Cervical Cementum Research Articles

Inactivation of Sufu in cementoblasts accelerates external tooth root resorption.

Cementum has been empirically regarded as an antiresorptive barrier against tooth roots. However, little is known about the factors of homeostasis and resistant mechanisms of tooth roots against resorption. Here, we investigated cementum factors and their interaction against resorption using transgenic mice exhibiting external cervical root resorption (ECRR). Ectopically thickened cervical cementum caused by functional inactivation of ectonucleotide pyrophosphotase/phosphodiesterase 1 (Enpp1) was susceptible to ECRR with aging. In addition, the inactivation of the suppressor of fused (Sufu), a Hedgehog signaling inhibitor, in cementoblasts led to ECRR. Interestingly, concurrent inactivation of Sufu and Enpp1 in cementoblasts remarkably exacerbated ECRR with higher Rankl expression. Cellular and molecular analyses using cementoblasts and bone marrow-derived macrophages indicated that Dickkopf-related protein 1 (Dkk1) induced by the inactivation of Sufu in cementoblasts has roles in the acceleration of ECRR triggered by Enpp1 inactivation. Using compound mutant mice for concurrent Wntless and Enpp1 inactivation, this synergistic cooperation of Dkk1 and Npp1 for resorption found in double mutant Sufu and Enpp1 mice was confirmed by the reproduction of amplified ECRR. On the basis of these findings, we conclude that proper Npp1 function and sustained Wnt activity in the cervical cementum are essential for the homeostasis of tooth roots against resorption in a physiological state.

Npp1 prevents external tooth root resorption by regulation of cervical cementum integrity

Tooth roots embedded in the alveolar bone do not typically undergo resorption while the bone continues remodeling in its physiological state. In this study, we analyzed genetically modified mice with the functional inactivation of nucleotide pyrophosphatase 1 (Npp1), encoded by ectonucleotide pyrophosphatase/phosphodiesterase 1 (Enpp1). This mutation leads to the formation of ectopic cervical cementum vulnerable to external tooth root resorption. Cementoblasts with the inactivation of Enpp1 extensively expressed non-collagenous matrix proteins enriched with bone sialoprotein (Bsp), dentin matrix protein 1 (Dmp1), and osteopontin (Opn), which have roles in mineralization through nucleation and in cell adhesion through the Arg-Gly-Asp (RGD) motif. In cementoblasts with the inactivation of Enpp1, β-catenin was significantly activated and induced the expression of these non-collagenous matrix proteins. In addition, adenosine triphosphate (ATP), which is the most preferred substrate of Npp1, accumulated extracellularly and autocrinally induced the expression of the receptor activator of nuclear factor κB ligand (Rankl) in cementoblasts with inactivated Npp1. Consequently, these results strongly suggest that functional Npp1 preserves cervical cementum integrity and supports the anti-resorptive properties of tooth roots through ATP homeostasis in the physiological state of cervical cementum.

Analysis of the nano and microstructures of the cervical cementum and saliva in periodontitis: A pilot study

ObjectivesDuring the progression of periodontitis, the structures of the cementum and saliva are altered due to pathological changes in the environment. This study aimed to analyze the nanostructures of the cervical cementum and saliva in patients with periodontitis. MethodsPatients with periodontitis (n = 10) and periodontally healthy controls (n = 8) were included. Single-rooted teeth with indications for extraction were obtained from individuals. The cervical-thirds of the roots were sectioned transversely to obtain 1 mm thick sections. Unstimulated whole saliva samples were collected from each individual. The nanostructures of the cementum and saliva were analyzed using small and wide-angle X-ray scattering methods. ResultsThe mean radius and distance values of the cementum nanoparticles in the periodontitis and control groups were 368 Å and 1152 Å, and 377 Å and 1186 Å, respectively. The mean radius and distance values of the saliva nanoparticles in the periodontitis and control groups were 425 Å and 1359 Å, and 468 Å and 1452 Å, respectively. More wide-angle X-ray scattering profile peaks were observed in the cementum of the controls. Similarities were observed between the 3D profiles of the cementum and the saliva nanoparticles. ConclusionsAccording to the results of the present study, (i) the cementum and saliva nanoparticles were of similar size in periodontitis and healthy controls, (ii) the cementum was more crystalline according to the (002) crystallographic plane in controls, and (iii) the similarities in the 3D-profile of the cementum and saliva nanoparticles suggest some interactions between them in the sulcus/periodontal pocket at the nanolevel.

Antagonistic interactions between osterix and pyrophosphate during cementum formation.

During cementum formation, the key roles of osterix (Osx) and inorganic pyrophosphate (PPi), mainly controlled by nucleotide pyrophosphatase 1 (Npp1; encoded by the Enpp1 gene) and progressive ankylosis protein (Ank), have been demonstrated by animal models displaying altered cementum formation. In this study, we analyzed the relationship of Osx and local PPi during cementum formation using compound mutant mice with their wildtype and corresponding single gene mutants. Importantly, functional defects in PPi regulation led to the induction of Osx expression at the cervical cementum as demonstrated by Enpp1 mutant mice and cementoblasts with the retroviral transduction of small hairpin RNA for Enpp1 or Ank. Conversely, cementoblasts exposed to inorganic PPi or with the enforced expression of Enpp1 or Ank reduced Osx expression in a concentration-dependent manner. Furthermore, the loss of Osx induced the higher expression of Npp1 and Ank at the apical region of the developing tooth root as observed in Osx-deficient mice. The activity of PPi-generating ectoenzymes (nucleoside triphosphate pyrophosphohydrolase, NTPPPHase) and the level of extracellular PPi were significantly increased in Osx-knockdown cementoblasts. However, the formation of ectopic cervical cementum was not completely diminished by inactivation of Osx in Enpp1 mutant mice. In addition, fibroblast growth factor (FGF) receptor 1 (Fgfr1) was strongly localized in cementoblasts lining the acellular cementum and involved in the inhibitory regulation of matrix accumulation and further mineralization by supporting PPi production. Taken together, these results suggest that local PPi suppresses matrix accumulation and further mineralization through an antagonistic interaction with Osx under the synergistic influence of FGF signaling during cementum formation.

Reduced Orthodontic Tooth Movement in Enpp1 Mutant Mice with Hypercementosis

Previous studies revealed that cementum formation is tightly regulated by inorganic pyrophosphate (PPi), a mineralization inhibitor. Local PPi concentrations are determined by regulators, including ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1), which increases PPi concentrations by adenosine triphosphate hydrolysis. Orthodontic forces stimulate alveolar bone remodelling, leading to orthodontic tooth movement (OTM). To better understand how disturbed mineral metabolism and the resulting altered periodontal structures affect OTM, we employed Enpp1 mutant mice that feature reduced PPi and increased cervical cementum in a model of OTM induced by a stretched closed-coil spring ligated between the maxillary left first molar and maxillary incisors. We analyzed tooth movement, osteoclast/odontoclast response, and tooth root resorption by micro–computed tomography, histology, histomorphometry, and immunohistochemistry. Preoperatively, we noted an altered periodontium in Enpp1 mutant mice, with significantly increased periodontal ligament (PDL) volume and thickness, as well as increased PDL-bone/tooth root surface area, compared to wild-type (WT) controls. After 11 d of orthodontic treatment, Enpp1 mutant mice displayed 38% reduced tooth movement versus WT mice. Molar roots in Enpp1 mutant mice exhibited less change in PDL width in compression and tension zones compared to WT mice. Root resorption was noted in both groups with no difference in average depths, but resorption lacunae in Enpp1 mutant mice were almost entirely limited to cementum, with 150% increased cementum resorption and 92% decreased dentin resorption. Osteoclast/odontoclast cells were reduced by 64% in Enpp1 mutant mice, with a predominance of tartrate-resistant acid phosphatase (TRAP)–positive cells on root surfaces, compared to WT mice. Increased numbers of TRAP-positive cells on root surfaces were associated with robust immunolocalization of osteopontin (OPN) and receptor-activator of NF-κB ligand (RANKL). Collectively, reduced response to orthodontic forces, decreased tooth movement, and altered osteoclast/odontoclast distribution suggests Enpp1 loss of function has direct effects on clastic function/recruitment and/or indirect effects on periodontal remodeling via altered periodontal structure or tissue mineralization.

Hypercementosis Associated with ENPP1 Mutations and GACI

Mineralization of bones and teeth is tightly regulated by levels of extracellular inorganic phosphate (Pi) and pyrophosphate (PPi). Three regulators that control pericellular concentrations of Pi and PPi include tissue-nonspecific alkaline phosphatase (TNAP), progressive ankylosis protein (ANK), and ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1). Inactivation of these factors results in mineralization disorders affecting teeth and their supporting structures. This study for the first time analyzed the effect of decreased PPi on dental development in individuals with generalized arterial calcification of infancy (GACI) due to loss-of-function mutations in the ENPP1 gene. Four of the 5 subjects reported a history of infraocclusion, overretained primary teeth, ankylosis, and/or slow orthodontic tooth movement, suggesting altered mineral metabolism contributing to disrupted tooth movement and exfoliation. All subjects had radiographic evidence of unusually protruding cervical root morphology in primary and/or secondary dentitions. High-resolution micro–computed tomography (micro-CT) analyses of extracted primary teeth from 3 GACI subjects revealed 4-fold increased cervical cementum thickness (P = 0.00007) and a 23% increase in cementum density (P = 0.009) compared to age-matched healthy control teeth. There were no differences in enamel and dentin densities between GACI and control teeth. Histology revealed dramatically expanded cervical cementum in GACI teeth, including cementocyte-like cells and unusual patterns of cementum resorption and repair. Micro-CT analysis of Enpp1 mutant mouse molars revealed 4-fold increased acellular cementum thickness (P = 0.002) and 5-fold increased cementum volume (P = 0.002), with no changes in enamel or dentin. Immunohistochemistry identified elevated ENPP1 expression in cementoblasts of human and mouse control teeth. Collectively, these findings reveal a novel dental phenotype in GACI and identify ENPP1 genetic mutations associated with hypercementosis. The sensitivity of cementum to reduced PPi levels in both human and mouse teeth establishes this as a well-conserved and fundamental biological process directing cementogenesis across species (ClinicalTrials.gov NCT00369421).

Wnt activity is associated with cementum-type transition.

Cellular and acellular cementum and the cells that form them are postulated to have different characteristics, and the relationship between these two tissues is not well understood. Based on the hypothesis that Wnt signaling is involved in the determination of cementum type, we examined Wnt activity along the tooth root and analyzed cementum formation in genetic mutant models. We generated mutant models with Wnt signaling upregulation (OC Catnblox(ex3)/+ ), downregulation (OC Wlsfl/fl ), and a compound mutant (Enpp1asj/asj ;OC Catnblox(ex3)/+ ) to compare cementum apposition patterns of ectonucleotide diphosphatase/phosphodiesterase (Enpp1) mutant (Enpp1asj/asj ). The analysis of structural morphology and histology was performed with hematoxylin and eosin and immunohistochemical staining and scanning electron microscopy. The cementum type of upper apical region of tooth roots in the molar is altered from the cellular form at the initial stage to the acellular form at the late stage of cementum formation. However, the basal part of this apical region is not altered and retains cellular cementum characters with strong Wnt activity. In the genetic mutant models for Wnt upregulation, cellular cementum is formed at the cervical region instead of acellular cementum. However, Enpp1 mutant mice have clearly different characteristics with cellular-type cementum even with dramatically increased cervical cementum matrix. In addition, we found that acellular-type formation could be altered into cellular-type formation by analyzing Wnt upregulation and compound mutant models. Cementum type is not determined by its specific location and could be transformed with Wnt activity during cementum formation.

Invasive cervical resorption: treatment challenges

Invasive cervical resorption is a relatively uncommon form of external root resorption. It is characterized by invasion of cervical region of the root by fibrovascular tissue derived from the periodontal ligament. This case presents an invasive cervical resorption occurring in maxillary lateral incisor, following damage in cervical cementum from avulsion and intracoronal bleaching procedure. Flap reflection, debridement and restoration with glass ionomer cement were performed in an attempt to repair the defect. But after 2 mon, more resorption extended apically. Considering root stability and recurrence potential, we decided to extract the tooth. Invasive cervical resorption in advanced stages may present great challenges for clinicians. Therefore, prevention and early detection must be stressed when dealing with patients presenting history of potential predisposing factors.

The Progressive Ankylosis Protein Regulates Cementum Apposition and Extracellular Matrix Composition

Background/Aims: Tooth root cementum is sensitive to modulation of inorganic pyrophosphate (PP_i), an inhibitor of hydroxyapatite precipitation. Factors increasing PP_i include progressive ankylosis protein (ANK) and ectonucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) while tissue nonspecific alkaline phosphatase hydrolyzes PP_i. Studies here aimed to define the role of ANK in root and cementum by analyzing tooth development in Ank knock-out (KO) mice versus wild type. Materials and Methods: Periodontal development in KO versus control mice was analyzed by histology, histomorphometry, immunohistochemistry, in situ hybridization, electron microscopy, and nanoindentation. Cementoblast cultures were used in vitro to provide mechanistic underpinnings for PP_i modulation of cell function. Results: Over the course of root development, Ank KO cervical cementum became 8- to 12-fold thicker than control cervical cementum. Periodontal ligament width was maintained and other dentoalveolar tissues, including apical cementum, were unaltered. Cervical cementum uncharacteristically included numerous cells, from rapid cementogenesis. Ank KO increased osteopontin and dentin matrix protein 1 gene and protein expression, and markedly increased NPP1 protein expression in cementoblasts but not in other cell types. Conditional ablation of Ank in joints and periodontia confirmed a local role for ANK in cementogenesis. In vitro studies employing cementoblasts indicated that Ank and Enpp1 mRNA levels increased in step with mineral nodule formation, supporting a role for these factors in regulation of cementum matrix mineralization. Conclusion: ANK, by modulating local PP_i, controls cervical cementum apposition and extracellular matrix. Loss of ANK created a local environment conducive to rapid cementogenesis; therefore, approaches modulating PP_i in periodontal tissues have potential to promote cementum regeneration.

Hybridization quality in cervical cementum and superficial dentin using current adhesives

Objectives The aim of this research was to determine the hybridization quality of adhesives to gingival cementum and close superficial dentin using both total-etch and self-etch, one-step and two-step adhesives in vitro. Methods Five adhesive systems were used and evaluated in this study; three kinds of two-step adhesives (total-etch—Single Bond and self-etch—Clearfil SE Bond and Clearfil Protect Bond) and two one-step adhesives (Clearfil S 3 Bond, G Bond). Fifteen extracted intact human third molars were used in this study. A diagonal cut which was approximately 45° to the long axis of the roots, with the initiating point located 2 mm below the buccal enamel–cementum junction and ascending towards the pulp chamber was prepared on each tooth. Flat cervical cementum and dentin surfaces were ground with wet 600-grit silicon carbide paper, and bonded with one of the adhesives and finished by applying a flowable resin composite. After 24 h storage at 37 °C in water, the bonded assemblies were sectioned into approximately 1 mm thick slabs. Two central slabs from each tooth were chosen. One slab was totally demineralized in 0.5 M EDTA and the other was not demineralized and immersed into 50% (w/v) solution of ammoniacal silver nitrate for 24 h, and successively exposed to photodeveloping solution for 8 h. The specimens were then processed for TEM observation. Both the stained demineralized silver unchallenged and unstained non-demineralized silver challenged resin–cervical cementum/proximal superficial dentin interface were observed and evaluated under a transmission electron microscope. Results The nanoleakage pathway and extent vary among the different adhesives used and also between the resin–cementum interface and resin–dentin interface. Two-step self-etch adhesives showed better hybridization quality both in cementum and proximal superficial dentin as compared to those of two-step total-etch adhesive and one-step self-etch adhesives. Significance Two-step self-etch adhesives may provide a better sealing in cervical cementum and the proximal superficial dentin region.

P2X4 is Up-regulated in Gingival Fibroblasts after Periodontal Surgery

Several studies have shown that surgical detachment of marginal gingiva close to the cervical cementum of molar teeth in a rat mandible is a distinct stimulus for alveolar bone resorption. Recently, we found that P2X4, an ATP-receptor, is significantly up-regulated in marginal gingival cells soon after surgery. We hypothesized that local release of ATP signaling through P2X4 elicits activation of osteoclasts on the alveolar bone surface. In this study, we identified intense immunoreactivity of gingival fibroblasts to P2X4-specific antibodies and a 6.4-fold increase in expression by real-time RT-PCR. Moreover, a single local application, at the time of surgery, of Apyrase (which degrades ATP) or Coomassie Brilliant Blue (an antagonist of purinoreceptors) significantly reduced alveolar bone loss. We propose that ATP flowing from cells after surgery can directly activate P2X4 receptors in the sensor cells of marginal gingiva through Ca(2+) signaling, or by direct activation of osteoclasts on the bone surface.

Feline odontoclastic resorptive lesions: unveiling the early lesion.

The purpose of this study was to increase understanding of the factors initiating feline odontoclastic resorptive lesions (FORLs). Fifty-six teeth (clinically and radiographically unaffected by ORLs) were harvested. Of these, 43 were from cats that had ORLs in other teeth (group A) and 13 were from cats with no clinical or radiographic evidence of ORLs in any teeth (group B). Twenty-six teeth in group A and one tooth in group B showed histological evidence of external root resorption (surface resorption and replacement resorption resulting in ankylosis). Some teeth in group B showed healed cementum resorption. It has previously been assumed that FORLs were similar to lesions associated with peripheral inflammatory root resorption, and were associated with periodontal disease. These histological findings suggest instead that a FORL is a non-inflammatory replacement resorption, resulting in ankylosis. The periodontal ligament of resorbing teeth lacked normal fibrous architecture, but was not inflamed. Resorption was not identified in cervical cementum. However, the histological appearance of the cervical cementum differed between the two groups. Several aetiopathogenetic explanatory models which arise from these observations are discussed.

Marginal integrity of different resin-based composites for posterior teeth: an in vitro dye-penetration study on eight resin-composite and compomer-/adhesive combinations with a particular look at the additional use of flow-composites

Objective: To determine improvements in marginal adaptation of resin-based composite restorative systems by means of flow-composites (Solitaire 2/Gluma Solid Bond, Solitaire 2/Flow Line/Gluma Solid Bond, Point 4/Optibond Solo Plus, Point 4/Revolution/Optibond Solo Plus) and to determine the equality of simplified bonding systems (Solitaire 2/Gluma Comfort Bond, Tetric Ceram/Tetric Flow/Excite, Dyract AP/Prime & Bond NT/NRC, Pertac II/Prompt-L-Pop) in marginal gap formation. Methods: The marginal dye penetration (2% methylene-blue) was investigated separately for the approximal boxes of Class II mod-cavities with one cervical margin of the approximal box within enamel, the other within cementum. The surface analysis determined the percentage of dye-penetrated cervical and lateral margins of the approximal boxes, while the in depth investigation reported the mean dye penetration (mm) at both different cervical margins. Results: After thermocycling (5000×, 5–55°C) the percentage of dye penetration at the cervical cementum margins ranged from 16.5±5.9% (Solitaire/Flow Line/Gluma Solid Bond) to 82.8±5.7% (Pertac II/Prompt L-Pop), for the cervical enamel margins from 10.1±5.2% (Dyract AP/NRC/P & B NT) to 72.7±7.9% (Pertac II/Prompt L-Pop), and for the lateral enamel margins of the approximal boxes from 4.8±2.3% (Dyract AP/NRC/P & B NT) to 53.9±6.8% (Pertac II/Prompt L-Pop). In the in-depth dye penetration investigation the mean dye penetration ranged from 0.2±0.2 mm (Point 4/Revolution/Optibond Solo Plus) to 1.7±0.2 mm (Pertac II/Prompt L-Pop) at the cementum margins. At the enamel margins only Pertac II/Prompt L-Pop and Solitaire 2/Gluma Solid Bond showed mean in depth dye-penetrations deeper than 0.1 mm. Significance: Pertac II/Prompt-L-Pop showed a statistically significant (significance level α=0.05, Wilcoxon test) higher percentage of dye-penetrated margins than most of the other restorative systems.

Structure and mineral content of human exposed cementum and changes following phosphoric acid etching.

The structural and mineral content of human cervical cementum exposed in the oral cavi-ty and changes following a 30% phosphoric acid etching were investigated with scanning electron microscopy, electron-probe microanalysis, and atomic absorption spectrometry. Ca and P concentrations, and the Ca/P molar ratio of the exposed cementum were significantly higher than in the unexposed cervical cementum. However, there was no significant difference in the amounts of Ca dissolved from the exposed and the unexposed cementum by acid etching. These results indicate that the amounts of dissolved Ca may be affected by the amounts of organic fibrous material in the cementum. The acid etching strongly marked the ends of the extrinsic Sharpey's fibers in the exposed cementum, whereas in the unexposed cementum these structures were more or less difficult to differentiate from the intrinsic matrix following polishing and acid etching. The acid-influenced surface layers were divided into two zones; a completely demineralized surfaces zone showing organic fibrous structures and a partially demineralized subsurface zone, although the surface zone of the exposed cementum was covered with an organic felt-like sheath.

PH Reversal following in vitro bleaching of pulpless teeth

Following gutta-percha obturation of the root canals of 20 extracted human maxillary central incisors, a “walking bleach” paste was sealed into the pulp chambers with Cavit temporary restorations. This paste was replaced in 4 days by a thick paste of calcium hydroxide. Cervical cementum or dentin pH readigns were then recorded after 2, 4, and 11 days. The data were analyzed by use of the analysis of variance and the Newman-Keuls test. Replacing the walking bleach with a calcium hydroxide paste was shown to be an excellent means of changing the acid pH produced by the bleaching procedure to an alkaline pH. Following gutta-percha obturation of the root canals of 20 extracted human maxillary central incisors, a “walking bleach” paste was sealed into the pulp chambers with Cavit temporary restorations. This paste was replaced in 4 days by a thick paste of calcium hydroxide. Cervical cementum or dentin pH readigns were then recorded after 2, 4, and 11 days. The data were analyzed by use of the analysis of variance and the Newman-Keuls test. Replacing the walking bleach with a calcium hydroxide paste was shown to be an excellent means of changing the acid pH produced by the bleaching procedure to an alkaline pH.

ヒトセメント質のフッ素濃度分布 第１編 同一個体２７歯についての検討

The purpose of this study was to investigate fluoride distribution patterns in different teeth from the same mouth. Fluoride distribution in the cementum was determined in 27 noncarious teeth from a single male cadaver aged 54 years, using the abrasive micro-sampling technique.The following results were obtained.1) The distribution pattern: the fluoride concentration was maximal at or near the external surface layer of the cementum and tended to decrease towards the deep layer and this was roughly consistent in all teeth except numbers (FDI) 15 and 45.2) There was very little difference in the distribution pattern between apical and cervical cementum.3) The distribution patterns of the same tooth types tended to be similar to each other.4) The distribution patterns tended to be roughly similar between right and left homologous teeth and between upper and lower homologous teeth. The patterns appeared to be more similar between upper and lower homologous teeth than between left and right homologous teeth.5) Although the total fluoride values in the cervical cementum were lower than those in the apical cementum, the average and maximum fluoride concentrations in the cervical cementum tended to be higher than those in the apical cementum.

The effects of age and fluoride exposure on fluoride, citrate and carbonate content of human cementum.

A study was conducted to determine the values of several chemical components of dental cementum. Extracted teeth from continuous residents of low, optimal, and high natural fluoride areas were selected to determine the effects of fluoride exposure and age on the fluoride, citrate and carbonate content of cervical and apical areas of sound and periodontally diseased human cementum. 1. For normal cementum the mean fluoride content of all 18 groups was 0.443 plus or minus 0.04%on an ash basis and 0.253 plus or minus 0.02% on a dry weight basis; the mean citrate content was 1.52 plus or minus 0.10% on an ash basis and 0.86 plus or minus 0.06% on a dry weight basis; the mean carbonate content was 4.95 plus or minus 0.39% on an ash basis and 2.79 plus or minus 0.22% on a dry weight basis. 2. For diseased cementum the mean fluoride content of all 12 groups was 0.575 plus or minus 0.03% on an ash basis and 0.342 plus or minus 0.02% on a dry weight basis; the mean citrate content was 1.19 plus or minus 0.07% on an ash basis and 0.71 plus or minus 0.05% on a dry weight basis; the mean carbonate content was 5.95 plus or minus 0.47% on an ash basis and 3.50 plus or minus 0.28% on a dry weight basis. 3. There is a general increment in fluoride content of normal cervical and apical cementum, both with age and fluoride exposure. For diseased cementum this held true for fluoride exposure but not age. 4. The mean fluoride content of cervical cementum is greater than that of apical cementum for both normal and diseased groups. For citrate and carbonate no definite statistical differences were noted between cervical and apical areas. 5. The diseased cementum has a significantly higher mean fluoride content, a significantly lower citrate content, and a slightly, but not statistically significant, higher carbonate content than normal cementum. 6. Unlike bone, no inverse fluoride/citrate or fluoride/carbonate relationship was observed. 7. For both normal and diseased groups the carbonate content of cementum of individuals over age 40 tended to be lower than for individuals 20-40 years of age.