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Increased tolerance to complete dentures after surgical modification of mylohyoid ridges
Increased tolerance to complete dentures after surgical modification of mylohyoid ridges B. Penhall, L.D.S., R.C.S.(Lond), F.D.S.R.C.S.(Edin),* D. Roder, B.D.S., M.P.H., D.D.Sc., F.R.A.C,D.S.,** and A. Esterman, University
G
of Adelaide, School of Dentistry,
eriatric services are making greater demands on dentistsasthe number of older peopleincreases.In 1981, 24,900 South Australians were 80 years of age or more, but this number is predicted to grow to 53,300 during the next 20 years.’ This constitutesan increaseof 114%, which is much larger than the corresponding8% for the community as a whole.’ Dentists will be spending much more of their time treating elderly patients by the end of this century. With prosthodontic treatment continuing to be a major requirement of this age group, the social importance of this care will increase. Elderly people experience difficulty wearing dentures for many reasons.Lossof elastic fibers with age diminishesthe quality of the soft tissuesthat cover the bony ridges. Xerostomia may be present which can have negative effects on healing and comfort. Lack of neuromuscular coordination may be an added problem. Bone resorption can leave little ridge for support; and prominent sites of muscle attachments, such as mylohyoid ridges or genial tubercles, can becomepainful as dentures impinge on them during chewing. Exostosesoften require special management if prosthetic treatment is to be successful.Many approaches may be tried; the most conservative is the use of resilient linings. Surgeons have advocated methods to modify edentulous ridges prior to making dentures. Some procedures, such as visor osteotomies,can be rather demanding for elderly patients. Fitzpatrick’ has describedan approach that involves simple smoothingof mylohyoid ridges. It is a procedure readily performed under local anesthesia and is generally well tolerated by the elderly patient. The procedure was describedby Brown’ and Downton,” but more recently it has beenmodified so that there is no longer a need to detach the mylohyoid muscle; instead, the muscle is peeleddown and away from the ridge and remains attached to the mucoperiosteum. Little statistical documentation of the outcome of this care is available, although Robe& did report a prelim-
230
M.Sc., F.I.S.**
./\delaide, :\ustralia
inary evaluation based on 36 patients. Nineteen had surgical treatment of the mylohyoid ridges prior to prosthetic care, whereas the other 17 did not. Results indicated that 16 of the patients who received surgery (84%) remained comfortable for a period of 5 years, whereas only four of the remainder (24%) were thus classified. This suggesteda marked benefit from the treatment. In the present study, clinical records compiled from one specialist clinical practice over an 8-year period were reviewed to further evaluate the outcome of this care when provided prior to making complete dentures.
MATERIAL
AND
METHODS
A total of 521 patients were included in this study, comprising all those who were referred by general practitioners and subsequently received complete dentures. Of these, 247 (group A) were thought not to have potentially troublesomemylohyoid ridges. However, the remainder (274) had ridges that ideally would require simplesurgery prior to making denturesto avoid discomfort from sharp ridges.While 183 (group B) had surgical correction, 91 (group C) did not becauseof personal preference, underlying medical conditions, or other reasons.The age-sexcharacteristicsof the groups are shown in Table I. Most patients manage their complete dentures without major difficulty after one or two postinsertion visits. Therefore, the need for three or more visits was used in this study as a crude index of an adverseoutcome. Becauseit was consideredthat outcome might be age and sex dependent, the percent of patients who required three or more postinsertion visits was analyzed for each treatment group using age-sex standardization. Direct standardization was used, with the standard population having the age-sex structure of the total population of 521 patients.” A more rigorous comparison of group B and C patients was undertaken. This was done by entering the three factors, age (expressed in years), sex (M = 1; F = 2), and group (B = 1; C = 2). into a stepwise logistic regressionmodel as independent variables..‘The AUGUST
1985
VOLUME
54
NUMBCH
z
MYLOHYOID
RIDGE
Table I. Number
MODIFICATION
of patients
by age, sex, and pretreatment
status of mylohyoid
ridges
Prominent Ridges Sex
Age (yrs)
MaIf?
<50 50-59 flo+
Female
<50
not prominent (Group A)
Surgically (Group
14 23 40 40 31 99 247
50-59 fPo+
Total
reduced B)
ridges Not
surgically (Group
9 14 24 35 49 52 183
reduced C)
I 8 12 11 17 42 91 --
Table II. Percent of patients to age, sex, and pretreatment
requiring three or more visits status of mylohyoid ridges*
after insertion
of full dentures Prominent
Ridges Sex
Age
(yrs)
not prominent (Group A)
reduced B)
Male
<50 50-59 60+
7.1 (1) 8.7 (2) 27.5 (11)
0 (0) 28.6 (4) 8.3 (2)
Female
<50 50-59 60+
17.5 (7) 22.6 (7) 14.1 (14) 17.4
5.7 (2) 6.1 (3) 3.8 (2) 7.2
Totalt
number of postinsertion visits (whether 23 or <3) was treated as the dependent variable. The logistic transformation enabled the development of a multivariate model that fitted the data well, as shown by a probability value of 0.9 for the chi square goodness of fit. The signs of the regression coefficients indicated whether the variables included in the model were positively or negatively related to the probability of the necessity for three or more postinsertion visits after other variables in the model were controlled. RESULTS It is apparent from Table II that group B patients (receiving surgery) performed better than either group C or group A patients. Of group B patients, only 7.2% required three or more postinsertion visits compared with 26.6% for group C patients and 17.4% for those in group A (Table 11). Table III shows the factors that emerged as significant predictors of the probability of three or more postinsertion visits being required when the logistic analysis was performed. This indicated that group C patients (not receiving surgery) were more likely to require three or more visits than those in group B. Females were less likely than males to require three or more visits, whereas age was not selected as a significant predictor. THE
Surgically (Group
JOURNAL
OF PROSTHETIC
DENTISTRY
Table III. Predictors visits Factor Sex(M=l;F=Z) Group (B = 1; C = 2)
Constant
according
ridges Not
surgically (Group
reduced C)
100 (1) 25.0 (2) 33.3 (4) 0 (0) 23.5 (4) 28.6 (12) 26.6
of excessive
postinsertion
Coefficient -0.369 +0.766 -1.674
+ SD +_ 0.199 t 0.190 ZIZ 0.199
DISCUSSION The results suggest that surgical smoothing of prominent mylohyoid ridges can assist patients to gain a greater measure of comfort with complete dentures in the short term. Indeed, patients who received surgery required fewer postinsertion visits than those in group A, who were not considered to need surgery in the first place. This may be explained by the fact that surgery was advised only when bony prominences were suchciently pronounced to be considered a potential source of trouble. While many patients in group A may have had prominent mylohyoid ridges that were not thought to be a potential problem, some could have proved to be troublesome. It has been stated previously that this was not a randomized trial. Rather it is a statistical record of outcomes in a specialist prosthodontic practice. It is 231
PENHALL,
especially important, therefore, to consider alternative explanations for the nonexperimental findings. In particular, the potential for bias from the nonrandom allocation of patients to groups B and C needs to be considered. The reasons why patients in Group C did not receive surgery included the following: 1. A history of major surgery and a desire to avoid further surgery: Subcategory 1 (7 patients) 2. Medical histories that contraindicated surgery: Subcategory 2 (49 patients) 3. A history of having tolerated dentures successfully under adverse conditions combined with the desirability of avoiding unnecessary surgery: Subcategory 3 (29 patients) 4. Major bone loss with little remaining mandible to support dentures: Subcategory 4 (6 patients) It might have been expected that patients in subcategory 4 would have fared poorly. Two (33.3%) of these were found to require three or.. more visits. This is essentially the same proportion as the 32.1% (18 of 56) for those in subcategories 1 and 2, for whom a relatively favorable outcome would have been anticipated. Notably, these proportions are higher than the 7% for group B patients, who were treated surgically. Patients in subcategory 3 might have been expected to have an excellent prognosis, since they had a history of tolerating dentures successfully under adverse circumstances. Nevertheless, with 10.3% (3 of 29) requiring at least three postinsertion visits, they did not perform better than group B patients. While the results of this study point to a positive impact of surgery on postinsertion comfort, the potential for confounding effects cannot be excluded. It would be ideal, therefore, if these findings could be confirmed with data from a randomized trial. In addition, since muscle attachments tend to re-form in time, it would be desirable to investigate the outcome in the longer term.
Three-dimensional analysis displacement during reline Nikzad Hamdi
S. Javid, D.M.D., M.Sc., M.Ed.,* A. Mohammed, D.D.S., M.Sc.D.,
RODER,
AND
ESTERMAN
SUMMARY Of 521 patients referred to a specialist prosthodontic practice for complete dentures, 274 were considered as candidates for simple surgery to smooth prominent mylohyoid ridges before denture construction. Of these, 183 were thus treated. The remaining 91 did not receive surgery because of personal preference, underlying medical conditions, or other reasons. The percent who required three or more postinsertion visits to achieve comfort with their dentures was 7% for those who received surgery, 27% for those who required but did not receive surgery, and 17% for those not deemed to require surgery. This suggests that the surgical smoothing of prominent mylohyoid ridges may markedly improve patients’ tolerance of dentures in the short term. However, the potential for confounding from extraneous factors in these nonexperimental circumstances must be considered. REFERENCES I.
2. 3. 4. 5.
6. 7.
,\ustralian Bureau of Statistics. Prqjeuions of the population of South Australia. 1981-2021. Adelaide. 1983. ilustralian Bureau of Statistics. Fitzpatrick BN: Current concepts in the surgical management of the atrophic mandible. Brown LJ: Surgical Dm J 95:215, 1953. Downton 1954. Roberts improving 142:151, Armitage England, Engelman Statistical
Aust solution
1~: Mylnhyoid BJ: The sucwss 1977.
Dent J 23:344, 1978. to a lower denture ridge
eflicacy of the with the romp&
resection. mylohyoid lower
DenL ridge denture.
problem Ret
Br 74~212,
reseuion Br Dent
in J
P: Statistical Methods in Medical Research. Oxford, 1974, Blackwell Scientific Publicarions, pp 385-388. L: PLR. Srepwise logistic regression. In: BMDP Sofrware. 1981. Berkeley. 1981, University of Califor-
nia.
of maxillary denture impression procedure
Cecile G. Michael, B.Ch.D., H.D.D., M.S.,** Ph.D.,**+ and Frank A. Colaizzi, D.M.D.****
University of Florida, Collegeof Dentistry, Gainesville,FIa. *Professor, **Associate ESY Pt.
232
Department Professor,
of Removable Cairo University,
Prosthodonrics. Faculty of Dentistry,
Cairo,
***Prufessor, ****Awxiatr Prosthodontics.
Department Professor
of Dental BiomaterAs. and Chairman, Depx’ment
AUGUST
1985
VOLUME
of Removable
54
NUMBER
2
G
of Adelaide, School of Dentistry,
eriatric services are making greater demands on dentistsasthe number of older peopleincreases.In 1981, 24,900 South Australians were 80 years of age or more, but this number is predicted to grow to 53,300 during the next 20 years.’ This constitutesan increaseof 114%, which is much larger than the corresponding8% for the community as a whole.’ Dentists will be spending much more of their time treating elderly patients by the end of this century. With prosthodontic treatment continuing to be a major requirement of this age group, the social importance of this care will increase. Elderly people experience difficulty wearing dentures for many reasons.Lossof elastic fibers with age diminishesthe quality of the soft tissuesthat cover the bony ridges. Xerostomia may be present which can have negative effects on healing and comfort. Lack of neuromuscular coordination may be an added problem. Bone resorption can leave little ridge for support; and prominent sites of muscle attachments, such as mylohyoid ridges or genial tubercles, can becomepainful as dentures impinge on them during chewing. Exostosesoften require special management if prosthetic treatment is to be successful.Many approaches may be tried; the most conservative is the use of resilient linings. Surgeons have advocated methods to modify edentulous ridges prior to making dentures. Some procedures, such as visor osteotomies,can be rather demanding for elderly patients. Fitzpatrick’ has describedan approach that involves simple smoothingof mylohyoid ridges. It is a procedure readily performed under local anesthesia and is generally well tolerated by the elderly patient. The procedure was describedby Brown’ and Downton,” but more recently it has beenmodified so that there is no longer a need to detach the mylohyoid muscle; instead, the muscle is peeleddown and away from the ridge and remains attached to the mucoperiosteum. Little statistical documentation of the outcome of this care is available, although Robe& did report a prelim-
230
M.Sc., F.I.S.**
./\delaide, :\ustralia
inary evaluation based on 36 patients. Nineteen had surgical treatment of the mylohyoid ridges prior to prosthetic care, whereas the other 17 did not. Results indicated that 16 of the patients who received surgery (84%) remained comfortable for a period of 5 years, whereas only four of the remainder (24%) were thus classified. This suggesteda marked benefit from the treatment. In the present study, clinical records compiled from one specialist clinical practice over an 8-year period were reviewed to further evaluate the outcome of this care when provided prior to making complete dentures.
MATERIAL
AND
METHODS
A total of 521 patients were included in this study, comprising all those who were referred by general practitioners and subsequently received complete dentures. Of these, 247 (group A) were thought not to have potentially troublesomemylohyoid ridges. However, the remainder (274) had ridges that ideally would require simplesurgery prior to making denturesto avoid discomfort from sharp ridges.While 183 (group B) had surgical correction, 91 (group C) did not becauseof personal preference, underlying medical conditions, or other reasons.The age-sexcharacteristicsof the groups are shown in Table I. Most patients manage their complete dentures without major difficulty after one or two postinsertion visits. Therefore, the need for three or more visits was used in this study as a crude index of an adverseoutcome. Becauseit was consideredthat outcome might be age and sex dependent, the percent of patients who required three or more postinsertion visits was analyzed for each treatment group using age-sex standardization. Direct standardization was used, with the standard population having the age-sex structure of the total population of 521 patients.” A more rigorous comparison of group B and C patients was undertaken. This was done by entering the three factors, age (expressed in years), sex (M = 1; F = 2), and group (B = 1; C = 2). into a stepwise logistic regressionmodel as independent variables..‘The AUGUST
1985
VOLUME
54
NUMBCH
z
MYLOHYOID
RIDGE
Table I. Number
MODIFICATION
of patients
by age, sex, and pretreatment
status of mylohyoid
ridges
Prominent Ridges Sex
Age (yrs)
MaIf?
<50 50-59 flo+
Female
<50
not prominent (Group A)
Surgically (Group
14 23 40 40 31 99 247
50-59 fPo+
Total
reduced B)
ridges Not
surgically (Group
9 14 24 35 49 52 183
reduced C)
I 8 12 11 17 42 91 --
Table II. Percent of patients to age, sex, and pretreatment
requiring three or more visits status of mylohyoid ridges*
after insertion
of full dentures Prominent
Ridges Sex
Age
(yrs)
not prominent (Group A)
reduced B)
Male
<50 50-59 60+
7.1 (1) 8.7 (2) 27.5 (11)
0 (0) 28.6 (4) 8.3 (2)
Female
<50 50-59 60+
17.5 (7) 22.6 (7) 14.1 (14) 17.4
5.7 (2) 6.1 (3) 3.8 (2) 7.2
Totalt
number of postinsertion visits (whether 23 or <3) was treated as the dependent variable. The logistic transformation enabled the development of a multivariate model that fitted the data well, as shown by a probability value of 0.9 for the chi square goodness of fit. The signs of the regression coefficients indicated whether the variables included in the model were positively or negatively related to the probability of the necessity for three or more postinsertion visits after other variables in the model were controlled. RESULTS It is apparent from Table II that group B patients (receiving surgery) performed better than either group C or group A patients. Of group B patients, only 7.2% required three or more postinsertion visits compared with 26.6% for group C patients and 17.4% for those in group A (Table 11). Table III shows the factors that emerged as significant predictors of the probability of three or more postinsertion visits being required when the logistic analysis was performed. This indicated that group C patients (not receiving surgery) were more likely to require three or more visits than those in group B. Females were less likely than males to require three or more visits, whereas age was not selected as a significant predictor. THE
Surgically (Group
JOURNAL
OF PROSTHETIC
DENTISTRY
Table III. Predictors visits Factor Sex(M=l;F=Z) Group (B = 1; C = 2)
Constant
according
ridges Not
surgically (Group
reduced C)
100 (1) 25.0 (2) 33.3 (4) 0 (0) 23.5 (4) 28.6 (12) 26.6
of excessive
postinsertion
Coefficient -0.369 +0.766 -1.674
+ SD +_ 0.199 t 0.190 ZIZ 0.199
DISCUSSION The results suggest that surgical smoothing of prominent mylohyoid ridges can assist patients to gain a greater measure of comfort with complete dentures in the short term. Indeed, patients who received surgery required fewer postinsertion visits than those in group A, who were not considered to need surgery in the first place. This may be explained by the fact that surgery was advised only when bony prominences were suchciently pronounced to be considered a potential source of trouble. While many patients in group A may have had prominent mylohyoid ridges that were not thought to be a potential problem, some could have proved to be troublesome. It has been stated previously that this was not a randomized trial. Rather it is a statistical record of outcomes in a specialist prosthodontic practice. It is 231
PENHALL,
especially important, therefore, to consider alternative explanations for the nonexperimental findings. In particular, the potential for bias from the nonrandom allocation of patients to groups B and C needs to be considered. The reasons why patients in Group C did not receive surgery included the following: 1. A history of major surgery and a desire to avoid further surgery: Subcategory 1 (7 patients) 2. Medical histories that contraindicated surgery: Subcategory 2 (49 patients) 3. A history of having tolerated dentures successfully under adverse conditions combined with the desirability of avoiding unnecessary surgery: Subcategory 3 (29 patients) 4. Major bone loss with little remaining mandible to support dentures: Subcategory 4 (6 patients) It might have been expected that patients in subcategory 4 would have fared poorly. Two (33.3%) of these were found to require three or.. more visits. This is essentially the same proportion as the 32.1% (18 of 56) for those in subcategories 1 and 2, for whom a relatively favorable outcome would have been anticipated. Notably, these proportions are higher than the 7% for group B patients, who were treated surgically. Patients in subcategory 3 might have been expected to have an excellent prognosis, since they had a history of tolerating dentures successfully under adverse circumstances. Nevertheless, with 10.3% (3 of 29) requiring at least three postinsertion visits, they did not perform better than group B patients. While the results of this study point to a positive impact of surgery on postinsertion comfort, the potential for confounding effects cannot be excluded. It would be ideal, therefore, if these findings could be confirmed with data from a randomized trial. In addition, since muscle attachments tend to re-form in time, it would be desirable to investigate the outcome in the longer term.
Three-dimensional analysis displacement during reline Nikzad Hamdi
S. Javid, D.M.D., M.Sc., M.Ed.,* A. Mohammed, D.D.S., M.Sc.D.,
RODER,
AND
ESTERMAN
SUMMARY Of 521 patients referred to a specialist prosthodontic practice for complete dentures, 274 were considered as candidates for simple surgery to smooth prominent mylohyoid ridges before denture construction. Of these, 183 were thus treated. The remaining 91 did not receive surgery because of personal preference, underlying medical conditions, or other reasons. The percent who required three or more postinsertion visits to achieve comfort with their dentures was 7% for those who received surgery, 27% for those who required but did not receive surgery, and 17% for those not deemed to require surgery. This suggests that the surgical smoothing of prominent mylohyoid ridges may markedly improve patients’ tolerance of dentures in the short term. However, the potential for confounding from extraneous factors in these nonexperimental circumstances must be considered. REFERENCES I.
2. 3. 4. 5.
6. 7.
,\ustralian Bureau of Statistics. Prqjeuions of the population of South Australia. 1981-2021. Adelaide. 1983. ilustralian Bureau of Statistics. Fitzpatrick BN: Current concepts in the surgical management of the atrophic mandible. Brown LJ: Surgical Dm J 95:215, 1953. Downton 1954. Roberts improving 142:151, Armitage England, Engelman Statistical
Aust solution
1~: Mylnhyoid BJ: The sucwss 1977.
Dent J 23:344, 1978. to a lower denture ridge
eflicacy of the with the romp&
resection. mylohyoid lower
DenL ridge denture.
problem Ret
Br 74~212,
reseuion Br Dent
in J
P: Statistical Methods in Medical Research. Oxford, 1974, Blackwell Scientific Publicarions, pp 385-388. L: PLR. Srepwise logistic regression. In: BMDP Sofrware. 1981. Berkeley. 1981, University of Califor-
nia.
of maxillary denture impression procedure
Cecile G. Michael, B.Ch.D., H.D.D., M.S.,** Ph.D.,**+ and Frank A. Colaizzi, D.M.D.****
University of Florida, Collegeof Dentistry, Gainesville,FIa. *Professor, **Associate ESY Pt.
232
Department Professor,
of Removable Cairo University,
Prosthodonrics. Faculty of Dentistry,
Cairo,
***Prufessor, ****Awxiatr Prosthodontics.
Department Professor
of Dental BiomaterAs. and Chairman, Depx’ment
AUGUST
1985
VOLUME
of Removable
54
NUMBER
2