Angulations of Anterior Teeth With Reference to the Alveolar Bone Measured by CBCT in a Chinese Population

Quantification of the apical palatal bone index for maxillary incisor immediate implant assessment: A retrospective cross-sectional study

BACKGROUND

Apical palatal bone is important in immediate implant evaluation. Current consensus gives qualitative suggestions regarding it, limiting its clinical decision-making value.

OBJECTIVES

To quantify the apical palatal bone dimension in maxillary incisors and reveal its quantitative correlation with other implant-related hard tissue indices to give practical advice for pre-immediate implant evaluation and design.

MATERIAL AND METHODS

A retrospective analysis of immediate implant-related hard tissue indices in maxillary incisors obtained by cone beam computed tomography (CBCT) was conducted. Palatal bone thickness at the apex level (Apical-P) on the sagittal section was selected as a parameter reflecting the apical palatal bone. Its quantitative correlation with other immediate implant-related hard tissue indices was revealed. Clinical advice of pre-immediate implant assessment was given based on the quantitative classification of Apical-P and its other correlated immediate implant-related hard tissue indices.

RESULTS

Apical-P positively correlated with cervical palatal bone, whole cervical buccal-palatal bone, sagittal root angle, and basal bone width indices. while negatively correlated with apical buccal bone, cervical buccal bone, and basal bone length indices. Six quantitative categories of Apical-P are proposed. Cases with Apical-P below 4 mm had an insufficient apical bone thickness to accommodate the implant placement, while Apical-P beyond 12 mm should be cautious about the severe implant inclination. Cases with Apical-P of 4-12 mm can generally achieve satisfying immediate implant outcomes via regulating the implant inclination.

CONCLUSIONS

Quantification of the apical palatal bone index for maxillary incisor immediate implant assessment can be achieved, providing a quantitative guide for immediate implant placement in the maxillary incisor zone.

Cone Beam Computed Tomography (CBCT) Evaluation of Alveolar Bone Thickness and Root Angulation in Anterior Maxilla for Planning Immediate Implant Placement

OBJECTIVE

 This retrospective study aimed to measure the labial, palatal, mesial, and distal bone thickness around maxillary central and lateral incisors and canines and height from crest to apex, using cone beam computed tomography (CBCT) images and compare the results based on gender. The second objective of the study was to measure root angulation on CBCT images and its relation with the labial cortical thicknesses.  Material and Methods: After the Institutional Review Board (IRB) approval, a total of 140 CBCT volumes were included in this study according to the set criteria. On each scan, right-side maxillary central, lateral incisors, and canine were selected for the measurements. All the measurements were done at three levels at the alveolar crest (L1), mid-root (L2), and apical region (L3) for each tooth.  Results: The Student's t-test was performed to compare the result of buccal, palatal, mesial, and distal bone thickness, angulation, and height of all subjects. Buccal alveolar bone thickness was minimum at the mid-root region, and the palatal bone thickness was minimum at the crestal region. The mesial bone thickness was minimum at the mid-root level, and distal bone thickness was minimum at the crest level. The available bone height was maximum at the lateral incisor and equal for the central incisor and canine. The canine was the most angulated tooth.

CONCLUSION

 Cone beam computed tomography is a reliable imaging modality to evaluate pre-surgical immediate implant sites and measure alveolar bone thickness. The canine was the most angulated tooth with more buccal alveolar bone thickness.

Buccal and palatal alveolar bone dimensions in the anterior maxilla: A micro-CT study

OBJECTIVE

Anterior maxillary immediate implant placement has become a popular procedure. It has aesthetic and functional risks. A prerequisite for success is sufficient alveolar bone for primary stability. Many cone-beam computed tomography (CBCT) studies have assessed alveolar bone dimensions in the anterior maxilla, with varying results. More accurate information on the alveolar bone dimensions in the anterior maxilla is required. The objective of the present study was to evaluate bone dimensions in the anterior maxilla using micro-CT, a high-resolution imaging tool.

MATERIALS AND METHODS

Seventy-two human skulls were scanned using micro-CT at the South African Nuclear Energy Corporation. Specialized software was used for 3-D rendering, segmentation, and visualization of the reconstructed volume data. Axial planes were created over each alveolus/tooth from canine to canine. Buccal and palatal bone dimensions were measured at crestal, 3 mm, 6 mm, and 9 mm levels.

RESULTS

Buccal bone rarely exceeded 0.5 mm, consisting of bundle bone only for all investigated teeth at all levels. Up to a third of teeth showed buccal fenestrations. Alveolar bone on the palatal side was thicker than buccal and increased from <1 mm at crestal level up to 3.77 mm, 4.56 mm, and 5.43 mm for centrals, laterals, and canines at the 9 mm level, respectively.

CONCLUSIONS

Immediate implants in the anterior maxillae has anatomical risks. Alveolar bone on the buccal aspect is very thin, with fenestrations in certain positions. Therefore, a thorough planning and individual approach are needed to avoid possible complications and achieve stable aesthetic and functional results in the long-term.

Analysis of the sagittal root angle and its correlation with hard and soft tissue indices in anterior teeth for immediate implant evaluation: a retrospective study

BACKGROUND

To assess the root angle characteristics of maxillary incisors, and to analyze the relationship between the root angle and other implant-related anatomical indices to use the sagittal root angle as an index for immediate implant evaluation and design.

METHODS

A random sample consisting of 400 cone-beam computed tomography (CBCT) images and 65 maxillary plaster models were selected for the present study. CBCT and stereolithography (STL) scan images were imported as DICOM files into coDiagnostiX software for matching the hard and soft tissue. The angle between the long axis of the anterior tooth and the corresponding alveolar bone and implant-related hard and soft tissue indices were measured in the sagittal section. Descriptive statistics, frequency analysis, multi-level comparisons, and correlation analyses were performed.

RESULTS

The average sagittal root angles were 15° at the central incisor and 19° at the lateral incisor. The root angle in males was significantly larger than that in females, and increased with age. The largest angle, 22.35°, was found in the lateral incisors of the oldest (> 50 years old) male group. The root angle was found to correlate with coronal buccal bone thickness, coronal palatal bone thickness, apical buccal bone thickness, palatal bone thickness, and the below apex bone thickness.

CONCLUSIONS

The sagittal root angle could reflect the distribution of other implant-related anatomical indices, which may provide additional reference for the evaluation of immediate implant placement.

Risk assessment of labial bone perforation in the anterior mandibular region: a virtual immediate implant placement study

BACKGROUND

This study investigated the prevalence of labial bone perforation (LBP) related to the associated anatomic factors in anterior mandibular region using a virtual immediate implant placement procedure.

METHODS

Series qualified CBCT images of 149 participants (894 teeth) were selected to analyze the assigned anatomical parameters, including concavity depth, concavity angle, torque, and deep bone thickness. Four classes of crestal and radicular dentoalveolar bone phenotypes (CRDAPs) of mandibular anterior teeth were categorized according to the thickness of dentoalveolar bone at both crestal and radicular zones. Data were adjusted for categorical (gender and CRDAP) and continuous (age, cavity angle, cavity depth, and deep bone thickness) variables using a multivariable logistic regression analysis with generalized estimating equation method.

RESULTS

The overall probability of LBP after virtual implant placement was 21.6%. There is statistically significant higher prevalence of LBP at canine (28.5%) and CRDAP class II (29.2%) regions (p < 0.001). After adjusting confounding variables, CRDAP class II and class IV regions are more likely to have LBP when compared with CRDAP class I (control) regions (p < 0.01). The risk of LBP at canine site is 6.31 times more likely than at the central incisor (control) (p < 0.01).

CONCLUSIONS

Using a virtual immediate implant placement technique, the prevalence of LBP is significantly higher at the mandibular canine site and thin radicular dentoalveolar phenotype in the anterior mandibular region.

Facial alveolar bone thickness and modifying factors of anterior maxillary teeth: a systematic review and meta-analysis of cone-beam computed tomography studies

Background

Understanding the anatomy of the facial alveolar bone (FAB), provides a prognostic tool for estimating the degree of dimensional ridge alterations after tooth extraction. This systematic review and meta-analysis aims to determine the FAB thickness and modifying factors of anterior maxillary teeth measured by CBCT scans. A secondary objective was to assess the facial distance from the cementoenamel junction (CEJ) to the bone crest.

Methods

An electronic search was made of Medline, Embase, Web of Science, Cochrane Library and Google Scholar up to December 2019. Studies that analyze and quantitatively compare FAB thickness at maxillary teeth by CBCT scans were included. The methodological quality of the included studies was appraised using the ROBINS-I tool and the overall meta-evidence certainty using the GRADE approach. A single means random-effects meta-analysis was performed to obtain the weighted mean for 95% confidence interval. A meta-regression of covariates and subgroup analysis was conducted. The nullity Q_h test and I² index for heterogeneity was estimated.

Results

2560 potentially relevant articles were recorded from which 29 studies were selected for the qualitative analysis, including 17,321 teeth. Seventeen studies considered the facial bone crest, and 12 the CEJ as a reference point for their measurements. Mean FAB thickness was ≤ 1 mm in maxillary incisors and canines (0.75–1.05 mm) and 1–2 mm in premolars. Patients over 50 years of age, females and thin gingival phenotype was associated with thinner FAB at some apico-coronal locations of maxillary incisors and canines. The geographical setting was an effect modifier that could explain up to 87% of the heterogeneity in FAB thickness, being Asian populations that showed the lowest FAB thickness values. The CEJ-bone crest distance was 2–2.5 mm in all teeth analyzed. Population over 50 years of age exhibited greater CEJ-bone crest distances, and males also showed a trend for greater distance. Evidence certainty has shown moderate quality in most analysis subsets.

Conclusions

Facial alveolar bone at anterior maxillary teeth is thin, heterogeneous in width along its apico-coronal dimensions, and increases in thickness in maxillary premolars. The CEJ-bone crest distance presented homogeneous and similar values in all teeth analyzed.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-01495-2.

Influence of the anterior arch shape and root position on root angulation in the maxillary esthetic area

Purpose

This study was conducted to characterize the relationship of the angulation between the tooth root axis and alveolar bone axis with anterior alveolar (AA) arch forms and sagittal root position (SRP) in the anterior esthetic region using cone-beam computed tomography (CBCT) images.

Materials and Methods

CBCT images that met the inclusion and exclusion criteria were categorized using a recent classification of AA arch forms and a SRP classification. Then, the angulation of the root axis and the alveolar bone axis was measured using mid-sagittal CBCT images of each tooth. The relationships of the angulation with each AA arch form and SRP classification were evaluated using 1-way analysis of variance and a linear regression model.

Results

Ninety-eight CBCT images were included in this study. SRP had a greater influence than the AA arch form on the angulation of the root axis and the alveolar bone axis (P<0.05). However, the combination of AA arch form and SRP was more predictive of the angulation of the root axis and the alveolar bone axis than either parameter individually.

Conclusion

The angulation of the root axis and alveolar bone axis demonstrated a relationship with the AA arch form and SRP in teeth in the anterior esthetic region. The influence of SRP was greater, but the combination of both parameters was more predictive of root-to-bone angulation than either parameter individually, implying that clinicians should account for both the AA arch form and SRP when planning implant placement procedures in this region.