MECHANISM OF
SECOND DENTITION
Diphyodont and Heterodont humans
 homodont: all tooth are alike;
 heterodont: teeth have diferent shapes;
 poliphyodont: changing of teeth for the whole lifetime
 diphyodont : 2 sets of teeth – mammals;
Root development - MOORREES et al.
• Root
¼ root
½ root
¾ root
completely
develped
• Apex open
•Apex ½
closed
•Apex
closed
MOORREES CF, FANNING EA, HUNT EE Jr. AGE VARIATION OF FORMATION STAGES FOR TEN PERMANENT TEETH.
J Dent Res. 1963 Nov-Dec; 42:1490-1502.
SECON DENTITION MECHANISM
 Mechanism – several factors responsible for normal second
dentition process
• Primary teeth period, after development of primary teeth –
transitory period: maxillary bones are preparing for the
permanent teeth arrival.
SECOND DENTITION
 Physiological developmental phenomenon;
 Dynamic process: root development, periodontal
development, functional occlusion.
SECOND DENTITION IMPORTANCE
 Normal develpment of the craniofacial complex;
 Treatment planing, timing - orthodontics;
 Cariology.
6 years: M1
 First permanent molars: at the end of the line;
• „Sechsjahrmolaren”;
• There are no changing of teeth, so it goes often
unnoticed by the parents!
ERUPTION - TIMETABLE
PERMANENT T.
1. Molars
1. incisos
Lateral incisor
Hidasi
Fehér
6
6-7
8
8
Upper
♂
4→5→3
♀
3→4→5 vagy
4→3→5
6-8
7-9
Eruption
sequences
Lower
Eruption
sequences
♂, ♀ 3→4→5
Canine
11
9-12
9-10
10-12
2. Molar
12
11-13
3. Molar
-
17-21
1. and 2. Praemolars
CHARACTERISTICE
Percentil presence of permanent teeth: prevalence of a
particular tooth at a given moment in the population.
 dierences between the arches;
 sexual dimorfizm;
Dental age determination!;
 dental status or the given age.
CHARACTERISTICS
 Average eruption time: the age when the percentil presence
of the tooth is 50%.
IMPORTANCE:
 describes the second dentition process;
 comparative studies between populations;
 acceleratio: comparison with older data!;
 Percenti presence: tooth type 15-40%
 Average eruotion time: tooth type 1-1,5 years.
BONE MATURATION
 Second dentition is paralell with bone maturation:
• Tanner-Whitehouse method TW2 (Tanner et al. 1975);
 Orthodontic diagnostic value!
GROWTH- TANNER
End of secondary
dentition
Chronological age
SECOND DENTITION CRITERIA




Presence of the permanent toothgerm
Optimal position of the toothgerm
Sufficient space
Physiological root resorption
PRESENCE OF THE PERMANENT
TOOTH GERM




Aplasia prevalence: 3-4%;
Gábris et al.: I2˃pm2˃ PM2˃i1
Persisting primary teeth
Bolk’s terminal reduction theory
APLASIA: 35; 31; 41; 45.


Persisting primary teeth: 75; 71; 72; 85
Bolk’s terminal reduction theory: EXEPTION
LOWER PERMANENT FIRST INCISORS
15
OPTIMAL POSITION OF THE
PERMANENT TOOTHGERM
Lower incidors: lingual eruption, erupting often in the
presence o the primary incisors;
 Extraction of the primary teeth;
Upper canines:
 Ectopia;
 Retentio/Impactio
MESIODENS
• DENS SUPERNUMERARIUS
• DENS SUPPLEMENTARIUS
17
Early primary teeth extraction
Physiological root resorption
 Genetical code!
PATHOLOGY
TIME
 SPACE


THE PATHOLOGICAL TRIAS:



Perturbance of the rootresoption;
Persisting primary models;
Retained permanent teeth.
PATHOLOGY
DENTITIO PRAECOX
 DENTITIO TARDA
 DENTITIO DIFFICILIS

INFRAOCCLUSIO SECUNDARIA
Partialis retentio; reinclusio;
 Submergentia;
 „Halbretention”
 „submerged deciduous teeth”

Eruption cyst/haematoma
Importance of the distal plane in primary
dentition