An Assessment of Root Cementum in Cleidocranial Dysplasia
Abstract
The purpose of this prospective study was to determine if there is a difference between the amount of cellular and acellular cementum on the roots of 2 teeth extracted from a subject with cleidocranial dysplasia (CCD) compared to 10 teeth extracted from 10 subjects unaffected by CCD. The cementum of 2 permanent teeth, which had been extracted from the CCD subject, was examined and histomorphometrically analyzed for comparison to the cementum of 10 anterior teeth that had been extracted from individuals who were unaffected by CCD. The percentage of the root covered by cellular or acellular cementum was quantified to determine if patients affected by CCD typically lack cellular cementum. In the roots of the 2 permanent teeth of the subject with CCD, a mean of 18.05 ± 10.67% was covered by cellular cementum and 76.90 ± 3.53% was covered by acellular cementum. In the 10 permanent teeth from subjects without CCD, a mean of 19.12 ± 15.60% of the root was covered by cellular cementum and 80.34 ± 15.71% was covered by acellular cementum. The findings indicate that there is no statistically significant difference between the amount of either cellular or acellular cementum covering the roots of the study subject with CCD and the roots of the 10 control teeth. The presumption that a lack of cellular cementum causes the increased number of unerupted teeth in patients with CCD is not supported by the findings of this study.
INTRODUCTION
Cleidocranial dysplasia (CCD) is a rare condition characterized by defects of the clavicles, skull, and sometimes other parts of the skeleton, together with a tendency toward retention of the deciduous dentition and failure of the succedaneous teeth to erupt. The disorder shows no predilection for either sex, and, although it is often inherited from either parent, sporadic cases are known to occur.1
Cleidocranial dysplasia has been mapped to chromosome 6p21, where the transcription factor CBFA1 is located, and it has been shown that mutations involving this gene cause CCD in humans.2,3
A mouse model with a mutated CBFA1 locus has recently been generated. Mice with a homozygous mutation in CBFA1 (CBFA1 -/-) have shown a complete lack of ossification of the skeleton owing to maturational arrest of osteoblasts and it has been suggested that both intramembranous and endochondral ossification are completely blocked. The study of Komori et al4 also indicated a lack of maturation of osteoclasts.
The most characteristic and pathognomonic feature of this disorder is hypoplasia or aplasia of the clavicles, which results in hypermobility of the shoulders.5 These individuals exhibit short stature and possess a characteristic craniofacial appearance, showing parietal and frontal bossing, hypoplastic maxilla and zygomas, and relative mandibular prognathism.6 Other cranial abnormalities include delayed closure of the midline cranial sutures with some fontanelles remaining patent throughout life.5
Many cases exhibit delayed eruption of teeth usually associated with a remarkable number of supernumerary teeth. Delayed eruption can occur even in regions without supernumerary teeth.7 Studies by Kreiborg,8 Jensen,9 and Lukinmaa et al,10 have indicated abnormal craniofacial bone remodeling, with diminished resorption on bone surfaces in the cranial base and the jaws, and delayed resorption of primary teeth.
CASE REPORT
A 22-year-old Caucasian male presented to his general dentist. At that time it was noted that the patient had multiple impacted permanent teeth as well as multiple retained primary teeth. The patient had no other obvious problems. The patient's chief complaint was, “my baby teeth never came out.” He related that both his mother and grandfather had a similar condition.
On physical examination, the patient exhibited frontoparietal bossing, a slight Class III skeletal profile, and an increased calvarium circumference. He was short in stature with slightly drooping shoulders. He also exhibited mild hypertelorism.
An intraoral clinical examination revealed the only teeth present were:
Permanent Teeth
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Maxillary right quadrant—the central incisor (11), and the first permanent molar (16),
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Maxillary left quadrant—the first permanent molar (26),
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Mandibular left quadrant—and the central and lateral incisors (31, 32), the second premolar (35) and the first and second molars (36, 37),
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Mandibular right quadrant—the central and lateral incisors (41, 42) and the first and second molars (46, 47).
Primary Teeth
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Maxillary right quadrant—the lateral incisor (52), the canine (53) and the first and second molars (54, 55),
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Maxillary left quadrant—all the primary teeth from central incisor to molar were present (61, 62, 63, 64, 65),
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Mandibular left quadrant—the canine (73) and the first molar (74),
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Mandibular right quadrant—the canine (83) and the first and second molars (84, 85).
The patient had a slight maxillary and mandibular transverse skeletal discrepancy (narrow arches) and a high arched palate. The mandibular corpus was elongated and the mandibular alveolar ridge exhibited alveolar bone height greater than normal.
Panoramic (Figure 1) and cephalometric radiographs and diagnostic plaster models were obtained. The radiographs revealed that all of the permanent teeth were present as well as one supernumerary maxillary left lateral incisor.
Citation: The Angle Orthodontist 71, 4; 10.1043/0003-3219(2001)071<0293:AAORCI>2.0.CO;2
A radiographic survey of the chest, hands, spine, and skull was performed. The results of the extended survey revealed numerous Wormian bones in the sutures of the skull (Figure 2), which suggested delayed closure of sutures. He had well-developed clavicles, although his shoulders drooped considerably, and no abnormality of the hand or vertebral bones except for a fusion defect of the spinous process of the L-5 vertebra.
Citation: The Angle Orthodontist 71, 4; 10.1043/0003-3219(2001)071<0293:AAORCI>2.0.CO;2
During the 30 months of orthodontic treatment, this patient was lost to follow-up for 14 months. When he returned, it was discovered that the left lateral incisor (22) was ankylosed. The wire had exerted an extrusive force on this tooth with an intrusive force on the left central incisor (21). This forced the left central incisor (21) labially and superiorly until this tooth had no buccal bony support. The patient also had developed a 2.5 × 2.5 × 1.5 cm, well-circumscribed radiolucency around the left lateral incisor (22) (Figure 3). The cyst and impacted tooth were removed, as well as left central incisor (21) and the left maxillary primary first molar (64).
Citation: The Angle Orthodontist 71, 4; 10.1043/0003-3219(2001)071<0293:AAORCI>2.0.CO;2
DIAGNOSIS
The aforementioned clinical observations were consistent with a diagnosis of cleidocranial dysplasia with multiple ankylosed teeth. The patient's mother and father both suffered from this as well. The cyst was submitted to the Armed Forces Institute of Pathology and for microscopic evaluation and diagnosis. It was diagnosed as an odontogenic keratocyst.
Since cleidocranial dysplasia is a systemic disorder that manifests itself as a condition in which teeth fail to erupt, it is logical to assume that the formation and maintenance of root cementum could be affected.
In the past, few authors have concerned themselves with the microscopic study of unerupted teeth.11 Of those who have previously examined unerupted teeth, the consensus was that there was an anomaly of the cementum. This anomaly was manifested as the almost complete absence of cellular cementum and an increase in the amount of acellular cementum on the roots of the affected teeth.11,12 This was thought to be the probable cause of the failure of eruption of a significant number of teeth in patients affected with CCD.
The purpose of this prospective study was to determine if there is a difference between the amount of cellular and acellular cementum on the roots of 2 teeth extracted from a subject with cleidocranial dysplasia (CCD) compared to teeth extracted from 10 subjects unaffected by CCD.
MATERIALS AND METHODS
The cementum of the left central (21) and lateral (22) incisors (teeth associated with the cyst or had poor bony support) that had been extracted from the CCD patient was examined. This cementum was compared to the cementum of 10 teeth that had been extracted from individuals who were unaffected by CCD. These anterior teeth from individuals unaffected by CCD were chosen randomly from teeth submitted to the pathological service at the University of Oklahoma. The percentage of the root covered by cellular or acellular cementum, or both, was quantified to determine if patients affected by CCD typically lack cellular cementum.
In order to study the teeth without decalcification, they were submitted to the Hard Tissue Research Laboratory at the University of Oklahoma College of Dentistry. All specimens were cut longitudinally in the mesial-distal axis on an EXAKT cutting/grinding system (EXAKT Apparatebau, Norderstedt, Germany) and placed in 10% neutral buffered formalin for 48 hours. This was followed by dehydration with a graded series of alcohols for 9 days at room temperature and pressure with constant shaking. After dehydration, the specimens were infiltrated with a light-curing embedding resin (Technovit 7200 VLC, Kulzer, Germany). Following 19 days of infiltration with constant shaking at room temperature and atmospheric pressure, the specimens were embedded and polymerized by 450 nm light with the temperature of the specimens never exceeding 40°C. The blocks containing the teeth were mounted on Plexiglas slides and the specimens were reduced to a thickness of 150 μm on the EXAKT cutting/grinding system. The specimens were then prepared to a thickness of 50 μm by the cutting/grinding method of Donath13,14 using the EXAKT microgrinding system and were stained with Stevenel's blue and Van Gieson's picro fuchsin. Microphotographs were obtained at 1.5× and microphotographs were obtained using a Zeus Axial microscope and an MC 100 spot camera.
The undeclacified sections were examined microscopically, digitized, and analyzed histomorphometrically to determine the percentage of root surface covered by cellular and acellular cementum. This analysis was performed on a Power Macintosh 8500/132 computer using the public domain image program developed at the United States National Institutes of Health (available on the Internet at http://rsb.info.nih.gov/nih-image/).
RESULTS
The arithmetic mean and standard deviation of cellular and acellular cementum for each group was calculated (Tables 1 and 2). Histomorphometric analysis of the surface of the roots of the 2 permanent teeth of the patient affected with CCD showed that, on 1 tooth 10.5% of the root was covered with cellular cementum and 79.4% of the root was covered with acellular cementum. Apical resorption was found on the extracted left central incisor involving 10.1% of the root length (Figure 4A through D). In the second tooth 25.6% was covered with cellular cementum and 74.4% of the root was covered with acellular cementum. The mean values for the 2 teeth from the subject with CCD were 18.05 ± 10.67% of the root surface was covered with cellular cementum and 76.90 ± 3.53% of the root was covered with acellular cementum.
Citation: The Angle Orthodontist 71, 4; 10.1043/0003-3219(2001)071<0293:AAORCI>2.0.CO;2
In the 10 permanent teeth from the subjects without CCD, a mean of 19.12 ± 15.60% was covered by cellular cementum and 80.34 ± 15.71% of the root was covered by acellular cementum.
Two statistical procedures used to compare the mean difference between the 2 samples yielded almost identical results. The Wilcoxon rank-sum test showed no significant difference between the 2 cellular groups (Z = −0.1076, P < .9143). Two-sample t-test also showed no significant difference (t = −0.091, df = 10, P = .9293). As for acellular cement groups, the Wilcoxon rank-sum test showed no significant difference (Z = −0.1076, P < .9143), as did the 2-sample t-test (t = −0.2971, df = 10, P < .7725).
DISCUSSION
It is well known that a complete layer of acellular cementum usually covers the dentin of the roots of teeth, although sometimes this layer is incomplete near the apex. Overlying the acellular cementum, in the apical half of the roots, are layers of cellular cementum, which increase in thickness with age. In 1956, Rushton12 noted that both erupted and nonerupted permanent teeth of patients with CCD exhibited a lack of cellular cementum. A histological examination of a retained primary tooth in this same patient showed normal cementum formation.
In normally developing persons, the apposition of cellular cementum is regarded as functioning in relation to the continued eruption and other movements of teeth. In addition, the apposition of cellular cementum affords a means whereby the periodontal fibers continue to be attached to a vital tissue. Where cellular cementum is lacking, this attachment function is performed by acellular cementum. This explanation is problematic because the bulk of acellular cementum is many times smaller than that of cellular cementum. One must suppose either that the deficiency of bulk is compensated by increased apposition of bone or that the teeth do not in fact undergo the continued movement in an occlusal and other direction which normal teeth undergo.12
Smith and Sydney11 made detailed histological observations of the teeth of patients exhibiting CCD and reported an almost complete lack of cellular cementum on both the erupted primary and unerupted permanent teeth. They concluded that cellular cementum formation must not be the only essential factor involved in normal tooth eruption, and that the dental space acquired by the eruption process must then be maintained by apposition of alveolar bone.
CONCLUSION
The cementum on 2 teeth from a subject with CCD was compared to the cementum on 10 teeth from subjects not affected with CCD. Based on our findings, in this case, we conclude that the observation of a preponderance of acellular cementum reported by Rushton12 and by Smith and Sydney11 may not be a distinguishing characteristic of teeth affected by CCD. Our study suggests that the difference in cementum is not significant between our CCD patient and control subjects and, therefore, the amount of cellular or acellular cementum may not be a factor in the increased number of nonerupted teeth in those suffering from CCD. More teeth from patients with CCD should be studied to see if this holds true in a larger sample.
Panoramic radiograph revealing numerous retained primary teeth and unerupted permanent teeth. All permanent teeth are present as well as a supernumerary maxillary left lateral incisor
Anteroposterior (AP) skull film showing numerous Wormian bones suggesting delayed sutural closure
Panoramic radiograph 14 months after Figure 1. A large radiolucent lesion is present surrounding the impacted tooth 11. Microscopic examination showed this to be an odontogenic keratocyst
(A) Low power photomicrograph showing resorption of 10.1% of the root surface at the apex of the erupted central incisor from the patient affected with CCD (original magnification × 5.5, Stevenel's blue and Van Gieson's picro fuchsin stain). (B) Area of resorption of the primary root from the patient affected with CCD. Small areas of cellular cementum (arrows) present (original magnification × 50, Stevenel's blue and Van Gieson's picro fuchsin stain). (C) An area of cellular cementum overlying a more mature area of cellular cementum (arrow at junction) from the root of the erupted central incisor from the patient affected with CCD (original magnification × 50, Stevenel's blue and Van Gieson's picro fuchsin stain). (D) Area of acellular cementum from the root of the unerupted canine from the patient affected with CCD (original magnification × 25, Stevenel's blue and Van Gieson's picro fuchsin stain)