title: Maximum clenching force of patients with moderate loss of posterior tooth support: a pilot study.
abstract: BACKGROUND
  Patients who have lost moderate posterior tooth support may also lose clenching force as a result of sensitivity to increased loading to the remaining teeth and possibly a loss of muscle strength, because clenching forces are limited to avoid stress to the remaining teeth. Few studies have correlated moderate posterior tooth loss with maximum clenching force.
  
  
  OBJECTIVE
  The purpose of this pilot study was to test the hypothesis that moderate loss of posterior tooth support will have a significant effect on maximum clenching force.
  
  
  METHODS
  The maximum clenching force of 44 adults, ages 28 to 76 (mean 46), with posterior tooth loss was compared with the maximum clenching force of a control group of 20 healthy full dentition adults, ages 18 to 55 (mean 30), by use of a bilateral strain-gauged transducer. The transducer consisted of 2 stainless steel plates separated by a steel sphere that balanced occlusal forces between right and left sides. Acrylic resin pads were fabricated for each patient to protect the cusps of the teeth. The overall accuracy was found to be within 2.3% of full scale over a range of 0 to 4000 N (0 to 900 lbs). The calibration reliability of the system was checked frequently by use of a dead weight of 222 N (50 lbs). Clenching forces were supported by first and second molars and second premolars when possible. The instrumentation, methods, and operator were the same for both groups. A 2-tailed Student t test (alpha=0.01) and a pooled estimate of the mean were used to determine possible statistical significance. To test for possible correlations between clenching force and lost tooth support and between clenching force and age, a linear regression correlation coefficient R was calculated.
  
  
  RESULTS
  For the 44 subjects with posterior tooth loss, the mean clenching force was 462 N (104 lbs), with a range of 98 to 1031 N (22 to 232 lbs). This compares with a mean of 720 N (162 lbs) with a range of 244 to 1243 N (55 to 280 lbs) for the full-dentition subjects. A 2-tailed t test showed that the average difference of 258 N (58 lbs) between the 2 groups was significant (P< or =.01). There was only a moderate negative association between clenching strength and loss of mandibular tooth support (R = -0.35). Clenching force was not well correlated with age as indicated by low R values (R = 0.21, missing tooth group and R = -0.03, full dentition group).
  
  
  CONCLUSIONS
  Within the limitations of this study the maximum clenching force was less (P< or =.01), by 258 N (58 lbs) on average, in subjects with moderate loss of posterior tooth support. Loss of maximum clenching force was associated with a modest negative correlation to the number of missing teeth in the mandibular arch (R = -0.35). The range of clenching force was surprisingly large for both the missing tooth (98 to 1031 N) and full dentition (244 to 1243 N) groups.
authors.affiliation: Department of Oral Biology; Box 100424, College of Dentistry, University of Florida, Gainesville, FL 32610, USA. cgibbs@dental.ufl.edu
authors.forename: Charles H
authors.initials: CH
authors.lastname: Gibbs
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Anusavice
authors.forename: Henry M
authors.initials: HM
authors.lastname: Young
authors.forename: Jack S
authors.initials: JS
authors.lastname: Jones
authors.forename: Josephine F
authors.initials: JF
authors.lastname: Esquivel-Upshaw
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D001641:Bicuspid; D001732:Bite Force; D002138:Calibration; D003724:Dental Arch / Q000503:physiopathology; D005260:Female; D006801:Humans; D007576:Jaw, Edentulous, Partially / Q000145:classification / Q000503:physiopathology*; D016014:Linear Models; D008297:Male; D008334:Mandible / Q000503:physiopathology; D008875:Middle Aged; D008963:Molar; D009119:Muscle Contraction / Q000502:physiology; D010865:Pilot Projects; D015203:Reproducibility of Results; D013223:Statistics as Topic; D016388:Tooth Loss / Q000145:classification / Q000503:physiopathology; D014159:Transducers