Almuzian Notes Flashcards

Question

Orthognathic surgery options for class ll dev ll

Answer 1

It mainly depend on the lower anterior facial height and the prominence of the chin as well as the presence of maxillary retrognathia. Surgical option involves: 1. Mandibular advancement with 3 point landing. 2. Bimaxillary osteotomy with clockwise rotation. 3. Total subapical osteotomy of lower jaw. 4. Adjunctive procedure include: • On occasion a reduction genioplasty may also be required to optimise the profile. • Where the lower facial height is average or mildly increased, the overbite may be reduced by a lower labial segment set-down at the time of surgery.

Answer 2

Space can be provided: A. Non-extraction basis by proclining LS if there is mild LLS crowding (Selwan-Barrnet) and the OJ as well as the skeletal problem are very mild B. Preserving Lee way space C. IPS (BOS recommendation not more than 0.25 per side per tooth) D. Molar distalization by • TAD for distalzation • lip pumper, • IO distalizer appliance • HG with URA as En mass appliance retraction with or without exraction of second molar or usually before eruption of second molars. • Hg to molar bands • HG with URA as Nudger appliance • URA+anterior bite plane with low pull HG this is called Acrylic Cervical-Occipital (ACOA) appliance popularized by Cetlin and Ten Hoeve (1983). E. Class II bite corrector mechanics F. Extraction of premolars or molars in the UA or both arches. However extraction might: • Makes OB worse. • However, Al-Mangoly 1993 found that extraction has no effects on the OB and space closure if the correct mechanics is used. • If only upper arch extractions are prescribed, a tooth size discrepancy will result due to the mesiodistal dimension of the upper premolar being greater than half the mesiodistal dimension of the lower first molar. The excess space in the upper arch should be taken up by a slight over-rotation of the upper first molar and over-torquing the upper labial segment or using the MBT philosophy using the contralateral second molar tube on the first molar • However, some authors have suggested that in borderline cases it would be a more sound clinical approach to complete levelling, aligning and overbite reduction before a final decision is made to extract teeth (Selwyn-Barnett, 1996).

Answer 3

1. Patient concern (dental or facial concern) 2. Patient age 3. Growth 4. Medical condition 5. Patient compliance 6. Family history of class III 7. Severity of skeletal problem in AP, V & T direction 8. Clinical condition of the teeth and oral tissues. 9. Amount of the OJ &OB 10. Degree of crowding 11. Degree of compensation 12. Presence of displacement

Answer 4

high angle cases require higher anchorage demand because: • Bone is less dense than bone of low angle case which favour teeth movement and anchorage loss • The direction of the occlusal plane favour the mesial movement of the anchor teeth • A weaker muscle fibres associated with high angle case produce less occlusal interlocking than normal (Benington and Hunt, 1999). 6. Occlusal interlock: cases with fraction Class II or III are associated with less inter-occlusal-locking resistance and hence more OA demands than full unit Class I, II or III.

Answer 5

Functional appliance: It must be remembered that a reactionary mesially directed force occurs in the mandible and the reactionary distally directed force occurs in the maxilla during the use of the functional appliance. This could lead to upper teeth distalization and lower teeth mesialisation. • The lip pumper: It mainly consists of a thick round stainless steel wire that fit in the headgear tube of the molar band and stays away from the labial surface of the incisor by the effect of the loop mesial to the entrance to the molar tube. The acrylic pad is embedded in the anterior part of the wire and act to actively displace the lip forward. The reciprocal force of the displaced lip will be transferred to the molars via the heavy wire and result in molar uprighting and distalisation. As a consequence of the change in the soft tissue equilibrium by the lip pumper, there is a proclination in the incisors under the effect of tongue as well as increase in the intercanine width (Cetlin & Ten Hoeve, 1983). The forces are originated from the deliberately displaced lower lip by the acrylic lip pad. However, the effects of lip bumper were described by O'Donnell 1998, Bjeregaard 1990 & Nevant 1991 & include: i. Molar distalization and tipping ii. Reduce anterior crowding iii. Incisor proclination and protrusion iv. Increase intercanine and interm

Answer 6

This relies on using the opposing arch to provide OA to the other arch. Care must be taken to realise that intermaxillary traction is an inefficient method of space closure and if prolonged can lead to excessive extrusion (cant of the occlusion) and tipping of the anchor teeth. Sometime elastic can be used in conjunction with sliding jigs, this was a mainstay of the original Tweed technique in which the force from Class II elastics aid in pushing the upper molars distally via a sliding jig. The force level is 250 gm per side is needed. In addition, the class II elastic help in correction of class II malocclusion by clockwise rotation of the occlusal plane which can be compensated in growing patient. This is why it should not be used for more than 6 months in adult patient (Tweed, 1967)

Answer 7

a. Using light force that is not overload the OA units. b. Laceback and bendback which used with SWA • Robinson in 1989, in a prospective study found a 2.47 mm difference in the lower incisor anteroposterior position between cases treated with or without lacebacks. In the laceback group there was a mean 1.0 mm distal movement of the incisors and a mean 1.76 mm mesial movement of the first molars (so the OA loss is 0.76mm). In contrast the non-laceback group demonstrated a mean 1.47 mm proclination of the incisors compared with a mean 1.53 mm forward movement of the molars (so the OA loss is 3mm). • Usmani et al. 2002, results showed that Lacebacks do not prevent ULS proclination, they have no effect on molar position, the amount of ULS proclination depend on the angulation of the canine and the laceback makes no difference. • Irvin et al. 2004, in first premolar extraction cases, the use of laceback ligatures conveys no difference in the anteroposterior or vertical position of the lower labial segment. Furthermore, the use of laceback ligatures creates a statistically and clinically significant increase in the loss of posterior anchorage • Sueri et al 2006 applied the MBT technique with extraction of the first premolars to study the effectiveness of laceback ligatures on maxillary canine retraction. Canine distalization was successfully achieved with laceback ligatures. Canine and molar movements were significantly smaller in laceback cases. • Fleming 2012 in their systematic review found that there is no evidence to support the use of lacebacks for the control of the sagittal position of the incisors during initial orthodontic alignment. c. Stopped arch and utilities. (It is a type of compound anchorage theory): The use of stopped arch wires recruits OA from the posterior and anterior teeth while sliding individual teeth along the archwire. Rajcich & Sadowsky (1997) showed that retraction of canines with sliding mechanics, where the molar is prevented from tipping or sliding mesially by an auxiliary arch and tip-back bends, incurs very little OA loss. d. Subdivision of desired movement Moving a single tooth at a time, rather than dividing the arch into more equal segments can preserve anchorage. For example, in extraction cases where OA is not at a premium, canines are usually retracted until sufficient space exists to align the incisors, and the complete labial segment is then retracted as a unit. According to the differential anchorage theory, this would be expected to reduce OA demand compared to En-masse retraction of the 6 anterior. Generally, the advantages of En-masse retraction are simplicity, and avoiding the need to repeat stages of treatment, such as realigning the teeth following sectional mechanics. Heo in 2007 showed no significant differences existed in the degree of anchorage loss of the upper posterior teeth and the amount of retraction of the upper anterior teeth associated with en masse retraction and two step retraction of the anterior teeth. Again TianMin Xu 2010 fond no difference between En-masse and two stage retraction. Similarly, a systematic review by Rizk et al 2018 confirmed the absence of difference between 1 and 2 phase space closure. A study by Alhadla et al 2016 showed that the posterior anchorage bend to T-loop used to retract the maxillary canine can enhance anchorage during maxillary canine retraction compared to continuous arch mechanics. A recent systematic review by Alharbi et al 2018 should that there is no statistical difference in terms of AP anchorage between Nance appliance, HG and TADs but the latter is the preferred option by patient and associated with less treatment duration and better occlusal outcomes.

Answer 8

1. Extraction of lower deciduous canines has been suggested for the correction of mild lower incisor crowding. Houston and Tulley (1989) state that in general terms this allows some correction of the incisor crowding. Stephens (1989), reported that the ideal age group for this would be 9-10 years of age to allow full development of the intercanine width. Proffit (1993) however warns that this may result in the lower incisors tipping lingually further reducing arch length. 2. Provide space for palatally lateral incisors. 3. Provide space for incisors whose eruption is late due to supernumeries. 4. Serial extraction 5. Balance extraction for maintaining ML integrity 6. Extraction of lower C`s may help in treatment mandibular displacement. 7. Extraction of upper deciduous canines is often suggested in order to attempt to encourage a palatally placed canine to erupt into a normal position. Research has shown that this indeed is quite successful with 70% erupting into favourable positions (Ericsson and Kurol, 1988).

Answer 9

• Timed extraction of 1o and 2o teeth for interceptive management of crowding • Originally advocated by Kjellgren 1947 to avoid the need for orthodontic treatment but now modified and used as an adjunct to fixed appliance treatment Extraction Sequence: 1. B`s as centrals erupt 2. C`s as laterals erupt (8½-9½ yrs) allows 1 & 2`s to align + move distally but 5 & 6`s drift mesially 3. D`s when 75% resorbed or 1st premolar roots are ½ to 2/3 formed, in order encourage 4`s to erupt • too early extraction > bone formation over D`s hence delays eruption of 4`s • too late extraction >3`s will erupt before 4`s 4. 4s as the 3`s erupt • allows 3`s to align • any residual space will close with mesial drift of 5 & 6`s Indications: Sever crowding in: 1. 8-9 yrs old 2. skeletal Class I 3. normal OJ and OB 4. 4`s developmentally ahead of 3`s 5. First permanent molars of good prognosis 6. all permanent teeth present Advantages of Serial Extractions 1. in theory no appliance treatment needed 2. appliance may be simpler and shorter 50% reduction in the treatment time (Little 1990) 3. Better stability and retention since tooth completes its formation in a site where it will remain when treatment is completed (Graber, 2011) Disadvantages of Serial Extractions 1. Exposed to multiple extractions (12 teeth) 2. No guarantee, extractions of D`s can lead to impaction of 4`s if the 3s erupt ahead of the 4s. Removal of twelve teeth is a traumatic experience and there is no guarantee that the lower premolar will erupt before the canine and as such the latter may be impacted. If this occurs extraction of the second deciduous molars may be an option with Holtz (1970) advocating the provision of a lingual arch retainer for space maintenance. The latter author also recommends disking of the second deciduous molars to provide space for premolar teeth. 3. Growth prediction problems: difficult to predict amount of incisor crowding because ICW  between 8-10yrs i.e. lower incisor crowding may resolve spontaneously 4. Space loss with extractions of C`s and especially D`s, by mesial drift of buccal segments, lower incisors tip lingually, both of these reduces arch length 5. Tipping of teeth into extractions site especially anterior teeth causing OB increasing. Little 1990 6. There was no difference between the serial extraction sample and a matched sample extracted and treated after full eruption except shorter time for active orthodontic treatment (Little 1990)

Answer 10

1. Hypoplasia 2. Severe displacement. If lateral incisor is severely crowded and the central and the canine are in acceptable contact. 3. Heavily restored or poor prognosis 4. Impaction or abnormal shape. 5. If root is severely resorbed from ectopic canine. 6. If contralateral lateral incisor is congenitally absent (2% population). 7. Diminutive size with increased OJ or ML or crowding

Answer 11

1. aesthetic considerations:  If the canine crown is bulbous.  If the canine crown is different shade to the central.  If the canine gingival margin height differs significantly from the central 2. Class III Incisal relationship – unfavourable anchorage balance.

Answer 12

1. Hypoplasia 2. Severe displacement 3. Heavily restored or poor prognosis 4. Impaction 5. Congenital absence of contralateral second premolars 6. Mild crowding (2-4mm per quadrant). Creekmore (1997), reviewing this subject concludes that as a rule of thumb, extraction of first premolars provides approximately 66% of the space for aligning/retracting the anterior teeth, whereas extraction of second premolars provides approximately half of the space 7. Where space closure by forward movement of the molars rather than retraction of the labial segments is indicated whilst taking into account the molar relationship. 8. anchorage consolidation

Answer 13

1. spontaneous alignment of incisors is less satisfactory 2. mesial tipping of molar tooth

Answer 14

Aim for extraction at the optimal time without balancing extraction 1. If the lower first molar is to be lost, compensating extraction of the upper first molar should be considered to avoid overeruption of this tooth, unless the lower second molar has already erupted and the upper first molar is in occlusal contact with it. 2. If the upper first molar is to be lost, do not compensate with extraction of the lower first molar if it is healthy.

Answer 15

1. First molar extractions can be delayed until the second molars have erupted and then the extraction space used for alignment with fixed appliances. 2. Alternatively, first molars can be extracted at the optimum time and the crowding treated once in the permanent dentition. If premolar extractions are likely to be required at this stage, the third molars should be present. 3. If the buccal segment crowding is bilateral, consider balancing extraction to provide suitable relief and maintain the centreline. Sometime asymmetrical balanced extraction (extraction of other poorer tooth than 6s) is indicated if there is sever crowding and if extraction is decided at early age with a risk of CL shift. Compensating extraction of upper first molars should be considered to prevent overeruption or relieve premolar crowding

Answer 16

1. Interceptive treatment I. Interceptive treatment of palatally displaced canines. An RCT by Bacceti 2011involving 120 subjects based on palatally displaced canines diagnosed on panoramic radiographs and they were randomly assigned to one of four study groups (RME followed by TPA therapy plus extraction of deciduous canines, TPA therapy plus extraction of deciduous canines, extraction of deciduous canines, EC group). The success of canine eruption was 80%, 79%, 62.5% and 28% respectively. The use of a TPA in absence of RME can be equally effective than the RME/TPA combination in PDC cases not requiring maxillary expansion, thus reducing the burden of treatment for the patient. II. Digit and tongue thrust habit breaker if a crib is soldered to TPA (Clark, 1983) III. Space maintainer after premature loss of primary molars to prevent crowding of the premolars or when the E space is required to relieve minimal crowding in the anterior teeth. There are many studies looking at the effectiveness of the lingual arch in maintaining the Leeway space. Brennan & Gianelly 2000 found that a lingual arch placed during the mixed dentition, the arch length decreased by 0.44 mm and there was a gain of 4.44 mm leeway space. However it was shown that intercanine is increased after using lingual arch due to the canines migrating distally. Other studies by Villalobos et al.(2000), DeBaets and Chiarini (1995) and Rebellato et al. (1997) also showed that lingual arch reduced the loss of leeway space but increase the possibility of lower incisor proclination. 2. Transverse anchorage and Arch width stabilization I. To improve arch width stability when aligning palatally impacted maxillary canine (Fleming &Sharma, 2010). II. CLP case after expansion of the maxillary arch to restore the arch form between the major and lesser segments and just before alveolar bone grafting (Harris & Hunt, 2008). III. As a retainer after RME or after surgical expansion or constriction of the palate in order to hold the osteotomies part together during healing period (Harris & Hunt 2008). IV. It is used to counteract the buccal tipping of the crown of the molars during intrusion of the anterior teeth using Segmented Burstone Arch Wires mechanics (Burstone, 1966). V. For the same reason its use is recommended with Class II bite correctors to counteract the buccal forces applied by the (TFBC) Twin Force Bite Corrector (Rothenberg, 2004). VI. Adjunct with HG to reduce buccal tipping of the molar and palatal cusp hanging the molar distalization (Baldini and Luder, 1982). However, a study by Wise et al. (1994) showed no difference with or without use of a TPA during molar distalization by HG. VII. TPA are used with palatally or buccally placed TAD to control molar tipping when posterior teeth are intruded to treat anterior open bites (Cousley 2010). 3. Vertical Anchorage: Placing the TPA 4mm away from the palate might introduce some intrusive effect by the tongue on the molars which can help in correcting or controlling the over eruption of maxillary molars (Goshgarion, 1972). 4. AP anchorage • The Nance appliance can be used to provide anchorage to distalize the molars such as the Pendulum Appliance (Hilgers 1992); Wilson rapid molar distalization (REF); the distal jet (Carano 1996): Jones Jig (REF) and the Lokar Distalising Appliance (Jones and White 1992). • TPA can be used to maintain molar position after distalization. (Prakash 2011). • TPA can be used at start of treatment when moderate anchorage requirement is needed since it would theoretically bring the roots of the upper molars in contact with cortical bone if they were forced to move mesially and would supplement their anchorage values (Cortical anchorage) (Radkowski 2007, Root, 1986). There are many studies that compare the effectiveness of the TPA with other methods of anchorage reinforcements: I. Zablocki & McNamara 2008, the mean anchor loss of 4.1 mm was seen in association with the TPA and 4.5 mm in control group. II. Feldmann, 2009, RCT to measure the anchorage loss with Onplant (1), TAD (2), EOT (3) & TPA (4). They found that after levelling/aligning phase: the anchorage was stable in the group 1,2 & 3 while group 4 showed 1.0 mm. while after space closure phase, the anchorage was stable in the group 1 & 2 but group 3 & 4 showed 1.6 and 1.0 mm of mesial drift of molars respectively. III. Stivaros 2010 compare Nance and TPA appliances and found that both appliances are effective in preserving anchorage with an average OA loss of around 1mm over 6 months and there is no difference in anchorage support between them but TPA well tolerated by the patient. IV. Feldmann, 2012, measured the patients’ perceptions in term of pain, discomfort, and jaw dysfunction with Onplant (1), TAD (2), EOT (3) & TPA (4). The results confirm that there were very few significant differences between patients’ perceptions of skeletal and conventional anchorage systems during orthodontic treatment V. Sharma et al. 2012 compared the use of TPA with TAD regarding the orthodontic anchorage and found 2.5 mm of mesial movement of the U6s with TPA while Mini-screw implants provided absolute anchorage during U3s retraction VI. TADs or TPA? Liu 2009 compared the use of TPA and TADs in he found that better dental, skeletal and soft tissue changes could be achieved by minicrew implants especially in hyperdivergent patients. Skeletal anchorage should be routinely recommended in patients with bialveolar dental protrusion. VII. Interesting, in a finite element study, Kojima et al. (2008) show that TPA provides no antero-posterior anchorage. VIII. Lee et al In both the anteroposterior and vertical directions, a TPA supported by 2 midpalatal miniscrews provided more stable anchorage than HG supported with TPA 5. Molars antirotation effect: Another advantage of TPA is the provision of antirotation effect on the molars during incisor retraction (Goshgarian, 1972). 6. Method of attachment for auxiliaries. • More recent novel ways of using TPAs is the incorporation of finger or ballista springs to aid eruption of impacted maxillary canine (Shaushua & Becker 2012) FIGURE: PHOTO NEEDED. • Lingual arches can be used to provide attachment to extrude multiple teeth after their failure of eruption like Jerusalem approach (Becker, 1997), the Belfast– Hamburg (Behlfelt, 1987), the Bronx approach (Berg, 2011) and the Toronto– Melbourne (Smylski 1974; Hall, 1978) in the management of multiple failures of eruption associated with Cleidocranial Dysplasia. In general, all these approach include timing extraction of primary and supernumerary teeth, surgical exposure of the permanent teeth followed by applying attachment to start teeth alignment • Modified Nance appliance with anteriorly positioned acrylic bottom can be used to treat anterior deep by acting as a ﬁxed acrylic frontal bite plane. Prakash, 2011

Answer 17

Types A. Custom made: 1-0·9mm stainless steel with four helices to increase flexibility B. Preformed ready type • A removable or fixed quadhelix constructed of Blue Elgiloy for increased flexibility/ adjustability and an Elgiloy based system called ORTHORAMA • Removable nickel titanium versions have also been introduced which may offer more favourable force delivery characteristics. But study showed that the factor effect the efficiency of the system is the size of the appliance and diameter of the wire not the material. Ingervall,1995 Design • The quadhelix is a fixed appliance retained by bands cemented on the permanent first molars. • It consists of a w-shaped 1mm spring, usually stainless steel, incorporating 4 helices to add flexibility and increase range of action. • The quad helix consists of a pair of anterior helices and a pair of posterior helices. • The portion of wire between the two anterior helices is called the anterior bridge. • The wire between the anterior and posterior helices is called the palatal bridge. • The free wire ends adjacent to the posterior helices are called outer arms.

Answer 18

1. Intermediate upper arch expansion 2. Bi-helix used in mandibular arch in grossly narrowed or distorted arches, or to aid correction of severe scissors bite 3. Expand the upper arch anteroposteriorly when its arm length increased 4. Provide access and space with cleft palate before bone grafting 5. Used with facemask same as RME 6. Molar derotation 7. Habit breaking effects 8. Method of attachment to align impacted teeth or to perform certain teeth movement 9. Provide some AP and transverse anchorage Advantages 1. Reduced need for patient compliance because it is fixed 2. Efficient : • The quadhelix produces a combination of buccal tipping and skeletal expansion, typically in the ratio.of 6:1. (Frank 1982) • Quad. (QH and RME success rates is 100%, Harrison and Asly 2008 Cochrane review) • Quadhelix versus buccal arch expansion — no difference in expansion achieved and buccal arch cheaper McNally 2003 • Herold (1989) compares the use of RME, a quadhelix and a removal appliance, and came to the conclusion that no method of expansion was substantially better than the other. Disadvantages 1. The limited amount of skeletal change, 2. Opening of the bite due to molar buccal tipping.

Answer 19

• The desirable force level of 400 g can be delivered by activating the appliance by approximately 8 mm, which equates to approximately one molar width. • Patients should be reviewed on a six-weekly basis. • Sometimes, the appliance can leave an imprint on the tongue; however, this will rapidly disappear following treatment. • Expansion should be continued until the palatal cusps of the upper molars meet edge-to-edge with the buccal cusps of the mandibular molars.

Answer 20

1. First, the gingival margins of the two central incisors should be at the same level. 2. Second, the gingival margins of the central incisors should be positioned more apically than the lateral incisors and should be at the same level as the canines. 3. Third, the contour of the labial gingival margins should mimic the cementoenamel junctions of the teeth. 4. Last, there should be a papilla between each tooth • The cause of These discrepancies could be Abrasion of the incisal edges delayed migration of the gingival margins. • The proper solution for the problem: orthodontic movement to reposition the gingival margins or surgical correction of gingival margin discrepancies.

Answer 21

1. Increased sclera show above the lower eyelid, normally assessed in the frontal facial examination, is also a sign of midface deficiency 2. Paranasal hollowing is a sign of midface deficiency, 3. Flattened upper lip 4. An obtuse nasolabial angle. 5. Class III problem 6. Upper arch narrow with cross bite and crowding 7. Wide Buccal corridor • Increased sclera show above the lower eyelid and below the iris is a sign of midface deficiency. • Paranasal hollowing/flatness is a sign of maxillary hypoplasia. This may be observed in frontal and profile examination of the face.

Answer 22

a. Vertical lip lines level 1. Lower lip should cover incisal third of maxillary incisors. 2. Maxillary incisor exposure at rest: 2–4 mm at rest. 3. Depends on: • Anterior maxillary height, • Upper lip length, • Clinical crown length, • Vertical maxillary incisor inclination • Lip activity during facial animation. • Combinations. Where the upper lip length is very short then the patient would expect to show more of the upper incisors. Any attempt to reduce the incisor exposure in relation to a short upper lip will lead to an unaesthetic reduced middle face height. Similarly, with a long upper lip, the patient would be expected to show less or no upper incisor, both at rest and during facial animation. b. Lip activity • A strap-like lower lip often retroclines incisors (commonly occurs in Class II division 2 malocclusions). (Mossy 1981) • Flaccid lips are less likely to significantly alter position with anteroposterior dental movement. c. Lip morphology • Vermilion show of lower lip 12mm, upper lip 9mm. (Fish & Epker 1981) • Full lips are less likely to significantly alter position with anteroposterior dental movement. • Thin lips are more likely to ‘flatten’ with incisor retraction. d. Lip posture Lip competency help to know the etiology of malocclusion and the possible treatment stability. Types of lip relationships are: 1. Competent: Lips held together at rest. 2. Lips habitually competent which are held apart at rest by more than 3–4 mm but the patient tries to posture his/her haw forward to achieve anterior lip seal like in CLII D1 cases. 3. Potentially competent (lips are unable to be held together due to increased inter-labial space) and the patient exert muscle effort to close them which can be seen in a form of active mentalis. The features of this condition are puckering of the chin area and flattening of the LMA. 4. Rolled blind upper lip, means the lip retract on smiling to show more gum. Lip incompetency is due to: • With aging the lip incompetency is reduced • Short lip • Increased LAFH due to VME • Increased LAFH due posterior growth rotation, • Over-eruption of BS, • AP skeletal malrelationships. • Proclined ULS or LLS

Answer 23

1. The term hypodontia is generally used to describe developmental tooth absence excluding the third molars (Goodman et al., 1994). Hypodontia may be sub-classified according to its severity, as mild (1–2 missing teeth) almost 80%, moderate (3–5 missing teeth almost 10%) or severe (≥6 missing teeth almost 1%). (Larmour 2005, Naini et al., 2011)

Answer 24

A. According to the number of teeth involved (Goodman et al., 1994). 1. Hypodontia refers to a lack of 1-6 teeth, excluding third molars 2. Oligodontia (sever hypodontia) refers to a lack of more than six teeth, excluding third molars Hobkirk et al., 1995 3. Anodontia refers to a complete absence of teeth in one or both dentitions. Very rare B. According to the inheritance pattern (Wright et al., 1993). 1. Non-syndromic hypodontia A. Nonsyndromic hypodontia can be subclassified according to method of occurrences (Burzynski and Escobar, 1983): • Familial or Inherited. This form can follow autosomal dominant, autosomal recessive or autosomal sex-linked patterns of inheritance, with considerable variation in both penetrance and expressivity. • Sporadically 33% of hypodontia cases B. Non-syndromic hypodontia can be sub-classified according to teeth involved and their number: 1. Localized incisor–premolar hypodontia (OMIM 106600), which affects only one or a few of these teeth. This is the most common form and is seen in around 8% of Caucasians (Nieminen et al, 1995). 2. Oligodontia (OMIM 604625) occurs in around 0.25% of Caucasians and can involve all classes of teeth (Sarnas & Rune, 1983). C. Candidate genes for nonsyndromic human hypodontia (Vastardis et al., 1996; Lammi et al., 2004; Suda et al., 201, Cobourne, 2007, Han et al., 2008): • MSX1 associated with premolar and lateral incisors. Usually associated with sever hypodontia. • EDA gene mutations usually includes the loss of mandibular and/or maxillary incisors and canines • PAX9. Associated with molars. • AXIN2 which is mainly associated with Finnish family hypodontia. 2. Syndromic hypodontia • Seen in association with Down syndrome, ectodermal dysplasia, CCDS, CLP & CP , Van de Wound syndrome, Rieger and Book syndrome. Larmour 2005, Shapira et al., 2000), (Kerwetzki and Homever, 1974; Marković, 1982b; Parsche et al., 1990), (Uthoff, 1989). • Candidate genes MSX1 (MSX1 represents a candidate gene for both syndromic and nonsydromic hypodontia).

Answer 25

Wide range of prevalence because of the geographic and ethical variation 1. Dentition: A. Deciduous teeth 0.1 – 0.9 % (1-9 in 1000) with the maxillary then mandibular lateral incisors being most commonly missing. As a rule, when the primary tooth is missing, its permanent counterpart will also be absent (Hall, 1983). B. In permanent dentition, 4-6% excluding 8s (Grahnen, 1956). Polder 2004 4.6% male and 6.4% in female • (Localized incisor–premolar hypodontia around 8% of Caucasians (Nieminen et al, 1995) • Oligodontia occurs in around 0.25% of Caucasians (Sarnas & Rune, 1983). 2. Ethnic variation • Ethnic variation exists, (Endo et al, 2006a; Buenviaje and Rapp, 1984; Zhu et al, 1996; Polder et al, 2004). • The incidence of missing permanent teeth, excluding the third molar, is 3.4 per cent in Swiss children, 4.4 per cent in American children, 4.6 per cent in Israeli children, 6.1 per cent in Swedish children, 8 per cent in Finnish children, and 9.6 per cent in Austrian children (Thilander and Myrberg, 1973; Brook, 1974; Aasheim and Ögaard, 1993; Slavkin, 1999). • The common missing tooth types in Caucasians being lower second premolars > upper lateral incisors > upper second premolars > lower central incisors Larmour 2005. • In some Asian populations, lower central incisors are reported to be commonly missing. 3. Gender • F:M = 3:2 (Larmour, 2005, (RØLling, 1980) 4. Teeth series • As a general rule, if only one or a few teeth are missing, the absent tooth will be the most distal tooth of any given type (Jorgenson, 1980; Schalk van der Weide et al., 1994). 5. Location: • Lower > upper (RØLling, 1980) • Left > right Wisth et al., 1974 (RØLling, 1980) but other show the opposite (Fekonja, 2005) 6. Teeth affected: • 25-35% of all third molars • Lower premolars most commonly absent and mainly symmetrical (2.6%) (RØLling, 1980). • Missing laterals: 2% More bilaterally than unilaterally. Familial tendency associated with peg contralateral laterals incisors and palatally impacted canines. It represents 20% of the hypodontia cases (Bren et al). • Lower incisor 0.2% of Caucasians but more common in Asian. • U3s developmentally absent 3's: 0.08% (Bren et al) • First and second molars, is rare (Simons et al, 1993). • The overall prevalence of peg-shaped maxillary permanent lateral incisors was 1.8%. he prevalence rates were higher among Mongoloid people, orthodontic patients, and women. Although the prevalence of unilateral and bilateral lateral incisors was the same, the left side was twice as common as the right side. Subjects with unilateral peg-shaped maxillary permanent lateral incisors might have a 55% chance of having lateral incisor hypodontia on the contralateral side.Hue et al meta-analysis 2013.

Answer 26

• Kokich VG (2003) • McLaughlin RP and Bennett JC (1991) • McLaughlin RP and Bennett JC (2003) • Poling 1999

Answer 27

I. Tooth Size Discrepancies • Tooth size discrepancy must be taken into account when treatment is planned initially, but many of the steps to deal with these problems are taken in the finishing stage of treatment. • As a general guideline, a 2 mm tooth size discrepancy noted from Bolton analysis is the threshold for clinical significance (Othman 2007) • Reduction of interproximal enamel (stripping) is the usual strategy to compensate for discrepancies caused by excess tooth size. • When the problem is tooth size deficiency, it is necessary to leave space between some teeth, which may or may not ultimately be closed by restorations. In case of a diminutive laterals, 2/3 of the space should be distal to lateral and 1/3 mesial. (for best aesthetic, Kokich 2003) • More generalized small deficiencies can be masked by altering incisor position in any of several ways. To a limited extent, torque of the upper incisors can be used to compensate: leaving the incisors slightly more upright makes them take up less room relative to the lower arch and can be used to mask large upper incisors, while slightly excessive torque can partially compensate for small upper incisors. These adjustments require third-order bends in the finishing archwires. It is also possible to compensate by slightly tipping teeth or by finishing the orthodontic treatment with mildly excessive overbite or overjet, depending on the individual circumstances. • Most of the cases have TSD with ULS smaller than LLS, so MBT used a total of 40 degree tip in all upper ULS while LLS have only 6, the difference is 34 which means that ULS occ

Answer 28

Four characteristics contribute to ideal gingival form. 1. First, the gingival margins of the two central incisors should be at the same level. 2. Second, the gingival margins of the central incisors should be positioned more apically than the lateral incisors and should be at the same level as the canines. 3. Third, the contour of the labial gingival margins should mimic the cementoenamel junctions of the teeth. 4. Last, there should be a papilla between each tooth • The cause of These discrepancies could be Abrasion of the incisal edges delayed migration of the gingival margins. • The proper solution for the problem: orthodontic movement to reposition the gingival margins or surgical correction of gingival margin discrepancies. To make the correct decision, it is necessary to evaluate 3 criteria. 1. First of all, the relationship between the gingival margin of the maxillary central incisors and the patient’s lip line should be assessed when the patient smiles. If a gingival margin discrepancy is present, but the patient’s lip does not move upward to expose the discrepancy, it does not require correction. If a gingival margin discrepancy is apparent, the next step is to evaluate the labial sulcular depth over the two central incisors. 2. If the shorter tooth has a deeper sulcus, excisional gingivectomy may be appropriate to move the gingival margin of the shorter tooth apically. However, if the sulcular depths of the short and long incisors are equivalent, gingival surgery will not help. So orthodontic extrution with selective grinbding or intrusion with build up will help. 3. Torque of the tooth 4. Vertical tooth discrepancy 5. The third step is to determine if the incisal edges have been abraded. This is best appreciated by evaluating the teeth from an incisal perspective. If one incisal edge is thicker labiolingually than the adjacent tooth, this may indicate that it has been abraded, and the tooth has overerupted. The best method of correcting the gingival margin discrepancy is to intrude the short central incisor

Answer 29

• Failed orthodontic expansion • Adult patient with skeletal maturity, once skeletal maturity has been reached, orthodontic treatment alone cannot provide a stable widening of the constricted maxilla in cases of deficiencies of more than 5 mm. The amount of distraction at the canine level mentioned varies from 3.4 to 5.0 mm, in the first premolar region 4.7 to 5.9 mm and in the first molar region 3.4 to 8.0 mm. • Sever maxillary transverse deficiency >5mm • Extremely thin, delicate gingival tissue or presence of significant buccal gingival recession in the canine-premolar region in the maxilla

Answer 30

• Better periodontal health than conventional expanders • improved nasal air flow; • elimination of the negative space i.e. cosmetic improvement of the buccal hollowing secondary to post-expansion prominence at the site of the lateral wall osteotomy • Tooth extractions for alignment of dental arches are often unnecessary Evidence • Surgical and non-surgical techniques: No significant difference in stability of expansion after 1 yr Berger et al., 1998. In summary, they reported on two groups of patients using both RME and SARME with a hyrax expander. In the RME group the ages ranged from 6 to 12 years. In the SARME group the ages ranged from 13 to 35 years. They concluded that there is no difference in the stability of SARME and RME. Problems • PD damage at area of osteotomy • Root damage at area of osteotomy • Oronasal fistula • Numbness of lip and palate due to osteotomy side effect • Risk of nasal septum deviation • asymmetrical expansion, nasal septum deviation • Rarely, life threatening epistaxis to a cerebrovascular accident, skullbase fracture with reversible oculomotor nerve pareses and orbital compart- ment syndrome

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