Estimation of the Possibility to Restore a Positive Overjet in Patients with Unilateral Cleft Lip and Palate

 

Patient population: Children and adolescents from 4 to 18 years with unilateral cleft lip and palate.

 

Measurement of the interalveolar relations using cephalometrics:

(1) prosthion (Pr): The point of gingival contact with the upper central incisors

(2) infradentale (Id): The point of gingival contact with the lower central incisors

(3) PL = line through the anterior and posterior nasal spine

(4) ML = the tangent to the mandibular body through the gnathion

(5) modified occlusal plane: plane originating at the point of meeting for the PL and ML lines, and passing through the center between the cusps of the upper and lower incisors during centric occlusion.

(6) Pr line = distance in mm from the Pr to the modified occlusal plane, using a line drawn perpendicular to the modified occlusal plane

(7) Id line = distance in mm from the Id to the modified occlusal plane, using a line drawn perpendicular to the modified occlusal plane

 

NOTE: To get the negative values for (Pr + Id) shown in the figures, one or both of the values for Pr and Id must be negative.

 

sum Pr + Id =

= (Pr line in mm) + (Id line in mm)

 

Nomogram (Figure 7, page 120):

• Plot of sum of Pr + Id vs age.

• This shows 5 parallel sets of lines for 0% (K), 25%, 50%, 75% and 100% probability to FAIL in being able to restore the positive overjet.

• Age range is from 4 to 18 years.

• Change in slope occurs at 10 and at 15 years.

Age Range	Slope of Lines with X = age
4 to 10	-0.3333
10 to 15	-0.500
15 to 18	-0.16667

 

 

Age Range	Probability of Failure	Intercept
4 to 10	0%	3.8333
	25%	2.8333
	50%	1.8333
	75%	0.8333
	100%	-0.1667
10 to 15	0%	5.5
	25%	4.5
	50%	3.5
	75%	2.5
	100%	1.5
15 to 18	0%	0.5
	25%	-0.5
	50%	-1.5
	75%	-2.5
	100%	-3.5

 

The location of the sum Pr + Id relative to the probability lines can result in the following likelihood of FAILING in attempts to correct the positive overjet:

(1) 0% (100% success)

(2) 1-24%

(3) 25%

(4) 26-49%

(5) 50%

(6) 51-74%

(7) 75%

(8) 76-99%

(9) 100% (0% success)