The Measurement And Analysis Of The Three-dimensional Structure And Root Position Of Natural Alveolar Bone In The Maxillary Anterior Region With CBCT Method

Purpose:This study aimed to measure the three-dimensional bone mass,root position and the root angle related to the alveolar bone and evaluate the anatomical factors related to immediate implantation in the maxillary anterior region.Materials and Methods:116 patients who qualified for the inclusion criteria were included in the CBCT image analysis.The measurement items included the root angle related to the alveolar bone(Angle’),labial,palatal,and basal alveolar plate height(LH,PH,AH),labial-palatal width of the alveolar bone(AB),the distance between the palatal plate and labial imaginary line(BD),the distance between the buccal plate and labial imaginary line(AD),interproximal alveolar bone width(EH,GF)and the mesial-distal width of the alveolar bone(EF).According to Kan’s classification(the classification of the sagittal root position,SRP classification),the root sagittal position was classified and the measurement item values in the four categories were compared.The Spearman correlation analysis was used to assess the relationship between age,angle and the measurement items,and the statistical standard was 0.05.Results:First,the mean height of the labial,palatal and basal alveolar plates(LH,PH,AH)were all greater than8 mm in the maxillary anterior region,excluding the height of basal alveolar bone(AH)in the canine teeth(6.01mm).1.4% had no available bone height and 20.67% were less than 3 mm in the apical area of canine.Second,the labial-palatal width of the alveolar bone(AB)at 1mm below the labial crest and the distance between the palatal plate and labial imaginary line(BD)oscillated around an average level of 8.15 mm and6.24 mm,respectively.The average value of mesial-distal width of alveolar bone(EF)at 1mm below the labial crest was larger than 8mm.Interproximal alveolar bone widths(EH,GF)were all greater than 2mm on average.Third,the angle values between the axis of the roots and the alveolar bone(Angle’)in the three sites were as follows: 23.08°(canine),21.46°(central incisor),and 18.47°(lateral incisor).The angle values between the axis of the roots and the alveolar bone(Angle’)in SRP I,II,IV category was 22.68°,14.18°,14.74°,respectively.The height of the basal alveolar bone(AH)of SRP II category was the lowest,which was 5% and 24% lower than the averages of SRP I and IV,respectively.Among the labial-palatal width of the alveolar bone(AB),the distance between the buccal plate and labial imaginary line(AD),the distance between the palatal plate and labial imaginary line(BD)and the mesial-distal width of the alveolar bone(EF),the values in SRP IV category were the lowest in four SRP classifications,which were 7.67 mm,1.60 mm,6.06 mm and 8.47 mm,respectively.Fourthly,there was a negative correlation between the height of labial or palatal alveolar bone(LH,PH)and age;the root angle related to the alveolar bone(Angle’)was negatively correlated with the height of the palatal bone(PH)or the height of the basal alveolar bone(AH);there was a positive correlation between the width of labial-palatal bone(AB)and the root angle related to the alveolar bone(Angle’).Conclusions:Within the limitations of the present study,the following conclusions can be drawn:First,the recommended diameter of the implant should not exceed 4.15 mm and 3.49 mm in the central and lateral incisor region,respectively.The implant should be placed on the palatal side of the natural tooth to obtain 2mm buccal bone thickness and initial stability.Second,the recommended maximum diameter of implant in canine region was 5.32 mm,and inadequate initial stability may exist in some sites because of insufficient apical bone height and socket preservation would be an appropriate treatment option.Third,the root angle related to the alveolar bone(Angle’)was between 18 and 24° in the maxillary anterior area and rich bone mass on the palatal side of the socket could provide sufficient initial stability for immediate implantation.Fourthly,there was correlations between root angle related to the alveolar bone(Angle’)and the width of the labial-palatal bone(AB),the height of the palatal alveolar bone(PH)or the height of the basal bone(AH).