Table 2.

Descriptive statistics of MSP categories frequency (%) and mean (SD) measurements of distance (mm) between apices of upper second premolar, first, second and third molars and maxillary sinus at both sides.

Variables	Teeth number
Category I		15	16	17	18	25	26	27	28
	Frequency	217	354	336	240	215	342	333	225
	Mean	−2.84	−2.82	−3.08	−3.11	−2.90	−2.84	−3.22	−3.13
	Percentage	40.6	66.2	62.8	44.9	40.2	63.9	62.2	42.1
Category II	Frequency	101	115	92	144	101	130	98	139
	Mean	1.19	1.22	1.22	1.37	1.04	1.16	1.29	1.27
	Percentage	18.9	21.5	17.2	26.9	18.9	24.3	18.3	26.0
Category III	Frequency	25	24	36	99	28	23	50	111
	Mean	5.80	5.13	5.33	6.34	4.73	4.19	5.06	6.54
	Percentage	4.7	4.5	6.7	18.5	5.2	4.3	9.3	20.7

Excessive MSP (Category I) was considered if the readings of the distance between floor of the sinus and the apex of the root was less than zero mm, Sinus approximation (MSP Category II) considered from 0 to 3 mm and No Sinus Approximation (MSP Category III) considered when the distance was >3 mm