S affected all parameters on day 6. Gingival contact hypersensitivity to D N C B can be elicited in beagle dogs; therefore, this study supports earlier observations on the role of cellular immunity in the pathogenesis of plaque-induced gingival inflammation. School of Dentistry, Carl Gustavs väg 34, S-214 21 Malmo, Sweden
CLINICAL AND STEREOLOGIC ANALYSIS OF THE COURSE OF EARLY GINGIVITIS IN DOGS Lindhe, J., Schroeder, H. E., Page, R. C , Munzel-Pedrazzoli, S., and Hugoson, A . J Periodont Res 9: 314, N o . 5, 1974. In order to observe the sequence of events occurring in gingival tissues of dogs following the accumulation of plaque, five German Pointers were placed on a 2% chlorhexidine mouthrinse for five months during the eruption of their permanent teeth. Clinical examinations of gingival index, plaque index and measurement of gingival exudate as well as biopsies from various areas for stereologic analysis were done. Tests were repeated on various days and lasted 28 days. The plaque and exudate accumulation was relatively constant within the first two weeks but increased in the last two weeks. There was no marked change in the cellular infiltration of the junctional epithelium except for the so-called "X-Lymphocytes'' The total collagen content of the gingival connec tive tissue remained constant. The tests showed that the histopathological alterations did not parallel clinical observations and one of the reasons given was the influence of the chlorhexidine on the gingival tissues. Department of Periodontology, Faculty of Odontology, Pack, S-400 33 Goteborg 33, Sweden
