Occlusal
force
after
partial
mandibular
resection
Mark Marunick, DDS, MS,a Bruce E. Mathes, DDS,b Barbara B. Klein, RDH,C and Mahmoud Seyedsadr, PhDd Wayne State University,
Harper Hospital, and University
of Detroit Dental School, Detroit, Mich.
Surgical resection of a segment or loss of mandibular continuity can adversely affect most of the structures essential for maximum occlusal force. Five subjects who had partial mandibular resections for treatment of squamous cell carcinoma were studied. Occlusal force was recorded before and after cancer treatment and following prosthetic rehabilitation. A gnathodynamometer was used to record anterior occlusal force. Five edentulous and five dentate cancer-free subjects matched for age were studied to establish comparable normative data. The null hypothesis that partial mandibular resection would not affect maximum occlusal force was rejected (p = 0.0101). Mandibular resection did alter maximum occlusal force. The impact of the decrease in maximum occlusal force on masticatory function is yet to be determined. (J PROSTHET DENT 1992;67:835-8.)
0
cclusal force is dependent upon the integrity of the muscles of mastication, temporomandibular joint (TMJ), mandible, dent&ion, and the status of the surrounding hard and soft tissues. All may be affected by radiation therapy and surgery, two of the modalities used to treat head and neck neoplasms.‘? 2 Trismus, xerostomia, edema, mucositis, and radiation caries have been documented as side effects of radiation therapy.3,4 The direct effects of radiation on tissue have been reported and may account for some of the side effects noted.5s 6 Most longterm alterations can be attributed to changes in tissue vascularity within the radiated field. The vascular damage leads to proliferation of fibroblasts and fibrosis, with further alterations in vascularity. The long-term effects on the muscles of mastication may lead to trismus and a decreased range of motion of the mandible. Preradiation extraction of teeth can adversely affect occlusion and create relative changes in maximal opening. Surgical resection of a portion of the mandible, muscles of mastication, and some teeth can cause an imbalance of the remaining muscles of mastication, altered and restricted mandibular movements, and a decreased forceful mandibular closure. Occlusal force has been studied in normal patients.7-12 These studies used electromyography (EMG) to measure muscle activity, a gnathodynamometer to measure bite strength, and pressure transducers to measure forces at the tissue-prosthesis interface. Few Research supported by National Institutes of Health grant CA 43838. BAssistant Professor, Department of Otolaryngology, Wayne State University. bGeneral Practice Residency, University of Detroit Dental School. CResearch Assistant, Department of Otolaryngology, Wayne State University. dAssistant Professor, Department of Radiation Oncology, Wayne State University. 10/l/35961
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
studies
have evaluated
these parameters
in patients
with
head and neck cancer, with those reported being retrospective. The purpose of this study was to evaluate the effects of radiation therapy and mandibular resection on maximal
occlusal
force in patients
treated
for head and
neck cancer. METHODS
AND
MATERIAL
Five subjects with head and neck cancer were evaluated before any treatment. The test group was composed of four men and one woman, with an age range of 43 to 72 years and mean of 57 years (Table I). A gnathodynamometer (Streeter Richards, Chicago, Ill.) was used to record anterior occlusal force between the natural teeth, denture teeth, and edentulous alveolar ridges.13 This custom-built
instrument
was length
immune
and in-
cluded simultaneous recording of maxillary and mandibular pressures, which were displayed on a quantimatic 9000 digital
scale. A silicone
gum rubber
(Dow Corning,
Mid-
land, Mich.) with a durometer reading of 50 was placed on the ends of the mouthpiece. Measurements were made at an interocclusal distance of 13 mm and were recorded seven times with rest between measurements. The lowest and highest values were discarded
and the mean was considered
representative of the maximum occlusal force for that day of testing.13 After preliminary evaluations, the subjects entered specific cancer treatment protocols. Methods and extent of
surgical resection were recorded, and additional information was obtained regarding radiation therapy including type, dose, port size, and fractionation technique. After oncologic treatment, occlusal force was evaluated. Subjects No. 3, 4, and 5 were treated with prostheses and were tested with and without their new prostheses. The
subjects had worn their new prostheses for 2 months before testing. All subjects served as their own controls.
Ten additional
835
MARUNICK
Table
I.
Profile
of the five subjects
ET AL
studied Dentition
Subject
No.
1
Age
(5-9
Sex
44
M
Pretreatment Partially
Mandibular diagnosis
Posttreatment
Edentulous
edentulous 2
3
43
63
M
M
Partially edentulous
Edentulous
Edentulous
Edentulous
4
57
M
Edentulous
Edentulous
5
72
F
Edentulous
Edentulous
Epidermoid carcinoma floor of mouth Squamous cell carcinoma floor of mouth
Carcinoma of the pharynx and base of the tongue Verrucous carcinoma of tonsil and soft palate Carcinoma of the mandibular alveolar ridge
cancer-free subjects matched on the basis of age and dental status (edentulous and natural dentition) were studied to establish normative values. Controls were tested on 3 different days using the same method of measurement as
was applied to the test subjects. The mean of the three test dates was considered representative for each control. All studies were performed according to the guidelines of the Wayne State University Human Subject Committee. The test-retest reliability of the occlusal force measurement was assessed using the 10 control subjects, five who were edentulous with complete dentures and five with natural teeth. The reliabi1it.y measure used was intraclass correlation (ICC) for the repeated measure design-that is, patients by three time periods. For the edentulous control subjects without dentures in place, the ICC was 0.90; with dentures in place, it was 0.97. For the subjects with natural dentition, the ICC was 0.99. An evaluation of the effects between the two control groups, edentulous with and without dentures and the natural dentition group, provided data relevant to the evaluation of validity. By t test, a significant advantage was seen for the natural dentition group compared with the edentulous group without dentures (p = 0.0205) and with dentures b = 0.0389). A paired t test was used to evaluate within the edentulous control group. A significant advantage was noted for the edentulous group with dentures
compared with the edentulous group without (p = 0.0359). 836
dentures
Mandibular continuity
Stage
T4, NOM0
Radiation therapy
Maintainedsegmental inner table Lost from left parasymphysis to right molar region; reconstructed with osseomyocutaneous flap Lost-distal to right midbody
T3, N2MO
T3, NlMO
GY)
60
(post surgery) 60
(post surgery)
50
(post surgery)
T3, NOM0
Lost-distal to right midbody
None
T3, NOM0
Lost-parasymphysis to left angle; reconstructed with synthe plate
None
RESULTS Pretreatment occlusal force for the two partial edentate test subjects ranged from 25.4 to 40.0 lb, with a mean of 32.7 lb. Posttreatment occlusal force decreased to 7.0 and 7.6 lb, with a mean of 7.3 lb. The percent decrease ranged from 72.0% to 81.0%) with a mean decrease of 78.0% (Table II). Pretreatment occlusal force for the edentulous test subjects with
maxillary
and mandibular
complete
dentures
ranged from 11.5 to 23.0 lb, with a mean of 19.1 lb. Posttreatment occlusal force ranged from 7.7 to 19.4 lb, with a mean of 12.7 lb. The decrease ranged from 15.0 % to 52.0 % , with a mean decrease of 33.0% (Table II). Pretreatment occlusal force for the edentulous test subjects when the dentures were removed ranged from 17.0 to 22.6 lb, with a mean of 20.3 lb. Posttreatment occlusal force decreased to a range of 7.9 to 9.3 lb and a mean of 8.4 lb. Without dentures, the percent decrease ranged from 54.0% to 62.0%, with a mean of 56.7% (Table II). Using a paired t test, a statistically significant difference was noted when comparing pretreatment occlusal force for all five subjects with posttreatment occlusal force for the edentulous
state without
a prosthesis
(p = 0.0101).
Using
a paired t test, a statistically significant difference was noted when comparing pretreatment occlusal force for the three edentulous subjects without a prosthesis with their posttreatment occlusal force without a prosthesis (p = 0.0307). No statistically significant difference was noted for the three subjects when comparing pretreatment JUNE
1992
VOLUME
67
NUMBER
6
OCCLUSAL
Table
FORCE
II.
Test
AFTER
RGSECTION
Occlusal force (lb) for test subjects Dental
subject
1
status
Pretreatment
PI< PE E- WOP E-WP E-WOP E-WP E-WOP E-WP
2 3 4 5
PE, Partially edentulous; *Months post surgery.
Posttreatment
25.4 40.0 26.6 11.5 17.0 22.8 21.5 23.0
E, edentulous;
WOP, without
prosthesis;
Dental
7.0 7.6 9.3 7.7 7.9 19.4 8.3 11.0
status
MO*
E-WOP E-WOP E-WOP E-WP E-WOP E-WP E-WOP E-WP
from
5 20 14 14 12 12 10 10
% Decrease pretreatment 72 81 54 32 54 15 62 52
WP, with prosthesis.
occlusal force with a prosthesis with posttreatment occlusal force with a prosthesis (p = 0.1498). Occlusal force for the dentate controls ranged from 60.6 to 187.5 lb, with a mean of 123.2 lb (Table III). Edentulous controls with maxillary and mandibular dentures demonstrated occlusal forces that ranged from 9.3 to 39.9 lb, with a mean of 26.2 lb. Wh.en the dentures were removed, occlusal force ranged from 4.4 to 12.3 lb, with a mean of 8.0 lb (Table IV).
Table
III.
Occlusal force for dentate controls (n = 5)
Subject No. 1 2 3 4 5 Average
number
Table
IV.
Age b-9
Sex
Occlusal force (lb)
49 55 56 62 41
F M F M F
137.3 55.2 60.6 75.6 187.5
of occluding
pairs of teeth = 13.
DISCUSSION Occlusal force was mea.sured at a vertical opening of 13.0 mm in the incisor region.13 Manns et a1.15reported measuring occlusal force from the distal borders of the canines and showed the biting strength is greatest at an increased vertical dimension of 10 to 20 mm. Occlusal forces for dentate and complete denture wearers have been reported by Gibbs et al.,s at a molar vertical opening of 10.0 mm, to average 162 lb and 35 lb, respectively. It is generally accepted that greater forces can be generated on the posterior teeth. Howell and Manly16 demonstrated that the range of maximum occlusal force on t.he first molar teeth was 91 to 198 lb, and on central incisors the force was 29 to 51 lb. Although it was not measured, it is unlikely, given the anatomic limitations, that Iposterior occlusal force would be significantly higher in the edentulous resected subjects that were studied. Using EMG, Kapur and Garrett17 estimated that denture wearers applied 22% to 39% of the muscle force applied b:y those with natural dentition. Although EMG was not used in this study, the values for occlusal force for the dentate and edentulous controls demonstrate a similar ditference. The subjects that were partially edentulous before treatment demonstrated the greatest decrease (78%) in occlusal force from pretreatment levels. This can be attributed to the fact that they were made edentulous in preparation for radiation therapy and mandibular resection. The effects of the separate interventions on occlusal force could not be determined, since the teeth were extracted at the time of the surgical resection. The pretreatment partially edentulous subjects No. 1 and 2 were not treated with prostheses; consequently, they were not tested with a prosthesis THE
JOURNAL
OF PROSTHETIC
DENTISTRY
Occlusal force for edentulous controls (n = 5) Occlusal
Subject No. 1 2 3 4 5 Abbreviations
force
(lb)
Age (yr)
Sex
WP
WOP
47 60 49 53 47
F F F F F
39.9 20.8 30.3 9.3 30.8
7.1 12.3 7.8 8.3 4.4
as in Table
II.
following treatment. Subject No. 1 developed a recurrence 8 months after surgery and was dropped from the study. Subject, No. 2 had insufficient interarch space to accommodate maxillary and mandibular prostheses. Postt,reatment occlusal force for the test subjects when using dentures (12.7 lb mean) was significantly lower than that of the controls (26.2 lb mean). Changes in forces produced may be the result of alterations following surgery, including loss of mandibular continuity, muscles of mastication, changes in tongue status, pain in supporting tissues, and uncoordinated mandibular movements. The surgery and radiation therapy decreased the subjects’ ability to attain forceful closure with dentures, since only a 4.3 lb (mean) increase in occlusal force (12.7 lb mean with dentures versus 8.4 lb mean without dentures) was recorded after treatment with dentures. Variations reported above and below the mean can be attributed to individual differences in muscle strength, ability to manipulate dentures, 837
MARUNICK
and retention and stability of the dentures. VerKendere et al.ls used EMG analysis to determine that wearing a prosthesis does not change the normal reflex activity of the masticatory muscles. This may not be true for patients following partial mandibular resection. Posttreatment evaluations showed significant decreases (15 % to 62 % ) in occlusal force regardless of prosthodontic treatment, indicating the impact of the t.reatment on the integrity of the structures essential for maximum occlusal force. Michael et al.lo reported that occlusal forces in the posterior region on the working side of denture wearers in the closed position were 4.2 lb for soft food and 11.3 lb for hard food. This would indicate the test subjects in this study have sufficient occlusal force to comminute food. Other factors that may limit ability to masticate are range of motion and tongue mobility.. The reduced force exhibited by the test subjects in the cmrent study could influence their diet selection or may be compensated for by increasing the time the forces are applied, as reported by Neil1 et aLg Consequently, many patients with partial mandibular resection may restrict the consistency of food consumed and take more time to eat a meal. Without a prosthesis, test subjects’ occlusal force following prosthodontic treatment are similar to that of the edentate controls without a prosthesis. These values ranged from 4.4 lb to 12.3 lb for the edentate controls and 7.0 lb to 14.0 lb for the test subjects. This observation indicates that a baseline limit of the supporting tissues exists in recording maximum occlusal force, which is unaffected by the treatment modalities used. CONCLUSIONS Based on these limited surgical resection with therapy can significantly Conventional prosthetic subjects studied to their els.
838
observations, partial mandibular or without combined radiation alter maximum occlusal force. treatment did not restore the pretreatment occlusal force lev-
ET AL
REFERENCES 1. Beumer J, Curtis T, Harrison RE. Radiation therapy of the oral cavity: sequelae and management. Part I. Head Neck Surg 1979;1:301-12. 2. Kirkegaard J, Lindelov B, Bretlau P. Traditional and new treatment strategies for oral squamous cell carcinomas. Ear Nose Throat J 1989; 68:593-604. 3. Driezen S, Daly TE, Drane JB, Brown LR. Oral complications of cancer radiotherapy. Postgrad Med 1977;61:85-92. 4. Engelmeier RL, King GE. Complications of head and neck radiation therapy and their management. J PROSTHET DENT 1983;49:514-22. 5. Beumer J, Silverman S, Benak SB. Hard and soft tissue necroses following radiation therapy for oral cancer. J PROSTHET DENT 1972; 27:640-4. 6. Baker DG. The radiobiological basis for tissue reactions in the oral cavity following therapeutic x-irradiation. Arch Otolaryngol1982;108:21-4. 7. Gibbs CH, Mahan PE, Lundeen HC, Brehnan K, Walsh EK, Sinkewicz SL, Ginsbe SB. Occlusal forces during chewing-influences of biting strength and food consistency. J PROSTHET DENT 1981;46:561-7. 8. Gibbs CH, Mahan PE, Mauderli A, Lundeen HC, Walsh EK. Limits of human bite strength. J PROSTHET DENT 19%56:226-g. 9. Neil1 DJ, Kydd WL, Nairn RI, Wilson J. Functional loading of the dentitian during mastication. J PROSTHET DENT 1989;62:218-28. 10. Michael CG, Javid NS, Colaizzi FA, Gibbs GH. Biting strength and chewing forces in complete denture wearers. J PROSTHET DENT 1990; 6354943. 11. Sposetti VJ, Gibbs
tivity
in overdenture
CH, Alderson TH, et al. Bite force and muscle acwearers before and after attachment placement. J
PROSTHET DENT 1986;55:265-73.
12. Cutright DE, Brudrik JS, Gay WD, Selting WJ. Tissue pressure under complete maxillary dentures. J PROSTHET DENT 1976;35:160-70. 13. Marunick MT, Mathog RH. Mastication in patients treated for head and neck cancer: a pilot study. J PROSTHET DENT 1990;63:566-73. 14. Deleted in galleys. 15. Manns A, Miralles R, Palarzi C. EMG, bite force, and elongation of the masseter muscle under voluntary isometric contractions and variations of vertical dimension. J PROSTHET DENT 1979;42:674-82. 16. Howell AH, Manly RS. An electronic strain gauge for measuring oral forces. J Dent Res 1948;27:705-12. 17. Kapur KK, Garrett NR. Studies of biologic parameters for denture design. Part II. Comparison of masseter muscle activity, masticatory performance, and salivary secretion rates between denture and natural dentition groups. J PROSTHET DENT 1964;52:408-13. 18. VerKendere MT, Lodter JP. The silent period duration of the masticatory muscles. J PROSTHET DENT 1989;61:733-6. Reprint
requests
to:
DR. MARK MARUNICK WAYNE STATE UNIVERSITY, 4201 ST. ANTOINE DETROIT, MI 48201
5G UHC
JUNE
1992
VOLUME
67
NUMBER
6
force
after
partial
mandibular
resection
Mark Marunick, DDS, MS,a Bruce E. Mathes, DDS,b Barbara B. Klein, RDH,C and Mahmoud Seyedsadr, PhDd Wayne State University,
Harper Hospital, and University
of Detroit Dental School, Detroit, Mich.
Surgical resection of a segment or loss of mandibular continuity can adversely affect most of the structures essential for maximum occlusal force. Five subjects who had partial mandibular resections for treatment of squamous cell carcinoma were studied. Occlusal force was recorded before and after cancer treatment and following prosthetic rehabilitation. A gnathodynamometer was used to record anterior occlusal force. Five edentulous and five dentate cancer-free subjects matched for age were studied to establish comparable normative data. The null hypothesis that partial mandibular resection would not affect maximum occlusal force was rejected (p = 0.0101). Mandibular resection did alter maximum occlusal force. The impact of the decrease in maximum occlusal force on masticatory function is yet to be determined. (J PROSTHET DENT 1992;67:835-8.)
0
cclusal force is dependent upon the integrity of the muscles of mastication, temporomandibular joint (TMJ), mandible, dent&ion, and the status of the surrounding hard and soft tissues. All may be affected by radiation therapy and surgery, two of the modalities used to treat head and neck neoplasms.‘? 2 Trismus, xerostomia, edema, mucositis, and radiation caries have been documented as side effects of radiation therapy.3,4 The direct effects of radiation on tissue have been reported and may account for some of the side effects noted.5s 6 Most longterm alterations can be attributed to changes in tissue vascularity within the radiated field. The vascular damage leads to proliferation of fibroblasts and fibrosis, with further alterations in vascularity. The long-term effects on the muscles of mastication may lead to trismus and a decreased range of motion of the mandible. Preradiation extraction of teeth can adversely affect occlusion and create relative changes in maximal opening. Surgical resection of a portion of the mandible, muscles of mastication, and some teeth can cause an imbalance of the remaining muscles of mastication, altered and restricted mandibular movements, and a decreased forceful mandibular closure. Occlusal force has been studied in normal patients.7-12 These studies used electromyography (EMG) to measure muscle activity, a gnathodynamometer to measure bite strength, and pressure transducers to measure forces at the tissue-prosthesis interface. Few Research supported by National Institutes of Health grant CA 43838. BAssistant Professor, Department of Otolaryngology, Wayne State University. bGeneral Practice Residency, University of Detroit Dental School. CResearch Assistant, Department of Otolaryngology, Wayne State University. dAssistant Professor, Department of Radiation Oncology, Wayne State University. 10/l/35961
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
studies
have evaluated
these parameters
in patients
with
head and neck cancer, with those reported being retrospective. The purpose of this study was to evaluate the effects of radiation therapy and mandibular resection on maximal
occlusal
force in patients
treated
for head and
neck cancer. METHODS
AND
MATERIAL
Five subjects with head and neck cancer were evaluated before any treatment. The test group was composed of four men and one woman, with an age range of 43 to 72 years and mean of 57 years (Table I). A gnathodynamometer (Streeter Richards, Chicago, Ill.) was used to record anterior occlusal force between the natural teeth, denture teeth, and edentulous alveolar ridges.13 This custom-built
instrument
was length
immune
and in-
cluded simultaneous recording of maxillary and mandibular pressures, which were displayed on a quantimatic 9000 digital
scale. A silicone
gum rubber
(Dow Corning,
Mid-
land, Mich.) with a durometer reading of 50 was placed on the ends of the mouthpiece. Measurements were made at an interocclusal distance of 13 mm and were recorded seven times with rest between measurements. The lowest and highest values were discarded
and the mean was considered
representative of the maximum occlusal force for that day of testing.13 After preliminary evaluations, the subjects entered specific cancer treatment protocols. Methods and extent of
surgical resection were recorded, and additional information was obtained regarding radiation therapy including type, dose, port size, and fractionation technique. After oncologic treatment, occlusal force was evaluated. Subjects No. 3, 4, and 5 were treated with prostheses and were tested with and without their new prostheses. The
subjects had worn their new prostheses for 2 months before testing. All subjects served as their own controls.
Ten additional
835
MARUNICK
Table
I.
Profile
of the five subjects
ET AL
studied Dentition
Subject
No.
1
Age
(5-9
Sex
44
M
Pretreatment Partially
Mandibular diagnosis
Posttreatment
Edentulous
edentulous 2
3
43
63
M
M
Partially edentulous
Edentulous
Edentulous
Edentulous
4
57
M
Edentulous
Edentulous
5
72
F
Edentulous
Edentulous
Epidermoid carcinoma floor of mouth Squamous cell carcinoma floor of mouth
Carcinoma of the pharynx and base of the tongue Verrucous carcinoma of tonsil and soft palate Carcinoma of the mandibular alveolar ridge
cancer-free subjects matched on the basis of age and dental status (edentulous and natural dentition) were studied to establish normative values. Controls were tested on 3 different days using the same method of measurement as
was applied to the test subjects. The mean of the three test dates was considered representative for each control. All studies were performed according to the guidelines of the Wayne State University Human Subject Committee. The test-retest reliability of the occlusal force measurement was assessed using the 10 control subjects, five who were edentulous with complete dentures and five with natural teeth. The reliabi1it.y measure used was intraclass correlation (ICC) for the repeated measure design-that is, patients by three time periods. For the edentulous control subjects without dentures in place, the ICC was 0.90; with dentures in place, it was 0.97. For the subjects with natural dentition, the ICC was 0.99. An evaluation of the effects between the two control groups, edentulous with and without dentures and the natural dentition group, provided data relevant to the evaluation of validity. By t test, a significant advantage was seen for the natural dentition group compared with the edentulous group without dentures (p = 0.0205) and with dentures b = 0.0389). A paired t test was used to evaluate within the edentulous control group. A significant advantage was noted for the edentulous group with dentures
compared with the edentulous group without (p = 0.0359). 836
dentures
Mandibular continuity
Stage
T4, NOM0
Radiation therapy
Maintainedsegmental inner table Lost from left parasymphysis to right molar region; reconstructed with osseomyocutaneous flap Lost-distal to right midbody
T3, N2MO
T3, NlMO
GY)
60
(post surgery) 60
(post surgery)
50
(post surgery)
T3, NOM0
Lost-distal to right midbody
None
T3, NOM0
Lost-parasymphysis to left angle; reconstructed with synthe plate
None
RESULTS Pretreatment occlusal force for the two partial edentate test subjects ranged from 25.4 to 40.0 lb, with a mean of 32.7 lb. Posttreatment occlusal force decreased to 7.0 and 7.6 lb, with a mean of 7.3 lb. The percent decrease ranged from 72.0% to 81.0%) with a mean decrease of 78.0% (Table II). Pretreatment occlusal force for the edentulous test subjects with
maxillary
and mandibular
complete
dentures
ranged from 11.5 to 23.0 lb, with a mean of 19.1 lb. Posttreatment occlusal force ranged from 7.7 to 19.4 lb, with a mean of 12.7 lb. The decrease ranged from 15.0 % to 52.0 % , with a mean decrease of 33.0% (Table II). Pretreatment occlusal force for the edentulous test subjects when the dentures were removed ranged from 17.0 to 22.6 lb, with a mean of 20.3 lb. Posttreatment occlusal force decreased to a range of 7.9 to 9.3 lb and a mean of 8.4 lb. Without dentures, the percent decrease ranged from 54.0% to 62.0%, with a mean of 56.7% (Table II). Using a paired t test, a statistically significant difference was noted when comparing pretreatment occlusal force for all five subjects with posttreatment occlusal force for the edentulous
state without
a prosthesis
(p = 0.0101).
Using
a paired t test, a statistically significant difference was noted when comparing pretreatment occlusal force for the three edentulous subjects without a prosthesis with their posttreatment occlusal force without a prosthesis (p = 0.0307). No statistically significant difference was noted for the three subjects when comparing pretreatment JUNE
1992
VOLUME
67
NUMBER
6
OCCLUSAL
Table
FORCE
II.
Test
AFTER
RGSECTION
Occlusal force (lb) for test subjects Dental
subject
1
status
Pretreatment
PI< PE E- WOP E-WP E-WOP E-WP E-WOP E-WP
2 3 4 5
PE, Partially edentulous; *Months post surgery.
Posttreatment
25.4 40.0 26.6 11.5 17.0 22.8 21.5 23.0
E, edentulous;
WOP, without
prosthesis;
Dental
7.0 7.6 9.3 7.7 7.9 19.4 8.3 11.0
status
MO*
E-WOP E-WOP E-WOP E-WP E-WOP E-WP E-WOP E-WP
from
5 20 14 14 12 12 10 10
% Decrease pretreatment 72 81 54 32 54 15 62 52
WP, with prosthesis.
occlusal force with a prosthesis with posttreatment occlusal force with a prosthesis (p = 0.1498). Occlusal force for the dentate controls ranged from 60.6 to 187.5 lb, with a mean of 123.2 lb (Table III). Edentulous controls with maxillary and mandibular dentures demonstrated occlusal forces that ranged from 9.3 to 39.9 lb, with a mean of 26.2 lb. Wh.en the dentures were removed, occlusal force ranged from 4.4 to 12.3 lb, with a mean of 8.0 lb (Table IV).
Table
III.
Occlusal force for dentate controls (n = 5)
Subject No. 1 2 3 4 5 Average
number
Table
IV.
Age b-9
Sex
Occlusal force (lb)
49 55 56 62 41
F M F M F
137.3 55.2 60.6 75.6 187.5
of occluding
pairs of teeth = 13.
DISCUSSION Occlusal force was mea.sured at a vertical opening of 13.0 mm in the incisor region.13 Manns et a1.15reported measuring occlusal force from the distal borders of the canines and showed the biting strength is greatest at an increased vertical dimension of 10 to 20 mm. Occlusal forces for dentate and complete denture wearers have been reported by Gibbs et al.,s at a molar vertical opening of 10.0 mm, to average 162 lb and 35 lb, respectively. It is generally accepted that greater forces can be generated on the posterior teeth. Howell and Manly16 demonstrated that the range of maximum occlusal force on t.he first molar teeth was 91 to 198 lb, and on central incisors the force was 29 to 51 lb. Although it was not measured, it is unlikely, given the anatomic limitations, that Iposterior occlusal force would be significantly higher in the edentulous resected subjects that were studied. Using EMG, Kapur and Garrett17 estimated that denture wearers applied 22% to 39% of the muscle force applied b:y those with natural dentition. Although EMG was not used in this study, the values for occlusal force for the dentate and edentulous controls demonstrate a similar ditference. The subjects that were partially edentulous before treatment demonstrated the greatest decrease (78%) in occlusal force from pretreatment levels. This can be attributed to the fact that they were made edentulous in preparation for radiation therapy and mandibular resection. The effects of the separate interventions on occlusal force could not be determined, since the teeth were extracted at the time of the surgical resection. The pretreatment partially edentulous subjects No. 1 and 2 were not treated with prostheses; consequently, they were not tested with a prosthesis THE
JOURNAL
OF PROSTHETIC
DENTISTRY
Occlusal force for edentulous controls (n = 5) Occlusal
Subject No. 1 2 3 4 5 Abbreviations
force
(lb)
Age (yr)
Sex
WP
WOP
47 60 49 53 47
F F F F F
39.9 20.8 30.3 9.3 30.8
7.1 12.3 7.8 8.3 4.4
as in Table
II.
following treatment. Subject No. 1 developed a recurrence 8 months after surgery and was dropped from the study. Subject, No. 2 had insufficient interarch space to accommodate maxillary and mandibular prostheses. Postt,reatment occlusal force for the test subjects when using dentures (12.7 lb mean) was significantly lower than that of the controls (26.2 lb mean). Changes in forces produced may be the result of alterations following surgery, including loss of mandibular continuity, muscles of mastication, changes in tongue status, pain in supporting tissues, and uncoordinated mandibular movements. The surgery and radiation therapy decreased the subjects’ ability to attain forceful closure with dentures, since only a 4.3 lb (mean) increase in occlusal force (12.7 lb mean with dentures versus 8.4 lb mean without dentures) was recorded after treatment with dentures. Variations reported above and below the mean can be attributed to individual differences in muscle strength, ability to manipulate dentures, 837
MARUNICK
and retention and stability of the dentures. VerKendere et al.ls used EMG analysis to determine that wearing a prosthesis does not change the normal reflex activity of the masticatory muscles. This may not be true for patients following partial mandibular resection. Posttreatment evaluations showed significant decreases (15 % to 62 % ) in occlusal force regardless of prosthodontic treatment, indicating the impact of the t.reatment on the integrity of the structures essential for maximum occlusal force. Michael et al.lo reported that occlusal forces in the posterior region on the working side of denture wearers in the closed position were 4.2 lb for soft food and 11.3 lb for hard food. This would indicate the test subjects in this study have sufficient occlusal force to comminute food. Other factors that may limit ability to masticate are range of motion and tongue mobility.. The reduced force exhibited by the test subjects in the cmrent study could influence their diet selection or may be compensated for by increasing the time the forces are applied, as reported by Neil1 et aLg Consequently, many patients with partial mandibular resection may restrict the consistency of food consumed and take more time to eat a meal. Without a prosthesis, test subjects’ occlusal force following prosthodontic treatment are similar to that of the edentate controls without a prosthesis. These values ranged from 4.4 lb to 12.3 lb for the edentate controls and 7.0 lb to 14.0 lb for the test subjects. This observation indicates that a baseline limit of the supporting tissues exists in recording maximum occlusal force, which is unaffected by the treatment modalities used. CONCLUSIONS Based on these limited surgical resection with therapy can significantly Conventional prosthetic subjects studied to their els.
838
observations, partial mandibular or without combined radiation alter maximum occlusal force. treatment did not restore the pretreatment occlusal force lev-
ET AL
REFERENCES 1. Beumer J, Curtis T, Harrison RE. Radiation therapy of the oral cavity: sequelae and management. Part I. Head Neck Surg 1979;1:301-12. 2. Kirkegaard J, Lindelov B, Bretlau P. Traditional and new treatment strategies for oral squamous cell carcinomas. Ear Nose Throat J 1989; 68:593-604. 3. Driezen S, Daly TE, Drane JB, Brown LR. Oral complications of cancer radiotherapy. Postgrad Med 1977;61:85-92. 4. Engelmeier RL, King GE. Complications of head and neck radiation therapy and their management. J PROSTHET DENT 1983;49:514-22. 5. Beumer J, Silverman S, Benak SB. Hard and soft tissue necroses following radiation therapy for oral cancer. J PROSTHET DENT 1972; 27:640-4. 6. Baker DG. The radiobiological basis for tissue reactions in the oral cavity following therapeutic x-irradiation. Arch Otolaryngol1982;108:21-4. 7. Gibbs CH, Mahan PE, Lundeen HC, Brehnan K, Walsh EK, Sinkewicz SL, Ginsbe SB. Occlusal forces during chewing-influences of biting strength and food consistency. J PROSTHET DENT 1981;46:561-7. 8. Gibbs CH, Mahan PE, Mauderli A, Lundeen HC, Walsh EK. Limits of human bite strength. J PROSTHET DENT 19%56:226-g. 9. Neil1 DJ, Kydd WL, Nairn RI, Wilson J. Functional loading of the dentitian during mastication. J PROSTHET DENT 1989;62:218-28. 10. Michael CG, Javid NS, Colaizzi FA, Gibbs GH. Biting strength and chewing forces in complete denture wearers. J PROSTHET DENT 1990; 6354943. 11. Sposetti VJ, Gibbs
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CH, Alderson TH, et al. Bite force and muscle acwearers before and after attachment placement. J
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12. Cutright DE, Brudrik JS, Gay WD, Selting WJ. Tissue pressure under complete maxillary dentures. J PROSTHET DENT 1976;35:160-70. 13. Marunick MT, Mathog RH. Mastication in patients treated for head and neck cancer: a pilot study. J PROSTHET DENT 1990;63:566-73. 14. Deleted in galleys. 15. Manns A, Miralles R, Palarzi C. EMG, bite force, and elongation of the masseter muscle under voluntary isometric contractions and variations of vertical dimension. J PROSTHET DENT 1979;42:674-82. 16. Howell AH, Manly RS. An electronic strain gauge for measuring oral forces. J Dent Res 1948;27:705-12. 17. Kapur KK, Garrett NR. Studies of biologic parameters for denture design. Part II. Comparison of masseter muscle activity, masticatory performance, and salivary secretion rates between denture and natural dentition groups. J PROSTHET DENT 1964;52:408-13. 18. VerKendere MT, Lodter JP. The silent period duration of the masticatory muscles. J PROSTHET DENT 1989;61:733-6. Reprint
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DR. MARK MARUNICK WAYNE STATE UNIVERSITY, 4201 ST. ANTOINE DETROIT, MI 48201
5G UHC
JUNE
1992
VOLUME
67
NUMBER
6
