Effect of occlusal vertical dimension on lip positions at smile.
BACKGROUND
In complete mouth reconstructive dentistry, the occlusal vertical dimension may be increased to provide adequate restorative space or to improve esthetics. The effect of increasing the occlusal vertical dimension on the smile is not well understood.


OBJECTIVE
The purpose of this study was to evaluate the effect of increasing the occlusal vertical dimension on the dimensions of the smile.


METHODS
Thirty dental students, 12 men and 18 women between the ages of 21 and 30 years old, participated in this study. Polyvinyl siloxane occlusal registrations 2, 4, 6, and 8 mm in thickness were fabricated from articulated stone casts. Posed smile images at occlusal vertical dimension +0, +2, +4, +6, and +8 mm were made with a digital single lens reflex camera mounted on a tripod. A wall-mounted head-positioning device, modified from a cephalometric unit, was used to stabilize the head position. Interlabial gap height, intercommissural width, incisal edge to upper lip, and incisal edge-to-lower lip measurements were made with computer software. The smile index was obtained by dividing width by height. The display zone area was measured by using computer software tracing. One-way repeated measures ANOVA (α=.05) was used for statistical analysis.


RESULTS
With an increase in the occlusal vertical dimension, the interlabial gap height, incisal edge to lower lip distance, and display zone area increased significantly (P<.001), whereas the smile index decreased significantly (P<.001). No significant changes were observed in the intercommissural width and incisal edge to upper lip distance.


CONCLUSIONS
The interlabial gap height, incisal edge-to-lower lip distance, and display zone area increase with increased occlusal vertical dimension. The smile index decreases with increased occlusal vertical dimension. However, the width of the smile and the length of the upper lip tend to remain unchanged.
International Team for Implantology Scholar, Center for Implant Dentistry, Department of Oral and Maxillofacial Surgery, University of Florida College of Dentistry, Gainesville, Fla. Electronic address: john.chou.dds@gmail.com.
Jang-Ching
JC
Chou
Program Director, Graduate Prosthodontics, Marquette University School of Dentistry, Milwaukee, Wis.
Geoffrey A
GA
Thompson
Director, Predoctoral Prosthodontics and Biomaterials, Marquette University School of Dentistry, Milwaukee, Wis.
Harshit A
HA
Aggarwal
Associate Professor, Department of Orthodontics, Rutgers School of Dental Medicine, Newark, NJ.
Jose A
JA
Bosio
Resident, Graduate Prosthodontics, Marquette University School of Dentistry, Milwaukee, Wis.
Jon P
JP
Irelan
D000328:Adult; D002508:Cephalometry / Q000379:methods; D003764:Dental Materials / Q000737:chemistry; D004955:Esthetics, Dental; D005260:Female; D006801:Humans; D007180:Incisor / Q000033:anatomy & histology; D007574:Jaw Relation Record / Q000295:instrumentation; D008046:Lip / Q000033:anatomy & histology*; D008297:Male; D003765:Models, Dental; D023861:Photography, Dental / Q000379:methods; D011145:Polyvinyls / Q000737:chemistry; D012833:Siloxanes / Q000737:chemistry; D012904:Smiling; D012984:Software; D014716:Vertical Dimension; D055815:Young Adult
D003764:Dental Materials; D011145:Polyvinyls; D012833:Siloxanes; C034183:vinyl polysiloxane