Yasmeen Al-Khatib Pedo Sheet No.7+8 29/03/2015 29/03/201 7+8 Dr. Suha Abu ghazaleh Yasmeen Al-Khatib 1
Yasmeen Al-Khatib Pedo Sheet No.7+8 29/03/2015 Eruption and Arch Development Lecture s Outline (lec. 7): Life cycle of teeth Pre-eruptive period Period of eruption of primary dentition Static period of primary dentition Life cycle of teeth will not be discussed in the lecture. The doctor gave us a handout regarding this topic that is required from us for the final and it talks about the histology of teeth as it starts development. Pre-eruptive period: Characteristic of the pre-eruptive period: Extends from the moment of birth up to 6 months of age or until the first tooth erupts. In general all infants look alike and bony face and skull show little differentiation from child to child. Generally, the face appears broad and flat due to lack of vertical growth. Bones of the cranium are separated by soft membrane filled gaps or called Fontanells that close at age of 2 years. The moment the baby is born, the head occupies ¼ of the bone of the whole body and changes to become 1/7 in adults. Neoborns have tiny mouth and no chin. The mandible is retrognathic and underdeveloped. Like adults, the maxillary anterior gum pad or the intercanine distance is typically wider than the lower anterior gum pad. They usually have an overjet of 5mm and an overbite of 0.5mm in most children. They do show marked increased in the palatal width and decrease in the overjet in the first 6 months. Newborns show hypertrophic labial frenum that has nothing to do with suckling as well as hypertrophic retroincisal papilla (incisive papilla). Newborns have large tongue due to the retrognathic mandible. The palate in the beginning is more straight and then gets concave during development. All the previous features are normal and you have to assure the parents who come complaining of any. 1
Common findings of the oral mucosa of newborns: 1) Epstein Pearls: They are small white/greyish lesions. They occur in about 80% of neonates. They are formed along the midpalatine raphe. Histological sections show remenants of epithelial tissues crowded along the palatine raphe. They disappear after few weeks of life. Parents should not be worried about them as they eventually disappear. 2) Bohn Nodules: They are formed around the buccal and lingual aspects of the dental ridge and on the palate but away from the midpalatine raphe. Histologically, they show mucus gland tissues. They also disappear spontaneously but take a little bit more time than Epstein Pearls within the early months. 3) Dental Lamina Cyst: Their location is on the crest of the maxillay and mandibular dental ridges that is exactly where teeth usually erupt from. Parents are more aware of this feature as they think that this is a tooth. They are remenants of the dental lamina under the microscope. And they also disappear through the first months of life. No treatment is required. Differential Diagnosis: - Natal Teeth: some newborns are born with teeth but you can differentiate it with the cyst that the natal teeth is hard and resembles a tooth in contrast to the cyst that is soft in texture. Infantile swallowing: Suckling is a reflex essential for the survival of the newborn. The infant places the tongue beneath the nipples in contact with the lower lip. Jaws are usually apart. The lips are pressing together thus getting a strong lip activity. Persistant infantile swallowing or tongue thrust can give rise to an anterior open bite. At 6 months, the baby starts eating solid food. We will get a gradual transition towards mature adult swallowing pattern and persists up to 5 years of age. The pattern is
that you get teeth together in contact. The tongue presses against the palate. And the lips are relaxed. Feeding of infants: We always recommend natural breastfeeding. Human milk is the preferred food for infants. For us as dentists, breastfeeding exerts beneficial orthopedic forces on the jaws during development. Natural breastfeeding promotes better jaw growth. There is a significant difference in the growth of the jaws and in muscle activity between breast-fed and bottle-fed infants. Also they found that there were less pacifier infants. use in breast-fed (اللهاية) We as dentists should inform the mother about the advantages of breastfeeding. In general we recommend breastfeeding up to 6 months of age.who recommends breastfeeding up to 2 years of age. Period of eruption of primary dentition: It starts at 6 months in most of the children and is established by 30-36 months. We expect most children by the age of 3 years to have all primary dentition erupted. Maximum jaw growth occurs during this period. Calcification: It starts between 4-6 months of intrauterine life for primary teeth. Like permanent teeth, primary teeth starts calcification from the cusp tips and incisal edges and continuous cervically. It is a very sensitive process that takes place over a very long period of time. Any severe systemic event during development of teeth will result in some dental anomalies distributed on teeth depending on the level of development. Thus they are called Chronological Enamel Defects. Different teeth will show different defects on the level of the crown depending on the stage of crown formation. Eruption: The term eruption in general means the movement of teeth within and through the bone of the jaw and the overlying mucosa to appear in the oral cavity and contact the opposing teeth. While Emergence is the term we usually use. It means the first sign of appearance of a tooth in the oral cavity.
3 phases of eruption: 1) Pre-eruptive phase: The period in which the root begins formation and begins to move towards the surface of the oral cavity from its bony part. Movement within bone. 2) Eruptive phase (Pre-function): The period of gingival emergence until contact is achieved with the opposing tooth. The tooth has emerged but is still not functioning because its still out of occlusion. 3) Functional eruptive phase: After the tooth meets its antagonist. It s a dynamic process and continuous throughout the life of the tooth. What causes eruption? We have many theories explaining eruption but still none of them is said to be the actual cause. Eruption is a multifactorial process. Theories were hard to do on humans so they are mostly animal studies. First theory: Rooth Formation: Space for the growing root is accommodated by occlusal movement of the tooth crown. Second theory: Hydrostatic Pressure within the periapical tissues pushing the tooth occlusally. Third theory: Bony Remodeling that is pushing the tooth occlusally. Fourth theory: Pulling of the tooth occlusally by the cells and fibers of the periodontal ligament. No hypothesis that fully explains tooth eruption. Its multifactorial. Deciduous teeth: - They are 20 in number, 10 in each jaw. - There are no premolars in the deciduous dentition. - First primary molars are replaced by permanent first premolars. - Permanent molars erupt distal to the primary second molars. Parents usually come with fear that there is a tooth erupting without another tooth being lost. So we have to assure them by telling them that this is a permanent tooth that is erupting in its normal place. This might be a motivation for the parents to enhance oral hygiene methods at the moment they know that this is permanent tooth.
- Beginning from the midline, teeth are central, lateral, canine, first molar and second molar. Tooth numbering: We have different systems: 1) The palmer notation: children s 20 teeth are labelled in letters from A to E in each quadrant. This notation is the one we still use. 1) Universal numbering system: mostly used in USA. Each tooth has its own number in permanent teeth or letter in primary teeth. 1) FDI system (two-digit notation): permanent teeth quadrants are designated as 1,2,3 and 4. Primary teeth quadrants are numbered 5,6,7 and 8. Then each tooth is given its own number plus the quadrant number. Chronology (timing): The first tooth to erupt is usually at 6 months and is usually the lower centeral incisor. 6 months is not a must. Many children become older than 1 year and they still don t have their lower central incisors. We should always be conservative. Always assure the parents that there is variation and they are normal. We should follow-up. All eruption schedules are estimates.
Because we use the estimated numbers for another society, we always find variations. Recently there is an article puplished talking about the eruption schedule in Jordanian population. No two individuals are alike. All estimates depend on race, gender, ethnicity, environment and heredity. In general, we need a reference to follow and that is the 6 months. (in months) Maxilla Mandible Central Incisor (A) 6-10 5-8 Laterial Incisor (B) 8-12 7-10 Canine (C) 16-20 16-20 First Molar (D) 11-18 11-18 Second Molar (E) 20-30 20-30 Sequence of eruption: A,B,D,C,E. Usually the mandible preceeding the maxilla. Rhythm of eryption: We usually get a symmetrical groups of 4 teeth erupting every 6 months in both jaw, simultaneously, and in pairs. The six/four rule for primary tooth emergence: - At 6 months: 4 teeth erupt (lower and upper As) - At 12 months: 8 teeth erupt (lower and upper As and Bs) - At 18 months: 12 teeth erupt (lower and upper As, Bs and Ds) - At 24 months: 16 teeth erupt (lower and upper As, Bs, Ds and Cs) - At 30-36 months: 20 teeth erupt (that is the full primary dentition) Static period of primaty dentition: All primary teeth are erupted and no permanent teeth yet. It is the period of stability of primary teeth from 3-6 years of age. The child has the 20 primary teeth in functional position and occlusion is well established. Occlusal features of primary dentition: - Usually in all children we have generalized spacing. - Incisor teeth tend to be spaced. - We also have the primate space that exist between upper B&C and lower C&D. - Upper incisors are usually upright and the incisal relation is more towards edgeto-edge relationship. - Long axis of primary teeth is parallel. - Absence of curve of spee.
- In general, primary dentition tend to be well-aligned if there were no caries. When their permanent teeth starts erupting, they start showling mal occlusion and some darkness in color. Usually parents don t like that and complain of this as the older primary dentition was perfect in their opinion. We should assure parents as it is a normal feature. Classification of occlusion of primary second molars: By looking at the distal aspect of the primary second molar, we either have flush terminal, mesial step (lower mesial to the upper) or distal step (lower distal to the upper). We should observe this classification before the 6s erupt because once the 6s have erupted we forget this classification and switch into angel s classification. Inter-arch relation of primary teeth: How do we get occlusion? It is mostly like the permanent teeth. Each tooth occludes with two opposing teeth, except for the lower central incisors (occludes only with the upper centrals) and the upper second molars (occludes only with the lower second molar). Canines are the key of occlusion of primary dentition and we need to look at the long axis of the canine. It should be placed in the midline between the lower D and C as a class I relation. Natural wearing of the canine is an important physiological process that facilitates movement of the mandible. If that did NOT happen, children raised on soft food usually come with a crossbite because there were no wearing of the canine. This case is very simple. We may have to carry out gradual selective grinding of the primary canines especially in the presence of a unilateral crossbite. Gradual grinding is important to avoid teeth sensititvity. Period of mixed dentition This is the start of the second lecture (lec. 8) Lecture s outline: Causes of shedding of primary teeth. Resorption pattern of anterior and posterior primary teeth. Chronology of eruption of permanent teeth. Eruption of permanent teeth. Period of mixed dentition starts from 6 years up to 12 years of age.
Shedding of primary teeth: - It is the result of the progressive resorption of the roots of teeth and their supporting tissues. - It s a physiological process. - It is accomplished by multinuclear odontoclasts. Odontoclasts are exactly like osteoclasts in function but are specific to dentition. - We have periods of rest and repair. - At the end, resorption predominates and the tooth eventually exfoliates. They either fall by themselves or patients come to us and we extract them. What are the causes of shedding of primary teeth? There is no known cause but there are proposed theories. First Theory: Pressure from the erupting successor tooth initiates resorption process. Eventhough, primary teeth with no permanent successor beneath it end up with resorption and shedding at last. This is why this theory is not that much supported because its not the only cause of shedding of primary teeth. When the successor is missing, shedding of the primary tooth is delayed but not stopped. But when there is an underlying permanent successor, shedding is accelerated. Second Theory: Forces of mastication that are greater than periodontal ligament of a deciduous teeth can withstand. We get trauma to the PDL and that initiates resorption. Resorption pattern: Anterior teeth: Permanent teeth undergo complex movement before they reach the position from which they will erupt (that is the pre-eruptive movement). Anterior teeth usually start erupting lingual to the primary teeth and then when the primary teeth sheds, they move more apically and occupy their own bony space. When you take the tooth out and look into the socket, you will find the permanent successor in there. As well as the primary teeth will show lingual resorption when taken out due to the pattern of resorption of permanent teeth. Premolars: The same thing applies here. Resorption starts lingual to the primary molars and then they move more apically in between the flaring roots of the primary molars. The change in position provides the premolar with adequate space to continue their development. This is the reason behind having divergent roots of primary molars.
Chronology of Eruption of permanent teeth: As we all know, the first tooth that erupts in permanent dentition is the first permanent molar and sometimes can be the centrals. Usually the lower teeth erupt before the upper teeth. (in years) Maxilla Mandible 1 7-8 6-7 2 8-9 7-8 3 11-12 9-10 4 10-11 10-12 5 10-12 11-12 6 6-7 6-7 7 12-13 11-13 8 17-21 17-21 Sequence of eruption: In the mandible: 6,1 2 3 4 5 7 8 In the maxilla: 6,1 2 4 5 3 7 8 Eruption timing in girls generally preceed boys by an average of 5 months. Premature loss of primary molars: Very early loss (at age of 5) of primary molars will lead to delayed eruption of the permanent premolars. If extraction was after the age of 5, the delayed eruption will decrease in magnitude. If extraction occurred at the age of 8,9,10 years, premolars eruption is accelerated. Sequence of eruption is very important. Always count the number of teeth when examining any patient either child or adult. Sequence of eruption and variations: - There is no significant variation in erupting of the 6s before the 1s or the opposite. - It is desirable that the mandibular canine erupts before the lower first and second premolars. This aids in maintaining adequate arch length and prevents lingual tipping of the incisors. - If the mandibular second molars (7s) erupt before the lower second premolars (5s), this will result in decreased arch length. This is due to mesial migration and tipping of the 6s and encroachment of space needed for the second premolars. - Untimely loss of the primary molars in the maxillary arch may allow the first permanent molars to drift and tip mesially resulting in the permanent canine to be blocked out of arch. - As we all know, the most teeth to be blocked and remain impacted are the canines in the upper jaw and the second premolars in the lower jaw.
Rhythm of eruption: We have three stages: 1) Early Mixed Dentition: we have incisors and the first molars erupted. 2) Late Mixed Dentition: we have the canines, premolars and second molars erupted. Teeth erupt symmetrically in both jaws simultaneously and in pairs. 3) Third Molar Eruption: is a late stage that is seen later on. We have rules to help us in memorizing: Rule of 4 for permanent tooth development: - At birth: the 4 first molars starts calcification (sometimes the centrals are involved). - At 4 years: all crowns have initiated calcification. - At 8 years: all crowns are complete. - At 12 years: all crowns have emerged. - At 16 years: all roots are complete (that is 3 years after eruption). Rule of 3: - Crowns are completed at least 3 years before eruption. - Roots are completed 3 years after eruption. - Teeth erupt when ¾ root development has completed. Hard tissue formation: 6s Upper 1s and 3s Lower 1s, 2s and 3s Upper 2s Upper and lower premolars and second molars Upper and lower third molars At birth of slightly before At 3-6 months At 10-12 months At 1 ½ -2 years At 7-10 years When is enamel completed? As we said, that s 3 years before eruption. 6s 2 ½ -3 years 1s, 2s and 4s 4-6 years 3s, 5s and 7s 6-8 years 8s 12-16 years
Eruption of permanent teeth: 1) Lingual eruption of mandibular permanent incisors: - It s a very common phenomenon. - It s a cause of concern to parents. - It is seen in patients with obvious arch length inadequate space and crowding. This is not a must because even children with no crowding and have spacing show lingual eruption of the permanent incisors. - Its not because of crowding. - The cause behind this is what we said before is that incisors start shedding the primary teeth lingually and then shift apically. In this case the bud did not move in an apical direction and erupted lingually. - When examining primary teeth, they may be very mobile and held only by soft tissue or they may not undergo normal resorption and stay solid in place. - Management is that we leave the primary teeth if they were mobile. If not, we extract them. - Position of the permanent incisor will improve over several months. It s a selfcorrecting case. - We should not extract any other primary teeth than the primary centrals. Some people think that the permanent teeth need more space and they extract the primary centrals and laterals and that is wrong! - The tongue plays and important role in influencing the permanent incisor into its normal position with time. - We should assure the parents, and follow up. - If the condition is identified before the age of 7 ½ years, we do not interfere, we only follow it up. - If it was in an older child and when the primary tooth shows no resorption on radiographs, we should extract the primary incisors. - Labial migration of the permanent incisors usually occurs naturally with or without the removal of the primary teeth. - Removal of the tooth during the first dental visit may not be a great introduction into dental surgery for a child who only came for check-up. - Still some parent are alarmed when they see such condition. - If that happened in the upper incisors, self-correction will not be achieved as there is not tongue and is much harder to control than the lower incisors. We
usually follow up or exert pressure using orthodontic appliances to push them anteriorly. 2) Ankylosed primary molars: - They are also referred to as Submerged Teeth or Teeth Infraocclusion. - The ankylosed tooth is in state of static retention. - Adjacent teeth keep erupting but this tooth remains still in place as it is ankylosed in bone. - The most affected teeth are the mandibular primary molars. - It is of unknown cause. - It is familial. Ankylosis was noticed in several members of the same family. - An absence of the permanent successor has been implicated with ankylosis. There is a strong relation between the congenital absence of the permanent teeth and ankylosed primary teeth. - As we said, normal resorption has periods of rest and repair. This condition occurs in the rest stage. Unity of the bone and the root of the primary teeth appears. - How do we diagnose it? Clinically, we see infraocclution. Upon tapping the tooth, you will hear a solid sound (that is bone) vs. normal cushioned sound (that is the PDL) Tooth is absolutely not mobile. Radiographically, you will observe break of the continuity of the PDL. - Management: Keep the tooth under observation. Tooth may later on undergo root resorption and shed by itself. We should always start conservative. If the permanent successor is missing, establish occlusion with a stainless steel crown or bounded restoration. We have to try our best to keep this tooth as there is no permanent tooth beneath it. Brining it into occlusion increases the functional forces on the PDL that will aid in removing the ankylosis. The last option is when the patient shows increased caries rate and loss in arch length, we might end up having to surgically take the tooth out and its not an easy procedure.
3) Eruption Sequestrum: - Seen in children at the time of eruption of the first permanent molars. - It is a hard tiny spicule of non-viable bone overlying the crown of an erupting permanent molar just before or immediately after the emergence of cusp tips through the oral mucosa. - The sequestrum develop from either osteogenic or odontogenic tissue. - Its position is generally found overlying the central fossa of the associated tooth and is embedded within soft tissue. - Some of these sequestrums sponateously resolve. If its causing local irritation, it is easily removed. Its very simple, we only give topical or infilteration anesthesia to avoid discomfort. 4) Ectopic eruption of the first permanent molars: - First permanent molars may be positioned too far mesially causing resorption of the distal root of the second primary molar. - Mostly affects the upper 6s that show mesial path of eruption. They end up being locked behind the Es causing root resorption of the Es. - We have two types: Reversible: molar frees itself and goes back to its normal path of eruption with the Es remaining in their position. Occurs by the age of 7 years. 2/3 are selfcorrecting. No significant differences were found in those children. Irreversible: molar remains unerupted and in contact with the cervical area of the roots of the second primary molar. Only the distal part erupts. It is considered irreversible by the age of 7-8 years. - Features of the irreversible type are: They showed significantly larger permanent first molars. More pronounced mesial angle of eruption. They have a tendency to have a shorter maxilla in relation to the cranial base. - What happens if it was ignored? Premature loss of Es and a resulatant decrease in arch length. Asymmetric shifting of the upper first molars into class II (only in one side). Supra-eruption of the opposing lower molar causing distortion of the curve of spee and potential occlusal interferences. - Prevelance is low 3%.
- It is seen more frequently in boys more than in girls. - It occurs in more than one quadrant most oftenly in the maxilla. - There is a familial tendency with the prevelance of 20% in affected siblings vs the overall 2-3% in general population. - Frequent occurance in 25% of the cleft lip and palate due to the maxilla positioning and nasal arch size. - Management: If it was detected early by the age of 5-6 years, we only observe and monitor it. If after the age of 7 years, it requires intervention. When the opposing molar reaches the level of the lower occlusal plane, intervention is indicated to stop it from over erupting. - Approaches include: use of seperators or distalizing ortho appliances. Seperators: The first thing we start with is the orthodontic elastic seperators. We gradually push the first molar distally. Every appointment we check the elastic and replace it with a larger one to increase the forces applied for distalization. We can also use separating metal springs. Brass ligature wires can also be used. We keep tightening it up every 3-5 days. Distalizating orthodontic appliances: used in severe ectopic eruption. 5) Incisor Liability: - It refers to when the permanent incisors are larger than the primary incisors. What matters here is how are we going to have enough space to accommodate the permanent incisors in a small space. Inter-dental spacing of the primary incisors: It is favorable for us but not to parents. Spacing in primary teeth provides larger space for the larger permanenet ones. Thus, no crowing is observed later on. Primary teeth alignment Permanent teeth alignment Crowding Almost will need extraction No spacing Possibly needs extraction in the future Fair spacing Mild-to-moderate crowding Good spacing No-to-mild crowding Excess spacing No crowding - Fair and good spacing are mostly preferred to be seen.
Inter-canine arch growth: It is a mechanism that helps in accommodating a larger space for the permanent dentition. The mandibular inter-canine arch growth occurs mostly during permanent incisor eruption and continues up to 9 years of age. Labial positioning of the permanent incisor: Permanent incisors erupts more labially angled. Favorable size ratio between the primary and permanent incisors: This is genetic. Favorable type: we have larger primary teeth and small permanent ones. Unfavorable type: we have smaller primary teeth and larger permanenet ones and we end up with crowding. 6) Leeway space: - Is the amount by which the combined size of the C,D and E exceeds the combined mesiodistal width of the permanent 3,4 and 5. - The average is 1.5 mm in the upper arch and 2.5 mm in the lower arch. 7) Late mesial shift: - Refers to mandibular permanent molars moving mesially and this is good if the primary molars are edge-to-edge. - It allows permanent molars to move into class I occlusion. The flush terminal pattern always leads to class I or class II occlusion or stays end-to-end. The mesial step leads to class I or class III occlusion. The distal step always leads to a class II occlusion. Wishing you all the best of luck ^_^ Yasmeen Al-Khatib :)