P a t t e r n o f t o o t h c o n t a c t s in e c c e n t r i c m a n d i b u l a r p o s i t i o n s in young adults Bengt Ingervall, DDS, OdontDr, a Roland Hiihner, DDS, DrMedDent, b and Stephan Kessi, DDS, DrMedDent b University of Bern, Bern, Switzerland
Tooth contact patterns in laterotrusion, protrusion of the mandible, and in the retruded position w e r e recorded in y o u n g m e n w i t h v a r y i n g t y p e s o f occlusion. The tooth contacts w e r e recorded clinically w i t h a l g i n a t e (irreversible hydrocolloid) indices. In addition, the functional s t a t e of the m a s t i c a t o r y s y s t e m w a s e v a l u a t e d by the recording o f signs and s y m p t o m s o f m a n d i b u l a r d y s f u n c t i o n and o f the a b r a s i o n of the teeth. On protrusion, m o s t subjects had contacts only on anterior teeth. P r o t r u s i v e contacts only on posterior t e e t h w e r e rare. On laterotrusion, most subjects had group function on the functional side. Contact on the nonfunctional side w a s found in h a l f of the subjects in a 1.5 m m l a t e r o t r u s i v e position and in one third of t h e m in a 3 m m l a t e r o t r u s i v e position. No correlation b e t w e e n the t y p e s o f tooth contacts and m a n d i b u l a r d y s f u n c t i o n w a s found. (J PROSTHET DENT 1991;66:169-76.)
T
h
e
prevalence of the two types of tooth contact-group function and canine protection--on the functional side during gliding occlusion has been studied in individuals with normal occlusion and in series randomly sampled according to the type of occlusion. H° Group function is defined as contact between opposing teeth in a segment or group. 1H3 A canine-protected occlusion implies contact only between the canines on the functional side. 14,15 In most of the above studies, the tooth contacts have been recorded in a lateral position corresponding to an edge-to-edge position of the canines approximately 3 mm lateral to the intercuspal position. An eccentric position of this magnitude is probably rarely used during natural function (chewing). A type of tooth contact in a lateral position closer to the intercuspal position would therefore be of interest. Only Yaffe and Ehrlich 5 have studied the pattern of tooth contact in the occlusal range between the intercuspal and the 3 mm lateral positions. They found that although group function prevailed in the whole range of the lateral excursion up to an edge-to-edge position of the canines, its prevalence decreased with increasing deviation of the mandible from the intercuspal position. The presence of tooth contacts on the nonfunctional side in lateral gliding has also been recorded in some of the above studies. I, 3, s-10 However, information is lacking regarding the prevalence of lateral gliding in the functional occlusal range, that is during the first millimeters of lateral gliding from the intercuspal position. Also little is known about the pattern of tooth contact in the retruded and in protruded mandibular positions. Two studies of the num-
aprofessor and Chairman, Department of Orthodontics. bPrivate practice. 10/1/28104
THE JOURNAL OF PROSTHETIC DENTISTRY
ber of tooth contacts in the retruded position of the mandible presented conflicting results. 16, i7 The type of tooth contact on protrusion has only occasionally been reported.4, 7,18-20 It is possible that the pattern of tooth contacts could influence the functional state of the masticatory system. Thus in a previous study, 4 individuals with group function were found to have less mandibular dysfunction than those with canine protection. Such a relation was, however, not found in other studies of nonpatient samples of young adults or of those with masticatory disturbances, s, 9, 21 In view of the lack of information regarding the pattern of tooth contacts in various excursive positions, especially within the functional range of movement, there seems to be a need for further studies. The aim of this investigation was to describe the tooth contact pattern in a sample of young ~adults regardless of the type of morphologic occlusion. A further mm was to ascertain a possible association between the pattern of tooth contacts and mandibular dysfunction. METHODS
Seventy-five men, most of them dental students, were included in the study. They varied between 20 and 33 years of age (median 24 years). They were selected irrespective of the type of occlusion or degree of restoration of the teeth. The number of teeth varied between 23 and 32 (median 29). The number of missing teeth, the number of teeth with one or more restored cusps, and the number of teeth restored with a crown is shown in Table I. In the table, the third molar is designated as tooth No. 8 and the central incisor is designated as tooth No. 1. Most of the missing teeth were third molars, followed by the first and, less frequently, the second premolars. Few teeth had restorations involving a cusp. Forty-one men (55%) had had orthodontic treatment,
169
INGERVALL, H.~tINER AND KESSI
amber of teeth with one or more restored cusps, and n u m b e r of teeth restored with Restored Upper arch, tooth
Missing
8 7 6 5 4 3 2 1
66 0 1 7 27 2 6 0
Restored L o w e r arch,
Cusp
Crown
1 1 1 4
14 3 1
1 2 2
T a b l e II. T y p e of occlusion and malocclusion in 75 men studied T y p e Of o c c l u s i o n or m a I o c e l u s i o n
Neutral Distal Mesia] Overlap ~.6 mm One or more incisors in crossbite Overbite ~5 mm Frontal open bite (one or more teeth) Lateral open bite (one or more teeth) Cmssbite of one or more posterior teeth Scissors bite of one or more posterior teeth
N u m b e r of
subjects
Missing
Cusp
8 7 6 5 4 3 2 1
84 0 4 6 15 1 1 2
1 3 21
56 16 3 1 3
75 21 4 1 4
26 1
35 1
3
4
I1
15
1
1
examination
The men were asked about subjective symptoms and were examined for clinical signs of mandibular dysfunct~ion: The clinical examination included the measurement ~ffthe movement of the mandible, the recording of pain and ~emporomandibular joint sounds on mandibular movement, deviation of the mandibular midline on opening, i,~cking or luxation of the t e m p o r o m a n d i b u l a r joints on ~~,:,vement of the mandible, and palpation of the mastica~,ory muscles and t e m p o r o m a n d i b u l a r joints. T h e anamnes~ic a n d clinical examination was done by the same exam-
Crown
1 6 1
1
T a b l e III. Prevalence (in percent) of signs and symptoms of m a n d i b u l a r dysfunction according to anamnestic and clinical dysfunction index of Helkimo*
Percent
including the removal of p e r m a n e n t teeth in 18. A removable orthodontic appliance had been used in 39 subjects and 13 had worn a fixed restoration. T h e type of occlusion was evaluated on dental casts. The results are given in Table II,
Functional
tooth
Grade
0
I II III
Anamnestie index (subject history)
74 21 5
Clinical index
26 62 11 1
*Helkimo M. Swed Dent J 1974;67:101-21.
iner and followed the protocol used in previous studies. 4, 22, 23 T h e recordings were used for the calculation of the anamnestic and clinical dysfunction index of Helkimo. 24 T h e anamnestic index of Helkimo 24 is made up of three grades, where grade 0 includes individuals who according to the subjective history are free from any s y m p t o m s of m a n d i b u l a r dysfunction. Grade I includes individuals with mild s y m p t o m s such as t e m p o r o m a n d i b u l a r joint sounds; grade II includes those with severe symptoms (difficulties in opening the mouth wide, locking, luxation, pain on movement of the mandible, and/or pain in the region of the t e m p o r o m a n d i b u l a r joint or the masticatory muscles). T h e clinical dysfunction index is based on the presence of five signs of m a n d i b u l a r dysfunction, each sign being judged on a t h r e e - p o i n t scale of severity. The five signs are impaired range of movement of the mandible, impaired function of the t e m p o r o m a n d i b u l a r joints, muscle pain, t e m p o r o m a n d i b u l a r joint pain, and pain on movement of the mandible. T h e clinical dysfunction index has four grades, grade 0 including individuals without signs of m a n d i b u l a r dysfunction to grade III, those with severe signs of dysfunction. The abrasion of the teeth was determined clinically according to the following scale: (1) no or only slight abrasion, (2) evident abrasion facets, and (3) abrasion into the dentin.
TOOTH CONTACTS IN MANDIBULAR POSITIONS
Table IV. Percentage of subjects with different degrees of abrasion of tooth groups
Table V. Percentage of subjects with different types of tooth contact on protrusion
Abrasion grade
Incisors
Canines Premolars Molars
1
2
3
9
20
71
12 40 41
12 44 39
76 16 20
Protrusion 1.5 m m
Edge-to-edge position
66 16 4
73 15 4
10
5
3 1
3 0
Only on incisors On incisors and canines On incisors, canines, and premolars On incisors, canines, premolars, and molars Only on premolars and molars Only on molars
R e c o r d i n g o f tooth c o n t a c t s Antagonistic tooth contacts were recorded with alginate (irreversible hydrocolloid) indices (Alginora, Unitec Co., Monrovia, Calif.) using a previously described method. 1 All recordings were made by the same examiner and were repeated. In the event of different results of the duplicate recordings, the existence of a tooth contact was checked with occlusal foil (polyvinylchloride [PVC] 0.01 ram). The tooth contacts were recorded in two laterotrusive positions to both sides, in two protrusive positions, and in the retruded position of the mandible. Tooth contacts were recorded on laterotrusion of 3 mm and 1.5 mm as measured at the mandibular midline. To enable the 3 mm laterotrusive position to be determined, marks were made on the upper central incisors with a water-resistant pencil 3 mm to both sides of the midline. The irreversible hydrocolloid mixture was placed on the occlusal surfaces of the mandibular teeth and the subject moved his mandible 3 mm laterally from the intercuspal position. The movement was not guided by the examiner who, however, placed a finger extraorally at the gonial angle of the laterotrusive side. It was found that this procedure made it easier for the subject to make a pure lateral movement. The same procedure was used for the recording of the tooth contacts in the 1.5 mm laterotrusive position except that the subject was asked to stop the lateral movement when the mandibular midline was halfway between the maxillary midline and the 3 mm mark. If the subject had an obvious canine-protected occlusion (contact only between the canines on the functional side) and clearly no contact on the nonfunctional side, no irreversible hydrocolloid index was made. The tooth contacts on protrusion were recorded in two positions, protrusion to the edge-to-edge occlusion of the maxillary and mandibular central incisors, and 1.5 mm protrusion from the intercuspal position. In both recordings, the protrusion was started from the intercuspal position after the irreversible hydrocolloid had been placed on the mandibular occlusal surfaces. For the determination of the 1.5 mm protrusive position, a sliding caliper was used at the central incisors. The mandible was thus advanced the amount of the overjet minus 1.5 mm. For the recording of the tooth contacts in the retruded
THE JOURNAL OF PROSTHETIC DENTISTRY
Table Vl. Percentage of subjects with different types of tooth contact in retruded position Percent o f subjects
Only on molars Only on premolars On molars and premolars On molars, premolars, canines, and incisors
28 13 39 20
mandibular position, a mandibular hinge movement was made by the examiner gripping the subject's chin with the forefinger beneath the chin and the thumb pressing against the lower incisors and alveolar process. From the terminal hinge movement, the mandible was brought to contact in the retruded position and stabilized there until the irreversible hydrocolloid had set. RESULTS
Mandibular d y s f u n c t i o n The prevalence of signs and symptoms of mandibular dysfunction are presented in Table III. Severe symptoms and evident signs of mandibular dysfunction (grade II) were rare and only one subject had a severe (grade III) clinical dysfunction index. The most prevalent type of subjective symptom was temporomandibular joint sounds (17 subjects), while other symptoms were rare or nonexistent. The most prevalent types of clinical signs of mandibular dysfunction were temporomandibular joint clicking (33 subjects), tenderness of masticatory muscles on palpation (24 subjects), and deviation of the mandibular midline on opening (23 subjects), with other signs rare or nonexistent. The degree of abrasion of the teeth is shown in Table IV. In most of the subjects, the incisors and canines were abraded into the dentin.
Tooth c o n t a c t s in p r o t r u s i v e p o s i t i o n s The median number of tooth contacts both on 1.5 mm protrusion and on protrusion to the edge-to-edge position
171
I N G E R V A L L , H A H N E R AND K E S S I
Numberl 80-
Although most contacts were on the second molars, there was a fairly even distribution of the tooth contacts in the retruded position on the posterior teeth.
60
Tooth contacts in laterotrusive positions
!
40
20
o~
1 !
i8
---1 7
6
5
4
I
20
,
312:1,
, upper
! I
TEETH lower
I I i
40
.....]
60 80
L~
F i g . 1. Distribution of tooth contacts in retruded position. Mean Of right and left sides.
was three, with a range for both positions of one to seven contacts. The types of tooth contacts on protrusion are shown in Table V~ The incisor contact was mostly on the central incisors. Contact on the upper central incisors was five to six times more prevalent t h a n on the lateral incisors. In both protrusive positions, most subjects had tooth contacts on the anterior teeth; protrusive contacts only on the posterior teeth were rare. Bilateral contacts were more common than u n i l a t e r a l A bilateral contact was thus found in 84% and in 885~ in the 1.5 m m and edge-to-edge protrusive positions, respectively.
Tooth contacts in the retruded position The anteroposterior distance between the retruded and intercuspal mandibular positions was measured at the incisors with sliding calipers. The median distance was 1 mm. The two m a n d i b u l a r positions coincided in 12% of subjeers. The number of tooth contacts in the retruded position varied between 1 and 10, with a median value of 3. The oontact was bilateral in 69 ?i of subjects. The distribution ~f subjects according to type of tooth contact in the retruded position is given in Table VI and in Fig. 1.
The distribution of the subjects by the n u m b e r of contacts on the functional and nonfunctional sides is given in Table VII. The median n u m b e r of tooth contacts on the functional side both on 1.5 m m and on 3 m m laterotrusion was two. The corresponding figures for nonfunctional side contact were one and zero, respectively. The distribution of subjects according to the type of tooth contact is given in Table VIII. On both 1.5 m m and 3 m m laterotrusion most subjects had group function. On 1.5 m m laterotrusion about half of the subjects had a balanced occlusion with simultaneous contact on both the functional and nonfunctional sides. This was less prevalent on 3 m m laterotrusion, where only about one third of the subjects had a balanced occlusion. On 1.5 m m laterotrusion a nonfunctional side contact was found bilaterally in 41% and unilaterally in 24% of the subjects, and on 3 m m laterotrusion in 19% bilaterally and in 24 5;, unilaterally. A bilateral nonfunctional side interference was found in one subject on 1.5 m m and in two subjects on 3 m m laterotrusion. The distribution of contacts in laterotrusion according to tooth type is shown in Figs. 2 and 3. On the functional side, the tooth contact was in both laterotrusive positions predominantly on the canines, followed in 1.5 mm laterotrusion by the first molar, with a more even distribution between the posterior teeth on 3 m m laterotrusion. On the nonfunctional side, tooth contact on the second molar predominated, especially on 3 m m laterotrusion.
Correlations To evaluate a possible association between the pattern of tooth contact and age and the functional state of the masticatory system as well as the degree of abrasion, Spearman rank correlation was used. The numbers of tooth contacts on laterotrusion and on protrusion were tested for correlation with age, the Helkimo index, 24 and the degree of abrasion. Age was positively correlated to the n u m b e r of tooth contacts on the functional side on 1.5 mm laterotrusion (0.01 < p < 0.05). No significant correlation was found between the n u m b e r of tooth contacts and the anamnestic or clinical dysfunction indices. Positive correlations were found between the abrasion of the incisors, the canines, and the premolars and the n u m b e r of tooth contacts on the functional side on 1.5 mm laterotrusion (0.01 < p < 0.05). Abrasion of the canines was, however, negatively correlated to the n u m b e r of tooth contacts on the nonfunctional side on 1.5 m m laterotrusion {0.01 < p < 0.05).
TOOTHCONTACTSIN MANDIBULARPOSITIONS
T a b l e VII. Percentage of subjects with varying number of tooth contacts on laterotrusion: Mean of right and left sides Number of contacts Functional side
0
N o n f u n c t i o n a l side
1
2
3
4
5
6
7
8
0
1
2
3
Percentage of subjects with laterotrusion of 1.5mm 4 35 3mm 3 42
21 25
21 19
11 4
5 5
3 1
0 0
0 1
46 67
40 27
11 5
0 1
T a b l e VIII. Percentage of subjects with canine protection and with group function, respectively, on functional side, and with contact on nonfunctional side N o n f u n c t i o n a l side
F u n c t i o n a l side
Laterotrusion to 1.5 mm Laterotrusion to 1.5 mm Laterotrusion to to 3 mm Laterotrusion to to 3 mm
Canine protection
Group function
Balanced contact
Interfering contact
right
28
67
49
5 (4 subjects)
left
23
76
48
1 (1 subject)
right
32
64
29
4 (3 subjects)
left
35
63
31
3 (2 subjects)
DISCUSSION The selection of men for this study was based on the availability of volunteers and was justified by the fact t h a t no sex differences in tooth contacts have been reported. The inclusion of men with varying types of occlusion and also of subjects who had had orthodontic t r e a t m e n t was deliberate so as to get a random sample of young a d u l t dentitions. I t can be expected t h a t many individuals in the age group studied have had varying types of orthodontic t r e a t m e n t but others still have malocclusion. The distribution of the subjects according to type of occlusion (Angle class) corresponds well with the prevalence in a large survey of occlusal conditions. 25 T h e men had well-preserved dentitions, with only a few teeth missing or restored. H y p o d o n t i a probably accounts for the lack of some third molars, second premolars, and incisors. Impaction m a y also be a factor with respect to missing third molars. The missing first premolars were probably mostly extracted for orthodontic reasons. The reliability of the method used for the recording of tooth contact has been studied in an earlier investigation. 1 The agreement between repeated recordings with irreversible hydrocolloid indices was found t o be over 80%. To further enhance the reliability of the registrations in the present investigation, the registration of tooth contact was
THE JOURNAL OF PROSTHETIC DENTISTRY
based on duplicate recordings,supplemented in doubtful cases with an occlusalfoiltest. Most of the m e n had no subjective symptoms of mandibular dysfunction but most had mild clinicalsigns of dysfunction. The clinicaldysfunction index grade I was more prevalent than in samples of m e n of young middle age or in 20-year-old individuals.4,22 There was, however, a lower prevalence of grade II dysfunction than in the series mentioned. The distribution of subjects by the clinical dysfunction index compares well with that in samples of dental students studied by Droukas et al.8 and by De Laat and van Steenberghe.I° Only a few studies of the pattern of tooth contacts on protrusion and in the retruded mandibular position are available for comparison with the resultsof this study. It isclearthat tooth contact of the canines on protrusion was much more prevalent (24 % to 30 %) in our sample than in the study of Scaife and Holt,7 who reported such contact in only 4.6% of their subjects.Sadowsky and BeGole 19 and Sadowsky and Polson2° report differing prevalences of posterior tooth contact on protrusion. In a group of previous orthodontic patients and in controlsthat were studied in Illinois,about 5 0 % of the subjects had posterior tooth contact,compared with only about 20% in a similar population from the Eastman Dental Center in
173
INGERVALL,
H~INER
AND
KESSI
Number 120
,:.:.:~..:.: ~::::~::::: ,.......,...
IO0
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Laterotrusion 1.Smm Laterotrusion
3 mm
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--7
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t
6i5
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ia
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upper TEETH lower
:;::;.::!~
20
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:.:.:.:.:.:, :.:.:.:.:.:, . .......
ii:i:i::::iii .......,..
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120
F i g . 2. Distribution of tooth contacts on functional side. Mean of right and left sides.
Rochester. 2° The authors suggested possible differences in the techniques of the different examiners as an explanation tor the conflicting results. In neither study is it clear in which mandibular position the recording of protrusive ~ooth contacts was made, Compared with the two studies mentioned previously and also compared with the investigation by Gazit and Lieberman, is a lower prevalence of posterior tooth contact on protrusion was found in this series- 18',_' and 12q~ on 1.5 m m protrusion and on protrusion on the edge-to-edge position, respectively. The present cesutts compare favorably with those of Madone and lngervatl. 4 however, who found posterior tooth contact in 14~c of their subjects. The relatively low prevalence of posterior tooth contact in the present group may possibly ~e due to the relatively high prevalence of deep overlap.
Such an occlusion will disocclude the posterior teeth on protrusion. Gillings et alfl 7 reported a mean of eight contacts in the retruded position, compared with a median number of two in the study of McNamara and Henry. 16 The median number in the present study was three and was thus close to the findings of McNamara and H e n r y ) 6 The report of the distribution of the contacts in the retruded position is new in this study and was not given in the two earlier investigations. The results of different studies of tooth contact on laterotrusion are given in Table IX. It is clear that these results differ widely. The reasons for this divergence are partly the varying criteria used for the selection of the samples studied. There is thus a great difference in the
TOOTH CONTACTS IN MANDIBULAR POSITIONS
Number 8o
6o [
J Laterotrusion
1.Smm
Laterotrusion
40
3 mm
20
o
I i
8
IV
7
6 .............,
i:!:!:!:~:~:!:
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ii
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upper
TEETH
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i!!i!!~!i!!!i~
iiiiiiiiiiiiil
40
::::::::::::::
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80
Fig. 3. Distribution of tooth contacts on nonfunctional side. Mean of right and left sides.
IX. Reported prevalence of canine protection on functional side in cusp-to-cusp position of canines and of nonfunctional side contact in adults Table
Canine
Study
Sample
protection
Weinberg 19646 Scaife and Holt 19697
Random
Ingervall 19721
Normal occlusion
Goldstein 19792 Sadowsky and BeGole 198019 Rinchuse and Sassouni 19833
Normal occlusion Normal occlusion and random Normal occlusion
Madone and Ingervall 19844 Sadowsky and Poison 198420 De Laat and van Steenberghe 1985l°
Normal occlusion Normal occlusion and random Random
Yaffe and Ehrlich 19875
Normal occlusion
This study
Random
prevalence of nonfunctional side tooth contact between this study and a previous study by one of the present authors, even though the same methods were used. 1 The discrepant prevalence therefore reflects the difference be-
T H E J O U R N A L OF P R O S T H E T I C D E N T I S T R Y
19 57 bilateral 16 unilateral 2 bilateral 18 unilateral 14 1
Nonfunctional side contact
64 bilateral 20 unilateral 88-91 68 bilateral 24 unilateral
44 13 bilateral 12 unilateral 27 bilateral 44 unilateral 17 bilateral 26 unilateral
41-88 61
19 bilateral 24 unilateral
tween normal occlusion and a sample with varying occlusal types. Differences of definition are also responsible for the varying results. Thus in the study by Ingervall,1 as in that by Rinchuse and Sassouni,3 canine protection was recorded
175
INGERVALL, HJ~HNER AND KESSI
only in the absence of tooth contact on the nonfunctional side. This is the reason for the low prevalence of canineprotected occlusion in these two studies. In the present investigation, the occlusion on the functional side, as is most common, was classified irrespective of the situation on the nonfunctional side. The results of this study with respect to the type of tooth contact in the occlusal range, from the intercuspal to the 3 m m lateral position, parallel those of Yaffe and Ehrlich. 5 Thus although group function was the most prevalent type of occlusion in both laterotrusive positions, it was less frequent in the 3 m m lateral position. The difference was not great, however. There was a greater difference between the two laterotrusive positions in the prevalence of nonfunctional side contact. The prevalence of such contact thus dropped from ,50 % to less than 30 % when the mandible was moved from a 1.5 m m to a 3 m m lateral position. The type of tooth contact in the excursive positions is obviously of minor importance as an etiologic factor in mandibular dysfunction, as no significant correlation was found between the number of tooth contacts and the dysflmction index. The results are therefore in line with those of recent studies of both investigational subjects and patients.S, 9, 21 However, the results are at variance with the investigation by Madone and Ingervall. 4 who reported on orthodontic patients. The positive correlations between abrasion and the number of functional side contacts in the 1.5 m m lateral position do not necessarily mean that abrasion is the causal factor for multiple tooth contact. It could be that tooth contact is a prerequisite for abrasion. In this context, it is important to mention that the coefficient of correlation was not greater for the abrasion of the canine than for the other types of teeth. The negative correlation between abrasion of the canines and contact on the nonfunctional side is interesting and would seem to imply that nonfunctional side contact protects the canine from abrasion. This hypothesis must, however, be verified by further investigations. CLINICAL
IMPLICATIONS
The results of this study clearly indicate the variety of functional tooth contact patterns that the dentist can expect to find in a population of young adult patients. Thus ()~ laterotrusion, for example, both group function and carune protection on the functional side as well as contact or ~c~ncontact on the nonfunctional side are prevalent. These ~,arying types of tooth contact patterns should be of no ¢~mcern with respect to mandibular dysfunction, as no as?.ociation between the pattern of tooth contact and dysh ~ c t i o n has been found in this or in similar studies, s, 9, 21 22)~e practice of prophylactically eliminating occlusal in~e~ference on the nonfunctional side may be questioned, as patients tend to adapt to this type of occlusion. 2s It may be ~ise to accept the existing pattern of tooth contacts and o~ly consider occlusal adjustment if mandibular dysfunct:,,n develops.
REFERENCES 1. Ingervall B. Tooth contacts on the functional and non-functional side in children and young adults. Arch Oral BiD] 1972;17:191-200. 2. Goldstein GR. The relationship of canine-protected occlusion to a periodontal index. J PROSTHET DENT 1979;41:277-83. 3. Rinchuse DJ, Sassouni V. An evaluation of functional occlusal interferences in orthodontically treated and untreated subjects. Angle Orthodont 1983;53:122-30. 4. Madone G, Ingervall B. Stability of results and function of the masticatory system in patients treated with the Herren type of activator. Eur J Orthodont 1984;6:92-106. 5. Yaffe A, Ehrlich J. The functional range of tooth contact in lateral gliding movements. J PROSTHET DENT 1987;57:730-3. 6. Weinberg LA. A cinematic study of centric and eccentric occlusions. J PROSTHET DENT 1964;14:290-3. 7. Scaife RR Jr, Holt JE. Natural occurrence of cuspid guidance. J PRosTHET DENT 1969;22:225-9. 8. Droukas B, Lind~e C, Carlsson GE. Relationship between occlusal factors and signs and symptoms of mandibular dysfunction. Acta Odontol Scand 1984;42:27%83. 9. Droukas B, Lind~e C, Carlsson GE. Occlusion and mandibular dysfunction: a clinicalstudy of patients referred for functional disturbances of the masticatory system. J PROSTHET DENT 1985;53:402-6. 10. De Laat A, van Steenberghe D. Occlusal relationships and temporomandibular joint dysfunction. Part I: epidemiologic findings. J PROSTHET DENT 1985;54:835-42. 11. Beyron HL. Characteristics of iunctionally optimal occlusion and principles of occlusal rehabilitation. J Am Dent Assoc 1954;48:648-56. 12. Beyron HL. Optimal occlusion. Dent Clin North Am 1969;13:54%54. 13. Krogh-Poulsen WG, Olsson A. Management of the occlusion of the teeth. In: Schwarz L, Chayes CH, eds. Facial pain and mandibular dysfunction. Philadelphia: WB Saunders Co, 1969. 14. D'Amico A. The canine teeth. Normal functional relation to the natural teeth of man. J South Calif Dent Assoc 1958;26:194-208. 15. D'Amico A. Functional occlusion of the natural teeth of man. J PROSTHET DENT 1961;11:899-915. 16. McNamara DC, Henry PJ. Terminal hinge contact in dentitions. J PROSTHET DENT 1974;32:405-11. 17. Gillings BRD, Graham CH, Duckmanton NA. Jaw movements in young adult men during chewing. J PROSTHET DENT 1973;29:616-27. 18. Gazit E, Lieberman MA. The intercuspal surface contact area registration: an additional tool for evaluation of normal occlusion. Angle Orthodont 1973;43:96-106. 19. Sadowsky C, BeGole EA. Long-term status of temporomandibular joint function and functional occlusion after orthodontic treatment. Am J Orthodont 1980;78:201-12. 20. Sadowsky C, Polson AM. Temporomandibular disorders and functional occlusion after orthodontic treatment: results of two long-term studies. Am J Orthod 1984;86:386-90. 21. De Laat A, van Steenberghe D, Lesaffre E. Occlusal relationships and temporomandibular joint dysfunction. Part II: Correlations between occlusal and articular parameters and symptoms of TMJ dysfunction by means of stepwise logistic regression. J PROSTHET DENT 1986;55:116-21. 22. Ingervall B, Mohlin B, Thilander B. Prevalence of symptoms of functional disturbances of the masticatory system in Swedish men. J Oral Rehabil 1980;7:185-97. 23. Egermark-Eriksson I, Carlsson GE. Ingervall B. Prevalence of mandibular dysfunction and oro-facial parafunction in 7-, 11- and 15-year old Swedish children. Eur J Orthodont 1981;3:163-72. 24. Helkimo M. Studies on function and dysfunction of the masticatory system. II. Index for anamnestic and clinical dysfunction and occlusal state. Swed Dent J 1974;67:101-21. 25. Ingervall B, Gebauer U, Thfier U. Malokklusionen bei Schweizer Rekruten im Jahre 1985. Schweiz Monatsschr Zahnmed 1987;97:136673. 26. Ingervall B, Carlsson GE. Masticatory muscle activity before and after elimination of balancing side occlusat interference. J Oral Rehabil 1982;9:183-92.
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DR. BENGT INGERVALL KLINIK FLrRKIEFERORTHOP~DIE FREIBURGSTRASSE 7 CH-3010 BERN SWITZERLAND
Tooth contact patterns in laterotrusion, protrusion of the mandible, and in the retruded position w e r e recorded in y o u n g m e n w i t h v a r y i n g t y p e s o f occlusion. The tooth contacts w e r e recorded clinically w i t h a l g i n a t e (irreversible hydrocolloid) indices. In addition, the functional s t a t e of the m a s t i c a t o r y s y s t e m w a s e v a l u a t e d by the recording o f signs and s y m p t o m s o f m a n d i b u l a r d y s f u n c t i o n and o f the a b r a s i o n of the teeth. On protrusion, m o s t subjects had contacts only on anterior teeth. P r o t r u s i v e contacts only on posterior t e e t h w e r e rare. On laterotrusion, most subjects had group function on the functional side. Contact on the nonfunctional side w a s found in h a l f of the subjects in a 1.5 m m l a t e r o t r u s i v e position and in one third of t h e m in a 3 m m l a t e r o t r u s i v e position. No correlation b e t w e e n the t y p e s o f tooth contacts and m a n d i b u l a r d y s f u n c t i o n w a s found. (J PROSTHET DENT 1991;66:169-76.)
T
h
e
prevalence of the two types of tooth contact-group function and canine protection--on the functional side during gliding occlusion has been studied in individuals with normal occlusion and in series randomly sampled according to the type of occlusion. H° Group function is defined as contact between opposing teeth in a segment or group. 1H3 A canine-protected occlusion implies contact only between the canines on the functional side. 14,15 In most of the above studies, the tooth contacts have been recorded in a lateral position corresponding to an edge-to-edge position of the canines approximately 3 mm lateral to the intercuspal position. An eccentric position of this magnitude is probably rarely used during natural function (chewing). A type of tooth contact in a lateral position closer to the intercuspal position would therefore be of interest. Only Yaffe and Ehrlich 5 have studied the pattern of tooth contact in the occlusal range between the intercuspal and the 3 mm lateral positions. They found that although group function prevailed in the whole range of the lateral excursion up to an edge-to-edge position of the canines, its prevalence decreased with increasing deviation of the mandible from the intercuspal position. The presence of tooth contacts on the nonfunctional side in lateral gliding has also been recorded in some of the above studies. I, 3, s-10 However, information is lacking regarding the prevalence of lateral gliding in the functional occlusal range, that is during the first millimeters of lateral gliding from the intercuspal position. Also little is known about the pattern of tooth contact in the retruded and in protruded mandibular positions. Two studies of the num-
aprofessor and Chairman, Department of Orthodontics. bPrivate practice. 10/1/28104
THE JOURNAL OF PROSTHETIC DENTISTRY
ber of tooth contacts in the retruded position of the mandible presented conflicting results. 16, i7 The type of tooth contact on protrusion has only occasionally been reported.4, 7,18-20 It is possible that the pattern of tooth contacts could influence the functional state of the masticatory system. Thus in a previous study, 4 individuals with group function were found to have less mandibular dysfunction than those with canine protection. Such a relation was, however, not found in other studies of nonpatient samples of young adults or of those with masticatory disturbances, s, 9, 21 In view of the lack of information regarding the pattern of tooth contacts in various excursive positions, especially within the functional range of movement, there seems to be a need for further studies. The aim of this investigation was to describe the tooth contact pattern in a sample of young ~adults regardless of the type of morphologic occlusion. A further mm was to ascertain a possible association between the pattern of tooth contacts and mandibular dysfunction. METHODS
Seventy-five men, most of them dental students, were included in the study. They varied between 20 and 33 years of age (median 24 years). They were selected irrespective of the type of occlusion or degree of restoration of the teeth. The number of teeth varied between 23 and 32 (median 29). The number of missing teeth, the number of teeth with one or more restored cusps, and the number of teeth restored with a crown is shown in Table I. In the table, the third molar is designated as tooth No. 8 and the central incisor is designated as tooth No. 1. Most of the missing teeth were third molars, followed by the first and, less frequently, the second premolars. Few teeth had restorations involving a cusp. Forty-one men (55%) had had orthodontic treatment,
169
INGERVALL, H.~tINER AND KESSI
amber of teeth with one or more restored cusps, and n u m b e r of teeth restored with Restored Upper arch, tooth
Missing
8 7 6 5 4 3 2 1
66 0 1 7 27 2 6 0
Restored L o w e r arch,
Cusp
Crown
1 1 1 4
14 3 1
1 2 2
T a b l e II. T y p e of occlusion and malocclusion in 75 men studied T y p e Of o c c l u s i o n or m a I o c e l u s i o n
Neutral Distal Mesia] Overlap ~.6 mm One or more incisors in crossbite Overbite ~5 mm Frontal open bite (one or more teeth) Lateral open bite (one or more teeth) Cmssbite of one or more posterior teeth Scissors bite of one or more posterior teeth
N u m b e r of
subjects
Missing
Cusp
8 7 6 5 4 3 2 1
84 0 4 6 15 1 1 2
1 3 21
56 16 3 1 3
75 21 4 1 4
26 1
35 1
3
4
I1
15
1
1
examination
The men were asked about subjective symptoms and were examined for clinical signs of mandibular dysfunct~ion: The clinical examination included the measurement ~ffthe movement of the mandible, the recording of pain and ~emporomandibular joint sounds on mandibular movement, deviation of the mandibular midline on opening, i,~cking or luxation of the t e m p o r o m a n d i b u l a r joints on ~~,:,vement of the mandible, and palpation of the mastica~,ory muscles and t e m p o r o m a n d i b u l a r joints. T h e anamnes~ic a n d clinical examination was done by the same exam-
Crown
1 6 1
1
T a b l e III. Prevalence (in percent) of signs and symptoms of m a n d i b u l a r dysfunction according to anamnestic and clinical dysfunction index of Helkimo*
Percent
including the removal of p e r m a n e n t teeth in 18. A removable orthodontic appliance had been used in 39 subjects and 13 had worn a fixed restoration. T h e type of occlusion was evaluated on dental casts. The results are given in Table II,
Functional
tooth
Grade
0
I II III
Anamnestie index (subject history)
74 21 5
Clinical index
26 62 11 1
*Helkimo M. Swed Dent J 1974;67:101-21.
iner and followed the protocol used in previous studies. 4, 22, 23 T h e recordings were used for the calculation of the anamnestic and clinical dysfunction index of Helkimo. 24 T h e anamnestic index of Helkimo 24 is made up of three grades, where grade 0 includes individuals who according to the subjective history are free from any s y m p t o m s of m a n d i b u l a r dysfunction. Grade I includes individuals with mild s y m p t o m s such as t e m p o r o m a n d i b u l a r joint sounds; grade II includes those with severe symptoms (difficulties in opening the mouth wide, locking, luxation, pain on movement of the mandible, and/or pain in the region of the t e m p o r o m a n d i b u l a r joint or the masticatory muscles). T h e clinical dysfunction index is based on the presence of five signs of m a n d i b u l a r dysfunction, each sign being judged on a t h r e e - p o i n t scale of severity. The five signs are impaired range of movement of the mandible, impaired function of the t e m p o r o m a n d i b u l a r joints, muscle pain, t e m p o r o m a n d i b u l a r joint pain, and pain on movement of the mandible. T h e clinical dysfunction index has four grades, grade 0 including individuals without signs of m a n d i b u l a r dysfunction to grade III, those with severe signs of dysfunction. The abrasion of the teeth was determined clinically according to the following scale: (1) no or only slight abrasion, (2) evident abrasion facets, and (3) abrasion into the dentin.
TOOTH CONTACTS IN MANDIBULAR POSITIONS
Table IV. Percentage of subjects with different degrees of abrasion of tooth groups
Table V. Percentage of subjects with different types of tooth contact on protrusion
Abrasion grade
Incisors
Canines Premolars Molars
1
2
3
9
20
71
12 40 41
12 44 39
76 16 20
Protrusion 1.5 m m
Edge-to-edge position
66 16 4
73 15 4
10
5
3 1
3 0
Only on incisors On incisors and canines On incisors, canines, and premolars On incisors, canines, premolars, and molars Only on premolars and molars Only on molars
R e c o r d i n g o f tooth c o n t a c t s Antagonistic tooth contacts were recorded with alginate (irreversible hydrocolloid) indices (Alginora, Unitec Co., Monrovia, Calif.) using a previously described method. 1 All recordings were made by the same examiner and were repeated. In the event of different results of the duplicate recordings, the existence of a tooth contact was checked with occlusal foil (polyvinylchloride [PVC] 0.01 ram). The tooth contacts were recorded in two laterotrusive positions to both sides, in two protrusive positions, and in the retruded position of the mandible. Tooth contacts were recorded on laterotrusion of 3 mm and 1.5 mm as measured at the mandibular midline. To enable the 3 mm laterotrusive position to be determined, marks were made on the upper central incisors with a water-resistant pencil 3 mm to both sides of the midline. The irreversible hydrocolloid mixture was placed on the occlusal surfaces of the mandibular teeth and the subject moved his mandible 3 mm laterally from the intercuspal position. The movement was not guided by the examiner who, however, placed a finger extraorally at the gonial angle of the laterotrusive side. It was found that this procedure made it easier for the subject to make a pure lateral movement. The same procedure was used for the recording of the tooth contacts in the 1.5 mm laterotrusive position except that the subject was asked to stop the lateral movement when the mandibular midline was halfway between the maxillary midline and the 3 mm mark. If the subject had an obvious canine-protected occlusion (contact only between the canines on the functional side) and clearly no contact on the nonfunctional side, no irreversible hydrocolloid index was made. The tooth contacts on protrusion were recorded in two positions, protrusion to the edge-to-edge occlusion of the maxillary and mandibular central incisors, and 1.5 mm protrusion from the intercuspal position. In both recordings, the protrusion was started from the intercuspal position after the irreversible hydrocolloid had been placed on the mandibular occlusal surfaces. For the determination of the 1.5 mm protrusive position, a sliding caliper was used at the central incisors. The mandible was thus advanced the amount of the overjet minus 1.5 mm. For the recording of the tooth contacts in the retruded
THE JOURNAL OF PROSTHETIC DENTISTRY
Table Vl. Percentage of subjects with different types of tooth contact in retruded position Percent o f subjects
Only on molars Only on premolars On molars and premolars On molars, premolars, canines, and incisors
28 13 39 20
mandibular position, a mandibular hinge movement was made by the examiner gripping the subject's chin with the forefinger beneath the chin and the thumb pressing against the lower incisors and alveolar process. From the terminal hinge movement, the mandible was brought to contact in the retruded position and stabilized there until the irreversible hydrocolloid had set. RESULTS
Mandibular d y s f u n c t i o n The prevalence of signs and symptoms of mandibular dysfunction are presented in Table III. Severe symptoms and evident signs of mandibular dysfunction (grade II) were rare and only one subject had a severe (grade III) clinical dysfunction index. The most prevalent type of subjective symptom was temporomandibular joint sounds (17 subjects), while other symptoms were rare or nonexistent. The most prevalent types of clinical signs of mandibular dysfunction were temporomandibular joint clicking (33 subjects), tenderness of masticatory muscles on palpation (24 subjects), and deviation of the mandibular midline on opening (23 subjects), with other signs rare or nonexistent. The degree of abrasion of the teeth is shown in Table IV. In most of the subjects, the incisors and canines were abraded into the dentin.
Tooth c o n t a c t s in p r o t r u s i v e p o s i t i o n s The median number of tooth contacts both on 1.5 mm protrusion and on protrusion to the edge-to-edge position
171
I N G E R V A L L , H A H N E R AND K E S S I
Numberl 80-
Although most contacts were on the second molars, there was a fairly even distribution of the tooth contacts in the retruded position on the posterior teeth.
60
Tooth contacts in laterotrusive positions
!
40
20
o~
1 !
i8
---1 7
6
5
4
I
20
,
312:1,
, upper
! I
TEETH lower
I I i
40
.....]
60 80
L~
F i g . 1. Distribution of tooth contacts in retruded position. Mean Of right and left sides.
was three, with a range for both positions of one to seven contacts. The types of tooth contacts on protrusion are shown in Table V~ The incisor contact was mostly on the central incisors. Contact on the upper central incisors was five to six times more prevalent t h a n on the lateral incisors. In both protrusive positions, most subjects had tooth contacts on the anterior teeth; protrusive contacts only on the posterior teeth were rare. Bilateral contacts were more common than u n i l a t e r a l A bilateral contact was thus found in 84% and in 885~ in the 1.5 m m and edge-to-edge protrusive positions, respectively.
Tooth contacts in the retruded position The anteroposterior distance between the retruded and intercuspal mandibular positions was measured at the incisors with sliding calipers. The median distance was 1 mm. The two m a n d i b u l a r positions coincided in 12% of subjeers. The number of tooth contacts in the retruded position varied between 1 and 10, with a median value of 3. The oontact was bilateral in 69 ?i of subjects. The distribution ~f subjects according to type of tooth contact in the retruded position is given in Table VI and in Fig. 1.
The distribution of the subjects by the n u m b e r of contacts on the functional and nonfunctional sides is given in Table VII. The median n u m b e r of tooth contacts on the functional side both on 1.5 m m and on 3 m m laterotrusion was two. The corresponding figures for nonfunctional side contact were one and zero, respectively. The distribution of subjects according to the type of tooth contact is given in Table VIII. On both 1.5 m m and 3 m m laterotrusion most subjects had group function. On 1.5 m m laterotrusion about half of the subjects had a balanced occlusion with simultaneous contact on both the functional and nonfunctional sides. This was less prevalent on 3 m m laterotrusion, where only about one third of the subjects had a balanced occlusion. On 1.5 m m laterotrusion a nonfunctional side contact was found bilaterally in 41% and unilaterally in 24% of the subjects, and on 3 m m laterotrusion in 19% bilaterally and in 24 5;, unilaterally. A bilateral nonfunctional side interference was found in one subject on 1.5 m m and in two subjects on 3 m m laterotrusion. The distribution of contacts in laterotrusion according to tooth type is shown in Figs. 2 and 3. On the functional side, the tooth contact was in both laterotrusive positions predominantly on the canines, followed in 1.5 mm laterotrusion by the first molar, with a more even distribution between the posterior teeth on 3 m m laterotrusion. On the nonfunctional side, tooth contact on the second molar predominated, especially on 3 m m laterotrusion.
Correlations To evaluate a possible association between the pattern of tooth contact and age and the functional state of the masticatory system as well as the degree of abrasion, Spearman rank correlation was used. The numbers of tooth contacts on laterotrusion and on protrusion were tested for correlation with age, the Helkimo index, 24 and the degree of abrasion. Age was positively correlated to the n u m b e r of tooth contacts on the functional side on 1.5 mm laterotrusion (0.01 < p < 0.05). No significant correlation was found between the n u m b e r of tooth contacts and the anamnestic or clinical dysfunction indices. Positive correlations were found between the abrasion of the incisors, the canines, and the premolars and the n u m b e r of tooth contacts on the functional side on 1.5 mm laterotrusion (0.01 < p < 0.05). Abrasion of the canines was, however, negatively correlated to the n u m b e r of tooth contacts on the nonfunctional side on 1.5 m m laterotrusion {0.01 < p < 0.05).
TOOTHCONTACTSIN MANDIBULARPOSITIONS
T a b l e VII. Percentage of subjects with varying number of tooth contacts on laterotrusion: Mean of right and left sides Number of contacts Functional side
0
N o n f u n c t i o n a l side
1
2
3
4
5
6
7
8
0
1
2
3
Percentage of subjects with laterotrusion of 1.5mm 4 35 3mm 3 42
21 25
21 19
11 4
5 5
3 1
0 0
0 1
46 67
40 27
11 5
0 1
T a b l e VIII. Percentage of subjects with canine protection and with group function, respectively, on functional side, and with contact on nonfunctional side N o n f u n c t i o n a l side
F u n c t i o n a l side
Laterotrusion to 1.5 mm Laterotrusion to 1.5 mm Laterotrusion to to 3 mm Laterotrusion to to 3 mm
Canine protection
Group function
Balanced contact
Interfering contact
right
28
67
49
5 (4 subjects)
left
23
76
48
1 (1 subject)
right
32
64
29
4 (3 subjects)
left
35
63
31
3 (2 subjects)
DISCUSSION The selection of men for this study was based on the availability of volunteers and was justified by the fact t h a t no sex differences in tooth contacts have been reported. The inclusion of men with varying types of occlusion and also of subjects who had had orthodontic t r e a t m e n t was deliberate so as to get a random sample of young a d u l t dentitions. I t can be expected t h a t many individuals in the age group studied have had varying types of orthodontic t r e a t m e n t but others still have malocclusion. The distribution of the subjects according to type of occlusion (Angle class) corresponds well with the prevalence in a large survey of occlusal conditions. 25 T h e men had well-preserved dentitions, with only a few teeth missing or restored. H y p o d o n t i a probably accounts for the lack of some third molars, second premolars, and incisors. Impaction m a y also be a factor with respect to missing third molars. The missing first premolars were probably mostly extracted for orthodontic reasons. The reliability of the method used for the recording of tooth contact has been studied in an earlier investigation. 1 The agreement between repeated recordings with irreversible hydrocolloid indices was found t o be over 80%. To further enhance the reliability of the registrations in the present investigation, the registration of tooth contact was
THE JOURNAL OF PROSTHETIC DENTISTRY
based on duplicate recordings,supplemented in doubtful cases with an occlusalfoiltest. Most of the m e n had no subjective symptoms of mandibular dysfunction but most had mild clinicalsigns of dysfunction. The clinicaldysfunction index grade I was more prevalent than in samples of m e n of young middle age or in 20-year-old individuals.4,22 There was, however, a lower prevalence of grade II dysfunction than in the series mentioned. The distribution of subjects by the clinical dysfunction index compares well with that in samples of dental students studied by Droukas et al.8 and by De Laat and van Steenberghe.I° Only a few studies of the pattern of tooth contacts on protrusion and in the retruded mandibular position are available for comparison with the resultsof this study. It isclearthat tooth contact of the canines on protrusion was much more prevalent (24 % to 30 %) in our sample than in the study of Scaife and Holt,7 who reported such contact in only 4.6% of their subjects.Sadowsky and BeGole 19 and Sadowsky and Polson2° report differing prevalences of posterior tooth contact on protrusion. In a group of previous orthodontic patients and in controlsthat were studied in Illinois,about 5 0 % of the subjects had posterior tooth contact,compared with only about 20% in a similar population from the Eastman Dental Center in
173
INGERVALL,
H~INER
AND
KESSI
Number 120
,:.:.:~..:.: ~::::~::::: ,.......,...
IO0
[~
Laterotrusion 1.Smm Laterotrusion
3 mm
!::iii~i~i!i::
8O
risisi~si~i: :.:.:.:.:.:
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~ii!iiiiiiiii ::::::::::::
i2i;!iiii;i
4O
iiiiiiiiiiil
~:~:::.::: ,.,,..:.:.:.
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:.{F i:.:,~~ ~'.:i::::::
0
--7
I
.....
8
I : 7
t
6i5
i
ia
4 ......
2
upper TEETH lower
:;::;.::!~
20
:~:::~ !!i!!!~!!! :_'::;::5:
:.:.:.:.:.:, :.:.:.:.:.:, . .......
ii:i:i::::iii .......,..
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:.::.+:.:
............ i~i!i~i~i ...... ...,..,..
. ......... :~i~!~i!i .....
_.~ ......... 60
i~i;
:i:i:i~:i
i
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i
_._M
I
....-:. • • ...:
!i!!!;!;!:
80
;+:+:. . -..:...
100 i
120
F i g . 2. Distribution of tooth contacts on functional side. Mean of right and left sides.
Rochester. 2° The authors suggested possible differences in the techniques of the different examiners as an explanation tor the conflicting results. In neither study is it clear in which mandibular position the recording of protrusive ~ooth contacts was made, Compared with the two studies mentioned previously and also compared with the investigation by Gazit and Lieberman, is a lower prevalence of posterior tooth contact on protrusion was found in this series- 18',_' and 12q~ on 1.5 m m protrusion and on protrusion on the edge-to-edge position, respectively. The present cesutts compare favorably with those of Madone and lngervatl. 4 however, who found posterior tooth contact in 14~c of their subjects. The relatively low prevalence of posterior tooth contact in the present group may possibly ~e due to the relatively high prevalence of deep overlap.
Such an occlusion will disocclude the posterior teeth on protrusion. Gillings et alfl 7 reported a mean of eight contacts in the retruded position, compared with a median number of two in the study of McNamara and Henry. 16 The median number in the present study was three and was thus close to the findings of McNamara and H e n r y ) 6 The report of the distribution of the contacts in the retruded position is new in this study and was not given in the two earlier investigations. The results of different studies of tooth contact on laterotrusion are given in Table IX. It is clear that these results differ widely. The reasons for this divergence are partly the varying criteria used for the selection of the samples studied. There is thus a great difference in the
TOOTH CONTACTS IN MANDIBULAR POSITIONS
Number 8o
6o [
J Laterotrusion
1.Smm
Laterotrusion
40
3 mm
20
o
I i
8
IV
7
6 .............,
i:!:!:!:~:~:!:
iiii!i!iii!i!i
20
ii
5
4
li i i i :i :i l I
'~
'
I
~
I
'
~
i
3
:
2
i
1
i
,
,
I
[:.'..~iiiiiiiiil lower
I
upper
TEETH
I
i!!i!!~!i!!!i~
iiiiiiiiiiiiil
40
::::::::::::::
60
80
Fig. 3. Distribution of tooth contacts on nonfunctional side. Mean of right and left sides.
IX. Reported prevalence of canine protection on functional side in cusp-to-cusp position of canines and of nonfunctional side contact in adults Table
Canine
Study
Sample
protection
Weinberg 19646 Scaife and Holt 19697
Random
Ingervall 19721
Normal occlusion
Goldstein 19792 Sadowsky and BeGole 198019 Rinchuse and Sassouni 19833
Normal occlusion Normal occlusion and random Normal occlusion
Madone and Ingervall 19844 Sadowsky and Poison 198420 De Laat and van Steenberghe 1985l°
Normal occlusion Normal occlusion and random Random
Yaffe and Ehrlich 19875
Normal occlusion
This study
Random
prevalence of nonfunctional side tooth contact between this study and a previous study by one of the present authors, even though the same methods were used. 1 The discrepant prevalence therefore reflects the difference be-
T H E J O U R N A L OF P R O S T H E T I C D E N T I S T R Y
19 57 bilateral 16 unilateral 2 bilateral 18 unilateral 14 1
Nonfunctional side contact
64 bilateral 20 unilateral 88-91 68 bilateral 24 unilateral
44 13 bilateral 12 unilateral 27 bilateral 44 unilateral 17 bilateral 26 unilateral
41-88 61
19 bilateral 24 unilateral
tween normal occlusion and a sample with varying occlusal types. Differences of definition are also responsible for the varying results. Thus in the study by Ingervall,1 as in that by Rinchuse and Sassouni,3 canine protection was recorded
175
INGERVALL, HJ~HNER AND KESSI
only in the absence of tooth contact on the nonfunctional side. This is the reason for the low prevalence of canineprotected occlusion in these two studies. In the present investigation, the occlusion on the functional side, as is most common, was classified irrespective of the situation on the nonfunctional side. The results of this study with respect to the type of tooth contact in the occlusal range, from the intercuspal to the 3 m m lateral position, parallel those of Yaffe and Ehrlich. 5 Thus although group function was the most prevalent type of occlusion in both laterotrusive positions, it was less frequent in the 3 m m lateral position. The difference was not great, however. There was a greater difference between the two laterotrusive positions in the prevalence of nonfunctional side contact. The prevalence of such contact thus dropped from ,50 % to less than 30 % when the mandible was moved from a 1.5 m m to a 3 m m lateral position. The type of tooth contact in the excursive positions is obviously of minor importance as an etiologic factor in mandibular dysfunction, as no significant correlation was found between the number of tooth contacts and the dysflmction index. The results are therefore in line with those of recent studies of both investigational subjects and patients.S, 9, 21 However, the results are at variance with the investigation by Madone and Ingervall. 4 who reported on orthodontic patients. The positive correlations between abrasion and the number of functional side contacts in the 1.5 m m lateral position do not necessarily mean that abrasion is the causal factor for multiple tooth contact. It could be that tooth contact is a prerequisite for abrasion. In this context, it is important to mention that the coefficient of correlation was not greater for the abrasion of the canine than for the other types of teeth. The negative correlation between abrasion of the canines and contact on the nonfunctional side is interesting and would seem to imply that nonfunctional side contact protects the canine from abrasion. This hypothesis must, however, be verified by further investigations. CLINICAL
IMPLICATIONS
The results of this study clearly indicate the variety of functional tooth contact patterns that the dentist can expect to find in a population of young adult patients. Thus ()~ laterotrusion, for example, both group function and carune protection on the functional side as well as contact or ~c~ncontact on the nonfunctional side are prevalent. These ~,arying types of tooth contact patterns should be of no ¢~mcern with respect to mandibular dysfunction, as no as?.ociation between the pattern of tooth contact and dysh ~ c t i o n has been found in this or in similar studies, s, 9, 21 22)~e practice of prophylactically eliminating occlusal in~e~ference on the nonfunctional side may be questioned, as patients tend to adapt to this type of occlusion. 2s It may be ~ise to accept the existing pattern of tooth contacts and o~ly consider occlusal adjustment if mandibular dysfunct:,,n develops.
REFERENCES 1. Ingervall B. Tooth contacts on the functional and non-functional side in children and young adults. Arch Oral BiD] 1972;17:191-200. 2. Goldstein GR. The relationship of canine-protected occlusion to a periodontal index. J PROSTHET DENT 1979;41:277-83. 3. Rinchuse DJ, Sassouni V. An evaluation of functional occlusal interferences in orthodontically treated and untreated subjects. Angle Orthodont 1983;53:122-30. 4. Madone G, Ingervall B. Stability of results and function of the masticatory system in patients treated with the Herren type of activator. Eur J Orthodont 1984;6:92-106. 5. Yaffe A, Ehrlich J. The functional range of tooth contact in lateral gliding movements. J PROSTHET DENT 1987;57:730-3. 6. Weinberg LA. A cinematic study of centric and eccentric occlusions. J PROSTHET DENT 1964;14:290-3. 7. Scaife RR Jr, Holt JE. Natural occurrence of cuspid guidance. J PRosTHET DENT 1969;22:225-9. 8. Droukas B, Lind~e C, Carlsson GE. Relationship between occlusal factors and signs and symptoms of mandibular dysfunction. Acta Odontol Scand 1984;42:27%83. 9. Droukas B, Lind~e C, Carlsson GE. Occlusion and mandibular dysfunction: a clinicalstudy of patients referred for functional disturbances of the masticatory system. J PROSTHET DENT 1985;53:402-6. 10. De Laat A, van Steenberghe D. Occlusal relationships and temporomandibular joint dysfunction. Part I: epidemiologic findings. J PROSTHET DENT 1985;54:835-42. 11. Beyron HL. Characteristics of iunctionally optimal occlusion and principles of occlusal rehabilitation. J Am Dent Assoc 1954;48:648-56. 12. Beyron HL. Optimal occlusion. Dent Clin North Am 1969;13:54%54. 13. Krogh-Poulsen WG, Olsson A. Management of the occlusion of the teeth. In: Schwarz L, Chayes CH, eds. Facial pain and mandibular dysfunction. Philadelphia: WB Saunders Co, 1969. 14. D'Amico A. The canine teeth. Normal functional relation to the natural teeth of man. J South Calif Dent Assoc 1958;26:194-208. 15. D'Amico A. Functional occlusion of the natural teeth of man. J PROSTHET DENT 1961;11:899-915. 16. McNamara DC, Henry PJ. Terminal hinge contact in dentitions. J PROSTHET DENT 1974;32:405-11. 17. Gillings BRD, Graham CH, Duckmanton NA. Jaw movements in young adult men during chewing. J PROSTHET DENT 1973;29:616-27. 18. Gazit E, Lieberman MA. The intercuspal surface contact area registration: an additional tool for evaluation of normal occlusion. Angle Orthodont 1973;43:96-106. 19. Sadowsky C, BeGole EA. Long-term status of temporomandibular joint function and functional occlusion after orthodontic treatment. Am J Orthodont 1980;78:201-12. 20. Sadowsky C, Polson AM. Temporomandibular disorders and functional occlusion after orthodontic treatment: results of two long-term studies. Am J Orthod 1984;86:386-90. 21. De Laat A, van Steenberghe D, Lesaffre E. Occlusal relationships and temporomandibular joint dysfunction. Part II: Correlations between occlusal and articular parameters and symptoms of TMJ dysfunction by means of stepwise logistic regression. J PROSTHET DENT 1986;55:116-21. 22. Ingervall B, Mohlin B, Thilander B. Prevalence of symptoms of functional disturbances of the masticatory system in Swedish men. J Oral Rehabil 1980;7:185-97. 23. Egermark-Eriksson I, Carlsson GE. Ingervall B. Prevalence of mandibular dysfunction and oro-facial parafunction in 7-, 11- and 15-year old Swedish children. Eur J Orthodont 1981;3:163-72. 24. Helkimo M. Studies on function and dysfunction of the masticatory system. II. Index for anamnestic and clinical dysfunction and occlusal state. Swed Dent J 1974;67:101-21. 25. Ingervall B, Gebauer U, Thfier U. Malokklusionen bei Schweizer Rekruten im Jahre 1985. Schweiz Monatsschr Zahnmed 1987;97:136673. 26. Ingervall B, Carlsson GE. Masticatory muscle activity before and after elimination of balancing side occlusat interference. J Oral Rehabil 1982;9:183-92.
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