Mind the gap
space closure part 2

Why space close for missing teeth?

Space closure has a number of advantages over space opening, however the two approaches have been debated in point / counterpoint debate in the AJODO  by Vincent Kokich and Bjorn Zachrisson in April 2011 (informally known as the USA Vs European debate, pre-Brexit for those in the UK unsure of their side)

• Aesthetics: Patients preferred the gingival papilla aesthetics of space closure, for most parameters however there was no difference in the aesthetic outcome of space closure Vs space opening (tooth shape, space, symmetry, gingival zenith, tooth height / width ratio) (Silveira et al., 2016)
• Periodontal health: Better health outcomes from space closure have been shown when compared with dental implants and bridges for gingival index, plaque index, bone loss, and probing depth (Silveira et al., 2016). However the statistically significant findings were of small clinical significance, for example bleeding on probing of 1.5 Vs 2.6 sites, where 16 sites had been assessed (Robertsson and Mohlin, 2000).
• One stage treatment: Treatment is completed in one stage in early adolescence, with no requirement to delay either orthodontic treatment or restorative management, a required consideration for space opening. With a delay in completion of orthodontic treatment until skeletal maturity for dental implant placement, an average of 11% relapse can occur, necessitating a further course of orthodontic treatment (Olsen and Kokich Sr, 2010).
• No prosthetic costs: An obvious advantage, the absence of no prosthetic tooth means no burden of prosthetic maintenance and costs, with the average orthodontic patient expected to live 67 years after they complete their treatment (UK life expectancy 81 years). However, there are restorative costs for patients receiving space closure, with composite bonding, its maintenance, and bleaching to consider. The cost saving has not been formally evidenced through cost effectiveness analysis of the two methods.
• No impact of growth: Vertical dental eruption, of average 1.02% per year until 30 years of age (Schwartz‐Arad and Bichacho, 2015), has no implication on the aesthetic outcome as the canine as the patient grows, as the canine will erupt at the same rate.

Why not to space close?

Colour: Around 1 in 2 (55%) of patients who had space closure were unhappy with the colour of the canine tooth 55% (De-Marchi et al., 2014). Options for bleaching are limited until patients reach 18 in the UK.

Size: Canine teeth are larger than lateral incisors by an average of 1mm, and premolars are typically 0.5mm smaller than lateral incisors (see Padhraig Fleming’s excellent diagram on tooth sizes), this discrepancy results in a lack of golden proportions.

Is the lack of canine guidance an issue?

The lack of canine guidance and its attainment, feature in both camps to support their approach, similar to Brexit where both parties argued the opposite way was best for the country (clearly Brexit is still on my mind). Space closure cases, as expected, mainly achieve group function occlusal scheme (93-100%), the prevalence of TMD (modified Helkimo) was found to match those of space opening cases as well as controls (Silveira et al., 2016, Rosa et al., 2016). Effective function and abfraction lesions were found not be significantly different to controls, however there is a recommendation to reduce the palatal aspect of the canine to avoid anterior interference and heavy anterior occlusal contacts (Kravitz et al., 2017). The conclusion from Bjorn Zacchrison was that there is “no evidence for establishment of class i canine relationship”, a bold statement, not just in typography, however there are no long term follow up studies beyond 10 years, which limit findings to younger patients only.

Orthodontic camouflage

Successful orthodontic camouflage requires four key considerations: vertical extrusion, in-out and torque

• Vertical camouflage: Gingival zeniths of canines typically mirror that of the central incisor, in order to appear as a lateral incisor, a canine requires vertical extrusion of 1-1.5mm
• In-out: Canine teeth have a curved labial face mesio-distally, as a result following alignment a mesial-in rotation is usually present. This can be accounted for through either a facial-plasty – reducing the curvature, or a mesial-out bend (Kravitz et al., 2017). In both methods the occlusal interference with the canine and lower incisor is reduced as well
• Torque: Torque can be managed through bracket selection and third order bends. In canine substitution the aim is to reduce the canine eminence through increasing the palatal root torque. High palatal root torque options such as the use of a central incisor bracket (+17 MBT or +12 Roth), or the use of a contralateral lower 2^nd premolar bracket (+17 MBT or +22 Roth) are preferred, as frequently a lack of palatal root torque is achieved (Thordarson et al., 1991). Third order bends can be placed or the use of torquing auxiliaries, such as a Goodman spring,
• Space closure can be challenging in canine substitution, specifically anterior anchorage in order to allow posterior teeth to be protracted. Temporary anchorage devices can be used to enable space closure. The use of buccal or palatal TADs can be used for either direct or indirect protraction to reliably achieve space closure without anterior anchorage loss of a reduced overjet.

Image courtesy of Robert Elliot UBC

Restorative camouflage

There are a number of restorative methods to achieve canine substitution, below are three key methods

• Composite build up. Canine cusp tips can be camouflaged through a build up, usually the mesial-incisal aspect but occasionally the distal-incisal aspect as well. Through this addition a relatively level incisal edge can be created, reducing the excessively wide embrasure to an ideal embrasure spaces of 30% between canine and central incisor. The longevity of composite build ups varies, with a mean failure rate of 24% at 8 years follow up, the main reason for restoration replacement being aesthetics of, colour, staining and wear, and less common due to fracture of loss of restoration. However this systematic review featured dental wear management and was not directly related to canine substitution (Demarco et al., 2015).
• Canines are typically 1mm wider than lateral incisors, and can be reduced up to 0.5mm at each proximal surface. A recent study showed upper canines have between 1.2-1.3mm of approximal enamel (Kailasam et al., 2021). Labio-lingual thickness of the canine is reduced to prevent occlusal inteferences with the opposing teeth, 10 year follow up of canines reduced in 2 planes showed no long term effects when compared to canines not reduced (Thordarson et al., 1991).
• Line angles. The visual transition from the proximal surface to the facial surface is termed the line angle. There are proximal and incisal-gingival line angles, which can alter the perception of size. If the proximal line angles are closer together the canine will appear smaller, and conversely line angles further from each other will make the canine appear wider. Through composite or a veneer the line angles can be altered.

Image from Peyton 2018 (Peyton, 2018)

So space closure is the best option?

The point / counterpoint between Bjorn Zacchrison and Vincent Kokich on space opening Vs space closure debate is evidence enough of there being no conclusive ‘best option’. At the reading of this subheading it would appear readers have been misled and wasted their time, however a mentor of mine once replied to the question of what technique is best in orthodontics with “it depends”, a statement pertinent to the topic of this blog series. In redemption of having misled the readers, below is an extensive list of factors for consideration when substituting canines:

• The canine has a wider and more convex labial surface than a lateral
• Need lots of reduction for normal occlusion and aesthetics
• The dentin may show through
• Possibility of sensitivity, decreased aesthetics or need for restorative intervention
• May need to restore mesio-incisal and disto-incisal edges for normal contour
• Canine may be 1-2 shades darker than the central therefore there may be a need to individually bleach the canine or do a veneer so that it is the same as the central
• Crown width at CEJ should be evaluated on pre-tx PA to determine final emergence profile. Canine with a narrow M-D width at CEJ is more aesthetic emergence profile than a wide CEJ.

We hope you have enjoyed part 2 of the blog, the next blog will be the final blog of this series entitled ‘What would Kokich do?’. This blog started with a conversation between Farooq Ahmed and James Andrews, to follow more conversations, clinical tips and commentaries on orthodontics please check us out on Instagram:

James Andrews’ Instagram page @dr.jamesandrews

Farooq Ahmed’s Instagram page @farooqahmed_orthodontist

• DE-MARCHI, L. M., PINI, N. I. P., RAMOS, A. L. & PASCOTTO, R. C. 2014. Smile attractiveness of patients treated for congenitally missing maxillary lateral incisors as rated by dentists, laypersons, and the patients themselves. The Journal of prosthetic dentistry, 112, 540-546.
• DEMARCO, F. F., COLLARES, K., COELHO-DE-SOUZA, F. H., CORREA, M. B., CENCI, M. S., MORAES, R. R. & OPDAM, N. J. 2015. Anterior composite restorations: A systematic review on long-term survival and reasons for failure. Dental materials, 31, 1214-1224.
• KAILASAM, V., RANGARAJAN, H., EASWARAN, H. N. & MUTHU, M. 2021. Proximal enamel thickness of the permanent teeth: A systematic review and meta-analysis. American Journal of Orthodontics and Dentofacial Orthopedics, 160, 793-804. e3.
• KRAVITZ, N. D., MILLER, S., PRAKASH, A. & EAPEN, J. C. 2017. Canine bracket guide for substitution cases. J Clin Orthod, 51, 450-453.
• OLSEN, T. M. & KOKICH SR, V. G. 2010. Postorthodontic root approximation after opening space for maxillary lateral incisor implants. American Journal of Orthodontics and Dentofacial Orthopedics, 137, e1-158. e8.
• PEYTON, J. H. 2018. “Get in Line”: Tips to Create Ideal Line Angles.
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• ROSA, M., LUCCHI, P., FERRARI, S., ZACHRISSON, B. U. & CAPRIOGLIO, A. 2016. Congenitally missing maxillary lateral incisors: long-term periodontal and functional evaluation after orthodontic space closure with first premolar intrusion and canine extrusion. American Journal of Orthodontics and Dentofacial Orthopedics, 149, 339-348.
• SCHWARTZ‐ARAD, D. & BICHACHO, N. 2015. Effect of age on single implant submersion rate in the central maxillary incisor region: a long‐term retrospective study. Clinical implant dentistry and related research, 17, 509-514.
• SILVEIRA, G. S., DE ALMEIDA, N. V., PEREIRA, D. M. T., MATTOS, C. T. & MUCHA, J. N. 2016. Prosthetic replacement vs space closure for maxillary lateral incisor agenesis: a systematic review. American Journal of Orthodontics and Dentofacial Orthopedics, 150, 228-237.
• THORDARSON, A., ZACHRISSON, B. U. & MJÖR, I. A. 1991. Remodeling of canines to the shape of lateral incisors by grinding: a long-term clinical and radiographic evaluation. American Journal of Orthodontics and Dentofacial Orthopedics, 100, 123-132.