2Gotfleib EL, Nelson AH, Vogels DS. 1990 study of orthodonric diagnosis and treatment procedures ; part 1 : results and trends. J Clin Orthod, 1991 ;25:145-56.
3O Connor BM. Contemporary trends in orthodontic praetice:a national survey. Am J Orthod Dentofac Orthop, 1993,103 : 163-90.
4Grossen J, Ingervall B. The effect of a lip bumper on lower dental arch dimensions and tooth position. Eur J Orthod, 1995, 17: 129-134.
5Wemer SP, Shivapuja PK, Harris EF. Sleletodental changes in the afolescent accruing from the use of the lip bumper. Angle Orthod, 1994,64 : 13-22.