title: Influence of the location of the parotid duct orifice on oral clearance.
abstract: OBJECTIVE
  To determine the location of the parotid duct orifice in relation to the maxillary molars and its influence on oral clearance on the buccal surfaces of the maxillary molars.
  
  
  METHODS
  A 2-mm hole was made at the centre of an adhesive therapeutic agent for aphthous stomatitis and the agent was placed on the mucosa so that the hole matched the parotid duct orifice. To locate the orifice, an impression of the buccal tooth surfaces and mucosa around the agent was taken with the teeth in centric occlusion. To evaluate the oral clearance rate, 12 subjects who displayed the parotid duct orifice within 1S.D. of the mean values obtained from the original 35 subjects were selected. 1% agar containing 1 mol/l potassium chloride was placed into three cylinders positioned horizontally, 6mm apart, in an acrylic holder centred over the mean duct location. The diffusion chambers were taken from the mouth at selected time intervals and the gel transferred quantitatively to flasks containing 300 ml of 100 ppm NaCl, which was assayed for potassium by atomic absorption spectrophotometry. Half-times for clearance were calculated.
  
  
  RESULTS
  The mean location of the parotid duct orifice was -0.4 mm (range -7.5 to +6.1 mm) mesial to the contact surface between the maxillary first and second molars (where negative values indicate mesial and positive values distal) and 7.2 mm (range +3.8 to +10.4 mm) above a line touching the buccal cusps of the upper molars. The clearance half-time values were shortest for the central cylinder whether salivary flow was unstimulated or stimulated and when flow was unstimulated the clearance half-time was shorter for the mesial than the distal cylinder.
  
  
  CONCLUSIONS
  The degree of individual variation in the location of the parotid duct orifice is great and its exact location will markedly affect oral clearance at different positions on the buccal surfaces of the upper molars.
authors.affiliation: Department of Human Development & Fostering, Division of Pediatric Dentistry, School of Dentistry, Meikai University, 1-1 Keyakidai, Sakado, Saitama 350-0283, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Suzuki
authors.forename: Shigeru
authors.initials: S
authors.lastname: Watanabe
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Ono
authors.forename: Hideo
authors.initials: H
authors.lastname: Ohashi
authors.forename: Chenghua
authors.initials: C
authors.lastname: Pai
authors.forename: Xianghui
authors.initials: X
authors.lastname: Xing
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Wang
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D003731:Dental Caries / Q000378:metabolism; D003733:Dental Caries Susceptibility; D005260:Female; D006801:Humans; D008297:Male; D008437:Maxilla / Q000033:anatomy & histology; D008963:Molar / Q000033:anatomy & histology; D009055:Mouth / Q000378:metabolism; D010306:Parotid Gland / Q000033:anatomy & histology*; D012463:Saliva / Q000378:metabolism*; D018987:Salivary Ducts / Q000033:anatomy & histology*; D012636:Secretory Rate / Q000502:physiology; D055815:Young Adult