Thursday, October 8, 2009

Arch width changes from 6 weeks to 45 years of age 10/9/09

Resident: Murphy
Date: 10/9/09
Article title: Arch width changes from 6 weeks to 45 years of age
Author(s): Bishara, Samir, Jane Jakobsen, et al.
Journal: American Journal of Orthodontics and Dentofacial Orthopedics
Vol.: 111, No. 4, pages 401-409

Major topic: Evaluation of maxillary and mandibular changes in arch widthType of Article: Clinical ReviewMethods: The purpose of this study was to study the changes in intercanine and intermolar widths over a 45 year span. In this study, 2 pools of patients were selected. In the first pool, 28 female and 33 male, healthy full term babies that would be accessible for frequent recall visits over the next 8 years(or so). These children were evaluated at 6 weeks, 1 year, and upon completion of the deciduous dentition. The second pool of was selected from the Iowa Growth Study. Originally 89 boys and 86 girls were selected to have models taken semiannually during childhood, annually during adolescence, and once in adulthood. Of the 175 children originally selected, 16 female and 15 males completed all the follow ups. On all of the casts, 5 maxillary and 7 mandibular landmarks were set from which the measurements were taken(see article for listing of landmarks). Variability between clinicians measurements was determined to be

Findings: There was a significant increase in max. interk9 width and intermolar arch width from 6 weeks to 2 years old in both boys and girls. The largest increase was between 6 weeks to 1 year. There was also a large increase in interk9 width from 3-8 years of age. Width decreased from age 13-45, however this was only statistically significant in the female subjects. In the mandible, interk9 and intermolar width increases up to 8 in boys and 13 in girls. After 13, there was a decrease in width in both sexes (correlating with the complete eruption of the permanent dentition). Furthermore, mandibular interk9 width is essentially set by 8 years of age, or after the complete eruption of the 4 incisors. (maybe it’s me, but the previous sentence stated that the width increases up to 13. Maybe this is just for the intermolar width, because the study ALSO says the interk9 width is set at 8. Am I missing something or is the study contradicting itself?)

Conclusions: Arch widths will change from birth to adulthood. The direction and magnitude of these changes do not provide a basis for expanding the arches in the average patient beyond its established dimension when canines and molars are completely erupted. Essentially, in terms of arch width, it is what it is, and we have to make due with what we’ve got.

Assessment of article: I think it’s a good article. Absolutely relevant to our ortho practice. As I stated previously, I found it a bit contradicting in places…or maybe it just didn’t clarify things well. Or maybe it’s me and I’m just slowly losing my mind.

Wednesday, October 7, 2009

A longitudinal study of dental arch width at the deciduous second molars on children 4 to 8 years of age

Dan Boboia
Article Review 10/9/09

Title: A longitudinal study of dental arch width at the deciduous second molars on children 4 to 8 years of age.
Author: Howard Meredith and Wayne Hopp
The Journal of Dental Research: December 1956, Vol. 35, #6
Major Topic:
1) To present findings on the reliability of records for maximum rectilinear distance between the buccal surfaces of the deciduous second molars at three different ages.
2) Statistically describe interbuccal width at deciduous second molars on 12 age-arch-sex subgroups of North American white children.
3) To analyze longitudinal data pertaining to growth in dental arch width between 4 and 8 years of age.
4) To investigate a number of dental arch relationships
Methods:
40 boys and 37 girls enrolled in a long-term research program at the University of Iowa Dept. of Orthodontics. There were 4 criteria for acceptance: age (<4), race (white), geographic location (vicinity to Iowa City), and availability for longitudinal study (willingness to participate and likelihood of continuing residence in the region).

Additional Criteria:
1) Max. and mnd. Casts were required to be on file at 4, 6, 8 years of age
2) 4 erupted deciduous second molars present at each age
3) 4 erupted deciduous first molars present at each age
4) All buccal surfaces of the deciduous second molars free of restorative dental work
5) A developmental record showing no orthodontic treatment

Dental stone casts made from alginate impressions were obtained within 2 weeks of pts. 4, 6, and 8 birthday; Maximum rectilinear distance determined by measuring between the buccal surfaces of the right and left deciduous molars with calipers

Summary of Findings:
1) Maximum transverse diameter of dental arches at the deciduous second molars can be determined with high dependability
2) Interbuccal width at the deciduous second molars differs with arch, sex, and age. Maxillary arch is 3.1 mm wider then mandibular arch, the male arches are 1.9 mm wider then female arches, and the dental arches at age 4 are 1.7 mm narrower then at age 8 years.
3) The maxillary arch is slightly more variable then the mandibular arch
4) Changes in arch width differ widely from child to child between the ages of 4 to 8 years some arches remain close to the same while others increase as much as 3.5 mm
5) The two dental arches are positively related with regard to both size at a given age and, and change in size with advanced age.
6) There is a moderately high relationship between width of a given arch at 4 years and width of the same arch at 8 years, but there is no relationship between width of a given arch at 4 years and change in the width between 4 and 8 years.
7) Correlations between dental arch widths and widths of the face are positive but fairly low.

Tuesday, October 6, 2009

10/09/2009 A New View on the Control of the Morphogenesis of the Skull

Resident: J. Hencler
Date: 10/09/2009

Article title: A New View on the Control of the Morphogenesis of the Skull
Author(s): J. Van Limborgh
Journal: Acta Morphol. Neerl.-Scand. 8 (1970) 143-160

Major topic: Development and morphogenesis of the skull

Type of Article: Review

Main Purpose:
Review and compare theories of skull development.

Findings:
There are 3 main problems concerning the control of the morphogenesis of the skull.
1. In the embryonic phase, is there any association between development of the skull and other primordial structures of the head?
2. Once the skull is formed, how are endochondral and intramembranous bone growth coordinated?
3. In which way is coordination between skull growth and other structures realized?

Key points in the article discussion:
Controlling factors include intrinsic genetic factors, epigenetic factors, and environmental factors. Intrinsic genetic factors are the genes inherent to the skull tissues. Epigenetic factors are genetically determined factors that manifest themselves in an indirect way. Epigenetic factors may originate from adjacent structures and have a local influence such as the brain or eyes or may be produced by distant structures and have a general influence such as hormones. Environmental factors originate from the external environment. Data now available suggest that processes of skull differentiation are mainly controlled by local epigenetic factors originating from adjacent structures of the head. Very few intrinsic genetic factors are involved. 3 theories concerning control of skull growth are as follows:
1. Sicher (1952): growth of the skull is largely controlled by intrinsic genetic factors. Only the modeling of the surface-configuration and the internal structure of the bones would be subjected to additional influences from local environmental factors, including muscular forces.
2. Scott (1962): Intrinsic growth-controlling factors are only present in the cartilage and in the periosteum. Growth of the sutures is secondary and entirely dependent on extra-sutural influences. Cartilaginous parts of the skull should be viewed as growth centers and sutural growth may be modified by local environmental influences.
3. Moss’ Functional Matrix Theory of Growth (1966): Growth of the skull is entirely secondary. Neither bone nor cartilage is the determinant for growth of the craniofacial skeleton but instead control lies in the adjacent soft tissues. Growth of the face occurs as a response to functional needs and neurotrophic influences and is mediated by the soft tissues in which the craniofacial bones are embedded.

Summary of conclusions:
This article found that none of the 3 relevant theories on the control of skull growth were satisfactory but that each of them contains certain points that are significant.
1. Growth of synchondroses and the resulting endochondral ossification is almost exclusively controlled by intrinsic genetic factors.
2. Intrinsic factors controlling intramembranous bone growth (growth of sutures and periosteum) are small in number.
3. Cartilaginous skull parts must be seen as growth centers.
4. Extent of sutural growth is controlled by both the cartilaginous growth and growth of the other head structures.
5. Extent of periosteal bone growth largely depends on the growth of adjacent structures.
6. The intramembranous process of bone formation can be additionally influenced by local environmental factors, muscle forces inclusive.

Assessment of article:
This was an interesting article that explained all 3 growth theories. Presently, Moss’ Functional Matrix Theory is generally accepted. This article was long and presented a very detailed review of the development, growth, and morphogenesis of the skull. Anyone interested in the finer detail of craniofacial growth should refer to this fabulous, intellectually stimulating article.

Sunday, October 4, 2009

10/09/2009 Available space for the incisors during dental development - a growth study based on physiologic age

Resident: J. Hencler
Date: 10/09/2009

Article title: Available space for the incisors during dental development - a growth study based on physiologic age

Author(s): Moorrees, DDS; Chadha, BDS
Journal: Angle Orthod.
Volume #35; Number 1; Pg 12-22
Year: 1965

Major topic: Spacing and crowding during incisor transition

Type of Article: Observational/investigative

Main Purpose:
Investigate available space for the incisors of the growing child by grouping children at similar stages of dental maturation with reference to tooth eruption instead of chronological age

Overview of method of research:
78 maxillary and 70 mandibular study casts were used for studying the available space in the incisor segment. Each tooth in an individual series of dental casts was classified according to one out of six stages:
1. Deciduous tooth present
2. Extracted
3. Exfoliated
4. The permanent successor emerging
5. ½ of the crown erupted
6. Fully erupted
The difference between each stage and the previous one in the series for each child was recorded, thus events occurring during specific eruption phases could be identified.

Findings:
Emergence of mandibular central and lateral incisors resulted in 1.6mm crowding in males and 1.8mm crowding in females. In the maxilla either a small excess or a small (0.2mm) lack of space for the erupting permanent incisors was encountered. Increments in the inter-canine distance and in arch length during eruption of the lateral incisors provided enough space for the alignment of these teeth, except in the mandible where 0.2 and 0.5mm crowding was noted for males and females, respectively. No changes were noted during the emergence of the permanent canines. Pattern of change in the maxillary and mandibular dentitions of the sexes was similar. Females recover better than males from the loss of available space. Graphs based on chronological age differed markedly from those based on dental age because they mask the severe changes and the amount of crowding encountered. After the eruption of the permanent canines the two methods of analysis gave similar end results for mean space values in the incisor segment.

Key points in the article discussion:
A precise description of dental development can make a more rational diagnosis in the mixed dentition possible, particularly with reference to the need for and timing of serial extraction. Available space is, to a large extent, dependent on tooth size so observing tooth emergence and eruption should provide a realistic account of the changes in available space. Contrastingly, combining early and late maturing children in the same chronological age has been shown to hide the actual loss of space during the incisor transition. The changes in arch length and arch width are consistent with the pattern of change in available space for the incisor segment. Incisors are largely relieved when the crowns of the lateral incisors are fully erupted while if growth increments in arch size are also completed at that time. A slight increase in arch width occurs in the maxillary arch when the permanent canines erupt. Increase in arch length is confined to the maxillary arch and explains why emerging incisors have nearly sufficient space for their alignment as opposed to the mandibular incisors. At the end of the incisor transition the spaces between the deciduous canines and molars are closed. Mesial migration of the permanent first molars occupies most of the leeway space between the crown diameters of the deciduous posterior teeth and their permanent successors reflected in a reduced arch length. The partitioning of leeway space is dependent on 1) the sequence of shedding and emergence of the deciduous second molars and the second premolars, respectively, 2) on the interdigitation of the cusps of the first permanent molars, and 3) on the position of the premolars in relation to the mesial aspect of the first molars. It appears that generally no significant relief of crowding in the incisor segment can be expected after the complete eruption of the lateral incisors. But we can prevent mesial migration of permanent first molars and use some leeway space to relieve minor incisor crowding.

Summary of conclusions:
The level of dental maturation gives decisive clues for diagnosis and treatment planning since it defines the timetable of individual development. Chronologically based methods often mask the characteristic features that distinguish one child from the next. The sources of variance for available space of the incisors are tooth size and growth of the alveolar processes.

Assessment of article:
Good article. Pertinent information that is still relevant today.

Saturday, October 3, 2009

Changes in the molar relationship between the deciduous and permanent dentitions: A longitudinal study

Resident: Roberts
Date: 10/9/09
Article title: Changes in the molar relationship between the deciduous and permanent dentitions: A longitudinal study
Author: Bishara, Samir, et al.
Journal: American Journal of Orthodontics and Dentofacial Orthopedics
Year: January 1998
Findings:
According to previous authors cited in this article, upto 50% of deciduous 2nd molars erupt to form a terminal plane relationship. Of the 50% of deciduous molars in flush terminal plane, 70% were cited in others places to develop into a class 1 relationship and 30% maintained an end to end relationship or developed into a class 2 relationship.
It has been suggested that for an initial cusp to cusp relationship to develop into a class 1 relationship, one of the two mechanisms has to occur.
1. Greater anterior growth of the mandible relative to the maxilla has to occur. (Measured by the Wits analysis; the difference in growth between point A and B on a cephalogram)
2. Greater leeway space in the mandible compared to that of the maxilla must be present.
This study was done to determine if indeed these two mechanisms or other dentofacial variables such as intercanine width and or arch length could propose a stronger relationship between that of the deciduous dentition and that of the permanent dentition.

Results within the population studied:
1). 61.6% of pts achieve ideal class 1 molar relationship, 34.3%- class 2, 4.1% - class 3.
2). Distal step – Class 2, mesial step – class 1, flush terminal plane 56% - class 1 and 44% class 2
3). A weak correlation was found between change in molar relationship and Wits analysis, and no correlation was found between the difference in leeway space between the maxilla and mandibular relationship.
4). This study concludes that only by looking at a number of dentofacial variables such as intercanine width, arch lengths, maxillary and mandibular relationships can molar classification be truly predicted.

Assesment: Not a bad article, oh yeah!

Friday, October 2, 2009

Biogenesis of the Successional Dentition 10/2/09

Resident: MurphyDate: 10/1/09
Article title: Biogenesis of the Successional Dentition
Author(s): Baume, Louis. Journal: J.D. Res, Vol 29, #3. 1949
Major topic: Comparing space accommodation between the deciduous and succedaneous dentition

Type of Article: Analysis
Findings: The maxillary and mandibular incisors are each wider than their deciduous predecessors. In order to accommodate these larger teeth, a physiological expansion of the arches is necessary. This sagital and tranverse expansion takes place between the ages of four and six. This study focuses on the changes which affect the dental arches during and after the eruption of the permanent incisors. 60 study casts where studied and labeled as stage 1, deciduous dentition completed, stage 2, perm. 1st incisors have erupted, and stage 3, all perm incisors are in. The cases were also separated by ebeing closed spacing cases, or open spacing cases. Measurements were taken between the deciduous canines and second molars at the gingival margin. As previous studies show, the eruption of the perm. Incisors presented a transverse widening of the mandibular arch of approx. 2.3mm(sd 5mm). This widening is due to lateral growth of the alveolar process, not necessarily to adjacent teeth being displaced. The maxilla also shows widening, although due to different reasons. These reasons being the eruption sequence (max. incrs erupting after man. Incrs.), and the second being differences in maxillary primate spaces. The breakdown of the numbers between all the different stages and case types was dizzying. The minimum increase in mandibular canine expansion was represented by the stage 1 and 2, type 1, with .5mm, and the largest being stage 3 type 2, with 5 mm. Again, the numbers are confusing. The bets thing to do is just take a look at the tables provided. Conclusions: Essentially, expansion of both arches in the anterior region is brought about by frontal and lateral growth to accommodate the larger succ. Teeth. There was greater increase in intercanine width and forward extension(1mm) of the arch in the max. as opposed to the mand., and greater increase associated with closed cases as opposed to open space cases. The strongest lateral growth of the mand. Arch was associated with the eruption of the mand 2nd incrs, and during the eruption of the perm max incrs. As previously noted, the ‘secondary’ spacing of the maxilla occurred when the underdeveloped maxillary arch widened during the eruption of the perm lower incisors. In terms of comparing spacing cases with closed cases, the spacing cases showed a more favorable alignment. 40% of the closed spaced had anterior crowding.
Assessment of article: I think this was a clinically relevant article that is absolutely worth reviewing. With that said….it was near impossible to read and try to process all the different numbers and stages and cases they were reviewing. The writing is clearly outdated (written in ’49) and fairly convoluted. Bascially try to understand the concepts, take a look at the tables, and move on.

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Thursday, October 1, 2009

Sutures and forces: A review

Department of Pediatric Dentistry
Lutheran Medical Center

Resident’s Name: Craig Elice Date: 10/2/2009
Article title: Sutures and forces: A review
Author(s): Wagemans P, van de Veide, et al.
Journal: Am J Orthod Dentofac Orthop
Volume (number): 94:129-41, 1988
Major topic: Sutures and forces, basic science
Type of Article: Review article
Main Purpose: This paper describes the biology behind sutures, and its response to extrinsic mechanical forces
Sutural Growth and its regulation: Most facial and cranial bone are of intramembranous origin and grow by apposition and resorption at the periosteum interface and by sutural growth. Theories exist to suggest that these growth centers are autonomous or affected by environmental extrinsic forces. Sicher is most famous for his view that sutures have intrinsic growth potential and uses epiphyseal plates as an example. Moss believes that sutures adapt to surrounding structures and forces A growing brain acts as a functional matrix to determine skeletal and sutural growth. Van Limborgh concurs that growth is controlled by few intrinsic genetic factors and many local nongenetic factors that originalte in adjacent structures of the head and neck. These latter theories are consistent with current thought.
Sutural Morphology: Generally, sutures are composed of several layers of cells which respond to external stimuli. A consensus among studies is that a suture is composed of osteocytic and fibrocytic cells, fibers, and blood vessels. The organization of these layers is still controversial as histologic animal studies show conflicting results. The morphology of the sutures is also influenced by age as the sutures becomore more complex with age and eventually the opposing bony edges can fuse. Biochemical analysis of the sutures indicate that a number of substances are detected in suture development. These substances include Type III and V collagen, geleatin, fibronectin and certain small proteoglycans. All of them play a role in sutural development, however it is unknown what specific role they play.
Translation and transduction of forces : It is difficult to quantify these forces because forces can not be isolated to a specific area without being connected to the surrounding tissues. When rapid palatal expansion was evaluated, force levels before and after sutural opening were similar most likely because when the suture opened, forces were still be absorbed by surrounding craniofacial complex thus interfering with the ability to measure the forces in an isolated area like the palatal suture. Studies also looked at the conversion of mechanical forces to cellular activity. It is thought that the mechanical energy is converted into electrical energy (Piezoelectricity). The effects of external mechanical forces was studied and it was proposed that the sutural response can be divided into several stages. Initially,, a traumatic response is noted where there is cellular death and resorption, followed by connective tissue repair. New bone is deposited in perpendicular or parallel to the areas of the suture in tension areas and resorption takes place in areas of compression. The long term effects appear to show some relapse either from elastic recoil of the tissues, or an imbalance with the surrounding tissues.
Conclusions: Research is being conducted to understand the effects of external forces on sutural growth and development. It is now understood that response of sutures to mechanical forces is determined by the duration and direction of the forces, morphology of the suture, and the age of the patient. However, it is unknown if all sutures react in a comparable manner to a given force or if sutures react differently to different magnitudes of force. The author suggests that the development of a good in vitro model that would accurately predict responses in vivo.
Assessment of article: Very complex article which was difficult to read and understand.

Dimensional Changes of the Dental Arches

Department of Pediatric Dentistry

Lutheran Medical Center


Kris Hendricks Date: 10-02-09

Article title: Dimensional Changes of The Dental Arches: Longitudinal Study From Birth To 25 Years

Author(s): J. H. Sillman, MA, DDS

Journal: AMJO

Volume (number):

Month, Year: Nov, 1964

Major topic: Changes in arch size and their correlation to age

Minor topic(s: Growth and Development

Type of Article: Longitudinal Study

Main Purpose:

To present mean dimensions of the total dental arches and the mean size of teeth as it correlates with chronologic age.

Overview of method of research:

750 dental casts were studied, taken from children ages 0-25years. 40 people were studied from birth to age 25, and there were an additional eight who were recorded from birth to ages between 12 and 19. 5 additional subjects recorded from age 1 or 2 to 16-19.

Measuring points were determined using a repeatable hard and soft tissue measuring points. These points can be read in the study, but are not important for our purposes.

The study divided up the dental stages into 6 groups: Edentulous, Deciduous, I1M1, Pm, M2, M3 or age greater than 19.

Data from measurements of mesiodistal tooth sizes were also collected and compiled.

Findings:

An attempt was made to give normative values of dental arch diameters based on age, which is available in the articles tables.

Key points/Summary :

The important information is for reference,which again can be derived from the tables. I chose not to reproduce them here.


Assessment of article:

Very boring to read, but this article strikes me as very important for dental knowledge overall. This is significant for treatment timing for those of us interested in mixed dentition orthodontics.

The biogenic course of the deciduous dentition

Resident: Adam J. Bottrill
Date: 02OCT09
Region: Providence
Article title: The biogenic course of the deciduous dentition
Author(s): Baume, Jouis J.
Journal: J. D. Res
Volume #; Number; Page #s: Vol. 29, No. 2, pp 123-132
Year: April, 1950
Major topic: Physiological tooth migration and its significance for the development of occlusion
Minor topic(s): NA
Type of Article: Review of literature
Main Purpose: Present a review of literature that appears to reveal that there is no truly authentic information on which the present-day concept of the development of occlusion is based.
Overview of method of research: Review

Key points in the article discussion:

A. History:
1. 1819, Delabarre: purpose of anterior deciduous teeth is to make allowances for the permanent dentition.
2. 1890, Zsigmondy: 1st to longitudinally measure and compare lengths of dental arches.
3. 1907, Angle: Malocclusion of the Teeth… and the focus shifted to the permanent 1st molars.
4. 1910, Zeilinsky: developed the “physiological mesial shift”
5. 1922, Franke: shortening of 3.7mm in the lower arch followed by shedding of deciduous teeth.
6. 1924, Simon: “orbit-cuspid” relationship. Suggested shifting of the permanent 1st molar position.
7. 1929, Lewis: concluded that measurements of changes in width of dental arches offer no solution in the diagnosis of developing malocclusion.

B. Study…. ?? to ascertain more detailed information on the physiological changes in the human dental arch.
1. Plaster reproductions of dental arches were made annually, over 8 years, on 30 children starting at less than 4.5 y.o.
2. Measurements: arch length, canine width, 2nd primary molar width.
3. Findings:
a. Generally, the length of maxillary arch remains the same between 4-6 y.o.
b. Generally, distance between 2nd deciduous molars remains unchanged between 4-6 y.o.
c. Generally, lower intercanine width also remains the same.
d. Average value of intercanine width at age of 5.5 y.o. is about 1.7mm higher than those without spacing. (1.5mm for mandibular)
4. Discussion:
a. From about the age of 4 y.o. until the eruption of the permanent molars, the sagittal dimension of the upper and lower arches remains the same. NOT A SINGLE CASE substantiated the theory that there is forward growth of the alveolar frontal sections during the period of primary dentition (which is what almost every textbook claimed at the time).
b. Only minor changes in the transverse dimensions of upper and lower deciduous arches were apparent during periods of observation (canine and molar width).
c. No increase in interdental spacing after deciduous teeth erupted. Also, no extension or expansion of arches took place between 3 and 5.5 y.o. children are either spaced or not spaced.
d. Confirmed “primate spacing.” And lack of this spacing due to insufficient alveolar growth… NOT always just large teeth. Seems to be hereditary and common among twins.
e. No essential changes in occlusion can take place during the period of the completed deciduous dentition. However, alveolar growth DOES occur.
5. Conclusion:
a. After deciduous dentition fully erupted, their sagittal and transverse dimensions were not altered except when subjected to inadequate environmental influences.
b. Arches either spread or closed. Spacing is congenital, not developmental.
c. Confirmed primate spacing.
d. Terminal plane remains constant.
e. Vertical alveolar growth concomitant with the development of successional tooth germs and sagittal growth concomitant with development of accessional tooth germ.
f. The present concept of physiological changes of the deciduous dentition through spacing and through mesial shifting of the mandibular teeth was not confirmed by the above observations.

Assessment of article: This is an old article…. not shenanigans then…. but MAY BE shenanigans now…

The Consideration of Dental Development In Serial Extraction

Resident’s Name: Brian Schmid DMD Date: 10/2/09
Article title: The Consideration of Dental Development In Serial Extraction
Author(s): Conrad Moorrees DDS, Elizabeth Fanning DDS and Anna Marie Groen
Journal: ?
Month, Year: January 1963
Major topic: All you ever wanted to know about serial extraction but were too afraid to ask
Type of Article: Literature Analysis
Findings: Variance in tooth size and arch size determine the presence of spacing and crowding; crowding can occur in patients with less than average tooth size or larger than average arch size. This can become complicated when predicting tooth and arch size in the developing dentition. The mean size difference between permanent and primary maxillary incisors is 7.4mm in males and 6.mm in females, with arch breadth increasing only ~3mm. In the mandible, the average difference in M-D widths is 5.1 ni males and females. On average, when primary tooth spacing is included there is enough room for the maxillary incisors and nearly enough in the mandible, leading to mild crowding there. During eruption of the maxillary incisors, 50% of children did have some crowding. During the second stage of dental development, the eruption of canines and premolars, the maxillary intercanine width increases 2mm in the maxilla and decreases slightly in the mandibular. The pattern of exfoliation, the location of the mandibular 2nd premolar and the depth of intercuspation of the 6 year molars dictates how much of the leeway space may be lost by mesial drift. Predicting adult intercanine width is difficult from age 9 years to adulthood and can vary from 1.2 to 1.6mm. In general, ¾ of root length is developed upon eruption of canines and premolars, canine being slightly longer when they pierce through the gingiva. Therefore, deciduous molars should not be extracted before ¼ root development if the tooth is near emergence or ½ if not. Primary canines should not be extracted before ½ root development of the permanent canines or the 1st premolar has already erupted. While we can predict leeway space well using dental casts and radiographs, predicting growth of arch size is very tricky and variable. It is best to be as conservative as possible when considering serial extraction and to monitor eruption of permanent teeth as well as root formation to optimize orthodontic diagnosis and proper treatment planning.

Assessment of article: Very good article.

Physiological tooth migration and its significance for the development of occlusion

Dan Boboia

Article Review 10/2/09

Title: Physiological tooth migration and its significance for the development of occlusion

Author: Louis Baume

The Journal of Dental Research: August 1950, Vol. 29, #4

Major Topic: Assessing the relationship between the degree of overbite of the deciduous dentition and that of the mixed permanent dentitions and the factors responsible for transitory change, if any, from the deciduous overbite to the permanent overbite in the same individual.

Methods:

52 series of plaster casts were made before and after eruption the permanent incisors. Each cast was classified according to degree of overbite as checked from the lingual aspect of plaster reproductions in occlusion. Overbite was classified as slight, medium, or severe:

slight – incisal edges of mnd. 1st incisors met the upper incisal 1/3 of the crowns of the opposing maxillary incisors

medium – lower 1st incisors occluded with the middle 1/3 of the upper incisor crowns

severe – the mandibular incisors met the protuberance of the cingulum or came in contact with the gingiva

Measurements were made if the length of the frontal portion of the upper and lower arches in deciduous and mixed dentition.

Deciduous:

Slight OB: 40% cases

Medium: 29% cases

Severe: 31% cases

Mixed:

Slight:19%

Medium: 27%

Severe: 54%

Findings:

Data reveals that during the transition from a deciduous to mixed dentition a developmental tendency toward the formation of a deeper bite occurs.

Summary:

1) Degree of incisal OB in the permanent dentition primarily was determined by the extent of mandibular forward growth which occurred during the eruption of the successional teeth. The lessened forward extent of the mandibular arch was responsible for a greater incidence of severe overbite in the mixed dentures.

2) The deciduous overbite was also a determining factor in that the slight overbite tended to increase during the period of the mixed dentition while a severe overbite became worse.

3) The definite overbite of the permanent dentition finally depended upon the eruption sequence of the permanent canines and premolars. If in the lower arch the sequence was canine, first premolar, second premolar and in the upper arch first premolar, canine, and second premolar, the best results were observed.

4) Incisal overbite developed independently of the mechanism of molar adjustment.

Assessment:

Well written; a good read!