J. Comp. Path. 1990Vol. 102
Some Anatomical Features of the Periodontium of the Deciduous and Permanent Dentition in the Beagle Dog T. Berglundh, I. Ericsson and J. Lindhe Department of Periodontology, School of Dentistry, University of Gothenburg, 8-400 33 Gothenburg, Sweden
Summary The present study describes some anatomical characteristics of teeth and periodontal tissues in the deciduous and permanent dentition of the beagle dog. Five animals were used. At the age of 10 weeks (Period A) and 15 months (Period B), respectively, a plaque control period was initiated. At the end of each plaque control period, clinical examinations were performed. Biopsies were obtained from the 0~P, 0aP (Period A) and P3, P4 (Period B) tooth regions and were examined with the light microscope. Histometric and morphometric measurements were made. The macroscopic and microscopic measurements revealed that marked differences exist between the teeth and the periodontium of the deciduous and the permanent dentition. The permanent premolar erupting into the position of the deciduous premolar was found to be significantly wider and higher than its precursor. Also the shape of the crown of the permanent premolar differed from that of the deciduous premolar. The sinuous contour of the buccal gingival margin was more accentuated in the deciduous than in the permanent dentition. The free gingiva was shorter and the periodontal ligament space was wider in the deciduous than in the permanent dentition. The free gingival unit in the deciduous dentition consisted of a larger volume of epithelium and a smaller volume of connective tissue than the corresponding unit in the permanent dentition. The connective tissue of the deciduous gingiva contained a larger proportion of fibroblasts and a lower .proportion of collagen fibres than the corresponding tissue of the permanent gmglva.
Introduction Periodontal disease in the dog is a naturally occurring disorder (Hamp, Viklands, Fars6-Madsen and Lindberg, I974; H a m p and Lindberg, 1977; Hamp, Olsson, Fars6-Madsen, Viklands and Fornell, 1984) which has m a n y features in common with human periodontal disease (Saxe, Greene, Bohannan and Vermillion, 1967; Lindhe, H a m p and L6e, 1973, 1975). Consequently, the dog, in particular the beagle dog, has proved to be a valuable and frequently employed research model for studying factors involved in the etiology and pathogenesis of gingivitis and destructive periodontitis (Egelberg, 1967; Attstr6m, 1971; Lindhe et al., 1975; Page and Schroeder, 1976). Most of the dog experiments so far presented have utilized the permanent 0021-9975/90/030311+ 11 $03.00/0
© 1990AcademicPressLimited
312
T. Berglundh
e t al.
dentition of the beagle while only few data are available on inflammatory lesions in the periodontium of its deciduous dentition (Hock, 1978; Matsson and Attstr6m, 1979a,b). Hock (1978) presented a clinical study of"gingivitis in the deciduous and succedaneous permanent teeth" in dogs and reported that there was a larger number of inflamed gingival units in the permanent than in the deciduous dentition. This observation was supported by data subsequently published by Matsson and Attstr6m (1979a), who found that the gingival tissue of the deciduous dentition in the beagle dog seemed to respond to plaque accumulation with less inflammation than the gingiva of the permanent dentition of the same animals. In an attempt to explain this reduced gingival inflammatory response to bacterial colonization on deciduous teeth, Matsson and Attstr6m (1979b) analysed some histological features of the gingival tissue of the two dentitions. They reported that the free gingiva of the deciduous dentition was smaller than the corresponding unit in the permanent dentition, but also that (i) the deciduous gingiva had a wider dento-gingival epithelium and (ii) a wider keratin layer of its oral epithelium than the gingiva in the permanent dentition. There are reasons to assume that such anatomical differences may partly explain why the deciduous gingiva may be less liable to develop clinical signs of gingivitis than the gingiva of the permanent dentition. Other factors of importance in this respect m a y be the amount and composition of the microbial flora that forms in the gingival sulci of the two dentitions, as well as the age of the host tissue. A series of clinical, microbiological and histological studies was designed to investigate further thelresponse of the beagle dog gingiva, in the deciduous as well as in the permanent dentition, to de novo dental plaque formation. The present study, which is the first in this series, describes some important macroscopic features of the deciduous and permanent dentition in the beagle and, in addition, data characterizing the build up of the periodontium of the deciduous and succedaneous permanent teeth. Materials and Methods
Five inbred beagle dogs were used. Throughout the entire period of observation the dogs were fed a pellet diet, which allowed a gross plaque accumulation. The experiment included two periods of observation: Period A (42 days during the deciduous dentition) and Period B (42 days during the permanent dentition). The outline of the experiment is presented in Fig. 1. Period A
The dogs were 10 weeks old at the start of Period A (Fig. 1). On Day 0, the teeth of the dogs were scaled and polished with rubber cups and Buffalo Prophylaxis Paste ~ (Buffalo Dental Manufacturing Co. Inc., Brooklyn, New York, USA). During the subsequent 6 weeks, the animals were exposed twice daily to meticulous mechanical tooth cleaning with a toothbrush (Butler 311) and dentifrice (Colgate Tartar Control®). During Period A, the mandibular right 3rd (u~P) and 2nd (0~P) premolars of the deciduous dentition were monitored and examined. On Day 42, i.e. following a 42-day period of plaque control, a clinical examination was performed and plaster models of the lower jaw dentition produced. The models were utilized for analyses of the anatomy of the teeth 03P and 0.,P. The various
Normal
Periodontiurn
of Dogs
3 13
GM
PeriodA
5
PeriodB 15 16 t Monlhs
I0
13
16
0
2l
42 0
Plaque control 5 dogs
Weeks
21
42 Days
Plaque conl Biopsy
Biopsy
/Si!,i .,Ll~--J~t~---li/Levell [. --w-2
--w-I--
4
Fig. 1.
Outline of the experiment. Five dogs were used. At the age of 10 weeks (Period A) and 15 months (Period B), respectively, a meticulous plaque control period of 42 days was initiated. At the end of each plaque control period clinical examinations were performed, plaster models of the lower jaw produced and biopsies obtained from the experimental tooth regions.
Fig. 2.
Schematic drawing demonstrating the various measures used in the tooth crown anatomy analysis; h-I = crown height; measured at the mid-portion of the buccal surface, from the central cusp to the gingival margin, h-2 = crown height; measured at the mid-portion of the lingual surface, from the central cusp to the gingival margin. 11-3=crown height; measured at the mesial surface, from the level of tile central cusp to the gingival margin, h-4= crown height; measured at the distal surface, from the level of the central cusp to the gingival margin, w-I = crown width; measured in buccolingual direction at the level of the gingival margin, w-2 = crown width; measured in mesio-distal direction at the level of the gingival margin.
Fig. 3.
Schematic drawing illustrating the linear distances which were measured at the histological sections (histometric measurements); 1. Gingival margin (GM) to the most apical cells of the junctional epithelium (JE), i.e, the height of the free marginal gingiva (hFMG= GM-JE). 2. The width of the free marginal gingiva (wFMG) at the level of the cemeoto-enamel junction (CEJ). The width of FMG was assessed in a direction perpendicular to the long axis of the root. 3. CEJ to the marginal bone crest (BC), i.e. the height ot the supra-alveolar connective tissue attachment (CEJBC). 4. The width of the periodontal ligament space (PDL) (i) at the level of BC and (ii) 1 mm apical to BC. 5. The number of collagen fibres (per mm), inserting in the root cementum within the supra-alveolar connective tissue attachment (CEJ-BC). 6. The root surface (R) to the epithelial] connective tissue interface measured at 5 levels between CEJ and BC, i.e. the width of the supraalveolar connective tissue. 7. The width of (i) the oral epithelium and 0i) its keratlnlzed layer measured at the five levels. 8. Mueo-gingivaljunction (MGJ) to the gingival groove (GG), i.e. the length of the attached gingiva (the free gingiva was excluded).
Fig. 4.
Schematic drawing describing the morphometric aspects studied. At Level 1 (large squares) a determination was made of the tissue proportions of the entire free marginal gingiva. At Level 4 (small, hatched squares) a cletermination was made of the connective tissue proportions, calculated at an area representing the central portion of the free marginal giugiva, as well as an assessment of the proportion of vascular structures in the connective tissue located immediately below the oral epithelium of the attacbed glngiva.
314
T. Berglundh
e t al.
macroscopic measurements performed (h-l, h-2, h-3, h-4, w-1 and w-2) are described in Fig. 2. After a clinical examination, biopsies containing the buccal part of the roots, the crown, the gingiva, the periodontal ligament and the supporting alveolar bone of 03P and 02P were removed en bloc under standardized conditions (Schroeder, Lindhe, Hugosson and M/inzel-Pedrazzoli, 1973). The tissue specimens were fixed in a mixture of 4 per cent paraformaldehyde and 5 per cent glutaraldehyde adjusted to pH 7'2 with 0"02 ~ sodium cacodylate, decalcified and divided into one mesial and one distal portion. The rnesial portion (root) of each tissue sample was embedded in paraffin. Bucco-lingual sections, parallel with the long axis of the root, were cut with the microtome set at 5 ~m. The sections were stained with hematoxylin-eosin (HE) or Mallory's connective tissue stain. From each tissue portion, five sections, 20 gm apart, representing the central part of the root, were analysed by the light microscope ( x 40). The microscopic (histometric) measurements are described in Fig. 3. The distal portion of each tissue sample was embedded in Epon as described by Schroeder (1969). Bucco-lingual sections, parallel with the long axis of the root, were cut with the microtome set at 3 gm. The sections were stained with PAS and toluidine blue (Schroeder, 1969). From each biopsy, five sections, representing the central part of the root, were used for morphometric analysis under the light microscope (Weibel, 1969, 1970; Lindhe and Rylander, 1975) (Fig. 4) as described below: At Level 1 (magn. x 200, Lattice: P 42; Weibel, 1969) a morphometric evaluation was performed of the entire cross-sectlonal area of the gingival tissue (GT) and test points were counted to determine the volume of the oral epithelium (OE), the junctional epithelium (JE) and the connective tissue (CT); the non-infiltrated (NCT) as well as the infiltrated (ICT) portion of CT. At Level 4 (magn. x 1000 and a lattice comprising 100 light points; Schroeder and Mtinzel-Pedrazzoli, 1973) determinations were made of the volume fraction occupied by collagen (Co), vessels (V), fibroblasts (Fi), inflammatory cells (I-cells) and residual tissue (R=matrix, nerves, unidentified cells and other tissue constituents) in Mid-CT (Fig. 4). A determination was also made of the proportion of vascular structures present in the connective tissue immediately below the oral epithelium of the attached gingiva. Period B
Period B started when the dogs were about 15 months old (Fig. 1). On Day 0 the teeth of the animals were scaled and polished with rubber cups and Buffalo Prophylaxis Pasteq~. A 42-day period of meticulous tooth cleaning was initiated. The mandibular left permanent 3rd (Ps) and 4th (P4) premolars were monitored and examined. On Day 42 a clinical examination was performed, plaster models of the lower jaw dentition produced and biopsies of Pa- and P4-tooth regions were harvested. The biopsies were fixed, decalcified, divided and analysed in the manner described for Period A. All clinical examinations, as well as biopsy procedures, were performed under general anaesthesia (intravenous injection of Pentothal-Sodium®).
Results The clinical examination performed at the end of Period A (deciduous dentition) and Period B ( p e r m a n e n t dentition) revealed that all buccal surfaces of the teeth monitored were free from clinically detectable plaque. In addition, the associated gingival tissues showed no signs of inflammation.
Normal
Periodontium
315
of Dogs
Macroscopic Measurements The results of the macroscopic measurements are presented in Table 1. The crowns of the permanent premolars, erupting into the position of the deciduous premolars, were generally found to be both higher and wider than the corresponding deciduous teeth. The crown height, measured at the distal surface (h-4; Fig. 2), did not differ between the deciduous and permanent teeth. The crown of the 2nd deciduous premolar, measured in mesio-distal direction (w-2; Fig. 2), was significantly wider than that of the 3rd permanent premolar (P
Some Anatomical Features of the Periodontium of the Deciduous and Permanent Dentition in the Beagle Dog T. Berglundh, I. Ericsson and J. Lindhe Department of Periodontology, School of Dentistry, University of Gothenburg, 8-400 33 Gothenburg, Sweden
Summary The present study describes some anatomical characteristics of teeth and periodontal tissues in the deciduous and permanent dentition of the beagle dog. Five animals were used. At the age of 10 weeks (Period A) and 15 months (Period B), respectively, a plaque control period was initiated. At the end of each plaque control period, clinical examinations were performed. Biopsies were obtained from the 0~P, 0aP (Period A) and P3, P4 (Period B) tooth regions and were examined with the light microscope. Histometric and morphometric measurements were made. The macroscopic and microscopic measurements revealed that marked differences exist between the teeth and the periodontium of the deciduous and the permanent dentition. The permanent premolar erupting into the position of the deciduous premolar was found to be significantly wider and higher than its precursor. Also the shape of the crown of the permanent premolar differed from that of the deciduous premolar. The sinuous contour of the buccal gingival margin was more accentuated in the deciduous than in the permanent dentition. The free gingiva was shorter and the periodontal ligament space was wider in the deciduous than in the permanent dentition. The free gingival unit in the deciduous dentition consisted of a larger volume of epithelium and a smaller volume of connective tissue than the corresponding unit in the permanent dentition. The connective tissue of the deciduous gingiva contained a larger proportion of fibroblasts and a lower .proportion of collagen fibres than the corresponding tissue of the permanent gmglva.
Introduction Periodontal disease in the dog is a naturally occurring disorder (Hamp, Viklands, Fars6-Madsen and Lindberg, I974; H a m p and Lindberg, 1977; Hamp, Olsson, Fars6-Madsen, Viklands and Fornell, 1984) which has m a n y features in common with human periodontal disease (Saxe, Greene, Bohannan and Vermillion, 1967; Lindhe, H a m p and L6e, 1973, 1975). Consequently, the dog, in particular the beagle dog, has proved to be a valuable and frequently employed research model for studying factors involved in the etiology and pathogenesis of gingivitis and destructive periodontitis (Egelberg, 1967; Attstr6m, 1971; Lindhe et al., 1975; Page and Schroeder, 1976). Most of the dog experiments so far presented have utilized the permanent 0021-9975/90/030311+ 11 $03.00/0
© 1990AcademicPressLimited
312
T. Berglundh
e t al.
dentition of the beagle while only few data are available on inflammatory lesions in the periodontium of its deciduous dentition (Hock, 1978; Matsson and Attstr6m, 1979a,b). Hock (1978) presented a clinical study of"gingivitis in the deciduous and succedaneous permanent teeth" in dogs and reported that there was a larger number of inflamed gingival units in the permanent than in the deciduous dentition. This observation was supported by data subsequently published by Matsson and Attstr6m (1979a), who found that the gingival tissue of the deciduous dentition in the beagle dog seemed to respond to plaque accumulation with less inflammation than the gingiva of the permanent dentition of the same animals. In an attempt to explain this reduced gingival inflammatory response to bacterial colonization on deciduous teeth, Matsson and Attstr6m (1979b) analysed some histological features of the gingival tissue of the two dentitions. They reported that the free gingiva of the deciduous dentition was smaller than the corresponding unit in the permanent dentition, but also that (i) the deciduous gingiva had a wider dento-gingival epithelium and (ii) a wider keratin layer of its oral epithelium than the gingiva in the permanent dentition. There are reasons to assume that such anatomical differences may partly explain why the deciduous gingiva may be less liable to develop clinical signs of gingivitis than the gingiva of the permanent dentition. Other factors of importance in this respect m a y be the amount and composition of the microbial flora that forms in the gingival sulci of the two dentitions, as well as the age of the host tissue. A series of clinical, microbiological and histological studies was designed to investigate further thelresponse of the beagle dog gingiva, in the deciduous as well as in the permanent dentition, to de novo dental plaque formation. The present study, which is the first in this series, describes some important macroscopic features of the deciduous and permanent dentition in the beagle and, in addition, data characterizing the build up of the periodontium of the deciduous and succedaneous permanent teeth. Materials and Methods
Five inbred beagle dogs were used. Throughout the entire period of observation the dogs were fed a pellet diet, which allowed a gross plaque accumulation. The experiment included two periods of observation: Period A (42 days during the deciduous dentition) and Period B (42 days during the permanent dentition). The outline of the experiment is presented in Fig. 1. Period A
The dogs were 10 weeks old at the start of Period A (Fig. 1). On Day 0, the teeth of the dogs were scaled and polished with rubber cups and Buffalo Prophylaxis Paste ~ (Buffalo Dental Manufacturing Co. Inc., Brooklyn, New York, USA). During the subsequent 6 weeks, the animals were exposed twice daily to meticulous mechanical tooth cleaning with a toothbrush (Butler 311) and dentifrice (Colgate Tartar Control®). During Period A, the mandibular right 3rd (u~P) and 2nd (0~P) premolars of the deciduous dentition were monitored and examined. On Day 42, i.e. following a 42-day period of plaque control, a clinical examination was performed and plaster models of the lower jaw dentition produced. The models were utilized for analyses of the anatomy of the teeth 03P and 0.,P. The various
Normal
Periodontiurn
of Dogs
3 13
GM
PeriodA
5
PeriodB 15 16 t Monlhs
I0
13
16
0
2l
42 0
Plaque control 5 dogs
Weeks
21
42 Days
Plaque conl Biopsy
Biopsy
/Si!,i .,Ll~--J~t~---li/Levell [. --w-2
--w-I--
4
Fig. 1.
Outline of the experiment. Five dogs were used. At the age of 10 weeks (Period A) and 15 months (Period B), respectively, a meticulous plaque control period of 42 days was initiated. At the end of each plaque control period clinical examinations were performed, plaster models of the lower jaw produced and biopsies obtained from the experimental tooth regions.
Fig. 2.
Schematic drawing demonstrating the various measures used in the tooth crown anatomy analysis; h-I = crown height; measured at the mid-portion of the buccal surface, from the central cusp to the gingival margin, h-2 = crown height; measured at the mid-portion of the lingual surface, from the central cusp to the gingival margin. 11-3=crown height; measured at the mesial surface, from the level of tile central cusp to the gingival margin, h-4= crown height; measured at the distal surface, from the level of the central cusp to the gingival margin, w-I = crown width; measured in buccolingual direction at the level of the gingival margin, w-2 = crown width; measured in mesio-distal direction at the level of the gingival margin.
Fig. 3.
Schematic drawing illustrating the linear distances which were measured at the histological sections (histometric measurements); 1. Gingival margin (GM) to the most apical cells of the junctional epithelium (JE), i.e, the height of the free marginal gingiva (hFMG= GM-JE). 2. The width of the free marginal gingiva (wFMG) at the level of the cemeoto-enamel junction (CEJ). The width of FMG was assessed in a direction perpendicular to the long axis of the root. 3. CEJ to the marginal bone crest (BC), i.e. the height ot the supra-alveolar connective tissue attachment (CEJBC). 4. The width of the periodontal ligament space (PDL) (i) at the level of BC and (ii) 1 mm apical to BC. 5. The number of collagen fibres (per mm), inserting in the root cementum within the supra-alveolar connective tissue attachment (CEJ-BC). 6. The root surface (R) to the epithelial] connective tissue interface measured at 5 levels between CEJ and BC, i.e. the width of the supraalveolar connective tissue. 7. The width of (i) the oral epithelium and 0i) its keratlnlzed layer measured at the five levels. 8. Mueo-gingivaljunction (MGJ) to the gingival groove (GG), i.e. the length of the attached gingiva (the free gingiva was excluded).
Fig. 4.
Schematic drawing describing the morphometric aspects studied. At Level 1 (large squares) a determination was made of the tissue proportions of the entire free marginal gingiva. At Level 4 (small, hatched squares) a cletermination was made of the connective tissue proportions, calculated at an area representing the central portion of the free marginal giugiva, as well as an assessment of the proportion of vascular structures in the connective tissue located immediately below the oral epithelium of the attacbed glngiva.
314
T. Berglundh
e t al.
macroscopic measurements performed (h-l, h-2, h-3, h-4, w-1 and w-2) are described in Fig. 2. After a clinical examination, biopsies containing the buccal part of the roots, the crown, the gingiva, the periodontal ligament and the supporting alveolar bone of 03P and 02P were removed en bloc under standardized conditions (Schroeder, Lindhe, Hugosson and M/inzel-Pedrazzoli, 1973). The tissue specimens were fixed in a mixture of 4 per cent paraformaldehyde and 5 per cent glutaraldehyde adjusted to pH 7'2 with 0"02 ~ sodium cacodylate, decalcified and divided into one mesial and one distal portion. The rnesial portion (root) of each tissue sample was embedded in paraffin. Bucco-lingual sections, parallel with the long axis of the root, were cut with the microtome set at 5 ~m. The sections were stained with hematoxylin-eosin (HE) or Mallory's connective tissue stain. From each tissue portion, five sections, 20 gm apart, representing the central part of the root, were analysed by the light microscope ( x 40). The microscopic (histometric) measurements are described in Fig. 3. The distal portion of each tissue sample was embedded in Epon as described by Schroeder (1969). Bucco-lingual sections, parallel with the long axis of the root, were cut with the microtome set at 3 gm. The sections were stained with PAS and toluidine blue (Schroeder, 1969). From each biopsy, five sections, representing the central part of the root, were used for morphometric analysis under the light microscope (Weibel, 1969, 1970; Lindhe and Rylander, 1975) (Fig. 4) as described below: At Level 1 (magn. x 200, Lattice: P 42; Weibel, 1969) a morphometric evaluation was performed of the entire cross-sectlonal area of the gingival tissue (GT) and test points were counted to determine the volume of the oral epithelium (OE), the junctional epithelium (JE) and the connective tissue (CT); the non-infiltrated (NCT) as well as the infiltrated (ICT) portion of CT. At Level 4 (magn. x 1000 and a lattice comprising 100 light points; Schroeder and Mtinzel-Pedrazzoli, 1973) determinations were made of the volume fraction occupied by collagen (Co), vessels (V), fibroblasts (Fi), inflammatory cells (I-cells) and residual tissue (R=matrix, nerves, unidentified cells and other tissue constituents) in Mid-CT (Fig. 4). A determination was also made of the proportion of vascular structures present in the connective tissue immediately below the oral epithelium of the attached gingiva. Period B
Period B started when the dogs were about 15 months old (Fig. 1). On Day 0 the teeth of the animals were scaled and polished with rubber cups and Buffalo Prophylaxis Pasteq~. A 42-day period of meticulous tooth cleaning was initiated. The mandibular left permanent 3rd (Ps) and 4th (P4) premolars were monitored and examined. On Day 42 a clinical examination was performed, plaster models of the lower jaw dentition produced and biopsies of Pa- and P4-tooth regions were harvested. The biopsies were fixed, decalcified, divided and analysed in the manner described for Period A. All clinical examinations, as well as biopsy procedures, were performed under general anaesthesia (intravenous injection of Pentothal-Sodium®).
Results The clinical examination performed at the end of Period A (deciduous dentition) and Period B ( p e r m a n e n t dentition) revealed that all buccal surfaces of the teeth monitored were free from clinically detectable plaque. In addition, the associated gingival tissues showed no signs of inflammation.
Normal
Periodontium
315
of Dogs
Macroscopic Measurements The results of the macroscopic measurements are presented in Table 1. The crowns of the permanent premolars, erupting into the position of the deciduous premolars, were generally found to be both higher and wider than the corresponding deciduous teeth. The crown height, measured at the distal surface (h-4; Fig. 2), did not differ between the deciduous and permanent teeth. The crown of the 2nd deciduous premolar, measured in mesio-distal direction (w-2; Fig. 2), was significantly wider than that of the 3rd permanent premolar (P
